Field Studies on the African Fruit Bat Epomophorus wahlbergi (Sundevall), with Special Reference to Male Calling

Social interactions, site attachment and group cohesion were studied in a free-living colony of Epomophorus fruit bats. Daily activities in an undisturbed colony were recorded. Special attention was paid to the peculiar calling behaviour of courting ♂♂ during the night. Structure and repetition rate of their sounds were analyzed in the laboratory. A special mode of acoustic interaction was found and related to the observed spacing out of calling ♂♂ By following feeding animals in the field and by analysis of their faeces we found that besides fruits they eat special leaves which afford steroidal sapogenins.     

Reproductive Behaviour in Zonocerus elegans (Orthoptera: Pyrgomorphidae) with Special Reference to Nuptial Gift Guarding

Egglaying aggregations, mate fidelity and male and female mate choice and mating behaviour of the African pyrgomorphid grasshopper Zonocerus elegans are described from the field. Several hundred males and females were individually marked at oviposition sites. Pairs remained stable over days, during egglaying and presumably also over the weeks prior to egglaying. In addition to long-term consorting with a female, males may try to obtain inseminations by “footpad”–tactics at oviposition sites. It is suggested that prolonged consorting and repeated copulations increase the female's reproductive output as well as the male's share in it. Our data and the literature indicate that males are involved not only in rival competition but also in a “battle of the sexes” which females are likely to win. The intra– and intersexual “war on two fronts” results behaviourally in elaborate mating tactics and anatomically in highly developed internal female genitalia and male copulatory organs (well known taxonomic characters). This applies not only to grasshoppers but also to other insects and arthropods.     

Localization of beta-glycerophosphatase and Mg++-activated adenosine triphosphatase in a moss haustorium,and the relation of these enzymes to the cell wall labyrinth

Summary Acid phosphatase and ATPase were localized in the bryophyte haustorium and in the surrounding paternal tissue of the gametophyte. Only cells with wall labyrinths are the sites of intense enzyme activity.The reaction products of both enzymes were found to occur in cell organelles, the plasma membrane and particularly in wall inclusions that are supposedly proteinaceous in nature.The intensity of the reaction is proportional to the state of differentiation of the labyrinth. The highest enzyme activity was encountered in the epidermal cells which are furnished with the most elaborate wall labyrinths. Somewhat lower was the activity in the other labyrinth cells with filiform ingrowths.These findings stress the role of the epidermis as an absorptive epithelium, and also show clearly that the enzyme activity associated with the plasma surface is in no reciprocal ratio to the degree of amplification of the surface area.     

Die Struktur der Hoch Endopolyploiden Kerne Im Endosperm von Zea Mays,Das Auffallende Verhalten Ihrer Nucleolen und Ihr Endopolyploidiegrad

Zusammenfassung Die endopolyploiden Kerne des Endosperms von Zea mays enthalten bei 3 eingehend und 10 stichprobenartig untersuchten Sippen durchgehend Chromatinstränge, die sich aus den perlschnurartig gebauten Endochromosomen zusammensetzen. Sie stehen zum Teil netzartig miteinander in Verbindung, so daß sie nicht individuell als Riesenchromosomen kenntlich sind. In ihren Verlauf schalten sich die endomitotisch herangewachsenen knobs in Form kompakter Endochromozentren oder±dichter Ansammlungen von Heterochromomeren ein.Die Endopolyploidisierung führt bei den drei Sippen WF 9, M 14 und WF 9 X M 14 und offenbar auch bei den zehn anderen bis zu 192-Ploidie, ausnahmsweise zu 384-Ploidie.Die Kerne von M 14 erscheinen bei höchstwahrscheinlich gleicher Polyploidiestufe im allgemeinen ärmer an Chromatin als die von WF 9, und auch innerhalb dieser Sippe gibt es analoge Schwankungen kleineren Ausmaßes. Sie beruhen vermutlich auf Spiralisierungseffekten.Sippenspezifische Unterschiede bestehen auch im Vorkommen von Sekundärnucleolen, kleineren Nucleolen, die dicht neben den Hauptnucleolen an den drei endo-nucleolar-organizing bodies entstehen und bei WF 9 häufiger, in höherer Zahl und größeren Dimensionen als bei M 14 auftreten. Bei der Sippe M 14 werden dagegen häufiger und gehäuft Vacuolen aus den Nucleolen ausgestoßen (=freie N.); auch finden sich reichlicher als bei WF 9 zusätzliche kleine Nucleolen in den Chromatinsträngen eingeschaltet oder an ihnen angeheftet (=festsitzende N.). Der Bastard nimmt bezüglich der Sekundärnucleolen eine Mittelstellung zwischen den Elternsippen ein; bezüglich der freien und festsitzenden Nucleolen verhält er sich ähnlich wie M 14, bezüglich der Protuberanzen ähnlich wie WF 9.Die verschiedenartigen Nucleolen—einschließlich der in Ausstoßung begriffenen Nucleolusvacuolen—enthalten RNS, was sich aus der Methylgrün-Pyroninfärbung, kombiniert mit Ribonuclease-Behandlung ergibt.

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The structure of the highly endopolyploid nuclei in the endosperm of Zea mays, their conspicuous nucleolar conditions and degree of endopolyploidy

Summary The endopolypoid nuclei in the endosperm of Zea mays (8 inbred lines and 5 hybrids, 2+1 were investigated intensively) throughout contain strands of chromatin, which are composed of endochromosomes having chromomeric constitution. Some of the strands join laterally and most of them cannot be recognized individually. Inserted within them are endopolyploid knobs of compact heterochromatin or assemblages of heterochromomeres.In the lines WF 9 and M 14, the hybrid WF 9 x M 14 and obviously in the others the largest nuclei are 192 n and exceptionally 384 n.Nuclei of M 14 most likely having the same degree of polyploidy as those of WF 9 seem to contain less chromatin and even within WF 9 there are similar variations; probably they result from different spiralization.The different lines also show specific differences concerning the secondary nucleoli; these are nucleoli developing with endopolyploidization side by side with the main nucleoli at the three endo-nucleolar-organizing-bodies; WF 9 shows them in more nuclei, in higher frequency and in larger dimensions than M 14. In M 14 on the contrary more vacuoles (=free nucleoli) are ejected from the nucleoli and this happens more often; small additional nucleoli are also more abundantly inserted in the chromatin-strands. The hybrid behaves intermediately concerning the secondary nucleoli, more like M 14 concerning inserted and free nucleoli and similar to WF 9 in expulsion of vacuoles.Staining with methylgreen-pyronin and treatment with ribonuclease show the different nucleoli including the ejected vacuoles to contain RNA.

     

Infection of cells with replication deficient adenovirus induces cell cycle alterations and leads to downregulation of E2F-1

Gene products of recombinant replication-deficient adenovirus vectors of the first generation (Ad vector) can induce cell cycle dysregulation and apoptosis after infection in eukaryotic cells. The mechanisms underlying this complex process are largely unknown. Therefore, we investigated the regulation of the pRb/E2F-1 complex, which controls transition from G(0)/G(1) to S phase of the cell cycle. As Ad vector infection results in a decrease in the number of cells in G(0)/G(1) phase of the cell cycle, we observed a decline of the pRb protein level and, surprisingly, also a decrease of the E2F-1 protein and mRNA level in infected cell lines. Furthermore, in contrast to the reduction of cells in the G(0)/G(1) phase we observed increased protein levels of p53 and p21 proteins. However, as experiments in p53 deficient cell lines indicated, the decrease of pRb and E2F-1 is independent of p53 and p21 expression. Moreover, results obtained with Rb deficient cell lines indicated that the reduced E2F-1 expression is independent of pRb. These results suggest that Ad vector-induced cell cycle dysregulation is associated with a specific downregulation of E2F-1 independent of Rb and p53 genomic status of cells.     

RNA interference silencing of the adaptor molecules ShcC and Fe65 differentially affect amyloid precursor protein processing and Abeta generation

The amyloid precursor protein (APP) and its pathogenic by-product amyloid-beta protein (Abeta) play central roles in Alzheimer disease (AD) neuropathogenesis. APP can be cleaved by beta-secretase (BACE) and alpha-secretase to produce APP-C99 and APP-C83. These C-terminal fragments can then be cleaved by gamma-secretase to produce Abeta and p3, respectively. p3 has been reported to promote apoptosis, and Abeta is the key component of senile plaques in AD brain. APP adaptor proteins with phosphotyrosine-binding domains, including ShcA (SHC1), ShcC (SHC3), and Fe65 (APBB1), can bind to and interact with the conserved YENPTY motif in the APP-C terminus. Here we have described for the first time the effects of RNA interference (RNAi) silencing of ShcA, ShcC, and Fe65 expression on APP processing and Abeta production. RNAi silencing of ShcC led to reductions in the levels of APP-C-terminal fragments (APP-CTFs) and Abeta in H4 human neuroglioma cells stably overexpressing full-length APP (H4-FL-APP cells) but not in those expressing APP-C99 (H4-APP-C99 cells). RNAi silencing of ShcC also led to reductions in BACE levels in H4-FL-APP cells. In contrast, RNAi silencing of the homologue ShcA had no effect on APP processing or Abeta levels. RNAi silencing of Fe65 increased APP-CTF levels, although also decreasing Abeta levels in H4-FL-APP cells. These findings suggest that pharmacologically blocking interaction of APP with ShcC and Fe65 may provide novel therapeutic strategies against AD.     

Cold-induced apoptosis of hepatocytes: mitochondrial permeability transition triggered by nonmitochondrial chelatable iron

We previously described that the cold-induced apoptosis of cultured hepatocytes is mediated by an increase in the cellular chelatable iron pool. We here set out to assess whether a mitochondrial permeability transition (MPT) is involved in cold-induced apoptosis. When cultured hepatocytes were rewarmed after 18 h of cold (4°C) incubation in cell culture medium or University of Wisconsin solution, the vast majority of cells rapidly lost mitochondrial membrane potential. This loss was due to MPT as assessed by confocal laser scanning microscopy and as evidenced by the inhibitory effect of the MPT inhibitors trifluoperazine plus fructose. The occurrence of the MPT was iron-dependent: it was strongly inhibited by the iron chelators 2,2′-dipyridyl and deferoxamine. Addition of trifluoperazine plus fructose also strongly inhibited cold-induced apoptosis, suggesting that the MPT constitutes a decisive intermediate event in the pathway leading to cold-induced apoptosis. Further experiments employing the non-site-specific iron indicator Phen Green SK and specifically mitochondrial iron indicators and chelators (rhodamine B-[(1,10-phenanthrolin-5-yl)aminocarbonyl]benzyl ester, RPA, and rhodamine B-[(2,2′-bipyridin-4-yl)aminocarbonyl]benzyl ester, RDA) suggest that it is the cold-induced increase in cytosolic chelatable iron that triggers the MPT and that mitochondrial chelatable iron is not involved in this process.