Extraordinary intraspecific diversity in oyster sperm bindin.

In free-spawning invertebrates sperm-egg incompatibility is a barrier to mating between species, and divergence of gamete recognition proteins (GRPs) can result in reproductive isolation. Of interest are processes that create reproductive protein diversity within species, because intraspecific variants are potentially involved in mate choice and early speciation. Sperm acrosomes of the Pacific oyster Crassostrea gigas contain the protein bindin that bonds sperm to egg during fertilization. Oyster bindin is a single-copy gene encoding a diversity of protein variants. Oyster bindins have a conserved N-terminal region followed by one to five tandem fucose-binding lectin (F-lectin) domains. These repeats have diversified by positive selection at eight sites clustered on the F-lectin's fucose binding face. Additional bindin variants result from recombination in an intron in each F-lectin repeat. Males also express alternatively spliced bindin cDNAs with one to five repeats, but typically translate only one or two isoforms into protein. Thus, positive selection, alternative splicing, and recombination can create thousands of bindin variants within C. gigas. Models of sexual conflict predict high male diversity when females are diverse and sexual conflict is strong. The amount of intraspecific polymorphism in male GRPs may be a consequence of the relative efficiency of local (molecular recognition) and global (electrical, cortical, and physical) polyspermy blocks that operate during fertilization.

A pilot study of factors associated with resilience to substance abuse in adolescent sons of alcoholic fathers.

This pilot study evaluated the association between substance abuse outcome and putative protective factors in sons of alcoholic fathers. A battery of questionnaires was anonymously self-administered to 24 sons of alcoholic fathers ages 16-19 years to identify relationships between alcohol and/or drug abuse and factors hypothesized to be related to parental alcoholism. Of the 24 subjects, 13 were categorized through self-identification and self-report screening measures as having alcohol and/or drug problems and 11 were categorized as not having substance abuse problems. Boys without substance problems: (1) had significantly higher maternal occupational status (p = .01); (2) experienced more good life events (p < .001), and (3) had a more internally oriented locus of control (p < .001). Good events and internal locus of control were highly correlated with each other (r = .620, p < .01). The fact that these preliminary findings are consistent with other literature despite marked methodologic and sample differences indicates that these putative components of resilience are robust and deserve further study towards improved substance abuse prevention in those at high risk.

Cocaine effects on pulsatile secretion of ACTH in men.

The effects of cocaine on pulsatile secretion of adrenocorticotropic hormone (ACTH) in men were studied under controlled clinical research ward conditions. Eight men with a Diagnostic and Statistical Manual of the American Psychiatric Association Version III, revised, diagnosis of concurrent cocaine and opioid dependence provided their informed consent for participation in this study. After an overnight fast, a challenge dose of cocaine (30 mg i.v.) or placebo was administered under single-blind conditions in a randomized order on 2 study days. Blood samples were collected at 2-min intervals for 76 min during base line and for an additional 76 min after i.v. administration of the challenge dose. Peak plasma cocaine levels of 313.8 +/- 46.5 ng/ml were detected within 2 min after cocaine administration. The cluster analysis program originally described by Veldhuis and Johnson (1986) was used to characterize ACTH pulsatile secretion (Iranmanesh et al., 1990). Acute cocaine administration (30 mg i.v.) significantly increased ACTH mean peak amplitude (P < .05), mean percent increase in peak amplitude, (P < .05), mean peak area (P < .04), total peak area (P < .04) and incremental peak height (P < .04). Mean ACTH valley levels (P < .02) and mean valley nadir (P < .02) were also significantly increased after cocaine administration. We postulate that cocaine stimulates the release of corticotropin releasing factor and that the cocaine-induced secretion of corticotropin releasing factor increases the amplitude of ACTH pulses, because ACTH pulse frequency was not altered by cocaine.

Histochemical Compartmentation of Photosynthesis in the Crassulacean Acid Metabolism Plant Crassula falcata.

The succulent leaf of the obligate Crassulacean acid metabolism plant Crassula falcata comprises two distinct types of parenchyma. The peripheral tissue is dark green, whereas the central tissue is relatively colorless. We have investigated whether the conventional interpretation of Crassulacean acid metabolism-simply, temporal separation of light and dark CO(2) fixation within individual cells-is sufficient. Ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) and chlorophyll, indicating the photosynthetic-carbon-reduction pathway, were concentrated in peripheral tissue. Specific activities of P-enolpyruvate carboxylase (4.1.1.31) and of NAD(+)-malic enzyme (1.1.1.39), indicating capacity for dark CO(2) fixation and release, respectively, were high in both types of parenchyma. Measured directly as malic acid decline at the beginning of the photoperiod, CO(2) "storage" occurred in both tissues. These data indicate that there is a spatial component to Crassulacean acid metabolism in C. falcata.

Histochemical technique : a general method for quantitative enzyme assays of single cell ;extracts' with a time resolution of seconds and a reading precision of femtomoles.

Biochemists who study single cells have been constrained by the lack of a general methodology of high time resolution and high measurement sensitivity for quantitatively assaying enzyme activities using natural substrates in solution. The methods we describe will remove this limitation. In brief, nanogram tissue samples are dissected from frozen-dried tissue. The samples are ;extracted' in microdroplets of assay cocktail. The enzyme activity, indicated fluorometrically by the oxidation/reduction of NAD(P), is followed in real time on a computer display. In the development of this method, we evaluated several parameters required for optimization; the most important of these evaluations, including numerous empirically derived relationships, are reported here and in supplemental material provided with reprints.With these methods, assays of pyruvate orthophosphate dikinase on samples enriched in bundlesheath cells and mesophyll cells of Flaveria brownii yielded the predictable results. Assays of this enzyme in guard cells dissected from Vicia faba leaflets gave results like those recently reported by another laboratory for protoplasts derived from these cells. The results of assays by this method and by enzymic cycling for NAD(P)triose-P dehydrogenase were comparable. Phosphoenolpyruvate carboxylase, the most extensively studied enzyme activity, was present at high levels in guard cells, which has been demonstrated previously in other reports based on diverse assay approaches.