PubMed Health⌕ Search

Biomedical subjects

R Teschke

Publications and source records attributed to R Teschke.

At least 19 recordsLinked to original sources
PubMed1988

Acquired immunodeficiency syndrome. Magnetic resonance patterns of brain involvement with pathologic correlation.

Magnetic resonance brain scans of 30 patients with either acquired immunodeficiency syndrome (AIDS) or AIDS-related complex were reviewed. Twenty patients had focally abnormal neurological examination results at the time of scanning. Pathological diagnosis was available in nine. Four patterns of abnormality were observed on T2-weighted images. Multiple discrete high-signal foci (pattern A) were found in patients with toxoplasmosis and progressive multifocal leukoencephalopathy. Large, bilateral patchy to confluent high-signal areas within the white matter (pattern B) represented a white matter encephalitis secondary to cytomegalovirus or human immunodeficiency virus. Generalized enlargement of the cortical sulci and ventricles (pattern C) probably reflected atrophic changes from the chronic human immunodeficiency virus infection and prolonged debilitating illness. Solitary high-signal-intensity lesions (pattern D) suggested a nonviral opportunistic infection. Differential diagnosis of brain abnormalities in patients with AIDS can be assisted by recognition of these characteristic patterns.

Acquired Immunodeficiency Syndrome↗
PubMed1988

[The liver and alcohol].

The liver is the main organ for alcohol metabolism and is therefore predisposed for various functional changes and irreversible alterations. The alcoholic fatty liver represents the early stage of alcohol-induced liver diseases and is completely reversible upon consequent alcohol abstinence. Already at this early stage a significant increase of gamma-glutamyltransferase activities is commonly found in the serum, which can mainly be attributed to an enzyme induction in the endoplasmic reticulum of the liver cell. Other stages of alcohol-induced liver diseases include the alcoholic hepatitis and the liver cirrhosis, which have a better prognosis upon consequent alcohol abstinence compared to continuous alcohol consumption. Many therapeutic studies with various drugs have been carried out in patients with alcohol-induced liver diseases, but at present a treatment with drugs in a sufficiently great number of patients has not been firmly established. The most important medical goal is to establish the diagnosis of alcohol-induced liver diseases already at the early stage of the fatty liver in order to initiate the necessary therapeutic measures with the aim of a consequent alcohol abstinence.

Alcoholism↗
PubMed1988

[The biochemistry of alcohol metabolism].

The metabolism of ethanol to acetaldehyde in the liver proceeds via alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MOS), whereas catalase plays no significant role. ADH is an enzyme of the cytosol, requires NAD+ as cofactor and exhibits a pH optimum in the alkaline range. The Km of ADH is about 2 mM for ethanol (equivalent to 0.1%). Thus, the enzyme is already saturated at low ethanol concentrations. Conversely, MEOS resides in the endoplasmic reticulum, requires NADPH and O2, is inhibited by CO and exhibits a km of about 10 mM corresponding to 0.5% ethanol. This enzyme system is therefore primarily the pathway of ethanol metabolism at intermediate to high ethanol concentrations. MEOS has many properties in common with other drug metabolizing enzymes and is characterized by inducibility following chronic ethanol consumption, which suggests the involvement of the microsomal system in the adaptive enhancement of ethanol clearance commonly observed in alcoholics. The product of ethanol oxidation by ADH, MEOS and catalase is acetaldehyde. Acetaldehyde is oxidized in the liver to acetate by NAD dependent aldehyde dehydrogenase. Four isozymes have been identified. Lack of isozyme I is responsible for the "flush-syndrome" commonly observed in asian people following alcohol intake. Ethanol metabolism is affected by the aging process and is decreased with advancing age.

Alcohol Dehydrogenase↗
PubMed1987

Influence of chronic alcohol consumption on hepatic heme and porphyrin metabolism.

To study the effect of prolonged alcohol consumption on hepatic heme and porphyrin metabolism, female Wistar rats were fed for 60 days a nutritionally adequate liquid diet containing 36% of total calories as ethanol, whereas the control diet was isocaloric and contained no alcohol. Compared to pair-fed controls, the administration of the alcohol diet resulted in an increased hepatic activity of delta-aminolevulinic acid synthase by 223% (112.3 +/- 19.6 nmoles/hr/100 g b.wt. vs. 362.8 +/- 42.5; P less than 0.01), an enhanced urinary excretion of delta-aminolevulinic acid by 101% (64.8 +/- 11.8 nmoles/day vs. 130.8 +/- 22.4; P less than 0.05), and an augmented urinary output of total porphyrins by 142% (1.2 +/- 0.2 nmoles/day vs. 2.9 +/- 0.5; P less than 0.05). Concomitantly, the hepatic content of cytochrome P-450 was significantly enhanced and that of hepatic catalase activity marginally increased, whereas the hepatic iron content remained unaltered. In summary, the feeding of rats with a liquid alcohol diet for 60 days results in changes of hepatic heme and porphyrin metabolism which are associated and may be causally related with an induction of hepatic hemoproteins and subsequent derepression of hepatic delta-aminolevulinic acid synthase, whereas hepatic iron appears to play no pathogenic role.

5-Aminolevulinate Synthetase↗
PubMed1987

Enhanced biliary gamma-glutamyltransferase excretion following prolonged alcohol consumption in rats.

In order to study the question of whether chronic ethanol consumption may alter the biliary excretion of gamma-glutamyltransferase (gamma-GT), female rats were pair-fed nutritionally adequate liquid diets containing either ethanol (36% of total calories) or isocaloric carbohydrates for 24 days. Compared to pair-fed controls, the administration of the alcohol-containing diet resulted in an increased biliary excretion of gamma-GT (5.84 +/- 0.73 mU 6 h-1 100 g-1 b.w. vs. 8.82 +/- 0.79, P less than 0.001). This was associated with a corresponding enhanced biliary output of total bile acids. An apparent linear relation between the biliary output rates of gamma-GT and those of total bile acids was observed both in alcohol-fed animals (r = 0.83) and in their pair-fed controls (r = 0.95). In addition, there was a significant increase of gamma-glutamyltransferase activities in the liver homogenate and in liver plasma membranes, both in fractions rich in bile canalicular and basolateral membranes and in those rich in blood sinusoidal site. Serum gamma-glutamyltransferase activities as well as serum bile acid concentrations were also enhanced by 96.8% (P less than 0.001) and 233% (P less than 0.001), respectively. These data show that chronic alcohol consumption enhances hepatic gamma-GT activities, leading to an increased efflux of gamma-GT into the bile and possibly into the blood out of the liver cell. Furthermore, these data suggest the involvement of bile acids with their solubilizing properties for the biliary excretion of gamma-GT.

Alcoholism↗
PubMed1987

Iron uptake by rat duodenal microvillous membrane vesicles: evidence for a carrier mediated transport system.

The mechanism of iron translocation from intestinal lumen to portal plasma is poorly understood. To examine these processes, uptake of Fe2+ and Fe3+ by rat duodenal microvillous membrane vesicles prepared by a Ca2+ precipitation procedure was studied. Membrane aliquots were incubated with increasing concentrations of 59FeCl3 in the presence of a one-thousand-fold molar excess of citrate or 59FeSO4 with a twenty-fold molar excess of L-ascorbic acid. After various time intervals the incubation reaction was stopped by addition of 0.1 mM FeCl3 (4 degrees C), and uptake of 59Fe was determined by a vacuum filtration assay. Initial uptake velocity of 59FeCl3 and 59FeSO4 was determined from the slope of the cumulative uptake curves, which was linear for the first 60 s. Initial uptake rates of both, 59Fe3+ and 59Fe2+ revealed an identical saturable uptake component with a Km of 19-22 nM and Vmax of 8 pmol min-1 mg protein-1. In addition, transport of Fe2+ revealed a linear unspecific uptake phase, which was predominant at high substrate concentrations. Saturable uptake of Fe2+ and Fe3+ was temperature dependent, and significantly reduced by trypsin pretreatment of the microvillous membrane vesicles, indicating the involvement of a protein in the uptake process. This suggestion was pursued by isolation of an iron binding protein from duodenal brushborder membranes. After solubilization of microvillous plasma membranes with 1% Triton X 100, affinity chromatography of the membrane protein mixture over an iron chelate gel derived from epoxy activated Sepharose and elution with 50 mM EDTA yielded a single 52,000 dalton protein. The protein co-chromatographed over an Ultro-Pac TSK G 3000SW HPLC column together with 59FeCl3 and 59FeSO4. It showed no immunologic activity to rabbit antibodies against whole rat serum or rat transferrin. Furthermore, by photoaffinity labelling technique a single iron binding protein with a molecular weight of about 52,000 dalton was identified in microvillous membranes of the rat duodenum. These data are compatible with the hypothesis that intestinal iron absorption is mediated by a specific carrier-dependent transport system.

Animals↗
PubMed1986

Biliary excretion of gamma-glutamyltransferase. Selective enhancement by acute ethanol administration.

To study the acute effect of ethanol on various constituents of the bile, female Wistar rats received by intravenous administration 0.9% NaCl solution either alone or containing in addition ethanol (0.1 ml ethanol 96% hr-1 100 g body weight-1). Compared to saline-treated controls there was a significant enhancement of biliary gamma-glutamyltransferase excretion after ethanol infusion for 5 hr by 166% (22.1 +/- 2.8 microU/min/100 g body weight vs. 58.2 +/- 13.7; P less than 0.0125), whereas no changes or only marginal alterations have been observed for bile flow and the biliary excretion of total bile acids and alkaline phosphatase. The selective enhancement of biliary gamma-glutamyltransferase excretion by ethanol can be ascribed to an increased solubilization of the membrane-bound enzyme originating from the bile canaliculi of the hepatocytes and/or the epithelial cells of the bile ducts. Since the biliary excretion of total bile acids remained unchanged by ethanol, the observed selective solubilization of gamma-glutamyltransferase may occur by a mechanism primarily not involving total bile acids and could be linked to a direct effect of ethanol on physico-chemical properties such as an increased fluidity of liver plasma membranes.

Alkaline Phosphatase↗
PubMed1986

Hepatic alcohol metabolizing enzymes after prolonged administration of sex hormones and alcohol in female rats.

To study the effect of sex hormones and alcohol on the hepatic activities of alcohol metabolizing enzymes, estradiol or testosterone were administered for 4 weeks to ovarectomized or sham operated adult female rats pair-fed nutritionally adequate liquid diets containing either alcohol (36% of total calories) or isocalorically replaced carbohydrates. Estradiol increased the hepatic activities of alcohol dehydrogenase and catalase in both ovarectomized and sham operated female rats on the control diet, whereas this enhancing property was virtually lost in animals on the alcohol diet. The hepatic activities of the microsomal ethanol-oxidizing system remained unaffected under these experimental conditions irrespective of the diet used. Testosterone increased the hepatic activities of the microsomal ethanol-oxidizing system and of catalase and decreased the alcohol dehydrogenase activity in female rats on the control diet, but these changes were either not reproducible or markedly reduced in similarly treated female rats fed the alcohol diet. Thus, sex hormones may strikingly influence the hepatic activities of alcohol metabolizing enzymes, but the changes are modulated by prolonged alcohol consumption.

Alcohol Dehydrogenase↗
PubMed1978

[Biochemical and pathophysiological aspects of alcohol metabolism (author's transl)].

The metabolism of ethanol to acetaldehyde proceeds in the liver via alcohol dehydrogenase (ADH) and the microsomal ethanol oxidizing system (MEOS), whereas catalase plays no significant role. ADH is localized in the cytosol, required required NAD+ as cofactor and exhibits a pH optimum in the alkaline range and a Km of less than 2 mM for ethanol. Conversely, the MEOS resides in the endoplasmic reticulum, requires NADPH and O2, is inhibited by CO, and exhibits a Km of about 10 mM for ethanol. The microsomal system also metabolizes higher aliphatic alcohols such as butanol which is not a substrate for catalase. Moreover, it could be separated from ADH and catalase by column chromatography. The MEOS exhibits a variety of properties similar to those of other microsomal drug metabolizing enzymes and is characterized by inducibility of its activity following chronic alcohol consumption, which suggests the involvement of the microsomal system in the adaptive enhancement of ethanol clearance commonly observed in alcoholics.

Acetaldehyde↗