Delineation of suppressor and helper activity within the OKT4-defined T lymphocyte subset in human newborns

Lymphocytes taken from the cord blood of newborns have active suppressor activity. Using in vitro PWM-stimulated cocultures, unfractionated T cells from newborns potently suppressed the expected immunoglobulin G (IgG) synthesis of their mothers' peripheral blood lymphocytes (PBL). Using positive and negative selection techniques, we characterized the active suppressor cell as expressing the OKT4+T8- phenotype. This cord blood lymphocyte subset suppressed maternal IgG synthesis after depletion of maternal suppressor cells, implicating the ability of newborn T cells to suppress directly rather than by inducing adult suppressor activity. Sublethal amounts (1500 rad) of gamma-irradiation fully abrogated the suppressor activity of cord blood T lymphocytes. Radioresistant cord T cells provided T cell help. Irradiation of cord OKT4+ and OKT8+ populations and their subsequent culture with maternal B cells determined that helper activity was a radioresistant subpopulation of the OKT4+ subset. These results indicate significant differences in the functional properties of T cell subsets from adults and newborns. Population studies determined that cord blood lymphocytes had a greater proportion of OKT4+ cells and lower proportion of OKT8+ cells than PBL from unrelated adults. The mothers tested had similar proportions of OKT4+ cells as their babies, and these levels are significantly higher than those of unrelated adults.     

Conjugal Transfer of Plasmid-Borne Multiple Antibiotic Resistance in Streptococcus faecalis var. zymogenes

A strain of Streptococcus faecalis var. zymogenes, designated JH1, had high-level resistance to the antibiotics streptomycin, kanamycin, neomycin, erythromycin, and tetracycline. These resistances were lost en bloc from approximately 0.1% of cells grown in nutrient broth at 45 C. The frequency of resistance loss was not increased by growth in the presence of the "curing" agents acriflavine or acridine orange, but after prolonged storage in nutrient agar 17% of cells became antibiotic sensitive. Covalently closed circular deoxyribonucleic acid (DNA) molecules were isolated from the parental strain and from antibiotic-sensitive segregants by using cesium chloride-ethidium bromide gradients. DNA molecular species were identified by using neutral sucrose gradients. Strain JH1 contained two covalently closed circular DNA species of molecular weights 50 x 10(6) and 38 x 10(6). An antibiotic-sensitive segregant, strain JH1-9, had lost the larger molecular species. A second sensitive segregant, strain JH1-5, had also lost the larger molecular species but a new molecular species of approximate molecular weight 6 x 10(6) was present. The antibiotic resistances that were curable from the parental strain were transferred to antibiotic-sensitive strains of S. faecalis and to strain JH1-9, during mixed incubation in nutrient broth at 37 C. Data to be described are interpreted to suggest that the transfer is by a conjugal mechanism. Analysis of the plasmid species in recipient clones showed that all had received the plasmid of molecular weight 50 x 10(6). Strain JH1-5 was not a good recipient. Analysis of one successful recipient clone of JH1-5 revealed that it had gained the 50 x 10(6) molecular weight plasmid but lost the 6 x 10(6) molecular weight species. These data are interpreted to mean that the multiple antibiotic resistance is borne by a transferable plasmid of 50 x 10(6) molecular weight, and that in clone JH1-5 this plasmid suffered a large deletion leaving only a 6 x 10(6) remnant which was incompatible with the complete replicon.     

Adaptation of cultured human lymphoblasts to growth in citrulline

DNA synthesis is initiated in unfertilized sea urchin eggs (Strongylocentrotus purpuratus and Lytechinus pictus) by exposing them to NH₄OH-sea water (ordinary sea water titrated to pH 9–9.1 with NH₄OH). The eggs are considered to be unfertilized eggs by visual and electro-biological criteria and because they can later be fertilized and then do give visible and electrobiological fertilization reactions. The incorporation of ³H-thymidine proceeds in rounds, the magnitude increasing in successive rounds. It is also reported that the treatment with NH₄OH activates the uptake of thymidine by the eggs, although the internal thymidine builds up more slowly in unfertilized eggs treated with NH₄OH than it does in fertilized eggs. The magnitude of the incorporation of exogenously supplied labelled thymidine into DNA is lower in the NH₄OH-treated unfertilized eggs than in normal fertilized eggs. This difference is not attributed to differences in the amount of DNA synthesized and the explanation is sought in thymidine uptake and nucleotide pathways.     

Studies on the fractionation of total transfer ribonucleic acid and purification of an alanine transfer ribonucleic acid from chick embryo

Chick embryo tRNA, prepared by a simple large-scale method, was fractionated on three different ion-exchange columns. In all cases simple chromatographic patterns for various tRNA species were observed, indicating the presence of only a few major species of tRNA for each amino acid. By repeated chromatography one species of alanine tRNA was purified to approx. 80% purity. T₁ ribonuclease digest of this purified tRNA gave a simple chromatographic pattern. Because of the simplicity of the method of preparation of tRNA from this readily available source and the presence of only a few species of tRNA for each amino acid, chick embryo is suited for the study of tRNA and its various functions in higher systems.     

The effect of adrenocorticotrophin on protein degradation in rat adrenal gland and liver

The rate of adrenal protein degradation appears to be slower in rats to which ACTH (adrenocorticotrophin) has been chronically administered. As measured by the exponential decay of radioactively labelled adrenal protein in vivo, the mean half-lives of total protein and of mitochondrial, microsomal and 18000g-supernatant protein were significantly longer in ACTH-treated animals. Experiments in which either [(3)H]leucine or NaH(14)CO(3) was used to label proteins showed that of the fractions studied, the effect on mitochondrial protein degradation was most pronounced. The half-lives of the same subcellular fractions in rat liver were not affected by ACTH. The possibility that the results might have been caused by changes in radioisotope reutilization and pool size is discussed.     

Studies on the macronucleus of Paramecium aurelia

Following specific incorporation of tritiated thymidine into the DNA of the macronucleus of Paramecium aurelia for varying periods of time the vast majority of silver grains in electron microscope autoradiographs are associated with the area containing the small bodies and matrix. At best only 5% of the silver grains overlying the macronucleus are attributable to the large bodies. This is consistent with the view that the large bodies are the nucleoli of the macronucleus.     

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.