Citations

We previously demonstrated that skeletal muscle blood flow is restored in the exercising forearm during experimental hypoperfusion via local dilator and/or myogenic mechanisms. This study examined the role of nitric oxide (NO) in the restoration of blood flow to the active muscles during hypoperfusion. Eleven healthy subjects (10 men/1 woman; 25 ± 1 yr of age) performed rhythmic forearm exercise (10% and 20% of maximum) while hypoperfusion was evoked by balloon inflation in the brachial artery above the elbow. Each trial included baseline, exercise, exercise with inflation, and exercise after deflation (3 min each). Forearm blood flow (FBF; ultrasound) and local (brachial artery catheter pressure, BAP) and systemic arterial pressure [mean arterial pressure (MAP); Finometer] were measured. The exercise bouts were repeated during NG-monomethyl-l-arginine (l-NMMA) infusion (NO synthase inhibition). Forearm vascular conductance (FVC; ml·min−1·100 mmHg−1) was calculated from BF (ml/min) and BAP (mmHg). FBF and FVC fell acutely with balloon inflation during all trials ( P < 0.01). Recovery of FBF and FVC [(inflation − nadir)/(steady-state exercise − nadir)] with l-NMMA administration was reduced during 20% exercise (FBF = 77 ± 7% vs. 88 ± 8%; FVC = 71 ± 8% vs. 90 ± 9%; P < 0.01) but not 10% exercise (FBF = 83 ± 4% vs. 81 ± 5%, P = 0.37; FVC = 75 ± 10% vs. 76 ± 7%; P = 0.44) compared with the respective control trial. The time to steady-state vasodilator response was substantially longer during the l-NMMA trials (10% = 74 ± 4 s vs. 61 ± 6 s; 20% = 53 ± 4 s vs. 41 ± 4 s; P < 0.05). Thus the magnitude and timing of the NO contribution to compensatory dilation during forearm exercise with hypoperfusion was dependent on exercise intensity. These observations suggest that NO is released by contracting muscles or that a portion of the dilation caused by ischemic metabolites is NO dependent.

Abstract Objective Emerging data demonstrate that a large fraction of the global burden of disease is amenable to surgical intervention. There is a paucity of data related to delivery of surgical care in low‐ and middle‐income countries, and no aggregate data describe the efforts of international organizations to provide surgical care in these settings. This study was designed to describe the roles and practices of international organizations delivering surgical care in developing nations with regard to surgical types and volume, outcomes tracking, and degree of integration with local health systems. Methods Between October 2008 and December 2008, an Internet‐based confidential questionnaire was distributed to 99 international organizations providing humanitarian surgical care to determine their size, scope, involvement in surgical data collection, and integration into local systems. Results Forty‐six international organizations responded (response rate 46%). Findings reveal that a majority of organizations that provide surgery track numbers of cases performed and immediate outcomes, such as mortality. In general, these groups have mechanisms in place to track volume and outcomes, provide for postintervention follow‐up, are committed to providing education, and work in conjunction with local health organizations and providers. Whereas most organizations surveyed provided fewer than 500 surgical procedures annually, more than half had the capacity to provide emergency services. In addition, a great diversity of specialized surgical care was provided, including obstetrics, orthopedic, plastic, and ophthalmologic surgery. Conclusions International organizations providing surgical services are diverse in size and breadth of surgical services provided yet, with consistency, provide rudimentary analysis, postoperative follow‐up care, and both education and integration of health services at the local level. The role of international organizations in the delivery of surgery is an important index, worthy of further evaluation.

We tested the hypothesis that adenosine contributes to augmented skeletal muscle vasodilation during hypoxic exercise. In separate protocols, subjects performed incremental rhythmic forearm exercise (10% and 20% of maximum) during normoxia and normocapnic hypoxia (80% arterial O2saturation). In protocol 1 ( n = 8), subjects received an intra-arterial administration of saline (control) and aminophylline (adenosine receptor antagonist). In protocol 2 ( n = 10), subjects received intra-arterial phentolamine (α-adrenoceptor antagonist) and combined phentolamine and aminophylline administration. Forearm vascular conductance (FVC; in ml·min−1·100 mmHg−1) was calculated from forearm blood flow (in ml/min) and blood pressure (in mmHg). In protocol 1, the change in FVC (ΔFVC; change from normoxic baseline) during hypoxic exercise with saline was 172 ± 29 and 314 ± 34 ml·min−1·100 mmHg−1(10% and 20%, respectively). Aminophylline administration did not affect ΔFVC during hypoxic exercise at 10% (190 ± 29 ml·min−1·100 mmHg−1, P = 0.4) or 20% (287 ± 48 ml·min−1·100 mmHg−1, P = 0.3). In protocol 2, ΔFVC due to hypoxic exercise with phentolamine infusion was 313 ± 30 and 453 ± 41 ml·min−1·100 mmHg−1(10% and 20% respectively). ΔFVC was similar at 10% (352 ± 39 ml·min−1·100 mmHg−1, P = 0.8) and 20% (528 ± 45 ml·min−1·100 mmHg−1, P = 0.2) hypoxic exercise with combined phentolamine and aminophylline. In contrast, ΔFVC to exogenous adenosine was reduced by aminophylline administration in both protocols ( P < 0.05 for both). These observations suggest that adenosine receptor activation is not obligatory for the augmented hyperemia during hypoxic exercise in humans.

Inclusions of TAR DNA-binding protein-43 (TDP-43), a nuclear protein that regulates transcription and RNA splicing, are the defining histopathological feature of frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-Us) and sporadic and familial forms of amyotrophic lateral sclerosis (ALS). In ALS and FTLD-U, aggregated, ubiquitinated, and N-terminally truncated TDP-43 can be isolated from brain tissue rich in neuronal and glial cytoplasmic inclusions. The loss of TDP-43 function resulting from inappropriate cleavage, translocation from the nucleus, or its sequestration into inclusions could play important roles in neurodegeneration. However, it is not known whether TDP-43 fragments directly mediate toxicity and, more specifically, whether their abnormal aggregation is a cause or consequence of pathogenesis. We report that the ectopic expression of a ≈25-kDa TDP-43 fragment corresponding to the C-terminal truncation product of caspase-cleaved TDP-43 leads to the formation of toxic, insoluble, and ubiquitin- and phospho-positive cytoplasmic inclusions within cells. The 25-kDa C-terminal fragment is more prone to phosphorylation at S409/S410 than full-length TDP-43, but phosphorylation at these sites is not required for inclusion formation or toxicity. Although this fragment shows no biological activity, its exogenous expression neither inhibits the function nor causes the sequestration of full-length nuclear TDP-43, suggesting that the 25-kDa fragment can induce cell death through a toxic gain-of-function. Finally, by generating a conformation-dependent antibody that detects C-terminal fragments, we show that this toxic cleavage product is specific for pathologic inclusions in human TDP-43 proteinopathies.

Abstract Family history is a strong predictor of colorectal cancer risk; however, a diagnosis of colorectal cancer among first-degree relatives has not been systematically investigated as a function of the colorectal cancer molecular subtypes related to tumor microsatellite instability (MSI) status. We investigated whether the observable familial colorectal cancer risks differed according to tumor MSI subtypes, stratified as MSI-High (&gt;30% instability), MSI-Low (&lt;30% instability), and MSS (no instability). Data from 3,143 population-based colorectal cancer cases from five institutions were assessed for family history according to the Amsterdam criteria and the Bethesda guidelines, age at diagnosis, sex, tumor location, and MSI status. The distribution of patient characteristics by MSI status was compared using polytomous logistic regression. Overall, 2.8% colorectal cancer cases met the Amsterdam criteria and 37% met the Bethesda guidelines. There were 14% MSI-High, 13% MSI-Low, and 73% MSS colorectal cancers. MSI-High (P &lt; 0.0001) and MSI-Low tumors (P = 0.01) were more proximally located than MSS tumors. MSI-High tumors were more common among females (P &lt; 0.001). The highest proportion of MSI-High tumors occurred in cases &lt;40 years of age whereas the age-dependent distribution of MSI-Low tumors was unchanged. MSI-High tumors showed a statistically significant association with increasing numbers of first-degree relatives with colorectal cancer (P = 0.002); this association disappeared, however, when MSI-High cases meeting Amsterdam criteria were removed from the analysis. MSI-Low tumors did not show a similar association with family history of colorectal cancer. Familial risk associated with MSI-High tumors is primarily driven by the Amsterdam-criteria patients. MSI-Low tumors may represent a distinct subtype of colorectal cancer with respect to certain epidemiologic variables studied here. (Cancer Epidemiol Biomarkers Prev 2009;18(3):967–75)

Abstract Microsatellite instability (MSI) occurs in 10% to 20% of colorectal cancers (CRC) and has been attributed to both MLH1 promoter hypermethylation and germline mutation in the mismatch repair (MMR) genes. We present results from a large population- and clinic-based study of MLH1 methylation, immunohistochemistry, and MMR germline mutations that enabled us to (a) estimate the prevalence of MMR germline mutations and MLH1 methylation among MSI-H cases and help us understand if all MSI-H CRC is explained by these mechanisms and (b) estimate the associations between MLH1 methylation and sex, age, and tumor location within the colon. MLH1 methylation was measured in 1,061 population-based and 172 clinic-based cases of CRC. Overall, we observed MLH1 methylation in 60% of population-based MSI-H cases and in 13% of clinic-based MSI-H cases. Within the population-based cases with MMR mutation screening and conclusive immunohistochemistry results, we identified a molecular event in MMR in 91% of MSI-H cases: 54% had MLH1 methylation, 14% had a germline mutation in a MMR gene, and 23% had immunohistochemistry evidence for loss of a MMR protein. We observed a striking age difference, with the prevalence of a MMR germline mutation more than 4-fold lower and the prevalence of MLH1 methylation more than 4-fold higher in cases diagnosed after the age of 50 years than in cases diagnosed before that age. We also determined that female sex is an independent predictor of MLH1 methylation within the MSI-H subgroup. These results reinforce the importance of distinguishing between the underlying causes of MSI in studies of etiology and prognosis. (Cancer Epidemiol Biomarkers Prev 2008;17(11):3208–15)

Abstract Recent publications have reported that common variants on 8q24 are associated with both prostate and colorectal cancers (CRC). In addition, one of these studies (the ARCTIC study) initially observed an association with a single nucleotide polymorphism (SNP) on 9p24 that was not confirmed in some of their validation data sets. In the research described here, we conducted a case-unaffected sibling analysis using population- and clinic-based discordant sibships (N = 1,567 sibships) from the Colon Cancer Family Registry (Colon CFR) to investigate the associations between common variants at 9p24 and 8q24 and risk of CRC. We also evaluated whether these associations differed by age, family history, and tumor characteristics, including microsatellite instability and tumor site. Associations were estimated using conditional logistic regression, treating sibship as the matching factor. Analyses were adjusted for age and sex, and stratified by ascertainment source (population versus clinic). We observed an association between a SNP on 9p24 (rs719725) and risk of CRC in the population-based series (AA versus CC: odds ratios, 1.46; 95% confidence interval, 1.06–2.02; AC versus CC: odds ratios, 1.50; 95% confidence interval, 1.14–1.98; P = 0.011 on 2 df). In the population-based series, we also detected statistically significant associations between two SNPs on 8q24, rs10505477 and rs6983267, and risk of CRC (P = 0.005 and P = 0.002, respectively). There was no evidence of statistically significant heterogeneity by age at diagnosis, family history of CRC, microsatellite instability, or tumor site at either locus and no evidence of interaction between SNPs on 8q24 and 9p24. These data suggest that common variants may play important roles in the risk of CRC. [Cancer Res 2007;67(23):11128–32]