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.     

The classification of free-living spirochetes

Summary The natural relationships among free-living and host-associated spirochetes were studied by investigating aspects of their morphology, physiology and DNA base composition. These studies indicated that the strictly and facultatively anaerobic, free-living spirochetes share characteristics which distinguish them from their host-associated counterparts and from the free-living leptospires.It is suggested that the strictly and facultatively anaerobic, free-living spirochetes be grouped in the genus Spirochaeta and that this genus include the following four species: S. plicatilis (type species), S. stenostrepta, S. zwelzerae (Treponema zuelzerae), and S. aurantia. The characteristics of these species are described.     

The DNA base composition of a flagellar mutant ofComamonas terrigena ATCC 8461

The lophotrichous flagellatedComamonas terrigena, ATCC 8461, spontaneously produces a peritrichous flagellate mutant which is physiologically like the parent. The DNA base composition of the parent and mutant were the same with 64% GC.     

The polymorphic marker DXS304 is within 5 centimorgans of the fragile X locus

The fragile X syndrome, which is the most common cause of inherited mental retardation, poses important diagnostic problems for genetic counseling. The development of diagnostic strategies based on DNA analysis has been impaired by the lack of polymorphic markers very close to the disease locus. Here we report that the polymorphic probe U6.2 (locus DXS304) is much closer to the fragile X locus than all the previously reported markers. A recombination fraction of 0.02 between DXS304 and the fragile X locus was estimated by multipoint linkage analysis (confidence interval 0.002 to 0.05). Our data suggest that DXS304 is distal to the fragile X locus. This marker thus represents a major improvement for carrier detection and prenatal diagnosis in fragile X families.     

Poly(ADPR)polymerase expression and activity during proliferation and differentiation of rat astrocyte and neuronal cultures.

Poly(ADPR)polymerase (poly(ADPR)P) mRNA and enzymatic activity levels were investigated in primary cultures of rat astrocytes and neurons in the absence or presence of basic fibroblast growth factor (bFGF) and nerve growth factor (NGF), respectively. In cultured rat astrocytes, a biphasic increase in poly(ADPR)P mRNA, associated with enhanced nuclear poly(ADPR)P enzymatic activity, were observed. The first rise in poly(ADPR)P mRNA and enzymatic activity is at the beginning of cell proliferation and the second with the occurrence of cell differentiation. In the presence of bFGF (5 ng/ml) the mRNA peaks and the differentiation-associated poly(ADPR)P enzymatic activity undergoes a 2-fold increase. In neuronal cultures an initial high level of poly(ADPR)P mRNA is followed by a decrease while differentiation is progressively achieved. A limited increase of poly(ADPR)P activity is observed during this phase. In the presence of NGF (50 ng/ml), similar poly(ADPR)P mRNA expression and enzymatic activity patterns are observed. The results suggest that poly(ADPR)P is involved at the onset of nerve-cell proliferation and differentiation.     

SOME IMMUNOCHEMICAL CHARACTERISTICS OF W1 AND W2 WOLFGRAM PROTEINS ISOLATED FROM RAT BRAIN MYELIN

Starting from a chloroform-methanol (2: 1 v/v) insoluble pellet of rat brain myelin, two pure proteins W1 and W2 were isolated by sodium dodecylsulphate preparative polyacrylamide gel electrophoresis. Their amino acid composition was compared. Antibodies against these proteins were prepared in rabbits. It was found that the two antigens have common antigenic similarities. The presence of one precipitin line of identity when myelin or isolated W1 and W2 from different animals were tested, led to the conclusion that there was no species specificity. The importance of the availability of such antisera is discussed.