PubMed Health⌕ Search

Biomedical subjects

K Komatsu

Publications and source records attributed to K Komatsu.

At least 19 recordsLinked to original sources
PubMed1992

Cloning and disruption of the cefG gene encoding acetyl coenzyme A: deacetylcephalosporin C o-acetyltransferase from Acremonium chrysogenum.

Acetyl CoA: deacetylcephalosporin C o-acetyltransferase(DCPC-ATF) catalyses the final step in the biosynthesis of cephalosporin C (CPC) in Acremonium chrysogenum. The gene encoding DCPC-ATF, cefG, has been isolated from an A. chrysogenum genomic library using a DCPC-ATF cDNA probe. Nucleotide sequence analysis revealed that cefG contains two short introns of 79bp and 65bp. The gene was found to be closely linked to the cefEF gene encoding deacetoxycephalosporin C synthetase/deacetylcephalosporin C synthetase, which catalyses the preceding two steps in the pathway. The two genes are separated by a 1114 bp segment from which they are divergently transcribed. Introduction of the cloned cefG gene to A.chrysogenum resulted in an increased level of DCPC-ATF activity. A plasmid carrying a cefG gene interrupted in the coding region by a selectable marker for resistance to hygromycin B was constructed and used to disrupt the cefG locus in A.chrysogenum. The cefG-disrupted strains were found to lack the ability to produce CPC, and accumulated its precursor, deacetylcephalosporin C in the culture broth. Southern hybridization analysis confirmed that the disruption resulted from a gene replacement event at the cefG locus.

Acetyltransferases↗
PubMed1992

Molecular cloning of acetyl coenzyme A: deacetylcephalosporin C o-acetyltransferase cDNA from Acremonium chrysogenum: sequence and expression of catalytic activity in yeast.

Acetyl CoA: deacetylcephalosporin C o-acetyltransferase(DCPC-ATF) catalyses the final step in the biosynthesis of cephalosporin C, the conversion of deacetylcephalosporin C to cephalosporin C. A cDNA encoding DCPC-ATF has been isolated from a cDNA library of a cephalosporin C producing fungus Acremonium chrysogenum using oligonucleotide probes based on N-terminal amino acid sequences of the enzyme. The cDNA contains a single large open reading frame for a putative precursor consisting of 12 amino acid(AA) leader peptide of unknown function, 274 AA large subunit and 126 AA small subunit at the carboxyl end. The cDNA was expressed in yeast exhibiting a functional DCPC-ATF activity. It was also indicated that the leader peptide was not essential for expression of the enzyme activity. The primary structure of DCPC-ATF shows significant homology with those of acetyl CoA: homoserine o-acetyltransferase in Saccharomyces cerevisiae and Ascobolas immersus.

Acetyltransferases↗
PubMed1992

The influence of pelvic nerve transection on the neuromuscular system of the canine urinary bladder.

We previously reported that bladder overdistension led to denervation and subsequent supersensitivity of the detrusor muscle to acetylcholine. Therefore, to exclude the influence of bladder overdistension, we produced a low-pressure bladder in female mongrel dogs using an indwelling urethral catheter, and performed pelvic neurectomy (decentralization). We examined the effects of decentralization on the neuromuscular system of the bladder. The contraction response levels of bladder strips in dogs 1 and 2 weeks after neurectomy was low, and significantly different from that of bladder strips in the control group. The dose-response curves of dogs 4 and 8 weeks after neurectomy showed a shift to the left when compared to those of the control group, indicating a significant increase in sensitivity of the bladder strips. Many cholinergic terminal and varicosity profiles had a normal ultrastructure in all of the groups subjected to neurectomy, while some had degenerating profiles representing clear axoplasm without any recognizable organelles. Microphotographs of bladder obtained from dogs with spontaneous catheter loss showed degenerating axons, which were observed more frequently than in bladders kept empty with indwelling urethral catheters. Micturition in the dogs with spontaneous catheter loss was achieved by overflow incontinence without catheterization. These findings suggest that post-synaptic nerve degeneration may be augmented by impairment of micturition, followed by decentralization. Our observations also suggest that post-synaptic nerve degeneration (denervation) plays an important role in the increased sensitivity of the detrusor muscle to acetylcholine in the parasympathetically decentralized urinary bladder, whether denervation is due to trans-synaptic degeneration or impairment of micturition.

Acetylcholine↗
PubMed1992

A case of tubulo-interstitial nephritis with exfoliative dermatitis and hepatitis due to phenobarbital hypersensitivity.

Severe exfoliative dermatitis and liver dysfunction developed in a 5-year-old girl 3 weeks after initiation of phenobarbital therapy. Liver function improved gradually after discontinuation of phenobarbital. During the convalescent stage an initially mild renal dysfunction was exacerbated by episodes of post-transfusion haemolysis. Liver biopsy revealed moderate parenchymal damage with subacute cellular infiltration. Renal biopsy demonstrated the cardinal findings of interstitial nephritis, excluding the possibility of acute tubular necrosis caused by haemolysis. Serial lymphocyte transformation studies and skin patch tests gave positive results for phenobarbital, supporting the view that these were unusual complications of phenobarbital hypersensitivity.

Chemical and Drug Induced Liver Injury↗
PubMed1992

Suppression of X-ray-induced chromosome aberrations in ataxia telangiectasia cells by introduction of a normal human chromosome 11.

We studied X-ray-induced chromosome aberrations in ataxia telangiectasia (AT) cells containing an introduced chromosome 11 or 12 derived from normal human fibroblasts. We used microcell-mediated chromosome transfer to introduce the normal chromosomes into AT cells belonging to complementation group D. Cells were irradiated with 1 Gy of X-rays in the G2 phase. All 5 hybrid clones with an introduced chromosome 11 showed a reduction in the frequency of chromatid-type aberrations to normal levels, whereas all 4 hybrid clones with an introduced chromosome 12 failed to show this reduction. This finding, taken together with our previous report that chromosome 11 can restore radioresistant cell killing in AT cells, indicates that a defective gene on chromosome 11 in AT cells is responsible for the hypersensitivity to not only cell killing but also chromosome aberrations. Our results suggest that a putative AT gene on chromosome 11 plays an important role in the repair process of radiation-induced DNA damage that leads to chromosome aberrations.

Animals↗
PubMed1992

Increased level of atrial natriuretic peptide messenger RNA in the hypothalamus and brainstem of spontaneously hypertensive rats.

OBJECTIVE: The aim of this study was to investigate atrial natriuretic peptide (ANP) gene expression in the central nervous system (CNS) during hypertension. METHODS: We measured and compared immunoreactive atrial natriuretic peptide (irANP) and ANP messenger RNA (mRNA) in the hypothalamus and brainstem of 17-week-old spontaneously hypertensive rats (SHR) with those of age-matched Wistar-Kyoto (WKY) rats using ribonuclease (RNase) protection assay for ANP mRNA and a specific radioimmunoassay for irANP. RESULTS: RNase protection assay revealed that the concentrations of ANP mRNA in the hypothalamus and brainstem of SHR were higher than those of WKY rats. IrANP concentrations in the hypothalamus and brainstem of SHR were determined by a specific radioimmunoassay and found to be higher than those of WKY rats. Elevated mRNA levels in the hypothalamus and brainstem of SHR indicated that increased level of irANP in the CNS resulted from increased synthesis of ANP. CONCLUSION: We propose that increased synthesis of brain ANP in SHR may reflect a compensatory mechanism induced by hypertension.

Animals↗
PubMed1992

Identification and characterization of virK, a virulence-associated large plasmid gene essential for intercellular spreading of Shigella flexneri.

Seven virulence loci have been identified by Tn5 insertion mutagenesis on the large 230 kb plasmid (pMYSH6000) of Shigella flexneri 2a. In this study, we used Tn10 insertion mutagenesis and identified a novel virulence locus on pMYSH6000 responsible for bacterial spread. Characterization of the invading bacteria of the Tn10 insertion mutants in the epithelial cells revealed that the bacteria were capable of at least some intracellular spreading but not intercellular spreading. Immunoblot analysis of lysates of the Tn10 insertion mutants with a VirG-specific antipeptide antibody revealed diminished levels of the 116 kDa VirG protein. The virG mRNA in the mutants, however, was expressed at the same level as that in the wild type. The DNA region required for the virulence phenotype was localized to a 1.6 kb DNA sequence in the SalI-K fragment on the plasmid, and thus the locus was designated virK. Expression of virK in Escherichia coli using a T7 RNA polymerase-dependent promoter system yielded a 36 kDa protein. The nucleotide sequence of 1642 bp encoding VirK function was determined, and an open reading frame encoding 316 amino acid residues was shown to encode the VirK protein. The virK region was highly conserved among the large virulence plasmids of shigellae and enteroinvasive Escherichia coli. These results suggest that VirK function is an essential virulence determinant for shigellae involved in the expression of virG gene product at post-transcriptional level.

Amino Acid Sequence↗
PubMed1992

The role of cholinergic neurons in stress-induced increase of interictal discharges in hippocampal-kindled rats.

This study aims to clarify the role of cholinergic neurons in the occurrence of epileptic seizures when emotional stress is loaded. The effects of stress and drugs on hippocampal interictal discharges were compared among groups of fully kindled male Wistar rats intraperitoneally given atropine, physostigmine and saline with and without immobilization, or pituitary-adrenocortical hormones without immobilization. Hippocampal interictal discharges increased during immobilization, because hippocampal cholinergic neurons were activated by emotional stress. Pituitary-adrenocortical hormones had no effects on the discharges.

Adrenocorticotropic Hormone↗
PubMed1992

Purification of acetyl coenzyme A: deacetylacephalosporin C O-acetyltransferase from Acremonium chrysogenum.

Acetyl CoA: deacetylcephalosporin C O-acetyltransferase, which catalyzes the final step of the biosynthetic pathway to cephalosporin C, was stabilized by a buffer solution containing 7-aminocephalosporanic acid and purified over 1300-fold from Acremonium chrysogenum. The purified enzyme has a molecular weight of 55,000 as measured by gel filtration. SDS-polyacrylamide gel electrophoresis showed two subunit bands corresponding to molecular weights of 27,000 and 14,000. The enzyme has an isoelectoric point at pH 4.0 and optimum activity at pH 7.5.

Acetyltransferases↗
PubMed1992

An adult case of severe chronic active Epstein-Barr virus infection syndrome.

A 23-year-old man with persisting high fever developed hepatosplenomegaly, lymphadenopathy and massive pericardial effusion. Immunological examination revealed a marked elevation of anti-Epstein-Barr virus antibodies (anti-viral capsid antigens IgG-antibody 1:10,240, anti-early antigens-DR IgG-antibody 1:5,120), decreased activities of Epstein-Barr virus specific cytotoxic T lymphocytes, natural killer cells and lymphokine activated killer cells. A liver biopsy showed moderate sinusoidal lymphocytosis with punched-out lesions. These findings suggested severe chronic active Epstein-Barr virus infection syndrome. The patient was treated with recombinant human interleukin-2, but it was discontinued because of an adverse reaction. Twelve months later, he died of suspected pulmonary infection.

Adult↗
PubMed1992

Intraocular penetration and effect on the retina of fluconazole.

The intraocular concentration of fluconazole was measured in nonvitrectomized and vitrectomized eyes after an intravenous administration of 5 or 25 mg/kg fluconazole in albino rabbits. Respective fluconazole concentrations in the aqueous, vitreous and serum 1 hour after administration were 2.87, 1.72 and 4.60 micrograms/ml at 5 mg/kg administration, and 14.93, 7.05 and 20.63 micrograms/ml at 25 mg/kg administration, indicating high and dose-dependent intraocular penetration of fluconazole. Intraocular penetration of intravenously administered fluconazole was moderately, not very much, enhanced by vitrectomy. The in-vitro electroretinogram (ERG) remained unchanged after perfusion with 20 micrograms/ml of fluconazole. The in-vivo ERG and the visual evoked potential was unchanged after the daily administration of 25 mg/kg fluconazole for 8 days. The toxicity of fluconazole on the retina would be low and within safety limits so far as it is used at clinical dosage. Fluconazole may have a place in the treatment of fungal ocular infections.

Animals↗
PubMed1992

Lung transplantation at the University of Pittsburgh.

Lung transplantation appears to be a therapeutic alternative for selected patients with end-stage pulmonary vascular and/or parenchymal disease. The greatest impediment to transplantation remains the availability of donor organs. This has become more significant as additional transplant centers become operational. The primary cause of death has been infection, and this most frequently occurs in the early post-transplant period. Significant progress has been made in curbing the morbidity and mortality from bacterial pneumonia and CMV infection, and this is the primary reason for improved survival rates. If the recipient survives the initial hospital stay, the likelihood of survival at 5 years is approximately 80%. The primary long-term complication is obliterative bronchiolitis which is poorly understood and difficult to treat. Nevertheless, the improvement in survival provides impetus to refine and improve the procedure so that survival can reach that attained by recipients of other major organ allografts.

Academic Medical Centers↗
PubMed1992

[Effects of blood-diltiazem-nitroglycerin-cardioplegia in coronary artery bypass grafting].

Forty-seven patients who underwent coronary artery bypass grafting using blood cardioplegia (BCP) were studied clinically. They were divided into 3 groups based on concentration of diltiazem (DTZ) and nitroglycerin (NTG). Group I (n = 12); DTZ 5 mg plus NTG 5 mg in BCP 1,000 ml, Group II (n = 10); NTG 25 mg in BCP 1,000 ml, Group III (n = 25); DTZ 5 mg plus NTG 25 mg in BCP 1,000 ml. From the standpoint of serum enzyme analysis, there was no significant difference between 3 groups, however, the incidence of perioperative myocardial infarction (PMI) and perioperative coronary spasm (PCS) were significantly higher in Group I than that in other groups. The present data suggests that intramyocardial concentration of NTG in Group II and III were 5 times higher than Group I. Increased dose of NTG in BCP would be benefit for myocardial protection in CABG.

Adult↗
PubMed1991

Chemical stimulation of the locus coeruleus: inhibitory effects on hemodynamics and renal sympathetic nerve activity.

We examined the role of the locus coeruleus (LC) in the regulation of the hemodynamics and sympathetic nerve activity in anesthetized rats. Unilateral microinjection into the LC of the excitatory amino acid, L-glutamate (Glu), elicited dose-dependent decreases in arterial pressure (AP) and heart rate (HR). The bradycardic response was partially attenuated after intravenous injection of atropine sulfate, but the greater part of this response still remained. Interruption of the ascending projections of the LC by midbrain transection did not affect the depressor and bradycardic responses elicited by chemical stimulation. The renal sympathetic nerve activity showed transient but strong inhibition with this stimulation. Cardiac output was measured using an electromagnetic flowmeter implanted in the ascending aorta. The stroke volume and total peripheral resistance (TPR) were calculated. Microinjection of Glu elicited a significant decrease in TPR and slight decreases in cardiac output and stroke volume. Microinjection of the inhibitory amino acid, gamma-aminobutyric acid (GABA), or the alpha 2-adrenergic agonist, clonidine, exerted no effect on AP and HR. The present results therefore suggest that: (1) the LC neurons have an inhibitory influence on the sympathetic nervous system, and stimulation of these neurons can elicit depressor and bradycardic responses; (2) the depressor response was produced predominantly as a result of a decrease in vascular resistance, rather than a decrease in cardiac output; (3) these inhibitory responses may be provided not via the ascending projections of the LC; and (4) the LC neurons do not have a tonic influence on the cardiovascular system.

Animals↗
PubMed1991

Staurosporine, a protein kinase inhibitor, attenuates intracellular Ca(2+)-dependent contractions of strips of rabbit aorta.

The protein kinase inhibitor staurosporine was found to be a potent relaxant of rabbit aortic strips contracted by various agonists. This relaxing effect was slow, long-lasting and in a non-competitive fashion against various agonists. The effect of staurosporine on the KCl-induced contraction was not altered by atropine, propranolol, theophylline or indomethacin. Staurosporine (5-200 nM) inhibited the contractile responses to prostaglandin F2 alpha (3 microM), endothelin (0.1 microM), phenylephrine (3 microM) and KCl (30 mM), with ED50 values of 10.8 +/- 0.6, 24.6 +/- 8.7, 48.8 +/- 7.0, 54.0 +/- 12.7 nM, respectively. Even in Ca(2+)-free physiological salt solution, staurosporine potently antagonized the contractile responses elicited by 10 microM prostaglandin F2 alpha and 0.1 microM endothelin; in fact it was more effective than it was in normal Ca2+ solution: ED50 of 11.3 +/- 3.8 vs. 21.0 +/- 4.4 nM (P less than 0.02), and of 10.6 +/- 3.6 vs. 24.6 +/- 4.3 nM (P less than 0.01), respectively. Thus, staurosporine has an equipotent inhibitory action on intracellular and extracellular calcium-dependent contractions of aortic tissues.

Alkaloids↗
PubMed1991

Prolonged effects of hypofunction on the mechanical strength of the periodontal ligament in rat mandibular molars.

The ultimate loads required to extract three mandibular molars in the dissected jaw were examined after elimination of the antagonistic teeth for up to 64 days. The ultimate loads in the experimental first and second molars decreased rapidly in the first few days, while those in the third molar remained low during the same period in both experimental and control groups. The ultimate loads in all three molars of the experimental animals then increased gradually towards the end of the experiment at rates similar to those in controls. Maximum relative reductions of the ultimate load were observed within the first 8 days in all three molars. An increase in the length of roots was also found in all hypofunctional molars. Daily rates of root elongation ranged from 13 to 19 microns/day in the control and from 18 to 26 microns/day in the experimental molars during the whole experiment. The greatest value (80 microns/day) was obtained during the first 8 days in the third molars of both control and experimental animals. Thus the mechanical strength of the periodontal ligament estimated in vitro may be increased by the development of teeth and by non-functional occlusal contacts with the opposing gingiva-covered alveolar ridge deprived of its tooth crowns. The ligament of the third molar was apparently immature at the beginning of the experiment.

Animals↗
PubMed1991

Synthesis and mechanism of hydrolysis of estrogen 6-sulfates: model compounds for demonstrating the carcinogenesis of estrogen.

To investigate the carcinogenesis of estrogen with respect to the chemical behavior of estrogen 6-sulfates, two epimeric 6-sulfates, pyridinium 3-methoxyestra-1,3,5(10)-trien-6 alpha-yl (8) and -6 beta-yl (11) sulfates, were synthesized as the model compounds, and their chemical reactivities were examined. These sulfates were shown to be highly reactive: in water, they were readily and quantitatively converted to a common product mixture, composed of 3-methoxyestra-1,3,5(10)-trien-6 alpha-ol (6) and -6 beta-ol (9) in an almost constant product ratio, with a predominant yield of the latter. The hydrolysis of both sulfates 8 and 11 proceeded in first-order kinetics with half-lives of 1.1 and 1.5 minutes, respectively. When the sulfates were hydrolyzed in 18O-water, the heavy-oxygen atom was shown to be incorporated quantitatively into the C-6 position of the products. These results demonstrate that estrogen 6-sulfates generate a highly reactive benzylic (C-6) carbocation in an aqueous solution, suggesting that the sulfates can act as carcinogens.

Chemical Phenomena↗