Effect of psoralen-induced photodermatitis on tryptophan metabolism in rats

Tryptophan metabolism ‘via kynurenine’ has been studied in rats before and after induction of experimental light-conditioned dermatitis with psoralen. Tryptophan load in animals during the acute phase of dermatitis (one day after induction) causes a markedly increased urinary excretion of total metabolites in comparison with that obtained before dermatitis. During this phase of the skin disease tryptophan pyrrolase activity is significantly increased and kynureninase activity significantly decreased in liver in respect to the control animals. Kynurenine aminotransferase activity shows no significant variations in both liver and kidneys. After 6 days of dermatitis, when the skin damage is in repair, both the excretory values of the urinary metabolites after L-tryptophan load and the enzymic activities are similar to those before dermatitis.     

Longevity and fecundity in the colorado potato beetle, Leptinotarsa decemlineata

Longevity, egg production and sensitivity towards induction of diapause of two laboratory cultures of Leptinotarsa decemlineata Say, the Colorado potato beetle, were compared. One culture was kept ab ovo under long-day conditions (LD: 16 hr photophase; 25°=LD culture); the other was raised ab ovo in short-day condition (SD: 10 hr photophase; 25°), kept in diapause during 9 months at 25° in dry sand and after termination of diapause brought to LD (=DP-LD culture). During 97 days, there were no significant differences in the longevities of the cultures (50% mortality: day 52 in DP-LD; day 58 in LD). The survival curve of each was almost linear, which is rather unusual in animals. If the regression line, representing each survival curve was linearly extrapolated beyond day 97 (end of experiment), a theoretical maximal life span of 121 days was found for the LD culture, and of 110 days for the DP-LD culture. Beetles did not enter a second diapause as easily as the first. The haemolymph protein pattern of old animals that had ceased reproduction was almost similar to that of young reproducing animals. In both cultures, the last egg was laid at day 86. Mated females produced 30–60 eggs per day as compared with virgin females which produced less than ten per day. Application of JH 1, 20-hydroxyecdysone, prostaglandin E₂, haemolymph or brain extracts of females did not increase egg production in virgins.

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Résumé La longévité, la fécondité et la sensibilité à l'induction de la diapause ont été comparées chez deux souches de laboratoire du doryphore, Leptinotarsa decemlineata. Une souche a été conservée ab ovo en jours longs (LD: 16 h de photophase; 25°=LD culture). L'autre souche a été élevée ab ovo en jours courts (SD: 10 h de photophase; 25°); elle est restée en diapause pendant 9 mois à 25° dans du sable sec et a été placée en LD après la fin de diapause (= DP-LD culture). Jusqu'au 97ième jour de l'expérience, il n'y avait pas de différence significative entre les longévités des deux souches. Les courbes de survie des deux souches étaient presque rectilignes, ce qui est plutôt rare chez des animaux.En extrapolant linéairement après le 97ième jour (fin de l'expérience) les lignes de régression linéaire correspondant aux deux courbes, une durée de vie maximale théorique de 121 jours a pu être déduite dans la souche LD et de 110 jours pour la souche DP-LD. Aucune différence significative n'a été observée entre les fécondités des deux souches. Le dernier uf a été pondu le 86ième jour. Les doryphores qui avaient déjà été en diapause, n'y retournaient pas aussi aisément que ceux qui n'avaient jamais été en diapause avant leur vie reproductive. Le protéinogramme de l'hémolymphe des animaux âgés ne différait pas de celui des jeunes animaux reproducteurs. Tandis que les femelles accouplées ont pondu 30 à 60 ufs par jour, les femelles vierges n'en ont pas émis généralement plus de 10. L'application d'hormone juvénile 1, de 20-hydroxyecdysone, de prostaglatine E², d'hémolymphe ou d'extraits céphaliques de femelles n'a pas accru la production d'ufs.

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This research was supported by the National Foundation of Scientific Research (N.F.W.O.) of Belgium.     

Rapid effects of nerve growth factor on the Na,K-pump in rat pheochromocytoma cells

Nerve growth factor (NGF) induces neuronal differentiation of rat pheochromocytoma cells (PC12). Here we show that NGF causes a stimulation of Na⁺,K⁺-pump mediated K⁺ influx, with a maximum at 30 min after addition of NGF. The stimulation of the Na⁺,K⁺-pump is completely blocked by the Na⁺-flux inhibitor amiloride (0.2 mM) and can be mimicked by the Na⁺ ionophore monensin. These results suggest that NGF causes a rapid enhancement of Na⁺ influx leading to an activation of the Na⁺,K⁺-pump, a mechanism similar to the action of other growth factors.     

Propidium iodide as a probe for the study of chromatin thermal denaturationin situ

Summary The possibility of using propidium iodide, a phenanthridinic fluorochrome specific for double-stranded nucleic acids, for the study of chromatin thermal denaturationin situ has been examined. Smears of lymphocytes and hepatocyte nuclei from 15-day-old rats were fixed in acetic acid-ethanol (13 v/v), treated with RNAse and submitted to different protein extraction procedures, namely, incubation with pepsin, trypsin and sodium chloride.Denaturation experiments were performed in Sörensen buffer at pH 7.4 containing 10% formamide at temperatures between 27 and 95°C. The samples were stained with propidium iodide and mounted in buffer or glycerol. Measurements were performed with a microfluorometer at a wavelength of 546 nm.The results indicate a higher thermostability of lymphocytes as compared to hepatocytes. The denaturation pattern suggests a certain organization complexity of chromatin, better emphasized by the derivative curves which show the presence of at least three fractions with different melting points. After protein extraction, the denaturation curves exhibit a somewhat simplified pattern, with the disappearance of the most stable peak in the derivative curves. The samples mounted in glycerine exhibit a better stability of staining with time, and an increased quantum efficiency of the fluorochrome with regard to those mounted in buffer.These data confirm the importance of protein-DNA interactions in the organization of chromatin and point to some differences, depending on the cell type and on functional activity.     

Une nouvelle sous-famille,les Poulpinae, et quatre nouvelles espèces de Saitoum radiolaires mésozoiques téthysiens

Studies of skeleton elements of several jurassic species of Saitoum allow to compare them with Poulpus from Trias. The sub-family Poulpinae is introduced, caracterised by three cephalic arcs and the collar position of the cephalic structure. Among the jurassic forms, 4 species are newly described: S. corniculum, S. elegans, S. levium and S. trichylum.