Neutrophil to Lymphocyte Ratio as a Predictor of Outcomes after Amputation.

BACKGROUND: The neutrophil-to-lymphocyte ratio (NLR) has become a prognostic marker for proinflammatory states. It is associated with outcomes in many clinical processes including critical limb ischemia. We sought to identify predictors of amputation failure and mortality, in addition to the role of NLR in patients undergoing above-knee amputations (AKAs) or below-knee amputations (BKAs). METHODS: All patients undergoing BKA or AKA between 2004 and 2014 at 3 institutions were identified and analyzed (n = 513). Patients were excluded if they did not have a complete blood count with differential within 7 days prior to their operations. Comparison groups were formed between patients requiring unplanned revision and those who did not, and additionally between survivors and nonsurvivors at 30 days postamputation. Patient demographics, intraoperative data, and postoperative courses were compared. A multinomial logistic regression model was created to further compare the groups. RESULTS: Four hundred and ten patients were included for analysis, of which 142 (35%) required unplanned revision. Nearly 5% of patients (19/410) died within 30 days of the initial amputation. On univariate analysis, those requiring revision were more likely to be current smokers compared to former smokers (P = 0.004 and P = 0.021, respectively), have a lower ankle-brachial index (ABI) (P = 0.019), and have undergone a BKA (P < 0.001). Patients with congestive heart failure (CHF) were less likely to require a revision after an amputation (P = 0.007). Postoperative NLR was higher in patients requiring revision (9.9 vs. 7.0, P < 0.001) and both preoperative and postoperative NLRs were higher in those with 30-day mortality (21.0 vs. 7.0, P < 0.001; 19.4 vs. 7.5, P < 0.001). A multinomial logistic regression model identified CHF (P = 0.004), ABI (P = 0.041), and elevated body mass index (BMI, P = 0.045) as predictors of revision, while coronary artery disease (CAD, P = 0.031), CHF (P = 0.029), and postoperative NLR (P < 0.001) were predictive of 30-day mortality. CONCLUSIONS: Postoperative elevated NLR, CAD, and CHF are predictors of 30-day mortality in patients undergoing major limb amputation, while CHF, elevated ABI, and high BMI are predictors of revision. This study suggests that NLR may have a role as a biomarker for poor outcomes in patients with underlying peripheral vascular disease and warrants further investigation.

Inferring developmental stage composition from gene expression in human malaria.

In the current era of malaria eradication, reducing transmission is critical. Assessment of transmissibility requires tools that can accurately identify the various developmental stages of the malaria parasite, particularly those required for transmission (sexual stages). Here, we present a method for estimating relative amounts of Plasmodium falciparum asexual and sexual stages from gene expression measurements. These are modeled using constrained linear regression to characterize stage-specific expression profiles within mixed-stage populations. The resulting profiles were analyzed functionally by gene set enrichment analysis (GSEA), confirming differentially active pathways such as increased mitochondrial activity and lipid metabolism during sexual development. We validated model predictions both from microarrays and from quantitative RT-PCR (qRT-PCR) measurements, based on the expression of a small set of key transcriptional markers. This sufficient marker set was identified by backward selection from the whole genome as available from expression arrays, targeting one sentinel marker per stage. The model as learned can be applied to any new microarray or qRT-PCR transcriptional measurement. We illustrate its use in vitro in inferring changes in stage distribution following stress and drug treatment and in vivo in identifying immature and mature sexual stage carriers within patient cohorts. We believe this approach will be a valuable resource for staging lab and field samples alike and will have wide applicability in epidemiological studies of malaria transmission.

Laparoscopic aortobifemoral bypass in a USA academic center.

BACKGROUND: Although aortoiliac occlusive disease (AIOD) is preferentially treated endovascularly, some patients are still better served with an aortobifemoral bypass (ABF). For those patients, surgical treatment options include both standard open operations as well as laparoscopic ABF (LapABF). Several European centers perform LapABF with favorable results instead of open surgery, but this has not been widely embraced in the United States. We reviewed our ten-year experience with LapABF, evolving from a completely laparoscopic to a standardized laparoscopic-assisted approach. METHODS: A retrospective review of all laparoscopic aortic operations performed at a single US academic institution from 2005 to 2015 was completed. Demographics, co-morbidities, intraoperative parameters and clinical outcomes were recorded. Patients were excluded from consideration for laparoscopic surgery if they had previous aortic surgery, aneurysmal disease or gastrointestinal pathology (e.g. diverticulitis or an enteric stoma). RESULTS: Thirty men and sixteen women were treated, (n=46) with a mean age of 55.7 (range 38-75 years). All operations were performed by a single surgeon. LapABF was successfully completed in 95.6%. A completely laparoscopic approach was undertaken in eight patients and a laparoscopic-assisted approach was used in the remaining 38 patients. Mean follow-up was 46 months (range 1 to 131). The indication for operation was claudication (n=35, 76%), rest pain (n=8, 17%) or tissue loss (n=3, 7%). Twenty-one limbs had a history of a prior failed aortoiliac endovascular intervention (23%). Median length of stay was 6 days (range 2-30). Within 30 days there were two myocardial infarctions (4.3%), one transient ischemic attack (2.2%) and one death (2.2%). Re-intervention was performed in 12 patients over the course of the study period (26.1%). Primary, primary-assisted and secondary patency was 79.4%, 93.9% and 94.9% at 60 months, respectively. Overall mortality was 17% with a mean duration of follow-up of 60 months (range 1-116). Multivariable analysis revealed coronary artery disease (CAD; P=0.03) conferred a sixteen-fold risk for death during long-term follow-up. CONCLUSIONS: In this large US series of LapABF, we observed acceptable long-term patency, short length of stay and minimal morbidity. We suggest that this standardized approach for laparoscopic-assisted ABF is a viable option for patients with AIOD not suitable for endovascular therapy. The use of laparoscopic-assisted ABF affords practitioners the benefits of a completely laparoscopic approach while reducing the duration and complexity of the operation. Given the rate of re-interventions in the early era practitioners should be aware of the learning curve with this approach.

Primary axillary venous aneurysm in a young patient presenting with cardiac arrest.

Primary venous aneurysms are rare and usually asymptomatic. Venous aneurysms are manifested more frequently in the lower extremities than in the upper extremities. Primary venous aneurysms of the upper extremities are more often reported as aesthetically displeasing bulges or incidental findings. Here, we report the rare case of an axillary primary venous aneurysm in a pediatric patient who presented with syncope and massive pulmonary embolism and highlight the management.

LKB1 destabilizes microtubules in myoblasts and contributes to myoblast differentiation.

BACKGROUND: Skeletal muscle myoblast differentiation and fusion into multinucleate myotubes is associated with dramatic cytoskeletal changes. We find that microtubules in differentiated myotubes are highly stabilized, but premature microtubule stabilization blocks differentiation. Factors responsible for microtubule destabilization in myoblasts have not been identified. FINDINGS: We find that a transient decrease in microtubule stabilization early during myoblast differentiation precedes the ultimate microtubule stabilization seen in differentiated myotubes. We report a role for the serine-threonine kinase LKB1 in both microtubule destabilization and myoblast differentiation. LKB1 overexpression reduced microtubule elongation in a Nocodazole washout assay, and LKB1 RNAi increased it, showing LKB1 destabilizes microtubule assembly in myoblasts. LKB1 levels and activity increased during myoblast differentiation, along with activation of the known LKB1 substrates AMP-activated protein kinase (AMPK) and microtubule affinity regulating kinases (MARKs). LKB1 overexpression accelerated differentiation, whereas RNAi impaired it. CONCLUSIONS: Reduced microtubule stability precedes myoblast differentiation and the associated ultimate microtubule stabilization seen in myotubes. LKB1 plays a positive role in microtubule destabilization in myoblasts and in myoblast differentiation. This work suggests a model by which LKB1-induced microtubule destabilization facilitates the cytoskeletal changes required for differentiation. Transient destabilization of microtubules might be a useful strategy for enhancing and/or synchronizing myoblast differentiation.

Heparin activates PKR by inducing dimerization.

Protein kinase R (PKR) is an interferon-induced kinase that plays a pivotal role in the innate immunity pathway. PKR is activated to undergo autophosphorylation upon binding to double-stranded RNAs or RNAs that contain duplex regions. Activated PKR phosphorylates the α subunit of eukaryotic initiation factor 2, thereby inhibiting protein synthesis. PKR is also activated by heparin, a highly sulfated glycosaminoglycan. We have used biophysical methods to define the mechanism of PKR activation by heparin. Heparins as short as hexasaccharide bind strongly to PKR and activate autophosphorylation. In contrast to double-stranded RNA, heparin activates PKR by binding to the kinase domain. Analytical ultracentrifugation measurements support a thermodynamic linkage model where heparin binding allosterically enhances PKR dimerization, thereby activating the kinase. These results indicate that PKR can be activated by small molecules and represents a viable target for the development of novel antiviral agents.