Decrease of calcium turnover during the onset of mineralocorticoid hypertension in the rat.

Administration of choline chloride i.p. to rats causes a dose-dependent increase in the brain concentration of the neurotransmitter, acetylcholine (ACh). This increase is maximal (22% after a 60-mg/kg dose) 40 minutes after injection. These observations suggest that precursor availability may influence brain ACh synthesis, just as brain tryptophan and tyrosine levels have previously been shown to control the synthesis of brain serotonin and catecholamines.     

Glucocorticoids in intracellular catabolism of myosin and actin

The catabolic effect of glucocorticoids on the structural proteins of contractile apparatus seems to be realized through the increased alkaline proteinase activity and accelerated synthesis of light enzyme subunits. The administration of large amounts of glucocorticoids increased the excretion of 3-methylhistidine in rats by 60%. Digestion of isolated myofibrils with alkaline proteinase resulted in the degradation of myosin heavy chain and actin. The turnover rate of actin and myosin heavy chain was decreased.     

Detection of RNAase inhibitor from different species and organs

Human placental alkaline RNAase inhibitor was purified to homogeneity. Activity was measured after each purification step. The final identification of the purified protein was done by two-dimensional polyacrylamide gel electrophoresis and by immunoblotting. Antibodies were prepared by immunization of rabbits with the highly purified inhibitor. The availability of the antiserum directed against the human inhibitor enabled the detection of RNAase inhibitor from various other organs and species. This procedure has the advantage over the usual activity test in that the inhibitor can be found even if its activity has been lost.     

Size-scaling of zooplankton foraging in Arctic charr

Prey capture rate (number of prey s⁻¹) and the mode of feeding of Arctic charr Salvelinus alpinus were studied by performing foraging experiments with two sizes (1·1 and 1·8 mm) of Daphnia longispina prey. Arctic charr were particulate feeders at all densities tested. Adjusted for the effect of prey density, the capture rate showed a hump-shaped relationship with Arctic charr size for both sizes of D. longispina . Estimated attack rates ( a ) also tended to show a hump-shaped relationship with fish size. The estimated size-scaling exponent of the attack rate function, however, was relatively small, implying small changes in attack rate over fish sizes. Simultaneous estimations of a and handling time were used in combination with published data on fish metabolism and dry mass rations of prey to estimate maintenance resource density of prey as a function of Arctic charr mass. Maintenance resource densities increased monotonically with Arctic charr size, and rapidly as optimum fish size relative to attack rate on prey was passed.     

Ultrastructure of Weddellomyces epicallopisma (Dothideales, Dacampiaceae, Ascomycota), especially of its ascospores]

An ultrastructural study of Weddellomyces epicallopisma (ascomata wall, asci, ascospores and vegetative hyphae), the first done on the family Dacampiaceae, confirms most of the observations made in light microscopy. Moreover it shows that ascospores are provided with an endospore (not visible in light microscope) and that the structure of the ascospore septum is more complex. The similarity of the wall structure between the ascospore and the hyphoid appendages, developed on the upper part of the ascoma, is emphasized.     

The susceptibility of Salvelinus fontinalis (Mitchill) to Gyrodactylus salaris Malmberg (Platyhelminthes; Monogenea) under experimental conditions

The host specificity of Gyrodaclylus Solaris is examined experimentally with respect to its ability to infect the brook trout, Salvelinus fontinalis . The parasite readily attached to and reproduced on parr of this host and infections grew for c. 20 days from first monitoring (c. 30 days from first infection) before declining. Parasites could persist on this host for up to 70 days before finally disappearing. The pattern of infection resembled that seen in many other gyrodactylid species on their normal hosts, and suggested the action of a host response, In this respect infections of G. salaris on parr of S. fontinalis , anadromous Salvelinus alpinus, Oncorhynchus mykiss, Thymallus thymallus and Baltic Salmo salar follow a normal pattern, while infections of Norwegian S. salar are unusual in a continued unchecked growth, until the host dies, under pooled laboratory conditions.