The triangle inequality in balanced genetical polymorphisms.

A simplified derivation of the "triangle inequality," first obtained by Lewontin, Ginzburg and Tuljapurkar (1978), is presented.

Sulfalene with pyrimethamine and chloroquine with pyrimethamine in single-dose treatment of Plasmodium falciparum infections. A trial in a rural population in northern Nigeria.

A comparative trial was carried out in northern Nigeria of the ability of the drug combinations chloroquine-pyrimethamine and sulfalene-pyrimethamine to clear the peripheral blood stream of asexual forms of P. falciparum within 7 days. The reappearance of asexual P. falciparum forms within the 70-day follow-up period and the occurrence of vomiting during the 2-3 hours following administration of the drugs were also recorded. The purpose of the trial was to choose the more suitable of the two drug combinations for repeated mass administration in the intervention phase of a collaborative field research project in the epidemiology and control of malaria in the African savannah. No differences were observed between the two drug combinations from a parasitological point of view. However, the sulfalene-pyrimethamine combination was found easier to administer and occasioned fewer records of vomiting. It was therefore recommended for use in the project.

Secondary association in populations due to heterogeneity.

This paper discusses the phenomenon of spurious or secondary association between factors in heterogeneous study populations. The mathematical basis of this phenomenon is set out and some numerical examples are given. The relevance of the findings to the interpretation of epidemiological studies is examined.

Equilibrium under inbreeding in balanced polymorphisms.

The results of a study on frequencies of genes causing lethal or sublethal disease are reported in relation to the level of consanguinity and heterozygote advantage in populations. The theoretical background of the population dynamics of genes under heterozygote advantage and in the presence of inbreeding is examined and the theoretical models are applied to the estimation of the level of heterosis for lethal and sublethal genes that are responsible for important public health problems in certain populations; these problems include beta-thalassaemia and sickle-cell anaemia. Estimates obtained from the proposed models show a high degree of internal consistency under widely different conditions; data on sickle-cell anaemia from several African populations and on beta-thalassaemia from Italy and Malta were analysed. The hypothesis that rare lethal genes, such as those for Tay-Sachs disease, are maintained in the human population by heterozygote advantage is examined and discussed.