Survival after lower-extremity amputation

BACKGROUND: Lower extremity amputation has long been considered an end-of-life event and it is unclear if survival after amputation has improved over time. STUDY DESIGN: A retrospective cohort comprised from a statewide, hospital discharge database was used to determine if survival after amputation improved with time. The cohort included all patients (older than 18 years) with nontraumatic, lower extremity amputations (1987 to 2000). Survival analysis was used to determine the adjusted hazard ratio of survival as it related to the era of amputation. RESULTS: A total of 13,807 patients (mean age +/- SD, 67 +/- 15, 58.5% men) underwent amputation. The gender and age standardized frequency of amputation remained essentially stable, with a 0.01% increase per year (95% CI, 0.006-0.01%). During followup, 49.2% (6,795/13,807) of patients died, with significantly (p < 0.001) worse outcomes for more proximal levels of amputation. After controlling for potential confounders, including age, gender, level of amputation, comorbid illness, emergency status of procedure, hospital type, and payer of the procedure, patients undergoing amputation in more recent years (1995 to 2000) had a 28% lower hazard of dying (hazard ratio 0.72 [95% CI, 0.67-0.77%) during the study period than those undergoing operation before 1995. Thirty-day survival did not improve by era (p = 0.2), although 1- and 5-year survival after amputation was significantly greater for all levels of amputation (p < 0.001). CONCLUSIONS: Although 30-day survival associated with amputation has remained stable in the state of Washington over the past 14 years, longterm survival after amputation has improved considerably with time. The reasons underlying this improvement should be explored so that further gains may be achieved.     

Carvedilol blockade of rat myocardial alpha1-adrenoceptors

Carvedilol is a combined alpha(1)- and beta-adrenoceptor antagonist. The ability of carvedilol to antagonize functional effects mediated through myocardial alpha(1)-adrenoceptors has never been investigated. We tested the ability of carvedilol to antagonize the inotropic effect mediated by myocardial alpha(1)-adrenoceptors compared to the antagonism of beta-adrenoceptors. Papillary muscles from rat heart left ventricle were mounted in an organ bath and concentration-response experiments for the inotropic effects of separate alpha(1)- and beta-adrenoceptor stimulation were performed in the absence and presence of carvedilol. Carvedilol antagonized myocardial alpha(1)-adrenoceptors with an inhibition constant (K(i)) of 11.0+/-3.0 nmol/l and the functional experiments were supported by radioligand-binding studies. Corresponding functional studies on the response to beta-adrenoceptor stimulation revealed a K(i) of 1.2+/-0.35 nmol/l. Thus, carvedilol antagonizes the myocardial alpha(1)-adrenoceptors with a 9-fold lower potency than the beta-adrenoceptors. Antagonism of myocardial alpha(1)-adrenoceptor evoked effects may contribute to clinical effects of carvedilol.     

Elevated level of beta-adrenoceptors in intact hepatocytes from partially hepatectomized rats

The binding characteristics of 125I-iodocyanopindolol (125I-ICYP) and 3H-CGP-12177 to intact hepatocytes and a particulate fraction prepared from hepatocytes from sham-operated and partially hepatectomized rats were compared. In the particulate fraction, the beta-adrenoceptor number increased 4-10-fold after partial hepatectomy. 125I-ICYP binding to intact cells demonstrated a high fraction of non-specific binding, although phentolamine was included in the assay to reduce non-specific binding. 3H-CGP-12177 binding to intact cells also demonstrated a higher fraction of non-specific binding than in most cell types. In intact cells, the beta-adrenoceptor number increased 5-6-fold after partial hepatectomy. The number of receptors was comparable in intact cells and the broken cell preparation, indicating that receptors are conserved during the preparation of the particulate fraction.     

Laser-induced modification of the patellar ligament tissue: comparative study of structural and optical changes

The effects of non-ablative infrared (IR) laser treatment of collagenous tissue have been commonly interpreted in terms of collagen denaturation spread over the laser-heated tissue area. In this work, the existing model is refined to account for the recently reported laser-treated tissue heterogeneity and complex collagen degradation pattern using comprehensive optical imaging and calorimetry toolkits. Patella ligament (PL) provided a simple model of type I collagen tissue containing its full structural content from triple-helix molecules to gross architecture. PL ex vivo was subjected to IR laser treatments (laser spot, 1.6 mm) of equal dose, where the tissue temperature reached the collagen denaturation temperature of 60 ± 2°C at the laser spot epicenterin the first regime, and was limited to 67 ± 2°C in the second regime. The collagen network was analyzed versus distance from the epicenter. Experimental characterization of the collagenous tissue at all structural levels included cross-polarization optical coherence tomography, nonlinear optical microscopy, light microscopy/histology, and differential scanning calorimetry. Regressive rearrangement of the PL collagen network was found to spread well outside the laser spot epicenter (>2 mm) and was accompanied by multilevel hierarchical reorganization of collagen. Four zones of distinct optical and morphological properties were identified, all elliptical in shape, and elongated in the direction perpendicular to the PL long axis. Although the collagen transformation into a random-coil molecular structure was occasionally observed, it was mechanical integrity of the supramolecular structures that was primarily compromised. We found that the structural rearrangement of the collagen network related primarily to the heat-induced thermo-mechanical effects rather than molecular unfolding. The current body of evidence supports the notion that the supramolecular collagen structure suffered degradation of various degrees, which gave rise to the observed zonal character of the laser-treated lesion.     

Prostanoid-mediated inotropic responses are attenuated in failing human and rat ventricular myocardium

Prostanoid-modulatory approaches in heart failure patients have displayed effects which may seem to be mutually incompatible. Both treatment with prostanoids and inhibition of prostanoid synthesis have resulted in increased mortality in heart failure patients. Currently, it is unknown if prostanoids mediate contractile effects in failing human heart and if this can explain some of the clinical effects seen after prostanoid modulatory treatments. Therefore, the objectives of this study were to determine if prostanoids could elicit direct inotropic responses in human ventricle, and if so to determine if they are modified in failing ventricle. Contractile force was measured in left ventricular strips from non-failing or failing human and rat hearts. The ratio of phosphorylated to non-phosphorylated myosin light chain 2 (MLC-2) was measured by Western blotting in myocardial strips, and the levels of prostanoid FP receptor mRNA and protein were measured in rat by real-time RT-PCR and receptor binding assays. In non-failing human hearts, prostanoids evoked a positive inotropic effect and an increase of MLC-2 phosphorylation which was absent in failing human hearts. In failing rat heart, the prostanoid FP receptor-mediated inotropic response and prostanoid FP receptor-density was reduced by ~40-50% compared to non-failing rat heart. Prostanoids mediate a sustained positive inotropic response in non-failing heart, which appears to be down regulated in failing heart. The pathophysiological significance of changes in prostanoid-mediated inotropic support in the failing heart remains to be determined.     

8-Bromo-cAMP and 8-CPT-cAMP Increase the Density of β-Adrenoceptors in Hepatocytes by a Mechanism Not Mimicking the Effect of cAMP

Abstract: Addition of 8-bromo-adenosine 3′,5′-cyclic monophosphate (8-bromo-cAMP) or 8-(4-chlorophenylthio)-adenosine 3′,5′-cyclic monophosphate (8-CPT-cAMP) to hepatocytes at the time of plating enhanced the acquisition of β-adrenoceptors that occurs spontaneously upon culturing as primary monolayers. This effect was partially suppressed by the phosphodiesterase inhibitor isobutyl methylxanthine, and was mimicked by 8-bromo-AMP, 8-bromo-adenosine, and the adenosine kinase inhibitor 5′-amino-5′-deoxyadenosine. Agents that elevated the intracellular level of cAMP, such as glucagon and forskolin, and Sp-8-bromo-adenosine 3′,5′-monophosphorothioate (Sp-8-bromo-cAMPS), a cAMP analogue that is resistant towards metabolic breakdown, did not significantly enhance β-adrenoceptor expression when used alone, but glucagon enhanced the effect of 8-bromo-adenosine. 8-Bromo-cAMP and 8-bromo-adenosine decreased cellular ATP-levels. These observations suggest that the enhanced β-adrenoceptor acquisition was mediated mainly through the action of metabolites of 8-bromo-cAMP and 8-CPT-cAMP, although there may be a cAMP-mediated component in the effect. Several mechanisms, including depletion of ATP, are probably involved, and might affect β-adrenoceptor degradation.