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Biomedical subjects

M Kretzschmar

Publications and source records attributed to M Kretzschmar.

At least 91 records · Page 5Linked to original sources
PubMed1991

Ontogenetic changes in hepatic glutathione system (synthesis, catabolism, export) of male Uje:WIST rats.

The age-courses of concentrations of reduced (GSH) and oxidized (GSSG) glutathione, of GSH synthesizing enzyme activities, of glutathione S-transferase (GST), of GSSG-reductase (GR) and of biliary GSH and GSSG export were measured in livers from male Uje:WIST rats. Additionally, the age-courses of plasma GSH and GSSG concentrations were investigated. The hepatic level of GSH showed a biphasic pattern with a first maximum immediately after birth and a small second peak at the 50th day of life. The GSSG level increased continuously up to day 60 of life. The cytosolic GSH synthesizing enzyme activities showed diverse developmental patterns indicating different regulation principles. The hepatic activity of GR was relatively constant in the different age groups after birth. The GST activity (with o-dinitrobenzene as substrate) was relatively low at birth (about 30% of the maximum measured at day 60 of life). The maximum of GSH plasma level was found at birth. With increasing age a significant decrease in this level was observed. The excretion rate of total GSH (GSH + 2 GSSG) in bile was found to increase about 9-fold between 15 and 105 days of age. The results indicate that changes of hepatic GSH concentration with age are dependent on numerous factors. The balance between synthesis, catabolism and export is important for the maintenance of this level.

Aging↗
PubMed1991

[Lipid peroxidation in pathologic pregnancy: pregnancy-induced hypertension. I].

Serum concentrations of thiobarbituric acid reagible substance (TBARS) as indicator of lipid peroxidation, alpha-tocopherol and selen have been investigated in women with normal pregnancy and patients suffered from pregnancy-induced hypertension. In the group of patients with pregnancy-induced hypertension we observed an increase in serum concentration of TBARS, where as the serum concentrations of alpha-tocopherol and selen were unchanged. There was no correlation between increase in TBARS concentration and the severity of hypertension.

Blood Pressure↗
PubMed1990

Role of glutathione in vanadate reduction in young and mature rats: evidence for direct participation of glutathione in vanadate inactivation.

The influence of renal glutathione content, modulated by the glutathione synthesis inhibitor buthionine sulphoximine or by glutathione infusion, on the polyuric and natriuretic effects of i.v. administered vanadate was investigated in 20- and 55-day-old rats. The modulation of renal glutathione content led to significant changes in urine volume and sodium excretion, independently of age. A decrease in the renal glutathione level led to intensification and prolongation of the diuretic effects of vanadate in 55-day-old animals. Treatment with glutathione abolished and treatment with buthionine sulphoximine increased the polyuric effect of vanadate. These observations indicate a role for renal glutathione in vanadate inactivation. Age-dependent differences in the polyuric and natriuretic effectiveness of vanadate are caused by differences in renal glutathione content during maturation of the kidney.

Aging↗
PubMed1990

The hepatic glutathione system--influences of xenobiotics.

The hepatic glutathione (GSH) system and the influences of xenobiotics have been reviewed. Key steps in the regulation of hepatic GSH are GSH biosynthesis, the GSH-peroxidase/reductase cycle, the cystathionine pathway, and the carrier-mediated export processes. Influences of xenobiotics on these different pathways are discussed. Xenobiotics may lead to liver injury after biotransformation to highly reactive electrophilic metabolites (mainly cytochrome P-450 mediated), which easily conjugate with GSH, thus producing GSH depletion. This GSH depletion and probably an additional loss of protein sulfhydryl groups cause a disturbance of the intracellular calcium homeostasis which leads to an irreversible cell injury. The different acinar distribution of cytochromes P-450 and of GSH and GSH-related detoxication pathways points to a greater susceptibility of perivenous hepatocytes to xenobiotic-induced damage. Also, the intracellular compartmentation of GSH is important for the understanding of hepatocellular injury induced by several xenobiotics.

Animals↗
PubMed1990

Glutathione levels in liver and brain of newborn rats: investigations of the influence of hypoxia and reoxidation on lipid peroxidation.

1. The levels of reduced glutathione (GSH) in the liver and brain of newborn rats were independent of the birth mechanism (Cesarean section or natural birth). A significant increase of GSH content could be demonstrated 3 h after birth in the liver only. 2. The influence of reversible hypoxia (9 vol. % O2 in the respired air for one hour) on GSH and oxidized glutathione (GSSG) levels and the content of thiobarbituric acid (TBA) reagible products were investigated in the liver and brain of newborn rats in dependence on the duration of reoxygenation. Only small changes were observed in the liver indicating a relative resistance of this organ to hypoxic stress and reoxygenation. Distinct effects were found in the brain, indicating that the glutathione status is altered by increased lipid peroxidation.

Animals↗
PubMed1989

A renewal equation with a birth-death process as a model for parasitic infections.

A model is derived for the description of parasitic diseases on host populations with age structure. The parasite population develops according to a linear birth-death-process. The parasites influence mortality and fertility of the hosts and are acquired with a rate depending on the mean parasite load of the host population. The model consists of a system of partial differential equations with initial and boundary conditions. From the boundary condition a renewal equation for the host population is derived. The model is then generalized to describe a multitype process. Existence and uniqueness of solutions are proved. Results concerning persistent solutions are indicated.

Age Factors↗
PubMed1989

Persistent solutions in a model for parasitic infections.

A model is discussed for the description of parasitic diseases on host populations with age structure. The parasite population develops according to a linear multitype birth-death-process. The parasites influence mortality and fertility of the hosts and are acquired with a rate depending on the mean parasite load of the host population. The model consists of a system of partial differential equations with initial and boundary conditions. Existence and stability of persistent solutions as well as the distribution of parasites on the host population are discussed.

Aging↗
PubMed1989

Hepatic actions of levonorgestrel: correlations between biochemical and morphological findings.

The influence of the synthetic sexual steroid levonorgestrel (LN) on rat liver in various doses and at different structural levels was investigated. A slight reactive hepatosis was found by histological examination after administration of LN in a dose of 10 mg per kg body wt. The same dose caused exclusively distinct lesions of the mitochondria, however, only in centrilobular parenchymal cells, whereas in the periportal hepatocytes only the lipid droplet content appears somewhat elevated. LN decreased the total glutathione content of the liver. The mitochondrial glutathione was decreased more intensively. One mg/kg body wt. of LN decreased the cytochrome P-450 content, but 10 mg/kg body wt. increased ethyl-morphine N-demethylation and 7-ethoxycoumarin O-deethylation activities. Distinct correlations could be shown between the biochemical changes and the ultrastructural findings.

Animals↗
PubMed1989

Glutathione synthesis and export in experimental liver cirrhosis induced by thioacetamide: relations to ultrastructural changes.

Micro-and macronodular experimental liver cirrhosis was induced in female rats by administration of 0.03% thioacetamide (TAA) in drinking water for 3 or 6 months, respectively. The glutathione (GSH) status (content, synthesis, export) and ultrastructural changes of liver were investigated 14 d after withdrawal of TAA. The hepatic level of GSH was increased after 6 months TAA treatment. The levels of oxidized glutathione (GSSG) were not changed after 3 months or 6 months TAA administration. The GSH synthesis was not disturbed in the cirrhotic livers; only the ratio between the 2 synthesizing enzymes was changed in macronodular liver cirrhosis. The plasma GSH content was reduced in both cases, independent of the stage of liver cirrhosis. The electron microscopic studies on cirrhotic rat livers revealed a series of characteristic structural changes, such as disorganization and total lack of the microvilli border, appearance of basement membrane-like deposits within the narrowed space of Disse, disappearance of the highly porous endothelial cell lining and partly an intensively detoriated blood supply within the pseudolobules. It is suggested that all these changes may contribute to a disturbance of the GSH export from the hepatocytes into the blood. It is very likely, however, that the alterations of the sinusoidal cell surface play the most important role. 1. The GSH/GSSG redox potential is shifted in favour of the reduced form in this cirrhosis model. This shift seems to be connected with later stages of cirrhogenesis. 2. A GSH export disturbance is responsible for the decreased plasma GSH level in liver cirrhosis.

Animals↗
PubMed1989

Perinatal activity of hepatic gamma-glutamyltranspeptidase in rats from large and small litters.

In rat pups, the activity of hepatic gamma-glutamyltranspeptidase (GGT) is not influenced by the process of labor. Maximum activities are observed prenatally occurring at the 21st day of gestation in fetuses from normal, large litters, but at the 20th day of gestation in fetuses from experimentally reduced litters (2 fetuses per litter). This different developmental pattern may depend on processes of fetal maturation rather than on processes of luteolysis.

Animals↗
PubMed1989

gamma-Glutamyltranspeptidase in liver homogenates of rats of different ages: enzyme kinetics and age course of Km and Vmax.

Optimum incubation conditions for the determination of gamma-glutamyltranspeptidase with liver homogenates from rats of different ages have been determined: about 1 mg protein/assay, 4.4 mM L-gamma-glutamyl-p-nitroanilide, 40 mM glycylglycine, 9.6 mM MgCl2 in 0.1 M Tris-HCl buffer, pH 8.0; final volume 1.3 ml. The enzyme activity is very high at birth, the increase before birth is not continuous. After birth the enzyme activity decreases quickly over the first postnatal days. The ENDRENYI-KWONG-plot was linear with homogenates from newborn and 3-day-old animals. For all other age groups the graphs showed an angle. Statistical analysis carried out that a two-enzyme model plots the experimental data only insignificantly better than a one-enzyme model. It may be concluded that there are different GGT isozymes which show different affinities towards the substrate and which show different developmental patterns.

Aging↗
PubMed1989

[Determination of the biliary excretion of reduced and oxidized glutathione].

An enzymatic method is presented for the detection of biliary excretion of reduced (GSH) and oxidized (GSSG) glutathione. The biliary excretion of GSH is 65.63 +/- 7.23 nmoles/kg b.w. x min and of GSSG 5.90 +/- 0.64 nmoles/kg b.w. x min in 55 day-old female rats, respectively. The recovery is 97.39 +/- 0.40% for GSH and 91.05 +/- 2.30% for GSSG. Cysteine which can be detected in bile, does not influence the accuracy of the results.

Animals↗
PubMed1976

[Determination of the gestational age in late pregnancy by sonography (author's transl)].

In 219 normal pregnancies between 28 and 42 weeks the relationships of different ultrasound measurements of the fetal head and the fetal body to the gestational age were determined in order to improve the accurate diagnosis of fetal maturity during the last trimester of pregnancy. With the A and B ultrasound apparatus of Kretz, the biparietal diameter was determined by the A mode, the fronto occipital plane and the largest abdominal diamter were determined by the B scan. The following ultrasound measurements were taken: the two horizontal and transverse diameters, the circumferences and the planes. The abdominal measurements showed a higher rate of growth, compared to the cranial measurements a lesser rate of growth retardation and a higher variation of the normals. The correlation of the abdominal measurements with the gestational age was worse than that of the cranial measurements. Wth the exception of the biparietal diameter in the A mode, the mean diameters of the cranial and abdominal measurements gave better results than the single diameters. Circumference and surface measurements showed no advantages. The best results were obtained by combined fetal head and body measurements using the summation of the biparietal diameter in the A mode and the mean abdominal diameter in the B scan.

Cephalometry↗
PubMed1975

[Estimation of fetal weight by ultrasound (author's transl)].

In attempt to estimate birth weight in utero several dimensions of fetal head and trunk cross-sections, obtained by ultrasonic A- and B-scan techniques (Kretz-Technik), were related to postnatal weights in 108 normal and abnormal pregnancies. Abdominal parameters showed better correlation with weights than did head parameters. Evaluations derived from mean diameter, circumference or area yielded more accurate estimations than those derived from single diameter. In addition, the combination of both head and abdomen measurements increased accuracy. The best results were obtained by planimetric determination of head and trunk cross-sectional areas. Using this method the standard error of estimates was 233 gm. as compared with 423 gm. employing biparietal diameter alone.

Abdomen↗