Nocturnal Blood Pressure Pattern Affects Left Ventricular Remodeling and Late Gadolinium Enhancement in Patients with Hypertension and Left Ventricular Hypertrophy

Background

Left ventricular hypertrophy (LVH) is an independent predictor of cardiac mortality, regardless of its etiology. Previous studies have shown that high nocturnal blood pressure (BP) affects LV geometry in hypertensive patients. It has been suggested that continuous pressure overload affects the development of LVH, but it is unknown whether persistent pressure influences myocardial fibrosis or whether the etiology of LVH is associated with myocardial fibrosis. Comprehensive cardiac magnetic resonance (CMR) including the late gadolinium enhancement (LGE) technique can evaluate both the severity of changes in LV geometry and myocardial fibrosis. We tested the hypothesis that the nocturnal non-dipper BP pattern causes LV remodeling and fibrosis in patients with hypertension and LVH.

Methods

Forty-seven hypertensive patients with LVH evaluated by echocardiography (29 men, age 73.0±10.4 years) were examined by comprehensive CMR and 24-h ambulatory blood pressure monitoring (ABPM).

Results and Conclusions

Among the 47 patients, twenty-four had nocturnal non-dipper BP patterns. Patients with nocturnal non-dipper BP patterns had larger LV masses and scar volumes independent of etiologies than those in patients with dipper BP patterns (p = 0.035 and p = 0.015, respectively). There was no significant difference in mean 24-h systolic BP between patients with and without nocturnal dipper BP patterns (p = 0.367). Among hypertensive patients with LVH, the nocturnal non-dipper blood pressure pattern is associated with both LV remodeling and myocardial fibrosis independent of LVH etiology.     

High Sensitivity of Late Gadolinium Enhancement for Predicting Microscopic Myocardial Scarring in Biopsied Specimens in Hypertrophic Cardiomyopathy

Background

Myocardial scarring can be assessed by cardiac magnetic resonance imaging with late gadolinium enhancement and by endomyocardial biopsy. However, accuracy of late gadolinium enhancement for predicting microscopic myocardial scarring in biopsied specimens remains unknown in hypertrophic cardiomyopathy. We investigated whether late gadolinium enhancement in the whole heart reflects microscopic myocardial scarring in the small biopsied specimens in hypertrophic cardiomyopathy.

Methods and Results

Twenty-one consecutive patients with hypertrophic cardiomyopathy who were examined both by cardiac magnetic resonance imaging and by endomyocardial biopsy were retrospectively studied. The right interventricular septum was the target site for endomyocardial biopsy in all patients. Late gadolinium enhancement in the ventricular septum had an excellent sensitivity (100%) with a low specificity (40%) for predicting microscopic myocardial scarring in biopsied specimens. The sensitivity of late gadolinium enhancement in the whole heart remained 100% with a specificity of 27% for predicting microscopic myocardial scarring in biopsied specimens. Quantitative assessments of fibrosis revealed that the extent of late gadolinium enhancement in the whole heart was the only independent variable related to the microscopic collagen fraction in biopsied specimens (β  =  0.59, 95% confident interval: 0.15 – 1.0, p  =  0.012).

Conclusions

Although there was a compromise in the specificity, the sensitivity of late gadolinium enhancement was excellent for prediction of microscopic myocardial scarring in hypertrophic cardiomyopathy. Moreover, the severity of late gadolinium enhancement was independently associated with the quantitative collagen fraction in biopsied specimens in hypertrophic cardiomyopathy. These findings indicate that late gadolinium enhancement can reflect both the presence and the extent of microscopic myocardial scarring in the small biopsied specimens in hypertrophic cardiomyopathy.     

Genetic Code Variations in Mitochondria: tRNA as a Major Determinant of Genetic Code Plasticity

Characteristic features of tRNA such as the anticodon sequence and modified nucleotides in the anticodon loop are thought to be crucial effectors for promoting or restricting codon reassignment. Our recent findings on basepairing rules between anticodon and codon in various metazoan mitochondria suggest that the complete loss of a codon is not necessarily essential for codon reassignment to take place. We postulate that a possible competition between two tRNAs with cognate anticodon sequences towards the relevant codon to be varied has a potential role in codon reassignment. Our proposition can be viewed as an expanded version of the codon capture theory proposed by Osawa and Jukes (J Mol Evol 28: 271–278, 1989). Received: 28 December 2000 / Accepted: 12 March 2001     

A Major Genetic Locus in Trypanosoma brucei Is a Determinant of Host Pathology

The progression and variation of pathology during infections can be due to components from both host or pathogen, and/or the interaction between them. The influence of host genetic variation on disease pathology during infections with trypanosomes has been well studied in recent years, but the role of parasite genetic variation has not been extensively studied. We have shown that there is parasite strain-specific variation in the level of splenomegaly and hepatomegaly in infected mice and used a forward genetic approach to identify the parasite loci that determine this variation. This approach allowed us to dissect and identify the parasite loci that determine the complex phenotypes induced by infection. Using the available trypanosome genetic map, a major quantitative trait locus (QTL) was identified on T. brucei chromosome 3 (LOD = 7.2) that accounted for approximately two thirds of the variance observed in each of two correlated phenotypes, splenomegaly and hepatomegaly, in the infected mice (named TbOrg1). In addition, a second locus was identified that contributed to splenomegaly, hepatomegaly and reticulocytosis (TbOrg2). This is the first use of quantitative trait locus mapping in a diploid protozoan and shows that there are trypanosome genes that directly contribute to the progression of pathology during infections and, therefore, that parasite genetic variation can be a critical factor in disease outcome. The identification of parasite loci is a first step towards identifying the genes that are responsible for these important traits and shows the power of genetic analysis as a tool for dissecting complex quantitative phenotypic traits.     

Effects of Different Pulmonary Vasodilators on Arterial Saturation in a Model of Pulmonary Hypertension

Background

Approved therapies for pulmonary arterial hypertension can induce oxygen desaturation when administered to patients with secondary forms of pulmonary hypertension (PH), probably due to an increase in ventilation/perfusion mismatch. Thus, so far these treatments have largely failed in secondary forms of PH.

Methods

We established an animal model of heterogeneous lung ventilation to evaluate the desaturation potential of mechanistically distinct vasoactive drugs launched or currently in clinical development for the treatment of PH. Single-lung ventilation was induced in five groups (N = 6) of anesthetized minipigs (7 weeks, 4 to 5 kg BW), and their hemodynamic parameters were monitored before and after intravenous injection of control (vehicle only), endothelin antagonist (bosentan; 0.3, 1, 3, 10 mg/kg), phosphodiesterase type 5 inhibitor (sildenafil; 3, 10, 30, 100 µg/kg), and soluble guanylate cyclase stimulators (BAY 41–8543 and riociguat; 1, 3, 10, 30 µg/kg). Cumulative doses were administered before successive unilateral ventilation cycles. The doses were chosen to achieve equal effect on blood pressure by the different pharmacologic principles.

Results

Single-lung ventilation resulted in transient increases in mean pulmonary artery pressure (mPAP) and desaturation. In contrast to control, all drugs dose-dependently decreased hypoxic mPAP (a positive treatment effect) and increased area under the arterial hemoglobin saturation curve (unwanted desaturation effect). Riociguat and bosentan reduced hypoxic mPAP to the greatest extent, while the soluble guanylate cyclase stimulators riociguat and BAY 41–8543 lowered arterial oxygen saturation of hemoglobin the least.

Conclusions

Future investigations will be required to confirm these findings in clinical settings.     

Antioxidant Levels Represent a Major Determinant in the Regenerative Capacity of Muscle Stem Cells

Stem cells are classically defined by their multipotent, long-term proliferation, and self-renewal capabilities. Here, we show that increased antioxidant capacity represents an additional functional characteristic of muscle-derived stem cells (MDSCs). Seeking to understand the superior regenerative capacity of MDSCs compared with myoblasts in cardiac and skeletal muscle transplantation, our group hypothesized that survival of the oxidative and inflammatory stress inherent to transplantation may play an important role. Evidence of increased enzymatic and nonenzymatic antioxidant capacity of MDSCs were observed in terms of higher levels of superoxide dismutase and glutathione, which appears to confer a differentiation and survival advantage. Further when glutathione levels of the MDSCs are lowered to that of myoblasts, the transplantation advantage of MDSCs over myoblasts is lost when transplanted into both skeletal and cardiac muscles. These findings elucidate an important cause for the superior regenerative capacity of MDSCs, and provide functional evidence for the emerging role of antioxidant capacity as a critical property for MDSC survival post-transplantation.     

Epistasis Is a Major Determinant of the Additive Genetic Variance in Mimulus guttatus

The influence of genetic interactions (epistasis) on the genetic variance of quantitative traits is a major unresolved problem relevant to medical, agricultural, and evolutionary genetics. The additive genetic component is typically a high proportion of the total genetic variance in quantitative traits, despite that underlying genes must interact to determine phenotype. This study estimates direct and interaction effects for 11 pairs of Quantitative Trait Loci (QTLs) affecting floral traits within a single population of Mimulus guttatus. With estimates of all 9 genotypes for each QTL pair, we are able to map from QTL effects to variance components as a function of population allele frequencies, and thus predict changes in variance components as allele frequencies change. This mapping requires an analytical framework that properly accounts for bias introduced by estimation errors. We find that even with abundant interactions between QTLs, most of the genetic variance is likely to be additive. However, the strong dependency of allelic average effects on genetic background implies that epistasis is a major determinant of the additive genetic variance, and thus, the population’s ability to respond to selection.     

Single Intraperitoneal Injection of Monocrotaline as a Novel Large Animal Model of Chronic Pulmonary Hypertension in Tibet Minipigs

Objective

The purpose of this study was to establish an animal model of chronic pulmonary hypertension with a single-dose intraperitoneal injection of monocrotaline (MCT) in young Tibet minipigs, so as to enable both invasive and noninvasive measurements and hence facilitate future studies.

Methods

Twenty-four minipigs (8-week-old) were randomized to receive single-dose injection of 12.0 mg/kg MCT (MCT group, n = 12) or placebo (control group, n = 12 each). On day 42, all animals were evaluated for pulmonary hypertension with conventional transthoracic echocardiography, right heart catheterization (RHC), and pathological changes. Findings of these studies were compared between the two groups.

Results

At echocardiography, the MCT group showed significantly higher pulmonary arterial mean pressure (PAMP) compared with the controls (P<0.001). The pulmonary valve curve showed v-shaped signals with reduction of a-waves in minipigs treated with MCT. In addition, the MCT group had longer pulmonary artery pre-ejection phases, and shorter acceleration time and ejection time. RHC revealed higher mean pulmonary arterial pressure (mPAP) in the MCT group than in the control group (P<0.01). A significant and positive correlation between the mPAP values and the PAMP values (R = 0.974, P<0.0001), and a negative correlation between the mPAP and ejection time (R = 0.680, P<0.0001) was noted. Pathology demonstrated evidence of pulmonary vascular remodeling and higer index of right ventricular hypertrophy in MCT-treated minipigs.

Conclusion

A chronic pulmonary hypertension model can be successfully established in young minipigs at six weeks after MCT injection. These minipig models exhibited features of pulmonary arterial hypertension that can be evaluated by both invasive (RHC) and noninvasive (echocardiography) measurements, and may be used as an easy and stable tool for future studies on pulmonary hypertension.     

Inhalation of the BKCa-Opener NS1619 Attenuates Right Ventricular Pressure and Improves Oxygenation in the Rat Monocrotaline Model of Pulmonary Hypertension

Background

Right heart failure is a fatal consequence of chronic pulmonary hypertension (PH). The development of PH is characterized by increased proliferation of vascular cells, in particular pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells. In the course of PH, an escalated right ventricular (RV) afterload occurs, which leads to increased perioperative morbidity and mortality. BK_Ca channels are ubiquitously expressed in vascular smooth muscle cells and their opening induces cell membrane hyperpolarization followed by vasodilation. Moreover, BK activation induces anti-proliferative effects in a multitude of cell types. On this basis, we hypothesized that treatment with the nebulized BK channel opener NS1619 might be a therapy option for pulmonary hypertension and tested this in rats.

Methods

(1) Rats received monocrotaline injection for PH induction. Twenty-four days later, rats were anesthetized and NS1619 or the solvent was administered by inhalation. Systemic hemodynamic parameters, RV hemodynamic parameters, and blood gas analyses were measured before as well as 30 and 120 minutes after inhalation. (2) Rat PASMCs were stimulated with PDGF-BB in the presence and absence of NS1619. AKT, ERK1 and ERK2 activation were investigated by western blot analyses, and relative cell number was determined 48 hours after stimulation.

Results

Inhalation of a 12 µM and 100 µM NS1619 solution significantly reduced RV pressure without affecting systemic arterial pressure. Blood gas analyses demonstrated significantly reduced carbon dioxide and improved oxygenation in NS1619-treated animals pointing towards a considerable pulmonary shunt-reducing effect. In PASMC’s, NS1619 (100 µM) significantly attenuated PASMC proliferation by a pathway independent of AKT and ERK1/2 activation.

Conclusion

NS1619 inhalation reduces RV pressure and improves oxygen supply and its application inhibits PASMC proliferation in vitro. Hence, BK opening might be a novel option for the treatment of pulmonary hypertension.     

Diaphragm Atrophy and Contractile Dysfunction in a Murine Model of Pulmonary Hypertension

Pulmonary hypertension (PH) causes loss of body weight and inspiratory (diaphragm) muscle dysfunction. A model of PH induced by drug (monocrotaline, MCT) has been extensively used in mice to examine the etiology of PH. However, it is unclear if PH induced by MCT in mice reproduces the loss of body weight and diaphragm muscle dysfunction seen in patients. This is a pre-requisite for widespread use of mice to examine mechanisms of cachexia and diaphragm abnormalities in PH. Thus, we measured body and soleus muscle weight, food intake, and diaphragm contractile properties in mice after 6–8 weeks of saline (control) or MCT (600 mg/kg) injections. Body weight progressively decreased in PH mice, while food intake was similar in both groups. PH decreased (P<0.05) diaphragm maximal isometric specific force, maximal shortening velocity, and peak power. Protein carbonyls in whole-diaphragm lysates and the abundance of select myofibrillar proteins were unchanged by PH. Our findings show diaphragm isometric and isotonic contractile abnormalities in a murine model of PH induced by MCT. Overall, the murine model of PH elicited by MCT mimics loss of body weight and diaphragm muscle weakness reported in PH patients.     

Compositional Bias is a Major Determinant of the Distribution Pattern and Abundance of Palindromes in Drosophila melanogaster

Palindromic sequences are important DNA motifs related to gene regulation, DNA replication and recombination, and thus, investigating the evolutionary forces shaping the distribution pattern and abundance of palindromes in the genome is substantially important. In this article, we analyzed the abundance of palindromes in the genome, and then explored the possible effects of several genomic factors on the palindrome distribution and abundance in Drosophila melanogaster. Our results show that the palindrome abundance in D. melanogaster deviates from random expectation and the uneven distribution of palindromes across the genome is associated with local GC content, recombination rate, and coding exon density. Our data suggest that base composition is the major determinant of the distribution pattern and abundance of palindromes and the correlation between palindrome density and recombination is a side-product of the effect of compositional bias on the palindrome abundance.     

Association of a Tandem Repeat Polymorphism in NFATc1 with Increased Risk of Perimembranous Ventricular Septal Defect in a Chinese Population

The nuclear factor of activated T lymphocytes (NFATc1) plays a critical role during valvular and septal development. Genetic variants may influence the biological function of the protein and thus play a role in susceptibility to valvuloseptal defects. Tandem repeat polymorphisms and a common nonsynonymous polymorphism (Cys751Gly) of NFATc1 were genotyped in a hospital-based case-control study of 241 patients with valvuloseptal cardiac defects and 557 controls. The risk of valvuloseptal defect associated with the variant homozygote (LL) was significantly greater than that of the wild-type homozygote. Based on stratification analyses by congenital heart disease types, individuals with the LL genotype were postulated to have a higher risk of perimembranous ventricular septal defect (adjusted OR?=?1.68, 95% CI?=?1.02-2.78). These findings suggest the usefulness of the NFATc1 tandem repeat polymorphism as a biomarker of perimembranous ventricular septal defect susceptibility.     

Ambient pH Is a Major Determinant in the Expression of Cuticle-Degrading Enzymes and Hydrophobin by Metarhizium anisopliae

Secretion of proteolytic and chitinolytic enzymes is a hallmark of infection processes of Metarhizium anisopliae in response to host (insect) cuticular signals. The regulation of these enzymes (subtilisin-like proteases [Pr1a and Pr1b], trypsin-like proteases [Pr2], metalloproteases, aspartyl proteases, aminopeptidase, and chitinases) and a hydrophobin was investigated by Northern analysis and/or enzyme assay. The production of each enzyme showed a differential expression pattern in response to ambient pH; enzymes were synthesized only at pHs at which they function effectively, irrespective of whether the medium contained an inductive cuticle substrate. Three aspartyl proteases (pH optimum, 3), and chitinase (pH optimum, 5) showed maximal accumulation at acidic pHs. The highest level of aminopeptidase (pH optimum, 7) was detected at pH 7. The highest levels of five metalloproteases (pH optima, ca. 7) were detected over the pH range 6 to 8. Two trypsins and several subtilisin-like Pr1 isoforms with pH optima of ca. 8 were produced only under alkaline conditions. Northern analysis of RNA species corresponding to seven cDNA sequences encoding proteases and chitinase confirmed that the ambient pH played a major role in gene expression of secreted proteins. Hydrophobin was expressed almost equally at pHs 5 and 8 but was not expressed at pH 3. During fungal penetration, the pH of infected cuticle rises from about 6.3 to 7.7. Consistent with pH regulation of enzyme production, serine and metalloproteases were produced in situ during infection, but no production of aspartyl proteases was found. We propose that the alkalinity of infected cuticle represents a physiological signal that triggers the production of virulence factors.     

Allelic Variation in Paralogs of GDP-l-Galactose Phosphorylase Is a Major Determinant of Vitamin C Concentrations in Apple Fruit

To identify the genetic factors underlying the regulation of fruit vitamin C (l-ascorbic acid [AsA]) concentrations, quantitative trait loci (QTL) studies were carried out in an F1 progeny derived from a cross between the apple (Malus × domestica) cultivars Telamon and Braeburn over three years. QTL were identified for AsA, glutathione, total antioxidant activity in both flesh and skin tissues, and various quality traits, including flesh browning. Four regions on chromosomes 10, 11, 16, and 17 contained stable fruit AsA-QTL clusters. Mapping of AsA metabolic genes identified colocations between orthologs of GDP-l-galactose phosphorylase (GGP), dehydroascorbate reductase (DHAR), and nucleobase-ascorbate transporter within these QTL clusters. Of particular interest are the three paralogs of MdGGP, which all colocated within AsA-QTL clusters. Allelic variants of MdGGP1 and MdGGP3 derived from the cultivar Braeburn parent were also consistently associated with higher fruit total AsA concentrations both within the mapping population (up to 10-fold) and across a range of commercial apple germplasm (up to 6-fold). Striking differences in the expression of the cv Braeburn MdGGP1 allele between fruit from high- and low-AsA genotypes clearly indicate a key role for MdGGP1 in the regulation of fruit AsA concentrations, and this MdGGP allele-specific single-nucleotide polymorphism marker represents an excellent candidate for directed breeding for enhanced fruit AsA concentrations. Interestingly, colocations were also found between MdDHAR3-3 and a stable QTL for browning in the cv Telamon parent, highlighting links between the redox status of the AsA pool and susceptibility to flesh browning.In plants, l-ascorbic acid (AsA; vitamin C) is essential for the detoxification of reactive oxygen species produced under stress or following exposure to pathogens. In addition to these antioxidant functions, AsA has been shown to be involved in a range of important cellular processes, including plant development and hormone signaling, cell cycle, cell expansion, senescence, and as a cofactor for a number of important enzymes (for review, see Davey et al., 2000; Smirnoff et al., 2001; Noctor, 2006). Fruit AsA concentrations have also been correlated with the maintenance of quality during postharvest storage (Davey and Keulemans, 2004; Davey et al., 2007) and have been linked to susceptibility to internal browning in both apple (Malus × domestica; Davey et al., 2006; Davey and Keulemans, 2009) and pear (Pyrus communis; Veltman et al., 1999; Franck et al., 2003). Finally, AsA is clearly an essential dietary component for humans, with a protective role proposed for many disorders and diseases (Diplock et al., 1998). Given its importance for all metabolically active tissues, there is widespread interest in unraveling the mechanisms underlying the genetic control of AsA concentrations in fruits as well as in how AsA interacts with other plant antioxidant pools.The concentration of AsA will be determined by the net rates of biosynthesis, recycling, degradation, and/or intercellular and intracellular transport, but the relative contribution of these various processes depends on several factors, including genetics, tissue type (Bulley et al., 2009), developmental stage (Hancock et al., 2007; Bulley et al., 2009; Ioannidi et al., 2009), and light intensity (Yabuta et al., 2007; Gautier et al., 2009). The biosynthesis of AsA proceeds via l-Gal (Wheeler et al., 1998), although conclusive evidence for all steps has only relatively recently become available (Conklin et al., 2006; Laing et al., 2007). Alternative biosynthetic routes involving uronic acids (Davey et al., 1999; Agius et al., 2003), l-gulose (Wolucka and Van Montagu, 2003), or myoinositol (Lorence et al., 2004) have been proposed in several plant species, including apple (Davey et al., 2004; Razavi et al., 2005; Fig. 1), but their physiological relevance and contribution to the AsA pool is still far from clear in most plant species, with the possible exception of strawberry (Fragaria × ananassa; Agius et al., 2003; Cruz-Rus et al., 2011; Zorrilla-Fontanesi et al., 2011).Open in a separate windowFigure 1.AsA biosynthetic and recycling pathways in plants: l-Gal pathway, reactions 1 to 9; l-gulose pathway, reactions 1 to 5 and 10 to 13; d-galacturonate pathway, reactions 14 to 16; myoinositol/glucuronate pathway, reactions 17 to 21; recycling pathway, reactions 22 to 27. Reactions with question marks are yet to be identified. Numbered reactions are as follows: 1, Glc-6-P isomerase; 2, Man-6-P isomerase (PMI; EC 5.3.1.8); 3, phosphomannomutase (PMM; EC 5.4.2.8); 4, GDP-d-Man pyrophosphorylase (GMP; EC 2.7.7.13); 5, GDP-d-Man 3′,5′-epimerase (GME; EC 5.1.3.18); 6, GDP-l-Gal-phosphorylase (VTC2 or GGP; EC 2.7.7.69); 7, l-Gal-1-P phosphatase (VTC4 or GPP; EC 3.1.3.25); 8, l-Gal dehydrogenase (GalDH; EC 1.1.1.48); 9, l-galactono-1,4-lactone dehydrogenase (GLDH; EC 1.3.2.3); 10, nucleotide pyrophosphatase or sugar-1-phosphate guanyltransferase; 11, sugar phosphatase; 12, sugar dehydrogenase; 13, l-gulono-1,4-lactone oxidase (EC 1.1.3.8); 14, d-galacturonate-1-phosphate uridyltransferase and d-galacturonate-1-phosphate phosphatase (possible); 15, d-galacturonate reductase (GalUR; EC 1.1.1.n9); 16, aldonolactonase; 17, myoinositol oxygenase (MIOX; EC 1.13.99.1); 18, d-glucuronate reductase (EC 1.1.1.19); 19, l-gulonolactonase; 20, d-glucuronate-1-phosphate uridyltransferase; 21, d-glucurono-1-phosphate phosphatase; 22, l-ascorbate peroxidase (APX; EC 1.11.1.11); 23, l-ascorbate oxidase (AO; EC 1.10.3.3); 24, monodehydroascorbate reductase (MDHAR; EC 1.6.5.4); 25, dehydroascorbate reductase (DHAR; EC 1.8.5.1); 26, GSH reductase (GR; EC 1.8.1.7). [See online article for color version of this figure.]As an antioxidant, AsA is able to accept electrons from a wide range of radical substrates, and in this process it becomes oxidized first to monodehydroascorbate and then to dehydroascorbate (DHA). These oxidized forms of AsA can be regenerated by the ascorbate-glutathione (GSH) cycle, so that GSH and the activities of GSH reductase, dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) maintain the size and redox status of the AsA pool (Noctor and Foyer, 1998; Fig. 1). Indeed, overexpression of an Arabidopsis (Arabidopsis thaliana) MDHAR (Eltayeb et al., 2007) and a wheat (Triticum aestivum) DHAR (Chen et al., 2003) have both been shown to increase foliar AsA concentrations in tobacco (Nicotiana tabacum). MDHAR activity has also been positively correlated with both AsA and fruit firmness in tomato (Solanum lycopersicum) after chilling stress (Stevens et al., 2008).Tissue AsA concentrations can also be maintained by intercellular transport, and there is evidence for the long-distance transport of AsA via the phloem from source (leaf) to sink (fruit) tissues (Franceschi and Tarlyn, 2002; Hancock et al., 2003). In apple, fruit AsA concentrations have been suggested to be partly dependent on the translocation of AsA from leaves (Li et al., 2009), but in black currant (Ribes nigrum), others concluded that the contribution of phloem AsA transport to fruit AsA concentrations was negligible (Hancock et al., 2007). While the actual mechanisms of long-distance transport of AsA have not been fully determined, attention has focused on the large family of Nucleobase-Ascorbate Transporters (NATs; de Koning and Diallinas, 2000), and NAT homologs have been found to be highly expressed in vascular tissues (Maurino et al., 2006).Genes involved in several of these mechanisms have been proposed to be key regulators of fruit AsA concentrations, including GDP-l-Gal phosphorylase (GGP) or vitamin c defective2 (VTC2) in kiwifruit (Actinidia deliciosa; Bulley et al., 2009, 2012) as well as GDP-Man-3,5-epimerase (GME; Gilbert et al., 2009), l-Gal-1-P-phosphatase (GPP or VTC4; Ioannidi et al., 2009), and MDHAR (Stevens et al., 2007) in tomato. However, apart from GGP (Bulley et al., 2012), overexpression of these structural genes has to date had limited success in altering the fruit AsA pool (Agius et al., 2003; Bulley et al., 2009; Haroldsen et al., 2011).In this work, we set out to identify potential genetic determinants of fruit AsA concentrations in apple fruit using a combination of molecular and genomic approaches. Initial quantitative trait loci (QTL) analyses of AsA concentrations (Davey et al., 2006) have been expanded to identify QTL for other antioxidants and fruit quality traits over three years, including results in 1 year comparing the concentrations of AsA in fruit and leaves. Alignments of the apple orthologs of genes involved in AsA biosynthesis, turnover, and transport against the whole genome sequence of cv Golden Delicious (Velasco et al., 2010) allowed us to identify candidate genes (CGs) colocating with stable QTL clusters. Using next-generation sequencing (RNA-Seq) data, polymorphic single-nucleotide polymorphism (SNP)-based markers were developed for these colocating CGs, and their positions on individual linkage groups were confirmed by linkage mapping in our mapping population. Finally, associations between allelic variants of these CGs and their expression levels in cultivars with contrasting AsA concentrations allowed us to develop allele-specific markers associated with high fruit AsA concentrations.     

Replication of Murine Cytomegalovirus in Differentiated Macrophages as a Determinant of Viral Pathogenesis

Blood monocytes or tissue macrophages play a pivotal role in the pathogenesis of murine cytomegalovirus (MCMV) infection, providing functions beneficial to both the virus and the host. In vitro and in vivo studies have indicated that differentiated macrophages support MCMV replication, are target cells for MCMV infection within tissues, and harbor latent MCMV DNA. However, this cell type presumably initiates early, antiviral immune responses as well. In addressing this paradoxical role of macrophages, we provide evidence that the proficiency of MCMV replication in macrophages positively correlates with virulence in vivo. An MCMV mutant from which the open reading frames M139, M140, and M141 had been deleted (RV10) was defective in its ability to replicate in macrophages in vitro and was highly attenuated for growth in vivo. However, depletion of splenic macrophages significantly enhanced, rather than deterred, replication of both wild-type (WT) virus and RV10 in the spleen. The ability of RV10 to replicate in intact or macrophage-depleted spleens was independent of cytokine production, as this mutant virus was a poor inducer of cytokines compared to WT virus in both intact organs and macrophage-depleted organs. Macrophages were, however, a major contributor to the production of tumor necrosis factor alpha and gamma interferon in response to WT virus infection. Thus, the data indicate that tissue macrophages serve a net protective role and may function as "filters" in protecting other highly permissive cell types from MCMV infection. The magnitude of virus replication in tissue macrophages may dictate the amount of virus accessible to the other cells. Concomitantly, infection of this cell type initiates the production of antiviral immune responses to guarantee efficient clearance of acute MCMV infection.     

Interventricular heterogeneity as a substrate for arrhythmogenesis of decoupled mitochondria during ischemia in the whole heart

Myocardial ischemia results in metabolic changes, which collapse the mitochondrial network, that increase the vulnerability of the heart to ventricular fibrillation (VF). It has been demonstrated at the single cell level that uncoupling the mitochondria using carbonyl cyanide p-(tri-fluoromethoxy)phenyl-hydrazone (FCCP) at low concentrations can be cardioprotective. The aim of our study was to investigate the effect of FCCP on arrhythmogenesis during ischemia in the whole rabbit heart. We performed optical mapping of isolated rabbit hearts (n = 33) during control and 20 min of global ischemia and reperfusion, both with and without pretreatment with the mitochondrial uncoupler FCCP at 100, 50, or 30 nM. No hearts went into VF during ischemia under the control condition, with or without the electromechanical uncoupler blebbistatin. We found that pretreatment with 100 (n = 4) and 50 (n = 6) nM FCCP, with or without blebbistatin, leads to VF during ischemia in all hearts, whereas pretreatment with 30 nM of FCCP led to three out of eight hearts going into VF during ischemia. We demonstrated that 30 nM of FCCP significantly increased interventricular (but not intraventricular) action potential duration and conduction velocity heterogeneity in the heart during ischemia, thus providing the substrate for VF. We showed that wavebreaks during VF occurred between the right and left ventricular junction. We also demonstrated that no VF occurred in the heart pretreated with 10 μM glibenclamide, which is known to abolish interventricular heterogeneity. Our results indicate that low concentrations of FCCP, although cardioprotective at the single cell level, are arrhythmogenic at the whole heart level. This is due to the fact that FCCP induces different electrophysiological changes to the right and left ventricle, thus increasing interventricular heterogeneity and providing the substrate for VF.     

Human Pentraxin 3 (PTX3) as a Novel Biomarker for the Diagnosis of Pulmonary Arterial Hypertension

Background

Although inflammation is an important feature of pulmonary arterial hypertension (PAH), the usefulness of local inflammatory markers as biomarkers for PAH is unknown. In this study, we tested whether plasma concentrations of human pentraxin 3 (PTX3), a local inflammatory marker, would be a useful biomarker for detecting PAH.

Methods

Plasma PTX3 concentrations were evaluated in 50 PAH patients (27 with idiopathic PAH, 17 with PAH associated with connective tissue disease (CTD-PAH), and six with congenital heart disease), 100 age and sex-matched healthy controls, and 34 disease-matched CTD patients without PAH. Plasma concentrations of B-type natriuretic peptide (BNP) and C-reactive protein (CRP) were also determined.

Results

Mean PTX3 levels were significantly higher in all PAH patients than in the healthy controls (4.40±0.37 vs. 1.94±0.09 ng/mL, respectively; P<0.001). Using a threshold level of 2.84 ng/mL, PTX3 yielded a sensitivity of 74.0% and a specificity of 84.0% for the detection of PAH. In CTD-PAH patients, mean PTX3 concentrations were significantly higher than in CTD patients without PAH (5.02±0.69 vs. 2.40±0.14 ng/mL, respectively; P<0.001). There was no significant correlation between plasma levels of PTX3 and BNP or CRP. Receiver operating characteristic (ROC) curves for screening PAH in patients with CTD revealed that PTX3 (area under the ROC curve 0.866) is superior to BNP. Using a PTX3 threshold of 2.85 ng/mL maximized true-positive and false-negative results (sensitivity 94.1%, specificity 73.5%).

Conclusion

Plasma concentrations of PTX3 may be a better biomarker of PAH than BNP, especially in patients with CTD.