Somatostatin regulates brain amyloid beta peptide Abeta42 through modulation of proteolytic degradation

Expression of somatostatin in the brain declines during aging in various mammals including apes and humans. A prominent decrease in this neuropeptide also represents a pathological characteristic of Alzheimer disease. Using in vitro and in vivo paradigms, we show that somatostatin regulates the metabolism of amyloid beta peptide (Abeta), the primary pathogenic agent of Alzheimer disease, in the brain through modulating proteolytic degradation catalyzed by neprilysin. Among various effector candidates, only somatostatin upregulated neprilysin activity in primary cortical neurons. A genetic deficiency of somatostatin altered hippocampal neprilysin activity and localization, and increased the quantity of a hydrophobic 42-mer form of Abeta, Abeta(42), in a manner similar to presenilin gene mutations that cause familial Alzheimer disease. These results indicate that the aging-induced downregulation of somatostatin expression may be a trigger for Abeta accumulation leading to late-onset sporadic Alzheimer disease, and suggest that somatostatin receptors may be pharmacological-target candidates for prevention and treatment of Alzheimer disease.     

Evaluation of adriamycin nephropathy by an in vivo electron paramagnetic resonance

A rat model for human minimal change nephropathy was obtained by the intravenous injection of adriamycin (ADR) at 5 mg/kg. By using an in vivo electron paramagnetic resonance (EPR) spectrometer operating at 700 MHz, the temporal changes in signal intensities of a nitroxide radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), in the kidneys of rats with ADR nephropathy were investigated. The decay rate of the EPR signal intensity obtained in the kidney is indicative of the renal reducing ability. It was found that the reducing ability in the kidney declined on the 7th day after ADR administration and recovered after the 14th day. Impairment of the reducing ability occurred before the appearance of continuous urinary protein. The in vitro EPR study showed that this impairment of in vivo renal reducing ability is related to impairment of the reducing ability in the mitochondria.     

Optimization of human serum albumin production in methylotrophic yeast Pichia pastoris by repeated fed-batch fermentation

An optimization method for repeated fed-batch fermentation was established with the aim of improving the recombinant human serum albumin (rHSA) production in Pichia pastoris. A simulation model for fed-batch fermentation was formulated and the optimal methanol-feeding policy calculated by dynamic programming method using five different methanol-feeding periods. The necessary state variables were collected from the calculated results and used for further optimization of repeated fed-batch fermentation. The optimal operation policy was investigated using the pre-collected state variables by estimating the overall profit per total methanol-feeding time. The calculated results indicated that the initial cell mass from the 2nd fed-batch fermentation on should be set at 35 or 40 g and methanol-feeding time at 264 h. In repeated fed-batch fermentation using the optimal operation policy, actual culture volume was in good agreement with the values simulated by model equations, but some discrepancy was observed in rHSA production. Minimum experiments were therefore carried out to re-evaluate rHSA production levels, which were then applied in re-calculations to determine the optimal operation policy. The optimal policy for repeated fed-batch fermentation established in the present study (i.e., 4-times-repeated fed-batch fermentation) achieved a 47% increase in annual rHSA production. Optimization of the culture period also brought about a 28% increase in annual rHSA production even in simple (not repeated) fed-batch fermentation.     

Regulation of the intracellular free iron pool by Dpr provides oxygen tolerance to Streptococcus mutans

Dpr is an iron-binding protein required for oxygen tolerance in Streptococcus mutans. We previously proposed that Dpr could confer oxygen tolerance to the bacterium by sequestering intracellular free iron ions that catalyze generation of highly toxic radicals (Y. Yamamoto, M. Higuchi, L. B. Poole, and Y. Kamio, J. Bacteriol. 182:3740-3747, 2000; Y. Yamamoto, L. B. Poole, R. R. Hantgan, and Y. Kamio, J. Bacteriol. 184:2931-2939, 2002). Here, we examined the intracellular free iron status of wild-type (WT) and dpr mutant strains of S. mutans, before and after exposure to air, by using electron spin resonance spectrometry. Under anaerobic conditions, free iron ion concentrations of WT and dpr strains were 225.9 +/- 2.6 and 333.0 +/- 61.3 microM, respectively. Exposure of WT cells to air for 1 h induced Dpr expression and reduced intracellular free iron ion concentrations to 22.5 +/- 5.3 microM; under these conditions, dpr mutant cells maintained intracellular iron concentration at 230.3 +/- 28.8 microM. A decrease in cell viability and genomic DNA degradation was observed in the dpr mutant exposed to air. These data indicate that regulation of the intracellular free iron pool by Dpr is required for oxygen tolerance in S. mutans.     

Investigation of the mechanism of meiotic DNA cleavage by VMA1-derived endonuclease uncovers a meiotic alteration in chromatin structure around the target site

VMA1-derived endonuclease (VDE), a homing endonuclease in Saccharomyces cerevisiae, is encoded by the mobile intein-coding sequence within the nuclear VMA1 gene. VDE recognizes and cleaves DNA at the 31-bp VDE recognition sequence (VRS) in the VMA1 gene lacking the intein-coding sequence during meiosis to insert a copy of the intein-coding sequence at the cleaved site. The mechanism underlying the meiosis specificity of VMA1 intein-coding sequence homing remains unclear. We studied various factors that might influence the cleavage activity in vivo and found that VDE binding to the VRS can be detected only when DNA cleavage by VDE takes place, implying that meiosis-specific DNA cleavage is regulated by the accessibility of VDE to its target site. As a possible candidate for the determinant of this accessibility, we analyzed chromatin structure around the VRS and revealed that local chromatin structure near the VRS is altered during meiosis. Although the meiotic chromatin alteration exhibits correlations with DNA binding and cleavage by VDE at the VMA1 locus, such a chromatin alteration is not necessarily observed when the VRS is embedded in ectopic gene loci. This suggests that nucleosome positioning or occupancy around the VRS by itself is not the sole mechanism for the regulation of meiosis-specific DNA cleavage by VDE and that other mechanisms are involved in the regulation.     

Fission Yeast Germinal Center (GC) Kinase Ppk11 Interacts with Pmo25 and Plays an Auxiliary Role in Concert with the Morphogenesis Orb6 Network (MOR) in Cell Morphogenesis

How cell morphology and the cell cycle are coordinately regulated is a fundamental subject in cell biology. In fission yeast, 2 germinal center kinases (GCKs), Sid1 and Nak1, play an essential role in septation/cytokinesis and cell separation/cell polarity control, respectively, as components of the septation initiation network (SIN) and the morphogenesis Orb6 network (MOR). Here we show that a third GCK, Ppk11, is also required for efficient cell separation particularly, at a high temperature. Although Ppk11 is not essential for cell division, this kinase plays an auxiliary role in concert with MOR in cell morphogenesis. Ppk11 physically interacts with the MOR component Pmo25 and is localized to the septum, by which Ppk11 is crucial for Pmo25 targeting/accumulation to the septum. The conserved C-terminal WDF motif of Ppk11 is essential for both septum accumulation of Pmo25 and efficient cell separation. In contrast its kinase activity is required only for cell separation. Thus, both interaction of Ppk11 with Pmo25 and Ppk11 kinase activity are critical for efficient cell separation.     

Vasotocin/isotocin-immunoreactive neurons in the medaka fish brain are sexually dimorphic and their numbers decrease after spawning in the female

In teleosts, the distribution of neurons in the preoptic-hypothalamic region and their associated neurohypophysial hormones, such as vasotocin (VT), appears to be different among species. This differential distribution is thought to reflect the social and/or sexual status of individuals within a species. In the present study, we analyzed the number, size and the distribution of vasotocin/isotocin (VT/IT) neurons in the brains of both male and female medaka (Oryzias latipes) using immunohistochemistry. VT/IT neurons were similarly located in an inverted L-shape in the nucleus preopticus in both gender, as has been already reported in salmonids. However, computer-assisted image analysis revealed sexual dimorphism in the number of VT/IT-immunoreactive (ir) neurons, with greater numbers found in males as compared to females. Further, in the female brain, the number of VT/IT-ir neurons decreased significantly after spawning. In pre-spawning compared to post-spawning females, the small-sized VT/IT-ir neurons dominated. Sexual differentiation of the medaka is fully dependent upon the steroid status during the early developmental stages and steroids are also known to trigger gender-specific behavior in the adult medaka. Our findings strongly suggest that VT and/or IT neurons may be functionally related to ovulation and/or the reproductive axes through connections to their steroidal status.     

Characterization and cDNA cloning of dipeptidyl peptidase IV from the venom of Gloydius blomhoffi brevicaudus

Dipeptidyl peptidase activity was investigated in snake venoms from Gloydius blomhoffi brevicaudus, Gloydius halys blomhoffii, Trimeresurus flavoviridis and Crotalus atrox. The strongest dipeptidyl peptidase IV (DPP IV) activity was found in venom from G. blomhoffi brevicaudus. The substrate specificity, susceptibility to inhibitors, and pH optimum of the partially purified enzyme were similar to those of known DPP IVs from bacteria and eukaryotes. The G. blomhoffi brevicaudus venom gland cDNA library was screened to isolate cDNA clones using probes based on amino acid sequences highly conserved in known DPP IVs. Two cDNA species encoding DPP IV were obtained, and designated as DPP IVa and DPP IVb. This is the first study to report the primary structure of DPP IV from a reptile. The deduced amino acid sequences for DPP IVa and DPP IVb both consist of 751amino acid residues and are highly homologous to each other. A putative catalytic triad for serine proteases, Ser-616, Asp-694, and His-726, is present. It is of particular interest that the deduced NH(2)-terminal sequence associated with the characteristic signal peptide is identical to that determined from the purified DPP IV. This indicates that the signal peptide of snake venom DPP IV is not cleaved off during biosynthesis, unlike those of other snake venom proteins.     

Maricurvus nonylphenolicus gen. nov., sp. nov., a nonylphenol-degrading bacterium isolated from seawater

A novel aerobic, Gram-negative bacterial strain, designated KU41E(T), which degrades p-n-nonylphenol, was isolated from seawater obtained from the coastal region of Ishigaki Island, Japan. Cells are motile, curved rods with a single polar flagellum. Strain KU41E(T) grew at 20-35 °C, pH 7.0-8.0, in the presence of 1.0-4.0% NaCl. The predominant respiratory lipoquinone was ubiquinone-8, and the major cellular fatty acids were summed feature 3 (C(15:0) iso 2OH and/or C(16:1) ω7c, 28.4%), C(18:1) ω7c (19.8%), and C(16:0) (17.0%). The DNA G + C content was 48.6 mol%. The 16S rRNA gene sequence analysis indicated that strain KU41E(T) is affiliated with the order Alteromonadales within the class Gammaproteobacteria and is most closely related to Pseudoteredinibacter isoporae SW-11(T) (93.6% similarity) and Teredinibacter turnerae T7902(T) (91.9% similarity). On the basis of physiological, chemotaxonomic, and phylogenetic data, strain KU41E(T) is suggested to represent a novel species of a new genus, for which the name Maricurvus nonylphenolicus gen. nov., sp. nov. is proposed. The type strain of M. nonylphenolicus is KU41E(T) (=JCM 17778(T)).