Synergism of v-myc and v-Ha-ras in the in vitro neoplastic progression of murine lymphoid cells.

Murine bone marrow was either singly or doubly infected with retroviral vectors expressing v-myc (OK10) or v-Ha-ras. The infected bone marrow was cultured in a system that supports the long-term growth of B-lineage lymphoid cells. While the v-myc vector by itself had no apparent effect on lymphoid culture establishment and growth, infection with the v-Ha-ras vector or coinfection with both v-myc and v-Ha-ras vectors led to the appearance of growth-stimulated cell populations. Clonal pre-B-cell lines stably expressing v-Ha-ras alone or both v-myc and v-Ha-ras grew out of these cultures. In comparison with cell lines expressing v-Ha-ras alone, cell lines expressing both v-myc and v-Ha-ras grew to higher densities, had reduced dependence on a feeder layer for growth, and had a marked increase in ability to grow in soft-agar medium. The cell lines expressing both oncogenes were highly tumorigenic in syngeneic animals. These experiments show that the v-myc oncogene in synergy with v-Ha-ras can play a direct role in the in vitro transformation of murine B lymphoid cells.     

Convenient,laboratory procedure for producing solid d-arabino-hexos-2-ulose (d-glucosone)

The production of solid d-arabino-hexos-2-ulose (d-glucosone) from d-glucose by use of an enzyme, pyranose-2-oxidase (EC 1.1.3.10), is described. The enzyme is extracted from the mycelia of Polyporus obtusus, partially purified, and then immobilized on activated CH-Sepharose 4B. The enzymic conversion of d-glucose into d-glucosone is simple and convenient, and provides a product free from residual d-glucose. Lyophilization of the filtered reaction-solution yields the product, solid d-glucosone. Assay methods have been developed for monitoring the enzymic reaction and evaluating the purity of the final product.     

Light-limited growth of two strains of the marine diatom Phaeodactylum tricornutum Bohlin: Chemical composition,carbon partitioning and the diel periodicity of physiological processes

Two isolates of the marine pennate diatom Phaeodactylum tricornutum Bohlin were grown in semi-continuous, nutrient-sufficient culture at varying irradiances on a 12-h light, 12-h dark illumination cycle. The reponse of the isolates to varying degrees of light limitation differed with respect to all of the compositional parameters measured, including growth rates, elemental composition, chlorophyll content, and the partitioning of cellular carbon into four biochemical classes: proteins, lipids, polysaccharides, and low-molecular weight intermediates. The isolates also differed with respect to the relative contributions of light-period and dark-period uptake to the total uptake of ammonium and phosphate ions, although in all cases uptake took place at a reduced rate in the dark. They did not differ with respect to the diel periodicity of cell division, chlorophyll synthesis, and biochemical synthesis. Slightly more cell division took place during the dark period than during the light period. The specific rate of chlorophyll synthesis in the light period, when expressed as a function of irradiance, saturated rapidly; the rate was nearly constant for all irradiances > 100 βE · m^?2 · s^?1. Chlorophyll synthesis in the dark was positively correlated with irradiance over the entire range of irradiances, except where photoinhibition was involved. Protein was synthesized in both the light and dark periods, but at a reduced rate in the dark. Polysaccharides were synthesized during the light period and consumed during the dark period. Lipids and low molecular weight intermediates were synthesized during the light period, but showed little net change during the dark period.     

Expression of terminal deoxynucleotidyl transferase in human thymus during ontogeny and development

Expression of the enzyme terminal deoxynucleotidyl transferase (TdT) was studied in human thymus during ontogeny and development. In five fetal thymus samples, the enzyme activity was barely detectable. At birth, the terminal transferase activity remained low. Maximum expression of the enzyme activity occurred between 10 and 40 mo of age. Analysis of six other enzyme activities, adenosine kinase, deoxyadenosine kinase, AMP deaminase, dAMP deaminase, 5' nucleotidase, and adenosine deaminase confirmed the normal status of the thymic tissue. A careful analysis of thymic architecture revealed that involution did not occur as a result of the disease process that necessitated cardiac surgery. By immunofluorescence, the TdT antigen was localized exclusively in the nucleus of cortical thymocytes. Protein immunoblotting studies indicated that human thymic terminal transferase exists as a single high m.w. species in individuals under 30 mo of age. Thereafter, a variant m.w. species is detectable. The increase in expression of this enzyme coincides with the increase observed in serum immunoglobulin levels during maturation and precedes the maximum development of the human thymus.     

Some properties of hepatic glycerol kinase and their relation to the control of glycerol utilization

1. Glycerol kinase (EC 2.7.1.30) is shown to catalyse a non-equilibrium reaction in rat liver; and, as it is the first enzyme in the pathway metabolizing glycerol, its properties may be pertinent to the metabolic regulation of glycerol uptake and utilization by this tissue. 2. The properties of hepatic glycerol kinase were studied by using a radiochemical technique to measure the enzyme activity. When the concentration of ATP is low the activity of glycerol kinase is inhibited by high concentrations of glycerol; but when the concentration of ATP is high there is no inhibition and the double-reciprocal plot is linear, providing a K(m) for glycerol of 3.16x10(-6)m. Glycerol kinase is activated by high ATP concentrations provided that the concentration of the second substrate (glycerol) is high; at low concentrations of glycerol ATP does not activate the enzyme so that the double-reciprocal plot is linear, providing a K(m) for ATP of 5.8x10(-5)m. It is suggested that these kinetics may be explained by a model similar to that described by Ferdinand (1966) for phosphofructokinase. 3. Hepatic glycerol kinase is inhibited by ADP and AMP, and raising the Mg(2+) concentration increases the inhibition by these two compounds; this suggests that ADP-Mg(2+) and AMP-Mg(2+) complexes are the inhibitory species. The physiological significance of these inhibitions may be to prevent phosphorylation of glycerol when the hepatic ATP concentration is low. It is suggested that this inhibition may provide an approach to the problem of measurement of rates of lipolysis by glycerol release in tissues that contain glycerol kinase (e.g. liver, kidney, muscle, adipose tissue). 4. Hepatic glycerol kinase is inhibited by l-3-glycerophosphate competitively with respect to glycerol. The physiological significance of this inhibition may be that factors that change the intracellular concentration of l-3-glycerophosphate could change glycerol uptake by the tissue. Thus it is suggested that thyroxine treatment or feeding rats on a diet high in glycerol, which increase the activity of glycerophosphate oxidase in liver and kidney cortex respectively, lead to an increased glycerol uptake through a decrease in the concentration of glycerophosphate in these tissues. It is known that ethanol administration decreases glycerol uptake by liver, and this can be explained by the increased concentration of l-3-glycerophosphate causing inhibition of glycerol kinase.     

Microbiological Evaluation of Pacific Shrimp Processing

Microbiological evaluation of Pacific shrimp (Pandalus jordani) processing was made from samples obtained at five key processing points. The microbial count of raw shrimp ranged from 1.3 x 10(6) to 3.0 x 10(6). The initial microbial flora, in order of predominance, was Acinetobacter-Moraxella, Flavobacterium, Pseudomonas, gram-positive cocci, and Bacillus species. No yeasts were isolated. Differences in processing practices influenced both microbial count and the shrimp flora. The microbial load, however, always increased after peeling and sorting operations and decreased after cooking, washing, and brining steps. Significantly, the gram-positive cocci were recovered with increasing frequency after each processing step, reaching 76% of the total load in a final product. Most of them, however, were coagulase-negative.