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11.
Virginia Edgcomb William Orsi John Bunge Sunok Jeon Richard Christen Chesley Leslin Mark Holder Gordon T Taylor Paula Suarez Ramon Varela Slava Epstein 《The ISME journal》2011,5(8):1344-1356
Microbial diversity and distribution are topics of intensive research. In two companion papers in this issue, we describe the results of the Cariaco Microbial Observatory (Caribbean Sea, Venezuela). The Basin contains the largest body of marine anoxic water, and presents an opportunity to study protistan communities across biogeochemical gradients. In the first paper, we survey 18S ribosomal RNA (rRNA) gene sequence diversity using both Sanger- and pyrosequencing-based approaches, employing multiple PCR primers, and state-of-the-art statistical analyses to estimate microbial richness missed by the survey. Sampling the Basin at three stations, in two seasons, and at four depths with distinct biogeochemical regimes, we obtained the largest, and arguably the least biased collection of over 6000 nearly full-length protistan rRNA gene sequences from a given oceanographic regime to date, and over 80 000 pyrosequencing tags. These represent all major and many minor protistan taxa, at frequencies globally similar between the two sequence collections. This large data set provided, via the recently developed parametric modeling, the first statistically sound prediction of the total size of protistan richness in a large and varied environment, such as the Cariaco Basin: over 36 000 species, defined as almost full-length 18S rRNA gene sequence clusters sharing over 99% sequence homology. This richness is a small fraction of the grand total of known protists (over 100 000–500 000 species), suggesting a degree of protistan endemism. 相似文献
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The effects of mammalian gonadotropins, methyltestosterone and partially purified salmon gonadotropin on spermiation and oocyte maturation were studied in adult grey mullet. Methyltestosterone was a potent spermiating agent in both prespawning and spawning trials. The most effective dose was 5 mg/100 g body weight. Human chorionic gonadotropin (HCG) was moderately effective at a dose rate of 20 IU/100 g body weight. Both hormones blocked resorption of milt in captive animals. The HCG, FSH/LH combination, Synahorin+mullet pituitary homogenate, and partially purified salmon gonadotropin were equally effective, at the doses used, in inducing oocyte maturation and preventing onset of atrophy before completion of vitellogenesis. Atrophy occurred in all experimental fish at mean oocyte diameter of 750 μ. The significance of this finding is discussed. (Oceanic Institute Contribution No. 98). 相似文献
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Abstract: The phosphorylcholine concentration of rat brain rises and falls in response to parallel changes in the concentration of circulating choline. A single oral dose of choline chloride (20 mmol/kg) elevated whole-brain concentrations of both choline and phosphorylcholine 5 h after administration; a greater proportion of exogenously administered choline was retained by the brain in its phosphorylated form than as the free arnine. Striatal phosphorylcholine concentrations were elevated within 2 h of choline administration and continued to be significantly greater than control values for up to 34 h after treatment. The response of striatal choline levels to exogenous choline was of shorter duration than that of phosphorylcholine and was correlated with a significant increase in striatal acetylcholine concentrations. The consumption of a choline-free diet for 7 days lowered both serum choline and striatal phosphorylcholine concentrations, but had no effect on striatal choline or acetylcholine. These results suggest that choline kinase is unsaturated by its substrate in vivo and may thus serve to modulate the response of brain choline concentrations to alterations in the supply of circulating choline. 相似文献
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Jin Wei Mia Madel Alfajaro Peter C. DeWeirdt Ruth E. Hanna William J. Lu-Culligan Wesley L. Cai Madison S. Strine Shang-Min Zhang Vincent R. Graziano Cameron O. Schmitz Jennifer S. Chen Madeleine C. Mankowski Renata B. Filler Neal G. Ravindra Victor Gasque Fernando J. de Miguel Ajinkya Patil Huacui Chen Craig B. Wilen 《Cell》2021,184(1):76-91.e13
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William Sellar 《BMJ (Clinical research ed.)》2000,321(7271):1297
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Diel emigration and colonization responses of blackfly larvae (Diptera: Simuliidae) to ultraviolet radiation 总被引:1,自引:0,他引:1
1. Total counts of blackfly larvae densities over 30- and 57-h periods in experimental channels during May of 1996 & 1997 indicate that ultraviolet radiation (UV; 290–400 nm) may be important in stimulating emigration.
2. Under experimentally controlled solar UV exposure, larval densities at dawn in UV-shielded channels were 161% and 168% higher than in the UV-exposed channels. Larval densities in UV-exposed channels then decreased by 68.2% and 81.1% between dawn and early afternoon of the two days; density decreases in UV-shielded channels were slight, and not statistically significant, during the same periods.
3. Larvae within UV-exposed channels occupied shaded microhabitats during hours of intense solar radiation, suggesting that simuliid larvae can detect and respond to UV radiation over very short periods of time.
4. A cyclical pattern of UV-induced emigration during hours of increasing solar flux (06.30–13.30) and net immigration in the hours of decreasing solar flux and at night emerged. Thus stream invertebrates may be very sensitive to environmental changes, resulting in either increased UV flux or decreased shading of streams. Diel cycles in invertebrate densities should be taken into account in research designs and sampling protocols in order to identify and interpret correctly results of both periodic surveys and experiments. 相似文献
2. Under experimentally controlled solar UV exposure, larval densities at dawn in UV-shielded channels were 161% and 168% higher than in the UV-exposed channels. Larval densities in UV-exposed channels then decreased by 68.2% and 81.1% between dawn and early afternoon of the two days; density decreases in UV-shielded channels were slight, and not statistically significant, during the same periods.
3. Larvae within UV-exposed channels occupied shaded microhabitats during hours of intense solar radiation, suggesting that simuliid larvae can detect and respond to UV radiation over very short periods of time.
4. A cyclical pattern of UV-induced emigration during hours of increasing solar flux (06.30–13.30) and net immigration in the hours of decreasing solar flux and at night emerged. Thus stream invertebrates may be very sensitive to environmental changes, resulting in either increased UV flux or decreased shading of streams. Diel cycles in invertebrate densities should be taken into account in research designs and sampling protocols in order to identify and interpret correctly results of both periodic surveys and experiments. 相似文献