The Expression of Two Splice Variants of Metabotropic Glutamate Receptor Subtype 5 in the Rat Brain and Neuronal Cells During Development

Abstract: We previously reported that a variant with extra amino acid residues exists in the metabotropic glutamate receptor subtype 5 (mGluR5). Either of the two isoforms, named mGluR5b and mGluR5a for the isoforms with and without the inserted sequence, respectively, generated Ca²⁺-activated Cl⁻ current when expressed in Xenopus oocytes. We herein report that these two isoforms are produced by the alternative splicing of the exon skipping type. When examined during the course of postnatal development, the major mGluR5 isotype mRNA was observed to switch from mGluR5a to mGluR5b in the rat hippocampus and the cerebral cortex. We also investigated two cell lines that could be differentiated into neuron-like cells in vitro. Whereas the mGluR5b mRNA was hardly detectable in either undifferentiated or differentiated NG108-15 cells, the relative amounts of the two variant mRNAs changed after the induction of differentiation in the P19 cells. An extracellular application of trans - d,l -1-amino-1,3-cyclopentanedicarboxylate on the neuron-like P19 cells induced intracellular Ca²⁺ mobilization, thus suggesting that the cells could express functional mGluR(s) coupled to phospholipase C and other components that could mediate the signal transduction pathway. This cell line may thus provide a model system for studying both mGluR5 expression and other mGluR-induced phenomena at the molecular level.     

A mutation at proline-115 in the A-factor receptor protein of Streptomyces griseus abolishes DNA-binding ability but not ligand-binding ability.

A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) and its specific receptor protein (ArpA) are required for streptomycin production and aerial mycelium formation in Streptomyces griseus. A mutant strain HO1 that produced streptomycin and formed aerial mycelium and spores was derived from an A-factor-deficient mutant, S. griseus HH1. The phenotypes of mutant HO1 were found to result from a single amino acid replacement of ArpA; the proline residue at position 115 in the wild-type ArpA was replaced by serine, yielding mutant ArpA (P115S). The mutant ArpA (P115S) was still able to form a homodimer and possessed A-factor-binding ability but lost the ability to bind DNA. The properties of P115S suggest that ArpA consists of two independently functional domains, one for A-factor binding and one for DNA binding, and that proline-115 plays an important role in DNA binding. This is in agreement with the idea that A-factor binding to the COOH-terminal domain of ArpA causes a subtle conformational change of the distal NH2-terminal DNA-binding domain, resulting in dissociation of ArpA from DNA.     

Strong adjuvant action of Klebsiella O3 lipopolysaccharide and its inhibition of systemic anaphylaxis

Abstract Immunization with lipopolysaccharide from Klebsiella O3 as an immunological adjuvant did not cause the death of mice in systemic anaphylaxis to bovine serum albumin. On the other hand, most mice immunized with lipopolysaccharide from Escherichia coli O111, Klebsiella O4 and Salmonella minnesota did die. Klebsiella O3 lipopolysaccharide enhanced IgM and IgG antibody response to BSA more markedly than Escherichia coli O111 lipopolysaccharide, while it affected the production of IgE antibody only slightly. Therefore, it is suggested that the inhibition of systemic anaphylaxis by Klebsiella O3 lipopolysaccharide adjuvant might be related to its strong adjuvant action on IgM and IgG class antibody production, and that high levels of circulating IgM and IgG antibodies might act as blocking antibodies in the development of IgE-mediated systemic anaphylaxis.     

Some aspects of infanticide and intermale competition among langurs,Presbytis entellus,at Dharwar,India

Conspecific infanticides by male langurs depresses population growth in their densely populated habitats. An infanticidal model developed from demographic parameters obtained in the Dharwar study area predicts an almost stable population. On the other hand, a non-infanticidal model predicts a population growth by 2.6% per year. The effect of frequent troop usurpation and infanticide on the control of population growth must be strong if the natality rate is high. For subadult and juvenile surplus males, it must be difficult to survive and to mature in the all-male party in its poor habitat. However, from calculations for living adult males and the number of troops at Dharwar, most adult males are thought to be able to obtain a troop within five years of first challenge of usurpation. Dominant males do not always take over a troop containing more females than do subordinate males. These simple assessments require further intensive field studies to determine the precise differences between infanticidal and non-infanticidal populations and whether or not dominant males make a greater genetic contribution than subordinate males to subsequent generations.     

Metronidazole-induced susceptibility of adult mice to intestinalClostridium botulinum colonization

Clostridium botulinum type A spore challenges were given orogastrically to adult mice that had been treated with metronidazole. The organism multiplied in the intestinal tract for up to five days if it was administered 9–48 h after the last dose of metronidazole. The known antibacterial spectrum of metronidazole indicated that obligate anaerobic bacteria are important in the natural resistance of adult mice to colonization byC. botulinum, but treatment with the antimicrobial agent did not reduce the number of these bacteria in the cecum and colon.     

Effects of an inhibitor of glucosylceramide synthase on glycosphingolipid synthesis and neurite outgrowth in murine neuroblastoma cell lines.

1-Phenyl-2-decanolyamino-3-morpholino-1-propanol (PDMP), an effective inhibitor of UDP-glucose:ceramide glucosyltransferase, caused inhibition of cell growth in murine neuroblastoma cell lines. Metabolic labeling of glycosphingolipids with [14C]galactose in NS-20Y, Neuro2a, and N1E-115 cells showed reduced incorporation of radioactivity into gangliosides and neutral glycosphingolipids when threo-PDMP was present in the medium. Treatment of NS-20Y cells with threo-PDMP resulted in a time-dependent decrease in mass levels of gangliosides and neutral glycosphingolipids. After 24 h in the presence of 50 microM threo-PDMP, neutral glycosphingolipid mass was reduced to 32%, where glucosylceramide was the most affected (90% decrease). The ganglioside mass was reduced to 57% of the original content. Neurite outgrowth from neuroblastoma cells in serum-free medium was significantly inhibited by threo-PDMP in a dose-dependent manner. Threo-PDMP also caused retraction of neurites which had been induced to extend in serum-free medium. Pretreatment of cells with GM1 partially restored the ability of NS-20Y cells for neurite outgrowth in the medium containing threo-PDMP. These results suggest a possible role for glycosphingolipids in neurite outgrowth of murine neuroblastoma cells.     

Ejaculations induced by p-chloroamphetamine (PCA) in rats, hamsters and mice.

The ejaculatory response induced by p-chloroamphetamine (PCA) in male rats, hamsters and mice was observed during 2 hours after the injection. The animals were treated intraperitoneally with PCA at doses ranging from 0.78125 to 160 mg/kg. The ED50 (effective dose in 50% of animals) values of PCA for the initiation of ejaculation in rats and hamsters were 1.3397 (1.0732-1.6725) and 0.1105 (0.0802-0.1522) mg/kg, respectively. On the other hand, no ejaculation was observed in any mice at any doses examined. So we concluded that there are species differences in the ejaculatory response, induced by PCA, among rats, hamsters and mice.     

Pre- and post-implantation losses of embryos in aging female IVCS mice

Mated female mice of the IVCS strain, aged 90 (control group), 180, 210, 240, 270, 300, 330, 360 and 420 days old, were studied for pre- and post-implantation loss of embryos. The percentage of pre-implantation loss in mice aged 90 to 210 days was 1.7/11.8 (14.4%) to 2.7/11.7 (23.1%). In mice aged 240 to 300 days it increased significantly as compared to the controls (46.5-90.2% versus 14.4%). It reached 100% in 300-days-old mice. The post-implantation loss of embryos and/or fetuses in mice aged 90 to 240 days was 1.0/10.2 (9.8%) to 2.5/9.0 (27.8%). In mice aged 270 to 300 days it increased significantly compared to the controls (100% versus 9.8%). The decrease in reproductive activity appeared first in a decrease in litter size, followed by a decrease in the number of blastocyst and implantation sites, and finally by anovulation during the process of aging in IVCS mice.     

Central effects of yohimbine on copulatory behavior in aged male rats

It is well known that yohimbine has a history of popular use because of its supposed aphrodisiac properties. The present study was done to determine whether yohimbine can modify the copulatory behavior of aged male rats. Adult male rats of the Wistar-Imamichi strain, 52 weeks of age and weighing 600-650g, were injected intracerebroventricularly with yohimbine hydrochloride (5, 10 micrograms/10 microliters/rat) or vehicle. Each male was then given the opportunity to mate with a receptive female for 30 min after administration of yohimbine or vehicle. Yohimbine produced significant decreases in the latency to initial mounting and significant increases in the number of mountings. However, there was no ejaculation in the yohimbine-and vehicle-treated males. This study is the first to clearly establish an important modulator of sexual arousal for yohimbine in aged male rats.