[A common antigenic epitope in influenza A virus (H1, H2, H5, H6) hemagglutinin]. / Obshchii antigennyi épitop v gemaggliutinine virusov grippa A (H1, H2, H5, H6).

Avian influenza A viruses belonging to hemagglutinin (HA) subtypes H5 and H6 were studied in the infectivity neutralization test and radioimmunoprecipitation assay (RIPA) with monoclonal antibody MAb C179. This MAb recognizes a conformational antigenic epitope in the stem region of HA formed by two regions (amino acid positions 318-322 in HA1 subunit and 47-58 in HA2), conserved in all H1 and H2 influenza viruses. MAb C179 reacts with HA of H5 viruses in RIPA and neutralizes these strains as efficiently as H2 viruses. C179 precipitates H6 subtype HA but does not neutralize the infectivity of these viruses. Comparison of amino acid sequences of H2, H5, and H6 strains showed identical epitope recognized by MAb C179 in H5 and H6 HAs, which differs from epitopes of H1 and H2 by two amino acids in the HA2 subunit. Causes of disagreement between immunoprecipitation of H6 HA by MAb C179 and neutralization of this serosubtype by this MAb are discussed.

Effect of adding impression material to mandibular denture space in Piezography.

The purpose of the study was to examine the effect of adding impression material on denture space using a piezographical record. Subjects were ten voluntary edentulous patients, aged from 61 to 84 years old. A maxillary trial denture with anterior artificial teeth and a mandibular base plate with a keel were inserted into the oral cavity. Three ml of tissue-conditioning materials was injected on the base plate for each trial. Afterwards, the patients were instructed to pronounce various phonemes, so that tongue, cheeks and lips conformed to the denture space. The impression complexes were cut at the level of the estimated occlusal plane. Occlusal analogues were made by duplicating the impression complexes. Measurements were performed for five analogues from the first to fifth additions for each subject. The data were compared using analysis of variance (ANOVA), and a Friedman's test followed by a Bonferroni test for multiple comparisons with a level of significance at 5%. At the molar and premolar positions, the bucco-lingual widths of the occlusal table increased significantly at incremental injection of impression materials from P1 to P4. The midpoints of the analogues were located at a distance of 1.5 mm buccally at the molar position and at a distance of 1.9 mm buccally at the premolar position from the top of the alveolar crest, independent of the addition of impression material. It was concluded that denture space was regulated by volume of material and was located slightly on the buccal side from the crest of the residual alveolar ridge.

Effects of antibiotics on fibrinolytic activity in vivo.

The effects of latamoxef, cefamandole, carbenicillin and cefotaxime on fibrinolytic system in rats were examined under feeding of an ordinary diet or a vitamin K-deficient diet for eight days. No obvious change was observed in UK-induced plasma clot lysis time, euglobulin lysis time and antiplasmin level in plasma. These findings of the in vitro and ex vivo studies suggest that these antibiotics cause no enhancement of fibrinolytic activity.

Gas-liquid chromatographic determination of sodium fluoroacetate (Compound 1080).

An analytical method is described for the determination of Compound 1080 (sodium fluoroacetate) residues in 1--10 g tissue. Sample extracts of tissues are cleaned up with silica gel, and Compound 1080 (as fluoroacetic acid) is separated by a micro-distillation procedure. The fluoroacetic acid in the distillate is derivatized with pentafluorobenzyl bromide to form pentafluorobenzyl fluoroacetate which is measured by electron capture gas-liquid chromatography. Recoveries of sodium fluoroacetate from fortified tissue samples averaged about 25%. Despite the limited recoveries, results were quite reproducible, and levels as low at 2 ppm were determined in fortified 1 g samples, and 0.2 ppm in 10 g samples. The method is relatively simple and has been used routinely in our laboratory for the analysis of various types of samples such as grain, and tissues from birds, rodents, and larger animals.

Effects of antibiotics on fibrinolytic activity.

Latamoxef, cefamandole, carbenicillin and cefotaxime were examined for their effects on fibrinolytic activity in vitro by means of the fibrin plate method, fibrin clot lysis time and euglobulin lysis time with human, rabbit and rat plasma. These antibiotics showed no fibrinolytic but weak antifibrinolytic activity at 1000 or 3000 micrograms/ml in some assay systems.

Flameless atomic absorption spectroscopic determination of heavy metals in whole-fish samples.

Flameless atomic absorption spectroscopy with a carbon rod atomizer was used to determine lead, cadmium, and chromium in whole-fish samples. Samples were dry-ashed, and the metals were separated by solvent extraction with ammonium pyrrolidine dithiocarbamate in methyl isobutyl ketone, and then back-partitioned into an aqueous acid solution for analysis. The back-partitioning step allows a direct comparison of sample solutions with aqueous solutions of the standard. Recoveries of the metals from fortified samples averaged 91% (+/-9.6) for lead and 100% (+/-5.6) for chromium at the 0.1-1 ppm level, and 100% (+/-13.3) for cadmium at the 0.01-0.1 ppm level.

Modified gas-liquid chromatographic method for determination of compound 1080 (sodium fluoroacetate).

A method capable of determining 0.1 ppm 1080 (sodium fluoroacetate) in 1 g animal tissue was developed. It involves extraction of 1080 from the sample with acetone-water, and then evaporation of the acetone followed by extraction of 1080 as fluoroacetic acid from water with ethyl acetate. Ethyl acetate is removed by volatilization from fluoroacetic acid which is retained as the triethanolammonium fluoroacetate salt. Fluoroacetic acid is subsequently derivatized with alpha-bromo-2,3,4,5,6-pentafluorotoluene and quantitated by gas-liquid chromatography with an electron capture detector. The method is rapid and requires no special apparatus or equipment and no more than 12 mL of any one solvent. Recoveries of 1080 from tissue samples fortified with 0.1-100 ppm averaged about 85%.

Comparison of reversed-phase and ion-pair chromatography for the determination of strychnine in animal tissues.

Ion-pair and reversed-phase high-performance liquid chromatography (HPLC) were evaluated for quantification of strychnine in mountain beaver tissues. Retention time shifts hindered strychnine quantification with both HPLC systems. Co-extracted free fatty acids released during storage formed ion-pairs with strychnine, resulting in increased retention by reversed-phase HPLC. Competition with co-extracted basic compounds is likely responsible for the decreased retention of strychnine by ion-pair HPLC. Following an acid-base clean-up, optimal results were obtained with reversed-phase HPLC. Ion-pair chromatography was then used for qualitative confirmation of strychnine residues.

Gas chromatographic analysis of coyote and magpie tissues for residues of compound 1080 (sodium fluoroacetate).

Tissues of coyotes and magpies administered known dosages of 1080 were analyzed for residues by an analytical method specifying gas chromatography and electron capture detection. The repeatability of the method was determined for the replicate analyses of coyote muscle tissue samples aged under different storage conditions. The average coefficient of variation (CV) was 6% for quadruplicate determinations of 1080 in fresh tissues, 12-14% for samples stored at - 10 degrees C for 30-60 days, and 24% for samples aged for 7 days at ambient temperatures. The larger CV value obtained for stored samples is attributed more to greater sample variability than to less precision of the analytical method. Residues of 1080 appear to be relatively stable in tissues; there was essentially no change in the concentration of 1080 in samples stored up to 28 days at ambient temperature. Residue levels in the muscle, heart, kidney, and intestine were comparable, slightly lower in the liver, and much higher in the stomach. The concentration of 1080 in the muscle tissue was related to the administered dosages. Correlation analyses of dosages and residue levels in coyote muscle tissue showed a correlation coefficient of 0.99 for 1080 administered by gavage, and 0.88 for 1080 administered by bait. A correlation coefficient of 0.99 was observed between dosages and mean residues in the breast muscle tissues of magpies. The average CV value was 3.5% for duplicate analyses of 1 g samples of magpie tissues.