Characterisation of a group of endogenous gammaretroviruses in the canine genome.

Bioinformatics were used to identify and characterise 39 pol, 34 gag and five env gammaretroviruses within the canine (Canis lupus familiaris) reference genome. These endogenous retroviruses are monophyletic to the Canidae, predate the divergence of dogs and foxes and are fixed in 20 canine breeds examined. They are transcribed in normal canine tissue but are unlikely to be replication competent in dogs.

Fos expression induced by activation of NMDA and neurokinin-1 receptors in the trigeminal subnucleus caudalis in vitro: role of protein kinases.

Activity-induced neuronal plasticity is partly facilitated by the expression of the immediate-early gene c-fos and the resulting transcription factor Fos. Expression of Fos is associated with nociceptive afferent activation, but a detailed stimulation-transcription pathway for Fos expression has not yet been determined in the trigeminal system. This study utilized a novel in vitro model to determine whether Fos expression can be induced in trigeminal subnucleus caudalis by NMDA or neurokinin-1 receptor activation, and whether inhibition of intracellular kinases has any effect on Fos expression induced by activation of these receptors. Brainstems of male Wistar rats were excised and maintained in artificial cerebrospinal fluid at 37°C. NMDA or the specific neurokinin-1 receptor agonist [Sar(9),Met(O(2))(11)]-SP was applied. These agonists were subsequently tested in the presence of the protein kinase A inhibitor Rp-cAMP or protein kinase C inhibitor chelerythrine chloride. In all experiments the sodium channel blocker tetrodotoxin was used to prevent indirect neuronal activation. Brainstems were processed immunocytochemically for Fos expression, and positive cells were counted in the trigeminal subnucleus caudalis. NMDA and [Sar(9),Met(O(2))(11)]-SP significantly increased Fos expression, but these increases could be prevented by chelerythrine chloride. Rp-cAMP had no effect on Fos induced by NMDA but caused a significant reduction in Fos induced by [Sar(9),Met(O(2))(11)]-SP. These data demonstrate that in trigeminal subnucleus caudalis activation of either NK1 or NMDA receptors alone induces Fos expression; protein kinases A and C are involved in NK1R-induced Fos while protein kinase A is not required for NMDA receptor-induced Fos.

Evaluation of barrier creams against sulphur mustard: (II) In vivo and in vitro studies using the domestic white pig.

Previous studies in our laboratory have demonstrated that barrier creams, comprising perfluorinated polymers, are effective against the chemical warfare agent sulphur mustard (SM) when evaluated using human skin in vitro. The purpose of this follow-up study was to further evaluate three candidate (perfluorinated) barrier creams against SM (vapour) using the domestic white pig. The severity and progression of the resulting skin lesions were quantified daily for three weeks post-exposure using biophysical measurements of transepidermal water loss (TEWL) and skin reflectance spectroscopy (SRS). Skin biopsies obtained post-mortem were evaluated by light microscopy and additional skin samples were obtained from adjacent (unexposed) skin sites for a comparative in vitro skin absorption study. Samples of SM vapour within the dosing chambers were measured ex vivo to ascertain the exposure dose (Ct). The three creams were highly effective against SM in vivo (Ct approximately 5000 mg.min.m(-3)): After 3 weeks, barrier cream pre-treated sites were not significantly different from control (unexposed) skin when evaluated by TEWL, SRS or histology. In contrast, skin exposed to SM without pre-treatment showed evidence of persistent damage that was consistent with the slow healing time observed in humans. The amount of SM absorbed in vitro in untreated pig skin was similar to that required to cause comparable lesions in human skin (8-20 and 4-10 microg.cm(-2), respectively), further validating the use of pigs as a toxicologically-relevant dermal model for SM exposure.

Transepidermal water loss does not correlate with skin barrier function in vitro.

The purpose of this study was to investigate the relationship between transepidermal water loss and skin permeability to tritiated water (3H2O) and the lipophilic penetrant sulfur mustard in vitro. No correlation was found between basal transepidermal water loss rates and the permeability of human epidermal membranes to 3H2O (p = 0.72) or sulfur mustard (p = 0.74). Similarly, there was no correlation between transepidermal water loss rates and the 3H2O permeability of full-thickness pig skin (p = 0.68). There was no correlation between transepidermal water loss rate and 3H2O permeability following up to 15 tape strips (p = 0.64) or up to four needle-stick punctures (p = 0.13). These data indicate that transepidermal water loss cannot be unconditionally ascribed to be a measure of skin barrier function. It is clear that further work should be conducted to interpret the significance of measuring transepidermal water loss by evaporimetry.