Fungal rhodopsins and opsin-related proteins: eukaryotic homologues of bacteriorhodopsin with unknown functions.

In the last decade, several genome sequencing projects revealed the existence of previously unknown photoreceptors. Among those are eukaryotic rhodopsins of haloarchaeal type, mostly represented by fungal sequences. We have classified and analyzed seventy-seven of these fungal proteins, which show a high similarity of their putative transmembrane regions to those of bacteriorhodopsin. Those sequences can be divided into the two subgroups, fungal rhodopsins (RDs) and opsin-related proteins (ORPs), the latter lacking the lysine residue necessary for retinal binding. We have analyzed the conservation pattern of the residues known to have functional or structural importance in bacteriorhodopsin and discussed dramatic differences in the conservation between RDs and ORPs. We found many cases of multiple forms of RDs and/or ORPs and examined possible reasons for such multiplicity. For some species the reason may lie in functional photobiological diversification, while for the others it follows the pattern of evolutionary recent genome duplication and possible functional redundancy.     

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.     

Copper resistance determinants in bacteria.

Copper is an essential trace element that is utilized in a number of oxygenases and electron transport proteins, but it is also a highly toxic heavy metal, against which all organisms must protect themselves. Known bacterial determinants of copper resistance are plasmid-encoded. The mechanisms which confer resistance must be integrated with the normal metabolism of copper. Different bacteria have adopted diverse strategies for copper resistance, and this review outlines what is known about bacterial copper resistance mechanisms and their genetic regulation.     

Stressful life events, social support networks, and the physical and mental health of urban black adults

The direct and the buffering effects of social support networks have been documented, but few studies have examined their health outcomes for blacks and, specifically, the differences in physical and mental health. This study uses six measures of social support to examine the relationships of social support to health outcomes for black males and females. The data are from a community sample of 451 urban black adults. Results show significant differences by sex according to source of social support and particular health outcomes. Number of nearby relatives and perceived social support have direct and buffering effects, respectively, on mental health for black females, but no significant influences emerge for black males. On the other hand, the number of confidants for black males and the degree of religiosity among black females were inversely related to physical health, suggesting differences in conceptual models of social support for mental and physical health.     

Flow cytometric analysis and sorting of plant chromosomes from Petunia hybrida protoplasts

A method to obtain a high metaphase index and thereafter a plant chromosome suspension is described for Petunia hybrida (2n = 14). Mesophyll protoplast cultures have been used, giving easily disrupted cell walls and a high percentage of dividing cells after 42 h. On 2.5 mM colchicine-treated cells, metaphase indexes reaching 10% were routinely obtained. The lysis medium in which the protoplast-derived cells were disrupted was a simplified culture medium. After chromosome release, samples were stained with Hoechst 33342 dye and analysed by flow cytofluorometry. The histogram of fluorescence intensities included three peaks of metaphase chromosomes and a duplication of this flow karyotype provoked by "monochromatid chromosome." This interpretation was established after flow sorting; micronuclei could also be observed and sorted. Of the 7 chromosomes, only the largest formed a distinct peak while the others were incompletely resolved, due to the similar DNA content of various chromosomes. Model distributions of Petunia hybrida chromosomes have been computed according to the relative chromosome length. The theoretical histograms indicated that low variability is indispensable for resolving distinctive chromosome peaks. The experimental flow karyotype was consistent with one of the models having CV of 2.5%.     

Activation of Dopamine Receptors Does Not Affect Phosphoinositide Turnover in NCB-20 Cells

Dopamine inhibits and serotonin stimulates adenylate cyclase activity in a neuroblastoma X Chinese hamster brain explant cell line (NCB-20). The inhibition of cyclic AMP accumulation by dopamine was blocked by pretreatment of the cells with pertussis toxin. Carbachol and bradykinin stimulated the accumulation of water-soluble inositol phosphates whereas thyrotropin-releasing hormone, vasopressin, neurotensin, and phenylephrine were without effect. Dopamine and serotonin had no significant effect on carbachol-induced phosphoinositide hydrolysis or the levels of the parent lipids within the membrane. Forskolin induced a much larger stimulation of cyclic AMP than did serotonin, and caused an increase in the levels of phosphatidylinositol-4-phosphate and phosphatidyl inositol-4,5-bisphosphate in the cell membrane.     

Direct and Continuous Detection of ATP Secretion from Primary Monolayer Cultures of Bovine Adrenal Chromaffin Cells

A method was developed for direct and continuous detection of secretion of ATP from primary monolayer cultures of bovine adrenal chromaffin cells. ATP, which is costored with catecholamines within adrenal chromaffin cells, was released into the incubation medium, where it reacted with firefly luciferin-luciferase producing light detected by a photomultiplier located directly below the culture well. Acetylcholine, nicotine, the Ca2+ ionophore A23187, BaCl2, and KCl induced release of ATP. Induction of release of ATP by acetylcholine was dose dependent, with a threshold at 10(-7) M and a maximum at 10(-4) M. The dose-response curve for nicotine was bell shaped, with a threshold at 10(-7) M, a maximum at 10(-5) M, and diminished release at higher concentrations, an observation indicative of desensitization. Investigation of the initial rates of ATP secretion revealed that 10(-4) M nicotine actually induced release of ATP at a faster rate than 10(-5) M nicotine. However, the rate of ATP release evoked by 10(-4) M nicotine began to decline by 6 s, a result indicating the onset of receptor desensitization, whereas release induced by 10(-5) M nicotine continued unabated. Induction of release of ATP by acetylcholine or nicotine was biphasic, with a rapid, initial phase of release followed by a plateau at 0.5-1.5 min and a second phase of release beginning at 1.5-2 min, reaching a maximum by 2-3 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of muscarinic and beta-adrenergic blockade on cysteamine-induced gastrin secretion by the isolated perfused rat stomach

Cysteamine-induced duodenal ulceration in rats is accompanied by increased circulating gastrin. Although cysteamine appears to exert a direct action on the gastrin cell some groups have provided evidence for an involvement of the autonomic nervous system. The current experiments were performed to determine whether beta-adrenergic or cholinergic (muscarinic) pathways are involved in the acute effect of cysteamine on gastrin secretion in the isolated perfused rat stomach. Cysteamine (1 mM) increased gastrin (IRG) secretion to a maximum ranging between 100% and 192% above basal. A cysteamine concentration of 5mM resulted in peak levels ranging between 150% and 1050% above basal. Addition of atropine or propranalol did not influence the responses obtained. The present results, therefore, do not support a role for either cholinergic or beta-adrenergic pathways in cysteamine-induced gastrin release at the level of the stomach and suggest that in vivo such autonomic effects are mediated extrinsically.