[Storage-induced rheologic and biochemical changes in erythrocyte concentrates with added solution and possible correlations]. / Lagerungsbedingte rheologische und biochemische Veränderungen von Erythrozytenkonzentraten in additiver Lösung und deren mögliche Zusammenhänge.

Rheological integrity is one of the essentials for red blood cells (rbc) in capillary circulation. The influences of metabolical/biochemical changes of rbc on their rheological properties are well known, but (to our knowledge) until now there are no published studies, which cover both quality aspects of packed rbc (prbc) in additive solutions. According to our standard operating procedures (SOP) we prepared prbc in additive solution (SAG-M) and plasma from 16 regular blood donations. The buffy coat was discharged. Following parameters were measured on day 1, 14 and 28: extracellular pH, ATP and 2,3-DPG content of rbc, prbc-viskosity, -filterability, -aggregability and filter clogging rate. For examination of the filterability a 5% rbc-suspension in phoshate buffered solution was prepared, the remaining tests were performed with rbc-samples adjusted to a hematokrit of 40% with fresh frozen autologous plasma. In correlation with the depletion of ATP a decrease of rbc flexibility and changes of shape (for example spherocytosis) are well known from the literature. Our results confirm the assumed time dependent deterioration of rheological patterns of prbc in SAG-M, reflecting in an increase of rbc-viscosity and filter clogging rate and a decrease of rbc-filterability and -aggregability. We also observed the expected decrease of pH, ATP and 2,3-DPG during storage. The influences of biochemical changes on rheological alterations are discussed. Therefore we recommend on demand rheological examinations in addition to metabolical/biochemical analyses for an extended quality assurance program, for instance for testing new additive solutions or major changes of SOP.

Adaptations of the reed frog Hyperolius viridiflavus (Amphibia, Anura, Hyperoliidae) to its arid environment : IV. Ecological significance of water economy with comments on thermoregulation and energy allocation.

After breeding African savanna dwelling reed-frogs of the "superspecies" Hyperolius viridiflavus face a severe dry season. The frogs withstand the adverse abiotic conditions in exposed positions, clinging to dry vegetation. Only juveniles (300-700 mg) are able to adjust water economy and metabolism to a prolonged dry season. Wet season frogs attain low levels of evaporative water loss (EWL) within 6-8 days after incipient water shortage. This time course is mainly determined by the animal's ability to lower metabolism and activity level to the minimum demands of a dry season. Barriers against diffusion of water which most probably are built up by the stratum corneum and/or the overlying film of dried mucus seem not to be essentially modified during adjustment to dry season conditions. Changeover to dry season physiology is greatly accelerated through preconditioning frogs to water shortage. AdultHyperoliusare unable to reduce activity and metabolism as fast and effectively as juveniles. Most probably these are the main reasons for their very restricted survival capability under dry season conditions; the generally poor energy reserves after the breeding period may further shorten their survival time. At the critical thermal maximum (CTM) Hyperolius uses skin gland secretions for evaporative cooling. Acclimation effects and regulation of evaporative cooling within some 1/10° C help to employ limited water reserves very economically. Dry adapted, dehydrated frogs take up water, whenever available, via specialized skin areas. Rate of uptake is high and is mainly determined by the actual stage of dehydration. The onset of the water-balance-response is also affected by preconditioning. Survival time of small (<500 mg) estivating Hyperolius is limited by their water reserves.Due to their unfavourable surface to volume ratio they loserelatively more water by evaporation than larger conspecifics. Therefore, smaller specimens should allocate energy preferably to growth, until reducing EWL so far to survive the average periods between the rare precipitations. In larger frogs (>500 mg) the amount of stored energy determines maximal survival time. When a critical size is reached in postmetamorphic growth, a change in energy allocation from body growth to energy storage would improve prospects of survival and should therefore be expected. Species specific differences in regard to EWL and CTM indicate a strong correlation between physiological properties and ecological demands.

Adaptations of the reed frog Hyperolius viridiflavus (Amphibia, Anura, Hyperoliidae) to its arid environment : II. Some aspects of the water economy of Hyperolius viridiflavus nitidulus under wet and dry season conditions.

Adaptations to aridity of the reedfrog Hyperolius viridiflavus nitidulus, living in different parts of the season-ally very dry and hot West African savanna, are investigated. 1. During the dry season mainly juveniles (weighing 200-600 mg) were found in the field. A very low rate of evaporative water loss (EWL; about 1.2% of the body weight/day under laboratory dry season conditions) enables the frogs to estivate unshaded on dry plants. There they are exposed to temperatures occasionally reaching 45° C and are to sustain high radiation loads. The EWL of wet season frogs (WSF) was on average 30 times higher. 2. In dry season frogs (DSF) a thin layer of desiccated mucus seals the body surface reducing water loss and securing tight attachment to the substrate. The DSF are not in a state of torpor but are able to become active at any moment. The highest tolerable water loss of DSF amounts to 50% of their initial body weight. Since uptake of water or food often is impossible for more than two months, the small DSF have to survive these harsh conditions with very limited reserves of energy and water. 3. The low EWL of DSF does not engender any cooling effects. Only above a certain high temperature limit, defined as the critical thermal maximum (CTM; 43-44°C) we found a steep increase of EWL-probably indicating evaporative cooling. The CTM is affected by the temperature during acclimatization. 4. In contrast to WSF cutaneous respiration is not found in DSF. All CO2 is delivered via the lungs by discontinuous ventilation. The simultaneous water loss via the respiratory tract makes up to 14.9+/-8.9% of the entire water loss. 5. A very fast water uptake (69.3+/-19.4%/h) via thin and vascular skin areas at the ventral flanks and the inner sides of the legs enables the frogs to use small quantities of water available for very short times only. This highly permeable skin is protected against desiccation by the typical squat resting position of the frogs. 6. DSF usually to neither urinate nor defecate; they are not proved to be uricotelic. Probably they store the nitrogenuous wastes as urea in the body fluids and as purines in the iridophores and connective tissues. It is suggested that there is no selective advantage for uricotelism in the small H. v. nitidulus.