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1.
Price's (1970) covariance theorem can be used to derive an expression for gene frequency change in kin selection models in which the fitness effect of an act is independent of the genotype of the recipient. This expression defines a coefficient of relatedness which subsumes r(Wright, 1922), b(Hamilton, 1972), ρ (Orlove &; Wood, 1978), and R(Michod &; Hamilton, 1980). The new coefficient extends the domain of Hamilton's rule to models in which the average gene frequency of actors differs from that of recipients.  相似文献   

2.
Hepatotoxic studies of xylidines differ with regard to the animal species and type of isomer. The aim of the present paper is to correlate electronic structure data and physical-chemical properties, studied by the authors during a few previous papers (Sahini & Weinberg, 1973; Sahini, Weinberg & Vasilescu 1976, Weinberg & Sahini, to be published; Weinberg & Sahini, 1980), with the hepatotoxic activity of xylidines. Two possible biochemical mechanisms are advanced by help of correlation equations.  相似文献   

3.
Parrish & Saila (1970), motivated by the experiments of Paine (1966), constructed a simple mathematical model for a two-prey-one-predator system. They were unable to find, in their model, a set of parametric values with which the three-species system can be stable, whereas a twoprey species system without a predator is unstable. Cramer & May (1972) showed that, in fact, such parametric values exist, and gave the necessary mathematical condition. I have investigated the complete conditions for the stability of the system around the equilibrium point, and show that the conditions must be more stringent than given by Cramer & May (1972). Also, it is shown that the present model can have a globally stable limit cycle in three species even when the equilibrium point is locally unstable.  相似文献   

4.
The Island Model introduced by Sewall Wright (1951) has proven to be a useful construction for studying the interaction of genetic drift, population subdivision, and mutation. Interest in the model has recently increased because of its relevance to certain questions involving the rate of differentiation of sub-populations under the neutral allele hypothesis (e.g., Smith, 1970; Latter, 1973). It is perhaps the only realistic population structure in which the test for neutrality proposed by Lewontin and Krakauer (1973) is valid (Lewontin and Krakauer, 1975). If data from natural populations is to be compared to the predictions of the Island Model, it is desirable to have an alternative model with the same migration pattern but with natural selection operating. In this paper one such model will be introduced where the stochastic element comes from random fluctuations in the environment rather than from genetic drift. The model is a direct extension of the one in the previous paper in this series (Gillespie, 1975) which dealt with a population which is subdivided into two patches with restricted migration between them.  相似文献   

5.
6.
This paper examines the conditions under which the classical inclusive fitness formulation of Hamilton (1964) provides an adequate approximation to the dynamics of gene frequency change and to conditions for genetic equilibrium, in the “additive” model of altruism between sibs of Uyenoyama and Feldman (1981). It is concluded that the classical formulation is adequate, provided that either the effect of the gene on the probability of behaving altruistically is low or the costs and benefits of altruism are small, unless the benefit/cost ratio k is very close to 2, the value that must be exceeded for altruism to be favoured. In addition, the gene for altruism must be underdominant, recessive or partially recessive in its effect on the probability of behaving altruistically, for the inclusive fitness predictions to break down significantly.  相似文献   

7.
A theory of 1f and conductance noise is given for ionic channels in nerve membrane. The theory is based on the assumption that the channels are in constant, stochastically independent, rotational motion within a fluid bilayer membrane. The resulting expression for the current noise power density S contains a conduction noise term consistent withStevens (1972) and Hill & Chen (1972) and a 1f noise term consistent with Lundstrom & McQueen (1974) and Clay & Shlesinger (1976). The expression for S also contains a third term which is the spectrum of the product of the single channel conduction noise and 1f noise correlation functions. This term is independent of the number of channels in the membrane, R. Consequently, the expression for S effectively reduces to a sum of 1f and conduction noise for R 10–100 which is in agreement with noise measurements on squid axon. The theory is applied in detail to potassium squid noise measurements of Conti, DeFelice & Wanke (1975) using the stochastic analysis of single file ion motion developed in our previous paper (Clay & Shlesinger (1976)).  相似文献   

8.
During recent years, numerous attempts have been made to correlate both quantitative (Davies &; Taylor, 1959; Engen, 1962; Beck, 1964; Engen, Cain &; Rovee, 1968; Cain, 1969; Dravnieks &; Laffoit, 1970; Laffort, 1969a,b) and qualitative (Davies, 1965; Amoore &; Venstrom, 1965; Döving, 1966a,b; Wright &; Michels, 1964; Leveteau &; MacLeod, 1969) odorous properties of single compounds to their molecular properties. These attempts have been only partially successful.In the present paper we will try to explain the several odorous properties of single compounds on the basis of the non-specific properties of odorants involved in solubility.This model is a first approach, and although it gives statistically highly significant relations, it is not as accurate as those advanced with respect to the physical and sensory dimensions of stimuli in the fields of vision and audition.We will first give the present definitions of the most suitable physicochemical parameters, and then advance quantitative and qualitative models for single compounds. Quantitative odorous properties are: odour threshold, rate of change of odour intensity with odorant concentration in the suprathreshold region, and the somewhat controversial upper odour intensity. Qualitative properties refer to odour character.  相似文献   

9.
The recent work of Cohen &; Benedek (1976) and Cohen et al. (1975, 1976) on the apparent interdependence of beef liver glutamate dohydrogenase catalytic activity and degree of polymerization is examined in the light of previously published equilibrium and kinetic results. It is shown that some of the hypotheses central to the Cohen &; Benedek (1976) model are in contradiction with existent data. Consideration of all available information leads to the conclusion that effector-induced depolymerization may simply be an incidental side reaction in the events leading to inhibition.  相似文献   

10.
This paper reviews literature on the evolutionary effects of warfare upon the hominid brain. Alexander &; Tinkle (1968) and Bigelow (1969) are found to be the first to propose that warfare was the principle evolutionary pressure that created the novel substance of the human brain, and that it acted at least from the early Pleistocene. These writers are distinguished from Darwin (1871), Keith (1947) and Wilson (1975) who saw warfare influencing the development of the brain only in historical or near-historical times.The warfare hypothesis of Alexander &; Tinkle is found to be an excellent explanation of the evolution of the human brain, but to be unsatisfactory from a biological viewpoint because they do not explain how warfare evolved in the first place, nor do they attempt to account for the apparent absence of warfare as a behavioral adaptation in species other than some eusocial insects.This author underpins the warfare hypothesis, arguing that it evolved as a necessary consequence of the circumstances of early hominids. Proficient tool use gave domination over predators and opened up new food resources, thereby diminishing two population controls. A population explosion resulted and, at critical densities, when starvation threatened, warfare was the genetically most successful behavioral adaptation. Alternative hypotheses are shown to be inadequate. Finally, the author asks why such an important hypothesis has been ignored for almost a decade.  相似文献   

11.
D J Roufa 《Cell》1978,13(1):129-138
ts14 is a temperature-sensitive Chinese hamster lung cell mutant that ceases protein biosynthesis within a short time of transfer to nonpermissive temperature (Haralson and Roufa, 1975; Roufa and Haralson, 1975; Roufa and Reed, 1975). This mutant contains a revertible, presumably a point mutation that renders its 60S ribosomal subunit thermolabile (Haralson and Roufa, 1975). In this report, we describe the relationship between the conditional ability of ts14 to synthesize protein during S phase and the replication of its DNA.After transfer to nonpermissive temperature (39°C), where ts14 synthesizes protein at a rate approximately 20 fold less than wild-type cells, synchronous cultures of the mutant performed all the processes required for replication of their DNA. During prolonged incubations at nonpermissive temperature, S phase ts14 completed approximately one round of DNA replication semi-conservatively as judged by density-transfer experiments. Pulse-labeling experiments performed on S phase cells revealed that ts14 synthesized the intermediates of discontinuous DNA replication at nonpermissive and permissive temperatures at similar rates. In these tests, the mutant was not substantially different from wild-type at both culture temperatures. At the nonpermissive temperature, however, ts14 synthesized significantly less nuclear protein (that is, histone) than did wild-type cells, and the mutant's chromatin appeared deficient in histone by virtue of its increased sensitivity to nuclease.  相似文献   

12.
In recent papers, it has been shown experimentally that the force-velocity relationship in single muscle fibres presents deviations from hyperbolicity at high values of the load (Edman, Mulieri & Scubon-Mulieri, 1976; Edman & Hwang,1977). It has been shown independently and on theoretical bases, that the parameter “b” in Hill's characteristic equation also presents deviations from its normal value at low values of the speed of shortening, i.e. at high values of the load (Morel, Pinset-Härström & Gingold, 1976). In the present paper, it is shown that both the experimental and the theoretical results are in excellent agreement and a theoretical force-velocity relationship is proposed.  相似文献   

13.
Nosema pulvisPerez, 1905, Ameson pulvis (Perez) Sprague, 1977, in muscles of the crabs Carcinus maenas and C. mediterraneus from the coast of France, was observed with the electron microscope. It was found to be structurally similar to the type species A. michaelis (Sprague, 1970). Sprague, 1977, having moniliform sporogonial plasmodia, unikaryotic sporoblasts, and hirsute sporulation stages. It is treated as distinct from A. michaelis because it has slightly smaller spores (by comparison with syntype material of A. michaelis) and appears to have fewer coils in the polar filament. The results require the removal of the genus Ameson from the family Nosematidae Labbé, 1899, where Sprague (1977) had placed it under the erroneous supposition that its sporoblasts are diplokaryotic. Ameson is transferred to family Unikaryonidae Sprague, 1977. Ameson is distinguished from PereziaLéger and Duboscq, 1909, shown by Ormieres et al. to have a similar developmental pattern, by presence of appendages on its sporulation stage. A. nelsoni (Sprague, 1950), the third, and only other species of Ameson, lacks the appendages and is transferred to genus Perezia.  相似文献   

14.
15.
Hamilton (1967) pointed out that Fisher's (1930) argument predicting an equality of the sex ratio may break down when there is local competition for mates. He considered in particular a model in which the environment consists of a number of isolated patches, each of which is colonized by a number of inseminated females; the offspring breed within the patch before dispersal. The present paper provides a careful derivation of the equilibrium sex ratio under this model in both diploid and haplo-diploid populations, and extends the model to consider the effects of having a finite number of patches.We suggest that the equilibrium sex ratio is not simply a function of the amount of inbreeding or sib-mating, as suggested by Maynard Smith (1978), but that the detailed breeding structure of the population must be taken into account.  相似文献   

16.
Uncommitted fibroblasts may exist (Kirkwood &; Holliday, 1975; Holliday, Huschtscha, Tarrant &; Kirkwood, 1977). I show that, even if such cells divide significantly faster than committed ones, the uncommitted cells would be overlooked if one uses current culture techniques. Some general guidelines for testing the model are outlined. Uncommitted cells would be useful in studying the biochemical mechanisms of aging and development.  相似文献   

17.
This answering of Poole, 1978, Poole, 1976 aims at rounding off our exchange of views, without losing the readership from an excess of toing and froing between the four contributions. So my final rejoinder only attempts at treating the general points raised by Poole (1978), rather than taking issue with all the minutiae, which would require too many quotes of quotes and counterquotes. The main nub of contention remains as to whether or not statistical fits can be meaningfully interpreted biologically.  相似文献   

18.
Plasmodium vaughaniNovy and MacNeal, 1904, Plasmodium tenueLaveran and Marullaz, 1914, and Plasmodium merulaeCorradetti and Scanga, 1972 are shown to differ. It is suggested that P. tenue and P. merulae should be considered as subspecies belonging to Plasmodium vaughani-complex.More investigations are needed for a sufficient knowledge of the complex, particularly because at least 36 species of birds harbor P. vaughani-like parasites and cover an immense geographical area in all the parts of the world.  相似文献   

19.
We have previously described simple models for active transport and have derived steady state equations for the unidirectional flux of substrate in terms of a minimal set of kinetic parameters. Here we consider how to maximize the pumping rate of a carrier-enzyme through the optimal utilization of the ATP hydrolysis reaction. The equations for net flux contain rate constants and dissociation constants and these determine the maximum velocities and affinities measured in transport kinetic analysis. It is assumed that the rate constants can evolve to the diffusion limited rate of substrate binding as has apparently occurred in the enzyme triosephosphate isomerase (Knowles & Albery, 1977). The dissociation constants of the rate limiting intermediates fit the affinities for substrates on different sides of the membrane and are dependent on the basic free energy levels (Hill, 1976) of the carrier substrate system. From our analysis it is clear that there are three ways to design a system with optimal affinities and that the choice is linked to the sequence of substrate binding. It is possible to use free energy differences of isomerization (Boyer, 1975) or ligand-ligand interactions (Weber, 1975) both of which have been described previously, but which are incorporated here into a unified treatment. A third possibility is to couple the binding step of a transported ligand to the progress of a chemical reaction as might occur, for example, if Na+ must be bound before the carrier can be phosphorylated. In this way the free energy of hydrolysis can be used not only to drive the overall pumping reaction, but also to fix differentially the affinity for substrate on either side of the membrane, as required for rapid pumping.  相似文献   

20.
When amebae of the cellular slime mold Dictyostelium discoideum Ax-3 reach stationary phase in liquid nutrient medium, an extracellular factor appears which will inhibit cell multiplication when added to a logarithmically multiplying culture (Yarger et al., 1974). Recently, Hanish (1975) presented evidence that an inhibitor also accumulated during log phase and concluded that the cessation of cell multiplication and the final cell concentration were controlled by the accumulation of this inhibitor to an effective level. We have reexamined this extremely interesting observation, but have found no evidence to support Hanish's conclusions.  相似文献   

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