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排序方式: 共有451条查询结果,搜索用时 15 毫秒
1.
Thorsten Thye Genevieve Scarisbrick Edmund N. L. Browne Margaret Amanua Chinbuah John Gyapong Ivy Osei Ellis Owusu-Dabo Stefan Niemann Sabine Rüsch-Gerdes Christian G. Meyer Rolf D. Horstmann 《PloS one》2009,4(7)
The gene of Cytotoxic T Lymphocyte-associated Antigen 4 (CTLA4), a negative regulator of T lymphocytes, contains a single-nucleotide polymorphism (SNP) at position +6230A->G (ct60A->G), which has been found associated with several autoimmune diseases and appears to reduce T-cell inhibitory activity. In Ghana, West Africa, we compared the frequencies of CTLA4 +6230 A/G and 6 haplotype-tagging SNPs in 2010 smear-positive, HIV-negative patients with pulmonary tuberculosis (TB) and 2346 controls matched for age, gender and ethnicity. We found no difference in allele frequencies between cases and controls. However, +6230A and a distinct CTLA4 haplotype and a diplotype comprising the +6230A allele were significantly less frequent among cases with large opacities in chest radiographs compared to those with small ones (Pcorrected [cor] = 0.002, Pcor = 0.00045, P = 0.0005, respectively). This finding suggests that an increased T-cell activity associated with the CTLA4 +6230G allele contributes to pathology rather than to protection in pulmonary TB. 相似文献
2.
F S Apple M A Rogers D C Casal L Lewis J L Ivy J W Lampe 《European journal of applied physiology and occupational physiology》1987,56(1):49-52
Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p less than 0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p less than 0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r = 0.97, p less than 0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners. 相似文献
3.
Ivy Liu 《Biometrical journal. Biometrische Zeitschrift》2003,45(6):730-750
For an r × ctable with ordinal responses, odds ratios are commonly used to describe the relationship between the row and column variables. This article shows two types of ordinal odds ratios where local‐global odds ratios are used to compare several groups on a c‐category ordinal response and a global odds ratio is used to measure the global association between a pair of ordinal responses. When there is a stratification factor, we consider Mantel‐Haenszel (MH) type estimators of these odds ratios to summarize the association from several strata. Like the ordinary MH estimator of the common odds ratio for several 2 × 2 contingency tables, the estimators are used when the association is not expected to vary drastically among the strata. Also, the estimators are consistent under the ordinary asymptotic framework in which the number of strata is fixed and also under sparse asymptotics in which the number of strata grows with the sample size. Compared to the maximum likelihood estimators, simulations find that the MH type estimators perform better especially when each stratum has few observations. This article provides variances and covariances formulae for the local‐global odds ratios estimators and applies the bootstrap method to obtain a standard error for the global odds ratio estimator. At the end, we discuss possible ways of testing the homogeneity assumption. 相似文献
4.
The purposes of the present study were to characterize the histochemical and enzymatic profiles of various hindlimb skeletal muscles, as well as to determine maximal O2 consumption (VO2max) and respiratory exchange ratios (R) during steady-state exercise in the obese Zucker rat. The changes that occurred in these parameters in response to a 6-wk training program were then assessed. Obese rats were randomly assigned to a sedentary or training group. Lean littermates served as a second control. Training consisted of treadmill running at 18 m/min up an 8% grade, 1.5 h/day, 5 day/wk for 6 wk. During week 6, VO2max and R during a steady-state run (74% max) were determined. After 2 days of inactivity, hindlimb muscles were excised, stained for fiber type and capillaries, and assayed for hexokinase, citrate synthase, cytochrome oxidase, and beta-hydroxyacetyl-CoA dehydrogenase. The obese sedentary rats demonstrated greater oxidative enzyme activities per gram of muscle tissue than their lean littermates, greater R values during submaximal exercise of the same relative intensity, and greater absolute VO2max values. Training resulted in a 20-56% increase in oxidative enzymes, a 10% increase in VO2max, and an increase in capillary density in the soleus and plantaris. There was no alteration in R values during exercise at 74% VO2max or in fiber type composition in response to exercise training. Results suggest that the muscle of the obese Zucker rat manifests a greater oxidative capacity than the muscle of its lean littermates. The apparent inability of the obese rat to increase its use of fat during submaximal exercise of the same relative intensity in response to training remains to be elucidated. 相似文献
5.
E F Coyle M T Hamilton J G Alonso S J Montain J L Ivy 《Journal of applied physiology》1991,70(2):834-840
The effects of hyperglycemia on muscle glycogen use and carbohydrate metabolism were evaluated in eight well-trained cyclists (average maximal O2 consumption 4.5 +/- 0.1 l/min) during 2 h of exercise at 73 +/- 2% of maximal O2 consumption. During the control trial (CT), plasma glucose concentration averaged 4.2 +/- 0.2 mM and plasma insulin remained between 6 and 9 microU/ml. During the hyperglycemic trial (HT), 20 g of glucose were infused intravenously after 8 min of exercise, after which a variable-rate infusion of 18% glucose was used to maintain plasma glucose at 10.8 +/- 0.4 mM throughout exercise. Plasma insulin remained low during the 1st h of HT, yet it increased significantly (to 16-24 microU/ml; P less than 0.05) during the 2nd h. The amount of muscle glycogen utilized in the vastus lateralis during exercise was similar during HT and CT (75 +/- 8 and 76 +/- 7 mmol/kg, respectively). As exercise duration increased, carbohydrate oxidation declined during CT but increased during HT. Consequently, after 2 h of exercise, carbohydrate oxidation was 40% higher during HT than during CT (P less than 0.01). The rate of glucose infusion required to maintain hyperglycemia (10 mM) remained very stable at 1.6 +/- 0.1 g/min during the 1st h. However, during the 2nd h of exercise, the rate of glucose infusion increased (P less than 0.01) to 2.6 +/- 0.1 g/min (37 mg.kg body wt-1.min-1) during the final 20 min of exercise. We conclude that hyperglycemia (i.e., 10 mM) in humans does not alter muscle glycogen use during 2 h of intense cycling.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
6.
Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
相似文献
7.
8.
Dunbar Ivy D.; Kinsella John P.; Abman Steven H. 《Journal of applied physiology》1996,81(6):2481-2487
Ivy, D. Dunbar, John P. Kinsella, and Steven H. Abman.Endothelin blockade augments pulmonary vasodilation in the ovine fetus. J. Appl. Physiol. 81(6):2481-2487, 1996.The physiological role of endothelin-1 (ET-1) inregulation of vascular tone in the perinatal lung is controversial.Recent studies suggest that ET-1 contributes to high basal pulmonaryvascular resistance in the normal fetus, but its role in the modulationof pulmonary vascular tone remains uncertain. We hypothesized that highET-1 activity opposes the vasodilator response to some physiological stimuli such as increased pressure. To test the hypothesis that ET-1modulates fetal pulmonary vascular responses to acute and prolongedphysiological stimuli, we performed a series of experiments in thelate-gestation ovine fetus. We studied the hemodynamic effects of twoET-1 antagonists, BQ-123 (a selectiveETA-receptor antagonist) andphosphoramidon (a nonselective ET-1-converting enzyme inhibitor) duringmechanical increases in pressure due to partial ductus arteriosuscompression in chronically prepared late-gestation fetal lambs. Incontrol studies, partial ductus arteriosus compression decreased theratio of pulmonary arterial pressure to pulmonary artery flow in theleft lung 34 ± 6% from baseline. Intrapulmonary infusions ofBQ-123 (0.5 µg/min for 10 min; 0.025 µg/min for 2 h) orphosphoramidon (1.0 mg/min for 10 min) augmented the peak vasodilatorresponse during ductus arteriosus compression (52 ± 3 and 49 ± 6% from baseline, respectively, P < 0.05 vs. control). In addition, unlike the transient vasodilator response to ductus arteriosus compression in control studies, ET-1blockade with BQ-123 or phosphoramidon prolonged the increase in flowcaused by ductus arteriosus compression. In summary,ETA-receptor blockade andET-1-converting enzyme inhibition augment and prolong fetal pulmonaryvasodilation during partial compression of the ductus arteriosus. Weconclude that ET-1 activity modulates acute and prolonged responses ofthe fetal pulmonary circulation to changes in vascular pressure. Wespeculate that ET-1 contributes to regulation and maintenance of highpulmonary vascular resistance in the normal ovine fetal lung. 相似文献
9.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:8,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
相似文献
10.