Showing papers in "Nature in 1973"
TL;DR: In this article, a series of monodisperse suspensions of the same chemical composition but of rather different particle sizes was used to study particle size dependent phenomena, such as Brownian motion, light scattering, sedimentation and electrophoresis of small particles.
Abstract: MANY properties of colloids and suspensions depend on the particle size. Series of monodisperse suspensions of the same chemical composition but of rather different particle sizes may be used to study particle size dependent phenomena, such as Brownian motion, light scattering, sedimentation and electrophoresis of small particles. We have used such series to demonstrate the increased tendency of metal suspensions to coagulate in the presence of electrolytes as the radius of the particles increases1.
7,739 citations
TL;DR: Game theory and computer simulation analyses show, however, that a “limited war” strategy benefits individual animals as well as the species.
Abstract: Conflicts between animals of the same species usually are of “limited war” type, not causing serious injury. This is often explained as due to group or species selection for behaviour benefiting the species rather than individuals. Game theory and computer simulation analyses show, however, that a “limited war” strategy benefits individual animals as well as the species.
5,524 citations
TL;DR: An unsuspected abnormality in all cells from the nine patients with chronic myelogenous leukaemia has been detected with quinacrine fluorescence and various Giemsa staining techniques, suggesting that there may be a hitherto undetected translocation between the long arm of 22 and thelong arm of 9, producing the 9q+ chromosome.
Abstract: CELLS from nine consecutive patients with chronic myelogenous leukaemia (CML) have been analysed with quinacrine fluorescence and various Giemsa staining techniques. The Philadelphia (Ph1) chromosome in all nine patients represents a deletion of the long arm of chromosome 22 (22q−)1,2. An unsuspected abnormality in all cells from the nine patients has been detected with these new staining techniques. It consists of the addition of dully fluorescing material to the end of the long arm of one chromosome 9 (9q+). In Giemsa-stained preparations, this material appears as an additional faint terminal band in one chromosome 9. The amount of additional material is approximately equal to the amount missing from the Ph1 (22q−) chromosome, suggesting that there may be a hitherto undetected translocation between the long arm of 22 and the long arm of 9, producing the 9q+ chromosome.
4,103 citations
TL;DR: An image of an object may be defined as a graphical representation of the spatial distribution of one or more of its properties as a result of interaction with a matter or radiation field characterized by a wavelength comparable to or smaller than the smallest features to be distinguished.
Abstract: AN image of an object may be defined as a graphical representation of the spatial distribution of one or more of its properties. Image formation usually requires that the object interact with a matter or radiation field characterized by a wavelength comparable to or smaller than the smallest features to be distinguished, so that the region of interaction may be restricted and a resolved image generated.
3,480 citations
TL;DR: In this paper, an attempt to identify criteria with which to assess or anticipate the effect of competitive exclusion both at individual sites and in different types of vegetation is described, where the authors identify criteria for assessing or anticipating competitive exclusion.
Abstract: IN maintaining or reconstructing types of herbaceous vegetation in which the density of flowering plants exceeds 20 species/m2—the so-called “species-rich” communities, success is often frustrated by competitive exclusion. Here I describe an attempt to identify criteria with which to assess or anticipate the effect of competitive exclusion both at individual sites and in different types of vegetation.
2,242 citations
TL;DR: This method can be used for predicting and assessing possible secondary structures for recently determined RNA sequences and new experimental and theoretical results allow us to improve the method, without making it more complicated.
Abstract: A SIMPLE method for estimating the most stable secondary structure of an RNA molecule from its sequence was proposed earlier1. This method can be used for predicting and assessing possible secondary structures for recently determined RNA sequences2–4. New experimental5–8 and theoretical9, 10 results allow us to improve the method, without making it more complicated.
2,029 citations
TL;DR: The pathogenesis of metastasis begins with the invasion of tissues, blood vessels and/or lymphatics by cells originating from a primary cancer, and most tumour emboli are initially arrested in the first capillary bed encountered, but some recirculate and are trapped in other organs.
Abstract: The pathogenesis of metastasis begins with the invasion of tissues, blood vessels and/or lymphatics by cells originating from a primary cancer. Following their release into the circulation, most tumour emboli are initially arrested in the first capillary bed encountered, but some recirculate and are trapped in other organs. After their initial arrest, tumour cells must invade the parenchyma, establish a micro-environment, escape host defence mechanisms and finally grow into secondary tumours1.
1,367 citations
TL;DR: If this class of mutant substitution is important, it can be predicted that the evolution is rapid in small populations or at the time of speciation5.
Abstract: RECENT advances in molecular genetics have had a great deal of influence on evolutionary theory, and in particular, the neutral mutation-random drift hypothesis of molecular evolution1,2 has stimulated much interest. The concept of neutral mutant substitution in the population by random genetic drift can be extended to include random fixation of very slightly deleterious mutations which have more chance of being selected against than of being selected for3,4. If this class of mutant substitution is important, we can predict that the evolution is rapid in small populations or at the time of speciation5. Here I shall organize the observed facts which indicate that this class is in fact important.
1,000 citations
TL;DR: It is suggested that a link in excitation-contraction coupling involves the movement of a fixed amount of charge free to move between different locations across the membrane.
Abstract: It is suggested that a link in excitation-contraction coupling involves the movement of a fixed amount of charge free to move between different locations across the membrane.
927 citations
TL;DR: POULTRY are a considerable reservoir of salmonellae and a common source of infection in human Salmonella epidemics, and in 1971 a severe outbreak ofSalmonella infantis infection occurred among Finnish broiler flocks.
Abstract: POULTRY are a considerable reservoir of salmonellae and a common source of infection in human Salmonella epidemics1. In 1971 a severe outbreak of Salmonella infantis infection occurred among Finnish broiler flocks, and 277 human cases2 were diagnosed as caused by the same serotype. The broiler industry suffered serious losses through confiscation of broiler meat and elimination of infected birds.
Abstract: This article presents evidence that the Mediterranean Sea was a desiccated deep basin some 6 million years ago.
TL;DR: It is shown here that existing evidence favours a model in which each filament rotates, which is commonly believed that each filament propagates a helical wave3.
Abstract: IT is widely agreed that bacteria swim by moving their flagella, but how this motion is generated remains obscure1,2. A flagellum has a helical filament, a proximal hook, and components at its base associated with the cell wall and the cytoplasmic membrane. If there are several flagella per cell, the filaments tend to form bundles and to move in unison. When viewed by high-speed cinematography, the bundles show a screw-like motion. It is commonly believed that each filament propagates a helical wave3. We will show here that existing evidence favours a model in which each filament rotates.
TL;DR: In this article, rare earth and minor element concentration variations in basalt recently erupted along the postglacial Reykjanes Ridge Axis and its northward extension over Iceland reflect the existence, spatial influence, and primordial nature of the Iceland hot mantle plume.
Abstract: Systematic rare earth and minor element concentration variations in basalt recently erupted along the post-glacial Reykjanes Ridge Axis and its northward extension over Iceland reflect the existence, spatial influence, and primordial nature of the Iceland hot mantle plume.
TL;DR: The authors describe a relationship between the distribution of opiate receptors and of neurotransmitters that varies dramatically throughout the human and monkey brain.
Abstract: The frequency of opiate receptors varies dramatically throughout the human and monkey brain. The authors describe a relationship between the distribution of opiate receptors and of neurotransmitters.
TL;DR: In this article, Bernhard et al. proposed that the function of this structure might be to suppress reflexions by effectively proving a graded transition of refractive index between the air and the cornea.
Abstract: THE problem of surface reflexion from lenses has led1 to the development of multilayer interference structures which can suppress the reflexion from glass surfaces by a factor of 10 or more throughout the visible spectrum. But observations on the corneas of nocturnal insects indicate that nature may have anticipated the problems2. Electron microscope studies of the corneal lenses of moths reveal that the outer surface is covered in a regular array of conical protuberances, typically of about 200 nm height and spacing. Bernhard2 proposed that the function of this structure might be to suppress reflexions by effectively proving a graded transition of refractive index between the air and the cornea. The proposal was substantiated by measurements with microwave radiation reflected from a model of the array, scaled up appropriately for the longer wavelengths.
TL;DR: This report will demonstrate the existence of clonal segregation of developmental pathways in the wing (dorsal mesothoracic) disk of Drosophila and show that these cell lineages are fixed.
Abstract: MOSAICS generated by genetic methods or by technical operations have been used to investigate cell autonomous and non-autonomous developmental processes. The use of cell autonomous genetic markers allows us to label cells for analysis of morphogenetic processes and to follow cell lineages in development1–4. If it can be shown that these cell lineages are fixed, a genetic analysis of development can be focused on how genes control clonal processes. This report will demonstrate the existence of clonal segregation of developmental pathways in the wing (dorsal mesothoracic) disk of Drosophila.
TL;DR: The use of thermoluminescence (TL) for dating archaeological ceramics is well established as mentioned in this paper, and the TL ages obtained were significantly lower than the accepted ages of the lava flows, some by an order of magnitude.
Abstract: THE use of thermoluminescence (TL) for dating archaeological ceramics is well established1. Recently we have been attempting to use similar techniques to date volcanic lava from geologically recent flows (5,000 to 50,000 yr old), by measuring the TL from the feldspars present. These included rhyolites from near Naples and basalts from Iceland and the Massif Central region of France; the latter were of particular interest because palaeomagnetic and potassium argon age measurements and related radiocarbon dates in the Chaine des Puys region have suggested a geomagnetic polarity excursion of the Earth's magnetic field within the past 50,000 yr (ref. 2). The basalts contained the plagioclase feldspars labradorite, andesine and bytownite, and the rhyolites contained the alkali feldspar sanidine. All of the TL ages obtained were significantly lower than the accepted ages of the lava flows, some by an order of magnitude.
TL;DR: Evidence is presented here for the control of morphogenesis by positional information specified by an autonomous timing mechanism that operates in a “progress zone” at the tip of the limb bud.
Abstract: Pattern formation by the cells of a growing organism depends on coordination of changes in space and time. Evidence is presented here for the control of morphogenesis by positional information specified by an autonomous timing mechanism that operates in a “progress zone” at the tip of the limb bud.
TL;DR: In this article, the authors found evidence for the processing of information about the locus of light stimuli presented in areas of the visual field which are "blind" by the traditional definition.
Abstract: IT is generally believed that total destruction of visual cortex and optic radiations in man should lead to blindness, and that regional (subtotal) destruction should correspondingly produce circumscribed areas of blindness (“scotomata”) in the visual field1. Such areas of blindness are defined by a patient's inability to detect and report visual stimuli projected into the affected region. Standard methods of visual field testing (perimetry) suggest that such scotomata may be “absolute”, that is the patient seems to be unable to distinguish between the presence and absence of visually presented targets whenever they are presented in the scotomatous area. Suspecting that the response of the visual system may depend on the task requirements, we used a technique which requires a localizing response from the patient2, in addition to clinical perimetry. As a result, we have found evidence for the processing of information about the locus of light stimuli presented in areas of the visual field which are “blind” by the traditional definition.
TL;DR: Examining children with developmental aphasia demonstrated inferior discrimination of sound quality to which a sequencing difficulty could be secondary and suggested that auditory perceptual deficits, particularly of sequencing, may be the primary dysfunction.
Abstract: SOME otherwise normal children fail to learn to speak and are designated developmental aphasics. Several authors have suggested that auditory perceptual deficits, particularly of sequencing, may be the primary dysfunction1–4. Efron5 suggested that the left temporal lobe mediates temporal analysis and that it is the disruption of this function which is central to adult aphasia. We examined children with developmental aphasia and demonstrated inferior discrimination of sound quality to which a sequencing difficulty could be secondary.
TL;DR: By use of signal averaging techniques, small transient currents are observed which are believed to be the gating currents of the sodium channels.
Abstract: “…IT seems difficult to escape the conclusion that the changes in ionic permeability depend on the movement of some component of the membrane which behaves as though it had a large charge or dipole moment”1. With these words Hodgkin and Huxley predicted the existence of gating currents: charge movement associated with molecular rearrangements that attend the opening and closing of the ionic channels in response to changes in the membrane field. The polarity of gating current of the sodium channels can be easily predicted: following a positive step change of membrane voltage, positively charged gating particles would move outward through the membrane field from closed to open position (or negatively charged particles would move inward), yielding an outward current. On repolarization after a voltage step that opened the channels, gating current would be inward, as particles moved from open to closed position. Hodgkin and Huxley were unable to observe gating currents experimentally, and concluded that the density of ionic channels in the membrane must be low. A later attempt by Chandler and Meves2 to detect such currents was also unsuccessful, and they estimated that there are less than 100 sodium channels μm−2, a prediction that has been borne out by later estimates of sodium channel density3,4. We report here that by use of signal averaging techniques, we have observed small transient currents which we believe are the gating currents of the sodium channels.
TL;DR: The fact that labelled calcium can be seen to enter sensitized cells during histamine secretion in the presence of antigen suggests that the entry of calcium into the mast cell may be the trigger for the release of histamine.
Abstract: Mast cells can be induced to secrete histamine by an ionophore, the action of which depends on the presence of calcium within a specific concentration range. The fact that labelled calcium can be seen to enter sensitized cells during histamine secretion in the presence of antigen suggests that the entry of calcium into the mast cell may be the trigger for the release of histamine.
TL;DR: Rodríguez et al. as mentioned in this paper investigated crystal formation by soil bacteria cultured on solid media and found that they can form aragonite (a form of CaCO3) crystals in cultures of Pseudomonas.
Abstract: CERTAIN bacteria form crystals from the solutes in their aqueous environment, and some authors have associated this activity with the extensive deposits of CaCO3 in such places as the Grand Bahama, in spite of the belief that physicochemical effects, such as rapid changes in pH, salinity and temperature, are responsible1–4. Drew5 isolated a denitrifying bacterium able to form CaCO3 crystals in liquid media and named it “Bacterium calcis” (later named Pseudomonas calcis6). Greenfield7 obtained aragonite (another form of CaCO3) crystals in cultures of Pseudomonas in an artificial seawater medium containing Na2CO3 or (NH4)2CO3. Buck and Greenfield reported the same result with marine yeast, and claimed that calcium crystals resulted from the accumulation of calcium deposits on the surface of the cells8. McCallum and Guhathakurta9 observed calcium carbonate deposition by marine bacteria isolated from Bahama Island sediments, and when these were cultured in different media aragonite crystals formed. Shinano10 described many marine bacteria able to form crystals in liquid media. Ramos-Cormenzana11 has also reported crystal formation by soil bacteria in solid media. This, together with the knowledge that previous research concerned only marine bacteria in liquid media, stimulated us to investigate crystal formation by soil bacteria cultured on solid media.
TL;DR: The inhibition of transport was also observed in membrane vesicles, even when they were derived from organisms for which growth and transport are not affected by the larger inhibitors.
Abstract: Most antimicrobial food additives are lipophilic acids which prevent growth by inhibiting the transport of substrate molecules into cells. The inhibition of transport was also observed in membrane vesicles, even when they were derived from organisms for which growth and transport are not affected by the larger inhibitors.
TL;DR: McCarthy as discussed by the authors estimated that the integrated production of CCl2F2 and CCl3F, the two principal compounds of the class, was about one megaton of each in mid 1971; they are unusually stable chemically and only slightly soluble in water and might therefore persist and accumulate in the atmosphere.
Abstract: DURING the past few decades the production of the chlorofluorocarbons, the propellant solvents for aerosol dispensers, has grown exponentially. R. L. McCarthy (unpublished) estimates that the integrated production of CCl2F2 and of CCl3F, the two principal compounds of the class, was about one megaton of each in mid 1971; they are unusually stable chemically and only slightly soluble in water and might therefore persist and accumulate in the atmosphere. Preliminary tests in 1970 showed that CCl3F was present in the air over Ireland at concentrations exceeding 10−11 by volume1.
TL;DR: Hydrodynamical effects appear to be important to obligate schooling species, and the endurance of the fish is found to be increased twice to six times when in schools.
Abstract: VARIOUS explanations for fish schooling have been put forward1, including the rate of predation2,3, social4 and genetic1 factors. Hydrodynamical effects appear to be important to obligate schooling species. They commonly show migratory movements4, and the schools usually consist of individuals of the same size range6,7 (with similar cruising speeds, as these depend on body-length) swimming in synchronization and in regular arrays8. The endurance of the fish is found to be increased twice to six times when in schools16. These factors may have practical significance, as many commercially important species are found in schools and knowledge of their possible speed and stamina can help design efficient fishing gear.
TL;DR: This work defines this behavioural sequence as satiety: its physiological basis is unknown, and states that within 10 min of starting to eat, a rat stops eating, grooms for a short period, then usually sleeps.
Abstract: WITHIN 10 min of starting to eat, a rat stops eating1, grooms for a short period, then usually sleeps. We define this behavioural sequence as satiety: its physiological basis is unknown. Beaumont2 presented the first evidence that the presence of food in the gut is important in generating satiety signals. In 1949, Janowitz and Grossman3 confirmed Pavlov's observation4 that oesophagostomized dogs, in which no food reached the stomach or intestines, ate prolonged meals.
TL;DR: In this article, it has been suggested that pseudotachylyte material on fault planes puts an upper limit on the magnitude of shear stresses associated with earthquake faulting, which has important implications with regard to the seismic source mechanism and the nature of cataclastic rocks produced by rapid faulting.
Abstract: At depths in the crust greater than perhaps 1 km, local melting with production of pseudotachylyte should take place on fault planes during seismic faulting1,2. But, although many ancient fault zones are now exposed at erosion levels which correspond to depths of several kilometres when the faults were active, very few of them contain pseudotachylyte; it has been suggested3,4 that the general absence of this material on fault planes puts an upper limit on the magnitude of shear stresses associated with earthquake faulting. In refs 1–4 earthquake fault models with heat generated by dry frictional sliding on a single plane across which there is a constant normal stress are used. Two other factors are probably dominant in controlling the temperature rise on a fault, and the second has important implications with regard to the seismic source mechanism, and the nature of cataclastic rocks produced by rapid faulting.
TL;DR: It is proposed that heparin acts to accelerate inhibitor function by binding to antithrombin and inducing an allosteric modification in it, which renders the arginine in its reactive site more accessible to the serine in the active centre of thrombin4.
Abstract: ANTITHROMBIN III (heparin cofactor) is known to inhibit thrombin1 and Factor Xa1–3 (activated Factor X). We have purified antithrombin4 from human plasma by a series of chromatographic and electrophoretic separation techniques. The homogeneity of the final product is demonstrated by disc gel electrophoresis, SDS gel electrophoresis and immunoelectrophoresis4. Using this preparation, we have shown that antithrombin forms a 1 : 1 stoichiometric complex with thrombin which cannot be dissociated with denaturing and reducing agents. Addition of heparin dramatically accelerates the rate of formation of this complex. Complex formation is completely dependent on an interaction between the serine active centre of thrombin and an arginine reactive site of antithrombin. Furthermore, e-amino lysyl groups of antithrombin serve as binding sites for the highly negatively charged heparin. Based on these data and other evidence, we have proposed that heparin acts to accelerate inhibitor function by binding to antithrombin and inducing an allosteric modification in it, which renders the arginine in its reactive site more accessible to the serine in the active centre of thrombin4.