Heartworm-positive dogs recover without complications from surgical sterilization using cardiovascular sparing anesthesia protocol.

Expedited home placement of heartworm-positive shelter dogs is desirable and may outweigh the perceived increase in anesthetic risk for pre-adoption sterilization; however, this issue has not been addressed in the literature. Our goal was to determine whether heartworm-positive dogs suffered clinically evident perioperative complications after sterilization under general anesthesia. Anticipated complications could result from anesthesia-induced changes in pulmonary vascular resistance and cardiac output leading to signs of thromboembolic disease and even death from dislodged parasites. The medical records of 15 hemodynamically stable, intact, heartworm-positive, mixed-breed shelter dogs with no or mild clinical signs were examined. Pre-operative evaluation of patients included a complete blood count, clinical chemistry profile, heartworm antigen and microfilariae screen, electrocardiogram, and thoracic radiographs. The anesthetic protocol for heartworm-positive dogs included acepromazine (0.01-0.05 mg/kg), butorphanol (0.1mg/kg IM) and meloxicam (0.2mg/kg IM), or carprofen (2mg/kg SQ) in the preanesthetic period; tiletamine/zolazepam (3-6 mg/kg IV) or ketamine/diazepam (3-6mg/kg/0.25-5mg/kg IV) to effect for induction; maintenance on isoflurane or sevoflurane and oxygen. A lidocaine testicular block was performed on 11 males. All dogs were monitored postoperatively for a minimum of 24h and then daily until discharge. There were no clinically evident perioperative complications in heartworm-positive dogs. Purposeful pre-operative evaluation of heartworm-positive dogs while utilizing cardiovascular-sparing anesthetic protocols may allow clinicians to proceed with sterilization of hemodynamically stable heartworm-positive shelter dogs prior to heartworm treatment.

Peripheral blood hematopoietic progenitor/stem cells proliferate to form colonies in liquid culture but require contact with vascular endothelial cells and GM-CSF.

To test the hypothesis whether peripheral blood hematopoietic progenitor/stem cells (PBSCs) interact with vascular endothelial cells during events leading to extramedullary hematopoiesis, we cocultured T-cell depleted, peripheral blood mononuclear cells obtained from cytokine treated primates in liquid culture containing a monolayer of porcine aortic endothelial cells (PAECs) for 7 days. Recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) added to cocultures of PBSC-PAEC stimulated colony formation, while only a few clusters were observed in cultures without GM-CSF. In contrast, colony formation was not stimulated when either interleukin 1 (IL-1) or IL-3 were added to the cultures. Colony and cluster formation in response to GM-CSF was dose dependent; 20 +/- 5 colonies/5,000 cells were formed at 3 U/ml, and optimal colony formation of 42 +/- 11/5,000 cells occurred at 100 U/ml. Colonies formed in the presence of GM-CSF were large, and most contained greater than 200 cells. Morphological and phenotypical characterization of cells from isolated colonies suggested that the majority of cells were predominantly immature myeloid elements. However, there was also a low but consistent frequency of megakaryocytic lineage cells. Thus, PBSCs interact with non-bone marrow--derived vascular endothelial cells and proliferate, but only in the presence of GM-CSF, suggesting that PBSC interaction with vascular endothelial cells in vivo could lead to extramedullary hematopoiesis.

The C-S lyases of higher plants: homogeneous beta-cystathionase of spinach leaves.

S-Substituted cysteines and their derivatives are prominent secondary amino acids in a number of plant families. The substituents are often specific and unique to each family. Cystathionine, however, is an ubiquitous S-substituted cysteine found in all autotrophic plants since it is an intermediate in the biosynthesis of methionine. beta-Cystathionase will produce homocysteine and pyruvate from cystathionine by a beta-elimination reaction. The present report describes the purification of this enzyme to homogeneity from spinach leaves and some of its properties. The enzyme has a molecular weight of 210,000 and consists of four identical subunits of Mr 53,000. It has a pH optimum for activity of 8.6-8.7 and utilizes pyridoxal-5'-phosphate as a cofactor. Its specificity is limited to L-cystathionine, L-djenkolate, and L-cystine as substrates with a relative activity of 100:126:17, respectively. It is not a glycoprotein unlike a number of previously described plant C-S lyases.

Heterogeneity of pig plasma amine oxidase: molecular and catalytic properties of chromatographically isolated forms.

Pig plasma amine oxidase was resolved into several fractions by ion-exchange and hydroxyapatite chromatography. These fractions were separately purified, and each fraction was analyzed for catalytic and structural properties. The relative amount of these fractions varied between preparations. Each fraction was composed of a unique set of bands on isoelectric focusing, as revealed by activity and protein staining. All the fractions contained 2 mol of Cu2+ and one "active-carbonyl" cofactor per 195 000 g of protein. There was no detectable difference in the amino acid contents of the fractions. The fractions all had similar catalytic properties using benzylamine as the substrate. The chromatographically resolved fractions had differing carbohydrate contents as revealed by gas chromatographic analysis and interaction with lectins. Further, some of the isoelectric focusing bands interacted with lectins of differing affinities. The results suggest that the heterogeneity may be due to variable carbohydrate content. Further, the practice of pooling the various chromatographic fractions may yield misleading results under certain circumstances.

Inhibition of carbon dioxide fixation by lead acetate in rat liver mitochondria.

These studies were undertaken to determine the mechanism by which intravenously administered lead salts inhibit hepatic gluconeogenesis. Within 1 h after the intravenous administration of lead acetate (10 mg), there is 97% inhibition of CO2 fixation in isolated rat liver mitochondria. This effect is concentration-dependent. The induction of phosphoenolpyruvate carboxykinase activity observed with starvation was also inhibited by intravenously administered lead acetate, but the activities of pyruvate kinase, glucose 6-phosphate dehydrogenase and pyruvate carboxylase were unaffected, as was the oxidation of palmitate and palmitoyl-CoA by mitochondria from Pb2+-treated animals. The addition of reduced glutathione to mitochondria from Pb2+-treated animals had no effect on the inhibited CO2 fixation. ATP concentrations in mitochondria from Pb2+-treated animals are decreased and the dose-response relationships for the effect of Pb2+ on CO2 fixation and ATP concentrations correspond. We conclude that the decrease in mitochondrial ATP in Pb2+-treated animals is probably responsible for the marked inhibition ov CO2 fixation, and hence the impairment of gluconeogenesis from alanine, lactate and pyruvate observed by others.

Disaggregation of endotoxin by isolated rat liver plasma membranes and lack of product binding.

The interaction of bacterial endotoxin with isolated rat liver cell membranes was studied to determine the extent and nature of any binding. Serratia marcescens endotoxin was incubated with isolated rat liver plasma membranes for varying periods of time at 37 C, and this mixture was then centrifuged through a discontinous sucrose density gradient. The membranes banded primarily at the 35 to 45% sucrose interface, whether or not they had been incubated with endotoxin. The endotoxin distributed itself throughout the gradient except when incubated with membranes, in which case it failed to sediment. This membrane-induced alteration in sedimentation could be prevented by heat inactivation of the membranes, and was found to be pH, time, temperature, and concentration dependent. There was neither associated degradation of the endotoxin, as measured by molecular sieve chromatography, nor loss in toxicity, as determined in lead-sensitized rats. These observations are consistent with an enzymatic disaggregation of the endotoxin by membranes and could represent a step in the uptake of the endotoxin by the reticuloendothelial system. No significant binding of this disaggregated endotoxin to the membranes could be detected, either after gradient separation or after repeated washing. This finding strongly suggests that, at least in cells that are active in the uptake of endotoxin, membrane-endotoxin interactions may be relatively transitory in nature, and that firm adherence to such membranes may not be a central feature of endotoxin toxicity.