黑线毛足鼠年龄和种群密度与肝毛细线虫感染率的关系

2004—2005年,在内蒙古锡林郭勒盟阿巴嘎旗和东乌珠穆沁旗研究了肝毛细线虫病对黑线毛足鼠种群感染情况,分析肝毛细线虫对黑线毛足鼠的感染率与鼠体年龄以及种群密度的关系。结果表明,黑线毛足鼠达到一定的年龄(或体质量)才可感染肝毛细线虫病,最低感染个体体质量为14.6g。肝毛细线虫对低龄鼠的感染检出率比较低,而对成体鼠感染检出率较高,其感染率和感染度均随着个体年龄的增长而增高(感染率与年龄:r=0.97,P<0.05;感染度与年龄:r=0.93,P<0.05)。此外,黑线毛足鼠体质量与肝毛细线虫感染率和感染度也存在显著的相关关系(感染率与体质量:r=0.99,P<0.05;感染度与体质量:r=0.95,P<0.05),黑线毛足鼠的种群密度则对肝毛细线虫的感染率(r=0.27,P>0.05)和平均感染度(r=0.41,P>0.05)没有明显的影响,其感染率可能与地区不同有关。     

Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.      

Mycotoxins of Alternaria alternata produced on ceiling tiles

The production of mycotoxins by Alternaria alternata in cellulosic ceiling tiles was examined with thin-layer chromatography and high-performance liquid chromatography procedures. Alternariol and alternariol monomethyl ether were found in ceiling tile extracts, whereas extracts of control rice cultures of all three isolates produced these mycotoxins plus altenuene and altertoxin I. Extensive fungal growth and mycotoxin production occurred in the ceiling tiles at relative humidities of 84–89% and 97%. Received 28 May 1997/ Accepted in revised form 06 October 1997     

Immunochemical identity of peroxisomal enoyl-CoA hydratase with the peroxisome-proliferation -associated 80,000 mol wt polypeptide in rat liver

Peroxisome proliferators, which induce proliferation of hepatic peroxisomes, have been shown previously to cause a marked increase in an 80,000 mol wt polypeptide predominantly in the light mitochondrial and microsomal fractions of liver of rodents. We now present evidence to show that this hepatic peroxisome-proliferation-associated polypeptide, referred to as polypeptide PPA-80, is immunochemically identical with the multifunctional peroxisome protein displaying heat-labile enoyl-CoA hydratase activity. This conclusion is based on the following observations: (a) the purified polypeptide PPA-80 and the heat- labile enoyl-CoA hydratase from livers of rats treated with the peroxisome proliferators Wy-14,643 {[4-chloro-6(2,3-xylidino)-2-pyrimidinylthio]acetic acid} exhibit identical minimum molecular weights of approximately 80,000 on SDS polyacrylamide gel electrophoresis; (b) these two proteins are immunochemically identical on the basis of ouchterlony double diffusion, immunotitration, rocket immunoelectrophoresis, and crossed immunoelectrophoresis analysis; and (c) the immunoprecipitates formed by antibodies to polypeptide PPA-80 when dissociated on a sephadex G-200 column yield enoyl-CoA hydratase activity. Whether the polypeptide PPA-80 exhibits the activity of other enzyme(s) of the peroxisomal β-oxidation system such as fatty acyl-CoA oxidase activity or displays immunochemical identity with such enzymes remains to be determined. The availability of antibodies to polypeptide PPA-80 and enoyl-CoA hydratase facilitated immunofluorescent and immunocytochemical localization of the polypeptide PPA- 80 and enoyl-CoA hydratase in the rat liver. The indirect immunofluorescent studies with these antibodies provided direct visual evidence for the marked induction of polypeptide PPA-80 and enoyl-CoA hydratase in the livers of rats treated with Wy-14,643. The present studies also provide immunocytochemical evidence for the localization of polypeptide PPA- 80 and the heat-labile enoyl-CoA hydratase in the peroxisome, but not in the mitochondria, of hepatic parenchymal cells. These studies, therefore, provide morphological evidence for the existence of fatty acyl-CoA oxidizing system in peroxisomes. An increase of polypeptide PPA-80 on SDS polyacrylamide gel electrophoretic analysis of the subcellular fractions of liver of rodents treated with lipid-lowering drugs should serve as a reliable and sensitive indicator of enhanced peroxisomal β- oxidation system.     

Water Flow in Wheat Seedlings after Small Water Deficits

Cultures of Scenedesmus obliquus when grown heterotrophically for 10 or 30 days without addition of fresh medium showed 85 and 98% loss of their photosynthetic capacity respectively. This loss in photosynthetic capacity was accompanied by an increase in quantum requirement. No major changes in the pigment amounts or types were detected which would explain the decay in photosynthetic capacity. Partial reactions mediated by photosystem II or I showed a more or less constant decay over a period of 30 days. Photosystem II reactions appeared less stable than those of photosystem I, decaying by 95% as compared with 70%, over this time period. The results of comparative studies on aged cells for their potential of cytochrome f photooxidation, fluorescence kinetics, 520 nm absorbance change and the variable influence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone on the photosynthetic capacity of such cells, suggest that it is the inherent ability of the cells to photooxidize plastohydroquinone which is affected primarily. In addition, secondary changes were noted in the activity of reactions on the water-splitting side of photosystem II and in the P700 — plastocyanin — cytochrome f complex.     

Electrical and adaptive properties of rod photoreceptors in bufo marinus. I. Effects of altered extracellular Ca(2+) levels

The effects of altering extracellular Ca(2+) levels on the electrical and adaptive properties of toad rods have been examined. The retina was continually superfused in control (1.6 mM Ca(2+)) or test ringer’s solutions, and rod electrical activity was recorded intracellularly. Low-calcium ringer’s (10(-9)M Ca(2+)) superfused for up to 6 min caused a substantial depolarization of the resting membrane potential, an increase in light-evoked response amplitudes, and a change in the waveform of the light-evoked responses. High Ca(2+) ringer’s (3.2 mM) hyperpolarized the cell membrane and decreased response amplitudes. However, under conditions of either low or high Ca(2+) superfusion for up to 6 min, in both dark-adapted and partially light-adapted states, receptor sensitivity was virtually unaffected; i.e., the V-log I curve for the receptor potential was always located on the intensity scale at a position predicted by the prevailing light level, not by Ca(2+) concentration. Thus, we speculate that cytosol Ca(2+) concentration is capable of regulating membrane potential levels and light-evoked response amplitudes, but not the major component of rod sensitivity. Low Ca(2+) ringer’s also shortened the period of receptor response saturation after a bright but nonbleaching light flash, hence accelerating the onset of both membrane potential and sensitivity recovery during dark adaptation.

Exposure of the retina to low Ca(2+) (10(-9)M) ringer’s for long periods (7-15 min) caused dark-adapted rods to lose responsiveness. Response amplitudes gradually decreased, and the rods became desensitized. These severe conditions of low Ca(2+) caused changes in the dark-adapted rod that mimic those observed in rods during light adaptation. We suggest that loss of receptor sensitivity during prolonged exposure to low Ca(2+) ringer’s results from a decrease of intracellular (intradisk) stores of Ca(2+); i.e., less Ca(2+) is thereby released per quantum catch.

     

A statistical test that supports a human/chimpanzee clade based on noncoding DNA sequence data

Using the aligned DNA sequence data of Miyamoto et al. and Maeda et al., all noncoding genetic material, and a simple statistical test, we show that a Homo/Pan clade is supported at approximately the 3% level of significance. The method accommodates polymorphism and different evolutionary rates for different sites. All assumptions on which the statistical study is based are made explicit. (See the Note added in proof, which--adding recently published data--improves the significance level to about 1%.      

Reflooding the Faguibine floodplain system,northern Mali: potential benefits and challenges

The Faguibine system, northern Mali, consists of a series of interconnected floodplains of which the flooded surface area declined from about 1 000 km² in the late 19th century to only some 90 km² in 2010. Flood extent depends on the height of the Niger River flood peak at Diré. Satellite imagery analysis indicated that a phase shift may have occurred in the year 2000, probably as a delayed consequence of the Sahelian drought of the 1970s compounded by the collapse of societal controls on water use during recent civil conflict. An economic evaluation of the system in 2011 showed US$100 000 per year of net income per flooded km² in Lake Faguibine, allowing vulnerable people to practise recession agriculture, to fish and to graze livestock. An intensive investment phase, combined with an approach of rebuilding local governance systems and environmental management capacity, could yield net benefits to the user communities of the order of ten times the maintenance costs, contributing to human well-being. The system is currently threatened by the building of the Fomi Dam in Guinea and by the planned expansion of irrigation upstream. There is also a risk of the return of a prolonged drought linked to the Atlantic multi-decadal oscillation index.     

Zerumbone induced apoptosis in liver cancer cells via modulation of Bax/Bcl-2 ratio

Background  

Zerumbone is a cytotoxic component isolated from Zingiber zerumbet Smith, a herbal plant which is also known as lempoyang. This new anticancer bioactive compound from Z. zerumbet was investigated for its activity and mechanism in human liver cancer cell lines.