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Showing papers in "Science in 1973"


Journal ArticleDOI
09 Feb 1973-Science
TL;DR: When hemolyzates from erythrocytes of selenium-deficient rats were incubated in vitro in the presence of ascorbate or H2O2, added glutathione failed to protect the hemoglobin from oxidative damage.
Abstract: When hemolyzates from erythrocytes of selenium-deficient rats were incubated in vitro in the presence of ascorbate or H(2)O(2), added glutathione failed to protect the hemoglobin from oxidative damage. This occurred because the erythrocytes were practically devoid of glutathione-peroxidase activity. Extensively purified preparations of glutathione peroxidase contained a large part of the (75)Se of erythrocytes labeled in vivo. Many of the nutritional effects of selenium can be explained by its role in glutathione peroxidase.

6,893 citations


Journal ArticleDOI
20 Jul 1973-Science
TL;DR: Anfinsen as discussed by the authors provided a sketch of the rich history of research that provided the foundation for his work on protein folding and the Thermodynamic Hypothesis, and outlined potential avenues of current and future scientific exploration.
Abstract: Stanford Moore, William Stein, and Anfinsen were awarded the Nobel Prize in Chemistry in 1972 for \"their contribution to the understanding of the connection between chemical structure and catalytic activity of the active center of the ribonuclease molecule.\" In his Nobel Lecture, Anfinsen provided a sketch of the rich history of research that provided the foundation for his work on protein folding and the \"Thermodynamic Hypothesis,\" and outlined potential avenues of current and future scientific exploration.

6,520 citations


Journal ArticleDOI
05 Jan 1973-Science
TL;DR: Theory and data suggest that a male in good condition at the end of the period of parental investment is expected to outreproduce a sister in similar condition, while she is expectedto outre produce him if both are in poor condition, and natural selection should favor parental ability to adjust the sex ratio of offspring produced according to parental able to invest.
Abstract: Theory and data suggest that a male in good condition at the end of the period of parental investment is expected to outreproduce a sister in similar condition, while she is expected to outreproduce him if both are in poor condition. Accordingly, natural selection should favor parental ability to adjust the sex ratio of offspring produced according to parental ability to invest. Data from mammals support the model: As maternal condition declines, the adult female tends to produce a lower ratio of males to females.

3,547 citations


Journal ArticleDOI
05 Jan 1973-Science
TL;DR: A peptide has been isolated from ovine hypothalamus which, at 1 x 10-9M, inhibits secretion in vitro of immunoreactive rat or human growth hormones and is similarly active in vivo in rats.
Abstract: A peptide has been isolated from ovine hypothalamus which, at 1 x 10(-9)M, inhibits secretion in vitro of immunoreactive rat or human growth hormones and is similarly active in vivo in rats. Its structure is H-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH The synthetic replicate is biologically active.

3,383 citations


Journal ArticleDOI
09 Mar 1973-Science
TL;DR: Tritiated naloxone, a powerful opiate antagonist, specifically binds to an opiate receptor of mammalian brain and guinea pig intestine that closely parallels their pharmacological potency.
Abstract: Tritiated naloxone, a powerful opiate antagonist, specifically binds to an opiate receptor of mammalian brain and guinea pig intestine. Competition for the opiate receptor by various opiates and their antagonists closely parallels their pharmacological potency. The opiate receptor is confined to nervous tissue.

2,319 citations


Journal ArticleDOI
12 Oct 1973-Science
TL;DR: Auditory evoked potentials were recorded from the vertex of subjects who listened selectively to a series of tone pipping in one ear and ignored concurrent tone pips in the other ear to study the response set established to recognize infrequent, higher pitched tone pipped in the attended series.
Abstract: Auditory evoked potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips in the other ear. The negative component of the evoked potential peaking at 80 to 110 milliseconds was substantially larger for the attended tones. This negative component indexed a stimulus set mode of selective attention toward the tone pips in one ear. A late positive component peaking at 250 to 400 milliseconds reflected the response set established to recognize infrequent, higher pitched tone pips in the attended series.

1,839 citations


Journal ArticleDOI
14 Dec 1973-Science
TL;DR: Numbers show prima facie inequalities in the input of resources that are associated with income transfer from areas of lower expenditure to areas of higher expenditure, which indicates that there is considerable uncertainty about the effectiveness of different levels of aggregate, as well as specific kinds of, health services.
Abstract: Health information about total populations is a prerequisite for sound decision-making and planning in the health care field. Experience with a population-based health data system in Vermont reveals that there are wide variations in resource input, utilization of services, and expenditures among neighboring communities. Results show prima facie inequalities in the input of resources that are associated with income transfer from areas of lower expenditure to areas of higher expenditure. Variations in utilization indicate that there is considerable uncertainty about the effectiveness of different levels of aggregate, as well as specific kinds of, health services. Informed choices in the public regulation of the health care sector require knowledge of the relation between medical care systems and the population groups being served, and they should take into account the effect of regulation on equality and effectiveness. When population-based data on small areas are available, decisions to expand hospitals, currently based on institutional pressures, can take into account a community's regional ranking in regard to bed input and utilization rates. Proposals by hospitals for unit price increases and the regulation of the actuarial rate of insurance programs can be evaluated in terms of per capita expenditures and income transfer between geographically defined populations. The PSRO's can evaluate the wide variations in level of services among residents of different communities. Coordinated exercise of the authority vested in these regulatory programs may lead to explicit strategies to deal directly with inequality and uncertainty concerning the effectiveness of health care delivery. Population-based health information systems, because they can provide information on the performance of health care systems and regulatory agencies, are an important step in the development of rational public policy for health.

1,784 citations


Journal ArticleDOI
10 Aug 1973-Science
TL;DR: Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane.
Abstract: Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane. This catalytic behavior, which is typical of platinum, is not exhibited at all by tungsten. The surface electronic properties of the latter are therefore modified by carbon in such a way that they resemble those of platinum.

1,738 citations


Journal ArticleDOI
19 Jan 1973-Science
TL;DR: It is clear that we cannot distinguish the sane from the insane in psychiatric hospitals as mentioned in this paper, and the consequences to patients hospitalized in such an environment-the powerlessness, depersonalization, segregation, mortification, and self-labeling-seem undoubtedly countertherapeutic.
Abstract: It is clear that we cannot distinguish the sane from the insane in psychiatric hospitals. The hospital itself imposes a special environment in which the meanings of behavior can easily be misunderstood. The consequences to patients hospitalized in such an environment-the powerlessness, depersonalization, segregation, mortification, and self-labeling-seem undoubtedly countertherapeutic. I do not, even now, understand this problem well enough to perceive solutions. But two matters seem to have some promise. The first concerns the proliferation of community mental health facilities, of crisis intervention centers, of the human potential movement, and of behavior therapies that, for all of their own problems, tend to avoid psychiatric labels, to focus on specific problems and behaviors, and to retain the individual in a relatively non-pejorative environment. Clearly, to the extent that we refrain from sending the distressed to insane places, our impressions of them are less likely to be distorted. (The risk of distorted perceptions, it seems to me, is always present, since we are much more sensitive to an individual's behaviors and verbalizations than we are to the subtle contextual stimuli that often promote them. At issue here is a matter of magnitude. And, as I have shown, the magnitude of distortion is exceedingly high in the extreme context that is a psychiatric hospital.) The second matter that might prove promising speaks to the need to increase the sensitivity of mental health workers and researchers to the Catch 22 position of psychiatric patients. Simply reading materials in this area will be of help to some such workers and researchers. For others, directly experiencing the impact of psychiatric hospitalization will be of enormous use. Clearly, further research into the social psychology of such total institutions will both facilitate treatment and deepen understanding. I and the other pseudopatients in the psychiatric setting had distinctly negative reactions. We do not pretend to describe the subjective experiences of true patients. Theirs may be different from ours, particularly with the passage of time and the necessary process of adaptation to one's environment. But we can and do speak to the relatively more objective indices of treatment within the hospital. It could be a mistake, and a very unfortunate one, to consider that what happened to us derived from malice or stupidity on the part of the staff. Quite the contrary, our overwhelming impression of them was of people who really cared, who were committed and who were uncommonly intelligent. Where they failed, as they sometimes did painfully, it would be more accurate to attribute those failures to the environment in which they, too, found themselves than to personal callousness. Their perceptions and behavior were controlled by the situation, rather than being motivated by a malicious disposition. In a more benign environment, one that was less attached to global diagnosis, their behaviors and judgments might have been more benign and effective.

1,734 citations




Journal ArticleDOI
28 Dec 1973-Science
TL;DR: It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes, and the relation between the ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested.
Abstract: A synthetic theory of the ecology of amphibian metamorphosis is founded on the observation that the large variation in length of larval period and body size at metamorphosis typical of a particular species of amphibian cannot be directly explained by differences in dates of hatching or egg sizes. It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes. The degree of skewing increases and the median of the distribution decreases with increasing initial densities of populations. The relative advantages of the largest members of a cohort may arise from a variety of mechanisms including the production of growth inhibitors, interference competition, and size-selective feeding behavior. These mechanisms result in a nonnormal distribution of competitive ability, a possible source of the density-dependent competition coefficient found in systems with many species (1). In our model the ranges of body sizes and dates of metamorphosis are determined by a minimum body size that must be obtained and a maximum body size that will not be exceeded at metamorphosis. Between these two size thresholds the endocrinological initiation of metamorphosis is expected to be related to the recent growth history of the individual larva. Species that exploit uncertain environments will have a wide range of possible sizes at metamorphosis. Species exploiting relatively certain environments will have a narrower range. The evolution of neoteny and direct development logically follow from the application of these ideas to the ecological context of the evolution of amphibian life histories. Species that live in constant aquatic habitats surrounded by hostile environments (desert ponds, caves, high-altitude lakes) may evolve permanent larvae genetically incapable of metamorphosis. Other populations may evolve a facultative metamorphosis such that populations are a mixture of neotenes and terrestrial adults. Direct development results from selection to escape the competition, predation, and environmental uncertainty characteristic of some aquatic habitats and is usually accompanied by parental care. The relation between our ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested and it remains an open problem for developmental biologists.

Journal ArticleDOI
23 Mar 1973-Science
TL;DR: The model proposed here promises useful answers in comparisons of living things on both the microscopic and the gross scale, as part of the growing science of form, which asks precisely how organisms are diverse and yet again how they are alike.
Abstract: Arguments based on elastic stability and flexure, as opposed to the more conventional ones based on yield strength, require that living organisms adopt forms whereby lengths increase as the ⅔ power of diameter. The somatic dimensions of several species of animals and of a wide variety of trees fit this rule well. It is a simple matter to show that energy metabolism during maximal sustained work depends on body cross-sectional area, not total body surface area as proposed by Rubner (1) and many after him. This result and the result requiring animal proportions to change with size amount to a derivation of Kleiber9s law, a statement only empirical until now, correlating the metabolically related variables with body weight raised to the ¾ power. In the present model, biological frequencies are predicted to go inversely as body weight to the ¼ power, and total body surface areas should correlate with body weight to the ⅝ power. All predictions of the proposed model are tested by comparison with existing data, and the fit is considered satisfactory. In The Fire of Life, Kleiber (5) wrote "When the concepts concerned with the relation of body size and metabolic rate are clarified, . . . then compartive physiology of metabolism will be of great help in solving one of the most intricate and interesting problems in biology, namely the regulation of the rate of cell metabolism." Although Hill (23) realized that "the essential point about a large animal is that its structure should be capable of bearing its own weight and this leaves less play for other factors," he was forced to use an oversimplified "geometric similarity" hypothesis in his important work on animal locomotion and muscular dynamics. It is my hope that the model proposed here promises useful answers in comparisons of living things on both the microscopic and the gross scale, as part of the growing science of form, which asks precisely how organisms are diverse and yet again how they are alike.


Journal ArticleDOI
25 May 1973-Science
TL;DR: Injection of rabbits with acetylcholine receptor highly purified from the electric organ of Electrophorus electricus emulsified in complete Freund's adjuvant resulted in the production of precipitating antibody to acetylCholine receptor.
Abstract: Injection of rabbits with acetylcholine receptor highly purified from the electric organ of Electrophorus electricus emulsified in complete Freund's adjuvant resulted in the production of precipitating antibody to acetylcholine receptor. After the second injection of antigen, the animals developed the flaccid paralysis and abnormal electromyographs characteristic of neuromuscular blockade. Treatment with the anticholinesterases edrophonium or neostigmine dramatically alleviated the paralysis and the fatigue seen in electromyography.

Journal ArticleDOI
04 May 1973-Science
TL;DR: In this article, aluminum concentrations approaching those used experimentally have been found in some regions of the brains of patients with Alzheimer's disease, which is an important pathological finding in senile and presenile dementia of the Alzheimer type.
Abstract: Neurofibrillary degeneration is an important pathological finding in senile and presenile dementia of the Alzheimer type Experimentally, aluminum induces neurofibrillary degeneration in neurons of higher mammals Aluminum concentrations approaching those used experimentally have been found in some regions of the brains of patients with Alzheimer's disease

Journal ArticleDOI
26 Jan 1973-Science
TL;DR: In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels".
Abstract: In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels." Each barrel is related to one sensory vibrissa on the muzzle. Individual vibrissae were carefully injured at birth; 12 to 43 days later, the corresponding barrels proved to be absent. Evidently the sensory periphery has an important influence on the structure of the somatosensory cortex.

Journal ArticleDOI
17 Aug 1973-Science
TL;DR: The arrangement of lipids and some proteins in the erythrocyte membrane has been discussed and the conclusions are listed here as a set of general guidelines for the structure of membranes of higher organisms: some of these rules may be wrong.
Abstract: The arrangement of lipids and some proteins in the erythrocyte membrane has been discussed. The conclusions from this are listed here as a set of general guidelines for the structure of membranes of higher organisms: some of these rules may be wrong. But at this stage it seems useful to sharpen our thoughts in this way and thereby focus attention on various specific points. 1) The basis of a membrane is a lipid bilayer with (i) choline phospholipids and glycolipids in the external half and (ii) amino (and possibly some choline) phospholipids in the cytoplasmic half. There is effectively no lipid exchange across the bilayer (unless enzymatically catalyzed) (68). 2) Some proteins extend across the bilayer. Where this is so, they will in general have carbohydrate on their surface remote from the cytoplasm. This carbohydrate may prevent the protein diffusing out of the membrane into the cytoplasm; it acts as a lock on the protein. 3) Just as lipids do not flip-flop, proteins do not rotate across the membrane. Lateral motion or rotation of lipids and proteins in the plane of the bilayer may be expected. 4) Most membrane protein is associated with the inner, cytoplasmic, urface of the membrane. Proteins are not usually associated exclusively with the outer half of the lipid bilayer. 5) Membrane proteins are a special class of cytoplasmic proteins, not of secreted proteins.

Journal ArticleDOI
07 Dec 1973-Science
TL;DR: Spherical 27-nanometer particles were visualized in stools obtained from hepatitis A patients in the acute phase of the disease and suggest that it is the etiologic agent of hepatitis A.
Abstract: Spherical 27-nanometer particles were visualized in stools obtained from hepatitis A patients in the acute phase of the disease. The particle was serologically specific for this disease, and every hepatitis A patient tested demonstrated a serologic response to this antigen. The findings suggest that it is the etiologic agent of hepatitis A.

Journal ArticleDOI
02 Nov 1973-Science
TL;DR: This analysis is but a preliminary investigation of a significant agricultural problem that deserves careful attention and greater study before the energy situation becomes more critical.
Abstract: The principal raw material of modern U.S. agriculture is fossil fuel, whereas the labor input is relatively small (about 9 hours per crop acre). As agriculture is dependent upon fossil energy, crop production costs will also soar when fuel costs increase two- to fivefold. A return of 2.8 kcal of corn per 1 kcal of fuel input may then be uneconomical. Green revolution agriculture also uses high energy crop production technology, especially with respect to fertilizers and pesticides. While one may not doubt the sincerity of the U.S. effort to share its agricultural technology so that the rest of the world can live and eat as it does, one must be realistic about the resources available to accomplish this mission. In the United States we are currently using an equivalent of 80 gallons of gasoline to produce an acre of corn. With fuel shortages and high prices to come, we wonder if many developing nations will be able to afford the technology of U.S. agriculture. Problems have already occurred with green revolution crops, particularly problems related to pests (57). More critical problems are expected when there is a world energy crisis. A careful assessment should be made of the benefits, costs, and risks of high energy-demand green revolution agriculture in order to be certain that this program will not aggravate the already serious world food situation (58). To reduce energy inputs, green revolution and U.S. agriculture might employ such alternatives as rotations and green manures to reduce the high energy demand of chemical fertilizers and pesticides. U.S. agriculture might also reduce energy expenditures by substituting some manpower currently displaced by mechanization. While no one knows for certain what changes will have to be made, we can be sure that when conventional energy resources become scarce and expensive, the impact on agriculture as an industry and a way of life will be significant. This analysis is but a preliminary investigation of a significant agricultural problem that deserves careful attention and greater study before the energy situation becomes more critical.

Journal ArticleDOI
05 Oct 1973-Science
TL;DR: Electro microscopic, histochemical, and biochemical studies demonstrate defects in two oxidative organelles in the cerebro-hepato-renal syndrome, which suggests a defect in electron transport prior to the cytochromes.
Abstract: The cerebro-hepato-renal syndrome is a rare familial malady with cerebral, renal, and skeletal abnormalities, severe hypotonia, cirrhosis, iron and lipid storage, and death within 6 months. Correlated electron microscopic, histochemical, and biochemical studies demonstrate defects in two oxidative organelles. Peroxisomes cannot be found in hepatocytes and renal proximal tubules. In hepatocytes and cortical astrocytes, mitochondria are distorted in their appearance and glycogen stores are increased. Oxygen consumnption of brain and liver mitochondrial preparations with succinate and with substrates reducing nicotinamide adenine dinucleotide is markedly diminished, but the consumption is normal with ascorbate and tetramethylphenylenediamine, which suggests a defect in electron transport prior to the cytochromes. Histochemical studies of mitochondrial oxidation point to a defect between the succinate dehydrogenase flavoprotein and coenzyme Q, possibly in the region of nonheme iron protein.

Journal ArticleDOI
02 Nov 1973-Science
TL;DR: The oxygen of anhydrous, high-temperature minerals in carbonaceous meteorites is strongly depleted in the heavy stable isotopes 17O and 18O and probably results from the admixture of a component of almost pure 16O.
Abstract: Oxygen isotope analysis of anhydrous high-temperature phases from carbonaceous meteorite chondrites indicates a high degree of O(17) and O(18) isotope depletion. The isotope decay is believed to be a result of nuclear rather than chemical processes caused by the admixture of a component consisting of almost pure O(16). It is theorized that this component may predate the solar system and may represent interstellar dust with a separate history of nucleosynthesis.

Journal ArticleDOI
K. H. Mann1
07 Dec 1973-Science
TL;DR: While the intertidal zone is inhabited primarily by the fucoids, or rockweeds, the sublittoral is dominated by fish, and the growth of seaweeds below lowtide level, in the sub littoral, is far richer than in the interTidal areas.
Abstract: [Fhe edge of the sea is one of the best habitats for plant growth in temperate latitudes. In favorable circumstances, net primary productivity may be as high as anywhere else on earthcomparable, for example, to a tropical rain forest. Seaweeds, which have successfully colonized this zone, are a unique form of life. They are attached to a hard substrate, not by a root system, but by a holdfast. Instead of relying on a rather localized supply of nuLtrients in the soil, they take their nutrients from the water that surrounds them. Because this water is kept in perpetual motion by tides and winds, the nutrient supply is virtually inexhauLstible. Even if the seaweeds aind plankton deplete the nutrients in surface waters, wind-induced or estuari ne mixing renews the supply by caus1ngQ upwelling of deeper water. TFhe -growth of seaweeds below lowtide level, in the sublittoral, is far richer than in the intertidal areas. Before the advent of underwater vehicles a,tnd scuiba g,ear, the al(ae of the intertidal zone were the focus Of attention .ind provided elegant examples of species zonatiotn in relation to gradients of environmenital factors, such as degree of exposure to air or anmount of wave ction (M). While the intertidal zone is inhabited primarily by the fucoids, or rockweeds, the sublittoral is dominated

Journal ArticleDOI
12 Oct 1973-Science
TL;DR: It is proposed that receptor transformation is an important step in estrogen action and that a principal role of the hormone is to induce conversion of the receptor protein to a biochemically functional form.
Abstract: The interaction of estradiol with uterine cells involves the association of the hormone with an extranuclear receptor protein, followed by temperature dependent translocation of the resulting complex to the nucleus. During this process, the steroid binding unit of the protein undergoes an alteration, called "receptor transformation," that can be recognized by an increase in its sedimentation rate from 3.8S to 5.2S, and by its acquisition of the ability to bind to isolated uterine nuclei and to alleviate a tissue specific deficiency in the RNA synthesizing capacity of such nuclei. Receptor transformation can be effected in the absence of nuclei by warming uterine cytosol with estradiol. This preparation of transformed complex resembles that extracted from nuclei both in its sedimentation rate (5.3S) and in its ability to bind to uterine nuclei and augment RNA synthesis, properties that are not shown by the native complex. It is proposed that receptor transformation is an important step in estrogen action and that a principal role of the hormone is to induce conversion of the receptor protein to a biochemically functional form.

Journal ArticleDOI
John A. Swets1
07 Dec 1973-Science
TL;DR: The ROC is an analytical technique that quite effectively isolates the effects of the observer's response bias, or decision criterion, in the study of discrimination behavior and enhances the understanding of the perceptual and cognitive phenomena that depend directly on these fundamental processes.
Abstract: The clinician looking, listening, or feeling for signs of a disease may far prefer a false alarm to a miss, particularly if the disease is serious and contagious. On the other hand, he may believe that the available therapy is marginally effective, expensive, and debilitating. The pilot seeing the landing lights only when they are a few yards away may decide that his plane is adequately aligned with the runway if he is alone and familiar with that plight. He may be more inclined to circle the field before another try at landing if he has many passengers and recent memory of another plane crashing under those circumstances. The Food and Drug administrator suspecting botulism in a canned food may not want to accept even a remote threat to the public health. But he may be less clearly biased if a recent false alarm has cost a canning company millions of dollars and left some damaged reputations. The making of almost any fine discrimination is beset with such considerations of probability and utility, which are extraneous and potentially confounding when one is attempting to measure the acuity of discrimination per se. The ROC is an analytical technique, with origins in statistical decision theory and electronic detection theory, that quite effectively isolates the effects of the observer9s response bias, or decision criterion, in the study of discrimination behavior. This capability, pursued through a century of psychological testing, provides a relatively pure measure of the discriminability of different stimuli and of the capacity of organisms to discriminate. The ROC also treats quantitatively the response, or decision, aspects of choice behavior. The decision parameter can then be functionally related to the probabilities of the stimulus alternatives and to the utilities of the various stimulus-response pairs, or to the observer9s expectations and motivations. In separating and quantifying discrimination and decision processes, the ROC promises a more reliable and valid solution to some practical problems and enhances our understanding of the perceptual and cognitive phenomena that depend directly on these fundamental processes. In several problem areas in psychology, effects that were supposed to reflect properties of the discrimination process have been shown by the ROC analysis to reflect instead properties of the decision process.

Journal ArticleDOI
12 Oct 1973-Science
TL;DR: Despite excessive glucagon responses to infusion of arginine, plasma glucagon did not rise in six juvenile-type diabetics during severe insulin-induced hypoglycemia, whereas glucagon in the controls rose significantly, indicating that pancreatic alpha cells are insensitive to glucose even in the presence of large amounts of circulating insulin.
Abstract: Despite excessive glucagon responses to infusion of arginine, plasma glucagon did not rise in six juvenile-type diabetics during severe insulin-induced hypoglycemia, whereas glucagon in the controls rose significantly. Thus in diabetics pancreatic alpha cells are insensitive to glucose even in the presence of large amounts of circulating insulin. An intrinsic defect common to both alpha and beta pancreatic cells-failure to recognize (or respond to) plasma glucose fluctuations-may be operative in juvenile diabetes.


Journal ArticleDOI
20 Jul 1973-Science
TL;DR: A narrow, jet-like current flows eastward at high speed during both transition periods between the two monsoons, demonstrating that a time-variable current can have profound effects in changing the mass structure in the ocean.
Abstract: At the surface of the Indian Ocean along the equator a narrow, jet-like current flows eastward at high speed during both transition periods between the two monsoons. The formation of the jet is accompanied by thermocline uplifting at the western origin of the jet and by sinking at its eastern terminus. This demonstrates that a time-variable current can have profound effects in changing the mass structure in the ocean.

Journal ArticleDOI
19 Oct 1973-Science
TL;DR: The number of acetylcholine receptors was determined in the neuromuscular junctions of patients with typical myasthenia gravis and in five controls, by means of 1251-labeled α-bungarotoxin binding.
Abstract: The number of acetylcholine receptors was determined in the neuromuscular junctions of eight patients with typical myasthenia gravis and in five controls, by means of (125)1-labeled alpha-bungarotoxin binding. The junctional acetylcholine receptors were reduced in the myasthenic muscles as compared with the controls. This reduction in receptors may account for the defect in neuromuscular transmission in myasthenia gravis.

Journal ArticleDOI
19 Jan 1973-Science
TL;DR: The results of experimental and theoretical models show that it is possible for local differentiation to evolve parapatrically in spite of considerable gene flow if the selection gradients are relatively uniform, andGene flow may be unimportant in the differentiation of populations along environmental gradients.
Abstract: There are many possible spatial patterns of selection and gene flow that can produce a given cline structure; the actual geography of natural selection and gene flow must be worked out before an attempt is made to explain a given natural cline in terms of a model. The results of experimental and theoretical models show that it is possible for local differentiation to evolve parapatrically in spite of considerable gene flow if the selection gradients are relatively uniform. Irregularities in environmental gradients increase the sensitivity of clines to the effects of gene flow in proportion to the increase in the differences in gene frequencies between the emigrants and the demes receiving the immigrants. It is not necessary for a sharp spatial environmental change to be present for distinct differentiation to occur. In some cases even a gentle environmental gradient can give rise to marked spatial differentiation along a genetically continuous series of demes; such environmental differences may be below the practical limits of resolution in field studies. Any asymmetry in gene flow does not lead to dedifferentiation if the environmental gradient is smooth; it merely shifts the position of the transition zone between the differentiated areas from that which would be expected if there were no asymmetry. Abrupt geographic differences in gene, genotype, or morph frequencies should not, therefore, be interpreted as evidence for environmental changes in the immediate vicinity of the steepest part of the cline; neither should they be interpreted as evidence for geographic barriers, sharp environmental differences, or sexual isolation among the differentiated groups of populations when there are no other sources of evidence for these phenomena. Gene flow may be unimportant in the differentiation of populations along environmental gradients.