Erythrocyte cation fluxes during the menstrual cycle in normal female subjects.

1. Studies of erythrocyte cation transport mechanisms in vitro were performed on eight normotensive, premenopausal female subjects at the mid-points of the follicular and luteal phases of their menstrual cycles. Concurrent plasma concentrations of 17 beta-oestradiol, progesterone, aldosterone and renin activity were measured. 2. Ouabain-resistant, frusemide-resistant rubidium influx (an index of passive potassium diffusion) was significantly lower in the luteal than the follicular phase. 3. In further studies in four of the eight subjects, the mean rate constant of the rubidium influx measurement was also lower in the luteal than in the follicular phase. 4. There were no changes in Na+-K+ co-transport, sodium pump activity or intracellular cation concentrations throughout the cycle. 5. There was a tenfold fall in the mean plasma 17 beta-oestradiol/progesterone ratio, as well as increases in plasma aldosterone concentration and renin activity between the mid-follicular and mid-luteal phases. 6. We conclude that changes in plasma oestrogen/progesterone ratio during the menstrual cycle may be associated with alterations in passive potassium diffusion.

Latitudinal variation in octanol dehydrogenase and acid phosphatase allele frequencies in Drosophila melanogaster.

The octanol dehydrogenase (Odh) and acid phosphatase (Acph) loci of Drosophila melanogaster are each polymorphic for two electrophoretically detectable alleles. The frequencies of the Odh and Acph alleles have been analysed in populations sampled from up to a 40 ° latitudinal range in each of Australasia, North America and Europe/Asia. Odh (S) frequency is found to be significantly negatively associated with distance from the equator in all three zones. The relationship of Acph (S) frequency to distance from the equator is significant and negative in Australasia but neither significant nor consistent in sign in North America and Europe/Asia.

Latitudinal relationships of esterase-6 and phosphoglucomutase gene frequencies in Drosophila melanogaster.

Geographic variation in Esterase-6 (Est-6) and Phosphoglucomutase (Pgm) gene frequencies in Australasian populations of Drosophila melanogaster are compared with analogous data collated from 16 previous reports for North America and Europe/Asia. A large-scale latitudinal cline is found on all three zoogeographic zones for Est-6 and overall, Est-61.00 frequency increases from about 20 per cent around 20 degrees latitude to about 80 per cent approaching 50 degrees latitude. In contrast, there is no consistent evidence for the latitudinal cline in Pgm gene frequencies in any of the three zones with Pgm1.00 frequency generally about 85 per cent and Pgm1.20 and Pgm0.70 frequencies each between 5 per cent and 10 per cent. The consistent Est-6 clines are attributed to latitudinal selection gradients but not consistent correlations are found between Est-6 gene frequencies and maximum or minimum temperature or rainfall which might be associated with these gradients. The directions of the Est-6 clines in fact run counter to expectations based on the in vitro thermostabilities of the respective allozymes.

Restriction endonuclease and molecular analyses of three rat genomes with special reference to chromosome rearrangement and speciation problems.

When differences are found between related species of organisms, it is often assumed that the differences themselves are causal factors either in speciation itself or in processes related to speciation. Two recent proposals on the functions of satellite DNA (Hatch et al., 1976 and Fry and Salser 1977) are that (a) large amounts of satellite DNA are important in facilitating chromosome rearrangements and hence cytogenetic evolution, and (b) satellite DNA differences between homologous chromosomes lead to pairing difficulties and are important in generating infertility barriers and hence speciation. If these proposals were to have some generality, one could expect organisms with very low amounts of highly repeated DNA to exhibit few chromosome rearrangements and to be evolutionarily conservative in a cytogenetic sense.--We have chosen two very closely related species of rat which are phenotypically almost indistinguishable and which have undergone massive genome reorganization. They differ by 11 major centric rearrangements (2n = 32, 2n = 50). We have characterised their genomes by restriction endonuclease digestions, thermal denaturations, analytical ultracentrifugations and reassociation techniques, and have found that they have virtually no highly repeated DNA. Thus the 11 major chromosomal rearrangements have been fixed in present day genomes with hardly any highly repeated DNA, centric or otherwise.--It appears therefore, that a large amount of highly repeated DNA is not obligatory for the formation and fixation of chromosome rearrangements. In addition, the existing literature reveals that one can find almost any situation at all, from species groups with high amounts of satellite DNA and no gross chromosomal rearrangements, to ones such as those described here, with tiny amounts of highly repeated DNA and massive chromosomal reorganisation. Since direct experimental data indicates that satellite DNA differences per se between homologous chromosomes do not cause infertility, speculations concerning modes of speciation based on satellite DNA differences between otherwise homologous chromosomes would appear to be ill founded.