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Showing papers in "Science in 1969"


Journal ArticleDOI
18 Apr 1969-Science
TL;DR: The principles of ecological succession bear importantly on the relationships between man and nature and needs to be examined as a basis for resolving man’s present environmental crisis.
Abstract: The principles of ecological succession bear importantly on the relationships between man and nature. The framework of successional theory needs to be examined as a basis for resolving man’s present environmental crisis. Most ideas pertaining to the development of ecological systems are based on descriptive data obtained by observing changes in biotic communities over long periods, or on highly theoretical assumptions; very few of the generally accepted hypotheses have been tested experimentally. Some of the confusion, vagueness, and lack of experimental work in this area stems from the tendency of ecologists to regard “succession” as a single straightforward idea; in actual fact, it entails an interacting complex of processes, some of which counteract one another.

4,419 citations


Journal ArticleDOI
25 Jul 1969-Science
TL;DR: Direct support for the idea that regulation of gene activity underlies cell differentiation comes from evidence that much of the genome in higher cell types is inactive and that different ribonucleic acids are synthesized in different cell types.
Abstract: Cell differentiation is based almost certainly on the regulation of gene activity, so that for each state of differentiation a certain set of genes is active in transcription and other genes are inactive. The establishment of this concept (1) has depended on evidence indicating that the cells of an organism generally contain identical genomes (2). Direct support for the idea that regulation of gene activity underlies cell differentiation comes from evidence that much of the genome in higher cell types is inactive (3) and that different ribonucleic acids (RNA) are synthesized in different cell types (4).

1,898 citations


Journal ArticleDOI
Jürgen Haffer1
11 Jul 1969-Science

1,863 citations


Journal ArticleDOI
09 May 1969-Science
TL;DR: It is postulated that the aduls syndrome represents a multifacted nueroendocrine disturbance arising from the disruption of developing nueral centers concered in the mediation of endocrine function.
Abstract: In newborn mice subcutaneous injectionis of monosodium glutamate induced acute neuronal necrosis in several regions of developing brain including the hypothanamus. As adults, treated animals showed stunted skeletal development, marked obesity, and female sterility. Pathological changes were also found in several organs associated with endocrine function. Studies of food consumption failed to demonstrate hyperphagia to explain the obesity. It is postulated that the aduls syndrome represents a multifacted nueroendocrine disturbance arising from the disruption of developing nueral centers concered in the mediation of endocrine function.

1,777 citations


Journal ArticleDOI
20 Jun 1969-Science
TL;DR: There is now a real possibility of solving the problem in complete detail, provided a way can be found to crystallize a recently purified globular subfragment of the myosin molecule, and some apparently paradoxical properties of the system are revealed.
Abstract: During the last few years the basic features of the sliding-filament model of contraction in striated muscle have gained general acceptance and it has been possible to concentrate attention on the detailed mechanism by which the relative sliding force between the actin and myosin filaments is developed. A number of observations have indicated in general outline how crossbridges between the filaments may be involved in the generation of this force but have also revealed some apparently paradoxical properties of the system. The most recent findings show a possible way in which these paradoxes can be resolved. Furthermore, there is now a real possibility of solving the problem in complete detail, provided a way can be found to crystallize a recently purified globular subfragment of the myosin molecule. In this article I discuss these new findings and their implications. According to the interdigitating filament model of striated muscle (1), the contractile material consists of long series of partially overlapping arrays of actin and myosin filaments which form the myofibrils. These overlapping arrays give rise to the characteristic band pattern visible in the light microscope. In vertebrate striated muscle the myosin-containing filaments are spaced out in a hexagonal lattice 400 The Mechanism of Muscular Contraction

1,615 citations


Book ChapterDOI
19 Sep 1969-Science
TL;DR: In this article, the authors present an approach for measuring the relative cost of risk relative to benefit relative to the cost of the risk of death due to accidents in the public use of technology.
Abstract: AN APPROACHED IS PRESENTED FOR ESTABLISHING A QUANTITATIVE MEASURE OF BENEFIT RELATIVE COST FOR ACCIDENTAL DEATHS ARISING FROM TECHNOLOGICAL DEVELOPMENTS IN PUBLIC USE. THE ANALYSIS IS BASED ON TWO ASSUMPTIONS: (1) HISTORICAL NATIONAL ACCIDENT RECORDS ARE ADEQUATE FOR REVEALING CONSISTENT PATTERNS OF FATALITIES IN THE PUBLIC USE OF TECHNOLOGY, AND (2) THAT SUCH HISTORICALLY REVEALED SOCIAL PREFERENCES AND COSTS ARE SUFFICIENTLY ENDURING TO PERMIT THEIR USE FOR PREDICTIVE PURPOSES. SOCIETAL ACTIVITIES FALL INTO TWO GENERAL CATEGORIES--THOSE IN WHICH THE INDIVIDUAL PARTICIPATES ON A "VOLUNTARY" BASIS AND THOSE IN WHICH THE PARTICIPATION IS "INVOLUNTARY" IMPOSED BY THE SOCIETY IN WHICH THE INDIVIDUAL LIVES. ALTHOUGH THIS STUDY IS EXPLORATORY, IT REVEALS SEVERAL INTERESTING POINTS: (1) THE INDICATIONS ARE THAT THE PUBLIC IS WILLING TO ACCEPT "VOLUNTARY" RISKS ROUGHLY 1000 TIMES GREATER THAN "INVOLUNTARY" RISKS. (2) THE STATISTICAL RISK OF DEATH FROM DISEASE APPEARS TO BE A PSYCHOLOGICAL YARDSTICK FOR ESTABLISHING THE LEVEL OF ACCEPTABILITY OF OTHER RISKS. (3) THE ACCEPTABILITY OF RISK APPEARS TO BE CRUDELY PROPORTIONAL TO THE THIRD POWER OF BENEFITS (REAL OR IMAGINED). (4) THE SOCIAL ACCEPTANCE OF RISK IS DIRECTLY INFLUENCED BY PUBLIC AWARENESS OF THE BENEFITS OF AN ACTIVITY, AS DETERMINED BY ADVERTISING, USEFULNESS, AND THE NUMBER OF PEOPLE PARTICIPATING. (5) IN A SAMPLE APPLICATION OF THESE CRITERIA TO ATOMIC POWER PLANT SAFETY, IT APPEARS THAT ENGINEERING DESIGN OBJECTIVELY DETERMINED BY ECONOMIC CRITERIA WOULD RESULT IN A DESIGN-TARGET RISK LEVEL VERY MUCH LOWER THAN THE PRESENT SOCIALLY ACCEPTED RISK FOR ELECTRIC POWER PLANTS. THIS METHODOLOGY FOR REVEALING EXISTING SOCIAL PREFERENCES AND VALUES MAY BE A MEANS OF PROVIDING THE INSIGHT IN SOCIAL BENEFIT RELATIVE TO COST THAT IS NECESSARY FOR JUDICIOUS NATIONAL DECISIONS IN NEW TECHNOLOGICAL DEVELOPMENTS. THE APPENDIX CONTAINS THE DOCUMENTATION FOR RISK BENEFIT ANALYSIS CALCULATED FOR MOTOR-VEHICLE TRAVEL, TRAVEL BY AIR ROUTE CARRIER, GENERAL AVIATION, RAILROAD TRAVEL, SKIING, HUNTING, SMOKING, VIETNAM, ELECTRIC POWER, NATURAL DISASTERS, AND DIEASES AND ACCIDENTS. /SRIS/

1,542 citations


Journal ArticleDOI
16 May 1969-Science
TL;DR: NonDarwinian evolution of protein and DNA, comparing expectations of evolution models for protein and amino acid changes is compared.
Abstract: NonDarwinian evolution of protein and DNA, comparing expectations of evolution models for protein and amino acid changes

1,480 citations


Journal ArticleDOI
04 Apr 1969-Science
TL;DR: Observers in both literate and preliterate cultures chose the predicted emotion for photographs of the face, although agreement was higher in the literate samples, suggesting that the pan-cultural element in facial displays of emotion is the association between facial muscular movements and discrete primary emotions.
Abstract: Observers in both literate and preliterate cultures chose the predicted emotion for photographs of the face, although agreement was higher in the literate samples. These findings suggest that the pan-cultural element in facial displays of emotion is the association between facial muscular movements and discrete primary emotions, although cultures may still differ in what evokes an emotion, in rules for controlling the display of emotion, and in behavioral consequences.

1,465 citations


Journal ArticleDOI
03 Jan 1969-Science
TL;DR: A method is presented by which hundreds of haploid plants of various species of Nicotiana can be raised from pollen grains, structures which develop in stages similar to those of zygotic embryos.
Abstract: A method is presented by which hundreds of haploid plants of various species of Nicotiana can be raised from pollen grains. Stamens should be excised when pollen grains have been individualized, but are still uninucleate and free of starch. When grown in vitro on a relatively simple medium, some pollen grains proliferate into embryo-like, structures which develop in stages similar to those of zygotic embryos. The plantlets mature and flower profusely, but do not set seed.

1,452 citations


Journal ArticleDOI
03 Oct 1969-Science
TL;DR: The two sets of variables primary production and the associated food chain dynamics may act additively to produce differences in fish production which are far more pronounced and dramatic than the observed variability of the individual causative factors.
Abstract: Numerous attempts have been made to estimate the production in the sea of fish and other organisms of existing or potential food value to man (1-4). These exercises, for the most part, are based on estimates of primary (photosynthetic) organic production rates in the ocean (5) and various assumed trophic-dynamic relationships between the photosynthetic producers and the organisms of interest to man. Included in the latter are the number of steps or links in the food chains and the efficiency of conversion of organic matter from each trophic level or link in the food chain to the next. Different estimates result from different choices in the number of trophic levels and in the efficiencies, as illustrated in Table 1 (2). Implicit in the above approach is the concept of the ocean as a single ecosystem in which the same food chains involving the same number of links and efficiencies apply throughout. However, the rate of primary production is known to be highly variable, differing by at least two full orders of magnitude from the richest to the most impoverished regions. This in itself would be expected to result in a highly irregular pattern of food production. In addition, the ecological conditions which determine the trophic dynamics of marine food chains also vary widely and in direct relationship to the absolute level of primary organic production. As is shown below, the two sets of variables primary production and the associated food chain dynamics may act additively to produce differences in fish production which are far more pronounced and dramatic than the observed variability of the individual causative factors.

1,423 citations


Journal ArticleDOI
15 Aug 1969-Science
TL;DR: The protein encoded by Nup160 directly interacts with that of another hybrid lethality gene, Nup96, indicating that at least two lethal hybrid incompatibility genes have evolved as byproducts of divergent coevolution among interacting components of the Drosophila nuclear pore complex.
Abstract: Speciation often involves the evolution of incompatible gene interactions that cause sterility or lethality in hybrids between populations. These so-called hybrid incompatibilities occur between two or more functionally divergent loci. We show that the nucleoporin 160kDa (Nup160) gene of the fruitfly Drosophila simulans is incompatible with one or more factors on the D. melanogaster X chromosome, causing hybrid lethality. Nup160 encodes a nuclear pore complex protein and shows evidence of adaptive evolution. Furthermore, the protein encoded by Nup160 directly interacts with that of another hybrid lethality gene, Nup96, indicating that at least two lethal hybrid incompatibility genes have evolved as byproducts of divergent coevolution among interacting components of the Drosophila nuclear pore complex.

Journal ArticleDOI
19 Sep 1969-Science
TL;DR: A systematic methodology for discovering social preference and value may be a means of providing the INSIGHT in SOCIAL BENEFIT RELATIVE to COST that is NECESSARY for JUDICIOUS NATIONAL DECISIONS in new TECHNOLOGICAL DEVELOPMENTS.

Journal ArticleDOI
25 Apr 1969-Science
TL;DR: It was concluded that focal brain stimulation in this region can induce analgesia in the absence of diffusely applied "whole brain" stimulation.
Abstract: Chronic monopolar electrodes were implanted in the region of the midbrain central gray in eight rats. In three rats, continuous 60 cycle-per-second sine-wave stimulation resulted in an electrical analgesia defined by the elimination of responses to aversive stimulation while general motor responsiveness was retained. Exploratory laparotomy was carried out in these animals during continuous brain stimulation without the use of chemical anesthetics. Following surgery, brain stimulation was terminated, and responses to aversive stimuli returned. Electrodes effective in inducing electrical analgesia at the lowest currents were located at the dorsolateral perimeter of the midbrain central gray. It was concluded that focal brain stimulation in this region can induce analgesia in the absence of diffusely applied "whole brain" stimulation.

Journal ArticleDOI
28 Feb 1969-Science
TL;DR: Visual systems of hamster brain, discussing relative visual localization and discrimination blindness produced by ablation of cortical or tectal areas is discussed.
Abstract: Visual systems of hamster brain, discussing relative visual localization and discrimination blindness produced by ablation of cortical or tectal areas

Journal ArticleDOI
Michel Jouvet1
03 Jan 1969-Science

Journal ArticleDOI
23 May 1969-Science
TL;DR: The presence of extrachromosomal nucleoli in amphibian oocytes has permitted isolation and electron microscopic observation of the genes coding for ribosomal RNA precursor molecules.
Abstract: The presence of extrachromosomal nucleoli in amphibian oocytes has permitted isolation and electron microscopic observation of the genes coding for ribosomal RNA precursor molecules. Visualization of these genes is possible because many precursor molecules are simultaneously synthesized on each gene. Individual genes are separated by stretches of DNA that apparently are not transcribed at the time of synthesis of precursor rRNA in the extrachromosomal nucleoli.

Journal ArticleDOI
19 Sep 1969-Science
TL;DR: Two diphosphonates containing the P-C-P bond retard the rate of dissolution of apatite crystals in vitro and inhibit bone resorption induced by parathyroid extract in mouse calvaria in tissue culture and in thyroparathyroidectomized rats in vivo.
Abstract: Two diphosphonates containing the P-C-P bond, Cl(2)C(PO(3)HNa)(2), and H(2)C(PO(3)HNa)(2) retard the rate of dissolution of apatite crystals in vitro. They inhibit bone resorption induced by parathyroid extract in mouse calvaria in tissue culture and in thyroparathyroidectomized rats in vivo.

Journal ArticleDOI
10 Jan 1969-Science
TL;DR: My purpose in this article is to discuss the merits of two classifications which depart from the traditional two kingdoms, the systems of Copeland (1-3) and Whittaker (4, 5).
Abstract: are those who consider questions in science which have no unequivocal , experimentally determined answer scarcely worth discussing. Such feeling, along with conservatism, may have been responsible for the long and almost unchallenged dominance of the system of two kingdoms-plants and animals-in the broad classification of organisms. The unchallenged position of these kingdoms has ended, however; alternative systems are being widely considered (1-18) and are appearing in many introductory biology texts (19-24). My purpose in this article is to discuss the merits of two classifications which depart from the traditional two kingdoms, the systems of Copeland (1-3) and Whittaker (4, 5). Two-Kingdom System Man is terrestrial, and he sees around him two major groups of organisms of very different adaptation to nutrition on land-the photosynthetic, rooted, higher plants, and the food-ingesting, motile, higher animals. So distinct in way of life, direction of evolution, and kind of body organization are these groups that a concept of dichotomy-plants versus animals-is almost inescapable if they are considered by themselves. The two groups became the nuclei around which concepts of the plant and animal kingdoms were developed by early naturalists. The kingdoms have been part of the formal classification of living things since Linnaeus (25). Mosses, liverworts, and macroscopic algae are clearly plants in their photo-synthetic and nonmotile way of life, and (though the photosynthetic process itself was not understood by early naturalists) these forms were grouped 150 with the higher land plants. The higher fungi on land are nonmotile, and their apparently \"rooted\" manner of growth suggested the plants. It thus seemed reasonable to assign fungi to the plant kingdom, and some students believed that they had evolved from algae. The wealth of unicellular life discovered by microscopists offered greater difficulty. Some forms were motile and ingested food, however, and were naturally regarded as one-celled animals or proto-zoans. Others were nonmotile and photosynthetic, hence one-celled plants. There remained a wide range of uni-cellular forms in which nonmotility and flagellate or pseudopodial motility, and ingestive, photosynthetic, and absorp-tive nutrition, were combined in various ways which were neither clearly plant-like nor animal-like. In a number of cases plant-like and animal-like unicells were connected by a series of closely related intergrading forms within the same major taxon. There remained also the bacteria which, though few are pho-tosynthetic and many are motile, seemed better treated as plants because of their walled cells. The plant and animal kingdoms …


Journal ArticleDOI
15 Aug 1969-Science
TL;DR: Two hexosaminidase components, separable by starch-gel electrophoresis and possessing both β-D-N-acetylglucosamininidase and β-O-NacetylgalactosaminIDase activity, are present in human tissues.
Abstract: Two hexosaminidase components, separable by starch-gel electrophoresis and possessing both beta-D-N-acetylglucosaminidase and beta-D-N-acetylgalactosaminidase activity, are present in human tissues. One of these, hexosaminidase component A, is absent in brain, liver, kidney, skin, cultured skin fibroblasts, blood plasma, and leukocytes from nine patients with Tay-Sachs disease. Hexosaminidase assay may facilitate the early diagnosis of individuals homozygous for Tay-Sachs disease.

Journal ArticleDOI
26 Dec 1969-Science
TL;DR: In the early 1900s, it was known that motile bacteria are attracted to a variety of small organic molecules as mentioned in this paper, but few scientists were interested in bacterial chemotaxis, probably because they were unwilling to believe that these lowly organisms possessed any capability for information processing or could exhibit even simple forms of behavior.
Abstract: For a hundred years it was known that motile bacteria are attracted to a variety of small organic molecules. However, few scientists were interested in bacterial chemotaxis, probably because they were unwilling to believe that these lowly organisms possessed any capability for information processing or could exhibit even simple forms of behavior. Despite evidence to the contrary, it was generally assumed that chemotaxis and metabolism were hopelessly entwined. Bacteria simply congregated where the food was; after all, that was where growth rates were fastest. Julius Adler broke this prejudice. Undaunted by peer pressure, Adler set out to uncover the molecular basis for bacterial chemotaxis and, in particular, to test rigorously the perceived connection between this phenomenon and metabolism. First he modified a method developed by Pfeffer in the 1880s to permit a quantitative analysis of chemotaxis with Escherichia coli, an experimentally tractable organism. Basically this method involves inserting a capillary containing an attractant solution into a suspension of bacteria and then counting the cells that swim into the tube after a defined incubation period. Legend has it that he searched the sewers of Madison, Wis., to find an intelligent strain of E. coli. Domesticated strains, which are used to a life of luxury, had become either stupid or paralyzed. The paper is written in a beautifully clear, Socratic style; questions are posed and answers are provided. With this quantitative assay, Adler presented five lines of evidence demonstrating that bacteria have chemoreceptors for attractants: (i) some metabolites fail to attract, (ii) some attractants cannot be metabolized, (iii) attractants can be detected even when cells are flooded with metabolites, (iv) competition is observed with structurally related attractants, and (v) mutants defective in chemotaxis can still metabolize the molecule in question. Moreover, using attractant competition and mutant analysis, he went on to identify at least five different chemoreceptors. Appropriately enough, the paper ends with a section entitled “Implications for neurobiology and behavioral biology.” Adler's elegantly simple experiments demonstrated that bacteria such as E. coli can sense and process environmental information with surprising sophistication. Now many scientists were “attracted” to chemotaxis, and the field grew exponentially. What is remarkable is the diversity of these scientific converts. They include mathematicians and physicists, biochemists and structural biologists, geneticists and molecular biologists, and neurobiologists. Despite the fact that the components of E. coli's “brain” have been identified and analyzed in great detail, important questions remain, including the basis for the large range of ligand sensitivity and the mechanisms of signal amplification and adaptation. Because these questions are fundamental to any sensory system, it is likely that bacterial chemotaxis will remain at the forefront of this important research field. Julius Adler spawned an enormously productive enterprise. THOMAS J. SILHAVY

Journal ArticleDOI
07 Mar 1969-Science
TL;DR: Measurements of serum freezing points in three Antarctic marine fishes indicated that they do not freeze in the -1.87�C seawater because their blood is isosmotic to seawater.
Abstract: Measurements of serum freezing points in three Antarctic marine fishes indicated that they do not freeze in the -1.87°C seawater because their blood is isosmotic to seawater. Concentrations of sodium chloride, urea, and free amino acids in the serum accounted for only half of the freezing-point depression of the serum. A protein containing carbohydrate was isolated which accounted for 30 percent of the freezing-point depression of the serum.

Journal ArticleDOI
19 Sep 1969-Science
TL;DR: Two diphosphonates containing the P-C-P bond inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D3.
Abstract: Two diphosphonates containing the P-C-P bond, CH(3)C(OH)(PO(3)HNa)(2) and H(2)C(PO(3)HNa)(2), inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D(3). The diphosphonates therefore have effects similar to those described for compounds containing the P-O-P bond but are active when administered orally.

Journal ArticleDOI
28 Feb 1969-Science
TL;DR: The activity of single neurons in precentral cortex of unanesthetized monkeys (Macaca mulatta) was conditioned by reinforcing high rates of neuronal discharge with delivery of a food pellet with auditory or visual feedback of unit firing rates.
Abstract: The activity of single neurons in precentral cortex of unanesthetized monkeys (Macaca mulatta) was conditioned by reinforcing high rates of neuronal discharge with delivery of a food pellet. Auditory or visual feedback of unit firing rates was usually provided in addition to food reinforcement. After several training sessions, monkeys could increase the activity of newly isolated cells by 50 to 500 percent above rates before reinforcement.


Journal ArticleDOI
03 Oct 1969-Science
TL;DR: Phosphonomycin is a newly discovered antibiotic produced by streptomycetes that is effective, when administered by the oral route, to mice infected with Gram-positive or Gram-negative microorganisms.
Abstract: Phosphonomycin is a newly discovered antibiotic produced by streptomycetes. It is effective, when administered by the oral route, to mice infected with Gram-positive or Gram-negative microorganisms. The antibiotic is bactericidal and inhibits cell-wall synthesis.

Journal ArticleDOI
07 Nov 1969-Science
TL;DR: An ovarian dysgenesia was observed when the mice were thymectomized at 3 days of age, but not at 7 days or later; it was prevented by thymus grafting.
Abstract: Neonatal thymectomy of mice, when no ectopic thymus existed, constantly resulted in developmental arrest of the ovary but not of the testis; it also caused sterility in the female. The ovaries of thymectomized mice were extremely small and were characterized by absence of follicles and corpora lutea. Such an ovarian dysgenesia was observed when the mice were thymectomized at 3 days of age, but not at 7 days or later; it was prevented by thymus grafting.

Journal ArticleDOI
07 Feb 1969-Science