Predicting postoperative nausea and vomiting in patients undergoing oral and maxillofacial surgery.

A common predictive measure of postoperative nausea and vomiting (PONV) is the Apfel score. Although tested in many different operations, it has not been tested extensively in oral and maxillofacial surgery (OMFS). This study was designed to determine whether it applied to OMFS and whether there were other factors in this population that would improve its accuracy. A retrospective chart review was carried out on a randomly selected group of patients who had OMFS during a 10-month period. In addition to the Apfel score risk factors, PONV data were collected in relation to type of anesthetic induction and maintenance, type of surgery, use of maxillomandibular fixation (MMF), use of opioids, and anesthesia and surgery times. One-hundred and sixty-seven patients were included in the analysis; 24% had nausea and 11% had nausea and vomiting. Patients who had orthognathic or temporomandibular joint surgery had the highest rate of PONV. Young age, anesthesia and operation time, and use of MMF were also associated with increased PONV. Adding age, MMF or limited postoperative mouth opening, and surgery type to the Apfel score should make it more predictive in OMFS.

Production of membrane whorls in rat liver by some inhibitors of protein synthesis.

Inhibitors of protein synthesis capable of differential effects on nascent peptide synthesis on membrane-bound and free polyribosomes were employed to investigate the structure and function of cellular membranes of liver. The formation of membranous whorls in the cytoplasm and distension of nuclear membranes were induced by inhibitors of protein synthesis (i.e., cycloheximide and emetine) which predominantly interfere with nascent peptide synthesis on membrane-bound polyribosomes in situ. Other inhibitors of protein synthesis such as puromycin and fusidic acid, which inhibit nascent peptide synthesis on both free and membrane-bound polyribosomes, and chloramphenicol, which inhibits mitochondrial protein synthesis, did not induce these alterations. Cycloheximide, puromycin, and chloramphenicol produce some common cellular lesions as reflected by similar alterations in morphology, such as swelling of mitochondria, degranulation of rough endoplasmic reticulum, and aggregation of free ribosomes. The process of whorl formation in the cytoplasm, the incorporation of [(3)H]leucine and of [(3)H]choline into endoplasmic reticulum and the total NADPH-cytochrome c reductase activity of the endoplasmic reticulum were determined. During maximum formation of membranous whorls, [(3)H]leucine incorporation into cytoplasmic membranes was inhibited, while [(3)H]choline incorporation into these structures was increased; maximum inhibition of protein synthesis and stimulation of choline incorporation into endoplasmic reticulum, however, preceded whorl formation. Cycloheximide decreased the activity of NADPH-cytochrome c reductase of rough endoplasmic reticulum, but increased NADPH-cytochrome c reductase activity of smooth endoplasmic reticulum. In addition, cycloheximide decreased the content of hemoprotein in both the microsomal and mitochondrial fractions of rat liver, and the activities of mixed function oxidase and of oxidative phosphorylation were impaired to different degrees. Succinate-stimulated microsomal oxidation was also inhibited. The possible mechanisms involved in the formation of membranous whorls, as well as their functions, are discussed.

Effects of 6-thioguanine on macromolecular events in regenerating rat liver.

Regenerating rat liver was used as a semisynchronous system in which to investigate the effects of 6-thioguanine on biochemical processes occurring in discrete phases of the cell cycle. 6-Thioguanine inhibited the first wave of DNA biosynthesis in regenerating rat liver. This effect appeared to be the result of a decrease, caused by 6-thioguanine, in the induction of several enzyme activities (i.e., thymidine kinase, deoxycytidylate deaminase, cytidine diphosphate reductase, and DNA polymerase) necessary for the initiation of DNA replication in regenerating liver. There was a fairly short period during which 6-thioguanine could be given to rats to accomplish the inhibition of the appearance of the induced activities of these enzymes; this period corresponded to the time just before enzyme induction. The inhibition of the induced synthesis of this group of enzymes occurred in the presence of an intact translational apparatus and intact polysomes and in the absence of interference with the incorporation of radioactive leucine and tyrosine into total protein of liver. Synthesis of polyadenylate-containing RNA was depressed in 6-thioguanine-treated rats, whereas the synthesis of polyadenylate-lacking RNA was unaffected. It is suggested that the inhibition of the synthesis of polyadenylate-containing RNA by 6-thioguanine is at least in part responsible for the observed decrease in induced enzyme activities and the resulting interference with DNA replication.

Effects of 6-thioguanine on RNA biosynthesis in regenerating rat liver.

6-Thioguanine, at a dose of 40 mg/kg body weight, was administered to rats at 12 hr after partial hepatectomy; 6 hr later, liver polysomes and cell sap were isolated and utilized to measure the effects of this antimetabolite on protein synthesis in vitro. When radioactive leucine was used to label peptides synthesized in vitro, no difference was observed between polyacrylamide gradient gel scans of systems derived from control regenerating liver and those from 6-thioguanine-treated regenerating liver. However, when radioactive tyrosine was used as the tracer to monitor synthesized peptides, a depression in the 30,000-molecular weight region of scans of products synthesized in systems derived from 6-thioguanine-treated regenerating liver was observed. Recombination experiments showed this effect to be due to the polysome component of the system. When equal amounts of polyadenylic acid-containing RNA from 6-thioguanine-treated or control regenerating liver were added to a wheat germ in vitro protein-synthesizing system, polyacrylamide gel scans of the products synthesized in the presence of radioactive tyrosine showed that more peptides were synthesized from polyadenylic acid-containing RNA from 6-thioguanine-treated rats than from control polyadenylic acid-containing RNA. That this phenomenon might be the result of incorporation of the analog into RNA was shown by the finding that all types of RNA containing 6-thioguainine, with the greatest concentration occurring in polyadenylic acid-containing RNA.

Mechanisms of sensitivity and resistance of murine tumors to 5-fluorouracil.

The biochemical basis for the resistance of murine leukemia P388 to 5-fluorouracil (FUra) was systematically investigated by examining the transport and metabolism of FUra, or its anabolites, as well as the inhibition of enzymes and processes known to be affected by the drug. Of these parameters, only three were found to be altered significantly in the resistant line: (a) the enzyme required for the phosphorylation of uridine 5'-monophosphate to uridine 5'-diphosphate was present at a significantly lower specific activity in the resistant line than in its sensitive counterpart; (b) the rates of generation and persistance of 5-fluoro-2'-deoxyuridine 5'-monophosphate were significantly lower and shorter in the variant; and (c) there was a 1.6- and 3-fold decrease in the incorporation of FUra into polyadenylic acid-containing RNA and polyadenylic acid-lacking RNA, respectively, in resistant versus sensitive cells. Taken together, these findings suggest a dual mechanism for resistance to FUra in these leukemic cells, namely, a depressed capacity to generate di- and triphosphates of the riboside and deoxyriboside of the drug leading to lower pools of the proximate antimetabolite, fluorouridine 5'-triphosphate, and accelerated excretion of 5-fluoro-2'-deoxyuridine 5'-monophosphate, so that thymidylate synthetase is perturbed in a less than lethal way.