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Carbohydrates
Sugars and chains of sugar units are the most abundant consdtuent

of living matter. New carbohydrates are still being discovered, as

are new roles for them in normal biological processes and disease

T
he four major classes of com
pounds essential to life are nucle
ic acids, proteins, lipids and car

bohydrates. Over the past 30 years the
first three classes have received much
attention from chemists and biologists

whereas during most of that time the
carbohydrates were largely neglected,
partly in the belief that their chemistry
and biology had been fully worked out.
In the past decade, however, research on
carbohydrates has been revived and is
now expanding rapidly. As a result of
many new developments carbohydrate
research is today broad and diverse.

The study of carbohydrates and their
derivatives has greatly enriched chemis
try, particularly with respect to the role
of molecular shape and conformation
in chemical reactions. Recent carbohy
drate investigations have played a deci
sive role in the characterization of vari
ous antibiotics and antitumor agents.
Such studies have led to the discovery of
new biosynthetic reactions and enzymic
control mechanisms and are contribut
ing significantly to the understanding of
many fundamental biological processes,
for example the interaction of cells with
their environment and with other cells.
As a result revolutionary new methods
for combating bacterial and viral infec
tions and for targeting drugs on diseased
cells and organs are being envisioned.
Carbohydrate research has also pro
vided a basis for recognizing the en
zyme deficiency underlying several ge
netic disorders and has led to the hope
that they can be treated effectively. A
common theme behind many of the
recent findings, which is also a powerful
driving force in carbohydrate research,
is the realization that monosaccharides
(the basic units of carbohydrates) can
serve, as nucleotides and amino acids
do, as code words in the molecular lan
guage of life, so that the specificity of
many natural compounds is written in
monosaccharides.

Carbohydrates are sugars or (like
starch and cellulose) chains of sugars.
To most people sugar is the common
household foodstuff, which to the chem
ist is sucrose. Chemically the molecule

by Nathan Sharon

of sucrose consists of two monosac
charides, or simple sugars, glucose and
fructose, that are hooked together; it
is thus a disaccharide. More than 200
different monosaccharides have been
found in nature, all of which are chemi
cally related to gl ucose or fructose. As a
rule they are white crystalline solids that
dissolve readily in water. Some of them
have not been obtained in amounts suffi
cient for testing their sweetness, but they
are still called sugars, as are the mon
osaccharides that are found to be not
sweet.

Glucose is the best-known’monosac
chari de; indeed, it has probably been in
vestigated more thoroughly than any
other organic compound. It was un
doubtedly known to the ancients be
cause of its occurrence in granulated
honey and wine must. References t

grape sugar, which is glucose, are to be
found in Moorish writings of the 12th
century. In 1747 the German pharma
cist Andreas Marggraf, whose isolation
of pure sucrose from sugar beets is an
example of the chemical art of the ti

at its best, wrote of isolating from raisins
“eine Art Zucker” (a type of sugar) dif
ferent from cane sugar; it was what is
now called glucose. The action of acids
on starch was shown to prod uce a sweet
syrup from which a crystalline sugar
was isolated by Constantine Kirchoff in
1811. Later workers established that the
sugar in grapes is identical with the sug
ar found in honey, in the urine of diabet
ics and in acid hydrolysates of starch
and cellulose. The French chemist Jean
Baptiste Andre Dumas gave it the name
glucose in 1838. The structure of gl u
cose and of several other monosac
charides, including fructose, galactose
and mannose, was established by about
1900, mainly by the brilliant work of
the German chemist Emil Fischer, who
thereby laid the foundations of carbohy
drate chemistry.

Monosaccharides rarely exist as such
in nature. They are found in the form of
various derivatives, from which they
can be liberated by hydrolysis with
aqueous mineral acids or with enzymes.
The most abundant of the derivatives

are polysaccharides, which are made up
of sugar units formed into giant mole
cules that can consist of as many as
26,000 monosaccharides (as in cell u
lose from the alga Valonia). Sugars also
occur frequently as oligosaccharides,
which are compounds made .up of from
two to 10 monosaccharides. Sugars are
frequently found in combination with
other natural substances.

The “Water of Carbon”

The name carbohydrate was original
ly assigned to compounds thought to be
hydrates of carbon, that is, to consist of
carbon, hydrogen and oxygen in the gen
eral formula C”(H20),,. Indeed, glucose
and other simple sugars such as galac
tose, mannose and fructose do have the
general formula CSHI20S. They are typ
ical hexose monosaccharides, meaning
that they have six carbon atoms. With
the accumulation of more data the defi
nition has been modified and broadened
to encompass numerous compounds
with little or no resemblance to the orig
inal “water of carbon . ” Carbohydrates
now include polyhydroxy aldehydes, ke
tones, alcohols, acids and amines, their
simple derivatives and the products
formed by the condensation of these
different compounds through glycosid
ic linkages (essentially oxygen bridges)
into oligomers (oligosaccharides) and
polymers (polysaccharides).

Much of the current interest in carbo
hydrates is focused on such substances
as glycoproteins and glycolipids, com
plex carbohydrates in which sugars are
linked respectively to proteins and lip
ids. They are termed glycoconjugates. It
should also be noted that in the excite
ment about nucleic acids a simple fact
is being forgotten: they too are complex
carbohydrates, since monosaccharides
are among their major constituents (ri
bose in RNA and deoxyribose in DNA).

Carbohydrates are the most abundant
group of biological compounds on the
earth, and the most abundant carbohy
drate is cellulose, a polymer of glucose;
it is the major structural material of
plants. Another abundant carbohydrate

CELL-SURF ACE ROLE of a carbohydrate, mannose, is indicated
in this scanning electron micrograph made by Fredric Silverblatt and
Craig Kuehn of the Veterans Administration Hospital in Sepulveda,
Calif. Cells from tissue on the inside of the human cheek occupy the

background of the micrograph; the white cylindrical objects are Esch
erichia coli bacteria. The mannose, which is on the cell membrane, is
not visible, but it is causing the E. coli to adhere to the tissue surface.
Such adherence to surfaces is the first step in a bacterial infection.

is chitin, a polymer of acetylglucos
amine; it is the major organic compo
nent of the exoskeleton of arthropods
such as insects, crabs and lobsters,
which make up the largest class of or
ganisms, comprising some 900,000 spe
cies (more than are found in all other
families and classes together). It has
been estimated that millions of tons of
chitin are formed yearly by a single spe
cies of crab!

Carbohydrates are also the fuel of
life, being the main source of energy for
living organisms and the central path
way of energy storage and supply for
most cells. They are the major prod ucts
through which the energy of the sun is
harnessed and converted into a form
that can be utilized by living organisms.
According to rough estimates, more
than 100 billion tons of carbohydrates
are formed each year on the earth from
carbon dioxide and water by the process
of photosynthesis. Polymers of glucose,
such as the starches and the glycogens,
are the mediums for the storage of ener
gy in plants and animals respectively.
Coal, peat and petroleum were probably
formed from carbohydrates by microbi
ological and chemical processes.

Carbohydrates comprise only about I
percent of the human body; proteins
comprise 15 percent, fatty substances 15
percent and inorganic substances 5 per
cent (the rest being water). Nevertheless,
carbohydrates are important constitu
ents of the human diet, accounting for
a high percentage of the calories con
sumed. Thus some 40 percent of the cal
orie intake of Americans (and some 50
percent of that of Britons and Israelis) is
in the form of carbohydrates: glucose,
fructose, lactose (milk sugar, a disaccha
ride of glucose and galactose), sucrose
and starch.

Sucrose is a major food sugar. Its
world production rose from eight mil
lion tons in 1900 to nearly 88 million in
1977. No other human food has shown
an increase in production on this order
in the same period. The amount of su
crose produced by a country is an in
dex of its average income. In the richer

e CARBON
OXYGEN

countries, such as the U.S., Britain, Aus
tralia and Sweden, the annual consump
tion is between 40 and 50 kilograms of
sucrose per person, whereas in the poor
er ones, such as India, Pakistan and Chi
na, it is five kilograms or less. It has of
ten been suggested that the high sucrose
diet may have detrimental effects on the
health of people in developed countries,
being responsible to some extent for the
increase in such diseases as diabetes,
obesity and dental cavities.

Carbohydrates are the raw materials
for industries of great economic im
portance, such as wood pulp and paper,
textile fibers and pharmaceuticals. The
principal industrial carbohydrate is un
doubtedly cellulose: its worldwide use is
estimated at 800 million tons per year.
Polysaccharides with gelling properties,
such as agar, pectic acid and carrageen
ans, are important in the food and cos
metic industries.

Research Difficulties

The major polysaccharides I have
mentioned-cellulose, starch, glycogen
and chitin-are relatively simple poly
mers: they are homopolymers, made up
of one type of monomer (glucose or ace
tylglucosamine). This seeming simplici
ty, perhaps even dullness, of structure is
probably one of the reasons .carbohy
drates seemed to lack interest.

Another important reason chemists
tended to shy away from the study of
carbohydrates stemmed from the many
chemical problems encountered in deal
ing with these materials. Sugars are mul
tifunctional compounds with several
hydroxyl (-OH) groups, usually four or
five in the hexose sugars, most of which
are of approximately equal chemical re
activity. The manipUlation of a single
selected hydroxyl group is often a seri
ous problem to this day. Blocking one
hydroxyl group or leaving one free can
be achieved only with great difficulty
and requires the careful design and exe
cution of a complex series of reactions.
The synthesis of a disaccharide is there
fore a considerable achievement; trisac-

charides have rarely been synthesized,
and there are only a few reports on the
synthesis of higher saccharides.

By way of contrast, in protein chemis
try peptide.s made up of dozens of amino
acids can readily be synthesized, not
only manually but also by automatic
methods. At least three proteins, insulin
(made up of 51 amino acids), ribonu
clease (124) and lysozyme (129), have
been synthesized. One reason for the rel
ative ease of such syntheses is that the
number of steps involved in the prepa
ration of a peptide is considerably less
than the number required for the syn
thesis of an oligosaccharide of similar
size. It is even more important that a far
larger number of isomeric oligosaccha
rides (the same in composition but dif
ferent in structure) than of oligopeptides
can be obtained from a given number of
corresponding monomers.

An added complication for the chem
ist is that whereas proteins and nucleic
acids are linear polymers, polysaccha
rides are commonly branched. This
characteristic greatly increases the num
ber of possible structures and therefore
the difficulties of studying polysaccha
rides. Luckily for carbohydrate chem
ists many of the possible structures are
apparently not formed in nature.

The recent revival of interest in carbo
hydrates can be ascribed primarily to
the introduction of much improved
methods. Carbohydrate chemists in the
first half of this century had to rely al
most exclusively on carefully controlled
chemical transformations and on opti
cal measurements (chiefly polarimetry)
in the investigation of the structures of
monosaccharides and their derivatives.
Work at that time was further limited by
the lack of good separation techniques
and by the need of a substantial quantity
(a gram or more) of material for many
of the experiments. The advent of chro
matography in its various forms and of
powerful instrumental analytical meth
ods, such as nuclear-magnetic-reso
nance spectroscopy (requiring only mil
ligrams of material), mass spectrometry
(requiring only micrograms) and X-ray-

THREE MONOSACCHARIDES are (left to right) glucose, fructose
and galactose. Carbobydrates being sugars or cbains of sugars, mono
saccbarides are tbe basic units of tbe cbains. Glucose, fructose, galac
tose and many otber simple sugars fit tbe original definition of carbo-

hydrates as h)draks of carbon, consisting of carbon, bydrogen and
oxygen in tbe general formula C”(H20),,. Witb glucose, fructose and
galactose tbe formula is C6H 1206; they are hexoses: they have six
carbon atoms. More than 200 monosaccharides have been found.

GLENLIVET
AGED 12 YEARS

diffraction analysis, and the availability
of highly specific enzymes acting on car
bohydrates have given rise to a com
plete transformation in the approach to
the problem of carbohydrate structure.
Moreover, combinations of these tech
niques can provide information faster,
more conveniently, in greater detail and
with smaller quantities of material than
was formerly possible. Maurice Stacey
of the University of Birmingham has
observed that ascertaining the constitu
tion of a new carbohydrate would have
taken three years in the 1930’s but can
now be done in less than three weeks.

New and Unusual Saccharides

One result of the introduction of the
powerful new techniques was the dis
covery of many new saccharides, both
simple and complex. In recent years the
number of rare sugars isolated from nat
ural sources has increased rapidly. They
have provided the carbohydrate chemist
with new and challenging problems of
structural determination and synthesis. I
shall illustrate this state of affairs with
examples from an area in which I have
been active, the amino sugars: sugars in
which one or more hydroxyls are re
placed by an amino group.

In 1875 a young physician named
George Ledderhose was working during
the summer semester in the laboratory
of Friedrich Wohler in Gottingen when
Ledderhose’s uncle, Felix Hoppe-Sey
ler, a noted physiological chemist, invit
ed him to dinner. At his uncle’s sugges
tion he took the remains of the lobster
they had eaten back to the laboratory,
where he found that the claws and the
shell dissolved in hot concentrated hy-

_ CARBON
C) OXYGEN
o HYDROGEN

SUCROSE

drochloric acid and that on evaporation
the solution yielded characteristic crys
tals. He soon identified the crystalline
compound as a new nitrogen-containing
sugar, which he named giycosamin.

During the next 20 years much evi
dence was gathered to indicate that the
new sugar has a structure derived by the
replacement of the hydroxyl group at
tached to carbon No.2 in the glucose
molecule by an amino group. With the
synthesis, which was still not definitive,
of the amino sugar by Emil Fischer
and H. Leuchs in 1903 the problem of
its structure appeared to have been
solved. The structure of glucosamine
was unequivocally established, howev
er, only in 1939, when Norman Haworth
achieved an unambiguous synthesis that
proved Fischer was correcLin assigning
the “gluco” structure to the amino sug
ar. A second amino sugar, galactos
amine, was isolated in 1914 by P. A.
Levene and Frederick B. La Forge at the
Rockefeller Institute for Medical Re
search from acid hydrolysates of carti
lage, tendon and aorta, but its structure
was firmly established only in 1945,
again attesting to the enormous difficul
ties such substances present. At the time
that was thought to be the end of the
amino-sugar story. By 1960, however,
some 20 new amino sugars had been dis
covered. The number is now over 60.

The first of the “new” amino sugars,
found in 1946, was N-methyl-L-glucos
amine, a constituent of the antibiotic
streptomycin. Soon many other new
amino sugars were identified in antibiot
ic substances. Indeed, some antibiotics
have an oligosaccharide-like structure.
They include the streptomycins, the
neomycins and other aminoglycoside

STRUCTURE OF SUCROSE is depicted. Sucrose is common household sugar. It is a disac
charide: it consists of two monosaccharide molecules (glucose and fructose) joined together.

antibiotics such as the kanamycins and
the paromomycins, all of which are
employed clinically against bacterial in
fections. Another aminoglycoside anti
biotic is puromycin, a well-known in
hibitor of protein synthesis. The potent
and clinically useful antitumor agents
daunomycin and adriamycin, which
have proved to be effective in the treat
ment of acute leukemia, are also amino
glycosides; they contain the rare 3-ami
no sugar daunosamine.

To learn more about the mode of ac
tion of these antibiotics and to improve
on them it is imperative to synthesize
analogues with different amino-sugar
constituents, because it is known that
structural features of the sugar compo
nents often exert a decisive influence on
the pharmacological properties of the
antibiotics. This objective has given
strong impetus to the development of
new methods of synthetic-amino-sugar
chemistry and has opened the way to the
preparation of new and improved anti
biotics that are remarkably effective
against microorganisms resistant to the
natural amino glycoside antibiotics. In
no case, however, are the monosaccha
ride constituents alone effective in vitro
in killing bacteria or in inhibiting the
growth of tumors.

Interestingly enough, several disac
charides such as trehalosamine are ac
tive against bacteria. Herbert A. Blough
and Robert L. Giuntoli of the University
of Pennsylvania School of Medicine re
ported last year that the monosaccha
ride 2-deoxyglucose applied to the site
of an infection is highly effective in the
treatment of genital herpes infection,
a widespread form of venereal disease
caused by the herpes simplex virus, for
which no cure had been available. The
sugar is believed to interfere with the
synthesis of glycoprotein in the virus by
virtue of its similarity to mannose, an
important constituent of the viral glyco
proteins.

New amino sugars and other types of
sugar have been isolated in recent years
not only from antibiotics but also from
other sources, in particular from the
polysaccharides of bacteria. One of the
most important is the 3-lactic-acid ether
of glucosamine, known as muramic
acid. This amino sugar, which is limited
to bacteria, was isolated for the first time
by R. E. Strange and F. A. Dark in Brit
ain in 1956. (For a while it was nick
named the strange and dark compound.)
Its acetylated derivative, acetylmuramic
acid, and acetylglucosamine form the
polysaccharide backbone of the pepti
doglycan in the wall of the bacterial cell.

Another new sugar is ribitol, a reduc
tion product of ribose. It is a constituent
of the teichoic acids, which were discov
ered by James Baddiley in Britain in the
1950’s. Teichoic acids are polymers of
ribitol phosphate or glycerol phosphate
found in Gram-positive bacteria. In the
cell wall of these organisms they act as

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immunological determinants and as re
ceptors of bacteriophages, that is, virus
es that infect bacteria.

An important sugar of unusual struc
ture is neuraminic acid, the parent com
pound of the sialic acids, which are
ubiquitous in nature except for plants.
Neuraminic acid is a nine-carbon sugar
acid with an amino group in its mole
cule. Today 20 sialic acids are known,
most of which were discovered during
the past decade by Roland Schauer of
the University of KieI. They are among
the major constituents of mucins, such
as those secreted by the respiratory and
urogenital tracts, and are also found in
the eye socket. By virtue of their nega
tive charge they impart to the mucin
molecules an extended rodlike struc
ture. They are therefore responsible for
the high viscosity of the mucins. Only
because of the mucins’ sialic acid can
they act as lubricants for the rotation of
the eyeball, preventing the cornea from
drying out and protecting it from dam
age by grains of dust.

In the oral cavity and the gastrointes
tinal tract the viscous glycoproteins in
corporating sialic acid envelop foods,
making them slippery and protecting the
tender mucous surfaces from mechani
cal damage. In the cervical canal of the
uterus a highly viscous plug of mucin
keeps bacteria out of the uterine cavity
and hence out of the abdominal cavity.
This viscous barrier is lowered at the
time of ovulation to admit spermatozoa.
Glycoproteins rich in sialic acid that are
secreted by mucous glands of the vagi
na also lubricate both coitus and child
birth.

A rare diamino sugar, the first of its
kind, that I have been studying for the
past 20 years is bacillosamine. I discov
ered it in a polysaccharide of Bacillus
Iichenz/ormis in 1958 while I was work
ing in the laboratory of Roger W. Jean
loz at the Massachusetts General Hospi
tal. Only recently, through the joint ef
forts of a number of co-workers, were
we able to establish its structure. We
then went on to synthesize the corre
sponding galactose derivative in the be
lief that it too must occur in nature. To
our great satisfaction 2,4-diamino 2,4,-
6-trideoxygalactose was identified last
year in natural products by workers in
Stockholm and Tokyo.

A major breakthrough, which opened
new horizons in biochemistry and had
an immediate impact on medicine, was
the discovery of sugar nucleotides and
their manifold roles as intermediates in
the biosynthesis of monosaccharides,
oligosaccharides and polysaccharides
and of complex carbohydrates. The first
sugar nucleotide, uridine diphosphate
glucose (UD P-glucose), was discovered
by Luis F. Leloir and his co-workers
in Argentina in 1949; for this discovery
Leloir received a Nobel prize in 1970.
At about the same time that Leloir de
scribed UD P-glucose James T. Park and

e CARBON
e OXY G E N

f3 LACTOSE

LACTOSE is a disaccharide consisting of glucose linked with galactose. It is the sugar of milk
and therefore (with such other sugars as glucose, fructose and sucrose) is one of the carhohy
drates making up a large part (40 percent in the U.S.) of the calorie intake in the human diet.

Marvin J. Johnson of the University of
Wisconsin observed the accumulation
of similar compounds in Staphylococcus
aureus bacteria that had been exposed to
penicillin.

More than 100 different sugar nucleo
tides have now been identified. Most of
them have the general structure of nu
cleoside diphospho sugar with any of
the five nucleosides: adenosine, guano
sine, cytidine, uridine and deoxythymi
dine. The sugar exhibits a large variety
of structures, some of which are extreme
ly rare.

Biosynthetic Intermediates

The nucleoside can be considered as a
handle that holds the sugar in a form
ready for transformation into other sug
ars or for transfer to suitable acceptors.
UDP-glucose is the sugar nucleotide
most commonly found in biological ma
terials and is the starting compound for
the formation of numerous other sug
ars. In many organisms it is converted
into UD P-galactose, which is the source
of galactose for the formation of lac
tose. UD P-glucose is also the donor
of glucose for the synthesis of gluco
sides (for example phenyl-/3-glucoside),
oligosaccharides (such as sucrose and
trehalose), polysaccharides (including
starch and glycogen) and other glucose
containing compounds.

The discovery of sugar nucleotides
led not only to the understanding of the
biosynthesis of unusual monosaccha
rides and of complex saccharides but
also to the discovery in 1965 by Phillips
W. Robbins of the Massachusetts In
stitute of Technology and by Jack L.
Strominger of the University of Wiscon
sin School of Medicine of a new type of
activated sugars: the lipid-linked sugars.
They are sugar derivatives linked by a
monophosphate or diphosphate bridge
to polyprenols, long-chain unsaturated

lipids. One example of such a lipid is
bactoprenol, which in the form of its
sugar diphospho derivative is an inter
mediate in the biosynthesis of bacterial
lipopolysaccharides and peptidoglycan.

In 1970 Leloir demonstrated for the
first time that similar compounds, the
dolichol phosphates, participate in the
biosynthesis of glycoproteins by animal
cells. In bacteria the lipid-linked inter
mediates, which are hydrophobic (wa
ter-repelling), serve for the transport
of activated sugars or oligosaccharides
from the cytoplasm of the cell through
the lipid-rich cell membrane to the cell
surface, where polysaccharides such
as the cell-wall peptidoglycan are laid
down. In animals the role of these inter
mediates remains to be established.

As a result of investigations of the
participation of the lipid-linked sugars
in the biosynthesis of complex carbohy
drates, new mechanisms for the assem
bly of biological polymers have been
discovered. For example, with proteins
and simple polysaccharides (such as gly
cogen) the biosynthesis proceeds by the
addition of a single monomeric unit, in
its activated form, to the growing poly
mer chain, whereas in complex carbohy
drates the mechanism is often different.
In the synthesis of the cell-wall pep
tidoglycan a peptide derivative of the
disaccharide acetylgl ucosamine-acetyl
muramic acid is first synthesized on the
lipid carrier. This repeating unit is sub
sequently polymerized and is only then
attached to a polymeric acceptor. A
similar mechanism operates in the bio
synthesis of bacterial lipopolysaccha
rides, except that the repeating unit con
sists of a trisaccharide of mannose,
rhamnose and galactose.

In the biosynthesis of the carbohy
drate units of glycoproteins linked to the
amino acid asparagine an oligosaccha
ride consisting of two residues of acetyl
glucosamine, nine of mannose and three

e CARBON
o OXY G E N
o HYDROGEN

CELLULOSE

e CARBON
o OXY G E N
o HYDRO G E N

AMYLOSE (STARCH)

e CARBON
o OXY G E N
o HYDROGEN

GLYCOGEN (WITH BRANCHING)

THREE POLYSACCHARIDES are (from Ihe lop) cellulose, starch
and glycogen. They are homopolymers, meaning that they are made
up of one type of monomer. In each of the polysaccharides depicted
the monomer is glucose. The individuality of these polysaccharides
and others arises from the length of the polymer chain (which in cel-

lulose may run to several thousand units), the type of linkage between
the sugar units and the occurrence of branches. Three basic units of
each polysaccharide are shown here. Cellulose is a major structural
component in plants. Starch and glycogen serve respectively in plants
and animals for the storage of the energy that is derived from food.

of glucose is first assembled on a lipid
carrier by a complex sequence of reac
tions in which both sugar nucleotides
and lipid-linked sugars participate. The
preassembled oligosaccharide is trans
ferred en bloc to specific asparagine res
idues on the growing polypeptide chain
and is then “processed” to its mature,
final form. This processing includes the
removal by special glycosidases of the
glucose and most of the mannose and
their replacement by tails consisting of
sialic acid, galactose and acetylglucos
amine (as has been found in many serum
glycoproteins and in certain viral glyco
proteins). The replacement proceeds by
the stepwise addition of the individu
al sugars from the corresponding sugar
nucleotides; for example, acetylglucos
amine is added by transfer from UDP
acetylglucosamine and galactose from
UDP-galactose.

Research on sugar nucleotides in rela
tion to the biosynthesis of bacterial-cell
wall peptidoglycan has led to the clarifi
cation of the mechanism of action of
penicillin, which is still the most useful
antibiotic. The unique effectiveness of
penicillin results from the fact that pep
tidoglycan is not found in any organisms
other than bacteria. It is therefore an
excellent target for selective chemo
therapeutic agents that kill the bacte
ria without affecting their host.

Genetic Diseases

A completely different reason for the
new wave of interest in carbohydrates
stems from the fact that many of the
hereditary or genetic diseases of man
for which the molecular basis has been
established are defects of carbohydrate
metabolism, mostly of complex saccha
rides. One of the diseases is galactos
emia, a rare familial defect in galactose
metabolism caused by the lack of a
single enzyme: galactose phosphate uri
dyl transferase. Because of the absence
of this enzyme afflicted infants cannot
utilize galactose or galactose-contain
ing compounds, in particular lactose.
Breast-feeding literally poisons such in
fants. The galactose, which is ordinarily
converted into glucose and eventually
into energy, accumulates in the infant’s
blood in the poisonous form of galac
tose phosphate, causing severe neural
retardation and often early death.

Mainly as a result of the efforts of
Herman M. KaJckar and his collabora
tors at the National Institute of Arthri
tis and Metabolic Disorders in the late
1950’s the diagnosis of galactosemia
can be made before the disease is far
advanced. The procedure tests for the
presence of the enzymes that metabolize
galactose. If one of the enzymes is miss
ing and the infant is given a diet free of
galactose, all symptoms of galactosemia
disappear and development becomes
normal.

Most other genetic defects of carbo-

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AGING JACK DANIELS WHISKEY calls
for hot summers, cold winters and a few men
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Summer’s heat causes our whiskey to seep
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CHARCOAL
MELLOWED

6
DROP

6
BY DROP

Tennessee Whiskey· 90 Proof· Distilled and Bottled by Jack Daniel Distillery
Lem Mollow, Prop., Inc., Route I, Lynchburg (Pop. 361), Tennessee 37352

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100

hydrate metabolism cause mental retar
dation and often early death. The best
characterized among them are the mu
copolysaccharidoses: disorders of mu
copolysaccharide metabolism, such as
Hurler’s syndrome and Hunter’s syn
drome, and disorders of glycolipid me
tabolism, such as Tay-Sachs disease,
which occurs at a relatively high inci
dence (one birth in 3,000 births) among
Ashkenazi (eastern European) Jews. In
most of these diseases the mlssmg en
zyme normally functions to degrade
complex saccharides.

In the mucopolysaccharidoses large
quantities of complex carbohydrates
(the mucopolysaccharides) accumulate
in the lysosorn,es, the subcellular organ
elles where large molecules are normal
ly broken down. Increased quantities of
mucopolysaccharides are also secreted
in the patient’s urine. Cells taken from
the skin of a patient and grown in tissue
culture also accumulate mucopolysac
charides. In the early 1970’s Elizabeth
F. Neufeld of the National Institute of
Arthritis, Metabolism, and Digestive
Diseases found that this accumula
tion can be prevented by providing the
cells with the missing polysaccharide
degrading enzymes. Unfortunately at
tempts to treat patients by administering
the appropriate enzymes have not yet
been successful.

A disease that is well known to be
closely linked with sugar metaboljsm is
diabetes. Although diabetes has now
been shown to be a family of different
disorders, all diabetics have one thing in
common: abnormally high levels of glu
cose in the blood. Moreover, in nearly
all diabetics similar complications de
velop, including heart disease, blind
ness, cataracts, blood-vessel damage,
nerve disorders and kidney damage. Is
the high blood sugar by itself the cause

_ CARBON
o OXYGEN

a-D-GLUCOSE

of diabetic complications? Many inves
tigators tend to believe that it is and
that tight control of blood sugar can pre
vent, arrest and possibly even reverse
the progress of these complications.

To understand what high blood sug
ar does biochemists and physicians are
asking how glucose damages cells at the
molecular level. One possible mecha
nism is that glucose combines with pro
teins in the body, altering their configu
ration and their function. Evidence of
how this process might occur was re
cently obtained by a number of groups,
including Anthony Cerami and Ronald
Koenig and their associates at Rockefel
ler University and H. Franklin Bunn,
Kenneth H. Gabbay and Paul M. Gal
lop at the Harvard Medical School.
These investigators found that glucose
attaches itself, in a process not requiring
enzymes, to the hemoglobin molecules
of diabetic patients, thereby altering the
electric charge and biochemical proper
ties of the hemoglobin.

The idea that glucose can combine
with amino acids and proteins is not
new. For a while it was the subject
of considerable research by biochem
ists and food chemists. Aharon Katzir
Katchalsky studied this reaction at the
Hebrew University of Jerusalem for his
doctoral degree, which he was awarded
in 1938, and I continued on the same
subject with him for my Ph.D. degree
(also from Hebrew University) in 1950-
53. Food chemists had long known that
the interaction of glucose and food pro
teins, a reaction known as nonenzymatic
browning because it proceeds without
enzymes and turns the protein brown,
causes a decrease in the digestibility and
nutritive value of protein. Hematolo
gists found some years ago that about 5
percent of the hemoglobin molecules of
normal people contain nonenzymatical-

a-B-GLUCOSAMINE

AMINO SUGAR is glucosamine, a constituent of lobster shell, glycoprotein and the cell wall
of fungi. In amino sugars one or more hydroxyl (-OH) groups of the sugar molecule are re
placed by an amino, or nitrogen-containing, group. Here the amino group replaces the hydrox
yl group on carbon No. 2 of the glucose molecule. More than 60 amino sugars are now known.

ly bound sugars. This attachment of sug
ar molecules to proteins is a slow proc
ess and does not normally happen to any
great extent with proteins that are rapid
ly broken down and resynthesized. Few
sugar molecules are expected to attach
themselves even to relatively stable pro
teins such as hemoglobin. Diabetics,
however, have so much glucose in their
blood that their level of glucosylated
hemoglobin molecules is two or three
tiJ;Iles higher than the norm. Attempts
are now being made to exploit this find
ing clinically.

Red blood cells and their hemoglobin
have a lifetime of about 120 days. Once
glucose has become attached to the he
moglobin it comes off slowly, so that the
amount of glucosylated hemoglobin in
the blood of a patient acts as an indica
tor for the total blood-sugar concentra
tion over the preceding few weeks. It is
hence a better index than anything now
available of how well controlled the pa
tient’s blood glucose has been over such
a period.

Since glucose attaches to hemoglobin,
it almost certainly attaches to other pro
teins in the same way and may therefore
change their properties and biological
functions. The process may be particu
larly damaging to proteins that are slow
to be replaced, such as those in the lining.
of blood vessels and in the insulating
material around nerve cells. Cerami has
recently demonstrated that a high con
centration of glucose leads to the gluco
sylation of proteins of the eye lens,
both in vitro and in vivo, and to a sub
sequent opacity of the protein matrix,
mimicking the opacity seen in diabetic
cataracts.

Biological Markers

Until recently it was not recognized
that nature can employ sugars for the
synthesis of highly specific compounds

e CARBON
OXYGEN

o N I TROG E N
o PHOSPHORUS
o HYDROG EN

UR ID I N E D I PHOSPHATE GLUCOSE

that can act as carriers of biological in
formation. This capability arises from
the fact that a large number of struc
tures can be formed from a small num
ber of monomers. In other words,
monosaccharides can serve as letters in
a vocabulary of biological specificity,
where the words are formed by varia
tions in the nature of the sugars present,
the type of linkage and the presence or
absence of branch points. It is now
known that the specificity of many natu
ral polymers is written in terms of sug
ars, not amino acids or nucleotides. This
idea is not entirely novel, but it has only
recently become well established.

In the 1920’s it was still believed that
the specific information in biological
polymers was carried only by proteins.
Between 1925 and 1937 Oswald T.
Avery of the Rockefeller Institute, to
gether with Michael Heidelberger and
Walther F. Goebel, demonstrated that
pure polysaccharides can carry specific
immunological messages as antigens:
substances that stimulate the produc
tion of an antibody specific to them
selves. Thus the highly purified Type III
pneumococcus “specific soluble sub
stance” was an antigen even though it
did not have any of the properties of a
protein. This substance was shown to be
polysaccharide, consisting of repeating
units of cellobiuronic acid (a disaccha
ride of glucose and glucuronic acid).

The chemical basis of the antigenicity
of polysaccharides was thoroughly clar
ified through the application of highly
sophisticated techniques developed by
Heidelberger and Elvin A. Kabat of the
Columbia University College of Physi
cians and Surgeons, Walter T. J. Mor
gan of the Lister Institute of Preventive
Medicine in London and many others.
Today it is well established that carbo
hydrates are ideally suited for the for
mation of specificity determinants that
can be recognized by complementary

structures, which presumably are car
bohydrate-binding proteins, on other
cells or molecules.

The first indication that sugars serve
as specificity determinants came from
the discovery in 1941 by George K.
Hirst in New York and by Ronald Hare
in Toronto that the influenza virus
caused red blood cells to agglutinate, or
clump. The molecular basis of this phe
nomenon was for a time obscure. Main
ly as a result of the efforts of Alfred
Gottschalk in Australia it was shown
that the influenza virus binds to the red
blood cell through sialic acid units on
the cell surface. If the sialic acid is re
moved from the cell surface by the en
zyme neuraminidase, the influenza virus
will no longer bind to the cell.

The role of carbohydrates in recogni
tion has been best demonstrated in the
control of the lifetime of glycoproteins
in the circulatory system and their up
take into the liver and of the uptake of
lysosomal enzymes by cells. As often
happens, these exciting discoveries orig
inated with an unexpected observation,
this one made in 1966 by G. Gilbert
Ashwell of the National Institute of Ar
thritis, Metabolism, and Digestive Dis
eases and by Anatol G. Morell of the
Albert Einstein College of Medicine in
the course of an effort to understand the
biological role of ceruloplasmin, a cop
per-transport protein found in the blood
serum of man and other animals. When
Ashwell and Morell removed sialic acid
from rabbit ceruloplasmin and rein
jected the modified ceruloplasmin into
the animals, it almost completely dis
appeared from the circulatory system
within 15 minutes. This was in striking
contrast to the native glycoprotein, al
most all of which remained in circula
tion after the same length of time. Fur
ther work has shown that with many
serum glycoproteins the removal of ter
minal sialic acid units to expose the un-

SUGAR NUCLEOTIDE, the first of more than 100 that have heen
found, is uridine diphosphate glucose (UDP-glucose). It is the start
ing compound for the biosynthesis of numerous other sugars. The
general structure is that of a sugar in association with a nucleoside

(adenosine, guanosine, cytidine, uridine or deoxythymidine) and phos
phorus in the form of phosphate. Here it is glucose, uridine and two
phosphate groups. The nucleotide holds the sugar in an activated
form for transformation to other sugars or transfer to acceptors.

102

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103

derlying galactose units results in the
rapid removal of the modified glyco
proteins from the circulatory system of
experimental animals and their uptake
by the parenchymal cells of the liver.
The surface of such a cell contains a re
ceptor specific for the binding of glyco
proteins that lack sialic acid.

Galactose hence serves as a recogni
tion marker that determines the survival
time of many serum glycoproteins in the
circulatory system of man, the rabbit
and the mouse. In bird and reptile spe
cies the recognition marker appears to
be primarily acetylglucosamine. Clear
ance systems in which fucose and man
nose are the markers have also been
found.

A particularly interesting marker is

1 . APPROACH

2 . B I ND I N G

LATENT AD E N Y LATE
CYCLASE

3 . CON FORMAT IONAL CHANGE

mannose-6-phosphate, a sugar deriva
tive that has recently been shown to act
mainly in directing the intracellular traf
fic of glycoprotein enzymes normally
present in lysosomes. This finding had
its origins in Neufeld’s discovery that
the enzyme deficiencies in cells from
patients afflicted by mucopolysaccha
ridoses such as Hurler’s and Hunter’s
syndromes can be corrected by provid
ing the cells with the missing enzymes.
In 1974 she showed further that uptake
into the cells depended on the presence
in the enzymes of a carbohydrate-recog
nition marker. In 1977 William S. Sly of
the Washington University School of
Medicine and Arnold Kaplan of the
Saint Louis University School of Medi
cine identified the recognition marker as

4. D ISSOCIAT IO N AND E NTRY

5 . P E N ETRAT I O N AND
” ACT I VAT IO N ” OF
A S U B U N IT

6. ACT I VAT ION OF
CYCLASE

ATP cAMP

ACTION OF GLYCOLIPID in binding the toxin of cholera bacteria is indicated. A glycolipid
is a compound in which a sugar is linked to a lipid; here it is the ganglioside, or acidic glyco

lipid, known as GM b which is found in the plasma membrane of cells. A cholera toxin, consist
ing of one A subunit (black) and five B subunits (white), approaches the plasma membrane
of an intestinal mucosal cell (1), is hound by the GM 1 (2) and as a result is changed in con
formation (3) in such a way that the A subunit is dissociated from the toxin and enters the mem
brane (4). There the A subunit becomes activated (5) so that it is able to activate the adenylate
cyclase system of the cell (6). The activation of the cyclase system causes the cell to secrete ex
cess quantities of fluid, giving rise (as large numbers of cells become overactive) to the huge
losses of liquid that often cause dehydration and death in cholera. If GM 1 is administered to
the patient so that much of it is not associated with cells, it can bind the cholera toxin and inhib
it the toxin’s effect. Other gangliosides evidently inhibit similarly the action of other toxins.

104

a phosphorylated sugar unit: mannose-
6-phosphate. The function of the mark
er is apparently to prevent the secretion
of the enzymes from the cells and to
direct them into the lysosomes. When
the enzymes are supplied from the out
side, it is this recognition signal that pro
motes their binding to the cell surface;
without binding they cannot enter the
cells and reach the lysosomes.

By the covalent (electron-sharing) at
tachment of carbohydrates to proteins
or by a modification of the sugars in
glycoproteins it may thereby be possible
to control the proteins’ lifetime in the
circulation and to direct them to the liv
er and perhaps also to other organs, as
well as into lysosomes. Such techniques
will have far-reaching uses for enzyme
replacement therapy in cases of genetic
disease and also for delivering drugs ac
curately into target organs and cells.

Other Biological Roles

Sugars on cell surfaces also appear to
determine the life span of circulating
cells and their distribution in the body.
This role was originally demonstrated in
1964 by Bertram M. Gesner and Victor
Ginsburg of the National Institute of
Arthritis, Metabolism, and Digestive
Diseases. They found that radioactively
labeled rat lymphocytes migrated to the
spleen when they were reinjected into
the animal. If before reinjection the sug
ar fucose was removed from the surface
of the cells by treatment with a specific
glycosidase, the lymphocytes migrated
to the liver instead, as if the fucose on
the lymphocytes served as a “ZIP” code
directing them where to go.

Old red blood cells – have less sialic
acid on their surface than young ones,
and so it has been postulated that the
decrease of sialic acid is the signal re
sponsible for the removal of the older
red blood cells from the circulatory sys
tem. This hypothesis seemed to be fur
ther substantiated by the finding that
when red blood cells are taken out of the
circulation, and when the sialic acid is
removed from their surface and they are
reinjected into the blood, their life span
is extremely short: only a couple of days
out of the normal lifetime of 120. In
spite of these striking correlations there
is considerable doubt whether the re
moval of sialic acid and the exposure of
galactose units on the surface of the red
blood cell are responsible for the remov
al of senescent red cells from the blood
under physiological conditions in vivo.

The well-known A B O blood-group
system was first described by Karl Land
steiner of the Rockefeller Institute in
1900, but it was not until 1953 that Wal
ter Morgan and Winifred Watkins of
the Lister Institute demonstrated that
the specificity of the major blood types
is determined by sugars. For example,
the difference between the blood types A
and B lies in a single sugar unit that

3 �� •

��

� • ��

•

��

MECHANISM OF ATTACHMENT of E. coli to a cell membrane,
as is shown in the micrograph on page 9 1 , and its inhibition by free
mannose is portrayed schematically. Bacteria approach a cell mem
brane (1) in which a glycoprotein is embedded. Here mannose (black

1 06

•

dots), which is part of the glycoprotein, is recognized by binding sites
on the E. coli. As a result the bacteria adhere to the host surface (2),
initiating an infection. If free mannose is available, however, it binds
to the bacteria first (3) and prevents them from attaching to the cell.

sticks out from the end of a carbohy
drate chain of a glycoprotein or gly
colipid on the surface of the red blood
cell. In blood type A the determinant is
acetylgalactosamine, in blood type B it
is galactose. The two monosaccharides
differ by only a small group of atoms,
but that little difference is sometimes a
matter of life and death, since using the
wrong type of blood in a transfusion can
have fatal results.

The enzymatic removal by specific
glycosidases of a-linked acetylgalac
tosamine from type A red blood cells or
of a -linked galactose from type B red
blood cells will convert both into type 0
cells. An effective conversion can, for
example, be carried out by purified a
galactosidase from coffee beans or soy
beans, as was demonstrated in our labo
ratory by Noam Harpaz and Harold
Flowers. Such a conversion may be use
ful clinically when type 0 cells of rare
subtypes are needed for transfusion.

The sugars that determine the speci
ficity of substances in the A B O blood
group are distributed in the biological
world in forms similar to those found in
human beings. The substances are there
fore also present in different mammals.
Hence the red blood cells of the dog, the
pig and the rabbit are invariably of type
B and in some cases may also belong
to type A. The ABO blood-group sub
stances are present in birds and amphib
ians and even in plants and bacteria.

Tamio Yamakawa of the University
of Tokyo has recently suggested that
dogs may possess a blood-group system
specified by the sialic acid in red-blood
cell glycolipids. Whereas all European
dogs so far examined have glycolipids
that incorporate acetylneuraminic acid,
Yamakawa and his co-workers have
shown that representative Japanese
dogs such as the Kishu and Shiba breeds
often have glycolylneuraminic acid in
stead and that this occurrence is genet
ically determined. Akita and Hokkaido
dogs from northern Japan seem to be
exceptional in having only acetylneur
aminic acid in their red-blood-cell gly
colipids. The origin of the Japanese dog
is still controversial, but since the glyco
lylneuraminic acid glycolipid is inherit
ed as a dominant trait, the findings sug
gest that the origins of the Akita and
Hokkaido breeds are different from
those of other Japanese dogs and that
the Akita and Hokkaido breeds are re
lated to European dogs.

Several toxins of bacteria and plants
are now known to recognize carbo
hydrate structures present in various
classes of cell-surface molecules. In
cluded are the cholera toxin and possi
bly the tetanus toxin, which bind to cer
tain glycolipids of the ganglioside type.
Gangliosides are unique acidic glycolip
ids that are selectively concentrated in
the plasma membrane of cells.

W. E. van Heyningen of the Universi
ty of Oxford showed in 1971 that gangli-

ntroducing instant
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T h e c a m e r a , d e s i g n e d a n d m a n u fac t u red by
M e k e l E n g i n e e r i n g , I n c , c a n t a k e m o t i o n p i c t u res at
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1 0 s e c o n d s of ac t i o n o v e r as m u c h a s 2 V2 m i n u t e s o f
f i l m , effe c t i v e l y s l o w i n g d ow n t h e m o t i o n b y 1 5 t i m e s .

T h e Po l a ro i d a n a l y z e r g i ve s y o u a n o r m a l f o rw a r d
s pe e d , fou r s l ow – m ot i o n s p e e d s , f r a m e – b y
f r a m e a d v a n c e m e n t , sto p act i o n a n d i n s t a n t
re p l ay. Yo u c o n t ro l a l l t h e s e s p e e d s w i t h a
h a n d – h e l d c o n t r o l

Afte r e x p o s u re , t h e c o l o r o r b l ac k a n d
w h i t e m o v i e c a s s ette i s i n s e rt e d i n t h e
a n a l y z e r. T h e re i t d ev e l o p s a u t o m at i c a l l y
i n 9 0 s e c o n d s a n d i s t h e n p roj e c t e d o n t h e

0 1 980 P o l a r o i d C o r p o r a t i o n · · P o l a r o l d ” 1;

s c re e n Yo u s e e t h e re s u l t s immedia tely. A n d y o u
c a n v i ew t h e p i c t u re s at a n y c o n v e n i e n t p l ac e .

T h i s s y s t e m l e t s y o u i n s t a n t l y t ro u b l e s h oot a n d
s o l v e e n g i n e e r i n g , f a b r i c at i o n a n d p ro c e s s i n g p ro b
l e m s t h at w o u l d o t h e rw i s e b e baffl i n g . I n v e st i g at e
v i t al p o rt i o n s of a n a s s e m b l y l i n e to s e e w h at ‘ s c a u s
i n g a h a n g – u p . A n a l yze a p l as t i c m o l d i n g o p e rat i o n
to d i s c o v e r w h y p a rt s a r e d ef e c t i ve . O b s e rv e a c u t
t i n g t o o l i n a m i l l i n g o r l a t h e o p e rat i o n to d et e r m i n e
t o o l eff i c i e n c y. F i n d o u t i f a f a s t – m ov i n g p a rt i s b o u n c
i n g e r rat i c a l l y a n d red u c i n g p ro d u c t i v i ty. T h e s e a n d a
t h o u s a n d ot h e r h i g h – s p e e d eve n t s c a n be a n a l y z e d .

F o r m o re i n f o r m at i o n or a d e m o n s t rat i o n on y o u r
own p re m i s e s , w r i t e to P o l a r o i d C o r p o r at i o n , D e pt .
A 4 4 9 , 5 7 5 Te c h n o l o g y S q u a r e , C a m b r i d g e , M a s s .
021 3 9 . O r c a l l u s t o l l – f r e e f r o m t h e c o n t i n e nt a l U . S . :
8 0 0 – 2 2 5-1 61 8 . I n M a s s ac h u s e tt s , c a l l c o l l e c t : 61 7-
54 7-51 7 7

Po aroid
I n stant Motion Analys i s

THE ATARI®
PERSONAL COMPUTERS.

YOU SHOULD KNOW
WHY SO MANY PEOPLE

ARE B UYING THEM.
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An Atari

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t::;:::.iit puter is also an

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How to turn a s m a l l business into
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receivable to inventory control . Yet they ‘re
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Periphera l s aren’t just a
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The most revo l utionary
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One of the things that ‘s revolutionary

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An Atari Personal Computer has a voice that teaches ,
asks questions, and tells your child whether he or she has
the right answer. If your child gets a wrong answer the

I g ATARI �@ I

Atari Personal C omputers are powerful
enough to handle almost any kind of
business application – from accounts � . (�.� :;. �’�l � … I”;’�;I!”.JilIi��·.L��M��{“H; ;”�/�AI. “‘ • • “” ,….. �’-‘I,��diJ-

�TA R I 400′”

•
–

,…

, ,

All progrilms referred to or shown will be ilvaililble ilS preprogrilmmed cilrtridges or c dSSettes in 1980. or ilre eXilmples of progrilms which ciln be written in A tdri BASIC.
A tilri reserves the right to modify programs or products without notice. *Prognms and peripherals not included.

computer doesn’t have to
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in o rder to save time . It waits
for your child to answer the

question correctly.
Atari has a wide

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personal computer on the market .
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There are several easy -to -learn programming lan
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What makes our computer games even more sana I computer is an extravagance in diffi cult fi nancial
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In fact . A tari has more color variations , more sounds ATA RI® Difficult fi nancial times may be your best reason
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PERSONAL COMPUTER SYSTEMS
1265 Borregas Ave . Dept . E, Sunnyvale, California 94086. Call toll-free 800- 5 3 8-8547 excluding

Hawaii and Alaska (in Calif. 800-672-1404) for the names of your nearest Atari retailers.

After 1/2 million owners,
6 billion miles and Motor Trends “Car of the Year” award, it stands alone.

T h e re ‘ s s o m e th i n g a b o u t
b e i n g new. Eve ryo n e watches
to s e e i f you ‘ l l work o u t .

B e l i eve u s , i t wa s n o d iffe r
e n t w h e n C i t a t i o n w a s i n t r o
d u ced . W e s a i d it was a w h o l e
n ew k i n d of c o m p a ct ca r. A n d
t h e n we h a d to p rove i t .

W e p u t C i t a t i o n to w o r k .
B e co m i n g t h e m o s t
s u ccessf u l n e w C h ev ro l et
ever i n trod u c ed . A n d

n ow, a ft e r 1 – 1 /2 yea r s , i t’s
t h e b e s t- s e l l i n g f r o n t – w h e e l
d rive i n A m e ri c a .

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a b o u t C i t a t i o n f rom t h e sta rt
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f r o n t- w h e e l d ri v e , roo m fo r
fi v e , wa g o n – l i ke u ti l i ty, even
h i d d e n sto r a g e s p a c e .

N ow, of c o u rse, you ‘ l l
b e h e a ri n g a b o u t a l ot
of f r o n t – w h e e l d rives

1981 CH EVY
CITATION

osides of the brain bound cholera tox
in and blocked its physiological effect.
Later work by van Heyningen, by Lars
Svennerholm and Jan Holmgren of the
University of Goteborg and by Pedro
Cuatrecasas of the Johns Hopkins Uni
versity School of Medicine showed that
the ganglioside G M 1 is the most effec
tive inhibitor. A close correlation was
found between the G M 1 content of in
testinal mucosal cells from different spe
cies and the amount of cholera toxin
that was bound. There is also considera
ble evidence that specific gangliosides
can inhibit the action (;)f tetanus toxin
and botulinum toxin. The existence on
cells of specific carbohydrates showing
a strong affinity with the toxins of viru
lent organisms such as cholera and diph
theria is of great medical importance,
since it may be possible to protect
against these diseases by the administra
tion of suitable gangliosides.

The cell-surface sugars of ganglio
sides serve for the attachment of other
biologically active molecules. Promi
nent among them is the potent antiviral
agent interferon. The incubation of gan
gliosides with interferon will inhibit in
terferon’s antiviral activity. Moreover,
mouse cells that do not respond to treat
ment with interferon become responsive
after tlie incorporation of gangliosides
into their surface membrane. These re
sults indicate that gangliosides and in
terferon can interact at the cell surface
and that these complex carbohydrates
may have a function in the antiviral ac
tivity of interferon.

Cell Recognition

Cell-surface sugars serve as receptors
for various other physiological and non
physiological agents. Among them are
lectins, which in binding to cells often
give rise to agglutination. If they bind to
lymphocytes, they induce cell growth
and division, a phenomenon known as
mitogenic stimulation.

Pronounced changes in cell-surface
sugars are observed during the develop
ment and differentiation of cells and on
the transformation of normal cells into
malignant ones. Many of the changes
were originally detected with the aid of
lectins. In particular the finding during
the 1960’s that malignant cells are much
more readily agglutinated by lectins
(such as wheat-germ agglutinin, conca
navalin A and soybean agglutinin) than
their normal counterparts focused the
attention of many investigators on cell
surface sugars. The excitement over
these findings is waning, however, be
cause it has proved to be extremely diffi
cult to identify the structural changes
that take place on the surface when
normal cells become malignant. It has
also not been possible to gain any insight
into the physiological meaning of these
changes. Moreover, the increased ag
glutination by lectins is not a property

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1 1 3

#1 in a series ofreports on newtechnology fromXerox
A bout a year ago, Xerox introduced the E thernet

network – a pioneering new development that
ma kes it poss ible to link different office mach ines into
a s ingle network tha t ‘s reliab le, flexible and eas ily
expanda b le.

The fo llo wing are some n otes explain ing the
tech n o log ica l underpin n ings of th is development. They
a re con trib uted by Xerox research scientist Da vid
B oggs.

The E thernet system was designed to meet
several ra ther ambitious obj ectives .

F i r s t , it had to allow many users wi thin a
given organization to access the same data . N ex t ,
it had to a l l o w the organization the economies
that come fro m reso urce shar i n g ; that i s , if
several people could share the same information
processing equipment , i t would cut down on
the amount and expense of hardware neede d . I n
a ddition, t h e resulting n e twork h a d to be flex
i b l e ; users had to be able to change components
easily so the network could grow smoo thly
as new capability was neede d . Finally, it had to
have maximum reliability – a system based on
the notion of shared information would look
pre tty silly if users couldn’t get a t the information
because the network was broken.

1 1 4

Collision Detection
The E thernet network uses a coaxial cable

to connect various pieces of information equip
ment. I nformation travels over the cable in
p ackets which are sent from one machine to
ano ther.

A key problem in any system of this type is
how to control access to the cable : what are the
rules determining when a piece of equipment can
talk? E therne t ‘s method resembles the unwritten
rules used by people at a p a r ty to decide who
gets to tell the next sto ry.

While someone is speaki n g , everyone else
w a i t s . When the current speaker stops, those who
w a n t to say something pause, and then l aunch
into their speeches . If they co llide with each other
( hear someone else talking, too ) , they all stop
and wait to start up again. Eventually one p a uses
the shortest time and starts talking so soon that
everyone else hears hi m and waits.

When a piece of equipment wants to use
the E thernet cable , i t l istens first to hear if any
o ther station is talking . When i t hears silence on
the cable, the station starts talking, b u t it also
l istens . I f i t hears o ther stations sending too , i t
s t o p s , as do the o ther stations. Then it waits a

random amount of time , on the order of micro
seconds, and tries again. The more times a
station collides, the longer, on the average, it
waits before trying again.

I n the technical literature , this technique
is called carrier-sense multiple-access with col
lision detection. I t is a modification of a me thod
developed by researchers at the University of
Hawaii and fur ther refined by my colleague Dr.
Robert Metcalfe . As long as the interval during
which stations elbow each other for control of
the cable is short relative to the interval during
which the winner uses the cable, it is very
efficient. Just as important, i t requires no central

Cl
Cl

control – there is no distinguished station to
break or become overloaded.

The System
With the foregoing problems solved,

. E thernet was ready for introduction. It consists
of a few relatively simple components:

Ether. This is the cable referred to earlier.
S ince it consists of j ust copper and p lastic,
its reliab ility is high and its cost is low.

Tr ansceiver s . These are small boxes that
insert and extract bits of informa tion as
they pass by on the cab l e .
Controller s . These a r e large scale inte
grated circuit chips which enable all sorts
of equipment, fr om communicating type
writers to mainfr ame computers, regardless
of the manufacturer, to connect to the
E therne t .
The resulting system is n o t only fast ( tr ans

mitting millions of bits of information per
second ) , it’s essentially modular in design. I t’s
l argely because of this modul arity that E thernet
succeeds in mee ting its objectives of economy,
reliability and expandabil i ty.

The system is economical simply because
it enables users to share b o th equipment and
information, cutting down on hardware costs.
It is reliable because control of the system is
distributed over many pieces of conm1Unicating
equipment, instead of being vested in a single
central controller where a single piece of mal
functioning equipment can i nm10bilize an
entire system. And Ethernet is expandable
because it readily accepts new pieces of infor-

,. mation processing equipment.
This enables an organization to
plug in new machines gradu
ally, as its needs dicta te, or as

technology develops new and better one s .

About The Author
David Boggs is one of the inventors of

E thernet . He is a member of the research staff
of the Computer S cience Laboratory at Xerox’s
P alo Alto Research
Center.

He holds a
B achelor’s degree in
Electrical Engineer
ing from P rince ton
University and a
Master’s degree
from S tanford
University, where
he is currently
pursuing a P h . D .

XEROX
XEROX ® J nd Ethl’rnCI 3 rt’ trademarks of XEROX CORPORATION.

1 1 5

1 1 6

SOME SERIOUS N OTES
ON MOVING.

By Victor Borge

When you move , make sure your mail arrives
at your new address right after you do .

The key is this: Notify everyone who regularly
sends you mail one full month before you move .

Your Post Office or Postman can supply you
with free Change-of-Address Kits to make no
tifying even easier.

One last serious note . Use your new ZIP Code .

Don’t make your mail come looking for you . (� J
Notify everyone a month before you move . � ®

©uSPS 1980

shared by all malignant cells, so that the
early hopes of employing lectins to iden
tify and perhaps to attack such cells se
lectively have faded.

Cell-surface sugars participate in fer
tilization in mammals, sea urchins, pro
tozoa and algae. Cellular association in
slime molds is mediated by the interac
tion of carbohydrate-binding proteins
on one cell with specific oligosaccharide
receptors on another cell. Thus differen
tiation in slime molds from a vegetative
(single cell) form to a cohesive (aggre
gated) form is accompanied by the ap
pearance of both cell-surface lectins and
specific glycoproteins. Moreover, sim
ple sugars such – as galactose and acetyl
galactosamine inhibit the aggregation of
cells in this system.

In recent years it has been demon
strated that cell-surface saccharides act
as receptors not only for viruses but
also for bacteria. This finding is proba
bly the best-documented example of a
specific cell-cell interaction mediated
by carbohydrates. It is a phenomenon
of great importance, since the adher
ence of bacteria to tissue surfaces is
the initial event in a bacterial infection.
Work done in our laboratory and else
where has demonstrated that bacteria
such as Escherichia coli and Salmonel
la typhim u rium adhere to epithelial cells
and to scavenging white blood cells
through units of mannose on the surface
of such cells. This carbohydrate-specific
interaction is mediated by a mannose
specific lectin present on the surface of
the bacteria. The lectin has been isolat
ed from E. coli by Yuval Eshdat of our
department. In collaboration with Da
vid Mirelman of our department and
Moshe Aronson and Itzhak Ofek of Tel
Aviv University we have also found
that colonization of the urinary tract of
mice infected with E. coli can be mark
edly diminished by the administration
of methyl a -mannoside, a sugar that ef
fectively inhibits the mannose-specific
adherence of the bacteria to epithelial
cells. Further studies of the sugars on
cell surfaces that act as receptors for
bacteria may lead to the design of im
proved inhibitors of adherence. Such in
hibitors might serve to prevent bacterial
infection by blocking its first step, the
adherence of the invading organism to
the epithelial surfaces of the host.

To sum up, carbohydrates are found
in wide variety, and many of them are
extremely complex. They perform nu
merous tasks in living organisms; most
important, like nucleic acids and pro
teins, they seem to serve as information
al molecules. Determining more about
these compounds and establishing in de
tail their chemical structure and confor
mation wil l not only result in a deeper
understanding of what life is but also
make it possible to combat more effec
tively ‘,arious diseases, such as those
caused by genetic defects or infectious
agents.

toda y ‘s quartz timepieces is revealed.
Most m aj o r com pa n i es wo u l d rat h e r

h a v e t h e s e facts re m a i n sec ret, b u t o n e
l itt l e – k n ow n c o m p a n y d e c i d ed t o s h ow
its ge n i u s to t h e wo r l d .

To effe c t i v e l y c o m p e t e i n w o r l d
m a rkets a n d w h e n l ac k i n g i n necessary
tec h n o l ogy, m a n y m a j o r c o m pa n i es
have t u rned to s m a l l e r m o re d y n a m i c
co m pa n i e s to b u i l d t h e i r p rod u c t s .
So m e t i m e s t h e p rod u ct i s b u i lt t o t h e
s p e c s of t h e m aj o r c o m p a n y . B u t m o re
often t h a n not, t h e o n l y u n i q u e p a rts
a re a l a be l a n d d i ffe r e n t o w n e r ‘ s
m a n u a l . T h i s p ract i c e i s q u ite p reva l e n t
i n t h e d i gital watch i n d u stry.

O n e company t h a t h a s been t h e rea l
sou rce be h i n d p rod ucts i nt rod u ced i n
the U . S. b y compan ies l i ke Mattei , Timex
and Texas I nstr u m e nts, is Olym pos Elec
tro n i c Co . , a l so known as Otro n .

O l y m pos E l ectro n i c n o w w a n t s t h e
wo r l d to k n ow i t s n a m e a n d ge n i u s .
W e feel l u c ky t o b e sel ected t o b r i n g
t h i s sto ry t o you .

Normal
Time

Dual Time
Zone

Dual
24 Hour
Alarms

Stopwatch

WE : 9
1 2 : 5 6 3′-1

WE :9 �i��!��:�4
1 1 : 5 6 3 ‘-1 hour tlme; model

12 selection (24 hr. ‘–___ -J shownl. a One o; two loud
6: 3 0 – I alarms set for

;. 6:30 am.

0 0 1 2 hr. chrono,
nn . n n n n split and lap tim· U U ‘ U U u u ing, with 1l100

‘–___ \….J sec. precision.

Hourly . n n the hour G Chimes on Chime ‘ U U with confir· mation.
.��1

r
ht [3 12 or 24 hr

Ll hl g ‘ O ‘ 3 U 2 S count down, g for I ” count up E.enlng Ilmer. Viewing

O l y m pos E l ectro n i c C o . is n o w i n
trod u c i n g p rod u ct s i nto t h i s c o u n t ry
u nd e r its own t rade n a m e -Ot ro n . We
a re i nt rod u c i n g o n e of t h e fi rst Ot ron
p rod u cts i nto t h e U . S .

1 2 o r 2 4 H O U R D U A L T I M E ,
D U A L ALA RM C H RONOG RA P H
T h e fi rst product we sel ected i s t h e

A l a r m C h ro n o X watc h . I t m a y be t h e
m o s t a d v a n c e d Q u a rtz t i m e p i ece i n
t h e w o r l d t o d a y f o r u n d e r $200.

We k n ow of n o ot h e r watc h t h at
com b i n e s t h e s e u n i q u e feat u res a n d
d e s i g n . It h a s both a 2 n d t i m e z o n e
c a pa b i l ity a n d a 2 n d sepa rate a l a r m . I t
c o m e s i n e i t h e r 1 2 o r 24 h o u r versi o n .
These feat u res a re j u st t h e begi n n i ng .
Co m pa re t h i s watc h feat u re -for-feat u re
aga i n st a n y ot h e r in t h e wo r l d . We
be l i eve you w i l l be c o n v i n ced t h at
t h e re is not a better watc h d o l l a r-for
d o l l a r a n yw h e r e .

T E ST E D TO 1 00 F E E T O F WAT E R
T h ree y e a r s a g o , t h e re w e r e n o

d i gi t a l water resistant a l a r m watc h e s .
Today t h ey e x i st i n s o m e m o re a d v a n c
ed m od e l s , b u t c o s t $ 1 00, $ 2 00 or
more. Our Alarm C h ro n o X i s s u b m e r
s i b l e t o 1 00 feet o f wate r . Its u n i q u e
a l a r m e m i t s s o u n d r i g h t t h r u t h e
sta i n l e s s steel c a s e . T h e O-ri n g c o n
st ructi o n a n d roc k h a rd m i n e ra l gl ass
lens p rov i d e a l o c k tight seal aga i n st
water to 1 00 feet – i t ‘ s g u a ra nteed .

T H I N N E SS A N D B O L D
MASC U L I N E D E S I G N

T h e A l a rm C h ro n o X i s a co m bi n a
t i o n of bo l d m a sc u l i n e d e s i g n a n d j u st
t h e r i g h t d e g r e e of t h i n n e s s . N o
sac r i f i c e i n fu n c t i o n o r m a sc u l i n ity, t h e
Ch ro n o X m e a s u res 8 . 9 m m f r o m t h e
top of its m i n e r a l g l ass l e n s to t h e b a c k
of its sta i n l e s s s t e e l c a s e . T h at’ s 1 . 6 m m
t h i n n e r t h a n t h e p opu l a r Se i ko A l a r m
C h ro n o g ra p h , 2 . 1 m m t h i n n e r t h a n t h e
C i t i z e n a n d 3 . 1 m m th i n n e r t h a n Texas
I n st r u m e nts . Yet Alarm C h ro n o X has
t h e sa m e b o l d d e s i g n of eac h . The
Sei ko se l l s fo r $250; t h e C i t i z e n fo r
$ 2 00; a n d t h e T . I . fo r $ 1 2 5 . . . What
does Ot ro n k n ow t h a t th ese ot h e r c o m
pa n i es d o n ‘ t ?

U N S U R PASS E D Q U A L I T Y A N D
ACC U RACY FOR U N D E R $70

Sta i n l ess ste e l case, a n d fi n e l y wove n
m e s h b r a c e l e t , m i n e ra l g l a s s l e n s ,
wate r res i st a n t t o 1 00 feet a n d q u a rtz
acc u racy to ± 5 sec o n d s per m o n t h .
T h a t ‘ s q u a l ity a n d a c c u racy fou n d o n l y
i n watc h e s cost i n g $200 o r m o r e . T h e
A l a r m C h ro n o X se l l s fo r $69 . 9 5 i n
sta i n l e s s steel case a n d $ 7 9 . 9 5 i n go l d
w i t h 3 m i c ro n s of r e a l g o l d o v e r
sta i n l e s s . Com p a re feat u res a n d p r i c e
f o r you rse l f before you ca l l to o r d e r .

O R D E R TO L L F R E E AT N O- R I S K
T h e A l a r m C h ro n o X i s offered w i t h a

1 5 d ay n o – r i s k t r i a l p e r i od . If d u ri n g 1 5
d ays, you fi n d t h e A l a r m C h ro n o X n ot
to yo u r l i ki n g ret u r n it for a p ro m pt re
fu n d of yo u r p u rc h ase p r i c e .

I n t h e u n l i ke l y eve nt t h at a n yt h i n g
s h o u l d go w ro n g after t h e t r i a l p e r i o d ,
yo u r A l a r m C h ro n o X i s b a c k e d b y a fu l l
year w a r r a n ty t h r u Ot ro n ‘ s Service by
m a i l repa i r fac i l ity in t h i s c o u n t r y .

To o r d e r yo u r A l a r m C h ro n o X fi l l o u t
t h e order fo rm b e l o w a n d s e n d it w i t h
c h e c k o r m o n ey o r d e r to u s . F o r fa ster
serv i c e , c red i t c a rd c u st o m e rs c a l l To l l
F ree 1 -800- 5 2 7 – 7066 . Do n ‘ t w a i t –
order today to i n s u re gett i n g a watch of
t h i s q u a l ity, w i t h t h e se fu n ct i o n s , at t h i s
price .

1 1 7

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