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Biomedical subjects

N Hashimoto

Publications and source records attributed to N Hashimoto.

At least 19 recordsLinked to original sources
PubMed1992

Differential regulation of mRNAs encoding three protein-tyrosine phosphatases by insulin and activation of protein kinase C.

Protein-tyrosine phosphatases (PTPases) play an essential role in the control of signalling through phosphotyrosine pathways. Since little is known about the regulation of these enzymes, we examined the effect of insulin and phorbol 12-myristate 13-acetate (PMA) treatment of well-differentiated rat hepatoma (Fao) cells on the expression of mRNAs encoding three major PTPase homologs in liver: PTPase1B, an intracellular enzyme with a single conserved PTPase domain, and two tandem-domain, transmembrane PTPases, known as LAR and LRP. Treatment of serum-deprived cells with 100 nM insulin increased the abundance of the 4.3 kb and 1.6 kb mRNAs encoding PTPase1B on Northern analysis by 1.6 and 3.1-fold, respectively (p < or = 0.02). Similarly, exposure to 100 ng/ml PMA increased the 4.3 and 1.6 kb PTPase1B mRNAs by 4.5 and 5.7-fold, respectively (p < or = 0.035). In contrast, treatment with insulin or PMA had no significant effect of the abundance of mRNA encoding either LAR or LRP. PMA appeared to have a transcriptional effect on the PTPase1B gene by a protein kinase C-mediated mechanism. The increase in PTPase1B mRNA expression by insulin and PMA suggests that this PTPase may provide feed-back regulation of signalling through the insulin action pathway as well as a potential link between the action of protein kinase C and the regulation of specific phosphotyrosine residues in cells.

Animals↗
PubMed1992

Insulin receptor protein-tyrosine phosphatases. Leukocyte common antigen-related phosphatase rapidly deactivates the insulin receptor kinase by preferential dephosphorylation of the receptor regulatory domain.

A number of protein-tyrosine phosphatase(s) (PTPases) have been shown to dephosphorylate the insulin receptor in vitro; however, it is not known whether any individual PTPase has specificity for certain phosphotyrosine residues of the receptor that regulate its intrinsic tyrosine kinase activity. We evaluated the deactivation of the insulin receptor kinase by three candidate enzymes that are expressed in insulin-sensitive rat tissues, including the receptor-like PTPases LAR and LRP, and the intracellular enzyme, PTPase1B. Purified insulin receptors were activated by insulin and receptor dephosphorylation, and kinase activity was quantitated after incubation with recombinant PTPases from an Escherichia coli expression system. When related to the level of overall receptor dephosphorylation, LAR deactivated the receptor kinase 3.1 and 2.1 times more rapidly than either PTPase1B or LRP, respectively (p less than 0.03). To assess whether these effects were associated with preferential dephosphorylation of the regulatory (Tyr-1150) domain of the receptor beta-subunit, we performed tryptic mapping of the insulin receptor beta-subunit after dephosphorylation by PTPases. Relative to the rate of initial loss of 32P from receptor C-terminal sites, LAR dephosphorylated the Tris-phosphorylated Tyr-1150 domain 3.5 and 3.7 times more rapidly than either PTPase1B or LRP, respectively (p less than 0.01). The accelerated deactivation of the insulin receptor kinase by LAR and its relative preference for regulatory phosphotyrosine residues further support a potential role for this transmembrane PTPase in the physiological regulation of insulin receptors in intact cells.

Animals↗
PubMed1992

Insulin receptor and epidermal growth factor receptor dephosphorylation by three major rat liver protein-tyrosine phosphatases expressed in a recombinant bacterial system.

Protein-tyrosine phosphatases (PTPases) play an essential role in the regulation of signal transduction mediated by reversible protein-tyrosine phosphorylation. In order to characterize individual rat hepatic PTPases that might have specificity for autophosphorylated receptor tyrosine kinases, we isolated cDNA segments encoding three PTPases (PTPase 1B, LAR and LRP) that are expressed in insulin-sensitive liver and skeletal muscle tissue, and evaluated their catalytic activity in vitro. The intrinsic PTPase activities of the full-length PTPase 1B protein and the cytoplasmic domains of LAR and LRP were studied by expression of recombinant cDNA constructs in the inducible bacterial vector pKK233-2 using extracts of a host strain of Escherichia coli that lacks endogenous PTPase activity. Each of the cloned cDNAs dephosphorylated a cognate phosphopeptide derived from the regulatory region of the insulin receptor. Despite having only 30-39% sequence identity in their catalytic domains, LAR and PTPase 1B had similar relative activities between the peptide substrate and intact insulin receptors, and also displayed similar initial rates of simultaneous dephosphorylation of insulin and epidermal growth factor (EGF) receptors. In contrast, LRP exhibited a higher rate of dephosphorylation of both intact receptors relative to the peptide substrate, and also dephosphorylated EGF receptors more rapidly than insulin receptors. These studies indicate that three PTPases with markedly divergent structures have the catalytic potential to dephosphorylate both insulin and EGF receptors in intact cells and that redundant PTPase activity may occur in vivo. For these PTPases to have specific physiological actions in intact cells, they must be influenced by steric effects of the additional protein segments of the native transmembrane enzymes, cellular compartmentalization and/or interactions with regulatory proteins.

Amino Acid Sequence↗
PubMed1992

Approaches to the molecular cloning of protein-tyrosine phosphatases in insulin-sensitive tissues.

The intrinsic tyrosyl kinase activity of the insulin receptor is regulated by a balance between insulin-induced receptor autophosphorylation, which stimulates the receptor kinase, and enzymatic dephosphorylation of the receptor, which deactivates its kinase activity. The cellular protein-tyrosine phosphatase (PTPase) enzymes responsible for reversing the activated state of the insulin receptor have not been characterized. Our laboratory is interested in identifying and cloning the specific PTPase(s) that regulate the phosphorylation state of the insulin receptor. This chapter will summarize the design and results of our initial molecular cloning studies to identify specific PTPases in insulin-sensitive tissues that may have a potential physiological role in insulin action and clinical insulin resistance.

Amino Acid Sequence↗
PubMed1992

Effect of nicardipine on haemodynamic response to stress in hypertension.

The effects of the calcium antagonist nicardipine on the pressor response to mental arithmetic, cold pressor and exercise tests have been studied in fifteen patients with established mild to moderate essential hypertension. Nicardipine 20 mg p.o. showed a hypotensive effect within 60 min, associated with a fall in total peripheral resistance and an increase in heart rate. As the pressor response to each stress was not affected by nicardipine, the peak blood pressure reached during each stress was lower. Nicardipine lowers blood pressure at rest as a result of arteriolar dilatation, associated with reflex tachycardia. The pressor responsiveness to various stresses was not affected by nicardipine.

Adult↗
PubMed1992

Abnormal messenger ribonucleic acid (mRNA) transcribed from a mutant insulin receptor gene in a patient with type A insulin resistance.

In a previous report on a 16-year-old Japanese girl with type A insulin resistance, we found that one allele of the insulin receptor gene was inherited from her mother and contained a 1.2 kilobase pair deletion which removed the 14th exon in the beta subunit. We extended investigation of the proband and found the deletion between two Alu sequences. To determine the effect of the deletion on the level of transcription and the splicing pattern of messenger ribonucleic acid (mRNA), we synthesized the complimentary DNA and used the polymerase chain reaction to amplify the region which included the deleted area. The deletion shifted the reading frame, resulting in a termination codon after amino acid 867 (Glu), thereby producing a truncated insulin receptor without a transmembrane region and cytoplasmic domain. We also sequenced each of 22 exons of the insulin receptor gene but found no mutation in exons of the insulin receptor gene, except for deletion of exon 14 of the maternal allele. Thus, the proband is a heterozygote for a single mutant allele. Abnormal mRNA transcribed from the mutant allele resulted in a decrease in insulin binding.

Adolescent↗
PubMed1992

Protective role of antigenic sites on the envelope protein of Hantaan virus defined by monoclonal antibodies.

To investigate the role of Hantaan virus envelope glycoprotein in infection, a panel of monoclonal antibodies (MAbs) was examined in vitro with several serological tests and in vivo by passive transfer experiments in mice. An antigenic site, specific for the inhibition of infected cell focus was detected with the focus inhibition neutralization test (FINT), in addition to the neutralization related antigenic sites, which were revealed by the ordinary focus reduction neutralization test (FRNT). Suckling mice were given the MAbs by passive transfer followed by lethal Hantaan virus challenge. All neutralizing MAbs detected by either FRNT or FINT protected all mice from lethal infection, confirming the importance of the antigenic sites as a protective antigen. Mice given non-neutralizing MAbs by passive transfer, however, began to die earlier than the control group; mean time to death (18.2 +/- 2.1 to 21.5 +/- 2.8 days) being significantly shorter than that of the control group (25.8 +/- 1.8, p less than 0.01, Mann-Whitney, U probability test). Virus titers in brains of mice which died early, were about 10 times higher than those of control mice. These results indicated the early death phenomenon of mice which was mediated by the anti-virus antibody.

Animals↗
PubMed1992

Antibody-dependent enhancement of hantavirus infection in macrophage cell lines.

Antibody-dependent enhancement (ADE) of hantavirus infections (strains Hantaan 76-118 and SR-11) was studied using macrophage-like cell lines (J774.1, P388D1, and U937). Significantly higher virus titers (1,000 to 4,000 FFU/ml) were obtained by pretreatment of the virus with immune serum as compared to normal serum (less than 20 FFU/ml). Monoclonal antibodies (MAbs) to strain Hantaan 76-118 were employed to determine the antigenic determinants responsible for the ADE activity. ADE of the infection occurred with MAbs to both G1 and G2 envelope glycoproteins, but not with MAbs to nucleocapsid protein. Antigenic determinants related to haemagglutination or virus neutralization were found to cause ADE of the infection.

Animals↗
PubMed1992

A nuclear extract, prepared from mass-isolated germinal vesicles, retains a factor able to sustain a cytoplasmic cycle of starfish oocytes.

The germinal vesicle (GV) of starfish oocytes contains a factor which is required to drive the cytoplasmic cycle of the meiotic division. Biochemical investigation of this factor has been difficult due to the small quantities of obtainable GV materials. To overcome this, we have developed a mass-isolation procedure for the GVs of starfish oocytes, which depends on the softening of the cortex of the oocytes by cytochalasins to enable the GVs to pass through the cortex by centrifugation. From the isolated GVs, we have prepared a soluble fraction which retains the activity to induce the cytoplasmic cycle in the meiotic division of oocytes. The factor was sensitive to both heat and papain, suggesting that it is a protein.

Animals↗
PubMed1992

A case of bovine sex cord tumour with annular tubules.

A case of sex cord tumour with annular tubules was found in the right ovary of a 17-month-old Holstein cow. The tumour was characterized by tubules encircling hyaline bodies, which were composed of concentric lamellae of basal lamina. Several irregular tubular structures and a small component of granulosa cell differentiation were seen. Immunohistochemically, the neoplastic cells stained positively for oestradiol or testosterone.

Animals↗
PubMed1992

Biotransformation of isoeugenol and eugenol by cultured cells of Eucalyptus perriniana.

Three new biotransformation products, eugenyl beta-rutinoside, and isoeugenyl beta-gentiobioside and beta-rutinoside, together with eugenyl beta-glucoside and beta-gentiobioside, and isoeugenyl beta-glucoside, were isolated from jar fermentor culture of Eucalyptus perriniana following administration of eugenol and isoeugenol, respectively. This is the first report of rhamnosylation in a biotransformation catalysed by cultured cells of E. perriniana.

Acetylation↗
PubMed1992

Aneurysm of the fenestrated basilar artery: report of two cases.

This report describes two patients with fenestrated basilar artery aneurysms, and one of the patients underwent a postmortem examination. In our cases, the aneurysms arose at the proximal end of the fenestration, which involved the proximal third of the basilar artery. Subtraction angiography and oblique projections were essential in diagnosing the aneurysms. Complete neck clipping was successfully performed through a lateral suboccipital approach in the two cases. Technical aspects of neck clipping of the aneurysm of this unique location are discussed. Pathogenesis of these rare aneurysms is also discussed with clinical and histopathological data.

Adult↗
PubMed1992

Alterations in cerebral vessels in experimental animals and their possible relationship to the development of aneurysms.

Aneurysmal changes were studied by light and electron microscopes in experimental monkeys to elucidate their pathogenesis. Early changes were found not at the medial defect but in one branch near the apex. Degeneration of the elastic lamina was always more than that of the media throughout the process of aneurysm formation. Endothelial injury was present even at the bifurcation without a bulge. The present study suggests that aneurysmal changes are initiated by degenerative changes in the endothelium, which are followed by alterations in the underlying elastic lamina and, in turn, in the medial layer.

Animals↗
PubMed1992

Central diabetes insipidus resulting from a nonneoplastic tiny mass lesion localized in the neurohypophyseal system.

With the advent of magnetic resonance imaging (MRI), the neurohypophyseal system can be clearly delineated and its functional integrity can be predicted. The authors describe seven cases of central diabetes insipidus (DI) that occurred spontaneously. MRI revealed that the normal hyperintensity of the pituitary posterior lobe, which has been thought to be the neurosecretory material containing antidiuretic hormone, was absent in all cases. In addition, enlargement of a part of the neurohypophyseal system was recognized in five of seven cases on MRI. Three of the five patients with enlargement of a part of the neurohypophyseal tract underwent biopsy and were demonstrated to have chronic inflammation of the neurohypophyseal system. It was demonstrated that the enlarged parts of the neurohypophyseal system had shrunk either spontaneously or after the biopsy in four of the five cases. All patients are alive and have not experienced progression or remission of the disease. This study indicates that some cases of idiopathic DI result from a tiny mass lesion, usually nonneoplastic, localized in the neurohypophyseal system.

Adolescent↗
PubMed1992

Development and application of protein G antibody assay for the detection of antibody to hantavirus.

A new serodiagnostic method designated protein-G antibody assay (PGA) was developed for detection of hantavirus infection in various species of animals. The assay procedure includes reacting the sera with hantavirus-infected cells on glass slides, followed by incubation of biotinylated protein G and amplification with the avidin-biotinylated peroxidase complex. Specific antibody in rabbit, rat, mouse and Mongolian gerbil serum was detected by this method. The PGA titres were similar to those of the neutralization titre. In the sera of Mongolian gerbils infected with strain SR-11, antibody was first detected 10 days post infection, and the titre increased to 1:256 at 18 days post-infection. PGA was evaluated using sera of urban rats (Rattus norvegicus) captured in an endemic area of hantavirus infection. The negative (much less than 1:1, 24/62, 38.7%) and positive groups (much greater than 1:16, 38/62, 61.3%) were clearly distinguished. PGA titres were closely related to IFA titres in the sera. Two of 10 sera from Clethrionomys rufocanus and one from Apodemus speciosus captured in the same endemic area were positive to both PGA and IFA. These data indicate that PGA is a simple and useful method for seroepizootiological surveys of hantavirus infection, especially in wild rodent reservoirs.

Animals↗
PubMed1992

Immunoelectron microscopy of Chlamydia psittaci with monoclonal antibodies.

An immunoelectron microscopic study was performed to determine the distribution of antigenic components on particles of Chlamydia psittaci and infected cells using a number of monoclonal antibodies (MAbs). Of three anti-lipopolysaccharide (LPS) antibodies (4D5, A2 and 4G5), two antibodies (4D5 and A2) reacted with the surface of reticulate bodies (RBs) but not with that of elementary bodies (EBs). The other antibody (4G5) reacted with both EBs and RBs. Examination of infected cells in thin sections revealed that 4D5 and A2 combined with the membranes of both EBs and RBs. These results indicate that each LPS epitope localized at a different position in the chlamydial membrane. Most MAbs directed to protein antigens reacted on the surface of both EBs and RBs though 3E9 specific for the 90 kDa and 50 kDa protein components combined with RBs only.

Antibodies, Monoclonal↗