Critical importance of microsome concentration in mutagenesis assay with V79 Chinese hamster cells.

For optimum mutagensis in V79 Chinese hamster cells, the amount of liver postmitochondrial fraction in the assay was found to be of critical importance, depending on the chemicals being tested. Benzo[a]pyrene (BP) required lower (1-5%) concentrations of the liver 15 000 X g supernatant (S15) from methylcholanthrene pretreated rats for a maximum induction of cytotoxicity and mutagenicity, as determined by 8-azaguanine- and ouabain-resistance. A sharp peak of mutagenicity and cytotoxicity was induced by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol BP) at a concentration of 1% of the S15 fraction. Little or no response was induced by these compounds with the S15 concentrations of more than 10%. Similarly, aflatoxin B1 induced a sharp peak of mutagenicity and cytotoxicity at a concentration of 2% of the liver S15 fraction from Aroclor-pretreated rats. Under the same condition, non-carcinogenic aflatoxin G2 did not induce cytotoxicity and mutagenicity. Analysis of BP metabolites by high-pressure liquid chromatography indicates that with the 30% S15 fraction, more than 80% of BP was metabolized during the first 15 min, while with the 2% S15 fraction, 7,8-diol BP increased continuously throughout the 120-min incubation period, suggesting a strong metabolic competition to rapidly remove BP and 7,8-diol BP with a high concentration of the S15. In contrast with these compounds, N-nitrosodimethylamine induced mutagenicity and cytotoxicity which increased linearly in proportion to the increasing amount of the S15 fraction from phenobarbitone- and Aroclor-pretreated rats. Various nitrosamines with different lipophilicity were examined at a high (30%) and low (2%) concentration of the S15 fraction from Aroclor-pretreated rats, in which ratios of mutation frequencies at 30% and 2% correlated inversely with lipophilicity of the compound. This result suggests that the lipid solubility of test compounds may be one factor which determines the concentration of post-mitochondrial supernatant for optimum mutagenesis.     

Role of adrenergic innervation in experimental renal hypertension

Renal hypertension was induced by ligation of the aorta between renal arteries in rats sympathectomized with 6-hydroxydopamine. In the early phase, equally severe hypertension developed in the denervated group as compared to innervated controls. Later, blood pressure was lower in the denervated rats. Initially, increases in plasma renin were seen in both groups; the levels, however, were markedly lower in the denervated rats. Later, the renin levels were similar and not different from baseline. It is concluded that adrenergic neural activity is not essential in the development of renal hypertension; the maintenance of the chronic state, however, depends in part on adrenergic innervation.     

Epicuticular waxes of two sorghum varieties

The epicuticular waxes of the two sorghum varieties Alliance A and SD 102 have been analyzed, after separation of the leaf blades from the sheaths. The major constituents were found to be free fatty acids but small amounts of esters, aldehydes, alcohols, n-alkanes and sterols were also detected. The typical chain lengths of aldehydes, free alcohols and free fatty acids were C₂₈ and C₃₀.     

Human natural killer cells express VLA-4 and VLA-5, which mediate their adhesion to fibronectin.

Very late Ag (VLA)-3, VLA-4, and VLA-5, belonging to the beta-1 subfamily of integrins, have been recently identified as receptors for different binding regions of fibronectin (FN). We have detected VLA-4 and VLA-5, but not VLA-3, on fresh CD3-, CD16+, CD56+ human NK cells by flow cytometry and immunochemical analyses using mAb directed against beta-1, alpha-3, alpha-4, and alpha-5 subunits. Binding assays, performed on FN-coated plates, showed that NK cells specifically adhere to FN and their binding capacity is increased by MgCl2 but not by CaCl2. Using as inhibitory probes a polyclonal antibody against the beta-1 chain of the human FN receptor, the synthetic peptide GRGDSP, which is able to inhibit cellular adhesion mediated by VLA-5, the CS1 fragment, which contains the principal adhesion site in the IIICS domain recognized by VLA-4, and functional mAb directed against alpha-4 or alpha-5 subunits, we show that both VLA-4 and VLA-5 mediate the adhesion of human NK cells to FN. The expression of these integrin receptors may be relevant for NK interaction with extracellular matrix components and other cell types.     

Preliminary study on the operating variables of SCP production from grape must

Summary The fermentation of grape must by Candida utilis ISS 28 was studied at different substrate concentrations, pH values, and nutrient supplementation in a shaken-flask fermenter, by using a composite design experiment.The experimental biomass yields were fitted to the only statistically significant factors with a mean standard error less than 8%, by using multiple regression analysis.Optimal conditions for maximum cell yield were established by plotting a series of loci at constant biomass yield and then verified experimentally, thus confirming the remarkable accuracy of the model     

The autonomic innervation of rat jugular vein

Summary The autonomic innervation of rat jugular vein was studied using glyoxylic acid fluorescence and acetylcholinesterase histochemical methods. The rat jugular vein is provided with both adrenergic and cholinergic nerve fibers organized in plexuses located at the adventitial-medial border. The existence of these nerve plexuses does not seem to support biochemical findings that suggest a lack of innervation in the rat jugular vein and which propose this blood vessel as a model for the analysis of drug-smooth muscle cell interaction without the interference of neuronal uptake mechanisms.     

Lysis of autologous human melanoma cells by in vitro allosensitized peripheral blood lymphocytes

Summary Peripheral blood lymphocytes (PBL) of melanoma patients were sensitized in vitro with lymphocytes of a single donor or with a pool of lymphocytes of 5–20 different donors. After 6–7 days, the cytotoxic activity of the sensitized PBL was tested against cultured autologous tumor cells and lymphocytes in a ⁵¹Cr-release assay. Tumor lysis was observed in 13 of 16 cases in which patients' PBL (Pt-PBL) were stimulated by a pool of allogeneic lymphocytes and in five out of seven cases when single sensitization was performed. In no case was lysis of autologous normal lymphocytes or blasts seen. Cultivation of Pt-PBL with irradiated autologous tumor cells never led to the induction of lymphocytes cytotoxic to melanoma cells. Lysability by pool-activated autologous Pt-PBL of fresh cryopreserved tumor cells was compared to that of short-term cultured tumor cells, and no significant differences were observed. Cold-target inhibition experiments indicated that the cytotoxicity of Pt-PBL was tumor-restricted since only autologous melanoma cells but not lymphocytes were able to inhibit the reaction. These results indicate that activation of Pt-PBL is necessary in order to elicit or amplify their antitumor activity.     

Nucleotide sequences of the trpG regions of Escherichia coli,Shigella dysenteriae,Salmonella typhimurium and Serratia marcescens

The nucleotide sequences of Serratia marcescens trpG and the corresponding regions of Escherichia coli, Shigella dysenteriae and Salmonella typhimurium trpD have been determined. Analysis of the nucleotide sequence divergence suggests the following evolutionary relationships: Serratia-[Salmonella, (Escherichia, Shigella)]. Partial reconstruction of ancestral nucleotide sequences and subsequent analysis of nucleotide substitutions show that the majority of nucleotide substitutions in the evolution of trp(G)D are transitions that result in a reduction of G + C content. Since most of the nucleotide substitutions are in the third position of codons, bias in synonymous codon usage also reflects G + C content. The trpE-trp(G)D junction in the four organisms is characterized by overlapping translation termination and initiation codons. The relative positions of trpE and trp(G)D thus became fixed in evolution before the fusion of trpG and trpD. Nucleotide sequences representing the fusion of trpG and trpD in Escherichia, Shigella and Salmonella are not more nor less divergent than other portions of the trp(G)D coding sequences.