Keratinization degree

Tables 1 and 2 Hst the important physical properties of formamide. Form amide is more highly hydrogen bonded than water at temperatures below 80°C but the degree of molecular association decreases rapidly with increa sing temperature. Because of its high dielectric constant, formamide is an excellent ionizing solvent for many inorganic salts and also for peptides, proteias (eg, keratin), polysaccharides (eg, cellulose [9004-34-6] starch [9005-25-8]) and resias.

According to Flory (10), the concept that proteins and carbohydrates are polymeric goes back to at least the work of Hlasiwetz and Habermann (11). In 1871 they proposed that these substances were made up of a number of species differing from one another with respect to the degree of molecular condensation. Flory also noted that Hlasiwetz and Habermann differentiate "soluble and unorganized" members of these substances, for example dextrin and albumin, from "insoluble organized" members, such as cellulose or keratin. This distinction is the precursor of the present day differentiation between non-crystalline and crystalline polymers. 

Almost nothing is known of the role played by individual amino acid residues in the tail domains of Type III IF proteins. Also, very little sequence regularity has been observed. Nonetheless, the degree of sequence similarity in the tail domains of these proteins suggests that a role analogous to that played by the H subdomains in the keratins is not... 

It is evident that specific residue-related features observed in the rod domain of one particular IF chain type are frequently not observed in the same place (if at all) in the other chain types and, of course, the large differences in head and tail structure and sequence between chain types preclude identical roles from occurring there as well. The highly specialized sequence characteristics thus define unique structural assemblies and functions, while still maintaining a high degree of structural uniformity, particularly in the manner of rod domain assembly. Even in this case, small but important differences in the An, A22, and A12 modes occur. Distinct IF structures have been identified for (1) unoxidized trichocyte keratin and epidermal keratin (2) oxidized trichocyte keratin (3) Type III and IV IF proteins and (4) the nuclear lam ins. 

Pruritus of the elderly is another common dermatosis associated with itch.5 One study has shown that elderly patients with generalized pruritus had a higher degree of skin dryness than in age matched control subjects.6 This study also demonstrated that skin surface conductance, a marker of stratum corneum water content, was decreased in elderly patients with generalized pruritus. The study was also successful in demonstrating an acquired abnormality in keratinization in these patients. This abnormality manifested with increased intracorneal cohesion compared with the controls. Another study showed an increase in histamine release and hypersensitivity in patients with senile pruritus.7 Paradoxically, oral anti-histamines are not very efficacious in the treatment of senile pruritus. 

Dermal Effects. In humans, benzene is a skin irritant. By defatting the keratin layer, it may cause erythema, vesiculation, and dry and scaly dermatitis (Sandmeyer 1981). Acute fatal exposure to benzene vapors caused second degree bums on the face, trunk, and limbs of the victims (Avis and Hutton 1993). Fifteen male workers were exposed to benzene vapors (>60 ppm) over several days... 

The possibility of ethanol-induced alterations in the protein domains of SC was considered by Kurihara-Bergstrom et al. [124], who examined human SC treated with perdeuterated ethanol-water systems by FT-IR. The penetration studies showed that the maximal permeability coefficient for salicylic acid and ethanol from saturated ethanol-water delivery systems was achieved at 0.63 volume fraction of ethanol. Infrared spectra of SC samples immersed in EtOD-D20 systems for 6 hours revealed the presence of keratin, predominantly in the a-helical conformation, up to 0.25 volume fraction EtOD. Above this concentration, the appearance of shoulders at 1688 and 1615 cm near the Amide I band at 1650 cm was interpreted as the formation of extended chains or distorted P-strands within the protein domain. An evaluation of lipid extraction was also made by comparing the intensities of the infrared bands arising primarily from stratum comeum proteins to those associated with lipid domains. A decreased absorbance of the C-H stretching bands relative to the N-H stretching band would indicate that some degree of lipid extraction had occurred. The ratio of these two bands decreased from 0.96 to 0.76 as volume fraction ethanol increased from 0.4 to 1.00, respectively, indicating lipid extraction. 

In psoriasis the 50-A fibrils which start in the basal or most inferior cell of the stratum malpighii are never transformed into the 70-A fibril found in the normal stratum corneum. They remain as 50-A fibrils poorly integrated into the surrounding denser matrix and do not assume the nicely arrayed keratin packing found in normal horn cells. In addition keratohyalin granules are not found in the cells of the intermediate layer, and the cytoplasmic and nuclear contents of the cell are removed only to a very limited degree. An alternative picture involving lipid has been discussed by Swanbeck (S30, S31). 

In the Freney and Lipson method the wool was treated with caustic soda dissolved in alcohol. The amount of moisture in the wool had a greai influence on the degree of unshrinkability obtained, and also upon tlu extent of the degradation of the keratin molecules. A moisture content I l 8 j er cent was recommended as the most suitable for practical working conditions. According to the instructions in the patent, the conditioned wool w as treated with 7 per cent of sodium hydroxide dissolved in 95 per cent alcohol at 25°C (77°F) for 2 minutes. There was a tendency for the temperature to rise during the reaction, and some means of cooling was necessary i o thai... 

---