Phosphoglucomutase is absent in Trypanosoma brucei and redundantly substituted by phosphomannomutase and phospho-N-acetylglucosamine mutase

The enzymes phosphomannomutase (PMM), phospho‐N‐acetylglucosamine mutase (PAGM) and phosphoglucomutase (PGM) reversibly catalyse the transfer of phosphate between the C6 and C1 hydroxyl groups of mannose, N‐acetylglucosamine and glucose respectively. Although genes for a candidate PMM and a PAGM enzymes have been found in the Trypanosoma brucei genome, there is, surprisingly, no candidate gene for PGM. The TbPMM and TbPAGM genes were cloned and expressed in Escherichia coli and the TbPMM enzyme was crystallized and its structure solved at 1.85 Å resolution. Antibodies to the recombinant proteins localized endogenous TbPMM to glycosomes in the bloodstream form of the parasite, while TbPAGM localized to both the cytosol and glycosomes. Both recombinant enzymes were able to interconvert glucose‐phosphates, as well as acting on their own definitive substrates. Analysis of sugar nucleotide levels in parasites with TbPMM or TbPAGM knocked down by RNA interference (RNAi) suggests that, in vivo, PGM activity is catalysed by both enzymes. This is the first example in any organism of PGM activity being completely replaced in this way and it explains why, uniquely, T. brucei has been able to lose its PGM gene. The RNAi data for TbPMM also showed that this is an essential gene for parasite growth.     

Gene regulatory divergence among species estimated by altered developmental patterns in interspecific hybrids

Disturbances in the schedules of gene expression in developing interspecific fish hybrids have been used to draw inferences about the extent of gene regulatory divergence between species and about the degree to which this gene regulatory divergence is correlated with structural gene divergence, as estimated by genetic distance. Sperm from each of 10 different species representing six genera within the family Centrarchidae was used to fertilize eggs of the Florida largemouth bass (Micropterus salmoides floridanus). The genetic distances (D; Nei 1978) between the parental species used to form the hybrids ranged from 0.133 to 0.974. The developmental success and temporal patterns of gene expression of each of the hybrids were compared with those of the Florida largemouth bass. As the genetic distance between the paternal species and the Florida largemouth bass increased, there was a general decline in developmental success in the hybrid embryos as demonstrated by the observed reductions in the percentage of hatching and by progressively earlier and more extensive morphological abnormalities. Concomitantly, progressively more marked alterations in developmental schedules of expression of 15 enzyme loci occurred in the hybrids as the genetic distance between parental species increased. However, observed deviations from this trend for a few species may represent an uncoupling of the rates and modes of evolution of structural genes from those for genes regulating developmental processes.      

Understanding physicians' response to AIDS.

Attempts to comprehend physicians'' extreme reaction to AIDS (acquired immune deficiency syndrome) have met with great difficulty since the disease brings into question traditional norms and assumptions. As the medical profession struggles to develop guidelines and policies to help it deal with this disease, it can draw on very little systematic research on the effect of AIDS on physicians'' attitudes and practices. We suggest a framework developed from the literature on physicians'' and society''s response to other disorders that would provide a basis for organizing the ever-increasing amount of information on physicians and AIDS and would guide systematic research aimed at understanding and predicting physicians'' participation in the prevention and management of AIDS. Within this framework we consider how characteristics of the disease, elements of the health care system and physicians'' attitudes interact to influence clinical and personal practices. AIDS had led to new delineations of physicians'' responsibility, modification of prevailing beliefs about physician autonomy and thus a redefinition of the role of the physician in North America.     

Activation of morphogenesis and proliferation by low specificity chemical effectors

Activation of highly specific biochemical processes by simple chemical agents is demonstrated for morphogenesis (anlage and development of female gametophyte in cereal) and mitosis (in cell cultures and animal and plant tissues). The effects of these agents are tissue-specific. Structure--activity relationship is analyzed in this group of compounds. Thus, the phenomenon reveals the exact pathways of the influence of allelopathic and anthropogenic chemical agents on evolution of plant biocenoses.     

A sociobehavioural perspective on genetic testing and counselling for heritable breast,ovarian and colon cancer.

Testing for susceptibility to heritable breast, ovarian and colon cancer has unique psychosocial costs. Negative test results may not be sufficient to relieve anxiety, and positive results can cause sufficient distress to compromise patient compliance with surveillance and risk reduction measures. More needs to be learned about how sociocultural factors affect the understanding of risk, how decisions to undergo testing are made and how information about increased risk affects family dynamics. As the demand for testing and counselling grows, health care providers will be faced with new challenges and dilemmas. A better understanding of genetics by the public is needed to mitigate deterministic attitudes that can lead to the neglect of health promotion. Also of concern are the socioeconomic implications of being identified as having a high risk for heritable cancer and the dangers inherent in using genetics to explain sociological phenomena. Health care providers must take the lead in ensuring that developments in genetics are used to the benefit of all.