The cannabinoid CB1 receptor is expressed in pancreatic delta-cells

Antagonists of cannabinoid CB1 receptor (CB1, CNR1) promote weight loss and decrease hyperglycemia in patients with type 2 diabetes. While the endocannabinoid system may modulate islet hormone secretion, the cell-type expressing CB1 receptor in islets has not been fully resolved. In this study, we verified receptor gene expression in rodent islets and cell lines and examined the distribution of CB1 receptor in mouse, rat, and human islets by confocal immunofluorescence (IF) microscopy. IF demonstrated CB1 receptor was present in β-cell lines, but co-localized solely with somatostatin in the islet δ-cells of Zucker rats, C57BL/6 mice, and humans; no CB1 receptor expression was observed in α-, β-, or pp-cells. Similarly, a rat somatostatinoma cell line, MSL-G2-Tu6, was found to express CB1 receptor. We also found monoacylglycerol lipase (MAGL) to be expressed in δ-cells and fatty acid amide hydrolase (FAAH) to be expressed in α-cells. The specific expression of CB1 in δ-cells suggests that the ECS may play a role in modulating islet hormone secretion. As there are some differences between our findings and previous reports, further studies, including detailed physiological studies of the effects of the ECS on islet function, are warranted.     

Testosterone, and winning and losing in human competition

Testosterone and cortisol were measured in six university tennis players across six matches during their varsity season. Testosterone rose just before most matches, and players with the highest prematch testosterone had the most positive improvement in mood before their matches. After matches, mean testosterone rose for winners relative to losers, especially for winners with very positive moods after their victories and who evaluated their own performance highly. Winners with rising testosterone had higher testosterone before their next match, in contrast to losers with falling testosterone, who had lower testosterone before their next match. Cortisol was not related to winning or losing, but it was related to seed (top players having low cortisol), and cortisol generally declined as the season progressed. These results are consistent with a biosocial theory of status.     

Numerous transposed sequences of mitochondrial cytochrome oxidase I-II in aphids of the genus Sitobion (Hemiptera: Aphididae)

Polymerase chain reaction (PCR) products corresponding to 803 bp of thecytochrome oxidase subunits I and II region of mitochondrial DNA (mtDNACOI-II) were deduced to consist of multiple haplotypes in three Sitobionspecies. We investigated the molecular basis of these observations. PCRproducts were cloned, and six clones from one individual per species weresequenced. In each individual, one sequence was found commonly, but alsotwo or three divergent sequences were seen. The divergent sequences wereshown to be nonmitochondrial by sequencing from purified mtDNA and Southernblotting experiments. All seven nonmitochondrial clones sequenced tocompletion were unique. Nonmitochondrial sequences have a high proportionof unique sites, and very few characters are shared betweennonmitochondrial clones to the exclusion of mtDNA. From these data, weinfer that fragments of mtDNA have been transposed separately (probablyinto aphid chromosomes), at a frequency only known to be equalled inhumans. The transposition phenomenon appears to occur infrequently or notat all in closely related genera and other aphids investigated. Patterns ofnucleotide substitution in mtDNA inferred over a parsimony tree are verydifferent from those in transposed sequences. Compared with mtDNA,nonmitochondrial sequences have less codon position bias, more evenexchanges between A, G, C and T, and a higher proportion of nonsynonymousreplacements. Although these data are consistent with the transposedsequences being under less constraint than mtDNA, changes in thenonmitochondrial sequences are not random: there remains significantposition bias, and probable excesses of synonymous replacements and ofconservative inferred amino acid replacements. We conclude that aproportion of the inferred change in the nonmitochondrial sequencesoccurred before transposition. We believe that Sitobion aphids (and otherspecies exhibiting mtDNA transposition) may be important for studying themolecular evolution of mtDNA and pseudogenes. However, our data highlightthe need to establish the true evolutionary relationships between sequencesin comparative investigations.