Search PubMed⌕ Search

Biomedical subjects

T Kawada

Publications and source records attributed to T Kawada.

At least 127 records · Page 7Linked to original sources

Effect of running training on brown adipose tissue activity in rats: a reevaluation.

The effect was investigated of running training on the thermogenic activity of brown adipose tissue (BAT) in rats. The exercised rats were trained on a rodent treadmill for 5 days per week and a total of 9 weeks. After the training, a significantly lower rate of increase in body weight was found, suggesting some training effect, whereas the training failed to induce a decrease in BAT mass. As previously reported (Yamashita, Yamamoto et al., 1993), there was also a markedly lower expression of uncoupling protein (UCP) mRNA in BAT from trained rats; nevertheless, no definite effect of the running training was noted on either UCP content or guanosine 5'-diphosphate binding in the mitochondria recovered from BAT. The results obtained suggest that running training has no overt effect on the thermogenic activity of BAT in rats.

Adipose Tissue, Brown↗

[Radiobiological considerations for stereotactic irradiation].

Stereotactic radiosurgery (SRS: stereotactic irradiation [STI] delivered in a single high dose) was initially developed by Leksell for non-malignant brain lesions, but there has been increasing interest in using it to treat small primary brain tumors or metastases. In more recent years, stereotactic radiotherapy (SRT: fractionated STI) has been developed, but radiobiological factors have not been sufficiently evaluated in relation to these techniques. Larson classified potential STI targets into four categories according to whether the target tissue is early- or late-responding and whether it is embedded within or only surrounded by normal tissue. We have actually calculated biologically effective doses for these categories to determine the indications for SRS and SRT, and to be able to choose suitable SRT schedules. Based on our calculations, theoretically SRS would be recommended for AVMs and benign tumors having distinct margins separating them from surrounding normal tissue and SRT would be recommended for low or high grade astrocytomas without clearly defined boundaries and metastasis. Recommended SRT schedules would be 49 Gy/7 fractions, 52 Gy/8 fractions or 54.9 Gy/9 fractions completed within 2 weeks. However, clinically, these indications and SRT schedules should be modified according to the many other factors involved in individual cases, such as tumor size, presence of tumor necrosis, the patient's general condition, prognosis, and so on.

Brain↗

[Lipid metabolism related nuclear receptor--the structure, function, expression and classification of peroxisome proliferation-activated receptor (PPAR)].

Peroxisome proliferator-activated receptors (PPARs) belongs to the nuclear hormone receptor superfamily. So far three different subtypes of PPAR (alpha, gamma, and delta (beta)) have been identified in amphibians, chicken, rodents and man. These receptors are transcription factors that control the beta-oxidation and transport pathways of fatty acids and adipocyte differentiation containing fatty acid synthesis under the modification of PPAR activation with CBP and its analogs. Thus, PPARs play an important role in lipid metabolism. Furthermore, altered fatty acid levels are associated with obesity, diabetes, hypertension and atherosclerosis, so PPARs may serve as molecular sensors in these metabolic disorders.

Activating Transcription Factor 2↗

[Schedule of stereotactic radiotherapy: a study considering the factors of repair and cell proliferation].

Stereotactic radiosurgery (SRS: stereotactic irradiation [STI] delivered in a single high dose) was initially developed by Leksell for non-malignant brain lesions, but there has been increasing interest in using it to treat small primary brain tumors or metastases. Recently, stereotactic radiotherapy (SRT: fractionated STI) has been recommended on the basis of radiobiological considerations for tumors in which both normal glial cells and tumor cells reside within the tumor margin. Strangely, the factors 'repair' and 'cell proliferation' have been neglected in the radiobiological evaluations of STI reported so far, mainly because of the complexity of the calculations. 'Half-time repair' which is the key value in the 'repair' factor may be larger for nervous tissue than for many other normal tissues because nerve cells have decreased ability to recover from damage. 'Cell proliferation' should be an important factor when the total radiation period is extended by applying SRT. In this study, we created models based on estimated 'half-time repair' and 'cell doubling time' and attempted to determine optimal SRT schedules. When repair and cell proliferation factors are also taken into consideration, the recommended SRT schedules would be 7 Gy x 7 fractions every other day for malignant tumors and 3.5 Gy x 12 fractions every other day for benign tumors. However, clinically, these schedules should be modified according to factors in individual cases, e. g., tumor size, presence of tumor necrosis, the patient's general condition, prognosis, and so on.

Brain↗

[A severe case of acute autonomic and sensory neuropathy].

Acute autonomic and sensory neuropathy (AASN) is a rare neuropathy characterized by acute autonomic dysfunction and objective sensory disturbances. A 26-year-old pregnant woman with severe autonomic and sensory dysfunction is reported. This patient suddenly developed marked nausea and vomitting in about 2 days after having a sore throat. She then developed signs of autonomic dysfunction including dilated non-reactive pupils, dryness of the eyes and oral mucous membranes, generalized anhidrosis, paralytic ileus, orthostatic hypotension, and continuous tachycardia. She also had severe generalized sensory impairments of all modalities, and all deep tendon reflexes were absent. Sensation was almost totally lost for all modalities below the neck. There was marked pseudoathetosis and sensory ataxia in all extremities. Motor examination was normal. She had inability to urinate. At this time she was 38 weeks pregnant, and when she showed signs of fetal distress, a Caesarean section was performed. Albumino-cytological dissociation was seen in the CSF. Serum noradrenaline was reduced, no sensory nerve action potentials could be elicited, and reduced coefficient of variation of the R-R interval on electrocardiography was observed. Plasma exchange was performed every other day for 3 days for about 3 weeks after the onset of the illness, but no favorable effects. Seven months after the onset, her autonomic dysfunction slightly improved, but there was no recovery from the sensory disturbances. Many symptoms and signs that characterize AASN occurred in this patient, and each was severe. The patient developed SIADH, sleep apnea, personality change, and amenorrhea in the course of the disease. We suggest that AASN patients might have both peripheral and central nervous system manifestations including seizures and personality changes.

Acute Disease↗

Expression of the putative membrane fatty acid transporter (FAT) in taste buds of the circumvallate papillae in rats.

The putative membrane fatty acid transporter (FAT) protein and its mRNA, originally expressed in adipose tissue, were found in the tongue of rats. Northern blot analysis showed a significant expression of FAT mRNA in the epithelial layer of circumvallate papillae. Immunohistochemical staining revealed that immunoreactivity for FAT is specifically localized in the apical part of taste bud cells, possibly gustatory cells, in the circumvallate papillae.

Animals↗

High-performance liquid chromatographic measurement of urocanic acid isomers and their ratios in naturally light-exposed skin and naturally shielded skin.

We have developed methods for sampling and extraction of trans-urocanic acid and cis-urocanic acid from human skin, and subsequent high-performance liquid chromatographic measurement of these isomers. Sampling involves applying cellophane adhesive tape to the skin for 10 s. Urocanic acid isomers were completely extracted by immersing the tape in KOH solution. The HPLC column was a Tosoh ODS 80TS (250x4.6 mm I.D., 7 microm average particle size) eluted with 20 mM potassium dihydrogenphosphate containing 1 g/l sodium heptanesulphonate (pH 3.7)-acetonitrile (93:7, v/v) at a flow-rate of 1.0 ml/min. The isomers were detected by UV absorbance at 264 nm. This technique was used to analyze the ratio of trans-urocanic acid/cis-urocanic acid on human skin at various sites on the body. It was found that the ratio was low in naturally light-exposed skin and high in naturally shielded skin.

Adult↗

omega-Conotoxin GVIA and desipramine insensitive norepinephrine efflux from cardiac sympathetic nerve terminal.

Using dialysis technique, prominent accumulation of norepinephrine (NE) in the myocardial interstitial space was observed under local administration of a monoamine oxidase inhibitor (pargyline, 10 mM), and a vesicle uptake inhibitor (reserpine, 10 microM). Accumulation of NE in the myocardial interstitial space was associated with a reduction of dihydroxyphenylglycol levels. Pretreatment with omega-conotoxin GVIA (10 microM) or desipramine (10 microM) did not suppress this response. A brisk increase in dialysate NE levels might occur as a consequence of exocytotic or neurotransporter insensitive efflux of NE.

Adrenergic Fibers↗

High-performance liquid chromatographic determination of myocardial interstitial dihydroxyphenylglycol.

This study describes a high-performance liquid chromatographic method with electrochemical detection (HPLC-ED) for monitoring dihydroxyphenylglycol (DHPG) in the myocardial interstitial space. Using a cardiac dialysis technique, 10-microl dialysates were sampled from the myocardial interstitial space (1-min fractions) and were injected directly into the HPLC-ED system. The in vitro quantification limit for DHPG was 250 fg in a 10-microl injection. The basal DHPG concentration of dialysate was 181+/-46 pg/ml. This system offers a new possibility for monitoring myocardial interstitial DHPG levels.

Animals↗

cGMP-kinase mediates cGMP- and cAMP-induced Ca2+ desensitization of skinned rat artery.

(Rp)-8-Bromo-guanosine 3',5'-cyclic monophosphorothioate (Rp-8-Br-cGMPS) inhibited competitively both isozymes of type I alpha and I beta cGMP-dependent protein kinase (cGMP-kinase) purified from porcine aorta with apparent Ki values (microM) of 3.7 for I alpha and 1.8 for I beta. The compound also inhibited bovine heart type II cAMP-dependent protein kinase (cAMP-kinase), but with a Ki of 25 microM. Thus, it is a selective inhibitor of cGMP-kinase. In alpha-toxin-skinned smooth muscle preparations from rat mesenteric artery, 8-Br-cGMP (10(-7) M) and 8-Br-cAMP (10(-6) M) produced a rightward shift of the concentration-contraction curves for Ca2+, denoting a decrease in Ca2+ sensitivity of the contractile elements. The shift by 8-Br-cAMP as well as by 8-Br-cGMP was completely reversed by Rp-8-Br-cGMPS, while a selective inhibitor of activation of cAMP-kinase, (Rp)-adenosine-3',5'-cyclic monophosphorothioate (Rp-cAMPS), was without effects on the shift produced by these two compounds. These findings indicate the pivotal role that the activation of cGMP-kinase plays in the production of a decrease in Ca2+ sensitivity of contractile elements.

8-Bromo Cyclic Adenosine Monophosphate↗

Radiotherapy for centrally recurrent cervical cancer of the vaginal stump following hysterectomy.

PURPOSE: This study was performed to establish the classification and the treatment modality for recurrent cervical cancer of the vaginal stump after hysterectomy. PATIENTS AND METHODS: Ninety patients with centrally recurrent cervical cancer of the vaginal stump following hysterectomy were treated with high-dose-rate intracavitary brachytherapy with or without external irradiation. The intervals between primary surgery and vaginal recurrences varied from 3 months to 36 years. Tumor size of the vaginal stump was determined by bimanual rectovaginal examination at the time of recurrence and was classified into three groups, i.e., small (no palpable tumor), medium (less than 3 cm), and large (3 cm or more). RESULTS: The 10-year survival rates for all patients were 52%. Survival was greatly influenced by the tumor sizes of the vaginal stump. The 10-year survival rates of patients with small, medium, and large size tumors were 72, 48, and 0%, respectively. All patients with large size tumors died within 5 years. Of 90 patients, 75 (83%) were determined by physical examination to be free of tumor on at least one visit within 2 months of the completion of treatment (CR). The remaining 15 patients (17%) had physical findings suggestive of residual tumor (Residual). The overall 10-year survival rate for all patients with CR was 63%, compared with 10% for the patients with Residual (P < 0.0001). The incidences of distant metastases of the patients with or without local failure were 55 and 13%, respectively (P < 0.0001). The patients with local failure had significantly higher incidence of metastases. Most patients with small size tumor were treated with brachytherapy alone, and the survival rates of these patients were not improved by combination with external irradiation. CONCLUSION: These results suggest that tumor size was a significant prognostic factor for recurrent cervical cancer of the vaginal stump. Patients with small size tumors were recommended to be treated with brachytherapy alone.

Adult↗

Caffeine enhances modulation of parasympathetic nerve activity in humans: quantification using power spectral analysis.

We investigated changes in autonomic nerve activity following caffeine intake by power spectral analysis of R-R intervals of heartbeats in humans. A beverage containing 240 mg of caffeine or a control beverage was given to 10 healthy volunteers, and R-R intervals were measured while subjects were sitting and controlling their respiration at a constant rate. After consumption of the caffeine-containing beverage, a transient and significant increase (P < 0.001) in spectral integrated values (areas under the curve) of high frequency power (high component, HC) was observed, and at 30 min the value was significantly greater than in controls (P < 0.02), suggesting an increase in vagal autonomic nerve activity. The effect of caffeine was also examined using decaffeinated coffee supplemented with exogenous caffeine (2 mg/kg body wt). A transient and significant increase (P < 0.0001) in HC was observed, and the value was significantly greater (P < 0.02) than when subjects consumed decaffeinated coffee without supplemental caffeine. The ratio of HC to total integrated value (which is also used as a selective indicator of vagal activity) was also significantly higher (P < 0.04) after caffeine consumption. Physiological variables accompanying the change in autonomic nerve activity (i.e., blood pressure, surface body temperature and heart rate) were not significantly affected by caffeine intake. These results suggest that power spectral analysis of heartbeat R-R intervals is an effective and noninvasive method for detecting subtle changes in autonomic nerve activity in response to food intake.

Adult↗

Changes in levels of mRNAs for cell wall-related enzymes in growing cotton fiber cells.

mRNAs for cell wall-related enzymes in developing cotton fiber cells were measured by reverse transcription-PCR analysis. Both endo-1,4-beta-glucanase and expansin mRNA levels were high during cell elongation but decreased when cell elongation ceased, and xyloglucan decreased. The endo-1,3-beta-glucanase mRNA level was very low in the elongating cells but increased gradually at the onset of secondary wall synthesis, accompanying the massive deposition of cellulose. Endoxyloglucan transferase and sucrose synthase mRNA levels were constant during all stages of growth.

Cell Wall↗

A new, concise dialysis approach to assessment of cardiac sympathetic nerve terminal abnormalities.

We applied a dialysis technique to the hearts of anesthetized cats and examined whether the concentration of dialysate norepinephrine (NE) reflected NE disposition at the cardiac sympathetic nerve terminals. Dialysis probes were implanted in the left ventricular wall, and dialysate NE concentrations were measured as an index of myocardial interstitial NE levels. Stimulation of stellate ganglia significantly increased dialysate NE responses that were suppressed by local administration of an NE-releasing inhibitor (omega-conotoxin GVIA, 10 microM). Increments in basal dialysate NE levels were correlated with concentrations of a locally administered neuronal uptake blocker (desipramine; 1, 10, and 100 microM). Desipramine (100 microM) augmented stimulation-induced dialysate NE responses. Local administration of a neuronal vesicle uptake blocker (reserpine, 1 and 10 microM) did not alter dialysate NE levels but increased dialysate dihydroxyphenylglycol levels. An NE-releasing amine (tyramine, 100 microg/ml) was locally administered to examine NE storage capacity at the nerve terminal. The tyramine-induced NE-releasing response was completely abolished by pretreatment with reserpine (1 mg/kg i.p.). Thus cardiac dialysis with local administration of a pharmacological tool offers a new, concise approach to assessment of neuronal NE release, uptake, vesicle uptake, and storage capacity by cardiac sympathetic nerve terminals.

Animals↗

Dynamic vagosympathetic interaction augments heart rate response irrespective of stimulation patterns.

We previously demonstrated that tonic stimulation of either the sympathetic or the vagal nervous system augmented the dynamic heart rate response to the other of the two systems. We characterized the phenomenon as bidirectional augmentation of heart rate regulation. The question remained unanswered, however, as to whether such augmentation could occur under simultaneous dynamic stimulation of the two systems. The transfer characteristics from nerve stimulation to heart rate were well described by linear systems analysis, although no attention was paid to the aphasic nature of the stimuli in relation to each R-R interval. When we stimulated the two nerves with statistically independent Gaussian white noises, gain of the transfer function increased by 63.2 +/- 47.4% relative to individual stimulation (P < 0.05). When we stimulated the two nerves with mutually reciprocal Gaussian white noises, gain of the transfer function increased by 54.9 +/- 49.1% (P < 0.05). Thus simultaneous dynamic stimulation of the sympathetic and vagal systems bidirectionally augmented heart rate regulation irrespective of the pattern of the stimulation signals.

Animals↗

Inhibition of NO synthesis minimally affects the dynamic baroreflex regulation of sympathetic nerve activity.

The purpose of this investigation was to examine the role of nitric oxide (NO) in the dynamic baroreflex regulation of cardiac sympathetic nerve activity. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses before and after the intravenous administration of NG-monomethyl-L-arginine. We characterized the dynamic properties relating carotid sinus pressure input to sympathetic nerve activity by means of a transfer function analysis. NG-monomethyl-L-arginine decreased the corner frequency of the transfer function (0.100 +/- 0.054 vs. 0.074 +/- 0.035 Hz; P < 0.05), whereas other parameters such as the steady-state gain and transmission lag time remained unchanged. Although cursory examination of these findings would suggest a possible contribution of NO in the dynamic baroreflex regulation of sympathetic nerve activity, quantitative assessment of the transfer function reveals only a minimal effect on the baroreflex regulation of arterial pressure, particularly under closed-loop conditions. We conclude that NO noticeably affects the dynamic baroreflex regulation of sympathetic nerve activity. However, it may not significantly affect arterial pressure regulation through central modulation of the carotid sinus baroreflex.

Animals↗

Inhibition of NO synthesis does not potentiate dynamic cardiovascular response to sympathetic nerve activity.

We examined whether the inhibition of nitric oxide (NO) synthesis potentiates the dynamic sympathetic regulation of the cardiovascular system through the baroreflex. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses to evoke random changes in sympathetic nerve activity (SNA). We estimated the transfer functions from SNA to both aortic pressure (AoP) and heart rate (HR). The inhibition of NO synthesis by NG-monomethyl-L-arginine (L-NMMA, 40 mg/ kg) altered neither the transfer function from SNA to AoP nor that from SNA to HR. In contrast, sodium nitroprusside (3-6 micrograms.kg-1.min-1) significantly decreased the steady-state gain (40.3 +/- 11.7% of the control, P < 0.05) of the transfer function from SNA to AoP without affecting the HR responses. We conclude that the basal release of NO may have a role in the tonic blood pressure regulation, whereas it may not be involved in the dynamic sympathetic regulation of AoP or HR through the baroreflex.

Animals↗