ALBERT

Notizen: Résumé Des chats porteurs d'électrodes corticales Ag-AgCl non polarisables et de lentilles de contact translucides, ont été entraînés, dans obscurité, à presser un levier pour obtenir 0,8 ml de lait. Ils montrent des périodes d'activité lente de haut voltage, c'est-à-dire un phénomène ECoG connu comme synchronisation de post-reinforcement sur le cortex pariéto-occipital. Quand cette synchronisation associée à la variation positive de contingent est supprimée dans l'obscurité, ces phénomènes dépendent de l'influx de la lumière diffuse et non de la perception visuelle.

Notizen: Abstract During the course of its embryonic development, the European lobster Homarus gammarus Linnaeus exhibits progressive increases in content of water (54.0 to 83.1%), ash (2.7 to 16.7%), protein (47.4 to 50.9%) and non-protein nitrogen (1.0 to 2.4%), and steady decreases in content of fat (43.8 to 25.4%) and energy (6343 to 5431 cal/g dry organic substance). Cumulative yolk utilization efficiency during the total development is 81.8% for dry weight; the corresponding value for energy is 60.1, for protein 75.6 and for fat 47.4%. Energy content of a single egg is 10.49 cal. Of 4.20 cal expended for metabolic processes of the embryo, only 13.3% energy is drawn from protein oxidation; fat oxidation supplies as much as 87.7% energy, that of carbohydrate only 2.3%. Embryonic development results in a remarkable decrease in net yolk utilization efficiency, which falls from 85.5% in the early developmental stages, to less than 70% in later developmental stages. The mean dry weight of a single egg membrane increases from 38 μg (2.2% of egg weight) in a freshly laid and attached egg, to 81 μg in an egg with an almost completely developed embryo. This result supports the earlier observation of Cheung (1966) that the formation of the inner chitinous egg membrane occurs after the egg is laid and attached to the setum. Protein seems to be the major constituent of the egg membrane (4049 cal/g dry weight), which has the following composition: protein 70.4%, non-protein nitrogen 0.13%, ash 2.83%. Initial permeability of the egg membrane to water (about 6% of the total water requirement is let in) is followed by a period during which the egg membrane is almost impermeable to water (stages I to III); the egg membrane becomes permeable to water again and lets in 85% of the total water requirement (the rest, i.e. 9%, is metabolic water) at a relatively advanced stage of development. These assumed changes in egg membrane permeability appear to be indicative of variations in the egg's osmoconcentration leading to shiftings in net transport of water. Rates of water and salt uptake during embryonic development are essentially parallel (Fig. 1). The egg membrane remains permeable to salts throughout development; salt intake almost doubles after the egg passes through stage III. A single egg, weighing 3.7 mg requires 4.9 mg water for successful completion of embryonic development. The imbibition of water by the developing marine demersal egg seems to (1) serve in osmotic hatching; (2) float the hatched larva by means of specific gravity reduction; (3) aid the larva to quickly adjust its body temperature. The simple osmotic hatching mechanism, proposed by previous workers, seems to be inadequate to account for the events and timing of the hatching process in the lobster. It is suggested that hatching time is determined not solely by increased internal pressure caused by inflow of water and salts, but also by some unknown internal factor. In the lobster egg, as well as in many other marine demersal eggs, protein metabolism is suppressed to a considerable extent, and fat metabolism is “geared up” Thus, the non-cleidoic lobster eggs exhibit metablic properties which are typical of cleidoic eggs. This finding is discussed in the light of Needham's (1950) concept of “cleidoicterrestrial and non cleidoic-aquatic eggs”.

Notizen: Summary The mean serum sodium, chloride and potassium concentrations and serum osmotic pressure of freshwaterA. dieffenbachii are 140.4 mmol 1−1,114.0 mmol 1−1, 6.66 mmol 1−1 and 307.7 mOsmol respectively. Gill tissue from freshwater specimens has a water content of 4234 mg g dry wt−1 (80.9% wet wt), a chloride space of 1852 mg water g dry wt−1 (35.2% wet wt) and an intracellular volume of 2449 mg water g dry wt (46.0% wet wt). Estimates of the intracellular sodium and potassium concentrations for the gill tissue of freshwater eels gave values of 28.9 mmol kg intracellular water−1 and 126.5 mmol kg intracellular water−1 respectively. On transfer of the fish to sea water serum concentrations of sodium and chloride and serum osmotic pressure show rapid initial increases followed by a more gradual decline eventually stabilising at new levels some 100 hours after transfer (Fig. 1). The serum sodium, chloride and potassium concentrations and serum osmotic pressure of seawater-adaptedA. dieffenbaehii are 162.8 mmol 1−1, 151.0 mmol 1−1, 6.70 mmol 1−1 and 376.9 mOsmol respectively. On transfer to sea water the water content and chloride space of the gill tissue is reduced and the intracellular volume is initially decreased but is rapidly restored to its original value (Fig. 2, 3). At the same time intracellular sodium and potassium concentrations are increased but the latter is fairly rapidly restored to pre-transfer levels (Fig. 4). The changes in intracellular potassium concentration can be explained largely by the changes in intracellular volume but intracellular sodium concentrations remain high on transfer because of the increased serum sodium concentration. The initial increases in serum concentrations on transfer to sea water are caused partly by the removal of water and partly by the addition of sodium and chloride ions to the internal body fluids.

Notizen: Summary Throughout the period of adaptation to sea water the net flux of potassium in the isolated gills remains constant. Initially on transfer to sea water a small net influx of sodium and chloride ions is recorded in the isolated gills. Within a short period of time a net outflux of sodium and chloride is recorded which progressively increases, reaching a maximum after approximately 100 hours of adaptation (Fig. 1). Despite unfavourable osmotic and ionic gradients the functioning of the isolated gill is such that the concentration of the fluid passing through it is actually reduced after some 10–15 hours of seawater adaptation (Fig. 2).

Notizen: Summary A comparison of results obtained in studies of serum concentrations in the whole fish with those obtained from preparations of isolated, perfused gills indicates that the rate at which ions are entering the gills of freshwaterAnguilla dieffenbachii on being placed in sea water may only amount to some 10% or less of the calculated rate of addition of ions to the fish as a whole. An additional major route for the entry of ions into the fish on being placed in sea water, other than via the gills, is therefore indicated and, from a consideration of the functioning of the main effector organs of ionic regulation in teleosts, it is concluded that the intestine is the major site of the initial addition of ions to the fish on transfer to sea water. The subsequent reduction and eventual stabilisation of serum ionic concentrations following transfer can be largely explained on both a qualitative and temporal basis by the changes in functioning of the gills, as demonstrated by the isolated, perfused preparations.