After the microscope has been adjusted for Kohler illumination, light intensity should never be regulated by using the...

Correct Answer: D

Rationale: After adjusting for Kohler illumination, the light intensity should not be regulated through the condenser because it is meant to adjust the focus and light distribution, not intensity. The correct way to regulate light intensity is through the rheostat, not the condenser. Using a neutral density filter can help reduce light intensity, but it is not the primary method for regulation in Kohler illumination. Kohler magnifier is not used for light intensity regulation but for viewing the image.

Correct Answer: C

Rationale: The correct answer is C: Pyruvate Kinase. This enzyme deficiency in the Embden-Meyerhof pathway leads to the accumulation of intermediates, causing red blood cell damage and hemolytic anemia. Pyruvate Kinase catalyzes the conversion of phosphoenolpyruvate to pyruvate, a crucial step in glycolysis. In contrast, choices A, B, and D are not directly related to the final step of glycolysis and do not lead to the accumulation of intermediates causing hemolytic anemia. Hexokinase is involved in the initial step of glycolysis, Phosphofructokinase in the committed step, and Glyceraldehyde 3-Phosphate Dehydrogenase in the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate.

Correct Answer: B

Rationale: The correct answer is B: Auer rods. A bone marrow biopsy in a patient with leukemia may show Auer rods, which are needle-shaped cytoplasmic inclusions found in myeloid cells. Auer rods are characteristic of acute myeloid leukemia. Smudge cells (choice A) are seen in chronic lymphocytic leukemia. Reed-Sternberg cells (choice C) are found in Hodgkin's lymphoma. Lytic lesions (choice D) are seen in multiple myeloma, but are not typically identified on a bone marrow biopsy. Thus, Auer rods are the most likely finding on a bone marrow biopsy in a patient with leukemia.

Correct Answer: C

Rationale: The correct answer is C: patchy, irregular fluorescence of the glomerular basement membrane. In acute glomerulonephritis, there is immune complex deposition in the glomeruli leading to inflammation. The immune complexes contain IgG antibodies, which will bind to the glomerular basement membrane. When stained with fluorescein-conjugated anti-human IgG antibody, the presence of IgG antibodies in the glomerular basement membrane will result in patchy, irregular fluorescence patterns. Choice A is incorrect as there should be fluorescence due to IgG deposition. Choice B is incorrect as the fluorescence pattern is not uniform. Choice D is incorrect as B cells are not typically involved in the pathology of acute glomerulonephritis.

Correct Answer: A

Rationale: The correct answer is A because C3b is not involved in altering vascular permeability. C3b plays a role in promoting phagocytosis by opsonizing pathogens, forming alternative-pathway C3 convertase for amplifying the complement cascade, and forming C5 convertase to initiate the terminal pathway. In contrast, altering vascular permeability is primarily mediated by other factors such as histamine and bradykinin. Therefore, C3b's involvement in altering vascular permeability is not supported by the functions it actually performs in the complement system.