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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 361 records · Page 20Linked to original sources
PubMed1997

Angioimmunoblastic lymphadenopathy with disseminated human herpesvirus 6 infection in a patient with acute myeloblastic leukemia.

A 47-year-old man with acute myeloblastic leukemia (AML) developed angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) 4 months after induction chemotherapy for AML. During a leukopenic period, the patient suffered from pericarditis with massive pericardial effusion in which human herpesvirus 6 (HHV-6) DNA was detected. Although complete remission of AML was achieved, fever persisted and atypical skin rash followed by generalized lymphadenopathy along with polyclonal hypergammaglobulinemia appeared. A diagnosis of AILD was made on a biopsy specimen of the inguinal lymph node. The patient died of fulminant hepatitis and the autopsy showed lymphomatous infiltrates involving the liver, bone marrow, lungs, spleen, kidneys and heart. HHV-6 DNA sequences were identified in the biopsy specimen of the lymph node and in the involved organ tissues. HHV-6 in this patient was variant B. It is known that HHV-6 can be reactivated in immunocompromised patients and causes severe complications. This unusual clinical course suggests that the immunosuppression associated with AML and the additional iatrogenic immunosuppression following cytopenia-inducing chemotherapy predisposed the patient to reactivated HHV-6 infection. The sequential detection of this virus before and after manifestation of AILD may support the evidence that HHV-6 infection could directly or indirectly trigger AILD. This is the first time that such a sequence of events has been reported to our knowledge. The possibility of HHV-6 infection should be considered when unexplained fever and generalized lymphadenopathy are seen in patients with leukemia, and administration of antiviral agents should be considered for the diagnostic evaluation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Dopamine-beta-hydroxylase activity is necessary for hypothalamo-pituitary-adrenal (HPA) responses to ether, and stress-induced facilitation of subsequent HPA responses to acute ether emerges as HPA responses are inhibited by increasing corticosterone (B).

To determine a role of norepinephrine (NE) in stress-induced HPA function, young male rats were treated with diethyldithiocarbamide (DDC) which inhibits dopamine-beta-hydroxylase, the enzyme that synthesizes NE from dopamine (DA). DDC injected 5 h prior to ether stress stimulated ACTH and corticosterone (B) during this time, and there was no further HPA response to ether. To control for elevated B feedback in DDC effects on HPA responses to ether, rats were adrenalectomized (Adx) and replaced with no (0% B), moderate (40% B) and high (80% B) levels of steroid 5 d prior to DDC or saline with ether stress 5 h later; Sham-Adx rats were included. In Adx rats increasing B inhibited thymus weight, median eminence CRF content, pituitary and plasma ACTH. In saline-treated rats, ether 5 h later caused increased CRF content and plasma ACTH in Sham-Adx and Adx, 0% B, increased ACTH in Adx, 40% B, and no response in Adx, 80% B. B treatment did not alter catecholamine content, and DDC treatment reduced NE content in the paraventricular nuclei by 50-60% in all groups. 5 h after DDC, pituitary ACTH was decreased in all rats with B and plasma ACTH was increased in sham-Adx and Adx, 40% B; thus DDC caused significant, prolonged stress which should facilitate subsequent HPA responses to acute stress. There was no HPA response to ether in Sham-Adx, Adx, 0% or 40% B groups, but there was a marked ACTH response to ether in the Adx, 80% B group treated with DDC. We conclude that: 1) the HPA response to ether stress is probably mediated by catecholamines; 2) DDC does not stimulate responses in the HPA axis in the absence of B; and, 3) facilitation of HPA responses to acute stress depends on increased steady-state B signals. Facilitated responses are probably not mediated by catecholamines. The consequence of facilitation is that under conditions of chronic stress and elevated B concentrations, as in depression or anorexia nervosa in man, or adjuvent-induced arthritis in rats, the HPA axis is continually responsive to new stimuli.

Adrenalectomy↗
PubMed1997

Proliferative effect of dextran sulfate sodium (DSS)-pulsed macrophages on T cells from mice with DSS-induced colitis and inhibition of effect by IgG.

The authors have previously reported that homologous immunoglobulin (Ig)G reduces the occurrence of dextran sulfate sodium (DSS)-induced colitis, mainly by suppressing recruitment of immunocompetent cells into colitis lesions. However, the mechanisms of cell recruitment and of its suppression by IgG remain unclear. In addressing these questions, this study focused on the activation of T cells in the presence of macrophages. The authors found that [3H]-thymidine uptake of T cells from DSS-induced colitis mice, but not from normal mice, was significantly enhanced when cultured with DSS-pulsed macrophages. From the profile of cytokine production, it was suggested that T helper 1 (Th1)-type cells become predominant during stimulation. Addition of homologous IgG significantly suppressed T cell proliferation in a dose-dependent manner, while no suppressive effect was observed with heterologous IgG. Mouse IgG F(ab')2, but not Fc, fragments partially mimicked the suppressive effect of whole IgG. These findings provide evidence that Th1-type cells may play an important role in the development of DSS-induced colitis and that homologous IgG exerts its protective action at least in part through the F(ab')2 portion.

Animals↗
PubMed1997

Subchorial hematoma: a probable cause of reversible nonimmune hydrops fetalis.

Nonimmune hydrops fetails diagnosed at 21 weeks' gestation with profound ascites, hydrothorax, and pericardial effusion receded gradually with regression of a subchorial placental lucencies immediately below the umbilical cord insertion. Careful inspection of the delivered placenta revealed that there was a yellowish lesion of fibrin deposits below the cord insertion site, which resulted from the absorption of hematoma. A subchorial placental hematoma, which detected as a subchorial placental lucencies by ultrasonography, can be a cause of reversible nonimmune hydrops fetalis.

Adult↗
PubMed1997

Inactivation of aconitase in yeast exposed to oxidative stress.

Inactivation of aconitase by oxidative stress was analyzed under the in vivo and in situ conditions of yeast cells. Treatment of yeast cells with paraquat caused a specific inactivation of aconitase without affecting the activity of other citric acid cycle enzymes. Addition of copper plus ascorbic acid to permeabilized yeast cells also inactivated aconitase, but did not affect other TCA cycle-related enzymes. Inactivation of aconitase was suggested to be due to the superoxide and hydroxyl radicals produced from the reaction of O2 with paraquat and by Fenton reaction with copper and ascorbic acid under the in vivo and in situ conditions of yeast, respectively. Citrate the substrate of aconitase effectively protected aconitase from the oxidative inactivation. Toxicity of oxygen to yeast cells can be explained by the specific inactivation of aconitase by oxygen radicals. Increased concentrations of citrate can act as a defense mechanism against oxidative inactivation of aconitase under the exposure of aerobically grown yeast to oxidative stress.

Aconitate Hydratase↗
PubMed1997

Protection by histidine against oxidative inactivation of AMP deaminase in yeast.

Oxidative inactivation of AMP deaminase and its protection were analyzed under the in situ conditions of yeast cells. AMP deaminase was readily inactivated by an exposure to hydrogen peroxide plus copper in permeabilized yeast cells. Addition of ascorbic acid further enhanced the inactivation of the enzyme, suggesting the hydroxyl radical produced by the Fenton reaction is responsible for the inactivation of the enzyme. Addition of histidine caused an effective protection against the inactivation of AMP deaminase by hydrogen peroxide-induced hydroxyl radical. The concentration of histidine required for half-maximal effect was within physiological range. Cysteine showed less effective protection against oxidative inactivation. Other amino acids as potent copper-chelating agents as well as trolox and taurine showed little or no effect. Histidine can act as a physiological "antioxidant" in yeast cells.

AMP Deaminase↗
PubMed1997

Structural and functional analysis of the promoter region of the human MCP-3 gene: transactivation of expression by novel recognition sequences adjacent to the transcription initiation site.

Human monocyte chemotactic factor-3 (MCP-3) belongs to the C-C chemokines, which are cytokines involved in cell recruitment in inflammation and cancer. Northern blotting and reverse transcriptase polymerase chain reaction (RT-PCR) analyses showed that the MCP-3 gene is expressed in many human tissues and tumor cell lines and that the expression level is increased by various stimuli. Measles virus and phorbol 12-myristate 13-acetate (PMA) induced MCP-3 mRNA after 6 hr of stimulation. Interferon-beta (IFN-beta) induced MCP-3 mRNA after 16 hr, a time point when the PMA-induced mRNA had the tendency to level off. No significant increase in MCP-3 mRNA levels was observed in MG-63 cells after stimulation with interleukin-1beta (IL-1beta). To elucidate the regulation of MCP-3 gene expression, we determined the sequence of 5 kb of the MCP-3 promoter. This sequence contained a microsatellite that was shown to be polymorphic in various cell lines. Next 5'-deletion mutants of the promoter were generated and transfected into MG-63 cells, demonstrating the presence of several positive and negative transcriptional regulatory elements. One of the positive elements was located at -37, only 21 bp upstream from the TATAA box. This element was similar to an AP-1 element and also to a homeodomain protein Pbx1 binding site. A deletion mutant from -110 to +52 possessed the highest promoter activity, and the longer deletion mutants had relatively low activities. The region between -190 and -172 contained an Ets-like element and inhibited promoter activity. Stimulation with PMA dramatically increased promoter activity through activation of a positive element present between -172 and -100. The same 5'-deletion mutants were transfected into HeLa and Jurkat cells. None of the deletion mutants had any significant activity in Jurkat cells. In HeLa cells, low levels of MCP-3 mRNA were detected by RT-PCR, but the profile of the promoter activities of the deletion mutants was different from that seen in MG-63 cells.

Base Sequence↗
PubMed1997

Identification and subcellular localization of a novel mammalian dynamin-related protein homologous to yeast Vps1p and Dnm1p.

The dynamin family of GTP-binding proteins are implicated in vesicular transport. These include mammalian dynamins I, II, III, and yeast Vps1p and Dnm1p. Dynamin is involved in the formation of clathrin-coated vesicles at the plasma membrane. On the other hand, Vps1p and Dnm1p appear to be involved in transport from the late Golgi compartment to vacuoles and in an endocytic process, respectively. In this study, we identified a novel human protein, named Dnm1p/Vps1p-like protein (DVLP). It resembled more closely Dnm1p and Vps1p than dynamins not only in the primary structure but also in the domain organization. DVLP mRNA was expressed ubiquitously, suggesting that this protein plays a fundamental role in cellular function. Immunofluorescence analysis of cells expressing epitope-tagged DVLP revealed that it showed a diffused perinuclear staining pattern that was not superimposed on that of the marker protein for the Golgi apparatus, trans-Golgi network, lysosomes, endosomes, or endoplasmic reticulum. These data suggest that DVLP is not involved in the formation of known coated vesicles.

Amino Acid Sequence↗
PubMed1997

Gabexate mesilate, a synthetic protease inhibitor, prevents compression-induced spinal cord injury by inhibiting activation of leukocytes in rats.

OBJECTIVE: Gabexate mesilate is a synthetic protease inhibitor capable of inhibiting both coagulation and cytokine production by monocytes. To investigate whether gabexate mesilate is useful for the prevention of posttraumatic spinal cord injury, we examined its effect on compression trauma-induced spinal cord injury in rats. DESIGN: Prospective, randomized, blinded, controlled study. SETTING: Research laboratory at a university medical center. SUBJECTS: Male Wistar rats weighing 300 to 350 g. INTERVENTIONS: Spinal cord injury was induced by applying a 20-g weight extradurally to the spinal cord at the level of the 12th thoracic vertebra for 20 mins. Spinal cord injury was evaluated by assessing the motor function of the rats 24 hrs posttrauma. The accumulation of leukocytes and histologic changes in the injured spinal cord tissue also were examined. Rats received gabexate mesilate (10 or 20 mg/kg i.p.) 30 mins before or after the compressive trauma. The effects of heparin or an inactive derivative of activated factor X (a selective inhibitor of thrombin generation) on compressive trauma-induced spinal cord injury also were examined. Leukocytopenia was induced by the administration of nitrogen mustard. MEASUREMENTS AND MAIN RESULTS: The motor disturbances observed following traumatic spinal cord compression, evaluated by Tarlov's score, and the accumulation of leukocytes in the injured tissue, evaluated by measuring tissue myeloperoxidase activity, were markedly reduced by leukocyte depletion induced by nitrogen mustard and by pre- or posttreatment of animals with gabexate mesilate. Neither heparin nor the inactive derivative of activated factor X prevented the motor disturbances and the accumulation of leukocytes. Histologic examination demonstrated that intramedullary hemorrhages observed 24 hrs after trauma at the 12th thoracic vertebra were significantly attenuated by nitrogen mustard-induced leukocytopenia and the administration of gabexate mesilate. CONCLUSIONS: The compression trauma-induced spinal cord injury demonstrated by this model was mainly mediated by leukocytes. Gabexate mesilate prevented spinal cord injury not by inhibiting coagulation, but by inhibiting the activation of leukocytes.

Amino Acid Chloromethyl Ketones↗
PubMed1997

Activation of angiotensin II-forming chymase in the cardiomyopathic hamster heart.

BACKGROUND: Angiotensin (ANG) II plays crucial roles in promoting cardiovascular tissue remodeling. Human chymase catalyzes ANG II formation, whereas rat chymase (rat mast cell protease 1) degrades ANG I to inactive fragments. Such species differences should be considered when the functions of chymase in human cardiovascular diseases are investigated assuming an analogy with animal models. OBJECTIVE: To further characterize the recently identified ANG II-forming hamster chymase, and to analyze pathophysiologic roles played by chymase in the cardiomyopathy of the hamster. METHODS: The gene organization and the primary structure of hamster chymase were determined through molecular cloning. Chymase and angiotensin converting enzyme messenger RNA levels, and chymase-like and angiotensin converting enzyme activities were measured in the heart of BIO 14.6 cardiomyopathic hamsters aged 4, 12, and 25 weeks. RESULTS: The hamster chymase gene is 3 kb long. It has five exons and four introns, and the deduced amino-acid sequence was homologous to other mammalian chymases. The chymase messenger RNA levels and chymase-like activities in the BIO 14.6 hamster hearts were increased significantly at the ages of 12 weeks (the fibrotic stage) and 25 weeks (the hypertrophic stage), but not at age 4 weeks (the premyolytic stage). CONCLUSIONS: These results indicate that heart chymase is activated concurrently with the development of cardiomyopathy. Thus, we conclude that heart chymase could play the primary role in accelerating ANG II formation, thereby causing deleterious changes in the cardiomyopathic heart.

Amino Acid Sequence↗
PubMed1997

Clinical and histological features of cytomegalovirus hepatitis in previously healthy adults.

It is well known that cytomegalovirus infection is often accompanied by hepatitis, but there have been few comparative studies with respect to clinical features of cytomegalovirus-associated hepatitis and other acute viral hepatitides. In the present study, clinical and pathological features of 11 acute sporadic cytomegalovirus hepatitis infections in previously healthy adults were compared with those of 45 acute sporadic viral hepatitis, including type A, type B and type C. As a result, the characteristics of cytomegalovirus hepatitis were a long-lasting fever, splenomegaly, atypical lymphocytosis, a mild transaminasemia, a low ratio of alanine aminotransferase level to lactate dehydrogenase level, and mild hepatic histopathological changes.

Acute Disease↗
PubMed1997

Amino acid residues in the alpha-subunit C-terminal domain of Escherichia coli RNA polymerase involved in activation of transcription from the mtr promoter.

To examine the role of the amino acid residues (between positions 258 and 275 and positions 297 and 298) of the alpha-subunit of RNA polymerase in TyrR-mediated activation of the mtr promoter, we have carried out in vitro transcription experiments using a set of mutant RNA polymerases with a supercoiled mtr template. Decreases in factor-independent transcription in vitro by mutant RNA polymerases L262A, R265A, and K297A suggested the presence of a possible UP element associated with the mtr promoter. Mutational studies have revealed that an AT-rich sequence centered at -41 of the mtr promoter (SeqA) functions like an UP element. In vivo and in vitro analyses using a mutant mtr promoter carrying a disrupted putative UP element showed that this AT-rich sequence is responsible for interactions with the alpha-subunit which influence transcription in the absence of TyrR protein. However, the putative UP element is not needed for activator-dependent activation of the mtr promoter by TyrR and phenylalanine. The results from in vitro studies indicated that the alpha-subunit residues leucine-262, arginine-265, and lysine-297 are critical for interaction with the putative UP element of the mtr promoter and play major roles in TyrR-dependent transcription activation. The residues at positions 258, 260, 261, 268, and 270 also play important roles in TyrR-dependent activation. Other residues, at positions 259, 263, 264, 266, 269, 271, 273, 275, and 298, appear to play less significant roles or no role in activation of mtr transcription.

Amino Acid Transport Systems↗
PubMed1997

Increase of methicillin resistance in Staphylococcus aureus caused by deletion of a gene whose product is homologous to lytic enzymes.

A spontaneous high-level methicillin-resistant mutant, SRM1648, for which the MIC of methicillin is 1,600 microg/ml, was isolated on a plate containing 400 microg of the antibiotic/ml on which had been cultured the low-level methicillin-resistant Staphylococcus aureus SR17238, for which the MIC is 6.3 microg/ml. Analysis of the chromosomal DNAs of the mutant and the parental strains by the restriction landmark genomic scanning method with two-dimensional electrophoresis of restriction fragments revealed a 1.6-kb deletion in the chromosome of the mutant. The HindIII fragment of 2.5 kb containing this deleted region was cloned into a plasmid vector and introduced into the parental strain. A deletion mutant reconstructed in the presence of a low concentration of methicillin by integration and excision of the recombinant plasmid exhibited a high level of resistance (methicillin MIC, 1,600 microg/ml), confirming that the deletion had caused the elevation of the resistance level. Sequence analysis indicated that the deletion occurred in three consecutive open reading frames (ORFs). The predicted amino acid sequence of the first ORF showed high homology with both RelA and SpoT of Escherichia coli, which are involved in the synthesis and hydrolysis of guanosine 5',3'-polyphosphate, and that of the third ORF showed a relatively high homology to the lytic enzyme encoded by the lytC gene of Bacillus subtilis. We also isolated another high-level resistant mutant with a deletion within the third ORF, which suggested that inactivation of some lytic enzyme resulted in the increased resistance.

Amino Acid Sequence↗
PubMed1997

Formation of potent hybrid promoters of the mutant llm gene by IS256 transposition in methicillin-resistant Staphylococcus aureus.

From high-level methicillin-resistant Staphylococcus aureus SRM551, the low-level heterogeneously resistant mutant, SRM563, was isolated by transposon mutagenesis. The transposon insertion occurred in the 3' region of the llm gene in the mutant (H. Maki, T. Yamaguchi, and K. Murakami, J. Bacteriol. 176:4993-5000, 1994). Resistant revertants were generated from the mutant strain SRM563 on the plate containing methicillin at a concentration of 12.5 microg/ml or more. In some revertants, the insertion sequence IS256 was observed to be transposed into one of five sites localized 88 to 212 bp upstream of the mutant llm at a frequency of 2.8 x 10(-7) in the bacterial population. The IS256 transposition created a new hybrid promoter in which the -35 region at the end of IS256 was properly arranged in relation to the -10-like sequence upstream of llm. The new promoters greatly enhanced the transcription of the mutant llm, as judged by blotting analysis of llm mRNA, with concomitant elevation of the methicillin resistance. Involvement of the insertion sequence in the heteroresistance characteristics of methicillin-resistant S. aureus was suggested.

Bacterial Proteins↗
PubMed1997

Nature of DNA binding and RNA polymerase interaction of the Bordetella pertussis BvgA transcriptional activator at the fha promoter.

The expression of virulence factor genes in Bordetella pertussis is mediated by the BvgA-BvgS two-component signal transduction system. The response regulator, BvgA, acts directly as a transcriptional activator at the loci encoding pertussis toxin (ptx) and filamentous hemagglutinin (fha). Previous studies have demonstrated that these two loci are differentially regulated by BvgA. As an initial step in gaining insight into the mechanism underlying this differential regulation, we initiated DNA binding and in vitro transcription analyses to examine the activities of BvgA and RNA polymerase (RNAP) purified from both B. pertussis and Escherichia coli at the fha promoter. We discovered that unphosphorylated BvgA binds to a single region (-100 to -70, relative to the start of transcription), whereas phosphorylated BvgA binds both this region and another, farther downstream, that extends to the -35 nucleotide. In the absence of BvgA, RNAP binds a region farther upstream than expected (-104 to -35). However, occupation of both sites by BvgA phosphate repositions RNAP to the site used in vivo. The binding of BvgA phosphate to the downstream site correlates with in vitro transcriptional activity at the fha promoter. As the DNA binding and transcription activities of the E. coli-derived RNAP are similar to those observed for the B. pertussis enzyme, we employed several mutant E. coli proteins in in vitro transcription analyses. We observed that polymerases carrying either a deletion of the C-terminal domain of the alpha subunit or substitution of alanine at either of two critical residues within this domain were severely impaired in the ability to mediate BvgA-activated transcription at fha.

Adhesins, Bacterial↗
PubMed1997

Activation of the catBCA promoter: probing the interaction of CatR and RNA polymerase through in vitro transcription.

The soil bacterium Pseudomonas putida is capable of degrading many aromatic compounds, including benzoate, through catechol as an intermediate. The catabolism of catechol is mediated by the catBCA operon, whose induction requires the pathway intermediate cis,cis-muconate as an inducer and the regulatory protein, CatR. CatR also regulates the plasmid-borne pheBA operon of P. putida PaW85, which is involved in phenol catabolism. We have used an in vitro transcription system to study the roles of CatR, cis,cis-muconate, Escherichia coli RNA polymerase, and promoter sequences in expression of the cat and phe operons. The assay confirmed the requirement of both CatR and cis,cis-muconate for transcript formation. We also examined the in vitro transcription of three site-directed mutants of the catBCA promoter; the results obtained compared favorably with previous in vivo data. The requirement of the alpha subunit of RNA polymerase for expression of the catBCA and the pheBA transcripts was also examined. The C-terminal region of the alpha subunit of RNA polymerase has been implicated in direct protein-protein contact with transcriptional regulatory proteins and/or direct contact with the DNA. We show that the carboxyl terminus of the alpha subunit is required for the expression of the catBCA and the pheBA operons because RNA polymerases with truncated alpha subunits were deficient in activation. Further experiments demonstrated the arginine at position 265 and the asparagine at position 268 of the alpha subunit as possible amino acids involved in activation. On the basis of these and previous results, we propose a model to explain the interaction of the different regulatory components leading to CatR-dependent activation of the catBCA operon.

Bacterial Proteins↗
PubMed1997

Activated protein C prevents LPS-induced pulmonary vascular injury by inhibiting cytokine production.

We investigated the effect of activated protein C (APC) on pulmonary vascular injury and the increase in tumor necrosis factor (TNF) levels in lipopolysaccharide (LPS)-treated rats to determine whether APC reduces LPS-induced endothelial damage by inhibiting cytokine production. Intravenously administered LPS (5 mg/kg) induced pulmonary vascular injury, as indicated by an increase in the lung wet-to-dry weight ratio. LPS-induced pulmonary vascular injury was prevented by APC but not by active site-blocked factor Xa [dansyl glutamyl-glycyl-arginyl chloromethyl detone-treated activated factor X (DEGR-Xa)], a selective inhibitor of thrombin generation, or inactivated APC [diisopropyl fluorophosphate-treated APC (DIP-APC)]. APC, but not DEGR-Xa or DIP-APC, significantly inhibited the LPS-induced increase in the plasma level of TNF. APC significantly inhibited the production of TNF by LPS-stimulated monocytes in a dose-dependent fashion in vitro, but DIP-APC did not. APC did not inhibit the functions of activated neutrophils in vitro. These findings suggest that APC prevented LPS-induced pulmonary vascular injury by inhibiting TNF production by monocytes and not via its anticoagulant activity. The serine protease activity of APC appears to be essential for inhibition of TNF production.

Amino Acid Chloromethyl Ketones↗