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BMC Veterinary Research (2)
Journal of Virology (1)
Kietzmann, Manfred (3)
Niedorf, Frank (3)
Bals, Robert (1)
Barton, Ann-Kristin (1)
Bicker, Gerd (1)
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Uhlenbruck, Sabine (1)
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Non-genomic action of beclomethasone dipropionate on bronchoconstriction caused by leukotriene C4 in precision cut lung slices in the horse
BMC Veterinary Research
Glucocorticoids have been proven to be effective in the therapy of recurrent airway obstruction (RAO) in horses via systemic as well as local (inhalative) administration. Elective analysis of the effects of this drug on bronchoconstriction in viable lung tissue offers an insight into the mechanism of action of the inflammatory cascade occurring during RAO which is still unclear. The mechanism of action of steroids in treatment of RAO is thought to be induced through classical genomic pathways. We aimed at electively studying the effects of the glucocorticoid beclomethasone dipropionate on equine precision-cut lung slices (PCLS).
PCLS were used to analyze ex-vivo effects of beclomethasone on inhibiting bronchoconstriction in the horse. The inhibiting effect was measured through instillation of a known mediator of inflammation and bronchoconstriction, leukotriene C4. For this, the accessory lobes of 13 horses subjected to euthanasia for reasons unrelated to the respiratory apparatus were used to obtain viable lung slices.
After 30 minutes of PCLS incubation, beclomethasone showed to significantly inhibit the contraction of the bronchioles after instillation with leukotriene C4. The EC50 values of the two contraction curves (LTC4 with and without BDP) differed significantly from each other (p = 0.002). The possibility of a non-genomic rapid mechanism of action seems likely since transcriptional activities require a longer lag period.
In human neuroendocrinology, high levels of glucocorticoids have been proven to function via a non-genomic mechanism of membrane receptors. The concentration of beclomethasone used on the lung slices in our study can be considered as high. This allows speculation about similar rapid non-genomic mechanisms of high-dosage inhaled glucocorticoids in the lower airways of horses. However, further assessment on a molecular basis is needed to confirm this.
Beclomethasone; Horse; Leukotriene; Non-genomic membrane receptors; Recurrent airway obstruction; RAO; Precision-cut lung slices; PCLS
Tissue distribution of cloxacillin after intramammary administration in the isolated perfused bovine udder
BMC Veterinary Research
Various intramammary suspensions containing cloxacillin benzathine are registered for use in cattle as antibiotics for intramammary use at drying off. To ensure antibacterial efficacy, the glandular tissue concentration of an antimicrobial agent must be sufficient. Since the possibilities to measure concentrations in the different areas of the glandular tissue in vivo are very limited, it was the aim of the present study to examine the distribution of cloxacillin in vitro using the isolated perfused bovine udder.
Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. 600 mg cloxacillin benzathine were administered as Orbenin Extra Dry Cow by the intramammary route to six front and rear quarters each. Samples of glandular tissue - at different distances from and vertical to the teat right up to the udder base - were gathered from the treated quarters after 6 h. Perfusate was also sampled before and hourly after treatment for 6 h. The cloxacillin content of the tissue samples and perfusate samples was analysed by high performance liquid chromatography.
The concentration of cloxacillin in the glandular tissue of front quarters measured 6 h after administration tended to decrease with increasing vertical distance from the teat. The decrease pattern of the concentration was not quite clear in rear quarters. A considerable variation in the tissue concentrations of cloxacillin was obvious, which reflects in vivo conditions. The concentrations measured in the perfusate samples were below the limit of quantification at all time points, indicating limited absorption of the antibiotic from the glandular tissue.
After intramammary administration of the dry off product containing cloxacillin benzathine concentrations of more than 0.5 μg/g (MIC) were reached in all regions of the front and rear quarters.
Differential Sensitivity of Differentiated Epithelial Cells to Respiratory Viruses Reveals Different Viral Strategies of Host Infection▿
Journal of Virology
To address the initiation of virus infection in the respiratory tract, we established two culture systems for differentiated bovine airway epithelial cells (BAEC). Filter-grown BAEC differentiated under air-liquid interface (ALI) conditions to generate a pseudo-stratified mucociliary epithelium. Alternatively, precision-cut lung slices (PCLS) from the bovine airways were generated that retained the original composition and distribution of differentiated epithelial cells. With both systems, epithelial cells were readily infected by bovine parainfluenza virus 3 (BPIV3). Ciliated cells were the most prominent cell type affected by BPIV3. Surprisingly, differentiated BAEC were resistant to infection by bovine respiratory syncytial virus (BRSV), when the virus was applied at the same multiplicity of infection that was sufficient for infection by BPIV3. In the case of PCLS, infection by BRSV was observed in cells located in lower cell layers but not in epithelial cells facing the lumen of the airways. The identity of the infected cells could not be determined because of a lack of specific antibodies. Increasing the virus titer 30-fold resulted in infection of the ALI cultures of BAEC, whereas in PCLS the ciliated epithelium was still refractory to infection by BRSV. These results indicate that differentiated BAEC are readily infected by BPIV3 but rather resistant to infection by BRSV. Disease caused by BRSV may require that calves encounter environmental stimuli that render BAEC susceptible to infection.
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