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Biomedical subjects

N Yamada

Publications and source records attributed to N Yamada.

At least 469 records · Page 26Linked to original sources
PubMed1994

The light-driven proton pump, cruxrhodopsin-2 in Haloarcula sp. arg-2 (bR+, hR-), and its coupled ATP formation.

Haloarcula sp. arg-2, a natural bacterial isolate from Andes heights, has a light-driven proton pump but not a light-driven anion pump. We have cloned and sequenced the gene encoding for the proton pump which has been named cruxrhodopsin-2. The gene consists of 768 bp encoding 255 amino acids with a molecular mass of 27,544 Da. The deduced amino acid sequence of cruxrhodopsin-2 is 77%, 50%, 48% and 48% identical to those of cruxrhodopsin-1, bacteriorhodopsin, archaerhodopsin-1 and archaerhodopsin-2, respectively. The charged amino acids important for the proton pump function were conserved among all these molecules. Cruxrhodopsin-2 accounted for 0.05 nmol/mg protein in arg-2, which was 20-30-fold less than the proportion of bacteriorhodopsin in Halobacterium salinarium R1M1. In contrast to R1M1, under anaerobic conditions, arg-2 showed light-induced proton extrusion concomitant with an increase in ATP level without transient proton uptake. Dicyclohexylcarbodiimide enhanced the rate and extent of proton extrusion and inhibited ATP formation in the light. The apparent stoichiometry of H+/ATP was estimated to be more than three in this natural bR+hR- strain.

Adenosine Triphosphate↗
PubMed1994

Hyperglycemia as a major determinant of distal polyneuropathy independent of age and diabetes duration in patients with recently diagnosed diabetes.

In an attempt to identify the potential risk factors for diabetic neuropathy in patients recently diagnosed as diabetics, 742 non-insulin-dependent diabetics under 70 years of age who had been diagnosed as diabetics less than 5 years before the initial visit were examined in a cross-sectional study conducted at a university hospital. Neuropathy was defined as the presence of symptoms consistent with distal polyneuropathy, or the absence of tendon reflexes. Of the patients, 21% displayed neuropathy in this study, with no differences between the genders. Age was higher, duration of diabetes was longer, body mass index was lower, and fasting plasma glucose level was higher in patients with neuropathy than in those without neuropathy, for both genders. Body height, maximal body mass index, ethanol use, smoking status, systolic and diastolic blood pressure and serum cholesterol level did not differ between the two groups. Logistic regression analysis showed that fasting plasma glucose level (chi 2 = 28.2) was a major determinant for neuropathy independent of diabetes duration (9.5), age (6.2) and maximal body mass index (3.9). Tight glycemic control from the onset of diabetes was concluded to be essential for the prevention of diabetic distal polyneuropathy.

Adult↗
PubMed1994

Human inositol 1,4,5-trisphosphate type-1 receptor, InsP3R1: structure, function, regulation of expression and chromosomal localization.

We have isolated cDNA clones encoding an inositol 1,4,5-trisphosphate receptor type 1 (InsP3R1) from human uteri and a leukaemic cell line, HL-60. Northern-blot analysis showed that approx. 10 kb of InsP3R1 mRNA is expressed in human uteri, oviducts and HL-60 cells. The predicted amino acid sequence of human InsP3R1 (2695 amino acids) has 99% identity with that of the mouse SI-/SII- splicing counterpart. Western-blot analysis with anti-(mouse InsP3R1) antibodies showed that InsP3R1 protein of human uteri and oviducts of approx 220 kDa is immunostained. Northern-blot analysis of HL-60 cell differentiation along the neutrophilic lineage induced by retinoic acid or dimethylsulphoxide showed an accompanying enhanced expression of InsP3R1 mRNA. Immunohistochemical analysis of the cerebella of spinocerebellar degeneration patients showed a variable loss of Purkinje cells with an altered pattern of immunostaining. The InsP3R1 gene (Insp3r1) was localized to the 3P25-26 region of human chromosome 3. The data presented here clearly show that InsP3R1 exists widely in human tissues and may play critical roles in various kinds of cellular functions.

Adult↗
PubMed1994

Metabolism of chylomicron remnants in transgenic mice expressing apolipoprotein E in the intestine.

Apolipoprotein E (apoE) has high affinity for the cell surface low density lipoprotein (LDL) receptor. To determine the role of apoE in plasma chylomicron clearance, a transgenic mouse line which overexpresses apoE in the intestine was established. Immunohistochemistry demonstrated that considerable amounts of apoE were localized to mucosal cells of the intestine. In an oral retinyl palmitate challenge test, both the peak height and area under the curve in transgenic mice were less than 25% of those in controls. We speculate that the apoE molecules produced in the intestine of transgenic mice were incorporated onto newly synthesized chylomicron particles before their secretion into the plasma and thereby contributed to rapid plasma clearance of chylomicron remnants. Gene expression of apoE in the intestine would be a promising way to control postprandial hyperlipemia.

Administration, Oral↗
PubMed1994

Antiepileptogenic and anticonvulsant effects of NBQX, a selective AMPA receptor antagonist, in the rat kindling model of epilepsy.

To investigate the role of non-NMDA receptors in epileptic seizures, we examined the antiepileptogenic and anticonvulsant effects of NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline), a potent and selective AMPA receptor antagonist, in the rat kindling model. Systemic administration of 10-40 mg/kg NBQX significantly and dose dependently suppressed previously kindled seizures from the amygdala (AM), assessed in terms of the motor seizure stage and afterdischarge (AD) duration. The maximal effects were observed at 0.5-1 h after drug injection. When the intensity of electrical stimulation was increased to twice the generalized seizure-triggering threshold (GST), the anticonvulsant effects of NBQX on AM-kindled seizures were not reversed, suggesting that the effects were not due to non-specific elevation of the GST. In contrast to AM-kindled seizures, 20-40 mg/kg NBQX significantly suppressed only the motor seizure stage without reducing the AD duration of previously hippocampal-kindled seizures. Daily administration of 15 or 30 mg/kg NBQX prior to each electrical stimulation of the AM markedly and significantly suppressed the development of kindling. During drug sessions, the growth of the AD duration was blocked almost completely, while the waveform of ADs became more complex. These results indicate that NBQX has potent antiepileptogenic and anticonvulsant actions on kindling, at least from the AM and that non-NMDA receptors have an important role in seizure propagation.

Amygdala↗
PubMed1994

Proliferating cell nuclear antigen labeling index of preoperative biopsy specimens in gastric carcinoma with special reference to prognosis.

BACKGROUND: Proliferating cell nuclear antigen (PCNA) is an auxiliary protein of DNA polymerase delta and is considered to correlate with the cell's proliferative state. Immunohistochemical methods with a anti-PCNA antibody (PC10) have particular advantages compared with other techniques because of the maintenance of the tissue architecture and simplicity of the methodology. The authors investigated the correlation between the tumor's proliferative activity and progression of gastric carcinoma using immunohistochemical staining with PC10. METHODS: One hundred eighty-nine endoscopic biopsy specimens from patients with gastric carcinoma before operation were investigated by immunohistochemical study, using anti-PCNA monoclonal antibody (PC10). The correlation of PCNA labeling index (percentage of positive cells in more than 500 tumor cells) with various clinicopathologic factors and prognosis was studied. RESULTS: The PCNA labeling index became higher as the histologic stage increased. In patients with lymph node metastasis, vascular invasion, liver metastasis, and peritoneal metastasis, the labeling index was significantly higher. In patients with high PCNA labeling index (50% or greater), prognosis was significantly poorer than in those with a low index (less than 50%). The rate of disease recurrence after curative resection was significantly higher in patients with high PCNA grade group. CONCLUSION: As a result of this study, PCNA labeling index is suggested to be correlated with the depth of invasion, organ metastasis, vascular invasion, and tumor stage and to be effective as a prognostic factor.

Adult↗
PubMed1994

Abnormalities of PIG-A transcripts in granulocytes from patients with paroxysmal nocturnal hemoglobinuria.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder in which there is a deficiency in the synthesis by hematopoietic cells of the glycosyl-phosphatidylinositol molecules that anchor proteins to the cell membrane. Recently, we demonstrated that a gene termed PIG-A (for phosphatidylinositol glycan class A), a component of glycosyl-phosphatidylinositol biosynthesis, was responsible for PNH in two patients. The present study was undertaken to elucidate whether PIG-A is the gene responsible for all cases of PNH and to characterize further the somatically acquired abnormalities of this gene. METHODS: We studied granulocytes from 15 patients with PNH. The cell content of CD55 and CD59 was assessed by fluorescence-activated flow cytometry. PIG-A transcripts were reverse-transcribed, amplified by the polymerase chain reaction, and cloned into plasmids. The structure of the cloned complementary DNA was analyzed by nucleotide sequencing, and its function was assessed on the basis of its ability to restore to normal the abnormal phenotype of a PIG-A-deficient cell line after transfection. RESULTS: Three patients had size abnormalities of PIG-A transcripts with different patterns, and in one patient a very low level of the PIG-A transcript was found. Eleven patients had transcripts of normal size, but the transfection assay revealed that in each patient some of them were nonfunctional. The percentage of nonfunctional PIG-A transcripts was correlated with the percentage of affected granulocytes (P < 0.001). Sequence analysis demonstrated somatic mutations in two of the patients. CONCLUSIONS: PIG-A is the gene responsible for PNH in all patients studied to date.

Base Sequence↗
PubMed1994

Identification of a protein, SPY75, with repetitive helix-turn-helix motifs and an SH3 domain as a major substrate for protein tyrosine kinase(s) activated by Fc epsilon RI cross-linking.

Cross-linking of the high affinity receptor for IgE (Fc epsilon RI) initiates various biochemical and morphologic changes leading to degranulation and synthesis and release of cytokines and lipid mediators. Tyrosine phosphorylation of several cellular proteins was previously reported as the earliest signaling event for the Fc epsilon RI signal transduction pathway. By amino acid sequence determination and cDNA cloning analysis, a 75-kDa protein, termed SPY75, was identified as a major tyrosine-phosphorylated protein in activated mouse mast cells. SPY75, barely tyrosine phosphorylated in resting cells, was rapidly and transiently tyrosine phosphorylated on Fc epsilon RI cross-linking in an Ag concentration-dependent manner. Similar SPY75 tyrosine phosphorylation was observed when Ag receptors on B and T lymphocytes were cross-linked by appropriate antibodies. However, IL-3, granulocyte macrophage-CSF, or stem cell factor did not induce tyrosine phosphorylation of SPY75 in PT-18 mast cells, despite their responsiveness to these cytokines. SPY75 was not physically associated with the receptor or other known signaling molecules. This protein, the mouse homologue of the human HS1 gene product, has putative repetitive helix-turn-helix motifs found in many DNA-binding proteins and a putative nuclear transport signal. It also has a Src homology 3 domain, which is found in many signaling molecules and cytoskeletal proteins. These structural features and the rapid tyrosine phosphorylation on Fc epsilon RI cross-linking suggest that the signal generated by Fc epsilon RI cross-linking is transmitted through tyrosine phosphorylation of SPY75.

Amino Acid Sequence↗
PubMed1994

Paroxysmal nocturnal haemoglobinuria (PNH) is caused by somatic mutations in the PIG-A gene.

Paroxysmal nocturnal haemoglobinuria (PNH), an acquired clonal blood disorder, is caused by the absence of glycosyl phosphatidylinositol (GPI)-anchored surface proteins due to a defect in a specific step of GPI-anchor synthesis. The cDNA of the X-linked gene, PIG-A, which encodes a protein required for this step has recently been isolated. We have carried out a molecular and functional analysis of the PIG-A gene in four cell lines deficient in GPI-linked proteins, obtained by Epstein-Barr virus (EBV) transformation of affected B-lymphocytes from PNH patients. In all four cell lines transfection with PIG-A cDNA restored normal expression of GPI-linked proteins. In three of the four cell lines the primary lesion is a frameshift mutation. In two of these there is a reduction in the amount of full-length mRNA. The fourth cell line contains a missense mutation in PIG-A. In each case the mutation was present in the affected granulocytes from peripheral blood of the patients, but not in normal sister cell lines from the same patient. These data prove that PNH is caused in most patients by a single mutation in the PIG-A gene. The nature of the mutation can vary and most likely occurs on the active X-chromosome in an early haematopoietic stem cell.

Amino Acid Sequence↗
PubMed1994

Antitumor effects of IST-622, a novel synthetic derivative of chartreusin, against murine and human tumor lines following oral administration.

The antitumor effects of 6-O-(3-ethoxypropionyl)-3',4'-O-exo- benzylidenechartreusin (IST-622), a new synthetic derivative of chartreusin (CT), were investigated. Following oral administration, IST-622 showed marked antitumor effects against various mouse tumors such as P388 and L1210 leukemias, B16 melanoma, Lewis lung carcinoma, Colon 26 and Colon 38 adenocarcinomas, and M5076 reticulum-cell sarcoma. The best antitumor effects were obtained by five intermittent treatments given every 4 days. In addition, IST-622 showed a significant growth-inhibitory effect against two human tumor xenografts, a large-cell lung cancer (Lu-116) and a gastric adenocarcinoma (St-4), among the seven lines tested. IST-622, which was rapidly metabolized into 3',4'-O-exo-benzylidenechartreusin (A-132) and not into CT in vivo or in culture medium, exhibited remarkable growth-inhibitory activity against P388 leukemia in vitro, its 50% growth-inhibitory concentration (IC50) being over 20-fold lower than that of CT. IST-622 showed an in vivo antitumor effect superior to that of authentic A-132, possibly resulting from a higher absorption ratio of IST-622 through the gastrointestinal tract. IST-622 is now under clinical phase I study in Japan.

Administration, Oral↗
PubMed1994

Left ventricular diastolic pulsus alternans in hypertrophic cardiomyopathy.

We examined left ventricular (LV) diastolic pulsus alternans associated with systolic pulsus alternans in a patient with hypertrophic cardiomyopathy. Alternation in abnormal LV diastolic pressure waveforms persistently declining into mid-diastole (incomplete relaxation) and normal diastolic pressure were noted. Diastolic pulsus alternans was not corrected by isoproterenol and may possibly be independent of systolic pulsus alternans.

Cardiac Catheterization↗
PubMed1994

Treatment of symptomatic hepatic cysts by percutaneous instillation of minocycline hydrochloride.

Nine patients with 16 symptomatic nonneoplastic congenital hepatic cysts were treated prospectively by ultrasonically guided percutaneous minocycline hydrochloride injection, and the usefulness of this treatment was evaluated. Seven of the patients had multiple hepatic cysts, and two solitary cysts. All the patients were women, ranging in age from 36 to 81 years. After cystic fluid had been aspirated with a 21-gauge PTC needle, minocycline hydrochloride was injected into all the cysts. The minocycline hydrochloride was dissolved in saline at a concentration of 200 mg in 9 ml, and mixed with 1 ml of 2% mepivacaine hydrochloride. The total quantity of minocycline hydrochloride injected varied from 100 mg to 1200 mg per hepatic cyst, depending on its size. Total or subtotal regression of the cysts was observed in all patients during follow-up periods ranging from 15 to 35 months. Seven patients became symptom-free, one showed symptom reduction, and one showed no change in symptoms. Minor side effects, eg, transient abdominal pain, slight right shoulder pain, and temperature elevation, were noted in three patients respectively. On the basis of these results, we conclude that ultrasonically guided percutaneous minocycline hydrochloride injection is useful for the treatment of symptomatic hepatic cysts.

Adult↗
PubMed1994

Elevated serum and urinary thrombomodulin levels in patients with non-insulin-dependent diabetes mellitus.

Increased plasma levels of soluble thrombomodulin have been reported in several disorders as a marker for vascular endothelial damage. Serum and urinary thrombomodulin levels were measured in 79 patients with non-insulin-dependent diabetes mellitus. Both levels were significantly higher (23.5 +/- 6.1 ng/ml and 146.6 +/- 64.9 ng/ml, respectively) than those of normal healthy controls (18.8 +/- 3.1 ng/ml, P < 0.001, and 96.8 +/- 60.3 ng/ml, P < 0.01). Serum thrombomodulin levels increased in keeping with urinary albumin levels. In urine thrombomodulin was lower in the macroalbuminuria group than in the microalbuminuria group, suggesting two mechanisms: intravascular overproduction and impaired renal clearance. Both serum and urinary thrombomodulin levels in diabetic patients might be predictors for very early nephropathy.

Adult↗
PubMed1994

Dextran sulfate, a competitive inhibitor for scavenger receptor, prevents the progression of atherosclerosis in Watanabe heritable hyperlipidemic rabbits.

Dextran sulfate competes with binding of modified LDL to the scavenger receptor in macrophages. To elucidate the role of dextran sulfate in the atherosclerotic process, 100 mg of dextran sulfate in drinking water was given to 5 Watanabe heritable hyperlipidemic (WHHL) rabbits for 12 months starting at age 4 months. During the experimental period, there were no significant differences in plasma cholesterol levels between dextran sulfate-treated and untreated rabbits. After 12 months' treatment, accumulation of cholesterol ester in total aorta was significantly suppressed in dextran sulfate-treated rabbits as compared with untreated rabbits (71.4 +/- 22.3 vs. 42.7 +/- 16.5 mg/g dry weight, P < 0.05). Furthermore, lesion area with atherosclerotic plaques in treated rabbits was significantly less than that in untreated rabbits (59.7 +/- 24.5 vs. 30.4 +/- 14.4%, P < 0.05). These results indicate that dextran sulfate might prevent the progression of atherosclerosis by competitively inhibiting the binding of modified LDL to scavenger receptors.

Animals↗
PubMed1994

Plasma lipid abnormalities and risk factors for coronary artery disease in Japanese subjects with diabetes mellitus and glucose intolerance.

We evaluated the plasma lipid levels of 3163 subjects including subjects with non-insulin-dependent diabetes mellitus (NIDDM), insulin-dependent diabetes mellitus (IDDM), impaired glucose tolerance (IGT), and normal glucose tolerance. Furthermore, we performed 100 g oral glucose tolerance tests on 2113 subjects, and analyzed the relationships of risk factors for coronary artery disease to glucose intolerance. Mean plasma cholesterol and triglyceride levels were highest in NIDDM (213 mg/dl and 148 mg/dl), and plasma HDL-cholesterol level was lowest in IGT and NIDDM (42 mg/dl), as compared to those in normal subjects (cholesterol, 200 mg/dl; triglycerides, 109 mg/dl; HDL-cholesterol, 52 mg/dl). Multiple regression analysis demonstrated a significant relationship of either blood pressure, plasma triglyceride or HDL cholesterol level to plasma insulin and glucose response after glucose loading.

Adult↗
PubMed1994

The effects of perinatal anoxia or hypoxia on hippocampal kindling development in rats.

The effects of anoxia and hypoxia (3% oxygen) at 10-12 post days of age on the development of ventral hippocampal kindling and its transfer to the contralateral ventral hippocampus were studied in adult male Sprague-Dawley rats. During oxygen deprivation, the heart rate decreased to 15% of the prehypoxic value in the animals exposed to anoxia and 40% in those exposed to hypoxia. As is observed in asphyxia of human newborns, our study included both ischemia and hypoxia. The susceptibility to kindling, which was measured by kindling rate, afterdischarge threshold, generalized seizure threshold, and total afterdischarge duration to stage 5, had a tendency to be enhanced in rats exposed to hypoxia compared with controls. The facilitating effects on primary site kindling were enhanced in the animals exposed to hypoxia compared with those exposed to anoxia. Transfer, which was indicated by kindling rate and afterdischarge threshold, was also slightly facilitated in the rats exposed to anoxia or hypoxia in the perinatal period. These results reveal that perinatal oxygen deficiency may not be sufficient to lead to the development of temporal lobe epilepsy. However, it is possible that perinatal hypoxia results in some pathophysiological change in the brain which leads to greater seizure susceptibility in adulthood.

Aging↗
PubMed1994

Correlation between bile acid malabsorption and pancreatic exocrine dysfunction in patients with chronic pancreatitis.

Fecal bile acid and fecal fat were determined in 18 normal subjects and 22 patients with chronic pancreatitis, and the relation of fecal bile acid excretion to exocrine pancreatic dysfunction was studied. In chronic pancreatitis fecal bile acid was approximately three times that of control subjects, and large amounts of primary bile acid were detected. A significant correlation between fecal bile acid excretion and bicarbonate secreted from the pancreas was found. This evidence of bile acid malabsorption was not observed until bicarbonate output was < 0.05 mEq/h/kg. A slight correlation between fecal bile acid and absorption rates of fat was demonstrated. These results suggest that bile acid malabsorption observed in chronic pancreatitis is related to an impairment of pancreatic bicarbonate secretion.

Adult↗