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Showing papers in "Science in 1976"


Journal ArticleDOI
20 Aug 1976-Science
TL;DR: Plasmodium falciparum can now be maintained in continuous culture in human erythrocytes incubated at 38 degrees C in RPMI 1640 medium with human serum under an atmosphere with 7 percent carbon dioxide and low oxygen.
Abstract: Plasmodium falciparum can now be maintained in continuous culture in human erythrocytes incubated at 38 degrees C in RPMI 1640 medium with human serum under an atmosphere with 7 percent carbon dioxide and low oxygen (1 or 5 percent). The original parasite material, derived from an infected Aotus trivirgatus monkey, was diluted more than 100 million times by the addition of human erythrocytes at 3- or 4-day intervals. The parasites continued to reproduce in their normal asexual cycle of approximately 48 hours but were no longer highly synchronous. The have remained infective to Aotus.

7,496 citations


Journal ArticleDOI
01 Oct 1976-Science
TL;DR: Each patient's cancer may require individual specific therapy, and even this may be thwarted by emergence of a genetically variant subline resistant to the treatment, which should be directed toward understanding and controlling the evolutionary process in tumors before it reaches the late stage usually seen in clinical cancer.
Abstract: It is proposed that most neoplasms arise from a single cell of origin, and tumor progression results from acquired genetic variability within the original clone allowing sequential selection of more aggressive sublines. Tumor cell populations are apparently more genetically unstable than normal cells, perhaps from activation of specific gene loci in the neoplasm, continued presence of carcinogen, or even nutritional deficiencies within the tumor. The acquired genetic insta0ility and associated selection process, most readily recognized cytogenetically, results in advanced human malignancies being highly individual karyotypically and biologically. Hence, each patient's cancer may require individual specific therapy, and even this may be thwarted by emergence of a genetically variant subline resistant to the treatment. More research should be directed toward understanding and controlling the evolutionary process in tumors before it reaches the late stage usually seen in clinical cancer.

6,179 citations


Journal ArticleDOI
10 Dec 1976-Science
TL;DR: It is concluded that changes in the earth's orbital geometry are the fundamental cause of the succession of Quaternary ice ages and a model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next sevem thousand years is toward extensive Northern Hemisphere glaciation.
Abstract: 1) Three indices of global climate have been monitored in the record of the past 450,000 years in Southern Hemisphere ocean-floor sediments. 2) Over the frequency range 10(-4) to 10(-5) cycle per year, climatic variance of these records is concentrated in three discrete spectral peaks at periods of 23,000, 42,000, and approximately 100,000 years. These peaks correspond to the dominant periods of the earth's solar orbit, and contain respectively about 10, 25, and 50 percent of the climatic variance. 3) The 42,000-year climatic component has the same period as variations in the obliquity of the earth's axis and retains a constant phase relationship with it. 4) The 23,000-year portion of the variance displays the same periods (about 23,000 and 19,000 years) as the quasi-periodic precession index. 5) The dominant, 100,000-year climatic [See table in the PDF file] component has an average period close to, and is in phase with, orbital eccentricity. Unlike the correlations between climate and the higher-frequency orbital variations (which can be explained on the assumption that the climate system responds linearly to orbital forcing), an explanation of the correlation between climate and eccentricity probably requires an assumption of nonlinearity. 6) It is concluded that changes in the earth's orbital geometry are the fundamental cause of the succession of Quaternary ice ages. 7) A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next sevem thousand years is toward extensive Northern Hemisphere glaciation.

3,408 citations


Journal ArticleDOI
10 Sep 1976-Science
TL;DR: The T cells exhibited a strict growth dependence upon Phytohemagglutinin-stimulated normal human lymphocytes and were consistently negative for Epstein-Barr viral information.
Abstract: Selective growth of T lymphocytes occurred when unfractionated normal human bone marrow cells were cultured with conditioned medium obtained from phytohemagglutinin-stimulated normal human lymphocytes (Ly-CM). Cultures of up to 90 percent T cells have been maintained for more than 9 months. The T cells exhibited a strict growth dependence upon Ly-CM and were consistently negative for Epstein-Barr viral information.

2,318 citations


Journal ArticleDOI
30 Apr 1976-Science
TL;DR: Clinical potencies of butyrophenones, phenothiazines, and related drugs correlate closely with their ability to inhibit tritiated haloperidol binding, providing a simple in vitro means for evaluating new drugs as potential antischizophrenic agents.
Abstract: Tritiated haloperidol and tritiated dopamine label postsynaptic dopamine receptors in mammalian brain. Clinical potencies of butyrophenones, phenothiazines, and related drugs correlate closely with their ability to inhibit tritiated haloperidol binding. These binding methods provide a simple in vitro means for evaluating new drugs as potential antischizophrenic agents.

2,114 citations


Journal ArticleDOI
18 Jun 1976-Science
TL;DR: In the years around a sunspot maximum there is seldom a day when a number of spots cannot be seen, and often hundreds are present.
Abstract: zero. In contrast, in the years around a sunspot maximum there is seldom a day when a number of spots cannot be seen, and often hundreds are present. Past counts of sunspot number are readily available from the year 1700 (3), [m and workers in solar and terrestrial studies often use the record as though it were of of uniform quality. In fact, it is not. Thus it is advisable, from time to time, to

1,853 citations


Journal ArticleDOI
03 Sep 1976-Science
TL;DR: The results indicate that active genes are probably associated with histones in a subunit conformation in which the associated DNA is particularly sensitive to digestion by deoxyribonuclease I.
Abstract: Ten percent digestion of isolated nuclei by pancreatic deoxyribonuclease I preferentially removes globin DNA sequences from nuclei obtained from chick red blood cells but not from nuclei obtained from fibroblasts, from brain, or from a population of red blood cell precursors. Moreover, the nontranscribed ovalbumin sequences in nuclei isolated from red blood cells and fibroblasts are retained after mild deoxyribonuclease I digestion. This suggests that active genes are preferentially digested by deoxyribonuclease I. In contrast, treatment of red cell nuclei with staphylococcal nuclease results in no preferential digestion of active globin genes. When the 11S monomers obtained after staphylococcal nuclease digestion of nuclei are then digested with deoxyribonuclease I, the active globin genes are again preferentially digested. The results indicate that active genes are probably associated with histones in a subunit conformation in which the associated DNA is particularly sensitive to digestion by deoxyribonuclease I.

1,612 citations


Journal ArticleDOI
M. S. Whittingham1
11 Jun 1976-Science
TL;DR: The electrochemical reaction of layered titanium disulfide with lithium giving the intercalation compound lithium titanium Disulfide is the basis of a new battery system.
Abstract: The electrochemical reaction of layered titanium disulfide with lithium giving the intercalation compound lithium titanium disulfide is the basis of a new battery system. This reaction occurs very rapidly and in a highly reversible manner at ambient temperatures as a result of structural retention. Titanium disulfide is one of a new generation of solid cathode materials.

1,419 citations


Journal ArticleDOI
15 Oct 1976-Science
TL;DR: It is shown that this algorithm successfully extracts information from random-dot stereograms, and its implications for the psychophysics and neurophysiology of the visual system are briefly discussed.
Abstract: The extraction of stereo-disparity information from two images depends upon establishing a correspondence between them. In this article we analyze the nature of the correspondence computation and derive a cooperative algorithm that implements it. We show that this algorithm successfully extracts information from random-dot stereograms, and its implications for the psychophysics and neurophysiology of the visual system are briefly discussed.

1,392 citations



Journal ArticleDOI
23 Jan 1976-Science
TL;DR: Evidence is presented from 20 species that the ratio of investment in monogynous ants is, indeed, about 1 : 3, and this discovery is subject to a series of tests, which provide quantitative evidence in support of kinship theory, sex ratio theory, and the assumption that the offspring is capable of acting counter to its parents' best interests.
Abstract: Halminton (1) was apparently the first to appreciate that the synthesis of Mendelian genetics with Darwin's theory of natural selection had profound implications for social theory. In particular, insofar as almost all social behavior is either selfish or altruistic (or has such effects), genetical reasoning suggests that an individual's social behavior should be adjusted to his or her degree of relatedness, r, to all individuals affected by the behavior. We call this theory kinship theory. The social insects provide a critical test of Hamilton's kinship theory. When such theory is combined with the sex ratio theory of Fisher (9), a body of consistent predictions emerges regarding the haplodiploid Hymenoptera. The evolution of female workers helping their mother reproduce is more likely in the Hymenoptera than in diploid groups, provided that such workers lay some of the male-producing eggs or bias the ratio of investment toward reproductive females. Once eusocial colonies appear, certain biases by sex in these colonies are expected to evolve. In general, but especially in eusocial ants, the ratio of investment should be biased in favor of females, and in it is expected to equilibrate at 1 : 3 (male to female). We present evidence from 20 species that the ratio of investment in monogynous ants is, indeed, about 1 : 3, and we subject this discovery to a series of tests. As expected, the slave-making ants produce a ratio of investment of 1 : 1, polygynoys ants produce many more males than expected on the basis of relative dry weight alone, solitary bees and wasps produce a ratio of investment near 1 : 1 (and no greater than 1 : 2), and the social bumblebees produce ratios of investment between 1 : 1 and 1 : 3. In addition, sex ratios in monogynous ants and in trapnested wasps are, as predicted by Fisher, inversely related to the relative cost in these species of producing a male instead of a female. Taken together, these data provide quantitative evidence in support of kinship theory, sex ratio theory, the assumption that the offspring is capable of acting counter to its parents' best interests, and the supposition that haplodiploidy has played a unique role in the evolution of the social insects. Finally, we outline a theory for the evolution of worker-queen conflict, a theory which explains the queen's advantage in competition over male-producing workers and the workers' advantage regarding the ratio of investment. The theory uses the asymmetries of haplodiploidy to explain how the evolved outcome of parent-offspring conflict in the social Hymenoptera is expected to be a function of certain social and life history parameters.

Journal ArticleDOI
23 Jul 1976-Science
TL;DR: Electron microscopy indicated that cilia from cells of these patients lack dynein arms, and it is likely that these patients have frequent bronchitis and sinusitis.
Abstract: Four subjects who produced immotile sperm were studied. In three of the subjects, who had frequent bronchitis and sinusitis, there was no mucociliary transport, as measured by tracheobronchial clearance. Electron microscopy indicated that cilia from cells of these patients lack dynein arms.

Journal ArticleDOI
13 Feb 1976-Science
TL;DR: Qualitatively, then, unequal crossover provides a reasonable and uncontrived explanation for the prevalence of highly repeated sequences in DNA and for the patterns of periodicity they evince.
Abstract: It is often supposed that highly repetitious DNA's arise only as a result of unusual mechanisms or in response to selective pressure. My arguments and simulations suggest, by contrast, that a pattern of tandem repeats is the natural state of DNA whose sequence is not maintained by selection. The simulations show that periodicities can develop readily from nonreptitious DNA as a result of the random accumulation of random mutations and random homology-dependent unequal crossovers. The lengths of these periodicities, and the patterns of subrepeats within them, would fluctuate in evolution, with the probability of a given pattern being dependent on the unknown exact nature of the crossover mechanism. Qualitatively, then, unequal crossover provides a reasonable and uncontrived explanation for the prevalence of highly repeated sequences in DNA and for the patterns of periodicity they evince.

Journal ArticleDOI
08 Oct 1976-Science
TL;DR: In canaries and zebra finches, three vocal control areas in the brain are strikingly larger in males than in females, believed to be the first report of such gross sexual dimorphism in a vertebrate brain.
Abstract: In canaries and zebra finches, three vocal control areas in the brain are strikingly larger in males than in females. A fourth, area X of the lobus parolfactorius, is well developed in males of both species, less well developed in femal canaries, and absent or not recognizable in femal zebra finches. These size differences correlate well with differences in singing behavior. Males of both species learn song by reference to auditory information, and females do not normally sing. Exogenous testosterone induces singing in female canaries but not in female zebra finches. This is believed to be the first report of such gross sexual dimorphism in a vertebrate brain.

Journal ArticleDOI
30 Jul 1976-Science
TL;DR: Ulastructural evidence of abundant type C viruses within beta cells of treated mice suggests that streptozotocin may activate murine leukemia virus in vivo in susceptible hosts.
Abstract: Multiple small injections of streptozotocin in mice produce pancreatic insulitis, with progression to nearly complete beta cell destruction and diabetes mellitus. The timing and appearance of the inflammatory islet lesions suggest but do not prove that streptozotocin acts by initiating a cell-mediated immune reaction. Ultrastructural evidence of abundant type C viruses within beta cells of treated mice suggests that streptozotocin may activate murine leukemia virus in vivo in susceptible hosts.



Journal ArticleDOI
25 Jun 1976-Science
TL;DR: Narcotic analgetics administered directly into the spinal subarachnoid space of the rat via a chronically inserted catheter produce a potent analgesia that can be antagonized by naloxone.
Abstract: Narcotic analgetics administered directly into the spinal subarachnoid space of the rat via a chronically inserted catheter produce a potent analgesia that can be antagonized by naloxone. The narcotics, acting only at the spinal level, changed cord function to block not only spinal reflexes but also the operant response to painful stimuli.

Journal ArticleDOI
10 Sep 1976-Science
TL;DR: The model is described, which can explain regulative behavior in cockroach legs, the imaginal disks of Drosophila, and regenerating and developing amphibian limbs, and suggests that it may have general applicability to epimorphic fields.
Abstract: We have described a formal model for pattern regulation in epimorphic fields in which positional information is specified in terms of polar coordinates in two dimensions. We propose that cells within epimorphic fields behave according to two simple rules, the shortest intercalation rule and the complete circle rule, for both of which there is direct experimental evidence. It is possible to understand a large number of different behaviors of epimorphic fields as a straight-forward consequence of these two rules, and the model therefore provides a context in which to view many of the results of experimental embryology. Although we have confined our discussion to cockroach legs, the imaginal disks of Drosophila, and regenerating and developing amphibian limbs, the fact that the model can explain regulative behavior in such evolutionarily diverse animals suggests that it may have general applicability to epimorphic fields. The predictions which the model makes should make it possible to assess its applicability to other developing systems, and to investigate the cellular mechanisms involved.

Journal ArticleDOI
05 Nov 1976-Science
TL;DR: The endogenous morphinomimetic brain peptides Met5-enkephalin and alpha-, beta-, and gamma-endorphins have been evaluated in rats after intracerebrospinal fluid injection and their potent and divergent responses to naturally occurring subtances suggest that alterations in their homeostatic regulation could have etiological significance in mental illness.
Abstract: The endogenous morphinomimetic brain peptides Met5-enkephalin and alpha-, beta-, and gamma-endorphins have been evaluated in rats after intracerebrospinal fluid injection. beta-Endorphin produces marked, prolonged muscular rigidity and immobility similar to a catatonic state, counteracted by the opiate antagonist naloxone; this effect occurs at molar doses 1/100 to 1/400 that at which the other peptides or morphine block the response to painful stimuli. All peptides evoked dose-related, naloxone-reversible, wet-dog shakes in rats that had not been exposed to drugs. beta-Endorphin produced hypothermia, whereas gamma-endorphin produced hyperthermia. Such potent and divergent responses to naturally occurring subtances suggest that alterations in their homeostatic regulation could have etiological significance in mental illness.


Journal ArticleDOI
26 Nov 1976-Science
TL;DR: Observations are attempted to unify observations and provide a reasonable interpretation of the role of gangliosides in mediating cell surface phenomena to predict that analyogous phenomena involving gangliosisides will be discovered in brain.
Abstract: Gangliosides are unique acidic glycolipids that are selectively concentrated in the plasma membrane of cells. Surface labeling studies have demonstrated that at least a portion of the oligosaccharde chain of gangliosides extends beyond the hydrophe) is imbedded in the membrane bilayer. It is becoming increasingly apparent that gangliosides participate in the internalization of environmental signals elicited by cholera toxin and glycoprotein hormones such as thyrotropic hormone and chorionic gonadotropin as well as other substances such as interferon and possibly serotonin. The mechanism by which cholera toxin binds to a specific ganglioside receptor on the celraction of trophic agents with gangliosides. We would predict that analyogous phenomena involving gangliosides will be discovered in brain. The biosynthesis of gangliosides proceeds by the ordered sequential addition of sugars to the lipid moiety. These reactions are catalyzed by a cluster of membrane-bound glycosyltransferases. Any alteration in the activity or specificity of one of these enzymes will result in a dramatic change in the ganglioside pattern of an afflicted cell or organ. The drastic consequences that accompany abnormalities of ganglioside synthesis have been documented in a heritable metabolic disorder in vivo and in tumorigenic transformation of cells in vitro. In this article, we have attempted to unify these observations and to provide a reasonable interpretation of the role of gangliosides in mediating cell surface phenomena.

Journal ArticleDOI
17 Sep 1976-Science
TL;DR: The present studies indicate that the effects of chronic hyperlipidemia are complex in that the condition results not only in the deposition of lipids in the atheromatous lesions but that it may produce the primary endothelial injury that initiates the process of atherosclerosis as well.
Abstract: These studies provide new insight into the complex mechanisms wherby hyperlipidemia causes progressive atherosclerosis. It has been shown that physical injury to the endothelial lining of arteries sets off a process which probably is an attempt at healing the injury but which can lead to atherosclerosis. It has also been found that chemical agents such as homocystine can produce a similar series of events leading to atherosclerosis. These events include focal loss of endothelium, exposure of subendothelial connective tissue, and adherence of platelets followed by release of factors that stimulate intimal smooth muscle proliferation. The present studies indicate that the effects of chronic hyperlipidemia are complex in that the condition results not only in the deposition of lipids in the atheromatous lesions but that it may produce the primary endothelial injury that initiates the process of atherosclerosis as well.

Journal ArticleDOI
10 Dec 1976-Science
TL;DR: This relationship between compressive strength and strain rate is applicable to trabecular and compact bone, and provides clinical guidelines for predicting bone strength on the basis of x-ray and densitometric examination.
Abstract: The compressive strength of bone is proportional to the square of the apparent density and to the strain rate raised to the 0.06 power. This relationship is applicable to trabecular and compact bone, and provides clinical guidelines for predicting bone strength on the basis of x-ray and densitometric examination.

Journal ArticleDOI
17 Sep 1976-Science
TL;DR: The waveform of the cortical event-related potential is extremely sensitive to variations in the sequence of stimuli preceding the eliciting event and a quantitative model was developed relating the waveform changes to changes in event expectancy.
Abstract: The waveform of the cortical event-related potential is extremely sensitive to variations in the sequence of stimuli preceding the eliciting event. The waveform changes were manifested primarily in the amplitudes of the negative component of the potential that peaked at 200 milliseconds, the positive component that peaked at 300 milliseconds, and the slow-wave components. A quantitative model was developed relating the waveform changes to changes in event expectancy. Expectancy is assumed to depend on a decaying memory for events within the prior sequence, the specific structure of the sequence, and the global probability of event occurrence. For stimuli relevant to the task, the less expected the stimulus the larger the amplitudes of late components of the event-related potentials.

Journal ArticleDOI
03 Dec 1976-Science
TL;DR: When albino rats are reared in cyclic light, a burst of rod outer segment disk shedding occurs in the retina soon after the onset of light, and the subsequent degradation of large phagosomes to smaller structures within pigment epithelial cells proceeds rapidly.
Abstract: When albino rats are reared in cyclic light, a burst of rod outer segment disk shedding occurs in the retina soon after the onset of light. The number of large packets of outer segment disks (phagosomes) in the pigment epithelium at this time is 2.5 to 5 times greater than at any other time of day or night. The subsequent degradation of large phagosomes to smaller structures within pigment epithelial cells proceeds rapidly. The burst of disk shedding follows a circadian rhythm for at least 3 days, since it occurs in continuous darkness at the same time without the onset of light.

Journal ArticleDOI
06 Feb 1976-Science
TL;DR: Rabbit aortic medial cells were grown on purified elastin membranes, which were then subjected to repeated elongation and relaxation or to agitation without stretching, which resulted in a two- to fourfold increase in rates of collagen, hyaluronate, and chondroitin 6-sulfate synthesis.
Abstract: Rabbit aortic medial cells were grown on purified elastin membranes, which were then subjected to repeated elongation and relaxation or to agitation without stretching. Cells remained attached to the membranes, and cyclic stretching resulted in a two- to fourfold increase in rates of collagen, hyaluronate, and chondroitin 6-sulfate synthesis over those in agitated or stationary preparations. Synthesis of types I and III collagen was increased to the same degree. Stretching did not increase rates of chondroitin 4-sulfate or dermatan sulfate synthesis. Differences were not attributable to differences in cell number, for DNA synthetic rates were not increased by stretching. The model system devised to demonstrate these effects provides a means for relating various modes of mechanical stimulation to cell metabolism.

Journal ArticleDOI
05 Mar 1976-Science
TL;DR: Analgesia produced by focal electrical stimulation of the brain is partially reversed by the narcotic antagonist naloxone and it is suggested that stimulation-produced analgesia may result, at least in part, from release of an endogenous, narcotic-like substance.
Abstract: Analgesia produced by focal electrical stimulation of the brain is partially reversed by the narcotic antagonist naloxone. The absence of complete reversal does not appear to be caused by inadequate doses of naloxone since doses higher than 1 milligram per kilogram of body weight did not increase the antagonism. It is suggested that stimulation-produced analgesia may result, at least in part, from release of an endogenous, narcotic-like substance, such as that recently reported by other investigators.

Journal ArticleDOI
06 Feb 1976-Science
TL;DR: There was a significant correlation between the concnetration of 5-HIAA and severity of depression in the lower, but not in the upper, mode, which suggests the existence of a biochemical subgroup of depressive disorder, characterized by a disturbance of serotonin turnover.
Abstract: The distribution of 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the cerebrospinal fluid of 68 depressed patients was bimodal. Twenty-nine percent of the patients were in the lower mode, with a concentration of 5-HIAA below 15 nanograms per milliliter. Although there were no differences in overall severity of depression between the two modes, there was a significant correlation between the concnetration of 5-HIAA and severity of depression in the lower, but not in the upper, mode. The finding suggests the existence of a biochemical subgroup of depressive disorder, characterized by a disturbance of serotonin turnover.

Journal ArticleDOI
26 Mar 1976-Science
TL;DR: An experiment in an oil field at Rangely, Colorado, has demonstrated the feasibility of earthquake control and confirmed the predicted effect of fluid pressure on earthquake activity and indicated that earthquakes can be controlled wherever the authors can control the fluid pressure in a fault zone.
Abstract: An experiment in an oil field at Rangely, Colorado, has demonstrated the feasibility of earthquake control. Variations in seismicity were produced by controlled variations in the fluid pressure in a seismically active zone. Precise earthquake locations revealed that the earthquakes clustered about a fault trending through a zone of high pore pressure produced by secondary recovery operations. Laboratory measurements of the frictional properties of the reservoir rocks and an in situ stress measurement made near the earthquake zone were used to predict the fluid pressure required to trigger earthquakes on preexisting fractures. Fluid pressure was controlled by alternately injecting and recovering water from wells that penetrated the seismic zone. Fluid pressure was monitored in observation wells, and a computer model of the reservoir was used to infer the fluid pressure distributions in the vicinity of the injection wells. The results of this experiment confirm the predicted effect of fluid pressure on earthquake activity and indicate that earthquakes can be controlled wherever we can control the fluid pressure in a fault zone.