Ribosomal subunits and ribosomal proteins of Tetrahymena thermophila. Effect of the presence of iodoacetamide during ribosome extraction on the properties of the subunits

Proteolytic degradation of ribosomal proteins occurs during the preparation of subunits of the cytoplasmic ribosomes of the protozoa Tetrahymena thermophila and the isolated subunits are inactive. Addition of 5 mM iodoacetamide to cell suspensions before extraction inhibits proteolytic activity and permits isolation of active subunits. The protein complements of these subunits have been characterized in two different two-dimensional electrophoretic systems, and their molecular weights have been determined.     

Current clinical laboratory practice: investigation of plasma lipids--which tests and when?

Clinical interest in the lipoproteins stems mainly from the association between serum cholesterol concentrations and coronary heart disease. Investigations of lipoproteins should be performed in patients with premature coronary heart disease, with a strong family history of coronary heart disease, or with certain cutaneous stigmata of hyperlipoproteinaemia and when fasting serum samples are seen to be lipaemic. Family studies should be performed in appropriate cases to identify relatives at increased risk of developing coronary heart disease. Patients with conditions known to cause secondary hyperlipoproteinaemia should be investigated if they fall into one of these categories but only after treatment of the underlying condition. Non-specialist laboratories should be able to measure total cholesterol and triglyceride concentrations and high density lipoprotein cholesterol concentrations. Lipoprotein electrophoresis has a limited role in such laboratories and is not necessary as a routine procedure. Specialist laboratories should in addition be able to measure individual lipoproteins and identify apolipoprotein E phenotypes.     

Effects of preparation and fixation on three quantitative fluorescent cytochemical procedures

A series of experiments was undertaken in which cells dissociated from the abdominal lymph nodes of mice were lightly centrifuged into slides and fixed either wet or after drying in 70% ethanol, 1% glutaraldehyde, 1% formaldehyde, or neutral formalin. Three fluorescent cytochemical methods were evaluated: staining of DNA with mithramycin; fluorochroming of basic groups of proteins with brilliant sulfaflavine (BSF); and staining of sulfhydryl and disulfide groups with N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM). In the case of mithramycin, the best results were obtained after fixation in 70% ethanol without drying. Staining of dried preparations fixed in 1% glutaraldehyde also yielded reasonably consistent results, although the fluorescence was lower, and the variability higher, than in the group fixed without drying in 70% ethanol. The use of fixatives containing formaldehyde resulted in fluorescence values of only about one-third those of the other two groups, and the variability of the data was higher. In material stained with BSF, satisfactory results were obtained in preparations fixed without drying in neutral formalin containing mersalyl acid. Other fixatives could be used, but the resulting coefficients of variation were higher than those of formalin-fixed material. Sulfhydryl to disulfide ratios approaching those expected from biochemical evidence were obtained in DACM-stained material only after fixation without drying in neutral formalin containing mersalyl acid. Inverted sulfhydryl-disulfide ratios were observed in material fixed without drying in 70% ethanol; and in dried material fixed in 1% formaldehyde, neutral formalin, or 1% glutaraldehyde.     

Evolution of a multigene family of chorion proteins in silkmoths.

The evolution of the A family of chorion genes was examined by comparing new protein and DNA sequences from the silkmoths Antheraea pernyi and Bombyx mori with previously known sequences from Antheraea polyphemus. The comparisons indicated that the A family and its major subfamilies are ancient and revealed how parts of the genes corresponding to distinct regions of the protein structure have evolved, both by base substitutions and by segmental reduplications and deletions.     

Influence of antibiotics and trace salts on lysine production by arthrobacter globiformis

A hydrocarbon utilizing strain of Arthrobacter globiformis Lb isolated from local soil has been found to yield lysine 3.4 g l^?1, keeping the medium optimal for pH, C- and N-sources. Addition of antibiotics and micronutrients to that optimal media stimulated cell growth and enhanced lysine yield.     

Reconstitution of the fusogenic activity of vesicular stomatitis virus.

Enveloped virus glycoproteins exhibit membrane fusion activity. We have analysed whether the G protein of vesicular stomatitis virus, reconstituted into liposomes, is able to fuse nucleated cells in a pH-dependent fashion. Proteoliposomes produced by octylglucoside dialysis did not exhibit cell fusion activity of the G protein. However, by making use of n-dodecyl octaethylene monoether (C12E8) as the solubilizing agent and by removal of the detergent in two steps, we were able to produce fusogenic G protein liposomes. These G protein liposomes fuse to the BHK-21 cell surface at pH 5.7-6.0 with an efficiency of fusion comparable with that of the parent virus. Physical and chemical analysis revealed that the fusogenic liposomes exhibited a protein to lipid weight ratio of 0.67 and showed an average diameter of 130 nm.