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M Bucher

Publications and source records attributed to M Bucher.

At least 19 recordsLinked to original sources
PubMed2000

The effect of urapidil and ramipril on hyperglycemia in streptozotocin diabetic rats.

Angiotensin-converting enzyme inhibitors and alpha1-adrenoceptor antagonists improve glucose disposal in diabetes mellitus. We compared the effect of the antihypertensive hybrid drug urapidil [alpha1-adrenoceptor antagonist serotonin 1A (5-hydroxytryptamine 1A, 5-HT1A) receptor agonist] on hyperglycemia in streptozotocin diabetic rats with the angiotensin-converting enzyme inhibitor ramipril. 5-HT1A receptor agonists induce hyperglycemia. This could be an important disadvantage during treatment of diabetes mellitus with urapidil. Diabetes was induced by streptozotocin (70 mg/kg i.p.). Treatment for 7 days (ramipril 10 mg/kg p.o.; urapidil 20 mg/kg p.o.) significantly decreased mean blood glucose values (urapidil: 15.7+/-0.9 mmol/l, P=0.007; ramipril: 15.0+/-0.8 mmol/l, P=0.038 vs. diabetic control group: 18.7+/-1.0 mmol/l). Both drugs reduced significantly blood pressure, urinary glucose, water consumption, and food requirement. Serotonin concentration in the brain (medulla oblongata, pituitary) was not affected. A normalization comparable with healthy control rats was observed only in a diabetic control group with insulin therapy. In conclusion, our results demonstrate that the antihypertensive drug urapidil has no detrimental effect on hyperglycemia compared with the angiotensin-converting enzyme inhibitor ramipril in experimental diabetes mellitus despite its 5-HT1A receptor agonistic properties.

Adrenergic alpha-Antagonists↗
PubMed1999

Pht2;1 encodes a low-affinity phosphate transporter from Arabidopsis.

An Arabidopsis genomic sequence was recently shown to share similarity with bacterial and eukaryotic phosphate (Pi) transporters. We have cloned the corresponding cDNA, which we named Pht2;1, and subsequently performed gene expression studies and functional analysis of the protein product. The cDNA encodes a 61-kD protein with a putative topology of 12 transmembrane (TM) domains interrupted by a large hydrophilic loop between TM8 and TM9. Two boxes of eight and nine amino acids, located in the N- and C-terminal domains, respectively, are highly conserved among species across all kingdoms (eubacteria, archea, fungi, plants, and animals). The Pht2;1 gene is predominantly expressed in green tissue, the amount of transcript staying constant in leaves irrespective of the Pi status of the shoot; in roots, however, there is a marginal increase in mRNA amounts in response to Pi deprivation. Although the protein is highly similar to eukaryotic sodium-dependent Pi transporters, functional analysis of the Pht2;1 protein in mutant yeast cells indicates that it is a proton/Pi symporter dependent on the electrochemical gradient across the plasma membrane. Its fairly high apparent K(m) for Pi (0.4 mM) and high mRNA content in the shoot, especially in leaves, suggest a role for shoot organs in Pi loading. Pht2;1 thus differs from members of the recently described plant Pi transporter family in primary structure, affinity for Pi, and presumed function.

Amino Acid Sequence↗
PubMed1998

Functional analysis and cell-specific expression of a phosphate transporter from tomato.

For a better understanding of the molecular and biochemical processes involved in orthophosphate (Pi) uptake at the root/soil interface, we cloned a Pi-transporter c DNA (LePT1) from a root air-specific cDNA library of tomato (Lycopersicon esculentum Mill.). The corresponding protein belongs to the growing family of ion transporters with twelve putative transmembrane domains. It is highly homologous to recently isolated Pi transporters from higher plants, yeast and fungi. When expressed in a Pi-uptake-deficient yeast mutant, the L. esculentum phosphate transporter 1 (LePT1) protein exhibits an apparent Km of 31 MicroM. The transporter is still active at submicromolar Pi concentrations and mediates highest Pi uptake at pH 5. The activity of LePT1 is dependent on the electrochemical membrane potential mediated by the yeast P-type H + - ATPase. Transcript levels of LePT1 in tomato seedlings are detectable in all vegetative organs under Pi-sufficient conditions, with highest concentrations in root hairs. In situ hybridization studies demonstrate cell-specific expression of LePT1 in the tomato root. The LePT1 mRNA is detectable in peripheral cell layers such as rhizodermal and root cap cells. Under Pi-deprivation condition, mRNA levels are also detectable in young stelar tissue. This work presents molecular and biochemical evidence for distinct root cells playing an important role in Pi acquisition at the root/soil interface.

Amino Acid Sequence↗
PubMed1997

Nitric oxide synthase isoform III gene expression in rat liver is up-regulated by lipopolysaccharide and lipoteichoic acid.

This study was done to investigate the influence of Gram-negative and Gram-positive sepsis on the expression of the three isoforms of nitric oxide synthase (NOS) gene in rat liver and kidney. Male Sprague-Dawley rats were treated with lipopolysaccharide (LPS, 10 mg/kg i.v.) as an in vivo model for Gram-negative sepsis or lipoteichoic acid (LTA, 10 mg/kg i.v.) as an in vivo model for Gram-positive sepsis. Animals were killed 12 h and 24 h after i.v. treatment. NOS mRNA of the three isoforms was determined by RNase protection assay. NOS II gene expression was strongly induced after LPS or LTA treatment in rat liver and kidney, indicating the efficacy of this treatment to induce sepsis. We found no change of NOS I gene expression after LPS or LTA injection in rat liver and kidney. NOS III gene expression was increased about 8-fold 12 h and about 5-fold 24 h after induction of sepsis in the rat liver whereas in the kidney there was no significant increase in NOS III gene expression. After correction for length NOS III mRNA was about 4- and 40-fold more abundant 12 h and 24 h after LPS treatment than NOS II mRNA in the liver, respectively. Twelve and 24 h after LTA treatment NOS III mRNA was about 18- and 140-fold more abundant than NOS II in the liver. These findings suggest that NOS III is an even more potent source of NO than NOS II in the liver after stimulation with LPS or LTA.

Animals↗
PubMed1997

Two genes encoding extension-like proteins are predominantly expressed in tomato root hair cells.

A differential screen of a tomato root hair cDNA library resulted in the cloning of two cDNAs, Dif10 and Dif54, whose corresponding genes are preferentially expressed in root hair cells as determined by analysis of mRNA levels in various tomato organs. Transcript levels showed no increase in leaves subjected to hormonal and environmental stress treatments. Sequence analysis of the cDNAs revealed high similarity to members of the extension family. Extensions are hydroxyproline-rich glycoproteins (HRGPs) located in the cell wall. In order to study the functional significance of HRGPs in root hairs, tomato seedling roots were treated with micromolar concentrations of 3,4-dehydro-L-proline (Dhp), a selective inhibitor of prolyl hydroxylase. Dhp treatment resulted in changes in root growth and the development of root hairs with reduced hair length, suggesting an important role of HRGPs in hair morphogenesis.

Amino Acid Sequence↗
PubMed1997

Effects of hypoxia on growth factor expression in the rat kidney in vivo.

There is accumulating evidence from in vitro studies suggesting that the genes of endothelin-1, PDGF, and VEGF are, like the erythropoietin gene, regulated by oxygen tension and by divalent cations. Hypoxia-induced stimulation of, such as endothelin-1, PDGF or VEGF might be involved in the pathogenesis of acute or chronic renal failure, and in renal "inflammatory" diseases (glomerulonephritis, vasculitis, allograft rejection). Hypoxia (8% O2) for six hours caused a 55-fold/1.6-fold increase of renal erythropoietin/endothelin-1 gene expression, whereas endothelin-3, PDGF-A, PDGF-B, and VEGF gene expression was unchanged. Carbon monoxide (0.1%) treatment for six hours stimulated renal erythropoietin gene expression 140-fold; however, endothelin-1, endothelin-3, PDGF-A, PDGF-B, and VEGF gene expression was not affected. Finally, cobalt treatment (60 mg/kg CoCl2) increased only renal erythropoietin/PDGF-B gene expression 5-fold/1.65-fold. These findings suggest that hypoxia is a rather weak stimulus for renal endothelin-1 gene expression, and that renal PDGF and VEGF gene expression in vivo is not sensitive to tissue hypoxia, in contrast to cell culture experiments. The in vivo regulation of endothelin-1, PDGF, and VEGF differs substantially from that of erythropoietin, suggesting that the basic gene regulatory mechanisms may not be the same.

Animals↗
PubMed1996

Preferential expression of an ammonium transporter and of two putative nitrate transporters in root hairs of tomato.

Root hairs as specialized epidermal cells represent part of the outermost interface between a plant and its soil environment. They make up to 70% of the root surface and, therefore, are likely to contribute significantly to nutrient uptake. To study uptake systems for mineral nitrogen, three genes homologous to Arabidopsis nitrate and ammonium transporters (AtNrt1 and AtAmt1) were isolated from a root hair-specific tomato cDNA library. Accumulation of LeNrt1-1, LeNrt1-2, and LeAmt1 transcripts was root-specific, with no detectable transcripts in stems or leaves. Expression was root cell type-specific and regulated by nitrogen availability. LeNrt1-2 mRNA accumulation was restricted to root hairs that had been exposed to nitrate. In contrast, LeNrt1-1 transcripts were detected in root hairs as well as other root tissues under all nitrogen treatments applied. Analogous to LeNrt1-1, the gene LeAmt1 was expressed under all nitrogen conditions tested, and root hair-specific mRNA accumulation was highest following exposure to ammonium. Expression of LeAMT1 in an ammonium uptake-deficient yeast strain restored growth on low ammonium medium, confirming its involvement in ammonium transport. Root hair specificity and characteristics of substrate regulation suggest an important role of the three genes in uptake of mineral nitrogen.

Amino Acid Sequence↗
PubMed1996

Cobalt but not hypoxia stimulates PDGF gene expression in rats.

This study was done to investigate the influence of different forms of acute tissue hypoxia on the expression of platelet-derived growth factor (PDGF) A chain (PDGF-A) and PDGF B chain (PDGF-B) genes in different rat organs. We found that acute normobaric hypoxia (8% O2), carbon monoxide inhalation (0.1% CO), or lowering the hematocrit to 12% for 6 h had no effect on PDGF-A or PDGF-B gene expression in lung, heart, kidney, and liver of Sprague-Dawley rats. Subcutaneous administration of cobaltous chloride dose dependently increased PDGF-B mRNA by 125% in lungs, by 60% in kidneys, but not in heart and liver. These findings suggest that acute tissue hypoxygenation is not a significant stimulus for PDGF-A and PDGF-B gene expression in these major rat organs. Cobalt appears to cause a tissue-specific increase of PDGF-B gene expression.

Administration, Cutaneous↗
PubMed1995

Aerobic fermentation in tobacco pollen.

We characterized the genes coding for the two dedicated enzymes of ethanolic fermentation, alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), and show that they are functional in pollen. Two PDC-encoding genes were isolated, which displayed reciprocal regulation: PDC1 was anaerobically induced in leaves, whereas PDC2 mRNA was absent in leaves, but constitutively present in pollen. A flux through the ethanolic fermentation pathway could be measured in pollen under all tested environmental and developmental conditions. Surprisingly, the major factor influencing the rate of ethanol production was not oxygen availability, but the composition of the incubation medium. Under optimal conditions for pollen tube growth, approximately two-thirds of the carbon consumed was fermented, and ethanol accumulated into the surrounding medium to a concentration exceeding 100 mM.

Alcohol Dehydrogenase↗
PubMed1994

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Journal Article↗
PubMed1994

Ethanolic fermentation in transgenic tobacco expressing Zymomonas mobilis pyruvate decarboxylase.

During oxygen limitation in higher plants, energy metabolism switches from respiration to fermentation. As part of this anaerobic response the expression of genes encoding pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) is strongly induced. In addition there is ample evidence for post-translational regulation. In order to understand this multi-level regulation of the anaerobic response, we provided tobacco with the constitutive capacity of ethanolic fermentation by expressing a PDC gene derived from the obligate anaerobe Zymomonas mobilis. The protein accumulated to high levels and was active in an in vitro assay. During the first 2-4 h of anoxia, acetaldehyde accumulated to 10- to 35-fold and ethanol to 8- to 20-fold higher levels than in wild-type. Under normoxic conditions no accumulation of acetaldehyde and ethanol could be measured. Instead, the two products may be immediately re-metabolized in tobacco leaf tissue. We show that aerobic fermentation takes place when the respiratory system is inhibited. Although these conditions enhance ethanolic fermentation under normoxia, they fail to increase ADH transcript levels. These results indicate that anaerobic transcription is triggered not by the metabolic consequences of oxygen limitation, but directly through an oxygen-sensing system.

Acetaldehyde↗
PubMed1993

Levels of parathyroid hormone-related protein in hypercalcemia of malignancy: comparison of midregional radioimmunoassay and two-site immunoradiometric assay.

Overproduction of parathyroid hormone-related protein (PTHrP) is a major cause of hypercalcemia of malignancy in patients with solid tumors. We measured plasma levels of the protein by a radioimmunoassay (RIA) against PTHrP(53-84) and by an immunoradiometric assay (IRMA) against PTHrP (1-86). Of 16 affected patients 7 had elevated PTHrP levels in both assays and 4 had elevated levels in the RIA only. Median levels were about tenfold higher in these patients when measured by RIA (median of 34 versus 2.2 pmol/l). Measurements from both assays were, however, highly correlated with each other in this patient group (P < 0.01). PTHrP was not elevated in 10 normocalcemic patients with lung carcinoma. During long-term follow-up of a patient with a mesothelioma of the pleura, PTHrP levels measured with both assays decreased during chemotherapy in parallel with a normalization of serum calcium. In another hypercalcemic patient suffering from renal carcinoma, PTHrP measured by IRMA decreased by 40% within 12 h after nephrectomy, whereas PTHrP measured by RIA did not show a significant decline. Direct comparison of the assay results thus pointed to the existence of heterogeneity of circulating forms of PTHrP in plasma. In conclusion, both immunoassays detected elevated levels of PTHrP in a fraction of patients with hypercalcemia of malignancy and thus may be a tumor marker during treatment of malignancies.

Adult↗
PubMed1993

Long-term anoxia tolerance. Multi-level regulation of gene expression in the amphibious plant Acorus calamus L.

Acorus calamus is a monocotyledonous wetland plant that can withstand extremely long periods of anoxia. We have investigated the expression of genes coding for pyruvate decarboxylase (Pdc), alcohol dehydrogenase (Adh), and fructose-1,6-bisphosphate aldolase (Ald) during periods of anoxia ranging from 2 h to 2 months. Upon anoxic incubation, Pdc mRNA levels peak at 6 h, followed by Adh and Ald, which peak at 12 and 72 h, respectively. Subsequently, the mRNA levels of all three genes decline within days to low levels. In contrast, alcohol dehydrogenase (ADH) protein levels increase steadily for at least a week and then remain constant. Native gel electrophoresis demonstrates the presence of two sets of ADH isozymes, one present constitutively, the other enhanced during anoxia. Translation initiation factor 4A protein levels, used as a control, remain constant during 2 months of anoxia. The results suggest that A. calamus has developed a complex anaerobic response consisting of differential regulation of transcription, translation, and posttranslational processes.

Alcohol Dehydrogenase↗