Comparison of nuclear and polysomal RNA fractions from goat brain

Phenol extracted RNA preparations from highly purified nuclei and polysomes of goat brain were fractionated by chromatography on oligo (dT)-cellulose and analyzed by electrophoresis on agarose-acrylamide composite gels. The electrophoretic profile of the polysomal polyadenylated RNA fraction showed a major band with a molecular weight of about 0.62 × 10⁶, which corresponds to the size of the tubulin mRNA. The nuclear polyadenylated RNA fraction also displayed a single major band, with an estimated molecular weight of 0.76 × 10⁶, which appears to be a potential precursor of tubulin mRNA.     

Ultraviolet light-induced inhibition of small nuclear RNA synthesis

Two apparently distinct types of inhibition of the synthesis of U1, U2, U3, U4, and U5 small nuclear RNA, induced by ultraviolet (UV) radiation, have been described before: immediate and delayed. Our present observation can be summarized as follows: a) neither the immediate nor the delayed inhibition appear to be mediated by the formation of cyclobutane pyrimidine dimers, since they were not prevented by photoreactivating light, in ICR 2A frog cells; b) the inhibition of U1 RNA synthesis, monitored in HeLA cells within the first few minutes after irradiation, extrapolated to a substantial suppression at time zero of postirradiation cell incubation, providing further support for the proposal that the immediate inhibition is a reaction separate from the delayed UV light-induced inhibition of U1 RNA synthesis; c) the transition from the pattern of the immediate inhibition to that of the delayed inhibition (disappearance of the UV-resistant fraction of U1 RNA synthesis and increased rate of inhibition) occurred gradually, without an apparent threshold, within the first 2 hr of incubation after irradiation; and d) the incident UV dose that resulted in a 37% level of residual U1 RNA synthesis (D37) during the delayed inhibition was about 7 J/m2, with an apparent UV dose threshold, and was about 60 J/m2 for the immediate inhibition.     

Mosquito larvae soluble fractions induce DNA synthesis alterations on human mononuclear cells.

Mosquito larvae soluble fractions obtained by molecular exclusion chromatography altered the mitotic rate of several epithelial cell populations in hepatectomised mice, as well as the proliferation of human mononuclear cells (MNC), stimulating or inhibiting them depending on the fraction and dose applied. The effect was also thermolabile, suggesting a proteic nature of the compounds involved. Analysis of cell viability after culture indicated that the extract did not have lethal toxic effects. One fraction with a molecular weight ranging between 12-80 kDa caused only an inhibitory effect. In the present study, we performed further characterisation of this fraction by assaying the effect of new fractions obtained from this one, by the use of a column with a lower molecular weight exclusion range. Assays were performed on the proliferation of adult human MNCs. Our results showed that two out of four of the sub-fractions analysed, with a MW of about 70 and 17 kDa, caused a dose-dependent response, either inhibiting or stimulating MNC proliferation respectively.     

Analysis of antigens from membrane and soluble fractions of Entamoeba histolytica

Axenic cultures of Entamoeba histolytica strains HK-9, HM-1, and Rahman were fractionated to provide plasma membranes, internal, vesiculated membranes, and a soluble cytosol. Each particulate fraction was solubilized and all fractions were analyzed by techniques designed to demonstrate molecular complexity and serologic reactivity. The cytosol contained more antigenic moieties than either membrane fraction; however, the antigens associated with the membranes had very high reactivity and lower nonspecific activity than the cytosol.