Evaluation of differences in patient and physician perception of benefit and risks of aspirin and antifibrinolytic therapy in cardiac surgery

It is unclear whether physicians and patients have similar concerns and preferences when considering benefit and risks of aspirin and antifibrinolytic therapy for cardiac surgery. We surveyed both groups to ascertain their perceptions and preferences for treatment in this setting. Both preoperative and postoperative cardiac surgical patients and the physician craft groups caring for them (cardiology, surgery, anaesthesia/critical care), were provided with estimates of benefits and risks of aspirin and antifibrinolytic therapy. All study participants were asked to stipulate the minimal absolute risk reduction required for them to agree to such therapy. When compared with the cardiac surgical patients they treat, physicians required a smaller thrombotic risk reduction with aspirin whilst accepting its known increased risk of bleeding. This was significantly different in a high-risk stroke setting (incidence 5%) where the required relative risk reduction with aspirin use for physicians was 20% versus patients 40% (P <0.001); and for myocardial infarction, physicians 20% versus patients 36% (P=0.051). For antifibrinolytic therapy, the tolerated increased relative risk of stroke for physicians was 20% versus patients 10% (P=0.004), and for myocardial infarction, physicians 16.7% versus patients 4.2% (P <0.001). The three physician craft groups had comparable tolerances of thrombotic risk. Patient and physician preferences for perioperative aspirin and antifibrinolytic therapy sometimes differ based on risk benefit analysis.

Role of Ca2+ stores in dopamine- and PACAP-evoked growth hormone release in goldfish

Growth hormone (GH) secretion, evoked by either pituitary adenylate cyclase-activating polypeptide (PACAP) or dopamine (DA), is dependent on both voltage-sensitive calcium channels (VSCC) and cAMP signaling in goldfish. We further characterized the involvement of Ca2+ in evoked release by PACAP and DA, by examining the sensitivity of evoked GH release to perturbations of Ca2+ signaling. Both VSCC and calmodulin/calmodulin-dependent kinase are involved in PACAP signaling as had been shown for DA. In spite of this apparent dependence on VSCC, blockade of TMB-8 but not ryanodine-sensitive intracellular Ca2+ stores inhibited both PACAP- and DA-evoked GH release. Using sarcoplasmic/endoplasmic reticulum Ca-ATPases (SERCA) inhibitors, we found BHQ blocked, whereas thapsigargin (Tg) enhanced stimulated GH release, suggesting that Tg-sensitive SERCA may counteract these cAMP-mobilizing neuroendocrine regulators by sequestering [Ca2+]i. As GH secretion stimulated by two endogenous gonadotropin-releasing hormones is not affected by Tg, it appears that distinct multiple Ca2+ stores mediate the hormone releasing response to different neuroendocrine regulators.

Osmotic and cryoprotectant permeation characteristics of islet cells isolated from the newborn pig pancreas

The development of effective protocols for the low-temperature banking of pancreatic islets is an important step in islet transplantation for the treatment of type I diabetes mellitus. We have been exploring the use of islets from the newborn pig as an alternative source of tissue for transplantation. Current cryopreservation protocols are empirically derived, but may be optimized by modeling osmotic responses during the cryopreservation process. This study determined the osmotic and cryoprotectant permeability parameters of cells isolated from the pancreas of newborn pigs. Key parameters are: the osmotically inactive fraction of cell volume, hydraulic conductivity, the permeability coefficients of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) at varying temperatures, and the activation energies of these transport processes. Newborn pig islets were dispersed into single cells and kinetic and equilibrium cell volumes were recorded during osmotic excursions using an electronic particle counter interfaced to a computer. Data were fitted to theoretical descriptions of the osmotic responses of cells, based on the Kedem-Katchalsky approach. The hydraulic conductivity (Lp) in the absence of cryoprotectant was calculated as 0.050 +/- 0.005, 0.071 +/- 0.006, and 0.300 +/- 0.016 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively (mean +/- SEM, n = 7, 6, or 9). These values give an activation energy value of 16.69 kcal/mol when put into an Arrhenius plot. The solute permeability (Ps) values for 1 M DMSO were 0.89 +/- 0.12, 1.86 +/- 0.28, and 5.33 +/- 0.26 microm/min at 4 degrees C, 10 degrees C, and 22 degrees C, respectively (n = 11, 8, or 10) giving an activation energy of 15.98 kcal/mol. The Lp values for cells exposed to 1 M DMSO were 0.071 +/- 0.006, 0.084 +/- 0.008, and 0.185 +/- 0.014 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively. The activation energy for these values was 8.95 kcal/mol. The Ps values for 2 M DMSO were 1.11 +/- 0.13, 1.74 +/- 0.19, and 7.68 +/- 0.12 microm/min for the same temperatures, with a calculated activation energy of 17.89 kcal/mol. The Lp values in the presence of 2 M DMSO were 0.070 +/- 0.006, 0.085 +/- 0.008, and 0.192 +/- 0.009 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively, with an activation energy of 9.40 kcal/mol. Solutions of 1 M EG gave Ps values of 1.01 +/- 0.13, 1.45 +/- 0.25, and 4.90 +/- 0.48 microm/min at the three test temperatures. The resulting activation energy was 14.60 kcal/mol. The corresponding Lp values were 0.071 +/- 0.007, 0.068 +/- 0.006, and 0.219 +/- 0.012 microm/min/atm with an activation energy of 10.96 kcal/mol. The solute permeabilities in the presence of 2 M EG for newborn pig islet cells were 1.03 +/- 0.15, 1.42 +/- 0.23, and 5.56 +/- 0.22 microm/min; the activation energy was 15.70. The Lp values for cells in the presence of 2 M EG were 0.068 +/- 0.008, 0.071 +/- 0.006, and 0.225 +/- 0.010 microm/min/atm; the activation energy for these values was 11.49 kcal/mol. These key cryobiological parameters permit the mathematical modeling of osmotic responses of intact islets during the cryopreservation process, which may lead to further improvements in the low temperature storage of islets from newborn pigs.