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Biomedical subjects

G Zimmer

Publications and source records attributed to G Zimmer.

At least 91 records · Page 5Linked to original sources
PubMed1993

Cathepsin D as a vitality marker in human skin wounds.

This paper shows the results obtained by studying the lysosomal enzyme Cathepsin D as a potential marker for the vitality of wounds in human specimens. We have analyzed 53 samples using enzymological and histological techniques. Our results show the ability of Cathepsin D to establish the vital origin of wounds inflicted 5 minutes or less before death, where the specific activity of cathepsin D reached 0.055 units at the wound edge and 0.01 units in their respective controls (P < 0.001). As previously demonstrated in an experimental series, Cathepsin D seems to be a very useful marker of high forensic interest in especially difficult cases. Further studies are in progress to check the influence of different factors such as drugs intake and clinical conditions on Cathepsin D activity.

Adolescent↗
PubMed1993

Molecular aspects of membrane stabilization by ursodeoxycholate [see comment].

BACKGROUND: Ursodeoxycholate, used for therapy in biliary liver diseases, prevents bile salt damage in animal experiments. Using isolated red blood cell and both canalicular and basolateral hepatocyte membranes, the present study examined this protective effect. METHODS: Membranes were incubated with chenodeoxycholate, with chenodeoxycholate and ursodeoxycholate simultaneously, and first with ursodeoxycholate followed by chenodeoxycholate. Changes in membrane structure were investigated by electron paramagnetic resonance spectroscopy, using different spin labels. Data were confirmed by analysis of membrane lipids and studies with 14C-labeled bile acids. RESULTS: The increase of polarity in the apolar domain of the membrane caused by chenodeoxycholate corresponded to the amount of solubilized lipids. After preincubation with ursodeoxycholate or its conjugates, membrane damage by subsequent chenodeoxycholate incubation was prevented. This effect was caused by binding of ursodeoxycholate in the apolar domain, of its conjugates in the interface of the membrane. CONCLUSIONS: Chenodeoxycholate solubilizes membrane lipids and permits water to permeate into plasma membranes. The steroid nucleus of ursodeoxycholate is bound to the apolar domain and that of the conjugates to the interface of the membrane, thus stabilizing membrane structure.

Animals↗
PubMed1993

Surface glycoprotein of influenza C virus: inactivation and restoration of the acetylesterase activity on nitrocellulose.

The influenza C glycoprotein HEF was analyzed for acetylesterase activity after SDS-polyacrylamide gel electrophoresis and transfer to nitrocellulose membranes. Using a histological esterase assay, the glycoprotein was detected as a colored band indicating that it is enzymatically active. The enzyme activity was not affected by low pH, but was abolished after denaturation by SDS as well as after breaking the disulfide bonds by reducing agents. Glycoprotein inactivated by SDS regained its enzyme activity if the ionic detergent was displaced by either bovine serum albumin or a nonionic detergent. The stability of the enzyme combined with the color assay provides a convenient tool to study the acetylesterase activity of the influenza C virus glycoprotein.

Acetylesterase↗
PubMed1993

Nitroxide radical biostability in skin.

Nitroxide radicals are important chemical tools in dermatologic research (e.g., for studying biophysical properties of skin lipids and epidermal membranes with the method of electron paramagnetic resonance, EPR, spectroscopy). However, nitroxides may loose their paramagnetic properties in biological tissues, which could limit their usefulness in biomedical applications. We analyzed the biostability of various chemical types of nitroxide radicals in keratinocytes, epidermis homogenate, and intact skin. EPR signal loss of imidazoline, pyrrolidine, piperidine, and oxazolidine nitroxides is attributed to their reduction to the corresponding hydroxylamine. The rate of nitroxide reduction in skin varies considerably with nitroxide ring structure and substitution. The order of nitroxide stability in isolated human keratinocytes, mouse epidermis homogenate, and intact mouse and human skin is imidazoline > pyrrolidine > di-t-butylnitroxide (DTBN) > piperidine > oxazolidine. Cationic nitroxides are reduced much faster than neutral or anionic probes, presumably due to transmembrane electron shuttle or internalization. The results indicate that imidazoline- and pyrrolidine-type nitroxides should be used when high biostability of nitroxides is needed. Piperidine-type nitroxides are versatile probes for studying one-electron transfer reactions in skin.

Animals↗
PubMed1993

Intracellular changes of HeLa cells after single or repeated treatment with cytostatics.

HeLa cells were treated once or repeatedly using the cytostatics doxorubicin (adriamycin, Ad, CAS 23214-92-8), cisplatin (Pt, CAS 15663-27-1) and fluorouracil (FU, CAS 51-21-8). Intracellular GSH (reduced glutathione) contents, activities of protein kinase C, cytotoxicity and membrane fluidity were investigated. During single treatment protein kinase C activities as well as membrane fluidity increased, whereas intracellular GSH decreased. With repeated treatments protein kinase C activities increased further. Membrane fluidity as well as intracellular GSH contents increased. The investigated parameters may be correlated with sensitivity of cells against cytostatics.

Antineoplastic Agents↗
PubMed1993

Cardioprotective efficiency of dihydrolipoic acid in working rat hearts during hypoxia and reoxygenation. 31P nuclear magnetic resonance investigations.

The working rat heart model was used for 31P nuclear magnetic resonance (NMR) studies during normoxia, hypoxia and reoxygenation. Aortic flows of about 35 ml/min could be achieved which equals 65% of the values obtained outside the NMR magnet. Addition of dihydrolipoic acid (DHL) at a concentration of 0.3 mumol/l during hypoxia accelerated the recovery of aortic flow and stabilized it during reoxygenation. During hypoxia, inorganic phosphate contents (Pi) were significantly higher in controls. The phosphate shift indicated a pH decrease in control to 6.98, in DHL treated hearts the calculated pH was 7.15. During both hypoxia and reoxygenation, the phosphocreatinine (PCr) contents were higher in the DHL treated hearts than in controls. In the controls, saturation transfer measurements revealed a decrease of the flux PCr-->ATP during initial reoxygenation, whereas after addition of 0.3 mumol/l of DHL during hypoxia creatine kinase flux remained constant or increased. In isolated rat heart mitochondria, creatine kinase activities were measured under saturating and non-saturating concentrations of PCr. An increase in activity was observed under low PCr (non-saturating) conditions in the presence of 0.7 nmol DHL per mg of protein. At higher concentrations of DHL, creatine kinase activity was increased under all conditions. An increase in ATP synthesis in the working rat heart under influence of DHL is corroborated by NMR spectroscopy.

Adenosine Triphosphate↗
PubMed1992

Decreased concentration of myofibrils and myofiber hypertrophy are structural determinants of impaired left ventricular function in patients with chronic heart diseases: a multiple logistic regression analysis.

OBJECTIVES: The aim of this study was to perform a multiple logistic regression analysis to identify independent structural determinants of impaired left ventricular function. BACKGROUND: The association between contractile failure and structural alterations of the myocardium has been demonstrated in several studies, and multiple interactions between myocardial structure and cardiac performance are likely. METHODS: Morphometric data assessed from 130 left ventricular biopsy specimens were analyzed. The endomyocardial specimens were obtained from 57 patients with normal coronary arteries (17 with normal left ventricular ejection fraction and 40 with impaired left ventricular function [dilated cardiomyopathy]), 15 patients with hypertrophic cardiomyopathy and 32 patients with aortic valve disease. Transmural biopsy specimens were assessed in 6 donor hearts before heart transplantation and in 20 patients with left anterior descending coronary artery disease whose specimens were obtained from the left ventricular anterior wall during aortocoronary bypass surgery. Global or regional left ventricular function was evaluated from left cineventriculograms. The volume fraction of cardiac fibrous tissue, intracellular volume fraction of myofibrils, volume fraction of myofibrils related to myocardial tissue (including fibrosis) and myofiber diameters were determined from semithin sections of the biopsy specimens with the use of light microscopic morphometry. RESULTS: Multiple logistic regression analysis revealed decreased volume fraction of myofibrils (p < 0.005) and increased fiber diameter (p < 0.002) as independent determinants of impaired left ventricular function. CONCLUSIONS: These data indicate that, independent of the underlying heart disease, both decreased concentration of contractile proteins and myocyte hypertrophy are independently associated with impaired left ventricular function.

Age Factors↗
PubMed1992

The effects of glucose, insulin and metformin on the order parameters of isolated red cell membranes. An electron paramagnetic resonance spectroscopic study.

Human red blood cell (RBC) membranes (RBC ghosts) were treated with glucose, insulin and metformin. The order parameters of RBC membranes were determined by 5- and 16-doxyl-stearic acid spin labels. Metabolic effects were excluded using an isolated system of RBC membranes. The membranes were incubated with glucose in physiological (5 mM), renal threshold (10 mM) and manifested diabetic (20 mM) concentrations for limited times. High concentrations of glucose (10, 20, 100 mM) increase the order parameters of RBC membranes significantly. Insulin by itself has a similar effect which is, however, not strictly concentration-dependent. By contrast, metformin at therapeutic concentrations (0.5 and 5.0 microM) decreases the order parameters. At 50 microM concentration the metformin effect is expressed less and recurs at 100 microM concentration. The effects are significant with 5-doxyl-stearic acid, but are not significant with the 16-doxyl derivative. When RBC membranes are co-incubated with 20 mM glucose and metformin at 0.5 and 5.0 microM concentrations the order parameters as determined by 5-doxyl-stearic acid remain normal (= control values). Higher concentrations of metformin (50 and 100 microM) cause an overshoot to very low order parameters. Insulin at 10, 100 and 200 mU/L does not influence significantly the effects of metformin. Addition of physiological amounts of bovine serum albumin does not abolish the effects of metformin. Metformin, at therapeutic concentrations (0.5 and 5.0 microM), maintains the normal fluidity at the polar interface of isolated RBC membranes by counterbalancing non-enzymatic glycosylation with 20 mM glucose in vitro.

Cyclic N-Oxides↗
PubMed1992

Use of influenza C virus for detection of 9-O-acetylated sialic acids on immobilized glycoconjugates by esterase activity.

An overlay and a solid-phase assay are presented which allow the specific detection of 9-O-acetylated sialic acids on sialoglycoconjugates immobilized on microtiter plates, nitrocellulose or separated on thin-layer chromatograms. The assay takes advantage of two different biological properties of influenza C virus, its high-affinity binding to 9-O-acetylated sialic acids and its sialate 9-O-acetylesterase that is used for detection of bound virus with fluorogenic or chromogenic substrates. Though simple and rapid, the assay is highly sensitive with a detection limit of 65 fmol 9-O-acetylated sialic acid in 9-O-acetylated ganglioside GD1a. Influenza C virus is able to bind to a wide spectrum of sialoglycoconjugates like mucins, serum glycoproteins or gangliosides containing naturally or synthetically O-acetylated sialic acids. 9-O-Acetyl-N-glycoloylneuraminic acid can also function as a high-affinity receptor determinant for influenza C virus. While the acetyl ester at the 9 position is essential for virus binding in all cases, a 4-O-acetyl group is not recognized. In addition to alpha(2.3) or alpha(2.6) bonds, 9-O-acetyl-N-acetylneuraminic acid in alpha(2.8) linkage to N-acetylneuraminic acid is also functionally active.

Acetylesterase↗
PubMed1992

Reduced capillary density in the myocardium of uremic rats--a stereological study.

Using stereological techniques capillaries, interstitium and myocardial fibers were analyzed in perfusion-fixed hearts of subtotally nephrectomized male Sprague-Dawley rats with uremia of 14 months duration (or their sham-operated controls). Uremic rats had higher systolic blood pressure (140 +/- 20.3 mm Hg vs. 119 +/- 6.61 mm Hg) and left ventricular weight/body weight ratio (3.37 +/- 0.09 mg/kg vs. 2.01 +/- 0.12 mg/kg) than controls, and had slight anemia (Hct 35.0 +/- 3.16% vs. 40.4 +/- 3.3%). Length density (Lv) of capillaries, that is, capillary length per unit myocardial volume, was significantly (P < 0.001) decreased in uremia (2485 +/- 264 mm/mm3 vs. 3329 +/- 194 mm/mm3) versus controls. In parallel, surface density and volume density of the capillary lumina were also reduced (7.95 +/- 1.69 cm3/cm3 vs. 11.4 +/- 1.8 cm3/cm3) in the uremic rats. We conclude that in experimental uremia, cardiac hypertrophy is not accompanied by a commensurate increase in capillaries.

Animals↗
PubMed1992

Electron paramagnetic resonance (EPR) imaging in skin: biophysical and biochemical microscopy.

Electron paramagnetic resonance (EPR) is a spectroscopic technique that allows detection of paramagnetic compounds, e.g., free radicals, in skin, and is used for measuring skin membrane fluidity and polarity. EPR imaging is concerned with spatially resolved EPR spectroscopy. We studied EPR images at X-band frequency (9 GHz) in the skin biopsies of hairless mice. Our particular imaging technique utilized a modulated field gradient to obtain cross-sectional images perpendicular to the skin surface. Employing nitroxide free radicals, this approach allows analysis of skin biophysical and biochemical features at the micrometer resolution level. By spin labeling drugs, pharmacokinetic properties of the labeled compound can be monitored in skin. We suggest that EPR imaging has a broad application potential in dermatologic research. In comparison to other spatially visualizing techniques, such as nuclear magnetic resonance (NMR) imaging and ultrasound, EPR imaging has significant advantages, such as high spatial resolution and providing specific biochemical and biophysical information that cannot be obtained by other methods in skin.

Animals↗
PubMed1992

Influence of alpha-lipoic acid on intracellular glutathione in vitro and in vivo.

The influence of alpha-lipoic acid (CAS 62-46-4) on the amount of intracellular glutathione (GSH) was investigated in vitro and in vivo. Using murine neuroblastoma as well as melanoma cell lines in vitro, a dose-dependent increase of GSH content was observed. Dependent on the source of tumor cells the increase was 30-70% compared to untreated controls. Normal lung tissue of mice also revealed about 50% increase in glutathione upon treatment with lipoic acid. This corresponds with protection from irradiation damage in these in vitro studies. Survival rate of irradiated murine neuroblastoma was increased at doses of 100 micrograms lipoic acid/d from 2% to about 10%. In agreement with the in vitro studies, in vivo experiments with whole body irradiation (5 and 8 Gy) in mice revealed that the number of surviving animals was doubled at a dose of 16 mg lipoic acid/kg. Improvement of cell viability and irradiation protection by the physiological compound lipoic acid runs parallel with an increase of intracellular GSH/GSSG ratio.

Animals↗
PubMed1992

Treatment of chronic active hepatitis and primary biliary cirrhosis with ursodeoxycholic acid.

Ursodeoxycholic acid (UDCA) improves liver function tests in patients with chronic active hepatitis (CAH) and primary biliary cirrhosis (PBC). UDCA will reduce biochemical parameters of both cholestasis and hepatocellular damage. The effects may be less beneficial in patients with advanced stages of chronic liver disease: in PBC we found the improvement of laboratory parameters in stage I and II very impressive, in stage III and IV it was less marked. Data of two controlled trials in PBC showed an improvement in liver histology, in one study the improvement was statistically significant. UDCA can be administered for at least 10 years without any adverse effects, the treatment is safe and improves life quality. The mode of action of UDCA seems to be in its displacement of toxic hydrophobic bile salts from the bile acid pool and the hepatocellular membrane. In in-vitro investigations a direct protective effect of UDCA on isolated sinusoidal hepatocyte membranes against toxic bile salts has been shown. This protective effect of a more general nature may explain the efficacy of UDCA in different chronic, especially cholestatic liver diseases.

Adult↗
PubMed1992

[Plasma-membrane fluidity studies of murine neuroblastoma and malignant melanoma cells under irradiation].

Murine neuroblastoma (C-1300 NMB) and malignant melanoma (B16) cells were radiated in presence of radiopharmaceutics. Sensibilization was carried out with BSO and protection with TMX. Changes in fluidity of the plasma membrane, in cellular GSH contents and cell cycle were observed. After radiation fluidity of the plasma membrane is increased, whereas intracellular GSH decreased. These changes were intensified by BSO and reduced by TMX. Fluidity of the plasma membrane correlates with intracellular GSH and also with cell cycle. It is suggested that changes in plasma membrane fluidity can be used as an additional parameter for the determination of sensitivity towards radiation.

Animals↗
PubMed1991

Dihydrolipoic acid activates oligomycin-sensitive thiol groups and increases ATP synthesis in mitochondria.

Investigations with dihydrolipoic acid in rat heart mitochondria and mitoplasts reveal an activation of ATP-synthase up to 45%, whereas ATPase activities decrease by 36%. In parallel with an increase in ATP synthesis oligomycin-sensitive mitochondrial -SH groups are activated at 2-4 nmol dihydrolipoic acid/mg protein. ATPase activation by the uncouplers carbonylcyanide-p-trifluoromethoxyphenylhydrazone and oleate is diminished by dihydrolipoic acid, and ATP synthesis depressed by oleate is partially restored. No such efficiency of dihydrolipoic acid is seen with palmitate-induced ATPase activation or decrease of ATP synthesis. This indicates different interference of oleate and palmitate with mitochondria. In addition to its known coenzymatic properties dihydrolipoic acid may act as a substitute for coenzyme A, thereby diminishing the uncoupling efficiency of oleate. Furthermore, dihydrolipoic acid is a very potent antioxidant, shifting the -SH-S-S- equilibrium in mitochondria to the reduced state and improving the energetic state of cells.

Adenosine Triphosphatases↗
PubMed1991

One- and two-dimensional electron paramagnetic resonance imaging in skin.

EPR imaging with modulated field gradients provides the possibility for obtaining an EPR spectrum in a selected volume. We demonstrate the feasibility of X-band (9.5 GHz) electron paramagnetic resonance (EPR) imaging in skin biopsies of hairless mice. One- (1D) and two-dimensional (2D) EPR images of the persistent free radical di-tertiary-butyl-nitroxide are measured. At a microwave frequency of 9.5 GHz (X-band), 2D images are obtained in skin biopsies with an actual point distinction resolution of 25 microns. In a biological model system, 2D images are measured at L-band frequency (2.0 GHz) with a pixel resolution of 61 microns, and a theoretical spatial resolution of 12.5 microns. In combination with the spin labeling and spin trapping technique, EPR imaging is the most direct approach to analyzing spatial distribution of physicochemical properties in skin, such as membrane fluidity and polarity, as well as detection of free radicals.

Animals↗
PubMed1991

Hemodynamic and mitochondrial parameters during hypoxia and reoxygenation in working rat hearts.

Hypoxia and reoxygenation in working rat hearts were investigated in this study. Cardiac hemodynamic parameters which decline immediately under hypoxic conditions, recover during reoxygenation. Biochemical and ultrastructural alterations exhibit a more complicated pattern. There is a primary phase in hypoxic perfusion up to 15 min with a steep increase of ADP contents and ATPase activities, and a severe fall of ATP/ADP ratios in mitochondria, as well as in tissue. High CAT (carboxyatractyloside) sensitivity of the ATPase is observed at 5 min of hypoxia. Furthermore, the number of ATPase particles visible at the inner mitochondrial membrane decreases. During the ensuing second phase of hypoxic perfusion (from 30 min on) the damage of mitochondrial ultrastructure becomes more evident. The amount of ATPase particles visible at the inner mitochondrial membrane further decreases. ATPase activities fluctuate, however, they remain connected with the membrane during hypoxia. ATP/ADP ratios attain values of almost 1. During reoxygenation (after 30 min of hypoxia) the levels of mitochondrial adenine nucleotides, oxidative phosphorylation rate and respiratory control index increase within 20 min and then slightly decline again. The ATP/ADP ratio is diminished in the course of reoxygenation. ATPase activity also decreases within 20 min of reoxygenation and the ADP/O ratio reaches control values. The ATPase activity gains its highest sensitivity towards CAT at 10 min of reoxygenation attaining a value similar to that of 5 min of hypoxic perfusion. It is suggested that hypoxia and reoxygenation under our conditions result in reversible derangement of ATPase and mitochondrial membrane structure.

Adenine Nucleotides↗