Assessment of parasympathetic reactivation after exercise

The objective of this study was to evaluate whether heart rate variability (HRV) can be used as an index of parasympathetic reactivation after exercise. Heart rate recovery after exercise has recently been shown to have prognostic significance and has been postulated to be related to abnormal recovery of parasympathetic tone. Ten normal subjects [5 men and 5 women; age 33 +/- 5 yr (mean +/- SE)] exercised to their maximum capacity, and 12 subjects (10 men and 2 women; age 61 +/- 10 yr) with coronary artery disease exercised for 16 min on two separate occasions, once in the absence of atropine and once with atropine (0.04 mg/kg) administered during exercise. The root mean square residual (RMS), which measures the deviation of the R-R intervals from a straight line, as well as the standard deviation (SD) and the root mean square successive difference of the R-R intervals (MSSD), were measured on successive 15-, 30-, and 60-s segments of a 5-min ECG obtained immediately after exercise. In recovery, the R-R interval was shorter with atropine (P < 0.0001). Without atropine, HRV, as measured by the MSSD and RMS, increased early in recovery from 4.1 +/- 0.4 and 3.7 +/- 0.4 ms in the first 15 s to 7.2 +/- 1.0 and 7.4 +/- 0.9 ms after 1 min, respectively (P < 0.0001). RMS (range 1.7-2.1 ms) and MSSD were less with atropine (P < 0.0001). RMS remained flat throughout recovery, whereas MSSD showed some decline over time from 3.0 to 2.2 ms (P < 0.002). RMS and MSSD were both directly related (r(2) = 0.47 and 0.56, respectively; P < 0.0001) to parasympathetic effect, defined as the difference in R-R interval without and with atropine. In conclusion, RMS and MSSD are parameters of HRV that can be used in the postexercise recovery period as indexes of parasympathetic reactivation after exercise. These tools may improve our understanding of parasympathetic reactivation after exercise and the prognostic significance of heart rate recovery.     

Epigenetics,oxidative stress,and Alzheimer disease

Alzheimer disease (AD) is a progressive neurodegenerative disorder whose clinical manifestations appear in old age. The sporadic nature of 90% of AD cases, the differential susceptibility to and course of the illness, as well as the late age onset of the disease suggest that epigenetic and environmental components play a role in the etiology of late-onset AD. Animal exposure studies demonstrated that AD may begin early in life and may involve an interplay between the environment, epigenetics, and oxidative stress. Early life exposure of rodents and primates to the xenobiotic metal lead (Pb) enhanced the expression of genes associated with AD, repressed the expression of others, and increased the burden of oxidative DNA damage in the aged brain. Epigenetic mechanisms that control gene expression and promote the accumulation of oxidative DNA damage are mediated through alterations in the methylation or oxidation of CpG dinucleotides. We found that environmental influences occurring during brain development inhibit DNA-methyltransferases, thus hypomethylating promoters of genes associated with AD such as the β-amyloid precursor protein (APP). This early life imprint was sustained and triggered later in life to increase the levels of APP and amyloid-β (Aβ). Increased Aβ levels promoted the production of reactive oxygen species, which damage DNA and accelerate neurodegenerative events. Whereas AD-associated genes were overexpressed late in life, others were repressed, suggesting that these early life perturbations result in hypomethylation as well as hypermethylation of genes. The hypermethylated genes are rendered susceptible to Aβ-enhanced oxidative DNA damage because methylcytosines restrict repair of adjacent hydroxyguanosines. Although the conditions leading to early life hypo- or hypermethylation of specific genes are not known, these changes can have an impact on gene expression and imprint susceptibility to oxidative DNA damage in the aged brain.     

Cationic amino acid transporters and Salmonella Typhimurium ArgT collectively regulate arginine availability towards intracellular Salmonella growth

Cationic amino acid transporters (mCAT1 and mCAT2B) regulate the arginine availability in macrophages. How in the infected cell a pathogen can alter the arginine metabolism of the host remains to be understood. We reveal here a novel mechanism by which Salmonella exploit mCAT1 and mCAT2B to acquire host arginine towards its own intracellular growth within antigen presenting cells. We demonstrate that Salmonella infected bone marrow derived macrophages and dendritic cells show enhanced arginine uptake and increased expression of mCAT1 and mCAT2B. We show that the mCAT1 transporter is in close proximity to Salmonella containing vacuole (SCV) specifically by live intracellular Salmonella in order to access the macrophage cytosolic arginine pool. Further, Lysosome associated membrane protein 1, a marker of SCV, also was found to colocalize with mCAT1 in the Salmonella infected cell. The intra vacuolar Salmonella then acquire the host arginine via its own arginine transporter, ArgT for growth. The argT knockout strain was unable to acquire host arginine and was attenuated in growth in both macrophages and in mice model of infection. Together, these data reveal survival strategies by which virulent Salmonella adapt to the harsh conditions prevailing in the infected host cells.     

THE EFFICIENCY OF THE ASSAY FOR HAEMOPIETIC COLONY FORMING CELLS

The quantitative efficiency of the spleen colony assay in mice is discussed in the light of recent findings on the kinetics of colony forming cells. Arguments are presented showing that the f factor, the 2 hr CFU recovery fraction in the spleen, markedly over-estimates the assay efficiency which is the ratio of the numbers of colony forming units and colony forming cells.     

A novel salt-tolerant L-myo-inositol-1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice: molecular cloning, bacterial overexpression, characterization, and functional introgression into tobacco-conferring salt tolerance phenotype

l-myo-Inositol-1-phosphate synthase (EC 5.5.1.4, MIPS), an evolutionarily conserved enzyme protein, catalyzes the synthesis of inositol, which is implicated in a number of metabolic reactions in the biological kingdom. Here we report on the isolation of the gene (PINO1) for a novel salt-tolerant MIPS from the wild halophytic rice, Porteresia coarctata (Roxb.) Tateoka. Identity of the PINO1 gene was confirmed by functional complementation in a yeast inositol auxotrophic strain. Comparison of the nucleotide and deduced amino acid sequences of PINO1 with that of the homologous gene from Oryza sativa L. (RINO1) revealed distinct differences in a stretch of 37 amino acids, between amino acids 174 and 210. Purified bacterially expressed PINO1 protein demonstrated a salt-tolerant character in vitro compared with the salt-sensitive RINO1 protein as with those purified from the native source or an expressed salt-sensitive mutant PINO1 protein wherein amino acids 174-210 have been deleted. Analysis of the salt effect on oligomerization and tryptophan fluorescence of the RINO1 and PINO1 proteins revealed that the structure of PINO1 protein is stable toward salt environment. Furthermore, introgression of PINO1 rendered transgenic tobacco plants capable of growth in 200-300 mm NaCl with retention of approximately 40-80% of the photosynthetic competence with concomitant increased inositol production compared with unstressed control. MIPS protein isolated from PINO1 transgenics showed salt-tolerant property in vitro confirming functional expression in planta of the PINO1 gene. To our knowledge, this is the first report of a salt-tolerant MIPS from any source.     

Diversification and evolution of L-myo-inositol 1-phosphate synthase

L-myo-Inositol 1-phosphate synthase (MIPS, EC 5.5.1.4), the key enzyme in the inositol and phosphoinositide biosynthetic pathway, is present throughout evolutionarily diverse organisms and is considered an ancient protein/gene. Analysis by multiple sequence alignment, phylogenetic tree generation and comparison of newly determined crystal structures provides new insight into the origin and evolutionary relationships among the various MIPS proteins/genes. The evolution of the MIPS protein/gene among the prokaryotes seems more diverse and complex than amongst the eukaryotes. However, conservation of a 'core catalytic structure' among the MIPS proteins implies an essential function of the enzyme in cellular metabolism throughout the biological kingdom.