Biomedical subjects

A Iwata

Publications and source records attributed to A Iwata.

At least 55 records · Page 3Linked to original sources

PubMed1998

Schwann cell proliferation as the cause of peripheral neuropathy in neurofibromatosis-2.

We report a 18-year-old man who developed slowly progressing right drop foot. Bilateral acoustic neurinoma was found and he was diagnosed as neurofibromatosis-2. Right sural nerve biopsy showed multiple small onion-bulb-like structures in the nerve fascicle. Electronmicroscopic and immunohistochemical studies on this structure confirmed cytological characteristics of Schwann cells, while previous reports suggest that this structure originates from perineural cells. The present report is the first to show both ultrastructurally and immunohistochemically that the onion-bulb-like structure is derived from Schwann cell.

Adolescent↗

PubMed1998

Foramen magnum syndrome caused by atlanto-occipital assimilation.

Atlanto-occipital assimilation is one of the most common congenital anomalies of the craniovertebral junction, and it usually is asymptomatic. We report a case of this malformation with unusual neurological symptoms which correlate with radiological findings. The anomaly caused the so-called foramen magnum syndrome, which was difficult to localize with neurological examination. The patient also had atlanto-axial dislocation, which was thought to enhance the symptoms with change of head/neck position.

Adult↗

PubMed1998

Two types of chicken 2',5'-oligoadenylate synthetase mRNA derived from alleles at a single locus.

We have isolated two types of chicken 2',5'-oligoadenylate synthetase cDNAs, A and B, which encode predicted proteins of 508 amino acids (58316 Da) and 476 amino acids (54336 Da), respectively. The region of A-protein comprising 33 amino acid residues from 385Ala to 417Cys is substituted by a single amino acid 385Tyr in B-protein. The homology between chicken and mammalian 2',5'-oligoadenylate synthetases is 49.5% over the amino-terminal 337 residues. Proteins expressed from A- and B-cDNAs in E. coli cells were both active in synthesizing 2',5'-oligoadenylate. However, the activity of B-protein was 10-15% of that of A-protein. Southern blotting hybridization indicated that the chicken synthetases are encoded by a single gene. RT-PCR and PCR analyses of RNA and DNA of chicken erythrocytes together with the sequence data of the PCR products showed that A- and B-mRNAs are derived from alleles at a single locus encoding chicken 2',5'-oligoadenylate synthetase, designated as OAS * A and OAS * B. Chickens carrying OAS * A/B produce two types of synthetase with molecular masses of 58 and 54 kDa, and those carrying OAS * A/A produce only a single type of 58 kDa.

2',5'-Oligoadenylate Synthetase↗

PubMed1998

Structure and function of smooth muscle myosin light chain kinase.

Myosin light chain kinase (MLCK) plays a central role in regulating the actin-myosin interaction of smooth muscle. MLCK phosphorylates the light chain of myosin in the presence of Ca2+ and calmodulin (CaM) thereby activating myosin so that it can interact with actin. Besides this kinase activity, MLCK shows i) actin-binding activity that can assemble actin filaments into their bundles and ii) myosin-binding activity that can form myosin filaments. To localize the actin- and myosin-binding activities in the MLCK molecule and to examine their possible role in regulating the actin-myosin interaction, we expressed various fragments of cDNA encoding MLCK in Escherichia coli as recombinant proteins. We found that MLCK consists of an N-terminal actin-binding domain, a central kinase domain, and a C-terminal myosin-binding domain. The Met1-Pro41 sequence is responsible for Ca2+/CaM-sensitive binding to actin. This binding site exerts an inhibitory effect on the actin-myosin interaction only when myosin is phosphorylated. MLCK binds to myosin at the C-terminal domain, the sequence of which is identical to telokin, an abundant myosin-binding protein in smooth muscle cells. This domain itself has no regulatory role in the interaction. However, the interaction was stimulated when this domain was extended to include the sequence known to regulate the activity of the kinase domain. The stimulation was observed only when myosin was unphosphorylated.

Actins↗

PubMed1998

Expression of immediate early gene c-fos in rat brain following increased intracranial pressure.

No attention has been given to an influence of the intracranial pressure (ICP) elevation on the brain at the level of the gene. In the present study, we originally attempted to evaluate the molecular biological changes of the brain, especially the expression of c-fos mRNA as a marker of cellular response, caused by increased ICP. Our results confirm that the neurons and non-neuronal cells are well able to tolerate the stress of increased ICP at the level of the gene, under the condition that cerebral blood flow (CBF) is maintained. A severe increase in ICP, which reduces CBF, enhances the c-fos mRNA expression in a similar fashion as in a forebrain ischemia model, except in the choroid plexus.

Animals↗

PubMed1998

Cis-acting elements in the lytic origin of DNA replication of Marek's disease virus type 1.

The replication origin of Marek's disease virus (MDV) type 1 was analysed by using a transient replication assay with plasmids containing various fragments of MDV strain Md5 genomic DNA. Plasmid pMBH, containing the BamHI-H fragment, showed replication activity in MDV-infected chicken embryonic fibroblasts (CEF). By deletion analysis of pMBH, two regions, the promoter-enhancer region of the MDV pp38 gene and the 132 bp tandem direct repeat, were shown to be required for replication activity. Replication of pMBH was not observed in uninfected CEF, suggesting that a trans-acting factor(s) encoded by the MDV genome was necessary for replication.

Animals↗

PubMed1998

Development of an enzyme-linked immunosorbent assay using recombinant chicken anemia virus proteins expressed in a baculovirus vector system.

Recombinant baculoviruses were constructed to express the putative proteins VP1, VP2 or VP3 of the chicken anemia virus (CAV). The recombinant VP1, VP2 or VP3 were detected by SDS-PAGE, and their molecular weights were 50, 30/27 and 16 kDa, respectively. The VP2 and VP3 reacted with sera from CAV-infected chickens in Western blot analysis and when used as an enzyme-linked immunosorbent assay (ELISA) antigen, but VP1 did not. Antibodies to CAV were detected, by ELISA using crude insect cell lysates containing VP2 or VP3, from 2 to 20 weeks or 2 to 7 weeks after CAV infection, respectively. These findings indicate that recombinant VP2 and VP3 expressed in the baculovirus vector system can be used as antigens to detect anti-CAV antibodies in ELISA.

Animals↗

PubMed1998

Transcriptional analysis of Marek's disease virus (MDV) genes in MDV-transformed lymphoblastoid cell lines without MDV-activated cells.

Spontaneously activated MDV is rarely included in MDV-transformed cells, while it may influence the results of transcriptional analysis. A population consisting of 10(3) MDV-transformed cells probably did not include spontaneously activated MDV, since the estimated frequency of MDV-transformed cells including activated MDV was below 0.01% according to limiting-dilution polymerase chain reaction (PCR) and the presence of the major early antigen pp38 in 6 transformed cell lines. Reverse transcriptase-PCR (RT-PCR) products corresponding to ICP27, pol, TK, US3, A41, gA, gB and UL50 genes were undetectable in 10(3) cells by Southern hybridization of the RT-PCR products. Transcripts of the VP16 and SORF2 genes were detected in the 10(3) cells of MSB-1, and the pp14 gene transcript was found in 10(3) cells of RPL-1 but not in 10(3) cells of HPRS-1, MOGA-2, MSB-1 or MTB-1. A transcript corresponding to the ICP4 sequence was detected as a 0.7 kbp RT-PCR product in 10(3) cells of these MDV cell lines but not in the retrovirus-transformed 1104B1 cell line. The transcript corresponding to the 0.7 kbp RT-PCR product suggested a splice by its size and sequence. Thus, transcriptional analysis of 10(3) MDV-transformed cells revealed that the transcript corresponding to the ICP4 sequence was a common transcript in latently infected MDV-transformed cells, while most of the genes did not transcribe in these cells.

Animals↗

PubMed1998

Angiotensin-converting enzyme inhibitor cilazapril suppresses expression of basic fibroblast growth factor messenger ribonucleic acid and protein in endothelial and intimal smooth muscle cells in a vascular injury model of spontaneous hypertensive rats.

The relationship between the expression of basic fibroblast growth factor (bFGF) messenger ribonucleic acid (mRNA) and protein, a potent mitogen for vascular smooth muscle cells in vivo, and administration of the angiotensin-converting enzyme inhibitor cilazapril, which suppresses smooth muscle cells proliferation in denuded arteries, was studied in spontaneously hypertensive rats using the in situ hybridization technique and immunohistochemical study. The effect of cilazapril on neointimal formation through modification of bFGF expression was evaluated using the increased tissue expression of the renin-angiotensin system in spontaneously hypertensive rats. Arterial injury was produced by using balloon catheter denudation in the left carotid artery of rats. The effects were evaluated 2 weeks later. bFGF mRNA and protein were observed only in the endothelial cells of sham-operated rats. bFGF mRNA and protein were observed in both endothelial cells and intimal smooth muscle cells in operated rats receiving only vehicle. Expression of bFGF mRNA and protein was suppressed in both endothelial cells and intimal smooth muscle cells of operated rats receiving cilazapril. These data suggest that cilazapril suppresses smooth muscle cell proliferation through modification of the expression of bFGF mRNA and bFGF protein in addition to other genes.

Angioplasty, Balloon↗

PubMed1998

[Pilot study of relapsed osteosarcoma and brain tumor with ifosfamide, carboplatin and etoposide (ICE therapy)].

Ifosfamide, Carboplatin and Etoposide (ICE) therapy was used to treat 4 patients, 2 with refractory osteosarcoma, and one each with relapsed brain tumor and newly diagnosed brain tumor. ICE therapy was administered in doses of Ifosfamide 1,800 mg/m2 x 5, Carboplatin 400 mg/m2 x 2 and Etoposide 100 mg/m2 x 5. A total of 30 courses were administered. Two cases of osteosarcoma had a stable disease (range, 3-9 months) and 2 cases of brain tumor had a complete response by magnetic resonance imaging. Moderate or severe toxicity evaluated on a per course basis included: neutropenia 83%, thrombocytopenia 93%, fever 30%, hepatotoxicity 3%, and hemorrhagic cystitis 3%. The median time to hematologic recovery was 20 days. ICE therapy is highly effective for the treatment of refractory or recurrent solid tumors with acceptable toxicity.

Adolescent↗

PubMed1998

Application of the human hepatitis B virus core antigen from transgenic tobacco plants for serological diagnosis.

BACKGROUND AND OBJECTIVES: The aim was to produce HBcAg from plants more cheaply than can be done by other currently available means, and to apply such antigen to immunoassay procedures for pretransfusion testing of donor blood. MATERIALS AND METHODS: Transgenic Nicotiana tabacum cv. SR-1 plants expressing the human hepatitis B virus (HBV) core antigen (HBcAg) gene were generated by Agrobacterium-mediated transformation. The recombinant product, called tHBcAg, can assemble itself into a spherical particle with a diameter of 25 to 30 nm, and can maintain two antigenic determinants of HBcAg, namely HBc/alpha and HBc/beta. Partly purified tHBcAg was used in the hemagglutination-inhibition (HI) test, as routinely used by the Japanese Blood Center, to test a panel of 524 blood units taken from HBV-positive donors. RESULTS: In the HI test, tHBcAg showed serologic properties comparable to that from Escherichia coli, the standard antigen used in the Japanese Blood Center. CONCLUSIONS: Transgenic plants can produce reagents for serologic testing and perhaps even such medical materials as oral vaccines.

Agrobacterium tumefaciens↗

PubMed1998

[A case of dural arteriovenous fistula accompanied by sinus occlusion. A serial study with CT scan].

A dural arteriovenous fistula (AVF) of the posterior fossa was found in a 58-year-old businessman suffering from a month's history of dementia. Bilateral transverse sinus thrombosis was also found and his symptom was attributed to venous congestion caused by the sinus occlusion. He had received partial resection of the right trigeminal neurinoma two years before, and the operation was thought to have caused the sinus occlusion. Dural AVF of the posterior fossa usually causes tinnitus or headache, whereas dementia seen in present case is relatively rare. In the present case, serial study of cranial CT scan demonstrated evolution of dural AVF after sinus occlusion. Venous congestion was thought to re-open the physiological micro-AVF to cause the dural AVF.

Arteriovenous Fistula↗

PubMed1998

[Changes in intraoperative blood glucose and ketone body concentrations during the repair of lipomyelomeningocele in children].

Blood glucose and ketone body (3-hydroxy-butyrate) concentrations were measured in 8 children (4.2 +/- 2.8 years old) during the repair of lipomyelomeningocele (9.0 +/- 2.6 hours) to elucidate whether lipid mobilization can be prevented by glucose infusion at the rate of 0.2 +/- 0.05 g.kg-1.h-1. The operation was followed in about 4 hours by a significant increase in blood glucose and ketone body concentrations, with their maximum value of 195 +/- 75 mg.dl-1 and 656 +/- 75 mumol.l-1, respectively (P < 0.05), as compared with the preoperative level. The lipid mobilization soon returned to normal state by increasing the rate of glucose infusion, as indicated by ketone body level of 92 +/- 58 mumol.l-1 at the end of operation. These results show that glucose infusion rate should be adjusted based on serial analysis of both blood sugar and ketone body concentrations in the anesthetic management of children undergoing a long operation.

3-Hydroxybutyric Acid↗

PubMed1997

The structure and function of the actin-binding domain of myosin light chain kinase of smooth muscle.

In addition to its kinase activity, the myosin light chain kinase (MLCK) of smooth muscle has an actin binding activity through which it can regulate the actin-myosin interaction of smooth muscle (Kohama, K., Okagaki, T., Hayakawa, K., Lin, Y., Ishikawa, R., Shimmen, T., and Inoue, A. (1992) Biochem. Biophys. Res. Commun. 184, 1204-1211). In this study, we have analyzed the actin binding activity of MLCK and related it to its amino acid sequence by producing native and recombinant fragments of MLCK. Parent MLCK exhibited both calcium ion (Ca2+) and calmodulin (Ca2+/CaM)-sensitive and Ca2+/CaM-insensitive binding to actin filaments. The native fragment, which consists of the Met1-Lys114 sequence (Kanoh, S., Ito, M., Niwa, E., Kawano, Y., and Hartshorne, D. J. (1993) Biochemistry 32, 8902-8907), and the recombinant NN fragment, which contains this 1-114 sequence, showed only Ca2+/CaM-sensitive binding. An inhibitory effect of the NN fragment on the actin-myosin interaction was observed by assaying in vitro motility and by measuring the actin-activated ATPase activity of myosin. The recombinant NN/41 fragment, which is constructed without the Met1-Pro41 sequence of the NN fragment, lost both the actin binding activity and the inhibitory effect. We confirmed the importance of the 1-41 sequence by using a few synthetic peptides to compete against the NN fragment in binding to actin filaments. The experiments using recombinant fragments and synthetic peptides also revealed that the site for CaM-binding is the Pro26-Pro41 sequence. The site for the Ca2+/CaM-insensitive binding, which is shown to be localized between the Ca2+/CaM-sensitive site and the central kinase domain of MLCK, exerted no regulatory effects on the actin-myosin interaction.

Actins↗

PubMed1997

Subarachnoid hemorrhage induces c-fos, c-jun and hsp70 mRNA expression in rat brain.

To detect stress responses of the brain to subarachnoid hemorrhage (SAH), we investigated the expression of immediate early genes (IEGs) and hsp70 mRNA by in situ hybridization. Experimental SAH was produced in 49 rats by endovascular penetration. We also monitored the intracranial pressure (ICP) changes. The genes c-fos and c-jun were induced in the cerebral cortex, hippocampus and dentate gyrus in the penetrated side. mRNA coding for hsp70 was induced in the cerebral cortex, hippocampus, thalamus, hypothalamus and caudoputamen in the penetrated side and extended to the contralateral hemisphere. IEGs in the cerebral cortex were completely blocked by MK-801 pretreatment, but hsp70 mRNA was not. This suggests that the expression of IEGs correlates with spreading depression. The IEGs and hsp70 expression may reflect the severity of SAH impact and relate to the mechanisms of symptomatic vasospasm.

Animals↗

PubMed1997

Thermoregulatory responses of prepubertal boys and young men during moderate exercise.

Seven prepubertal boys (aged 10-11 years) and eleven young men (aged 21-25 years), matched for skinfold thickness and maximal oxygen uptake (VO2max) per unit of mass, cycled at an intensity of approximately 40% VO2max for 45 min in a warm condition (30 degrees C, 45% relative humidity). During exercise no age-related differences were observed for the increases in rectal temperature (Tre) and heart rate (HR), although the absolute Tre and HR were significantly greater for the boys because of a higher initial baseline (P < 0.05). Total body sweating rate [181 (SEM 12) vs 245 (SEM 12) g.m-2(.)45 min-1; P < 0.002] and local sweating rates (msw) on chest, back, and forearm were significantly lower for the boys (P < 0.001), as was metabolic heat production [203 (SEM 9) vs 276 (SEM 9) W.m-2; P < 0.01]. The lower msw in the boys was due to a lower output per activated sweat gland, even though they had a higher activated sweat gland density regardless of site. In contrast, cutaneous blood flow by laser Doppler flowmetry (LDF) in the boys was significantly greater on the chest and back, compared to the men (P < 0.003). The age-related differences in cutaneous vascular conductance (CVC) were more marked because of lower mean arterial pressure in the boys during exercise. However, forearm LDF and CVC were significantly lower for the boys (P < 0.008). No significant differences in LDF among sites were observed for the boys, whereas for the men LDF on the forearm was significantly greater than on the chest and back (P < 0.01). The boys showed lower mean skin temperatures (especially on the back and chest despite greater increments of LDF) after starting to sweat, whereas the men remained unchanged, suggesting that the heat loss on the trunk in the boys was promoted by greater increments of LDF despite lower msw, compared to the young men. It was concluded that during moderate exercise in an air temperature at 30 degrees C, prepubertal boys could thermoregulate as efficiently as young men by greater vasodilatation on their trunk despite lower msw. Furthermore regional differences may exist in the maturation-related modification of vasodilatation.

Adult↗

PubMed1997

The effect of change in skin temperature due to evaporative cooling on sweating response during exercise.

The purpose of this study was to investigate whether there are any effects of skin temperature changes on sweating response in the first few minutes of mild exercise. Six healthy males performed a bicycle exercise at 100 W (50 rpm) for 30 min under an ambient temperature of 23 degrees C (40% RH). Esophageal temperature (Tes), mean skin temperature (Tsk), local skin temperature at the lower left scapula (Tsl), local sweating rate (Msw) and cutaneous blood flow by laser-Doppler flowmetry (LDF) were measured continuously. Although Tsl decreased markedly just after the onset of sweating, Tsk did not change. Msw did not increase constantly in the early stages of exercise, and there was a temporary interruption in the increase of Msw. This interruption in sweating was affected by the rate of change in Tsl rather than by the absolute value of Tsl, since there was a positive and significant correlation between the time of the interruption in the increase of Msw and the rate of decrease in Tsl (y = 6.47 x +0.04; r = 0.86, P < 0.05). The results suggest that sweating response in the early stages of exercise may be influenced by changes in local skin temperature due to evaporative cooling.

Adult↗

PubMed1997

Expression of basic fibroblast growth factor mRNA after transient focal ischemia: comparison with expression of c-fos, c-jun, and hsp 70 mRNA.

We have reported that basic fibroblast growth factor (bFGF) prevents retrograde degeneration of thalamic neurons after middle cerebral artery (MCA) occlusion. To identify the protective mechanism of bFGF, we examined bFGF mRNA expression in a model of transient focal ischemia with in situ hybridization. Compared to c-fos, c-jun, and hsp 70 mRNA expression, upregulation of the bFGF mRNA expression was delayed until 6 h after reperfusion. By 12 h, bFGF mRNA was markedly induced in the peri-infarcted cortex, cingulate cortex, and peri-infarcted white matter. At 24 h and 2 days the induction of bFGF mRNA in these regions persisted, and disappeared by 5 day. The quantitative assessment of bFGF mRNA expression revealed that optical density ratios of the cingulate gyrus and the caudoputamen were significantly higher at 12 h, 24 h, and 2 d after reperfusion than those in sham controls. Microscopic observation indicated bFGF mRNA signals were present in several types of cortical cells, including neurons and nonneuronal cells. Since intrinsic bFGF, released from the damaged tissue, can influence the healing response through receptors upregulated by injury, it is reasonable that this pattern of bFGF mRNA expression parallels the bFGFR mRNA expression previously reported.

Animals↗