Microglia perform both neuroprotective and neurotoxic functions in the brain, with this depending on their state of activation and their release of mediators. Upon P2X(7) receptor stimulation, for example, microglia release small amounts of TNF, which protect neurons, whereas LPS causes massive TNF release leading to neuroinflammation. Here we report that, in rat primary cultured microglia, nicotine enhances P2X(7) receptor-mediated TNF release, whilst suppressing LPS-induced TNF release but without affecting TNF mRNA expression via activation of alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs). In microglia, nicotine elicited a transient increase in intracellular Ca(2+) levels, which was abolished by specific blockers of alpha7 nAChRs. However, this response was independent of extracellular Ca(2+) and blocked by U73122, an inhibitor of phospholipase C (PLC), and xestospongin C, a blocker of the IP(3) receptor. Repeated experiments showed that currents were not detected in nicotine-stimulated microglia. Moreover, nicotine modulation of LPS-induced TNF release was also blocked by xestospongin C. Upon LPS stimulation, inhibition of TNF release by nicotine was associated with the suppression of JNK and p38 MAP kinase activation, which regulate the post-transcriptional steps of TNF synthesis. In contrast, nicotine did not alter any MAP kinase activation, but enhanced Ca(2+) response in P2X(7) receptor-activated microglia. In conclusion, microglial alpha7 nAChRs might drive a signaling process involving the activation of PLC and Ca(2+) release from intracellular Ca(2+) stores, rather than function as conventional ion channels. This novel alpha7 nAChR signal may be involved in the nicotine modification of microglia activation towards a neuroprotective role by suppressing the inflammatory state and strengthening the protective function.

The genetic basis of sexual isolation that contributes to speciation is one of the unsolved questions in evolutionary biology. Drosophila ananassae and Drosophila pallidosa are closely related, and postmating isolation has not developed between them. However, females of both species discriminate their mating partners, and this discrimination contributes to strong sexual isolation between them. By using surgical treatments, we demonstrate that male courtship songs play a dominant role in female mate discrimination. The absence of the song of D. pallidosa dramatically increased interspecies mating with D. ananassae females but reduced intraspecies mating with D. pallidosa females. Furthermore, genetic analysis and chromosomal introgression by repeated backcrosses to D. pallidosa males identified possible loci that control female discrimination in each species. These loci were mapped on distinct positions near the Delta locus on the middle of the left arm of the second chromosome. Because the mate discrimination we studied is well developed and is the only known mechanism that prevents gene flow between them, these loci may have played crucial roles in the evolution of reproductive isolation, and therefore, in the speciation process between these two species.

Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disease characterized by various symptoms including cerebellar ataxia. Recently, several missense mutations in the protein kinase C␥ (␥PKC) gene have been found in different SCA14 families. To elucidate how the mutant ␥PKC causes SCA14, we examined the molecular properties of seven mutant (H101Y, G118D, S119P, S119F, Q127R, G128D, and F643L) ␥PKCs fused with green fluorescent protein (␥PKC-GFP). Wild-type ␥PKC-GFP was expressed ubiquitously in the cytoplasm of CHO cells, whereas mutant ␥PKC-GFP tended to aggregate in the cytoplasm. The insolubility of mutant ␥PKC-GFP to Triton X-100 was increased and correlated with the extent of aggregation. ␥PKC-GFP in the Triton-insoluble fraction was rarely phosphorylated at Thr 514 , whereas ␥PKC-GFP in the Triton-soluble fraction was phosphorylated. Furthermore, the stimulation of the P2Y receptor triggered the rapid aggregation of mutant ␥PKC-GFP within 10 min after transient translocation to the plasma membrane. Overexpression of the mutant ␥PKC-GFP caused cell death that was more prominent than wild type. The cytotoxicity was exacerbated in parallel with the expression level of the mutant. These results indicate that SCA14 mutations make ␥PKC form cytoplasmic aggregates, suggesting the involvement of this property in the etiology of SCA14.

It has been shown that centrally administered neuropeptide Y (NPY) delays gastric emptying. To determine the receptor subtypes of NPY mediating the inhibitory effects on gastric emptying, effects of intracerebroventricular injection of NPY, [Leu31,Pro34]NPY (a Y1 agonist) and NPY-(3-36) (a Y2 agonist) on solid gastric emptying and postprandial antropyloric motility were studied in conscious rats. Intracerebroventricular injection of NPY and NPY-(3-36), but not [Leu31,Pro34] NPY, delayed solid gastric emptying in a dose-dependent manner (0.03-3 nmol). After the feeding (40 min), contractions with low frequency and high amplitude of the antrum were frequently observed, and the peak contraction of the antrum occurred most often 3-6 s before the peak contraction of the pylorus. Intracerebroventricular injection of NPY and NPY-(3-36) (3 nmol), but not [Leu31,Pro34]NPY, significantly reduced antral contractions and the number of antropyloric coordination events. It is suggested that centrally administered NPY impairs postprandial antral contractions and antropyloric coordination via Y2 receptors, resulting in delayed gastric emptying.

No abstract

Under the application of tensile stress to a multi-lamentary Bi 2 Sr 2 Ca 2 Cu 3 O 10+x (Bi2223) composite tape sample composed of a series of sections, the relation of superconducting properties (voltage-current curve, critical current and n-value) of sections to those of the sample were studied experimentally and analytically. The voltage-current curve of the most extensively cracked section whose critical current was the lowest among the sections, was the nearest in position to the voltage-current curve of the sample and played a dominant role in determination of the critical current of the sample. On the other hand, the n-value of the sample was signi cantly affected not only by the voltage-current curve of the most extensively cracked section but also on the position in relation to the voltage-current curves between the most extensively cracked section and the other sections. The denser the voltage-current curve of the other sections in the neighborhood of the voltage-current curve of the most extensively cracked section, the higher the n-value of sample became. In analysis of the experimental results, an equivalent crackcurrent shunting model, in which multiple cracks existing inside were replaced by an equivalent crack, was employed. With this model, the measured critical current and n-value of both sections and sample, and the correlation between n-value and critical current both for sections and sample, were described satisfactorily.

No abstract

rec mutations result in an extremely low level of recombination and a high frequency of primary non-disjunction in the female meiosis of Drosophila melanogaster . Here we demonstrate that the rec gene encodes a novel protein related to the mini-chromosome maintenance (MCM) proteins. Six MCM proteins (MCM2 -7) are conserved in eukaryotic genomes, and they function as heterohexamers in the initiation and progression of mitotic DNA replication. Three rec alleles, rec 1 , rec 2 and rec 3 , were found to possess mutations within this gene, and P element-mediated germline transformation with a wild-type rec cDNA fully rescued the rec mutant phenotypes. The 885 amino acid REC protein has an MCM domain in the middle of its sequence and, like MCM2, 4, 6 and 7, REC contains a putative Zn-finger motif. Phylogenetic analyses revealed that REC is distantly related to the six conserved MCM proteins. Database searches reveal that there are candidates for orthologs of REC in other higher eukaryotes, including human. We addressed whether rec is involved in DNA repair in the mitotic division after the DNA damage caused by methylmethane sulfonate (MMS) or by X-rays. These analyses suggest that the rec gene has no, or only a minor, role in DNA repair and recombination in somatic cells.