Dissociation of intracellular lysosomal rupture from the cell death caused by silica

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins.     

Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges

Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges.     

每搏量变异度在围手术期容量治疗监测中的应用

每搏量变异度是动态的容量监测指标.机械通气患者心肺的相互作用是每搏量变异度的产生基础,通过动脉压力波形分析技术可以进行连续监测.每搏量变异度能够准确预测容量治疗反应,与静态的血流动力学参数相比,对于优化心输出量和组织氧供更有优势,但也存在一定的局限性.每搏量变异度受多种因素影响且不能用于自主呼吸和心律失常的患者.临床应用时应该综合考虑其影响因素,结合其他的指标和方法指导容量治疗.     

Neuroprotection against CCl4 induced brain damage with crocin in Wistar rats

Owing to its lipophilic property, carbon tetrachloride (CCl₄) is rapidly absorbed by both the liver and brain. We investigated the protective effects of crocin against brain damage caused by CCl₄. Fifty rats were divided into five groups of ten: control, corn oil, crocin, CCl₄ and CCl₄ + crocin. CCl₄ administration decreased glutathione (GSH) and total antioxidant status (TAS) levels, and catalase (CAT) activity, while significant increases were observed in malondialdehyde (MDA) and total oxidant status (TOS) levels and superoxide dismutase (SOD) activity. The cerebral cortex nuclear lamina developed a spongy appearance, neuronal degeneration was observed in the hippocampus, and heterochromatic and pyknotic neurons with increased cytoplasmic eosinophilia were observed in the hippocampus after CCl₄ treatment. Because crocin exhibits strong antioxidant properties, crocin treatment increased GSH and TAS levels and CAT activities, and decreased MDA and TOS levels and SOD activity; significant improvements also were observed in histologic architecture. We found that crocin administration nearly eliminated CCl₄ induced brain damage by preventing oxidative stress.     

RsfA (YbeB) proteins are conserved ribosomal silencing factors

The YbeB (DUF143) family of uncharacterized proteins is encoded by almost all bacterial and eukaryotic genomes but not archaea. While they have been shown to be associated with ribosomes, their molecular function remains unclear. Here we show that YbeB is a ribosomal silencing factor (RsfA) in the stationary growth phase and during the transition from rich to poor media. A knock-out of the rsfA gene shows two strong phenotypes: (i) the viability of the mutant cells are sharply impaired during stationary phase (as shown by viability competition assays), and (ii) during transition from rich to poor media the mutant cells adapt slowly and show a growth block of more than 10 hours (as shown by growth competition assays). RsfA silences translation by binding to the L14 protein of the large ribosomal subunit and, as a consequence, impairs subunit joining (as shown by molecular modeling, reporter gene analysis, in vitro translation assays, and sucrose gradient analysis). This particular interaction is conserved in all species tested, including Escherichia coli, Treponema pallidum, Streptococcus pneumoniae, Synechocystis PCC 6803, as well as human mitochondria and maize chloroplasts (as demonstrated by yeast two-hybrid tests, pull-downs, and mutagenesis). RsfA is unrelated to the eukaryotic ribosomal anti-association/60S-assembly factor eIF6, which also binds to L14, and is the first such factor in bacteria and organelles. RsfA helps cells to adapt to slow-growth/stationary phase conditions by down-regulating protein synthesis, one of the most energy-consuming processes in both bacterial and eukaryotic cells.     

Cicada acoustic communication: potential sound partitioning in a multispecies community from Mexico (Hemiptera: Cicadomorpha: Cicadidae)

Multispecies cicada communities in neotropical rainforests produce a complex and intense acoustic environment. In a fragment of a Mexican rainforest (Veracruz, Mexico), a cicada community at the end of the dry season consisted of nine species ( Daza montezuma; Pacarina schumanni; Miranha imbellis; Dorisiana sutori; Fidicinoides picea; Fidicinoides pronoe; Quesada gigas; one species of the genus Neocicada and one uncaught canopy species). Seven of the nine species formed dense choruses at dawn and at dusk. Each species showed preferences in the height of calling sites. Males of the species were solitary or gregarious, and followed a 'call-fly' or a 'call-stay' calling strategy. Acoustic signals of each species had particular time and frequency patterns. All these specific features appear to separate the nine species acoustically and lead to a partitioning of the acoustic environment. The acoustic partitioning might decrease the risk of heterospecific courting and mating.© 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 379–394.     

Food provision to nestlings in the Hoopoe Upupa epops: implications for the conservation of a small endangered population in the Swiss Alps

In an attempt to recognize the possible ecological causes of the decline of a population of Hoopoes Upupa epops in the Swiss Alps, we collected data on resource exploitation. The prey provisioned to nestlings by parents was investigated at four breeding sites using photographs (n = 4353, 80% of which enabled prey identification). Molecrickets Gryllotalpa gryllotalpa and Lepidoptera (larvae and pupae) were dominant in nestling diet (93% frequency; 97% biomass). Although Molecrickets were provisioned less frequently (26%) than Lepidoptera (67%), they represented 68% of the total biomass (vs 29% for Lepidoptera). There was an overall negative relationship between the proportion of Molecricket biomass in the diet and the parents' feeding rate, whereas a comparison between broods showed that a higher provisioning activity did not lead to an increase in the biomass supplied to the chicks. A diet based on Molecrickets therefore appears to be energetically advantageous. As Molecrickets are a traditional prey of Hoopoes in central Europe, this might be relevant to other populations. In the study area, Molecrickets occur only on the intensively cultivated plain, whereas the majority of Hoopoe pairs nest at various altitudes on the foothills adjacent to the plain as the latter provides at present almost no suitable nesting sites. Hoopoes breeding higher up on the foothills seem to experience greater provisioning costs and have, on average, lower breeding success. Providing nest sites on the plain is the main conservation measure proposed for the local Hoopoe population. Further attention should also be paid to Molecrickets as these may be crucial for Hoopoes.     

Cyclic Expression of A Nuclear Protein In A Dinoflagellate

Nuclei of the dinoflagellate Crypthecodinium cohnii strain Whd were isolated and nuclear proteins were extracted in three fractions, corresponding to the increasing affinity of these proteins to genomic DNA. One fraction contained two major bands (48- and 46-kDa) and antibodies specific to this fraction revealed two major bands by Western blot on nuclear extracts, corresponding to the 46- and 48-kDa bands. The 48-kDa protein was detected in G1 phase but not in M phase cells. An expression cDNA library of C. cohnii was screened with these antibodies, and two different open reading frames were isolated. Dinoflagellate nuclear associated protein (Dinap1), one of these coding sequences, was produced in E. coli and appeared to correspond to the 48-kDa nuclear protein. No homologue of this sequence was found in the data bases, but two regions were identified, one including two putative zinc finger repeats, and one coding for two potential W/W domains. The second coding sequence showed a low similarity to non-specific sterol carrier proteins. Immunocytolocalization with specific polyclonal antibodies to recombinant Dinap1 showed that the nucleus was immunoreactive only during the G1 phase: the nucleoplasm was immunostained, while chromosome cores and nuclear envelopes were negative.