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41.
42.
The inhibitory effect of trifluoroperazine (25-200 microM) on the sarcoplasmic reticulum calcium pump was studied in sarcoplasmic reticulum vesicles isolated from skeletal muscle. It was found that the lowest effective concentrations of trifluoroperazine (10 microM) displaces the Ca2+ dependence of sarcoplasmic reticulum ATPase to higher Ca2+ concentrations. Higher trifluoroperazine concentrations (100 microM) inhibit the enzyme even at saturating Ca2+. If trifluoroperazine is added to vesicles filled with calcium in the presence of ATP, inhibition of the catalytic cycle is accompanied by rapid release of accumulated calcium. ATPase inhibition and calcium release are produced by identical concentrations of trifluoroperazine and, most likely, by the same enzyme perturbation. These effects are related to partition of trifluoroperazine ino the sarcoplasmic reticulum membrane, and consequent alteration of the enzyme assembly within the membrane structure, and of the bilayer surface properties. The effect of trifluoroperazine was also studied on dissociated ('chemically skinned') cardiac cells undergoing phasic contractile activity which is totally dependent on calcium uptake and release by sarcoplasmic reticulum, and is not influenced by inhibitors of slow calcium channels. It was found that trifluoroperazine interferes with calcium transport by sarcoplasmic reticulum in situ, as well as with the role of sarcoplasmic reticulum in contractile activation. 相似文献
43.
Metabolic acidosis produces a phosphaturia which is independent of parathyroid hormone or dietary phosphorus intake. To study the underlying mechanism, inorganic phosphate (Pi) and glucose transport were studied in brush-border membrane vesicles prepared from the renal cortex of parathyroidectomized rats gavaged for three days with either 7.5 ml of 1.6% NaCl (control) or 1.5% NH4Cl (acidosis). At killing, blood pH and plasma bicarbonate were and , respectively, in control and () and () in acidotic rats. Serum Pi was similar in both groups, while 24 h urine Pi excretion was higher in the acidotic group (). Peak sodium-dependent uptake of Pi, measured after 1.5 min of incubation, was higher in controls than acidotic rats ( vs. protein, ), whereas peak glucose uptake at 1.5 min was not significantly different between the groups. Equilibrium values for Pi and glucose uptake were similar in the two groups. for Pi uptake in the control and acidotic animals were not different, 0.036 and 0.040 mM, respectively. By contrast, was higher in controls than in the acidotic group, 3.13 vs. 1.15 nmol/mg protein per 15 s. These results suggest that metabolic acidosis directly inhibits Pi uptake by the brush border of the proximal tubule by decreasing the availability of Pi carriers of the renal brush-border membrane. 相似文献
44.
Three photosynthetic enzymes were characterised in extractsfrom leaves and aerial roots of Aranda Christine 130.The enzymes from both tissues were similar in activity and kineticproperties. Grana-containing chloroplasts were found in rootcells of Vanda suauis. Thus components crucial to photosynthesisare present in aerial roots of these leafy orchids. (Received March 22, 1983; Accepted July 7, 1983) 相似文献
45.
Population dynamics of microfilarial production and eosinophilic levels in slow lorises infected with Breinlia sergenti, Petter (Filarioidea: Dipetalonematidae). International Journal for Parsitology 4: 383388. Observations have been made on microfilarial and eosinophilic levels in slow lorises infected with Breinlia sergenti. Animals given a single inoculation of 100-150 infective larvae exhibited three different patterns of microfilaraemia while superinfected animals showed enhanced microfilarial levels. It appeared that the number of inoculations as well as the interval between inocula are important factors in enhancing microfilarial levels. Two different types of incubation periods were seen, one at 100-120 days and the other at 200 days. The eosinophilic levels were investigated in some of the animals and an attempt was made to correlate these levels with the microfilaraemia. Cortisone injection appeared to promote a vigorous eosinophilia in some of the infected animals tested. 相似文献
46.
Comparison of the requirements for ribonucleic acid synthesis with the requirements for deoxyribonucleic acid synthesis in animal tissues 总被引:2,自引:0,他引:2
Ribonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat-denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal cofactors. 相似文献
47.
48.
R W Butcher R J Ho H C Meng E W Sutherland 《The Journal of biological chemistry》1965,240(11):4515-4523
49.
An investigation was made of the anatomical structure of the shoot apex ofSenecio vulgaris L. a photoperiodically neutral plant, and compared with the formation of successive leaf primordia along the axis up to the initiation of the terminal inflorescence. In the shoot apex of a germinating plant a central zone can first be distinguished from the peripheral zone which is composed of small and intensely stained cells. Later, a rib meristem appears. At the time of the initiation of the middle (the largest) leaves, the shoot apex has a distinct small central zone and a well developed peripheral zone and rib meristem. Between these zones there is a group of cells dividing in all directions, the subcentral zone. At the time of initiation of the last leaves, the central zone extends to the flanks and gradually ceases to be distinguishable. At the same time, the subcentral zone increases in size. This is caused first by cell division and later, with the initiation of the last, most reduced leaves, by enlargement of the cells. Vacuolization in the inner part of the apex and the arrangement of the superficial cells in rows parallel to the surface of the apex, is a preparatory step to the initiation of the inflorescence. 相似文献
50.