Detection and pharmacokinetics of tetrahydrogestrinone in horses.

The anti-doping rules of national and international sport federations ban any use of tetrahydrogestrinone (THG) in human as well as in horse sports. Initiated by the THG doping scandals in human sports a method for the detection of 3-keto-4,9,11-triene steroids in horse blood and urine was developed. The method comprises the isolation of the analytes by a combination of solid phase and liquid-liquid extraction after hydrolysis and solvolysis of the steroid conjugates. The concentrations of THG in blood and urine samples were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A THG excretion study on horses was conducted to verify the method capability for the analysis of postadministration urine samples. In addition, blood samples were collected to allow for determination of the pharmacokinetics of THG in horses. Following the administration of a single oral dose of 25 microg THG per kg bodyweight to 10 horses, samples were collected at appropriate intervals. The plasma levels of THG reached maximal concentrations of 1.5-4.8 ng/mL. Twenty-four hours after the administration plasma levels returned to baseline. In urine, THG was detectable for 36 h. Urinary peak concentrations of total THG ranged from 16 to 206 ng/mL. For the 10 horses tested, the mean plasma clearance of THG was 2250 mL/h/kg and the plasma elimination half-life was 1.9 h.

Characterisation of epidermal lipid composition and skin morphology of animal skin ex vivo.

Epidermal lipids and skin morphology are assumed to substantially influence skin permeability. Although these parameters have been studied extensively, available data are hard to interpret as data have been gathered at different experimental conditions. Therefore, the aim of this study was to provide detailed information on these parameters for four different mammalian skin types. Lipids were extracted from heat separated epidermis, the total epidermal lipid content was measured and the epidermal lipid composition was quantitatively determined by high-performance thin-layer chromatography. Furthermore, vertical and horizontal cryostate skin slices were analysed by light microscopy for thickness of the horny layer, epidermal thickness, density, depth of anchorage and diameter of the hair follicles. The highest total epidermal lipid content was detected in rat epidermis, followed by bovine udder, dog and pig epidermis. Considering the amount of single lipid fractions, cholesterol, cholesteryl ester and free fatty acids were found to be the major constituents of epidermal lipids in all the examined species. However, as confirmed by hierarchical cluster analysis the epidermal lipid profile and morphology showed marked differences between all the examined species.

Reactivity of equine airways--a study on precision-cut lung slices.

A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of approximately 250 microm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found to be viable for at least 24 h. The airways were not precontracted, as indicated by a missing dilatory effect of 1 mmol/L clenbuterol. Bronchoconstriction induced by both methacholine and histamine was found to be dose dependent. EC(50) values based on luminal area were 1.12 micromol/L x / / 3.82 for methacholine and 0.68 micromol/L x / / 6.99 for histamine. In conclusion, the PCLS technique is promising for studies on small airways in the equine lung. In the present study the basic principles of in vitro (ex vivo) examinations with equine PCLS on airway reactivity were developed.

Non-steroidal and steroidal anti-inflammatory drugs vary in their modulation of dendritic cell function in the elicitation phase of allergic contact dermatitis.

The role of dendritic cells (DCs) in allergic contact dermatitis has been clearly demonstrated for the induction phase. However, the situation during the elicitation phase is very complex within a distinct inflammatory response. This study was performed to exploit DC migration in the elicitation phase in a mouse model of allergic contact dermatitis and to evaluate the effects of steroidal and non-steroidal anti-inflammatory drugs (NSAIDs) on DC migration through skin in the elicitation phase of allergic contact dermatitis. Topically and systemically administered acetylsalicylic acid (ASA) did not reduce the inflammatory response. However, systemically administered ASA significantly reduced the DC migration to the draining lymph node. In contrast, topically administered indomethacin reduced the inflammatory response, but had only minor effects on DC migration, whereas diflorasone diacetate reduced both inflammatory reaction and DC migration. Thus, NSAIDs may differ in their inhibitory action in immunological inflammation.

Noninvasive reflection spectra provide quantitative information about the spatial distribution of skin chromophores.

In this work, a new method of analyzing noninvasive reflection spectra is presented. The approach explicitly models the inhomogeneity of chromophore distributions in living tissues and thus extracts not only apparent chromophore concentrations but also relative chromophore distributions in tissues. Furthermore, it works with spectra obtained with short source-detector separations where the diffusion theory of light transport through turbid media is not valid, and formerly presented methods thus fail. The effect of inhomogeneously distributed chromophores in a multicompartment model of tissues on measured reflection spectra is explained and an algorithm to deconvolute tissue spectra based on this model is presented. It is evaluated using simulated spectra and measurements on phantoms, which are made up of partially printed pieces of paper to simulate inhomogeneous dye distributions. Its applicability to real tissue is proven using reflection spectra obtained with 130 microm source-detector separation from a hemoperfusion stop experiment. The proposed model accurately determines apparent chromophore concentrations and corresponding distributions in simulated spectra and phantoms. Regarding real tissue spectra, the results correspond to former publications and the spectral reconstruction yields only minimal residuals, indicating a complete and accurate spectral deconvolution. In conclusion, the presented approach is a suitable extension and amendment to existing models of light transport through inhomogeneous samples.