The genetics and expression of an esterase locus inAnopheles gambiae

The main polymorphic system of esterase isoenzymes in adults of the G3 laboratory strain ofAnopheles gambiae consists of two to five major bands of activity per individual. The bands are designated 5S, 5F, 13, 14, and 15. In genetic crosses, the genes which coded for the bands assorted as three codominant alleles, Est A, Est B, and Est C, at a single autosomal locus. Homozygotes for the Est C allele were significantly underrepresented among backcross progeny. The developmental pattern of esterase expression was examined. Esterase gene expression in embryos was first detectable between 2 and 12 hr after oviposition. The initiation or termination of expression of some of the bands corresponded to boundaries between developmental stages. Most of the esterase fractions were not specifically localized within the tissues tested, with the exception of a series of bands which were restricted largely to adult male testes.     

Mechanism for the opioid-induced twitch potentiations of frog's skeletal muscle

The twitch-potentiating effects of opioids in the frog's skeletal muscle which are naloxone resistant and nonstereospecific were further studied. The rapid kinetics of the onset and of the offset (following washout) of the opioid effect indicates that the site for this action is the surface membrane of the muscle fibre. On the other hand, the lack of any twitch-potentiating effect by naloxone methylbromide, a quaternary derivative of naloxone, suggests that opioids which potentiate the twitch must enter the lipid phase of the membrane to act. Intracellular microelectrode experiments revealed no relation between the opioid effects on membrane electrical events and twitch potentiation. Blocking slow calcium channels with D-600 did not modify the opioid-induced twitch potentiation. The twitch potentiation was antagonized by increasing the extracellular calcium concentration, [Ca2+]o, to 8.64 mM. The effects of closely spaced multiple electrical pulses revealed that the opioids decreased the summated response relative to predrug controls. The results suggest that opioids facilitate the process of excitation-contraction coupling in the frog's skeletal muscle by the release of an additional amount of "trigger calcium" following a single electrical stimulus, thereby generating a potentiated twitch.     

Heterogeneity of Lethals in a "Simple" Lethal Complementation Group

Of 24 ethyl methanesulphonate-induced, recessive-lethal mutations in the region 9E1-9F13 of the X chromosome of Drosophila melanogaster, eight fall into a typically homogeneous lethal complementation group associated with the raspberry (ras) locus. Mutations in this group have previously been shown to be pleiotropic, affecting not only ras but also two other genetic entities, gua 1 and pur 1, which yield auxotrophic mutations.--The eight new mutations have been characterized phenotypically in double heterozygotes with gua 1, pur 1 and ras mutations. Despite their homogeneity in lethal complementation tests, the mutations prove quite diverse. For example, two mutations have little or no effect on eye color in double heterozygotes with ras2. The differences between the lethals are allele-specific and cannot be explained as a trivial outcome of a hypomorphic series.--Taken alone, the lethal complementation studies mask the complexity of the locus and the diversity of its recessive lethal alleles. By extension, we argue that the general use of lethal saturation studies provides an unduly simplified image of genetic organization. We suggest that the reason why recessive lethal mutations rarely present complex complementation patterns is that complex loci tend to produce mutations that affect several subfunctions.     

Proceedings of the fifty-fourth Annual Meeting of the American Association of physical anthropologists to be held in Knoxville,Tennessee—Holiday Inn World's fair April 10–13, 1985

Empirical analyses and models of the lineal effects of fission indicate that considerable genetic differentiation may occur at the time of group formation, thus confusing the usual positive relationship between historical affiliation and genetic differentiation. We analyze the effects of fission pattern on variation in highly heritable morphological traits among eight social groups on Cayo Santiago. The analysis is performed using general network autocorrelation methods that quantitatively and directly measure the amount of variation in social group mean morphology that can be explained by fission. All of the fission autocorrelation coefficients are strongly negative, indicating that groups most recently formed by fission are most dissimilar. Also, most of the variation between groups can be explained by the fission pattern, indicating that lineal fission is the most important process generating between-group variation on Cayo Santiago.     

Amino acid sequence of an invertebrate FBP aldolase (from Drosophila melanogaster)

The complete amino acid sequence of FBP aldolase from Drosophila melanogaster has been determined. The enzyme contains four identical subunits of 360 amino acid residues. The primary structure of the monomer was established using automated Edman degradation on fragments prepared by CNBr-cleavage, by partial acid cleavage at the unique Asp-Pro bond and by oxidative cleavage at the three tryptophan residues. Manual Edman-Chang degradation was used on smaller peptides obtained by digestion with Staphylococcus aureus V8 protease, trypsin or chymotrypsin. The primary structure of Drosophila aldolase exhibits very extensive homology with the sequence of rabbit muscle aldolase (71% identity), thus explaining the early observation that Drosophila and mammalian aldolases form active interspecies hybrid quaternary structures (Brenner-Holzach, O. and Leuthardt, F., Eur. J. Biochem. (1972) 31, 423-426).     

Spin probe clustering in human erythrocyte ghosts

Summary A model has been developed for 5-nitroxide stearate, I(12,3), distribution in human erythrocyte ghosts which accurately predicts ESR spectral alterations observed with increased probe/total lipid (P/L) at 37°C. This spin probe occupies a class of high-affinity, noninteracting sites at low loading. Saturation occurs with increasing probe concentration, and, at higher loading, the probe inserts itself at initially dilute sites to form membranebound clusters of variable size. No low probe remains at high P/L where all I(12,3) clusters in a concentrated phase. This model allows determination of the dilute/clustered probe ratio, and shows that I(12,3) segregates in erythrocytes at what might otherwise be considered low P/L (e.g., 1/359). These findings validate the earlier use of empirical parameters to estimate probe sequestration in biological membranes.     

Transport of hydrophobic ions in erythrocyte membrane: I. Zero membrane potential properties

Summary The permeability and partition coefficients of tetraphenylarsonium (TPA) and several other organic cations were studied in the human erythrocyte using an ion-selective electrode. The permeability constant for the different cations could be explained quite well by differences in oil/water partition coefficients. No evidence for facilitated transport could be found. Binding of the organic ions occurred to both the cell membrane and to intracellular contents. Partitioning to the membrane remained relatively constant despite variation from ion intracellular binding with blood samples from different donors. TPA flux is stimulated by substoichiometric amounts of tetraphenylboron and other organic anions, suggesting an ion-pairing mechanism.