Aberrant expression of the secreted mucins was also demonstrated. Chronic bronchitis is a respiratory disease marked by overproduction of mucus and mucins. It is lined with an epithelium that has goblet cells which produce protective mucins. It is viscous because it contains large proteins known as mucins. The release of mucins is performed by sheddases. Currently, eight different mucins have been identified for humans. In 1950 it was used by Steedman as a selective dye for mucins. Diff-Quik stain highlights cytoplasmic elements such as mucins, fat droplets and neurosecretory granules. They have a high molecular weight and exist as either membrane-bound or secretory mucins. Bismarck brown Y stains acid mucins to yellow color. The film contains mucins and proline-rich glycoprotein from the saliva. Like other mucins, MUC-4 is a high-molecular weight glycoprotein. It was characterized shortly after, and it was found to be carried primarily by mucins. Goblet cells accomplish this by secreting mucins, large glycoproteins formed mostly by carbohydrates. Changes in mucins are important in numerous diseases, including cancer and inflammatory bowel disease.