Showing papers in "Science in 1972"
TL;DR: Results strongly indicate that the bivalent antibodies produce an aggregation of the surface immunoglobulin molecules in the plane of the membrane, which can occur only if the immunoglOBulin molecules are free to diffuse in the membrane.
Abstract: A fluid mosaic model is presented for the gross organization and structure of the proteins and lipids of biological membranes. The model is consistent with the restrictions imposed by thermodynamics. In this model, the proteins that are integral to the membrane are a heterogeneous set of globular molecules, each arranged in an amphipathic structure, that is, with the ionic and highly polar groups protruding from the membrane into the aqueous phase, and the nonpolar groups largely buried in the hydrophobic interior of the membrane. These globular molecules are partially embedded in a matrix of phospholipid. The bulk of the phospholipid is organized as a discontinuous, fluid bilayer, although a small fraction of the lipid may interact specifically with the membrane proteins. The fluid mosaic structure is therefore formally analogous to a two-dimensional oriented solution of integral proteins (or lipoproteins) in the viscous phospholipid bilayer solvent. Recent experiments with a wide variety of techniqes and several different membrane systems are described, all of which abet consistent with, and add much detail to, the fluid mosaic model. It therefore seems appropriate to suggest possible mechanisms for various membrane functions and membrane-mediated phenomena in the light of the model. As examples, experimentally testable mechanisms are suggested for cell surface changes in malignant transformation, and for cooperative effects exhibited in the interactions of membranes with some specific ligands. Note added in proof: Since this article was written, we have obtained electron microscopic evidence (69) that the concanavalin A binding sites on the membranes of SV40 virus-transformed mouse fibroblasts (3T3 cells) are more clustered than the sites on the membranes of normal cells, as predicted by the hypothesis represented in Fig. 7B. T-here has also appeared a study by Taylor et al. (70) showing the remarkable effects produced on lymphocytes by the addition of antibodies directed to their surface immunoglobulin molecules. The antibodies induce a redistribution and pinocytosis of these surface immunoglobulins, so that within about 30 minutes at 37 degrees C the surface immunoglobulins are completely swept out of the membrane. These effects do not occur, however, if the bivalent antibodies are replaced by their univalent Fab fragments or if the antibody experiments are carried out at 0 degrees C instead of 37 degrees C. These and related results strongly indicate that the bivalent antibodies produce an aggregation of the surface immunoglobulin molecules in the plane of the membrane, which can occur only if the immunoglobulin molecules are free to diffuse in the membrane. This aggregation then appears to trigger off the pinocytosis of the membrane components by some unknown mechanism. Such membrane transformations may be of crucial importance in the induction of an antibody response to an antigen, as well as iv other processes of cell differentiation.
7,790 citations
TL;DR: In 1971, the Institute for Scientfic Information decided to undertake a systematic analysis of journal citation patterns across the whole of science and technology.
Abstract: As a communications system, the network of journals that play a paramount role in the exchange of scientific and technical information is little understood Periodically since 1927, when Gross and Gross published their study (1) of references in 1 year’s issues of the Journal of the American Chemical Socie/y, pieces of the network have been illuminated by the work of Bradford (2), Allen (3), Gross and Woodford (4), Hooker (5), Henkle (6), Fussier (7), Brown (8), and others (9) Nevertheless, there is still no map of the journal network as a whok To date, studies of the network and of the interrelation of its components have been limited in the number of journak, the areas of scientific study, and the periods of time their authors were able to consider, Such shortcomings have not been due to any lack of purpose, insight, or energy on the part of investigators, but to the practical difficulty of compiling and manipulating manually the enormous amount of necessary data A solution to this problem of data is available in the data base used to produce the Science Citation Index ( SCI ) (10) The coverage of the SCI is international and multidisciplinary; it has grown from 600 journals in 1964 to 2400 journals in 1972, and now includes the world’s most important scientific and technical journals in mow disciplines The SCI is published quarterly and is cumulated annually and quinquennially, but the data base from which the volumes are compiled is maintained on magnetic tape and is updated weekly At the end of 1971, this data base contained more than 27 mi[tion references to about 10 million different published items These references appeared over the past decade in the footnotes and bibliographies of more than 2 million journal articles, communications, letters, and so on The data base is, thus, not only multidisciplinary, it covers a substantial period of time and, being in machine-readable form, is amenable to extensive manipulation by computer In 1971, the Institute for Scientfic Information (1S1) decided to undertake a systematic analysis of journal citation patterns across the whole of science and technology It began by extracting from the data base all references pobIished during the last quarter of 1969 in the 2200 journals then covered by the SCL The resultant sample was about 1 million citations of journals, books, reports, theses, and so forth To test whether this 3-month sample was representative of the year as a whole, it was matched against another sample made by selecting every 27th reference from the approximately 4 million references collected over the entire year The two samples were similar enough in scope (number of diflerent items cited) and detail (relative frequency of their citation by different journals) to
2,560 citations
TL;DR: Fluorescamine is a new reagent for the detection of primary amines in the picomole range that is almost instantaneous at room temperature in aqueous media and the products are highly fluorescent, whereas the reagent and its degradation products are nonfluorescent.
Abstract: Fluorescamine is a new reagent for the detection of primary amines in the picomole range. Its reaction with amines is almost instantaneous at room temperature in aqueous media. The products are highly fluorescent, whereas the reagent and its degradation products are nonfluorescent. Applications are discussed.
2,510 citations
TL;DR: This article opposes the reductionist hypothesis, arguing that if everything obeys the same fundamental laws, then the only scientists who are studying anything really fundamental are those who are working on those laws.
Abstract: The reductionist hypothesis may still be a topic for controversy among philosophers, but among the great majority of active scientists I think it is accepted without question. The workings of our minds and bodies, and of all the animate or inanimate matter of which we have any detailed knowledge, are assumed to be controlled by the same set of fundamental laws, which except under certain extreme conditions we feel we know pretty well. It seems inevitable to go on uncritically to what appears at first sight to be an obvious corollary of reductionism: that if everything obeys the same fundamental laws, then the only scientists who are studying anything really fundamental are those who are working on those laws. In practice, that amounts to some astrophysicists, some elementary particle physicists, some logicians and other mathematicians, and few others. This point of view, which it is the main purpose of this article to oppose, is expressed in a rather wellknown passage by Weisskopf (1):
1,847 citations
1,652 citations
TL;DR: The chapter presents a description of the specific immune responses that are under the control of H-linked Ir genes in guinea pigs, mice, and rats.
Abstract: Publisher Summary This chapter provides information on histocompatibility-linked immune response genes. The genetic study of the capacity to form specific immune responses has revealed that the recognition of antigens as immunogens by individual animals and inbred strains is governed by the product of individual dominant genes located in the genome in close relationship with the genes coding for the molecules bearing the major histocompatibility specificities. These genes are termed as “histocompatibility,” or “H-linked Ir genes.” The presence of relevant genes permit immune responses to be formed, characterized by cellular immunity and antibody synthesis against the determinants on the antigens concerned. Three types of antigens are most useful in the identification of H-linked Ir genes: (1) synthetic polypeptides with limited structural heterogeneity; (2) alloantigens that differ slightly from their autologous counterparts, and (3) complex multideterminants antigens administered in limiting immunizing doses in conditions where only the most immunogenic determinants are recognized. Thus, the discovery of specific H-linked Ir genes depends upon experiments wherein the immunological system is presented with a challenge of highly restricted heterogeneity and specificity. The chapter presents a description of the specific immune responses that are under the control of H-linked Ir genes in guinea pigs, mice, and rats.
1,171 citations
TL;DR: The extreme sensitivity of tubulin to calcium ions explains the failure of previous efforts to obtain polymerization and suggests a possible mechanism for regulation of microtubule polymerization in vivo.
Abstract: Isolated rat brain tubulin can be repolymerized in vitro in solutions containing adenosine triphosphate or guanosine triphosphate, magnesium ions, and a good calcium chelator. The extreme sensitivity of tubulin to calcium ions explains the failure of previous efforts to obtain polymerization and suggests a possible mechanism for regulation of microtubule polymerization in vivo.
1,148 citations
TL;DR: The transport of a factor out of damaged leaves takes place rapidly after the wound is inflicted and the levels of proteinase inhibitor, in both damaged and adjacent leaves, rises strikingly within a few hours.
Abstract: Wounding of the leaves of potato or tomato plants by adult Colorado potato beetles, or their larvae, induces a rapid accumulation of a proteinase inhibitor throughout the plants' tissues that are exposed to air. This effect of insect damage can be simulated by mechanically wounding the leaves. The transport of a factor out of damaged leaves takes place rapidly after the wound is inflicted and the levels of proteinase inhibitor, in both damaged and adjacent leaves, rises strikingly within a few hours. The rapid accumulation of a powerful inhibitor of major intestinal proteinases of animals in response to wounding of the leaves is probably a defense mechanism.
1,142 citations
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TL;DR: The authors' model of the sulfur cycle can draw some conclusions that man is now contributing about one half as much as nature to the total atmospheric burden of sulfur compounds, but by A.D. 2000 he will be contributing about as much, and in the Northern Hemisphere alone he is more than matching nature.
Abstract: Even granting our uncertainties about parts of our model of the sulfur cycle, we can draw some conclusions from it: 1) Man is now contributing about one half as much as nature to the total atmospheric burden of sulfur compounds, but by A.D. 2000 he will be contributing about as much, and in the Northern Hemisphere alone he will be more than matching nature. 2) In industrialized regions he is overwhelming natural processes, and the removal processes are slow enough (several days, at least) so that the increased concentration is marked for hundreds to thousands of kilometers downwind. 3) Our main areas of uncertainty, and ones that demand immediate attention because of their importance to the regional air pollution question, are: (i) the rates of conversion of H(2)S and SO(2) to sulfate particles in polluted as well as unpolluted atmospheres; (ii) the efficiency of removal of sulfur compounds by precipitation in polluted air. And for a better understanding of the global model we need to know: (i) the amount of biogenic H(2)S that enters the atmosphere over the continents and coastal areas; (ii) means of distinguishing man-made and biogenic contributions to excess sulfate in air and precipitation; (iii) the volcanic production of sulfur compounds, and their influence on the particle concentration in the stratosphere; (iv) the large-scale atmospheric circulation patterns that exchange air between stratosphere and troposphere (although absolute amounts of sulfate particles involved are small relative to the lower tropospheric burden); (v) the role of the oceans as sources or sinks for SO(2).
TL;DR: Plastic particles, in concentrations averaging 3500 pieces and 290 grams per square kilometer, are widespread in the western Sargasso Sea and could be a source of some of the polychlorinated biphenyls recently observed in oceanic organisms.
Abstract: Plastic particles, in concentrations averaging 3500 pieces and 290 grams per square kilometer, are widespread in the western Sargasso Sea. Pieces are brittle, apparently due to the weathering of the plasticizers, and many are in a pellet shape about 0.25 to 0.5 centimeters in diameter. The particles are surfaces for the attachment of diatoms and hydroids. Increasing production of plastics, combined with present waste-disposal practices, will undoubtedly lead to increases in the concentration of these particles. Plastics could be a source of some of the polychlorinated biphenyls recently observed in oceanic organisms.
TL;DR: The main determinant of brain tryPTophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids that compete with it for uptake into the brain.
Abstract: When plasma tryptophan is elevated by the injection of tryptophan or insulin, or by the consumption of carbohydrates, brain tryptophan and serotonin also rise; however, when even larger elevations of plasma tryptophan are produced by the ingestion of protein-containing diets, brain tryptophan and serotonin do not change. The main determinant of brain tryptophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids (that is, tyrosine, phenylalanine, leucine, isoleucine, and valine) that compete with it for uptake into the brain.
TL;DR: The Zhabotinsky-Zaikin reagent propagates waves of chemical activity that include spiral waves, resembling involutes of the circle, that appear, persist, and eventually exclude all concentric ring waves.
Abstract: The Zhabotinsky-Zaikin reagent propagates waves of chemical activity. Reaction kinetics remain to be fully resolved, but certain features of wave behavior are determined by purely geometrical considerations. If a wave is broken, then spiral waves, resembling involutes of the circle, appear, persist, and eventually exclude all concentric ring waves.
TL;DR: Virazole is a synthetic nucleoside active in tissue culture against at least 16 DNA and RNA viruses and applied topically, it inhibits herpetic keratitis in rabbits and tail lesions induced by herpes, vaccinia, and vesicular stomatitis viruses in mice.
Abstract: Virazole is a synthetic nucleoside active in tissue culture against at least 16 DNA and RNA viruses. Applied topically, it inhibits herpetic keratitis in rabbits and tail lesions induced by herpes, vaccinia, and vesicular stomatitis viruses in mice. Injected intraperitoneally into mice, it inhibits splenomegaly and hepatomegaly induced by Friend leukemia virus and respiratory infections caused by influenza A(O), A(2), and B viruses and parainfluenza 1 virus. infections is also effective.
TL;DR: Mouse embryos survived freezing to -196�C and when approximately 1000 of the survivors, including some frozen to -269�C (4�K), were transferred into foster mothers, 65 percent of the recipients became pregnant and more than 40 percent gave rise to normal, living full-term fetuses or newborn mice.
Abstract: Mouse embryos survived freezing to -196 degrees C. Survival required slow cooling (0.3 degrees to 2 degrees C per minute) and slow warming (4 degrees to 25 degrees C per minute). Depending on the specific rates used, 50 to 70 percent of more than 2500 frozen and thawed early embryos developed into blastocysts in culture after storage at -196 degrees C for up to 8 days. When approximately 1000 of the survivors, including some frozen to -269 degrees C (4 degrees K), were transferred into foster mothers, 65 percent of the recipients became pregnant. More than 40 percent of the embryos in these pregnant mice gave rise to normal, living full-term fetuses or newborn mice.
TL;DR: Solar evolution implies, for contemporary albedos and atmospheric composition, global mean temperatures below the freezing point of seawater less than 2.3 aeons ago, contrary to geologic and paleontological evidence, but ammonia mixing ratios of the order of a few parts per million in the middle Precambrian atmosphere resolve this and other problems.
Abstract: Solar evolution implies, for contemporary albedos and atmospheric composition, global mean temperatures below the freezing point of seawater less than 2.3 aeons ago, contrary to geologic and paleontological evidence. Ammonia mixing ratios of the order of a few parts per million in the middle Precambrian atmosphere resolve this and other problems. Possible temperature evolutionary tracks for Earth and Mars are described. A runaway greenhouse efect will occur on Earth about 4.5 aeons from now, when clement conditions will prevail on Mars.
TL;DR: This retrograde movement of protein from axon terminal to cell body suggests a possible mechanism by which neurons respond to their target areas.
Abstract: When horseradish peroxidase is injected into the optic tectum of a chick, axons of ganglion cells transport it centripetally to their cell bodies in the retina at a rate of about 72 millimeters per day. After intraocular injections in the young chick, the peroxidase is transported centripetally along efferent axons, and is concentrated in cell bodies within the isthmo-optic nucleus. This retrograde movement of protein from axon terminal to cell body suggests a possible mechanism by which neurons respond to their target areas.
TL;DR: White, opaque spherules are selectively consumed by 8 species of fish out of 14 species examined, and a chaetognath, and ingestion of the plastic may lead to intestinal blockage in smaller fish.
Abstract: Polystyrene spherules averaging 0.5 millimeter in diameter (range 0.1 to 2 millimeters) are abundant in the coastal waters of southern New England. Two types are present, a crystalline (clear) form and a white, opaque form with pigmentation resulting from a diene rubber. The spherules have bacteria on their surfaces and contain polychlorinated biphenyls, apparently absorbed from ambient seawater, in a concentration of 5 parts per million. White, opaque spherules are selectively consumed by 8 species of fish out of 14 species examined, and a chaetognath. Ingestion of the plastic may lead to intestinal blockage in smaller fish.
TL;DR: Preparations of secretory iminunoglobuilin A isolated from human parotid fluid specifically inhibited the adherence of Streptococcus strains to epithelial cells, which can explain how secretory immunoglobulins function in the disposal of bacterial antigens.
Abstract: Preparations of secretory iminunoglobuilin A (S-IgA) isolated from human parotid fluid specifically inhibited the adherence of Streptococcus strains to epithelial cells Since bacterial adherence is a prerequisite for colonization of mucous surfaces S-IgA-mediated inhibition of adherence would limit bacterial colonization This mechanism can explain how secretory immunoglobulins function in the disposal of bacterial antigens
TL;DR: A rapid, convenient technique for precision pressure measurement in the diamond-anvil high-pressure cell, which makes use of the sharp-line (R-line) luminescence of ruby, has been developed and line-broadening has been observed in some instances and has been tentatively identified with nonhydrostatic conditions surrounding the ruby sample.
Abstract: A rapid, convenient technique for precision pressure measurement in the diamond-anvil high-pressure cell, which makes use of the sharp-line (R-line) luminescence of ruby, has been developed. The observed shift is -0.77 ±0.03 reciprocal centimeters per kilobar for R 1 and -0.84± 0.03 reciprocal centimeters per kilobar for R 2 to lower energy and is approximately linear in the range studied (to 22 kilobars). Line-broadening has been observed in some instances and has been tentatively identified with nonhydrostatic conditions surrounding the ruby sample.
TL;DR: The abnormal MEG, including a measurenment of the direct-current component, suggests that the MEG may yield some information which is new and different from that provided by the EEG.
Abstract: Measurements of the brain's magnetic field, called magnetoencephalograms (MEG's), have been taken with a superconducting magnetometer in a heavily shielded room. This magnetometer has been adjusted to a much higher sensitivity than was previously attainable, and as a result MEG's can, for the first time, be taken directly, without noise averaging. MEG's are shown, simultaneously with the electroencephalogram (EEG), of the alpha rhythm of a normal subject and of the slow waves from an abnormal subject. The normal MEG shows the alpha rhythm, as does the EEG, when the subject's eyes are closed; however, this MEG also shows that higher detector sensitivity, by a factor of 3, would be necessary in order to clearly show the smaller brain events when the eyes are open. The abnormal MEG, including a measurenment of the direct-current component, suggests that the MEG may yield some information which is new and different from that provided by the EEG.
TL;DR: A sustained effort is proposed to be made to formulate a complete set of ethicoscientific criteria to guide the development and clinical application of gene therapy techniques, which could go a long way toward ensuring that gene therapy is used in humans only in those instances where it will prove beneficial, and toward preventing its misuse through premature application.
Abstract: In our view, gene therapy may ameliorate some human genetic diseases in the future. For this reason, we believe that research directed at the development of techniques for gene therapy should continue. For the foreseeable future, however, we oppose any further attempts at gene therapy in human patients because (i) our understanding of such basic processes as gene regulation and genetic recombination in human cells is inadequate; (ii) our understanding of the details of the relation between the molecular defect and the disease state is rudimentary for essentially all genetic diseases; and (iii) we have no information on the short-range and long-term side effects of gene therapy. We therefore propose that a sustained effort be made to formulate a complete set of ethicoscientific criteria to guide the development and clinical application of gene therapy techniques. Such an endeavor could go a long way toward ensuring that gene therapy is used in humans only in those instances where it will prove beneficial, and toward preventing its misuse through premature application. Two recent papers have provided new demonstrations of directed genetic modification of mammalian cells. Munyon et al. (44) restored the ability to synthesize the enzyme thymidine kinase to thymidine kinase-deficient mouse cells by infection with ultraviolet-irradiated herpes simplex virus. In their experiments the DNA from herpes simplex virus, which contains a gene coding for thymidine kinase, may have formed a hereditable association with the mouse cells. Merril et al. (45) reported that treatment of fibroblasts from patients with galactosemia with exogenous DNA caused increased activity of a missing enzyme, alpha-D-galactose-l-phosphate uridyltransferase. They also provided some evidence that the change persisted after subculturing the treated cells. If this latter report can be confirmed, the feasibility of directed genetic modification of human cells would be clearly demonstrated, considerably enhancing the technical prospects for gene therapy.
TL;DR: A protein of molecular weight ∼ 12,000 which binds long-chain fatty acids and certain other lipids has been identified in cytosol of intestinal mucosa, liver, myocardium, adipose tissue, and kidney and appears to be identical with the smaller of two previously described cytoplasmic anion-binding proteins.
Abstract: A protein of molecular weight approximately 12,000 which binds long-chain fatty acids and certain other lipids has been identified in cytosol of intestinal mucosa, liver, myocardium, adipose tissue, and kidney. Binding is noncovalent and is greater for unsaturated than for saturated and medium-chain fatty acids. This protein appears to be identical with the smaller of two previously described cytoplasmic anion-binding proteins. Binding of long-chain fatty acids by this protein is greater than that of other anions tested, including sulfobromophthalein, and does not depend on negative charge alone. The presence of this binding protein may explain previously observed differences in intestinal absorption among fatty acids, and the protein may participate in the utilization of long-chain fatty acids by many mammalian tissues.
TL;DR: An object's meaningful context may affect the course of perceptual recognition and not just peripheral scanning or memory.
Abstract: When a briefly presented real-world scene was jumbled, the accuracy of identifying a single, cued object was less than that when the scene was coherent Jumbling remained an effective variable even when the subject knew where to look and what to look for Thus an object's meaningful context may affect the course of perceptual recognition and not just peripheral scanning or memory
TL;DR: The magnetic compass of European robins does not use the polarity of the magnetic field for detecting the north direction, so birds take the direction on the magnetic north-south axis for "north" where field lines and gravity vector form the smaller angle.
Abstract: The magnetic compass of European robins does not use the polarity of the magnetic field for detecting the north direction. The birds derive their north direction from interpreting the inclination of the axial direction of the magnetic field lines in space, and they take the direction on the magnetic north-south axis for "north" where field lines and gravity vector form the smaller angle.
TL;DR: 1,25-Dihydroxycholecalciferol stimulated the release of previously incorporated 4545Ca from fetal rat bones in organ culture, at concentrations of 10-10 to 10-8M, suggesting brief exposure to maximum doses of either agent leads to prolonged bone resorption.
Abstract: 1,25-Dihydroxycholecalciferol (DHCC), isolated from kidney homogenates incubated with 25-hydroxycholecalciferol (HCC), stimulated the release of previously incorporated (45)45Ca from fetal rat bones in organ culture, at concentrations of 10(-10) to 10(-8)M. The dose response curves for 1,25-DHCC and 25-HCC, the parent compound, are parallel, but 1,25-DHCC is about 100 times as potent on a weight basis. Brief exposure to maximum doses of either agent leads to prolonged bone resorption.
TL;DR: Japanese quail given 20 parts per million of mercury as methylmercury in diets containing 17 percent tuna survived longer than quails given this concentration of methylmerCury in a corn-soya diet.
Abstract: Japanese quail given 20 parts per million of mercury as methylmercury in diets containing 17 percent (by weight) tuna survived longer than quail given this concentration of methylmercury in a corn-soya diet. Tuna has a relatively high content of selenium and tends to accumulate additional selenium when mercury is present. A content of selenium in the diet comparable to that supplied by tuna decreased methylmercury toxicity in rats. Selenium in tuna, far from being a hazard in itself, may lessen the danger to man of mercury in tuna.