Resident Dendritic Cells in the Epidermis: Langerhans Cells, Merkel Cells and Melanocytes

Résumé— En plus des kératinocytes, l'épiderme contient des cellules résidentes de morphologie dendritique. Ce sont principalement la cellule de Langerhans, la cellule de Merkel et le mélanocyte. Ces cellules ont des fonctions diverses dans le tégument. Le mélanocyte assure la pigmentation cutanée et la protection contre les radiations U.V., et pourrait intervenir également dans la modulation de l'inflammation cutanée. La cellule de Langerhans intervient dans la surveillance immunologique des surfaces corporelles ecternes. La cellule de Merkel a des fonctions neuroendocrines. Cet article donne un aperçu de la structure et de la fonction de ces trois importantes populations cellulaires dans la peau. [Resident dentritic cells in the epidermis: Langerhans cells, Merkel cells and melanocytes (Cellules dentritiques résidentes de l'épiderme: cellules de Langerhans, cellules de Merkel et mélanocytes). Resumen— La epidermis contiene, además de los queratinocitos, células résidentes de morfologia dendria dendritica. Estas son principalmente las células de Langerhans, las células de Merkel y los melanocitos. Estas células tienen varias funciones en el integumento. Los melanocitos se encargan de la pigmentación y protección de la piel contra la radiación ultravioleta y tarrtbién participan en la regulación de la inflamación cutánea. Las células de Langerhans ayudan en la regulación inmunológica en la superficie externa. Las células de Merkel tienen funciones neuroendocrinas. Esta revisión da un repaso general a la estructura y función de tres importantes células de la piel. [Resident dendsuitic cells in the epidermis: Langerhans cells, Merkel cells and Melanocytes (Células résidentes en la epidermis: células de Langerhans, células de Merkel y melanocitos). Abstract— In addition to the keratinocytes, the epidermis contains resident cells of dendritic morphology. These are principally the Langerhans cell, Merkel cell and melanocyte. These cells have a number of different functions in the integument. The melanocyte is responsible for skin pigmentation and protection against UV radiation, and may also play a role in the modulation of cutaneous inflammation. The Langerhans cell aids in the immunological monitoring of the body's external surfaces. The Merkel cell has neuroendocrine functions. This review gives an overview of the structure and function of these three important cells of the skin.     

Use of Powdered Egg Yolk vs Fresh Egg Yolk for the Cryopreservation of Ovine Semen

Egg yolk is a common additive to sperm cryopreservation diluents. Because of its animal origin, however, it also represents a potential risk of microbiological contamination in the diluent. This potential contamination can be avoided by using powdered egg yolk, instead of fresh egg yolk, as it is pasteurized. This study was conducted to determine ram sperm cryosurvival was affected by the type of egg yolk used (powdered egg yolk or fresh egg yolk) and by yolk concentration (10, 15 or 20%) in the diluent. Microbiological analyses were also performed to quantify the microbiological contamination in the diluents containing the two types of egg yolk. Sperm cryosurvival was determined by motility and morphology analyses after thawing. Motility parameters were assessed using a computer-assisted sperm analysis (CASA) system, and the percentage of sperm with a normal apical ridge was evaluated using a differential interference contrast microscope. No significant differences were observed between diluents in the percentage of sperm with normal apical ridge. However, higher percentages of total motile cells were observed for samples containing powdered egg yolk (69%) compared to samples containing fresh egg yolk (60%). However, sperm in diluents containing fresh egg yolk, exhibited higher values for average-path velocity, straight-line velocity and beat cross frequency and lower values for amplitude of lateral head displacement (p <0.05), compared to cells in diluents containing powdered egg yolk. Microbiological contamination was similar (<200 CFU/ml) in both diluents, and no bacterial growth was observed in either, when antibiotics were added. Therefore, powdered egg yolk can be effective used in diluents for the freezing of ram semen. However, the in vivo fertility of sperm frozen in diluents containing powdered egg yolk should be tested, as some motility parameters were different for sperm treated with powdered egg yolk compared to fresh egg yolk.     

Canine CYP2B11 metabolizes and is inhibited by anesthetic agents often co-administered in dogs

Baratta, M. T., Zaya, M. J., White, J. A., Locuson, C. W. Canine CYP2B11 metabolizes and is inhibited by anesthetic agents often co-administered in dogs. J. vet. Pharmacol. Therap. 33 , 50–55.
Medetomidine is a well-established sedative and analgesic for dogs and cats. As a premedicant for anesthesia regimens that also include other agents, medetomidine can also provide a dose-sparing effect. While there are likely several reasons for the dose-sparing effect of medetomidine, the role of metabolic drug–drug interactions at the single enzyme level has not yet been examined. Using a panel of individually expressed canine cytochromes P450 cloned from beagle liver, this report demonstrates that medetomidine is an extremely potent CYP2B11 inhibitor (IC₅₀ < 10 n m ) and that ketamine and midazolam are CYP2B11 substrates with high intrinsic clearances. These in vitro findings suggest that under some circumstances, medetomidine (i.e. 'perpetrator') may inhibit the metabolic clearance of some high metabolic clearance drugs (i.e. 'victims') with which it is commonly co-administered via the CYP2B11 pathway. However, as the dose-sparing effect of medetomidine premedication commonly results in anesthetic dose reduction, any increased plasma concentrations of victim drugs caused by medetomidine would still be lower than if no dose reduction had been made. Further studies are needed to characterize whether medetomidine possesses the potential to cause pharmacokinetic interactions. In conclusion, the ability of recombinant P450s to define canine-specific drug clearance pathways and P450 inhibitors should prove useful in identifying drug combinations that may require dose adjustments in dogs.     

A third cryptic virus in beet (Beta vulgaris)

Japanese leaf beet Beta vulgaris var. cicla cv. Fudanso plants were found to contain four double-stranded RNA (dsRNA) components in apparently healthy beet plants. Two were identified as from beet cryptic virus 1 (BCV1), but the other two showed different mobilities on gel electrophoresis and were transcribed into complementary DNA (cDNA) and cloned. Hybridization analysis showed no significant sequence homology between these two dsRNAs and the dsRNA components of BCV1 or the other known cryptic virus of beet, BCV2. Slot- and dot-blot hybridization were used with cDNA clones as probes to identify plants containing these two dsRNA components. Virus particles were purified from these plants and were shown to contain the two new dsRNA components, thus demonstrating the existence of a new beet cryptic virus, which we have called BCV3.     

A NEW TECHNIQUE FOR SOIL PIT ILLUSTRATIONS

The difficulty of illustrating soil pit detail can be overcome by using selected grey density slices of original photographs. The technique of density slicing for illustrations involves the separate printing of a particular shade of grey from the original, which picks out the detail required.     

Pesticide use and residues on Queensland wool

Objective To determine practices for control of louse infestation and blowfly strike in Queensland sheep flocks that are associated with organophosphorous and synthetic pyrethroid residues on wool.
Design Information on residues was obtained from a survey of Queensland wool clips. Information on pesticide use was obtained from a trace-back postal survey. The association between pesticide use and residues was assessed using generalised linear models, controlling for potential confounding by flock location.
Procedure Between 1995 and 1997 Queensland wool clips were randomly sampled. Samples were tested for the presence and amount (mg per kg of greasy wool) of organophosphorous and synthetic pyrethroid pesticides. A questionnaire seeking information on flock characteristics and pesticide use was sent to the manager of each flock from which a wool sample was tested.
Results The median amount of OP and SP residue was 0.8 and 0.25 mg/kg, respectively, and 91 and 95% of wool samples contained < 8 mg/kg of OP and SP residues, respectively. The frequency of OP pesticide use for louse control was significantly (P = 0.005) associated with mean OP residue amount, and the timing of SP use for louse control, in relation to shearing, was significantly (P < 0.001) associated with mean SP residue amount.
Conclusion Most Queensland wool clips have acceptable amounts of residues after the use of OP and SP pesticides, but wool growers can further reduce residues by effectively controlling louse infestation with pesticide applications early after shearing and the use of non-chemical methods of ectoparasite control.