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Biomedical subjects

J Hiernaux

Publications and source records attributed to J Hiernaux.

At least 37 records · Page 2Linked to original sources
PubMed1976

A model for competing polymers leading to their spatial separation.

A model for a prebiotic polymer synthesis in a gradient of monomer is presented. In the absence of mutations the synthesis of the polymer proceeds in the region where the monomer concentration is the highest. However if a favorable mutation occurs, the latter accumulates in the high concentration zone and the initial polymer is restricted to a poorer monomer concentration region.

Biological Evolution↗
PubMed1976

Blood polymorphism frequencies in the Sara Majingay of Chad.

Blood samples of 258 Sara Majingay of Ndila (Southern Chad) were analysed. Phenotype and allele frequencies are given for 22 polymorphisms. For each of these, the Majingay are compared to a number of other African populations. Then they are included in a set of 8 African populations between which multivariate distances for 25 alleles at 9 loci are computed. A two-dimensional representation is derived from the matrix of distances, and is discussed. It bears the stamp of gene flow in central Ethiopia, where an Arab admixture is evident, and in Southern Africa, where a reciprocal gene flow has marked the gene pools of Khoisan and Bantu speakers to a varying degree. The Majingay stand relatively near to the Bedik, another population of West-Central Africa. The non-Arab or non-Khoisan components of the gene pool of the other populations do not seem to differ largely from the gene pools of the West-Central African populations.

Acid Phosphatase↗
PubMed1975

Model for the positional differentiation of the cap in Acetabularia.

A late stage during the biological cycle of the unicellular alga Acetabularia is the differentiation of a cap at the apical end of the stalk. A minimal model of the spatio-temporal regulation of this event is proposed on the basis of biological data available and current hypotheses. This involves the interaction between a diffusing inhibitor specific to the translation of cap mRNAs and a graded distribution of these messengers. The model accounts for delayed protein synthesis which occurs preferably at the apex and is likely to initiate the formation of the cap. The biological and theoretical implications are discussed.

Acetabularia↗
PubMed1975

Climate and the weight/height relationship in sub-Saharan Africa.

25 populations of the rain forest and 44 of the open country, all descended from the West-Central African stock which lived in the latter biome, are compared for body weight and height. On a log weight/height diagram, the 69 populations cluster along a straight line which intersects the lines of equal body weight/surface ratio: the shorter the body size, the lower the ratio tends to be. The rain forest populations are concentrated in the lower part of the bivariate distribution. The shortest one, the Mbuti Pygmies, has a very low ratio despite a relatively heavy weight. The shorter stature of the rain forest populations seems to be largely genetic in origin; it probably results from selective pressure exerted by the thermal stres in this hot and wet biome where sweating is of low thermolytic efficiency. The amount of reduction of adult stature depends for a large part on the number of generations spent in the forest by the population. Line A (in figure 1) is similar to a growth trend. The 69 populations differ genetically by the target that growth has to reach on a common log weight/height trend line. They achieve this differentiation through different speeds of growth.

Adaptation, Physiological↗
PubMed1974

Models for positional information and positional differentiation.

It is commonly thought that the formation of patterns in developing organisms is due to the existence of a gradient of a morphogen that determines the fate of cells as a function of position in the organism. A model is presented based on a molecular mechanism where the gradient is established by the active transport of a morphogen between source and sink. The cellular differentiation and the subsequent spatial pattern formation results from the interaction of this morphogen with the genetic regulatory mechanisms of cells. Some properties of the model are given and discussed in relation to grafting experiments in hydra.

Animals↗
PubMed1967

Adaptation and race.

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Adaptation, Biological↗