The spontaneous and veratridine-evoked release of radioactive d-aspartic acid, previously taken up by rat substantia nigra slices, was studied by using a superfusion system. Veratridine (25 μM, 1 min) markedly produced a 14-fold increase in d-[3H]aspartic acid release from nigral slices. Omission of Ca2+ and increasing Mg2+ concentration to 12 mM in the superfusion medium did substantially block d-[3H]aspartate release induced by veratridine depolarization. Nevertheless, veratridine was able to evoke [3H]amino acid release which seemed to be, at least, 30% Ca2+-independent. Additional experiments showed that tetrodotoxin (0.01–0.1 μM), a blocker of voltage-dependent Na+ channels, totally abolished veratridine-evoked release of d-[3H]aspartate from nigral slices.Lesion studies were performed in order to learn about the nature of the neuronal compartment in the substantia nigra upon which veratridine-depolarization acted to induce d-[3H]aspartate release. Unilateral ablation of the fronto-parietal cortex was accompanied by a significant decrease in the accumulation of nigral d-[3H]aspartate and by a large loss from ipsilateral nigral slices in d-[3H]aspartate release evoked by veratridine. In contrast, both the accumulation and veratridine-evoked release of [3H]dopamine, remained unchanged in the ipsilateral substantia nigra slices to the lesion.The findings reported suggest that d-[3H]aspartic acid may be taken up and then released, in a Ca2+-dependent manner, by nerve terminals located in the substantia nigra. In addition, the results shown provide support to the view that l-glutamate and/or l-aspartate may act as neurotransmitters at the cortico-nigral neuronal pathway. 相似文献
Echinocandins, the lipopeptide class of glucan synthase inhibitors, are an alternative to ergosterol-synthesis inhibitors to treat candidiasis and aspergillosis. Their oral absorption, however, is low and they can only be used parenterally. During a natural product screening program for novel types of glucan synthesis inhibitors with improved bioavailability, a fungal extract was found that inhibited the growth of both a wild-type Saccharomyces cerevisiae strain and the null mutant of the FKS1 gene (fks1::HIS). The mutant strain was more sensitive to growth inhibition, suggesting that the fungal extract could contain an inhibitor of glucan synthesis. A novel acidic steroid, named arundifungin, was purified from a fungal extract obtained from a liquid culture of Arthrinium arundinis collected in Costa Rica. Arundifungin caused the same pattern of hallmark morphological alterations in Aspergillus fumigatus hyphae as echinocandins, further supporting the idea that arundifungin belongs to a new class of glucan synthesis inhibitors. Moreover, its antifungal spectrum was comparable to those of echinocandins and papulacandins, preferentially inhibiting the growth of Candida and Aspergillus strains, with very poor activity against Cryptococcus. Arundifungin was also detected in nine other fungal isolates which were ecologically and taxonomically unrelated, as assessed by sequencing of the ITS1 region. Further, it was also found in two more Arthrinium spp from tropical and temperate regions, in five psychrotolerant conspecific isolates collected on Macquarie Island (South Pacific) and belonging to the Leotiales, and in two endophytes collected in central Spain (a sterile fungus belonging to the Leotiales and an undetermined coelomycete). 相似文献
A total of 200 samples of feedstuffs and mixed feeds used for poultry and pig nutrition in Colombia were analysed for zearalenone
using a LC technique with a limit of detection of 20 μg/kg. Samples of grain sorghum, maize, processed soybean, rice meal,
cottonseed meal, and poultry and pig feeds, representative of the Colombian production for the 1995–1996 harvest, were taken
at feed manufacturing plants located in different cities of the country. Zearalenone was detected in 25 of 45 samples of sorghum,
2 of 33 samples of maize, 7 of 22 samples of rice meal, 9 of 17 samples of cottonseed meal, 11 of 30 samples of poultry feed
and 6 of 16 samples of pig feed. Zearalenone was not detected in soybean or other feedstuff s analysed (wheat by- products,
cassava meal, palm). Overall levels of zearalenone ranged from 29 to 3956 μg/kg, with a mean value of 436 μg/kg. Only one
of the 6 positive samples of pig feed had a zearalenone concentration above 500 μg/kg, which is normally considered as the
safe level for pigs. 相似文献
Nitro-arachidonic acid (NO2-AA) is a cell signaling nitroalkene that exerts anti-inflammatory activities during macrophage activation. While angiotensin II (ANG II) produces an increase in reactive oxygen species (ROS) production and mitochondrial dysfunction in renal tubular cells, little is known regarding the potential protective effects of NO2-AA in ANG II-mediated kidney injury. As such, this study examines the impact of NO2-AA on ANG II-induced mitochondrial dysfunction in an immortalized renal proximal tubule cell line (HK-2 cells). Treatment of HK-2 cells with ANG II increases the production of superoxide (O2●-), nitric oxide (●NO), inducible nitric oxide synthase (NOS2) expression, peroxynitrite (ONOO-) and mitochondrial dysfunction. Using high-resolution respirometry, it was observed that the presence of NO2-AA prevented ANG II-mediated mitochondrial dysfunction. Attempting to address mechanism, we treated isolated rat kidney mitochondria with ONOO-, a key mediator of ANG II-induced mitochondrial damage, in the presence or absence of NO2-AA. Whereas the activity of succinate dehydrogenase (SDH) and ATP synthase (ATPase) were diminished upon exposure to ONOO-, they were restored by pre-incubating the mitochondria with NO2-AA. Moreover, NO2-AA prevents oxidation and nitration of mitochondrial proteins. Combined, these data demonstrate that ANG II-mediated oxidative damage and mitochondrial dysfunction is abrogated by NO2-AA, identifying this compound as a promising pharmacological tool to prevent ANG II–induced renal disease. 相似文献
Golgi phosphoprotein 3 (GOLPH3) has been implicated in the development of carcinomas in many human tissues, and is currently considered a bona fide oncoprotein. Importantly, several tumor types show overexpression of GOLPH3, which is associated with tumor progress and poor prognosis. However, the underlying molecular mechanisms that connect GOLPH3 function with tumorigenicity are poorly understood. Experimental evidence shows that depletion of GOLPH3 abolishes transformation and proliferation of tumor cells in GOLPH3-overexpressing cell lines. Conversely, GOLPH3 overexpression drives transformation of primary cell lines and enhances mouse xenograft tumor growth in vivo. This evidence suggests that overexpression of GOLPH3 could result in distinct features of GOLPH3 in tumor cells compared to that of non-tumorigenic cells. GOLPH3 is a peripheral membrane protein mostly localized at the trans-Golgi network, and its association with Golgi membranes depends on binding to phosphatidylinositol-4-phosphate. GOLPH3 is also contained in a large cytosolic pool that rapidly exchanges with Golgi-associated pools. GOLPH3 has also been observed associated with vesicles and tubules arising from the Golgi, as well as other cellular compartments, and hence it has been implicated in several membrane trafficking events. Whether these and other features are typical to all different types of cells is unknown. Moreover, it remains undetermined how GOLPH3 acts as an oncoprotein at the Golgi. Therefore, to better understand the roles of GOLPH3 in cancer cells, we sought to compare some of its biochemical and cellular properties in the human breast cancer cell lines MCF7 and MDA-MB-231 with that of the non-tumorigenic breast human cell line MCF 10A. We found unexpected differences that support the notion that in different cancer cells, overexpression of GOLPH3 functions in diverse fashions, which may influence specific tumorigenic phenotypes. 相似文献
In this study, we describe the microstructure and ultrastructure of the epipodial papillae and epipodial tentacles of Haliotis tuberculata using light and electron microscopy. The epipodial papillae vary morphologically; they are subdivided into several subpapillae whose surface is covered by small micropapillae. The epipodial tentacles are large extendable conically elongated structures whose surface is differentiated in two regions: the dorsal region with long corrugated folds, and a ventral region composed of three parts, a basal part with the same structure as the dorsal, a middle part with shorter corrugated folds and an apical part with large micropapillae. Although the thin sections and ultrastructure examination show that the epithelium of both organs is morphologically similar and composed of supporting cells, sensory cells and different types of secretory cells, there is a certain specialization in their secretory product. Although the epithelium of both structures was positive for acidic glycoconjugates, the tentacle epithelium was also positive for neutral sugars. Further specific differences were revealed by lectin histochemistry. Because papillae and tentacles can be extended or retracted depending on environmental conditions, they probably have tactile and olfactory functions. 相似文献
Capsule Features of the breeding population and temporary settlement area influence the behaviour of Eagle Owls Bubo bubo prospecting for breeding sites during natal dispersal.
Aims To understand how prospecting behaviour during natal dispersal is affected by (i) the main characteristics of the breeding and dispersing portions of the population and (ii) main prey availability.
Methods We explored the ten-year dynamics and characteristics of radio-tagged breeders and dispersers of an Eagle Owl population.
Results During the first years following natal dispersal there was little prospecting behaviour of nesting sites and birds remained mainly within non-breeding settlement areas, bordering the sector occupied by the breeding population. Settlement areas had an abundant food supply, and low intraspecific competition and mortality. We suggest that these features of the settlement areas may reduce the willingness of individuals to search for breeding sites and may have the potential to impact on the viability of breeding populations.
Conclusion From a conservation perspective, the lengthy use of the temporary settlement areas by juvenile Eagle Owls suggests that the sites should be considered as important as the breeding areas when planning conservation strategies. Reducing juvenile mortality in settlement areas may represent an overlooked conservation strategy for long-lived species and may have a crucial effect on the viability some animal populations. 相似文献