Mitochondrial K(ATP) channel as an end effector of cardioprotection during late preconditioning: triggering role of nitric oxide.

Nitric oxide (NO) has been implicated in the "second-window" of ischemic preconditioning (PC). However, the identity of the end effector after initiation of preconditioning by NO is not known. It is likely that NO is involved in opening of mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels. We hypothesized that NO is an important trigger for the opening of mitoK(ATP) channels in the late phase of preconditioning and inducible nitric oxide synthase (iNOS) up-regulation via NF kappa B plays a critical role in diazoxide-induced cardioprotection. To examine this, diazoxide (7 mg/kg) was administered to wild-type (WT) mice and mice lacking the gene 24 hours before 40 minutes of global ischemia. Hearts were perfused in a Langendorff mode and effects of activation of mitoK(ATP) channel and other interventions on functional, biochemical and pathological changes in ischemic hearts were assessed. In hearts from WT mice treated diazoxide, left-ventricular-developed pressure, end-diastolic pressure and coronary flow were significantly improved after ischemia/reperfusion (I/R); lactate dehydrogenase (LDH) release was also significantly decreased, while ATP contents were significantly higher. Administration of 5-HD, a specific blocker of mitoK(ATP) channel or l -NAME, an inhibitor of iNOS before I/R, during diazoxide-pretreatment completely blocked the late cardioprotection against ischemia. Late cardioprotection was also blocked by inhibition of either PKC- delta by rottlerin or NF kappa B by DDTC before diazoxide pretreatment. Diazoxide pretreatment significantly increased nuclear translocation of p65 which was blocked by protein kinase C (PKC) or nitric oxide synthase (NOS) inhibition. Diazoxide was totally inefffective in iNOS knockout mice. These results suggest that diazoxide activates NF kappa B via PKC signaling pathway and that leads to iNOS up-regulation after 24 hours. NO which is generated upon ischemic stress triggers the opening of mitoK(ATP)channel as an end effector of cardioprotection during late PC.     

Caustic ingestion: Has the role of the gastroenterologist burnt out?

Caustic ingestion is a frequent presentation to EDs and encompasses a wide range of injury to the gastrointestinal tract. Endoscopy has long been considered the gold standard of investigation, even in patients with low likelihood of severe injury, and informs the decision for emergency surgery. However, recent evidence suggests that computed tomography (CT) scan can accurately diagnose digestive tract necrosis and, more importantly, guide towards more judicious use of surgical management, with improved mortality and digestive autonomy. CT scan also accurately predicts risk of stricture formation. We propose an algorithm for the use of CT scan, rather than endoscopy, as the first‐line investigation in the assessment of caustic ingestion.     

Differential expression of retinoic acid receptors and p53 protein in normal, premalignant, and malignant esophageal tissues

Purpose: Esophageal cancer remains a significant health problem worldwide. The very low 5-year survival rates and rapid increase in the incidence of adenocarcinoma indicate the urgent need for early identification of and new approaches to the prevention and treatment of this cancer. Methods: To find biomarkers for early identification of the disease, we analyzed nuclear retinoic retinoid receptor mRNAs, p53 protein, and the proliferation marker Ki 67 in surgical specimens of normal, mildly, and severely dysplastic and malignant esophageal tissues. Results: Nuclear retinoid receptors (RAR-α, RAR-γ, and RXR-α) were expressed in most (79%–100%) normal, dysplastic, and malignant esophageal mucosae, whereas expression of RAR-β was progressively lost from normal esophagus to carcinoma (84%–54%). In contrast, expression of p53 protein and Ki 67 were dramatically increased in severely dysplastic and cancerous tissues of the esophagus (from 5% to 62%). Conclusions: Loss of RAR-β expression and accumulation of p53 and Ki 67 proteins may serve as biomarkers for esophageal cancer. Received: 17 April 2000 / Accepted: 12 July 2000     

Short-Term Comparative Outcomes Associated with the Use of GP IIb/IIIa Antagonists in Patients Undergoing Coronary Intervention

Background:Platelet glycoprotein (GP) IIb/IIIa antagonists reduce the occurrence of death, myocardial infarction (MI) and urgent revascularization among patients undergoing percutaneous coronary intervention (PCI). Despite a similar mechanism of platelet inhibition, the three currently approved agents vary widely in cost. Purpose: The purpose of this prospectively designed, retrospective analysis was to determine clinical outcomes for patients receiving abciximab, tirofiban or eptifibatide as adjunctive therapy during PCI at a single center. We hypothesized that there would be no difference in outcomes during hospitalization following PCI in patients receiving tirofiban or eptifibatide compared with those patients who received abciximab. Outcomes examined included in-hospital mortality, hemorrhagic procedural complications, need for recatheterization, peak creatine kinase following intervention and length of hospital stay (LOS). Results: Two hundred and sixty seven consecutive patients in whom GP IIb/IIIa antagonist therapy was initiated in the catheterization laboratory for PCI were analyzed. Abciximab-treated patients were more likely to be undergoing primary (p<0.001) and rescue (p=0.022) PCI and to have received fibrinolytic therapy (p=0.013) when compared to patients receiving tirofiban or eptifibatide. There were no significant differences between abciximab- and non abciximab-treated patients in either the primary PCI or non primary PCI groups in any of the studied endpoints. In patients undergoing primary PCI, abciximab-treated patients when compared with non abciximab-treated patients exhibited a trend toward an increase in hospital LOS (7.8±7.0 d vs 6.2±3.9, p=0.19) and in the frequency of hemmorhagic complications (22.1% vs 5.3%, p=0.11). In patients not receiving fibrinolytic therapy, abciximab-treated patients experienced a trend toward increased hemmorhagic complications following PCI when compared to non abciximab-treated patients (10.2% vs 6.0%, p=0.28). Complications distant from the vascular access site comprised 62.5% of hemmorhagic complications in the abciximab-treated group, but only 20% of the complications in the non-abciximab treated population (p<0.001). These data suggest no differences in acute outcomes between groups of patients receiving abciximab or other approved GP IIb/IIIa antagonists highlighting a potential significant cost saving. These data will require interpretation following the publication of comparative trials.     

Effects of genetic fusion of factor IX to albumin on in vivo clearance in mice and rabbits

Individuals with haemophilia B require replacement therapy with recombinant or plasma-derived coagulation factor IX (fIX). More benefit per injected dose might be obtained if fIX clearance could be slowed. The contribution of overall size to fIX clearance was explored, using genetic fusion to albumin. Recombinant murine fIX (MIX), and three proteins with C-terminal epitope tags were expressed in HEK 293 cells: tagged MIX (MIXT), tagged mouse serum albumin (MSAT) and MFUST, in which MIX and MSAT were fused in a single polypeptide chain. Proteins MFUST and MIXT were two- to threefold less active in clotting assays than MIX. In mice, the area under the clearance curve (AUC) was reduced for MFUST compared with MSAT or plasma-derived MSA (pd-MSA); the terminal catabolic half-life (t(0.5)) did not differ amongst the three proteins. Two minutes after injection, >40% of the injected MFUST was found in the liver, compared with <10% of either MSAT or pd-MSA. In rabbits, the AUC for MFUST was reduced compared to MIXT, MSAT, or pd-MSA, while the t(0.5) of the fusion protein fell between that of MIXT and MSAT or pd-MSA. Similar results were obtained with non-radioactive fused or non-fused recombinant human fIX in fIX knockout mice. The clearance behaviour of the fusion protein thus more closely resembled that of fIX than that of albumin despite a modest increase in terminal half-life, suggesting that fIX-specific interactions that are important in determining clearance were maintained in spite of the increased size of the fusion protein.     

Kruppel-like factor 6 (KLF6) is a tumor-suppressor gene frequently inactivated in colorectal cancer

BACKGROUND & AIMS: Kruppel-like factor 6 (KLF6) is a ubiquitous zinc finger tumor suppressor that is often mutated in prostate cancer. Our aims were to establish the frequency of KLF6 inactivation in sporadic and inflammatory bowel disease (IBD)-associated colorectal cancers (CRC); to correlate these abnormalities with mutation and/or loss of TP53, APC, and K-RAS; and to characterize the behavior of mutant KLF6 in colon-derived cell lines. METHODS: We analyzed DNA isolated from 50 microdissected CRC cases, including 35 sporadic and 15 IBD-associated tumors. Microsatellite analysis and direct sequencing were used to establish the incidence of microsatellite instability, KLF6 and TP53 allelic imbalance, and KLF6, K-RAS, TP53, and APC mutation. Loss of growth suppressive function of the CRC-derived KLF6 mutants was characterized by in vitro thymidine incorporation assays and Western blotting. RESULTS: KLF6 was inactivated by loss and/or mutation in most sporadic and IBD-related CRCs. The KLF6 locus was deleted in at least 55% of tumors, and mutations were identified in 44%. Rates of KLF6 loss and mutation were similar to those of TP53 and K-RAS in the same samples. KLF6 mutations were present in tumors with either microsatellite or chromosomal instability and were more common, particularly in the IBD-related cancers, in the presence of wild-type APC. Unlike wild-type KLF6, cancer-derived KLF6 mutants neither suppressed growth nor induced p21 following transfection into cultured cells. CONCLUSIONS: Deregulation of KLF6 by a combination of allelic imbalance and mutation may play a role in the development of CRC.     

Risk of bacterial exposure to the endoscopist’s face during endoscopy

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