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Biomedical subjects

U Sprandel

Publications and source records attributed to U Sprandel.

At least 19 recordsLinked to original sources
PubMed1990

Temperature-induced shape transformation of carrier erythrocytes.

Erythrocytes have been proposed as cellular carriers for enzymes and drugs for protected delivery, slow release, or targeting to specific organs. Several studies have established the heterogeneity of resealed carrier erythrocytes concerning various characteristics, including morphology. Carrier erythrocytes were prepared by hypo-osmotic dialysis and consecutive iso-osmotic resealing at different temperatures, and the morphology of these cells was studied by scanning electron microscopy. Different cell shapes could be prepared by temperature variations during resealing or incubation. All intermediate shapes of echinocytosis were observed at low temperatures or with depleted energy supply but could be reversed to biconcave discocytes. Resealing at 4 degrees C resulted in highest percentage of echinocytes III, spherocytes, and leaky cells. Spontaneous resealing of 20% of the cells was obtained at high lysis temperatures. Combining low temperatures for lysis and high temperatures for resealing and sufficient energy supply are advantageous for highest recovery of biconcave discocytes. Shape of the erythrocyte, is the result of divergent forces, and temperature during resealing was found to be an important factor.

Drug Carriers↗
PubMed1985

Osmotic fragility of drug carrier erythrocytes.

Erythrocytes have been proposed as biogradable cellular carriers for drugs. Potentials of this therapeutic approach are organ-specific targeting, protection and prolonged in vivo function of the encapsulated drugs. Previous studies demonstrated the advantage of a hypo-osmotic dialysis procedure for macromolecule loading resulting in cells that are closely similar to normal erythrocytes. Osmotic fragility of unloaded and loaded "carrier" erythrocytes was studied both in respect of shelf-life and in vivo survival. Sudden haemolysis which is characteristic for normal erythrocytes was never obtained with carrier erythrocytes. Haemolysis appeared at all osmotic pressures and increased stepwise indicating the existence of various cell populations. However, the majority of cells were haemolysed at lower values of the osmotic fragility curve. Osmotic fragility was highly increased when cytotoxic chemotherapeutics were encapsulated, and these cells appeared as spherocytes using scanning electron microscopy. Osmotic fragility proved to be a simple but reliable method for the in vitro evaluation of carrier erythrocytes and the effect of the encapsulated substances.

Erythrocyte Aging↗
PubMed1979

In vitro studies on resealed erythrocyte ghosts as protein carriers.

Resealed erythrocyte ghosts have been proposed as in vivo carriers for enzyme replacement therapy of inherited metabolic diseases. In comparative studies of methods for reversible hypotonic haemolysis of erythrocytes, a five-fold increased entrapment of human serum albumin was obtained by use of a dialysis procedure instead of direct dilution. The percentage incorporation of protein was also affected by varying mixing procedure, haematocrit, lysis, and resealing times but not by varying buffer composition or added protein concentrations over a wide range. Higher protein entrapment was observed with time-expired blood compared to fresh blood and this may be ascribed to increased osmotic fragility of the erythrocyte membrane in stored cells. Haemolysed and resealed ghosts prepared by any method used were smaller than normal erythrocytes as measured with a Coulter Counter and with a fluorescence-activated cell sorter, and protein entrapment reduced the ghost size further.

Blood Preservation↗
PubMed1977

[Cystic degeneration of the vessel walls. The differential diagnosis of obliterative angiopathies: (author's transl)].

Cystic degeneration of the vessel wall is a rare disease predominantly localized in the region of the popliteal artery. It appears in the frequent clinical picture of intermittent claudication. Two cases are presented. The etiology of this syndrome is not clear. The appearance of intermittent claudication, preferably in middle-aged men without risk factors is typical for an obliterative angiopathy. Angiophically there are smooth-walled stenoses or occlusions, especially of the popliteal artery, with an otherwise inconspicuous vascular system. The prognosis after surgical treatment by excision or resection is good.

Adult↗
PubMed1976

Metabolism of maltose in perfused rat liver and in isolated hepatocytes.

The conversion of 14C-maltose into glucose, lactate and 14 CO2 was studied in perfused livers from fed and fasted rats and in isolated hepatocytes. Maximal glucose production was 30 mM x g-1 x h-1; half-maximal rates were found with 3 mM maltose. About 0.01 % of the radioactivity infused was recovered as 14CO2. The addition of maltose had no effect on rates of oxygen consumption, lactate production or ketogenesis. The data suggest that maltose did not serve as a major substrate for biosynthetic or energy producing processes under the conditions of the perfused rat liver.

Animals↗
PubMed1975

[Streptozotocin diabetes in a miniature pig (author's transl)].

The intravenous application of 60 mg streptozotocin/kg body weight to a Hanford miniature pig 8 days after a first dose of 30 mg/kg led to a diabetes with loss of insulin response to glucose, hyperglycaemia, glucosuria and a considerable increase of triglycerides and cholesterol. The application of 40 mg streptozotocin/kg to a second pig had no effect.

Animals↗