Search PubMed⌕ Search

Biomedical subjects

K Uchida

Publications and source records attributed to K Uchida.

At least 1,081 records · Page 60Linked to original sources
PubMed1990

Formation of diastereoisomeric 3a-hydroxypyrroloindoles from a tryptophan residue analog mediated by iron (II)-EDTA and L-ascorbate.

Oxygenation of a tryptophan residue analog by ascorbate in the presence of catalytic amounts of iron(II) and ethylenediaminetetraacetic acid (EDTA) has been studied. Under physiological conditions, reaction of the tryptophan derivative (N-t-butoxycarbonyl-L-tryptophan) with Fe(II)-EDTA and ascorbate resulted mainly in the oxygenation of the indole moiety of the substrate. In this reaction, cis and trans diastereoisomeric alcohols 3a-hydroxy-1-t-butoxycarbonyl-1,2,3,3a,8,8a-hexahydropyrrolo[2,3- b]indoles have been successfully identified in the metal-catalyzed free radical oxidation of indole compounds. Hydroxylation at C-5 and C-6 and a ring opening reaction between C-2 and C-3 have also been confirmed. The reaction of Fe(II)-EDTA/ascorbate with the tryptophan derivative was apparently nonselective with regard to position and was significantly suppressed by the hydroxyl radical scavengers (mannitol and dimethylsulfoxide), suggesting the participation of the hydroxyl radical as the actual oxidizing species.

Ascorbic Acid↗
PubMed1990

Tetrahydrobiopterin-dependent production of L-dopa in NRK fibroblasts transfected with tyrosine hydroxylase cDNA: future use for intracerebral grafting.

In the present study, tyrosine hydroxylase (TH; EC 1.14.16.2) cDNA was transfected into cultured fibroblasts and the production of L-3,4-dihydroxyphenylalanine (L-DOPA) was determined. Type 2 TH cDNA was transfected into fibroblasts (NRK-49F) derived from the normal rat kidney, and the expression of the TH minigene was screened by immunocytochemical staining and immunoblotting analysis with TH antiserum. Several clones of the NRK transfectants that produce TH molecules were obtained. The expressed TH molecules showed high enzyme activity in a complete assay system in vitro. However, L-DOPA was not detected in the cultured cells due to the possible absence of de novo synthesis of (6R)-L-erythro-tetrahydrobiopterin (BH4) in these cells. When BH4 was added to the medium, a large amount of L-DOPA was detected not only in the cells but also in the medium. These findings may aid in regulating the amount of L-DOPA secretion from cells after they are transplanted into the brain.

Animals↗
PubMed1990

[The effect of angiotensin I converting enzyme inhibitor (SQ 14225) on plasma 18-hydroxycorticosterone and aldosterone in sodium depleted conscious rats].

Altered sodium intake is known to cause a greater change in plasma 18-hydroxycorticosterone (18-OHB) level than in plasma aldosterone level, resulting in an increase of plasma 18-OHB/aldosterone ratio in sodium-depleted man and rats. To evaluate the role of endogenous angiotensin II in the high plasma 18-OHB/aldosterone ratio in sodium-depleted rats, we examined the effect of the angiotensin I converting enzyme inhibitor SQ 14225 on plasma 18-OHB and aldosterone in sodium-depleted (SD) and sodium-repleted (SR) conscious rats. Plasma renin activity (PRA) and plasma angiotensin II were higher in the SD rats than in the SR rats. The ingestion of SQ 14225 caused an increase in PRA and a decrease in plasma angiotensin II, whereas these changes were more prominent in the SD rats than in the SR rats. Plasma 18-OHB and aldosterone levels were higher in the SD rats than in the SR rats. The plasma 18-OHB/aldosterone ratio was also higher in the SD rats than in the SR rats. The ingestion of SQ 14225 caused decreases in plasma 18-OHB and aldosterone levels in both the SR and SD rats, whereas the SQ 14225-induced decreases in plasma 18-OHB and aldosterone levels were more prominent in the SD rats than in the SR rats. Thus, the ingestion of SQ 14225 induced a decrease in the plasma 18-OHB/aldosterone ratio in both the SR and SD rats. The decrease in plasma 18-OHB/aldosterone ratio was more prominent in the SD rats than in the SR rats.(ABSTRACT TRUNCATED AT 250 WORDS)

18-Hydroxycorticosterone↗
PubMed1990

Effect of warfarin on plasma and liver vitamin K levels and vitamin K epoxide reductase activity in relation to plasma clotting factor levels in rats.

Changes in plasma and liver vitamin K1 and vitamin K1 epoxide levels, liver microsomal vitamin K epoxide reductase activity, and plasma clotting factor II and VII levels were determined in rats after a single injection of warfarin (2.5 mg/kg, s.c.). The plasma and liver vitamin K1 levels gradually decreased after warfarin injection, attaining the lowest values at 2-3 hrs and remaining low for 48 hrs. They then returned to the control levels at 72 hrs. The changes in vitamin K1 epoxide levels were opposite, with an increase being seen soon after the warfarin injection, the highest values at 3 hrs and a gradual decrease to the initial levels occurring subsequently. The combined levels of vitamin K1 plus vitamin K1 epoxide, however, remained almost constant in both plasma and liver after the warfarin injection. The liver vitamin K epoxide reductase activity decreased to its lowest level soon after the injection and then gradually increased after 12 hrs, but the activity at 72 hrs was only about 30% of the initial activity. The plasma clotting factor levels gradually decreased after the injection, bottomed at 24 hrs and then began to increase, recovering almost to the initial levels at 72 hrs. A positive correlation was found between plasma and liver levels for both vitamin K1 and vitamin K1 epoxide, and the slope of the vitamin K1 epoxide curve was steeper than that for vitamin K1 in the warfarin-treated rats. A similar positive correlation was found for both vitamin K1 and vitamin K1 epoxide after vitamin K1 injection in normal untreated rats, but the slope of the vitamin K1 epoxide curve was much shallower. These results suggest that warfarin inhibits vitamin K epoxide reductase and decreases blood clotting factor synthesis, thus increasing plasma and liver vitamin K1 epoxide levels. A vitamin K epoxide reductase activity one third of that in normal rats is sufficient to maintain normal reduction of vitamin K1 epoxide and synthesis of blood clotting factors.

Animals↗
PubMed1990

Non-PTS uptake and subsequent metabolism of glucose in Pediococcus halophilus as demonstrated with a double mutant defective in phosphoenolpyruvate:mannose phosphotransferase system and in phosphofructokinase.

Pediococcus halophilus possesses phosphoenolpyruvate:mannose phosphotransferase system (man:PTS) as a main glucose transporter. A man:PTS defective (man:PTSd) strain X-160 could, however, utilize glucose. A possible glucose-transport mechanism other than PTS was studied with the strain X-160 and its derivative, man:PTSd phosphofructokinase defective (PFK-) strain M-13. Glucose uptake by X-160 at pH 5.5 was inhibited by any of carbonylcyanide m-chlorophenylhydrazone, nigericin, N,N'-dicyclohexylcarbodiimide, or iodoacetic acid. The double mutant M-13 could still transport glucose and accumulated intracellularly a large amount of hexose-phosphates (ca. 8 mM glucose 6-phosphate and ca. 2 mM fructose 6-phosphate). Protonophores also inhibited the glucose transport at pH 5.5, as determined by the amounts of accumulated hexose-phosphates (less than 4 mM). These showed involvement of proton motive force (delta P) in the non-PTS glucose transport. It was concluded that the non-PTS glucose transporter operated in concert with hexokinase or glucokinase for the metabolism of glucose in the man:PTSd strain.

Biological Transport, Active↗
PubMed1990

Location of sites of dopamine storage in megakaryocytes by autoradiography.

We have used quantitative electron microscope autoradiography to study the subcellular sites of 3H-dopamine uptake in mouse megakaryocytes after a single intraperitoneal injection. Autoradiographic grains were found to be associated almost exclusively with the vesicles of precursors of monoamine-storage organelles. The labeling intensity (radioactivity) of the demarcation membrane system which is continuous with the plasmalemma was also significantly greater than would be expected. On the other hand, radioactivity associated with the remaining sites in the cytoplasm was not significantly different from that expected of a random distribution. In order to compare 3H-dopamine uptake during cell maturation, light microscope autoradiographic studies were also done. Immature megakaryocytes were labeled slightly, but the number of silver grains increased significantly in maturing cells. Mature megakaryocytes were 2.7 times more radioactive than the maturing cells. Our results suggest that the megakaryocytes were able to accumulate dopamine from the early stages of cell maturation and to store dopamine in precursors of monoamine-storage organelles.

Animals↗
PubMed1990

Effects of alpha-difluromethylornithine on the development of deeply invasive urinary bladder carcinomas in mice.

alpha-Difluoromethylornithine (DFMO), was examined for its ability to suppress the development of invasive urinary bladder carcinoma in C3H/He male mice. Continuous administration of 0.2% DFMO in water following carcinogen treatment (0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine, BHBN, in drinking water for 8 weeks) was effective in suppressing urinary bladder carcinomas (P less than 0.05) as compared with the control group. However, when comparison was made based on tumors involving the entire urinary tract, protective effects could not be demonstrated. Coadministration of DFMO (0.2%) and BHBN (0.01%) did not alter tumor induction by the latter. These results were in sharp contrast to the protective effects in rats. Since bladder tumors in rats are of low grade and superficial whereas those in mice are of high grade and deeply invasive, our data indicate that DFMO has little to no effects against the development of aggressive forms of bladder carcinoma.

Animals↗
PubMed1990

Distribution of microtubules and microfilaments in thyroid follicular epithelial cells of normal, TSH-treated, aged, and hypophysectomized rats.

We investigated the distribution of microtubules and microfilaments in rat thyroid follicular epithelial cells by applying an immunofluorescence technique with monoclonal antibodies against tubulin and by staining sections with rhodamine-phalloidin. In normal thyroid cells, microtubules run longitudinally from the apical region to the basal region intersecting with each other. In addition, intense labelling with tubulin antibodies was observed in the apical part of the cell. The ultrastructural examinations showed that microtubules often run along the apical plasma membrane. Dot-like labelling with anti-tubulin antibodies was often observed in the perinuclear space, but not microtubules were recognized in the nucleus. Microfilaments bound to rhodamine-phalloidin were distributed mainly beneath the apical plasma membrane, and the portion along the basolateral membrane was scarcely positive. The apical pole of the follicle cell was also decorated by anti-microtubule-associated protein-2 (MAP-2). After TSH stimulation, the intensity of immunocytochemical staining against tubulin was remarkably increased in the cytoplasm. Simultaneously, at the apical region, the staining intensity of rhodamine-phalloidin was increased. Microtubules and microfilaments appeared in the pseudopods after TSH injection. In hypophysectomized or aged rats, thyroid follicular epithelial cells decreased in height, and both immunofluorescent labelling against tubulin and rhodamine-phalloidin labelling were markedly decreased. These results indicate that the distribution and polymerization of microtubules and microfilaments in thyroid follicular epithelial cells vary with the functional stage.

Actin Cytoskeleton↗
PubMed1990

Regulation of poly(ADP-ribose) polymerase mRNA levels during compensatory and mitogen-induced growth of rat liver.

Poly(ADP-ribose) polymerase mRNA levels were studied in hepatic regeneration following partial hepatectomy, and in hyperplasia induced by the mitogen lead nitrate. A significant increase in the level of poly(ADP-ribose) polymerase mRNA was found 8 h after partial hepatectomy when no detectable increase of DNA synthesis could be observed; the level of poly(ADP-ribose) polymerase transcripts increased up to six-fold within 1-2 days. A similar increase of the level of poly(ADP-ribose) polymerase mRNA was found 24 h after treatment with lead nitrate. A twofold increase in poly(ADP-ribose) polymerase activity was observed 2 days after (a) partial hepatectomy and (b) lead nitrate treatment. From these results an important role of poly(ADP-ribose) polymerase in cell proliferation could be suggested.

Animals↗
PubMed1990

Surface electromyographic electrode pair with built-in buffer-amplifiers.

By means of a surface electrode with an operational amplifier, a new electrode unit suitable for an electromyographic-biofeedback apparatus and for portable electromyography used outside a Faraday cage was developed. The operational amplifier, which has an output impedance lower than 10 ohms, functions as an efficient buffer amplifier and is able to protect the EMG signals from background noises. This new electrode unit is small (32 x 12 x 5 mm), waterproof, and inexpensive. Because its structure is simple, it can be built in any laboratory.

Amplifiers, Electronic↗
PubMed1990

Involvement of urine in epithelial-stromal interactions in urinary bladder carcinogenesis.

The role of urine in epithelial-stromal interactions in urinary bladder carcinogenesis was investigated using the 'Stroma' bladder model established in our laboratory. Rats treated with 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BHBN) in drinking water for 4 weeks or age-matched untreated rats served as donors of bladders with denuded epithelium ('stroma' bladders), which were resurfaced 4 days later with urothelial cells from rats treated with 0.05% BHBN for 4 weeks. Subsequently, the transplants received weekly injections of normal rat urine or saline. In the urine-free environment, cell implants developed hyperplastic changes but few tumor formations with no significant difference between the two types of 'stroma' bladder. In contrast, urine instillation stimulated neoplastic growth, and tumor-enhancing effect was significantly accelerated in the BHBN-treated 'stroma' bladder group as compared to the control group. These results suggest that epithelial-stromal interactions are altered in such a way that bladder carcinogenesis is enhanced by prior exposure of the bladder stroma to carcinogen and subsequent urine contact.

Animals↗
PubMed1990

Stimulation of urinary bladder tumorigenesis by carcinogen-exposed stroma.

There is evidence to suggest that control mechanisms, either growth-stimulatory, inhibitory or inductive, may play a role in carcinogenesis. To test the hypothesis that treatment of rat urinary bladder with carcinogen induces alterations in the stroma which result in modified epithelial-stromal interactions, experiments were conducted using a rat model specifically designed for the study. Following exposure of Fischer F344 rats in drinking water to the urinary bladder carcinogen, N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN) for four weeks, bladders were removed and subjected to a brief detergent treatment to completely remove epithelium. The bladders without epithelium ("stroma" bladder) were heterotopically transplanted to syngeneic recipients. Four days later, the denuded mucosa surface was resurfaced with intraluminal instillation of urothelial cells, either untreated or treated with BHBN for six weeks (6w-BHBN) or 10 weeks (10w-BHBN). Examination at 12 weeks posttransplant of the "stroma" bladders that had received 6w-BHBN urothelial cells showed a higher tumor incidence of carcinoma in the BHBN-exposed "stroma" bladders as compared with the incidence in the carcinogen-unexposed "stroma" bladders (p less than 0.05). Examination at 18 weeks posttransplant showed 100% incidence of tumors in all "stroma" bladders irrespective of the lengths of BHBN exposure of urothelial cells. However, among the bladders that had received 6w-BHBN urothelial cells, carcinogen-exposed "stroma" bladders proved to be better "soil" for neoplastic cells to proliferate; the mean tumor volume as well as the mean total tumor volume per bladder were significantly higher than in the control "stroma" bladders (p less than 0.01 for each comparison). Similarly, among the bladders that had been resurfaced with 10w-BHBN urothelial cells, the mean total tumor volume per bladder was greater in the carcinogen-treated "stroma" bladders than in the controls (p less than 0.05). No proliferative or neoplastic changes were observed in the BHBN exposed "stroma" bladders which had been resurfaced with normal urothelial cells. Our data indicate that neoplastic growth of carcinogen treated urothelium is enhanced when such cells interact with the stroma which has also been exposed to carcinogen.

Animals↗
PubMed1990

Synthesis of thromboxane receptor antagonists with bicyclo[3.1.0]hexane ring systems.

Thromboxane A2 receptor antagonists 11a, 15a, 26a, 30a, 34a, 36a, 46a, 52a, 61a, 72a, and 82a, which contain 6-oxabicyclo[3.1.0]hexane, 6-thiabicyclo[3.1.0]hexane, bicyclo[3.1.0]hexane, or 6,6-dimethylbicyclo[3.1.0]hexane ring systems with heptenoic and (phenylsulfonyl)amino side chains, and their corresponding sodium salts and methyl esters were synthesized. This study then examined the inhibitory effects of their sodium salts for the platelet aggregation induced by arachidonic acid with rabbit platelet-rich plasma and platelet aggregation induced by collagen with rat washed platelets.

Animals↗
PubMed1990

A radioimmunoassay of bile acids.

A radioimmunoassay for beta-muricholic acid was developed using an antiserum which was prepared by injecting beta-muricholic acid conjugated with bovine serum albumin into rabbits. The antiserum reacted with glyco-beta-muricholic, tauro-beta-muricholic and beta-muricholic acids, but not with other bile acids. The radioimmunoassay showed good reproducibility with inter- and intra-assay coefficients of variations of 6% to 15%. When the validity of the method was examined by comparing it with a gas-liquid chromatography method, a linear correlation was obtained.

Animals↗
PubMed1990

The influence of delivery mode on biological inactive renin level in umbilical cord blood.

In order to investigate the influence of delivery mode on biological inactive renin levels in fetal circulation, plasma inactive renin (PIR), plasma renin activity (PRA) and plasma total renin (PTR) were measured in umbilical venous blood samples of 21 infants delivered vaginally after spontaneous labor and of 9 infants delivered by elective cesarean section after the onset of labor. Biological renin activities were measured by bioassay. The PIR levels in infants delivered vaginally were significantly lower than those in infants delivered by cesarean section, while the PRA levels were the opposite. However, the PTR levels were not significantly different between the two groups. These results suggest that the plasma levels of biological inactive renin in infants delivered vaginally may decrease, probably due to its conversion to active renin in the second stage of labor.

Adult↗
PubMed1990

Changes in free amino acid concentration in the hemolymph of the female Culex pipiens pallens (Diptera: Culicidae), after a blood meal.

The analysis of the free amino acids in the hemolymph of female Culex pipiens pallens L. indicated that asparagine, glutamine, glycine, leucine, serine, threonine, tyrosine, and valine noticeably increased in concentration during a blood meal digestion at 22 degrees C. The concentrations started to rise at about 4 h, reaching maximal level at 12-24 h, and then gradually returned to the prefeeding level by the fifth day after the blood meal. Before the sharp increase, the concentrations of asparagine, glutamine, glycine, serine, threonine, and tyrosine declined slightly during the first 1-2 h, probably because of hemolymph dilution by water absorbed from the blood meal. Histidine and lysine also showed a minor decrease soon after blood feeding, followed by a moderate but noticeable increase, delaying maximal concentrations until 48 h after the blood meal. Proline and alanine both exhibited a high hemolymph content and changed greatly, but with a large variation between the two samples analyzed. The changing pattern of individual hemolymph amino acids depended to a large extent upon the content of each amino acid in the blood meal given to the mosquitoes. Other free amino acids detected in the hemolymph were at very small concentrations and except for phenylalanine did not show any changes after a blood meal. The total free amino acid concentration was 50 nmol (or 6 micrograms) per microliters hemolymph before a blood meal, and increased to a maximal concentration of 88 nmol (or 11 micrograms) per microliters hemolymph at 18 h after the blood meal.

Amino Acids↗
PubMed1990

Effect of vitamin C depletion on serum cholesterol and lipoprotein levels in ODS (od/od) rats unable to synthesize ascorbic acid.

The effect of ascorbic acid deficiency on serum and liver cholesterol, phospholipid and triglyceride levels, serum lipoprotein levels and serum lipoprotein cholesterol levels were examined in male rats with a hereditary defect in ascorbic acid synthesis (ODS rats). Male homozygotes (od/od) and male rats of their parent strain (+/+) were each divided into four treatment groups and were fed vitamin C-deficient or vitamin C-replete diets containing either 0 or 0.5% cholesterol. During the 3-wk feeding-period the ODS (od/od) rats fed the vitamin C-deficient diet gradually decreased food intake, resulting in a lower body weight than that of od/od rats given ascorbic acid. The serum cholesterol level was significantly higher in the vitamin C-deficient od/od rats fed the cholesterol diet, and it tended to be higher in those fed the control (0% cholesterol) diet, whereas the liver lipid levels remained unchanged relative to those in od/od rats fed the vitamin C-replete diet. The serum very low density lipoprotein and high density lipoprotein (HDL) cholesterol levels were lower in od/od rats fed the vitamin C-deficient diet without cholesterol, but intermediate density lipoprotein and low density lipoprotein cholesterol levels were markedly higher in the vitamin C-deficient od/od rats than in od/od rats given ascorbic acid, regardless of dietary cholesterol level. The ratio of HDL2 cholesterol to HDL3 cholesterol was also higher in the vitamin C-deficient od/od rats. The parent strain of the od/od rats (+/+) showed no change due to vitamin C deficiency. These results suggest that vitamin C deficiency delays low density lipoprotein metabolism and produces hypercholesterolemia in male od/od rats.

Animals↗