Selective Utilization of Pyrimidine Deoxyribonucleosides for Deoxyribonucleic Acid Synthesis in Pneumococcus

When pyrimidine deoxyribonucleosides are supplied to growing cultures of Diplococcus pneumoniae, they are selectively used for incorporation into deoxyribonucleic acid (DNA). Differently labeled molecules of deoxyuridine, thymidine, and deoxycytidine were used to study the precursor pathways of this organism. Each of these preformed pyrimidine deoxynucleosides is incorporated intact (i.e., without cleavage of the glycosidic bond) and is predominantly recoverable as DNA thymidine. During the utilization of deoxycytidine and deoxyuridine by pneumococci, large proportions of the available precursor are converted to free thymidine, which is secreted back into the growth medium. The biochemical pathways for selective incorporation into DNA and the regulation of concentrations of intracellular thymidine compounds by excretion of free thymidine are discussed.     

Lysophosphatidylcholine concentrations and metabolism in aortic intima plus inner media: effect of nutritionally induced atherosclerosis

The concentration of lysophosphatidylcholine (monoacyl sn-glycerol 3-phosphorylcholine) in intima plus inner media of atherosclerotic aorta from squirrel monkeys was nearly eight times that in comparable control tissue. Plasma levels of the same compound were somewhat elevated in the atherosclerotic group. The metabolism of fatty acyl CoA's and lysophosphatides was studied in cell-free preparations of intima plus inner media from squirrel monkey aorta. Linoleic acid was incorporated predominantly into phosphatidylcholine (as opposed to other phospholipids) when linoleoyl-1-(14)C CoA was the substrate. The extent of this reaction was dependent on the concentration of lysophosphatidylcholine. Lysophosphatidylethanolamine (monoacyl sn-glycerol 3-phosphorylethanolamine) stimulated the incorporation of linoleate into phosphatidylethanolamine. 1-Palmitoyl-1'-(14)C sn-glycerol 3-phosphorylcholine ((14)C-lysophosphatidylcholine) was incorporated into phosphatidylcholine only in the presence of acyl CoA's or ATP plus CoA. Incorporation of (14)C with (14)C-lysophosphatidylcholine plus linoleoyl CoA equaled that with linoleoyl-1-(14)C CoA and lysophosphatidylcholine. Various other lines of evidence are presented to support the importance of the fatty acyl CoA:lysophosphatide fatty acyl transferase mechanism in aortic phospholipid metabolism. Cell-free preparations of aortic intima plus inner media from squirrel monkeys with early, nutritionally-induced atherosclerosis utilized linoleoyl-1-(14)C CoA more than preparations from control monkeys when incubations were carried out without added lysophosphatidylcholine and for long periods (30 min). With optimum levels of labeled linoleoyl CoA and unlabeled lysophosphatidylcholine, or unlabeled linoleoyl CoA and labeled lysophosphatidylcholine, there were no differences in substrate utilization between control and atherosclerotic tissues. We conclude that the concentrations of lysophosphatidylcholine, which are higher in atherosclerotic than in control aortic tissues, could be a factor controlling rates of fatty acid incorporation into phosphatidylcholine.     

Incomplete bacteriophage-like particles in ultraviolet-irradiated haemophilus

Incomplete phagelike particles were found in competent and incompetent cells of Haemophilus influenzae Rd (transformable) lysed after exposure to ultraviolet radiation.     

Die Zytologie vonRubus Gremlii Focke undRubus candicans Wh.

Zusammenfassung Es wurde fürRubus Gremlii die Chromosomenzahl 2n=28, fürRubus candicans 2n=21 festgestellt. Die Angabe vonMarks fürRubus candicans 2n=35 bezieht sich vielleicht aufRubus Linkianus, der wahrscheinlich mitRubus candicans nicht näher verwandt ist.     

Results of Treatment of Thyrotoxicosis after Postoperative Relapse

Ninety patients who had a recurrence of thyrotoxicosis after thyroidectomy have been reviewed. All 10 patients who had a second operation and 18 out of 20 patients treated with a full course of antithyroid drugs relapsed. These results differ greatly from the results of treatment of the first episode of thyrotoxicosis, whether by thyroidectomy or antithyroid drugs. Radioiodine is the treatment of choice in this group of patients, despite the high incidence of hypothyroidism.     

Partial purification of a legume nodulation factor present in coconut water

The nodulation of adventitious roots growing from segments of bean hypocotyl tissue was used as a bioassay for the material present in coconut water which stimulated nodulation. The active material in coconut water is acidic, but it was not possible to extract it from an acid solution with organic solvents. A purification of approximately 70-fold (on a dry wt basis) was obtained using activated charcoal, but at least 10 different compounds were present in the active fractions. A purified fraction of coconut water, which is stimulatory to the growth of carrot root explants, was active in the nodulation assay at a concentration of 2 μg/ml. This represents a 4000-fold purification of the diffusible fraction of coconut water. The charcoal fractionation procedure can be applied to the active material present in extracts of bean leaves.