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L Gauna

Publications and source records attributed to L Gauna.

6 recordsLinked to original sources
PubMed2001

Thiols and polyamines in the potentiation of malathion toxicity in larval stages of the toad Bufo arenarum.

Treatment with exogenous spermidine enhanced acute malathion toxicity during larval development of the toad Bufo arenarum Hensel. The polyamine was rapidly incorporated in the larvae with a subsequent metabolization to putrescine and spermine, which were excreted to the media. Endogenous polyamine levels were not changed by either spermidine or malathion treatments. However, 0.5-mM spermidine modified malathion uptake and bioavailability increasing the concentration of the xenobiotic in the larvae. The amount of reduced thiols was decreased by both compounds, but the depletion was insufficient to induce cytotoxicity. The oxidative degradation of polyamines competes for the pool of reduced glutathione used in the conjugation of malathion in the larvae, thus leading to the reported potentiation of toxicity. Our results suggest that exposure to thiols-depleting agents may induce alteration of organophosphate degradation in amphibian larvae.

Animals↗
PubMed2001

The thymus of the hairless rhino-j (hr/rh-j) mice.

The hairless (hr) gene is expressed in a large number of tissues, primarily the skin, and a mutation in the hr gene is responsible for the typical cutaneous phenotype of hairless mice. Mutant hr mouse strains show immune defects involving especially T cells and macrophages, as well as an age-related immunodeficiency and an accelerated atrophy of the thymus. These data suggest that the hr mutation causes a defect of this organ, although hr transcripts have not been detected in fetal or adult mice thymus. The present study analyses the thymus of young (3 mo) and adult (9 mo) homozygous hr-rh-j mice (a strain of hairless mice) by means of structural techniques and immunohistochemistry to selectively identify thymic epithelial cells, dendritic cells, and macrophages. There were structural alterations in the thymus of both young and adult rh-rh-j mice, which were more severe in older animals. These alterations consisted of relative cortical atrophy, enlargement of blood vessels, proliferation of perivascular connective tissue, and the appearance of cysts. hr-rh-j mice also showed a decrease in the number of epithelial and dendritic cells, and macrophages. Taken together, present results strongly suggest degeneration and accelerated age-dependent regression of the thymus in hr-rh-j mice, which could explain at least in part the immune defects reported in hairless mouse strains.

Aging↗
PubMed1993

Is buffering capacity the principle role of the jelly coat in Bufo arenarum fertilization?

1. Dejellied Bufo arenarum oocytes can be fertilized in Ringer-Phosphate buffer with the same efficiency as jellied (control) oocytes. 2. Ringer-Phosphate buffer at pH = 7.4 not only provides buffering capacity but also the delta pH necessary for the acrosomal reaction. 3. The use of Ringer-TRIS buffer at pH = 7.4 does not render as good as Ringer-Phosphate buffer results, in terms of fertilization percentages. 4. Insemination of oocytes in Ringer-TRIS buffer interferes with early development.

Animals↗