Biomedical subjects

C Tanaka

Publications and source records attributed to C Tanaka.

493 records · Page 28Linked to original sources

PubMedDate not supplied

Neurochemical and pathological alterations following infusion of leupeptin, a protease inhibitor, into the rat brain.

It is known that proteases participate in cellular protein turnover and eliminate abnormal and potentially toxic proteins. Disturbed proteolysis may be responsible for generating the pathological features of some neurodegenerative disorders. Alzheimer disease, for instance, is the most common neurodegenerative disorder and a condition in which proteins of the cell membrane and cytoskeleton are abnormally processed and accumulated in the brain. It is of interest to investigate the effect of protease inhibitors on neurons and neurotransmitter systems in the brain. We examined neurochemical and morphological neuronal changes in the rat brain following long-term intracerebroventricular infusion of leupeptin, a potent calcium-activated protease (calpain) inhibitor. Leupeptin (5 mg) was infused into the lateral ventricle using an osmotic minipump for 14 days. We found a significant reduction of regional choline acetyltransferase activities in the hippocampus, and of somatostatin concentrations in the hypothalamus and entorhinal cortex. Moreover, leupeptin caused a wide-spread, highly significant decrease in neuropeptide-Y concentrations. Leupeptin infusion produced severe degeneration of neuronal processes in both axons and dendrites, and accumulation of electron-dense bodies in the hippocampus. The results indicate that long-term intracerebroventricular infusion of leupeptin in the rat produces neurochemical and morphological changes resembling those of some neurodegenerative disease and aging. Abnormal proteolysis caused by either reduced protease or enhanced protease inhibitor activities might play an important role in these conditions.

Animals↗

PubMedDate not supplied

Prenatal management of fetal cardiac tumors. Two case reports.

Although primary cardiac tumors are extremely rare, their prenatal and neonatal management is very important because fetal arrhythmia is a frequent complication and such tumors may be the only manifestation of tuberous sclerosis. We present 2 cases of fetal cardiac tumor in which cardiac function was assessed by color Doppler ultrasonography. In both cases, there was no evidence of tuberous sclerosis or cardiac failure and tumor regression was noted 8 months after birth. Ultrasonographic examination of fetal cardiac function was useful in the management of these tumors.

Adult↗

PubMedDate not supplied

Proton NMR relaxation times in ischemic brain edema.

The state of water in cerebral ischemia was studied by using the proton nuclear magnetic resonance (1H-NMR) method. Cerebral ischemia was induced experimentally in Mongolian gerbils by unilateral ligation of the common carotid artery. Longitudinal (T1) and transverse (T2) relaxation times of the ischemic brain were measured with a pulse FT-NMR spectrometer and the water content was determined by the wet/dry method. Quantitative analysis of the relaxation times was performed sequentially during the initial 7 hours following ligation and the data were compared with those of brain edema previously reported by S. Naruse in the rat. Characteristic findings in brain ischemia include prolongation of the slow component of T2 and increase in the water content. A quantitative comparison of relaxation rate and water content demonstrates that ischemic brain edema in Mongolian gerbils is different from cytotoxic and vasogenic types of brain edema. When R2 (1/T2) was plotted against the water content, the slope value of ischemia in the gerbil was between the slope values of the TET intoxication and cold injury induced edemas reported previously. From these results, it might be said that ischemic brain edema includes both the cytotoxic and vasogenic types of brain edema. Glycerol was demonstrated to affect brain ischemia by decreasing the water content and by shortening the slow component of T2. By analysis of the relaxation times and water content, we examined the pathophysiological characteristics of water molecules in ischemic brain tissue.

Animals↗

PubMedDate not supplied

Transmembrane signalling systems in the brain of patients with Parkinson's disease.

The clinical efficacy of dopamine (DA) replacement therapy for patients with Parkinson's disease (PD) depends on the preservation of postsynaptic DA receptors and their intracellular signalling mechanisms in the striatum long after degeneration of the nigrostriatal DA pathway. DA activates adenylyl cyclase (AC) and phospholipase C (PLC) via the D1 receptor, and inhibits through the D2 receptor, thereby regulating the production of intracellular second messengers, cyclic adenosine 3',5'-monophosphate (cAMP), 1,2-diacylglycerol (DAG) and Ca2+. Recent advances in molecular biology have made it possible to monitor the intracellular signal transduction cascade following receptor activation by various transmitters. The authors review the literature addressing this issue, summarized as follows: (1) striatal D1 and D2 receptor densities remain constant, at least in treated and non-demented patients; (2) DA-sensitive AC activity appears to be increased in the putamen of treated patients, although this remains to be confirmed; (3) levels of cAMP-dependent protein kinase (PKA) are normal in non-demented patients, consistent with unchanged levels of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32,000); (4) levels of Ca2+/phospholipid-dependent protein kinase (PKC) and of inositol 1,4,5-trisphosphate (InsP3) receptor also remain unchanged in non-demented patients; (5) the above three second messenger sites as well as densities of D1 and D2 receptors are decreased in the striatum of demented PD patients (PDD). We tentatively conclude that postreceptor signalling function is intact in the striatum of non-demented PD patients and that there is a clear difference between non-demented patients and PDD, i.e. striatal dopaminoceptive neurons are affected in PDD.

Brain↗

PubMedDate not supplied

Circulating levels of endostatin in cancer patients.

Endostatin is a negative regulator of angiogenesis. We examined plasma endostatin levels (PESLs) in cancer patients and healthy controls. PESLs were detected by competitive enzyme immunoassay in 147 patients with primary breast cancer, 44 patients with other histological types of cancer, 26 patients with recurrent breast cancer, 17 patients with benign breast disease and 221 healthy controls. PESLs were elevated in those patients with cancer or benign breast disease. In patients with primary breast cancer, significantly higher PESLs were found in post-menopausal patients than in pre-menopausal patients (p<0.01), although there were no differences in the other clinicopathological characteristics evaluated. PESLs in primary breast cancer patients did not change after surgery, but they increased after administration of the adjuvant tamoxifen. When we applied an age-matched cut-off value as a mean of the values for the female controls, we found that node-negative breast cancer patients with high PESLs had a significantly more favorable relapse-free survival time than those with low PESLs (p<0.05, log-rank test). Our data demonstrate that PESLs are detectable in healthy controls, and that cancer patients have elevated PESLs. A larger study is warranted to clarify the clinical significance of circulating endostatin.

Adult↗

PubMedDate not supplied

[Paradoxical embolism with Chiari network, subsequently being accompanied by probable incomplete infarction: a case report].

We presented a patient of paradoxical embolism with Chiari network, subsequently being accompanied by probable incomplete infarction. This 21-year-old man suffered from consciousness disorder, aphasia and right hemiparesis, and hospitalized in November 6, 1999. Magnetic resonance imaging showed mixed intensity on T1 and T2-weighted images in part of the areas of the left anterior and middle cerebral arteries. Cerebral angiography revealed the early venous fillings and the capillary blushs. These findings implicated stroke in young adult. Still more transcranial color-flow imaging showed high intensity transient signals with "Chirp" sounds on the left middle cerebral artery. Transesophageal echocardiography detected Chiari network. Chiari network was thought the course of cerebral infarction. Over again 123I-IMP single-photon emission CT findings revealed the marked reduction of his cerebral blood flow comprehensively in the left hemispherium. It was suggested that the recanalization after the paradoxical cerebral embolism had caused incomplete infarction.

Adult↗

PubMedDate not supplied

Nor-binaltorphimine: a potent and selective kappa-opioid receptor antagonist with long-lasting activity in vivo.

The kappa-receptor selectivity of nor-binaltorphimine (nor-BNI), a highly selective kappa-opioid receptor antagonist in vitro, was examined in vivo by measuring the time course of the antagonistic action of nor-BNI (5 and 20 mg/kg, s.c.) against the responses to U-50488H (10 mg/kg, s.c.), morphine (10 mg/kg, s.c.) and fentanyl (50 micrograms/kg, s.c.) in mice. In the tail pinch test, nor-BNI partially antagonized morphine and fentanyl analgesia, but not U-50488H analgesia in the first 30 min after s.c. administration. However, the kappa-antagonistic action gradually increased, reaching a plateau at 2 hr. This antagonistic action was maintained for at least 4 days. In contrast, the mu-antagonistic action declined to the control level at 2 or 4 hr after nor-BNI administration. In the acetic acid-induced writhing test, nor-BNI also exerted a more potent and selective kappa-antagonistic action at 24 hr than at 1 hr after its s.c. administration. Nor-BNI also showed a long-lasting kappa-antagonism against the hyperthermic response induced by U-50488H (5 mg/kg, s.c.). Thus, we found that nor-BNI is a slow-onset, long-lasting, selective kappa-antagonist in vivo.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗