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Biomedical subjects

H Weber

Publications and source records attributed to H Weber.

At least 73 records · Page 4Linked to original sources
PubMed2000

Differential gene expression in response to mechanical wounding and insect feeding in Arabidopsis.

Wounding in multicellular eukaryotes results in marked changes in gene expression that contribute to tissue defense and repair. Using a cDNA microarray technique, we analyzed the timing, dynamics, and regulation of the expression of 150 genes in mechanically wounded leaves of Arabidopsis. Temporal accumulation of a group of transcripts was correlated with the appearance of oxylipin signals of the jasmonate family. Analysis of the coronatine-insensitive coi1-1 Arabidopsis mutant that is also insensitive to jasmonate allowed us to identify a large number of COI1-dependent and COI1-independent wound-inducible genes. Water stress was found to contribute to the regulation of an unexpectedly large fraction of these genes. Comparing the results of mechanical wounding with damage by feeding larvae of the cabbage butterfly (Pieris rapae) resulted in very different transcript profiles. One gene was specifically induced by insect feeding but not by wounding; moreover, there was a relative lack of water stress-induced gene expression during insect feeding. These results help reveal a feeding strategy of P. rapae that may minimize the activation of a subset of water stress-inducible, defense-related genes.

Animals↗
PubMed2000

Antidotal effects of 2,3-dimercaptopropane-1-sulfonic acid (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) on the organotoxicity of dibutyltin dichloride (DBTC) in rats.

1. Dialkyltin compounds have been widely used in industry and agriculture, mainly as biocides, catalysts and plast stabilizer. In dependence on the length of the alkyl chains these organotins exert toxic effects on the immune system, the bile duct, liver and pancreas. It has been supposed that similar to organoarsenic the toxicity of the dialkyltin compounds is related to reactions with biological dithiol groups. Therefore, in the present study, the antidotal effects of 2,3-dimercapto-propane-1-sulfonic acid (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) on the organotoxic effects of dibutyltin dichloride (DBTC, single administration of 27 micromol kg(-1) b.w. i.v.) in rats were studied using different doses (100 and 500 micromol kg(-1) b.w.) and routes of administration (i.p. and p.o.) of both chelators. Several parameters of organotoxicity (thymus weight and cellularity, bile duct diameter, histological lesions of pancreas and liver, activities of amylase, lipase and alkaline phosphatase, bilirubin and hyaluronic acid in serum) were measured from 6 h to 8 weeks. 2. DMPS and DMSA diminished the DBTC induced bile duct, pancreas and liver lesions stronger than the thymus atrophy. Moreover, the development of a fibrosis of the pancreas and a cirrhosis of liver several weeks after single administration of DBTC to rats was inhibited by DMPS and DMSA. The antidotal effects on serum parameter were observed after both administration routes of the chelators. DMPS was more effective than DMSA in most measured parameters. The decrease in the biliary excretion of organotin by DMPS and DMSA seems to be the reason for the pronounced protective effects of DMPS and DMSA on bile duct, pancreas and liver. 3. For the treatment of poisonings with dibutyltin compounds, the administration of DMPS or DMSA can be recommended.

Alkaline Phosphatase↗
PubMed2000

A role for GATA5 in Xenopus endoderm specification.

The endoderm gives rise to the gut and tissues that develop as outgrowths of the gut tube, including the lungs, liver and pancreas. Here we show that GATA5, a zinc-finger transcription factor, is expressed in the yolk-rich vegetal cells of Xenopus embryos from the early gastrula stage onwards, when these cells become committed to form endoderm. At mid-gastrula stages, GATA5 is restricted to the sub-blastoporal endoderm and is the first molecular marker for this subset of endodermal cells so far identified. We show that GATA4 and GATA5 are potent inducers of endodermal marker genes in animal cap assays, while other GATA factors induce these genes only weakly, if at all. When injected into the dorsal marginal zone, GATA5 respecifies prospective mesoderm towards an endodermal fate, thereby disrupting the convergence and extension movements normally undergone by the dorsal mesoderm. The resulting phenotype is very similar to those seen after injection of dominant negative versions of the FGF-receptor or the T-box transcription factor, Xbra and can be rescued by eFGF. The ability of GATA5 to respecify ectodermal and mesodermal cells towards endoderm suggests an important role for GATA5 in the formation of this germlayer. In animal cap assays, GATA5 is induced by concentrations of activin above those known to induce dorsal mesoderm and heart, in an FGF-independent manner. These data indicate that the emerging view for endodermal induction in general, namely that it is specified by high levels of TGF-beta in the absence of FGF signalling, is specifically true for sub-blastoporal endoderm.

Animals↗
PubMed2000

Malignant melanoma in a Eurasian otter (Lutra lutra).

An 11-yr-old female Eurasian otter (Lutra lutra) presented with multiple cutaneous nodules identified histologically as malignant melanomas of spindle cell and epithelioid cell type. Metastases were detected in lymph nodes and liver, and the tumor, which was derived from melanocytes, showed aggressive biological behavior. Only occasional reports exist of neoplastic disease in otters.

Animals↗
PubMed2000

Collagen patch coated with fibrin glue components. Treatment of suture hole bleedings in vascular reconstruction.

BACKGROUND: Bleeding from suture holes during vascular reconstruction, particularly when polytetrafluoroethylene (PTFE) prostheses are used, is still a problem which can lead to intraoperative delay and increased blood loss. The aim of this prospective, randomised, open, controlled multicentre study was to evaluate whether the use of a new local haemostyptic would reduce intraoperative blood loss and the time to haemostasis. METHODS: Thirty patients received a new haemostyptic (TachoComb H, Nycomed Pharma AG), whereas another 30 patients were treated with compresses. The vascular reconstructions were either anastomoses or patch angioplasties and were performed using PTFE vascular prostheses. RESULTS: The mean time to haemostasis of suture hole bleeding in the haemostyptic group (326.0 sec) was significantly shorter compared to the control group (514.3 sec) (p=0.006). The median intraoperative blood loss was 24.5 g in the treatment group and 57.3 g in the control group (p=0.045). CONCLUSIONS: It was shown that collagen patches coated with components of fibrin glue significantly reduce the time to haemostasis as well as blood loss at the operation site in patients undergoing vascular reconstruction with PTFE grafts.

Aged↗
PubMed1999

Short- and long-term outcomes of Wiktor stent implantation at low versus high pressures. Austrian Wiktor Stent Study Group.

A prospective, randomized, multicenter trial was conducted to evaluate whether high-pressure postdilation of the Wiktor stent provides short- and long-term benefits compared with the conventional low-pressure implantation technique. From June 1995 through May 1996, 181 patients were randomly assigned to either low-pressure (6 to 12 atm, group A, n = 94) Wiktor stent placement or to high-pressure postdilation (> or = 13 atm, group B, n = 87) after stent deployment. All patients were followed up clinically for 7 +/- 3 months, with an angiographic follow-up in 154 patients (85%). After stent implantation, neither minimal lumen diameter (MLD) nor percent diameter stenosis (%DS) differed significantly between the 2 groups (MLD, 2.8 +/- 0.5 vs 2.9 +/- 0.5 mm; %DS, 17 +/- 8% vs 16 +/- 9% for groups A and B, respectively). However, a trend toward a larger mean lumen diameter within the stent was observed in group B (3.3 +/- 0.6 vs 3.5 +/- 0.5 mm for groups A and B, respectively; difference between means 0.14 mm, 95% confidence interval -0.01 to 0.29, p = 0.08). Angiographic follow-up revealed similar MLD and %DS in both treatment groups (MLD, 2.1 +/- 0.7 vs 2.2 +/- 0.8 mm; %DS, 31 +/- 17% vs 30 +/- 24% for groups A and B, respectively, p = NS). Acute stent thrombosis occurred in 2 patients (1%) (1 patient in each group), and subacute thrombosis in 1 patient (0.6%) in group A. There was 1 death in group A, and target lesion restenosis (> or = 50% DS) was observed in 15% of patients with no differences between the groups. In conclusion, this study demonstrated favorable short- and long-term results of Wiktor stent implantation. Despite a trend toward additional initial lumen gain by high-pressure postdilation, this did not translate into a measurable improvement in long-term outcome.

Aged↗
PubMed1999

Relaxant activity in rat aorta and trachea, conversion to a muscarinic receptor antagonist and structure-activity relationships of new K(ATP) activating 6-varied benzopyrans.

To characterize ATP-sensitive channels (K(ATP) channels) benzopyrans with different substituents at position 6 were synthesized as new K(ATP)-activators. Their relaxant potencies were determined in rat aorta and trachea. In aorta, pEC50-values (-log, M) ranged from 7.37 to 5.43; in trachea, pEC50-values were 0.3 to 0.8 log units lower. Functional data were compared with binding data obtained in calf tracheal cells using the cyanoguanidine [3H]P1075 (N-cyano-N'-1,1-dimethyl[2,3(n)-3H]propyl)-N11-(3-pyridinyl)guanidine) as radioligand. A high correlation (r = 0.96) between pEC50- and pKD-values indicated that tracheal relaxation produced by benzopyrans is mediated via K(ATP) channels without signal amplification. The permanently charged trimethylammonium derivative designed as a probe for the membrane site of action completely lost its affinity for K(ATP) channels, but converted to an antagonist for muscarinic acetylcholine receptors (pK(B) = 6.12+/-0.10), as confirmed in radioligand binding studies (pK(D) = 5.77+/-0.04). Structure-activity analyses revealed that the 6-substituent influences biological activity by a direct receptor interaction of its own and not indirectly by withdrawing electrons from the benzopyran nucleus. The variance of the biological activity is primarily determined by electrostatic properties, but desolvation energies additionally contribute.

Animals↗
PubMed1999

The course of pancreatic fibrosis induced by dibutyltin dichloride (DBTC).

In summary, in addition to an acute interstitial pancreatitis the organotin compound DBTC induced a pancreatic fibrosis in rats. The course of the pancreatic fibrosis was studied 2-36 weeks after single i.v. treatment of rats with 6 or 8 mg/kg DBTC. The pancreatic fibrosis induced by DBTC differs from other experimental models of acute pancreatitis. Extensive infiltration by mononuclear cells is present in fibrotic areas without pancreatic atrophy or lipomatosis. The presence of chronic inflammatory lesions characterized by the destruction of exocrine parenchyma and fibrosis and in the later stages the endocrine parenchyma, indicate a chronic pancreatitis. In completion of the experimental model of the DBTC-induced acute interstitial pancreatitis in rats, the described late fibrotic effects on rat pancreas may be used as an experimental model of chronic pancreatitis.

Alkaline Phosphatase↗
PubMed1999

6-Substituted benzopyrans as potassium channel activators: synthesis, vasodilator properties, and multivariate analysis.

During the last 10 years compounds have been discovered which can activate or block KATP channels. In particular, K channel activators (KCA) have been found to be smooth muscle relaxants with their main utility in hypertension and bronchodilation. In this paper we describe the synthesis of new KCA of the benzopyran type with a fixed 4-substituent and a systematic variation in the 6-position. The relaxant potency in rat aorta and trachea was used for biological characterization of the benzopyrans. In both biological test systems, they exhibit potency ranges of more than 3 log units. Structure-activity relationships are investigated by principal component analysis (PCA) and partial least-squares (PLS) analysis. Most striking outliers in an initial PLS analysis of the entire database were the unsubstituted 6-H compound 13 as well as 34 and 35. For the remaining set of 31 compounds, a 3-component PLS model explains the variance in biological activity to 81% in the aortic and to 82% in the tracheal test system. 6-Substituents influence affinity by a direct (presumably dipolar) interaction with the receptor site. According to the 2D-plot of the partial PLS weights, a strong electronegativity as well as high values for the integy moment and for the heat of formation in water dominate the first component; low values for substituent size (as defined by globularity or surface) are in addition favorable for high potency. High lipophilicity and low minimum energies of interaction dominate the second component. Chemical descriptors for the biological potency of the test set in rat aorta and rat trachea are very similar according to the almost identical projection of the Y-variables onto the X-component space.

Animals↗
PubMed1999

Dietary protein restriction stress in the domestic fowl (Gallus gallus domesticus) alters adrenocorticotropin-transmembranous signaling and corticosterone negative feedback in adrenal steroidogenic cells.

Previous work with growing chickens (Gallus gallus domesticus) indicates that transient dietary protein restriction induces long-term enhancement of adrenal steroidogenic function in response to adrenocorticotropin (ACTH). The present study investigated two possible cellular functions mediating this enhanced response: (a) ACTH signal transduction and dissemination and (b) short-loop feedback inhibition of ACTH-induced corticosterone production by exogenous corticosterone. Cockerels (2 weeks old) were fed isocaloric synthetic diets containing either 20% (control) or 8% (restriction) soy protein for 4 weeks. Adrenal glands were processed for the isolation of adrenal steroidogenic cells nearly devoid of chromaffin cells ( approximately 90% adrenal steroidogenic cells). Results of experiments to assess signal transduction and dissemination indicated that protein restriction selectively enhanced ACTH-induced corticosterone production mediated by the cyclic AMP (cAMP)-dependent pathway. In addition, protein restriction substantially counteracted exogenous corticosterone-dependent inhibition of acute ACTH-induced corticosterone production (by 40.7% vs control). The proximal portion of the cAMP pathway seemed most affected by this stressor. Protein-restricted cells exhibited enhanced homologous sensitization to ACTH (136% greater than that of control cells) which appeared to be localized at a step(s) prior to or at the formation to cAMP. Also, maximal ACTH-induced cAMP production and sensitivity to ACTH in terms of cAMP production by protein-restricted cells were, respectively, 2.2 and 15.8 times those of control cells. However, variable results were obtained from other experiments designed to pinpoint the altered early steps in ACTH-transmembranous signaling. For example, with intact cells, cAMP responses to cholera toxin (CT) and forskolin (FSK) did not corroborate the results suggesting an augmentation of ACTH-signal transduction induced by protein restriction. Furthermore, basal and stimulatable (by ACTH, CT, FSK, and NaF) adenylyl cyclase activities from membranes from protein-restricted cells were, respectively, 47.2 and 40.2% less than those from control cells (normalized to 10(7) cell equivalents of crude membranes). Collectively, these findings suggest that protein restriction stress potentiates ACTH-induced corticosterone secretion by chicken adrenal steroidogenic cells in at least two ways: (1) on the proximal end, by modulating unknown factors which enhance cellular sensitivity to ACTH, ACTH receptor-adenylyl cyclase coupling, and adenylyl cyclase activity, and (2) on the distal end, by suppressing end-product corticosterone negative feedback, thus facilitating an increase in net corticosterone secretion.

Adenylyl Cyclases↗
PubMed1999

Concentration-dependent, biphasic effect of prostaglandins on avian corticosteroidogenesis in vitro.

Previous work with mammalian and frog adrenocortical tissue and cells indicates that prostaglandins (PGs) can directly stimulate corticosteroidogenesis. However, work with avian adrenal preparations is absent. Therefore, the present studies with isolated chicken (Gallus gallus domesticus) and turkey (Meleagris gallopavo) adrenal steroidogenic cells were conducted to determine whether PGs can directly influence avian corticosteroidogenesis as well. Cells (1 x 10(5) cells/ml) were incubated with a wide range of concentrations of PGs in the presence of indomethacin (1 microg/ml) (to attenuate endogenous PG production) and 1-methyl-3-isobutylxanthine (0.5 mM) [to preserve cyclic AMP (cAMP)] for 2 h. Corticosterone and cAMP production were measured by highly specific radioimmunoassay. PGI2 was without effect. With the exception of PGF2alpha, which had a slight stimulation in chicken but not in turkey cells, the influence of the other PGs on corticosterone production was biphasic. For the stimulatory phase (up to a concentration of 5 x 10(-5) M), there were prostanoid structural and avian species differences in both potency and efficacy of PGs. Overall, PGs were 11 times more potent in turkey cells than in chicken cells. However, the order of potency for stimulation was similar for both chicken and turkey cells: for chicken cells the order was PGE2 > PGE1 > PGA1 > PGB2 > PGB1 > PGF2alpha and for turkey cells it was PGE2 > PGE1 > PGA1 > PGB2 = PGB1. In contrast, PG efficacy for stimulation was greater for chicken cells. In addition, the orders of efficacy were different from the orders of potency. In chicken cells, the order of efficacy was PGE2 = PGA1 > PGE1 > PGB2 > PGB1 > PGF2alpha and for turkey cells it was PGB2 = PGE2 > PGA1 > PGE1 > PGB1. Because of the greater maximal corticosterone response over basal production of chicken cells to PGs, they were used to assess the interaction of PGs with ACTH and to examine more fully the inhibitory phase of PGs. Cells were incubated with PGs in the presence of threshold (2.5 x 10(-11) M), half-maximal (1 x 10(-10) M), and maximal (1 x 10(-7) M) steroidogenic concentrations of ACTH. With the exception of PGF2alpha, the average efficacy of PGs to elevate corticosterone was increased 55% by a threshold steroidogenic concentration of ACTH. However, with higher concentrations of ACTH, this enhancement of efficacy disappeared as did the stimulatory effect of some PGs. The results suggest that the steroidogenic actions of PGs and ACTH converge on the same pool of steroidogenic enzymes leading to corticosterone. At concentrations greater than 5 x 10(-5) M, several PGs (notably PGA1, PGA2, PGB1, and PGB2) inhibited both ACTH-induced and basal corticosterone production. PGA1 and PGA2 were the most potent inhibitors. Corticosterone and cAMP production were closely associated in the biphasic action of PGs, suggesting that the effect of PGs was mediated by the changing levels of intracellular cAMP. Collectively, these data suggest that PGs may be important modulators of corticosteroidogenesis in the avian adrenal gland.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Phosphoenolpyruvate carboxylase in developing seeds of Vicia faba L.: gene expression and metabolic regulation.

To analyze the role of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31) during seed development, two cDNA clones encoding two isoforms of PEPCase were isolated from a seed-specific library of Vicia faba. The two sequences (VfPEPCase1 and VfPEPCase2) have a sequence identity of 82 and 89% on the nucleotide and amino acid levels. The VfPEPCase1 mRNA was found to be predominantly expressed in roots and developing cotyledons whereas the VfPEPCase2 mRNA was more abundant in green and maternal tissues. In the cotyledons, PEPCase mRNAs accumulated from early to mid cotyledon stage and decreased thereafter. The PEPCase activity increased continuously during cotyledon development. The enzyme was strongly activated by glucose-6-phosphate, but not by glucose, fructose or sucrose. Asparagine was weakly activating whereas malate, aspartate and glutamate were inhibitory. The inhibitors became less effective with increasing pH. Aspartate was a much stronger inhibitor of cotyledonary PEPCase than glutamate at both pH 7.0 and 7.5. The sensitivity of PEPCase to malate inhibition decreased from early to mid cotyledon stage at a time when storage proteins are synthesized. This indicates activation on the protein level, possibly by protein phosphorylation. Nitrogen starvation in the presence of hexoses but not sucrose decreased mRNA levels of VfPEPCase1 and enzyme activity, indicating control on the mRNA level by both carbon and nitrogen. It is concluded that in developing cotyledons PEPCase is probably important for the synthesis of organic acids to provide carbon skeletons for amino acid synthesis.

Base Sequence↗
PubMed1999

Seed maturation: genetic programmes and control signals.

Seed maturation is mainly governed by a few genes best studied in maize and Arabidopsis. The isolation of the LEC1 and FUS3 genes, besides the previously known VP1/AB/3 genes, and their identification as transcriptional regulators provides the first direct hints as to their molecular mode of action. With the identification of new effector genes, the investigation of the role of hormones with new methods such as immunomodulation and the increasingly recognised role of metabolites like sugars as important modulators of seed development, we increasingly understand the complexity and structure of the regulatory network underlying seed maturation.

Abscisic Acid↗
PubMed1999

Hyperthermia, inducing pancreatic heat-shock proteins, fails to prevent cerulein-induced stress kinase activation.

The dually phosphorylated c-jun kinase and p38 mitogen-activated protein (MAP) kinase, also termed stress kinases, are members of the MAP kinase family. They are activated early during cerulein pancreatitis induction and have been proposed as regulators during pancreatitis development by us and others. We recently showed that hyperthermia preconditioning induces expression of pancreatic heat-shock proteins (HSP) and protects against cerulein pancreatitis. Because it was further reported that HSP70 can prevent activation of stress kinases in lymphoid tumor cells, we investigated whether hyperthermia preconditioning might reduce hyperstimulation-mediated activation of pancreatic stress kinases. Pancreatic HSP expression was induced by whole-body hyperthermia preconditioning. Without prior HSP induction, cerulein led to a rapid and dose-dependent increase in serum lipase and amylase levels, pancreatic wet weight through edema formation, and activation of pancreatic MAP kinases. Hyperthermia preconditioning, although strongly inducing HSP70 and almost completely preventing edema formation, as well as the increase of serum amylase and lipase, did not reduce cerulein-mediated stress kinase activation. This indicates that in the pancreas, cerulein can strongly activate MAP kinases even when pancreatitis development is greatly inhibited, and that pancreatic HSPs do not inhibit activation of pancreatic stress kinases in vivo.

Animals↗
PubMed1999

Divinyl ether fatty acid synthesis in late blight-diseased potato leaves.

We conducted a study of the patterns and dynamics of oxidized fatty acid derivatives (oxylipins) in potato leaves infected with the late-blight pathogen Phytophthora infestans. Two 18-carbon divinyl ether fatty acids, colneleic acid and colnelenic acid, accumulated during disease development. To date, there are no reports that such compounds have been detected in higher plants. The divinyl ether fatty acids accumulate more rapidly in potato cultivar Matilda (a cultivar with increased resistance to late blight) than in cultivar Bintje, a susceptible cultivar. Colnelenic acid reached levels of up to approximately 24 nmol (7 microgram) per g fresh weight of tissue in infected leaves. By contrast, levels of members of the jasmonic acid family did not change significantly during pathogenesis. The divinyl ethers also accumulated during the incompatible interaction of tobacco with tobacco mosaic virus. Colneleic and colnelenic acids were found to be inhibitory to P. infestans, suggesting a function in plant defense for divinyl ethers, which are unstable compounds rarely encountered in biological systems.

Ethers↗
PubMed1999

[Occlusion of a coronary endoprosthesis after a negative stress test].

The frequency of early occlusion of coronary stents has fallen with the use of a powerful association of platelet antiaggregants (ticlopidine and aspirin) in the first month. The authors report the case of coronary stent occlusion after a negative exercise stress test, 11 days after implantation in a centre of cardiac rehabilitation. According to the literature, this type of complication would appear to be rare and related to the small size of the stent and the conditions of implantation (acute phase). It would be useful to compile a registry of complications related to coronary angioplasty during rehabilitation to determine their prevalence and, if necessary, change the protocols of physical training of these patients.

Adult↗