Search PubMed⌕ Search

Biomedical subjects

M Kojima

Publications and source records attributed to M Kojima.

At least 829 records · Page 46Linked to original sources
PubMed1983

Mouse alloantibodies capable of blocking cytotoxic T cell function. IV. Comparative analysis of the blocking effects of anti-Lyt-2 and anti-H-2 antibodies on allogeneic and PHA-mediated killing.

Blocking of cell-mediated lympholysis (CML) by anti-Lyt-2 antibodies was compared with that by anti-H-2 antibodies which most likely inhibit CML by blocking antigen recognition by cytotoxic T lymphocytes (CTLs). Both antibodies were shown to inhibit the early Mg2+-dependent process of killing. Moreover, the anti-H-2-sensitive event was found to be reversible by the antibody as was the case with the anti-Lyt-2-sensitive event, suggesting that the two antibodies block the same event taking place during the Mg2+-dependent stage. Both types of antibody were also shown to be capable of inhibiting the phytohemagglutinin (PHA)-mediated non-specific killing activity of CTLs. However, in the case of anti-Lyt-2 antibodies, available monoclonal antibodies failed to inhibit PHA-mediated killing whereas conventional antisera did. The results thus suggest multiplicity and heterogeneity of Lyt-2 determinants or the existence of multiple products of Lyt-2-linked genes. In addition, an anti-H-2 antiserum also exerted a specific inhibitory effect on PHA-mediated killing. Thus there appears to be a general requirement for involvement of the Lyt-2 molecules on CTLs and major histocompatibility complex (MHC) products on the target cells. The implications of these observations are discussed.

Animals↗
PubMed1983

Substance P modulates the sensitivity of the nicotinic receptor in amphibian cholinergic transmission.

The effect of substance P on the sensitivity of nicotinic acetylcholine (ACh) receptors of bullfrog sympathetic ganglion cells and frog skeletal muscle endplate was examined electrophysiologically. The amplitude of ACh-induced postsynaptic potential (ACh potential) and current (ACh current) were reversibly and dose-dependently reduced by substance P at low concentrations (0.42-42 microM). The mean amplitude of the miniature endplate potential (m.e.p.p.) was also reduced by substance P (4.2 microM). Substance P (4.2 microM) shifted the S-shaped dose-response curve of the ACh current downward. A Lineweaver-Burk plot constructed from the dose-response curve revealed that substance P depressed the maximum response (Vmax) without changing the apparent affinity (Km) of ACh for the receptor. Substance P (0.42-42 microM) did not alter the reversal potential of the ACh current of the endplate. The half-decay time of endplate current (e.p.c.) and its voltage-dependency were not altered by substance P in these concentrations. The depression of the ACh current by substance P may not be due to a blockade of the opened channel which has been activated by the preceding combination of ACh with the receptor. These results suggest that substance P suppresses the sensitivity of nicotinic ACh-receptors of the sympathetic ganglion cell and skeletal muscle endplate, acting on a certain allosteric site but not the recognition site of ACh in the receptor-ionic channel complex.

Animals↗
PubMed1983

Age-dependent changes in electrophysiologic characteristics of fast and slow action potentials in rat papillary muscle.

Isolated papillary muscles from juvenile (about 2 months old, average weight of 250 g) and young adult rats (about 4 months old, average weight 485 g) were studied for age-dependent differences in the characteristics of fast and slow action potentials (APs). The fast and slow APs were recorded in 5.4 mM and 25 mM K+-Tyrode solutions, respectively (stimulation rate of 1 Hz). For the slow APs, the dose-response curves for isoproterenol versus Vmax (the maximum rate of rise of the APs), overshoot, and AP amplitude were linear between 10(-9) M and 10(-6) M (10(-5 M in some cases) in the juvenile and young adult rats. Isoproterenol pretreatment (1 mg/kg s.c., 1 h prior) decreased the slope of the dose-response curve, and saturation was achieved at a lower concentration. The Vmax, overshoot, and amplitude of both the fast and slow APs were somewhat smaller in the young adult rats than in the juvenile rats; there were no differences in the resting potential, AP duration, or threshold voltage. These results suggest that activation of a greater fraction of the beta-adrenergic receptors is coupled directly or indirectly to activation of a greater fraction of the slow channels. The pretreatment data suggest that down-regulation of the beta-adrenergic receptor may occur. The conductance per channel for the fast Na+ channels and slow channels, and (or) the number of both types of functional channels, may decrease with age.

Action Potentials↗
PubMed1983

Epidural hematomas of the posterior fossa in children.

The authors report 3 cases of epidural hematoma of the posterior fossa in children. The clinical signs and symptoms are discussed. Onset of symptoms is not necessarily acute. The radiological findings are discussed. Epidural hematomas of the posterior fossa in children have a tendency to liquefy earlier than supratentorial hematomas. We emphasize the value of computed tomography for the diagnosis of epidural hematoma of the posterior fossa. One should keep in mind the possibility of the presence of an epidural hematoma of the posterior fossa in the treatment of head injury in children, even in the case of a minor head injury.

Cerebral Angiography↗
PubMed1983

Immunohistochemical study on the distribution of serotonin-containing cell bodies in the brain stem of the dog.

The distribution of serotonin-containing neurons in the brain of the dog was studied by use of PAP immunohistochemistry. The lower brain stem was endowed with extensively scattered serotonergic cell bodies, a large portion of which was located in the raphe nuclei. At the same time, prominent distribution of serotonergic neurons in lateral areas outside the raphe nuclei was also demonstrated. Our observations on the brain stem were, in principle, consistent with those on rats, cats and monkeys, with only minor differences.

Animals↗
PubMed1983

A histological study on microthrombi in autopsy cases of DIC.

Microthrombi in 43 untreated and 26 treated cases of DIC were studied histologically and immunohistochemically. In the untreated cases, four types of microthrombi (intraluminal microthrombi with or without fibroblastic and/or smooth muscle cell reaction) were identified. Microthrombi in the former three types showed various degrees of thrombolysis. Failure of thrombolysis seemed to lead the organization of microthrombi. These morphological findings were considered to indicate the course of DIC and the degree of disappearance of the microthrombi in DIC. Microthrombi in the hepatic sinusoids and glomerular capillaries were studied with special reference to the removal processes of the microthrombi. Pathogenesis of renal cortical necrosis in DIC was also discussed. The number of microthrombi was markedly decreased by heparin and gabexate mesilate treatment. The incidences of microthrombi in the liver, kidney, lung, and heart were compared in the two treated groups.

Disseminated Intravascular Coagulation↗
PubMed1983

Immunohistochemical studies on the peptidergic nerve fibers in the pineal organ of the dog.

The distribution of vasopressin-, oxytocin- and LHRH-containing nerve fibers in the pineal organ of the dog was demonstrated by use of the peroxidase-antiperoxidase immunohistochemical technique. These neuropeptide-containing fibers penetrated through the pineal stalk from the brain, mainly from the posterior commissural region, into the pineal organ. The vasopressin fibers were the most prominent in number, oxytocin fibers and LHRH fibers were the least. Most of these fibers were found in the proximal part of the pineal organ, but some of them were also observed in the distal part. These peptidergic fibers were distributed not only in the perivascular spaces but among the parenchymal cells.

Animals↗
PubMed1983

Cosynthesis and protoplast fusion by mutants of bialaphos (AMPBA) producing Streptomyces hygroscopicus.

Cosynthesis in mixed culture and protoplast fusion of non-producing mutants of Streptomyces hygroscopicus which may produce biosynthetic intermediates of bialaphos (AMPBA) were studied. Non-producing mutants were obtained by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) treatment, and six stable non-producing mutants were used for cosynthesis and protoplast fusion studies. The biosynthetic block sites of the non-producers were consistent with studies of the biosynthetic pathway of AMPBA.

Mutation↗
PubMed1983

Discovery, isolation and structure of novel cephamycins of Streptomyces chartreusis.

By the use of HPLC technique after treatment with beta-lactamases, two novel cephamycins, SF-1623 and SF-1623B, were discovered and isolated from the fermentation broth of Streptomyces chartreusis SF-1623. The structures of SF-1623 and SF-1623B were determined to contain 3-sulfothiomethyl and 3-hydroxymethyl groups respectively, by chemical and enzymatic transformation reactions. Studies on the fermentation condition and process for the large scale preparation of antibiotic SF-1623 are also described.

Bacteria↗
PubMed1983

Studies on a new nucleoside antibiotic, dapiramicin. I. Producing organism, assay method and fermentation.

A new antibiotic, dapiramicin, has been isolated from the fermentation broth of Micromonospora sp. SF-1917. Since the dapiramicin exhibited essentially no in vitro activity by usual bioassays, two assay methods for dapiramicin were developed, HPLC and a new bioassay by growth inhibition of fungal mycelia on a slide glass. Fermentation of dapiramicin is also described.

Antifungal Agents↗
PubMed1983

Histopathological features of plasma cell dyscrasia with polyneuropathy and endocrine disturbances, with special reference to germinal center lesions.

The biopsy and autopsy materials of 41 cases showing clinical manifestations consistent with those of plasma cell dyscrasia with polyneuropathy and endocrine disturbances were studied by light microscopy and immunohistochemistry. The results obtained are as follows: 1) Lymph node swelling was generalized and the size of the nodes varies up to that of a thumb tip. 2) Angiosclerosis in the germinal centers of swollen lymph nodes is one pathognomonic feature in this disorder and was common to all the cases examined and occurred in the early stage. 3) The other feature is monoclonal proliferation of plasma cells (plasmacytoma) occurring not only in the bone marrow (five biopsy cases, seven autopsy cases) but also in the lymph nodes (nine biopsy cases, four autopsy cases). 4) If all the bone lesions detected roentgenologically are regarded as being due to monoclonal proliferation of plasma cells, it was demonstrated in 26 of 31 biopsy cases (84%) and in 14 of 16 autopsy cases (88%). This suggests that the plasmocytoma participates in the development of clinical manifestations of the disorder. 5) Besides the characteristic lesions in the lymph nodes, proliferation of small blood vessels and hemangioma-like lesions were found in the spleen, subcutaneous connective tissue and visceral adipose tissues, and hemangiomatous verrucae were also seen in the skin. As to the pathogenesis of the vascular lesions, vasculitis may be suggested. 6) The histologic features in the other organs and tissues seem to be closely related to the development of varied clinical manifestations and are represented by atrophy in the sural nerves, gastrocnemius muscles, and endocrine or reproductive organs.

Adult↗
PubMed1983

The role of Kupffer's cells in disseminated intravascular coagulation. A morphologic study in thrombin-infused rabbits.

We studied ultrastructural changes of Kupffer's cells in rabbits during experimental disseminated intravascular coagulation (DIC) induced by thrombin infusion. We observed three steps of fibrin clearance by Kupffer's cells: adsorption on the cell coat, invagination of the plasma membrane, and formation of bristle-coated vesicles adjoining the invaginated fibrin. There was no direct evidence of phagocytosis of fibrin by Kupffer's cells. Pinocytosis revealed by bristle-coated vesicles seemed to be one of the microthrombiclearing mechanisms of Kupffer's cells. Dissemination of microthrombi to systemic organs seemed to depend on the speed of fibrin formation and the clearing ability of Kupffer's cells. This hypothesis was supported by the finding that pretreatment with latex particles increased the severity of DIC.

Animals↗
PubMed1983

Gamma heavy chain disease. Ultrastructural and immunohistochemical study.

Electron microscopic and immunohistochemical studies were carried out on materials obtained from three patients of gamma heavy chain disease (gamma-HCD). Electron microscopically, proliferating cells showed various stages of maturation from immunoblast to plasma cell, and the majority of proliferating cells were proplasmacytes and plasma cells. From the intracytoplasmic immunoglobulin studies by immunoperoxidase method (PAP method) and electron microscopical enzyme-labeled antibody technique, proliferating cells, such as the immunoblast, plasmablast, proplasmacyte, and plasma cell, showed positive reaction to anti-gamma-heavy chain serum and anti-Fc fragment (IgG) serum, and also in a third case with Bence Jones protein, proliferating cells showed positive reaction to anti-kappa light chain serum. We would conclude that proliferating cells in gamma-HCD might be a single clone proliferation of B-cell synthesizing gamma-HCD protein, and the predominant proliferation cells are proplasmacytes and plasma cells situated near mature plasma cells in the B-cell line.

Aged↗