An approach to a physico-chemical model of olfactory stimulation in vertebrates by single compounds

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.     

Co-operative response of chemically excitable membrane: I. Formulation: Unified theory of co-operativity

The lattice-model of Changeux, Thiery, Tung & Kittel (1966) was extended in order to examine the co-operative response of chemically excitable membrane and the exact mathematical correspondence to the Ising model was shown. In this model, two conformational states S and R with different affinities for the ligand are assumed to be accessible to each protomer, which is interacting with the nearest-neighbor protomers. The model is applicable to any kind of symmetrically interacting system consisting of oligomers and lattices and is an extension of previously proposed models of allosteric protein. It includes the model of Monod, Wyman, & Changeux (1965) and that of Koshland, Némethy & Filmer (1966) as the extreme cases of the oligomer. By assuming that a state-transition from S to R in a protomer is accompanied by a unit increase in conductance, the characteristics of dose-response curves of chemically excitable membrane are examined. The Hill's coefficient n_H of dose-response curve, the measure of the co-operativity, is shown to be proportional to the square of the mean fluctuation of the state function, the fraction of protomers in R state.     

Kinship and covariance

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.     

The role of migration in the genetic structure of populations in temporally and spatially varying environments II. Island Models

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.     

Pattern regulation in tergite of Drosophila: a model

Roseland & Schneiderman's (1979) observations on the presence of the intersegmental region anterior to the posterior duplications in the tergite of Drosophila, led them to postulate intercalary regeneration by shortest route to account for pattern duplications. Our observations on the absence of the intersegmental region in these posterior duplications, on the other hand, suggest that pattern duplication in Drosophila abdomen could be explained on the basis of a diffusion morphogen model. Based on the interpretations of the results of grafting experiments in Calliphora (Pearson, 1977) and cauterization studies in Drosophila (Roseland & Schneiderman, 1979), we suggest that the larval epidermal cells located between the dorsal histoblast nests could be the source of this morphogen. During normal development, this morphogen appears to be responsible for the posterior orientation of the cuticular outgrowths in the posterior half of the tergite and the differentiation of the macrochaetae, pigment band and posterior hairy region. Thus, the posteriorizing effects of the morphogen resemble those of the zone of polarizing activity (ZPA) of the developing appendages of the vertebrate embryos.     

Does a functional relationship exist between the polymerization and catalytic activity of beef liver glutamate dehydrogenase?

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.     

Complexity-stability relationship of two-prey-one-predator species system model: Local and global stability

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.     

Cotranslational cleavage of immunoglobulin light chain precursors by plasmacytoma microsomes.

Murine plasmacytoma endoplasmic reticulum which has been freed of ribosomes by EDTA treatment is capable of the cotranslational proteolytic processing of representative λ₁,λ₂, and k immunoglobulin light chain precursors. Messenger RNA fractions from the MOPC-104E, MOPC-315, and MOPC-46B tumor lines were used to direct the synthesis of the light chain precursors in a cell-free system derived from Krebs II ascites cells. The precursor cleavage activity of the plasmacytoma membranes is comparable in activity and in characteristics to that of two well-defined membrane preparations: Krebs II ascites intracellular membranes (E. Szczesna and I. Boime, 1976, Proc. Nat. Acad. Sci. USA73, 1179–1183) and EDTA-treated rough endoplasmic reticulum from canine pancreas (34., 35., J. Cell Biol.67, 852–862). The efficiency of the cleavage reaction appears to be dependent upon the precursor being utilized as a substrate. An assay suitable for a preliminary characterization of the plasmacytoma membrane preparations is described.     

A stochastic model of animal growth

The plasticity of growth of animals in time, due to the resilience of their response to the ways they can be fed, suggests the difficulty of describing growth by a stochastic model in the time domain. A model is presented which avoids this difficulty by describing growth as a Markov process in the food-consumed domain, assuming that, at conception, (1) the maximum mature weight as a number α of biomass units of mass μ, and (2) the probability B of production of a biomass unit per unit of food consumed, are specified. Constancy of α, μ and B, as the animal feeds, is the basis of the proposed Markov process. The mean growth from infancy to maturity in the food-consumed domain is then the old law of diminishing returns empirically formulated first by Spillman (1924) for cattle and swine, and confirmed by Titus, Jull &; Hendricks (1934) for fowl, and by Parks (1972) across species from mice to steers. The solution also leads to the possibility that the distribution of weights in a population of growing animals of the same species, is related to the distribution of mature weights among the individuals. An experiment by Lister &; McCance (1967) with well-fed and severely undernourished pigs, shows the stability of growth in the foodconsumed domain compared to the plasticity in the time domain. Other implications of the model are discussed.     

The Plasmodium vaughani--Complex

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.     

A general theory of chromosome pairing based on the palindromic DNA model of Sobell with modifications and amplifications

A model for chromosome pairing is presented. It is based on the presence of segments of symmetric sequences of bases (palindromes) in the DNA at specific places in the chromosome. Palindromic DNA has been characterized by Wilson &; Thomas (1974), who state that these sequences are a regular feature of eukaryotic DNA. Sobell (1972) has suggested that they may be involved in synapsis and genetic recombination. Sobell's model is modified and amplified in an attempt to develop a general theory of chromosome pairing that explains congressional pairing, synapsis, non-homologous pairing, the initiation of crossing over, and interference.     

An autoradiographic analysis of the time of appearance of neurons in the developing chick neural retina

The pattern of incorporation of [³H]thymidine into the chick neural retina has been used to establish the time and order in which different classes of neuroepithelial cells withdraw from the cell cycle and initiate migration and differentiation.The posterior pole of the retina is the first to form during development. In this region most neuroepithelial cells complete mitotic activity between the third and sixth day of incubation. Presumptive ganglion cells initiate the withdrawal process, and they are soon followed by the neuroepithelial precursors of amacrine, horizontal, and receptor cells. Bipolar cell precursors are the last to begin and the last to complete cell cycle activity. It is worthy of note, however, that, in any given region of the retina, neuroepithelial cells of all types cease mitosis in close, overlapping succession.These results are in reasonable agreement with those previously published on the chick retina by Fujita and Horii (1963), and other investigators on the mouse (Mus), killifish (Fundulus), and toad (Xenopus). The present data are also consistent with those proposals of Angevine (1970), Jacobson, 1968a, Jacobson, 1968b, Jacobson, 1970, and others that relate the cessation of mitotic activity of neuroepithelial cells to the determination of neuronal size, axon length, and the specification of neuronal connections.     

A note on the sampling theory for infinite alleles and infinite sites models

This note considers sampling theory for a selectively neutral locus where it is supposed that the data provide nucleotide sequences for the genes sampled. It thus anticipates that technical advances will soon provide data of this form in volume approaching that currently obtained from electrophoresis. The assumption made on the nature of the data will require us to use, in the terminology ofKimura (Theor. Pop. Biol.2, 174–208 (1971)), the “infinite sites” model of Karlin and McGregor (Proc. Fifth Berkeley Symp. Math. Statist. Prob.4, 415–438 (1967)) rather that the “infinite alleles” model of Kimura and Crow (Genetics49, 174–738 (1964)). We emphasize that these two models refer not to two different real-world circumstances, but rather to two different assumptions concerning our capacity to investigate the real world. We compare our results where appropriate with corresponding sampling theory of Ewens (Theor. Pop. Biol.3, 87–112 (1972)) for the “infinite alleles” model. Note finally that some of our results depend on an assumption of independence of behavior at individual sites; a parallel paper byWatterson (submitted for publication (1974)) assumes no recombination between sites. Real-world behavior will lie between these two assumptions, closer to the situation assumed by Watterson than in this note. Our analysis provides upper bounds for increased efficiency in using complete nucleotide sequences.     

Fusion of chick embryo skeletal myoblasts: interactions of prostaglandin E1, adenosine 3':5' monophosphate, and calcium influx

In the accompanying paper (J. D. David, W. M. See, and C.-A. Higginbotham, 1981, Develop. Biol.82, 297–307) we demonstrated that a net calcium influx into fusion-competent myoblasts is a requisite step in membrane fusion. Zalin and Montague, 1974, Zalin, 1977 has shown that a prostaglandin E₁ (PGE₁)-dependent transient rise in cAMP occurs 5–6 hr prior to myoblast fusion. In this communication we show that (1) the increase in intracellular cAMP precedes, and/or is independent of, the calcium influx; (2) the calcium influx is either directly or indirectly dependent on PGE₁ activity as well as PGE₁ synthesis; and (3) although the cAMP increase may be essential for fusion, it is not sufficient in the absence of calcium influx. Our experiments define fusion competency, at a minimum, as (1) the accumulation of extracellular PGE₁ receptors; (2) the accumulation of intracellular cAMP receptors; and (3) the ability to respond to a calcium influx.     

Cytogenetic study of the Endemic Malagasy lemur: Hapalemur,I. Geoffroy, 1851

The genus Hapalemur Gray, 1870 is comprised of two species: H. simus Gray, 1870 and H. griseus Link, 1795. Hapalemur griseus contains, according to Osman Hill (1953), two species: H. g. griseus (Link, 1795) and H. g. olivaceus (I. Geoffroy, 1851). Recent ecological investigation by Petter & Peyrieras (1970) has helped the discovery of a third subspecies of H. griseus in the region of Lake Alaotra. Whilst making the cytogenetic study of the genus Hapalemur, we have completed the chromosomal evolution's schema, originated by Chu & Swomley (1961).     

The absence of a growth inhibitor during the log phase of growth of Dictyostelium discoideum

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.     

The fine structure of Ameson pulvis (Microspora,Microsporida) and its implications regarding classification and chromosome cycle

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.     

Homage to the red queen. II. Coevolutionary response to enrichment of exploitation ecosystems

The model of predator-victim coevolution developed in the preceding paper (Schaffer and Rosenzweig, 1978) is used to analyze the coevolutionary response to ecosystem enrichment. It is shown that coevolution tends to oppose the destabilization that results from the enrichment itself. In the circumstance that the victims' r and K are proportional, gradual enrichment followed by coevolutionary adjustment actually enhances ecosystem stability.     

Local mate competition and the sex ratio

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.