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.     

Purification and characterization of Xenopus laevis type I topoisomerase

A topoisomerase activity was purified from mature ovaries and from nuclei of stage 6 oocytes of Xenopus laevis. From both preparations we obtained a single polypeptide chain having an estimated molecular weight of 67,000. The enzyme purified from ovaries is active in the presence of 150 mM monovalent cation, but its activity is more than 1 order of magnitude higher in the presence of 6 mM Mg2+; the enzyme purified from nuclei requires Mg2+ through all the steps of purification. Enucleated oocytes are devoid of topoisomerase activity but are able to convert the nuclear enzyme to a species active also in the presence of monovalent cations. The difference in ionic requirement between the nuclear topoisomerase and the enzyme purified from ovaries as well as the topoisomerases from other eukaryotic sources, which are most active in the presence of monovalent cations, may depend on the source of the enzyme and/or on the extraction procedure. Ovarian and nuclear topoisomerases catalyze relaxation of both negatively and positively superhelical DNA; the relaxed isomers produced in the presence of Mg2+ have a few positive superhelical turns.     

Membrane interactions between secretion granules and plasmalemma in three exocrine glands

Three types of membrane interactions were studied in three exocrine systems (the acinar cells of the rat parotid, rat lacrimal gland, and guinea pig pancrease) by freeze- fracture and thin-section electron microscopy: exocytosis, induced in vivo by specific pharmacological stimulations; the mutual apposition of secretory granule membranes in the intact cell; membrane appositions induced in vitro by centrifugation of the isolated granules. In all three glandular cells, the distribution of intramembrane particles (IMP) on the fracture faces of the luminal plasmagranule membrane particles (IMP) on the fracture faces of the lumenal plasmalemma appeared random before stimulation. However, after injection of secretagogues, IMP were rapidly clearly from the areas of granule- plasmalemma apposition in the parotid cells and, especially, in lacrimocytes. In the latter, the cleared areas appeared as large bulges toward the lumen, whereas in the parotid they were less pronounced. Exocytotic openings were usually large and the fracture faces of their rims were covered with IMP. In contrast, in stimulated pancreatic acinar cells, the IMP distribution remained apparently random after stimulation. Exocytoses were established through the formation of narrown necks, and no images which might correspond to early stages of membrane fusion were revealed. Within the cytoplasm of parotid and lacrimal cells (but not in the pancreas), both at rest and after stimulation, secretion granules were often closely apposed by means of flat, circular areas, also devoid of IMP. In thin sections, the images corresponding to IMP-free areas were close granule-granule and granule-plasmalemma appositions, sometimes with focal merging of the membrane outer layers to yield pentalaminar structures. Isolated secretion granules were forced together in vitro by centrifugation. Under these conditions, increasing the centrifugal force from 1,600 to 50,000 g for 10 min resulted in a progressive, statistically significant increase of the frequency of IMP-free flat appositions between parotid granules. In contrast, no such areas were seen between freeze-fractured pancreatic granules, although some focal pentalaminar appositions appeared in section after centrifugation at 50 and 100,000 g for 10 min. On the basis of the observation that, in secretory cells, IMP clearing always develops in deformed membrane areas (bulges, depressions, flat areas), it is suggested that it might result from the forced mechanical apposition of the interacting membranes. This might be a preliminary process not sufficient to initiate fusion. In the pancreas, IMP clearing could occur over surface areas too small to be detected. In stimulated parotid and lacrimal glands they were exceptional. These structures were either attached at the sites of continuity between granule and plasma membranes, or free in the acinar lumen, with a preferential location within exocytotic pockets or in their proximity. Experiments designed to investigate the nature of these blisters and vesicles revealed that they probably arise artifactually during glutaraldehyde fixation. In fact, (a) they were large and numerous in poorly fixed samples but were never observed in thin sections of specimens fixed in one step with glutaraldehyde and OsO(4); and (b) no increase in concentration of phospholipids was observed in the parotid saliva and pancreatic juice after stimulation of protein discharge, as was to be expected if release of membrane material were occurring after exocytosis.