南方4种草本植物对铝胁迫生理响应的研究

 不同的植物对铝胁迫的生理响应不同, 因而对铝毒的耐性也不相同。设置5种铝浓度,进行砂培法处理,研究了4种我国南方红壤广泛分布的草本植物——牵牛(Pharbitis nil)、望江南(Cassia occidentlis)、光头稗(Echinochloa colonum)和合萌(Aeschynomene indica)的种子萌发、光合色素、脯氨酸含量、丙二醛(MDA)含量、可溶性糖(SS)含量、质膜透性(MP)、过氧化氢酶 (CAT) 活性以及过氧化物酶 (POD)活性的变化。结果表明铝对4种植物的生理特性都有明显的影响。4种植物的种子在10 000 mg·L－1 Al3+处理条件下都不能萌发。2 000 mg·L－1 Al3+处理都不利于4种植物的生长,与对照相比,2 000 mg·L－1 Al3+处理时4种草本植物叶绿素和叶绿素总含量显著降低(p<0.05);MDA含量和MP显著增加(p<0.05);脯氨酸含量极显著增加(p<0.01);POD和CAT活性极显著降低(p<0.01)。中低铝(80和400 mg·L－1)处理时,牵牛和合萌与对照相比,MP和MDA含量降低,POD和CAT活性升高;望江南的反应与牵牛和合萌的反应相反;光头稗在80 mg·L－1 Al3+处理时,与牵牛和合萌的变化一致,在400 mg·L－1 Al3+处理时,则相反。植物在中低铝处理条件下,通过维持较高的POD和CAT活性和脯氨酸、叶绿素含量,较低的MP和MDA含量来增加其对铝的耐性。     

Multiple-locus variable-number tandem repeat analysis for strain typing of Clostridium perfringens

Clostridium perfringens is ubiquitous in the environment and causes diseases in man and animals, with syndromes ranging from enteritis, enterotoxemia, and sudden death to food poisoning and gas gangrene. Understanding the epidemiology of these infections and of the evolution of virulence in C. perfringens necessitate an efficient, time and cost effective strain typing method. Multiple-locus variable-number tandem repeat analysis (MLVA) has been applied to typing of other pathogens and we describe here the development of a MLVA scheme for C. perfringens. We characterized five variable tandem repeat (VNTR) loci, four of which are contained within protein encoding genes and screened 112 C. perfringens isolates to evaluate typability, reproducibility, and discriminatory power of the scheme. All the isolates were assigned a MLVA genotype and the technique has excellent reproducibility, with a numerical index of discrimination for the five VNTR loci of 0.995. Thus MLVA is an efficient tool for C. perfringens strain typing, and being PCR based makes it rapid, easy, and cost effective. In addition, it can be employed in epidemiological, ecological, and evolutionary investigations of the organism.     

Heavy metal contamination of water and fish in peri-urban dams around Bulawayo,Zimbabwe

Urban effluents are significant sources of heavy metal pollution in fresh water. Metal contamination in dams around the city of Bulawayo, Zimbabwe, were monitored during October 2014 to assess ecological and public health risks. Heavy metals were measured in water, sediment and fish in dams located downstream of effluent discharge zones in Bulawayo and were compared to those in a pristine upstream dam. Water conductivity indicated pollution of downstream dams. Levels of lead (0.13–0.28 ppm) and cadmium (0.02–0.06 ppm) in water from downstream dams exceeded WHO safe limits for drinking water. Cadmium levels in polluted dams also exceeded the safe limit for agricultural use. Sediments of effluent-polluted dams had metal contamination factors ranging from 8.8 to 31.2 relative to the control, and fish from the dams had higher metal content and were unfit for human consumption. Metal levels were also measured along an urban stream to establish the sources of metals. The city’s industrial zone had the highest levels of metals, suggesting that industrial effluents were major sources of contamination. The environmental consequences and human health risks of the pollution of peri-urban water bodies from urban effluents are discussed.     

Missed opportunities for HIV testing and late-stage diagnosis among HIV-infected patients in Uganda

Background

Late diagnosis of HIV infection is a major challenge to the scale-up of HIV prevention and treatment. In 2005 Uganda adopted provider-initiated HIV testing in the health care setting to ensure earlier HIV diagnosis and linkage to care. We provided HIV testing to patients at Mulago hospital in Uganda, and performed CD4 tests to assess disease stage at diagnosis.

Methods

Patients who had never tested for HIV or tested negative over one year prior to recruitment were enrolled between May 2008 and March 2010. Participants who tested HIV positive had a blood draw for CD4. Late HIV diagnosis was defined as CD4≤250 cells/mm. Predictors of late HIV diagnosis were analyzed using multi-variable logistic regression.

Results

Of 1966 participants, 616 (31.3%) were HIV infected; 47.6% of these (291) had CD4 counts ≤250. Overall, 66.7% (408) of the HIV infected participants had never received care in a medical clinic. Receiving care in a non-medical setting (home, traditional healer and drug stores) had a threefold increase in the odds of late diagnosis (OR = 3.2; 95%CI: 2.1–4.9) compared to receiving no health care.

Conclusions

Late HIV diagnosis remains prevalent five years after introducing provider-initiated HIV testing in Uganda. Many individuals diagnosed with advanced HIV did not have prior exposure to medical clinics and could not have benefitted from the expansion of provider initiated HIV testing within health facilities. In addition to provider-initiated testing, approaches that reach individuals using non-hospital based encounters should be expanded to ensure early HIV diagnosis.     

Interactions of Cd with Zn, Cu, Mn and Fe for lettuce (Lactuca sativa L.) in hydroponic culture

Abstract. The effect and accumulation of cadmium (Cd) in lettuce grown by means of the hydroponic technique was investigated by multivariate analysis, and was found to be affected by the concentration of other trace elements. Particularly iron acted in a strongly antagonistic way against Cd. Consequently, no absolute toxicity limits for Cd can be drawn without considering other trace elements.     

Clostridium perfringens: insight into virulence evolution and population structure

Clostridium perfringens is an important pathogen in veterinary and medical fields. Diseases caused by this organism are in many cases life threatening or fatal. At the same time, it is part of the ecological community of the intestinal tract of man and animals. Virulence in this species is not fully understood and it does seem that there is erratic distribution of the toxin/enzyme genes within C. perfringens population. We used the recently developed multiple-locus variable-number tandem repeat analysis (MLVA) scheme to investigate the evolution of virulence and population structure of this species. Analysis of the phylogenetic signal indicates that acquisition of the major toxin genes as well as other plasmid-borne toxin genes is a recent evolutionary event and their maintenance is essentially a function of the selective advantage they confer in certain niches under different conditions. In addition, it indicates the ability of virulent strains to cause disease in different host species. More interestingly, there is evidence that certain normal flora strains are virulent when they gain access to a different host species. Analysis of the population structure indicates that recombination events are the major tool that shapes the population and this panmixia is interrupted by frequent clonal expansion that mostly corresponds to disease processes. The signature of positive selection was detected in alpha toxin gene, suggesting the possibility of adaptive alleles on the other chromosomally encoded determinants. Finally, C. perfringens proved to have a dynamic population and availability of more genome sequences and use of comparative proteomics and animal modeling would provide more insight into the virulence of this organism.     

Seed characteristics and fatty acid composition of castor (<i>Ricinus communis</i> L.) varieties in Northeast China

Oil content and fatty acid composition were investigated on 12 castor varieties and strains by using the soxhlet extraction method and capillary gas chromatography. This was made to provide a reference and theoretical basis for castorbean breeding with high oil content, determine variability of seed compounds for breeding purposes, and broaden chemical material choices. Results revealed that crude fat percentage in seeds ranged from 18.91 to 35.84% with an average of 25.91%; the absolute content of ricinoleic acid varied between 171.65 g/kg and 314.03 g/kg with an average of 222.43 g/kg, and kernel crude fat percentage was between 24.28 and 46.97% with an average of 34.30%. All these study variables were highest in the 2129 strain. The percentage of ricinoleic acid in crude fat was between 83.85 to 87.62%, and the highest value was found in the zhebi4 accession. The other fatty acids appeared in small concentrations, and showed small amplitude: 1.12 to 1.61%, 1.21 to 1.61%, 3.53 to 4.80%, 5.35 to 6.38%, 0.52 to 0.79%, 0.05 to 0.08% and 0.43 to 0.55%, for palmitic, stearic, oleic, linolic, linolenic, arachidic, and arachidonic acids, respectively. One hundred seed weight was determined for each accession. One hundred seed weight ranged from 25.7 g to 34.0 g with an average of 29.9 g. There was a significant correlation between seed weight and oil content, but the correlation value was low (r=0.51). Cluster analysis by SSPS based on the content of fatty acid composition revealed that the accessions were divided into three independent clusters. These findings will clearly provide useful information for further research in breeding and utilization of castor oil.