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1.
The sequential cytological events of the regeneration process, after partial excision of the gastrocnemius muscle in the rat, were followed by light and electron microscopy. During the first 2 days after injury leukocytes and macrophages infiltrate into the traumatized area. Myogenic regeneration is then characterized by mainly two repair mechanisms. Mononucleated cells, that populate the excised area, most probably fuse together to give rise to newly formed multinucleated myotubes that further develop to striated myofibers. Another mechanism involves the repair of injured muscle fibers by the possible fusion of mononucleated cells with their necrotic cut ends. Consequently, by addition of nuclei and new muscular material, sarcoplasmic outgrowths from the injured fibers are formed. It is concluded that mainly two repair mechanisms are involved in the regeneration process following partial excision of a muscle: addition of new muscle fibers in a process similar to that of embryonic myogenesis and also meristic growth from the injured fibers. 相似文献
2.
Calcium control of glycogen synthase activities in mouse diaphragms, rat adipocytes and rat hepatocytes 总被引:1,自引:0,他引:1
The following article provides evidence that cellular calcium controls the activity of glycogen synthase in all three major glycogen storage tissues; muscle, fat, and liver. Depletion of cellular calcium resulted in a moderate increase of glycogen synthase %I activities in intact mouse diaphragms, in isolated rat adipocytes, and in rat hepatocytes. The increase in %I activity of glycogen synthase was more pronounced when the uridine di-phosphoglucose concentration in the glycogen synthase assay was lowered from 4.4 mM to 0.2 mM. Calcium depletion resulted in an approximately two-fold decrease in the Ka values for glucose-6-phosphate in all three tissues. The activities of glycogen synthase also correlated well with the content of cell-associated calcium in rat hepatocytes. The glucose-6-phosphate independent activities of glycogen synthase in extracts of calcium-replete and calcium-depleted tissue approached the same value following the exposure to crude phosphoprotein phosphatase. The activities of glycogen phosphorylase decreased in calcium-depleted tissues and cells. Insulin stimulated the activity of glycogen synthase in muscle and fat in the absence of added sugar and in the absence of extracellular calcium. It is concluded that glycogen synthase is under the control of calcium in the three main glycogen storage tissues. The actions of calcium are probably mediated through the actions of calcium-sensitive protein kinase(s). 相似文献
3.
Regular chewing was studied in the specialized Malagasy insectivore Tenrec ecaudatus with the aid of precisely correlated electromyography of the main adductors, digastrics, and two hyoid muscles and cineradiography for which metallic markers were placed in the mandibles, tongue, and hyoid bone. During the power stroke the body of the mandible moves dorsally and medially. The medially directed component of movement at this time is greatly increased by simultaneous rotation of the mandible about its longitudinal axis. The highly mobile symphysis, spherical dentary condyle, loss of superficial masseter muscle and zygoma, and the simplified zalamnodont molars all appear to be related to the large amount of mandibular rotation that occurs during occlusion. The balancing side lateral pterygoid muscle (inferior head) apparently shifts the working side mandible laterally during the last part of opening and the first part of closing. The working side temporalis and the superficial masseter muscle are both responsible for the shift back to the midline. The temporalis is usually active to the same extent on the working and balancing sides during the power stroke. The level of activity (amplitude) of the temporalis and duration of the power stroke increase with harder foods. Whenever soft foods are chewed, the superficial masseter is only active on the working side; whenever foods of increasing hardness are chewed, its level of activity on the balancing side increases to approach that of the working side. Mandibular rotation is greatly reduced when hard foods are chewed. 相似文献
4.
Mixed and muscarinic cholinergic agonists (acetylcholine, carbamylcholine, methacholine, oxotremorine, and pilocarpine) accelerated in a dose-dependent manner the progesterone-induced maturation of Xenopus laevis oocytes. None of these agonists induced oocyte maturation in the absence of progesterone. The accelerating effect of cholinergic agonists was blocked in a dose-dependent manner by specific muscarinic antagonists (atropine and scopolamine) but not by specific nicotinic antagonists (d-tubocurarine and hexamethonium). The specific nicotinic agonist, dimethylphenylpiperazine, alone induced maturation in the absence of progesterone. The optimal promoting effect of acetylcholine was observed when oocytes were exposed to acetylcholine for 30 min, 5 min after the addition of progesterone, and was markedly better than when oocytes were exposed to acetylcholine throughout their incubation with progesterone. The effect of acetylcholine was observed in both follicle-enclosed and in defolliculated oocytes, indicating that follicular cells were not the target of the cholinergic drugs. 相似文献
5.
Neurotransmitter-caused increase in [3H]inositol incorporation into phosphatidylinositol de novo synthesis vs exchange 总被引:1,自引:0,他引:1
[3H]inositol and 32Pi were simultaneously incorporated into rat parotid phosphatidylinositol. The ratio of [3H]/32Pi incorporation dropped dramatically following stimulation with muscarinic or alpha-adrenergic agonists and returned to control values following the addition of appropriate antagonists. The drop in [3H]/32Pi ratio can be explained by a rapid increase in de- novo synthesis of phosphatidylinositol following its receptor-mediated breakdown. The change in this ratio also provided evidence for the existence of CDP-DG + inositol in equilibrium phosphatidylinositol exchange reaction in the intact tissue. 相似文献
6.
Fish biomass (Tilapia sp.) were raised at high stocking density in 1-m(3) tanks containing 450 L of water. The water was changed continously by means of a jet flow regulator. The jet flow regulator maintained adequate dissolved oxygen (DO) and a low ammonia level, while the suspended solids were discarded. In such a system, an annual yield of above 15 kg/m(3) can be expected. The application of the jet flow regulator in aquaculture is discussed. 相似文献
7.
E. Yefenof I. Gafanovitch E. Oron M. Bar E. Klein 《Cancer immunology, immunotherapy : CII》1996,41(6):389-396
Polysaccharide K (PSK) is a biological response modifier used for adjuvant immunotherapy of malignant diseases. We studied the potential applicability of PSK for preventing tumor progression using an experimental model of murine lymphoma. Mice inoculated with the radiation leukemia virus (RadLV) develop thymic lymphomas after a latency of 3–6 months. However, 2 weeks after virus inoculation, prelymphoma cells can already be detected in the thymus. We found that PSK treatment induced hyperresponsiveness to concanavalin A and heightened production of interleukin-2 (IL-2) and IL-4 in spleen cells of both control and prelymphoma mice. The response was transient and was accompanied with a dominant usage of T cells expressing V8, but other T cell subsets were also stimulated by PSK. T lymphoma cells expressing V8.2 underwent apoptosis when incubated with PSK. Treatment of RadLV-inoculated mice with PSK delayed the onset of overt lymphoma (and mortality) but could not protect the mice from the disease. Combined treatment with PSK and a RadLV-specific immunotoxin prevented synergistically the progression of the prelymphoma cells to frank lymphoma. The results suggest that PSK contains a superantigen-like component that selectively activates V8+ T cells. Its administration prelymphoma mice interfered with the process of lymphoma progression. 相似文献
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10.
The isoelectrofocusing patterns of l-amino acid oxidase (LAO) from venom gland homogenates and of the secreted venom of Vipera palaestinae have been compared. The LAO isozyme profile of actively synthesizing gland spans over a wider range of pIs (4.8–6.0) and includes more variants as compared with the profile of the secreted venom. A basic shift of the isoelectrofocusing pattern of LAO obtained by treatment of the gland homogenate or the venom with neuraminidase indicates that sialic acid residues are responsible for the changes in the electronegativity of the isozymes. Analyses of subcellular fractions show that the microsomal fraction of the venom gland homogenate exhibits the highest multiplicity of molecular forms of LAO, whereas the fraction including the secretory granules has an isozyme profile similar to the venom. Double labelling experiments show that the newly synthesized LAO include isozymes which span over a wide range of pIs, whereas later on labelling of the more acidic isozymes is prominent. The results obtained may suggest that the sialic acid residues which are attached to LAO during its transport serve as “markers” for secretion. 相似文献