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Biomedical subjects

M Murakami

Publications and source records attributed to M Murakami.

At least 847 records · Page 47Linked to original sources
PubMed1992

Biochemical characterization of 25 distinct carcinoembryonic antigen (CEA) epitopes recognized by 57 monoclonal antibodies and categorized into seven groups in terms of domain structure of the CEA molecule.

The chemical nature of 25 distinct carcinoembryonic antigen (CEA) epitopes, which were recognized by 57 different monoclonal antibodies and categorized into 7 groups (Groups A to G) in terms of domain structure of the CEA molecule, was analyzed and the findings obtained were compared with the results of our previous studies using recombinant CEA proteins. All 21 epitopes of Groups A to F defined by 48 MAbs were resistant to periodate oxidation and were to a greater or lesser extent retained after deglycosylation of CEA, indicating that they are all protein in nature. The 21 epitopes were detected in recombinant CEA proteins expressed in Chinese hamster ovary (CHO) cells. Seven of the 21 epitopes of protein nature were partially or completely sensitive to reduction and alkylation of CEA and not detected or only slightly revealed in the recombinant CEA proteins expressed in E. coli, indicating that those epitopes are dependent on the tertiary structure of the peptide chain, which is formed by disulfide bonds. All 4 epitopes of Group G defined by 9 MAbs were sensitive to mild periodate oxidation and deglycosylation, but resistant to reduction and alkylation and to digestion with pepsin or pronase, indicating that those 4 epitopes are carbohydrate in nature. Although none of the 4 epitopes of Group G were detected in the recombinant CEA proteins expressed in E. coli, two were detected in those expressed in CHO cells. The biochemical studies reported here thus provide information as to the nature of the epitopes on the CEA molecule and help form the basis for selecting the anti-CEA MAbs for use in biological study and potential clinical applications of CEA.

Animals↗
PubMed1992

Immunochemical detection of arachidonoyl-preferential phospholipase A2.

Monoclonal antibodies were raised against rabbit platelet cytosolic arachidonoyl-preferential phospholipase A2. The antibodies precipitated the arachidonoyl-preferential phospholipase A2 activity in the soluble fraction of a rabbit platelet lysate in combination with an immobilized anti-mouse immunoglobulin antibody, and reacted predominantly with a protein exhibiting a molecular weight of approximately 88,000 on immunoblotting analysis. All three antibodies established so far reacted with human platelet arachidonoyl-preferential phospholipase A2 as effectively as the rabbit platelet enzyme. One of them reacted with the rat platelet arachidonoyl-preferential enzyme, whereas none of them reacted with rabbit platelet secretory 14-kDa group II phospholipase A2. The existence of an immunologically related phospholipase A2 was further shown in rabbit granulocytes, brain, lung, and liver, rat and mouse mast cells, and human monocytoma U937 cells. Thus, an arachidonoyl-preferential phospholipase A2 with similar structural properties appeared to be expressed in a variety of cells and tissues.

Animals↗
PubMed1992

Detection of three distinct phospholipases A2 in cultured mast cells.

Phospholipase A2 activity in lysates of mast cells such as rat mastocytoma RBL-2H3 cells and mouse bone marrow-derived IL-3-dependent mast cells (BMMC) was measured using phosphatidylcholine (PC), phosphatidylethanolamine (PE), or phosphatidylserine (PS) as a substrate. Both types of cells exhibited phospholipase A2 activity with a similar pH profile; the optimum pH observed with PS as a substrate was 5.5-7.4, whereas that with PE or PC was 8.0-9.0. PE and PC bearing an arachidonate at the sn-2 position were cleaved more efficiently by PE, PC-hydrolyzing phospholipase A2 than phospholipids with a linoleate. A monoclonal antibody raised against rabbit platelet 85-kDa cytosolic phospholipase A2 absorbed the PE, PC-hydrolyzing activity. PS-hydrolyzing activity was purified from RBL-2H3 cells and BMMC by sequential heparin-Sepharose, butyl-Toyo-pearl, and reverse-phase HPLC. On reverse-phase HPLC, the PS-hydrolyzing activity of RBL cells was separated into two peaks, A and B. The peak B activity was inhibited by the anti-rat 14-kDa group II phospholipase A2 antibody, while the peak A activity was not. The partially purified peak A activity hydrolyzed PS about 10-fold more efficiently than PE at optimum pH of 5.5-7.4. No appreciable hydrolysis was observed with PC or phosphatidylinositol (PI). Thus, mast cells may express at least three distinct phospholipases A2; 14-kDa group II phospholipase A2, 85-kDa cytosolic arachidonate preferential phospholipase A2, and a novel phospholipase A2 that shows high substrate specificity for PS.

Animals↗
PubMed1992

Case report: hypertension in Cushing's syndrome.

Pathogenesis of hypertension in Cushing's syndrome has remained controversial. A 56-year-old Japanese man with Cushing's syndrome due to adrenal carcinoma has been followed up for more than 6 years. During the followup period, left adrenalectomy and hemihepatectomy due to metastatic lesion were performed. Blood pressure, serum cortisol, and urinary excretion of 17-OHCS, as well as other routine biochemicals, have been measured periodically. These data revealed that there is a marked correlation between the levels of blood pressure and serum cortisol or urinary excretion of 17-OHCS. This finding suggests that cortisol production by tumor is a determinant factor in hypertension in Cushing's syndrome.

Adrenal Gland Neoplasms↗
PubMed1992

Helicobacter pylori has an ulcerogenic action in the ischemic stomach of rats.

Helicobacter pylori (H. pylori) is now accepted as an important cause of chronic active gastritis. There also seems to be an association between the colonization of H. pylori in the gastric mucosa and peptic ulceration. However, it has not demonstrated that the instillation of H. pylori into the stomach produces the ulcerative gastric lesions in animals or humans. We carried out an experiment to study whether or not H. pylori has an ulcerogenic action in the ischemic stomach of rats, using an ex vivo gastric chamber. The rat stomachs were exposed to 1 ml of H. pylori solution (200 IU of urease/ml) and 1 ml of urea (400 mg/dl) for 60 min after the creation of ischemia in the stomach (by withdrawal of 3 ml of blood). The exposure of the stomach to both H. pylori and urea resulted in severe hemorrhagic gastric mucosal lesions with a marked decrease in potential difference (PD) with a concomitant increase in ammonia concentration in rats with ischemia, whereas gastric lesions and a fall in PD were hardly observed in rats without ischemia. These results have demonstrated that H. pylori has an ulcerogenic action on the stomach subjected to mucosal ischemia.

Animals↗
PubMed1992

Depressor systems contribute to hypertension induced by glucocorticoid excess in dogs.

OBJECTIVE: The aim of this study was to investigate the role of depressor systems in glucocorticoid-induced hypertension. METHODS: The serial changes in cardiorenal hemodynamics, urinary excretions of kallikrein and prostaglandins (PGE2 and the prostacyclin derivative 6-keto-PGF1 alpha) before, and during the administration of both low and high doses of dexamethasone (9 alpha-fluoro-16 alpha-methylprednisolone) and after the cessation of dexamethasone were examined in conscious trained dogs. In addition, pressor responses to prostaglandin, bradykinin, bradykinin antagonist and indomethacin were studied during the administration of dexamethasone. RESULTS: High-dose dexamethasone induced a significant elevation in mean arterial pressure (MAP) that was accompanied by a significant reduction in the urinary excretion of kallikrein, PGE2 and 6-keto-PGF1 alpha. In contrast, low-dose dexamethasone treatment had no significant effect upon MAP but induced a transient elevation in the urinary excretion of kallikrein, PGE2 and 6-keto-PGF1 alpha. Furthermore, additional oral administration of indomethacin produced a significant elevation in MAP in dogs treated with low-dose dexamethasone; but did not affect the hemodynamics of animals with high-dose dexamethasone. Whilst i.v. administration of either bradykinin or prostacyclin induced a significant reduction in MAP in high-dose but not low-dose dexamethasone-treated dogs, administration of a competitive bradykinin antagonist, D-Arg-[Hyp3, Thi5,8, D-Phe7]-bradykinin induced a significant elevation in MAP in low-dose but not high-dose dexamethasone-treated dogs. CONCLUSION: Depressor systems play an important role in regulation of blood pressure in glucocorticoid-treated dogs.

Animals↗
PubMed1992

Inhibition by glibenclamide of negative chronotropic and inotropic responses to pinacidil, acetylcholine, and adenosine in the isolated dog heart.

The blocking effects of glibenclamide on the chronotropic and inotropic responses to K+ channel openers pinacidil (ATP-sensitive) and acetylcholine (ACh) or adenosine (receptor-operated) were investigated in the isolated, blood-perfused canine atrium or ventricle. Glibenclamide (0.1-3 mumol) induced no significant cardiac effects. Cumulative administration of pinacidil (0.03-3 mumol) dose-dependently decreased sinus rate much less than the contractile force of the atrial and ventricular muscles. Glibenclamide similarly inhibited the negative chronotropic and inotropic responses to pinacidil in a dose-related manner. A high dose of glibenclamide (3 mumol) slightly but significantly attenuated the negative chronotropic and inotropic responses to ACh and adenosine but not to verapamil. These results demonstrate that glibenclamide inhibits the negative chronotropic and inotropic responses to the ATP-sensitive K+ channel opener pinacidil and the receptor-operated K+ channel openers ACh and adenosine but more selectively antagonizes the responses to pinacidil in the dog heart and suggest that in contrast to ACh and adenosine, an ATP-sensitive K+ channel opener has a greater effect on the ventricle than on the sinoatrial node.

Acetylcholine↗
PubMed1992

Cardiac effects of vecuronium and its interaction with autonomic nervous system in isolated perfused canine hearts.

The chronotropic and inotropic effects of vecuronium bromide and its interaction with the autonomic nervous system were investigated in the isolated, cross-circulated right atrial and left ventricular preparations of the dog. Vecuronium, injected into the external jugular vein of the support dog, induced dose-dependent decreases in heart rate and arterial blood pressure, and increased atrial contractile force with no change in sinus rate in isolated atrial preparations. Vecuronium (1-3,000 micrograms), injected into the sinus node artery of the isolated atrium, induced dose-dependent increases in atrial contractile force with small increases in sinus rate. Vecuronium also increased the ventricular contractile force in a dose-dependent manner. The positive inotropic effect was attenuated in part by propranolol, but not by either tetrodotoxin or imipramine. Vecuronium inhibited in a dose-related manner the negative chronotropic and inotropic responses to parasympathetic nerve stimulation and carbachol (CCh) and the negative followed by positive cardiac responses to nicotine, but did not attenuate the positive responses to sympathetic nerve stimulation. The ID50s for the responses to parasympathetic stimulation, CCh, and nicotine were not significantly different. Vecuronium enhanced the positive chronotropic and inotropic responses to sympathetic nerve stimulation, tyramine, norepinephrine, and isoproterenol. These results indicate that (a) vecuronium causes the positive inotropic responses mediated by nonadrenergic mechanisms and beta-adrenoceptors, (b) vecuronium blocks ganglionic and presynaptic nicotinic and postsynaptic muscarinic receptor-mediated responses similarly, and (c) vecuronium enhances beta-adrenoceptor-mediated responses in the dog heart.

Animals↗
PubMed1992

Epitopes predominantly retained on the carcinoembryonic antigen molecules in plasma of patients with malignant tumors but not on those in plasma of normal individuals.

We have previously reported that a group of monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA), designated Group F MAbs, are able to discriminate CEA in tumor tissues from normal fecal antigen-2, a soluble form CEA-counterpart in normal adult feces, and that the protein epitopes recognized by them are present on the domain A3-B3 of the CEA molecule. In this study, we further investigated the molecular localization of the epitopes recognized by the Group F MAbs using three new recombinant CEA proteins with restricted domain structures expressed in Chinese hamster ovary cells, and found that the epitopes for the Group F MAbs are present on domain B3 close to the anchoring device of the CEA molecule. The epitopes for the Group F MAbs were retained on the CEA molecules in the plasma of patients with malignant tumors and on the CEA molecules spontaneously released into the culture media from established tumor cell lines. However, a large part of the CEA molecules in the plasma of normal individuals were found to lack the epitopes for the Group F MAbs. These results provide a basis for the improved cancer diagnosis by using our CEA assay system utilizing a Group F MAb, and indicate the potential clinical utility of the Group F MAbs.

Animals↗
PubMed1992

In vitro induction of IgG anti-DNA antibody from high density B cells of systemic lupus erythematosus patients by an HLA DR-restricted T cell clone.

An HLA-DR restricted T cell clone (26G11) which recognized a lymphoid cell-derived autoantigen associated with DR4 molecule was shown to induce not only autologous but also allogenic DR4+ B cells to produce large amounts of antibodies of the IgG and IgM classes. Using the helper activity of this clone, we investigated the mechanism of anti-DNA antibody production in DR-matched patients with systemic lupus erythematosus (SLE). When cultured with 26G11 cells, B cells from DR-matched normal control subjects produced large amounts of IgM anti-DNA antibody, but did not produce IgG anti-DNA antibody which is thought to have a pathological role in SLE. In contrast, B cells from DR-matched patients with active SLE spontaneously produced a fairly large amount of IgG anti-DNA antibody, and the production was augmented by the T cell clone. Little IgG anti-DNA antibody was produced by the B cells of patients with inactive SLE in either the presence or absence of T cell clone. We next fractionated B cells into low density B (LD-B) and high density B (HD-B) cells by centrifugation on discontinuous Percoll density gradients. IgG anti-DNA antibody was spontaneously produced by LD-B cells of active SLE patients but not by those either of inactive SLE patients or normal controls. On the other hand, although IgG anti-DNA antibody was not spontaneously produced by the HD-B cells of both active and inactive SLE patients, it could easily be induced by their culture with the T cell clone. Our results clearly show the existence of IgG anti-DNA antibody-producing B cells in the peripheral blood of SLE patients irrespective of their disease activity and suggest that autoreactive T cells may play a pathogenic role in SLE through the induction of autoantibody production.

Antibodies, Antinuclear↗
PubMed1992

Meningeal malignant melanoma in a child: immunocytological diagnosis.

A 10 year old boy, who was thought to have had a traumatic intracranial hemorrhage, was transferred to our Children's Medical Center. In spite of conservative treatment, he developed dysarthria, systemic convulsions, unconsciousness, quadriplegia, and consecutive paralysis of the cranial nerves. Magnetic resonance imaging scans demonstrated areas of increased signal intensity around the brain stem. The cerebrospinal fluid (CSF) contained a few large cells with abundant melanin-like granules, and numerous bizarre cells. The latter were considered to be malignant melanoma cells on immunocytological examination. Chemotherapy with dimethyltriazenoimidazole carboxamide (DTIC) and interferon beta (IFN-beta) was ineffective and he expired. Autopsy revealed diffuse infiltration of malignant melanoma cells into the meninges. We think that immunocytological examination of CSF is advisable for correct and rapid diagnosis.

Antibodies, Monoclonal↗
PubMed1992

Improvement of large intestinal absorption of insulin by chemical modification with palmitic acid in rats.

The intestinal absorption of 125I-labelled palmitoyl insulin was examined following administration into in-situ closed large intestinal loops of rats. When mono- and dipalmitoyl insulins (Palins-1 and Palins-2, respectively) were administered in polyoxyethylene hydrogenated castor oil (HCO 60) micellar system into intestinal loops, a marked increase in plasma radioactivity and a corresponding disappearance of residual radioactivity in the intestinal lumen were observed in the following rank order: Palins-2 greater than Palins-1 greater than native insulin. In addition, the derivatives were more stable than native insulin in the mucosal tissue homogenates of the large intestine. These results suggest that chemical modification of insulin with palmitic acid may not only increase the lipophilicity of insulin but also reduce its degradation, resulting in the increased transfer of insulin across the large intestinal mucous membrane. The linoleic acid-HCO 60 mixed micelles system did not have a significant effect on the large intestinal absorption of radioactivity associated with the lipophilic insulin analogues.

Animals↗
PubMed1992

Improvement of intestinal absorption of thyrotropin-releasing hormone by chemical modification with lauric acid.

Intestinal absorption of 125I-labelled lauryl thyrotropin-releasing hormone (Lau-TRH), a novel lipophilic derivative of TRH, was examined by rat in-situ closed intestinal loops. At a dose of 1 mumol per rat into the small intestine, a significant increase in percent of dose in plasma radioactivity of Lau-TRH was observed in comparison with that of TRH. A dose-dependent decrease in percent of dose in plasma radioactivity of TRH was noted, suggesting a saturable process of TRH transport. In contrast, the percent of dose in plasma radioactivity of Lau-TRH increased with increasing dose of Lau-TRH. The stability of TRH and Lau-TRH was studied in plasma and rat small intestinal homogenates. Lau-TRH was more stable than TRH in rat plasma. These results suggest that chemical modification of TRH with lauric acid may not only increase the lipophilicity of TRH but also reduce the degradation of TRH, resulting in the increased plasma radioactivity of TRH. On the other hand, Lau-TRH was gradually converted to TRH in the intestinal mucosal homogenate. These findings indicate that chemical modification of TRH with lauric acid might be a useful approach for improving the intestinal absorption of this peptide.

Animals↗
PubMed1992

Terminal 22q deletion associated with a partial deficiency of arylsulphatase A.

A 7 month old girl with psychomotor retardation, hypotonia, and minor malformations was found to have a terminal deletion of the long arm of chromosome 22, del(22)(q13.31). The partial deficiency of arylsulphatase A (ARSA) and the normal level of NADH diaphorase 1 (DIA1) suggests that the ARSA locus can be regionally assigned to 22q13.31----qter and the DIA1 locus can be excluded from the same segment. This report is the third published case with a terminal 22q deletion.

Cerebroside-Sulfatase↗
PubMed1992

Influences of hypothyroidism on TRH concentrations and preproTRH mRNA levels in rat hypothalamus: a simple and reliable method to detect preproTRH mRNA level.

To gain further insight into the regulation of hypothalamic TRH by thyroid hormones, we measured TRH concentration in specific hypothalamic nuclei and preproTRH mRNA levels in the anterior hypothalamus. Adult male rats were decapitated 1, 7, 14 days after thyroidectomy. Micropunches by the method of Palkovitz from seven hypothalamic nuclei and median eminence were used for measurement of TRH by radioimmunoassay. As compared with normal levels, TRH concentration significantly decreased in the median eminence and five hypothalamic nuclei including paraventricular nucleus (PVN), posterior nucleus, anterior nucleus, arcuate nucleus, and ventromedial nucleus pars lateralis, by 7 days after thyroidectomy. No significant changes were observed in dorsomedial nucleus or ventromedial nucleus pars medialis until 14 days after thyroidectomy. A rapid and simple method to detect specific mRNA for preproTRH was developed using the polymerase chain reaction and a single anterior hypothalamic section. PreproTRH mRNA levels in the anterior hypothalamus increased approximately twice 7 days after thyroidectomy. These data indicate that thyroidectomy caused a marked increase in preproTRH mRNA levels of the anterior hypothalamus, while it significantly reduced TRH concentrations not only in PVN and median eminence but also in other specific hypothalamic nuclei, suggesting that these nuclei might be involved in the thyrotropin regulation in the hypothalamus.

Animals↗
PubMed1992

Identification of inositol 1,4,5-trisphosphate binding in human pheochromocytoma.

An attempt was made to identify a specific binding of inositol 1,4,5-trisphosphate (IP3) to human chromaffin cell tumors. Crude microsomal fractions of pheochromocytomas possessed significant binding sites for [3H]IP3 with high- and low-affinity constants (Kd = 5.46 and 538 nM, respectively). The binding to these sites was rapid, saturable (reached equilibrium by 1 min at 0 degrees C) and reversible. Competition studies with other inositol phosphate analogs indicated the stereotypic specific binding for IP3. Although no significant difference was observed in the binding densities of IP3 between pheochromocytomas and adrenal nonfunctioning adenomas, the values of high-affinity constants were significantly lower in the former than the latter group (5.77 +/- 1.07, n = 5 vs. 11.30 +/- 1.98 nM, n = 4, p less than 0.05). The present data indicate that characteristics of IP3 binding sites are congruous with their receptor functions and that changes in its binding sites may contribute to the biochemical dissimilitudes in pheochromocytomas.

Adenoma↗
PubMed1992

Different posttranslational processing of human preprothyrotropin-releasing hormone in the human placenta and hypothalamus.

We scrutinized the possible existence of human prepro-THR messenger RNA (mRNA) and of its posttranslational processing products in the human placenta. Human placental mRNA of preproTRH was found to have a single species identical to that predicted from the hypothalamic mRNA, and could be reverse transcribed to complementary DNA (cDNA) encoding preproTRH in a size similar to the hypothalamic counterpart by means of reverse-transcriptase-polymerase chain reaction. Five different intervening peptides, designated human TRH-associated peptide (hTAP) [hTAP-1, preproTRH(90-111); hTAP-2, preproTRH(120-132); hTAP-3, preproTRH(141-149); hTAP-4, preproTRH(158-183); hTAP-5, preproTRH(192-224)], and a TRH precursor comprising the TRH progenitor sequence (octa-TRH) were synthesized, and six different antisera raised against individual peptides were used to develop specific RIA systems. Significant concentrations of hTAP-5 and octa-TRH-like immunoreactivities were quantitated in acid extracts of human placentae. In human hypothalamic extracts, immunoreactivities of hTAP-3, hTAP-4, hTAP-5, and octa-TRH, were apparently detected. Chromotographic analysis showed a single peak corresponding to each authentic peptide in RIA systems of hTAPs detected. In placentae, a single peak of octa-TRH-like substance was observed, and two octa-TRH-like substances with different molecular weights detected in hypothalami. The present data indicate that unique posttranslational processing steps of human preproTRH differ in human placentae and hypothalami, and that the human tissues involve profound amounts of several preproTRH-related peptides which do not comprise the TRH progenitor sequence.

Aged↗