Effects of spinal or general anesthesia on F₂-isoprostanes and isofurans during ischemia/reperfusion of the leg in patients undergoing knee replacement surgery

General and spinal anesthesia are used extensively in orthopedic surgery. However, these methods of anesthesia may result in different amounts of oxygen being delivered to the patient. Ischemia/reperfusion injury after release of the tourniquet initiates free radical-mediated oxidative stress. F₂-isoprostanes are reliable markers of in vivo lipid peroxidation. However, under conditions of high oxygen tension, isofurans are formed. We aimed to compare plasma isofurans and F₂-isoprostanes in spinal versus general anesthesia in patients undergoing knee-replacement surgery in a randomized, blinded study. Thirty-nine patients were randomized to spinal (SA; n = 19) or general anesthesia (GA; n = 20). Blood was collected before anesthesia, and a tourniquet was then applied to the limb during surgery. After release of the tourniquet, blood samples were collected at 30 min, 2 h, and 24 h for measurement of plasma F₂-isoprostanes and isofurans by gas chromatography–mass spectrometry. The two groups were comparable in age and body mass index. Plasma F₂-isoprostanes were significantly lower in the GA patients compared with the SA patients (p = 0.045). In contrast, the GA patients had significantly elevated plasma isofurans (p = 0.032). Increased isofurans during GA compared with SA are likely to reflect increased oxidative stress due to elevated oxygen concentrations during GA. Further studies are required to assess the implications of these findings on perioperative outcomes.     

Individual vocal production in a sperm whale (Physeter macrocephalus) social unit

The vocal repertoires of group‐living animals may communicate individual or group identity. Female and juvenile sperm whales live in long‐term social units that can be assigned to vocal clans based on the pattern of clicks in coda vocalizations. An unusual set of circumstances allowed us to record the vocalizations of photo‐identified individuals within a single social unit over a 41 d period. Using click interpulse intervals, we were able to assign codas to individuals and investigate coda production at the individual level within a social unit for the first time. Adult females in the unit vocalized at approximately equal rates. A calf and juvenile, both male, vocalized less often than the adult females. Repertoires were indistinguishable for all unit members apart from a mother and her calf, which possessed significantly different repertoires—even from one another. We suggest that similarity among the coda repertoires of most unit members indicates a function in advertising unit identity. In contrast, the distinctive repertoires of the calf and its mother may facilitate reunions between these whales. We hypothesize that sperm whales may be able to vary their vocal repertoires as their reproductive status alters the trade‐off between the benefits of individual and group identification.     

Impact of death and dying on the personal lives and practices of palliative and hospice care professionals

Background

Working within the landscape of death and dying, professionals in palliative and hospice care provide insight into the nature of mortality that may be of benefit to individuals facing the end of life. Much less is known about how these professionals incorporate these experiences into their personal lives and clinical practices.

Methods

This ethnographic inquiry used semi-structured interviews and participant observation to elicit an in-depth understanding of the impact of death and dying on the personal lives of national key leaders (n = 6) and frontline clinicians (n = 24) involved in end-of-life care in Canada. Analysis of findings occurred in the field through constant comparative method and member checking, with more formal levels of analysis occurring after the data-collection phase.

Results

Eleven specific themes, organized under three overarching categories (past, present and future), were discovered. Early life experiences with death were a common and prominent feature, serving as a major motivator in participants’ career path of end-of-life care. Clinical exposure to death and dying taught participants to live in the present, cultivate a spiritual life, reflect on their own mortality and reflect deeply on the continuity of life.

Interpretation

Participants reported that their work provided a unique opportunity for them to discover meaning in life through the lessons of their patients, and an opportunity to incorporate these teachings in their own lives. Although Western society has been described as a “death-denying” culture, the participants felt that their frequent exposure to death and dying was largely positive, fostering meaning in the present and curiosity about the continuity of life.Although preserving life is a central goal of medicine, in the end, death is an unavoidable outcome. Professionals in palliative and hospice care, working within the landscape of death and dying, are able to provide insight into death-related experiences and have the opportunity to incorporate these experiences into their personal and professional lives. The ability for death to foster meaning in life has been attested to by wisdom traditions and palliative care professionals alike. The latter usually provide rich accounts of the struggles of dying individuals, and in some instances, accounts of individuals who discovered meaning and purpose within this landscape.Although an expansive body of literature has evolved exploring the spiritual and existential impact of death and dying, these studies focused predominately on the impact on patients and occasionally on family members.^1–5 A small number of studies discussed the residual impact of end-of-life care within a localized group of health care providers; however, there is limited cross-sectional research explicitly investigating the long-term effect of death and dying on the personal and professional lives of individuals who are exposed to death and dying on a frequent basis.^6–15To address these gaps in the literature, this study explored the impact of death and dying on the lives of key leaders and frontline professionals in palliative and hospice care — individuals who arguably provide society and health care practitioners with the most authoritative discourse on end of life and its effect on life in general. This study was part of a larger ethnographic inquiry on the spirituality of palliative and hospice care professionals in Canada.     

Synthesis and structure-activity relationships of nitrobenzyl phosphoramide mustards as nitroreductase-activated prodrugs

A series of nitrobenzyl phosphoramide mustards and their analogs was designed and synthesized to explore their structure-activity relationships as substrates of nitroreductases from Escherichia coli and trypanosomes and as potential antiproliferative and antiparasitic agents. The position of the nitro group on the phenyl ring was important with the 4-nitrobenzyl phosphoramide mustard (1) offering the best combination of enzyme activity and antiproliferative effect against both mammalian and trypanosomatid cells. A preference was observed for halogen substitutions ortho to benzyl phosphoramide mustard but distinct differences were found in their SAR of substituted 4-nitrobenzyl phosphoramide mustards in E. coli nitroreductase-expressing cells and in trypanosomatids expressing endogenous nitroreductases.     

The pharmacokinetics of cefazolin in patients undergoing elective & semi-elective abdominal aortic aneurysm open repair surgery

Background

Surgical site infections are common, so effective antibiotic concentrations at the sites of infection are required. Surgery can lead to physiological changes influencing the pharmacokinetics of antibiotics. The aim of the study is to evaluate contemporary peri-operative prophylactic dosing of cefazolin by determining plasma and subcutaneous interstitial fluid concentrations in patients undergoing elective of semi-elective abdominal aortic aneurysm (AAA) open repair surgery.

Methods/Design

This is an observational pharmacokinetic study of patients undergoing AAA open repair surgery at the Royal Brisbane and Women's Hospital. All patients will be administered 2-g cefazolin by intravenous injection within 30-minutes of the procedure. Participants will have samples from blood and urine, collected at different intervals. Patients will also have a microdialysis catheter inserted into subcutaneous tissue to measure interstitial fluid penetration by cefazolin. Participants will be administered indocyanine green and sodium bromide as well as have cardiac output monitoring performed and tetrapolar bioimpedance to determine physiological changes occurring during surgery. Analysis of samples will be performed using validated liquid chromatography tandem mass-spectrometry. Pharmacokinetic analysis will be performed using non-linear mixed effects modeling to determine individual and population pharmacokinetic parameters and the effect of peri-operative physiological changes on cefazolin disposition.

Discussion

The study will describe cefazolin levels in plasma and the interstitial fluid of tissues during AAA open repair surgery. The effect of physiological changes to the patient mediated by surgery will also be determined. The results of this study will guide clinicians and pharmacists to effectively dose cefazolin in order to maximize the concentration of antibiotics in the tissues which are the most common site of surgical site infections.     

Basal metabolic rate of endotherms can be modeled using heat-transfer principles and physiological concepts: reply to "can the basal metabolic rate of endotherms be explained by biophysical modeling?"

Our recent article (Roberts et al. 2010 ) proposes a mechanistic model for the relation between basal metabolic rate (BMR) and body mass (M) in mammals. The model is based on heat-transfer principles in the form of an equation for distributed heat generation within the body. The model can also be written in the form of the allometric equation BMR = aM(b), in which a is the coefficient of the mass term and b is the allometric exponent. The model generates two interesting results: it predicts that b takes the value 2/3, indicating that BMR is proportional to surface area in endotherms. It also provides an explanation of the physiological components that make up a, that is, respiratory heat loss, core-skin thermal conductance, and core-skin thermal gradient. Some of the ideas in our article have been questioned (Seymour and White 2011 ), and this is our response to those questions. We specifically address the following points: whether a heat-transfer model can explain the level of BMR in mammals, whether our test of the model is inadequate because it uses the same literature data that generated the values of the physiological variables, and whether geometry and empirical values combine to make a "coincidence" that makes the model only appear to conform to real processes.     

Salmonella bongori provides insights into the evolution of the Salmonellae

The genus Salmonella contains two species, S. bongori and S. enterica. Compared to the well-studied S. enterica there is a marked lack of information regarding the genetic makeup and diversity of S. bongori. S. bongori has been found predominantly associated with cold-blooded animals, but it can infect humans. To define the phylogeny of this species, and compare it to S. enterica, we have sequenced 28 isolates representing most of the known diversity of S. bongori. This cross-species analysis allowed us to confidently differentiate ancestral functions from those acquired following speciation, which include both metabolic and virulence-associated capacities. We show that, although S. bongori inherited a basic set of Salmonella common virulence functions, it has subsequently elaborated on this in a different direction to S. enterica. It is an established feature of S. enterica evolution that the acquisition of the type III secretion systems (T3SS-1 and T3SS-2) has been followed by the sequential acquisition of genes encoding secreted targets, termed effectors proteins. We show that this is also true of S. bongori, which has acquired an array of novel effector proteins (sboA-L). All but two of these effectors have no significant S. enterica homologues and instead are highly similar to those found in enteropathogenic Escherichia coli (EPEC). Remarkably, SboH is found to be a chimeric effector protein, encoded by a fusion of the T3SS-1 effector gene sopA and a gene highly similar to the EPEC effector nleH from enteropathogenic E. coli. We demonstrate that representatives of these new effectors are translocated and that SboH, similarly to NleH, blocks intrinsic apoptotic pathways while being targeted to the mitochondria by the SopA part of the fusion. This work suggests that S. bongori has inherited the ancestral Salmonella virulence gene set, but has adapted by incorporating virulence determinants that resemble those employed by EPEC.     

Human neutrophil clearance of bacterial pathogens triggers anti-microbial γδ T cell responses in early infection

Human blood Vγ9/Vδ2 T cells, monocytes and neutrophils share a responsiveness toward inflammatory chemokines and are rapidly recruited to sites of infection. Studying their interaction in vitro and relating these findings to in vivo observations in patients may therefore provide crucial insight into inflammatory events. Our present data demonstrate that Vγ9/Vδ2 T cells provide potent survival signals resulting in neutrophil activation and the release of the neutrophil chemoattractant CXCL8 (IL-8). In turn, Vγ9/Vδ2 T cells readily respond to neutrophils harboring phagocytosed bacteria, as evidenced by expression of CD69, interferon (IFN)-γ and tumor necrosis factor (TNF)-α. This response is dependent on the ability of these bacteria to produce the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), requires cell-cell contact of Vγ9/Vδ2 T cells with accessory monocytes through lymphocyte function-associated antigen-1 (LFA-1), and results in a TNF-α dependent proliferation of Vγ9/Vδ2 T cells. The antibiotic fosmidomycin, which targets the HMB-PP biosynthesis pathway, not only has a direct antibacterial effect on most HMB-PP producing bacteria but also possesses rapid anti-inflammatory properties by inhibiting γδ T cell responses in vitro. Patients with acute peritoneal-dialysis (PD)-associated bacterial peritonitis--characterized by an excessive influx of neutrophils and monocytes into the peritoneal cavity--show a selective activation of local Vγ9/Vδ2 T cells by HMB-PP producing but not by HMB-PP deficient bacterial pathogens. The γδ T cell-driven perpetuation of inflammatory responses during acute peritonitis is associated with elevated peritoneal levels of γδ T cells and TNF-α and detrimental clinical outcomes in infections caused by HMB-PP positive microorganisms. Taken together, our findings indicate a direct link between invading pathogens, neutrophils, monocytes and microbe-responsive γδ T cells in early infection and suggest novel diagnostic and therapeutic approaches.     

Genome-wide gene-environment study identifies glutamate receptor gene GRIN2A as a Parkinson's disease modifier gene via interaction with coffee

Our aim was to identify genes that influence the inverse association of coffee with the risk of developing Parkinson''s disease (PD). We used genome-wide genotype data and lifetime caffeinated-coffee-consumption data on 1,458 persons with PD and 931 without PD from the NeuroGenetics Research Consortium (NGRC), and we performed a genome-wide association and interaction study (GWAIS), testing each SNP''s main-effect plus its interaction with coffee, adjusting for sex, age, and two principal components. We then stratified subjects as heavy or light coffee-drinkers and performed genome-wide association study (GWAS) in each group. We replicated the most significant SNP. Finally, we imputed the NGRC dataset, increasing genomic coverage to examine the region of interest in detail. The primary analyses (GWAIS, GWAS, Replication) were performed using genotyped data. In GWAIS, the most significant signal came from rs4998386 and the neighboring SNPs in GRIN2A. GRIN2A encodes an NMDA-glutamate-receptor subunit and regulates excitatory neurotransmission in the brain. Achieving P_2df = 10⁻⁶, GRIN2A surpassed all known PD susceptibility genes in significance in the GWAIS. In stratified GWAS, the GRIN2A signal was present in heavy coffee-drinkers (OR = 0.43; P = 6×10⁻⁷) but not in light coffee-drinkers. The a priori Replication hypothesis that “Among heavy coffee-drinkers, rs4998386_T carriers have lower PD risk than rs4998386_CC carriers” was confirmed: OR_Replication = 0.59, P_Replication = 10⁻³; OR_Pooled = 0.51, P_Pooled = 7×10⁻⁸. Compared to light coffee-drinkers with rs4998386_CC genotype, heavy coffee-drinkers with rs4998386_CC genotype had 18% lower risk (P = 3×10⁻³), whereas heavy coffee-drinkers with rs4998386_TC genotype had 59% lower risk (P = 6×10⁻¹³). Imputation revealed a block of SNPs that achieved P_2df<5×10⁻⁸ in GWAIS, and OR = 0.41, P = 3×10⁻⁸ in heavy coffee-drinkers. This study is proof of concept that inclusion of environmental factors can help identify genes that are missed in GWAS. Both adenosine antagonists (caffeine-like) and glutamate antagonists (GRIN2A-related) are being tested in clinical trials for treatment of PD. GRIN2A may be a useful pharmacogenetic marker for subdividing individuals in clinical trials to determine which medications might work best for which patients.     

CREST maps somatic structural variation in cancer genomes with base-pair resolution

We developed 'clipping reveals structure' (CREST), an algorithm that uses next-generation sequencing reads with partial alignments to a reference genome to directly map structural variations at the nucleotide level of resolution. Application of CREST to whole-genome sequencing data from five pediatric T-lineage acute lymphoblastic leukemias (T-ALLs) and a human melanoma cell line, COLO-829, identified 160 somatic structural variations. Experimental validation exceeded 80%, demonstrating that CREST had a high predictive accuracy.