Immunochemical study of nutritionally variant streptococci

Nutritionally variant streptococci (NVS) have been characterized by their growth as satellite colonies around colonies of staphylococci or several other gram-positive or gram-negative bacterial strains. The majority of the NVS strains were isolated from patients with subacute bacterial endocarditis. Organisms identified as NVS were subdivided into three serotypes by rocket-line electrophoresis and hemagglutination inhibition assays. Ninety-nine of 103 strains expressed one or more of the three serotype antigens; however, a group antigen was not demonstrated in the various extracts of these streptococci. Surface protein studies confirmed the NVS differentiation into serotypes. Serotype I organisms expressed surface protein(s) specific for the serotype, whereas the serotype II and III NVS demonstrated common protein(s) on their surface. Furthermore, SDS extraction released a greater amount of radioiodinatable surface protein from serotypes I and III bacteria than serotype II. Finally, there was no correlation between the serotype or the disease of the patients from which the NVS strains were isolated.     

Appearance of the liver form of pyruvate kinase in differentiating cultured foetal hepatocytes

Abstract. From about the 16th day of gestation three forms of pyruvate kinase are present in foetal rat liver (L, R, and M2). Hepatocytes isolated from 15-day-old foetuses do not possess the liver form of pyruvate kinase, but after three days in culture this enzyme can be detected. No effect on the appearance of the enzyme could be seen by administration of insulin and fructose.
Hepatocytes isolated from 19-day-old foetuses exhibit three forms of the enzyme (L, R, and M2) on day 1 of culture but thereafter only two forms are detectable (L and M2). A decrease in activity of the L form is observed. This could be retarded by administration of insulin and fructose.     

Schiffs bases and derived secondary amines as plant growth inhibitors

Seventy-two Schiffs bases, 44 corresponding secondary amines, and 12 N-acetylated compounds were tested on their growth activity. Eighty-one compounds were active as growth inhibitors in at least one of three bioassays.     

Simulated responses to hypothetical fundamental niches

Abstract. Two graphical models of plant competition, the ‘ghost of competition past’ and the ‘hierarchical’ model are compared using a greatly simplified individual-based forest dynamics simulation. Assumed fundamental niche shapes are used to determine the basic growth responses of the species, but competition alters the realized niche. Differences in the two models, amount of niche overlap, disturbance, and removal and invasion of species are examined in simulation experiments. Without disturbance, the realized niche responses reveal abrupt boundaries between species in all cases, and thus the responses are generally platykurtic to rectangular with little overlap. In some cases overlap through the extension of abundance of weaker competitors into the area of greater resources — dominated by better competitors but still within their fundamental niche — creates skewed distributions, as have been observed and simulated in the past. When species are removed or invade, the abrupt boundaries and the lack of difference in final response shape indicate that past removals may be difficult to detect. This difficulty may be important because former species may be influencing the responses that are observed in common non-equilibrium distributions. Even when assumptions favor the illustration of a competitive hierarchy, actual distributions and dynamics do not differentiate between it and a model of the ghost of competition past.     

A requirement for DNA synthesis in foetal hepatocyte differentiation

In hepatocyte cultures derived from 15-day-old foetal rats, the appearance of the liver (L) form of pyruvate kinase is blocked when cytosine arabinoside is added on the 2nd day of culture. When added on the 3rd day of culture, the inhibitor of DNA synthesis does not prevent the appearance of the enzyme. If cytosine arabinoside is added on the 2nd day of culture and removed on the 4th day, the enzyme is detected by the 6th day of culture. The specificity of the action of cytosine arabinoside for the L form of pyruvate kinase is in contrast with the lack of effect observed on total protein synthesis and the activity of the embryonic (M2) form of the enzyme.     

Separation of meso and racemic 2,3-butanediol by aqueous liquid chromatography

Fermentation of xylose by Klebsiella pneumoniae (ATCC 8724) producers meso and nonmeso 2,3-butaneodiol. The enzyme Kinetic of 2,3-butanediol stereoisomer formation from acetone is currently under study in our laboratory. Modeling of these kinetics requires resolution of meso and racemic 2,3-butanediol and positive identification of these resolved components. We report their resolution by aqueous liquid chromatography on both an analytical and a preparative scale. The resolved stereoisomer were identified by a combination of gas chromatography, gas chromatography/mass spectroscopy, ¹³C-NMR spectroscopy, optical activity, and, melting points of the m-dinitrobenzoyl eaters of meso and racemic 2,3-butanediol. An aqueous liquid chromatographic technique for resolving and qualifying major components of a butanediol fermentation mixture in 40 min is presented.     

Is group progressive relaxation training as effective with hyperactive children as individual EMG biofeedback treatment?

This study examined whether group progressive relaxation training was as effective as individual EMG biofeedback training in facilitating the academic achievement and self-control of 45 hyperactive elementary school children. Academic achievement was assessed with the Gates-MacGinities Reading Tests, and self-control was measured with the Nowicki-Strickland and the Teacher Rating scales. Eight sessions were scheduled at weekly intervals. Progressive relaxation was conducted in groups of seven or eight and was induced with a commercial audiocassette program. EMG training augmented frontalis biofeedback with those taped exercises. A placebo group listened to taped children's stories. Multivariate analysis of variance indicated no significant differences among the three contrast groups when all dependent variables were considered together. However, univariate F values and discriminant analysis disclosed locus of control to be significantly more internal for the progressive relaxation condition. Also, differences between the two relaxation and the placebo groups, though not statistically significant, were all in the expected direction. While the relative efficacy of group progressive relaxation could not be established conclusively, the data appeared sufficiently positive to warrant further investigation of this cost-effective prospective intervention.The opinions expressed by the authors are not necessarily those of their respective institutions.     

Cooperativity of ligand binding as a function of monomer-dimer equilibrium parameters and acceptor concentration

A general monomer-dimer equilibrium system involving ligand interactions ispresented. Cooperativity features of specific limited models are analyzed by selecting the appropriate family of equilibrium constants from this general scheme. Each system is then characterized in terms of Hill coefficient dependency on alterations in values of equilibrium constants and total acceptor concentration. This method permits comparison of predicted cooperativity trends between systems. Contrasting reports concerning cooperativity dependencies for certain defined equilibrium systems are compared and the discrepancies resolved. Characteristics of cooperativity binding patterns are shown to include symmetry about dimerization association constant values, both positive and negative cooperativity for a single set of parameters, and significant changes in cooperativity features with relatively small changes in equilibrium parameters.