Immuno-enzyme cytochemical demonstration of mesotocinergic nerve fibres in the pars intermedia of the amphibian hypophysis

Summary Immuno-enzyme cytochemical investigations showed that the whole amphibian pars intermedia of the hypophysis is innervated by an intercellular network of peptidergic varicose nerve fibres which contain mesotocin or (and) parts of the mesotocin molecule. The pars intermedia does not contain vasotocinergic fibres. The mesotocinergic fibres are branches of axons leaving the pituitary stalk and the neural lobe. In animals of which the hypothalamic magnocellular neurosecretory preoptic nuclei had been completely removed, the immuno-reactive mesotocinergic fibres of the pars intermedia had totally disappeared. From this result, it is concluded that the mesotocinergic fibres of the pars intermedia of the amphibian hypophysis are axons of neurosecretory perikarya located in the hypothalamic magnocellular neurosecretory preoptic nuclei.Dedicated to Professor Berta Scharrer on the accasion of her 70th birthdayThis investigation was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek     

Remarks on oxygen effects

Oxygen concentration will influence the alpha- and beta-effect (two-component theory of radiation effects) independently. The beta-effect is reduced by a dose-modifying factor gamma. Oxygen, in competition with enzyme repair actions fortifies a part of the beta-lesions and this model leads to a simple equation for the factor gamma. The alpha-effect is also enhanced by oxygen. Measurements of OER indicate that the reduction of the effect from aerobic to anoxic condition might be about 70%. The functional dependence of oxygen concentration has not been investigated. For small oxygen concentrations of 0.15 to 0.5 muM/l and doses below 1000 R Révész and Littbrand have found that oxygen can protect the irradiated cells and thus increase survivals with about 10%. This is explained as a scavenger action where radical hydrogen atoms are oxidized and hydrated electrons captured by oxygen moelcules. When the oxygen concentration is increased, or with higher doses, the usual sensitizing effect of oxygen exceeds the protection effect. The influence of oxygen on alpha-effects are mainly connected with indirect radiation effects and thus depend on temperature and milieu.     

Ultrastructure of the prothoracic gland cells of the last instar of Galleria mellonella in relation to the state of development

The prothoracic glands of the last instar of Galleria mellonella undergo characteristic alterations of their cellular fine structure closely related to cellular activity. During progressive secretory activity of the gland cells there are extensive plasmalemmal infoldings and formation of a pronounced lacunar system. Mitochondria of the active cell phase are characterized by a specific increase in size and paler colour of the matrix. In contrast to the alterations, nuclei, ER and Golgi cisterns do not undergo any submicroscopic changes during the different phases of cellular activity. The relationship between the substructural phenomena and the specific phases of cellular activity are discussed.     

Changes in parotid acinar cells accompanying salivary secretion in rats on sympathetic or parasympathetic nerve stimulation

Morphological and secretory effects of stimulating autonomic nerves have been studied in parotid glands of rats. Sympathetic stimulation evoked a slow flow of saliva which had a high concentration of amylase. After long term sympathetic stimulation secretory granules were heavily depleted from the parotid acinar cells. Parasympathetic stimulation evoked a copious flow of saliva with a low concentration of amylase. However, at high frequency stimulation the total amount of amylase secreted on parasympathetic stimulation was as great or even greater than on symphatetic stimulation, nevertheless, any loss of secretory granules from the acinar cells was very small. It is concluded that secretion of parotid acinar granules in the rat is prinicipally a sympathetic function. Secretion of fluid is more effectively produced by parasympathetic stimulation and much of the amylase in such saliva appears to have arisen from sources other than the secretory granules.     

Equilibrium and stability in laboratory model of sewage ponds and polluted rivers

The persistence under controlled chemical and physical conditions and the ability to respond to defined environmental changes was follow d in extremely simple (homogenous or 2-phase) ecosystems with continuous or semicontinuous flow. In the homogenous case the Aufwuchs was removed. Primary productivity and community respiration were computed by means of continuous recording of dissolved oxygen. Under constant environmental conditions the systems usually exhibited slow oscillations of the ecosystem parameters around an equilibrium state. The temporal variations of functional criteria such as elimination rate of easily degradable organic substances or daily oxygen amplitude were slight in comparison to the significant random oscillations in individual numbers of the predominating species of phytoplankton and zooplankton. One of the mechanisms responsible for this functional stability may be the inverse relationship between biomass and activity per unit biomass as observed also in the laboratory models. If the sewage pond microecosystems after a shut down in the inflow were operated without any exchange of nutrients and gases they nevertheless maintained a very high level both of autotrophic and heterotrophic metabolism. Step forcing of nutrient (sewage) concentration, dilution rate or day length produced a new equilibrium state within 1 or 2 days, if the functional criteria mentioned above were taken as output signals. Also in the case of pulse forcing such a rapid adaptation was to be observed. This may contribute to the fact, that the turnover rate of the population was in the same range as the renewal rate of the water. The results are discussed with respect to short and long term effects of abatement of pollution from flowing and standing waters.