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Biomedical subjects

A Yamauchi

Publications and source records attributed to A Yamauchi.

At least 145 records · Page 8Linked to original sources
PubMed1996

Hyperglycemia decreases dehydroepiandrosterone in Japanese male with impaired glucose tolerance and low insulin response.

Recent studies indicate that experimentally induced hyperinsulinemia may reduce serum dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulfate (DHEA-S). Serum DHEA and DHEA-S decrease in diabetic patients, but the mechanism by which hyperglycemia decreases DHEA and DHEA-S is unknown. In this study, we investigated the effect of hyperglycemia on DHEA and DHEA-S in impaired glucose tolerance (IGT) by means of the 75g-oral glucose tolerance test (OGTT). We selected 30 male IGT patients receiving diet therapy only, whose insulinogenic Index was under 0.3. Oral glucose challenge significantly reduced DHEA (P = 0.0001) and DHEA-S (P < 0.05) at 60 and 120 min after OGTT. Setting the value of DHEA and DHEA-S at time zero as 100%, we calculated the DHEA and DHEA-S values at 60 and 120 min after OGTT as %DHEA(-S) 60 min and %DHEA(-S) 120 min, respectively. DHEA and DHEA-S at time zero showed no correlation with BMI, HbA1c, the sum of insulin values (sigma IRI) or the area under the curve of plasma glucose (AUC). We found decreases in %DHEA 60 min (r = -0.411, P < 0.05), %DHEA-S 60 min (r = -0.508, P < 0.01) and %DHEA-S 120 min (r = -0.393, P < 0.05) as AUC increased, but sigma IRI showed no correlation with %DHEA(-S) 60 min or %DHEA(-S)120 min. We conclude that the depression of DHEA and DHEA-S after OGTT is attributable to hyperglycemia in male Japanese IGT with low insulin response.

Dehydroepiandrosterone↗
PubMed1996

Depression of dehydroepiandrosterone in Japanese diabetic men--comparison between non-insulin-dependent diabetes mellitus and impaired glucose tolerance.

Hyperglycemia is known to reduce dehydroepiandrosterone (DHEA) circulating levels; however, the mechanism by which hyperglycemia decreases DHEA is not elucidated. In this study, serum DHEA and DHEA sulfate (DHEA-S) levels were compared in 50 men with non-insulin-dependent diabetes mellitus (NIDDM) and 50 age-matched men with impaired glucose tolerance (IGT) receiving only diet therapy. Serum concentrations of DHEA and DHEA-S in the NIDDM group were significantly lower than in the IGT group (7.8 and 9.7 nmol/l vs 3.4 and 4.9 mumol/l, respectively; p < 0.01) but there was no significant difference in immunoreactive insulin between the two groups. When the results from both groups were combined, HbA1C was significantly inversely related to DHEA (r = -0.243, p < 0.01) and DHEA-S (r = -0.305, p < 0.01). Immunoreactive insulin showed no correlation with DHEA and DHEA-S. Multiple regression analysis showed that HbA1C was independently negatively related to both DHEA and DHEA-S. We conclude that hyperglycemia may decrease serum DHEA and DHEA-S in Japanese men with NIDDM, but the depression of DHEA(-S) is independent of serum insulin level.

Dehydroepiandrosterone↗
PubMed1996

Aldose reductase and myo-inositol transporter mRNA are independently regulated in rat renal medulla.

During antidiuresis, renal papillary cells accumulate organic osmolytes preferentially over inorganic ions. It has been previously demonstrated that sodium infusion increased all of these organic osmolytes except myo-inositol (1). Conversely, urea infusion increased only glycerophosphorylcholine significantly. In addition to sodium and urea, potassium localized in tissue and urine influenced the composition of organic osmolytes. The goal of this study was to clarify how the level of mRNA of osmoregulatory protein is regulated by the extracellular solutes and how it affects the accumulation of organic osmolytes. To clarify the relationship between intra- or extracellular solutes and the regulation of Na/myo-inositol cotransporter and aldose reductase, mRNA of these osmo-regulatory proteins were determined in water-deprived sodium chloride-, potassium chloride-, and urea-loaded rats. Medullary content of sorbitol and myo-inositol, and aldose-reductase enzymatic activity were measured simultaneously in these animals. In water-deprived, sodium-loaded, and potassium-loaded rats, the inner medullary sorbitol content increased significantly in accordance with the rise in the enzymatic activity and the level of aldose reductase mRNA. In urea-loaded rats, both the sorbitol content and the level of aldose reductase mRNA were equal to that in hydrated rats. In the outer and inner medullary tissues, the level of myo-inositol transporter mRNA was increased in all hyperosmolality protocols, including urea infusion, which corresponded with the rise in myo-inositol content. In conclusion, potassium chloride infusion is as effective as water deprivation and sodium chloride infusion in raising the level of aldose reductase and myo-inositol transporter mRNA, whereas urea influenced only myo-inositol transporter. Although aldose reductase and myo-inositol transporter are osmoregulatory proteins in the renal medulla, the levels of aldose reductase and sodium-dependent myo-inositol transporter mRNA are regulated independently.

Aldehyde Reductase↗
PubMed1996

A low-affinity vasopressin V2-receptor gene in a kindred with X-linked nephrogenic diabetes insipidus.

In this study, a mutation in vasopressin Type 2 receptor (V2R) in a patient with hereditary nephrogenic diabetes insipidus (NDI) has been identified and characterized. The sequencing of the V2R gene from the patient revealed that there was a missense mutation (TAT to TGT) resulting in the substitution of 205Tyr for Cys in the putative third extracellular domain. The expression analysis in COS cells showed that the binding affinity of the mutant receptor (KD = 19.8 nM) for arginine vasopressin was much lower than that of the wild-type receptor (KD = 1.8 nM) so that intracellular cAMP production stimulated by arginine vasopressin was impaired in cells with the mutant V2R. From these results, it was concluded that the single amino-acid substitution of V2R is responsible for this familial disease.

Adult↗
PubMed1996

McArdle's disease with non-insulin-dependent diabetes mellitus: the beneficial effects of hyperglycemia and hyperinsulinemia for exercise intolerance.

A 64-year-old female with McArdle's disease and non-insulin-dependent diabetes mellitus (NIDDM) is reported. She had none of the characteristic symptoms of McArdle's disease such as muscle cramps but her serum creatine kinase level was elevated. Muscle biopsy with negative muscle phosphorylase staining showed McArdle's disease. Modified forearm ischemic exercise test was done at two conditions; fasting and two hours after a meal. When fasting, the level of lactic acid did not elevate after exercise. After a meal, however, the serum lactic acid level rose with the elevation of plasma glucose and IRI. Thus, we suggested that high plasma glucose and insulin due to NIDDM may induce blood-borne glucose uptake with exercise.

Biopsy↗
PubMed1996

Angiotensin I-converting enzyme insertion/deletion polymorphism: potential significance in nephrology.

Angiotensin I-converting enzyme (ACE) plays a pivotal role in cardiovascular homeostasis and by activating angiotensin I into angiotensin II and inactivating bradykinin. These two peptides play antagonistic roles on the cardiovascular system by regulating vascular tone and vascular smooth muscle cell proliferation. Identification of the ACE gene as a genetic marker for various forms of cardiovascular disease is a recent result of the progress made in molecular biology and genetics. The insertion/deletion (ID) polymorphism of the ACE gene defined by the presence or absence of the 287 base pair Alu sequence situated in intron 16 has been investigated as a possible genetic marker for a variety of cardiovascular disease including myocardial infarction, essential hypertension, cardiomyopathy, and diabetic vascular complications. This paper reviews prior reports and briefly describes our recent study on the association of the ACE I/D polymorphism and antiproteinuric effect of ACE inhibitors in patients with proteinuria.

Cardiovascular Diseases↗
PubMed1996

[Regulation of osmolyte transporter gene expression by tonicity].

In response to exposure to hypertonic environment, cells accumulate small organic solutes termed osmolytes that protect them from the adverse effects of hypertonicity. Some osmolytes (myo-inositol, betaine and taurine) are accumulated by specific transporters. Those transporters have been cloned by expression cloning techniques. Transcription of osmolyte transporters is induced by hypertonicity. In situ hybridization reveals the localization of the Na+/myo-inositol cotransporter and the betaine transporter (BGT1) mRNAs in the kidney. The BGT1 gene was cloned and its 5' flanking region has been characterized A 13 bp tonicity responsive enhancer (TONE) has been identified. Analysis of transgenic mice harboring a 5' flanking region of the BGT1 gene, that included TONE, showed that it provides inducible reporter expression in kidney medulla.

Animals↗
PubMed1995

Phosphatase toward MAP kinase is regulated by osmolarity in Madin-Darby canine kidney (MDCK) cells.

We have reported that MAP kinase and its activator were activated by increase in extracellular osmolarity in Madin-Darby canine kidney (MDCK) cells [J. Clin. Invest. 93 (1994) 2387-2392]. The activation of MAP kinase quickly disappeared when cells in hypertonicity were shifted to isotonicity. Present study was planned to elucidate the mechanism for the inactivation of MAP kinase when osmolarity decreased. Combination of two different phosphatase inhibitors, 10(-6) M okadaic acid and 0.2 mM sodium orthovanadate, blocked the inactivation of MAP kinase after the decrease in osmolarity. We also demonstrated that phosphatase toward MAP kinase was activated in response to the decrease in osmolarity. These results suggest that MAP kinase is inactivated by phosphatase that is activated when osmolarity decreased.

Animals↗
PubMed1995

IL-12 synergizes with IL-2 to induce lymphokine-activated cytotoxicity and perforin and granzyme gene expression in fresh human NK cells.

NK-mediated cytotoxicity is regulated by a variety of cytokines and is thought to involve perforin and granzymes. The effects of IL-2 and IL-12 on the expression and activation of cytolysis were examined in freshly isolated human NK cells. A dose-dependent increase in cytolysis of the NK-sensitive target cell, K562, and the NK-insensitive but lymphokine-activated killer (LAK) cell-sensitive target, UCLA-SO-M14, was observed after short term culture of purified human NK cells in either IL-2 or IL-12. Moreover, the two cytokines often synergized to produce augmented lytic activity. A suboptimal dose of IL-2 (60 IU/ml) combined with IL-12 (2 U/ml) could induce lytic activity equal to twice the additive effect of each cytokine alone. Northern analyses revealed time-dependent increases in mRNAs encoding for perforin and granzymes A and B following treatment with IL-2 alone or IL-2 plus IL-12. IL-2 and IL-12 also synergized for the induction of granzyme mRNAs, in that treatment with both cytokines increased mRNA levels approximately 50% above the sum of each cytokine alone, as quantitated by phosphorimage analysis, and normalized to GAPDH gene expression. However, the synergy between IL-2 and IL-12 for the induction of mRNA was less dramatic than for lytic activity. Results of experiments in which cytokine-treated cells were pulsed with actinomycin D indicated that the increased granzyme and perforin gene mRNA levels in response to IL-2, IL-12, or the combination were not due to increased transcript stability. The data suggest that low doses of IL-2 and IL-12 synergize to augment NK- and induce LAK-mediated cytotoxicity and that this increase is associated with enhanced transcription of perforin and granzyme genes in a synergistic fashion.

Cells, Cultured↗
PubMed1995

The canine betaine gamma-amino-n-butyric acid transporter gene: diverse mRNA isoforms are regulated by hypertonicity and are expressed in a tissue-specific manner.

The Na(+)- and Cl(-)-coupled betaine transporter, designated BGT1, a member of the neurotransmitter transporter gene family, is responsible for accumulation of betaine in hypertonic Madin-Darby canine kidney (MDCK) cells and presumably in the hypertonic renal medulla. The canine gene for the betaine gamma-amino-n-butyric acid transporter has been cloned and analyzed. The gene extends over 28 kb and consists of 18 exons. The 5' end of the gene has three alternative first exons (1A, 1B, and 1C+D). Analysis of BGT1 mRNA revealed that there is considerable divergence in the 5' untranslated sequence resulting from three different 5' end motifs (A, B, and C) followed by an alternative motif (D) as well as two internal acceptor sites for splicing. Eight kinds of BGT1 mRNA were classified into three types (A, B, and C) according to the 5' end sequence. Northern blot analysis using probes specific for the A, B, or C motif revealed that hypertonicity induces all three types in MDCK cells. Reverse transcription and polymerase chain reaction showed that each type was expressed in a tissue-specific manner. Primer extension and/or RNase protection assays as well as transfection assays into MDCK cells demonstrated that exons 1A, 1B, and 1C+D have independent transcription initiation sites under control of independent promoters. Diverse mRNA isoforms are regulated by hypertonicity and are expressed in a tissue-specific manner.

Animals↗
PubMed1995

Retrospective analysis of hemodialyzed diabetic patients in Japan.

We retrospectively analyzed the courses of 37 non-insulin dependent diabetics (hemodialyzed:HD group) with end-stage renal disease (ESRD), to identify factors predisposing to renal failure. The factors analyzed were: diabetic (non-proliferative and proliferative) retinopathy, family histories of diabetes and hypertension, smoking, dyslipidemia, first examination proteinuria and non-compliance. These factors were statistically compared in 37 NIDDM without renal failure (non-HD group). There were no significant differences in age or duration of diabetes between the two groups. Significant differences (P < 0.001) were, however, recognized in diabetic proliferative retinopathy and hypertension between the two groups. Hypertension was present in 35/36 (97.2%) HD patients and in 21/36 (58.3%) non-HD patients. A family history of hypertension was recognized in 16/37 HD (43.2%) and in 7/33 (21.2%) non-HD (P < 0.05). Differences were recognized in HDL-cholesterol, LDL-cholesterol and TG levels (38.2 +/- 12.5 mg/dl and 56.7 +/- 18.5 mg/dl, 140.4 +/- 57.1 mg/dl and 115.6 +/- 33.6 mg/dl, 169.9 +/- 89.4 mg/dl and 115.7 +/- 75.1 mg/dl, in HD and non-HD, respectively, P < 0.05). First visit proteinuria was found in all HD patients, and in 6/34 (17.6%) non-HD. The difference in previous treatment refusal, for 7 or more years, was significant with 23/36 (58.9%) HD patients and only 1/25 (4.0%) non-HD patients (P < 0.001) having a history of prolonged non-compliance with diabetic treatment. Diabetic retinopathy, non-proliferative and proliferative, hypertension and a family history of hypertension, elevated triglyceride and LDL-cholesterol, low HDL-cholesterol, first visit proteinuria, and prolonged non-compliance correlated with progression to ESRD. We advocate expanding diabetic education to include prevention of complications such as diabetic nephropathy.

Aged↗
PubMed1995

The role of shared receptor motifs and common Stat proteins in the generation of cytokine pleiotropy and redundancy by IL-2, IL-4, IL-7, IL-13, and IL-15.

To understand the molecular bases for cytokine redundancy and pleiotropy, we have compared the Stat proteins activated in peripheral blood lymphocytes (PBLs) by cytokines with shared and distinct actions. Interleukin-2 (IL-2) rapidly activated Stat5 in fresh PBL, and Stat3 and Stat5 in preactivated PBL. IL-7 and IL-15 induced the same complexes as IL-2, a feature explained by the existence of similar tyrosine-phosphorylated motifs in the cytoplasmic domains of IL-2R beta and IL-7R that can serve as docking sites for Stat proteins. IL-13 Induced the same complexes as IL-4, a finding explained by our studies implicating IL-4R as a shared component of the receptors. These studies demonstrate that a single cytokine can activate different combinations of Stat proteins under different physiological conditions, and also indicate two mechanisms by which distinct cytokines can activate the same Stat protein.

Amino Acid Sequence↗
PubMed1995

Na+/myo-inositol cotransport is regulated by tonicity in cultured rat mesangial cells.

Mesangial cells are considered to be faced with osmotic stress under physiological (such as extraglomerular mesangial cells) and pathophysiological (for example, diabetes mellitus) conditions. To see if mesangial cells have an osmoregulatory mechanism, like renal medullary cells, we measured the intracellular contents of organic osmolytes in isotonic and hypertonic conditions. Cultured rat mesangial cells are well tolerant of acute increase in osmolality up to 500 mOsm/kg. The myo-inositol content increased in hypertonic cells more than six-fold the value in isotonic cells. The contents of glycerophosphorylcholine and sorbitol also increased but were less than that of myo-inositol. The Na(+)-dependent myo-inositol uptake in hypertonic cells was a 12-fold uptake in isotonic cells, reaching a maximum 24 hours after the switch to a hypertonic medium. The uptake rate increased as medium osmolality increased from 300 to 500 mOsm/kg. Raffinose is the most effective solute to increase the myo-inositol uptake. NaCl, glucose and mannitol also increased the uptake rate (NaCl > glucose > mannitol). The increased uptake by hypertonicity was the result of an increase in Vmax without change in Km and was dependent on RNA and protein synthesis. These results indicate that mesangial cells respond to extracellular hypertonicity by increasing myo-inositol transport activity and accumulating myo-inositol into the cells, suggesting that myo-inositol functions as an organic osmolyte in mesangial cells.

Animals↗
PubMed1995

Human peripheral blood CD4+ and CD8+ T cells express Th1-like cytokine mRNA and proteins following in vitro stimulation with heat-inactivated Brucella abortus.

Defining the pattern of lymphokine production associated with Brucella abortus is critical for advancing the development of B. abortus as a vaccine carrier. In the present study we investigated the ability of heat-inactivated B. abortus or lipopolysaccharide from B. abortus to induce lymphokine production from purified human T cells in vitro. Gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-5 induction was assayed by mRNA-specific PCR and by enzyme-linked immunosorbent assay and bioassay for protein production. Following depletion of monocytes and B cells, B. abortus increased IFN-gamma and IL-2 mRNA expression in purified T cells compared with expression in unstimulated cells. In contrast, no IL-5 mRNA expression and only transient low-level IL-4 mRNA expression and no IL-4 protein secretion were detected. Phytohemagglutinin or phorbol myristate acetate plus ionomycin induced mRNA and protein for all these cytokines. Similar results were obtained with LPS purified from B. abortus. Removal of NK cells did not reduce lymphokine production, and enriched NK cells did not express IFN-gamma mRNA or secrete IFN-gamma protein in response to B. abortus, indicating that NK cells were not the responding population. Both CD4+ and CD8+ populations produced IFN-gamma and IL-2 in response to B. abortus. Preincubation of resting T cells with B. abortus or LPS from B. abortus for 7 days induced their differentiation into Th1-like cells as judged by their subsequent lymphokine response to phorbol myristate acetate plus ionomycin. These results suggest that B. abortus can induce differentiation of Th0 into Th1-type cells.

Base Sequence↗
PubMed1995

Localization and rapid regulation of Na+/myo-inositol cotransporter in rat kidney.

myo-inositol, a major compatible osmolyte in renal medulla, is accumulated in several kinds of cells under hypertonic conditions via Na+/myo-inositol cotransporter (SMIT). To investigate the physiological role of the SMIT, we sought to determine its localization by in situ hybridization and its acute regulation by NaCl and furosemide administration. Northern analysis demonstrated that SMIT is strongly expressed in the medulla and at low levels in the cortex of kidney. Intraperitoneal injection of NaCl rapidly induced SMIT mRNA in both the cortex and medulla, and furosemide completely abolished this induction. In situ hybridization revealed that SMIT it predominantly present in the medullary and cortical thick ascending limbs of Henle's loop (TALH) and macula densa cells. Less intense signals were seen in the inner medullary collecting ducts (IMCD). NaCl loading increased the signals throughout the TALH, and furosemide reduced the signals. SMIT in the IMCD is less sensitive to these kinds of acute regulation. Thus, the distribution pattern of SMIT does not correspond to the corticomedullary osmotic gradient, and SMIT in the TALH and macula densa cells is regulated very rapidly. These results suggest that SMIT expression in TALH may be regulated by intracellular and/or peritubular tonicity close to the basolateral membrane, which is supposed to be proportional to the magnitude of NaCl reabsorption.

Animals↗
PubMed1995

Maximum single leg force production: cockroaches righting on photoelastic gelatin

Integrating studies of mechanics, neural control and isolated muscle function are possible using arthropod legs. To evaluate leg performance, we measured the ground reaction forces generated by individual legs of the six-legged cockroach Blaberus discoidalis (3.1 g), during an emergency behavior, righting or over-turning. We used a photoelastic method to measure the forces generated by individual legs simultaneously. A gelatin track placed between crossed polarizing filters was illuminated from below, and a high-speed video camera recorded the stress-induced optical signals from above. The size and skew of the optical patterns were found to be related to the magnitude and direction of the force. We discovered that the ground reaction forces generated during the righting behavior of the death-head cockroach were eight times greater than those observed during high-speed running, supporting the possibility that relative leg forces (leg force per unit body weight) during running and maximal leg activity differ more in small arthropods than in larger vertebrates. Non-geometric scaling of relative leg force (i.e. scaling to less than body mass-0.33), along with the reduced force-generating ability of a single leg in animals with many legs, may help to explain why the maximum relative leg force production by six-legged cockroaches, as well as by some other small insects, can be similar to the relative single leg forces produced by two- and four-legged vertebrates that are almost 1000 times more massive. Leg number and body mass alone, however, appear to be insufficient to explain the variation observed in relative leg force production at a given body mass, because enormous diversity in musculo-skeletal parameters exists. The maximal relative leg force of the cockroach B. discoidalis during righting was at the low end of a 100-fold variation observed for smaller insects wedging (pushing through a small crevice) and pulling loads. Thus, this cockroach can be characterized as a moderately strong insect with the capacity for relatively high speed. Results from the present study question the predictive strength of the simple geometric scaling arguments involving a strength:weight ratio as they are applied to small arthropods and encourage further consideration of the importance of leg number, muscle force production and mechanical advantage in the derivation of general principles of leg performance.

Journal Article↗
PubMed1995

Activators of protein kinase A and of protein kinase C inhibit MDCK cell myo-inositol and betaine uptake.

Amino acid sequences of the myo-inositol and betaine cotransporters that are induced in MDCK cells by hypertonicity include consensus sequences for phosphorylation by protein kinase A and by protein kinase C. To test for the effect of activation of protein kinases A and C on the activity of those cotransporters, MDCK cells were exposed to activators of each kinase and the activity of both cotransporters was assayed. Incubation with 8-bromoadenosine 3':5'-cyclic monophosphate (8Br-cAMP) or 3-isobutyl-1-methylxanthine (IBMX), activators of protein kinase A, and incubation with an active phorbol ester or with an active diacylglycerol, activators of protein kinase C, inhibited the activity of both cotransporters by about 30%. The relative effect of the activation of protein kinase A and of protein kinase C was similar in hypertonic and isotonic cells. The effects of activators of protein kinase A and of protein kinase C were not additive. The two cotransporters behaved differently when protein kinase C activity was down-regulated by prolonged incubation with a higher concentration of phorbol 12-myristate 13-acetate. There was a doubling of activity of the myo-inositol cotransporter and no change in the activity of the betaine cotransporter in hypertonic and isotonic cells. Although the mechanisms of the effects of activation of the two kinases remain to be established, it is clear that the kinases can mediate post-translational regulation of the uptake of compatible osmolytes.

1-Methyl-3-isobutylxanthine↗