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C J Lumsden

Publications and source records attributed to C J Lumsden.

30 records · Page 2Linked to original sources
PubMed1988

In vivo characterization of insulin uptake by dog renal cortical epithelium.

In vivo 125I-labeled insulin uptake by dog renal tubular epithelium was studied using the single-pass multiple indicator dilution (MID) method and analyzed by a computer-assisted model of transcapillary exchange and substrate-cell interaction. Anesthetized dogs received an intrarenal arterial bolus of multiple tracers: [3H]dextran greater than 70 kDa (plasma reference), [14C]inulin (extracellular reference), and 125I-insulin. Rapid serial sampling of the renal venous and urine outflows was performed. The renal venous outflow curves of 125I-insulin fell below [14C]inulin implying postglomerular extraction and antiluminal membrane (ALM) uptake. The fractional urine recovery of 125I-insulin was less than 0.03, indicating luminal tubular uptake of filtered hormone. After intravenous infusion of unlabeled insulin, repeat MID runs with tracer revealed saturable ALM uptake as evidenced by the 125I-insulin renal venous outflow curves approaching [14C]inulin. Luminal tubular uptake was unchanged and therefore unsaturable. The 125I-insulin renal venous data were studied using three mathematical models, incorporating postglomerular reversible binding, irreversible binding or transport. The best fit was obtained using the transport model. The modeling analysis is consistent with either uptake into a virtual epithelial membrane space (i.e., insulin never enters the cell but binds to or is distributed along the ALM) or insulin actually enters the intracellular compartment. In vivo uptake of 125I-insulin ALM is characterized by a Km of 15.44 nM.

Animals↗
PubMed1986

Gene-culture coevolution of complex social behavior: human altruism and mate choice.

The hypothesis is examined that genes bias the development of complex social behavior in one direction over alternatives. Studies of altruism and political attitudes in twins estimate that approximately 50% of the variance is associated with direct genetic inheritance, virtually 0% with the twin's common family environment, and the remainder with each twin's specific environment. Studies of human marriages show that spouses choose each other on the basis of similarity, assorting on the most genetically influenced of a set of homogeneous attributes. These data imply a genetic canalization of social influences such that, within the constraints allowed by the total spectrum of cultural alternatives, people create environments maximally compatible with their genotypes.

Altruism↗
PubMed1986

Exchange of multiple indicators across renal-like epithelia: a modeling study of six physiological regimes.

Multiple indicator dilution (MID) provides a means of quantifying the unidirectional steady-state fluxes of in vivo tracer movement within organs. In this report a MID model of tracer exchange across renal-like epithelia is developed in mathematical form. Six regimes of epithelial transport function are defined on the basis of the relative sizes of the tracer fluxes. Evidence for the existence of each regime has previously been obtained empirically. These are net secretion, net reabsorption, kinetic sink, antiluminal drive, antiluminal equilibration, and antiluminal trapping. By means of the mathematical model, the indicator dilution properties of the six regimes are compared. The principal similarities and differences among the regimes are documented and related to the physical basis of the transport processes. The findings suggest that over a wide range of physiologically meaningful flux magnitudes the functional regimes can be distinguished via existing empirical methods of MID. The model provides an improved basis for carrying out these distinctions in specific applications.

Animals↗
PubMed1985

Color categorization: a possible concordance between genes and culture.

A marked correspondence is found to relate the categories of infant wavelength discrimination and the ethnographic distribution of adult color terms. The structure of the infant category system accounts for at least 75% of the variance in the world ethnographic categories (P less than 0.001). Such a correspondence is predicted to be favored by natural selection when perceptual mechanisms interact with their associated cultural traits.

Adult↗
PubMed1984

Computational analysis of models for cotransport.

The order of substrate interaction with a cotransport carrier is studied by numerically fitting theoretical models to empirical data for a Na+-D-glucose pathway. Our analysis is based on a least-squares minimization routine developed at CERN, and uses data derived from tracer flux of substrate under equilibrium exchange conditions. Random, Ordered mirror, and Ordered glide models are considered and the applicability of both Random and Glide systems to the experimental observations is demonstrated. A more detailed study of the Glide model provides an estimation of the relative values of the individual rate constants describing each kinetic step in the mechanism. We argue that parameterization of competing models can result in tests which will distinguish between them, even when these contain many unknowns in the proposed structure of the kinetic mechanism. The essence of this means of model discrimination is the ability to find a single set of parameter values that fits a variety of experimental observations. The ability to obtain numerical estimates of obtain numerical estimates of individual rate constants is also a useful tool in investigation of the kinetic fine structure of the carrier. For the data at hand we conclude that a complete parameterization of the Glide model cannot be attained, possibly due to a heterogeneity in the temperature at which the experiments have been performed. Three solutions to the Glide model are presented, each of which corresponds to a fit of the Glide model to a subset of the experimental data.

Biological Transport↗
PubMed1980

Gene-culture translation in the avoidance of sibling incest.

A preliminary analysis is made of the relation between the epigenetic rules of brother-sister incest avoidance, which operate during individual development, and the frequency of occurrence of this form of incest among cultures.

Journal Article↗
PubMed1980

Translation of epigenetic rules of individual behavior into ethnographic patterns.

The pivotal process in gene-culture coevolution is envisaged to be the evolution of behavioral epigenesis. From premises based on the known properties of enculturation and usage diffusion within societies, a probabilistic model is constructed to estimate the degree to which rules governing individual development canalize ethnographic curves (the probability density distributions of societies engaged in varying patterns of usage). The results indicate that under most conceivable conditions the translation from individual epigenesis to social pattern is amplified, to an extent that differences in bias too faint to be detected in ordinary developmental studies can generate conspicuous variation in the ethnographic curves. Examples are cited of sufficiently biased epigenesis in human behavior.

Journal Article↗