Shape of a cell is maintained by which?

Correct Answer: A

Rationale: The correct answer is A: Microtubules. Microtubules are structural components of the cytoskeleton that help maintain the shape of a cell by providing support and stability. They also play a crucial role in cell division, intracellular transport, and cell motility. Spindle fibers are involved in cell division, ribosomes are responsible for protein synthesis, and centrioles are involved in organizing the microtubules during cell division. Therefore, the correct choice is A as it directly relates to maintaining cell shape.

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.

Correct Answer: C

Rationale: The correct answer is C: Release of histamine. Early local inflammation is characterized by the release of histamine from mast cells and basophils in response to tissue injury. Histamine causes vasodilation and increased vascular permeability, leading to redness, swelling, and heat at the site of inflammation. Fever (choice A) typically occurs during systemic inflammation, not in early local inflammation. Anaphylactic shock (choice B) is a severe, systemic allergic reaction involving widespread histamine release, not confined to the local area of inflammation. The attack of cytotoxic T cells (choice D) is part of the adaptive immune response and is not typically involved in the early stages of inflammation.