Search results for "Hydrogen-ion concentration"

Expression and characterization of the recombinant juvenile hormone epoxide hydrolase (JHEH) from Manduca sexta.

1998

The cDNA of the microsomal Juvenile Hormone Epoxide Hydrolase (JHEH) from Manduca sexta was expressed in vitro in the baculovirus system. In insect cell culture, the recombinant enzyme (Ms-JHEH) was produced at a high level (100 fold over background EH catalytic activity). As expected, Ms-JHEH was localized in the microsomal fraction with a molecular mass of approximately 50 kDa. Ms-JHEH showed a substrate and inhibitor spectrum similar to the wild type JHEH isolated from eggs of M. sexta. Its enzymatic activity was the highest for Juvenile Hormone III. Ms-JHEH hydrolyzed several trans-epoxides faster than cis-epoxides. A putative hydroxyl-acyl enzyme intermediate was isolated suggesting a …

Synthesis of azoxystrobin transformation products and selection of monoclonal antibodies for immunoassay development

2012

The use of agrochemicals for crop protection may result in the presence of toxic residues in soils and aquatic environments, besides in foodstuffs. Most often just the parent compound is included in the definition of pesticide residue, even though chemicals resulting from biotransformation and degradation routes might also be of toxicological relevance. Azoxystrobin is a broad-spectrum systemic fungicide widely used worldwide to combat pathogenic fungi affecting plants. We herein report the synthesis and detailed chemical characterization of several of the most relevant metabolites and degradates of azoxystrobin. These compounds were further employed as ligands for screening a collection of…

Possible reason for preferential damage to renal tubular epithelial cells evoked by amphotericin B

1996

An important determinant of nephrotoxicity, which is the major complication of long-term amphotericin B treatment, is dysfunction of distal tubular epithelial cells. The underlying cause for this rather selective damage to the cells is unknown. In the present investigation, it was shown that kidney epithelial cells were initially damaged by amphotericin B at concentrations of 2.5 to 10 micrograms/ml, as demonstrable by a dramatic drop in cellular K+ levels. Cells could recover from the initial toxic action of the polyene if they were kept in medium of neutral pH, and cellular K+ levels returned to normal after 6 h. However, the recovery mechanisms failed at lower pHs of 5.6 to 6.0. At low p…

Improving opportunities for effective management of gastro-oesophageal reflux disease

2002

The recent introduction of proton pump inhibitors has extraordinarily improved the therapeutic approach to gastro-oesophageal reflux disease. The concept of decreasing gastric acid secretion and increasing the pH in the lower oesophagus has been demonstrated to be therapeutically effective and the higher the level of pH achieved, the better the results. In spite of the evident efficacy of these molecules, there are still many patients who will continue to have symptoms despite medical treatment. Proton pump inhibitors suppress gastric acidity, but this effect shows a remarkable interindividual variation depending on different reasons. Thus, it is still possible to optimise medical therapy f…

Endothelial Cell Swelling and Brain Perfusion

1997

Background: Whereas the contribution of glial swelling to no-reflow conditions in the ischemic penumbra or during reperfusion after global ischemia is widely discussed, little is known about cell volume control of endothelial cells under reperfusion conditions. Methods: The effect of extracellular acidosis-a key mediator of secondary brain damage-on cell volume was studied in the GM7373 endothelial cell line. Experiments were performed at pH = 6.0 in the presence or absence of bicarbonate, and during exposure to inhibitors of specific transport systems such as ethyl isopropyl amiloride or 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. Results: Endothelial swelling to 111.1 ± 3.4% was f…

pH stability of ophthalmic solutions.

2004

Background In this study, we evaluated the pH value of 17 ophthalmic solutions, and we investigated whether the pH of these solutions changed over time after the bottle was opened. Methods Fifteen bottles of each type of solution were chosen at random from different production lots. A 0.05-ml increment was taken from each bottle and was measured daily using a micropH 2002 Crison pH-meter over a period of 30 days. Results The results revealed differences between the pH values of the solutions; nine solutions presented pH values within ocular comfort range and eight solutions presented pH values between 3.5 and 6.4. Ten solutions presented non-statistically significant variations over time ( …

Hyperammonemic encephalopathy after urinary diversion. Diet therapy

2016

Unpredictable Performance of pH-Dependent Coatings Accentuates the Need for Improved Predictive in Vitro Test Systems.

2017

First introduced in the second half of the 19th century, enteric coatings are commonly used to protect acid-labile drugs, reduce the risk of gastric side effects due to irritating drugs, or for local drug delivery to the lower gastrointestinal (GI) tract. The currently available enteric-coatings are based on pH-sensitive weakly acidic polymers. Despite the long history of their use, the causes behind their performance often being unpredictable have not been properly investigated with most of the attention being focused only on the gastric emptying. However, little attention has been given to the postgastric emptying disintegration and dissolution of these dosage forms. This lack of attentio…

Splenic respiratory gas exchange and glucose uptake in patients with splenomegaly in hypersplenism and Hodgkin's disease.

1977

Blood samples are taken from the splenic artery, vein and pulp of patients suffering from Hodgkin's disease (n=10) or hypersplenism (n=7) and undergoing splenectomy. In these samples, the relevant parameters of the respiratory gas exchange as well as glucose and lactate concentrations are determined. In hypersplenism (mean splenic wet weight: 543 g) the mean oxygen consumption of the splenic tissue amounts to 0.9 ml O2/100 g/min taking into account a mean splenic blood flow of 80 ml/100 g/min. The glucose uptake and the lactate release are 9 mg/100 g/min and 5.5 mg/100 g/min, respectively. These values are in close agreement with the results obtained in the normal and undisturbed spleen in …

Gastroesophageal reflux in young children treated for esophageal atresia: evaluation with pH-multichannel intraluminal impedance

2011

Objectives: Gastroesophageal reflux (GER) and dismotility occur frequently after repair of esophageal atresia (EA). GER-associated complications can manifest either early or later; then precocious diagnosis and treatment are essential. The aim of the study was to evaluate characteristics of GER and esophageal clearance in children treated for EA with distal tracheoesophageal fistula, using pH-multichannel intraluminal impedance (pH-MII). Patients and Methods: Twenty-two children (ages 3‐40 months) treated for EA at birth, and 20 normal children of similar age with suspected GER disease were included in the study. Impedance parameters were analyzed according to age and symptoms. Results: Ref…