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Biomedical subjects

K Nakai

Publications and source records attributed to K Nakai.

At least 73 records · Page 4Linked to original sources
PubMed2001

Unilateral spatial neglect associated with chronic subdural haematoma: a case report.

A 69-year-old right-handed man who exhibited unilateral spatial neglect in association with a chronic subdural haematoma, presented with mild left arm and leg weakness first noted 4 weeks prior to admission. Neurologic examination on admission revealed a mild left hemiparesis, including the face. Neuropsychologic examination revealed left unilateral spatial neglect, but no language disturbance. Minimal support was necessary to maintain activities of daily living. Computed tomography revealed a large right temporoparietal, extraaxial hypodense fluid collection containing scattered hypodense foci. The haematoma was evacuated via a right parietal burr hole. Following surgery, the patient dramatically improved neurologically and neuropsychologically, as well as in independent performance of daily activities. It is suggested that the improvement in ADL provides a behavioural correlate of improvement in the latter, represented a behavioural correlate of improved cerebral function, and that either direct compression by the chronic subdural haematoma or an interhemispheric pressure difference had caused unilateral spatial neglect. Such neglect is an unusual consequence of chronic subdural haematoma.

Activities of Daily Living↗
PubMed2001

Expression of c-fos, heat shock protein 70, neurotrophins, and cyclooxygenase-2 mRNA in response to focal cerebral ischemia/reperfusion in rats and their modification by magnesium sulfate.

The marginal area surrounding a region of ischemic brain tissue, designated as the penumbra, is of interest as a potential area for the rescue of neurons from cell death. Despite its clinical importance, relatively little is known about the molecular events leading to changes in brain cells in the penumbra following ischemia. In the first part of this study, we used in situ hybridization to investigate the temporal and spatial expression of c-fos, heat shock protein 70 (HSP70), neurotrophins and inducible cyclooxygenase-2 (COX-2) in the rat brain following a 2-h occlusion of the middle cerebral artery (MCA) with reperfusion. In the penumbra and surrounding cortex, upregulation of c-fos, brain-derived neurotrophic factor (BDNF), and COX-2 mRNAs was observed, while expression of HSP70 mRNA was restricted to the penumbra. This spatial discrepancy of mRNA expression suggests that different mechanisms are involved in the regulation of c-fos/BDNF/COX-2 and HSP70 expression. Intravenous infusion of magnesium sulfate (25 mg/kg) decreased both the infarct volume and upregulation of these mRNAs, suggesting its therapeutic potential.

Animals↗
PubMed2001

ORI-GENE: gene classification based on the evolutionary tree.

MOTIVATION: Genome projects have produced large amounts of data on the sequences of new genes whose functions are as yet unknown. The functions of new genes are usually inferred by comparing their sequences with those of known genes, but evaluation of the sequence homology of individual genes does not make the most of the available sequence information. Therefore, new methods and tools for extracting more biological information from homology searches would be advantageous. RESULTS: We have developed a computational tool, ORI-GENE, to analyze the results of sequence homology searches from the perspective of the evolution of selected sets of new genes. ORI-GENE has a graphical interface and accomplishes two important tasks: first, based on the output of homology searches, it identifies species with similar genes and displays their pattern of distribution on the phylogenetic tree. This function enables one to infer the way in which a given gene may have propagated among species over time. Second, from the distribution patterns, it predicts the point at which a given gene may have been first acquired (i.e. its 'origin'), then classifies the gene on that basis. Because it makes use of available evolutionary information to show the way in which genes cluster among species, ORI-GENE should be an effective tool for the screening and classification of new genes revealed by genome analysis. AVAILABILITY: ORI-GENE is retrievable via the Internet at: http://www.rtc.riken.go.jp/jouhou/ORI-GENE.

Animals↗
PubMed2001

Supercharged gastric tube pull-up procedure for total esophageal reconstruction.

Total esophageal reconstruction using a gastric tube is complicated because it sometimes causes postoperative complications such as anastomotic leakage, stenosis, or fistula formation resulting from insufficient blood flow at the distal end. To overcome this problem, during the past 5 years the authors performed seven additional microvascular anastomoses using the short gastric vessels of the gastric tube. No postoperative complications occurred except partial tracheal necrosis in 1 patient. Postoperative radiographic examination showed no reflux or stasis in all patients, and no evidence of necrosis at the anastomotic site of the pulled-up gastric tube was observed by postoperative endoscopy. This technique reduces risk and may contribute to the successful reconstruction of the digestive tract after total esophagectomy.

Aged↗
PubMed2001

Volume supplementation with iso-sodium solution prevents hypernatremia after head injury.

OBJECTIVE: To evaluate our developed volume supplement protocol in preventing hypernatremia after head injury. METHODS: Iso-sodium solution was infused to keep the 8-hour water balance positive in 20 head-injured patients with hypotonic urine. RESULTS: Serum sodium concentrations moved to within a normal range in 6 patients and were temporarily increased in 12 patients. Seven of the 12 showed a negative cumulative water balance and slightly low creatinine clearance. Mean arterial pressure in the other five patients was lower after supplementation and was positively related to sodium excretion. Hypernatremia could not be prevented in the other two patients and they did not survive. Creatinine clearance was below 40 mL/min/m2 in these two patients before supplementation. CONCLUSION: Our protocol worked effectively in patients in whom renal function was preserved. Decreased creatinine clearance because of preexisting dehydration and lower arterial pressure disturbed increase in urinary sodium excretion and temporarily aggravated the hypernatremia.

Blood Volume↗
PubMed2001

Inhibition of experimental vasospasm by pretreatment with ultraviolet light irradiation in a rat femoral artery model.

OBJECTIVE: Chronic cerebral vasospasm is resistant to conventional treatments despite recent advances in treatment modalities. We studied the preventive effect of ultraviolet (UV) irradiation on development of vasospasm and its mechanism in a rat femoral artery model. METHODS: The rat femoral artery model for vasospasm was used in this investigation (n = 108). The femoral arteries were divided into four groups: empty and no irradiation (control), UV irradiation (UV group), blood placement (VS group), and blood placement after UV irradiation (VS + UV group). Luminal area was measured, and smooth muscle cell counts in the medial layer of the vessel wall were obtained. An immunohistochemical study was performed with cross sections of fixed femoral arteries at 12 hours and 1, 3, 5, 7, and 49 days after blood placement. The rings of femoral arteries on Day 7 were subjected to pharmacological study. RESULTS: Pretreatment with UV irradiation (VS + UV group) resulted not only in significant inhibition of chronic vasospasm but also in a significant decrease in smooth muscle cells compared with the VS group on Days 5 and 7. The UV-treated arteries (UV and VS + UV groups) exhibited a significant number of Bax- and Bcl-2-positive cells on Days 5 and 7, but few CPP-32 positive cells were observed at the same time points. In the pharmacological study, contractile response to KCI or phenylephrine was reduced significantly in the UV-treated arteries. CONCLUSION: These results imply that UV irradiation prevents chronic vasospasm and suggest that UV-induced cell death plays an important role in the preventive effect without causing complications during the chronic period.

Animals↗
PubMed2001

Molecular characteristic-based epidemiology of hepatitis B, C, and E viruses and GB virus C/hepatitis G virus in Myanmar.

We carried out a molecular characteristic-based epidemiological survey of various hepatitis viruses, including hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis E virus (HEV), and GB virus C (GBV-C)/hepatitis G virus (HGV), in Myanmar. The study population of 403 subjects consisted of 213 healthy individuals residing in the city of Yangon, Myanmar, and the surrounding suburbs and 190 liver disease patients (155 virus-related liver disease patients and 35 nonviral disease patients). The infection rates of the viruses among the 213 healthy subjects were as follows: 8% for HBV (16 patients), 2% for HCV (4 patients), and 8% for GBV-C/HGV (17 patients). In contrast, for 155 patients with acute hepatitis, chronic hepatitis, liver cirrhosis, or hepatocellular carcinoma, the infection rates were 30% for HBV (46 patients), 27% for HCV (41 patients), and 11% for GBV-C/HGV (17 patients). In the nonviral liver disease group of 35 patients with alcoholic liver disease, fatty liver, liver abscess, and biliary disease, the infection rates were 6% for HBV (2 patients), 20% for HCV (7 patients), and 26% for GBV-C/HGV (9 patients). The most common viral genotypes were type C of HBV (77%), type 3b of HCV (67%), and type 2 of GBV-C/HGV (67%). Moreover, testing for HEV among 371 subjects resulted in the detection of anti-HEV immunoglobulin G (IgG) in 117 patients (32%). The age prevalence of anti-HEV IgG was 3% for patients younger than 20 years and 30% or more for patients 20 years of age or older. Furthermore, a high prevalence of anti-HEV IgG (24%) was also found in swine living together with humans in Yangon. These results suggest that these hepatitis virus infections are widespread in Myanmar and have led to a high incidence of acute and chronic liver disease patients in the region.

Adolescent↗
PubMed2001

Correlation between C677T MTHFR gene polymorphism, plasma homocysteine levels and the incidence of CAD.

The lesions of coronary atherosclerosis represent the result of a complex, multicellular, inflammatory-healing response in the coronary arterial wall. In vivo and in vitro cellular and molecular studies have suggested a role for tissue homocysteine in endothelial cell injury and adverse extra-cellular matrix remodeling. Gene polymorphisms in relation with numerous risk factors might increase the incidence of coronary artery disease (CAD). In this review we have focused on the correlations between plasma homocysteine levels, the incidence of cardiovascular disease and the cytosine-to-thymidine substitution at nucleotide 677 (C677T) of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, coding for a key enzyme in methionine-homocysteine metabolism. The role of the C677T MTHFR gene polymorphism in the causation of CAD is controversial. We reviewed 12 recent case-control studies comprising 5370 genotyped patients with CAD and 4961 genotyped participants without CAD. There was no significant difference between those with and without CAD in the frequency of the C677T polymorphism (34.9 vs 33.6%). The frequency of homozygous C677T polymorphism in these groups was 10.9 versus 12.8%, respectively, although there were some ethnic differences in the C677T MTHFR polymorphism. In the analysis of the 12 studies, the odds ratio of CAD associated with the TT genotype (homozygous C677T polymorphism) was 1.18. Only slightly higher plasma homocysteine levels were observed in participants with the val/val (TT) genotype (14.4+/-2.9 micro mol/L in TT genotype vs 11.1+/-1.9 and 11.9+/-2 micro mol/L in CC and CT genotype, respectively). In addition, the relation between homocysteine increase after methionine loading and MTHFR genotypes is also controversial. However, hyperhomocysteinemia because of the C677T MTHFR allele may be corrected with oral folic acid therapy. Further investigations on the relationships between MTHFR genotypes and the incidence of CAD should be based on larger samples, paying attention to the differences between various ethnic populations. Individual therapeutic strategies based on single nucleotide polymorphism may become increasingly important for preventive treatment against polygenic CAD.

Clinical Trials as Topic↗
PubMed2001

Enhancement of the response to levodopa therapy after intrastriatal transplantation of autologous sympathetic neurons in patients with Parkinson disease.

OBJECT: There is growing evidence to indicate that tissue transplantation can potentially be a restorative neurosurgical treatment for patients with Parkinson disease (PD). In this study the authors investigated the clinical effect of unilateral intrastriatal grafting of autologous sympathetic neurons in patients with PD. METHODS: Four patients with PD who had been observed for 1 year after graft placement of autologous sympathetic neurons were selected for an analysis of the effect of that procedure. Sympathetic ganglion tissue was endoscopically excised from the thoracic sympathetic trunk and grafted into the unilateral caudate head and putamen of the PD patients. No changes were made in the patients' preoperative regimens of antiparkinsonian medications, and clinical evaluations were made principally according to those established by the Core Assessment Program for Intracerebral Transplantation Committee. Whereas the sympathetic neuron grafts failed to affect clinical scores reflecting the patients' motor performance, which was evaluated during either the "on" or "off' phases, the grafts significantly increased the duration of the levodopa-induced on period with consequent reduction in the percentage of time spent in the off phase. This beneficial effect may be explained by the results of the present in vitro experiment, which show that human sympathetic neurons have the ability to convert exogenous levodopa to dopamine and to store this synthesized dopamine. CONCLUSIONS: Sympathetic neuron autografts were found to improve performance status in patients with PD by reducing the time spent in the off phase. This clearly indicates that sympathetic ganglion tissue, the use of which involves few ethical issues, can be an efficacious donor source in cell transplantation therapy for PD. Further studies are needed to determine whether the grafts may provide long-lasting clinical benefits.

Antiparkinson Agents↗
PubMed2001

[Simultaneous carotid and coronary artery surgery in asymptomatic carotid artery stenosis--report of three cases].

Some patients with coronary artery disease are diagnosed as having additional carotid artery disease. This subset of patients has been identified as a high-risk group for cardiac and cerebral complications following surgical intervention. Three patients who underwent combined CEA/CABG for coexistent asymptomatic carotid occlusive disease are reported. Case 1: A 69-year-old female who suffered chest pain on exertion. Her coronary angiogram showed severe stenosis of three vessels. Her carotid angiogram showed 98% stenosis of the right internal carotid artery and poor collateral circulation. The severe stenosis of her carotid artery was considered as a risk factor for perioperative cerebral stroke. Intraoperatively, CEA preceded the CABG. Postoperative course was uneventful. Case 2: A 64-year-old male. Intermittent claudication was his initial symptom. His coronary angiogram showed stenosis in three vessels and carotid angiogram showed 75% stenosis in the right carotid artery. Simultaneous CABG and CEA was performed. His postoperative course was uneventful. Case 3: A 62-year-old male whose ECG indicated ischemic heart disease, although he had no symptoms. His coronary angiogram showed stenosis in three vessels, and 80% stenosis of his right carotid artery was observed by carotid angiogram. He underwent simultaneous surgery, and had an uneventful postoperative course. It has been reported that 1.5-8.7% of CABG patients have severe carotid artery stenosis, and perioperative cerebral stroke occurs in 0.9-16%. Simultaneous surgery was successful in our three patients who had asymptomatic carotid artery stenosis. Using this surgical approach for critical coexistent disease may minimize the incidence of perioperative cerebrovascular complications in patients undergoing CABG.

Aged↗
PubMed2001

Preparation and characterization of SNO-PEG-hemoglobin as a candidate for oxygen transporting material.

Acellular hemoglobin (Hb) derivates developed as oxygen carriers are known to cause hypertensive reactions due to their nitric oxide (NO) scavenging action. To modulate this undesired activity, we have developed a new Hb derivative, s-nitrosylated polyethylene glycol (PEG)-modified hemoglobin (SNO-PEG-Hb), which can deliver oxygen and NO. After human Hb was modified with PEG to increase its molecular weight, the free sulfhydryl groups of Hb were s-nitrosylated with s-nitrosoglutathione. Administration of unmodified Hb into anesthetized rats caused a hypertensive reaction, while s-nitrosylated Hb derivatives such as SNO-Hb and SNO-PEG-Hb did not raise blood pressure. The plasma half-lives of heme and NO bound to SNO-PEG-Hb were 11.5 and 2.4 hours respectively, indicating that the s-nitrosylated Hb derivative may act as a slow-releasing agent for NO. Based on these findings, SNO-PEG-Hb is a useful candidate for a blood substitute and tool for oxygen therapeutics.

Analysis of Variance↗
PubMed2001

Early full donor myeloid chimerism after reduced-intensity stem cell transplantation using a combination of fludarabine and busulfan.

BACKGROUND AND OBJECTIVES: The aim of this study was to evaluate lineage-specific chimerism reconstitution after reduced-intensity allogeneic stem cell transplantation (RIST) using a combination of fludarabine (30 mg/m2 for 6 days) and busulfan (4 mg/kg for 2 days). DESIGN AND METHODS: We prospectively enrolled 8 consecutive patients with hematologic malignancies who were not candidates for conventional transplantation because of either high age or organ dysfunction. Host-donor chimerism was evaluated using polymerase chain reaction-based amplification of a polymorphic short tandem repeat region. RESULTS: All of our patients achieved engraftment within a median of 11 days after transplantation. On day 30, full donor myeloid cell chimerism (>90%) was achieved in 7 patients whereas full donor T-cell chimerism was achieved in only one patient. Thus, in contrast to other reported results, full donor chimerism was achieved earlier in the myeloid lineage than the T-cell lineage. On day 60, however, T-cell chimerism caught up with myeloid chimerism. Two patients developed grade II-IV acute graft-versus-host disease (GVHD) before the detection of full donor T-cell chimerism. INTERPRETATION AND CONCLUSIONS: Our findings suggest that the kinetics of lineage-specific chimerism depend on the agents used in the conditioning regimen, and may provide insight into the chimerism kinetics and pathogenesis of GVHD. Thus, the strategy for controlling immunosuppression after RIST should be modified according to the type of conditioning regimen applied.

Adult↗
PubMed2000

Attenuation of hypothermia-induced platelet activation and platelet adhesion to artificial surfaces in vitro by modification of hemoglobin to carry S-nitric oxide and polyethylene glycol.

Hypothermic cardiopulmonary bypass alters platelet function and hypothermia is associated with postoperative myocardial ischemia. Thrombogenic surfaces such as extracorporeal circuits, vascular graft materials, and components of atherosclerotic plaque induce activation of platelets. The effects of human hemoglobin (Hb) covalently modified to carry S-nitric oxide (NO) functional groups (SNO-Hb), polyethylene glycol (PEG-Hb), and SNO-PEG-Hb on platelet activation were studied. Platelet activation was assessed by cytometric analysis of GPIIb-IIIa activation and P-selectin expression at hypothermic condition (22 degrees C) after stimulation with Hb derivatives. Platelet adhesion and aggregation were measured in a parallel glass plate chamber coated with unmodified Hb, SNO-Hb, PEG-Hb, SNO-PEG-Hb, and collagen. Platelet binding of antibodies to GPIIb-IIIa and P-selectin was significantly enhanced by hypothermic condition and by unmodified Hb. There was significantly less platelet binding of antibodies to GPIIb-IIIa and P-selectin with SNO-Hb, PEG-Hb, and SNO-PEG-Hb compared with unmodified Hb. There was significantly less platelet attachment, adhesion, and aggregation on the SNO-Hb, PEG-Hb and SNO-PEG-Hb coated surfaces compared with unmodified Hb-coated and -uncoated surfaces. SNO-Hb, PEG-Hb, and SNO-PEG-Hb induced less platelet activation at hypothermic temperature, and induced less platelet adhesion and aggregation on thrombogenic surfaces compared with unmodified Hb. The inhibitory effect may be derived from antiadhesive properties of Hb, antiplatelet actions of NO, and molecular barrier action of PEG.

Adult↗
PubMed2000

Cycloprodigiosin hydrochloride, H(+)/CL(-) symporter, induces apoptosis and differentiation in HL-60 cells.

Cycloprodigiosin hydrochloride (cPrG * HCl), a novel H(+)/Cl(-) symporter, induces acidification of the cytosol and leads to apoptosis in rat and human liver cancer cells. In the present study, the effect of cPrG * HCl on a promyelocytic leukemia cell line (HL-60) was examined. cPrG * HCl lowered intracellular pH and induced apoptosis through up-regulation of Fas ligand, activation of stress-activated protein kinase (SAPK/JNK) and caspase. Apoptosis induced by cPrG * HCl was strongly suppressed when a cell-permeable weak base, imidazole, was present, indicating that cytosol acidification introduced by cPrG * HCl triggered caspase activation, leading to apoptosis. Concomitantly, cell differentiation into monocyte was also induced by cPrG * HCl both morphologically and functionally. However, the cPrG * HCl-induced differentiation was not suppressed by addition of imidazole, indicating that the differentiation process is unrelated to cytosol acidification. Further, the differentiation induced by cPrG * HCl was blocked by tyrosine kinase inhibitors (lavendustin A and HMA) but unaffected by the inhibitors of A-kinase (H-89) or C-kinase (H-7). Taken together, these findings suggest that cPrG * HCl, through apoptosis and differentiation induction, may be useful in leukemia treatment.

Antiporters↗
PubMed2000

Formation Process of MCM-41 Precursor and Porous Texture of MCM-41.

The formation process of the MCM-41 precursors (silicate/surfactant complex) was investigated on the basis of the pH titration curves of Na(4)SiO(4) in the presence of [C(16)H(33)N(CH(3))(3)]Cl. Measurements of the pH titration curves were carried out using the computer-controlled gravimetric titrator constructed in our laboratory. The white precipitate (MCM-41 precursor) was abruptly formed at pH 11.1 (298 K) and at pH 9.9 (343 K). Formation of the MCM-41 precursor can be explained by coagulation of the rod-like micelle colloids whose surface is covered by the condensed silicate anions of (HSiO(3))(n)(n-). The porous texture of the MCM-41 samples whose precursors were synthesized under different conditions was analyzed on the basis of the adsorption isotherms of nitrogen at 77 K. It has been shown that the MCM-41 sample whose precursor was prepared at pH 9.9 and 343 K shows one sharp peak (r(p) = 1.65 nm) in the pore size distribution curve, but the MCM-41 samples whose precursors were prepared at pH 6.5-5.0 and 343 K give two peaks (r(p) = 1.66 nm and r(p) = 2.12-2.36 nm). The appearance of the second peak (r(p) = 2.12-2.36 nm) has been considered to be in connection with the destruction of the MCM-41 precursor into small fragments in acidic medium. Copyright 2000 Academic Press.

Journal Article↗