Adenosine mediates transforming growth factor-beta 1 release in kidney glomeruli of diabetic rats

Up regulation of the transforming growth factor-beta 1 (TGF-β1) axis has been recognized as a pathogenic event for progression of glomerulosclerosis in diabetic nephropathy. We demonstrate that glomeruli isolated from diabetic rats accumulate up to sixfold more extracellular adenosine than normal rats. Both decreased nucleoside uptake activity by the equilibrative nucleoside transporter 1 and increased AMP hydrolysis contribute to raise extracellular adenosine. Ex vivo assays indicate that activation of the low affinity adenosine A_2B receptor subtype (A_2BAR) mediates TGF-β1 release from glomeruli of diabetic rats, a pathogenic event that could support progression of glomerulopathy when the bioavailability of adenosine is increased.     

Vanadium compounds

The direct effect of different vanadium compounds upon alkaline phosphatase (ALP) activity was investigated. Vanadate and vanadyl inhibited both the soluble and particulate ALP activity from UMR.106 cells and from bovine intestinal ALP. We have also shown the inhibition of ALP activity in the soluble fraction of osteoblasts by peroxo and hydroperoxo vanadium compounds. ALP activity in the particulate fraction was not inhibited by these species; nor was the bovine intestinal ALP. Using inhibitors of Tyr-phosphatase (PTPases), the soluble ALP was partially characterized as a PTPase. The major activity in the particulate fraction represents the bone-specific ALP-activity. This study demonstrates that different forms of vanadium are direct inhibitors of ALP activity. This effect is dependent on the enzymatic activity investigated and on the origin of the ALP.     

Ecology of cryptogamic epiphytes and their communities in deciduous forests in mediterranean Spain

A distribution of the epiphytic bryophyte and lichen vegetation of deciduous forests from the centre and north of the supramediterranean belt from the Spanish Iberian Peninsula was established using numerrical (PCA, CCA) and traditional floristic characteristics. Four groups have been established in relation to several syntaxa. Derived by numerical classification, possible successional trends between the groups with respect to changes in moisture, light and diameter of the trees are described. Nevertheless, patterns with succession in epiphytic communities are very complex to establish.     

Female control of sperm ejection and retention in the cornsilk fly Euxesta eluta (Diptera: Ulidiidae)

Promiscuous mating systems provide the opportunity for females to bias fertilization toward particular males. However, distinguishing between male sperm competition and active female sperm choice is difficult for species with internal fertilization. Nevertheless, species that store and use sperm of different males in different storing structures and species where females are able to expel all or part of the ejaculates after copulation may be able to bias fertilization. We report a series of experiments aimed at providing evidence of female sperm choice in Euxesta eluta (Hendel), a species of ulidiid fly that expels and consumes ejaculates after copulation. We found no evidence of greater reproductive success for females mated singly, multiply with the same male, or mated multiply with different males. Female E. eluta possesses two spherical spermathecae and a bursa copulatrix for sperm storage, with a ventral receptacle. There was no significant difference in storing more sperm in spermathecae 24 h after copulation than immediately after copulation. Females mated with protein-fed males had greater reproductive success than similar females mated to protein-deprived males. Protein-fed females prevented to consume the ejaculate, retained more sperm when mated to protein-fed males than when mated to protein-deprived males. Our results suggest that female E. eluta can exert control of sperm retention of higher quality males through ejaculate ejection.     

Pharmacological Characterization of the Voltage-Dependent Ca2+ Channels Present in Synaptosomes from Rat and Chicken Central Nervous System

Abstract: The voltage-dependent calcium channels present in mammalian and chicken brain synaptosomes were characterized pharmacologically using specific blockers of L-type channels (1,4-dihydropyridines), N-type channels (ω-conotoxin GVIA), and P-type channels [funnel web toxin (FTX) and ω-agatoxin IVA]. K⁺-induced Ca²⁺ uptake by chicken synaptosomes was blocked by ω-conotoxin GVIA (IC₅₀ = 250 nM). This toxin at 5 µM did not block Ca²⁺ entry into rat frontal cortex synaptosomes. FTX and ω-agatoxin IVA blocked Ca²⁺ uptake by rat synaptosomes (IC₅₀ = 0.17 µl/ml and 40 nM, respectively). Likewise, in chicken synaptosomes, FTX and ω-agatoxin IVA affected Ca²⁺ uptake. FTX (3 µl/ml) exerted a maximal inhibition of 40% with an IC₅₀ similar to the one obtained in rat preparations, whereas with ω-agatoxin IVA saturation was not reached even at 5 µM. In chicken preparations, the combined effect of saturating concentrations of FTX (1 µl/ml) and different concentrations of ω-conotoxin GVIA showed no additive effects. However, the effect of saturating concentrations of FTX and ω-conotoxin GVIA was never greater than the one observed with ω-conotoxin GVIA. We also found that 60% of the Ca²⁺ uptake by rat and chicken synaptosomes was inhibited by ω-conotoxin MVIID (1 µM), a toxin that has a high index of discrimination against N-type channels. Conversely, nitrendipine (10 µM) had no significant effect on Ca²⁺ uptake in either the rat or the chicken. In conclusion, Ca²⁺ uptake by rat synaptosomes is potently inhibited by different P-type Ca²⁺ channel blockers, thus indicating that P-type channels are predominant in this preparation. In contrast, Ca²⁺ uptake by chicken synaptosomes is sensitive to ω-conotoxin GVIA, FTX, ω-agatoxin IVA, and ω-conotoxin MVIID. This suggests that a channel subtype with a mixed pharmacology is present in chicken synaptosomes.     

Neurotrophic Effects of l-DOPA in Postnatal Midbrain Dopamine Neuron/Cortical Astrocyte Cocultures

Abstract: l -DOPA is toxic to catecholamine neurons in culture, but the toxicity is reduced by exposure to astrocytes. We tested the effect of l -DOPA on dopamine neurons using postnatal ventral midbrain neuron/cortical astrocyte cocultures in serum-free, glia-conditioned medium. l -DOPA (50 µ M ) protected against dopamine neuronal cell death and increased the number and branching of dopamine processes. In contrast to embryonically derived glia-free cultures, where l -DOPA is toxic, postnatal midbrain cultures did not show toxicity at 200 µ M l -DOPA. The stereoisomer d -DOPA (50–400 µ M ) was not neurotrophic. The aromatic amino acid decarboxylase inhibitor carbidopa (25 µ M ) did not block the neurotrophic effect. These data suggest that the neurotrophic effect of l -DOPA is stereospecific but independent of the production of dopamine. However, l -DOPA increased the level of glutathione. Inhibition of glutathione peroxidase by l -buthionine sulfoximine (3 µ M for 24 h) blocked the neurotrophic action of L-DOPA. N -Acetyl- l -cysteine (250 µ M for 48 h), which promotes glutathione synthesis, had a neurotrophic effect similar to that of l -DOPA. These data suggest that the neurotrophic effect of l -DOPA may be mediated, at least in part, by elevation of glutathione content.