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Biomedical subjects

A Koyama

Publications and source records attributed to A Koyama.

At least 73 records · Page 4Linked to original sources
PubMed1998

Biosynthesis of methylguanidine in the hepatic peroxisomes and the effect of the induction of peroxisomal enzymes by clofibrate.

A state of peroxidation is one of the factors contributing to uremia. For example, we have reported that certain species of reactive oxygen, particularly the hydroxyl radical, play an important role in the biosynthesis of methylguanidine which contributes to toxicity in patients with uremia. However, it is uncertain which enzymes are involved in the synthesis of methylguanidine from creatinine. In this study, we attempt to show methylguanidine synthesis in the presence of peroxisomal enzymes that catalyze the beta-oxidation of fatty acids. In addition, we investigate the effect of clofibrate, which induces peroxisomal enzymes or glutathione peroxidase activity, on methylguanidine synthesis in the peroxisomal fraction. Male Wistar rats were fed with the chow containing 0.5% clofibrate to induce peroxisomal enzymes and control rats were fed with ordinary laboratory chow. Peroxisomal fractions were obtained from liver homogenates by centrifugation, and incubated with creatinine in 0.1 M potassium phosphate buffer pH 7.4 at 37 degrees C. Results show that methylguanidine is synthesized from creatinine concomitant with the synthesis of hydrogen peroxide from endogenous substrates in the peroxisomal fraction. This methylguanidine synthesis is inhibited by the addition of dimethylsulfoxide, glutathione, or sodium azide (p < 0.01). The rate of methylguanidine synthesis in clofibrate-treated rats was significantly less than that in control rats (p < 0.02). These results suggest that methylguanidine is synthesized in the peroxisomal fraction, and reactive oxygen species which are generated through this enzymatic reaction, participate in methylguanidine synthesis. Moreover, the induction of a scavenger system, especially glutathione peroxidase takes precedent over the generation of reactive oxygen species in peroxisomes treated with clofibrate.

Animals↗
PubMed1998

Optical monitoring of living brain tissue.

Optical methods can usefully augment classical techniques such as electrical recording for investigating cellular and network physiology. Here, recent developments in optical methods--including confocal and nonlinear fluorescence imaging, semiconductor array imaging, and improved fluorescent indicators of ion concentration and transmembrane electrical potential--are briefly reviewed, and examples are offered that may suggest potential applications to experimental studies in alcoholism research.

Alcoholism↗
PubMed1998

[Functional difference between the left supplementary motor area and the left premotor area in a task of confrontation naming and word fluency].

We assessed the faculty of confrontation naming and word fluency of the 11 patients afflicted with frontal lobe infarction or hemorrhage. All the patients were right-handed and manifested transcortical motor aphasia due to cerebrovascular diseases. We carried out the Western Aphasia Battery, and we adopted V-A; the naming task involved confrontation naming of 20 objects, and V-B; the word fluency task involved the naming as many animals as possible in a one minute period. Six patients who have lesions in the left medial frontal lobe performed excellency in the confrontation naming task but exhibited poor word fluency, and 5 patients who have lesions in the left dorso-lateral frontal lobe performed poorly in both tasks. This results suggests that the left dorso-lateral frontal lobe is important in confrontation naming, while the left medial frontal lobe is important in word fluency. Mushiake et al. (1991) showed that the premotor area was involved in visually guided sequential movements, and the supplementary motor area was involved internally determined sequential movements in primates. Regarding language function as analogous to movement, confrontation naming is analogous to visually guided movements and word fluency is analogous to internally determined movements. Thus, our results suggest that the functional difference between the left medial frontal lobe, which includes the supplementary motor area, and the left dorso-lateral frontal lobe, which includes the premotor area, which was demonstrated in primates for movement is also true of language function in humans.

Aphasia, Broca↗
PubMed1998

[A case of glomerulonephritis with singular high titer of anticardiolipin antibody].

We report here a case of severe membranoproliferative glomerulonephritis with a singular high titer of anticardiolipin antibody (aCL). A 19-year-old Japanese female was admitted to Tsukuba Gakuen Hospital after complaining of general edema for 5 months. She had no past history of thrombosis, thrombocytopenia, or spontaneous abortion. Laboratory findings revealed that she had nephrotic syndrome and moderate renal dysfunction. Immunological test showed a high titer of aCL with a high-normal limit of antinuclear antibody, negativity for anti-beta(2) glycoprotein I antibody and negativity for anti-DNA antibody. In the renal biopsy tissue, most glomeruli showed global sclerosis and the remaining glomeruli revealed membranoproliferative change with crescent formation. Steroid therapy with warfarin and dipyridamole was effective and her renal function improved gradually. This case lacked the typical symptoms of primary antiphospholipid syndrome and did not satisfy the criteria of SLE. In spite of these findings, the singular high titer of aCL with membranoproliferative glomerulonephritis characterized this case.

Adult↗
PubMed1998

[A case of systemic AA amyloidosis complicating Crohn's disease].

Although systemic AA amyloidosis complicating Crohn's disease has been found in 0.5 to 6% in America and Europe, it is relatively rare in Japan. We report a case of systemic AA amyloidosis complicating Crohn's disease. In 1979, a 26-year-old Japanese man presented with diarrhea, melena and perianal abscesses, and was diagnosed as having Crohn's disease. He was treated with oral prednisolone, salazosulfapyridine and diet therapy. However, the gastrointestinal symptoms recurred and he was hospitalized several times. In 1991, his thyroid gland was found to be swollen, but with normal thyroid function, and his thyroid gland became larger subsequently. In October 1995, he showed renal dysfunction (blood urea nitrogen 33.2 mg/dl; serum creatinine 1.5 mg/dl) with proteinuria. His renal function had been deteriorating rapidly. On September 13, 1996, he was admitted to the Tsukuba University Hospital. At the time of admission, his renal function showed a blood urea nitrogen of 129.5 mg/dl with a creatinine of 5.4 mg/dl. The urine contained 0.8 g of protein per 24 hours. He presented with diarrhea for several days before admission and was treated with central venous hyperalimentation. Despite supportive care, he developed end-stage renal failure, then hemodialysis was initiated on October 7. His condition was complicated by a complete auriculoventricular block on October 18. He died of hemoperitoneum on October 25. On postmortem examination, extensive amyloid deposits were found in multiple organs including kidneys, intestine, heart, thyroid gland, lungs, liver, spleen, pancreas, gall bladder, adrenal glands, testis, prostate, bone marrow and parathyroid glands. Analysis of amyloid protein in the autopsy specimens showed type AA.

Adult↗
PubMed1998

[Difference between transcortical sensory aphasia following the left frontal lesion and transcortical sensory aphasia following the left posterior lesion].

We assessed the difference between transcortical sensory aphasia (TCSA) following the left frontal lesions (F-TCSA) and TCSA following the left posterior lesions (P-TCSA). All the patients were right-handed and the 7 patients had the lesions in the only frontal lobe and the 10 patients had the lesions only in the left temporo-parieto-occipital regions. We administered pointing tasks, using 90 line drawings representing single nouns. We presented 6 line drawings a pointing board, and we used two kinds of pointing boards: one showed the line drawings each belonging to different categories (random categorized pointing task), the other showed the line drawings each belonging to only either two different categories (two categorized pointing task) and we presented 15 pointing boards each alternatively. The result was that regarding the patients of P-TCSA showed different number of correct answers between the random categorized pointing task and the two categorized pointing task with statistical significance. Regarding the patients of F-TCSA showed no difference between them. The results indicated that disturbance of P-TCSA on the pointing task was the disturbance of semantic process per se. And the disturbance of F-TCSA on the pointing task was that of not only semantic process but also the whole process including comprehending the presented words, searching the line drawings, comparing the line drawings with the presented word and final selection, which demanded persistent multiple memory process consistent with working memory.

Aphasia, Wernicke↗
PubMed1997

A novel nonenzymatic pathway for the generation of nitric oxide by the reaction of hydrogen peroxide and D- or L-arginine.

Nitric oxide (NO) is a biologically active molecule known to be enzymatically synthesized from L-arginine in the presence of NO synthetase (NOS). In this study, we demonstrate a novel non-enzymatic pathway for NO synthesis involving hydrogen peroxide and D- or L-arginine. We employed two measures of NO generation. The first consists in the demonstration of the oxidative metabolites of NO (NO2 + NO3 = NOx) and the second is the confirmatory finding of chemiluminescence derived from NO. The results show that NOx increases in the incubation mixture containing hydrogen peroxide coupled with D-arginine, L-arginine, L-canavanine, and even the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). However, chemiluminescence was detected only from the reactions of hydrogen peroxide and D- or L-arginine and was diminished by the addition of carboxy-2-phenyl-4, 4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO), a specific scavenger of NO, confirming NO generation in the reaction.

Amino Acids↗
PubMed1997

Giant calcifying epithelioma of Malherbe (pilomatrixoma): imaging features.

We present a case of giant calcifying epithelioma of Malherbe (pilomatrixoma) in the right upper arm of a 62-year-old man. It measured 18 x 12 x 8 cm in size, making it the largest of all the cases reported previously. CT clearly demonstrated a well-defined, subcutaneous mass with amorphous calcifications. The mass showed intermediate signal intensity on T2*-weighted MR images and slight contrast uptake on contrast-enhanced MR images. Histopathologically, this tumor showed no aggressive or malignant nature. The patient is without evidence of recurrence or metastasis 3 years following the resection.

Arm↗
PubMed1997

Natural history and risk factors for immunoglobulin A nephropathy in Japan. Research Group on Progressive Renal Diseases.

The Research Group on Progressive Renal Diseases conducted a national survey, in Japan, of cases of primary glomerulonephritis (GN) in 1985 and 1993. The results of the survey, reported here, revealed a high prevalence and relatively poor prognosis for immunoglobulin A nephropathy (IgAN). Using immunofluorescent microscopy, 47.2% of 1,063 patients were diagnosed as having IgAN; 62.8% of patients had diffuse mesangial proliferative GN, and focal mesangial proliferative GN was observed in 23.0%. Nearly 70% of the patients had no clinical symptoms, and the IgAN was detected by routine physical examination. The mean period of observation was 11.8 +/- 6.3 years. Renal survival rates for the 502 cases of IgAN, in which the start of dialysis and renal-related death were end points, were 96%, 85%, 75%, and 61% at 5, 10, 15, and 20 years, respectively, from the time of the detection of the earliest known renal abnormalities. Renal survival rates of patients with diffuse mesangial proliferative GN were 96%, 83%, 75%, and 59% at 5, 10, 15, and 20 years, respectively. At the end of the observation period, 20% of patients had improved, 45.8% showed no change, 13.5% had deteriorated, and 20.4% had renal-related death. The risk factors for renal failure by logistic multivariate analysis were serum creatinine concentration > or =1.4 mg/dL (relative risk, 3.5) and levels of urinary protein > or = +(dipstick) (relative risk, 6.4), determined at the time of biopsy. These parameters can be useful for assessing prognosis during the relatively advanced stages of this disease. It is important to note that a relatively high percentage of patients with IgAN progressed to end-stage renal failure even when their histologic findings comprised only minor glomerular abnormalities or focal proliferative changes.

Adolescent↗
PubMed1997

Thiobarbituric acid reactive substances are increased in the subcutaneous fat tissue of patients with end-stage renal disease.

BACKGROUND: Patients with end-stage renal disease are thought to be in a highly peroxidative state, based on studies showing decreased serum antioxidant activity and increased peroxidative products. In this study we confirm these findings by examining lipid peroxidation in subcutaneous fat tissue in uraemia. SUBJECTS AND METHODS: Twenty-seven subcutaneous fat samples were taken from patients with end-stage renal disease when they underwent intervention for arteriovenous fistula for haemodialyis or for catheter insertion for continuous ambulatory peritoneal dialysis. The control samples were taken from 11 patients with normal renal function and without any history of renal disease who had surgical interventions. Lipid peroxides were measured as thiobarbituric acid reactive substance. RESULTS: The concentration of thiobarbituric acid reactive substances in subcutaneous fat tissue in the patients with end-stage renal disease is 1.223 +/- 0.636 nmol/mg fat tissue (mean +/- SD) whereas the level in the control group is 0.097 +/- 0.054 nmol/mg fat tissue. A comparison of the two groups by Student's t test revealed a highly significant difference (P < 0.001). CONCLUSIONS: This study supports the finding of a severe peroxidative state in patients with end-stage renal disease.

Adipose Tissue↗
PubMed1997

Clinical evaluation of nuclear matrix protein 22 (NMP22) in urine as a novel marker for urothelial cancer.

OBJECTIVES: This study was undertaken to determine the clinical usefulness of nuclear matrix protein 22 (NMP22) as a novel urine marker for urothelial cancer, particularly, to substitute for voided-urine cytology. METHODS: NMP22 values were determined for 280 patients and 20 healthy volunteers by NMP22 Test Kit based on an enzyme-linked immunosorbent assay. RESULTS: When the cut-off value was set at 10 U/ml, the positive rate of urinary NMP22 for urothelial cancer was 80.9% (38/47), whereas that for posttreatment cases and benign diseases was 35.7% (74/207). When urinary NMP22 and voided-urine cytology were compared, the test for urinary NMP22 showed higher sensitivity than cytology in patients with urothelial cancer. When urinary NMP22 values were determined pre- and postoperatively in patients with urothelial cancer, the postoperative value decreased in all patients, and were below the cut-off value in all except one patient. CONCLUSIONS: Urinary NMP22 is a useful diagnostic marker as a substitute for voided-urine cytology for the surveillance of urothelial cancer.

Adenocarcinoma↗
PubMed1997

Favorable effect of hemodialysis on decreased serum antioxidant activity in hemodialysis patients demonstrated by electron spin resonance.

There is considerable evidence that uremic patients are in a highly peroxidative state. The purpose of this study was to investigate the serum antioxidant activity that may regulate, or represent, the redox state in vivo. Serum from pre- and posthemodialysis patients and from healthy control subjects was added to a system generating the hydroxyl radical, and then the signal intensities of reactive oxygen species were measured by electron spin resonance and spin-trapping technique. The electron spin resonance signals of the reaction mixture containing prehemodialysis sera were significantly stronger than those of the reaction mixture containing healthy sera (P < 0.001, n = 19), and there was no significant difference in the signals between the reaction mixture containing posthemodialysis and healthy sera. These findings demonstrated that serum antioxidant activity in hemodialysis patients is significantly decreased, and this pathological condition is improved by hemodialysis treatment.

Adult↗