Which anti-clotting substance acts on factors V and VIII?

Correct Answer: B

Rationale: The correct answer is B: Protein C. Protein C is an anti-clotting substance that inhibits factors V and VIII in the coagulation cascade. Factor V and VIII are essential for the conversion of prothrombin to thrombin, a key step in blood clot formation. By inhibiting these factors, Protein C helps regulate the clotting process. Rationale: A: ATIII primarily inhibits factors IIa (thrombin) and Xa. C: TFPI (Tissue Factor Pathway Inhibitor) inhibits the extrinsic pathway of coagulation by binding to and inhibiting factor VIIa. D: Plasmin is involved in fibrinolysis, breaking down blood clots, and does not directly inhibit factors V and VIII in the coagulation cascade.

Correct Answer: B

Rationale: The correct answer is B: Trypanosoma brucei gambiense. This parasite causes African Trypanosomiasis (sleeping sickness), characterized by fever, lymphadenopathy, and neurological symptoms. Choice A, Trypanosoma cruzi, causes Chagas disease, not presenting with lymphadenopathy. Choice C, Leishmania donovani, causes visceral leishmaniasis with hepatosplenomegaly, not cervical lymphadenopathy. Choice D, Onchocerca volvulus, causes onchocerciasis (river blindness) with skin and eye manifestations, not cervical lymphadenopathy.

Correct Answer: B

Rationale: The correct answer is B: Basophilic stippling. Basophilic stippling is a finding seen in blood smears of individuals with hookworm infection anemia. It represents aggregates of ribosomes in red blood cells due to lead poisoning or thalassemia. Howell-Jolly bodies (A) are nuclear remnants in red blood cells, typically seen in conditions causing splenic dysfunction. Target cells (C) are seen in liver disease or hemoglobinopathies. Spherocytes (D) are seen in conditions like hereditary spherocytosis or autoimmune hemolytic anemia.

Correct Answer: D

Rationale: The correct answer is D, "RA with excess blasts in transformation". This choice indicates progression to acute myeloid leukemia, which has the poorest prognosis among MDS subtypes. Refractory anemia (A) has a relatively better prognosis compared to transformation. RA with ring sideroblasts (B) and RA with excess blasts (C) are also MDS subtypes, but they do not indicate the same level of disease progression as RA with excess blasts in transformation. Therefore, choice D is the correct answer due to its association with the most severe outcome in MDS.

Correct Answer: B

Rationale: The correct answer is B: Promastigote. In vitro diagnosis of leishmaniasis involves culturing the promastigote stage of the parasite. Promastigotes are the infective stage found in the sandfly vector and are typically used for laboratory diagnosis. Amastigotes are the intracellular forms found in mammalian hosts, not in vitro. Trypomastigotes are seen in Trypanosoma species, not Leishmania. Schizonts are not typically used for diagnosis of leishmaniasis.