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71.
Judy Y. Su 《Pflügers Archiv : European journal of physiology》1992,421(1):1-6
Ryanodine, a blocker for Ca2+-release channels of the sarcoplasmic reticulum (SR Ca2+-release channels), induces depression of myocardial contraction in isolated intact muscle, which is consistent with depression of the caffeine-induced tension transient in skinned muscle fibers. In isolated SR, ryanodine binds to a specific receptor with high affinity, and this binding is enhanced by caffeine and increasing Ca2+ and decreased by increasing Mg2+. The aim of this study was to test the hypothesis that depression of myocardial contraction is mediated by changes in ryanodine-receptor binding properties. Accordingly, factors (caffeine, Ca2+, and Mg2+) affecting ryanodine-receptor binding properties in the isolated SR membrane were studied in skinned myocardial fibers from adult rabbits. The depression of the caffeine-induced tension transient by ryanodine (ryanodine depression) influenced by these three factors was measured. In a dose-dependent manner, increasing caffeine or Ca2+ concentrations enhanced the ryanodine depression. The concentrations for 50% ryanodine depression (IC50) approximated 7mM for caffeine, and pCa 5.25 for Ca2+. When 1 M ryanodine and 25 mM caffeine were combined, ryanodine depression was independent of Ca2+ at low Ca2+ concentrations (20%–30% at pCa>8 and 7.5) and was a direct function of Ca2+ at higher concentrations (pCa 7.5–6.0 with IC50 approx. pCa 6.75). In contrast, increasing Mg2+ reduced the ryanodine depression with IC50 approximately equal to pMg 3.3. In conclusion, the caffeineor Ca2+-enhanced, and Mg2+-reduced ryanodine depression observed in this study is consistent with known ryanodinereceptor binding properties. 相似文献
72.
目的:DNA甲基化和组蛋白乙酰化是基因表达调控的主要形式。人类免疫缺陷病毒(HIV-1)可引起T淋巴细胞DNA甲基化酶上调。本文旨在明确HIV-1对细胞周期依赖刺激酶抑制剂p21^WAF1表达的影响。方法:建立HIV-1感染的Hut78细胞系;以RT-PCR和Westem blotting 分析p21^WAF1表达情况;以亚硫酸氢钠修饰DNA和基因测序,研究p21^WAF1基因启动子甲基化,以Western blot-ting 和染色体免疫测定探究总组蛋白和与p21^WAF1基因启动子相关的组蛋白乙酰化水平。并以GST pull-down和免疫沉淀分析HIV-1导致乙酰化及乙酰化引起p21^WAF1过表达的可能机理。结果:HIV-1感染后,其反式激活蛋白Tat与辅助转录因子P/CAF、hGCN5结合,共同刺激组蛋白H3乙酰化。尽管p21^WAF1启动子部分区域有甲基化发生,但p21^WAF1表达仍上调。这可能与E2A对p21^WAF1的作用有关。结论:HIV-1感染可引起T淋巴细胞p21^WAF1基因的甲基化和乙酰化紊乱,导致p21^WAF1表达增强。 相似文献
73.
74.
Jason B. Mattingley Louise A. Corben John L. Bradshaw Judy A. Bradshaw Jim G. Phillips Malcolm K. Horne 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,120(2):243-256
Patients with unilateral neglect following right hemisphere damage may have difficulty in moving towards contralesional targets.
To test the hypothesis that this impairment arises from competing motor programs triggered by irrelevant ipsilesional stimuli,
we examined 16 right hemisphere patients, eight with left visual neglect and eight without, in addition to eight healthy control
subjects. In experiment 1 subjects performed sequences of movements using their right hand to targets on the contralesional
or ipsilesional side of the responding limb. The locations of successive targets in each sequence were either predictable
or unpredictable. In separate blocks of trials, targets appeared either alone or with a simultaneous distractor located at
the immediately preceding target location. Neglect patients were significantly slower to execute movements to contralesional
targets, but only for unpredictable movements and in the presence of a concurrent ipsilesional distractor. In contrast, healthy
controls and right hemisphere patients without neglect showed no directional asymmetries of movement execution. In experiment
2 subjects were required to interrupt a predictable, reciprocating sequence of leftward and rightward movements in order to
move to an occasional, unpredictable target that occurred either in the direction opposite to that expected, or in the same
direction but twice the extent. Neglect patients were significantly slower in reprogramming the direction and extent of movements
towards contralesional versus ipsilesional targets, and they also made significantly more errors when executing such movements.
Right hemisphere patients without neglect showed a similar bias in reprogramming direction (but not extent) for contralesional
targets, whereas healthy controls showed no directional asymmetry in either condition. On the basis of these findings we propose
that neglect involves a competitive bias in favour of motor programs for actions directed towards ipsilesional versus contralesional
events. We suggest that programming errors and increased latencies for contralesional movements arise because the damaged
right hemisphere can no longer effectively inhibit the release of inappropriate motor programs towards ipsilesional events.
Received: 1 October 1996 / Accepted: 21 October 1997 相似文献
75.
Two sets of "weight for height" reference data that are widely used internationally for children and adolescents (NCHS) and for adults (Fogarty) show a marked discontinuity such that young adults might be considered obese by one set and underweight by the other. In view of the need for continuous data for the nutritional assessment of populations, a compromise set of reference values is proposed, calculated from the NCHS data, which is considered the more reliable of the two sets. The proposed values are a single set, which may be applied to all ages and to both sexes: they are close to the Fogarty data for tall adults but for shorter adults there remains a discrepancy, which may represent an error in the Fogarty data. 相似文献
76.
Summary The mechanism of quinidine action on rabbit cardiac and skeletal muscle was examined with functionally skinned muscle-fiber preparations. By using these preparations we could correlate measurements of muscle tension with the effect of quinidine on the Ca2+ activation of the contractile proteins and on the Ca2+ uptake and release from the sarcoplasmic reticulum (SR).
Effect of quinidine on the contractile proteins. Quinidine concentrations above 0.5 mmol/l increased the maximal Ca2+-activated tension development 12% for papillary muscle and 5% for soleus (slow-twitch). Adductor magnus (fast-twitch) showed no significant change. Quinidine (0.1–1.0 mmol/l) also increased the submaximal Ca2+-activated tension development for the three muscle types (papillary muscle=soleus>adductor magnus) and shifted the [Ca2+]-tension curves to the left in a dose-dependent fashion.
Effects of quinidine on the Ca
2+ uptake and release from the SR. Sarcoplasmic reticulum of skinned fibers was loaded with Ca2+ (uptake phase), then Ca2+ was released by 25 mmol/l caffeine (release phase) giving a tension transient. The area under the tension transient was used to estimate the amount of Ca2+ released. Quinidine (>0.5 mmol/l) decreased the Ca2+ uptake (soleus>adductor magnus>papillary muscle) and increased the Ca2+ release [papillary muscle=soleus adductor magnus (only at 1.5 mmol/l, the highest concentration tested)] from the SR of all three muscles in a dose-dependent manner. Quinidine at low concentration (0.1 and 0.5 mmol/l) increased the caffeine-induced tension transient of papillary muscle and higher quinidine concentrations (1.0 and 1.5 mmol/l) decreased the caffeine-induced tension transient of soleus and adductor magnus during both the uptake and release phases. The decreased Ca2+ uptake of papillary muscle in 1.5 mmol/l quinidine was antagonized by increasing the free Mg2+ from 0.032 to 0.32 mmol/l.In summary, quinidine has similar mechanisms of action in all three muscles: increased Ca2+ activation of the contractile proteins, decreased Ca2+ uptake and increased Ca2+ release from the SR in functionally skinned muscle fibers. We conclude that quinidine-induced decreases in Ca2+ uptake by the SR could be responsible for quinidine-induced myocardial depression and that quinidine-induced increases in Ca2+ activation of the contractile proteins and Ca2+ release from the SR could be responsible for the increases in skeletal muscle contraction caused by quinidine. 相似文献
77.
Winnie K. W. So Judy Y. W. Chan Bernard M. H. Law Kai Chow Choi Jessica Y. L. Ching Kam Leung Chan Raymond S. Y. Tang Carmen W. H. Chan Justin C. Y. Wu Stephen K. W. Tsui 《Nutrients》2021,13(2)
Rice bran exhibits chemopreventive properties that may help to prevent colorectal cancer (CRC), and a short-term rice bran dietary intervention may promote intestinal health via modification of the intestinal microbiota. We conducted a pilot, double-blind, randomised placebo-controlled trial to assess the feasibility of implementing a long-term (24-week) rice bran dietary intervention in Chinese subjects with a high risk of CRC, and to examine its effects on the composition of their intestinal microbiota. Forty subjects were randomised into the intervention group (n = 19) or the control group (n = 20). The intervention participants consumed 30 g of rice bran over 24-h intervals for 24 weeks, whilst the control participants consumed 30 g of rice powder on the same schedule. High rates of retention (97.5%) and compliance (≥91.3%) were observed. No adverse effects were reported. The intervention significantly enhanced the intestinal abundance of Firmicutes and Lactobacillus, and tended to increase the Firmicutes/Bacteroidetes ratio and the intestinal abundance of Prevotella_9 and the health-promoting Lactobacillales and Bifidobacteria, but had no effect on bacterial diversity. Overall, a 24-week rice bran dietary intervention was feasible, and may increase intestinal health by inducing health-promoting modification of the intestinal microbiota. Further larger-scale studies involving a longer intervention duration and multiple follow-up outcome assessments are recommended. 相似文献
78.
79.
80.
Sarah A. Collier Li Deng Elizabeth A. Adam Katharine M. Benedict Elizabeth M. Beshearse Anna J. Blackstock Beau B. Bruce Gordana Derado Chris Edens Kathleen E. Fullerton Julia W. Gargano Aimee L. Geissler Aron J. Hall Arie H. Havelaar Vincent R. Hill Robert M. Hoekstra Sujan C. Reddy Elaine Scallan Erin K. Stokes Jonathan S. Yoder Michael J. Beach 《Emerging infectious diseases》2021,27(1):140
Provision of safe drinking water in the United States is a great public health achievement. However, new waterborne disease challenges have emerged (e.g., aging infrastructure, chlorine-tolerant and biofilm-related pathogens, increased recreational water use). Comprehensive estimates of the health burden for all water exposure routes (ingestion, contact, inhalation) and sources (drinking, recreational, environmental) are needed. We estimated total illnesses, emergency department (ED) visits, hospitalizations, deaths, and direct healthcare costs for 17 waterborne infectious diseases. About 7.15 million waterborne illnesses occur annually (95% credible interval [CrI] 3.88 million–12.0 million), results in 601,000 ED visits (95% CrI 364,000–866,000), 118,000 hospitalizations (95% CrI 86,800–150,000), and 6,630 deaths (95% CrI 4,520–8,870) and incurring US $3.33 billion (95% CrI 1.37 billion–8.77 billion) in direct healthcare costs. Otitis externa and norovirus infection were the most common illnesses. Most hospitalizations and deaths were caused by biofilm-associated pathogens (nontuberculous mycobacteria, Pseudomonas, Legionella), costing US $2.39 billion annually. 相似文献