The cardiac Na-H exchanger: a key downstream mediator for the cellular hypertrophic effects of paracrine, autocrine and hormonal factors.

The major mechanism by which the heart cell regulates intracellular pH is the Na(+)-H(+) exchanger (NHE) with the NHE-1 isoform as the primary cardiac subtype. Although NHE-1 has been implicated in mediating ischemic injury, more recent evidence implicates the antiporter as a key mediator of hypertrophy, which is produced by various autocrine, paracrine and hormonal factors such as endothelin-1, angiotensin II, and alpha(1) adrenoceptor agonists. These agonists activate the antiporter via phosphorylation-dependent processes. NHE-1 inhibition is likely conducive to attenuating the remodelling process after myocardial infarction. These effects probably occur independently of infarct size reduction and involve attenuation of subsequent postinfarction heart failure. As such, inhibitors of NHE offer substantial promise for clinical development that will attenuate acute responses to myocardial postinfarction and chronic pos t infarction, which evolve toward heart failure. The regulation of NHE-1 is discussed as is its potential role in mediating cardiomyocyte hypertrophy.     

Ingestion of Salmonella enterica Serotype Poona by a Free-Living Nematode, Caenorhabditis elegans, and Protection against Inactivation by Produce Sanitizers

Free-living nematodes are known to ingest food-borne pathogens and may serve as vectors to contaminate preharvest fruits and vegetables. Caenorhabditis elegans was selected as a model to study the effectiveness of sanitizers in killing Salmonella enterica serotype Poona ingested by free-living nematodes. Aqueous suspensions of adult worms that had fed on S. enterica serotype Poona were treated with produce sanitizers. Treatment with 20 μg of free chlorine/ml significantly (α = 0.05) reduced the population of S. enterica serotype Poona compared to results for treating worms with water (control). However, there was no significant difference in the number of S. enterica serotype Poona cells surviving treatments with 20 to 500 μg of chlorine/ml, suggesting that reductions caused by treatment with 20 μg of chlorine/ml resulted from inactivation of S. enterica serotype Poona on the surface of C. elegans but not cells protected by the worm cuticle after ingestion. Treatment with Sanova (850 or 1,200 μg/ml), an acidified sodium chlorite sanitizer, caused reductions of 5.74 and 6.34 log₁₀ CFU/worm, respectively, compared to reductions from treating worms with water. Treatment with 20 or 40 μg of Tsunami 200/ml, a peroxyacetic acid-based sanitizer, resulted in reductions of 4.83 and 5.34 log₁₀ CFU/worm, respectively, compared to numbers detected on or in worms treated with water. Among the organic acids evaluated at a concentration of 2%, acetic acid was the least effective in killing S. enterica serotype Poona and lactic acid was the most effective. Treatment with up to 500 μg of chlorine/ml, 1% hydrogen peroxide, 2,550 μg of Sanova/ml, 40 μg of Tsunami 200/ml, or 2% acetic, citric, or lactic acid had no effect on the viability or reproductive behavior of C. elegans. Treatments were also applied to cantaloupe rind and lettuce inoculated with S. enterica serotype Poona or C. elegans that had ingested S. enterica serotype Poona. Protection of ingested S. enterica serotype Poona against sanitizers applied to cantaloupe was not evident; however, ingestion afforded protection of the pathogen on lettuce. These results indicate that S. enterica serotype Poona ingested by C. elegans may be protected against treatment with chlorine and other sanitizers, although the basis for this protection remains unclear.     

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.     

PCR-based gene targeting of the inducible nitric oxide synthase (NOS2) locus in murine ES cells,a new and more cost-effective approach

Gene targeting by double homologous recombination in murine embryonic stem (ES) cells is a powerful tool used to study the cellular consequences of specific genetic mutations. A typical targeting construct consists of a neomycin phosphotransferase (neo) gene flanked by genomic DNA fragments that are homologous to sequences in the target chromosomal locus. Homologous DNA fragments are typically cloned from a murine genomic DNA library. Here we describe an alternative approach whereby the inducible nitric oxide synthase (NOS2) gene locus is partially mapped and homologous DNA sequences obtained using a long-range PCR method. A 7 kb NOS2 amplicon is used to construct a targeting vector where theneo gene is flanked by PCR-derived homologous DNA sequences. The vector also includes a thymidine kinase (tk) negative-selectable marker gene. Following transfection into ES cells, the PCR-based targeting vector undergoes efficient homologous recombination into the NOS2 locus. Thus, PCR-based gene targeting can be a valuable alternative to the conventional cloning approach. It expedites the acquisition of homologous genomic DNA sequences and simplifies the construction of targeting plasmids by making use of defined cloning sites. This approach should result in substantial time and cost savings for appropriate homologous recombination projects.     

Phylogenetic analysis of cytochromeb sequences in the dasyurid marsupial subfamily phascogalinae: Systematics and the evolution of reproductive strategies

We report DNA sequence variation in 861 bp of the mitochondrial cytochromeb gene from 10 species of the dasyurid marsupial subfamily Phascogalinae (including the New Guinean genusMurexia) and an outgroup planigale (Planigale ingrami). Phylogenetic analyses of these sequences indicate that (1) the subfamily consists of three major clades corresponding to (a)Phascogale, (b) AustralianAntechinus, and (c) New Guinean Antechinus andMurexia; (2) Antechinus habbema constitutes the earliest branch of the New Guinean clade; and (3); Antechinus melanurus and A. naso are sister species within the New Guinean clade. Among Australian antechnuses,A. stuartii andA. swainsonii are more closely related to each other than either is toA. flavipes, a result that is seemingly at odds with all previous systematic studies. Although resolution is limited, it appears thatAntechnius andMurexia species form a clade to the exclusion ofPhascogale. This relationship suggests that male semelparity is not a strong synapomorphy for Australian antechinuses and phascogales, despite its apparent physiological similarity in the two groups.To whom correspondence should be addressed.     

β-Sheet Models for the Ordered Filamentous Structure Formed by a Peptide That Enhances the Action of Insulin

Certain peptides with sequences related to part of the major histocompatibility complex class I antigen enhance the action of insulin. These peptides also aggregate into fibrous structures that seem to be related to their biological activity. In the current study, the 17-residue peptide with amino acid sequence Gly-Asn-Glu-Gln-Ser-Phe-Arg-Val-Asp-Leu-Arg-Thr-Leu-Leu-Arg-Tyr-Ala is used as a representative example of these bioactive molecules. As seen by electron microscopy, the peptide associates into gently twisted ribbons, 50 Å thick, in which the amount of twist decreases as the ribbons become wider. X-ray diffraction analysis suggests that the peptides are arranged as in an antiparallel β-sheet extending essentially endlessly along the fiber axis. The amino acid sequence of the peptide is such that one side of the β-sheet is predominantly polar while the opposite side is nonpolar. This allows the β-sheets to form multilayers with alternating hydrophobic and hydrophilic interfaces. The length of the extended peptide (≈54 Å) determines the thickness of the ribbon and the tendency of individual β-sheets to twist accounts for the twisting of the ribbons. An alternative model is also discussed, again based on antiparallel β-sheets, but with adjacent sheets interdigitated in a “side-by-side” fashion rather than forming stacked layers. Comparable inactive peptides such as Gly-Asn-Glu-Gln-Ser- A_l_a_-Arg-Val-Asp-Leu-Arg-Thr-Leu-Leu-Arg-Tyr-T_y_r_ (changed amino acids underlined) do not form ordered filamentous structures.     

Assessing post-induction cellular response in a recombinant E. coli lactose-inducible system by monitoring β-galactosidase levels

Summary A synthetic lactose-inducible promoter was chosen to study host cell responses to the over-expression of heterologous genes. Fermentations were conducted to compare the effect of induction strategies on the synthesis of -galactosidase versus the production of recombinant protein. The levels of lactose, IPTG and glucose during induction were manipulated to adjust the utilization of lactose as the inducer and/or the carbon source. In addition, the involvement of the gal operon in lactose metabolism was also explored in order to optimize lactose transport and utilization during induction.     

Effects of fish predation and habitat type on stream benthic communities

The influence of habitat on interactions between a fish predator (brown trout Salmo trutta) and a benthic invertebrate community was studied in nine field enclosures (8 ×3 m) in a creek in southern Sweden. Three habitat treatments were tested, a shallow sandy habitat, a deep habitat containing a mixture of large and small cobbles and a moderately deep habitat with large cobbles. The one month-long experiment showed that there were no major differences in the abundance and biomass of the benthic macroinvertebrate fauna among these habitats as no functional groups of invertebrates and only a few taxa differed between treatments. Invertebrate drift rates decreased over time, which was probably related to seasonal changes in invertebrate life cycles or to effects of predation independent of habitat type, as there was no difference between treatments.     

Closed system O2 uptake: a simple technique of nodule oxygen permeability estimation

Regulation of nitrogen fixation in response to various environmentalconditions often involves an adjustment in nodule permeabilityand, because of the importance of nodule permeability in nitrogenfixation, several methods to estimate it have been developed.In the present study, these methods are reviewed and their limitationsare highlighted. A simple, rapid and inexpensive technique thatcan be used to estimate permeability of nodules and respirationof other plant tissues is described. The technique was evaluatedby comparing it to the lag-phase technique as an independentand reliable method for estimating nodule permeability. Overa wide range of nodule permeability estimates, the closed systemO₂ uptake technique was linearly related to lag-phase permeabilityestimates. The technique was tested further by studying theresponse to sub- and supra-ambient pO₂ in the root environment,and the responses agreed well with published reports on theeffect of O² on nodule permeability. The technique was foundto be very satisfactory in estimating nodule permeability andmay be used to measure the ability of other plant tissues totake up O². Key words: Soybean, Glycine max, nitrogen fixation, root, respiration