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Effects of glucocorticoids on circulating concentrations of thyroxine (T4) and triiodothyronine (T3) and on peripheral monodeiodination in pre- and post-hatching chickens.

The administration of either glucocorticoids (dexamethasone or corticosterone) or adrenocorticotropic hormone (ACTH) to chicken embryos was followed by increase in the circulating concentration of triiodothyronine (T3), the T3 to thyroxine (T4) ratio and the activity of liver T4-5' monodeiodinase. No consistent changes in plasma concentrations of T4 or GH were observed. In post-hatching chicks, corticosterone and dexamethasone depressed the circulating concentrations of both T4 and T3. Iopanoc acid, an inhibitor of liver T4-5' monodeiodinase, elevated plasma concentrations of T4 and depressed those of T3 in both chicken embryos and young chicks. It is suggested that glucocorticoids affect circulating concentrations of T4 and T3 both by affecting the activity of the liver T4-5' monodeiodinase and by influencing the hypothalamo-pituitary axis.

Adrenocorticotropic Hormone↗

Carrier-mediated transport of the organic cation procaine amide ethobromide by isolated rat liver parenchymal cells.

Using hepatocytes isolated by collagenase perfusion, we studied the kinetic characteristics of the uptake process for procaine amide ethobromide (PAEB). Determination of initial uptake velocities (Vo) at substrate concentrations from 30 to 400 micrometer demonstrated a saturable process with a Km of 54 +/- 10 micrometer and a Vmax of 0.13 +/- 0.01 nmol/min/mg of protein. Pretreatment of cells with metabolic inhibitors and reduction of the incubation temperature significantly reduced the Vo of 100 micrometer PAEB. Replacement of sodium ions with lithium had no effect, while replacement with choline decreased Vo by 75%. The intracellular concentration of PAEB was 18 times the medium concentration after 90 min, but 33% of that was in the acetylated form. Uptake of N4-acetyl PAEB occurred at a much lower rate and reached a cell/medium ratio of only 6 after 90 min. Only one of seven quaternary amines tested inhibited PAEB uptake at an inhibitor/substrate ratio (I/S) of 7.5, while four out of five tertiary amines significantly decreased Vo at an I/S of 0.75 and all five decreased it at a ratio of 7.5. Some organic acids and steroidal compounds also significantly decreased PAEB Vo at an I/S of 0.75, while others from each group had no effect at an I/S of 7.5. Because uptake is saturable, requires metabolic energy, and occurs against an electrochemical gradient, it is suggested that the hepatic accumulation of PAEB occurs via an active, carrier-medicated transport process.

Animals↗

Interaction of ligandin with radiographic contrast media.

Ligandin (Y protein) is an abundant cytoplasmic glutathione transferase present in liver, kidney and gut in various animals and man. Its interaction with four radiologic contrast media (Telepaque, 3-(3 amino-2,4,6, triiodophenyl -2 ethylpropanoic acid, sodium salt; Hypaque, sodium -3, 5-diacetamido-2,4,6,-triiodobenzoate; Cholografin, N,N'adipyl-bis-(3-amino-2,4,6-triiodobenzoic acid) N-methyl-glucosamine; Diodrast, 3,5-Diiodo-4-pyridone-N-acetic acid, Diethanolamine Salt was investigated by observing inhibitory effects on the enzyme-catalyzed conjugation of glutathione with 1-chloro-2, 4-dinitrobenzene. Lineweaver-Burk plots of reciprocal initial velocity versus reciprocal inhibitor concentrations at fixed glutathione and chlorodinitrobenzene concentrations demonstrate non-competitive inhibition by all contrast media except Diodrast. No conjugates of contrast media with glutathione were formed. It is postulated that intracellular accumulation of contrast media is aided by intracellular binding with ligandin. Inhibition of the GSH transferase activity of ligandin can disrupt the mercapturate formation, an important detoxification process.

Contrast Media↗

Liquid chromatography-electrospray ionization mass spectrometry for direct identification and quantification of iophenoxic acid in serum.

A liquid chromatographic-electrospray ionization mass spectrometric technique was developed for direct quantitation of iophenoxic acid (IA) in serum. IA was spiked into canine, feline, bovine, equine, and porcine sera, extracted, and quantified using negative ion monitoring following chromatographic separation on a Luna C18(2) 3 microm (100 mm x 2.1mm) reversed-phase column. The limit of detection was 25 ng/mL and the limit of quantification was 50 ng/mL. Inter- and intra-assay accuracy (86-113% and 87-115%, respectively) and precision (1.8-7.7%) were calculated. Analysis of serum collected from feral pigs, raccoons, and opossums following ingestion of IA-marked baits confirmed the appropriateness of this method for bait acceptance studies.

Animals↗

High-performance liquid chromatographic determination of iophenoxic acid in serum.

Iophenoxic acid (IPA), a marker used to investigate the feeding behaviour of bait-consuming animals has previously been indirectly determined by measuring protein-bound iodine levels in serum or plasma. For the first time a method is reported for the direct determination of IPA in biological fluids. IPA was determined in de-proteinized serum by high-performance liquid chromatography (HPLC) on a C18 column with a mobile phase of acetonitrile-water. Isocratic and gradient systems are described with limits of detection of 0.2 microgram/ml (isocratic) and 0.05 microgram/ml (gradient). Recoveries from fox serum were 85% at 0.5 microgram/ml, 95% at 5 micrograms/ml and 91% at 50 micrograms/ml.

Animals↗

Plasma marking of arctic foxes with iophenoxic acid.

Six arctic foxes (Alopex lagopus) were marked with iophenoxic acid (IA), a substance which elevates concentrations of protein-bound iodine in blood plasma. Buccal absorption of IA was determined by placing 20 mg IA dissolved in 100% ethyl alcohol on the tongue. Blood samples collected from 1 to 36 wk following exposure showed that all foxes were marked already at 1 wk and continued until 13 wk; two foxes were still marked at 36 wk. Clearance rates for iodine varied with initial dose response, and those foxes with high 1-wk iodine concentrations excreted iodine more rapidly than those with lower initial concentrations; by 13-wk excretion rates were similar.

Alaska↗

Acceptance of simulated oral rabies vaccine baits by urban raccoons.

In summer 1986, a study was conducted to evaluate raccoon (Procyon lotor) acceptance of oral baits that could be used for rabies vaccination. One thousand wax-coated sponge bait cubes were filled with 5 mg of a seromarker (iophenoxic acid), placed in polyethylene bags, and hand-distributed in an 80 ha area within an urban National Park in Washington, D. C. (USA). After 3 wk, target and nontarget animals were trapped and blood samples collected to evaluate bait uptake. Thirty-three of 52 (63%) raccoons had elevated blood iodine levels indicating they had eaten at least one bait, 13 (25%) were negative, and six (12%) had marginal values. These results indicate that sponge baits hand-placed at a density of 12.4/ha can reach a significant proportion of an urban raccoon population. Implications for oral rabies vaccination of raccoons are discussed.

Animals↗

[Pre- and postoperative study of the bile ducts with spiral computerized tomography].

PURPOSE: To investigate the capabilities of Helical CT in imaging the biliary tract after administration of an oral cholecystographic contrast agent. MATERIAL AND METHODS: Forty-five adult patients and one 8-year-old child were examined with Helical CT 12 hours after the oral administration of hyopanoic acid (3 g). All the examinations were performed with the following parameters: thickness 5 mm, pitch factor 1.5, standard reconstruction algorithm, acquisition time 20-30 s, image index 2.5 mm, 130 kV, 125 mA. In 37 cases CT was performed in patients candidate to laparoscopic cholecystectomy, in 8 cases to assess the positioning of surgical clips in patients with postcholecystectomy syndrome and in 1 case (the 8-year-old child) to confirm the US diagnosis of choledochal cystic dilatation. Helical CT images were reconstructed with a Volume Rendering (VR) software. RESULTS: The extrahepatic biliary tract was visualized in all the cases with CT and VR. II grade biliary ducts were visualized in 87% (CT) and 91% (VR), III grade ducts in 76% (CT) and 78% (VR), IV grade ducts in 28% and 35%, respectively. No statistically significant difference was found between CT and VR in the visualization of the biliary structures (p > 0.05), while three-dimensional VR reconstructions improved the evaluation of the anatomical relations in the biliary tract in comparison with CT both in normal cases and in patients with congenital abnormalities of the biliary tract. Also, three-dimensional VR reconstructions were superior in assessing the correct positioning of surgical clips in patients with postcholecystectomy syndrome (p < 0.05). DISCUSSION AND CONCLUSIONS: Cholecysto-cholangio-CT with VR reconstructions is a reliable imaging technique for the biliary tract in patients candidate to laparoscopic cholecystectomy, to diagnose choledochal cystic dilatation and to assess the positioning of surgical clips.

Administration, Oral↗