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排序方式: 共有173条查询结果,搜索用时 140 毫秒
151.
JH Curtis 《BMJ (Clinical research ed.)》1998,317(7162):856-857
152.
Forearm training reduces the exercise pressor reflex during ischemic rhythmic handgrip 总被引:1,自引:0,他引:1
Mostoufi-Moab Sogol; Widmaier Eric J.; Cornett Jacob A.; Gray Kristen; Sinoway Lawrence I. 《Journal of applied physiology》1998,84(1):277-283
Mostoufi-Moab, Sogol, Eric J. Widmaier, Jacob A. Cornett,Kristen Gray, and Lawrence I. Sinoway. Forearm training reduces the exercise pressor reflex during ischemic rhythmic handgrip. J. Appl. Physiol. 84(1): 277-283, 1998.We examined the effects of unilateral, nondominant forearmtraining (4 wk) on blood pressure and forearm metabolites duringischemic and nonischemic rhythmic handgrip (30 1-s contractions/min at25% maximal voluntary contraction). Contractions were performed by 10 subjects with the forearm enclosed in a pressurized Plexiglas tank toinduce ischemic conditions. Training increased the endurance time inthe nondominant arm by 102% (protocol1). In protocol 2,tank pressure was increased in increments of 10 mmHg/min to +50 mmHg.Training raised the positive-pressure threshold necessary to engage thepressor response. In protocol 3,handgrip was performed at +50 mmHg and venous blood samples wereanalyzed. Training attenuated mean arterial pressure (109 ± 5 and98 ± 4 mmHg pre- and posttraining, respectively, P < 0.01), venous lactate (2.9 ± 0.4 and 1.8 ± 0.3 mmol/l pre- and posttraining, respectively,P < 0.01), and the pH response (7.21 ± 0.02 and 7.25 ± 0.01, pre- and posttraining, respectively, P < 0.01). However, deep venousO2 saturation was unchanged.Training increased the positive-pressure threshold for metaboreceptorengagement, reduced metabolite concentrations, and reduced meanarterial pressure during ischemic exercise. 相似文献
153.
Choline acetyltransferase activity of spinal cord cell cultures increased by co-culture with muscle and by muscle-conditioned medium 总被引:9,自引:3,他引:6
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Activity of the enzyme choline acetyltransferase (CAT), which mediates the synthesis of the neurotransmitter, acetylcholine, was increased up to 20- fold in spinal cord (SC) cells grown in culture with muscle cells for 2 wk. This increase was directly related to the duration of co-culture as well as to the cell density of both the SC and muscle involved and was not affected by the presence of the acetylcholine receptor blocking agent, α-bungarotoxin. Glutamic acid decarboxylase (GAD) activity was often markedly decreased in SC-muscle cultures while the activities of acetylcholinesterase and several other enzymes were little changed. Increased CAT activity was also observed when SC cultures were maintained in medium which had been conditioned by muscle cells or by undifferentiated cells from embryonic muscle. Muscle-conditioned medium (CM) did not affect the activities of SC cell GAD or acetylcholinesterase. Dilution or concentration of the CM directly affected its ability to increase SC CAT activity , as did the duration and timing of exposure of the SC cells to the CM. The medium could be conditioned by muscle cells in the presence or absence of serum, and remained effective after dialysis or heating to 58 degrees C. Membrane filtration data were consistent with the conclusion that the active material(s) in CM had a molecular weight in excess of 50,000 daltons. We conclude that large molecular weight material that is released by muscle cells is capable of producing a specific increase in CAT activity of SC cells. 相似文献
154.
155.
Chandra Mohini Chaturvedi Adity Chowdhury Lawrence E. Cornett 《Chronobiology international》2001,18(6):947-956
Possible circadian variations in plasma levels of arginine vasotocin (AVT) and mesotocin (MT) were assessed in domestic hens (Gallus domesticus) under a 12h:12h light-dark (LD) schedule. Blood samples were taken at 4h intervals, and neurohypophyseal hormone levels were determined by radioimmunoassay. Marked circadian changes in both AVT and MT were observed in hens provided free access to water. Minimal and maximal AVT levels occurred at 08:00 and 20:00, respectively. Minimal MT levels occurred at 20:00, whereas maximal MT levels occurred over a broad time period of 04:00 to 12:00. In water-deprived hens, plasma AVT levels were elevated at each time point, and the circadian variations in plasma AVT and MT levels were attenuated. These results demonstrate that rhythmicity in neurohypophyseal function in a lower vertebrate species, like that in mammals, is disrupted by osmotic stress. (Chronobiology International, 18(6), 947-956, 2001) 相似文献
156.
Srivastava R Cornett LE Chaturvedi CM 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2008,151(4):551-559
Avian neurohypophysial hormone arginine vasotocin (AVT) is known to regulate shell gland contractility during oviposition. While studying the role of estrogen in the expression and regulation of AVT and its oxytocic-like receptor VT3, using in situ hybridization and immunohistochemistry, it was observed that the expression of AVT and its receptor was not detected in the shell gland of sexually immature Japanese quail. However, administration of estrogen to these birds not only stimulates the growth and activity (as assessed by increased mucosal fold length, total protein content and alkaline phosphatase level) of the shell gland but also upregulates the expression of AVT and VT3. Further, administration of estrogen antagonist tamoxifen to sexually mature bird shows opposite results. On the other hand, localization of ir-AVT, observed in the ovary of sexually mature bird, was not detected in the estrogen treated sexually immature quail. It is concluded that estrogen not only affects the growth and differentiation of avian oviduct, but also regulates the expression of shell gland AVT and its receptor VT3. Present findings suggest that the locally synthesized AVT acts in a paracrine way to upregulate VT3 receptor and thus facilitates the endocrine function of neurohypophysial AVT during oviposition. 相似文献
157.
Yulia A Koryakina Tristan W Fowler Stacie M Jones Bradley J Schnackenberg Lawrence E Cornett Richard C Kurten 《Respiratory research》2008,9(1):32
Background
The β2-adrenergic receptor (β2AR) is a primary target for medications used to treat asthma. Due to the low abundance of β2AR, very few studies have reported its localization in tissues. However, the intracellular location of β2AR in lung tissue, especially in airway smooth muscle cells, is very likely to have a significant impact on how the airways respond to β-agonist medications. Thus, a method for visualizing β2AR in tissues would be of utility. The purpose of this study was to develop an immunofluorescent labeling technique for localizing native and recombinant β2AR in primary cell cultures.Methods
A panel of six different antibodies were evaluated in indirect immunofluorescence assays for their ability to recognize human and rat β2AR expressed in HEK 293 cells. Antibodies capable of recognizing rat β2AR were identified and used to localize native β2AR in primary cultures of rat airway smooth muscle and epithelial cells. β2AR expression was confirmed by performing ligand binding assays using the β-adrenergic antagonist [3H] dihydroalprenolol ([3H]DHA).Results
Among the six antibodies tested, we identified three of interest. An antibody developed against the C-terminal 15 amino acids of the human β2AR (Ab-Bethyl) specifically recognized human but not rat β2AR. An antibody developed against the C-terminal domain of the mouse β2AR (Ab-sc570) specifically recognized rat but not human β2AR. An antibody developed against 78 amino acids of the C-terminus of the human β2AR (Ab-13989) was capable of recognizing both rat and human β2ARs. In HEK 293 cells, the receptors were predominantly localized to the cell surface. By contrast, about half of the native rat β2AR that we visualized in primary cultures of rat airway epithelial and smooth muscle cells using Ab-sc570 and Ab-13989 was found inside cells rather than on their surface.Conclusion
Antibodies have been identified that recognize human β2AR, rat β2AR or both rat and human β2AR. Interestingly, the pattern of expression in transfected cells expressing millions of receptors was dramatically different from that in primary cell cultures expressing only a few thousand native receptors. We anticipate that these antibodies will provide a valuable tool for evaluating the expression and trafficking of β2AR in tissues. 相似文献158.
We recently reported that bile salts play a role in the regulation of mucin
secretion by cultured dog gallbladder epithelial cells. In this study we
have examined whether bile salts also influence mucin secretion by the
human epithelial colon cell line LS174T. Solutions of bile salts were
applied to monolayers of LS174T cells. Mucin secretion was quantified by
measuring the secretion of [3H]GlcNAc labeled glycoproteins. Both
unconjugated bile salts as well as taurine conjugated bile salts stimulated
mucin secretion by the colon cells in a dose-dependent fashion. Hydrophobic
bile salts were more potent stimulators than hydrophilic bile salts. Free
(unconjugated) bile salts were more stimulatory compared with their taurine
conjugated counterparts. Stimulation of mucin secretion by LS174T cells was
found to occur at much lower bile salt concentrations than in the
experiments with the dog gallbladder epithelial cells. The protein kinase C
activators PMA and PDB had no stimulatory effect on mucin secretion. We
conclude that mucin secretion by the human colon epithelial cell line
LS174T is regulated by bile salts. We suggest that regulation of mucin
secretion by bile salts might be a common mechanism, by which different
epithelia protect themselves against the detergent action of bile salts, to
which they are exposed throughout the gastrointestinal tract.
相似文献
159.
Manum SB Van Konijnenburg-Van Cittert JH Wilde V 《Review of Palaeobotany and Palynology》2000,109(3-4):255-269
The Late Jurassic to Early Cretaceous genus Tritaenia Maegdefrau et Rudolf 1969 is problematic because of: (1) missing authentic material of its type species, T. linkii (Roemer 1839) Maegdefrau et Rudolf; and (2) Watson and Harrison's (1998) synonymization of T. linkii with Pseudotorellia heterophylla Watson. This paper: (1) rectifies the status of T. linkii on the basis of newly recovered specimens carrying the original author's authentication; and (2) gives the basis for rejecting Watson and Harrison's claim that T. linkii and T. crassa (Seward) Bose et Manum 1991 represent linear leaves of the heterophyllous taxon Pseudotorellia heterophylla. The three species of Tritaenia known to date (T. crassa, T. linkii, T. scotica) are reviewed, and the genus is compared with other Mesozoic so-called 'Sciadopitys-like' hypostomatic leaves with a median stomatal zone, many of which occur in mass accumulations such as T. linkii. Deciduousness is indicated for T. linkii and T. crassa by their occurrence in mass accumulations and the possession of well-developed abscission scars. Known mass accumulations of fossil foliage are reviewed and their implications for palaeoenvironmental interpretations discussed. 相似文献
160.
Thevelein JM Cauwenberg L Colombo S De Winde JH Donation M Dumortier F Kraakman L Lemaire K Ma P Nauwelaers D Rolland F Teunissen A Van Dijck P Versele M Wera S Winderickx J 《Enzyme and microbial technology》2000,26(9-10):819-825
Yeast cells growing in the presence of glucose or a related rapidly-fermented sugar differ strongly in a variety of physiological properties compared to cells growing in the absence of glucose. Part of these differences appear to be caused by the protein kinase A (PKA) and related signal transduction pathways. Addition of glucose to cells previously deprived of glucose triggers cAMP accumulation, which is apparently mediated by the Gpr1-Gpa2 G-protein coupled receptor system. However, the resulting effect on PKA-controlled properties is only transient when there is no complete growth medium present. When an essential nutrient is lacking, the cells arrest in the stationary phase G0. At the same time they acquire all characteristics of cells with low PKA activity, even if there is ample glucose present. When the essential nutrient is added again, a similar PKA-dependent protein phosphorylation cascade is triggered as observed after addition of glucose to glucose-deprived cells, but which is not cAMP-mediated. Because the pathway involved requires a fermentable carbon source and a complete growth medium, at least for its sustained activation, it has been called “fermentable growth medium (FGM)-induced pathway.” 相似文献