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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 793 records · Page 44Linked to original sources
PubMed1991

Evidence that differentiates between precursor cleavages at dibasic and Arg-X-Lys/Arg-Arg sites.

It is well known that precursor cleavage at paired basic amino acids (e.g., Lys-Arg, Arg-Arg) within the regulated secretory pathway is one of the key steps to produce bioactive peptides. On the other hand, we have recently shown that precursors with an Arg residue at the fourth residue upstream of the cleavage site besides the basic pair, i.e. with the Arg-X-Lys/Arg-Arg (RXK/RR) motif, are cleaved within the constitutive secretory pathway. To discriminate between the precursor cleavage at RXK/RR sites within the constitutive pathway and that at dibasic sites within the regulated pathway, we examined the effects of drugs affecting the secretory process, intracellular Ca2+ depletion, and a protease inhibitor on these cleavages. Chloroquine (a weak base), depletion of intracellular Ca2+ by A23187 (a Ca2+ ionophore), and the Pittsburgh-type mutant of alpha 1-protease inhibitor differentially affected these two cleavages. Brefeldin A, which impedes protein transport from the endoplasmic reticulum to the Golgi complex, inhibited both cleavages. Colchicine (an anti-microtubular drug) had no discernible effect on either cleavage. These observations support the notion that the precursor cleavages at dibasic and RXK/RR sites occur in different subcellular compartments, and are catalyzed by different processing endoproteases.

Amino Acid Sequence↗
PubMed1991

Hepatoid carcinoma of the ovary: a case report.

A case of a right ovarian tumor in a 64-year-old patient showing high blood levels of alpha-fetoprotein (AFP) is reported. Histologically, the tumor resembled hepatocellular carcinoma with hyaline globules. Localization of AFP was detected by the immunoperoxidase method. Electron microscopically, the rough-surfaced endoplasmic reticulum had developed into a meshwork, and the mitochondria were present within this meshwork. Because a transition from adenocarcinoma to a region resembling hepatocellular carcinoma was observed, this tumor was considered to originate as a common epithelial carcinoma. In the blood, 67% of the AFP was bound with concanavalin A (Con A), and the fraction pattern obtained by lentil agglutinin affinity chromatography (LCA) was of the germ cell type. From these results, the current case may be labeled clinicopathologically a hepatoid carcinoma of the ovary as described by Ishikura and Scully.

Adenocarcinoma↗
PubMed1991

Changes in gene expression of the renin-angiotensin system in two-kidney, one clip hypertensive rats.

To investigate the molecular mechanism of sustained hypertension in two-kidney, one clip (2K1C) hypertensive rats, possible changes in renin gene expression in the kidney and angiotensinogen in the liver were studied. In 2K1C rats 4 weeks after clipping, the plasma renin and angiotensin II levels were significantly higher than those in sham-operated rats, but the plasma angiotensinogen levels were similar in the two groups. At this time, expression of the renin gene in the ischaemic kidney of 2K1C rats was 2.6-times that in sham-operated rats (P less than 0.05), but expressions of the angiotensinogen gene were similar in the two groups. Sixteen weeks after clipping, the plasma renin and angiotensin II levels in 2K1C rats were not significantly higher than those in sham-operated controls, but expression of the renin gene in the kidney was still 2.2-times higher in 2K1C rats than in controls (P less than 0.05). The plasma angiotensinogen level was significantly higher in 2K1C rats than in controls (P less than 0.05), and expression of the angiotensinogen gene in the liver was 2.9-times higher in 2K1C rats than in controls (P less than 0.01). These results indicate that the roles of the renin-angiotensin system in maintenance of hypertension in 2K1C rats differ in the acute and chronic phases: in the acute phase, over-expression of the renal renin gene coupled to increased renin secretion plays the major role in elevating the blood pressure; in the chronic phase, a counter-regulatory mechanism may affect the post-transcriptional fate of renin.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensinogen↗
PubMed1991

Characterization of endothelin receptor subtypes.

Scatchard-plot analysis of [125I]ET-1 and [125I]ET-3 binding to rat lung membranes exhibited almost the same Kd values whereas the concentration of the binding sites of ET-1 is approximately four times higher than that of ET-3. This result suggests the presence of at least two distinct subtypes of ET receptors: an ET-1-specific type and an ET-3-specific or ET-1 and ET-3 nonselective type. On the other hand, in rat brain membranes, a curvilinear Scatchard plot was obtained for [125I]ET-3 in contrast to a linear plot for [125I]ET-1. This finding also demonstrates the existence of the two different receptor subtypes having the same affinity for ET-1, but one of which has a high affinity and the other has a low affinity for ET-3. Moreover, these data indicate that an ET receptor subtype exists in rat brain different from the subtype in rat lung. To obtain the bases for a further detailed characterization of the receptor, we have purified the rat lung ET receptor to homogeneity by ET-1-affinity chromatography. The purified receptor exhibits a molecular mass of 45 kDa, in good agreement with that estimated from the affinity labeling.

Animals↗
PubMed1991

Genetic studies on experimental autoimmune gastritis induced by neonatal thymectomy using recombinant inbred strains between a high-incidence strain, BALB/c, and a low-incidence strain, DBA/2.

Thymectomy on day 3 after birth induced autoimmune gastritis (AIG) at the age of 2 months in 51-73% of BALB/c mice, and in only 3-5% of DBA/2 mice. AIG was detected by histological and serological (immunofluorescence staining for detecting anti-parietal cell autoantibody) examination. However, autoantibody was weakly positive in almost all of these DBA/2 mice when measured by ELISA using extract of murine gastric mucosa as the antigen. To investigate genetically the mechanism controlling the incidence of AIG, II recombinant inbred strains established by brother-sister mating of (BALB/c x DBA/2) F2 mice (C x D2 strains) were used. Among 26 markers tested, the Mls-1 locus on BALB/c chromosome 1 and the Hc locus coding a complement component (C5) on BALB/c chromosome 2 were found to be associated with high susceptibility to AIG. However, if one or both of the loci were of DBA/2 origin, mice showed medium or low susceptibility to AIG. For further analysis, F1, F2 and back-cross generations of these two strains were tested, but segregation of a single susceptibility or insusceptibility gene was not obtained. Taken together, it seems probable that two or more genes are involved in the induction mechanism of AIG. We did not detect C5 deposition in AIG lesions, nor complement-dependent cytotoxic antibody to parietal cells in serum from AIG mice. However, injection of irradiated spleen cells of DBA/2 mice into BALB/c mice thymectomized on day 3 augmented the incidence of AIG from 71 to 100%, but not that of oophoritis (33%). A relationship between Mls-1a determinants and the pathogenesis of AIG was further suggested from the fact that V beta 6 TcR-expressing T cells increased in number in AIG-bearing compared with normal BALB/c mice.

Animals↗
PubMed1991

Identification of methicillin-resistant strains of staphylococci by polymerase chain reaction.

A simple and reliable method using a polymerase chain reaction (PCR) was devised to identify methicillin-resistant staphylococci. By using lysates of the strain to be tested as templates and 22-mer oligonucleotides as primers, a 533-bp region of mecA, the structural gene of a low-affinity penicillin-binding protein (PBP 2'), was amplified by PCR and detected by agarose gel electrophoresis. Results obtained by this method were compared with those obtained by broth microdilution MIC determination for 210 and 100 clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci, respectively. Of 99 mecA-negative S. aureus isolates, 100% of the strains were methicillin susceptible and 98% of the strains were oxacillin susceptible. Three strains (3%) of 111 mecA-positive S. aureus isolates exhibited almost the same susceptibility to beta-lactams as the mecA-negative ones and did not produce detectable amounts of PBP 2' despite the presence of the mecA gene. One of them yielded typically methicillin-resistant variants at a low frequency with concomitant recovery of PBP 2' production. The mecA gene was also found in coagulase-negative Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus sciuri, Staphylococcus saprophyticus, and Staphylococcus caprae and conferred resistance on most of the bacteria.

Bacterial Proteins↗
PubMed1991

Synthesis of fluorine and iodine analogues of clorgyline and selective inhibition of monoamine oxidase A.

A series of fluorine and iodine analogues of clorgyline was synthesized and evaluated for inhibitory potency and selectivity toward monoamine oxidase A (MAO-A). Among them, N-[3-(2,4-dichloro-6-iodophenoxy)propyl]-N-methyl-2-propynylami ne (3d), N-[3-(4-chloro-2-fluorophenoxy)propyl]-N-methyl-2-propynylamine (3f) and N-[3-(2-chloro-4-fluorophenoxy)propyl]-N-methyl-2-propynylamine (3g) were found to have high inhibitory potency and selectivity toward MAO-A comparable to those of clorgyline itself. Thus, they were considered for advanced development as radiofluorinated and radioiodinated ligands that may be useful for functional MAO-A studies in the living brain with positron emission tomography and single photon emission computer tomography.

Animals↗
PubMed1991

Synthesis of [125I]iodoclorgyline, a selective monoamine oxidase A inhibitor, and its biodistribution in mice.

A new radioiodinated monoamine oxidase A (MAO-A) specific inhibitor, [125I]iodoclorgyline, was synthesized from its tin precursor by iododestannylation reaction using sodium [125I]iodide and hydrogen peroxide with high yield and site specificity. The product possessed a high radiochemical purity as well as high specific activity. The method can be readily applicable for labeling with 123I, a very suitable radioisotope for in vivo imaging with single photon emission computer tomography (SPECT). Biodistribution studies of the [125I]iodoclorgyline in mice showed high initial uptake in the brain, and brain radioactivity reached a constant level at 60 min after intravenous injection. The results suggested that [125I]iodoclorgyline might have potential as a radiopharmaceutical for MAO-A studies in the brain with SPECT.

Animals↗
PubMed1991

Histopathology and distribution of cells harboring bovine leukemia virus (BLV) proviral sequences in ovine lymphosarcoma induced by BLV inoculation.

Six sheep with lymphosarcoma induced by hypodermic inoculation of bovine leukemia virus (BLV) materials were examined to elucidate the relation between pathologic lesions and integration of BLV provirus in cellular DNAs. Antibodies to BLV gp-antigens had been detected since the 3rd week after the inoculation, and BLV was positive when checked 3 months later. Lymphosarcomas followed the leukemic phase in 4 sheep. The other 2 sheep showed initial lesions of lymphosarcoma and were aleukemic clinically. Five animals were killed by enthanasia and autopsied at 2.5 to 3.5 years postinoculation (pi) because of their diseased condition. One animal died 10 years pi following the 4th leukemic episode. Sarcomatous lesions were confirmed grossly and histologically, and the proliferating neoplastic cells were classified into lymphocytic, prolymphocytic, lymphoblastic and histiocytic types. Integration of BLV provirus in cellular DNAs of the peripheral blood lymphocytes (PBL) and neoplastic cells of sarcomatous lesions was examined by Southern blotting technique. BLV provirus was demonstrated in the PBL of all infected animals and in most of the sarcomatous lesions of the spleen, kidney and lymph nodes except 4 lymph nodes showing slight neoplastic infiltration. The results indicated that ovine lymphosarcoma could be caused by BLV and the cells carrying proviral information seemed to be disseminated and proliferate in the lesions.

Animals↗
PubMed1991

A case of renin producing leiomyosarcoma originating in the lung.

A 54-year-old woman was referred to our hospital for the treatment of a tumor of the right chest wall. Clinical examination revealed hypertension, hypokalemia, metabolic alkalosis, hyperaldosteronism and hyperreninemia. Computed tomography and an abdominal echogram indicated a tumor in the right phrenic area and two tumors in the retroperitoneum near the pancreas head. After the surgical resection of these tumors, the primary reninism was diminished. The pathological diagnosis of these tumors was leiomyosarcoma. Plasma active and inactive (trypsin-activated) renin activities (PRA) were 85.7 and 38.9 ng angiotensin I/ml/h, respectively. These PRA did not respond to either postural stimulation or suppression by the volume expansion. Active and inactive renin activities in a right phrenic area tumor were 208 and 32 ng angiotensin I/mg protein /h, respectively. Those of an abdominal tumor were 196 and 30 ng angiotensin I/mg protein/h, respectively. Renin mRNA identical in molecular size to that of the human kidney was identified by northern blot analysis. This is the first case report of renin producing leiomyosarcoma derived from the lung, which is characterized by relatively lower plasma prorenin concentrations.

Abdomen↗
PubMed1991

Chronic effects of tolbutamide on myocardial tension during ischemia and reperfusion in perfused hearts isolated from insulin dependent and non insulin dependent diabetic rats.

The chronic effects of tolbutamide on myocardial contractility of the diabetic heart during ischemia and reperfusion were evaluated in perfused, isolated rat hearts. Five experimental groups were used: (1) control rats (C), (2) insulin dependent diabetic rats (IDDM, single intravenous injection of 60 mg/kg streptozotocin (STZ) in male Sprague-Dawley rats), (3) non insulin dependent diabetic rats (NIDDM; single subcutaneous injection of 90 mg/kg STZ in 5 day neonates), (4) tolbutamide-treated IDDM and (5) NIDDM (T-IDDM, T-NIDDM; giving tolbutamide 100 mg/kg/day for 6 weeks via an orogastric tube every day, respectively). At 14 weeks of age, experiments were performed using a Langendorff perfused heart preparation. After equilibration, T (myocardial developed tension), +dT/dt (contraction velocity), -dT/dt (relaxation velocity) and RT (resting tension) were measured during a 15 min period of global ischemia, followed by reperfusion for 20 min. Basal values of T increased in both T-IDDM and T-NIDDM, compared to IDDM and NIDDM, respectively. The percent recovery rate of +dT/dt in T-IDDM increased significantly during both ischemia and reperfusion, but the change in T-NIDDM was not significant. The recovery rates of -dT/dt in T-IDDM and T-NIDDM were significantly higher throughout reperfusion than in IDDM and NIDDM, respectively. On the other hand, that of T in T-IDDM and T-NIDDM were significantly higher than IDDM and NIDDM throughout ischemia and reperfusion, respectively. The RT was significantly higher in IDDM than in C and NIDDM throughout ischemia and reperfusion. The RT was significantly lower during ischemia in IDDM, but it did not differ significantly from IDDM during reperfusion. These results indicate that chronic oral administration of tolbutamide directly improved myocardial contractility throughout ischemia and reperfusion regardless of the improvement of glycemia. The improvement was also greater in IDDM than in NIDDM.

Animals↗
PubMed1991

Histological examination of chick embryos with bilateral microphthalmus with reference to laterality in the visual apparatuses.

The histological abnormalities of chick embryos with bilateral microphthalmus were examined in serial paraffin sections with special reference to laterality in the visual apparatuses, including the cornea, lens, neural retina and pigment epithelium. There was marked laterality in the above structures; some eyeballs had individual, if incomplete, sublayers of the cornea and the neural retina, and others not. The sublayers of the neural retina were occasionally observed even in eyeballs at the stage of optic vesicle formation, in contrast to the previous notion that the pigment epithelium induces the maturation of the primordial neural retina after optic vesicle differentiation into the optic cup. There was also a case where developmental differences between the right and left eyeballs were absent except in the lens. These findings suggest that chick embryos with bilateral microphthalmus exhibit a more complex histological profile or diversity than previously considered, possibly as a result of the differential actions of various mutagens and endogenous trophic factors on the developing visual system.

Animals↗
PubMed1991

Structure and sequence analysis of the human activin beta A subunit gene.

The cloned genomic DNA containing the human activin beta A subunit gene were analyzed by restriction endonuclease mapping, Southern blotting and DNA sequencing. The activin gene is composed of two exons interrupted by the 9-kb intron. The TATA, CCAAT and CT-stretch sequences were found in the 5'-flanking region of the gene. An intronic sequence contained SV40 enhancer core element in the vicinity of the exon 1. In the 3'-flanking region, we identified eight consensus polyadenylation sequences, five ATTTA motifs, CA element consisting of (CA)14, AP-1 binding site and two SV40 enhancer core elements. A dot matrix analysis revealed the high degree of conservation between the human and rat sequences within the 3'-flanking region, suggesting a possible functional significance.

Activins↗
PubMed1991

[An elderly case of idiopathic retroperitoneal fibrosis].

An elderly case of idiopathic retroperitoneal fibrosis (IRPF) with bilateral ureteral obstruction was reported. A 74-year-old man was admitted with complaints of general fatigue and loss of appetite. An elastic hard mass with a smooth surface was palpated in the left upper quadrant of the abdomen. Abnormal ESR and CRP were noticed. Abdominal ultrasonography showed both a homoechoic mass which surrounded the aorta in the retroperitoneal space and bilateral hydronephrosis. Computed tomography revealed a retroperitoneal mass involving bilateral ureters. Magnetic resonance imaging demonstrated a mass with a sharp image and signal intensity. Furthermore the morphological relationship between the mass and the ureters and major vessels clearly indicated the characteristics of benign retroperitoneal fibrosis. Based upon the above findings, a diagnosis of IRPF was made. After confirming the histological diagnosis by biopsy, treatment consisting of bilateral ureterolysis, intra-abdominal transposition of ureters and oral administration of prednisolone was performed, resulting in a normalization of laboratory findings. Analysis of 86 previously cases of IRPF reported up to 1990 in Japan, revealed the peak age to be in the 7th decade with predominance in males (males: females = 57:29).

Acute Kidney Injury↗
PubMed1991

Isolation and characterization of the alkaline protease gene of Aspergillus oryzae.

The genomic DNA for the alkaline protease (Alp) of the fungus Aspergillus oryzae was isolated using synthetic oligonucleotides as hydridization probes, and the complete nucleotide sequence was identified. The Alp gene is 1374 nucleotides long and contains three introns, one of which is in the pro region and two in the mature coding region. Sequences related to the TATA box (TATAAAT) and the CAAT box (CCAAAT) were found in the 5'-noncoding region. Primer extension analysis showed that three transcriptional start points are present.

Amino Acid Sequence↗