Epidermis effect

For the topical treatment of some chronic inflammatory skin diseases (like atopic dermatitis) immunosuppressive macrolides (like TRL and pimecrolimus) that permeate the inflamed epidermis are of benefit for patients. Severe side effects comparable to those after systemic application of TRL in transplanted patients (see above) have not been observed so far. For the treatment of psoriasis vulgaris these drugs are less effective. The CD2 antagonist alefacept may be a suitable alternative to allergic reactions. 

Photosynthesis and gas exchange of leaves are affected by many stresses including drought, flooding, salinity, chilling, high temperature, soil compaction and inadequate nutrition. Many, but not all, of these stresses have symptoms in common. For example, stomatal conductance and the rate of assimilation of CO2 per unit leaf area often decrease when stress occurs. Further, it is possible that several of the stresses may exert their effects, in part, by increasing the levels of the hormone abscisic acid (ABA) in the leaf epidermis. This hormone is known to close stomata when applied to leaves. 

We have already stressed the potential importance of lipid-rich membranes in the skin as potential targets for ROS-induced damage and ageing of human skin is morphologically identical to changes found by peroxidative processes (Serri et al., 1977). The involvement of AA metabolites in skin disease, and in particular psoriasis, has been the subject of much recent interest. Studies have included topical and intradermal administrations of AA metabolites, and assay of such products in clinical specimens. Results show that concentration of AA, 12-hydroxy-eicosatetraenoic acid (12-HETE), PG and leu-kotrienes are increased in psoriatic lesions (Hammarstrom etal., 1975 Camp etal., 1983 Brain etal., 1984 Duell et al., 1988) and also that full-thickness epidermis from normal and diseased skin has the enzymatic capacity to convert AA to some of the same metabolites (Hammarstrom etal., 1975, 1979 Camp etal., 1983 Brain etal., 1984 Ziboh et al., 1984 DueU et al., 1988). The biological effect of both 12-HETE and leukotrienes was confirmed by both topical application and intradermal injection, which caused epidermal inflammation and... 

The selection of vehicle is based on the type of lesion and location of the infection. Solutions are recommended for hairy areas and oozing lesions, while creams are better for moderately scaling and non-oozing lesions. For hyperkeratotic lesions, ointments can be considered. The selected formulation should be applied to the affected area after it is cleaned and dried. The medication should be rubbed into the infected area for improved penetration. Since most patients do not rub in sprays and powders, penetration of the epidermis is minimal, making them less effective than other formulations. Sprays and powders should be considered as adjuvant therapy with a cream or lotion or as prophylactic therapy to prevent recurrence. 

Baltic herring, Clupea harengus, eggs exposed from fertilization through 500, 2000, 6000, or 12,000 Histopathology of epidermis and kidney in larvae at 6000 pg/L and higher no measurable effects at 2000 p/L and lower 53, 54... 

Reproductive impairment seems to be one of the more sensitive indicators of zinc stress in freshwater teleosts, with effects evident in the range 50 to 340 pg Zn/L (Spear 1981). In some cases, reproduction was almost totally inhibited at zinc concentrations that had no effect on survival, growth, or maturation of these same fish (Brungs 1969). Zinc-induced developmental abnormalities were documented in marine teleosts, but concentrations tested were grossly elevated. Eggs of the Baltic herring (Clupea harengus), for example, exposed to >6 mg Zn/L have an altered rate of development and produce deformed larvae with cellular disruptions in the brain, muscle, and epidermis (Somasundaram 1985 Somasundaram et al. 1985). 

It is possible to identify various factors that confer on chemicals the ability to induce skin sensitization and allergic contact dermatitis. These include the capacity to gain access to the viable epidermis across the stratum corneum, to associate stably with host proteins, to provoke a certain degree of proinflammatory cytokine production by skin cells, and to be recognized by specific T lymphocytes. The effectiveness with which these requirements are met, and possibly other properties of the chemical that influence the vigor of induced immune responses, together with the extent of exposure, will dictate the degree to which sensitization is achieved. 

The cause of phenol s corrosive properties does not relate to its ability to form solvated protons (as indicated by the value of Ka) but its ability to penetrate the skin and disrupt the chemical processes occurring within the epidermis, to painful effect. 

If the substances have passed the stratum comeum, they also generally diffuse into the living part of the epidermis, reach the circulation, and then have systemic effects depending on the amount absorbed. Because these are often constituents of formulations, one generally expects them to have little direct influence on skin penetration. However, their amphiphilic properties allow them to form new systems with the body s constituents and even to change the physical state of water in the skin. By this means, a pathway is cleared for other hydrophilic substances to gain entry into the general circulation. 

Hydrogen cyanide is moderately lipid-soluble, which, along with its small size, allows it to rapidly cross mucous membranes, to be taken up instantly after inhalation, and to penetrate the epidermis. In addition, some cyanide compounds, such as potassium cyanide, have a corrosive effect on the skin that can increase the rate of percutaneous absorption (NIOSH 1976). Information regarding dermal absorption in animals and evidence that cyanide can be absorbed through the skin of humans is provided in Sections 2.3.1.3 and 2.2.3, respectively. 

The human skin model assay involves measuring the effects of corrosives on viable cells in a reconstituted human skin equivalent. To be accepted as a valid human skin model, several criteria must be met. The artificial skin must comprise a functional stratum corneum with an underlying layer of viable cells. Furthermore, the barrier function of the stratum corneum, as well as the viability of the epidermis, must be verified with appropriate experimental setups. The chemicals to be tested are applied up to 4 h as a liquid or a wet powder onto the skin model. Afterwards, careful washing has to be performed, followed by investigation of the cell viability [e.g., with a (MTT)] reduction assay). 

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