Skin capillary permeability, effect

The circulatory effects are manifested as arteriolar dilation and increased capillary permeability, causing plasma loss. The localized redness, edema (hives, wheal), and diffuse redness seen in allergic urticaria (rash) or physical skin injury result from these circulatory changes. Vasodilation also causes a decrease in blood pressure. 

Exposure to lewisite is very painful. Both the vapor and liquid lewisite can penetrate skin. Reddening of the skin is followed by tissue destruction (EPA, 1985a Goldman and Dacre, 1989 Pohanish, 2002 Sidell et al, 1997). Amounts as small as 0.5 ml may cause severe systemic effects and 2 ml may be lethal. Severe edema develops secondary to increased capillary permeability. Dermal bums are deeper than those seen with mustard gas and are quicker to appear (Goldman and Dacre, 1989 Sidell et al, 1997). 

Lewisite, a vesicant with HD-Uke properties, causes a similar constellation of signs and symptoms involving the skin, eyes, and airways as well as systemic effects (e.g. increased capillary permeability) after absorption. However, it does not produce immunological suppression like mustard. Another difference is that the management of lewisite toxicity includes an antidote, British Anti-Lewisite (BAL) (Yue/u/.,2003). 

E. Systemic Effects. Liquid arsenical vesicants on the skin, as well as inhaled vapor, are absorbed and may cause systemic poisoning. A manifestation of this is a change in capillary permeability, which permits loss of sufficient fluid from the bloodstream to cause hemoconcentration, shock, and death. 

The IgE-mediated PCA reaction in the rat was one of the first in vivo animal models in which cromol5m was shown to be effective and has since been used extensively in screening for similar compounds. In this method, inflammatory mediators released by immediate hypersensitivity reactions in the skin produce a local increase in capillary permeability. 

Several of the mediators stored or synthesized and released by the mast cells have an effect on capillary permeability. An increase in capillary permeability permits the influx of several blood proteins into the adjacent tissues, thereby causing disturbances in osmotic equilibrium and tissular edema. In the skin, this is manifested by the formation of an urticarial wheal and by erythema. In addition, contraction of the nonstriated muscle fibers wherever they occur and increase in the secretion from exocrine glands are common features. Since the major mediators present in tissue mast cells and blood basophils are either preformed (e.g., histamine) or arise within seconds following the triggering event, it is understandable that anaphylactic reactions develop very rapidly following contact with antigen they also have a relatively limited duration. 

Flavonoids are able to reduce capillary permeability and increase capillary resistance. Sophora japonica Liruieo. is used in cosmetics because of the protective effects of rutin on the blood-vessel walls. This active compound protects blood vessels against fragility and improves microcirculation and miaonutrients transportation. The result is an improved skin texture and appearance. Several studies have demonstrated that rutin efficiently reduces oedema. This anti-oedema action is one of the main reasons for adding it to formulations aimed at the treatment of tired legs or varices and as a coadjuvant in anticellulite treatments (Tang et al, 2002). 

These mediators can produce a number of effects including bronchiolar constriction, capillary dilatation, or urticaria (i.e., hives). In severe episodes of type I reactions a life-threatening anaphylaxis can develop in humans due to extreme bronchoconstriction and precipitate hypotension. Epinephrine is the principal drug used in the acute management of these critical effects since it achieves (1) an elevated blood pressure via activation of alpha receptors in peripheral resistance blood vessels and (2) relaxation of bronchiolar smooth muscle via activation of (32 receptors in the lung. Relief from the dermatological problem (i.e., hives) is also achieved via vasoconstriction of capillaries in the skin that reduce permeability, and, hence, fluid accumulation. Penicillin is a classic example of a drug that can cause a type I reaction. 

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