Biomedical subjects

Y Kuroda

Publications and source records attributed to Y Kuroda.

At least 505 records · Page 28Linked to original sources

PubMed1994

Effects of adrenalectomy and type I or type II glucocorticoid receptor activation on 5-HT1A and 5-HT2 receptor binding and 5-HT transporter mRNA expression in rat brain.

We evaluated the effects of adrenalectomy (ADX) and replacement with glucocorticoid receptor agonists on serotonin (5-HT) 5-HT1A and 5-HT2 receptor binding in rat brain. 5-HT1A receptor binding was increased in the CA2-CA4 and the dentate gyrus of the hippocampus 1 week after ADX. This effect was prevented by the systemic administration of aldosterone (10 micrograms/microliters/h) but not by RU28362 (10 micrograms/microliters/h). No significant effect was observed on 5-HT2 receptor binding in rat cortex. The expression of 5-HT transporter mRNA was unchanged in the raphe nucleus as measured by in situ hybridization.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1994

Experimental carcinogenesis in the rat intestine induced by two different carcinogens--evaluation of carcinogenic action and its effect on ornithine decarboxylase activity.

Carcinogenesis in the rat intestine induced with 1,2-dimethylhydrazine (DMH), N-methyl-N-nitrosourea (MNU), and their combinatorial use was studied. Intestinal tumors, including both adenoma and adenocarcinoma, were induced in all the rats given the carcinogens. The tumor frequently occurred in the intestinal tract extending from the duodenum to the colon in the DMH treated group. In the MNU treated group, the tumor occurred in the colon, especially on the distal side. Distribution of tumors in the group treated with both carcinogens was similar to that seen in the MNU-treated group. Neither obvious macroscopic nor histological differences were observed between groups treated with these carcinogens. In addition, we investigated the effect of carcinogens on ornithine decarboxylase (ODC) activity in rat colon. Tumor tissues showed a remarkably high level of enzyme activity compared with the normal-appearing mucosa, and there was a correlation between the level of the ODC activity and the histological grade of malignancy. ODC activity in the normal-appearing mucosa of the carcinogens-treated rats was significantly higher than that of control rats, and the number of tumors per rat was correlated with the level of ODC activity. These results indicate that mucosal ODC may be a pertinent biological marker for local carcinogenic activity.

1,2-Dimethylhydrazine↗

PubMed1994

Individual ionization constants of all the carboxyl groups in ribonuclease HI from Escherichia coli determined by NMR.

All of the individual carboxyl groups (the side-chain carboxyl groups of Asp and Glu, and the C-terminal alpha-carboxyl group) in Escherichia coli ribonuclease HI, which is an enzyme that cleaves the RNA strand of a RNA/DNA hybrid, were pH-titrated, and their ionization constants (pKa) were determined from an analysis of the pH-dependent chemical shifts of the carboxyl carbon resonances obtained from 1H-13C heteronuclear two-dimensional NMR. The pKa values in the enzyme varied widely among individual residues, for example, in the unusual pKa values for two important catalytic residues, Asp10 (pKa 6.1) and Asp70 (pKa 2.6). Moreover, remarkable two-step titrations were observed for these carboxylates. The binding of Mg2+ ion to the enzyme, which is the cofactor necessary for catalytic activity, caused no significant change in the pKa values of the carboxyl groups, except for that of Asp10. The variations of the pKas that were dependent on the microenvironment in the protein were theoretically reproduced to compare with the experimental results by a numerical calculation, using a continuum electrostatic model. Most of the significant pKa decreases were brought about through strong electrostatic interactions with the neighboring basic amino acids, Arg or Lys. The pKa shifts and the two-step titrations of Asp10 and -70, which are close to each other, were interpreted to be due to the neighboring effect of two functional groups, as observed in the interacting titratable groups of a dicarboxyl compound or in the active site carboxylates of lysozyme and aspartic protease. The role of Asp10 in the catalytic action is either to be the proton donor to the RNA moiety or the binding partner of the Mg2+ ion cofactor. Asp70, on the other hand, is considered to be the proton acceptor from a water molecule.

Amino Acid Sequence↗

PubMed1994

Identification of mutations in DNA polymerase beta mRNAs from patients with Werner syndrome.

Werner syndrome (WS) is a rare autosomal recessive disorder characterized by prematurely aged appearance. Genetic linkage analysis has placed the relevant gene in subchromosomal band 8p12. DNA polymerase beta gene has been mapped to chromosome 8p12-11 and thought to be involved in DNA repair and possibly in recombination. Somatic cells from WS patients exhibit chromosomal instability, a markedly reduced replicative life span and slow growth. The functions of DNA polymerase beta gene and its position prompted us to examine this gene in WS patients. We have found the novel DNA polymerase beta cDNA species in blood samples from WS patients, which contain 107 bp insertions or 87 bp deletions in the catalytic domain of DNA polymerase beta. These mutations change the structure of DNA polymerase beta and thus the capacity of the DNA repair system would be impaired, which may account for the high mutation rate observed in WS.

Amino Acid Sequence↗

PubMed1994

Role of adenosine in preservation by the two-layer method of ischemically damaged canine pancreas.

The purpose of this study was to clarify the role of adenosine in preservation of ischemically damaged pancreas by the two-layer (Euro-Collins solution [EC]/perfluorochemical [PFC]) method using a canine model. Twenty-four-hour preservation of the pancreas graft subjected to 60-min warm ischemia was successful by the two-layer (EC with adenosine/PFC) method (4/5, 80%), but neither simple cold storage in EC (0/5, 0%), nor EC with adenosine (1/5, 20%), nor the two-layer (EC/PFC) method (0/3, 0%) was successful. Tissue ATP concentrations at the end of preservation by the two-layer (EC with adenosine/PFC) method were significantly higher compared with the two-layer (EC/PFC) method (7.23 +/- 2.17 vs. 1.56 +/- 0.40 mumol/g dry weight, P < 0.01). Studies with [2-3H]adenosine demonstrated that only part of adenosine was converted to inosine, hypoxanthine, and adenine, whereas the remainder was incorporated into adenine nucleotides in the pancreas graft. In addition, hypoxanthine, inosine, and adenine did not substitute for adenosine. We conclude that provision of adenosine to ischemically damaged pancreas during preservation by the two-layer (EC/PFC) method allows ATP synthesis within the graft via direct phosphorylation of adenosine. Metabolic processes vital to repair damaged cells and maintain cellular integrity can be maintained, which makes it possible to preserve ischemically damaged pancreas.

Adenosine↗

PubMed1994

Protective effect of preservation of canine pancreas by the two-layer (University of Wisconsin solution/perfluorochemical) method against rewarming ischemic injury during implantation.

Rewarming ischemia during implantation severely compromises posttransplant pancreas graft survival because the graft has already been subjected to warm and cold ischemia before implantation. The purpose of this study was to examine whether preservation of the pancreas graft by the two-layer method ameliorates rewarming ischemic injury of the graft during implantation using a canine model. After flushing with cold University of Wisconsin solution (UW), the pancreas grafts were preserved by the two-layer (UW/perfluorochemical [PFC]) method (group 1) or simple cold storage in UW (group 2) for 24 hr and then autotransplanted. In control, the pancreas grafts were flushed out with cold UW and immediately autotransplanted without preservation (group 3). After completion of vascular anastomosis, vascular clamp was not released until 90, 120, or 150 min of rewarming ischemia, including anastomosis time, had elapsed. After 90 min of rewarming ischemia, graft survival rates were 5/5, 100%, 5/5, 100%, and 5/5, 100%, in groups 1, 2, and 3, respectively. After 120 min, all the grafts in groups 2 and 3 failed (0/5, 0%, and 0/5, 0%, respectively); however, all the grafts in group 1 survived (5/5, 100%). Even after 150 min, 1 of 3 grafts in group 1 survived (1/3, 33%). After 24 hr preservation, tissue ATP levels of the grafts in group 1 were about 2-fold the reference values before harvesting (8.23 +/- 0.72 vs. 4.44 +/- 0.49 mumol/g dry weight, P < 0.05) and significantly higher compared with group 2 (8.23 +/- 0.72 vs. 1.76 +/- 0.52 mumol/g dry weight, P < 0.01). After 120 min of rewarming ischemia, tissue ATP levels in group 1 were 84% of the reference values and significantly higher compared with group 2 (3.75 +/- 0.25 vs. 1.57 +/- 0.48 mumol/g dry weight, P < 0.05). Two hours after reperfusion, ATP levels in group 1 were 42% of reference values but significantly higher compared with group 2 (1.86 +/- 0.36 vs. 1.03 +/- 0.18 mumol/g dry weight, P < 0.05). We conclude that the two-layer (UW/PFC) method ameliorates rewarming ischemic injury of the pancreas graft during implantation by increasing tissue ATP contents during preservation and consequently maintaining tissue ATP levels during implantation.

Adenosine↗

PubMed1994

Solution structure of a de novo helical protein by 2D-NMR spectroscopy.

The de novo design of proteins represents a critical test for our knowledge of protein structure. However, no structure of a successfully designed protein has yet been reported. This paper reports the design and the tertiary structure of a de novo 35-residue helix-loop-helix protein (ALIN), with helices arranged in an anti-parallel manner. For the helical region, we designed sequences that have high helicities even as isolated peptides. A flexible loop containing glycine residues was used to connect the two helices and the interhelical hydrophobic interaction was stabilized by the introduction of an SS-bridge. This arrangement of two consecutive helices bridged by a disulfide bond is not observed in any natural proteins. The protein is highly soluble and monomeric in aqueous solution. The structure of ALIN, determined by 1H-NMR and distance geometry calculation, agrees well with the design. In addition, the exchange rates of amide protons indicate the presence of stable hydrogen bonds in the helical region. ALIN is the first de novo designed protein with a stable tertiary fold confirmed by NMR.

Amino Acid Sequence↗

PubMed1994

Aluminum promotes the aggregation of Alzheimer's amyloid beta-protein in vitro.

Amyloid beta-protein is the major component of senile plaques in the brains of Alzheimer's disease and has an intrinsic tendency to form insoluble aggregates. The aggregation of amyloid beta-protein has been suggested to enhance its neurotoxicity and to play a key role in the amyloid deposition. Here we show, using gel-electrophoresis and immunoblotting, that the aggregation of synthetic amyloid beta-protein (beta 1-40) is promoted by aluminum, a suspected risk factor in Alzheimer's disease. High molecular weight aggregates were observed, and the amount of precipitated protein was estimated using high performance liquid chromatography. The results suggest the possibility that aluminum directly influences the process of aggregation and the deposition of senile plaques.

Aluminum Chloride↗

PubMed1994

Diminished erythropoietin-induced erythroid growth in patients with renal anemia is restored by recombinant human erythroid differentiation factor.

An examination of the in vitro sensitivity of marrow burst-forming units for erythroid (BFU-E) to various concentrations of human recombinant erythropoietin (rEpo) and interleukin-3 (IL-3, 20 ng/mL) in serum-deprived methylcellulose cultures revealed that cells obtained from patients with chronic renal failure showed a defective response to rEpo, particularly at lower concentrations. This poor response was not corrected by the addition of neutralizing antibodies to antitumor necrosis factor-alpha or antiinterleukin-1 alpha/beta. When purified CD34+ cells from these patients were tested for dose-dependent growth to rEpo, the curve resembled that of normal donors, indicating that there was an intrinsic defect in the patients' progenitor/accessory cell interactions. Using unseparated cells from the patients, we then tested whether the interaction between erythroid differentiation factor (EDF) and rEpo affected BFU-E growth. Although EDF, either alone or in combination with IL-3, did not affect the growth of BFU-E in the absence of rEpo, the reduced sensitivity to rEpo in the patients was brought closer to normal limits by the addition of 10 ng/mL EDF to the cultures. The present results may suggest the possibility that, in patients with renal anemia, concomitant administration of EDF may increase the therapeutic ratio of rEpo therapy by enhancing the sensitivity of progenitor cells to rEpo, thereby decreasing the therapeutic dose of costly rEpo.

Activins↗

PubMed1994

Signal-averaged electrocardiographic late potentials in children with complete heart block.

The purpose of this study was to examine signal-averaged electrocardiographic (SA-ECG) late potentials to predict ventricular arrhythmias during intrinsic cardiac rhythm and during ventricular pacing in children with complete heart block (CHB). Recordings of SA-ECG were obtained from eight patients (aged 3-18 years) with documented CHB. The etiology of CHB was congenital in four cases and acquired in four cases. Six of these patients underwent permanent pacemaker implantation. Comparisons of the SA-ECG were made before and during ventricular pacing. Abnormalities of SA-ECG during intrinsic cardiac rhythm were noted in four patients, all of whom were older than 14 years. Although there was no significant difference in SA-ECG parameters between patients with congenital CHB and acquired CHB, abnormal SA-ECG was noted in one of four patients with congenital CHB and in three of four patients with acquired CHB. Two patients without permanent pacemaker implantation had normal SA-ECG, but four of six patients with permanent pacemaker implantation had abnormal SA-ECG. Three of the four patients had abnormal SA-ECG during ventricular pacing, but the abnormal SA-ECG in one patient had normalized during ventricular pacing. It is important to record SA-ECG before and during ventricular pacing to detect late potentials in patients with CHB. It may be useful to record SA-ECG while changing the pacing site to find ideal sites for electrode implantation for the potential prevention of ventricular arrhythmias.

Action Potentials↗

PubMed1994

High-dose chemotherapy and blood stem cell autografts for children with first relapsed acute lymphoblastic leukemia: a pilot study of the Children's Cancer and Leukemia Study Group of Japan (CCLSG).

This study was performed to determine the value of high-dose chemotherapy and peripheral blood stem cell autografts (PBSCT) in the treatment of children with first relapsed acute lymphoblastic leukemia (ALL). Eighteen children underwent PBSCT during the second complete remission (CR) and had a minimum 10 month follow-up. The median age of the patients was 11 yr (range, 2-17 yr). Fifteen patients received the "MCVAC" regimen, one received high-dose MCNU+busulfan therapy, one received high-dose melphalan+VP-16, and one received melphalan+carboplatin+cytosine arabinoside+MCNU. None of these regimens included total body irradiation. Eight patients developed recurrence of the disease at 1 to 19 mo (median, 3 mo) after PBSCT. Patients in whom the first relapse occurred sooner, that is, within 16 mo of initial therapy, tended to have a better survival rate than those who developed relapse after 30 mo (six of seven survived versus four of 11; not significant). Although the preliminary data provided little conclusive information, it did suggest that incorporation of PBSCT in the salvage protocol of relapsed childhood ALL can be justified.

Adolescent↗

PubMed1994

Thermodynamic characterization of an artificially designed amphiphilic alpha-helical peptide containing periodic prolines: observations of high thermal stability and cold denaturation.

To investigate the structural stability of proteins, we analyzed the thermodynamics of an artificially designed 30-residue peptide. The designed peptide, NH2-EELLPLAEALAPLLEALLPLAEALAPLLKK-COOH (PERI COIL-1), with prolines at i + 7 positions, forms a pentameric alpha-helical structure in aqueous solution. The thermal denaturation curves of the CD at 222 nm (pH 7.5) show an unusual cold denaturation occurring well above 0 degrees C and no thermal denaturation is observable under 90 degrees C. This conformational change is reversible and depends on peptide concentration. A 2-state model between the monomeric denatured state (5D) and the pentameric helical state (H5) was sufficient to analyze 5 thermal denaturation curves of PERI COIL-1 with concentrations between 23 and 286 microM. The analysis was carried out by a nonlinear least-squares method using 3 fitting parameters: the midpoint temperature, Tm, the enthalpy change, delta H(Tm), and the heat capacity change, delta Cp. The association number (n = 5) was determined by sedimentation equilibrium and was not used as a fitting parameter. The heat capacity change suggests that the hydrophobic residues are buried in the helical state and exposed in the denatured one, as it occurs normally for natural globular proteins. On the other hand, the enthalpy and the entropy changes have values close to those found for coiled-coils and are quite distinct from typical values reported for natural globular proteins. In particular, the enthalpy change extrapolated at 110 degrees C is about 3 kJ/mol per amino acid residue, i.e., half of the value found for globular proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1994

Synergy among erythropoietin, interleukin 3, stem cell factor (c-kit ligand) and interferon-gamma on early human hematopoiesis.

The stimulatory effect of interferon-gamma (IFN-gamma) on human early hematopoiesis was investigated using CD34+ cells that were purified from peripheral blood as a target. In the presence of human interleukin 3 (IL-3) and stem cell factor (SCF), the growth of colony forming units for granulocyte/macrophage (CFU-GM) in serum-free methylcellulose culture was enhanced up to 5.5-fold over baseline colony formation (n = 10, mean +/- SE, 3.18 +/- 1.00) by coculture with 2.5 x 10(3) U/ml IFN-gamma, whereas burst forming units-erythroid (BFU-E) growth induced by additional erythropoietin (Epo) was reduced dose-dependently. Liquid-suspension culture of the target cells for 24 h with IFN-gamma before secondary plating in serum-free methylcellulose resulted in a marked increase in the colony numbers; 3.62 +/- 1.04-fold for CFU-GM and 5.72 +/- 2.32-fold for BFU-E (n = 5). The effect was most striking in the growth of erythroid lineage supported by Epo alone in serum-free culture. Delayed addition of IFN-gamma between days 4 and 7 of methylcellulose culture suppressed CFU-GM growth, but not that of BFU-E. These results suggest that IFN-gamma is an essential cytokine that affects human hematopoiesis and exerts a bimodal effect on stem cell maturation; potentiating or replacing the effect of early-acting cytokines such as SCF or IL-3, and suppressing the growth of matured progenitor cells.

Antigens, CD↗

PubMed1994

Diffuse astrocytic swelling and increased second messenger activity following acute Haemophilus influenzae meningitis--evidence from a rat model.

Despite numerous epidemiological analyses of bacterial meningitis there is very little pathological data concerning the acute glial and neuronal responses to the disease. We have developed a safe, easily used rat model for Haemophilus influenzae type b meningitis. We measured cerebral blood flow, glucose utilisation and second messenger activity in this model, and carried out parallel light and ultrastructural analysis of glial and neuronal responses. Only protein kinase C activity was changed from control values. We obtained evidence for massive astrocytic swelling and neuronal degeneration. We posit that cytotoxic mechanisms may contribute to the pathology of meningitis.

Adenylyl Cyclases↗

PubMed1994

Effects of the altered serotonergic signalling by neonatal treatment with 5,7-dihydroxytryptamine, ritanserin or clomipramine on the adrenocortical stress response and the glucocorticoid receptor binding in the hippocampus in adult rats.

The aim of the present study is to investigate the effect of neonatal alterations in 5-HT signalling on the regulation of endocrine stress response in adult rats. The neonatal blockade of 5-HT transmission by 5,7-DHT or ritanserin treatment did not alter the density of glucocorticoid receptor (GR) binding sites in the hippocampus, although a 5,7-DHT-induced lesion was clearly shown to decrease in 5-HT content by greater than 80% in the hippocampus. In addition, the animals pretreated with the blockade of 5-HT transmission during early life did not exhibit a hyperresponsiveness of the adrenocortical response to stress. On the other hand, the neonatal administration of the 5-HT uptake inhibitor, clomipramine, was shown to lower the stress responsiveness of the adrenocortical axis in adulthood.

5,7-Dihydroxytryptamine↗

PubMed1994

Time course of oxygen uptake and heart rate during Bruce treadmill test in patients following surgery for tetralogy of Fallot.

Exercise performance was examined in 14 patients with a prior history of surgical repair for tetralogy of Fallot. Using a Bruce protocol, we evaluated the time course of oxygen uptake and heart rate in these patients and compared them with a standard curve obtained from 63 sex- and age-matched healthy children. Five of the 14 patients had unusual findings. The heart rate increased rapidly in four of them, while the oxygen uptake increased gradually (95% confidence lower limit). It is hypothesized that a reduction in stroke volume during exercise was responsible for these abnormal findings. The remaining unusual finding was in a patient who was known to have myocardial fibrosis and vacuolization. In this particular case, the time course of oxygen uptake and heart rate were both below the 95% coefficient of variation from the beginning to the end of exercise. In patients who have undergone surgical repair for tetralogy of Fallot, the analysis of oxygen uptake time course and the heart rate may provide valuable information for the long-term follow-up.

Adolescent↗

PubMed1994

Ringed grafting for an abdominal aortic aneurysm in a 92-year-old patient: report of a case.

We report herein the case of a 92-year-old man with an abdominal aortic aneurysm who underwent successful surgical resection using a ringed graft. His postoperative course was uneventful, and he was discharged after 42 days, following which he attended the outpatient department twice a month for regular check-ups. He finally died of pneumonia which developed from an upper respiratory tract infection 6 months after his operation. Thus, surgical treatment should always be considered when an aneurysm is detected, even in very aged patients for whom the activities of daily living are possible.

Aged↗

PubMed1994

Direct hemoperfusion under infrahepatic inferior vena caval isolation for the intraarterial chemotherapy of pelvic tumors.

A new simple technique consisting of direct hemoperfusion under infrahepatic inferior vena caval isolation for intraarterial chemotherapy of pelvic tumors is herein described. The inferior vena cava is occluded at the infrahepatic level by means of balloon inflation using a balloon-tipped catheter (16F), which is placed through the right greater saphenous vein. The isolated infrahepatic vena caval blood is withdrawn by a centrifugal pump through a catheter (16F) in the contralateral greater saphenous vein and is filtered by direct hemoperfusion during intraarterial infusion of anticancer drugs. Venous reentry is provided by the central lumen of the balloon-tipped catheter. This procedure was used sequentially on two different occasions to treat a patient with an extensive pelvic tumor. Good hemodynamic stability and a reduction of the systemic drug toxicities were confirmed in both trials. Therefore, we believe that this technique is technically feasible and highly effective in reducing systemic toxicities during high-dose intraarterial chemotherapy for pelvic tumors.

Aged↗