Mycobacterium tuberculosis encodes a YhhN family membrane protein with lysoplasmalogenase activity that protects against toxic host lysolipids

The pathogen Mycobacterium tuberculosis (M.tb) resides in human macrophages, wherein it exploits host lipids for survival. However, little is known about the interaction between M.tb and macrophage plasmalogens, a subclass of glycerophospholipids with a vinyl ether bond at the sn-1 position of the glycerol backbone. Lysoplasmalogens, produced from plasmalogens by hydrolysis at the sn-2 carbon by phospholipase A₂, are potentially toxic but can be broken down by host lysoplasmalogenase, an integral membrane protein of the YhhN family that hydrolyzes the vinyl ether bond to release a fatty aldehyde and glycerophospho-ethanolamine or glycerophospho-choline. Curiously, M.tb encodes its own YhhN protein (MtbYhhN), despite having no endogenous plasmalogens. To understand the purpose of this protein, the gene for MtbYhhN (Rv1401) was cloned and expressed in Mycobacterium smegmatis (M.smeg). We found the partially purified protein exhibited abundant lysoplasmalogenase activity specific for lysoplasmenylethanolamine or lysoplasmenylcholine (pLPC) (V_max∼15.5 μmol/min/mg; K_m∼83 μM). Based on cell density, we determined that lysoplasmenylethanolamine, pLPC, lysophosphatidylcholine, and lysophosphatidylethanolamine were not toxic to M.smeg cells, but pLPC and LPC were highly toxic to M.smeg spheroplasts, which are cell wall–deficient mycobacterial forms. Importantly, spheroplasts prepared from M.smeg cells overexpressing MtbYhhN were protected from membrane disruption/lysis by pLPC, which was rapidly depleted from the media. Finally, we found that overexpression of full-length MtbYhhN in M.smeg increased its survival within human macrophages by 2.6-fold compared to vector controls. These data support the hypothesis that MtbYhhN protein confers a growth advantage for mycobacteria in macrophages by cleaving toxic host pLPC into potentially energy-producing products.     

Cre-lox recombination: Cre-ative tools for plant biotechnology

Targeted insertion and the precise deletion of DNA from transgenic plant chromosomes increase the potential of plant biotechnology for commercial applications and basic research. The Cre–lox recombination system is one of the best characterized and most widely used systems for these purposes. Cre–lox has many applications, but it is primarily used for the controlled excision of DNA fragments, in particular selectable marker genes, from the nuclear and chloroplast genomes, and for the targeted insertion of DNA into specific sites in the nuclear genome. Recent developments, including regulated expression of cre and the creative use of wild-type and modified lox sites, have improved the potential of these applications. After almost 15 years of research and development in plants, the Cre–lox system continues to provide an efficient and precise tool for plant biotechnologists.     

Cell signaling: life or death decisions of ras proteins

The discovery of a new downstream target for the Ras GTPases - a Nore1-Mst1 protein complex - reveals a mechanism by which Ras can promote apoptosis, and suggests that the influence of Ras on cell survival or death depends upon the relative level of activation of its various target proteins.     

Life-history traits of the lizard Sceloporus undulatus from two populations raised in a common laboratory environment

Hatchling Sceloporus undulatus elongatus from Washington Co., Utah and S. u. garmani from Woods Co., Oklahoma were raised to maturity and reproduction under identical laboratory conditions with ad libitum food availability. Growth, allometry, age and size of maturity, clutch size and egg mass were compared among lab-raised cohorts from the two populations, among lab-raised and field-caught animals (including their field-caught mothers) and, for growth, with values obtained by previously published field studies on the same or nearby populations. For all traits population differences observed in previous field studies and current field samples resulted from both a plastic response to proximate environmental conditions and intrinsic (possibly genetic) difference. The most plastic traits were growth and age of maturity. Cohorts from both populations expressed the ability to mature in less than 6 months in the laboratory but only the S.u. garmani express early maturity in the field. Allometric differences generated during growth in the lab were not observed in field samples but may reflect an adaptive physiological difference. The least plastic trait was egg mass. The only trait for which the rank order of the difference in the field was reversed in the lab was growth rate. S.u. elongatus grew significantly faster than S.u. garmani in the lab but much slower in the field. The tendency of S.u. garmani females to breed at minimum size of maturity may be greater than that of S.u. elongatus.     

PCR Detection of Salmonella enterica Serotype Montevideo in and on Raw Tomatoes Using Primers Derived from hilA

Salmonellae have been some of the most frequently reported etiological agents in fresh-produce-associated outbreaks of human infections in recent years. PCR assays using four innovative pairs of primers derived from hilA and sirA, positive regulators of Salmonella invasive genes, were developed to identify Salmonella enterica serotype Montevideo on and in tomatoes. Based on examination of 83 Salmonella strains and 22 non-Salmonella strains, we concluded that a pair of hilA primers detects Salmonella specifically. The detection limits of the PCR assay were 10¹ and 10⁰ CFU/ml after enrichment at 37°C for 6 and 9 h, respectively. When the assay was validated by detecting S. enterica serotype Montevideo in and on artificially inoculated tomatoes, 10² and 10¹ CFU/g were detected, respectively, after enrichment for 6 h at 37°C. Our results suggest that the hilA-based PCR assay is sensitive and specific, and can be used for rapid detection of Salmonellae in or on fresh produce.     

Biofeedback Via Telehealth: A New Frontier for Applied Psychophysiology

Psychophysiological diagnostic and therapeutic methods, to include biofeedback, have been found to be empirically effective in the treatment of a variety of physical disorders. In many areas of the country, however, certified biofeedback practitioners are not well distributed, limiting patient access to this treatment modality. Psychologists at Tripler Army Medical Center have pioneered efforts to develop and provide these needed services via a telehealth venue. Such capability significantly improves access to care, particularly for patient's located at considerable distance from the provider. As the telecommunications infrastructure in rural and remote areas is often quite basic, such a system must be capable of operating within these limited parameters. The system developed by the authors provides real-time video and audio interactivity and allows the therapist to monitor and control biofeedback equipment located at the remote site. The authors discuss the clinical applications, the technology, and relevant practical and ethical issues.     

Nutrition and Physical Activity Program to Attenuate Obesity and Promote Physical and Metabolic Fitness in Elementary School Children

Obesity and low levels of physical and metabolic fitness are risk factors for cardiovascular disease and diabetes. The purpose of this investigation was to attenuate obesity and improve physical and metabolic fitness in elementary school children. Schools have the opportunity, mechanisms, and personnel in place to deliver nutrition education, fitness activities, and a school food service that is nutritious and healthy. Cohorts from grades 3 to 5 in two school districts in rural Nebraska (Intervention/Control) participated in a 2-year study of physical activity and modified school lunch program. Data collection for aerobic capacity, body composition, blood chemistry, nutrition knowledge, energy intake, and physical activity was at the beginning and end of each year. Int received enhanced physical activity, grade specific nutrition education, and a lower fat and sodium school lunch program. Con continued with a regular school lunch and team sports activity program. At year 2, Int lunches had significantly less energy (9%), fat (25%), sodium (21%), and more fiber (17%). However, measures of 24-hour energy intake for Int and Con showed significant differences for sodium only. Physical activity in the classroom was 6% greater for Int compared to Con (p < 0.05) but physical activity outside of school was ?16 % less for Int compared to Con (p < 0.05). Body weight and body fat were not different between schools for normal weight or obese children. No differences were found for cholesterol, insulin, and glucose; however, HDL cholesterol was significantly greater and cholesterol/HDL was significantly less for Int compared to Con (p < 0.05). It appears that compensation in both energy intake and physical activity outside of school may be responsible for the lack of differences between Int and Con.     

Stimulation of in vitro shoot proliferation from nodal explants of cassava by thidiazuron, benzyladenine and gibberellic acid

Multiple shoots were produced from nodal explants of cassava (Manihot esculenta Crantz) by a two-step procedure: a 6- to 8-day exposure to 0.11–0.22 µM thidiazuron (TDZ) in liquid Murashige and Skoog (MS) medium followed by culture on agar-solidified MS medium supplemented with 2.2 µM 6-benzyladenine (BA) and 1.6 M gibberellic acid (GA₃). TDZ caused the nodal explants to expand and this expansion (growth) continued during culture with BA and GA₃. From this expanded explant, clusters of buds and fasciated stems developed continuously and these gave rise to shoots. The shoot proliferation process was open-ended, yielding an average of 31.5 shoots per nodal explant after 10 weeks of culture with genotype CG 1–56. A positive response was also obtained from seven other genotypes evaluated with this protocol.Abbreviations BA 6-benzyladenine - BM basal medium - DPU 1,3-diphenylurea - GA₃ gibberellie acid - 2iP isopentenyladenine - MSM multiple shoot medium - NAA 1-naphthaleneacetic acid - PGR plant growth regulator - TDZ thidiazuron - Z zeatin