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排序方式: 共有523条查询结果,搜索用时 281 毫秒
1.
Jaya K. Matthews Amanda Ridley Protais Niyigaba Beth A. Kaplin Cyril C. Grueter 《American journal of primatology》2019,81(4)
Almost all primates experience seasonal fluctuations in the availability of key food sources. However, the degree to which this fluctuation impacts foraging behavior varies considerably. Eastern chimpanzees (Pan troglodytes schweinfurthii) in Nyungwe National Park, Rwanda, live in a montane forest environment characterized by lower primary productivity and resource diversity than low‐elevation forests. Little is known about chimpanzee feeding ecology in montane forests, and research to date predominantly relies on indirect methods such as fecal analyses. This study is the first to use mostly observational data to examine how seasonal food availability impacts the feeding ecology of montane forest chimpanzees. We examine seasonal changes in chimpanzee diet and fallback foods (FBFs) using instantaneous scan samples and fecal analyses, supported by inspection of feeding remains. Chimpanzee fruit abundance peaked during the major dry season, with a consequent change in chimpanzee diet reflecting the abundance and diversity of key fruit species. Terrestrial herbaceous vegetation was consumed throughout the year and is defined as a “filler” FBF. In contrast to studies conducted in lower‐elevation chimpanzee sites, figs (especially Ficus lutea) were preferred resources, flowers were consumed at seasonally high rates and the proportion of non‐fig fruits in the diet were relatively low in the current study. These divergences likely result from the comparatively low environmental diversity and productivity in higher‐elevation environments. 相似文献
2.
OBJECTIVE--To determine the effectiveness of regional intensive therapy units. DESIGN--Retrospective and prospective study of patients transferred to a regional intensive therapy unit over four years. SETTING--Glasgow regional intensive therapy unit. MAIN OUTCOME MEASURES--Severity of illness was assessed at the time of referral to the unit with the acute physiological and chronic health evaluation (APACHE) scoring system. Mortality was calculated. RESULTS--A significant association was found between increasing duration of illness before transfer and mortality, which was independent of the severity of illness. Mortality also varied depending on the referring hospital. CONCLUSIONS--When transfer of critically ill patients is required this should be done as early as possible to make best use of the services available. The mortality of patients transferred after 10 days casts doubt on whether further aggressive intensive therapy is appropriate. 相似文献
3.
Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation. 总被引:21,自引:1,他引:20 下载免费PDF全文
The cellular responses to ras and nuclear oncogenes were investigated in purified populations of rat Schwann cells. v-Ha-ras and SV40 large T cooperate to transform Schwann cells, inducing growth in soft agar and allowing proliferation in the absence of added mitogens. Expression of large T alone reduces their growth factor requirements but is insufficient to induce full transformation. In contrast, expression of v-Ha-ras leads to proliferation arrest in Schwann cells expressing a temperature-sensitive mutant of large T at the restrictive temperature. Cells arrest in either the G1 or G2/M phases of the cell cycle, and can re-enter cell division at the permissive temperature even after prolonged periods at the restrictive conditions. Oncogenic ras proteins also inhibit DNA synthesis when microinjected into Schwann cells. Adenovirus E1a and c-myc oncogenes behave similarly to SV40 large T. They cooperate with Ha-ras oncogenes to transform Schwann cells, and prevent ras-induced growth arrest. Thus nuclear oncogenes fundamentally alter the response of Schwann cells to a ras oncogene from cell cycle arrest to transformation. 相似文献
4.
Rats are known to respond to a cold stimulus by increasing the activity and amount of the uncoupling protein in brown adipose tissue. A 48 h cold stimulus was found to increase the synthesis of uncoupling protein 3.g-fold in 4–5 week old rats whereas no change was observed with newborn rabbits. The lack of response in the latter case may reflect a difference between rabbits and rats or that synthesis is already maximal in newborn rabbits. 相似文献
5.
Complete nucleotide and derived amino acid sequence of cDNA encoding the mitochondrial uncoupling protein of rat brown adipose tissue: lack of a mitochondrial targeting presequence. 总被引:7,自引:0,他引:7 下载免费PDF全文
R G Ridley H V Patel G E Gerber R C Morton K B Freeman 《Nucleic acids research》1986,14(10):4025-4035
A cDNA clone spanning the entire amino acid sequence of the nuclear-encoded uncoupling protein of rat brown adipose tissue mitochondria has been isolated and sequenced. With the exception of the N-terminal methionine the deduced N-terminus of the newly synthesized uncoupling protein is identical to the N-terminal 30 amino acids of the native uncoupling protein as determined by protein sequencing. This proves that the protein contains no N-terminal mitochondrial targeting prepiece and that a targeting region must reside within the amino acid sequence of the mature protein. 相似文献
6.
Mitochondrial proteins are synthesized in mitochondria and on cytosolic ribosomes. Several approaches used to establish the site of synthesis and the identity of mitochondrially synthesized proteins are described. These include the specific inhibition of mitochondrial translation by inhibitors or mutation and the specific elimination of cytosolic translation either by using isolated mitochondria or specific inhibitors. Experimental approaches to study the import of proteins into mitochondria are also discussed. 相似文献
7.
8.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
9.
Barrera Lawrence N. Ridley P. Matthew Bermejo-Rodriguez Camino Costello Eithne Perez-Mancera Pedro A. 《Journal of physiology and biochemistry》2023,79(1):193-204
Journal of Physiology and Biochemistry - Pancreatic ductal adenocarcinoma (PDAC) is the deadliest of the common cancers. A major hallmark of PDAC is an abundant and dense fibrotic stroma, the... 相似文献
10.