In vitro and in vivo characterization of recombinant human butyrylcholinesterase (Protexia) as a potential nerve agent bioscavenger.

Previous studies in rodents and nonhuman primates have demonstrated that pretreatment with cholinesterases can provide significant protection against behavioral and lethal effects of nerve agent intoxication. Human butyrylcholinesterase (HuBuChE) purified from plasma has been shown to protect against up to 5 x LD50s of nerve agents in guinea pigs and non-human primates, and is currently being explored as a bioscavenger pretreatment for human use. A recombinant form of HuBuChE has been expressed in the milk of transgenic goats as a product called Protexia. Protexia was supplied by Nexia Biotechnologies (Que., Canada) as a purified solution with a specific activity of 600 U/mg. Initial in vitro studies using radiolabeled 3H-soman or 3H-DFP (diisopropyl fluorophosphate) demonstrated that these inhibitors specifically bind to Protexia. When Protexia was mixed with soman, sarin, tabun or VX using varying molar ratios of enzyme to nerve agent (8:1, 4:1, 1:1 and 1:4, respectively), the data indicated that 50% inhibition of enzyme activity occurs around the 1:1 molar ratio for each of the nerve agents. Protexia was further characterized for its interaction with pyridostigmine bromide and six unique carbamate inhibitors of cholinesterase. IC50 and Ki values for Protexia were determined to be very similar to those of HuBuChE purified from human plasma. These data suggest that Protexia has biochemical properties very similar to those HuBuChE when compared in vitro. Together these data the continued development of the goat milk-derived recombinant HuBuChE Protexia as a potential bioscavenger of organophosphorus nerve agents.

Cerebral blood flow during cardiopulmonary bypass: influence of temperature and pH management strategy.

Because disordered autoregulation of cerebral blood flow may underlie neurologic injury associated with cardiopulmonary bypass (CPB), we studied the effects of normothermic (37 degrees C) and hypothermic (18 degrees C) CPB on cerebral vascular reactivity in 6 to 8-week-old piglets. Hypothermic CPB animals were subdivided into alpha-stat and pH-stat groups (n = 6 animals each group) according to acid-base management protocol. Cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), cerebral vascular resistance (CVR), and CBF response to hypercapnia were examined before, during, and 1 hour after CPB and used to calculate CVR per millimeter of mercury change in arterial partial pressure of CO2: (CVRnormocapnia - CVRhypercapnia)/(PaCO2 hypercapnia - PaCO2 normocapnia). Before CPB, CBF, CMRO2, and vascular reactivity to elevated CO2 were similar in the three groups; these parameters remained unchanged by normothermic CPB. However, during hypothermic CPB, CBF and CMRO2 decreased in both alpha-stat and pH-stat groups; in the alpha-stat group, CBF decreased from 27 +/- 5 mL.min-1.100 g-1 (normothermic CPB) to 5 +/- 1 mL.min-1.100 g-1 (hypothermic CPB) (p < 0.05) and CMRO2 decreased from 1.8 +/- 0.21 to 0.24 +/- 0.04 mL.min-1.100 g-1 (p < 0.05), whereas in the pH-stat group CBF decreased from 28 +/- 2 to 9 +/- 1 mL.min-1. 100 g-1 (p < 0.05) and CMRO2 decreased from 1.63 +/- 0.07 to 0.31 +/- 0.09 mL.min-1.100 g-1 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Review of blood transfusion practices in thoracic surgery.

Between September 1, 1989, and August 31, 1990, 516 patients were admitted to the Royal Brompton National Heart and Lung Hospital for thoracic operations. A prospective audit recorded the nature and extent of operation, the histologic diagnosis, and the number of units of blood prepared and transfused during hospitalization. Cross-matched blood was requested in 243 patients but only 16.1% of these received transfusion. In total, 1,295 units of whole blood or red cell concentrate were cross-matched and made immediately available in the operating suite at the time of operation. Only 322 units were administered (cross-match to transfusion ratio of 4.02:1). Almost half of the patients who received transfusions received 2 units or less, a third received 3 or 4 units, 10% between 5 and 10 units, and 8.4% required more than 10 units during their hospital stay. The nature and extent of resection was an indicator of the need for transfusion. Other important predisposing factors included a previous thoracic operation, resection for inflammatory disease, decortication of empyema thoracis, chest wall resection, or thoracoplasty. Other thoracic procedures such as pleurodesis, pleurectomy, open lung biopsy, pectus correction, operation for bullous lung disease, and mediastinoscopy had a negligible transfusion requirement. The data suggest that understanding risk factors for transfusion requirements of patients undergoing thoracic surgical procedures should optimize present resources. This is critical when exploiting the limited availability of donated blood and blood products. Similarly, anticipation of transfusion requirements takes best advantage of manpower within the blood bank and minimizes unnecessary and avoidable blood wastage and expenditure.

Abnormal cutaneous topobiology: the molecular basis for dermatopathologic mononuclear cell patterns in inflammatory skin disease.

Because of the identification and characterization of various adhesion molecules (lymphocyte function associated antigen-1, intercellular adhesion molecule-1), chemotactic factors (interleukin-8, monocyte chemotactic/activating factor), and their modulatory cytokines (gamma interferon, tumor necrosis factor), it is possible to begin to ascribe specific molecules to cutaneous cellular reaction patterns. The abnormal topobiology, or altered spatial distribution, of mononuclear cells, which gives rise to disease-specific patterns, was described in molecular terms. A large number of diverse skin diseases were classified into six different groups, with each group highlighting distinctive cell types, adhesion molecules, chemotactic factors, and cytokines. The diseases within each group, which share functional anatomical reaction zones, were postulated to share common pathophysiologic pathways. Thus, it is now possible, as one scans the microscopic field, to look past the static images of red- and blue-stained cells and appreciate a dynamic and detailed medley of molecularly defined events emanating from the eyepiece.

Does hypothermic fibrillatory arrest improve myocardial protection during emergency revascularization?

Hypothermic fibrillatory arrest (HFA) was compared with conventional hypothermic cardioplegic arrest (HCA) in a model of acute regional ischemia. In 20 pigs, the left anterior descending coronary artery was occluded for 30 minutes before cardiopulmonary bypass. In the HCA group (n = 10), the heart was arrested with a hyperkalemic cold crystalloid solution, whereas in HFA animals (n = 10), the heart was vented and allowed to fibrillate spontaneously without cross-clamping. Miniature pH probes monitored intramyocardial pH during 45 minutes of arrest (HCA or HFA, both with systemic and topical myocardial cooling) and during two hours of coronary reperfusion. Hypothermic fibrillatory arrest did not ameliorate the acidosis in the ischemic (left anterior descending) region; indeed, after two hours of coronary reperfusion, there was a trend toward more acidosis in the postischemic left anterior descending territory in the HFA group. However, HFA did prevent acidosis in the nonischemic (left circumflex) territory. Infarct size expressed as percent of region at risk was 18.1% +/- 3.2% (mean +/- standard error of the mean) in the HCA animals and 18.8% +/- 4.4% in the HFA animals. These results demonstrate that HFA offers no advantage over HCA in protection of regionally ischemic myocardium in a model with minimal collateral circulation.