Influence of amphotericin B on leucine uptake in 3T3 cells

By studying the effect of leucine competitors we found that activation of the specific leucine-transport system underlies the enhancement of leucine uptake in mouse 3T3 fibroblast cells induced by sublethal doses of Amphotericin B (synergic effect). The relation of the antibiotic activity and the alteration of the membrane cholesterol interaction with lipids is discussed.     

Supernumerary chromosome system,C-banding pattern characterization and multiple nucleolus organizer regions in Moenkhausia sanctaefilomenae (Pisces,Characidae)

Chromosomes of Moenkhausia sanctaefilomenae (10 males and 20 females) collected from a tributary of the Tietê River (Botucatu, S.P. Brazil) were examined using kidney and testicular cells. Both males and females presented 2n=50 chromosomes and 1 to 8 small supernumerary microchromosomes. C-banding demonstrated positively stained heterochromatic blocks in almost every chromosome and a pattern of interstitial bands located in the same position in relation to the centromere on the long arm of a large number of chromosomes. Two large NORs were detected in pair 19 of all the silver-stained metaphases; zero to 6 additional small NORs were detected in other chromosomes. A general survey of the occurrence of supernumerary chromosomes in fishes is presented.     

Isolation and partial characterization of a protein kinase NII from wheat germ chromatin

A protein kinase, type NII, has been purified from wheat germ chromatin. The enzyme, which uses both ATP and GTP as phosphoryl donors, catalyzes the phosphorylation of casein, phosvitin and E. coli RNA polymerase, but not of histone proteins. Polypeptide bands at 46 kDa, 37 kDa and 25 kDa were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autophosphorylation of the 25 kDa subunit was observed following incubation of the purified kinase with (-³²P)ATP and (-³²P)GTP.     

Inhibition of MEL cells' capacity to undergo erythroid differentiation by chemicals added during induction

Erythroid differentiation of murine erythroleukemia (MEL) cells, as induced by dimethyl sulfoxide, can be suppressed by chemicals at very low concentrations, not affecting cell viability and proliferation, if present in the culture medium between 18 and 24 h after addition of the inducer. The effect is apparent on the progeny of the treated cells and is determined, between day 3 and 5 following DMSO induction, as percent value of cells expressing the erythroid phenotype. Cultures showing decreased values are no longer terminal and a large number of clones, incapable of expressing the erythroid phenotype, can be isolated from them. In contrast, induced cultures are terminal if the added chemicals do not decrease the expression of the erythroid phenotype. Incorporation of thymidine into induced cultures reveals that maximal sensitivity of MEL cells to chemicals coincides with DNA duplication. In all affected cells, the inhibition to undergo erythroid differentiation is transmitted from one cell generation to the next.     

Spermatophore development and sperm ultrastructure inCraterostigmus tasmanianus (Chilopoda,Craterostigmomorpha)

 Spermatophore development and ultrastructure of the mature sperm of Craterostigmus tasmanianus were studied using light and electron microscopy. In C. tasmanianus, as in the Scolopendromorpha, the spermatophore develops within the vas deferens. The latter consists of three parts, each with a different morphology. The first may be involved in guiding the sperm to roll up into typical ring-like structures, while the other two, which show an evident secretory activity, secrete the acellular wall of the spermatophores. The ultrastructure of mature spermatozoa showed that a very close similarity exists between Craterostigmomorpha and Lithobiomorpha, especially regarding the organization of the connecting piece. Based on this similarity, we consider the Craterostigmomorpha together with the Scolopendromorpha, Geophilomorpha and Lithobiomorpha (=Pleurostigmophora) to be the sister group of the Scutigeromorpha. Accepted: 2 June 1996     

Sex chromosome polymorphism and heterogametic males revealed by two cloned DNA probes in the ZW/ZZ fish Leporinus elongatus

In order to study the divergence of teleost sex chromosomes, subtractive cloning was carried out between genomic DNA of males and females of the rainbow trout (XX/XY) and of Leporinus elongatus (ZW/ZZ). Inserts cloned in a plasmid vector were individually tested on Southern blots of DNA of males and females for sex specificity. No sex-specific insert was obtained from trout, but two out of ten inserts cloned from L. elongatus showed sex-specific patterns in this species: one corresponds to a sequence present on both Z and W chromosomes, while the other is W specific. Sequences of these two inserts show neither clear homology with other known sequences, nor an open reading frame. They cross-hybridize with the genomic DNA of Leporinus friderici, but without sex-specific patterns. Twenty-four L. elongatus adults were sexed by gonadal observation, chromosomed examination and Southern hybridization with one or the other insert. Ten males and 11 females had chromosomes and hybridization patterns typical of their sex. One ZW female was recognized as a male with the W-specific probe. This was also the case for two unusual ZW males, one having a male hybridization pattern with the other probe. These three atypical individuals may result from single genetic exchanges between four regions of the Z and the W, giving rise to three atypical W chromosomes. Finding males with such atypical heterochromosomes in a female heterogametic species may indicate that a gradual transition occurs between the heterogametic systems.     

An Ultrastructural Investigation on Vitellophage Invasion of the Yolk Mass during and after Germ Band Formation in Embryos of the Stick Insect Carausius morosus Br.

Developing embryos of the stick insect Carausius morosus were examined ultrastructurally with a view to studying vitellophage invasion of the yolk mass during and after germ band formation. Newly laid eggs in C.morosus have a unique yolk fluid compartment surrounded by a narrow fringe of cytoplasm comprising several small yolk granules. Vitellophages originate mainly from a thin layer of stem cells, the so-called yolk cell membrane, interposed between the germ band and the yolk mass. Throughout development, a thin basal lamina separates the yolk cell membrane from the overlying embryo.
Vitellophages extend from the yolk cell membrane with long cytoplasmic processes or filopodia to invade the central yolk mass. Along their route of entrance, filopodia engulf portions of the yolk mass and sequester it into membrane-bounded granules. As this process continues, the yolk mass is gradually partitioned into a number of yolk granules inside the vitellophages.
Later in development, the yolk cell membrane is gradually replaced by the endodermal cells that emerge from the anterior and posterior embryonic rudiments. From this stage of development onwards, vitellophages remain attached to the basal lamina through long filopodia extending between the endodermal cells. Yolk confined in different vitellophagic cells appears heterogeneous both in density and texture, suggesting that yolk degradation may be spatially differentiated.     

Trypanosoma cruzi glycoprotein of Mr 56000: characterization and assessment of its potential to protect against fatal parasite infections

A ∼ 56 000 Da membrane glycoprotein purified from epimastigotes of Trypanosoma cruzi was characterized biochemically and tested for its efficacy to induce protection in mice from a lethal challenge with this protozoan parasite. Immunofluorescence assays with live and formalin-fixed epimastigotes and trypomastigotes localized the glycoprotein to the flagellum, the body of the parasite, and the cell membrane. Immunoblotting demonstrated the glyco-protein's presence in nearly equal amounts in all developmental stages of several T. cruzi isolates. Mice immunized with the purified glycoprotein and challenged with 10000 infectious trypomastigote forms of isolate Y survived the controls by up to four days. This significant protection makes this antigen a potential candidate for a multi-subunit vaccine against 7. cruzi.