Phosphatidylinositol and phosphatidic acid transport between the ER and plasma membrane during PLC activation requires the Nir2 protein.

Phospholipase C (PLC)-mediated hydrolysis of the limited pool of plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] requires replenishment from a larger pool of phosphatidylinositol (PtdIns) via sequential phosphorylation by PtdIns 4-kinases and phosphatidylinositol 4-phosphate (PtdIns4P) 5-kinases. Since PtdIns is synthesized in the endoplasmic reticulum (ER) and PtdIns(4,5)P2 is generated in the PM, it has been postulated that PtdIns transfer proteins (PITPs) provide the means for this lipid transfer function. Recent studies identified the large PITP protein, Nir2 as important for PtdIns transfer from the ER to the PM. It was also found that Nir2 was required for the transfer of phosphatidic acid (PtdOH) from the PM to the ER. In Nir2-depleted cells, activation of PLC leads to PtdOH accumulation in the PM and PtdIns synthesis becomes severely impaired. In quiescent cells, Nir2 is localized to the ER via interaction of its FFAT domain with ER-bound VAMP-associated proteins VAP-A and-B. After PLC activation, Nir2 also binds to the PM via interaction of its C-terminal domains with diacylglycerol (DAG) and PtdOH. Through these interactions, Nir2 functions in ER-PM contact zones. Mutations in VAP-B that have been identified in familial forms of amyotrophic lateral sclerosis (ALS or Lou-Gehrig's disease) cause aggregation of the VAP-B protein, which then impairs its binding to several proteins, including Nir2. These findings have shed new lights on the importance of non-vesicular lipid transfer of PtdIns and PtdOH in ER-PM contact zones with a possible link to a devastating human disease.

Impairment of exogenous lactate clearance in experimental hyperdynamic septic shock is not related to total liver hypoperfusion.

INTRODUCTION: Although the prognostic value of persistent hyperlactatemia in septic shock is unequivocal, its physiological determinants are controversial. Particularly, the role of impaired hepatic clearance has been underestimated and is only considered relevant in patients with liver ischemia or cirrhosis. Our objectives were to establish whether endotoxemia impairs whole body net lactate clearance, and to explore a potential role for total liver hypoperfusion during the early phase of septic shock. METHODS: After anesthesia, 12 sheep were subjected to hemodynamic/perfusion monitoring including hepatic and portal catheterization, and a hepatic ultrasound flow probe. After stabilization (point A), sheep were alternatively assigned to lipopolysaccharide (LPS) (5 mcg/kg bolus followed by 4 mcg/kg/h) or sham for a three-hour study period. After 60 minutes of shock, animals were fluid resuscitated to normalize mean arterial pressure. Repeated series of measurements were performed immediately after fluid resuscitation (point B), and one (point C) and two hours later (point D). Monitoring included systemic and regional hemodynamics, blood gases and lactate measurements, and ex-vivo hepatic mitochondrial respiration at point D. Parallel exogenous lactate and sorbitol clearances were performed at points B and D. Both groups included an intravenous bolus followed by serial blood sampling to draw a curve using the least squares method. RESULTS: Significant hyperlactatemia was already present in LPS as compared to sham animals at point B (4.7 (3.1 to 6.7) versus 1.8 (1.5 to 3.7) mmol/L), increasing to 10.2 (7.8 to 12.3) mmol/L at point D. A significant increase in portal and hepatic lactate levels in LPS animals was also observed. No within-group difference in hepatic DO2, VO2 or O2 extraction, total hepatic blood flow (point D: 915 (773 to 1,046) versus 655 (593 to 1,175) ml/min), mitochondrial respiration, liver enzymes or sorbitol clearance was found. However, there was a highly significant decrease in lactate clearance in LPS animals (point B: 46 (30 to 180) versus 1,212 (743 to 2,116) ml/min, P < 0.01; point D: 113 (65 to 322) versus 944 (363 to 1,235) ml/min, P < 0.01). CONCLUSIONS: Endotoxemia induces an early and severe impairment in lactate clearance that is not related to total liver hypoperfusion.

Utility of Routine Blood Cultures for Upper Extremity Abscesses.

BACKGROUND: Patients with skin and soft tissue infections (SSTIs) are often admitted by the emergency department for intravenous antibiotic therapy and surgical drainage of abscesses if necessary. As part of the initial diagnostic workup, blood cultures are routinely drawn at our institution in patients with SSTIs. This study seeks to identify the utility of performing blood cultures in patients with upper extremity abscesses as it relates to the number of incision and drainage (I&D) procedures performed, patient readmission rates, and length of hospital stay. METHODS: A retrospective chart review of 314 patients aged 18 to 89 years who underwent 1 or more I&D procedures of upper extremity abscesses were included in the study. Patient demographic data, comorbidities, laboratory values, wound and blood culture results, number of I&D procedures performed, length of stay, and readmission rates were evaluated. RESULTS: Increasing age and white blood count were associated with an increased number of I&Ds performed. Obtaining blood cultures, whether positive or negative, was associated with increased length of stay. There was no association between obtaining blood cultures and number of procedures performed on multivariable analysis. Positive blood cultures were associated with increased readmission rates. CONCLUSIONS: Routinely obtaining blood cultures in patients with upper extremity abscesses may not be beneficial. Obtaining blood cultures is not associated with an increased number of I&D procedures or readmission rates. Furthermore, obtaining blood cultures, regardless of positivity, is associated with increased lengths of hospital stay.