Rapid preparation of pure glomeruli and tubular fragments from rabbit kidney : Distribution of alkaline phosphatase

A simple rapid method for separating glomeruli and tubular fragments is described. The alkaline phosphatase activity of the glomeruli based on the tissue proteins, or on the DNA, was about 4%, or 1%, respectively of that of the tubular fraction. Alkaline phosphatase can be used as a chemical marker of the purity of glomerular fractions in studies on the structure, antigenicity, and biochemical function of glomeruli.     

Behaviour of neuroblasts in the presence of glial cells, fibroblasts and meningeal cells in culture

Dissociated nerve cells from 7-day-old chick embryo cerebral hemispheres were cultivated on plastic surfaces, astroblast layers, fibroblast layers and meningeal cell layers. The cell suspensions obtained by mechanical dissociation and plated on these layers contained primarily neuroblasts. The neuroblasts cultured on astroblast layers behaved differently from those cultured on fibroblast or on meningeal cell layers. They adhered within 2 h to the preformed astroblast monolayers and remained scattered over it. In contrast, in the two other cases, the neuroblasts formed floating aggregates which adhered to the layers only after 24 h. Neuroblasts behaved on monolayers made of fibroblasts or meningeal cells as on plastic surfaces.The neuronal cells grown on astroblast layers were much more differentiated than those plated on plastic or on the two other layers studied. After 2–3 weeks of culture the neurons were large and the fibres were longer, thicker and more ramified. However, the fibroblast and the meningeal cells enhanced slightly the growth of the neuroblasts relative to plastic surfaces. These results support the possibility of specific interactions between astroblasts and neuroblasts.     

Rates of RNA synthesis during early embryogenesis in Drosophila melanogaster

We determined the absolute rates of RNA synthesis during embryogenesis in Drosophila melanogaster by measuring the incorporation of ³H-5-orotic acid into RNA, and the specific activity of the UTP pool. Initially (preblastoderm) the rate of RNA synthesis is relatively high, but declines to a lower level by gastrulation. The data suggest that RNA synthesis is initiated during very early embryogenesis.     

Folic acid as a dietary factor affecting the wing morph of the planthopper, Laodelphax striatellus (hemiptera, delphacidae)

A factor effecting the production of brachypterous adults in Laodelphax striatellus was studied by comparing a diet on which brachypterous adults sometimes developed and a diet on which they never developed. By substituting components distinctive of the latter diet into the former, or by varying the concentration of certain components of the latter diet, the production of brachypterous adults was found to vary with the concentration of a vitamin, folic acid. Brachypterous adults were produced only when the diet contained folic acid at concentrations between 0.5 mg/l and 7.5 mg/l.

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Résumé Un facteur efficace pour la production d'adultes brachyptères chez Laodelphax striatellus a été recherché en comparant une nourriture sur laquelle des adultes brachyptères se développent parfois et une nourriture sur laquelle ils ne se développent jamais. En substituant les constituants spécifiques de cette dernière par ceux de la première ou en variant les concentrations de certains des constituants de la dernière on a montré que la production d'adultes brachyptères varie avec la concentration d'une vitamine, l'acide folique. Ceux-ci sont produits seulement lorsque l'alimentation contient de l'acide folique à des concentrations comprises entre 0,5 mg/l et 7,5 mg/l.

     

Himasthla quissetensis: uptake and utilization of glucose by rediae as determined by autoradiography and respirometry

Daughter rediae of Himasthla quissetensis removed from the digestive gland of Nassarius obsoletus were placed in sterilized seawater fortified with antibiotics. When [³H]-glucose was added to this medium and autoradiographs were made after 3, 9, and 24 hr of exposure, labeling was observed associated with the redial walls and developing germ balls and cercariae within the brood chambers. Respirometric determinations on starved rediae suspended in the seawater medium with and without glucose revealed the rate of oxygen utilization by rediae exposed to exogenous glucose is significantly elevated. These results are interpreted to mean that the daughter rediae of H. quissetensis can take up and utilize glucose.