Exposure of Dunnocks (Prunella modularis) to their Previous Wintering Site Modifies Autumnal Activity Pattern: Evidence for Site Recognition?

We caught dunnocks at a wintering site near Pisa/Italy prior to their departure for breeding territories and held them indoors north of this site (Andechs/Germany) on a simulated photoperiod of 52.5 °N. After birds had gone through a reproductive cycle and postnuptial moult they developed migratory restlessness in autumn. At this time one group was transferred back to the previous wintering site (Pisa) where birds were held in individual activity cages in an outdoor aviary, allowing them to perceive as much environmental information as possible. A second group was transferred to a control site near Tour du Valat/France of approximately the same latitude and climate, but different longitude and held in an identical aviary. The diurnal activity pattern changed after transfer back to the previous wintering site, but not after transfer to the control site. Specifically, the amount of morning activity was reduced while afternoon activity was increased. This effect was restricted to those individuals that had been developing nocturnal migratory restlessness the previous spring. It was absent in individuals without migratory restlessness in spring, indicating that the different patterns were not due to unspecific effects from the testing sites. These results are consistent with the hypothesis that birds were able to derive information about their locality and to recognize their previous wintering site, resulting in suppression of migratory state by experience. The results are not definitely conclusive, however, because of several difficulties in the interpretation of perch-hopping activity, which are discussed in detail.     

Influence of lactate on isoproterenol-induced lipolysis and beta-adrenoceptors distribution in human fat cells

The influence of lactate on human adipocytes lipolysis and the possible relationship between lactate-induced metabolic effects and beta-adrenoceptor binding sites were investigated. beta-sites were identified in membranes with (125I)-cyanopindolol and in intact cells with (125I)-cyanopindolol and (3H)-CGP 12177. Lactate reduced isoproterenol-induced lipolysis in a dose-response fashion and such inhibition became significant only at 16 mmol/l lactate. Exposure of human fat cells to 16 mmol/l lactate significantly reduced beta-adrenoceptors density on crude membranes. When the binding assay was performed on intact cells using (125I)-cyanopindolol at 37 degrees C, the radioligand identified the same number of receptors, regardless of the presence of lactate in the preincubation medium. When (3H)-CGP 12177 was used, it bound to about 35% less receptors in lactate pre-treated cells than in control. Seemingly, at 37 degrees C, because of its lipophilicity, (125I)-cyanopindolol can cross the plasma membrane and bind to intracellular sites whereas, (3H)-CGP 1277, due to its hydrophilicity, identifies surface receptors only. Thus, the present in vitro study provides evidence that high levels of lactate, similar to the concentrations usually achieved in overt lactic acidosis, are able per se to inhibit human lipolysis and to redistribute beta-adrenoceptors from cell surface to a domain not accessible to hydrophilic ligands.     

Applications of artificial ionization

Summary The effects of positive and negative ions on man and on animals have been widely studied by numerous teams of researchers. It is well-known that negative ions have beeeficial effects on chronic and allergy-related bronchopathies in man; they stimulate the activity of the endocrine glands and psychomotor, muscular and cerebral functions. They have a beneficial effect on general circulation, and in particular on the microcirculatory system, such that they are suggested for use in prophylaxis and prevention of senescence, in acute, chronic and allergy-related pneumopathies, and in neuro-vegetative dystonia. The use of artificial negative ion producers may be a useful tool for both preventive and therapeutic purposes, as well as hygienic/domestic applications. Systematic measurements ere taken of negative ions artificially produced in a confined space. The spatial distribution of artificially-produced negative ions in a confined space is presented. Applications relative to artificial generators are also suggested in order to obtain repeatable experimental conditions.     

A unified neural network model of spatiotemporal processing in X and Y retinal ganglion cells

This article makes use of a push-pull shunting network, which was introduced in the companion article, to model certain properties of X and Y retinal ganglion cells. Input to the push-pull network is preprocessed by a nonlinear mechanism for temporal adaptation, which is ascribed here to photoreceptor dynamics. The complete circuit is used to show that a simple change in receptive field morphology within a single model equation can change the network's response characteristics to closely resemble those of either X or Y cells. Specifically, an increase in width of the receptive field center mechanism is sufficient to account for generation of on-off (Y-like) instead of null (X-like) responses to modulated gratings. In agreement with experimental data, the Y cell on-off response is independent of spatial phase. Also, the model accurately predicts that on-off responses can be observed in X cells for particular stimulus configurations. Taken together, the results show how the retina combines individually inadequate modules to efficiently handle the tasks required for accurate spatial and temporal visual information processing. The model is also able to clarify a number of controversial experimental findings on the nature of spatiotemporal visual processing in the retina.     

Phenylarsine oxide induces the cyclosporin A-sensitive membrane permeability transition in rat liver mitochondria

This paper reports an investigation on the effects of the hydrophobic, bifunctional SH group reagent phenylarsine oxide (PhAsO) on mitochondrial membrane permeability. We show that PhAsO is a potent inducer of the mitochondrial permeability transition in a process which is sensitive to both the oxygen radical scavanger BHT and to cyclosporin A. The PhAsO-induced permeability transition is stimulated by Ca²⁺ but takes place also in the presence of EGTA in a process that maintains its sensitivity to BHT and cyclosporin A. Our findings suggest that, at variance from other known inducers of the permeability transition, PhAsO reacts directly with functional SH groups that are inaccessible to hydrophilic reagents in the absence of Ca²⁺.     

Rheology of hydroxyethyl guar gum derivatives

The rheological properties of aqueous solutions of hydroxyethyl guar gum, a synthetic derivative of guar gum, have been studied under continuous and oscillatory shear flow conditions. Data obtained from both experimental techniques were satisfactorily fitted according to Cross-type models. The effect of polymer concentration, molecular weight and temperature on the rheological behavior of hydroxyethyl guar gum systems have been investigated and discussed in terms of rheological parameters like the zero-shear viscosity η₀ and the characteristic times λ and λ′.     

Hidden smectic properties of a chiral side-chain co-oligomer

We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature.     

Genetic determinants of glutamine synthetase inDrosophila melanogaster: A gene for glutamine synthetase I resides in the 21B3-6 region

Recombinational and deletion mapping of electrophoretic variants of the glutamine synthetase I isozyme (GSI) in Drosophila melanogaster locates the gene in the 21B region on the second chromosome. We have conducted a genetic analysis of the region extending cytologically from 21A to 21B4-6. Recessive lethal mutations were generated by ethyl methanesulfonate (EMS) and ethyl nitrosourea (ENU) mutagenesis and by hybrid dysgenesis (HD). These lethals fall into seven functional groups, which were partially ordered by complementation with cytologically defined deficiencies of this region generated by hybrid dysgenesis. Two of the EMS- and two of the ENU-induced lethals fulfill biochemical criteria expected for null alleles of the GSI gene.     

Estimation of the size of freshwater ciliate populations by a sub-sampling technique

A technique is described for the estimation of the size of ciliate populations based on replicated counts. Sample drops were taken by automatic pipettes of different volume from activated sludge and from a small oligotrophic stream. Specific aims were: 1) the estimation of the number of species; 2) the estimation of the number of individual in each species; 3) the selection of a suitable sub-sample size and number of replicates. For each volume the cumulative increase in species taken in successive sub-samples was determined. For each species the minimum permissible sub-sample volume and the number of replicates required for an allowable error of 10% and 25% were determined. Lastly, the relationship between the mean number of individuals counted for each species and the relative coefficient of variation was visualized.