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91.
Several types of reagents that react with amino acid side chains induced repetitive phasic contracture of skinned skeletal muscle from frogs. The presence of 10 mM procaine or 5 mM magnesium in the medium or disruption of the sarcoplasmic reticulum (SR) eliminated this contracture, indicating that the calcium-induced calcium-release mechanism of SR is involved in the contraction. Dithiothreitol inhibited the contracture induced by chloramine T, N-acetylimidazole, or p-chloromercuriphenylsulfonic acid (pCMPS) but not in the case of carbodiimide, phenylglyoxal, trinitrobenzenesulfonic acid, diethylpyrocarbonate (DEP), or N-chlorosuccinimide (NCS). Therefore, modification of groups other than the sulfhydryl ones seems to induce contractures under such conditions. The amplitude of the caffeine-induced contracture decreased after treatment with pCMPS, DEP, or NCS. NCS shifted the pCa-tension curve toward low pCa in the SR-disrupted fibers. This shift would explain the decrease in the caffeine contracture. It is tentatively concluded that pCMPS and DEP release a large amount of calcium from SR. 相似文献
92.
93.
Intensity of light diffraction from striated muscle as a function of incident angle. 总被引:1,自引:1,他引:0
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In a recently developed theory of light diffraction by single striated muscle fibers, we considered only the case of normal beam incidence. The present investigation represents both an experimental and theoretical extension of the previous work to arbitrary incident angle. Angle scan profiles over a 50 degrees range of incident angle (+25 degrees to -25 degrees) were obtained at different sarcomere lengths. Left and right first-order scan peak separations were found to be a function of sarcomere length (separation angle = 2 theta B), and good agreement was found between theory and experiment. Our theoretical analysis further showed that a myofibrillar population with a single common skew angle can yield an angle scan profile containing many peaks. Thus, it is not necessary to associate each peak with a different skew population. Finally, we have found that symmetry angle, theta s, also varies with sarcomere length, but not in a regular manner. Its value at a given sarcomere length is a function of a particular region of a given fiber and represents the average skew angle of all the myofibril populations illuminated. The intensity of a diffraction order line is considered to be principally the resultant of two interference phenomena. The first is a volume-grating phenomenon which results from the periodic A-I band structure of the fiber (with some contribution from Z bands and H zones). The second is Bragg reflection from skew planes, if the correct relation between incident angle and skew angle is met. This may result in intensity asymmetry between the left and right first order lines. 相似文献
94.
Toshiharu Oba Chieko Kurono Ritsuko Nakajima Tetsuo Takaishi Kazuto Ishida Geraldine A Fuller Wuthichai Klomkleaw Mamoru Yamaguchi 《Journal of applied physiology》2002,93(6):1999-2008
We studied whether hydrogen peroxide (H(2)O(2)) at =10 microM activates the ryanodine receptor and decreases releasable Ca(2+) content in the sarcoplasmic reticulum after fatigue. Exposure of rabbit or frog skeletal muscle ryanodine receptors to 10 microM H(2)O(2) enhanced channel activity in lipid bilayers when the redox potential was defined at cis = -220 mV and trans = -180 mV. Channel activation by 10 microM H(2)O(2) was also observed when cis potential was set at -220 mV without defining trans potential, but the effect was less. Reduction of trans redox potential from -180 to -220 mV did not alter channel activity. H(2)O(2) at 500 microM failed to activate the channel when the redox potential was not controlled. Stimulation of the frog muscle fiber for 2 min (50 Hz, a duty cycle of 200 ms/s) decreased tetanus tension by approximately 50%. After 1 min, tetanus recovered rapidly to approximately 70% of control and thereafter slowly approached the control level. Amplitudes of caffeine- and 4-chloro-m-cresol-induced contractures were decreased after a 60-min rest. The decrease is not enhanced by exposure to 10 microM H(2)O(2). These results suggest that H(2)O(2) markedly activates the ryanodine receptor under the redox control in vitro, but externally applied H(2)O(2) may not play an important role in the postfatigue recovery process. 相似文献
95.
96.
Induction of Furano-terpene Production and Formation of the Enzyme System from Mevalonate to Isopentenyl Pyrophosphate in Sweet Potato Root Tissue Injured by Ceratocystis fimbriata and by Toxic Chemicals 总被引:3,自引:2,他引:1
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When sweet potato (Ipomoea batatas) root tissue was infected by Ceratocystis fimbriata, activity of the enzyme system from mevalonate to isopentenyl pyrophosphate, especially of pyrophosphomevalonate decarboxylase (EC 4.1.1.33), was increased in the noninfected tissue adjacent to the infected region, preceding the furano-terpene production in the infected region. Cutting and incubation of sweet potato slices did not produce furano-terpenes, and only slightly increased the activity of the enzyme system from mevalonate to isopentenyl pyrophosphate. The enzymic activity in diseased tissue was localized in the soluble fraction, and was higher in the tissue from the surface to a depth of about 5 mm with gradual decrease toward the inner part. 相似文献
97.
Lactate dehydrogenase [L-lactate: NAD oxidoreductase, EC 1.1.1.27] was isolated from sweet potato root tissues. Two species of the enzyme (isozymes I and II) were separated by DE-52 cellulose column chromatography from healthy, cut, and black-rot diseased tissues. Isozymes I and II were purified from healthy and diseased tissues, respectively. Reduction of pyruvate by NADH with either isozyme I or II was inhibited by pyruvate at high concentrations, by NAD+ and by several mononucleotides. Isozyme I was inhibited by a lower concentration of adenine nucleotide than isozyme II, and Km for pyruvate was increased markedly at acidic pH in the case of isozyme I, but only slightly in the case of isozyme II. The molecular weights of both isozymes were determined to be 150,000 and they were found to be charge isomers by polyacrylamide gel electrophoresis. The enzyme activity increased in response to infection by black-rot fungus but decreased in response to cutting. 相似文献
98.
Rios FS Oba ET Fernandes MN Kalinin AL Rantin FT 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2005,140(3):281-287
Adult specimens of traira (Hoplias malabaricus Bloch) were subjected to long-term starvation (30 to 240 days) and re-fed for 30 days after 90 and 240 days of food deprivation. Counting of immature erythrocytes in peripheral blood showed that erythropoiesis decreased significantly during the first 30 days of food deprivation. The results suggest that a process of senescence takes place in the pre-existent red blood cells and that the cells are not replaced during starvation. After 240 days of starvation, H. malabaricus had a significantly reduced number of red blood cells, causing changes in hematocrit and blood indices (mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration). Furthermore, during this period, the fish presented leukopenia (lymphocytopenia) and thrombocytopenia. After re-feeding, the number of leukocytes and thrombocytes recovered, but the red blood cell number remained reduced and there was a significant increase in abnormal red cell nuclei. 相似文献
99.
Feng Z Qi J Tsuge T Oba Y Kobayashi T Suzuki Y Sakagami Y Ojika M 《Bioscience, biotechnology, and biochemistry》2005,69(7):1372-1380
A bacterial artificial chromosome (BAC) library was constructed to isolate the biosynthetic gene cluster for the polyketide/peptide hybrid-type antibiotic cystothiazole A from the myxobacterium Cystobacter fuscus strain AJ-13278. Sequence analysis of a 63.9 kb contiguous region that encompasses the biosynthetic gene cluster (cta) led to the identification of a polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) hybrid gene cluster 32.1 kb in size, which consists of six open reading frames (ORFs), ctaB to ctaG, as well as downstream genes ctaJ and ctaK (1.0 and 0.9 kb, respectively) responsible for the final biosynthetic steps. The genes ctaB, ctaE, and ctaF encode PKSs, the genes ctaC and ctaG encode NRPSs, and ctaD encodes an NRPS-PKS hybrid enzyme. Disruption of ctaD impaired cystothiazole A production. Additionally, two downstream genes, ctaJ and ctaK, which encode a nitrilase and an O-methyltransferase, respectively, must be responsible for the final methyl ester formation in the cystothiazole A biosynthesis. 相似文献
100.