Purification, biochemistry and molecular cloning of an insect glycosylasparaginase from Spodoptera frugiperda.

Glycosylasparaginase (EC 3.5.1.26) from Sf9 cells (Spodoptera frugiperda) was purified to homogeneity with a specific activity of 2.1 unit/mg. The enzyme is composed of two non-identical alpha/beta subunits joined by strong non-covalent forces and has one glycosylation site located in the alpha subunit. Molecular masses of the subunits were determined to be 28 kDa and 17 kDa by SDS-PAGE. Native enzyme existed in quaternary structures of either heterodimer (alpha beta) or heterotetramer (alpha 2 beta 2). These forms exhibited different ionic characteristics during DE52 anion exchange chromatography, and their molecular masses were determined to be 47 kDa and 101 kDa by gel filtration. The enzyme was thermostable, requiring 65-70 degrees C to be denatured, and it had a broad pH optimum from 4-10.5 with a pKa around 6. SDS easily inactivated the enzyme. The K(m) of glycosylasparaginase for its normal substrate GlcNAc-Asn was 0.88 mM. The enzyme also exhibited asparaginase activity with a K(m) of 3.0 mM for asparagine. N-terminal amino acids of the denatured subunits were sequenced and degenerate primers were designed for cloning its cDNA using PCR and 5' and 3' RACE. Glycosylasparaginase cDNAs from bovine and rat were also cloned using similar strategies, and primary structures of glycosylasparaginases from six species (human, bovine, rat, mouse, Sf9 cells and Flavobacterium) have been compared and related to a recent crystal structure of the human enzyme.

The effectiveness of clonidine as an analgesic in paediatric adenotonsillectomy.

PURPOSE: To compare the analgesic effects of preoperative oral clonidine with intraoperative intravenous fentanyl in children undergoing tonsillectomy or adenotonsillectomy. METHODS: This randomized, controlled, double-blind study of 36 ASA I-II children, age 7-12 yr undergoing adenotonsillectomy was conducted at a tertiary care paediatric teaching hospital. Either 4 micrograms.kg-1 clonidine po was given 60-90 min preoperatively or 3 micrograms.kg-1 fentanyl i.v. was given intraoperatively. Postoperatively visual analog pain scores (VAS) were recorded at rest and on swallowing every 10 min for the first 30 min and then every 15 min for two hours. Morphine 0.05 mg.kg-1 i.v. was given for VAS > or = 5. If > 3 doses were required, 1.5 mg.kg-1 codeine po and 20 mg.kg-1 acetaminophen po were given. Sedation and anxiety scores were recorded preoperatively. Haemodynamic changes, blood loss, recovery scores, and the incidence of vomiting, hypotension, and airway obstruction were recorded. RESULTS: Children who received clonidine had a higher incidence of preoperative sedation (63%) than those receiving fentanyl (6%). Preinduction mean arterial pressure was lower in the clonidine group but required no intervention. VAS scores were similar throughout the observation period. There was no difference either in the number of morphine or codeine rescue doses administered or in the incidence of side effects. CONCLUSION: Oral clonidine is an effective analgesic and sedative for children undergoing tonsillectomy or adenotonsillectomy.

Plasma concentration of flumazenil following intranasal administration in children.

PURPOSE: A pharmacokinetic study in children to determine plasma flumazenil concentrations after the intranasal administration of 40 microg x kg(-1). METHODS: Following institutional approval and informed written consent, 11 ASA physical status I-II patients, aged two to six years, undergoing general anesthesia for dental surgery were recruited. After induction, 40 microg x kg(-1) flumazenil Anexate, Roche, 0.1 mg x mL(-1) (0.4 mL x kg(-1))) were administered via a syringe as drops, prior to nasal intubation. Venous plasma samples were drawn prior to administration of flumazenil (t = 0), and then at 2, 4, 6, 8, 10, 15, 20, 30, 40, 60, and 120 min thereafter. The plasma samples were immediately processed by the on-site laboratory and then stored at -70 degrees C, before batch analysis via high performance liquid chromatography assay. Pharmacokinetic data calculations were performed using WinNonLin software (Scientific Consulting Inc.). RESULTS: Eleven patients were studied, but data for one patient were discarded due to insufficient sampling. The median age was 4.3 yr (range 3 to 6), with a median weight of 18.9 kg (range 14.9 to 22.2). There were seven boys and three girls. Mean Cmax was 67.8 ng x mL(-1) (SD 41.9), with Tmax at two minutes. The calculated half-life was 122 min (SD 99). CONCLUSION: The mean plasma concentrations of flumazenil attained were similar to those reported after intravenous administration, and may be sufficient to antagonize the side-effects of benzodiazepines. This route of administration may be useful when the intravenous route is not readily available.