Assessment: Clinical Medicine and Cellular Pathology

Pages: 3 (952 words)  ·  Bibliography Sources: 3  ·  Level: Master's  ·  Topic: Disease  ·  Buy This Paper

Cystic Fibrosis

Clinical Medicine and Cellular Pathology

Cellular Biochemistry

The CFTR (cystic fibrosis transmembrane conductance regulator) gene product is a 168 kD cAMP-regulated chloride channel expressed on epithelial cells in the airways, intestine, reproductive tissues, pancreas, and sweat and salivary glands (Li and Naren, 2005). The channel typically resides on the luminal side of the apical membranes and regulates salt and water transport into and out of the cytoplasm, using ATP hydrolysis for energy. 12 helices make up the hydrophobic transmembrane region, which consists of two repeats having 6 helices each, with a linking hydrophilic cytoplasmic domain encoding a number of consensus phosphorylation sites. The N-terminus extends into the cytoplasmic space and has regulatory properties by virtue of interacting with other membrane-bound proteins, while the C-terminus tail binds PDZ-containing regulatory proteins that may enhance dimer formation and transporter activity. Since chloride transport affects the electrical properties of membrane polarity, the activity of other transporters, including sodium, potassium, and bicarbonate, is also affected. The complexity of interactions with other regulatory proteins is still incompletely understood, but what is known suggests that CFTR activity can be altered by a number of different regulatory pathways in the cell.

Blood Chemistry

Pancreatic insufficiency is detectable in 75% of newborns with cystic fibrosis and is caused by a buildup in bicarbonate and an inability to produce ductal fluid from the ductal epithelial cells (Rodrigues et al., 2008). Without ductal fluid to flush canaliculi of acini-secreted, digestive enzymes, they become obstructed and the enzymes fail to reach the duodenum. Nutrient malabsorption results and is evidenced by large, pale feces with a distinct smell. Since the enzymes are unable to be secreted into the duodenum, the pancreas begins to auto-digest. After months or years of auto-digestion diabetes develops.

Because pancreatic insufficiency is so prevalent in newborns with cystic fibrosis, routine blood screening for immunoreactive trypsinogen (IRT) protein has been instituted in a number of countries (Rodrigues et al., 2008). The source of the trypsin is the diseased pancreas, which releases trapped digestive enzymes into the circulatory system. Even in cystic fibrosis patients with pancreatic sufficiency, the test is still valuable because pancreatic function is often already impaired.

Unfortunately, there the IRT test alone produces a false positive rate of approximately 25% (Rodrigues et al., 2008). Researchers have thus been trying to improve blood tests for detecting cystic fibrosis in newborns. Additional testing for elevated serum levels of pancreatitis-associated protein (PAP), meconium lactase, and the more common CFTR mutations seem to produce high specificity and good sensitivity through various combinations. General acceptance of these testing protocols will probably take time though.

Immunology

Since CFTR is expressed in a number of different tissues, the disease manifests in a number of locations. The primary defining features are chronic lung and pancreatic disease (Rodrigues et al., 2008). At the cellular level, impaired chloride transport results in sodium… [END OF PREVIEW]

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Clinical Medicine and Cellular Pathology.  (2012, February 28).  Retrieved July 24, 2019, from https://www.essaytown.com/subjects/paper/clinical-medicine-cellular-pathology/655935

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"Clinical Medicine and Cellular Pathology."  Essaytown.com.  February 28, 2012.  Accessed July 24, 2019.
https://www.essaytown.com/subjects/paper/clinical-medicine-cellular-pathology/655935.