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R Albrecht

Publications and source records attributed to R Albrecht.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Characterization of 24-hour survival rate and duration of survival of hydroxyethyl starch cryopreserved erythrocytes after autologous transfusion in the dog].

BACKGROUND: Cryopreservation of erythrocytes using hydroxyethyl starch (HES) as cryoprotecting additive could result in a nearly unlimited storage stability of preserved red cells. In addition, it would allow its immediate use for transfusion. In order to assess the therapeutic efficacy of erythrocytes cryopreserved with HES, their 24-hour post-transfusion survival and long-term survival was evaluated. MATERIALS AND METHODS: The experiments were carried out with dog erythrocytes as an animal model for human erythrocytes. To each of 6 German shepherd dogs a 15-ml sample of erythrocyte suspension, labeled with 51Cr (25 microCi) after thawing, was autologously injected. Caused by hemolysis 29% of the formerly cryopreserved erythrocytes have not been labeled. To each of 6 control animals 15 ml of a suspension of freshly drawn and 51Cr-labeled erythrocytes was injected. The 51Cr radioactivity in later taken blood samples was a measure for the number of injected erythrocytes having remained in the circulation until the moment of blood withdrawal. The effect of cryopreservation was assessed by comparison of the test group with the control group. RESULTS: In both groups 30% of the applied cells left the circulation within 30 min. This was effected by pharmacological enlargement of the dogs' spleen and not by hemolysis of the erythrocytes. After the first 24 h all of the cryopreserved labeled erythrocytes had survived to the same amount (> 95%) as the labeled fresh red cells. Between 12 h and 20 days after injection, in both groups the 51Cr activity decreased exponentially by 4.8 and 4.5%/d. This difference was not significant. The area under the curve amounted to 1253 and 1257% d, respectively. CONCLUSIONS: There exists a subpopulation of red cells that is destroyed by freezing stress. As a result the freed stroma would be a serious transfusion risk. All erythrocytes having survived the cryopreservation procedure resemble the fresh erythrocytes with regard to the in-vivo survival; their therapeutic efficacy is not impaired. In the context of in-vitro results with human erythrocytes it can be expected that at the present developmental state of the cryopreservation procedure at least 93% of the human erythrocytes cryopreserved with HES have a normal 24-hour and long-term post-transfusion survival.

Animals↗
PubMed1993

Effects of protein deficiency on lipid peroxidation in the small intestine and liver of rats.

This study investigated the influence of protein restriction on lipid peroxide content (thiobarbituric acid-reactive substances) and the intracellular antioxidant defence system in the small intestine and the liver. Weanling male Sprague-Dawley rats were divided into two groups: a low-protein group fed ad lib. a diet containing 6% casein for 4 wk, and a control group fed a diet containing 22% casein but restricted to the same dietary intake as that of the low-protein group. Compared with pair-fed controls, the protein-deficient rats exhibited a decrease in glutathione content in the small intestine and the liver. Thiobarbituric acid-reactive substances were increased in the intestine only. Data on the enzymatic antioxidant defence system in the protein-deficient animals showed an increase in catalase activity in the intestine but a decrease of this activity in the liver. The activity of selenium-dependent glutathione peroxidase was decreased in the liver and remained unchanged in the intestine. Superoxide dismutase was not modified by protein deficiency in either tissue. In control rats, enzyme activities were 6-43 times higher in the liver than in the intestine. The deleterious effects of protein deficiency appeared more marked in the intestine.

Animals↗
PubMed1993

Dictyostelium mutants lacking the cytoskeletal protein coronin are defective in cytokinesis and cell motility.

Coronin is an actin-binding protein in Dictyostelium discoideum that is enriched at the leading edge of the cells and in projections of the cell surface called crowns. The polypeptide sequence of coronin is distinguished by its similarities to the beta-subunits of trimeric G proteins (E. L. de Hostos, B. Bradtke, F. Lottspeich, R. Guggenheim, and G. Gerisch, 1991. EMBO (Eur. Mol. Biol. Organ.) J. 10:4097-4104). To elucidate the in vivo function of coronin, null mutants have been generated by gene replacement. The mutant cells lacking coronin grow and migrate more slowly than wild-type cells. When these cor- cells grow in liquid medium they become multinucleate, indicating a role of coronin in cytokinesis. To explore this role, coronin has been localized in mitotic wild-type cells by immunofluorescence labeling. During separation of the daughter cells, coronin is strongly accumulated at their distal portions including the leading edges. This contrasts with the localization of myosin II in the cleavage furrow and suggests that coronin functions independently of the conventional myosin in facilitating cytokinesis.

Actins↗
PubMed1993

Oxidative stress may contribute to the intestinal dysfunction of weanling rats fed a low protein diet.

Intestinal function is impaired in malnutrition. Because oxidative stress is a component of gastrointestinal injury, and malnutrition may reduce antioxidant defenses, we investigated the involvement of oxidative stress in the intestinal dysfunction due to malnutrition. Weanling rats were fed either a normal protein (22% casein) or a low protein (6% casein) diet for 4 wk. In intestinal homogenates, we assessed free radical damage and enzymatic antioxidant defenses. In jejunal fragments mounted in Ussing chambers, we measured ionic transport by short-circuit current (Isc) and protein permeability by transepithelial fluxes of beta-lactoglobulin. Catalase activity and the thiobarbituric acid-reacting substances concentration were greater in intestinal mucosa of the low protein group, whereas the glutathione concentration and the activities of superoxide dismutase and Se-dependent glutathione peroxidase were the same as in the normal protein group intestinal mucosa. Both basal Isc and the delta Isc induced by glucose and forskolin, as well as beta-lactoglobulin fluxes, were higher in the low protein group. Exogenous H2O2 stress increased Isc significantly more in the low protein than the normal protein group but did not alter protein permeability. These results show that malnutrition induces both intestinal free radical damage and altered epithelial transport, suggesting that oxidative stress may contribute to the intestinal dysfunction associated with malnutrition.

Animals↗
PubMed1993

Actin-associated proteins in motility and chemotaxis of Dictyostelium cells.

The amoeboid cells of Dictyostelium discoideum are amenable to a combined biochemical, genetic, and cell biological approach that can be focussed to the study of molecular interactions underlying the chemotactic responses of eukaryotic cells. In these responses the actin-based motility system is involved. This system is characterised in Dictyostelium cells by a large number and variety of regulatory proteins. Most of these proteins belong to families that are likewise represented in the cytoskeletons of higher eukaryotes including man. Elimination of some of these actin-binding proteins by chemical mutagenesis or gene disruption is being used to simplify the system by separating essential proteins from non-essential ones. These studies are complemented by the selection and analysis of mutants with altered motility or chemotaxis. Quantitative motion analysis of mutants is employed to establish a link between defects on the molecular level and alterations in cell behaviour. Dictyostelium cells respond to local stimulation by extending a newly formed leading edge towards a chemoattractant within less than a minute, thereby changing their polarity. The leading edge is formed by the recruitment of soluble proteins from the cytoplasm and their coassembly with actin into a complicated framework of microfilaments. Patterns of assembly are shown in this report for two proteins, the talin-like filopodin and coronin. Elucidation of the control mechanisms of this ordered assembly will provide the key for understanding the molecular processes responsible for a chemotactic response.

Actins↗
PubMed1993

[Principles of muscle efficiency in weightlessness].

Depending on the time spent in a space station, weightlessness causes varying changes to various organs and regulatory mechanisms of the human organism, among them the structures of the active and passive locomotor system. Experience has shown that regular physical activity using varying forms of training is necessary to keep astronauts and cosmonauts healthy, efficient and fit for work and to prepare them for a safe return to terrestrial conditions. One of the main tasks of physical activity is therefore to counteract the changes in the neuromuscular function, muscle strength, endurance and fatigability under conditions of weightlessness. So far, the diagnostics of these changes was limited to dynamometric measurements before and after space flights as no dynamometric method had been devised which was precise enough under conditions of weightlessness. The development and the introduction of the dynamoergometer Motomir is described against the background of previous results obtained by dynamometric, ergometric, morphometric, biochemical, histochemical and neuromuscular examinations before and after missions of varying duration under conditions of weightlessness. This device was used for the first valid and reproducible examinations of muscle strength and endurance aboard the space station Mir during the Austro-Russian space mission Austromir. The results of the examinations with this speed-controlled dynamometer and training device obtained during a short-term flight of 10 days and a long-term flight of 6 months are described and compared to previous results in the literature. Based on the existing training devices, training methods and training plans and the results of the Motomir Study, plans for devices and methodologies for future long-term space flights of up to 3 years' duration will be discussed. Finally, the possible use of a speed-controlled dynamometer and training device for rehabilitation on earth after injuries, surgery and immobilization of the active and passive locomotor system as well as in the bed-rest syndrome is being presented.

Animals↗
PubMed1992

Effect of phenoclor DP6 on enzyme-altered foci and lipid peroxidation in livers of aflatoxin B1-initiated rats.

This study investigates the capacity of phenoclor DP6 to promote aflatoxin B1 (AFB1)-induced putative preneoplastic foci in the liver. In male Sprague-Dawley rats pretreated with AFB1 (ip injection of 1 or 2 mg/kg body weight once weekly for 3 consecutive wk) and given a diet containing 50 ppm phenoclor DP6 for 11 days, the number of area of putative liver preneoplastic lesions were increased approximately four-fold as indicated by the number and gamma-glutamyl transpeptidase activity of enzyme-altered foci; this change was also accompanied by an increase in hepatic microsomal lipid peroxidation and a decrease in Se-glutathione peroxidase and superoxide dismutase activities. The results indicate that phenoclor DP6 exerts a promoting effect in AFB1-initiated rats.

Aflatoxin B1↗
PubMed1992

Effect of prototypic polychlorinated biphenyls on hepatic and renal vitamin contents and on drug-metabolizing enzymes in rats fed diets containing low or high levels of retinyl palmitate.

Two groups of weanling male Sprague-Dawley rats fed a diet supplemented with either 0.6 or 6 retinol equivalents/g diet were each separated into three further groups receiving 300 mumol 2,2',4,4',5,5'-hexachlorobiphenyl/kg body weight, 300 mumol 3,3',4,4'-tetrachlorobiphenyl kg/body weight or vehicle only (corn oil). Only the coplanar (3,4)2Cl congener caused a slight reduction in food intake, thymic atrophy and led to a significant decrease in the liver vitamin A storage. The vitamin A lost by the liver was approximately the same in both dietary groups; however an increased renal accumulation of vitamin A was observed in the high vitamin A group. Serum retinol was reduced by (3,4)2Cl treatment but remained unchanged by (2,4,5)2Cl exposure. Total amounts of ascorbic acid and its oxidation products were increased in the liver and in the kidney by both xenobiotics while niacin and thiamine concentrations were lowered by (3,4)2Cl only. Microsomes from vitamin A-deficient rats exhibited a marked decrease in the anisotropy parameter. After (2,4,5)2Cl exposure, an increase in membrane fluidity was observed linked to a decrease in cholesterol/phospholipid (C/P) ratio. Treatment with (3,4)2Cl caused a significant decrease in the index of fluorescence polarization only in the low vitamin A group even if the C/P ratio was enhanced in both dietary groups. This study shows that the polychlorinated biphenyl with the 3-methylcholanthrene-type pattern of induction of cytochrome P-450 has more profound effects on B group vitamins and particularly vitamin A homeostasis than does the phenobarbital-type inducer. Moreover, this situation, which has been found to be similar to that in vitamin A deficiency, is not ameliorated by a high dietary vitamin A intake.

Animals↗
PubMed1992

Dietary restriction decreases thiobarbituric acid-reactive substances generation in the small intestine and in the liver of young rats.

This study investigated the influence of dietary restriction on thiobarbituric acid-reactive substances (TBARS) contents and on the intracellular antioxidant defence system in the small intestine or liver of young rats. Four weeks of diet restriction (-40%) lowered the TBARS level in both organs. No variations were found for the superoxide dismutase and catalase activities; only liver seleno-dependent glutathione peroxidase was enhanced by the restriction. The protection appeared more marked in the intestine than in the liver, and would be dependent on glutathione concentration.

Animals↗
PubMed1992

Activation-dependent changes in human platelet PECAM-1: phosphorylation, cytoskeletal association, and surface membrane redistribution.

PECAM-1 is a recently described member of the immunoglobulin gene (Ig) superfamily that is expressed on the surface on platelets, several leukocyte subsets, and at the endothelial cell intracellular junction. Recent studies have shown that the extracellular domain of PECAM-1, which is comprised of 6 Ig-like homology units, participates in mediating cell-cell adhesion, plays a role in initiating endothelial cell contact, and may later serve to stabilize the endothelial cell monolayer. PECAM-1 also has a relatively large 108 amino acid cytoplasmic domain, with potential sites for phosphorylation, lipid modification, and other posttranslational events that could potentially modulate its adhesive function or regulate its subcellular distribution. Virtually nothing is known about the contribution of the intracellular region of the PECAM-1 molecule to either of these cellular processes. Using human platelets as a model, we now demonstrate that PECAM-1 becomes highly phosphorylated in response to cellular activation, and coincident with phosphorylation associates with the cytoskeleton of activated, but not resting, platelets. The engagement of PECAM-1 with the platelet cytoskeleton enables it to move large distances within the plane of the membrane of fully-spread, adherent platelets. This redistribution may similarly account for the ability of PECAM-1 to localize to the intracellular borders of endothelial cells once cell-cell contact has been achieved.

Antigens, Differentiation, Myelomonocytic↗
PubMed1991

Peptidergic innervation of the Bursa Fabricii: interrelation with T-lymphocyte subsets.

In birds, B-lymphocytes mature in a special immune organ, the Bursa Fabricii. This organ thus offers unique possibilities for the study of the microenvironment of B-lymphocyte differentiation. We previously reported tachykinin-, vasoactive intestinal peptide-, calcitonin gene-related peptide- and galanin-immunoreactive (ir) fibres in the chicken bursa. As judged from light microscopic studies, each of the peptides was found in fibres contacting B-lymphocytes. Vasoactive intestinal peptide-ir fibres contacted macrophages. Now, we demonstrate neuropeptide Y, indicating the sympathetic nervous system, in fibres associated with arteries, not entering the follicles. CD4- and CD8-positive T-lymphocytes were dispersed in bursal follicles and the connective tissue, most densely in subepithelial regions. We could not find close apposition of fibres with either T-cell subset. We conclude that the potential neuro-immune axis in the Bursa Fabricii may represent a neuro-B-cell-link with only indirect participation of T-lymphocytes. The sympathetic input may influence the bursal microenvironment primarily by regulating the blood supply.

Animals↗
PubMed1990

A time course investigation of vitamin A level and lipid composition of the liver endoplasmic reticulum in rats following treatment with congeneric polychlorobiphenyls.

The drug metabolizing enzyme activities, the vitamin A content and the fatty acid composition in the endoplasmic reticulum membrane were studied in rat liver after a single injection of the polychlorobiphenyls (PCBs) 3,3',4,4'-tetrachlorobiphenyl [(3,4)2Cl] or 2,2',4,4',5,5'-hexachloro-biphenyl [(2,4,5)2Cl], 300 mumol/kg each. The microsomal vitamin A level was markedly lowered 3 days after treatment with (3,4)2Cl, a coplanar type inducer of cytochrome P-450. A marked increase in microsomal AHH and UDPGT activities occurred within 3 days after injection of (3,4)2Cl whereas (2,4,5,)2Cl treatment enhanced APDM activity only. Arachidonic, stearic and linoleic acid microsomal contents were enhanced by the two congeners. (3,4)2Cl caused the proportion of docosahexaenoic acid to decrease. No highly significant correlation was found between the vitamin A content and lipid components in the microsomal membrane. However, the vitamin A level was inversely related to the activities of drug metabolizing enzymes induced by coplanar compounds (cytochrome P-450 towards benzo[a]pyrene and UDP glucuronosyl transferase towards 4-nitrophenol).

Animals↗
PubMed1990

Lipid peroxidation of rat liver microsomes membranes related to a protein deficiency and/or a PCB treatment.

In this study, we investigated the influence of protein deficiency on lipid peroxidation (LP) and cellular defense systems against oxidative damage in control or polychlorinated biphenyl (PCB) treated rats. Rats were fed either a standard diet (22% casein) or a low protein diet (3.5% casein) for 1, 2 and 6 weeks. Five days prior to killing, one half of the animals were given a single i.p. injection of Phenoclor DP6 (50 mg/kg body weight). In protein deficient rats, liver vitamin E was depressed and ascorbate level was lowered. Total and selenium-dependent glutathione peroxidases (GSH-Px) activities were decreased whereas glutathione reductase (GSH-red) was enhanced. Enzymatic and non enzymatic LP ('spontaneous' or with ADP-Fe2+) were increased. Phenoclor DP6 treatment enhanced liver ascorbate concentration. Microsomal LP was increased. Total and selenium-GSHPx remained unmodified while GSH-red was increased. Liver glutathione and alpha-tocopherol contents appeared to be independent of the PCB injection. Our data suggest that low protein intake and PCB exposure may reduce liver defensive protection against electrophilic species.

Animals↗
PubMed1990

[Mucosa protection--an assessable value? An experimental study in rats].

Reduced mucosaprotection is a main factor for development of peptic ulcer disease. The quantity is difficult to estimate. We did it by measuring the acid output as the aggressive factor and we sized the resulting mucosalesions. In the gastric corpus we could not find any change in mucosaprotectionindex after cimetidine, pirenzepine and vagotomy. But in the duodenum protection was increased after pirenzepine and vagotomy.

Animals↗