Regulation of glyoxysomal enzymes during germination of cucumber. Temporal changes in translatable mRNAs for isocitrate lyase and malate synthase

The relative levels of translatable messenger RNA for isocitrate lyase and malate synthase were determined in the dry seed and for the first seven days of development of cucumber cotyledons. After extraction and quantification of total and poly(A)-rich RNA each day, the RNA fractions were translated in an optimized wheat germ system and the specific polypeptides were immunoprecipitated quantitatively. The radiolabeled isocitrate lyase and malate synthase polypeptides were then fractionated on dodecylsulphate/polyacrylamide gels, visualized by exposure to X-ray film and quantified densitometrically. The relative levels of translatable messenger RNA for these enzymes rise and fall with a developmental program similar to the enzyme activities, but preceding the latter by about one day. This implies that the rise in enzyme activity is dependent upon a prior postgerminative increase in translatable messenger RNA for the enzymes. These studies also suggest that messenger RNA levels may be regulated, at least in part, by light.     

Testing Hypotheses about Linkage Disequilibrium with Multiple Alleles

For loci with multiple alleles, hypotheses about linkage disequilibrium may be tested on the complete set of gametic data, or on various collapsed sets of data. Collapsing data into a few alleles at each locus can change the power of the tests, as implied in a recent paper by Zouros, Golding and Mackay (1977). We show that the nature of such changes can be found from properties of the noncentral chi-square distribution, and that the magnitude and direction of these changes depend on the levels of linkage disequilibria, allelic frequencies and degrees of freedom.     

Population Differentiation under the Charge State Model

The extent of divergence between partially isolated sub-populations for electrophoretically detectable alleles was formulated assuming the island model of migration and the charge state model of mutation. At equilibrium the ratio of the variance of charge between the means of k different islands to the average within-island variance of charge was shown to be approximately 4Nemk2/(k-1)2 where Ne is the effective size of each island population and m is the migration rate. This ratio was calculated from published data for eight polymorphic loci in six island populations of Drosophila willistoni. Under the assumption that all variants are selectively neutral, migration rates of greater than 10 adults per generation per island are required to explain the observed similarity of the allelic profiles in D. willistoni. Since the islands studied appear to be virtually completely isolated it was concluded either that the observed protein variants are adaptive and maintained in populations by some form of balancing selection or that the observed variants themselves are neutral but natural selection acts to restrict the appearance of more extreme variants in the charge carried.     

Effect of oral contraceptives and pregnancy on erythrocyte deformability and surface charge.

Erythrocyte deformability and surface charge were studied in normal premenopausal women, oral contraceptive users, and pregnant women. The increased incidence of thrombosis in women taking oral contraceptives could not be explained by decreased erythrocyte deformability or surface charge. However, the decreased erythrocyte deformability of late pregnancy may relate to thrombosis during this period and to increased hemolysis in patients with certain hemoglobinopathies.