Calcium mobilization and exocytosis after one mechanical stretch of lung epithelial cells

Deep inflation of the lung stimulates surfactant secretion by unknown mechanisms. The hypothesis that mechanical distension directly stimulates type II cells to secrete surfactant was tested by stretching type II cells cultured on silastic membranes. The intracellular Ca2+ concentration was measured in single cells, before and after stretching. A single stretch of alveolar type II cells caused a transient (less than 60 seconds) increase in cytosolic Ca2+ followed by a sustained (15 to 30 minutes) stimulation of surfactant secretion. Both Ca2+ mobilization and exocytosis exhibited dose-dependence to the magnitude of the stretch-stimulus. Thus, mechanical factors can trigger complex cellular events in nonneuron, nonmuscle cells and may be involved in regulating normal lung functions.     

Growth performance of hybrid striped bass (Morone chrysops × M. saxatilis) fed with commercial pike perch and trout diets

Two commercial trout diets (Oncorhynchus mykiss) and one commercial pike perch diet (Sander lucioperca) were fed to hybrid striped bass (Morone chrysops × M. saxatilis) (mean initial weight ± SD of 60.7 g ± 12.1; mean initial length SD of 17.2 cm ± 1.1) for 69 days at rations of approximately 1% average body weight. While final body weight (FBW), final length (FBL) and condition factor (Cf) were not significantly influenced by diets, specific growth rate (SGR) in hybrid striped bass fed with the pike perch diet (1.15) was significantly higher than those fed with either of the two trout diets (1.04 and 1.07). The feed conversion ratio (FCR) in hybrid striped bass fed with the pike perch diet (1.0) was significantly lower than the FCR in hybrid striped bass fed with either of the two trout diets (1.1 and 1.2). When hybrid striped bass (mean initial body weight: 65.7 ± 4.5 and 127.7 ± 2.9 g) were fed with the pike perch diet twice per day until satiation for 52 days, the SGR was 1.7 and 1.15% d^?1 in fishes with an average body weight of 116 and 183 g, respectively. Present results demonstrate that growth performance in hybrid striped bass can be improved when fishes are fed with commercial pike perch diets rather than using commercial trout diets as is the current practice.

     

Nahrungsaufnahme und Natalität bei palaearktischen Simuliiden (Diptera) 1. Blutfütterung vonBoophthora erythrocephala De Geer 1776 undWilhelmia lineata Meigen 1804 am Kaninchen

Zusammenfassung Während mehrer r Monate wurden Weibchen vonBoophthora erythrocephala undWilhelmia lineata am Kaninchenohr gefüttert und die Überlebensrate während der Eireifungsphase,

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Nutrition and Reproduction in Palaearctic Blackflies (Simuliidae: Diptera). I. Bloodfeeding ofBoophthora erythrocephala De Geer andWilhelmia lineata Meigen on RabbitsFemales of the mammalophilic species,Boophthora erythrocephala andWilhelmia lineata, feed on cattle and horses in the field. When fed on the rabbit's ear under laboratory conditions, they differ considerably in bloodsucking activity, in mortality during digestion of blood, natality, and hatching rates of first instar larvae. InB. erythrocephala 641 wild-caught- fed in 74,1% without seasonal variation. When females were kept up to four days before feeding their bloodsucking activity did not decrease. Laboratory-emerged- usually fed in even higher rates (416/533) and 4–6 days old flies fed more frequently than younger or older females. Survival rates during digestion of blood in 4 days were 60% in wild-caught, 40% in laboratory-emerged-, and 74% in cattle-fed-. Only 29% of wild-caught and the cattle-fed- but 50% of the laboratory-emerged flies could be induced to lay eggs on wet substrate. Natality of cattle- (219 eggs/) and laboratory-emerged fed on the rabbit (225 eggs/) were significantly higher than in wild-caught rabbit-fed- (191 eggs/). The number of eggs developing to first instar larvae generally was low (42%). InW. lineata wild-caught- fed less successfully (162/407) and showed considerable seasonal variation. The best results were obtained in September and October. Keeping them in the laboratory for 1–4 days reduced the bloodsucking activity. In laboratory-emerged- the best feeding result (347/724) were obtained with 4–6 day old flies but their survival during maturation of eggs remained low (55%). It was higher with wild-caught (67%) and cattle-fed- (78%). In all cases 60% of them could be induced to oviposit. The rabbit-fed wildcaught or laboratory-emerged flies produced significantly more eggs (183 resp. 197 eggs/) than cattle-fed ones (138 eggs/). Most egg batches contained only 16% fertilized eggs. In laboratory-emerged- ofB. erythrocephala andW. lineata the potential natality was highest in spring, lowest in summer and increased again in autumn. The number of eggs/ was affected by the blood volume. Starting with laboratory-emerged flies fed on the rabbit a production factor of 10.9 is calculated forB. erythrocephala and of 5.4 forW. lineata rearing from the imago to the first instar larva. When the larvae are reated to adults with 44% efficiency a reproduction of 2.4 resp. 1.2 per generation of females results.

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Mit 4 Abbildungen und 4 Tabellen     

Growth performance and RNA/DNA ratio of noble crayfish (Astacus astacus) and narrow‐clawed crayfish (Pontastacus leptodactylus) fed fish waste diets

New and viable species for aquaponics and integrated multi‐trophic aquaculture (IMTA) in freshwater systems can improve yields and sustainability of aquaculture. Freshwater crayfish species such as Astacus astacus and Pontastacus leptodactylus are omnivorous feeders and considered candidates for feeding on faecal matters in existing aquaculture systems. Feeding trials were conducted to determine growth response and RNA/DNA ratio in freshwater crayfish fed fish waste. Carapace length and wet weight were measured to determine the growth response. Juvenile A. astacus was fed faeces of hybrid striped bass (Morone chrysops × Morone saxatilis) and rainbow trout (Oncorhynchus mykiss), while adult P. leptodactylus was fed with two commercial pellet diets and pikeperch (Sander lucioperca) faeces. The nutritional composition of hybrid striped bass faeces was close to optimal diet composition of A. astacus, and crayfish showed significantly higher carapace growth, weight gain and weight gain per moult as the group fed rainbow trout faeces. The growth of P. leptodactylus was significantly lower in terms of weight gain and weight gain percentage per moult for crayfish fed on pikeperch faeces. Thus, this study can recommend a co‐cultivation of hybrid striped bass and A. astacus within one system, but cannot recommend co‐cultivation of P. leptodactylus with pikeperch. Additionally, this study showed controversial results of RNA/DNA ratio and weight gain of both crayfish species. Thus, RNA/DNA ratio cannot be approved for investigations on crayfish physiological status in controlled feeding experiments if animals are fed with an inadequate diet.     

Adaptive significance of C partitioning and regulation of specific leaf area in Betula pendula

Carbon allocation and regulation of specific leaf area (sigma) define key processes underlying the adaptation of plants to varying habitats. In this study, the general principles governing adaptation and a dynamic optimality model of plant adaptation are reviewed. The central new elements of this model are: (i) differential root carbon costs for maintaining a defined nutrient status; (ii) a simple formula for optimal sigma at steady-state as a function of nitrogen (N) status and irradiance; and (iii) generic rules for the time propagation of adapting traits. The model was applied to a large data set compiled by Ingestad et al. (1995) and McDonald et al. (1986a, 1986b) for birch seedlings (Betula pendula Roth) during stationary logarithmic growth and during transient changes in response to a range of irradiances and nutrient supply rates. In the stationary case, large variations in the fraction of leaf dry mass to total dry mass (f(L)), sigma and N concentration were simulated with high accuracy. The independently calibrated model described the temporal response of seedlings following a sharp decrease in N supply, which includes phenomena such as the temporary C accumulation in leaves and damped oscillations in N concentration. Dynamics in sigma were more sensitive to variation in light than in N supply. Nevertheless, adaptive adjustments in f(L), sigma and N concentration were strongly coupled, underlining the relevance of a whole-plant perspective when modeling plant growth and regulation. The high coincidence between model calculations and measured values supports the notion that plant acclimation can be both understood and predicted as a growth-optimizing mechanism.     

Expression of Plasmodium falciparum circumsporozoite proteins in Escherichia coli for potential use in a human malaria vaccine

The circumsporozoite (CS) protein of the human malaria parasite Plasmodium falciparum may be the most promising target for the development of a malaria vaccine. In this study, proteins composed of 16, 32, or 48 tandem copies of a tetrapeptide repeating sequence found in the CS protein were efficiently expressed in the bacterium Escherichia coli. When injected into mice, these recombinant products resulted in the production of high titers of antibodies that reacted with the authentic CS protein on live sporozoites and blocked sporozoite invasion of human hepatoma cells in vitro. These CS protein derivatives are therefore candidates for a human malaria vaccine.     

EMS-induced genic male sterility in Arabidopsis thaliana: A model selection experiment

Summary Seeds of Arabidopsis thaliana were treated with EMS to initiate a small-scale selection program for genic male sterility. Six lines of independent origin were obtained. Of these, four were discontinued in M₅, as they segregated incompletes, and two are maintained by full-sib mating, viz. line 97, which shows complete expression throughout the inflorescence, and line 112, which shows complete expression except in the later flowers. At the same time the additional aims were reached of unreduced female fertility and perfect phenotypic resemblance to the original line. The six mutations arose at five different loci. An attempt to extract a cytoplasmic male sterile failed.

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Efficacy of murine malaria sporozoite vaccines: implications for human vaccine development

As part of a study of potential vaccines against malaria, the protective efficacy of sporozoite subunit vaccines was determined by using the Plasmodium berghei murine malaria model. Mice were immunized with recombinant DNA-produced or synthetic peptide-carrier subunit vaccines derived from the repetitive epitopes of the Plasmodium berghei circumsporozoite gene, or with radiation-attenuated sporozoites. Immunization with subunit vaccines elicited humoral responses that were equivalent to or greater than those elicited by irradiated sporozoites, yet the protection against sporozoite challenge induced by either of the subunit vaccines was far less than that achieved by immunization with attenuated sporozoites. Passive and adoptive transfer studies demonstrated that subunit vaccines elicited predominantly antibody-mediated protection that was easily overcome whereas irradiated sporozoites induced potent cell-mediated immunity that protected against high challenge doses of sporozoites. These studies indicate that new strategies designed to induce cellular immunity will be required for efficacious sporozoite vaccines.