PubMed Health⌕ Search

Biomedical subjects

T Nakata

Publications and source records attributed to T Nakata.

At least 19 recordsLinked to original sources
PubMed1992

Chronological expression of microtubule-associated proteins (MAPs) in EC cell P19 after neuronal induction by retinoic acid.

Pluripotent murine embryonal carcinoma (EC) P19 cells are induced at a high rate into neural cells using retinoic acid and serum-free medium. EM observation revealed great increase of microtubules (MTs) after neuronal induction. To study the expression of microtubule-associated proteins (MAPs), immunoblotting and immunocytochemistry were performed with phosphorylated MAP1B (pMAP1B)-, MAP2-, and MAP1A-specific monoclonal antibodies. They did not stain undifferentiated cells. Early MAPs (pMAP1B and MAP2C) appeared 12 h after the neuronal induction, changing to late MAPs (MAP1A and MAP2A/B) at 3-5 days. These expression patterns are quite similar to those of neural cells in vivo. Anti-pMAP1B stained not only neurites but also the cell body and varicosities. But after extraction of the soluble component by permeabilization, pMAP1B was found in only MT-domains of the neurites at LM and EM levels, indicating that some part of pMAP1B is a structural component of neurite MTs and others exist in a soluble form. After culturing for more than 5 days, pMAP1B disappeared from the soma, but still remained in the distal ends of neurites. Here we showed that P19 is a good model system for studying the expression of MAPs on the continuous course of neuronal differentiation.

Animals↗
PubMed1992

Cyclin-dependent kinase 2 (cdk2) in the murine Cdc2 kinase TS mutant.

Kinases of the mammalian cdc2 family including cdk2 (cyclin-dependent kinase 2) are thought to be involved in both the G2/M transition and DNA replication. To investigate the role of cdc2 kinase and cdk2 in cell cycle progression, murine tsFT210 cells bearing a temperature-sensitive cdc2 mutation were used. These kinases were purified by column chromatography, using a peptide with the consensus phosphorylation site of cdc2 kinase as the substrate. In this mutant, cdc2 kinase activity was temperature sensitive and cdk2 activity was not. At the restrictive temperature, the mutant was only arrested in the G2 phase and not in the G1-S phase, suggesting that cdk2 did not compensate for cdc2 kinase at the G2/M transition but did function at the G1-S phase. This suggestion was supported by the finding that transfection of cdk2 cDNA did not improve the growth of the mutant cell line at the restrictive temperature, although transfection of cdc2 cDNA did.

Animals↗
PubMed1992

Quantification of antimyosin uptake and infarct size at various stages of myocardial infarction.

We studied with quantitative techniques the clinical efficacy of indium-111 antimyosin at a later stage of myocardial infarction in 18 patients at various stages after infarction. Antimyosin accumulation was detected irrespective of infarct age and size and quantified as an infarct weight with a tomographic technique. Higher intensities in a planar image were observed in anterior Q wave infarct group (36 +/- 5 g) but not in inferior and non-Q wave anterior infarct groups because of the smaller infarct weights (8 +/- 3 g, 13 +/- 6 g, respectively). Infarct area calculated from thallium-201 tomography significantly correlated with left ventricular ejection fraction in both recent (less than 2 weeks) and older (2-week- to 6-month-old) infarct groups (r = -0.969, P less than 0.001; r = -0.860, P less than 0.001, respectively), whereas there was a significant negative correlation between infarct weight and left ventricular ejection fraction in the recent infarct group (r = -0.731, P less than 0.05) but not in the older infarct group. Thus, antimyosin tomography can detect myocardial necrosis with a high sensitivity regardless of infarct age, size, and location. However, the accumulation might be affected by infarct age and correspond to necrotic mass but not necessarily to infarct volume itself at a later stage probably because of the presence of necrosed and scarred tissues in infarcted myocardium.

Aged↗
PubMed1992

Interaction of dynamin with microtubules: its structure and GTPase activity investigated by using highly purified dynamin.

We purified a large amount of dynamin with high enzymatical activity from rat brain tissue by a new procedure. Dynamin 0.48 mg was obtained from 20 g of rat brain. The purity of dynamin was almost 98%. Dynamin plays a role of GTPase rather than ATPase. In the absence of microtubules, Michaelis constant (Km) and maximum velocity (Vmax) for dynamin GTPase were 370 microM and 0.25 min-1, respectively, and in their presence, both were significantly accelerated up to 25 microM and 5.5 min-1. On the other hand, the ATPase activity was very low in the absence of microtubules, and even in their presence, Km and Vmax for dynamin ATPase were 0.2 mM and 0.91 min-1. Despite slow GTPase turnover rate in the absence of microtubules, binding of GTP and its nonhydrolizing analogues was very fast, indicating that GTP binding step is not rate limiting. Dynamin did not cause a one-directional consistent microtubule sliding movement just like kinesin or dynein in the presence of 2 mM ATP or 2 mM GTP. We observed the molecular structure of dynamin with low-angle rotary shadowing technique and revealed that the dynamin molecule is globular in shape. Gel filtration assay revealed that these globules were the oligomers of 100-kDa dynamin polypeptide. Dynamin bound to microtubules with a 1:1 approximately 1.2 molar ratio in the absence of GTP. Quick-freeze deep-etch electron microscopy of the dynamin-microtubule complex showed that dynamin decorates the surface of microtubules helically, like a screw bolt, very orderly and tightly with 11.4 +/- 0.9 (SD)nm period. Contrary to the previous report, microtubules make bundles by the attachment of the dynamin helixes around each adjacent microtubule, and no cross-bridge formation was observed.

Amino Acid Sequence↗
PubMed1992

High expression of manganese superoxide dismutase in 7,12-dimethylbenz[a]anthracene-induced ovarian cancer and increased serum levels in the tumor-bearing rats.

Manganese superoxide dismutase (Mn-SOD) is strongly expressed in human ovarian cancer, and the serum level of the enzyme is a useful marker for the diagnosis and monitoring of human ovarian cancer. In the present study we found that Mn-SOD was highly expressed in primary and transplanted ovarian cancers in rats induced by 7,12-dimethylbenz[a]anthracene (DMBA), as judged by enzyme-linked immunosorbent assay as well as by Northern blot analysis. The serum levels of Mn-SOD in the tumor-bearing rats were also higher than those in control rats. The antibody strongly reacted with rat ovarian carcinoma tissues. These data suggest that DMBA-induced ovarian cancer in rats is a good experimental model for human ovarian cancer, and that Mn-SOD is also a good marker for disease in the animal model.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Decreased hypothalamic and medullary GABA turnover in spontaneously hypertensive rats.

OBJECTIVE: The aim was to assess whether Gamma-aminobutyric acid (GABA) neurone activities in the central nervous system, especially in the hypothalamus and medulla oblangata, are altered in hypertension. METHODS: Central GABA content and turnover rate were measured in spontaneously hypertensive rats (SHR) and their normotensive Wistar Kyoto controls (WKY). GABA content was determined with high performance liquid chromatography, and in vivo GABA turnover rates were estimated by GABA accumulation after injection of amino-oxyacetic acid, a selective inhibitor of GABA degrading system. Two groups of nine week old male rats (32 SHR and 32 WKY) were used. RESULTS: GABA concentrations in cerebrospinal fluid were lower in SHR than in WKY. Since hypothalamus and medulla oblongata are the possible active sites of this system, basal GABA contents and in vivo GABA turnover rates were measured in hypothalamus and medulla oblongata. Basal GABA content in the medulla oblongata and hypothalamus was almost equal in SHR and WKY. On the other hand, GABA turnover rates were significantly lower in SHR than in WKY in both the hypothalamus and the medulla. CONCLUSIONS: Since it is known that GABA is an inhibitory neurotransmitter in the central nervous system and that it controls autonomic and cardiovascular activities, the findings suggest that the decreased hypothalamic and medullary GABAergic activities may permit sympathetic hyperactivity to contribute to the increase in blood pressure in SHR.

Aminooxyacetic Acid↗
PubMed1992

Role of sympathetic nerve inhibition in the vasodepressor effect of bromocriptine in normotensive and hypertensive rats.

This study aimed to elucidate the mechanism of the hypotensive effect of bromocriptine (BRC), and to investigate whether or not the effects of BRC on the sympathetic nervous system are altered in hypertension. BRC was administered intravenously to normotensive and spontaneously hypertensive rats (SHR). It elicited hypotensive effects dose-dependently in urethane-anaesthetized normotensive rats, an effect which was antagonized with metoclopramide. Pretreatment with intravenous hexamethonium attenuated the hypotensive effect of BRC. BRC decreased plasma norepinephrine (NE) without inhibiting the sympathetic nerve spikes recorded from the postganglionic sympathetic nerve bundle. The hypotensive effect of BRC was significantly greater in SHR than in Wistar Kyoto Rats (WKY). Decrease in NE by BRC was also significantly greater in SHR than in WKY. These results suggest that the hypotensive effect of BRC is induced by suppression of NE release, not by inhibition of sympathetic nerve spikes, and that the dopaminergic presynaptic inhibition is attenuated in SHR.

Animals↗
PubMed1992

Expression of Mn-superoxide dismutase in carcinogenesis.

Human liver manganese superoxide dismutase (Mn-SOD) was highly purified by a simple procedure and crystallized. A monoclonal antibody against Mn-SOD, whose antigen-binding epitope is a C-terminus peptide was developed. Using this antibody, an enzyme-linked immunosorbent assay (ELISA) was developed. We found that Mn-SOD is highly expressed in human ovarian cancer and the serum level of the enzyme is a useful marker for the diagnosis and monitoring of the epithelial type of ovarian cancer. Tumor necrosis factor-alpha (TNF), lipopolysaccharide, IL-1 and phorbol ester induced the m-RNA of Mn-SOD as well as protein levels in TNF-resistant cells. No such induction was observed in Cu, Zn-SOD. Studies on the induction mechanisms indicated that at least two separate signal-transducing pathways are involved in expression of the Mn-SOD gene. One is triggered by protein kinase C activation itself in the absence of new protein synthesis. The other can be activated by stimulations with various cytokines in which a protein factor that can be induced by phorbol ester treatments is involved.

Biomarkers, Tumor↗
PubMed1992

Manidipine inhibits the progression of hypertension and atherosclerosis in endothelium-injured and cholesterol-fed Goldblatt 2K1C rats.

In the present study, arteriosclerotic change of the aorta was induced in rats. The effects of manidipine hydrochloride on the resulting hypertension and arteriosclerotic change were studied. In endothelium-injured cholesterol-fed Goldblatt 2K1C rats, moderate elevation of blood pressure was noted at 3, 4, and 5 weeks. Laboratory studies performed at the end of 6 weeks also showed hypercholesterolemia, accompanied by a reduction of triglycerides and HDL cholesterol. Regular doses of manidipine (200 or 500 mg/kg) resulted in a dose dependent inhibition of the blood pressure elevation and a reduction of HDL cholesterol, but had no effect on cholesterol or triglyceride levels. Morphological studies in endothelium-injured rats afflicted with hypercholesterolemia and hypertension, showed medial thickening and intimal hyperplasia. Hyperplasia of the intima was a result of excessive proliferation of the smooth muscle cells. These cells showed an unusually large number of fat droplets and were considered indicative of atheromatous plaque formation. In rats treated with manidipine, hyperplasia of the media was completely suppressed while hyperplasia of the intima was reduced by a minimum of 50%. This study demonstrated that hypercholesterolemia and hypertension produced arteriosclerotic change in endothelium-injured rats, which was inhibited by manidipine. It is not known whether antiarteriosclerotic action was involved in the antihypertensive effect of manidipine.

Animals↗
PubMed1992

Effect of manidipine on cardiac hypertrophy and coronary circulation in DOCA/salt hypertensive rats.

The effect of manidipine on cardiac hypertrophy, coronary circulation, left ventricular weight and maximal coronary flow in hypertension was measured in DOCA/salt treated systolic hypertensive rats with and without manidipine treatment. Normotensive rats were used as controls. After feeding with 0.05% manidipine-containing food, blood pressure was reduced only in DOCA/salt hypertensive rats, but not in control rats. After 3 weeks of treatment, sodium excretion was significantly increased in DOCA/salt-treated rats with or without manidipine treatment. Hearts were removed and perfused with modified Krebs-Henseleit solution with adenosine (5 x 10(-5) M) in a Langendorff apparatus. Maximal coronary flow (MCF) was significantly decreased only in DOCA/salt hypertensive rats without treatment, while manidipine treatment restored MCF. Left ventricular weight/body weight was also markedly greater in DOCA/salt-treated rats not given manidipine. Left ventricular weight in DOCA/salt-treated rats given manidipine was significantly reduced compared with DOCA/salt hypertensive rats without treatment, although it was heavier than in the control animals. Morphological examination showed that the increased wall/lumen ratio in DOCA/salt hypertensive rats was reduced by manidipine treatment. These findings suggest that treatment with manidipine in DOCA/salt hypertensive rats lowered high blood pressure and improved impaired coronary circulation with a reduction in left ventricular and vascular hypertrophy.

Aldosterone↗
PubMed1992

[Nd-YAG laser treatment for central airway lesions].

YAG laser treatment was conducted in 55 patients with central airway lesions over the last 8 years. The malignant lesions comprised 1 primary tracheal cancer, 1 chondroma of the trachea, 34 primary lung cancer, and 10 metastatic lung tumor. The benign lesions comprised one each of hamartoma, lipoma, bronchial lithiasis, post-tracheotomy granuloma, and bronchial web, and 3 other cases. Nd-YAG laser treatment was performed in 55 patients with airway lesions, with a success rate of 73%. The success rates in the above patients were 70% for primary lung cancer, 60% for metastatic lung tumor, 100% for primary tracheal cancer and chondroma of trachea, and 89% for benign lesions. In 34 patients with primary lung cancer, palliative widening of the airway was planned with the exception of 2 patients with endoscopically early lung cancer for whom curative vaporization was intended, 6 months-survival rate was 59.3% in patients in whom various combined treatments were performed after the laser treatment. For all patients with hamartoma or lipoma in those with benign lesions, curative vaporization was performed. The severe complication of lethal massive hemoptysis occurred in 3 patients. We consider that Nd-YAG laser treatment is a powerful therapeutic means of performing lifesaving or emergency, curative, and supplemental treatment.

Adult↗
PubMed1992

[Role of oxygen radical and superoxide dismutase in ovulation in the rat].

We studied the effect of Cu,Zn-superoxide dismutase (SOD) and Mn-SOD, which are specific scavenging enzymes of the superoxide anion radical, on ovulation and examined the localization of SOD in rat ovaries. The results were as follows. 1) The number of ova in the Cu,Zn-SOD (8 mg x 4) administrated group (27.8 +/- 5.4 : p less than 0.01) was significantly reduced compared to the control group (49.0 +/- 3.3). Similarly, the number of ova in the Mn-SOD (2 mg x 2) administrated group (16.9 +/- 7.6 : p less than 0.01) was significantly reduced compared to the control (52.9 +/- 6.3). 2) In the rat ovary, Cu,Zn-SOD examined by the immunohistological method was found to be localized in the granulosa cells of mature Graafian follicles, growing follicles, primordial follicles and epithelial cells of the fallopian tubes. Mn-SOD was localized in the external theca cells of mature Graafian follicles and the corpus luteum. The activity of SOD estimated by the modified nitroblue tetrazolium method was consistent with the immunohistological localization of both SODs. We considered that oxygen radicals and SODs play an important role in rat ovulation, and Cu,ZN-SOD and Mn-SOD have a different localization and action in the rat ovary.

Animals↗
PubMed1992

[Induction of manganese superoxide dismutase in ovarian carcinoma].

A monoclonal antibody against manganese superoxide dismutase (Mn-SOD) was assessed for its use in detecting a marker for epithelial ovarian carcinoma. An enzyme-linked immunosorbent assay has been developed to detect serum Mn-SOD. With this assay, only 1.7% of the 240 healthy females tested had more than 130 ng per milliliter of serum Mn-SOD. In contrast, 39 of 66 patients (59.1%) with epithelial ovarian carcinoma showed high levels of Mn-SOD. The serum Mn-SOD increased according to the clinical stage and declined to reflect the effect of therapy. The determination of Mn-SOD levels proved to be a clinical useful marker for monitoring the response to treatment and to early detection of the recurrence of epithelial ovarian carcinomas.

Adolescent↗
PubMed1992

Organization of cortical cytoskeleton of cultured chromaffin cells and involvement in secretion as revealed by quick-freeze, deep-etching, and double-label immunoelectron microscopy.

We have studied the organization of the cytoskeleton in both unstimulated and stimulated cultured chromaffin cells, as well as its relationship with their secretory process by exocytosis. We found the spatial heterogeneity in the intensity of cortical rhodamine-phalloidin staining within a cell. The overall staining pattern or intensity was minimally altered after stimulation, although dopamine-beta-hydroxylase (DBH) antigen, a marker for the chromaffin granule membrane, was exposed preferentially on the plasma membrane areas with lower intensity of rhodamine-phalloidin staining. Using the quick-freeze, deep-etch technique, we found the heterogeneity in the organization of cortical cytoskeletal networks--some regions have actin filament bundles running parallel to the plasma membrane interspersed between granules and the plasma membrane, while others have few actin filaments beneath the plasma membrane before stimulation. Actin filaments were rarely observed in the inner cytoplasm. We did not observe the overall change in its organization after stimulation. Double-label immunogold EM using anti-DBH antibody and anti-actin antibody combined with statistical analysis showed that (1) DBH was exposed on the plasma membrane preferentially where actin was sparse after stimulation (significant at less than 0.1%), although (2) regions having sparse actin were not always the sites for DBH exposure, and (3) the cortical actin zone was sometimes disrupted at the DBH-exposed sites after stimulation. The present data suggested that (1) secretion is related to heterogeneous organization of cortical cytoskeleton after stimulation and (2) massive synchronized reorganization of the cytoskeleton in the whole cell is not necessary for secretion, although small changes of the cytoskeleton might occur under local regulation at each exocytotic site at the moment of the release.

Actins↗
PubMed1991

Sympathetic inhibition and attenuation of spontaneous hypertension by PVN lesions in rats.

To determine whether the paraventricular nucleus (PVN) contributes to the development of hypertension in spontaneously hypertensive rats (SHR), we compared cardiovascular responses to ganglionic blockade with hexamethonium or vasopressin antagonism with dPVAVP in sham-operated or PVN lesioned SHR and Wistar-Kyoto rats (WKY). Lesions were produced electrolytically when the rats were 5 weeks old. During the next 3 weeks, tail-cuff measurements showed that the development of hypertension in SHR was inhibited, while systolic pressure in WKY was unaffected. Mean pressures recorded directly from the femoral artery at 8 weeks of age were lower in lesioned than in sham-operated SHR (141 +/- 5 vs 110 +/- 3 mm Hg, P less than 0.05), but did not differ in corresponding WKY groups (110 +/- 4 vs 112 +/- 5 mm Hg). Depressor responses to ganglionic blockade induced by i.v. injection of hexamethonium (25 mg/kg) were significantly larger in sham-operated than in lesioned SHR (-41 +/- 4% vs -28 +/- 3%, P less than 0.05). By contrast, vasopressin antagonism with dPVAVP did not alter blood pressure in all rat groups. In 24-h urine samples, excretion of vasopressin was unaffected, but that of norepinephrine was significantly reduced in lesioned SHR. These findings suggest that the PVN contributes to the development of spontaneous hypertension by sympathetic activation without increasing vasopressin secretion.

Animals↗
PubMed1991

Effect of environmental stress on release of norepinephrine in posterior nucleus of the hypothalamus in awake rats: role of sinoaortic nerves.

Norepinephrine(NE) release in posterior nucleus(PH) of the hypothalamus was examined before and during acute shaker (oscillation) stress in sinoaortic denervated(SAD) and sham-operated(SO) rats. NE in PH extracellular fluid of freely moving rats was collected by microdialysis and measured by sensitive radioenzymatic assay. Three days after SAD or SO operation, mean arterial pressure(MAP) and heart rate(HR) were significantly higher in SAD rats than SO rats. Baseline levels of NE in PH dialysate were also significantly elevated in SAD rats. Although five minutes of shaker stress elicited pressor and tachycardic responses coupled with increased NE release in PH of both groups, the increases in MAP and dialysate NE were larger in SAD than SO rats. These findings indicate that noradrenergic neurons in the PH respond to stress-induced stimuli and receive tonic input from baroreflex pathways.

Animals↗