Ultrastructural changes in the Golgi apparatus and secretory granules of HL-60 cells treated with the imino sugar N-butyldeoxynojirimycin

The imino sugar N-butyldeoxynojirimycin inhibits the N-linked oligosaccharide processing enzymes α-glucosidases I and II, and the ceramide specific glucosyltransferase which catalyses the first step in glucosphingolipid biosynthesis. We have studied the effects of this compound on the ultrastructure of HL-60 cells to identify novel activities of this compound. Treatment of HL-60 cells with this imino sugar results in several morphological changes within the cell, none of which result in cytotoxicity. The plasma membrane stains heavily with potassium ferrocyanide within 30 min following addition of the compound to the medium, and there is then a time dependent involvement of all other intracellular membranes. Secretory granules become enlarged and lose their dense core morphology and appear either empty and vacuolated or have low density contents. However, the most striking effect of NB-DNJ treatment is on the Golgi apparatus. The Golgi exhibits a time-dependent change from typical Golgi morphology to a structure almost completely devoid of cisternae and consisting predominantly of vesicles. All the observed changes are fully reversible on withdrawal of the compound.     

Parasitoid vibrations as potential releasing stimulus of evasive behaviour in a leafminer

Abstract. The aim of this study was to characterize the vibratory signals produced by the parasitoid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae) while foraging on apple leaves infested by one of its hosts, the spotted tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera: Gracillariidae).This leafminer changes its behaviour as a function of the parasitoid's behaviour to escape parasitization.We propose that the leafminer uses vibrations triggered by the parasitoid to detect the presence of its enemy.We measured vibrations produced by a foraging parasitoid on a mine with a laser vibrometer.By recording concurrently the behaviour of the parasitoid on video, vibrations could be assigned to particular behaviours.Subsequently, vibrations were characterized by their dominant frequencies and intensities.The behaviours Landing and Take-off both produced strong impact-like vibrations characterized by an initial irregular phase during which frequencies up to 25 kHz occurred followed by a slow decaying regular phase.Vibrations elicited by Moving, Standing and Probing showed no clear temporal pattern.During Probing , dominant frequencies of up to 5.6 kHz were observed frequently at intensities well above the background noise (>10 dB).During Moving and Standing , vibrations were more scarce and of lower frequencies and intensities.Due to their impact-like nature, vibrations produced by Landing and Take-off are probably not specific to the parasitoid.Vibrations produced by Moving and Standing are difficult to detect and not reliable because of their non-specificity.Therefore, only Probing provides a reliable and detectable source of information for the host.The vibrations elicited during Probing could account for the evasive behaviour that is observed in this and other leafminers.     

Pollination ecology of Arum italicum (Araceae)

The pollination ecology of Arum italicum was studied in south-western France. This plant attracts olfactory dung-breeding flies through deceit. These insects are principally represented by Diptera, all belonging to saprophyte families. The volatilization of the odouriferous compounds, responsible for their attraction, is achieved through the production of heat by the appendix. The insects are trapped for 24 h in order to participate in both sexual phases of the protogynous inflorescence. The male flowers produce three heat events during flowering. These peaks of heat seem to be involved in the spathe movements, since they occur during the opening of the inflorescence and the liberation of the insects. The last male heat event may be linked with the liberation of pollen and its dispersion by stimulating trapped flies. According to their frequency and pollen-load, two Psychoda species appear to be the most efficient pollinators ( P. crassipenis and P. pusilla ). Nevertheless, each of the other attracted species could play a significant role under different spatio-temporal conditions. Experiments on self-pollination have shown that obligate cross-pollination is necessary for A. italicum to set seeds. Moreover, hand- and natural-pollinated plants showed similarly high abortion frequencies suggesting that seed set may be more constrained by resources rather than by pollination limitation.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 205–214.     

How did an annual plant react to Pleistocene glaciations? Postglacial history of Rhinanthus angustifolius in Europe

The impact of climate fluctuations during the Pleistocene on the geographic structure of genetic variation in plant populations is well documented, but there is a lack of studies of annual species at the European scale. The present study aimed to infer the history of the widespread European annual Rhinanthus angustifolius C. C. Gmelin (Orobanchaceae). We explored variation in chloroplast DNA (cpDNA) sequences and amplified fragment length polymorphism (AFLP) in twenty-nine populations covering the entire distribution area of the species. Five AFLP groups were identified, suggesting at least two glacial refugial areas: one area in southwestern Europe and one large eastern area in the Balkan/Caucasus. Recolonization of previously glaciated areas mainly took place from the east of Europe. Despite the difference in life-history traits, the patterns found for the annual R. angustifolius show similarities with those of perennial species in terms of genetic diversity and geographic organization of genetic variation. Although organelle markers have typically been preferred in phylogeographic studies, the cpDNA variation in R. angustifolius did not show any clear geographic structure. The absence of geographic structure in the cpDNA variation may reflect persistence of ancestral polymorphisms or hybridization and introgression with closely-related species.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 1–13.     

Partial purification and characterisation of an inhibitor of hepatocyte proliferation derived from nonparenchymal cells after partial hepatectomy.

We have investigated the influences that nonparenchymal cells from regenerating rat liver exert on hepatocyte proliferation. When primary adult rat hepatocytes isolated from resting liver were co-cultured with nonparenchymal cells (NPCs) from resting liver of a different syngeneic animal, the proliferative response of hepatocytes to epidermal growth factor (EGF) was unaffected by the presence of NPCs. In the presence of NPCs taken from livers that had undergone partial hepatectomy 24 hours before (regen-NPCs), the response of hepatocytes from resting liver to EGF, TGF-alpha, and hepatocyte growth factor (HGF) was markedly inhibited. Inhibitory activity was not dependent on cell-to-cell contact, and conditioned-medium from regen-NPCs, but not normal NPCs, inhibited EGF-induced hepatocyte DNA synthesis by approximately 50%. After concentration by gel chromatography and lyophilisation, inhibition was 98%. The inhibitory activity migrated on SDS-PAGE gel electrophoresis with an apparent molecular weight of 14 to 17 kDa and was trypsin-sensitive but relatively heat-stable. The effects of blocking antibodies established that it was not TGF-beta 1, IL1-beta, or IL6. Investigations of regen-NPCs taken at different time points demonstrated that inhibitory activity was released into conditioned medium of cells harvested at 24 and 48 hours after partial hepatectomy, but not 10 or 72 hours. This powerful inhibitor of hepatocyte response to proliferogens is released by cultures of NPCs with a time course suggesting that it may be involved in terminating the surge of hepatocyte replication induced by partial hepatectomy.     

Fusion between vesicles from the pathway of receptor-mediated endocytosis in a cell-free system

Fusion between endocytic vesicles containing 125I-transferrin and ones containing anti-transferrin antibody was monitored by the formation of an immune complex. Fusion required ATP and only occurred between specific populations of vesicles. Cytosol was also required. Trypsinisation of the preparations or pre-treatment with N-ethylmaleimide abolished the fusion reaction.