SEASONAL VARIATION IN SEXUAL SELECTION IN THE MOTTLED SCULPIN

Seasonal variation in sexual and natural selection in male mottled sculpins (Cottus bairdi) can be evaluated by calculating selection differentials, which measure the magnitude of phenotypic change resulting from selection, and by calculating indices of the opportunity for selection, which indicate the potential for phenotypic selection in a given interval. Selection differentials are high at the beginning of the breeding season and decline throughout the breeding season. The magnitude and direction of selection differentials depend on when spawning occurs and are independent of the size or age of the females that spawn. Annual selection differentials due to differences in mating success (female choice) are nearly constant between years. Annual selection differentials associated with hatching success are variable. Opportunities for selection (I = fitness variance/[mean fitness]²) show clear seasonal patterns. They are highest at the beginning and at the end of the spawning season. However, this variation is dependent on the mean used to calculate I, and hence variation in I values does not indicate a significant change in the variance of male fitness.     

Allelic variants of Ly-5 in inbred and natural populations of mice

Allelic variants of Ly-5 in inbred commensal and other natural populations of mice were analyzed by patterns of restriction fragment length polymorphisms (RFLP) and Southern hybridization using an Ly-5 cDNA probe and by cell-surface staining with a panel of antibodies directed against polymorphic and nonpolymorphic Ly-5 determinants. New Ly-5 alleles were defined by RFLPs generated by both Eco RI and Bam HI restriction enzyme digests. The Mus musculus subspecies and other species within the genus Mus showed a strong correlation between allelic variants defined by restriction enzymes and serologic specificities. The data also suggest the conservation of the Ly-5 gene throughout the genus Mus.     

Behavior ofPseudomonas fluorescens within the hydrodynamic boundary layers of surface microenvironments

Phase, darkfield, and computer-enhanced microscopy were used to observe the surface microenvironment of flow cells during bacterial colonization. Microbial behavior was consistent with the assumptions used previously to derive surface colonization kinetics and to calculate surface growth and attachment rates from cell number and distribution. Surface microcolonies consisted of closely packed cells. Each colony contained 2ⁿ cells, where n is the number of cell divisions following attachment. Initially, cells were freely motile while attached, performing circular looping movements within the plane of the solid-liquid interface. Subsequently, cells attached apically, maintained a fixed position on the surface, and rotated. This type of attachment was reversible and did not necessarily lead to the formation of microcolonies. Cells became irreversibly attached by progressing from apical to longitudinal attachment. Longitudinally attached cells increased in length, then divided, separated, moved apart laterally, and slid next to one another. This resulted in tight cell packing and permitted simultaneous growth and adherence. After approximately 4 generations, individual cells emigrated from developing microcolonies to recolonize the surface at new locations. Surface colonization byPseudomonas fluorescens can thus be subdivided into the following sequential colonization phases: motile attachment phase, reversible attachment phase, irreversible attachment phase, growth phase, and recolonization phase.     

Ion selectivity of epithelial Na channels

Epithelial Na channels are apparently pore-forming membrane proteins which conduct Na much better than any other biologically abundant ion. The conductance to Na can be 100 to 1000 times higher than that to K. The only other ions that can readily get through this channel are protons and Li. Small organic cations cannot pass through the channel, and water may also be impermeant. The selectivity properties of epithelial Na channels appear to be determined by at least three factors: A high field-strength anionic site, most likely a carboxyl residue of glutamic or aspartic acid residues on the channel protein, probably accounts for the high conductance through these channels of Na and Li and to the low conductance of K, Rb and Cs. A restriction in the size of the pore at its narrowest point probably accounts for the low conductance of organic cations as well as the possible exclusion of water molecules. The outer mouth of the channel appears to be negatively charged and may control access to the region of highest selectivity and may serve as a preliminary selectivity filter, attracting cations over anions. These conclusions are illustrated by the cartoon of the channel in Fig. 3. This picture is obviously both fanciful and simplified, but its general points will hopefully be testable. It leaves open a number of important questions, including: does amiloride block the channel by binding within the outer mouth? what does the inner mouth of the channel look like, and does this part of the channel contribute to selectivity? and what, if any, are the interactions between the features of the channel that impart selectivity and those that control the regulation of the channel by hormonal and other factors?     

Modulating effect of cystamine and unsaturated fatty acids on gamma-glutamyl transpeptidase: Relation to cellular oxidative status

Summary Cell surface gamma-glutamyl transpeptidese activity in cultured neoplastic astrocytes was significantly increased upon treatment of the cells with the hepatoprotective disulfide, cystamine. The cystamine effect was sensitive to cycloheximide and could be significantly depressed by exogenous glutathione. Surface gamma-glutamyl transpeptidase activity was also modulated by the presence in the culture medium of the unsaturated fatty acids, linoleic acid and arachidonic acid. Metabolism of the fatty acids via the cyclooxygenase pathway was not a prerequisite for their modulation of the glycoprotein ectoenzyme. Lipoxygenase, however, was found to potentiate the unsaturated fatty acid effect in neoplastic astrocytes. Lipoxygenase is reported to catalyze the conversion of unsaturated fatty acids to their corresponding peroxides. The data indicate an oxidative influence on the control of gamma-glutamyl transpeptidase activity.     

Freeze-Thawing of Aquaspirillum magnetotacticum Cells Selectively Releases Periplasmic Proteins

Cells of the gram-negative bacterium Aquaspirillum magnetotacticum, when suspended in buffer and freeze-thawed, produced pinkish orange supernatant fluid. The fluid contained ≤2.0% of total extractable outer membrane component 2-keto-3-deoxyoctonate or of the cytoplasmic membrane marker succinic dehydrogenase. Electrophoretic banding patterns and difference spectra of proteins and hemoproteins released by freeze-thawing cells were distinct from those of membrane-associated substances and similar to those of periplasmic substances obtained by applying conventional fractionation methods to this organism.     

The nature of phonons and solitary waves in alpha-helical proteins.

A parametric study of the Davydov model of energy transduction in alpha-helical proteins is described. Previous investigations have shown that the Davydov model predicts that nonlinear interactions between phonons and amide-I excitations can stabilize the latter and produce a long-lived combined excitation (the so-called Davydov soliton), which propagates along the helix. The dynamics of this solitary wave are approximately those of solitons described using the nonlinear Schr?dinger equation. The present study extends these previous investigations by analyzing the effect of helix length and nonlinear coupling efficiency on the phonon spectrum in short and medium length alpha-helical segments. The phonon energy accompanying amide-I excitation shows periodic variation in time with fluctuations that follow three different time scales. The phonon spectrum is highly dependent upon chain length but a majority of the energy remains localized in normal mode vibrations even in the long chain alpha-helices. Variation of the phonon-exciton coupling coefficient changes the amplitudes but not the frequencies of the phonon spectrum. The computed spectra contain frequencies ranging from 200 GHz to 6 THz, and as the chain length is increased, the long period oscillations increase in amplitude. The most important prediction of this study, however, is that the dynamics predicted by the numerical calculations have more in common with dynamics described by using the Frohlich polaron model than by using the Davydov soliton. Accordingly, the relevance of the Davydov soliton model was applied to energy transduction in alpha-helical proteins is questionable.(ABSTRACT TRUNCATED AT 250 WORDS)