A comparison of cryptophytan phycocyanins

The spectroscopically different phycocyanins present in the type strain of Hemiselmis virescens, Millport 64, and in a second strain of this cryptophytan species, Plymouth 157, have been purified and compared. They are similar in native molecular weight and in subunit structure, both containing alpha and beta subunits with molecular weights of approximately 10000 and 19000 respectively. However, they do not have the same chromophore composition. Both subunits of the phycocyanin of Plymouth 157 contain two bilins with absorption maxima at 600 and 660 nm, respectively. Only the beta subunit of Milllport 64 carries these chromophores; its alpha subunit bears another chromophore, with absorption maxima at 368 and 694 nm. The spectroscopic differences between the two native phycocyanins can be entirely accounted for by their differing chromophore compositions. The phycocyanin of Millport 64 is the only biliprotein so far described which contains three chemically different chromophores.     

Bonafide,type-specific human papillomavirus persistence among HIV-positive pregnant women: predictive value for cytological abnormalities,a longitudinal cohort study

This study investigated the rate of human papillomavirus (HPV) persistence, associated risk factors, and predictors of cytological alteration outcomes in a cohort of human immunodeficiency virus-infected pregnant women over an 18-month period. HPV was typed through L1 gene sequencing in cervical smears collected during gestation and at 12 months after delivery. Outcomes were defined as nonpersistence (clearance of the HPV in the 2nd sample), re-infection (detection of different types of HPV in the 2 samples), and type-specific HPV persistence (the same HPV type found in both samples). An unfavourable cytological outcome was considered when the second exam showed progression to squamous intraepithelial lesion or high squamous intraepithelial lesion. Ninety patients were studied. HPV DNA persistence occurred in 50% of the cases composed of type-specific persistence (30%) or re-infection (20%). A low CD4⁺T-cell count at entry was a risk factor for type-specific, re-infection, or HPV DNA persistence. The odds ratio (OR) was almost three times higher in the type-specific group when compared with the re-infection group (OR = 2.8; 95% confidence interval: 0.43-22.79). Our findings show that bonafide (type-specific) HPV persistence is a stronger predictor for the development of cytological abnormalities, highlighting the need for HPV typing as opposed to HPV DNA testing in the clinical setting.     

Two developmentally temporal quantitative trait loci underlie convergent evolution of increased branchial bone length in sticklebacks

In convergent evolution, similar phenotypes evolve repeatedly in independent populations, often reflecting adaptation to similar environments. Understanding whether convergent evolution proceeds via similar or different genetic and developmental mechanisms offers insight towards the repeatability and predictability of evolution. Oceanic populations of threespine stickleback fish, Gasterosteus aculeatus, have repeatedly colonized countless freshwater lakes and streams, where new diets lead to morphological adaptations related to feeding. Here, we show that heritable increases in branchial bone length have convergently evolved in two independently derived freshwater stickleback populations. In both populations, an increased bone growth rate in juveniles underlies the convergent adult phenotype, and one population also has a longer cartilage template. Using F₂ crosses from these two freshwater populations, we show that two quantitative trait loci (QTL) control branchial bone length at distinct points in development. In both populations, a QTL on chromosome 21 controls bone length throughout juvenile development, and a QTL on chromosome 4 controls bone length only in adults. In addition to these similar developmental profiles, these QTL show similar chromosomal locations in both populations. Our results suggest that sticklebacks have convergently evolved longer branchial bones using similar genetic and developmental programmes in two independently derived populations.     

Survival Mechanisms of Entomopathogenic Nematodes

Entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) are isolated from a wide variety of ecosystems ranging from sub-Arctic to arid and tropical climates. It is expected that natural populations of these nematodes will be pre-adapted to specific ecological conditions in their environments. However, little is known about the survival strategies of entomopathogenic nematodes. This review focuses on the main survival mechanisms involved in the long-term persistence of nematodes: extreme temperature tolerance (cold and heat), desiccation tolerance, osmotic tolerance, pesticide resistance and limitations of aeration. Physiological and biochemical mechanisms for survival are discussed. The review addresses the implications of the survival strategies on the establishment of exotic and indigenous steinernematids and heterorhabditids.     

An evaluation in the Ames test of the mutagenicity of the sewage and industrial effluents from the Baikal Paper and Pulp Combine

The use of the Ames test for the analysis of industrial effluents from cellulose production and sewage waters varying in the degree of purification with the aid of a metabolic activation system from rat and fish liver with Salmonella strains TA 98 and TA 100 revealed a strong direct mutagenic effect of strain TA 100 in samples after cellulose chlorination. The multistage procedure of sewage water purification allows to remove practically completely the mutagenic substances. A simultaneous study of cytotoxic effects of industrial effluents on mammalian cells shows that the mutagenic activity is exhibited in not toxic concentrations. The urgency of a regular biological control over the genotoxicity of industrial effluents from the sulfate production of cellulose is under discussion.