Validity of the nearest-neighbor approximation in the evaluation of the electrophoretic manifestations of DNA curvature

The validity of a theoretical nearest-neighbor model based on conformational energy calculations, for translating the deterministic fluctuations of DNA base sequences in superstructural elements, is tested on the electrophoretic data of 450 multimeric, duplex oligonucleotides with different sequence, periodicity, and complexity, corresponding to all the experimental data so far published. An accurate semiempirical linear relation between the gel electrophoretic retardation and the dispersion of the theoretical curvature was found which allows a prediction of electrophoretic anomalies of DNA tracts, e.g., the cyclic permutation gel assays, with great confidence. Such a pattern of agreement allows the interpretation of the gel electrophoresis retardation as due to an increase of activation energy required in straightening the DNA axis.     

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.     

Synaptosomal phospholipid pool in rabbit brain and its effect on GABA uptake

Rabbit synaptosomes have been used to study the effect of the base-exchange reaction in membrane phospholipids on -aminobutyric acid (GABA) transport in vitro. The uptake of GABA was measured after a base-exchange reaction with ethanolamine, choline, orl-serine and after subsequent displacement of these exchanged moieties from lipid by bases of similar or different structures which were added to the synaptosomal medium. Serine incorporation stimulated GABA transport, but its displacement from membrane lipid by choline or ethanolamine induced an inhibition of GABA transport. Ethanolamine incorporation inhibited GABA transport, but its displacement by serine or choline resulted in stimulation of GABA uptake. Choline incorporation also inhibited GABA transport, although less than ethanolamine. The pool size of synaptosomal phospholipids, presumably involved in GABA uptake, accounted for 0.2 to 10% of the total content of membrane phospholipid. Thus, alteration of phospholipid compositior by exchange of the lipid hydrophilic head-groups influences the extent GABA uptake into rabbit synaptosomes.     

The epoxide hydrolase catalyzed hydrolysis of trans-3-bromo-1,2-epoxycyclohexane. A direct proof for a general base catalyzed mechanism of the enzymatic hydration

The hydrolysis of (±)-$\text{trans}$-3-bromo-1,2-epoxycyclohexane in the presence of rabbit liver microsomes was investigated, and found to yield, beside $\text{c}$-3-bromocyclohexane-$\text{r}$-1,$\text{t}$-2-diol, 2,3-epoxycyclohexanol. It was demonstrated that the latter compound was the only product of the enzymatic reaction, whereas the diol resulted from a non enzymatic hydration in the reaction medium. These data provide the first direct proof for a general base catalysis in the enzymatic epoxide hydration, previously hypothesized on the basis of several lines of indirect evidence, and disprove alternative mechanisms involving protonation of the oxirane oxygen.     

Relationships between polyamine metabolism and RNA synthesis in post-ischemic liver cell repair

In liver cells recovering from reversible ischemia the increase in RNA synthesis by isolated nuclei is preceded by activation of ornithine decarboxylase, leading in turn to an increase in putrescine concentration. Treatment of the animals with 1,3-diaminopropane and putrescine prevents ornithine decarboxylase activation but does not hinder the enhancement of RNA synthesis in post-ischemic liver nuclei; therefore, ornithine decarboxylase activation does not seem to be a necessary prerequisite for the increase in RNA synthesis. Hypophysectomy does not prevent the post-ischemic increases of ornithine decarboxylase and RNA synthesis; but pre-treatment of the animals with cycloheximide—which has a dual effect on the activity of ornithine decarboxylase—abolishes the post-ischemic enhancement of RNA synthesis. In contrast with regenerating liver, changes in ornithine decarboxylase activity and putrescine concentrations in reversible ischemia are not associated to changes in S-adenosylmethionine decarboxylase activity and in spermine and spermidine concentrations that seem to be characteristic of tissues where increases in RNA synthesis are followed by DNA synthesis and cell multiplication.