Anemia

Correct Answer: D

Rationale: The correct answer is D because anemia is defined as having abnormally low amounts of hemoglobin or red blood cells, leading to reduced oxygen-carrying capacity. This results in symptoms such as fatigue and weakness. Choice A is incorrect because anemia is not related to cancer of white blood cells. Choice B is incorrect as anemia does not result in extra leukocytes; rather, it leads to a decrease in red blood cells. Choice C is incorrect as anemia is not usually fatal if treated promptly and effectively.

Correct Answer: D

Rationale: The correct answer is D: Anemia. Anemia is the medical term for a condition where there is a decrease in the number of red blood cells or hemoglobin in the blood. The formation of abnormal red blood cells can lead to anemia, affecting the oxygen-carrying capacity of the blood. Leukocytosis (A) is an increase in white blood cells, thrombocytosis (B) is an increase in platelets, and hemolysis (C) is the breakdown of red blood cells, none of which specifically refer to the formation of abnormal red blood cells.

Correct Answer: B

Rationale: Barry Marshall drank a pure culture of H. pylori to demonstrate an association between H. pylori infection and gastric ulcers. This is because he wanted to prove the theory that the bacteria is a primary cause of stomach ulcers, contradicting the prevailing belief at the time. Choice A is incorrect because the direct link between H. pylori and gastric cancer was not the primary focus of his experiment. Choice C is incorrect as his goal was to show the bacterial link to ulcers, not to disprove stress as a factor. Choice D is incorrect because only choice B accurately reflects his intended purpose.

Correct Answer: A

Rationale: The correct answer is A: Selectins expressed on endothelial cells. Rolling of neutrophils on endothelial cells is a crucial step in the process of inflammation and immune response. Selectins are cell adhesion molecules expressed on endothelial cells that facilitate the initial interaction between leukocytes (such as neutrophils) and endothelial cells. This interaction allows for the rolling of neutrophils along the endothelial surface, which is essential for the subsequent steps of adhesion and transmigration into the tissues. Integrins (Choice B) are involved in the firm adhesion of leukocytes to endothelial cells, not in the initial rolling process. Chemokines (Choice C) such as CXCL-8 are signaling molecules that help in the recruitment of leukocytes but do not directly mediate the rolling process. TNF (Choice D) is a pro-inflammatory cytokine but is not directly involved in the rolling of neutrophils on endothelial cells.

Correct Answer: C

Rationale: The correct answer is C because secondary lymphoid tissues, like lymph nodes and spleen, are where lymphocytes encounter antigens and become activated. This process leads to the proliferation and differentiation of lymphocytes, enabling them to mount an immune response against specific pathogens. Choices A, B, and D are incorrect because A pertains to primary lymphoid tissues, B describes a localized immune response, and D refers to the process of gene rearrangement that occurs in the primary lymphoid tissues during lymphocyte development.