Pyruvate Kinase of Streptococcus lactis

The kinetic properties of pyruvate kinase (ATP:pyruvate-phosphotransferase, EC 2.7.1.40) from Streptococcus lactis have been investigated. Positive homotropic kinetics were observed with phosphoenolpyruvate and adenosine 5′-diphosphate, resulting in a sigmoid relationship between reaction velocity and substrate concentrations. This relationship was abolished with an excess of the heterotropic effector fructose-1,6-diphosphate, giving a typical Michaelis-Menten relationship. Increasing the concentration of fructose-1,6-diphosphate increased the apparent V_max values and decreased the K_m values for both substrates. Catalysis by pyruvate kinase proceeded optimally at pH 6.9 to 7.5 and was markedly inhibited by inorganic phosphate and sulfate ions. Under certain conditions adenosine 5′-triphosphate also caused inhibition. The K_m values for phosphoenolpyruvate and adenosine 5′-diphosphate in the presence of 2 mM fructose-1,6-diphosphate were 0.17 mM and 1 mM, respectively. The concentration of fructose-1,6-diphosphate giving one-half maximal velocity with 2 mM phosphoenolpyruvate and 5 mM adenosine 5′-diphosphate was 0.07 mM. The intracellular concentrations of these metabolites (0.8 mM phosphoenolpyruvate, 2.4 mM adenosine 5′-diphosphate, and 18 mM fructose-1,6-diphosphate) suggest that the pyruvate kinase in S. lactis approaches maximal activity in exponentially growing cells. The role of pyruvate kinase in the regulation of the glycolytic pathway in lactic streptococci is discussed.     

Effect of LSD on mitotic and meiotic plant chromosomes

LSD was found to induce chromosomal aberrations in root tip cells of Allium cepa, Hordeum vulgare and Secale cereale. Aberrations occurred in the form of chromatid and isochromatid breaks with most of these breaks failing to rejoin. The distribution of chromosome breaks was not uniform over the length of chromosomes, and a majority of the breaks were localized at the centromeric regions. For a given dose of LSD (30 g/ml), onion appeared to be more susceptible than barley or rye. The diploid and tetraploid rye used in the study showed no appreciable difference in sensitivity to LSD treatment. — A preliminary study on meiotic chromosomes in LSD-treated diploid rye revealed the presence of univalents, chromosome breaks and fragments, suggesting that LSD can induce meiotic abnormalities in plant material.Contribution from the Department of Agronomy, University of Kentucky. The investigation reported in this paper (73-3-75) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Computer-assisted Follow-up Register for the North-East of Scotland

An automated follow-up register for the detection of iatrogenic thyroid disease has been established as a joint venture between the general practitioners in the north-east of Scotland and the thyroid clinic of Aberdeen General Hospitals.The data-processing operations in the system are handled by an International Computers Limited 4/50 computer. Patients are followed up at predetermined intervals and the system has been designed to process, screen, and store clinical and biochemical follow-up data and report results to the patients, general practitioners, and the hospital records department.     

Purine Ribonucleosidase g from Aspergillus foetidus

Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.     

The identification of hybrids ofPhaseolus vulgar is L. ×Phaseolus coccineus L. Using immunoehemical methods

F₁ generace hybrid?Ph. vulgaris L. XPh. coccineus L. je v bílkovinných znacích zhruba intermedierní. V F₂ generaci se objevuje ?těpení a r?zné stupně matro- ?i patroklinity.