A New Medium for the Detection and Enumeration of Clostridium perfringens in Foods

S ummary . This paper describes the development and use of a selective diagnostic medium for the detection and enumeration of Clostridium perfringens in foods. The medium gives higher counts of Cl. perfringens and fewer false positives than existing media.     

Hot-water treatment before tissue culture reduces initial contamination in Lilium and Acer

Plant Cell, Tissue and Organ Culture (PCTOC) -     

1,25-Dihydroxyvitamin D3 enhances the growth of tumors in athymic mice inoculated with receptor rich osteosarcoma cells

We tested the influence of daily subcutaneous injections of 12.5 and 25 pmol of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the growth of tumors arising from intracutaneous inoculations of athymic nude mice with rat osteogenic sarcoma cells (ROS) and human melanoma cells. Both doses of 1,25(OH)2D3 increased plasma calcium levels after 3 weeks and produced a striking enhancement in tumor weight when the mice received 1,25(OH)2D3 receptor-rich ROS17/2.8 cells. In contrast, 1,25(OH)2D3 caused no consistent effect on tumor weight in mice given G-361 melanoma cells with low receptor copy number or receptor deficient ROS 24/1 cells. Thus, 1,25(OH)2D3 stimulated tumor growth in a receptor dependent fashion, in vivo, instead of inhibiting it as predicted from the reduction of proliferation of cultured cells in the presence of 1,25(OH)2D3.     

Electric birefringence of eukaryotic ribosomes

Eukaryotic 60S ribosomal subunits were studied by transient electric birefringence. Conformations of subunits in active and inactive states upon changes in magnesium concentration were compared by electric birefringence and orientational relaxation time measurements. Active subunits exhibit a positive birefringence and a relaxation time of the order of 8 microseconds. In the presence of EDTA, inactive subunits show no birefringence. When Mg2+ is reverted in the cold to its initial level, the electro-optical properties of the subunits are partially restored although the particles remain biologically inactive.     

Beak and radula growth in Octopus vulgaris

The dry weight and the crest length of the upper and lower beak, the length of the radula ribbon, the average width of the base of the six proximal and distal rachidian teeth as well as the total number of these teeth have all been related to the live body weight of octopuses between 1.1 and 4440 g. From any one of these parameters it is possible to estimate the size and approximate age of the animal.     

An argument for the existence of a natural complex between protein L5 and 5 S RNA in rat liver 60-S ribosomal subunits

Electrophoresis of the 60-S ribosomal subunits from rat liver in the presence of citrate ions removes the 7 S ribonucleoprotein complex between protein L5 and 5 S RNA though this complex is not released by dialysis or by centrifugation through a sucrose cushion in the same buffer. Using acetate instead of citrate, the subunits remain intact in all cases. On the other hand, in the presence of EDTA, the complex is always released. The poly(U) directed polyphenylalanine synthesis is correlated in each case with the presence of this complex within the subunits. The melting curves of subunits which have been treated with citrate, acetate or EDTA and then taken back in the buffer in which they were stored suggest that the specific RNA-protein interactions are preserved in the presence of acetate and of citrate but not of EDTA. As a whole, the results support the interpretation that the association of protein L5 and 5 S RNA exists within the active subunits.     

Influence of agents that affect intracellular calcium regulation on progesterone secretion in small and large luteal cells of the sheep

Enriched fractions of small and large luteal cells were incubated for 2 h with 1 or 10 microM calcium ionophore, A23187: unstimulated secretion of progesterone and viability in small cells were not affected but these measures were decreased (P less than 0.01) for unstimulated large cells and were significantly correlated (P less than 0.05). This effect in large cells was independent of extracellular calcium. Therefore, incubations of the two cell types were made in the presence of increasing concentrations of a protein kinase C activator, phorbol 12-myristate 13-acetate (TPA). Secretion of progesterone and viability were not augmented in unstimulated small cells, but TPA prevented (P less than 0.05) the full stimulation of secretion of progesterone by LH. Secretion of progesterone in unstimulated large cells was inhibited (P less than 0.01) by TPA (100 nM and 10 microM), although viability was unaffected. The non-tumour promoting phorbol ester, 4 alpha-phorbol didecanoate, had no effect on large cells. Extracellular calcium was not required for the observed effect of TPA. Sphingosine, an agent inhibitory to protein kinase C activity, inhibited (P less than 0.01) secretion of progesterone in small and large cells, and also reduced (P less than 0.01) cell viability. These values were significantly correlated (P less than 0.05) in both cell types. The above observations suggest that protein kinase C may invoke negative regulation on progesterone production in unstimulated large and hormone-stimulated small luteal cells of sheep. Since sphingosine significantly reduced viability in small and large cells and ionophore selectively inhibited viability in large cells, the ability of these agents to influence calcium-mediated intracellular regulation of steroidogenesis is still uncertain.