Showing papers in "Nature in 1979"
TL;DR: Pharmacological and biochemical criteria can be used to separate those dopamine receptors which are linked to the enzyme adenylyl cyclase and those which are not.
Abstract: Pharmacological and biochemical criteria can be used to separate those dopamine receptors which are linked to the enzyme adenylyl cyclase and those which are not.
3,746 citations
TL;DR: It is reported here that taxol acts as a promoter of calf brain microtubule assembly in vitro, in contrast to plant products such as colchicine and podophyllotoxin, which inhibit assembly.
Abstract: TAXOL (Fig. 1) was isolated from the plant Taxus brevifolia (western yew) by Wani et al., who reported that the molecule has antitumour activity in several experimental systems1. In our laboratory we have found that taxol, a low molecular weight neutral compound, completely inhibits division of exponentially growing HeLa cells at low concentrations of drug (0.25 µM) that have no significant effects on DNA, RNA or protein synthesis during a 4-h incubation with the cells. HeLa cells incubated with taxol for 20 h are blocked in late G2 and/or M (ref. 2). We report here that taxol acts as a promoter of calf brain microtubule assembly in vitro, in contrast to plant products such as colchicine and podophyllotoxin, which inhibit assembly. Taxol decreases the lag time for microtubule assembly and shifts the equilibrium for assembly in favour of the microtubule, thereby decreasing the critical concentration of tubulin required for assembly. Microtubules polymerised in the presence of taxol are resistant to depolymerisation by cold (4 °C) and CaCl2 (4 mM).
3,430 citations
TL;DR: Consideration is given to the relation between the ecology and evolution of the transmission processes and the overall dynamics, and to the mechanisms that can produce cyclic patterns, or multiple stable states, in the levels of infection in the host population.
Abstract: If the host population is taken to be a dynamic variable (rather than constant, as conventionally assumed), a wider understanding of the population biology of infectious diseases emerges. In this first part of a two-part article, mathematical models are developed, shown to fit data from laboratory experiments, and used to explore the evolutionary relations among transmission parameters. In the second part of the article, to be published in next week's issue, the models are extended to include indirectly transmitted infections, and the general implications for infectious diseases are considered.
2,652 citations
TL;DR: The primary production in the oceans results from allochthonous nutrient inputs to the euphotic zone (new production) and from nutrient recycling in the surface waters (regenerated production) as discussed by the authors.
Abstract: Primary production in the oceans results from allochthonous nutrient inputs to the euphotic zone (new production) and from nutrient recycling in the surface waters (regenerated production). Global new production is of the order of 3.4−4.7 × 109 tons of carbon per year and approximates the sinking flux of paniculate organic matter to the deep ocean.
2,439 citations
TL;DR: It is reported here that the T antigen in a line of SV40-transformed mouse cells forms an oligomeric complex with a specific cell coded protein.
Abstract: THE early region of the small DNA tumour virus, simian virus 40 (SV40), is known to code for at least two polypeptides, the t and T antigens (‘small t’ and ‘large T’) Both these polypeptides are expressed in cells transformed by the virus1–4, and the T antigen has been shown to be essential for both the initiation and maintenance of the transformed state5–9 We therefore need to know how this T protein interacts with components of the host cell in order to understand the mechanism of SV40-induced transformation We report here that the T antigen in a line of SV40-transformed mouse cells forms an oligomeric complex with a specific cell coded protein
2,400 citations
TL;DR: In this paper, the photoelectrocatalytic reduction of carbon dioxide to form organic compounds such as formic acid, formaldeyde, methyl alcohol and methane, in the presence of photosensitive semiconductor powders suspended in water as catalysts, is described.
Abstract: WE report here the photoelectrocatalytic reduction of carbon dioxide to form organic compounds such as formic acid, formaldeyde, methyl alcohol and methane, in the presence of photosensitive semiconductor powders suspended in water as catalysts. Photocatalytic reaction kinetics were elucidated by reference to the theory of charge transfer at photoexcited semiconductors.
2,362 citations
TL;DR: It is now recognised that receptor-mediated endocytosis has a fundamental role in the growth, nutrition and differentiation of animal cells.
Abstract: Proteins and peptides can enter cells by receptor-mediated endocytosis, a coupled process by which selected extracellular proteins or peptides are first bound to specific cell surface receptors and then rapidly internalised by the cell. Internalisation follows clustering of the receptors in specialised regions of the cell surface called coated pits that invaginate to form intracellular coated vesicles. It is now recognised that receptor-mediated endocytosis has a fundamental role in the growth, nutrition and differentiation of animal cells.
1,956 citations
TL;DR: The DNA fragment d(CpGpCpC pGp CpG pG) crystallises as a left-handed double helical molecule with Watson–Crick base pairs and an antiparallel organisation of the sugar phosphate chains.
Abstract: The DNA fragment d(CpGpCpGpCpG) crystallises as a left-handed double helical molecule with Watson-Crick base pairs and an antiparallel organisation of the sugar phosphate chains. The helix has two nucleotides in the asymmetric unit and contains twelve base pairs per turn. It differs significantly from right-handed B-DNA.
1,773 citations
TL;DR: The nucleotide sequence of a 1,091-base pair cloned cDNA insert encoding bovine corticotropin-β-lipotropin precursor mRNA indicates that the precursor protein consists of repetitive units and includes a third melanotropin sequence in its cryptic portion.
Abstract: The nucleotide sequence of a 1,091-base pair cloned cDNA insert encoding bovine corticotropin-beta-lipotropin precursor mRNA is reported. The corresponding amino acid sequence indicates that the precursor protein consists of repetitive units and includes a third melanotropin sequence in its cryptic portion. Pairs of lysine and arginine residues separate the component peptides of the precursor.
1,689 citations
TL;DR: Measurement of energy balance during voluntary over-eating in rats unequivocally establishes the quantitative importance of diet-induced thermogenesis in energy balance and suggests that this tissue may determine metabolic efficiency and resistance to obesity.
Abstract: Measurement of energy balance during voluntary overeating in rats unequivocally establishes the quantitative importance of diet-induced thermogenesis in energy balance. Like cold-induced thermogenesis, this form of heat production involves changes in the activity of the sympathetic nervous system and brown adipose tissue which suggest that this tissue may determine metabolic efficiency and resistance to obesity.
1,432 citations
TL;DR: Direct observation of the interaction between vitamin E and vitamin C and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E is reported, which is felt to be an important feature in the maintenance of vitamin E levels in tissues.
Abstract: VITAMIN E (α-tocopherol) and vitamin C (ascorbic acid) react rapidly with organic free radicals, and it is widely accepted that the antioxidant properties of these compounds are responsible in part for their biological activity1–5. Tissue vitamin C levels are often considerably greater than those of vitamin E, for example in liver the values are approximately 2 mM and 0.02 mM, respectively. Nevertheless, vitamin E is considerably more lipophilic than vitamin C, and in biomembranes has been found to be the more potent antioxidant, particularly with respect to lipid peroxidation; penetration to a precise site in the membrane may be an important feature of the protection against highly reactive radicals6. Tappel has suggested that the two vitamins act synergistically, vitamin E acting as the primary antioxidant and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E7. We now report direct observation of this interaction, which we feel may be an important feature in the maintenance of vitamin E levels in tissues.
TL;DR: This book contains chapters on plant nutrients, the soil as a plant nutrient medium, nutrient uptake assimilation, plant water relationships, nutrition and plant growth, fertilizer application, and more.
Abstract: A 'textbook for students of agriculture, horticulture and forestry'. It contains chapters on plant nutrients, the soil as a plant nutrient medium, nutrient uptake assimilation, plant water relationships, nutrition and plant growth, fertilizer application; a chapter on each of N, S, P, K, Ca, Mg, Fe, Mn, Zn, Cu, Mo, B (their occurrence in the soil, physiological importance and role in crop nutrition); and two final chapters covering Cl, Si, Co, and V; and (the elements with more toxic effects) I, Br, F, Al, Ni, Cr, Se, Ph, and Cd. Throughout the book virtually none of the numerous examples is taken from forestry. ADDITIONAL ABSTRACT:The topics considered are: plant Other CABI sites
TL;DR: In this paper, it was shown that stomatal aperture capacity is determined by the capacity of the mesophyll tissue to fix carbon, and that the diffusive conductance of the epidermis to CO2 transfer, g, changes in nearly the same proportion as the rate of assimilation of CO2.
Abstract: Previous studies on the Physiology of stomata in higher plants suggest that stomata influence the rate of CO2 fixation in leaf mesophyll tissue. We believe that an equally important stomatal function has not been fully recognised; that stomatal aperture is determined by the capacity of the mesophyll tissue to fix carbon. We altered the capacity of leaves to fix carbon by various means, and found invariably that the diffusive conductance of the epidermis to CO2 transfer, g, (which mainly depends on the number and dimensions of the stomata) changes in nearly the same proportion as the rate of assimilation of CO2. Thus, the intercellular concentration of CO2 (ci), calculated as ci = ca–A/g (where ca is ambient concentration of CO2, A is assimilation rate of CO2), tends to remain constant providing ca is kept constant. We used routine techniques1 to measure A and estimate g in leaves placed singly in chambers. Conductance takes account of CO2 transfer through both stomata and leaf boundary layer, the conductance of the latter being 0.5 mol m−2 s−1.
TL;DR: This work reports the derivation and characterisation of two additional cell lines from primary liver carcinomas which retain the capacity to synthesise many human plasma proteins, including both albumin and α-fetoprotein (AFP), and presents evidence that HBsAg synthesis and secretion in this cell line are correlated with the growth state of the culture.
Abstract: A significant aspect of primary hepatic carcinoma in man is the high positive correlation of hepatocellular carcinoma with infection with hepatitis B virus (HBV)1. Analysis of the relationship between HBV infection and oncogenesis is difficult because natural infection with HBV is limited to man and experimental infection has been achieved only in chimpanzees and gibbons. Furthermore, because HBV has not been successfully propagated in cell culture, basic study of virus-cell interaction of the aetiological agent of one of the most widespread infections of man has been impossible. Recently, however, a cell line (PLC/PRF/5) derived from a human hepatoma biopsy was described which produces the HRV surface antigen (HBsAg) and so provides a tool for the experimental investigation of HBV in viro. We now report the derivation and characterisation of two additional cell lines primary liver carcinomas. In contrast to the PLC/PRF/5 cell line, these cell lines retain the capacity to synthesise many human plasma proteins, including both albumin and alpha-fetoprotein (AFP). One of these lines also produces BHsAg. We also present evidence that HBsAg synthesis and secretion in this cell line are correlated with the growth state of the culture. This finding is in contrast to the continuous HBsAg production found in the PLC/PRF/5 cell line.
TL;DR: Additional evidence is presented by showing that in baboons the infusion of exogenous insulin into the CSF elicits a reliable and predictable decrease in food intake and body weight.
Abstract: Body adiposity is normally maintained within rigid limits1–3. Although it is not clear that this regulation fits a strict negative feedback pattern, animals do maintain a relatively constant body adiposity4. It has been postulated that this regulation is mediated by some signal which informs centres controlling food intake, probably located in the brain, as to the present state of adiposity5,6. The identity of the signal is unknown, but the direct correlation between body adiposity and basal insulin levels in the plasma7–9, suggests insulin as a possible candidate. This hormone is present in the cerebrospinal fluid (CSF) of many species10–13, and is a slow integral over time of the level within the plasma14. Thus, the level of insulin in the CSF is relatively resistant to short-term plasma fluctuations of insulin. Obese humans have higher levels of CSF insulin than lean controls and the CSF insulin level of both obese and lean humans is reduced proportionately after a prolonged fast15. We have therefore postulated16 that the feedback system responding to body adiposity uses the concentration of insulin in the CSF as a major signal. Additional support for such a role is found in recent reports that insulin receptors are present in several regions of the brain and spinal cord17–20. We now present additional evidence for our hypothesis by showing that in baboons the infusion of exogenous insulin into the CSF elicits a reliable and predictable decrease in food intake and body weight.
TL;DR: It is concluded that X-ray diffraction can provide the spatial distribution of the dynamic features of a protein.
Abstract: X-ray diffraction at four temperatures from 220 to 300 K coupled with crystallographic refinement yields the mean-square displacements and conformational potentials of all 1,261 non-hydrogen atoms of metmyoglobin. The results are interpreted to indicate a condensed core around the haem, semi-liquid regions towards the outside and a possible pathway for ligands. It is concluded that X-ray diffraction can provide the spatial distribution of the dynamic features of a protein.
TL;DR: The rare earth elements (REE) have been mobilised and fractionated during supracrustal alteration of the Torrongo granodiorite as mentioned in this paper, and the residual products are especially depleted in the heavy REE.
Abstract: The rare earth elements (REE) have been mobilised and fractionated during supracrustal alteration of the Torrongo granodiorite. Compared with the parent granodiorite, incipiently and moderately altered rocks are particularly enriched in the heavy REE, while the extremely altered residual products are especially depleted in the heavy REE. Mobilisation of the REE probably results from pH changes of soil and ground waters as they encounter different chemical environments while fractionation may largely result from mineralogical controls. Submarine and subaerial weathering processes may affect REE similarly, producing intensively weathered materials appreciably depleted in the REE. Spilitisation and hydrothermal alteration processes may affect basaltic rocks in much the same way as do weathering processes.
TL;DR: In this article, a cosmological test that is a sensitive estimator of Λ is proposed, which involves no correction for evolutionary effects and hints at the statistical problem that its realisation entails.
Abstract: The cosmological constant has recently been questioned because of difficulties in fitting the standard Λ=0 cosmological models to observational data1,2. We propose here a cosmological test that is a sensitive estimator of Λ. This test is unusual in that it involves no correction for evolutionary effects. We present here the idealised conception of the method, and hint at the statistical problem that its realisation entails.
TL;DR: The neuronal structure and connectivity underlying receptive field organisation of cells in the cat visual cortex have been investigated using a micropipette filled with a histochemical marker to visualise the dendritic and axonal arborisations of functionally identified neurones.
Abstract: The neuronal structure and connectivity underlying receptive field organisation of cells in the cat visual cortex have been investigated. Intracellular recordings were made using a micropipette filled with a histochemical marker, which was injected into the cells after their receptive fields had been characterised. This allowed visualisation of the dendritic and axonal arborisations of functionally identified neurones
TL;DR: The complete nucleotide sequence of hepatitis B virus genome (subtype ayw) cloned in Escherichia coli has been determined using the Maxam and Gilbert method and the dideoxynucleotide method.
Abstract: The complete nucleotide sequence of hepatitis B virus genome (subtype ayw) cloned in Escherichia coli has been determined using the Maxam and Gilbert method and the dideoxynucleotide method. This sequence is 3,182 nucleotides long. Location of the nonsense codons shows that the coding capacity of the L chain is larger than the coding capacity of the Schain. Eight open regions, able to code for polypeptide chains larger than 100 amino acids, have been located. Region 6, which is the largest, covers more than 80% of the genome. The gene S which codes for polypeptide I of the Hbs Ag and was previously located between coordinates 95.1 and 73.6 is contained in region 7.
TL;DR: Growth rates of natural phytoplankton populations in oceanic waters may be near maximal and hence non-nutrient limited, but the uniformly low biomass and residual nutrient levels in such waters does not preclude the possibility of high growth rates because Zooplankon grazing and nutrient regeneration within the euphotic zone may keep this highly dynamic system in a balanced state.
Abstract: The chemical composition of oceanic phytoplankton (by atoms) typically occurs in the proportions C106 N16 P1. Yet, in laboratory growth conditions these proportions are only observed for marine phytoplankton at high growth rates when non-nutrient limitation is approached. Thus growth rates of natural phytoplankton populations in oceanic waters may be near maximal and hence non-nutrient limited. The uniformly low biomass and residual nutrient levels in such waters does not preclude the possibility of high growth rates because Zooplankton grazing and nutrient regeneration within the euphotic zone may keep this highly dynamic system in a balanced state.
TL;DR: A yeast DNA sequence that behaves as a chromosomal replicator, ars1 (autonomously replicating sequence), has been isolated and allows autonomous replication of all co-linear DNA.
Abstract: A yeast DNA sequence that behaves as a chromosomal replicator, ars1 (autonomously replicating sequence), has been isolated. On transformation, ars1 allows autonomous replication of all co-linear DNA. The replicator can integrate into other replication units and can function in multimeric form. The 850-base pair ars1 element has no detectable homology to other yeast sequences. Such replicator-containing plasmids can be used for the isolation of DNA sequences in yeast cells as well as for the study of chromosomal DNA replication.
TL;DR: It is shown that similar events occur in the guinea pig perfused lung before inhibition by steroids of phospholipase A2 activity (and thus TXA2 generation), and a steroid-induced factor is discovered which mimics the anti-phospholipases effects of these anti-inflammatory agents.
Abstract: ASPIRIN prevents prostaglandin (PG) generation by directly inhibiting the cyclo-oxygenase enzyme responsible for PG biosynthesis1–3. In addition, there is now conclusive evidence that anti-inflammatory steroids can also prevent PG generation4–13. Unlike the aspirin-like drugs, steroids have no anti-cyclo-oxygenase activity but exert their action by preventing the release from phospholipids of the fatty acid substrates required for PG biosynthesis4–9,12,13. We have shown that stimulation of thromboxane A2 (TXA2) release by agents such as histamine, 5-hydroxytryptamine and rabbit aorta contracting substance-releasing factor (RCS–RF) (but not arachidonic acid) is inhibited by anti-inflammatory steroids, and that their potency in this action closely parallels their anti-inflammatory activity12,13. Furthermore, their mechanism of action involves the inhibition of phospholipase A2 activity, and thus of arachidonate release within the lung12,13. In several other tissues, the mechanism of steroid hormone action depends on the combination of thesteroid with a cytosolic receptor protein, the translocation of this drug–receptor complex to the nucleus and the initiation of protein biosynthesis14–16. We now show that similar events occur in the guinea pig perfused lung before inhibition by steroids of phospholipase A2 activity (and thus TXA2 generation). We have discovered a steroid-induced factor which mimics the anti-phospholipase effects of these anti-inflammatory agents.
TL;DR: The isolation, structure determination and biological activity of this new plant growth promoter, named (22R, 23R, 24S)-2α-3α,22,23-tetrahydroxy-24-methyl-6,7-s-5α-cholestano-6-7-lactone or brassinolide is reported.
Abstract: Extracts of Brassica napus L. (rape) pollen (family, Cruciferae) have been reported to produce a novel growth-promoting effect when applied to young pinto bean plants1,2. Fractions that are active in the bean second-internode assay3 give rise to both increased cell elongation and cell division4. The validity of these early reports has been questioned because biological activity was not correlated with any one pure compound5. Subsequently, we showed that isolation of the growth promoter was complicated by the presence of chromatographically similar, inactive components that were identified as 6-D-glucopyranosyl esters of long-chain fatty acids6. We now report the isolation, structure determination and biological activity of this new plant growth promoter, named (22R, 23R, 24S)-2α-3α,22,23-tetrahydroxy-24-methyl-6,7-s-5α-cholestano-6,7-lactone or brassinolide (Fig. 1).
TL;DR: It is demonstrated that, after 3 weeks, most of the Langerhans cells in parental skin which had been transplanted on to F1 hybrids were of recipient origin whereas keratinocytes remained of donor origin; this indicates that the LC are derived from a mobile pool of cells.
Abstract: Langerhans cells constitute a morphologically well characterised subpopulation (3--8%) of mammalian epidermal cells which, in contrast to the bulk of epidermal cells, bear Fc-IgG and C3 receptors, express immune response-associated (Ia) antigens and function as antigen-presenting cells and allogeneic stimulatory cells to primed T lymphocytes. The ontogeny of Langerhans cells has been a subject of considerable debate since their discovery. Although some studies suggest that Langerhans cells are of mesenchymal as opposed to neural or melanocytic origin, direct evidence for this has not been presented. In this study we demonstrate that, after 3 weeks, most of the Langerhans cells (LC) in parenteral skin which had been transplanted on to F1 hybrids were of recipient origin whereas keratinocytes remained of donor origin; this indicates that the LC are derived from a mobile pool of cells. Furthermore, in studies of skin from radiation-induced bone marrow chimaeric animals we found that, depending on the strain combination, up to 80% of the epidermal LC were derived from the bone marrow of the donor animals.
TL;DR: Difficulties arise in describing these two QSOs as two distinct objects and the possibility that they are two images of the same object formed by a gravitational lens is discussed.
Abstract: 0957 + 561 A, B are two QSOs of mag 17 with 5.7 arc s separation at redshift 1.405. Their spectra leave little doubt that they are associated. Difficulties arise in describing them as two distinct objects and the possibility that they are two images of the same object formed by a gravitational lens is discussed.
TL;DR: It is reported here the widespread occurrence of a small, marine, chroococcalean cyanobacterium belonging to the genus Synechococcus.
Abstract: IN marked contrast to their freshwater counterparts, marine planktonic cyanobacteria are restricted to a few nostocalean genera, of which only Trichodesmium is capable of forming extensive water blooms1–3. We report here the widespread occurrence of a small, marine, chroococcalean cyanobacterium belonging to the genus Synechococcus.
TL;DR: The worldwide inventories of the natural and anthropogenic sources and emissions of airborne cadmium, copper, lead, nickel and zinc are presented here.
Abstract: FEW (if any) recent studies on the atmospheric cycle of trace metals have considered the flux of the metals into the atmosphere on a global scale. Information on worldwide emissions is needed to assess the transboundary movement of pollutant metals and to validate models of the global atmospheric circulation patterns. The worldwide inventories of the natural and anthropogenic sources and emissions of airborne cadmium, copper, lead, nickel and zinc are presented here. The data summarised here are taken from very detailed studies published elsehwere1–5.
TL;DR: The authors have isolated a calcium-dependent regulatory protein from macrophages and call it gelsolin, providing a possible link to abundant indirect evidence implicating calcium in the regulation of locomotion, secretion and endocytosis.
Abstract: The peripheral cytoplasm of macrophages is involved in the control of locomotion, secretion and endocytosis, events common to many eukaryotic cells. During these activities, the cortical cytoplasm, which contains numerous actin filaments1,2, appears to undergo reversible gel–sol transformations3: cycles of gelation and solation are demonstrable in suitably prepared macrophage extracts, and the gels contain tangled actin filaments4. These changes in consistency of cytoplasmic actin may regulate motile events in the macrophage periphery. Calcium in micromolar concentrations prevents gelation of crude macrophage cytoplasmic extracts4, providing a possible link to abundant indirect evidence implicating calcium in the regulation of locomotion, secretion and endocytosis5. Similar calcium-sensitive gelation phenomena occur in crude cell extracts from diverse cell types and may have a relevance for control of cell movements in general6–11. Actin gelation results from the cross-linking of actin filaments (F-actin) by other proteins. In macrophages, a high molecular weight actin-binding protein (ABP) is the principal actin cross-linking protein12. Cross-linking of actin by these purified actin-binding proteins, however, is insensitive to changes in the calcium concentration4,12, so that another factor must mediate the expression of a calcium effect. We have now isolated such a calcium-dependent regulatory protein from macrophages and call it gelsolin.
TL;DR: This hypothetical structure and gel-blotting analysis of total embryo and myeloma DNA suggest that the somatic recombination may be accompanied by excision of an entire DNA segment between a V gene and a J DNA segment, which may generate antibody diversity by modulation of the precise recombination sites.
Abstract: The entire nucleotide sequence of a 1.7-kilobase embryonic DNA fragment containing five joining (J) DNA segments for mouse immunoglobulin kappa chain gene has been determined. Each J DNA segment can encode amino acid residues 96--108. Comparison of one of the five J DNA sequences with those of an embryonic variable (V) gene and a complete kappa chain gene permitted localisation of a precise recombination site. The 5'-flanking regions of J DNA segments could form an inverted stem structure with the 3'-non-coding region of embryonic V genes. This hypothetical structure and gel-blotting analysis of total embryo and myeloma DNA suggest that the somatic recombination may be accompanied by excision of an entire DNA segment between a V gene and a J DNA segment. Antibody diversity may in part be generated by modulation of the precise recombination sites.