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Showing papers in "Nature in 1968"


Journal ArticleDOI
17 Feb 1968-Nature
TL;DR: Calculating the rate of evolution in terms of nucleotide substitutions seems to give a value so high that many of the mutations involved must be neutral ones.
Abstract: Calculating the rate of evolution in terms of nucleotide substitutions seems to give a value so high that many of the mutations involved must be neutral ones.

3,297 citations


Journal ArticleDOI
18 May 1968-Nature
TL;DR: Patients with xeroderma pigmentosum develop fatal skin cancers when exposed to sunlight, and so the failure of DNA repair in the skin must be related to carcinogenesis.
Abstract: Normal skin fibroblasts can repair ultraviolet radiation damage to DNA by inserting new bases into DNA in the form of small patches. Cells from patients with the hereditary disease xeroderma pigmentosum carry a mutation such that repair replication of DNA is either absent or much reduced in comparison to normal fibroblasts. Patients with xeroderma pigmentosum develop fatal skin cancers when exposed to sunlight, and so the failure of DNA repair in the skin must be related to carcinogenesis.

1,649 citations


Journal ArticleDOI
01 Jan 1968-Nature
TL;DR: In this article, the first report of a curious class of astronomical radio sources, distinguished by their rapid and extremely regular pulsations, was made by Hewish et al. They are now understood to be rapidly rotating, magnetized neutron stars, or pulsars.
Abstract: Unusual signals from pulsating radio sources have been recorded at the Mullard Radio Astronomy Observatory The radiation seems to come from local objects within the galaxy, and may be associated with oscillations of white dwarf or neutron stars 1968 saw the first report of a curious class of astronomical radio sources, distinguished by their rapid and extremely regular pulsations Hewish et al associated them with unusually stable oscillations in compact stars They are now understood to be rapidly rotating, magnetized neutron stars, or pulsars

1,554 citations


Journal ArticleDOI
01 Jul 1968-Nature
TL;DR: The Thermophysical Properties Research Literature Retrieval Guide as discussed by the authors was published by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore.
Abstract: Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

1,240 citations


Journal ArticleDOI
13 Jan 1968-Nature
TL;DR: General principles are formulated for the objective reconstruction of a three dimensional object from a set of electron microscope images and applied to the calculation of aThree dimensional density map of the tail of bacteriophage T4.
Abstract: General principles are formulated for the objective reconstruction of a three dimensional object from a set of electron microscope images. These principles are applied to the calculation of a three dimensional density map of the tail of bacteriophage T4.

1,239 citations


Journal ArticleDOI
George Wald1
24 Aug 1968-Nature
TL;DR: The article that follows consists of most of the lecture delivered by Professor Wald last December when he received the Nobel Prize for Medicine in Stockholm.
Abstract: In 1967 Professor Wald, together with Professors H. K. Hartline and R. Granit, received the Nobel Prize for Medicine. The article that follows consists of most of the lecture delivered by Professor Wald last December when he received the prize in Stockholm.

965 citations


Journal ArticleDOI
13 Jul 1968-Nature
TL;DR: The structure of the contacts between unlike subunits suggests that the tetramer, rather than the αβ dimer, is the functional unit of haemoglobin.
Abstract: The secondary structure of the haemoglobin chains is similar to that of myoglobin, but some of the helical segments are more irregular and some parts of the non-helical segments have different conformations. The structure of the contacts between unlike subunits suggests that the tetramer, rather than the αβ dimer, is the functional unit of haemoglobin.

847 citations


Journal ArticleDOI
23 Mar 1968-Nature
TL;DR: An endonuclease which degrades foreign DNA has been isolated and requires S-adenosylmethionine, ATP and Mg++.
Abstract: An endonuclease which degrades foreign DNA has been isolated. The enzyme requires S-adenosylmethionine, ATP and Mg++.

765 citations


Journal ArticleDOI
07 Sep 1968-Nature
TL;DR: It is calculated that the initiation of a round of DNA replication always takes place at a time when the cell mass/chromosome origin reaches a particular critical value, which provides an explanation for the increase in size of cells with increase in the rate of growth.
Abstract: ROUNDS of DNA replication are initiated in Escherichia coli at different stages in the cell cycle of bacteria growing at different rates1. It is possible to calculate that the initiation of a round of DNA replication always takes place at a time when the cell mass/chromosome origin reaches a particular critical value. In other words, the mass at which initiation takes place is always an integral multiple of a particular mass. This constancy in turn provides an explanation for the increase in size of cells with increase in the rate of growth.

706 citations


Journal ArticleDOI
14 Dec 1968-Nature
TL;DR: Polychlorinated biphenyls are widely dispersed in the global ecosystem, and are powerful inducers of hepatic enzymes which degrade oestradiol, which could account for a large part of the aberration in calcium metabolism which has been observed in many species of birds since the Second World War.
Abstract: Polychlorinated biphenyls are widely dispersed in the global ecosystem, and are powerful inducers of hepatic enzymes which degrade oestradiol. Together with other chlorinated biocides, such as DDT, they could account for a large part of the aberration in calcium metabolism which has been observed in many species of birds since the Second World War.

702 citations


Journal ArticleDOI
30 Nov 1968-Nature
TL;DR: This study attempted to determine the degree to which circulating, radioactive corticosterone enters and remains in the brain, because the limbic system of the brain is implicated in the control of the secretion of ACTH and in the affective behavioural responses.
Abstract: CORTICOSTERONE is one of the principal steroids secreted by the rat adrenal gland1–3 and it is well established that various noxious psychological and physiological stimuli promote the release of this substance into the blood. Because we are interested in the action of such corti-costeroids on biochemical processes in the brain, we attempted to determine the degree to which circulating, radioactive corticosterone enters and remains in the brain. Furthermore, because the limbic system of the brain is implicated in the control of the secretion of ACTH4–6 and in the affective behavioural responses7–9, we were particularly interested to see whether structures in the limbic system retain corticosterone in a higher concentration than other areas of the brain. Published work on the uptake of the oestradiol by the brain10–13 indicates that the hypothalamus retains that hormone.

Journal ArticleDOI
11 May 1968-Nature
TL;DR: Professor Waddington outlines some of the points discussed at the meetings of the International Union of Biological Sciences, and the essays arising from the first symposium have recently been published under the title Towards a Theoretical Biology.
Abstract: Two symposia on theoretical biology were held in 1966 and 1967 at the instigation of the International Union of Biological Sciences. The meetings were organized by Professor Waddington, and in this article he outlines some of the points discussed at the meetings. The essays arising from the first symposium have recently been published under the title Towards a Theoretical Biology.

Journal ArticleDOI
27 Jan 1968-Nature
TL;DR: Part of the mouse mutant “nude” syndrome was sulphydryl group deficiency and abnormal keratinization of hair follicles, and necrosis of the liver, associated with Toxoplasma gondii infection.
Abstract: THE mouse mutant “nude” has been described by Flanagan1. It is an autosomal recessive. The homozygotes, nu nu, are hairless and their growth is retarded. More than half die before weaning and none survives for as long as 25 weeks. Other parts of the syndrome were: sulphydryl group deficiency and abnormal keratinization of hair follicles, and necrosis of the liver, associated with Toxoplasma gondii infection. No single primary defect of development responsible for these pleiotropic effects could be suggested.

Journal ArticleDOI
Thomas Gold1
01 Jan 1968-Nature
TL;DR: The constancy of frequency in the recently discovered pulsed radio sources can be accounted for by the rotation of a neutron star as discussed by the authors, where relativistic velocities will set up in any plasma in the surrounding magnetosphere, leading to radiation in the pattern of a rotating beacon.
Abstract: The constancy of frequency in the recently discovered pulsed radio sources can be accounted for by the rotation of a neutron star. Because of the strong magnetic fields and high rotation speeds, relativistic velocities will be set up in any plasma in the surrounding magnetosphere, leading to radiation in the pattern of a rotating beacon.

Journal ArticleDOI
09 Mar 1968-Nature
TL;DR: An isolated and severe defect of memory, with preservation of other intellectual functions, including span of attention, may occur as the result of localized brain pathology in amnesic patients.
Abstract: A SPECIFIC isolated and severe defect of memory, with preservation of other intellectual functions, including span of attention, may occur as the result of localized brain pathology. In amnesic patients the memory defect is so marked that performance on tests of recent memory declines sharply within a matter of minutes1.

Journal ArticleDOI
01 Dec 1968-Nature

Journal ArticleDOI
01 Apr 1968-Nature
TL;DR: A simple but effective rote-learning facility can be provided within the framework of a suitable programming language to improve the efficiency of computer programs during execution.
Abstract: It would be useful if computers could learn from experience and thus automatically improve the efficiency of their own programs during execution A simple but effective rote-learning facility can be provided within the framework of a suitable programming language

Journal ArticleDOI
31 Aug 1968-Nature
TL;DR: The haemoglobin molecule is insensitive to replacements of most amino-acid residues on its surface, but extremely sensitive to even quite small alterations of internal non-polar contacts, especially those near the haems.
Abstract: The haemoglobin molecule is insensitive to replacements of most amino-acid residues on its surface, but extremely sensitive to even quite small alterations of internal non-polar contacts, especially those near the haems. Replacements at the contacts between α and β-subunits affect respiratory function.

Journal ArticleDOI
01 May 1968-Nature
TL;DR: Emsley and Waugh as mentioned in this paper published the Guide to the NMR Empirical Method A Workbook, which is based on the Bible jun.. Pp. xi + 305.
Abstract: Progress in Nuclear Magnetic Resonance Spectroscopy Vol. 2. Edited by J. W. Emsley, J. Feeney and L. H. Sutcliffe. Pp. vii + 269. (Oxford, London and New York: Pergamon Press, Ltd, 1967.) 90s. net. Advances in Magnetic Resonance Vol. 2. By John S. Waugh. Pp. xii + 269. (New York: Academic Press, Inc.; London: Academic Press, Inc. (London), Ltd, 1966.) $12.00. Guide to the NMR Empirical Method A Workbook. By Roy H. Bible jun.. Pp. xi + 305. (New York: Plenum Press, 1967.) $9.50.

Journal ArticleDOI
01 Aug 1968-Nature
TL;DR: The authors The Selected Readings of R. C. Oldfield and J.C. Marshall, published by Penguin Books: Harmondsworth, Middlesex, 1968. Pp. 392.
Abstract: Language Selected Readings. Edited by R. C. Oldfield and J. C. Marshall. (Penguin Modern Psychology.) Pp. 392. (Penguin Books: Harmondsworth, Middlesex, 1968.) 8s. 6d.

Journal ArticleDOI
22 Jun 1968-Nature
TL;DR: Experiments with dogs have shown that both prostaglandin E2 and F2α are released when the spleen is contracted by nerve stimulation or by adrenaline.
Abstract: Experiments with dogs have shown that both prostaglandin E2 and F2α are released when the spleen is contracted by nerve stimulation or by adrenaline. The prostaglandins are not released from the nerves, but derive from smooth muscle cells or other cells with similar adrenergic innervation. The prostaglandin release is not the cause of splenic contraction.

Journal ArticleDOI
12 Oct 1968-Nature
TL;DR: It was discovered later that the spent catalyst of an acetaldehyde reactor, which caused the pollution, contained approximately 1 per cent methyl mercury; and the biological methylation of mercury was thought to be insignificant.
Abstract: THERE have been incidences of extensive alkyl-mercury poisoning in Japan and Sweden. In Japan a large number of people belonging to the fishing population around Minamata Bay were seriously affected by what is now called Minamata disease. This incident was traced back to pollution of the bay with the mercury containing effluent of a large chemical plant. When methyl thiomethyl-mercury was isolated from shellfish in the area of the bay it was suggested that mercury could be alkylated by “plankton and other marine life”2. It was discovered later that the spent catalyst of an acetaldehyde reactor, which caused the pollution, contained approximately 1 per cent methyl mercury; and the biological methylation of mercury was thought to be insignificant.

Journal ArticleDOI
20 Jul 1968-Nature
TL;DR: Nuclear chromatin of prostate, but not other tissues which are insensitive to androgen, contains an androgen receptor which can selectively retain dihydrotestosterone (DHT, 5α-androstane-17β-ol-3-one)—the most potent endogenous androgen for the growth of ventral prostate of rat13,14.
Abstract: MUCH attention is being given to the effect of gonadal hormones on various biochemical events in the cell nuclei of the target tissues1–7. It is not known whether steroids act directly at nuclear sites; oestradiol-17β seems to associate with nuclear components without alteration of the oestrogen molecule8,9. Ventral prostate can retain androgens to a somewhat greater extent than the blood10,11, but studying the method of androgen retention is complicated by the rapid and multiple transformations of androgens injected into the experimental animals10–12. Consequently, we have asked two simple questions: (1) which metabolite(s) of testosterone can associate with isolated prostatic nuclei; and (2) is such association selective ? The results reported in this paper suggest to us that nuclear chromatin of prostate, but not other tissues which are insensitive to androgen, contains an androgen receptor which can selectively retain dihydrotestosterone (DHT, 5α-androstane-17β-ol-3-one)—the most potent endogenous androgen for the growth of ventral prostate of rat13,14.

Journal ArticleDOI
14 Sep 1968-Nature
TL;DR: A working hypothesis is suggested for the events which occur between biochemical stimulation and the liberation of secretory granules into the extracellular space.
Abstract: RELEASE of insulin from beta cells of the islets of Langer-hans occurs as a result of the movement of secretory granules to the surface of the cells. Here the membranous sacs encasing the granules fuse with the plasma membrane, rupture and liberate the granules into the extracellular space1. This process is called emiocytosis. Although glucose represents the most important physiologic stimulus for the release of insulin from the beta cells, it has been shown recently that the rates of secretion of insulin are also altered in the presence of a wide variety of other agents2. So far, little information is available concerning the relationship between the biochemical effects of these agents and the process of emiocytosis. We suggest here a working hypothesis for the events which occur between biochemical stimulation and the liberation of secretory granules into the extracellular space.

Journal ArticleDOI
06 Jul 1968-Nature
TL;DR: In this form the technique has been successfully applied to studies on the heterogeneity of myoglobins, cytochrome c6, lactoperoxidase7 and a number of other proteins (see review by Haglund8).
Abstract: THE principle of isoelectric fractionation was applied to the separation of amino-acids as early as 1912 by Ikeda and Suzuki (Japanese patent quoted in ref. 8), but the technique did not become practical for the fractionation of macromolecular ampholytes such as proteins until the introduction of natural pH gradients1 and suitable carrier ampholytes2–4. Svensson described an apparatus for isoelectric focusing in shallow pH gradients formed by low molecular weight ampholytes and stabilized by sucrose density gradients3. In this form the technique has been successfully applied to studies on the heterogeneity of myoglobins4,5, cytochrome c6, lactoperoxidase7 and a number of other proteins (see review by Haglund8).

Journal ArticleDOI
24 Feb 1968-Nature
TL;DR: A new class of metabolite, with a pyrrole-like structure, has been demonstrated in the tissues of animals poisoned by pyrrolizidine alkaloids and evidence has been found of the types of reactions such metabolites might undergo with tissue constituents.
Abstract: A new class of metabolite, with a pyrrole-like structure, has been demonstrated in the tissues of animals poisoned by pyrrolizidine alkaloids. There is some correlation between the degree of hepato-toxicity and the amount of “pyrrole” found in the liver. Evidence has been found of the types of reactions such metabolites might undergo with tissue constituents.

Journal ArticleDOI
Jan Drenth1, J.N. Jansonius1, R. Koekoek1, H. M. Swen1, B.G. Wolthers1 
08 Jun 1968-Nature
TL;DR: A three-dimensional X-ray study at a resolution of 2.8 A has revealed that the single polypeptide chain of 211 residues is folded into two distinct parts which are divided by a cleft as mentioned in this paper.
Abstract: A three-dimensional X-ray study at a resolution of 2.8 A has revealed that the single polypeptide chain of 211 residues is folded into two distinct parts which are divided by a cleft. The active site, consisting of a cysteine and a histidine, lies at the surface of the cleft. Apart from four short α-helical segments and one short segment of β-structure, the conformation of the chain is irregular.

Journal ArticleDOI
24 Feb 1968-Nature
TL;DR: Alamethicin, a cyclopeptide, can induce action potentials in biomolecular lipid membranes with high affinity for Na6(CO3)2, Na2SO4.
Abstract: Alamethicin, a cyclopeptide, can induce action potentials in biomolecular lipid membranes.

Journal ArticleDOI
04 May 1968-Nature
TL;DR: Two optical techniques—light scattering and birefringence—have been used to detect rapid structural changes accompanying the action potentials in two types of non-myelinated nerve fibre.
Abstract: Two optical techniques—light scattering and birefringence—have been used to detect rapid structural changes accompanying the action potentials in two types of non-myelinated nerve fibre. Changes in light scattering originate from at least two different phenomena, while a large part of the birefringence change seems to be directly dependent on the potential difference across the axon membrane, and arises in radially oriented molecules associated with the membrane.

Journal ArticleDOI
06 Apr 1968-Nature
TL;DR: Observations in mouse oocytes with increasing maternal age evidently apply to man and are perhaps relevant in the aetiology of Down's syndrome and infertility in older mothers.
Abstract: A decrease in the frequency of chiasmata, a change in their location on the chromosome and an increase in the frequency of univalents have been found in mouse oocytes with increasing maternal age. Many of the univalents displayed a non-chiasmate association, others were not associated. Several of these observations evidently apply to man and are perhaps relevant in the aetiology of Down's syndrome and infertility in older mothers.