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Biomedical subjects

K Nakai

Publications and source records attributed to K Nakai.

At least 91 records · Page 5Linked to original sources
PubMed2000

Dephosphorylation-induced decrease of anti-apoptotic function of Bcl-2 in neuronally differentiated P19 cells following ischemic insults.

It is known that Bcl-2 has a protective effect against neuronal ischemia. Some reports speculate anti-apoptotic function of Bcl-2 depends not on the expression level but on the phosphorylation state. We found induction of apoptosis and CPP32 activation by energy impairment (3-nitropropionic acid (3-NP)-treatment or glucose-deprivation) in the neuronally differentiated P19 cells. Time course study of cell viability following ischemic insults showed that the number of viable cells decreased along with the increase in the amount of dephosphorylated Bcl-2 without obvious quantitative alteration of the protein. Then, we generated differentiated P19 cells overexpressing wild-type Bcl-2 (P19/wt. Bcl-2) or phosphorylation-negative Bcl-2 mutant (P19/mut.Bcl-2), in which alanine was substituted for serine 70. When the cell viability was examined within 24 h, P19/mut.Bcl-2 was more vulnerable to energy impairment as compared with P19/wt.Bcl-2. In addition, overexpression of wild-type Bcl-2 inhibited DNA laddering and CPP32 activation induced by the insults, while that of mutant Bcl-2 did not. These findings suggest that the phosphorylation state, as well as the expression level, of Bcl-2 plays an important role to modulate its protective effect against ischemic insults.

Animals↗
PubMed2000

Treatment of restenosis after percutaneous transluminal angioplasty for internal carotid artery stenosis.

The efficacy of repeated percutaneous transluminal angioplasty (PTA) and carotid endarterectomy (CEA) was examined in patients with restenosis after PTA for carotid stenosis. After percutaneous transluminal angioplasty (PTA) for 63 cases of internal carotid stenoses 13 cases of restenosis appeared. They were treated by PTA or carotid endarterectomy. The treatment was chosen by the patient after explanation of each treatment. We initially treated seven patients by repeat PTA and six by carotid endarterectomy. The degree of stenosis improved from 82% to 30% on average after repeated PTA. However, one patient in the PTA group had restenosis, and carotid endarterectomy was then performed. The other cases also had restenosis and were treated by PTA. The six cases treated by carotid endarterectomy were successfully treated without difficulty. The success rate of PTA was 5/7 (71%) in the restenosis cases. Patients with a greater residual stenosis after initial PTA had significantly more frequent restenosis. Repeat PTA and CEA both appeared effective treatment for restenosis after initial PTA, although PTA had a restenosis rate similar to that of initial PTA.

Aged↗
PubMed2000

Structuring WAN and LAN for EPR use in community health care.

After describing determinants for the creation of a successfully used community health care network, our new project of making a mechanism fostering steady development of WAN and LAN among community is presented. Most of the difficulties that inhibit the sound development of community health care system are solved.

Community Health Services↗
PubMed2000

Role of phospholipase A2 in cholesterol gallstone formation is associated with biliary phospholipid species selection at the site of hepatic excretion: indirect evidence.

Phospholipase A2 plays a role in cholesterol gallstone development by hydrolyzing bile phospholipids into lysolecithin and free fatty acids. Lysolecithin and polyunsaturated free fatty acids are known to stimulate the synthesis and/or secretion of gallbladder mucin via a prostanoid pathway, leading to enhancing cholesterol crystal nucleation and growth, and therefore, the action of phospholipase A2 is associated, in part, with bile phospholipid fatty acid. To clarify this hypothesis, we evaluated the effect on bile lipid metastability in vitro of replacing phospholipids with lysolecithin and various free fatty acids. Supersaturated model biles were created with an identical composition (cholesterol saturation index, 1.8; egg yolk lecithin, 34 mM; taurocholate, 120 mM; cholesterol, 25 mM) except for 5%, 10%, or 20% replacement of egg yolk lecithin with a combination of palmitoyl-lysolecithin and a free fatty acid (palmitate, stearate, oleate, linoleate, or arachidonate), followed by time-sequentially monitoring of vesicles and cholesterol crystals using spectrophotometer and video-enhanced differential contrast microscopy. Replacement with hydrophilic fatty acids (linoleate and arachidonate) reduced vesicle formation and promoted cholesterol crystallization, whereas an enhanced cholesterol-holding capacity was evident after replacement with hydrophobic fatty acids (palmitate and stearate). These results indicate that the effect of phospholipase A2 on bile lithogenecity is modulated by the fatty acid species in bile phospholipids, and therefore, that the role of phospholipase A2 in cholesterol gallstone formation is dependent, in part, on biliary phospholipid species selection at the site of hepatic excretion.

Bile↗
PubMed2000

Fetal striatal transplants reinstate the electrophysiological response of pallidal neurons to systemic apomorphine challenge in rats with excitotoxic striatal lesions.

Previous studies with single-unit recording and 2-[14C]deoxyglucose quantitative autoradiography have shown that systemic administration of apomorphine increases the functional activity of pallidal neurons, and that the enhancement in the globus pallidus (GP) activity is abolished by striatal lesions. The present study employing electrophysiological techniques tested whether embryonic striatal tissue implanted in the excitotoxically damaged striatum of rats may affect the lesion-induced alteration in the neuronal response of GP to apomorphine. Systemically administered apomorphine significantly increased spontaneously firing rates of GP cells. The blockade of dopamine receptors with haloperidol reversed the increased rate to baseline levels. Quinolinate-induced striatal lesions attenuated the rate-increasing effect of apomorphine. Embryonic striatal grafts placed in the lesioned striatum restored the response of GP cells to systemic apomorphine. The graft-mediated restoration of the GP neuron response to apomorphine were accompanied by an improvement in the motor asymmetry induced by this drug. Considering previous anatomical data to demonstrate extensive innervation of the GP by embryonic striatal grafts, the present results suggest that the grafts reconstruct the functional striatopallidal pathway which is capable of transmitting apomorphine-induced changes in the neuronal activity.

Action Potentials↗
PubMed2000

Apraxia and cerebral haemorrhage: the relationship between haematoma volume and prognosis.

In this study, we examined twenty-five patients with left putaminal haemorrhage to investigate the relations between ideational apraxia (IA) and intracerebral haemorrhage. Apraxias were determined at 1 and 6 months after the stroke onset. Extension and volume of haematoma were examined with CT scan within 2 days of stroke onset. IA was present in 10 cases at 1 month and disappeared in 6 cases (transient IA) and persisted in 4 cases(persisted IA) at 6 months from the onset. Although the haematoma volume related to the existence of IA, there was no significant difference between transient and persistent IA. All three patients with the haematoma volume larger than 40 ml in the transient IA group were younger than 50 years old. All cases with persistent IA were older than 50 years old. Consequently, the existence of IA seems to be partially dependent on the haematoma volume which may cause the organic damage of subcortical white matter. However, patient's age is also important to determine the prognosis of IA. This maybe related to the nature of the haemorrhage and the mode of the onset. These factors remain to be determined.

Adult↗
PubMed2000

An alternative-exon database and its statistical analysis.

We compiled a comprehensive database of alternative exons from the literature and analyzed them statistically. Most alternative exons are cassette exons and are expressed in more than two tissues. Of all exons whose expression was reported to be specific for a certain tissue, the majority were expressed in the brain. Whereas the length of constitutive exons follows a normal distribution, the distribution of alternative exons is skewed toward smaller ones. Furthermore, alternative-exon splice sites deviate more from the consensus: their 3' splice sites are characterized by a higher purine content in the polypyrimidine stretch, and their 5' splice sites deviate from the consensus sequence mostly at the +4 and +5 positions. Furthermore, for exons expressed in a single tissue, adenosine is more frequently used at the -3 position of the 3' splice site. In addition to the known AC-rich and purine-rich exonic sequence elements, sequence comparison using a Gibbs algorithm identified several motifs in exons surrounded by weak splice sites and in tissue-specific exons. Together, these data indicate a combinatorial effect of weak splice sites, atypical nucleotide usage at certain positions, and functional enhancers as an important contribution to alternative-exon regulation.

Algorithms↗
PubMed2000

Factors affecting gallstone recurrence after successful extracorporeal shock wave lithotripsy.

Ninety-six patients treated successively for symptomatic cholelithiasis with extracorporeal shock wave lithotripsy (ESWL) and oral bile acid therapy consisting of ursodeoxycholic acid in daily dosages of 600 mg were prospectively followed for gallstone recurrence for a median of 13 months. Ultrasonography was performed to detect stone recurrence at 3, 6, and 12 months, and then yearly after the termination of therapy. Recurrent stones were found in 17 patients (18%). The cumulative probability of gallstone recurrence was 15.8% at 12 months, 26.1% at 24 months, and 30.7% at 36 months. The probability of stone recurrence over the entire period of observation was not dependent on stone number, whereas the median interval to detection of recurrence was significantly shorter in the patients with multiple stones (2 months) than in those with solitary stones (8 months) (p < 0.05). The rate of impaired gallbladder contractility was higher in patients with recurrence (8/15, 53.3%) when compared with those with no recurrence (15/72, 20.8%) (p < 0.01). Neither age, gender, or stone characteristics predicted stone recurrence. Only one patient with a recurrence reported biliary pain. Of the 15 patients with recurrent stones who opted for further nonsurgical treatment, complete stone disappearance was achieved in 10. Impaired gallbladder function may predict gallstone recurrence after ESWL.

Cholagogues and Choleretics↗
PubMed2000

Genetic polymorphism of 5,10-methylenetetrahydrofolate increases risk of myocardial infarction and is correlated to elevated levels of homocysteine in the Japanese general population.

BACKGROUND: Hyperhomocysteinemia, an independent and graded risk factor for coronary artery disease, can result from both environmental and hereditary factors. C677T mutation of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene [alanine/valine (A/V) polymorphism], one of the key enzymes involved in catalyzing the remethylation of homocysteine, has recently been reported. OBJECTIVE: To evaluate the incidence of the MTHFR genotypes and their significance in determining the risk for myocardial infarction of Japanese men. METHOD: The subjects consisted of 199 healthy men (mean age, 60 years) and 230 male patients with myocardial infarction (mean age, 59 years). The coronary-artery lesions were evaluated by coronary angiography. The MTHFR genotype was analyzed by polymerase chain reaction and then by digestion with Hinfl. Total plasma levels of homocysteine for each MTHFR genotype were compared with those in healthy controls. RESULTS: The prevalences of the A and V alleles among the healthy male subjects were 0.652 and 0.348 in the Hardy-Weinberg equilibrium. The total levels of homocysteine in the plasma of the healthy male subjects were 8.6 +/- 3.3, 8.9 +/- 4.1, and 11.6 +/- 5.6 mumol/l, for AA, AV, and VV genotypes, respectively. Individuals with the VV homozygous mutant genotype thus had the highest plasma levels of homocysteine. Logistic analysis revealed that the levels of high-density lipoprotein cholesterol, hypertension, diabetes mellitus, MTHFR VV genotype, and triglycerides were all independent risk factors for myocardial infarction. The VV genotype was more prevalent among patients with myocardial infarction (mean age, 59 years) than it was among the control subjects (17.0 versus 10.6%, P < 0.05). However, there were no differences in the numbers of stenotic coronary arteries among the MTHFR genotypes. CONCLUSION: The VV genotype of MTHFR increases plasma levels of homocysteine in healthy controls, and this mutation indicates a genetic predisposition toward a greater than normal risk of myocardial infarction for Japanese men.

Cohort Studies↗
PubMed2000

Interhemispheric neuroepithelial cyst associated with agenesis of the corpus callosum. A case report and review of the literature.

This report describes a neonatal case in whom a large interhemispheric cyst associated with agenesis of the corpus callosum was revealed by fetal ultrasonography and demonstrated by MRI to be multilobulated. Endoscopic fenestration of cysts was initially designed in view of the development of the patient's brain and surgical invasiveness. One year later, when motor paresis of the left arm and progressive enlargement of the cyst on MRI were revealed, open surgery was performed. The histological diagnosis was a neuroepithelial cyst with the feature of choroid plexus epithelia. The clinicopathological features of interhemispheric epithelial cysts associated with agenesis of the corpus callosum are reviewed in the light of differential diagnosis and therapeutic considerations.

Agenesis of Corpus Callosum↗
PubMed2000

International harmonization of bioequivalence studies and issues shared in common.

In the course of a review of the current health insurance system in Japan, promotion of the use of generic products of lower price is expected in direction for minifying the drug costs which occupy about 20% thereof. However, the use of generic products has not increased so much as expected. One of the reasons to explain the fact might be that concerns exist about switchability from an innovator product to a generic product or among generic products because of bias in bioequivalence. Namely, hesitation about the difference in quality between generic products and innovator products, particularly in bioequivalence due to differences in the manufacturing process and pharmaceutical technology, exists among professionals in medical practice. The bioequivalence study to guarantee that a generic product is bioequivalent to an innovator product in terms of effectiveness and safety is most important in assuring the quality of generic products. There are various specifications and study methods to prove bioequivalence which differ slightly from one to another in different countries. We have investigated bioequivalence studies which are conducted in the major countries. Consequently, we clarified that bioequivalence studies are in international harmonization in terms of the major portions thereof. However, different conditions, e.g., selection of subjects, food effect, application of multiple dose study, and in vitro dissolution study, are still employed for the studies. Therefore, we consider that these differences constitute the topics to be reviewed in future.

Biological Availability↗
PubMed2000

New bioequivalence studies: individual bioequivalence and population bioequivalence.

The bioequivalence study which is currently conducted in different countries is the so-called average bioequivalence approach; this approach has been indicated to be insufficient for assessing switchability between two formulations (i.e., from the reference formulation to the test formulation). In the U.S., therefore, the population bioequivalence approach and the individual bioequivalence approach were recently proposed as the studies which would replace the current average bioequivalence approach. The average bioequivalence approach compares only the mean parameters of the test and reference formulations in the subject groups which received them. In contrast, the population bioequivalence approach guarantees prescribability by assessing the total variances of bioavailability values of the test and reference formulations in addition to the average bioequivalence. The individual bioequivalence approach guarantees switchability from the reference formulation to the test formulation by assessing the intrasubject variance and subject-by-formulation interaction in addition to the average bioequivalence. We introduce the individual bioequivalence approach and the population bioequivalence approach in comparison with the current average bioequivalence approach and have discussed the characteristics and issues of each of these three bioequivalence approaches.

Biological Availability↗