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.     

Modelling water flow through undisturbed soil cores using a transfer function model derived from 3HOH and Cl transport

Large undisturbed soil cores (20 cm diam. × 25–30 cm long) were irrigated at rates of 0.5–4 cm h^?1 with 0.005 M CaCl₂ solution labelled with ³HOH. The cores were used at varying initial water contents and flow in all cases was unsaturated. Breakthrough curves for Cl and ³HOH were markedly asymmetric and unlike those reported for columns of packed aggregates. The data could be satisfactorily described using a density distribution function of the logarithm of cumulative drainage D. The mean and standard deviation of In D were estimated by a curve-fitting procedure from Cl and ³HOH effluent concentrations in each core. The mean pore water velocity and fraction of the soil water that participated in solute transport (the mobile volume) were also calculated. The apparent velocity of Cl movement was always greater than that of ³HOH which suggested that the mobile volume involved in convective and diffusive transport of Cl was less than that for ³HOH. We suggest that Cl and ³HOH diffused at different rates out of flowing water films in a relatively few large conducting channels into essentially immobile water within the surrounding soil matrix. The difference in mobile volume for Cl and ³HOH was used to calculate the perimeter of voids in any horizontal cross-section of the soil through which water flowed, assuming a planar interface between the mobile and immobile water.     

Morphologic Effects of Experimental Distention of Equine Small Intestine

The morphologic effects of induced intraluminal hydrostatic pressures (IHPs) of 0, 9, and 18 cm H₂O were evaluated in 33 isolated equine jejunal segments. Fifteen segments were distended with Tyrode's solution for 1 hour and nine segments for 4 hours. Tyrode's solution was added as needed to maintain the prescribed pressures. Nine other segments were left undisturbed for 4 hours after the initial distention period. On decompression of the intestinal segments, progressive peristaltic contractions resumed in all segments. Evaluation of intestinal sections by light microscopy and transmission electron microscopy showed edema of the villi and submucosa and separation of the epithelial cells adjacent to the basement membrane in all segments. The epithelial cell necrosis found in ischemic intestine was not seen. This study indicates that the necrosis found at the villous tips in distended sections of small intestine remote from the site of obstruction cannot be reproduced by IHP increases of 4 hours duration.     

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.