... This protein con-tains high levels of the sulfur-containing AMINOACID, CYSTEINE. The cysteine sulfur atoms of adja-cent keratin chains cross-link with each other,making keratin resistant ... passes through the convolutedtubules of the nephron, where most of the sodiumchloride is reabsorbed into the blood. The tubuleshelp regulate the sodium content and the pH of the blood by exchanging ... developingtropical and subtropical nations. In low socioeco-nomic regions of Africa, the Near East, Asia, and Central and South America, the disease often be-gins with the birth of a second child. The weaned,first-born...