Can transposable element copy number distribution parameters be estimated from natural populations of Drosophila melanogaster?

The copy frequency distribution of a transposable element family in a Drosophila melanogaster natural population is generally characterised by the values of the Charlesworths' model parameters α and β (Charlesworth & Charlesworth, 1983). The estimation of these parameters is made using the observed distribution of the occupied sites in a population sample. Several results have been interpreted as due either to the influence of stochastic factors or to deterministic factors (transposition, excision, selection…). The accuracy of this method was tested by estimations performed on samples from simulated populations. The results show that with the sample size usually used for natural population studies, the confidence intervals are too large to reasonably deduce either the element copy number distribution or the values of transposition and excision rate and selective coefficients.     

Specificity of the interaction of furfural with DNA

Furfural or 2-furaldehyde is a dietary mutagen and is present in various frequently consumed food products. The alkaline unwinding assay and protection of cleavage sites from the action of various restriction enzymes was used to study the interaction of furfural with DNA. Alkaline unwinding experiments showed the formation of an increasing number of strand breaks in duplex DNA both with increasing furfural concentration and with time of reaction. Treatment of lambda phage DNA with furfural protected cleavage with restriction endonucleases DraI and SspI but not with ApaI, BssHII and SacII. These results indicate that under the conditions used furfural reacts exclusively with AT base pairs. A minimum of 3-4 consecutive AT base pairs are required for this reaction. This was determined by the use of several restriction enzymes whose hexanucleotide recognition sequences contain subsets of AT base pairs.     

An enzyme with properties similar to those of beta-N-acetylhexosaminidase S is expressed in the promyelocytic cell line HL-60.

Extracts of the human promyelocytic cell line HL-60 contain a form of beta-N-acetylhexosaminidase that is not retained on columns of benzeneboronate-agarose ('phenylboronate-agarose') and has a pI value lower than that of beta-N-acetylhexosaminidase A. It is clearly distinct from beta-N-acetylhexosaminidase A in its behaviour on DEAE-cellulose columns, and it requires a higher concentration of salt for its elution. This 'extra' form has a higher ratio of activity towards 4-methylumbelliferyl beta-N-acetylglucosaminide 6-sulphate and 4-methylumbelliferyl beta-N-acetylglucosaminide than has beta-N-acetylhexosaminidase A and is less stable when heated at 50 degrees C. It has a pH optimum of 4.5 and is therefore not beta-N-acetylglucosaminidase C. Anti-(human beta-N-acetylhexosaminidase alpha-subunit) serum precipitated both beta-N-acetylhexosaminidase A and the 'extra' form, whereas an anti-(beta-subunit) serum precipitated beta-N-acetylhexosaminidase A but not the 'extra' form. Western blotting and immunodetection of polypeptides derived from the 'extra' form revealed a band corresponding in size to mature alpha-subunits. On the basis of this and of its behaviour on isoelectric focusing, chromatofocusing and its kinetic properties, we conclude that the 'extra' form is composed of alpha-subunits and resembles beta-N-acetylhexosaminidase S, the residual form in Sandhoff's disease.     

Detecting base pair substitutions in DNA fragments by temperature-gradient gel electrophoresis.

A vertical gel electrophoresis apparatus is described which can distinguish DNA fragments differing by single base pair substitutions. The system employs a homogenous polyacrylamide gel containing urea-formamide and a temperature gradient which runs either perpendicular or parallel to the direction of electrophoresis. The temperature-gradient system simplifies several features of the denaturant-gradient system (1) and is relatively inexpensive to construct. Eight homologous 373 bp DNAs differing by one, two, or nine base pair substitutions were examined. DNA electrophoretic mobility changed abruptly with the temperature induced unwinding of DNA domains. GC to AT substitutions at different locations within the first melting domain, as well as an AT to TA transversion were separated with temperature gradients parallel to the electrophoretic direction. The relative stabilities of the DNAs observed in the gels were compared to predictions of DNA melting theory. General agreement was observed however complete correspondence was not obtained.     

Basal prostaglandin synthesis by the isolated perfused rat kidney

In order to assess the main characteristics of the prostaglandin (PG) biosynthesis by the isolated perfused rat kidney, the urinary and venous outputs of PGE2, PGF2alpha, 6-keto-PGF1alpha and of thromboxane (Tx)B2 were followed during 120 min after an equilibration period of 30 min. Single pass kidneys were perfused with a Krebs-Henseleit solution added with Polygeline at a constant flow rate providing a perfusion pressure about 90 mm Hg. From the beginning of the study, major differences could be observed in the renal biosynthetic rate of the 4 PG studied which were mainly excreted into the venous effluent. During the perfusion, urinary and venous outputs of PGE2, PGF2alpha and of TxB2 remained stable whereas those of 6-keto-PGF1alpha sharply increased and were found inversely related to the glomerular filtration rate (r = -0.95; p n 0.001). Finally, the urinary and venous outputs of each of the four PGs studied were found positively related. It is concluded that the isolated perfused rat kidney is a valuable preparation for studying the biosynthesis of PGs and that, at least in thi model, the urinary excretion of PGs is a good index of their renal synthesis.     

Effect of alkylated and intercalated DNA on the generation of superoxide anion by riboflavin

Superoxide anion (O ₂ ^.– ) was photogenerated upon illumination of riboflavin in fluorescent light. The rate of O ₂ ^.– formation was stimulated by double stranded DNA but not by denatured DNA or RNA. Depurinated DNA, which was predominantly depleted in guanine residues, did not exhibit the stimulatory effect, indicating an interaction of riboflavin, or active oxygen species derived from it, with guanine bases. Also, the stimulation of O ₂ ^.– photogeneration was not observed with ethidium bromide but was seen with proflavin-intercalated DNA. Since ethidium bromide intercalates preferentially between purines and pyrimidines, and proflavin prefers dA-dT rich sites, these results were interpreted to suggest that the interaction of riboflavin with DNA is mainly with GC or CG base pairs.     

Modulation of rat granulocyte traffic by a surface active agent in vitro and bleomycin injury

Pluronic F68 (F68) is a nonionic surfactant which has been reported to inhibit the in vitro adherence and migration of polymorphonuclear leukocytes (PMN) obtained from some species. We demonstrated similar effects on PMN obtained from rats, with diminished adherence to nylon wool and diminished chemotaxis toward zymosan-activated serum. We then examined the in vivo effects of 12-hr F68 infusion on the injury induced by intratracheal bleomycin instillation (ITB) in rats. When sacrificed 24 hr following injury, rats demonstrated neutrophilia, neutrophil-prominent lung lavage cellularity, and increased lung weights. F68 decreased lavage leukocyte counts and lung weight gain in ITB-injured animals. Lung weights of ITB-injured animals correlated (r = 0.81, P less than 0.001) with logarithmic values of lavage PMN. F68 also enhanced neutrophilia and decreased spleen weight gain in injured animals. The acute effects of F68 on circulating leukocyte counts, osmolality, and total complement were also examined. The data demonstrate that F68 can affect PMN traffic both in vitro and in vivo. The data also confirm the prominence of PMN in lavage fluid early in ITB injury, and suggest that an influx of relatively few PMN is associated with lung weight gain in this model.     

Somaclonal variation as a tool to develop pest resistant plants of Torenia fournieri ‘Compacta Blue’

Callus cultures of Torenia fournieri Compacta Blue were initiated on a modified Murashige and Skoog salt medium (MS) with 2.26 M 2,4-dichlorophenoxyacetic acid. Shoots were regenerated from these cultures using MS medium amended with 2.46 M indolebutyric acid and 8.88 M benzyladenine. These shoot cultures were subjected to two-spotted spidermite (Tetranychus urticae Koch.) and the greenhouse whitefly [Trialeurodes vaporariorum (Westwood)]. Pests were allowed to feed until such time that their populations started to decrease due to lack of food. The remaining live tissue of the Torenia was placed on MS medium amended with 2.28 M zeatin to induce new adventitious shoots and plantlets. Newly regenerated plantlets were acclimated to greenhouse conditions and evaluated for resistance to the pest to which they were subjected in vitro. Highly significant differences in pest numbers were found in somaclones for both the two-spotted spidermite and greenhouse whitefly when compared to control plants. A wide range of variability was observed among the somaclonal population. There were significantly fewer mite eggs laid on plants regenerated from in vitro cultures screened with two-spotted spidermites than on seed sown controls. Regenerants from cultures screened with whiteflies in vitro had fewer eggs, immatures and live adults than controls.Abbreviations BA benzyladenine - IBA indolebutyric acid - 2,4-d 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog salt medium Storrs Agricultural Research Station Scientific Publication 1641.