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Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 415 records · Page 23Linked to original sources
PubMed1996

Cisternal talc injection in dog can induce delayed and prolonged arterial constriction resembling cerebral vasospasm morphologically and pharmacologically.

BACKGROUND: The possible role of inflammation in the pathogenesis of cerebral vasospasm has been noted in recent studies. In order to examine the role of inflammation, we examined the vasocontractile activity of talc, which is known to cause severe inflammation, using a canine cisternal talc injection model. METHODS: Under general anesthesia, a sterile talc powder suspended in saline was injected into the cisterna magna of the dog. Serial vertebral angiography and postmortem histologic changes of the harvested basilar artery were examined. The morphologic and pharmacologic features of talc-induced vessel spasm were compared with the usual autologous blood-induced artery spasm. RESULTS: Cisternal injection of sterile talc powder caused no early spasm, but induced definite basilar arterial constriction 2 days after injection. This vascular constriction was observed to continue up to 7 days after injection. Ultrastructural study of the constricted vessel revealed several morphologic changes, such as corrugation of the elastic lamina, subintimal proliferation, migration of smooth muscle cells, detachment of endothelial cells, etc.; findings that are compatible with the changes observed in vasospasm. Pharmacologic study showed a moderate decrease in the maximal contraction to KCl and UTP. Endothelium-dependent relaxation was markedly disturbed, while endothelium-independent relaxation was preserved. These pharmacologic properties were also similar to those reported in vasospasm. CONCLUSIONS: Our present study indicates that the several changes of vascular properties, which had been considered to be specific to cerebral vasospasm, can be regarded as a nonspecific biologic defense reaction against the foreign body. The analysis of the common pathway from talc and autologous blood to vasospasm may lead to the pathogenesis of cerebral vasospasm.

Animals↗
PubMed1996

Successful removal of cryptic arteriovenous malformation located at the upper ventral pons via subtemporal transtentorial approach.

BACKGROUND: Lesions located at the ventral portion of the brain stem are still difficult to access surgically. We report herein a case of ventral pontine cryptic arteriovenous malformation that was successfully removed via a subtemporal-transtentorial approach. CASE REPORT: An 18-year-old female patient experienced repetitive hemorrhagic attacks leading to a massive pontine hemorrhage with several neurologic deficits. Since angiography and magnetic resonance imaging failed to delineate the hemorrhagic origin, a combination of multiple approaches was initially attempted. The subtemporal-transtentorial approach made it possible to obtain an adequate operative view in this case. An angioma observed at the septum of the multilocular hematoma was totally removed. Pathologic examination of the resected specimen revealed it to be an arteriovenous malformation. Postoperatively, the patient showed unexpectedly good recovery despite the original massive pontine hemorrhage. CONCLUSIONS: Several surgical approaches to the ventral pons have been proposed in the literature. While the subtemporal-transtentorial approach was useful in our patient, multiple routes should be considered to access a massive lesion of unknown extent at the ventral pons. The unexpected recovery observed in our patient suggests that surgery is an option in the treatment of this type of lesion.

Adolescent↗
PubMed1996

Insulin regulated PKC isoform mRNA in rat adipocytes.

Insulin and 12-O-tetradecanoyl phorbol-13-acetate (TPA) induce both glucose uptake and translocation of protein kinase C (PKC) from cytosol to membrane in insulin-sensitive tissues as previously reported by several investigators. We examined insulin-mediated PKC beta I, beta II, and epsilon translocation from cytosol to cytoskeleton, and expression of PKC alpha, beta I, beta II, gamma, and epsilon isoforms using the reverse transcription polymerase chain reaction (RT-PCR) method during treatment with insulin for 240 min in rat adipocytes. Insulin-induced increases in PKC beta I, beta II, and epsilon were greater in the cytoskeleton fraction than those in the membrane fraction. Insulin induced time-dependent increases in PKC alpha, gamma, epsilon and zeta mRNA levels for up to 240 min (555%, 117%, 236% and 138% increase, respectively). TPA also induced time-dependent increases in PKC alpha and gamma (34% and 500% increase, respectively) but not in PKC zeta. However, PKC beta I mRNA was decreased for up to 60 min and then maintained at under the basal level during stimulation with insulin and TPA. On the other hand, PKC beta II mRNA was markedly increased for up to 240 min. These results suggest that insulin-regulated PKC alpha, gamma and epsilon mRNA levels and PKC beta mRNA alternative splicing may occur in rat adipocytes.

Adipocytes↗
PubMed1996

Hsp47: a collagen-specific molecular chaperone.

Hsp47 is a novel stress protein in the endoplasmic reticulum that binds specifically to various types of collagens and procollagens. Hsp47 transiently associates with procollagen and is involved in collagen processing and/or secretion under normal conditions. Under conditions of stress, Hsp47 is part of the quality control system for procollagen, including the prevention of the secretion of procollagen with abnormal conformation. In addition to its role as a molecular chaperone, Hsp47 synthesis always parallels that of collagen in developing tissues and various cell lines, and in collagen-related pathological conditions such as fibrosis.

Animals↗
PubMed1996

A novel inotropic vasodilator, OPC-18790, reduces myocardial oxygen consumption and improves mechanical efficiency with congestive heart failure.

We analyzed the left ventricular (LV) pressure-volume relation and obtained direct measurements of myocardial oxygen consumption (MVO2) before and after drug administration in 21 patients with New York Heart Association functional class II to III congestive heart failure to compare the mechanoenergetic effects of OPC-18790, a novel inotropic agent, and dobutamine. Pressure-volume data were obtained by the conductance method, and MVO2 measurements were obtained with a double-thermistor coronary sinus catheter before and after administration of OPC-18790 and dobutamine. The LV end-diastolic volume index decreased significantly without an increase in the heart rate after administration of OPC-18790, unlike that after administration of dobutamine. Both drugs significantly increased the LV contractility index (Emax) and caused similar improvements in ventricular-arterial coupling. OPC-18790 significantly reduced MVo2, whereas dobutamine increased MVo2. The ratio of the pressure-volume area to myocardial oxygen consumption (PVA/MVo2) remained unchanged after administration of OPC-18790 and decreased after administration of dobutamine. The ratio of external work to the pressure-volume area (EW/PVA) was similarly increased by both drugs, resulting in an improvement in mechanical efficiency (EW/MVo2) with OPC-18790 (p < 0.05) and in a deterioration with dobutamine (p < 0.05). OPC-18790 had an energetic advantage over dobutamine in spite of its positive inotropic effect. Our findings suggest that OPC-18790 may be useful for the treatment of patients with congestive heart failure.

Cardiotonic Agents↗
PubMed1996

Identification of host factors that regulate the influenza virus RNA polymerase activity.

Transcription and replication of the influenza virus RNA genome take place in the nuclei of infected cells. Ribonucleoprotein (RNP) complexes consisting of viral RNA, RNA polymerase, and nucleocapsid protein (NP) are proven to be the catalytic unit for RNA synthesis, while it has been indicated that the viral RNA polymerase activity is modulated by host-derived nuclear factors. Here we have identified such host factors present in nuclear extracts prepared from uninfected HeLa cells with biochemical complementation assays using the in vitro RNA synthesis system. The stimulatory activity was not absorbed to phosphocellulose but was tightly bound to Q-Sepharose. The eluate recovered from Q-Sepharose was able to stimulate the RNA synthesis catalyzed by both RNP complexes and purified RNA polymerase and NP. The stimulatory activity was further separated into two distinct fractions, designated RAF-1 (RNA polymerase activating factor-1) and RAF-2 fractions, through phenyl-Sepharose column chromatography. When these fractions were fractionated through a gel filtration column, RAF-1 and RAF-2 activities were recovered in fractions corresponding to the molecular mass of 350 kDa and 60 kDa, respectively. Furthermore, the RAF-2 fraction was shown to contain an inhibitory activity, tentatively designated RIF-1 (RNA polymerase inhibitory factor-1). RIF-1 sedimented as fast as bovine serum albumin in glycerol density gradient centrifugation. Roles of these host factors are discussed in the context of viral RNA transcription and replication.

Biological Factors↗
PubMed1996

Impaired response of left ventricular relaxation to exercise-induced adrenergic stimulation in patients with hypertrophic cardiomyopathy.

OBJECTIVES: We investigated the effect of adrenergic stimulation on left ventricular relaxation in patients with hypertrophic cardiomyopathy. BACKGROUND: Exercise-induced decreases in acceleration of left ventricular relaxation have been observed in patients with hypertrophic cardiomyopathy. However, data on sequential changes in left ventricular relaxation during exercise are limited. METHODS: We measured right (fluid filled) and left (high fidelity micromanometer) ventricular pressures during moderate supine ergometer exercise and during rapid right atrial pacing in four groups of patients: 9 with severe hypertrophic cardiomyopathy, 9 with moderate hypertrophic cardiomyopathy, 10 with hypertension and moderate hypertrophy and 5 control subjects. RESULTS: There was a curvilinear relation between the time constant of relaxation (tau) and heart rate in all groups during exercise. There was no difference in the slope of this relation between the two hypertrophic cardiomyopathy subgroups. Although the slope of this relation between tau and heart rate was steeper in the hypertensive than the moderate hypertrophic cardiomyopathy group (p < 0.001, analysis of covariance), the decrease in tau during right atrial pacing was similar in both groups. There were no significant differences in plasma levels of catecholamines at rest or at peak exercise among groups or in maximal heart rate during pacing. CONCLUSIONS: Pacing-induced changes in tau in hypertrophic cardiomyopathy were similar to those in hypertensive hypertrophy, but remarkable decrease in exercise-induced acceleration of tau were observed only in hypertrophic cardiomyopathy. Our results may indicate a depressed left ventricular relaxation response to exercise-induced adrenergic stimulation in hypertrophic cardiomyopathy.

Adult↗
PubMed1996

Cervical myelopathy in elderly patients: clinical results and MRI findings before and after decompression surgery.

We examined 173 patients with cervical myelopathy of various causes. Seventy-seven patients underwent anterior decompression and fusion at not more than two levels, while 96 underwent posterior decompression by an expansive laminoplasty. Patients were followed up for between one and 4 1/2 years and the outcome was assessed both from a functional and a radiological point of view. The functional assessment used was according to the Japanese Orthopaedic Association (JOA) score (the higher the better), and the imaging outcome was assessed by a midline sagittal MRI assigned to three categories either for restoration of cord morphology, improvement or unchanged. Patients were divided into two groups: those 65 years old and older (50 patients), and those younger than 65 years old (123 patients). The data allowed the following conclusions to be reached: Older patients were likely to have more levels, and higher levels affected, and as a result were more likely to require a posterior operation. The recovery rate after an anterior operation was the same as that after a posterior operation. The pre- and post-operative JOA scores were higher in younger patients who tended to have milder disease with fewer levels affected. Younger patients had better morphological restoration. The recovery was likely to be better if the postoperative morphology was better. The morphology postoperatively was likely to be better if there had been less compression preoperatively. If the morphology was restored the disease duration was likely to have been less. The patients did better if the cord morphology was restored to normal, and this was easier to achieve in younger patients who had fewer levels involved and had less cord distortion preoperatively.

Adult↗
PubMed1996

NAP-I is a functional homologue of TAF-I that is required for replication and transcription of the adenovirus genome in a chromatin-like structure.

BACKGROUND: For the activation of replication and transcription from DNA in a chromatin structure, a variety of factors are thought to be needed that alter the chromatin structure. Template activating factor-I (TAF-I) has been identified as such a host factor required for replication of the adenovirus (Ad) genome complexed with viral basic core proteins (Ad core). TAF-I also stimulates transcription from the Ad core DNA. RESULTS: Using mutant TAF-I proteins, we have demonstrated that the acidic stretch present in the carboxyl terminal region is essential for the stimulation of transcription from the Ad core. A genomic footprinting experiment with restriction endonuclease has revealed that TAF-I causes a structural change in the Ad core. TAF-I has been shown to have significant amino acid similarity to nucleosome assembly protein-I (NAP-I), which is involved in the formation of the chromatin structure. We have shown that TAF-I can be substituted by NAP-I in the activation of the cell-free Ad core transcription system. Two of the tripartite acidic regions and the region homologous to TAF-I in NAP-I are required for the maximal TAF-I activity of NAP-I. Furthermore, TAF-I has been shown to have NAP-I activity, and the acidic region of TAF-I is required for this activity. CONCLUSIONS: Since TAF-I causes the structural change of the Ad core and thereby activates transcription, TAF-I is thought to be one of the proteins which is involved in chromatin remodeling. NAP-I is structurally related to TAF-I and functionally substitutes for TAF-I. Furthermore, TAF-I has NAP-I activity. These observations suggest that this type of molecule has dual functions, possibly by participating in facilitating the assembly of the chromatin structure as well as perturbing the chromatin structure to allow transcription to proceed.

Adenoviridae↗
PubMed1996

Intracellular interaction of collagen-specific stress protein HSP47 with newly synthesized procollagen.

Heat shock protein 47 (HSP47), a collagen-specific stress protein, has been postulated to be a collagen-specific molecular chaperone localized in the ER. We previously demonstrated that HSP47 transiently associated with newly synthesized procollagen in the ER (Nakai, A., M. Satoh, K. Hirayoshi, and K. Nagata. 1992. J. Cell Biol. 117:903-914). In the present work, we examined the location where HSP47 binds to and dissociates from newly synthesized procollagen within the cells, and whether HSP47 associates with nascent single procollagen polypeptide chains and/or with mature triple-helix procollagen. This was accomplished by biochemical coprecipitation with anti-HSP47 and anticollagen antibodies, combined with pulse-label and chase experiments in the presence or absence of various inhibitors for protein secretion, as well as by confocal laser microscopic observation of the cells double stained with both antibodies. We further examined whether the RDEL (Arg-Asp-Glu-Leu) sequence at the COOH terminus of HSP47 can act as an ER-retention signal, as the KDEL sequence does. When the secretion of procollagen was inhibited by the presence of alpha, alpha'-dipyridyl, an iron chelator that inhibits procollagen triple-helix formation, or by the presence of brefeldin A. which inhibits protein transport between the ER and the Golgi apparatus, procollagen was found to be bound to HSP47 during the chase period in the intermediate compartment. In contrast, the dissociation of procollagen chains from HSP47 was not inhibited when procollagen secretion was inhibited by monensin or bafilomycin A1, both of which are known to be inhibitors of post-cis-Golgi transport. These findings suggest that HSP47 and procollagen dissociated between the post-ER and the cis-Golgi compartments. HSP47 was shown to bind to nascent, single-polypeptide chains of newly synthesized procollagen, as well as to the mature triple-helix form of procollagen. HSP47 with the RDEL sequence deleted was secreted out of the cells, which suggests that the RDEL sequence actually acts as an ER-retention signal, as the KDEL sequence does. This secreted HSP47 did not acquire endoglycosidase H resistance. The biological significance of the interaction between HSP47 and procollagen in the central secretory pathway, as well as possible mechanisms for this pathway, will be discussed.

2,2'-Dipyridyl↗
PubMed1996

Purification and characterization of a novel serine proteinase from the microsomal fraction of bovine pancreas.

A novel trypsin-like serine proteinase was purified to homogeneity from the bovine pancreas microsome fraction. The enzyme was solubilized with 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS), and purified by a series of column chromatographic steps on Ultrogel AcA-34, trypsin inhibitor-Sepharose 4B, and arginine-Sepharose 4B. The molecular mass of this pancreas trypsin-like proteinase (bPTLP) was estimated to be 29.5 kDa by SDS-PAGE under reducing conditions. The NH2-terminal sequence of bPTLP is very homologous, but not identical to those of other serine proteinases, especially such as elastases IV, II, and III. Substrate specificity studies involving a synthetic substrate and glucagon indicated that the enzyme hydrolyzes Arg-X, Lys-X, and Leu-X bonds. The best synthetic substrate for bPTLP was t-butyloxycarbonyl Gln-Arg-Arg-4-methylcoumaryl 7-amide. The enzyme failed to hydrolyze the substrate for chymotrypsin and elastase. The enzyme activity was inhibited by diisopropyl fluorophosphate, p-amidinophenylmethane sulfonylfluoride, and leupeptin, indicating that it is a serine-proteinase. These findings show that bPTLP is a novel serine-proteinase which differs from all known proteinases. The physiological function of the enzyme has yet to be determined.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of a new rat P450 (CYP3A18) cDNA encoding P450(6)beta-2 catalyzing testosterone 6 beta- and 16 alpha-hydroxylations.

A cytochrome P450 cDNA, encoding a new form of CYP3A protein, was isolated from a liver cDNA library of a male rat using anti-P450(6)beta-1 and anti-P450(6)beta-2 antibodies and the CYP3A2 cDNA. The cDNA (CYP3A18 cDNA) consisted of 1987 nucleotides, in which were contained an open reading frame of 1491 bp (corresponding to 497 amino acids), 5'-(59 bp) and 3'-noncoding regions (437 bp). The deduced amino acid sequence of CYP3A18 cDNA was completely identical in the first 27 N-terminal residues of P450(6)beta-2 previously isolated by us (Nagata et al. J Biochem 1990: 107, 718-725) from livers of rats treated with dexamethasone, and also shared higher extents of similarity with hamster CYP3A10 (78.5%) than with rat CYP3As previously sequenced (66.3-69.3%). Northern blot analyses indicated a male-dominant expression of this new CYP3A mRNA and enhanced expression in dexamethasone-or pregnenolone-16 alpha-carbonitrile (PCN)-treated, but not phenobarbital-or 3-methylcholanthrene-treated rats. Expressed CYP3A18 protein in COS-1 cells migrated at a position identical to that of purified P450(6)beta-2 on sodium dodecyl sulfate-acrylamide gel electrophoresis and catalyzed 16 beta- and 6 alpha-hydroxylations of testosterone. In contrast to CYP3A1 and CYP3A2, cytochrome b5 was not essential for maximal catalytic activities of recombinant CYP3A18 protein. These results, together with ontogenic profiles of CYP3A18 mRNA and P450(6)beta-2 protein, indicate that the newly isolated CYP3A18 cDNA encodes P450(6)beta-2 in rat liver.

Amino Acid Sequence↗
PubMed1996

A cb-type cytochrome-c oxidase terminates the respiratory chain in Helicobacter pylori.

A Helicobacter pylori membrane fraction oxidized yeast and equine cytochrome c, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). When ascorbate was used as reductant, the Vmax and apparent Km values were 612 nmol electron min-1 (mg protein)-1 and 14 microM for yeast, and 419 nmol electron min-1 (mg protein)-1 and 19 microM for equine cytochrome c, respectively. For TMPD oxidation, the Vmax and Km values were 640 nmol electron min-1 (mg protein)-1 and 182 microM, respectively. These oxidase activities showed a high affinity for oxygen. Inhibition of both cytochrome-c and TMPD oxidase activities by 50% was caused by about 4 microM cyanide and about 0.5 mM azide. Redox difference spectra of the membrane solubilized with Triton X-100 showed b- or c-type cytochromes but not aa3-type cytochromes. c-type and a part of some b-type cytochromes were reduced with ascorbate plus TMPD. A CO difference spectrum revealed that protohaem, but not an aa3-type cytochrome, may be interacting with CO/oxygen. Only protohaem was detected in the haem fraction extracted from the membrane. Three polypeptides (60, 38 and 29 kDa) were found to be bearing haem c after SDS-PAGE of the membrane. From these results, it was suggested that the cbb3-type cytochrome-c oxidase, having a haem-copper binuclear centre like the cytochrome aa3-type oxidase, but differing in a few other properties, functions as a terminal oxidase in the respiratory chain of H. pylori.

Animals↗
PubMed1996

Interleukin-1 receptor antagonist and interleukin-4 in gingival crevicular fluid of patients with inflammatory periodontal disease.

Interleukin-1 receptor antagonist (IL-1ra) and interleukin-4 (IL-4) were detected in gingival crevicular fluid (GCF) by an immunochemical method. However, we could not detect IL-4 in GCF from severe inflammation sites. In addition, we sought to detect which cells had produced cytokines in moderately inflamed gingival tissues by means of immunohistochemistry. The cell types expressing CD 68 were identified as monocytes/macrophages and stained positively for IL-1ra. The helper T cells identified by immunostaining for CD 4 stained positively for IL-4. These results suggest that IL-4 is one of the mediators regulating the degree of local inflammation in periodontal disease.

Adult↗
PubMed1996

Mechanism for inhibition of influenza virus RNA polymerase activity by matrix protein.

Influenza virus M1 protein has been shown to inhibit the transcription catalyzed by viral ribonucleoprotein complexes isolated from virions. Here, this inhibition mechanism was studied with the recombinant M1 protein purified from Escherichia coli expressing it from cDNA. RNA mobility shift assays indicated that both soluble and aggregate forms of the recombinant M1, which were separated by the glycerol density gradient, were bound to RNA. Once an M1-RNA complex was formed, free M1 was bound to the M1-RNA complex cooperatively rather than to free RNA. In addition, the recombinant M1 was capable of binding to preformed RNA-nucleocapsid protein complexes. The mechanism for inhibition of the viral RNA polymerase activity was analyzed by the in vitro RNA synthesis systems that depend on an exogenously added RNA template. These systems were more sensitive for evaluating the inhibition by M1 than the RNA synthesis system depending on an endogenous RNA template. The RNA synthesis inhibition was examined at four steps: cleavage of capped RNA; incorporation of the first nucleotide, GMP; limited elongation; and synthesis of full-size product. M1 inhibited RNA synthesis mainly at the early steps. The experiments with M1 mutant proteins containing amino acid deletions suggested that the M1 region between amino acid residues 91 and 111 was essential for anti-RNA synthesis activity, RNA binding, and oligomerization of M1 on RNA.

Base Sequence↗
PubMed1996

A family of multiple endocrine neoplasia type 2A: genetic analysis and clinical features.

Since a heterozygous missense mutation of the RET proto-oncogene in the germline was found to cause multiple endocrine neoplasia type 2A (MEN 2A) in 1993, some 20 different mutations of this gene have been identified in MEN 2A kindreds. We report an MEN 2A family in which serine (AGC) substitutes for cysteine (TGC) at codon 618 in exon 10 of the RET proto-oncogene. The mutation was identified by sequencing PCR products of exons 10 and 11 in the proband. Since this mutation results in creation of a new cleavage site for Alu I restriction enzyme, most of the other members of the family were screened by digestion of the PCR product of exon 10 with this enzyme. Eleven of 20 subjects across four generations examined have the mutation of the RET proto-oncogene, and all of the adult gene carriers except one woman had MTC. Characteristics of this family are 1) pheochromocytoma has been found in only the proband, 2) no obvious hyperparathyroidism has been observed, and 3) the prognosis is favorable, with nobody dying of MEN 2A itself. Genetic analysis of MEN 2A is definitely useful and essential for screening of a MEN 2A family. It is very important to accumulate cases with MEN 2A and investigate the phenotype and the prognosis in each mutation.

Adult↗