Infections of cardiac implantable electronic devices: a retrospective multicenter observational study

Infections of cardiac implantable electronic devices (CIED) can cause significant morbidity, mortality, and financial burden. Although staphylococcal organisms account for most infections of these cardiac devices, approximately 20% of all CIED-related infections are caused by non-Staphylococcus species. Herein we describe and compare the demographics, clinical presentation, and outcomes of Staphylococcus aureus and non-staphylococcal infections of CIED.We performed a retrospective, multicenter, observational study of patients from 4 academic hospitals in Houston between 2002 and 2009. All 80 identified non-staphylococcal CIED-related infections were matched, at a 1:1 ratio, to S. aureus infections.Although the demographics and general comorbidities in the 2 study groups were relatively similar, the S. aureus group had a higher proportion of patients with coronary artery disease, diabetes mellitus, and end-stage renal disease. Additionally, 81% of S. aureus compared with only 48.5% of the non-staphylococcal CIED-related infections were health care-associated (p < 0.001). Furthermore, when compared to non-staphylococcal infections, the S. aureus group had more indwelling intravascular foreign material (p < 0.001), more rapid clinical progression (p < 0.001), and overall worse clinical presentation (p < 0.001). However, after stratifying by clinical presentation, the mortality rates in the 2 groups were similar (p = 0.45).Since approximately one-fifth of all CIED-related infections are caused by non-staphylococcal organisms, and untimely antibiotic treatment can result in serious complications, it may be prudent to broaden empiric antimicrobial therapy to cover both Gram-positive and -negative bacteria, until the causative organism is identified.     

Impaired microvascular flow motion in subclinical diabetic feet with sudomotor dysfunction

Impaired cutaneous blood flow and sweating dysfunction might be among the earliest manifestations of diabetic autonomic neuropathy. This study assessed the pathophysiological basis underlying skin vasomotion changes and their relation with progressive sudomotor dysfunction and other autonomic and somatic measures in subclinical diabetic feet. Laser Doppler skin perfusion was assessed on 68 diabetic and 25 control subjects. The low-frequency vasomotion was transformed into three frequency intervals 0.0095-0.021, 0.021-0.052 and 0.052-0.145 Hz, respectively, for the investigation of endothelial, neurogenic and myogenic effects on microcirculatory alterations. The diabetic patients were categorized into three groups by increasing severity of sudomotor dysfunction: SSR+ (sympathetic skin response present; 27 patients), SSR- (SSR absent; 23 patients) and at-risk (SSR absent and of preulcerative cracked skin; 18 patients). All diabetic patients underwent nerve conduction and cardiovascular autonomic studies. The total spectral and endothelial activity was significantly decreased only in the at-risk group. The SSR- group had lower neurogenic vasomotion than the SSR+ group (p<0.05). Although no statistical difference was noted between any group in absolute myogenic spectrum, the SSR- group had higher normalized myogenic activity than the SSR+ group (p<0.01). The larger drop in orthostatic pressure was paralleled by a reduction in the myogenic amplitude (r=-0.33, p<0.01). These results suggested that early impairment of low-frequency flow motion correlated closely with the presence of sudomotor dysfunction of subclinical feet mainly in neurogenic and endothelial components. Impaired systemic vascular tone as manifested by orthostatic hypotension was proportional to the degree of myogenic dysregulation in diabetic patients.     

Postprandial lipoprotein metabolism in familial hypercholesterolemia: thinking outside the box

Familial hypercholesterolemia (FH) is a dominantly inherited disorder principally due to mutations in the low-density lipoprotein (LDL) receptor that classically cause markedly elevated plasma LDL cholesterol concentrations and premature coronary heart disease (CHD). However, elevated plasma LDL cholesterol alone does not fully account for the increase or variation in risk of CHD. We propose a hypothetical model for the role of postprandial dyslipoproteinemia based on the overproduction and decreased catabolism of triglyceride-rich lipoproteins, which may be a consequence of LDL receptor deficiency. Expression of postprandial dyslipoproteinemia in FH may also depend on the type of pathogenic gene variants and on coexistent conditions, particularly obesity and insulin resistance. Further research is required to investigate our model proposed and to test whether treating postprandial dyslipoproteinemia decreases CHD risk in FH incremental to standard therapy.     

Rapid creation of Arabidopsis doubled haploid lines for quantitative trait locus mapping

Quantitative trait loci (QTL) mapping is a powerful tool for investigating the genetic basis of natural variation. QTL can be mapped using a number of different population designs, but recombinant inbred lines (RILs) are among the most effective. Unfortunately, homozygous RIL populations are time consuming to construct, typically requiring at least six generations of selfing starting from a heterozygous F(1). Haploid plants produced from an F(1) combine the two parental genomes and have only one allele at every locus. Converting these sterile haploids into fertile diploids (termed "doubled haploids," DHs) produces immortal homozygous lines in only two steps. Here we describe a unique technique for rapidly creating recombinant doubled haploid populations in Arabidopsis thaliana: centromere-mediated genome elimination. We generated a population of 238 doubled haploid lines that combine two parental genomes and genotyped them by reduced representation Illumina sequencing. The recombination rate and parental allele frequencies in our population are similar to those found in existing RIL sets. We phenotyped this population for traits related to flowering time and for petiole length and successfully mapped QTL controlling each trait. Our work demonstrates that doubled haploid populations offer a rapid, easy alternative to RILs for Arabidopsis genetic analysis.     

Three differentiation states risk-stratify bladder cancer into distinct subtypes

Current clinical judgment in bladder cancer (BC) relies primarily on pathological stage and grade. We investigated whether a molecular classification of tumor cell differentiation, based on a developmental biology approach, can provide additional prognostic information. Exploiting large preexisting gene-expression databases, we developed a biologically supervised computational model to predict markers that correspond with BC differentiation. To provide mechanistic insight, we assessed relative tumorigenicity and differentiation potential via xenotransplantation. We then correlated the prognostic utility of the identified markers to outcomes within gene expression and formalin-fixed paraffin-embedded (FFPE) tissue datasets. Our data indicate that BC can be subclassified into three subtypes, on the basis of their differentiation states: basal, intermediate, and differentiated, where only the most primitive tumor cell subpopulation within each subtype is capable of generating xenograft tumors and recapitulating downstream populations. We found that keratin 14 (KRT14) marks the most primitive differentiation state that precedes KRT5 and KRT20 expression. Furthermore, KRT14 expression is consistently associated with worse prognosis in both univariate and multivariate analyses. We identify here three distinct BC subtypes on the basis of their differentiation states, each harboring a unique tumor-initiating population.     

Molecular basis of bacterial protein Hen1 activating the ligase activity of bacterial protein Pnkp for RNA repair

Ribotoxins cleave essential RNAs for cell killing in vivo, and the bacterial polynucleotide kinase-phosphatase (Pnkp)/hua enhancer 1 (Hen1) complex has been shown to repair ribotoxin-cleaved RNAs in vitro. Bacterial Pnkp/Hen1 is distinguished from other RNA repair systems by performing 3'-terminal 2'-O-methylation during RNA repair, which prevents the repaired RNA from repeated cleavage at the same site. To ensure the opportunity of 2'-O-methylation by bacterial Hen1 during RNA repair and, therefore, maintain the quality of the repaired RNA, Pnkp/Hen1 has evolved to require the participation of Hen1 in RNA ligation, because Pnkp alone is unable to carry out the reaction despite possessing all signature motifs of an RNA ligase. However, the precise role of Hen1 in RNA ligation is unknown. Here, we present the crystal structure of an active RNA ligase consisting of the C-terminal half of Pnkp (Pnkp-C) and the N-terminal half of Hen1 (Hen1-N) from Clostridium thermocellum. The structure reveals that the N-terminal domain of Clostridium thermocellum (Cth) Hen1, shaped like a left hand, grabs the flexible insertion module of CthPnkp and locks its conformation via further interaction with the C-terminal addition module of CthPnkp. Formation of the CthPnkp-C/Hen1-N heterodimer creates a ligation pocket with a width for two strands of RNA, depth for two nucleotides, and the adenosine monophosphate (AMP)-binding pocket at the bottom. The structure, combined with functional analyses, provides insight into the mechanism of how Hen1 activates the RNA ligase activity of Pnkp for RNA repair.