When glutamine-rich polypeptides are in a β-sheet conformation, glutamines can brace the structure by forming inter-strand hydrogen bonding between its amide carbonyls and nitrogens of both the backbone and side chains. The onset age for Huntingtons disease shows an inverse correlation with the length of the polyglutamine sequence, with analogous findings in a C. elegans model system with engineered polyglutamine peptides.Other polypeptides and proteins such as amylin and the β amyloid peptide do not have a simple consensus sequence and are thought to aggregate through the sequence segments enriched with hydrophobic residues, or residues with high propensity to form β-sheet structure. Among the hydrophobic residues, aromatic amino-acids are found to have the highest amyloidogenic propensity.Cross-polymerization (fibrils of one polypeptide sequence causing other fibrils of another sequence to form) is observed in vitro and possibly in vivo. This phenomenon is important, since it would explain interspecies prion propagation and differential rates of prion propagation, as well as a statistical link between Alzheimers and type 2 diabetes. In general, the more similar the peptide sequence the more efficient cross-polymerization is, though entirely dissimilar sequences can cross-polymerize and highly similar sequences can even be "blockers" that prevent polymerization. Amyloid toxicity
The reasons why amyloid cause diseases are unclear. In some cases, the deposits physically disrupt tissue architecture, suggesting disruption of function by some bulk process. An emerging consensus implicates prefibrillar intermediates, rather than mature amyloid fibers, in causing cell death, particularly in neurodegenerative diseases.
A chest injury, also known as chest trauma, is any form of physical injury to the chest including the ribs, heart and lungs. Chest injuries account for 25% of all deaths from traumatic injury. Typically chest injuries are caused by blunt mechanisms such as direct, indirect, compression, contusion, deceleration, or blasts- caused by motor vehicle collisions or penetrating mechanisms such as stabbings. Classification
Chest injuries can be classified as blunt or penetrating. Blunt and penetrating injuries have different pathophysiologies and clinical courses. Specific types of injuries include:

Injuries to the chest wall
Chest wall contusions or hematomas. Rib fractures
Flail chest
Sternal fractures
Fractures of the shoulder girdle
Pulmonary injury (injury to the lung) and injuries involving the pleural space
Pulmonary contusion
Pulmonary laceration
Pneumothorax
Hemothorax
Hemopneumothorax
Injury to the airways
Tracheobronchial tear
Cardiac injury
Pericardial tamponade
Myocardial contusion
Traumatic arrest
Hemopericardium
Blood vessel injuries
Traumatic aortic rupture
Thoracic aorta injury
Aortic dissection
And injuries to other structures within the torso
Esophageal injury (Boerhaave syndrome)
Diaphragm injury

Diagnosis
Most blunt injuries are managed with relatively simple interventions like tracheal intubation and mechanical ventilation and chest tube insertion. Diagnosis of blunt injuries may be more difficult and require additional investigations such as CT scanning. Penetrating injuries often require surgery, and complex investigations are usually not needed to come to a diagnosis. Patients with penetrating trauma may deteriorate rapidly, but may also recover much faster than patients with blunt injury. See also
Transmediastinal gunshot wound
Commotio thoracis

References


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