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91.
Effects of electrically induced fatigue on the twitch and tetanus of paralyzed soleus muscle in humans 总被引:1,自引:0,他引:1
Shields Richard K.; Law Laura Frey; Reiling Brenda; Sass Kelly; Wilwert Jason 《Journal of applied physiology》1997,82(5):1499-1507
Shields, Richard K., Laura Frey Law, Brenda Reiling, KellySass, and Jason Wilwert. Effects of electrically induced fatigueon the twitch and tetanus of paralyzed soleus muscle in humans.J. Appl. Physiol. 82(5):1499-1507, 1997.We analyzed the twitch and summated torque(tetanus) during repetitive activation and recovery of the human soleusmuscle in individuals with spinal cord injury. Thirteen individualswith complete paralysis (9 chronic, 4 acute) had the tibial nerveactivated every 1,500 ms with a 20-Hz train (7 stimuli) for 300 ms anda single pulse at 1,100 ms. The stimulation protocol lasted 3 min andincluded 120 twitches and 120 tetani. Minimal changes were found forthe acute group. The chronic group showed a significant reduction inthe torque and a significant slowing of the contractile speeds of boththe twitch and tetanus. The decrease in the peak twitch torque was significantly greater than the decrease in the peak tetanus torque early during the fatigue protocol for the chronic group. The twitch time to peak and half relaxation time were prolonged during fatigue, which was associated with improved fusion of the tetanus torque. At theend of the fatigue protocol, the decrease in the peak twitch torque wasnot significantly different from the decrease in the peak tetanustorque. After 5 min of rest, the contractile speeds recovered causingthe tetanus to become unfused, but the tetanus torque became lessdepressed than the twitch torque. The differential responses for thetwitch and the tetanus suggest an interplay between optimal fusioncreated from contractile speed slowing and excitation contractioncoupling compromise. These issues make the optimal design of functionalelectrical stimulation systems a formidable task. 相似文献
92.
Kingston Janene K.; Geor Raymond J.; McCutcheon Laura Jill 《Journal of applied physiology》1997,83(4):1133-1143
Kingston, Janene K., Raymond J. Geor, and Laura JillMcCutcheon. Rate and composition of sweat fluid losses areunaltered by hypohydration during prolonged exercise in horses.J. Appl. Physiol. 83(4):1133-1143, 1997. Rate and ionic composition of sweat fluid losses and partitioning of evaporative heat loss into respiratory and cutaneous components were determined in six horses during three 15-km phases of exercise at ~40% of maximalO2 uptake. Pattern of change insweat rate (SR) and composition was similar during each phase. SRincreased rapidly for the first 20 min of exercise but remained at~24-28ml · m2 · min1during the remainder of each phase. Similarly, the concentrations of Naand Cl in sweat increased until 30 min of exercise but were unchangedthereafter. Sweat osmolality and concentrations of Na and Cl werepositively correlated with SR. Sweat K concentration decreased duringexercise but was not correlated with SR. Fluid losses were 33.8 ± 1.5 liters, resulting in decreases of ~21% in plasma volume and~11% in total body water. The ~6% hypohydration was notassociated with an alteration in SR, sweat composition, or heatstorage. Respiratory and cutaneous evaporative heat loss represented~23 and 70%, respectively, of the total heat dissipated, and thepartitioning of heat loss was similar in each exercise phase. Weconclude that SR and the relative proportions of respiratory andcutaneous evaporative heat loss are unchanged in horses during prolonged low-intensity exercise despite moderate hypohydration. 相似文献
93.
W. Austin Spruill Alton L. Steiner Laura L. Tres A. L. Kierszenbaum 《Molecular and cellular biochemistry》1984,60(2):147-157
Summary Protein-bound cyclic AMP (cAMP) levels in cultured rat Sertoli cells have been determined after exposure to follicle-stimulating hormone (FSH) and agents which elevate intracellular cAMP or mimic cAMP action. Changes in the content of protein-bound cAMP were correlated with changes in receptor availability determined by measuring [3H] cAMP binding. Using the photoaffinity analog of cAMP, 8-N3 [32P] cAMP, two major cAMP-binding proteins in Sertoli cell cytosol, with molecular weights of 47 000 and 53 000 daltons, were identified as regulatory subunits of type I and type II cAMP-dependent protein kinases, respectively. Densitometric analysis of autoradiograms demonstrated differential activation of the two isozymes in response to treatment with FSH and other agents. Results of this study demonstrate the value of measuring changes in protein-bound cAMP and the utility of the photoaffinity labeling technique in correlating hormone-dependent processes in which activation of cAMP-dependent protein kinase occurs. 相似文献
94.
Differentiating cells of D. discoideum in suspension bind ConA. The proportion of the bound lectin which is competitively removed by methyl-α-
mannopyranoside decreases with the time of exposure. Ferritin conjugated ConA is seen to bind both to the cell surface and to be taken into the cells, the proportion of the ConA inside the cells increasing with time. The surface bound ConA is removed by washing with methyl-α-
mannopyranoside while the endocytosed ConA appears unaffected. It is suggested that much of the [125I]ConA, uncompetable by methyl-α-
mannopyranoside in our and other binding studies, may be this intracellular ConA. 相似文献
95.
Methionine sulfoximine caused ammonia accumulation and photosyntheticrate inhibition in leaf discs from two C4 species, Zea maysL. cv. F. M. Cross (Hybrid) and Sorghum bicolor L. Moench cv.NC-70X, as well as one C3 plant species, Datura stramonium L.cv. stramonium. Similar results were obtained earlier with theC3 species Spinacia oleracea L. The effect occurred in the absenceof inorganic nitrogen reduction and was light dependent. Ammoniaaccumulation rates were similar in all four species examined.The results support a role for glutamine synthetase in leafammonia recycling in both C4 and C3 leaves.
1 Current address: Cetus Madison Corporation, 2208 Parview Road,Middleton, WI 53562, U.S.A. (Received November 2, 1981; Accepted April 28, 1982) 相似文献
96.
Thomas P. Cogley John R. Anderson Laura J. Cogley 《International journal for parasitology》1982,12(5):473-480
Cogley T. P., Anderson J. R. and Cooley L. J. 1982. Migration of Gasterophilus intestinalis larvae (Diptera: Gasterophilidae) in the equine oral cavity. International Journal for Parasitology12: 473–480. Larvae of G. intestinalis pursued a specific migratory pathway within the equine oral cavity en route to the stomach. The larval migration included the following sequence: burrowing in the tongue mucosa, invasion of the interdental spaces, transitory attachment at the root of the tongue and movement to the stomach. The molt from first to second instar did not occur in the tongue, as commonly believed, but between the interdental spaces. Ninety five percent of the larvae invading the interdental spaces were associated with gingiva of the upper molars. SEM analysis revealed further details of the oral migration: (1) air holes excavated in the epithelium which connect with deeper burrows; (2) an intimate association between air holes and posterior spiracles of larvae; (3) precise impressions of larvae in tissue immediately surrounding the most recently formed burrows; and (4) initial larval entry into the tongue through the use of natural disruptions or healing lesions. Factors influencing the development of the oral migration are discussed. 相似文献
97.
- 1. 1. Anesthetic alcohols (pentanol, hexanol and heptanol) were found to increase the fluidity of red cell membrane lipids as monitored by the fluorescence depolarization of diphenylhexatriene. The relative potency of the alcohols was found to be parallel to their relative membrane/water partition coefficients.
- 2. 2. Hexanol had biphasic effect on erythritol uptake by simple diffusion by red cells. At concentrations less than 9 mM, hexanol had no significant effect. At concentrations greater than 9 mM, there was an approximately linear increase in erythritol permeability with increasing alcohol concentration.
- 3. 3. The facilitated transport of uridine was markedly inhibited by hexanol. Hexanol at 6 mM produced a 65% inhibition of uridine (4 mM) uptake. Hexanol decreased both the apparent Km and V values for the equilibrium exchange of uridine.
- 4. 4. The facilitated transport of galactose was only slightly inhibited by hexanol.
- 5. 5. Hexanol was without effect on the passive and active fluxes of Na+ and K+ in red cells with altered cation contents. Cells that were slightly depleted of K+ and cells that were highly K+-depleted were both insensitive to hexanol.
Keywords: Anesthetic alcohol; Transport; (Human erythrocyte membrane) 相似文献
98.
(p-Amidinophenyl)methanesulfonyl fluoride, an irreversible inhibitor of serine proteases 总被引:4,自引:0,他引:4
p-(Amidinophenyl)methanesulfonyl fluoride (p-APMSF) has been synthesized and shown to be a specific, irreversible inhibitor of the class of plasma serine proteases which demonstrate substrate specificity for the positively charged side chains of the amino acid lysine or arginine. In equimolar concentration, this compound causes immediate and complete irreversible inhibition of bovine trypsin and human thrombin. A 5-10-fold molar excess of reagent over enzyme is required to achieve complete irreversible inhibition of bovine Factor Xa, human plasmin, human C1-r, and human C1-s. the Ki of p-APMSF for all of the above-mentioned proteases is between 1 and 2 microM. In contrast, p-APMSF in large molar excess does not inactivate chymotrypsin or acetylcholinesterase. The unique reactivity of p-APMSF has been further shown in comparison with the related compound p-nitrophenyl (p-amidinophenyl)methanesulfonate which is an active-site titrant for thrombin but reacts poorly with Factor Xa, C1-r, and C1-s and is not hydrolyzed by bovine trypsin or human plasmin. Similarly, (p-amidinophenyl)methanesulfonate has a Ki of 30 microM for thrombin but is a poor inhibitor of trypsin, Factor Xa, C1-r, C1-s, and plasmin. Studies with bovine trypsin have demonstrated that the inhibitory activity of p-APMSF is the result of its interaction with the diisopropyl fluorophosphate reactive site. The unique reactivity of this inhibitor classifies it as one of the most effective active site directed reagents for this class of serine proteases. Collectively, these results suggest that the primary substrate binding site of these enzymes, which share a high degree of structural homology, do in fact significantly differ from each other in their ability to interact with low molecular weight inhibitors and synthetic substrates. 相似文献
99.
Elisabetta Colletti Laura Frontali Claudio Palleschi Micheline Wesolowski Hiroshi Fukuhara 《Molecular & general genetics : MGG》1979,175(1):1-4
Summary In S. cerevisiae four isoacceptor mitochondrial tRNAs for serine have been separated by reversed phase chromatography. At least two of these species are products of different genes. In this work the deletion mapping technique has been used to locate two genes for tRNAser. The gene for tRNAser previously localized in the oli I region of the mitochondrial genome has been found to code for tRNA
ser
2
, and another gene coding for tRNA
ser
1
has been detected in the region where most of other tRNA genes are found. Results of fine mapping experiments allowed to localize this gene in the proximity of the gene for tRNAarg. 相似文献
100.
Henrika G. M. Tiedink Laura H. J. De Haan Wim M. F. Jongen Jan H. Koeman 《Cell biology and toxicology》1991,7(4):371-386
4-chloro-methoxyindole is a naturally occurring compound in Vicia faba which can easily react with nitrite to form a N-nitroso compound. In this in vitro study, the potential genotoxic effects of nitrosated 4-chloro-6-methoxyindole and its structural analogue 4-chloroindole were evaluated for the first time by using both Salmonella and Chinese hamster V79 cells. Additionally, the inhibition of gap junctional intercellular communication in V79 cells by these compounds was determined; this is a validated parameter for tumor-promoting activity. Most assays were also performed with nitrosated indole-3-acetonitrile, a naturally occurring compound in brassicas. Both nitrosated chloroindoles were highly mutagenic to Salmonella typhimurium TA100 without the need of exogenous metabolic activation and were potent inducers of Sister Chromatid Exchanges. Nitrosated indole-3-acetonitrile generated the same effects, although at much higher concentrations. Equivocal results were obtained for the nitrosated chloroindoles in a forward mutation assay using the hypoxanthine guaninephosphoribosyltransferase locus. All nitrosated indole compounds significantly inhibited gap junctional intercellular communication. These results indicate that nitrosated chloroindoles and nitrosated indole-3-acetonitrile should be considered as mutagens and agents with potential tumor-promoting capacity.Abbreviations BrdU
5-bromo-2-deoxyuridine
- 4Cl
4-chloroindole
- 4C6MI
4-chloro-6-methoxy-indole
- DMSO
dimethyl sulfoxide
- EBSS
Earle's balanced salt solution
- EMS
ethyl methanesulfonate
- GJIC
gap junctional intercellular communication
- HBSS
Hanks balanced salt solution
- HGPRT
hypoxanthine guaninephosphoribosyl transferase
- I3A
indole-3-acetonitrile
- MNNG
1-methyl-1-nitroso-3-nitroguanidine
- NOC
N-nitroso compounds
- NQO
4-nitroquinolone-N-oxide
- SCE
sister chromatid exchange
- 6TG
6-thioguanine
- TPA
12-O-tetradecanoylphorbol-13-acetate 相似文献