Antibiotic sensitivity of the erythromycin-resistant strain E of Rickettsia prowazekii cultured in the vector's body

Experiments on the laboratory cultures of lice infected by Weigl's method revealed that the spontaneous, erythromycin-resistant mutant of R. prowazekii strain E, adapted to the vector's organism, retained its resistance to erythromycin during 50 successive passages without the maintenance concentrations of this antibiotic. The above strain remained sensitive to tetracycline and levomycetin. Its level of sensitivity to the latter antibiotics was similar to that of R. prowazekii strains cultivated in the vector's organism for a long time.     

Oxidised glutathione reductase activity in mouse epidermis: TPA induced change and its modulation by vitamin A

Single cutaneous application of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) increased epidermal oxidised glutathione reductase activity in adult mouse by almost 100%. Pretreatment of animals with vitamin A for a week resulted in 75% inhibition of TPA induced change in the enzyme activity which remained unaffected in skin treated with vitamin A alone. This biochemical change in skin induced by TPA and modulated by vitamin A has been discussed in relation to epidermal hyperplasia.     

Effets de la consanguinité sur des caractères morphologiques quantitatifs chez Culex pipiens autogenicus Roub.

The influence of inbreeding on several morphological characters as proboscis, wings, leg and palp segments was examined in strictly inbred lines of C. pipiens autogenicus, starting with females from a natural population. The results show the importance of ccological conditions, especially temperature, during larval development of the population. We report a progressive average size reduction from the second inbred generation. The length variability increases in practically all cases, depending on the degree of inbreeding, which is often more marked in certain organs. The symmetry regulation is strongly affected. We observe highly significant individual values in the highly inbred generations. The distribution values clearly mark a left/right disturbance. The progression of asymmetry as a function of the degree of inbreeding is more marked in certain organs in the two sexes. The results show the importance of the advantage of heterozygotes.     

The discrimination between Rb+ and K+ by Escherichia coli is changed after bacteriophage T7 infection

Rb+ and K+ have similar chemical properties. They share the uptake systems in Escherichia coli and can replace each other inside the cell. These common features led to experiments in which the radioactive isotope 86Rb was used to trace intracellular K+ fluxes. However, the E. coli pumps discriminate between these two ions and one should thus be cautious using 86Rb+ as a tracer for K+. We now report that T7 infection alters the degree of discrimination in such a way that changes of intracellular Rb+ do not reflect changes of K+. It has been observed that shortly after infection the 86Rb+ level was strongly reduced (Ponta, H., Altendorf, K.-H. and Schweiger, M. (1976) Mol. Gen. Genet. 149, 145-150). In contrast, determination of the K+ content showed no change directly after infection (Kuhn, A., Jütte, H. and Kellenberger, E. (1983) J. Virol. 47, 540-552). The efflux of 86Rb was only evident when Rb+ was used in trace amounts. In media conditions under which intracellular K+ was mainly replaced by Rb+, 86Rb+ efflux was not observed.     

Selective staining of human platelet glycoproteins using nitrocellulose transfer of electrophoresed proteins and peroxidase-conjugated lectins

Platelet proteins (0.5-5 micrograms) were electrophoresed in a one-dimensional or an unreduced-reduced, two-dimensional sodium dodecyl sulfate gel system. The separated proteins were then transferred electrophoretically to nitrocellulose and reacted with peroxidase-conjugated lectins. Visualization of specific glycoproteins which bound the lectins was made by the chromogenic reaction catalyzed by peroxidase utilizing 3,3'-diaminobenzidine as the substrate. Wheat germ agglutinin specifically reacted with and allowed the visualization of glycoprotein Ib. Peanut agglutinin also specifically stained glycoprotein Ib after treatment of the nitrocellulose transferred proteins with neuraminidase. Ricinus communis agglutinin I stained thrombospondin, a 260 kDa protein, and factor VIII. Concanavalin A stained mainly glycoproteins IIb, III, IV, and V. Glycoproteins Ia, Ic, IIa, and other minor glycoproteins could be separated by unreduced-reduced, two-dimensional gel electrophoresis and were stained weakly with wheat germ agglutinin conjugates. These techniques were found to be reproducible as well as easily applied to the analysis and identification of platelet glycoproteins, particularly when dealing with a limited amount of platelets.     

Taste receptor activity and feeding behaviour reveal mechanisms of white spruce natural resistance to Eastern spruce budworm Choristoneura fumiferana

The pattern of feeding of Eastern spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera, Tortricidae) is compared on foliage from white spruce Picea glauca (Moench) Voss. (Pinaceae) trees previously determined to be susceptible and resistant to defoliation by budworm. No differences are observed in electrophysiological responses from taste sensilla to aqueous extracts of the two foliage types, nor is there a preference for either extract type in a choice test. Acetone extracts from the two foliage types are both preferred to a control sucrose solution, although neither elicits a preference relative to the other. These results suggest that there is no difference in phagostimulatory power of internal leaf contents of the two foliage types. Longer‐term observation of feeding behaviour in a no‐choice situation shows no difference in meal duration, confirming the lack of difference in phagostimulatory power. However, on average, intermeal intervals are twice as long on the resistant foliage, leading to an overall lower food consumption during the assay. This result suggests an anti‐digestive or toxic effect of the resistant foliage that slows behaviour and limits food intake. Previous research has shown that waxes of the resistant foliage deter initiation of feeding by the spruce budworm and that this foliage contains higher levels of tannins and monoterpenes. The data suggest that the resistant foliage contains a post‐ingestive second line of defence against the spruce budworm.     

Effects of antimicrotubular agents in cAMP production and in steroidogenic response of isolated rat Leydig cells

In dispersed rat Leydig cells, colchicine was found to stimulate basal cAMP production and testosterone secretion in a dose and time-dependent manner, but to a lesser extent than LH. However, these drugs are unable to stimulate adenylate cyclase activity in plasma membranes isolated from these cells. The amount of testosterone secreted at 150 min under the influence of colchicine and LH added simultaneously was not different from the amount produced during stimulation by LH alone. It is only after exposure of the cells for 1 hr to colchicine that the accumulation of cAMP in response to LH was inhibited; furthermore, both intracellular and medium testosterone accumulation in response to the hormone were reduced. Similar effects were observed with two other alkaloids, vinblastine and podophyllotoxin. The three drugs also inhibited the stimulation of testosterone secretion by 8-Br-cAMP or choleratoxin. These studies suggest that the state of microtubule polymerization and/or tubulin can influence the process of steroidogenesis in rat Leydig cells.