Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.      

The rabbit alpha-like globin gene cluster is polymorphic both in the sizes of BamHI fragments and in the numbers of duplicated sets of genes

The alpha-like globin gene cluster in rabbits contains embryonic zeta- globin genes, an adult alpha-globin gene, and theta-globin genes of undetermined function. The basic arrangement of genes, deduced from analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3'. However, the pattern of restriction fragments containing zeta- and theta-globin genes varies among individual rabbits. Analysis of BamHI fragments of genomic DNA from 24 New Zealand white rabbits revealed eight different patterns of fragments containing zeta-globin genes. The large BamHI fragments containing genes zeta 0 and zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary in size. In contrast to this constancy in the size of the restriction fragments, the copy number of the zeta 2 and zeta 3 genes does vary among different rabbits. No length polymorphism was detected in the BamHI fragments containing the theta-globin genes, but again the copy number varies for restriction fragments containing the theta 2 gene. The alpha 1- and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI fragment. The combined data from hybridization with both zeta and theta probes shows that the BamHI cleavage pattern does not vary within the region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern genomic blot-hybridization patterns for the progeny of parental rabbits with different zeta-globin gene patterns shows that the polymorphic patterns are inherited in a Mendelian fashion. Two different haplotypes have been mapped based on the genomic blot-hybridization data. The variation in the alpha-like globin gene cluster in the rabbit population results both from differences in the copy number of the duplication block containing the zeta-zeta-theta gene set and from the presence or absence of polymorphic BamHI sites.      

Mutation of the NADH oxidase gene (nox) reveals an overlap of the oxygen- and acid-mediated stress responses in Streptococcus mutans

NADH oxidase (Nox) is a flavin-containing enzyme used by Streptococcus mutans to reduce dissolved oxygen encountered during growth in the oral cavity. In this study, we characterized the role of the NADH oxidase in the oxidative and acid stress responses of S. mutans. A nox-defective mutant strain of S. mutans and its parental strain, the genomic type strain UA159, were exposed to various oxygen concentrations at pH values of 5 and 7 to better understand the adaptive mechanisms used by the organism to withstand environmental pressures. With the loss of nox, the activities of oxygen stress response enzymes such as superoxide dismutase and glutathione oxidoreductase were elevated compared to those in controls, resulting in a greater adaptation to oxygen stress. In contrast, the loss of nox led to a decreased ability to grow in a low-pH environment despite an increased resistance to severe acid challenge. Analysis of the membrane fatty acid composition revealed that for both the nox mutant and UA159 parent strain, growth in an oxygen-rich environment resulted in high proportions of unsaturated membrane fatty acids, independent of external pH. The data indicate that S. mutans membrane fatty acid composition is responsive to oxidative stress, as well as changes in environmental pH, as previously reported (E. M. Fozo and R. G. Quivey, Jr., Appl. Environ. Microbiol. 70:929-936, 2004). The heightened ability of the nox strain to survive acidic and oxidative environmental stress suggests a multifaceted response system that is partially dependent on oxygen metabolites.     

Role of DNA base excision repair in the mutability and virulence of Streptococcus mutans

The oral pathogen, Streptococcus mutans, possesses inducible DNA repair defences for protection against pH fluctuations and production of reactive oxygen metabolites such as hydrogen peroxide (H(2) O(2) ), which are present in the oral cavity. DNA base excision repair (BER) has a critical role in genome maintenance by preventing the accumulation of mutations associated with environmental factors and normal products of cellular metabolism. In this study, we examined the consequences of compromising the DNA glycosylases (Fpg and MutY) and endonucleases (Smx and Smn) of the BER pathway and their relative role in adaptation and virulence. Enzymatic characterization of the BER system showed that it protects the organism against the effects of the highly mutagenic lesion, 7,8-dihydro-8-oxo-2'-deoxyguanine (8-oxo-dG). S. mutans strains lacking a functional Fpg, MutY or Smn showed elevated spontaneous mutation frequencies; and, these mutator phenotypes correlated with the ability of the strains to survive killing by acid and oxidative agents. In addition, in the Galleria mellonella virulence model, strains of S. mutans deficient in Fpg, MutY and Smn showed increased virulence as compared with the parent strain. Our results suggest that, for S. mutans, mutator phenotypes, due to loss of BER enzymes, may confer an advantage to virulence of the organism.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Acid adaptation in Streptococcus mutans UA159 alleviates sensitization to environmental stress due to RecA deficiency

Abstract A RecA-deficient stain of Streptococcus mutans , isolated previously, was found to be more susceptible than the prototroph organism to acid killing and also showed reduced colony-forming ability on sucrose-containing medium. The deficient strain was able to grow in chemostat culture at a low pH value of 5 and did not show reduced capacity to produce acid in standard pH-drop experiments with excess glucose. Moreover, it was able to undergo an adaptive response when grown at a low pH to become more resistant to acid killing and also to killing by ultraviolet radiation or hydrogen peroxide. In fact, after adaptation, it was nearly as resistant as the prototroph strain. These findings were interpreted, in part, in terms of an acid-inducible DNA repair system which functions independently of RecA.     

Mechanisms of the antinociceptive action of (?) Epicatechin obtained from the hydroalcoholic fraction of Combretum leprosum Mart & Eic in rodents

ABSTRACT: BACKGROUND: The mechanisms of the antinociceptive activity of () epicatechin (EPI), a compound isolated from the hydroalcoholic fraction of Combreum leprosum Mart & Eicher. METHODS: were assessed in the model of chemical nociception induced by glutamate (20 mumol/paw). To evaluate the mechanisms involved, the animals , male Swiss mice (25-30 g), received EPI (50 mg/kg p.o.) after pretreatment with naloxone (2 mg/kg s.c. opioid antagonist), glibenclamide (2 mg/kg s.c. antagonist K + channels sensitive to ATP), ketanserin (0.3 mg/kg s.c. antagonist of receptor 5-HT2A), yoimbine (0.15 mg/kg s.c. alpha2 adrenergic receptor antagonist), pindolol (1 mg/kg s.c. 5-HT1a/1b receptor antagonist), atropine (0.1 mg/kg s.c. muscarinic antagonist) and caffeine (3 mg/kg s.c. adenosine receptor antagonist), ondansetron (0.5 mg/kg s.c. for 5-HT3 receptor) and L-arginine (600 mg/kg i.p.). RESULTS: The antinociceptive effect of EPI was reversed by pretreatment with naloxone and glibenclamide, ketanserin, yoimbine, atropine and pindolol, which demonstrates the involvement of opioid receptors and potassium channels sensitive to ATP, the serotoninergic (receptor 5HT1A and 5HT2A), adrenergic (receptor alpha 2) and cholinergic (muscarinic receptor) systems in the activities that were observed. The effects of EPI, however, were not reversed by pretreatment with caffeine, L-arginine or ondansetron, which shows that there is no involvement of 5HT3 receptors or the purinergic and nitrergic systems in the antinociceptive effect of EPI. In the Open Field and Rotarod test, EPI had no significant effect, which shows that there was no central nervous system depressant or muscle relaxant effect on the results. CONCLUSIONS: This study demonstrates that the antinociceptive activity of EPI in the glutamate model involves the participation of the opioid system, serotonin, adrenergic and cholinergic.     

Differences in need for antihypertensive drugs among those aware and unaware of their hypertensive status: a cross sectional survey

Peripheral arterial disease (PAD) is a common, progressive manifestation of atherothrombotic vascular disease, which should be managed no different to cardiac disease. Indeed, there is growing evidence that PAD patients are a high risk group, although still relatively under-detected and under treated. This is despite the fact that PAD patients are an increased mortality rate comparable to those with pre-existing or established cardiovascular disease [myocardial infarction, stroke]. With a holistic approach to atherothrombotic vascular disease, our management of PAD can only get better.