Effect of amino acid substitutions in the rad50 ATP binding domain on DNA double strand break repair in yeast

The Saccharomyces cerevisiae Rad50-Mre11-Xrs2 complex plays a central role in the cellular response to DNA double strand breaks. Rad50 has a globular ATPase head domain with a long coiled-coil tail. DNA binding by Rad50 is ATP-dependent and the Rad50-Mre11-Xrs2 complex possesses DNA unwinding and endonuclease activities that are regulated by ATP. Here we have examined the role of the Rad50 Walker type A ATP binding motif in DNA double strand break repair by a combination of genetic and biochemical approaches. Replacement of the conserved lysine residue within the Walker A motif with alanine, glutamate, or arginine results in the same DNA damage sensitivity and homologous recombination defect as the rad50 deletion mutation. The Walker A mutations also cause a deficiency in non-homologous end-joining. As expected, complexes containing the rad50 Walker A mutant proteins are defective in ATPase, ATP-dependent DNA unwinding, and ATP-stimulated endonuclease activities. Although the DNA end-bridging activity of the Rad50-Mre11-Xrs2 complex is ATP-independent, the end-bridging activity of complexes containing the rad50 Walker A mutant proteins is salt-sensitive. These results provide a molecular explanation for the observed in vivo defects of the rad50 Walker mutant strains and reveal a novel ATP-independent function for Rad50 in DNA end-bridging.     

Intentional weight loss, blood lipids and coronary morbidity and mortality

PURPOSE OF REVIEW: Although weight reduction has been recommended to reduce cardiovascular risk, studies on the association between weight loss and coronary morbidity and mortality show conflicting results. This review summarizes findings from large studies examining this issue and accentuates the importance of carrying out additional well-designed research. RECENT FINDINGS: Many observational studies report that weight loss in older men and women is associated with increased cardiovascular morbidity and mortality. Recent studies suggest that this association may arise from the confounding effect of preexisting disease. Many studies do not report whether weight loss is intentional or unintentional. Unintentional weight loss may mask beneficial changes in cardiovascular risk due to intentional weight loss. In addition to issues related to the cause of weight loss, use of reported rather than measured weight may bias the results of large studies. However, one recent observational study with a methodology aimed at overcoming these limitations found that individuals who intentionally lost weight experienced a decreased coronary risk. SUMMARY: Weight reduction in overweight individuals is not universally associated with good health. This is true even if the weight loss results in normal body mass index. Reports of increased coronary risk associated with intentional weight loss may be explained by comorbidities that are also associated with weight loss. Individuals who are overweight and at high coronary risk may benefit from professionally supervised dieting and avoiding regain of lost weight. Clinical trials on cardiovascular outcomes in individuals who lose weight under supervised dieting are needed to assess this recommendation definitively.     

Neuroendocrine cells along the digestive tract express neuropilin-2

Neuropilin-2 (np-2) is a receptor for semaphorin-3F (sema-3F) and semaphorin-3C (sema-3C). These semaphorins repel tips of growing axons that express np-2. In addition, np-2 functions as a receptor for heparin binding forms of the angiogenic factor vascular endothelial growth factor (VEGF) such as VEGF145 and VEGF165. We report that np-2 is strongly expressed in neuroendocrine cells located all along the human digestive tract. Confocal fluorescent microscopy revealed that np-2 is concentrated in vesicle-like structures located near the nucleus at the basolateral side of these cells. In the colon, the np-2-expressing subpopulation of neuroendocrine cell is almost identical with the serotonin-producing subpopulation of neuroendocrine cells. Gastrointestinal carcinoid tumors are digestive tract tumors that develop from neuroendocrine cells. Interestingly, most of the carcinoid tumors derived from the colon and the appendix did not contain np-2-producing cells. However, some carcinoid tumors derived from the small intestine and stomach did express low levels of np-2 in isolated foci of cells. By contrast, strong serotonin and chromogranin-A expression was observed in all of the carcinoid tumors that were examined. These results suggest that loss of np-2 expression may accompany tumor progression in carcinoid tumors.     

The “Good Enough” Body Size as Judged by People of Varying Age and Weight

Objective: To examine the concept of the “good enough” body size acceptability across a wide range of ages and weight status. Research Methods and Procedures: Subjects were 303 children, 427 adolescents, 261 young adults, and 326 middle‐age adults who selected acceptable body sizes from an array of drawings representing their own age and gender. They also selected body sizes representing their own actual and ideal size. Results: A large majority (87%) of subjects considered their own body size socially acceptable. This finding applied to both genders in all age groups and to underweight, normal weight, and overweight subjects. Even among obese subjects, 48% considered their own body size socially acceptable. For the large percentage of subjects who reported a discrepancy between their actual and ideal body sizes, most considered their own body size acceptable. This finding also applied to both genders in all age groups and to underweight, normal weight, and overweight subjects. Discussion: Most male and female subjects across a wide range of ages and status considered their own body size to be within the range of socially acceptable body sizes even though, for many, it did not match their ideal. The implications of expanding body size research to include the conceptual framework of body size acceptability is discussed in terms of contributing to a paradigm of positive psychology.     

Use of chromomycin A3 staining in bovine sperm cells for detection of protamine deficiency

Sperm chromatin integrity is essential for accurate transmission of male genetic information, and normal sperm chromatin structure is important for fertilization. Protamine is a nuclear protein that plays a key role in sperm DNA integrity, because it is responsible for sperm DNA stability and packing until the paternal genome is delivered into the oocyte during fertilization. Our aim was to investigate protamine deficiency in sperm cells of Bos indicus bulls (Nelore) using chromomycin A₃ (CMA₃) staining. Frozen semen from 14 bulls were thawed, then fixed in Carnoy's solution. Smears were prepared and analyzed by microscopy. As a positive control of CMA₃ staining, sperm from one bull was subjected to deprotamination of nuclei. The percentage of CMA₃-positive bovine sperm did not vary among batches. Only two bulls showed a higher percentage of CMA₃-positive sperm cells compared to the others. CMA₃ is a simple and useful tool for detecting sperm protamine deficiency in bulls.     

Monitoring of clinical signs in goats with transmissible spongiform encephalopathies

Background  

As there is limited information about the clinical signs of BSE and scrapie in goats, studies were conducted to describe the clinical progression of scrapie and BSE in goats and to evaluate a short clinical protocol for its use in detecting scrapie-affected goats in two herds with previously confirmed scrapie cases. Clinical assessments were carried out in five goats intracerebrally infected with the BSE agent as well as five reported scrapie suspects and 346 goats subject to cull from the two herds, 24 of which were retained for further monitoring. The brain and selected lymphoid tissue were examined by postmortem tests for disease confirmation.     

Bacterial membrane potential analyzed by spectrofluorocytometry

Cells ofMycobacterium smegmatis 607 in their late exponential growth were stained with rhodamine 123. The stained bacterial populations were analyzed by fluorocytometry and spectrofluorometry. Responses of the bacterial membrane potential to agents such as valinomycin, graimicidin, nigericin, and sodium azide were analyzed with the two techniques mentioned above. The results have shown that the flow cytometric technique allowed detection of changes in bacterial membrane potential and allowed population response analysis to ionophore activity. The applications of this technique are promising for the rapid detection of membrane potential mutants and for the estimation of the viability of a bacterial population.