Hair matrix

The hair matrix possesses a large monitoring window (months/years) that allows a retrospective analysis and the study of past history. Hair is also characterized by a high stability and a minimum possibility of adulteration [41, 42], The structure of the hair can be considered as a repeated network of keratin fibers. There are also melanins, lipids, and all the compounds of cells that led to the formation of the stem. The growth of hair is in the range of 0.6-1.4 cm/month [43,44],... 

Appendageal structures commonly found within the skin are the hairs, hair follicles, associated sebaceous glands, apocrine and eccrine sweat glands, and arrector pili muscles. Hairs are formed by epidermal invaginations. These keratinized structures traverse the dermis and may extend into the hypodermis. The free part of the hair above the surface of the skin is the hair shaft, and the part deep within the dermis is the hair root, which forms an expanded knob-like structure called the hair bulb. This is composed of a matrix of epithelial cells in different stages of differentiation. Hair is composed of three concentric epithelial cell layers the outermost thin cuticle, a densely packed keratinized cortex, and a central medulla of cuboidal cells. The hair follicle consists of four major components (1) internal root sheath (internal root sheath cuticle, granular layer, pale epithelial layer) (2) external root sheath (several layers similar to the epidermis) (3) dermal papilla (connective tissue) and (4) hair matrix (comparable to the stratum basale of the epidermis). 

C. Can Exogenously Applied Drugs be Incorporated into the Hair Matrix ... 

Drugs placed on the surface of hair must have some mechanism for entry into the hair matrix. If a solid is placed on the hair surface, most of it can be readily removed. However, after the deposition of the solid drugs onto the hair surface, hair may be bathed at some point in an aqueous media, be that sweat, sebum, normal hygienic solutions, or during the hair analysis procedure. Alternatively, an individual might come in contact with a solution of a drug by transfer of sweat from another individual. It is for these reasons that we and others studied solution phase transfer as the vector for admission and incorporation of drugs into hair. 

Some possible criticisms of the use of radiotracers for monitoring the uptake and release of cocaine are that the tracer chemically reacts with the hair matrix or contains radiolabeled impurities which show preferential binding. Both criticisms are unlikely because (1) the radiotracer never exceeds 1% of the urdabeled drug, and (2) hair exposed to drugs without the radiotracer and analyzed by GC/MS show the parent drug present in amounts indicated by the radiotracer analysis. 

Marques and colleagues also suggest the loss of drugs from the hair matrix due to cosmetic treatments. In studying the concentration of cocaine in the hair of mother/ infant pairs, they found that it was possible to increase the correlation between the amount of cocaine in the mother s hair and the infant s hair by eliminating... 

M. Does the Hair Matrix Protect Previously Deposited Materials from Modification by the External Environment Are Metabolites Adequate to Determine Usage ... 

The two most prevalent types of extraction procedures are (1) digestion of the hair matrix and extraction of the drug from the digest with liquid-liquid or solid-phase extraction procedures, or (2) extraction of the drug from the intact hair matrix. 

Several variables must be considered in the analysis of hair besides the decontamination procedure. The most important is the method by which drugs are to be extracted from the hair matrix. Because no extraction solution can remove all of the drug present, dissolution of the hair matrix before extraction of the drug appears essential to achieve complete removal for analytical purposes. 

Due to the low amount of specimen used for hair analysis and the low concentration of drugs and their metabolites in hair, extraction procedures are mostly necessary to concentrate the analytes in the tested solution. Various methods have been used for this step. The variety of described procedures show that there is no universal solution. The choice of an extraction procedure may be influenced by the kind of drug and drug metabolite(s) to be analyzed and the method used for the subsequent analysis. Preceding the real extraction, there are four treatments with more or less intermethodical differences to prepare the hair matrix for the extraction ... 

Hunt SJ, Abell E. Malignant hair matrix mmor ( malignant trichoepithelioma ) arising in the setting of multiple hereditary trichoepithelioma. Am J Dermatopathol. 1991 13 275-281. 

Melanocytes are located in the basal layer of the epidermis (Figure 1.1). They can be found in the external root sheath and hair matrix of hair follicles, in the sweat gland ducts, and in sebaceous glands. Melanocytes have dendritic processes that either extend between adjacent keratinocytes or run parallel to the dermal surface. 

The hair follicle consists of four major components (1) internal root sheath (internal epithehal root sheath), (2) external root sheath (external epithelial root sheath), (3) dermal papilla, and (4) hair matrix. The cells covering the dermal papilla and composing most of the hair bulb are the hair matrix cells. These are comparable to stratum basale cells of regular epidermis except that they are more lipid deficient and produce harder keratin than their epidermal counterparts. 

The anagen or growth phase is characterized by the high metabolic selectivity of the hair matrix and lasts 2-6 years. The maximum length reached by the hair depends on the duration of the eycle. There are large individual differences in this. The metabolism of the hair matrix is wound down over a period of 1-2 weeks in the catagen or transition phase. The dead hair root then remains in the scalp for another 1-6 months in the telogen phase and then falls out (Fig. 2). 

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