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961.
We investigate the mechanisms of circulations in Lake Biwa using model results that are driven by the momentum and heat fluxes
evaluated from meteorological parameters observed around and on the lake. The kinetic energy budget shows that the wind stress
over the lake, which has positive (negative) curl over the northern (southern) region of the lake throughout the year, generates
the current system of multiple gyres in the stratified season (May–January), while the thermal forcing makes a minor contribution.
This mechanism is quite different from the previous picture, in which the thermal forcing was dominant in forming the gyre
system during the heating season. In the cooling season, the overturning of the lake occurs not in a simple one-dimensional
(vertical) process, but in a time-dependent three-dimensional one. Cold water that is formed in the shallow eastern region
descends the bottom slope to the deep lake in December to March while such a descent hardly occurs in the western region.
A large shallow area (small heat capacity) as well as intense cooling in the eastern region effectively produces cold water.
Wind again plays an important role by intensifying the cooling through its higher speed and by driving slope current. Further,
the fluctuating wind direction causes significantly time-dependent behaviors of the slope current or bottom water formation. 相似文献
962.
Michiko C. Ojimi Naoko Isomura Michio Hidaka 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2009,152(2):240-244
The polyp (scyphistoma) of the jellyfish Cassiopea sp. can be maintained in culture for a long time, as polyps repeatedly reproduce asexually via formation of vegetative buds or propagules. The medusa, which is the sexually reproducing stage, typically has a relatively short life span. As a first step to understand the difference in life spans of the polyp and medusa stages of Cassiopea sp., we measured telomerase activity in different life cycle stages. We found telomerase activity in tissues of aposymbiotic polyps and propagules and symbiotic ephyrae (newly budded medusae) and adult medusae. No significant difference in telomerase activity was found between polyps and the bell region of the medusae. The cloned elongation products of the stretch PCR contained the TTAGGG repeats suggesting that the jellyfish has the ‘vertebrate’ telomere motif (TTAGGG)n. This is the first study to show that somatic tissues of both polyp and medusa stages of a cnidarian had telomerase activity. Telomerase activity in somatic tissues may be related to the presence of multipotent interstitial cells and high regenerative capacity of cnidarians. 相似文献
963.
Nucleotide sequences of the rDNA intergenic spacer (IGS) region in Pythium ultimum were determined in 16 clones obtained from three isolates differing in production of sexual organs. Several sequences with
different lengths were detected in each isolate, showing heterogeneity in the IGS region. In addition, several tandem repeat
regions were detected in all the clones. The sequences, length, and number of each copy largely varied among repeat regions.
Length heterogeneity arose from the complex combination of the number of copy within the repeat regions. Furthermore, the
nucleotide sequence of each copy and the number of repetition varied not only between isolates but also between clones from
an isolate. Based on the sequence similarity and the number of copies in repeat regions, specific patterns different between
homothallic P. ultimum and the Pythium group HS (hyphal swellings) were recognized in a few regions. These results suggest that these two groups have slight genetic
differences in the IGS region, although the differences in most of the repeat regions were not enough to identify each group. 相似文献
964.
Michio X. Watanabe Stephanie P. Jones Hisato Iwata Eun-Young Kim Sean W. Kennedy 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2009,149(4):605-612
In this study we investigated the effect of a single-compound exposure or two compound co-exposure to tetrachlorodibenzo-p-dioxin (TCDD) plus perfluorooctane sulfonate (PFOS) or perfluorooctanoic acid (PFOA) on the mRNA expression of cytochromes P450 (CYP) 1A4, 4V2 and 3A37, ethoxyresorufin-O-deethylase (EROD) activity and cell viability in chicken (Gallus gallus domesticus) embryo primary hepatocyte cultures. Cell viability after 24 h of incubation was significantly decreased in cells exposed to PFOS at concentrations between 30 µM and 60 µM with or without co-exposure to TCDD (0.3 nM at maximum). PFOA did not decrease cell viability even at maximum concentrations of 60 µM. TCDD induced CYP1A4 mRNA and EROD activity substantially as reported previously. PFOS also increased CYP1A4 mRNA in a concentration-dependent manner. Co-exposure of cells to PFOS plus TCDD did not change CYP1A4 mRNA levels compared to cells treated with TCDD alone. PFOS alone did not induce CYP4V2 mRNA, however 40–50 µM PFOS plus TCDD (0.3 nM) induced CYP4V2 mRNA compared to TCDD alone (P < 0.05). This trend was similar to that observed with co-exposure to TCDD plus PFOA, suggesting that PFOA alone did not induce CYP4V2 mRNA, whereas co-exposure to TCDD plus PFOA induced the expression levels. PFOS alone decreased CYP3A37 mRNA by a maximum of 45%, however after co-exposure to TCDD, recovery of mRNA expression to levels measured in DMSO-treated cells was observed. Our data suggest a complex gene response to mixtures of dioxin-like and perfluorinated compounds. 相似文献
965.
Akihiko Noguchi Satoko Matsumura Mari Dezawa Mari Tada Masako Yanazawa Akane Ito Manami Akioka Satoru Kikuchi Michio Sato Shouji Ideno Munehiro Noda Atsushi Fukunari Shin-ichi Muramatsu Yutaka Itokazu Kazuki Sato Hitoshi Takahashi David B. Teplow Yo-ichi Nabeshima Akiyoshi Kakita Kazutomo Imahori Minako Hoshi 《The Journal of biological chemistry》2009,284(47):32895-32905
Amyloid β-protein (Aβ) assemblies are thought to play primary roles in Alzheimer disease (AD). They are considered to acquire surface tertiary structures, not present in physiologic monomers, that are responsible for exerting toxicity, probably through abnormal interactions with their target(s). Therefore, Aβ assemblies having distinct surface tertiary structures should cause neurotoxicity through distinct mechanisms. Aiming to clarify the molecular basis of neuronal loss, which is a central phenotype in neurodegenerative diseases such as AD, we report here the selective immunoisolation of neurotoxic 10–15-nm spherical Aβ assemblies termed native amylospheroids (native ASPDs) from AD and dementia with Lewy bodies brains, using ASPD tertiary structure-dependent antibodies. In AD patients, the amount of native ASPDs was correlated with the pathologic severity of disease. Native ASPDs are anti-pan oligomer A11 antibody-negative, high mass (>100 kDa) assemblies that induce degeneration particularly of mature neurons, including those of human origin, in vitro. Importantly, their immunospecificity strongly suggests that native ASPDs have a distinct surface tertiary structure from other reported assemblies such as dimers, Aβ-derived diffusible ligands, and A11-positive assemblies. Only ASPD tertiary structure-dependent antibodies could block ASPD-induced neurodegeneration. ASPDs bind presynaptic target(s) on mature neurons and have a mode of toxicity different from those of other assemblies, which have been reported to exert their toxicity through binding postsynaptic targets and probably perturbing glutamatergic synaptic transmission. Thus, our findings indicate that native ASPDs with a distinct toxic surface induce neuronal loss through a different mechanism from other Aβ assemblies. 相似文献
966.
Yoshida T Yamagishi S Nakamura K Matsui T Imaizumi T Inoue H Ueno T Sata M 《Life sciences》2006,79(21):1981-1987
There is a growing body of evidence to show that that C-reactive protein (CRP), an acute phase reactant, is one of the most valuable predictors of future cardiovascular events. Since CRP proteins directly contribute to the development and progression of atherosclerosis as well, reduction of CRP levels may be a novel therapeutic target for the treatment of cardiovascular disease. In this study, we examined whether pigment epithelium-derived factor (PEDF) could block the interleukin-6-induced CRP expression in cultured human hepatoma cells and the way that it might achieve this effect. PEDF inhibited the IL-6-induced CRP expression in Hep3B cells at both mRNA and proteins levels. PEDF suppressed the intracellular reactive oxygen species generation in IL-6-exposed Hep3B cells. Anti-oxidants mimicked the effects of PEDF. PEDF was also found to inhibit the IL-6-elicited Rac-1 activation, whereas dominant-negative Rac-1 dose-dependently decreased the CRP mRNA levels. PEDF blocked the IL-6-induced STAT3 phosphorylations and NF-kappaB p65 activity in Hep3B cells. Our present study suggests that PEDF could be one of the potent suppressors of CRP production by the liver and may play a protective role against atherosclerosis. 相似文献
967.
Recombinant peptides related to vitellogenesis-inhibiting hormone (VIH) of the American lobster Homarus americanus were expressed in bacterial cells, and then purified after being allowed to refold. Biological activities of the recombinant VIHs having an amidated C-terminus (rHoa-VIH-amide) and a free carboxyl-terminus (rHoa-VIH-OH) were examined using an ovarian fragment incubation system derived from the kuruma prawn, Marsupenaeus japonicus. The rHoa-VIH-amide significantly reduced vitellogenin mRNA levels in the ovary, while rHoa-VIH-OH had no effect. This is the first report that describes the production of a crustacean VIH having biological activity and the importance of the C-terminal amidation for its vitellogenesis-inhibiting activity. 相似文献
968.
Tool-use for drinking water by immature chimpanzees of Mahale: prevalence of an unessential behavior 总被引:3,自引:3,他引:0
Matsusaka T Nishie H Shimada M Kutsukake N Zamma K Nakamura M Nishida T 《Primates; journal of primatology》2006,47(2):113-122
Use of leaves or sticks for drinking water has only rarely been observed during long-term study of wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale. Recently, however, we observed 42 episodes of tool-use for drinking water (73 tools and two cases of using tool-sets) between 1999 and 2004. Interestingly, all of the performers were immature chimpanzees aged from 2 to 10 years. Immature chimpanzees sometimes observed the tool-using performance of others and subsequently reproduced the behavior, while adults usually paid no attention to the performance. This tool-use did not seem to occur out of necessity: (1) chimpanzees often used tools along streams where they could drink water without tools, (2) they used tools for drinking water from tree holes during the wet season when they could easily obtain water from many streams, and (3) the tool-using performance sometimes contained playful aspects. Between-site comparisons revealed that chimpanzees at drier habitats used tools for drinking water more frequently and in a more conventional manner. However, some variations could not be explained by ecological conditions. Such variations and the increase in this tool-use in recent years at Mahale strongly suggest that social learning plays an important role in the process of acquiring the behavior. We should note here that such behaviors that lack obvious benefits or necessity can be prevalent in a group. 相似文献
969.
Mukai K Watanabe H Kubota M Chaen H Fukuda S Kurimoto M 《Applied and environmental microbiology》2006,72(2):1065-1071
A glycosyltransferase, involved in the synthesis of cyclic maltosylmaltose [CMM; cyclo-{-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->}] from starch, was purified to homogeneity from the culture supernatant of Arthrobacter globiformis M6. The CMM-forming enzyme had a molecular mass of 71.7 kDa and a pI of 3.6. The enzyme was most active at pH 6.0 and 50 degrees C and was stable from pH 5.0 to 9.0 and up to 30 degrees C. The addition of 1 mM Ca2+ enhanced the thermal stability of the enzyme up to 45 degrees C. The enzyme acted on maltooligosaccharides that have degrees of polymerization of > or =3, amylose, and soluble starch to produce CMM but failed to act on cyclomaltodextrins, pullulan, and dextran. The mechanism for the synthesis of CMM from maltotetraose was determined as follows: (i) maltotetraose + maltotetraose --> 6(4)-O-alpha-maltosyl-maltotetraose + maltose and (ii) 6(4)-O-alpha-maltosyl-maltotetraose --> CMM + maltose. Thus, the CMM-forming enzyme was found to be a novel maltosyltransferase (6MT) catalyzing both intermolecular and intramolecular alpha-1,6-maltosyl transfer reactions. The gene for 6MT, designated cmmA, was isolated from a genomic library of A. globiformis M6. The cmmA gene consisted of 1,872 bp encoding a signal peptide of 40 amino acids and a mature protein of 583 amino acids with a calculated molecular mass of 64,637. The deduced amino acid sequence showed similarities to alpha-amylase and cyclomaltodextrin glucanotransferase. The four conserved regions common in the alpha-amylase family enzymes were also found in 6MT, indicating that 6MT should be assigned to this family. 相似文献
970.
Yuko Mizukami Mitsuru kato Tadashi Takamizo Michio Kanbe Susumu Inami Kazumi Hattori 《Plant Cell, Tissue and Organ Culture》2006,84(1):80-89
Non-embryogenic protoplasts of Medicago rugosa and M. scutellata were electro-fused with iodoacetic acid-treated protoplasts of M. sativa (alfalfa). Putative somatic hybrid callus were obtained and some plants regenerated from both combinations. Hybridity of regenerants was confirmed by morphology, molecular means and cytological observations. Parental specific bands were recognized in somatic hybrids by Southern analysis. The somatic hybrids were perennial and their morphology was similar to M. sativa. Cytological observations were carried out on the somatic hybrids, their vegetative clones and self-pollinated offspring. Original somatic hybrids were aneuploids (2n=31–59), but during vegetative proliferation, their chromosome numbers reduced to 32. Those clones of hybrids formed seeds from M. sativa (+) M. rugosa by self-crossing. Chromosomal rearrangements within the parental genomes were observed in vegetative clones of hybrids and their S1 offspring by Genomic in situ Hybridization (GISH). Some of S1 offspring from M. sativa (+) M. rugosa showed better spring growth than parental M. sativa and tend to be tolerant to Alfalfa weevil. It was considered that these traits were introduced from the genome transferring M.␣rugosa chromosome to M. sativa. The cell fusion may still have a potential in transferring alien chromosomes in order to increase the genetic variation for crop breeding. 相似文献