Thirty-two-year-old Jason is a general laborer, who fell ill ...

[jwb375]

Thirty-two-year-old Jason is a general laborer, who fell ill shortly after working on a job digging up old water pipes for the town he lived in.
 
  The task involved working around shallow pools of stagnant water. Ten days after the contract ended, Jason developed a fever and aching muscles. He also had nausea, vomiting, and diarrhea. Jason's friend took him to his physician who listened carefully to Jason's history. She told him she suspected West Nile fever and ordered serological testing. Jason went home to recover and was feeling better by the end of the week.
 
  Jason's physician ordered serological tests. How would antibody titers assist the doctor in confirming his diagnosis?
 
  When Jason was feeling at his worst, he had extreme malaise, vomiting, and diarrhea. What stage of the illness was he experiencing at that time? What are the physiological mechanisms that give rise to the signs and symptoms of infectious illness?
 
  West Nile virus has a single-stranded RNA genome. How does this virus replicate? In general terms, what are the various effects viruses can have on host cells?

Question 2

Carlton, a 6-year-old boy, was playing on a sandy beach with his mother. He began to run along the shoreline when he stepped on the sharp edge of a shell, giving himself a deep cut on his foot.
 
  His mother washed his foot in the lake and put on his running shoe to take him home. One day later, Carlton's foot looked worse. The gash was red and painful. The foot was warm to touch and appeared swollen. Carlton's mom put some gauze over the wound and prepared to take him to the local community health clinic.
 
  What is the physiologic mechanism causing the wound to become red, hot, swollen, and painful? How is this different than the inflammatory response that might occur in an internal organ?
 
  What are the immunologic events that are happening at the local level during Carlton's acute inflammatory response?
 
  Nutrition plays an important factor in wound healing. What stages of wound healing would be affected by a deficiency in vitamins A and C?

[vseab]

Answer to Question 1

Antibody titers (or levels) indicate the presence of infection. Certain titers are elevated during the acute phase of a specific illness and tend to decline during convalescence.

When Jason was feeling at his worst, he was experiencing the acute phase of the illness. At this time, there is rapid proliferation and spread of the pathogen within the body. Toxic by-products of microbial metabolism and cell lysis contribute to the specific signs and symptoms of the invading pathogen. The host's immune response generates inflammation and tissue damage, further adding to the clinical presentation.

Viruses have either a single DNA or RNA strand. In order to replicate, they require the genetic material of a host and cannot replicate outside of a living cell. Once in the host cell, they may replicate and migrate from the cell through budding or through cellular lysis. Alternatively, they may lie in a state of latency to create disease at a later time or alter the genetic material of the host cell to create malignant transformation.

Answer to Question 2

Carlton's signs are typical of acute inflammation. Local vasodilation creates erythema and warmth. The edema is a result of increased vessel permeability and migration of exudate into the surrounding tissue. The engorgement of fluid at the area of injury contributes to the sensation of pain.
Visceral inflammation has a slightly different presentation: heat is less likely to occur because core temperature is preserved at a homeostatic level, and pain becomes apparent only when stretch receptors on the surfaces of the viscera are stimulated.

In an acute response, leukocytosis occurs to increase the number of circulating white blood cells to support the immune response. The movement of white blood cells to the site of injury occurs as a result of chemotaxis. Margination and emigration are the events that describe the movement of circulating leukocytes from the blood to the injured tissue; local blood stasis allows leukocytes to move to the perimeter of vessels and pass (or emigrate) through capillary walls. Neutrophils arrive early to phagocytose microbes and cellular debris. Monocytes travel in the blood and migrate to injured tissue where they become macrophages. These cells are capable of engulfing greater quantities of foreign material and are able to move to the lymphatic system, where they prime specific immunity.

While the components of nutritional intake are valuable to all stages of wound healing, some have more specific qualities. Both vitamin A and C assist collagen synthesis, but vitamin C has a direct influence on collagen assembly and the removal of by-products that result from collagen manufacturing. A deficiency in vitamin C would therefore affect the onset of the proliferation stage and the effectiveness of the remodeling phase where collagen production and lay down are critical. Vitamin A stimulates capillary growth and epithelialization. A deficiency in vitamin A would hinder angiogenesis in the inflammatory phase of wound healing and epithelialization in the latter component of the proliferation phase.

[jwb375]

Excellent

[ryhom]

Gracias!