Muscle interstitial glucose and lactate levels during dynamic exercise in humans determined by microdialysis.

The purpose of the present study was to use the microdialysis technique to determine skeletal muscle interstitial glucose and lactate concentrations during dynamic incremental exercise in humans. Microdialysis probes were inserted into the vastus lateralis muscle, and subjects performed knee extensor exercise at workloads of 10, 20, 30, 40, and 50 W. The in vivo probe recoveries determined at rest by the internal reference method for glucose and lactate were 28.7 +/- 2.5 and 32.0 +/- 2.7%, respectively. As exercise intensity increased, probe recovery also increased, and at the highest workload probe recovery for glucose (61.0 +/- 3.9%) and lactate (66. 3 +/- 3.6%) had more than doubled. At rest the interstitial glucose concentration (3.5 +/- 0.2 mM) was lower than both the arterial (5.6 +/- 0.2 mM) and venous (5.3 +/- 0.3 mM) plasma water glucose levels. The interstitial glucose levels remained lower (P < 0.05) than the arterial and venous plasma water glucose concentrations during exercise at all intensities and at 10, 20, 30, and 50 W, respectively. At rest the interstitial lactate concentration (2.5 +/- 0.2 mM) was higher (P < 0.05) than both the arterial (0.9 +/- 0. 2 mM) and venous (1.1 +/- 0.2 mM) plasma water lactate levels. This relationship was maintained (P < 0.05) during exercise at workloads of 10, 20, and 30 W. These data suggest that interstitial glucose delivery at rest is flow limited and that during exercise changes in the interstitial concentrations of glucose and lactate mirror the changes observed in the venous plasma water compartments. Furthermore, skeletal muscle contraction results in an increase in the diffusion coefficient of glucose and lactate within the interstitial space as reflected by an elevation in probe recovery during exercise.     

Non‐surgical method for the induction of delayed implantation and recovery of viable blastocysts in rats and mice by the use of tamoxifen and Depo‐Provera

Implantational delay in rats and mice is experimentally induced by withdrawal of oestrogen and maintenance of progesterone. The oestrogen is normally removed by ovariectomy. We report here that the use of the antioestrogenic effect of the drug tamoxifen in combination with Depo‐Provera (which counteracts the oestrogenic effects of the tamoxifen) may be used to put the embryos both of rats and mice into delay of implantation. These delayed embryos retain their developmental potential and give rise to live born young when transferred to pseudopregnant recipient females. They are a good source of ES cells. Mol. Reprod. Dev. 52:29–32, 1999. © 1999 Wiley‐Liss, Inc.     

Overexpression of multidrug resistance-associated protein 1 protects against cardiotoxicity by augmenting the doxorubicin efflux from cardiomyocytes

Doxorubicin is a commonly used anti-cancer drug used in treating a variety of malignancies. However, a major adverse effect is cardiotoxicity, which is dose dependent and can be either acute or chronic. Doxorubicin causes injury by DNA damage, the formation of free reactive oxygen radicals and induction of apoptosis. Our aim is to induce expression of the multidrug resistance-associated protein 1 (MRP1) in cardiomyocytes derived from human iPS cells (hiPSC-CM), to determine whether this will allow cells to effectively remove doxorubicin and confer cardioprotection. We generated a lentivirus vector encoding MRP1 (LV.MRP1) and validated its function in HEK293T cells and stem cell-derived cardiomyocytes (hiPSC-CM) by quantitative PCR and western blot analysis. The activity of the overexpressed MRP1 was also tested, by quantifying the amount of fluorescent dye exported from the cell by the transporter. We demonstrated reduced dye sequestration in cells overexpressing MRP1. Finally, we demonstrated that hiPSC-CM transduced with LV.MRP1 were protected against doxorubicin injury. In conclusion, we have shown that we can successfully overexpress MRP1 protein in hiPSC-CM, with functional transporter activity leading to protection against doxorubicin-induced toxicity.     

A floxed allele of the androgen receptor gene causes hyperandrogenization in male mice.

We previously generated a conditional floxed mouse line to study androgen action, in which exon 3 of the androgen receptor (AR) gene is flanked by loxP sites, with the neomycin resistance gene present in intron 3. Deletion of exon 3 in global AR knockout mice causes androgen insensitivity syndrome, characterized by genotypic males lacking normal masculinization. We now report that male mice carrying the floxed allele (AR(lox)) have the reverse phenotype, termed hyperandrogenization. AR(lox) mice have increased mass of androgen-dependent tissues, including kidney, (P < 0.001), seminal vesicle (P < 0.001), levator ani muscle (P = 0.001), and heart (P < 0.05). Serum testosterone is not significantly different. Testis mass is normal, histology shows normal spermatogenesis, and AR(lox) males are fertile. AR(lox) males also have normal AR mRNA levels in kidney, brain, levator ani, liver, and testis. This study reaffirms the need to investigate the potential phenotypic effects of floxed alleles in the absence of cre in tissue-specific knockout studies. In addition, this androgen hypersensitivity model may be useful to further investigate the effects of subtle perturbations of androgen action in a range of androgen-responsive systems in the male.     

The tragedy of the commons in microbial populations: insights from theoretical, comparative and experimental studies

First principles of thermodynamics imply that metabolic pathways are faced with a trade-off between the rate and yield of ATP production. Simple evolutionary models argue that this trade-off generates a fundamental social conflict in microbial populations: average fitness in a population is highest if all individuals exploit common resources efficiently, but individual reproductive rate is maximized by consuming common resources at the highest possible rate, a scenario known as the tragedy of the commons. In this paper, I review studies that have addressed two key questions: What is the evidence that the rate-yield trade-off is an evolutionary constraint on metabolic pathways? And, if so, what determines evolutionary outcome of the conflicts generated by this trade-off? Comparative studies and microbial experiments provide evidence that the rate-yield trade-off is an evolutionary constraint that is driven by thermodynamic constraints that are common to all metabolic pathways and pathway-specific constraints that reflect the evolutionary history of populations. Microbial selection experiments show that the evolutionary consequences of this trade-off depend on both kin selection and biochemical constraints. In well-mixed populations with low relatedness, genotypes with rapid and efficient metabolism can coexist as a result of negative frequency-dependent selection generated by density-dependent biochemical costs of rapid metabolism. Kin selection can promote the maintenance of efficient metabolism in structured populations with high relatedness by ensuring that genotypes with efficient metabolic pathways gain an indirect fitness benefit from their competitive restraint. I conclude by suggesting avenues for future research and by discussing the broader implications of this work for microbial social evolution.     

The structure of the O-antigen in the endotoxin of the emerging food pathogen Cronobacter (Enterobacter) muytjensii strain 3270

Strains of the Gram-negative bacterium Cronobacter (formerly known as Enterobacter) sakazakii have been identified as emerging opportunistic pathogens that can cause enterocolitis, bacteraemia, meningitis, and brain abscess, and they have been particularly associated with meningitis in neonates where infant milk formulae have been epidemiologically linked to the disease. A study of the lipopolysaccharides produced by clinical isolates using chemical, 2D ¹H and ¹³C NMR, and MS methods revealed that the O-polysaccharide produced by Cronobactermuytjensii strain 3270, isolated from powdered infant formula from Denmark, was a linear unbranched polymer of a repeating pentasaccharide unit composed of 2-acetamido-2-deoxy-d-galactose (d-GalNAc), 2-acetamido-2-deoxy-d-glucose (d-GlcNAc), 3-acetamido-3-deoxy-d-quinovose (d-Qui3NAc), l-rhamnose (l-Rha), and d-glucuronic acid (d-GlcA) in equimolar ratio, and has the structureThe specific structural characteristics of the O-polysaccharides of C.muytjensii may be of value in the identification and tracking of the bacterial pathogen.     

Effect of ambient air pollution on the incidence of appendicitis

Background

The pathogenesis of appendicitis is unclear. We evaluated whether exposure to air pollution was associated with an increased incidence of appendicitis.

Methods

We identified 5191 adults who had been admitted to hospital with appendicitis between Apr. 1, 1999, and Dec. 31, 2006. The air pollutants studied were ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and suspended particulate matter of less than 10 μ and less than 2.5 μ in diameter. We estimated the odds of appendicitis relative to short-term increases in concentrations of selected pollutants, alone and in combination, after controlling for temperature and relative humidity as well as the effects of age, sex and season.

Results

An increase in the interquartile range of the 5-day average of ozone was associated with appendicitis (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.03–1.25). In summer (July–August), the effects were most pronounced for ozone (OR 1.32, 95% CI 1.10–1.57), sulfur dioxide (OR 1.30, 95% CI 1.03–1.63), nitrogen dioxide (OR 1.76, 95% CI 1.20–2.58), carbon monoxide (OR 1.35, 95% CI 1.01–1.80) and particulate matter less than 10 μ in diameter (OR 1.20, 95% CI 1.05–1.38). We observed a significant effect of the air pollutants in the summer months among men but not among women (e.g., OR for increase in the 5-day average of nitrogen dioxide 2.05, 95% CI 1.21–3.47, among men and 1.48, 95% CI 0.85–2.59, among women). The double-pollutant model of exposure to ozone and nitrogen dioxide in the summer months was associated with attenuation of the effects of ozone (OR 1.22, 95% CI 1.01–1.48) and nitrogen dioxide (OR 1.48, 95% CI 0.97–2.24).

Interpretation

Our findings suggest that some cases of appendicitis may be triggered by short-term exposure to air pollution. If these findings are confirmed, measures to improve air quality may help to decrease rates of appendicitis.Appendicitis was introduced into the medical vernacular in 1886.¹ Since then, the prevailing theory of its pathogenesis implicated an obstruction of the appendiceal orifice by a fecalith or lymphoid hyperplasia.² However, this notion does not completely account for variations in incidence observed by age,^3,4 sex,^3,4 ethnic background,^3,4 family history,⁵ temporal–spatial clustering⁶ and seasonality,^3,4 nor does it completely explain the trends in incidence of appendicitis in developed and developing nations.^3,7,8The incidence of appendicitis increased dramatically in industrialized nations in the 19th century and in the early part of the 20th century.¹ Without explanation, it decreased in the middle and latter part of the 20th century.³ The decrease coincided with legislation to improve air quality. For example, after the United States Clean Air Act was passed in 1970,⁹ the incidence of appendicitis decreased by 14.6% from 1970 to 1984.³ Likewise, a 36% drop in incidence was reported in the United Kingdom between 1975 and 1994¹⁰ after legislation was passed in 1956 and 1968 to improve air quality and in the 1970s to control industrial sources of air pollution. Furthermore, appendicitis is less common in developing nations; however, as these countries become more industrialized, the incidence of appendicitis has been increasing.⁷Air pollution is known to be a risk factor for multiple conditions, to exacerbate disease states and to increase all-cause mortality.¹¹ It has a direct effect on pulmonary diseases such as asthma¹¹ and on nonpulmonary diseases including myocardial infarction, stroke and cancer.^11–13 Inflammation induced by exposure to air pollution contributes to some adverse health effects.^14–17 Similar to the effects of air pollution, a proinflammatory response has been associated with appendicitis.^18–20We conducted a case–crossover study involving a population-based cohort of patients admitted to hospital with appendicitis to determine whether short-term increases in concentrations of selected air pollutants were associated with hospital admission because of appendicitis.     

Divergent trends in anadromous salmonid populations in Norwegian and Scottish rivers

The Atlantic salmon (Salmo salar) is a charismatic anadromous fish of high conservation and economic value. Concerns have been expressed regarding the long-term viability of fisheries throughout the species''s distributional range because of abundance variations that cannot currently be explained or predicted. Here, we analyse long-term catch data obtained over a wide geographical range and across a range of spatial subscales to understand more fully the factors that drive population abundance. We use rod catch data from 84 Norwegian rivers over 125 years (1876–2000) and 48 Scottish rivers over 51 years (1952–2002). The temporal correlation in catches is very long-term, with trends persisting over several decades. The spatial correlation is relatively short-range, indicating strong local-scale effects on catch. Furthermore, Scottish salmon populations exhibit recent negative trends in contrast to some more positive trends in Norway—especially in the north.     

Sandfly Fever Sicilian Virus-Leishmania major co-infection modulates innate inflammatory response favoring myeloid cell infections and skin hyperinflammation

BackgroundThe leishmaniases are a group of sandfly-transmitted diseases caused by species of the protozoan parasite, Leishmania. With an annual incidence of 1 million cases, 1 billion people living in Leishmania-endemic regions, and nearly 30,000 deaths each year, leishmaniasis is a major global public health concern. While phlebotomine sandflies are well-known as vectors of Leishmania, they are also the vectors of various phleboviruses, including Sandfly Fever Sicilian Virus (SFSV).Cutaneous leishmaniasis (CL), caused by Leishmania major (L. major), among other species, results in development of skin lesions on the infected host. Importantly, there exists much variation in the clinical manifestation between individuals. We propose that phleboviruses, vectored by and found in the same sandfly guts as Leishmania, may be a factor in determining CL severity. It was reported by our group that Leishmania exosomes are released into the gut of the sandfly vector and co-inoculated during blood meals, where they exacerbate CL skin lesions. We hypothesized that, when taking a blood meal, the sandfly vector infects the host with Leishmania parasites and exosomes as well as phleboviruses, and that this viral co-infection results in a modulation of leishmaniasis.Methodology/Principal findingsIn vitro, we observed modulation by SFSV in MAP kinase signaling as well as in the IRF3 pathway that resulted in a pro-inflammatory phenotype. Additionally, we found that SFSV and L. major co-infection resulted in an exacerbation of leishmaniasis in vivo, and by using endosomal (Toll-like receptor) TLR3, and MAVS knock-out mice, deduced that SFSV’s hyperinflammatory effect was TLR3- and MAVS-dependent. Critically, we observed that L. major and SFSV co-infected C57BL/6 mice demonstrated significantly higher parasite burden than mice solely infected with L. major. Furthermore, viral presence increased leukocyte influx in vivo. This influx was accompanied by elevated total extracellular vesicle numbers. Interestingly, L. major displayed higher infectiveness with coincident phleboviral infection compared to L. major infection alone.Conclusion/SignificanceOverall our work represents novel findings that contribute towards understanding the causal mechanisms governing cutaneous leishmaniasis pathology. Better comprehension of the potential role of viral co-infection could lead to treatment regimens with enhanced effectiveness.