Biomedical subjects

K Ohtsuka

Publications and source records attributed to K Ohtsuka.

At least 37 records · Page 2Linked to original sources

PubMed2000

Roles of molecular chaperones in the nervous system.

Heat shock proteins (HSPs) are induced not only by heat shock but also by various other environmental stresses. HSPs such as Hsp90, Hsp70, Hsp60, Hsp40 and Hsp28 are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from deleterious stresses. Recently, Hsc70 and Hsp40 were found to be localized to the synapse in the mammalian central nervous system, indicating a synaptic role for these HSPs. Molecular chaperones are able to inhibit the aggregation of partially denatured proteins and refold them. In addition, molecular chaperones, especially Hsp70, protect the brain and heart from severe ischemia. In these respects, there are expectations for the use of molecular chaperones for protection against and therapeutic treatment of inherited diseases caused by protein misfolding. In this study, we review Hsp70 and Hsp40, and refer to the roles of these molecules in the synapse and cytoprotective functions of HSPs in stress tolerance and neurodegenerative diseases.

Animals↗

PubMed2000

Murine cDNA encoding a novel type I HSP40/DNAJ homolog, mmDjA4(1).

We have cloned a cDNA encoding a novel type I HSP40/DNAJ protein from the mouse EST database, and designated it mmDjA4 (Mus musculus type I DnaJ homolog 4). This cDNA encodes 397 amino acid residues whose sequence shows 67 and 51% identity with the previously identified murine Hsj2 and mDj3, respectively. The sequence of mmDjA4 contains the four repeats of CxxCxGxG motif which are characteristic of type I HSP40/DNAJ proteins, and a CaaX prenylation motif at the carboxy terminus. Northern blot analysis showed that mmDjA4 is specifically expressed in mouse testis and heart. This is the fourth member of the mammalian type I HSP40/DNAJ family to be identified.

Amino Acid Sequence↗

PubMed2000

Co-expression of human chaperone Hsp70 and Hsdj or Hsp40 co-factor increases solubility of overexpressed target proteins in insect cells.

The insect-baculovirus expression system has proved particularly useful for producing recombinant proteins that are biologically active. Overexpression of foreign proteins using the recombinant baculovirus system is often accompanied by aggregation of the overexpressed protein, which is thought to be due to a limitation of the translated protein folding in the infected cells. Co-infection of a recombinant baculovirus capable of expressing the human chaperone Hsp70 slightly increased the solubility of the overexpressed Epstein-Barr virus replication protein, BZLF1. Co-expression of Hsp70 and its co-factor, Hsdj or Hsp40, was here found to improve the solubility of the target protein several fold. Thus, a baculovirus expression system producing these molecular chaperones may find application for improved production of target foreign gene products in insect cells.

Animals↗

PubMed2000

Modulation of the chaperone activities of Hsc70/Hsp40 by Hsp105alpha and Hsp105beta.

Hsp105alpha and Hsp105beta are stress proteins found in various mammals including human, mouse, and rat, which belong to the Hsp105/Hsp110 protein family. To elucidate their physiological functions, we examined here the chaperone activity of these stress proteins. Hsp105alpha and Hsp105beta prevented the aggregation of firefly luciferase during thermal denaturation, whereas the thermally denatured luciferase was not reactivated by itself or by rabbit reticulocyte lysate (RRL). On the other hand, Hsp105alpha and Hsp105beta suppressed the reactivation of thermally denatured luciferase by RRL and of chemically denatured luciferase by Hsc70/Hsp40 or RRL. Furthermore, although Hsp105alpha and Hsp105beta did not show ATPase activity, the addition of Hsp105alpha or Hsp105beta to Hsc70/Hsp40 enhanced the amount of hydrolysis of ATP greater than that of the Hsp40-stimulated Hsc70 ATPase activity. These findings suggest that Hsp105alpha and Hsp105beta are not only chaperones that prevent thermal aggregation of proteins, but also regulators of the Hsc70 chaperone system in mammalian cells.

Adenosine Triphosphatases↗

PubMed2000

A new system for the anterior restoration and fixation of thoracic spinal deformities using an endoscopic approach.

STUDY DESIGN: A report on the results of animal experiments in which the authors' new system that enables the anterior correction and fixation of thoracic spinal deformity by use of a thoracic endoscope and small incisions was used. The results suggest that the new approach involving thoracoscopic anterior correction and fusion for thoracic spinal deformity could be adapted successfully for the clinic. OBJECTIVE: To develop a new system that enables the anterior correction and fixation of thoracic spinal deformity by use of a thoracic endoscope and small incisions. SUMMARY OF BACKGROUND DATA: Anterior correction and fusion through open thoracotomy have been applied mainly for thoracic scoliosis because this approach provides effective correction with short fusion. However, excellent visualization of the spine during thoracic surgical procedures led to the development of thoracoscopic spine surgery. Therefore, the authors postulated that a thoracoscopic approach could allow not only discectomy but also correction and fusion of the deformed thoracic spine in a single surgical event. METHODS: The vertebral columns and attached thoracic walls were dissected from fresh porcine cadavers and used in the experimental surgery to evaluate the new system. As a next step, thoracoscopic surgery using this new system was performed on four or five vertebrae of five live pigs with an average weight of 50 kg. Initially, the discs and rib heads were removed through the thoracic wall. For each vertebra, a screw connected to a shaft used as a screw holder was inserted through the thoracic wall in a posterior to anterior direction. Each shaft then was linked outside the body to an outrigger. This outrigger was used to both create and restore scoliosis. A rod then was introduced through the thoracic wall and fixed to the screw heads. RESULTS: The animal experiments clearly showed that it was possible to change the Cobb angles of the spine through the use of the outrigger apparatus. In cadaver experiments, it was possible to create scoliosis and re-store it by 25 degrees to 35 degrees. Also, surgery on live pigs resulted in scoliosis of approximately 30 degrees, which means approximately 5 degrees to 10 degrees for each disc space. The procedures used also demonstrated that it was possible to fix a rod, introduced into the pleural cavity through a port, with screw heads. CONCLUSIONS: The use of this system successfully changed the Cobb angle of the spine, which suggests that its use should make it possible to correct spinal deformities. This apparatus also succeeded in fixing the rods in the screw heads, which raises the possibility of its use in spinal fixation. The authors believe that this apparatus could be adapted successfully for clinical use. Studies currently are under way in clinics using the new system.

Animals↗

PubMed2000

Chaperones Hsp70 and Hsp40 suppress aggregate formation and apoptosis in cultured neuronal cells expressing truncated androgen receptor protein with expanded polyglutamine tract.

Spinal and bulbar muscular atrophy (SBMA) is one of a group of human inherited neurodegenerative diseases caused by polyglutamine expansion. We have previously demonstrated that the SBMA gene product, the androgen receptor protein, is toxic and aggregates when truncated. Heat shock proteins function as molecular chaperones, which recognize and renaturate misfolded protein (aggregate). We thus assessed the effect of a variety of chaperones in a cultured neuronal cell model of SBMA. Overexpression of chaperones reduces aggregate formation and suppresses apoptosis in a cultured neuronal cell model of SBMA to differing degrees depending on the chaperones and their combinations. Combination of Hsp70 and Hsp40 was the most effective among the chaperones in reducing aggregate formation and providing cellular protection, reflecting that Hsp70 and Hsp40 act together in chaperoning mutant and disabled proteins. Although Hdj2/Hsdj chaperone has been previously reported to suppress expanded polyglutamine tract-formed aggregate, Hsdj/Hdj2 showed little effect in our system. These findings indicate that chaperones may be one of the key factors in the developing of CAG repeat disease and suggested that increasing expression level or enhancing the function of chaperones will provide an avenue for the treatment of CAG repeat disease.

Apoptosis↗

PubMed2000

Normal-tension glaucoma with reversed ophthalmic artery flow.

PURPOSE: To describe a case of normal-tension glaucoma with bilateral complete occlusion of the internal carotid artery. METHODS: A 58-year-old man who had a 2-year history of normal-tension glaucoma in the left eye presented with ocular ischemic syndrome. To evaluate the orbital circulation, cerebral angiography and color Doppler imaging were performed. RESULTS: Cerebral angiography showed bilateral complete occlusion of the internal carotid artery and collateral blood supply through the right and left ophthalmic arteries, in which the flow was reversed. Moreover, color Doppler imaging revealed lower blood flow velocities in the left central retinal and short posterior ciliary arteries, suggesting a steal phenomenon. CONCLUSION: Normal-tension glaucoma in the present case may be caused by chronic reduction of retrobulbar blood flow resulting from a steal phenomenon.

Blood Flow Velocity↗

PubMed2000

Open-angle glaucoma associated with Graves disease.

PURPOSE: To estimate the prevalence of open-angle glaucoma, including normal-tension glaucoma, in association with Graves disease. METHODS: In a prospective study, a complete ophthalmic examination including applanation tonometry, exophthalmometry, automated static threshold perimetry, and computed tomography of the orbit was performed in 104 consecutive Japanese patients with Graves disease (age range, 11 to 86 years; mean, 42 years; 80 women, 24 men). Ocular hypertension was defined as an intraocular pressure greater than 21 mm Hg on at least two occasions during the period of follow-up. RESULTS: Of the 104 patients, 14 (13%) exhibited typical glaucomatous visual field defects in automatic static threshold perimetry in the absence of compressive optic neuropathy. The intraocular pressure in seven of the 14 patients was consistently less than 21 mm Hg during the follow-up period. Thus, these patients were diagnosed as having normal-tension glaucoma. Of the 104 patients, 23 (22%) were diagnosed as having ocular hypertension. CONCLUSIONS: The prevalence of normal-tension glaucoma as well as open-angle glaucoma and ocular hypertension was significantly higher among patients with Graves disease than in the general population.

Adolescent↗

PubMed2000

Improvement of urological-management abilities in individuals with tetraplegia by reconstructive hand surgery.

OBJECTIVE: To evaluate whether reconstructive hand surgery could improve the ability of tetraplegic patients to perform clean intermittent self-catheterization (CIC). MATERIALS AND METHODS: The subjects were patients with complete traumatic tetraplegia admitted to the Nagano Rehabilitation Center between 1977 and 1996. A total of 63 subjects were included in this study with an age range of 18-73 years (mean 38.2 years). Reconstructive hand surgery was performed on 44 hands (28 cases). Current urological conditions were assessed by interview or mail questionnaire. RESULTS: Fifty-one per cent (22/43) of the patients with C6 level of tetraplegia and 86% (12/14) of those with C7 or C8 neurological level of injury could perform CIC independently and only one subject needed assisted CIC. CONCLUSION: CIC is the preferred option for people with tetraplegia. Reconstructive hand surgery is thus recommended to make urological management more independent for a selected group of people with tetraplegia.

Adolescent↗

PubMed2000

Eicosapentaenoic acid stimulates nitric oxide production and decreases cardiac noradrenaline in diabetic rats.

1. The aim of the present study was to investigate whether long-term oral administration of eicosapentaenoic acid increases nitric oxide (NO) production and affects cardiac sympathetic activity in rats with diabetes mellitus. 2. We measured changes in urinary excretion of NO3-, a stable NO metabolite, and cardiac noradrenaline (NA) concentrations in non-diabetic rats and streptozotocin-induced diabetic rats treated with either ethyl icosapentate (EPA-E; 100 mg/kg per day; n = 10), a purified ethyl esterification product of eicosapentaenoic acid, or vehicle (distilled water; n = 10) for 6 weeks. The effects of N(G)-nitro-L-arginine (L-NNA), a NO synthase inhibitor, on urinary NO3- excretion and cardiac NA concentrations were also investigated in diabetic rats treated with EPA-E. 3. Urinary NO3- excretion was higher at weeks 5 and 6 in diabetic rats treated with EPA-E than in diabetic rats treated with vehicle (week 5: 120+/-8 vs 51+/-11 micromol/g per day, respectively (P<0.01); week 6: 279+/-83 vs 73+/-9 micromol/g per day, respectively (P<0.01)). Cardiac NA concentrations were higher in diabetic rats than in non-diabetic rats and were decreased in the left atrium and both ventricles in diabetic rats treated with EPA-E compared with control. Systemic administration of L-NNA abolished the increase in urinary excretion of NO3- and the decrease in cardiac NA concentrations in diabetic rats treated with EPA-E. 4. Long-term oral administration of EPA-E may stimulate NO production and increased NO is likely to play a role in inhibiting enhanced cardiac sympathetic activity in diabetic rats.

Animals↗

PubMed2000

Fas/Fas ligand expression and characteristics of primed CD45RO+ T cells in the inflamed mucosa of ulcerative colitis.

BACKGROUND: Chronic immune activation in the colon is characteristic of ulcerative colitis (UC). Fas/Fas ligand (FasL) system is a mechanism responsible for activation-induced cell death (AICD), which maintains homeostasis within the immune system. Thus, Fas/FasL expression on activated colonic T cells of UC patients, as well as the susceptibility of such T cells to AICD was investigated in order to determine the role of activated colonic T cells in the long lasting inflammation in UC. METHODS: Fas, FasL, and CD45RO expression on peripheral blood and colonic T cells of UC patients were assayed by flow cytometry. Apoptosis of colonic T cells induced by anti Fas antibody was assessed using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. RESULTS: The majority of colonic T cells expressed both CD45RO and Fas in the colonic mucosa, a situation that was quite different from that in the peripheral blood. The number of CD45RO+CD8+ and Fas+CD8+ T cells was significantly lower in UC patients than the controls, unlike the number of Fas+CD4+ T cells. In contrast, the number of both CD45RO+CD4+ and CD45RO+CD8+ T cells in UC mucosa expressing FasL was significantly higher than in the controls. While Fas mediated apoptosis of CD45RO+CD8+ T cells was higher in UC patients than the controls, the number of apoptotic CD45RO+CD4+ T cells from UC mucosa was not. CONCLUSIONS: In UC patients, CD45RO+CD4+ T cells are less sensitive to apoptotic signals mediated by Fas. These phenomena may contribute to the pathogenesis of UC.

Adult↗

PubMed2000

Serum levels of soluble Fas in patients with Graves' ophthalmopathy.

AIM: To assess levels of soluble Fas (sFas) in the sera of patients with Graves' ophthalmopathy. METHODS: The subjects in this study were 43 patients with Graves' ophthalmopathy and 11 normal subjects. Serum levels of sFas were determined by sandwich enzyme linked immunosorbent assay. In addition, serum levels of thyroid stimulating antibody (TSAB) were also measured in all the patients. RESULTS: The mean serum level of sFas was 1.35 (SD 2.03) ng/ml in patients with Graves' ophthalmopathy, and 0.93 (0.32) ng/ml in normal subjects. Serum levels of sFas in the subgroup of 24 patients with diplopia (1.98 (2.56) ng/ml) were significantly higher than those in the subgroup of 19 patients without diplopia (0.56 (0.24) ng/ml) and normal subjects (p <0.001). Serum levels of sFas in the subgroup of 27 patients with extraocular muscle hypertrophy (1.81 (2. 46) ng/ml) were significantly higher than those in the subgroup of 16 patients without extraocular muscle hypertrophy (0.58 (0.26) ng/ml) among the patients with Graves' ophthalmopathy and normal subjects (p <0.001). Serum levels of sFas were not significantly different between the subgroup of 24 patients with proptosis (1.15 (0.98) ng/ml) and the subgroup of 19 patients without proptosis (1. 61 (2.88)). In contrast, the serum levels of TSAB in the subgroup of patients with proptosis (723% (1161%)) were significantly higher than those in the subgroup of patients without proptosis (194% (122%)) (p <0.05). CONCLUSIONS: Elevated sFas levels were associated with extraocular muscle disorders but not with proptosis. On the other hand, elevated TSAB levels were associated with proptosis but not with extraocular muscle disorders, suggesting different immunological mechanisms for the extraocular muscle disorders and proptosis in Graves' ophthalmopathy. Determination of the serum levels of sFas and TSAB could provide useful markers for evaluation of the immunological processes involved in the development of Graves' ophthalmopathy.

Adolescent↗

PubMed2000

Role of FMRFamide-activated brain sodium channel in salt-sensitive hypertension.

FMRFamide, a cardioexcitatory neuropeptide, directly activates a newly cloned amiloride-sensitive sodium channel that is expressed specifically in the brain and blocked by benzamil hydrochloride. In the present study, we investigated the effects of short- and long-term intracerebroventricular infusion of FMRFamide on arterial pressure, sympathetic activity, vasopressin release, and brain renin-angiotensin system genes in rats and studied the role of FMRFamide-activated brain sodium channels in salt-sensitive hypertension. The intracerebroventricular preinjection of FMRFamide and subsequent intracerebroventricular infusion of 0.15 mol/L NaCl increased mean arterial pressure (FMRFamide: 30 nmol/kg +13+/-2.6 mm Hg, P<0.01; 100 nmol/kg +21+/-1.8 mm Hg, P<0.01), heart rate, abdominal sympathetic activity, and plasma vasopressin concentration compared with vehicle. The intracerebroventricular copreinjection with either benzamil or CV-11974 abolished these increases. In rats administered a high-salt diet (8% NaCl), the continuous intracerebroventricular infusion of FMRFamide (50 and 200 nmol. kg(-1). d(-1)) for 5 days increased mean arterial pressure, heart rate, urinary excretion of vasopressin and norepinephrine, and mRNAs of renin, angiotensin I-converting enzyme, and angiotensin II type 1 receptor in hypothalamus and brain stem compared with vehicle. These increases were abolished by intracerebroventricular coinfusion of benzamil. In rats administered a low-salt diet (0.3% NaCl), however, increases in these variables were smaller than those in rats receiving a high-salt diet. Together, these findings suggest that brain FMRFamide-activated sodium channels may be involved in the mechanism of salt-sensitive hypertension through regulation of the brain renin-angiotensin system.

Amiloride↗

PubMed2000

Mammalian HSP40/DNAJ homologs: cloning of novel cDNAs and a proposal for their classification and nomenclature.

We have cloned 10 novel full-length cDNAs of mouse and human HSP40/DNAJ homologs using expressed sequence tag (EST) clones found in the DDBJ/GenBank/EMBL DNA database. In this report, we tentatively designated them mHsp40, mDj3, mDj4, mDj5, mDj6, mDj7, mDj8, hDj9, mDj10, and mDj11. Based on the identity of the deduced amino acid sequences, mHsp40, mDj3, and mDj11 are orthologs of human Hsp40, rat Rdj2, and human Tpr2, respectively. We determined that mDj4 is identical with the recently isolated mouse Mrj (mammalian relative of DnaJ). PSORT analysis (a program that predicts the subcellular localization site of a given protein from its amino acid sequences) revealed that hDj9 has an N-terminal signal peptide; hence, its localization might be extracellular, suggesting that there may be a partner Hsp70 protein that acts together with the hDj9 outside of the cell. The same analysis indicated that mDj7 and mDj10 may have transmembrane domains. In order to simplify the complicated and confusing nomenclature of recently identified mammalian HSP40/DNAJ homologs, we propose here some new rules for their nomenclature. This proposed nomenclature includes the name of species with 2 lowercase letters such as hs (Homo sapiens), mm (Mus musculus) and rn (Rattus norvegicus); Dj standing for DnaJ; the name of types with A, B, and C, which were previously classified as type I, II, and III according to the domain structure of the homologs; and finally Arabic numerals according to the chronological order of registration of the sequence data into the database.

Amino Acid Sequence↗

PubMed2000

Cloning and expression of murine Hsp40 gene: differences in initiation sites between heat-induced and constitutive transcripts.

We have isolated cDNA and genomic clones of murine Hsp40 (mmDjB1). The murine Hsp40 gene was expressed at a high level in testis and was induced by heat shock. The transcriptional initiation sites were different between heat-induced transcripts and constitutive ones. The heat-induced transcripts initiated 22 to 28 bp downstream of the TATA box, whereas constitutive transcripts initiated from multiple sites, many of which initiated upstream of the TATA box. To our knowledge, this is the first report on the heat shock-dependent usage of transcriptional start sites of a heat shock gene.

3T3 Cells↗

PubMed2000

Eosinophilic granuloma of the spine: early spontaneous disappearance of tumor detected on magnetic resonance imaging. Case report.

Two cases of eosinophilic granuloma (EG) of the spine associated with neurological deficits are presented. The patients were treated conservatively by using external fixation with a brace as well as bed rest. Neurological deficits and pain diminished and finally disappeared as the tumor mass decreased in size, as seen on magnetic resonance (MR) imaging. During the 5-year follow-up period no recurrence of the tumors was detected on MR images. Surgical treatment for spinal EG in children presenting with typical vertebra plana is not recommended except for those with severe or progressive palsy and for those in whom the disease requires differential diagnosis.

Cervical Vertebrae↗

PubMed2000

Effects of superior colliculus inhibition on visual motion processing in the lateral suprasylvian visual area of the cat.

PURPOSE: To clarify whether visual inputs of the tectothalamocortical pathway influence motion processing within the lateral suprasylvian (LS) area of the cat. METHODS: This study was conducted in five cats. Tungsten microelectrodes were used for recording visual evoked potentials. The electrodes were introduced into the LS area. An array of 120 randomly located dots was projected onto the stimulus field (40 degrees x 40 degrees) in front of the animal by a slide projector. The dots were moved rightward and leftward alternatively with interstimulus intervals by a mirror attached to a galvanometer, the movements of which were controlled by a microcomputer. Each motion sequence consisted of an abrupt onset of motion that continued for 100 msec followed by an abrupt offset and a stationary phase of 900 msec; the total duration of each sequence was thus 1000 msec. The velocity of the motion was varied in 12 steps. The onset of motion was used as the trigger for recording evoked potentials. Single or multiple injections (two to three) of muscimol were made, mainly into the rostral superior colliculus (SC). The amplitudes of evoked potentials before and after the muscimol injection were compared. RESULTS: A large negative wave (N1) with the peak latency of 89.80+/-16.39 msec (mean +/- SD, n = 191) was recorded consistently. The amplitude of N1 was not altered by the muscimol injection into the SC when the velocity of motion was 50 deg/sec or less. When the velocity of motion was 75 deg/sec or more, however, the amplitude of N1 was reduced to 62% to 72% of that noted before the muscimol injection. CONCLUSIONS: These findings suggest that the LS area processes the visual motion inputs reaching through the two parallel pathways, the geniculostriate pathway and the tectothalamocortical pathway, when the velocity of visual motion is 75 deg/sec or more.

Animals↗

PubMed1999

Divergent axon collaterals from the rostral superior colliculus to the pretectal accommodation-related areas and the omnipause neuron area in the cat.

Results of previous studies have suggested that the rostral superior colliculus (SC), which corresponds to the representation of the central visual field, is involved in the control of accommodation and active fixation. To clarify the functional interaction between accommodation and active fixation in the rostral SC, this study was performed to investigate the axon collaterals diverging from the rostral SC to the pretectal accommodation-related areas and the omnipause neuron area in the raphe interpositus (RIP) of the cat by using a fluorescent double-labeling technique. This study was conducted on four cats, weighing 2.5-3.5 kg. Retrogradely labeled neurons in the SC were examined following injections of Fast Blue into the RIP and Diamidino Yellow into the pretectal accommodation-related areas, which were identified with microstimulation techniques. Neurons projecting to the RIP were located mainly in the intermediate layers in the rostral SC, whereas neurons projecting to the pretectal accommodation-related areas were scattered in the superficial and intermediate layers of the rostral SC. The population of double-labeled neurons was highest in the rostral SC, which corresponds to the representation of the central visual field. The presence of double-labeled cells indicated that the accommodation-related area in the rostral SC contains neurons whose axons collateralize to project to both the pretectal accommodation-related areas and the ominipause neuron area in the RIP. Neurons in the rostral SC may be involved in the interaction between accommodation and active fixation.

Accommodation, Ocular↗