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排序方式: 共有571条查询结果,搜索用时 31 毫秒
41.
Crowell DN Packard CE Pierson CA Giner JL Downes BP Chary SN 《Physiologia plantarum》2003,118(1):29-37
We have identified a mutant of Arabidopsis thaliana ( lvr111 ) that exhibits a variegated phenotype, reduced isoprenoid pigmentation, and dwarfism in comparison with wild-type plants. Segregation analysis indicated that this phenotype was caused by a single, semi-dominant mutation and PCR-based marker mapping placed the mutation near position 56 on the RI map of chromosome IV. The lvr111 lesion was identified by genomic PCR and sequence analysis as a missense mutation (D306N) in the CLA1 gene (AT4g15560) and complementation analysis confirmed the allelic relationship between lvr111 and CLA1 . CLA1 encodes 1-deoxy- d -xylulose 5-phosphate synthase, which catalyses the first step of the non-mevalonate isoprenoid biosynthetic pathway. These observations demonstrate that, unlike the albinism caused by severe alleles of CLA1 , weaker alleles are associated with leaf variegation. 相似文献
42.
Sarah M Boomer Daniel P Lodge Bryan E Dutton Beverly Pierson 《Applied and environmental microbiology》2002,68(1):346-355
We characterized and compared five geographically isolated hot springs with distinct red-layer communities in Yellowstone National Park. Individual red-layer communities were observed to thrive in temperatures ranging from 35 to 60 degrees C and at pH 7 to 9. All communities were dominated by red filamentous bacteria and contained bacteriochlorophyll a (Bchl a), suggesting that they represented novel green nonsulfur (GNS) bacteria. The in vivo absorption spectra of individual sites were different, with two sites showing unusual Bchl a protein absorption bands beyond 900 nm. We prepared and analyzed 16S rRNA libraries from all of these sites by using a combination of general bacterial primers and new GNS-specific primers described here. These studies confirmed the presence of novel GNS-like bacteria in all five communities. All GNS-like clones were most similar to Roseiflexus castenholzii, a red filamentous bacterium from Japan that also contains only Bchl a. Phylogenies constructed by using GNS-like clones from Yellowstone red-layer communities suggest the presence of a moderately diverse new "red" cluster within the GNS lineage. Within this cluster, at least two well-supported subclusters emerged: YRL-A was most similar to Roseiflexus and YRL-B appeared to be novel, containing no known isolates. While these patterns showed some site specificity, they did not correlate with observed Bchl a spectrum differences or obvious features of the habitat. 相似文献
43.
Intrinsic stability of episomal circles formed during human immunodeficiency virus type 1 replication 下载免费PDF全文
Pierson TC Kieffer TL Ruff CT Buck C Gange SJ Siliciano RF 《Journal of virology》2002,76(8):4138-4144
The development of surrogate markers capable of detecting residual ongoing human immunodeficiency virus type 1 (HIV-1) replication in patients receiving highly active antiretroviral therapy is an important step in understanding viral dynamics and in developing new treatment strategies. In this study, we evaluated the utility of circular forms of the viral genome for the detection of recent infection of cells by HIV-1. We measured the fate of both one-long terminal repeat (1-LTR) and 2-LTR circles following in vitro infection of logarithmically growing CD4+ T cells under conditions in which cell death was not a significant contributing factor. Circular forms of the viral genome were found to be highly stable and to decrease in concentration only as a function of dilution resulting from cell division. We conclude that these DNA circles are not intrinsically unstable in all cell types and suggest that the utility of 2-LTR circle assays in measuring recent HIV-1 infection of susceptible cells in vivo needs to be reevaluated. 相似文献
44.
45.
Influence of GnRH administration on timing of the LH surge and ovulation in dwarf goats 总被引:1,自引:0,他引:1
This study was conducted to determine whether or not exogenous gonadotropin releasing hormone (GnRH) alters the timing or improves the synchrony of estrus, the LH surge, and ovulation following estrous synchronization in dwarf goats, and to assess the effects of season on these parameters. In January and June, estrus was synchronized in 12 Pygmy and Nigerian Dwarf goats with a 10-day progestagen sponge, 125 microg cloprostenol i.m. 48 h before sponge removal, and 300 IU equine chorionic gonadotrophin (eCG) i.m. at sponge removal. Six of the 12 goats were given 50 microg GnRH i.m. 24h after sponge removal. Onset of estrus was monitored using two males. Samples for plasma LH were collected at 2 h intervals beginning 22 h after sponge removal and ending at 48 h in January and at 58 h in June. Time of ovulation time was confirmed by laparoscopy at 36, 50, 60, and 74 h in January and at 50, 60, and 74 h in June. Administration of GnRH had no significant effect on the onset of estrus; however, it reduced the interval from sponge removal to the LH surge and improved the synchrony of the LH surge (P<0.05). Treatment with GnRH also reduced the interval from sponge removal to ovulation and improved the synchrony of ovulation (P<0.05). Season had a significant effect on the timing and the synchrony of estrus with and without GnRH treatment (P<0.05). A seasonal shift was also observed in the timing of the LH surge in the absence of GnRH treatment (P<0.05). Further research is required to determine the optimum time for GnRH administration and the minimum effective dose in dwarf goats. 相似文献
46.
Engler MM Engler MB Pierson DM Molteni LB Molteni A 《Experimental biology and medicine (Maywood, N.J.)》2003,228(3):299-307
Previous studies have shown that docosahexaenoic acid (DHA) has an antihypertensive effect in spontaneously hypertensive rats (SHR). To investigate possible mechanisms for this effect, vascular pathology and reactivity were determined in SHR treated with dietary DHA. SHR (7 weeks) were fed a purified diet with either a combination of corn/soybean oils or a DHA-enriched oil for 6 weeks. Histological evaluation of heart tissue, aorta, coronary, and renal arteries was performed. Vascular responses were determined in isolated aortic rings. Contractile responses to agonists, including norepinephrine (10(-9) to 10(-4) M), potassium chloride (5-55 mM), and angiotensin II (5 x 10(-7) M) were assessed. Vasorelaxant responses to acetylcholine (10(-9) to 10 (-4) M), sodium nitroprusside (10(-9) to 10(-6) M), papaverine (10(-5) to 10(-4) M), and methoxyverapamil (D600, 1-100 microM) were determined. DHA-fed SHR had significantly reduced blood pressure (P < 0.001) and vascular wall thicknesses in the coronary, thoracic, and abdominal aorta compared with controls (P < 0.05) Contractile responses to agonists mediated by receptor stimulation and potassium depolarization were not altered in DHA-fed SHR. Endothelial-dependent relaxations to acetylcholine were not altered which suggests endothelial-derived nitric oxide production/release is not affected by dietary DHA. Other mechanisms of vascular relaxation, including intracellular cyclic nucleotides, cGMP, and cAMP were not altered by dietary DHA because aortic relaxant responses to sodium nitroprusside and papaverine were similar in control and DHA-fed SHR. No significant differences were seen in relaxant responses to the calcium channel blocker, D600, or contractile responses to norepinephrine in the absence of extracellular calcium. These results suggest that dietary DHA does not affect mechanisms related to extracellular calcium channels or intracellular calcium mobilization. Moreover, the contractile and vasorelaxant responses are not differentially altered with dietary DHA in this in vivo SHR model. The findings demonstrate that dietary DHA reduces systolic blood pressure and vascular wall thickness in SHR. This may contribute to decrease arterial stiffness and pulse pressure, in addition to the antihypertensive properties of DHA. The antihypertensive properties of DHA are not related to alterations in vascular responses. 相似文献
47.
Growth of Streptomyces hygroscopicus under conditions of simulated microgravity in a rotating-wall bioreactor resulted in a pellet form of growth, lowered dry
cell weight, and inhibition of rapamycin production. With the addition of Teflon beads to the bioreactor, growth became much
less pelleted, dry cell weight increased but rapamycin production was still markedly inhibited. Growth under simulated microgravity
favored extracellular production of rapamycin, in contrast to a greater percentage of cell-bound rapamycin observed under
normal gravity conditions.
Received: 20 September 1999 / Received revision: 18 November 1999 / Accepted: 19 November 1999 相似文献
48.
Gallagher D Ruts E Visser M Heshka S Baumgartner RN Wang J Pierson RN Pi-Sunyer FX Heymsfield SB 《American journal of physiology. Endocrinology and metabolism》2000,279(2):E366-E375
Skeletal muscle loss or sarcopenia in aging has been suggested in cross-sectional studies but has not been shown in elderly subjects using appropriate measurement techniques combined with a longitudinal study design. Longitudinal skeletal muscle mass changes after age 60 yr were investigated in independently living, healthy men (n = 24) and women (n = 54; mean age 73 yr) with a mean +/- SD follow-up time of 4.7 +/- 2.3 yr. Measurements included regional skeletal muscle mass, four additional lean components (fat-free body mass, body cell mass, total body water, and bone mineral), and total body fat. Total appendicular skeletal muscle (TSM) mass decreased in men (-0.8 +/- 1.2 kg, P = 0.002), consisting of leg skeletal muscle (LSM) loss (-0.7 +/- 0.8 kg, P = 0.001) and a trend toward loss of arm skeletal muscle (ASM; -0.2 +/- 0.4 kg, P = 0.06). In women, TSM mass decreased (-0.4 +/- 1.2 kg, P = 0.006) and consisted of LSM loss (-0.3 +/- 0.8 kg, P = 0.005) and a tendency for a loss of ASM (-0.1 +/- 0.6 kg, P = 0.20). Multiple regression modeling indicates greater rates of LSM loss in men. Body weight in men at follow-up did not change significantly (-0.5 +/- 3.0 kg, P = 0.44) and fat mass increased (+1.2 +/- 2.4 kg, P = 0.03). Body weight and fat mass in women were nonsignificantly reduced (-0.8 +/- 3.9 kg, P = 0.15 and -0.8 +/- 3.5 kg, P = 0.12). These observations suggest that sarcopenia is a progressive process, particularly in elderly men, and occurs even in healthy independently living older adults who may not manifest weight loss. 相似文献
49.
Wagner RD Warner T Pierson C Roberts L Farmer J Dohnalek M Hilty M Balish E 《Revista iberoamericana de micología》1998,15(4):265-270
Two commercially available Bifidobacterium spp. (Bifidobacterium infantis and Bifidobacterium lactis) were compared for their capacities to protect immunodeficient bg/bg-nu/nuand bg/bg-nu/+mice from orogastric and lethal candidiasis. Both Bifidobacterium spp. prolonged the survival of Candida albicans-colonized adult and neonatal bg/bg-nu/numice. The bifidobacteria affected the production of antibodies to C. albicans, inhibited disseminated candidiasis, suppressed weight loss associated with C. albicans infection, inhibited the growth of C. albicans in the alimentary tract, inhibited systemic candidiasis of endogenous origin, and decreased the severity of gastric candidiasis in both mouse strains. B. infantis inhibited systemic candidiasis of endogenous origin better than B. lactis; however, B. lactis was significantly more effective at inhibiting C. albicans colonization of the alimentary tract, suppressing gastric candidiasis, and protecting bg/bg-nu/numice from lethal candidiasis than B. infantis. These results show that Bifidobacterium spp. can protect immunodeficient mice from candidiasis but different species manifest quantitative and qualitative differences in their probiotic and biotherapeutic effects. 相似文献
50.
Donald G. Harris Prabhjot K. Benipal Xiangfei Cheng Lars Burdorf Agnes M. Azimzadeh Richard N. Pierson III 《PloS one》2015,10(4)