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91.
Isolation and characterization of rat liver mitochondrial DNA 总被引:6,自引:0,他引:6
A T Leffler E Creskoff S W Luborsky V McFarland P T Mora 《Journal of molecular biology》1970,48(3):455-468
92.
93.
P Echeverria B A Harrison C Tirapat A McFarland 《Applied and environmental microbiology》1983,46(1):32-36
The village of Ban Pong in northeastern Thailand was studied from January through December 1981 to determine the importance of flies as a source of enteric pathogens. The number of flies (predominantly Musca domestica) increased in kitchens and animal pens in the hot dry spring, when the incidence of diarrhea was highest in the village. Enterotoxigenic Escherichia coli, Shigella spp., non-O1 Vibrio cholerae, and Vibrio fluvalis were isolated from fly pools in yards (69%), animal pens (38%), bathrooms (35%), and kitchens (8%). Enterotoxigenic E. coli was isolated from one fly pool in May and from another in June, when the incidence of such infections was highest in the village. Flies often carry and presumably disseminate enteric pathogens in rural Thailand. 相似文献
94.
95.
ABSTRACTSleep deprivation impairs performance on cognitive tasks, but it is unclear which cognitive processes it degrades. We administered a semantic matching task with variable stimulus onset asynchrony (SOA) and both speeded and self-paced trial blocks. The task was administered at the baseline and 24 hours later after 30.8 hours of total sleep deprivation (TSD) or matching well-rested control. After sleep deprivation, the 20% slowest response times (RTs) were significantly increased. However, the semantic encoding time component of the RTs remained at baseline level. Thus, the performance impairment induced by sleep deprivation on this task occurred in cognitive processes downstream of semantic encoding. 相似文献
96.
Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction. 相似文献
97.
The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems. 相似文献
98.
Sandra G. Velleman Douglas C. McFarland Zaikai Li Neal H. Ferrin Robert Whitmoyer James E. Dennis 《Development, growth & differentiation》1997,39(5):563-570
Skeletal muscle fibers are surrounded by an extracellular matrix. The extracellular matrix is composed of glycoproteins, collagen, and proteoglycans. Proteoglycans have been suggested to play an important functional role in tissue differentiation. However, an understanding of how the extracellular matrix affects skeletal muscle development and function is largely unknown. In the avian genetic muscle weakness, low score normal (LSN), a late embryonic increase in the expression of decorin is followed by a subsequent increase in collagen crosslinking. The sarcomere organization, collagen fibril diameter and organization were investigated using transmission electron microscopy. Measurements were made at 20 days of embryonic development and 6 weeks posthatch. These studies showed changes in sarcomere organization and deterioration of muscle fibril structure in the LSN pectoral muscle. In vitro satellite cell cultures were developed and assayed for mitochondrial activity, and protein synthesis and degradation. In these analyses, mitochondrial activity from LSN satellite cells was significantly higher than those from normal pectoral muscle satellite cells. Protein synthesis rates between the normal and LSN satellite cell-derived myotubes were similar, but protein degradation rates were higher in the LSN cultures. Based on the reported functions of decorin as a regulator of cell proliferation and collagen fibril organization, it is possible that the late embryonic increase in decorin may be influencing the alterations in LSN sarcomere and collagen organization. 相似文献
99.
L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three
loci in all vertebrates examined, with the exception of lampreys, which
have a single LDH locus. Biochemical characterizations of LDH proteins have
suggested that a gene duplication early in vertebrate evolution gave rise
to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of
lineages more recently. Although some phylogenetic studies of LDH protein
sequences have supported this pattern of gene duplication, others have
contradicted it. In particular, a number of studies have suggested that
Ldh-C represents the earliest divergence among vertebrate LDHs and that it
may have diverged from the other loci well before the origin of
vertebrates. Such hypotheses make explicit statements about the
relationship of vertebrate and invertebrate LDHs, but to date, no closely
related invertebrate LDH sequences have been available for comparison. We
have attempted to provide further data on the timing of gene duplications
leading to multiple vertebrate LDHs by determining the cDNA sequence of the
LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other
LDH sequences provide strong support for the duplications giving rise to
multiple vertebrate LDHs having occurred after vertebrates diverged from
tunicates. The timing of these LDH duplications is consistent with data
from a number of other gene families suggesting widespread gene duplication
near the origin of vertebrates. With respect to the relationships among
vertebrate LDHs, our data are not consistent with previous claims that
Ldh-C represented the earliest divergence. However, the precise
relationships among some of the main lineages of vertebrate LDHs were not
resolved in our analyses.
相似文献
100.
Pharmaceutical probiotics have been used as alternative treatments or preventative therapies for a variety of clinical diseases. The overuse of antibiotics and emergence of multiple-antibiotic resistant pathogens has refocused clinical attention on the field of probiotics. Anaerobic infections which seem to respond well to probiotics are infections which involve the disruption of normal microbial flora. Gastrointestinal infections (travelers' diarrhea, antibiotic-associated diarrhea,Clostridium difficile disease, rotavirus diarrhea) have been studied using the following pharmaceutical probiotics:Saccharomyces boulardii, Lactobacillus casei GG, Lactobacillus acidophilus, Lactobacillus bulgaricus, Bifidobacterium bifidum, Streptococcus thermophilus and Enterococcus faecium. Vaginitis has been experimentally studied using L. acidophilus and L. casei GG. The efficacy, safety and mechanisms of action of these various probiotics are reviewed. Requirements for drug approval are similar for biologic probiotics and new drug entities and these requirements involve preclinical tolerability studies, pharmacokinetic studies and large, well-controlled blinded clinical trials. 相似文献