Factors affecting male-production in Hydatina

Ohne Zusammenfassung

---

Factors affecting male-production in Hydatina

     

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.     

Genetic diversity and molecular fingerprinting of Prunus cerasus var. austera from central Italy

In central Italy, Prunus cerasus var. austera is cultivated as small stands or scattered trees in marginal areas for the production of jam and wine. Thanks to the healthy attributes of its products and its ability to grow in different environmental conditions, this variety has gained new interest in the development of marginal areas. We assessed the level of the genetic variability of P. cerasus var. austera germplasm from central Italy and identified a ‘core collection’ representative of the present genetic diversity. A total of 161 trees, morphologically identified as var. austera, and one tree, identified as var. caproniana were collected and genotyped by 14 SSRs. Two individuals provided by a commercial plant nursery, one of P. cerasus var. caproniana and one of P. cerasus var. austera, were used as control. Thirteen SSRs presented private alleles in austera. Seven individuals morphologically identified as austera revealed private alleles specific to caproniana. The PCoA and Bayesian clustering analysis showed a main genetic group including var. austera, while a second group included all the caproniana-like genotypes. A core collection of 31 trees (46% of austera genotypes) was selected. This study can be considered as a starting point for future investigations on this variety.     

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.     

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.     

Characterization and localization of cis-diamminedichloro-platinum(II) adducts on a purified oligonucleotide containing the codons 12 and 13 of H-ras proto-oncogene.

The use of substrates containing well defined adducts at precise sites, is required to perform a careful analysis of the toxic and mutagenic potential of a lesion. As a first step in this direction the octamer 5'-d(CCGGCGGT), containing the sequence of the codons 12 d(GGC) and 13 d(GGT) of the human H-ras gene, was reacted with the antitumoral drug cis-diamminedichloroplatinum(II). The platinated products have been purified by HPLC. A first set of experiments, including enzymatic digestions with nuclease P1 followed by alkaline phosphatase and acid-catalysed hydrolysis, allowed us to determine which bases were engaged in the cis-DDP lesions. Our results indicate that only guanine residues were chelated with cisplatin to yield bifunctional adducts. Furthermore, by performing enzymatic digestions with phosphodiesterases, we have located the adducts with respect to the 5' end of the octamer. Among the purified and characterized platinated oligonucleotides, three present a particular interest, since we have shown here that the cis-d(GpG) adduct is precisely situated either at the d(GGC) or at the d(GGT) or at both sites of their sequence.     

Sucrose-Modulated Morphogenesis in Anagallis arvensis L.

Sucrose was found to have a modulating effect on the morphogenesisof Anagallis arvensis L. leaves cultured in a Murashige-Skoogmedium. Root formation and growth seem to be more independentthan other morphogenetic expressions. Roots formed without exogenoussugars at 25°C but sucrose seemed to be necessary at 32and 35°C. Sucrose at 3% improved shoot formation at 25°Cand had an inhibitory effect at 6%concentration and 35°C.Shoot growth (internode length) is inhibited by sucrose concentrationshigher than 3%. Sucrose could also replace light irradiancein regulating shoot and leaf growth. A higher sucrose concentration,than that required for roots and shoots formation, is necessaryfor flower and fruit formation, but sucrose could not replacethe photoperiod requirement for flowering in culture medium. (Received June 17, 1985; Accepted December 24, 1985)