Relationships between blood pressure, polymorphism of angiotensin-converting enzyme (ACE), body composition and biochemical characteristics in elderly Slovaks

Epidemiological studies have demonstrated that several specific environmental factors and candidate genes influence the human variation in blood pressure. The aim of this study was to investigate variables associated with blood pressure; with a particular emphasis on the differences in insertion/deletion (I/D) polymorphism of the human angiotensin-converting enzyme (ACE), the body composition and the recognized risk factors for atherosclerosis among elderly males and females. A total of 374 participants (174 males and 200 females) aged from 60 to 90 years were recruited from different parts of Slovakia. The elderly were not bed-ridden, nor mentally impaired, they were able to manage their daily activities by themselves. The ACE I/D polymorphism was determined by PCR amplification of the ACE gene sequence. Body composition variables were obtained by bioelectrical impedance analysis, using the BIA 101 soft tissue-body impedance analyzer (Akern, S.r.l.). The subjects were determined to be hypertensive (blood pressure > or = 140/90 mm Hg) or normotensive (blood pressure < or = 140/90 mm Hg ). These two subgroups of males and females did not differ significantly in their mean ages. As expected, the hypertensive subjects of both sexes showed significantly higher mean values in systolic (SBP) and diastolic blood pressure (DBP), in body mass index (BMI), and in the mean values of their plasma glucose and extracellular water (ECW). The genotype distribution and allele frequencies in the whole sample (D = 0.5474, I = 0.4526) fell within the Hardy-Weinberg equilibrium. The frequency of the deleterious D allele in the normotensive (0.5532) and hypertensive (0.5516) subjects was not significantly different. The ACE I/D genotypes did not associate either with the systolic (p = 0.836) or diastolic BP (p = 0.629). From the other variables that may induce differences in blood pressure, a statistical effect was detected for glucose, Na/K, and Apo A1/ApoB ratios and physical activity on SBP, and for ApoA1, physical activity, BMI and total cholesterol on DBP.     

Characterization of a new liver- and kidney-specific pfkfb3 isozyme that is downregulated by cell proliferation and dedifferentiation

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase (PFK-2) catalyzes the synthesis and degradation of fructose 2,6-bisphosphate (Fru-2,6-P₂), a signalling molecule that controls the balance between glycolysis and gluconeogenesis in several cell types. Four genes, designated Pfkfb1-4, code several PFK-2 isozymes that differ in their kinetic properties, molecular masses, and regulation by protein kinases. In rat tissues, Pfkfb3 gene accounts for eight splice variants and two of them, ubiquitous and inducible PFK-2 isozymes, have been extensively studied and related to cell proliferation and tumour metabolism. Here, we characterize a new kidney- and liver-specific Pfkfb3 isozyme, a product of the RB2K3 splice variant, and demonstrate that its expression, in primary cultured hepatocytes, depends on hepatic cell proliferation and dedifferentiation. In parallel, our results provide further evidence that ubiquitous PFK-2 is a crucial isozyme in supporting growing and proliferant cell metabolism.     

Expression of glucose transporter-2, glucokinase and mitochondrial glycerolphosphate dehydrogenase in pancreatic islets during rat ontogenesis.

To gain better insight into the insulin secretory activity of fetal beta cells in response to glucose, the expression of glucose transporter 2 (GLUT-2), glucokinase and mitochondrial glycerol phosphate dehydrogenase (mGDH) were studied. Expression of GLUT-2 mRNA and protein in pancreatic islets and liver was significantly lower in fetal and suckling rats than in adult rats. The glucokinase content of fetal islets was significantly higher than of suckling and adult rats, and in liver the enzyme appeared for the first time on about day 20 of extrauterine life. The highest content of hexokinase I was found in fetal islets, after which it decreased progressively to the adult values. Glucokinase mRNA was abundantly expressed in the islets of all the experimental groups, whereas in liver it was only present in adults and 20-day-old suckling rats. In fetal islets, GLUT-2 and glucokinase protein and their mRNA increased as a function of increasing glucose concentration, whereas reduced mitochondrial citrate synthase, succinate dehydrogenase and cytochrome c oxidase activities and mGDH expression were observed. These findings, together with those reported by others, may help to explain the decreased insulin secretory activity of fetal beta cells in response to glucose.     

Characterization of the parB-Like yyaA Gene of Bacillus subtilis

We have characterized the yyaA gene of Bacillus subtilis, located near the origin of chromosome replication (oriC). Its protein product is similar to the Spo0J protein, which belongs to the ParB family of chromosome- and plasmid-partitioning proteins. Insertional inactivation of the yyaA gene had no apparent effect on chromosome organization and partitioning during vegetative growth or sporulation. Subcellular localization of YyaA by immunofluorescence microscopy indicated that it colocalizes with the nucleoid, and gel retardation studies confirmed that YyaA binds relatively nonspecifically to DNA. Overexpression of yyaA caused a sporulation defect characterized by the formation of multiple septa within the cell. This phenotype indicates that YyaA may have a regulatory role at the onset of sporulation.     

Structure and function of threonine synthase from yeast.

Threonine synthase catalyzes the final step of threonine biosynthesis, the pyridoxal 5'-phosphate (PLP)-dependent conversion of O-phosphohomoserine into threonine and inorganic phosphate. Threonine is an essential nutrient for mammals, and its biosynthetic machinery is restricted to bacteria, plants, and fungi; therefore, threonine synthase represents an interesting pharmaceutical target. The crystal structure of threonine synthase from Saccharomyces cerevisiae has been solved at 2.7 A resolution using multiwavelength anomalous diffraction. The structure reveals a monomer as active unit, which is subdivided into three distinct domains: a small N-terminal domain, a PLP-binding domain that covalently anchors the cofactor and a so-called large domain, which contains the main of the protein body. All three domains show the typical open alpha/beta architecture. The cofactor is bound at the interface of all three domains, buried deeply within a wide canyon that penetrates the whole molecule. Based on structural alignments with related enzymes, an enzyme-substrate complex was modeled into the active site of yeast threonine synthase, which revealed essentials for substrate binding and catalysis. Furthermore, the comparison with related enzymes of the beta-family of PLP-dependent enzymes indicated structural determinants of the oligomeric state and thus rationalized for the first time how a PLP enzyme acts in monomeric form.     

The growth response of plants to elevated CO2 under non-optimal environmental conditions

Under benign environmental conditions, plant growth is generally stimulated by elevated atmospheric CO₂ concentrations. When environmental conditions become sub- or supra-optimal for growth, changes in the biomass enhancement ratio (BER; total plant biomass at elevated CO₂ divided by plant biomass at the current CO₂ level) may occur. We analysed literature sources that studied CO₂2environment interactions on the growth of herbaceous species and tree seedlings during the vegetative phase. For each experiment we calculated the difference in BER for plants that were grown under 'optimal' and 'non-optimal' conditions. Assuming that interactions would be most apparent if the environmental stress strongly diminished growth, we scaled the difference in the BER values by the growth reduction due to the stress factor. In our compilation we found a large variability in CO₂2environment interactions between experiments. To test the impact of experimental design, we simulated a range of analyses with a plant-to-plant variation in size common in experimental plant populations, in combination with a number of replicates generally used in CO₂2environment studies. A similar variation in results was found as in the compilation of real experiments, showing the strong impact of stochasticity. We therefore caution against strong inferences derived from single experiments and suggest rather a reliance on average interactions across a range of experiments. Averaged over the literature data available, low soil nutrient supply or sub-optimal temperatures were found to reduce the proportional growth stimulation of elevated CO₂. In contrast, BER increased when plants were grown at low water supply, albeit relatively modestly. Reduced irradiance or high salinity caused BER to increase in some cases and decrease in others, resulting in an average interaction with elevated CO₂ that was not significant. Under high ozone concentrations, the relative growth enhancement by elevated CO₂ was strongly increased, to the extent that high CO₂ even compensated in an absolute way for the harmful effect of ozone on growth. No systematic difference in response was found between herbaceous and woody species for any of the environmental variables considered.     

Effect of herbicide diclofop-methyl on proton extrusion from Lolium multiflorum seedlings differing in resistance and in fungal endophyte (Neotyphodium sp.) infection

Lolium multiflorum (Italian ryegrass), an annual weed invading wheat and barley cropping systems, has evolved resistance to diclofop-methyl (DM) herbicide. Earlier studies on the mode of action of DM in susceptible L. multiflorum and L. rigidum populations have shown that herbicide promotes oxidative stress leading to senescence, a process reversible through the action of auxins. The disruption of cell membrane potential ( E _m ) appears to be correlated with DM phytotoxicity in susceptible populations, suggesting that the continuous H⁺ extrusion from plasmalemma to extracellular space is inhibited. L. multiflorum usually establishes a symbiotic relationship with fungal endophytes of the Neotyphodium genus. This fungus confers to host plants higher survival at sublethal dosages of DM, probably due to the production of auxinic compounds. Our goal was to characterize DM-resistant and DM-susceptible L. multiflorum populations infected (E+) and non-infected (E−) with endophytes, by studying the capacity of H⁺ bumping of plasmalemma of intact roots under DM selection. We correlated the effects of DM on H⁺ disruption with plant survival. DM inhibited acidification markedly more in susceptible than in resistant populations. Continued extrusion of H⁺ by DM-resistant cell membranes was positively related to plant survival and growth. There was no detectable difference in the capacity of bumping H⁺ between DM-susceptible E+ and E− seedlings, even though survival was higher in E+ plants. The basis for the differential response in H⁺ extrusion between resistant and susceptible populations of L. multiflorum is discussed.