Effects of salmon calcitonin and anti-salmon calcitonin antibody on plasma calcium concentrations in the goldfish,Carassius auratus

The role of calcitonin (CT) in plasma calcium regulation was studied by the administration of exogenous CT and anti-salmon(s) CT antibody using goldfish,Carasius auratus, loaded or otherwise with calcium. CT elicited a decrease in plasma calcium concentrations at a dose of 10 ng/g body weight 1 h after administration. However, no effects were observed following doses of 30 ng and 50 ng/g 1 h, nor for the three doses 3 h after administration. In calcium-loaded fish, the effect of CT was different depending on the dosage of CT. Ten ng and 50 ng/g induced a decrease and an increase in plasma calcium concentrations, respectively, 3 h after administration. Anti-sCT antibody (0.02 μg or 0.1 μg/g) did not affect plasma calcium concentrations. In calcium-loaded fish, neither dose of anti-sCT antibody changed plasma calcium concentrations 1 h after administration. However, following a dose of 0.1 μg/g, plasma calcium concentrations decreased after 3 h. A positive correlation between plasma calcium concentrations and the gonad somatic index (GSI) in females was no longer apparent after administration of anti-sCT antibody. There was no relationship between plasma calcium concentrations and GSI in control and anti-sCT antibody-treated males. These results suggested that CT regulates plasma calcium concentrations in different ways depending on the dosage with CT having a role in calcium physiology during vitellogenesis.     

Inhibitory control of shivering and nonshivering thermogenesis by preoptic warm-sensitive neurons

To investigate the characteristics of efferent projections from the preoptic area for the control of shivering and nonshivering thermogenesis, we tested the effects of thermal stimulation and injecting excitatory substances into the preoptic area on shivering and nonshivering thermogenesis in anesthetized rats. Preoptic warming and injection of glutamate suppressed shivering at ambient temperatures of 15–21°C. Likewise, preoptic warming and d,l-homocysteic acid injection suppressed nonshivering thermogenesis elicited by electrical stimulation of the ventromedial hypothalamic nucleus. Inhibitory signals from warm-sensitive neurons, thus, contribute a larger efferent signal for heat production than do signals from cold-sensitive neurons.     

Dietary fructooligosaccharides induce immunoregulation of intestinal IgA secretion by murine Peyer's patch cells

Probiotic supplements induce immunological responses in the host, and dietary fructooligosaccharides (FOS) stimulate the growth of selected intestinal microflora. In this study we investigated the immunological influences of orally administrated FOS. BALB/c mice were orally administered 0-7.5% FOS for 6 weeks, and the intestinal mucosal immune responses were measured. In the 2.5%-FOS group, fecal IgA was significantly increased. IgA secretion by Peyer's patch (PP) cells was upregulated in a dose-dependent way in response to FOS and CD4+ T cells from PP showed a dose-dependent increase in production of interferon-gamma and interleukin (IL) 10, and a high response in production of IL-5 and IL-6. In contrast, FOS suppressed serum IgG1. Our findings suggest that FOS supplementation changes the intestinal environment of microflora, and leads to upregulation of IgA secretion in CD4+ PP cells in intestinal mucosa, and to suppression of the systemic immune response to type 2 helper T (Th2) dominant.     

Characterization of two β-decarboxylating dehydrogenases from <Emphasis Type="Italic">Sulfolobus acidocaldarius</Emphasis>

Sulfolobus acidocaldarius, a hyperthermoacidophilic archaeon, possesses two β-decarboxylating dehydrogenase genes, saci_0600 and saci_2375, in its genome, which suggests that it uses these enzymes for three similar reactions in lysine biosynthesis through 2-aminoadipate, leucine biosynthesis, and the tricarboxylic acid cycle. To elucidate their roles, these two genes were expressed in Escherichia coli in the present study and their gene products were characterized. Saci_0600 recognized 3-isopropylmalate as a substrate, but exhibited slight and no activity for homoisocitrate and isocitrate, respectively. Saci_2375 exhibited distinct and similar activities for isocitrate and homoisocitrate, but no detectable activity for 3-isopropylmalate. These results suggest that Saci_0600 is a 3-isopropylmalate dehydrogenase for leucine biosynthesis and Saci_2375 is a dual function enzyme serving as isocitrate-homoisocitrate dehydrogenase. The crystal structure of Saci_0600 was determined as a closed-form complex that binds 3-isopropylmalate and Mg²⁺, thereby revealing the structural basis for the extreme thermostability and novel-type recognition of the 3-isopropyl moiety of the substrate.     

The antimutagenic properties of a polysaccharide produced by Bifidobacterium longum and its cultured milk against some heterocyclic amines

The antimutagenicity and fermentation pattern of three Bifidobacterium longum strains (B. longum, B. longum PS+, and B. longum PS-) in skim milk were studied. The increase in fermentation time significantly increased antimutagenicity with all strains tested against the mutagenicity of both 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in an Ames-like test using streptomycin-dependent strain SD510 of Salmonella typhimurium TA98. Bifidobacterium longum PS+, a polysaccharide-producing strain, had a longer lag phase but showed the highest inhibition percentage against both mutagens tested. The viability of B. longum PS+ cells was not affected by the low pH of 4.1, probably owing to the protection offered by the polysaccharide produced. The antimutagenicity of the fermented milk against Trp-P-1 was dose dependent. The strains were also able to bind with different amino acid pyrolysates, and B. longum showed the highest binding. Acetone extracts of fermented skim milk dissolved in water showed less antimutagenicity than extracts dissolved in dimethylsulfoxide. The isolated crude polysaccharide from B. longum PS+ showed a dose-dependent inhibition of the mutagenicity of Trp-P-1. Thus, we conclude that the polysaccharide of B. longum PS+ can be used as an antimutagen.     

Phosphorylation of FTDP-17 mutant tau by cyclin-dependent kinase 5 complexed with p35, p25, or p39

One of the major pathological hallmarks of Alzheimer disease is neurofibrillary tangles. Neurofibrillary tangles are bundles of paired helical filaments composed of hyperphosphorylated tau. Cyclin-dependent kinase 5 (Cdk5) is one of the tau protein kinases that increase paired helical filament epitopes in tau by phosphorylation. Recently, various mutations of tau have been identified in frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17). Here, we investigated the phosphorylation of FTDP-17 mutant tau proteins, K257T, P301L, P301S, and R406W, by Cdk5 complexed with p35, p25, or p39 in vitro and in cultured cells. The extent of phosphorylation by all Cdk5 species was slightly lower in mutant tau than in wild-type tau. Major phosphorylation sites, including Ser202, Ser235, and Ser404, were the same among the wild-type, K257T, P301L, and P301S tau proteins phosphorylated by any Cdk5. On the other hand, R406W tau was less phosphorylated at Ser404 than were the other variants. This was not due to the simple replacement of amino acid Arg406 with Trp close to the phosphorylation site, because Ser404 in a R406W peptide was equally phosphorylated in a wild-type peptide. The decreased phosphorylation of mutant tau by Cdk5s was canceled when tau protein bound to microtubules was phosphorylated. These results indicate that FTDP-17 mutations do not affect the phosphorylatability of tau by Cdk5 complexed with p35, p25, or p39 and may explain part of the discrepancy reported previously between in vivo and in vitro phosphorylation of FTDP-17 tau mutants.