Factors affecting male-production in Hydatina

Ohne Zusammenfassung

---

Factors affecting male-production in Hydatina

     

Atx1-like chaperones and their cognate P-type ATPases: copper-binding and transfer

Copper is an essential yet toxic metal ion. To satisfy cellular requirements, while, at the same time, minimizing toxicity, complex systems of copper trafficking have evolved in all cell types. The best conserved and most widely distributed of these involve Atx1-like chaperones and P_1B-type ATPase transporters. Here, we discuss current understanding of how these chaperones bind Cu(I) and transfer it to the Atx1-like N-terminal domains of their cognate transporter.     

Legionella pneumophila in Cooling Towers: Fluctuations in Counts, Determination of Genetic Variability by Pulsed-Field Gel Electrophoresis (PFGE), and Persistence of PFGE Patterns

The concentrations of Legionella pneumophila in cooling towers may vary considerably over short periods of time, producing significant fluctuations throughout the year. Despite genetic variability, in small geographical areas the same indistinguishable pulsed-field gel electrophoresis patterns may be shared among different cooling towers and persist over time.     

Chloride cell responses to long-term exposure to distilled and hard water in the gill of the armored catfish, Hypostomus tietensis (Loricariidae)

The morphological changes in the gill chloride cells of the armored catfish, Hypostomus tietensis , were investigated after 15 days' exposure to either distilled or hard water. The thickness of the water–blood barrier in the lamellae increased significantly in fish kept in distilled water due to the high proliferation of chloride cells. The apical surface of about 68% of chloride cells was sharply reduced by the development of an apical crypt with a sponge-like surface, although no change in the chloride cell fractional area was found. In contrast, H. tietensis kept in Na⁺, Cl⁻ and Ca²⁺ rich water displayed no significant changes in the number of chloride cells or in their apical surface morphology compared with the control fish. Chloride cell response to ion challenge in H. tietensis suggested the involvement of different strategies to maintain homeostasis in ion-poor water, which may be related to the life history of species.     

The assessment of total energy expenditure of female farmers under field conditions.

The paper reviews methods, and their difficulties, in the measurement of the daily energy expenditure of rural women under field conditions in developing countries. Since all methods need to be validated against a reference method which is usually based on indirect calorimetry, examples of the use of this technique are given. The energy costs of most agricultural and daily tasks of rural women in developing countries have been measured. Large intra- and inter-individual variations in the cost of a single activity occur, so repeated measurements are needed to obtain a valid mean energy cost for a specific activity for a homogeneous group of individuals. Much work remains to be done on the assessment of the duration and the intensity of the physical activity of the rural adolescent and adult female population. Studies indicate that the workload of most rural women in developing countries is excessive and frequently associated with acute poverty.     

SV40 immortalizes myogenic cells: DNA synthesis and mitosis in differentiating myotubes

Primary skeletal muscle myoblasts have a limited proliferative capacity in cell culture and cease to proliferate after several passages. We examined the effects of several oncogenes on the immortalization and differentiation of primary cultures of rat skeletal muscle myoblasts. Retroviruses containing a SV40 large T antigen (LT) gene very efficiently immortalize myogenic cells. The immortalized cell lines retain a very high differentiation capacity and form, in the appropriate culture conditions, a very dense network of muscle fibers. As in primary culture, cell fusion is associated with the synthesis of large amounts of muscle-specific proteins. However, unlike normal myoblasts (and previously established myogenic cell lines), nuclei in the multinucleated fibers of SV40-immortalized cells synthesize DNA and enter mitosis. Thus, withdrawal from DNA synthesis is not obligatory for cell fusion and biochemical differentiation. Using a retrovirus coding for a temperature-sensitive SV40 LT, myogenic cell lines were produced in which the SV40 LT could be inactivated by a shift from 33 degrees C to 39 degrees C. The inactivation of LT induced massive cell fusion and synthesis of muscle proteins. The nuclei in those fibers did not synthesize DNA, nor did they undergo mitosis. This approach enabled the reproducible establishment of myogenic cell lines from very small populations of myoblasts or single primary myogenic clones. Activated p53 also readily immortalized cells in primary muscle cultures, however the cells of eight out of the nine cell lines isolated had a fibroblastic morphology and could not be induced to form multinucleated fibers.     

Acclimatation sur la côte d'azur et en corse deSerangium parcesetosum [Col.: Coccinellidae] prédateur de l'aleurode des citrus,Dialeurodes citri [Hom.: Aleyrodidae]

Résumé La CoccinelleSerangium parcesetosum Sicard originaire de l'Inde a été importée en France en 1985 de Géorgie soviétique où elle avait été introduite pour lutter contre l'Aleurode des CitrusDialeurodes citri Ashmead. Les premiers lachers ont été effectués sur la C?te d'Azur et en Corse où elle semble désormais bien acclimatée.