DISTRIBUTION QUANTITATIVE DES DIVERS PHOSPHO-LIPIDES DANS LES NEURONES ET LES CELLULES GLIALES ISOLES DU CORTEX CEREBRAL DE RAT ADULTE

Resumé–— On décrit une méhode de préparation de neurones et de cellules gliales à partir du cortex cérébral, basée sur la dissociation du tissu à travers un tamis en nylon suivie ď une ultracentrifugation différentielle sur gradients de sucrose et de Ficoll.
On a dosé le DNA, ľazote protéque et les divers phospholipides. II ressort que le taux ď DNA par cellule est identique dans les neurones et les cellules gliales. Par contre, la quantité absolue ďazote protéique est 2.8 fois plus élevée dans les cellules gliales, celle des lipides totaux et des divers phospholipides 5-6 fois plus élevée.
La proportion de chacun des phospholipides dérminée par rapport aux phospholipides totaux est similaire dans les deux types cellulaires.     

Histoplasmosis in Montreal During the Fall of 1963, with Observations on Erythema Multiforme

Although Montreal is in an endemic area, significant clinical histoplasmosis with systemic manifestations has been, until recently, infrequently diagnosed. However, since the autumn of 1963, 31 cases of clinically significant histoplasmosis have been seen by the authors. These were divided into two groups: (1) patients in whom the diagnosis was established on the basis of histological and/or cultural demonstration of the fungus; (2) patients in whom the diagnosis was based on a positive histoplasmin skin test, a complement fixation antibody titre of 1:32 or greater and compatible clinical and radiological findings. An additional group of 11 patients who presented with erythema multiforme was investigated and a heretofore unrecognized relationship between histoplasmosis and erythema multiforme was established.     

Cell function in the ovary of drosophila

Summary The relative DNA content of the ovarian nurse nuclei of Drosophila melanogaster has been measured by high-resolution autoradiography of DNA uniformly labelled with adenine-8-¹⁴C.The various nurse nuclei show a defined pattern of DNA classes. The posterior nuclei, i. e. those nearest to the oocyte, achieve eight reduplications of DNA by stages 8–9, thus reaching 512n, and all have lost some DNA by stage 10. The nuclei in the middle of the chamber achieve seven reduplications of DNA by stage 9, thus reaching 256n, and though there is loss of DNA in the majority of these nuclei at stage 10 some of them might enter a new reduplication cycle. The anterior nuclei, i. e. those more distant from the oocyte, achieve more than seven reduplications by stage 10 and show no loss of DNA.After stage 6 of the ovarian chambers the pattern of DNA enrichment and later degradation is clearly polarized in that there is a posterioranterior gradient for the level of ploidy, the order in time in which this is attained, and the loss of DNA. The dominant end of the gradient is towards the developing oocyte.The measured nuclear volume where DNA is present is well correlated with ploidy till stage 9. Compared with earlier stages, at stage 10 DNA shares less in the nuclear contents than other materials. The nuclear volume when calculated as a sphere is a gross overestimation, except for the earliest stages.Various possibilities likely to bring about differences in the amount of DNA among nurse nuclei within and between chambers are discussed.Research worker of the British Empire Cancer Campaign.     

Comparison of two serologically distinct ribonucleic acid bacteriophages. II. Properties of the nucleic acids and coat proteins

Overby, L. R. (University of Illinois, Urbana), G. H. Barlow, R. H. Doi, Monique Jacob, and S. Spiegelman. Comparison of two serologically distinct ribonucleic acid bacteriophages. II. Properties of the nucleic acids and coat proteins. J. Bacteriol. 92:739-745. 1966.-The ribonucleic acid (RNA) molecules and coat proteins of two RNA coliphages, MS-2 and Qbeta, have been characterized. MS-2 RNA shows an S(20,w) of 25.8 and a molecular weight by light scattering of 10(6). The corresponding parameters for Qbeta-RNA were 28.9 and 0.9 x 10(6). A difference in base composition was reflected in the adenine-uracil ratio, which was 0.95 for MS-2 and 0.75 for Qbeta. The two RNA preparations are readily separated by chromatography on columns of methylated albumin. Both gave identical bouyant densities in cesium sulfate of 1.64 g/ml. The coat protein subunits were of similar molecular weights: 15,500 (Qbeta) and 14,000 (MS-2). They differed, however, in that the Qbeta-protein lacked tryptophan and histidine, whereas the MS-2 protein lacked only histidine.     

Effect of chloramphenicol on ribonucleic acid synthesis in liver cells in suspension

1. Chloramphenicol has a stimulatory effect on the incorporation of radioactive phosphate into the RNA of perfused rat-liver slices, whole liver homogenates or the liver-cell suspensions, and no effect on the incorporation of [(14)C]adenine and [(14)C]uracil into the RNA of the tissue slices. 2. Chloramphenicol completely inhibits the incorporation of labelled adenine and uracil into the RNA of the cell suspensions, or into the RNA of homogenates derived from the whole liver tissues. 3. Chloramphenicol has at most a slight inhibitory effect on the transport of labelled adenine or uracil in the hepatic cells in suspension; in the slices, the transport of these bases is not inhibited at all. 4. The above observations indicate that: (a) unlike the tissue slices, hepatic cells in suspension are permeable to chloramphenicol; (b) in the presence of chloramphenicol, for reasons that are not clear, the conversion of the base into the appropriate nucleotide does not proceed.