Genetic relationship among bacteria classified as vibrios

Genetic relatedness among six bacterial strains currently classified as vibrios was determined by biochemical tests, deoxyribonucleic acid base composition analysis, and the detection of nucleic acid homology by the membrane filter method. Varying degrees of genetic homology existed among vibrios having similar base compositions. The bovine isolate which had a substantially different per cent guanine plus cytosine content was shown to be genetically different from the remaining vibrio strains. The use of nucleic acid homology studies in classifying vibrio strains is discussed.     

Decarboxylation of α-Keto Acids by Streptococcus lactis var. maltigenes

Decarboxylation rates for a series of C-3 to C-6 alpha-keto acids were determined in the presence of resting cells and cell-free extracts of Streptococcus lactis var. maltigenes. The C-5 and C-6 acids branched at the penultimate carbon atom were converted most rapidly to the respective aldehydes in the manner described for alpha-carboxylases. Pyruvate and alpha-ketobutyrate did not behave as alpha-carboxylase substrates, in that O(2) was absorbed when they were reacted with resting cells. The same effect with pyruvate was noted in a nonmalty S. lactis, accounting for CO(2) produced by some "homofermentative" streptococci. Mixed substrate reactions indicated that the same enzyme was responsible for decarboxylation of alpha-ketoisocaproate and alpha-ketoisovalerate, but it appeared unlikely that this enzyme was responsible for the decarboxylation of pyruvate. Ultrasonic disruption of cells of the malty culture resulted in an extract inactive for decarboxylation of pyruvate in the absence of ferricyanide. Dialyzed cell-free extracts were inactive against all keto acids and could not be reactivated.     

Mental Health: The Search for a Definition

Various attempts to define the concept of “mental health” are examined. Value judgments permeate much mental health literature. Their use militates against obtaining an objective definition, capable of universal application. The acceptance of a definition including a value judgment implies taking an attitude toward a particular society and its social ideals.Present limits of competence only allow us to describe “mental health” conceptually. Such “untechnical” proposals are liable to be confused with “technical” (“scientific”) propositions. Multiple criteria are likely to be helpful in improving our concept of “mental health”.The intrusion of morals into the world of health is discussed as part of the contemporary intellectual dilemma of determined human behaviour versus human responsibility and the reality of moral values.It is suggested that “mental health” might consist simply of an individual''s possession of insight into his own personality, combined with an honest recognition and acceptance of his condition.     

The de-repression of thiamine biosynthesis by adenosine. A tool for investigating this biosynthetic pathway

1. Growth of Salmonella typhimurium LT2 in the presence of adenosine was shown to cause enormous synthesis of thiamine in washed-cell suspensions. 2. Evidence that this was due to de-repression and not an accumulation of precursors was obtained by using a mutant blocked in the biosynthesis of the thiazole moiety, which showed a similarly large synthesis of the pyrimidine of thiamine. 3. The specific requirements for a source of energy, nitrogen and sulphur were investigated, and indicated new synthesis in this system.     

ORGANOGENESIS IN THE CARPELLATE FLOWER OF DRIMYS LANCEOLATA

This study of floral development in Drimys lanceolata in Section Tasmannia provides a basis for comparison with D. winteri, a member of the section Wintera, which has been described previously. The carpellate flowers of D. lanceolata have 2 sepals, 4–6 petals, and a solitary carpel, which form in acropetal succession. In symmetry the flower and its apical meristem are bilateral rather than radial, as in the flower of Drimys winteri. The floral apex of D. lanceolata is zonate while that of D. winteri is organized as a mantle and core. Preceding carpel initiation the floral apex of D. lanceolata is narrowly wedge-shaped, while that of D. winteri is low-convex. The entire apex is utilized in carpel initiation in D. lanceolata, involving many subsurface cell divisions over the entire summit. No apical residuum remains, and the carpel is terminal. In this feature the contrast with D. winteri is particularly marked, since in the latter, carpels are initiated laterally around the floral apex, which c an be recognized as an apical residuum after all appendages have formed.     

Effects of platelet-derived growth factor and fibroblast growth factor on free intracellular calcium and mitogenesis

Although increased free intracellular calcium (Cai) may be one of the main regulators of cell growth and differentiation, studies in cell populations have implied that not all growth factors produce Cai increases. In order to examine in more detail whether Cai increases were related to mitogenesis, we used digital image analysis of intracellular Fura-2 fluorescence to measure Cai in individual BALB/c 3T3 cells stimulated with either platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF). We found that PDGF induced larger and more prolonged Cai increases than FGF did, but that both growth factors induced an initial rapid increase in Cai (less than 2 min) followed by a later sustained increase (greater than 20 min). Only the prolonged Cai increase required extracellular calcium. Following PDGF treatment (1-8 units/ml), the percentage of cells with a large peak Cai increase (greater than twofold) correlated with the percentage of cells made competent (subsequent growth in 1% platelet-poor-plasma). In contrast, purified bovine basic FGF (200-800 pg/ml) and recombinant human acidic FGF (10-300 ng/ml) produced peak Cai increases that were not directly correlated with mitogenesis. In addition, concentrations of intracellular Quin 2 that inhibited Cai transients also inhibited PDGF stimulation but not FGF stimulation of mitogenesis. Thus, Cai increases are necessary for mitogenesis in BALB/c 3T3 cells stimulated by PDGF, but not that stimulated by FGF.