Selenium-induced alterations in ionic currents of rat cardiomyocytes

In the present study, rats were treated with sodium selenite (5 micromol/kg body weight/day, ip) for 4 weeks and the parameters of contractile activity, action potential, L-type Ca2+-current (ICaL), as well as transient outward (Ito), inward rectifier (IK1), and steady state (Iss) K+-currents were investigated. Sodium selenite treatment increased rat blood glucose level and lowered plasma insulin level, significantly. This treatment also caused slightly prolongation in action potential with no significant effects on spontaneous contraction parameters and intracellular Ca2+ transients of the heart preparations. These effects were associated with marked alterations in the kinetics of both ICaL and Ito including a significant slowing in both inactivation time constants of ICaL and a significant shift to negative potential at half-inactivation of these channels without any change in the current density. Also, there was a significantly faster inactivation of Ito and no shift in half-inactivation of this channel without any change in its current density. Consequently, there was a approximately 50% increase in total charges carried by Ca2+ current and approximately 50% decrease in total charges carried by K+ currents of the treated rat cardiomyocytes. Additionally we observed a significant inhibition in IK1 density in treated rat cardiomyocytes. Oxidized glutathione level was significantly increased (70%) while the observed decrease in reduced glutathione was much less. Since a shift in redox state of regulatory proteins is related with cell dysfunction, selenium-induced increase in blood glucose and decrease in plasma insulin may correlate these alterations. These alterations, in the kinetics of the channels and in IK1 density, might lead to proarrhythmic effect of chronic selenium supplementation.     

Variations among cell lines in the synthesis of sphingolipids in de novo and recycling pathways

There are several pathways for the incorporation of sugars into glycosphingolipids (GSL). Sugars can be added to ceramide that contains sphinganine (dihydrosphingosine) synthesized de novo (pathway 1), to ceramide synthesized from sphingoid bases produced by hydrolysis of sphingolipids (pathway 2), and into GSL recycling from the endosomal pathway through the Golgi (pathway 3). We reported previously the surprising observation that SW13 cells, a human adrenal carcinoma cell line, synthesize most of their GSL in pathway 2. We now present data on the synthesis of GSL in four additional cell lines. Approximately 90% of sugar incorporation took place in pathway 2, and 10% or less in pathway 1, in human foreskin fibroblasts and NB41A3 neuroblastoma cells. In contrast, approximately 50-90% of sugar incorporation took place in pathway 1 in C2C12 myoblasts. The C2C12 cells divide more rapidly and synthesize 10-14 times as much GSL as the other three cell lines. In C6 glioma cells, approximately 30% of sugar incorporation occurred in pathway 1 and 60% in pathway 2. There was no relation between the utilization of pathways for GSL and sphingomyelin synthesis in foreskin fibroblasts and C2C12 cells. In both cells pathways 1 and 2 each accounted for 50% of incorporation of choline into sphingomyelin. In five of the six cell lines that we have studied, most GSL synthesis takes place in pathway 2. We suggest that when the need for synthesis is relatively low, as in slowly dividing cells, GSL are synthesized predominantly from sphingoid bases salvaged from the hydrolytic pathway. When cells are dividing more rapidly, the need for increased synthesis is met by upregulating the de novo pathway.      

Genetic structure of Anogeissus dhofarica (Combretaceae) populations endemic to the monsoonal fog oases of the southern Arabian Peninsula

Anogeissus dhofarica (Combretaceae) is an endemic tree of the monsoon affected coastal mountains of the southern Arabian Peninsula, being the character species of the Hybantho durae–Anogeissetum dhofaricae association, a drought deciduous, monsoon forest community found only in the Dhofar region of southern Oman and the eastern Al‐Mahra region of south‐east Yemen. Due to the steep precipitation gradient from the centre to the edges in this monsoon affected area, A. dhofarica is found in two different habitat types: in continuous woodland belts of the Hawf and Dhofar mountains, and in isolated, scattered woodland patches, as found especially in the Fartak Mts (south‐east Yemen). Fifteen populations (212 individuals) from across the whole distribution area of the species were analysed using amplified fragment length polymorphism fingerprinting to: (1) evaluate the consequences of population fragmentation on the genetic diversity harboured in isolated patches versus cohering stands of the species and (2) to reconstruct the phylogeographical pattern of A. dhofarica as a consequence of oscillations in the monsoon activity during the Pleistocene and Holocene. The analysis of among‐population genetic differentiation and within‐population genetic diversity in A. dhofarica populations resulted in a lack of genetic pauperization and genetic differentiation of populations of the distinctly isolated patches of the Fartak Mts compared to the more luxurious forests of the Hawf and Dhofar regions. This is considered to be due to the high buffer capacity against the loss of genetic diversity caused by the long‐lived life‐form of the species combined with the capability to propagate clonally and the relatively recent fragmentation of Anogeissus forests into the described patches rather than due to high values of gene flow among remnant populations caused by bee pollination and anemochorical and hydrochorical diaspore dispersal. The phylogeographical pattern of the species argues for a quite recent fragmentation of a once continuous forest belt of A. dhofarica that is rather connected with climate changes in the Holocene than triggered by aridity–humidity oscillations reported for the Pleistocene. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97 , 40–51.     

The role of gender differences in beta-adrenergic receptor responsiveness of diabetic rat heart

Since the mechanisms responsible for gender differences in cardiac contractile function have not been fully elucidated, we focused to determine the effect of gender difference on β-adrenergic receptors (β-ARs) signal transduction in ventricular cardiomyocytes from insulin-dependent diabetic (streptozotocin-induced) rats. Dose-response curves of left ventricular developed pressure (LVDP) to isoproterenol (ISO) in females showed that there was only a ∼30% decrease in the maximum response without a significant shift in EC₅₀ in diabetic females. On the other hand, diabetes induced a clear rightward shift in the potency (5–10 folds) without a significant change in the maximum response in the males. In order to further determine of the underlying mechanism for this difference, we measured cAMP production and obtained dose-response curves with ISO stimulation in isolated cardiomyocytes. In diabetic females, there was no obvious change in the cAMP dose-response curve. On the other hand, there was a significant decrease in the maximum response without any apparent change in the potency of diabetic males. Our findings indicate that male and female rats are affected differently by diabetes in terms of LVDP responses to β-ARs stimulation. Also, the difference between their β-ARs induced cAMP responses may underlie this disparity.     

Selenium alters the lipid content and protein profile of rat heart: an FTIR microspectroscopic study

Cardiovascular disease is one of the most important causes of morbidity and mortality in Western countries. In addition, it is well documented that selenium (Se) deficiency has been linked to cardiovascular diseases. This study was undertaken to present the effect of sodium selenite on left and right myocardia, and small veins of normal control rat heart at molecular level by using Fourier transform infrared (FTIR) microspectroscopy. The results mainly reveal that, Se treatment causes an increase in lipid content both in the saturated and unsaturated lipids, and an alteration in protein profile with a decrease in alpha-helix and an increase in beta-sheet structure of the rat heart which might be reflecting a slight subtoxic effect of selenium supplementation on normal rat heart at the dose used in this study.     

The Modified Sequential Treatment Regimen Containing Levofloxacin for Helicobacter pylori Eradication in Turkey

Background:  Eradication rates of Helicobacter pylori have declined to unacceptable levels in recent years. New and effective treatment options are warranted both as a first and second line treatment.
Aim:  To test an effectiveness of modified sequential therapy with levofloxacin for H. pylori eradication in Turkey.
Material and Methods:  Helicobacter pylori infected dyspeptic patients were included to the study. Subjects were treated with modified sequential therapy consisting of rabeprazole 20 mg b.i.d. and amoxicillin 1 g b.i.d., for 7 days followed by rabeprazole 20 mg b.i.d, levofloxacin 500 mg q.d. and metronidazole 500 mg b.i.d for the remaining 7 days.
Results:  Sixty-three treatment naive patients and 37 previous treatment failures were enrolled to the study (59 F, 41 M, age: 21–80 years). There was five drop out. Helicobacter pylori eradication was achieved in 80 patients, intention-to-treat (ITT): 80% (95% CI: 71–87%) and per-protocol (PP): 84.2% (95% CI: 75–91%), totally. In treatment naive patients ITT and PP eradication rates were 82.5% (95% CI: 71–91%), and 86.7% (95% CI: 75–94%), respectively. As a second line treatment eradication was successful in ITT 75.7%.(95% CI: 59–88%), and PP 80% (95% CI: 63–92%).Mild side effects were reported by 8 patients (8.4%).
Conclusions:  Sequential therapy using "rabeprazole and amoxicillin 7 days followed by rabeprazole, metronidazole and levofloxacin for 7 days" is a new regimen with acceptable eradication rates in naïve patients in Turkey. Further modifications in the dose or duration of this new sequential therapy might increase its effectiveness as both first and second line treatment.     

Effects of intra- and extracellular factors on anti-aging klotho gene expression

Inactivation of the klotho gene in mice causes serious systemic disorders, resembling human aging. However, at the molecular level, its action mechanisms are not well understood. The stimulatory or inhibitory effects of cis- and trans-regulatory factors on the klotho gene expression are also still unclear. We studied the effects of intra- and extracellular factors on human klotho gene expression. For this purpose, pHKP-Luc and pHKP-GFP reporter vectors were constructed with the 2.1-kbp upstream region of human klotho, covering its promoter region, using luciferase and GFP genes as the reporter. A series of vectors that have deletions in the upstream region of the klotho gene were constructed to assay cis-acting factors. Deletion of some parts of the klotho gene upstream region significantly affected reporter gene expression in HEK293 cells. p16 and p53 proteins inhibited reporter luciferase expression under the control of human klotho promoter in a dose-dependent manner. Calcium and phosphate ions stimulated klotho expression. p21, PTH, IGF-1, and angiotensin-II had no significant effect on klotho expression in HEK293 cells.     

Dietary selenium- and vitamin E-induced alterations in some rabbit tissues

The present study was designed to investigate and compare the effects of dietary selenium (Se) and vitamin E on some physiological parameters and histological changes in liver, heart, and skin tissues, as well as the blood parameters and the related enzymes. Both sex young rabbits were fed with deficient (9.8 μg/kg diet), adequate (225 μg/kg diet), and rich (4.2 mg/kg diet) Se and vitamin E diets for 12–15 wk for this purpose. As the plasma Se levels and the erythrocyte glutathione (GSH) peroxidase activity decreased (79.8±9.4 ng/ml and 2.0±0.3 U/g Hb, respectively) in the deficient group, these values increased (100.4±2.7 ng/mL and 14.5±4.3 U/g Hb) in the rich group significantly with respect to the control group. The other antioxidant enzyme activities and the related element levels did not change significantly in either one of the experimental groups. Although the platelet counts of the two experimental groups were not different from the control values, the collagen and the adenosine diphosphate (ADP) stimulated platelet aggregation rate and intensity increased in the deficient group (p<0.05) and decreased very significantly (p<0.001) in the rich group. In both of the experimental groups, as the percentage values of the neutrophils decreased, the lymphocytes and the eosinophils increased significantly. According to the light microscopic investigations, the observed lesions of considerable intensity within the tissues that elicit cell degenerations were more pronounced in the animals fed with the rich diet than in those fed with the deficient diet. The deficiency as well as toxicity of Se and the deficiency of vitamin E caused several alterations in the physiological functions of the tissues, and these alterations were supported by the histological lesions within these tissues.     

Parallels,nonparallels, and plasticity in population differentiation of threespine stickleback within a lake

The frequent occurrence of parallel phenotypic divergence in similar habitats is often evoked when emphasizing the role of ecology in adaptive radiation and speciation. However, because phenotypic plasticity can contribute to the observed pattern of divergence, confirmation of divergence at loci underlying phenotypic traits is important for confirming adaptive divergence. In the present study, we examine parallel morphological, neutral, and potentially adaptive genetic divergence of threespine stickleback inhabiting different habitats within a lake. Three genetic clusters best explained the neutral genetic structure within the lake; however, morphological differences were only weakly connected to genetic clusters and there was considerable phenotypic variation within clusters. Among the factors that could contribute to the observed pattern of morphological and genetic divergence are phenotypic plasticity, selective mortality of hybrids, and habitat choice based on morphology. Several loci are identified as outliers indicating divergent selection between the morphs and some parallels in morphological and adaptive genetic divergence are found in stickleback spawning at two lava sites. However, neutral genetic structure indicates considerable genetic connectivity among the two lava sites, and the parallels in morphology may therefore represent selective distribution of phenotypes rather than parallel divergence. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 803–813.