Exam 22: Stem Cells and Tissue Renewal

Each gut stem cell …

The differentiation of bone marrow stromal cells into bone or fat cells depends on chemical and mechanical signals. In each of the following conditions, indicate whether you would expect the stromal cells to differentiate into bone (B) or fat (F) cells. Your answer would be a three-letter string composed of letters B and F only, e.g. FBB. ( ) The cells are embedded in a stiff hydrogel. ( ) The cells are embedded in a soft hydrogel. ( ) The cells are treated with a Rho inhibitor. The monomeric GTPase Rho is required for the assembly of actin stress fibers and actin-myosin bundles.

An increasing number of lymphomas are being treated with "stem-cell transplantation" therapy that is composed of the following overall steps. Sort these steps into the correct order. Your answer would be a three-letter string composed of letters A to C only, e.g. BAC. (A) Injection of cells into the blood (B) Harvesting and isolating selected cells from the patient's bone marrow (C) Heavy x-ray irradiation of the patient

All blood cells in our body …

Indicate whether each of the following descriptions better matches bone (B) or cartilage (C). Your answer would be a four-letter string composed of letters B and C only, e.g. CCCC. ( ) Its extracellular matrix is mainly composed of type I collagen and calcium crystals. ( ) Its extracellular matrix is made by osteoblasts. ( ) It grows by expansion (as opposed to surface apposition). ( ) Its cells are connected via canaliculi and form gap junctions.

In addition to fibroblasts themselves, the fibroblast family of connective-tissue cells includes all of the following EXCEPT …

Which of the following cell types in our body are typically renewed independently of stem cells? Your answer would be a string composed of a subset of the letters A to E in alphabetical order, e.g. BDE. (A) Red blood cells (B) ? Cells of pancreatic islets (C) Hepatocytes of the liver (D) Epithelial cells of the epidermis (E) Neutrophils of the blood

Only cells that express a puromycin-resistance (PR) gene can grow in the presence of the drug puromycin. Ganciclovir is a nontoxic drug that is converted to a lethal toxin in a cell that expresses thymidine kinase (TK). Thy-1 is a fibroblast-specific marker protein. Which of the following selection strategies is the most reasonable one to use in experiments that attempt to generate induced pluripotent stem cells (iPS cells) from fibroblasts?

Indicate true (T) and false (F) statements below regarding blood leukocytes. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTT. ( ) Most white blood cells use blood merely as a transportation medium, and function in other tissues. ( ) Some granulocytes are professional phagocytes. ( ) Monocytes typically give rise to macrophages and polymorphonuclear leukocytes. ( ) Natural killer cells have a lymphoid origin.

Sort the following events to reflect the order in which they occur for formation of new blood capillaries in conditions of insufficient oxygen supply. Your answer would be a four-letter string composed of letters A to D only, e.g. DACB. (A) New tip cells are formed on the sides of nearby capillaries. (B) Stalk cells divide and hollow out to form tubes. (C) VEGF is secreted by the cell. (D) The level of intracellular HIF1? increases.

Blood platelets in an adult human …

Which of the following cells in a healthy adult human show the highest turnover?

Indicate whether each of the following descriptions better applies to cardiac (C), skeletal (K), myoepithelial (M), or smooth (O) muscle cells. Your answer would be a four-letter string composed of letters C, K, M, and O only, e.g. MMKC. ( ) They are derived from the ectoderm layer, similar to epithelial cells. ( ) They form the lining of cavities such as the urinary bladder. ( ) They are responsible for most voluntary muscle movements. ( ) They form multinucleated and exceptionally long muscle fibers.

BrdU (bromodeoxyuridine) is a thymidine analog that can be naturally incorporated into DNA (in place of thymidine) and detected by specific anti-BrdU antibodies. In an experiment to study the regeneration capabilities of Schmidtea mediterranea, you first fed the worms with BrdU-containing food for 30 minutes. After two hours, you fixed and incubated the worms with a fluorescently labeled anti-BrdU antibody, and observed its tissues with a fluorescence microscope. The result was that some nuclei are labeled with fluorescence while others are unlabeled. Would you expect to observe neoblasts mostly among cells that have (Y) or have not (N) been labeled with fluorescence? Are the neoblasts expected to be scattered throughout the body (S) or localized to a certain region (L)? If you fixed the worms after a week, instead of two hours, would you expect the number of nuclei with detectable fluorescence to increase (I), remain unchanged (U), or decrease (D) compared to these results? Write down your answer as a three-letter string, e.g. YSD.

The schematic drawing below shows the cross section of a crypt in the gut epithelium of a mammal. Indicate whether each of the following descriptions better applies to the areas labeled A, B, or C. Your answer would be a four-letter string composed of letters A to C only, e.g. CCBB. ( ) The stem cells reside in this area. ( ) This area contains the most rapidly dividing cells. ( ) Cells in this area would show the least radioactivity following a pulse of tritiated thymidine. ( ) This area contains cells of the innate immune system.

In each of the following examples of contact signaling between adjacent cells in the mammalian gut epithelia, indicate whether the signaling is mainly mediated by Delta (D) or Ephrin (E) signals. Your answer would be a three-letter string composed of letters D and E only, e.g. EDE. ( ) Separation of crypt cell types from villus cell types ( ) Regulation of stem-cell differentiation by Paneth cells ( ) Differentiation of transit amplifying cells into either secretory cells or absorptive cells

Indicate true (T) and false (F) statements below regarding erythropoiesis. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF. ( ) Oxygen stimulates the secretion of erythropoietin. ( ) Each human erythrocyte lives for a few days on average. ( ) All erythrocytes express "DON'T EAT ME" signals on their surface to prevent phagocytosis. ( ) It only takes 1 to 2 days for erythrocyte numbers to rise following stimulation with erythropoietin.

Sort the following events to reflect the order in which they typically take place during the reprogramming of fibroblasts to induced pluripotent stem cells. Your answer would be a four-letter string composed of letters A to D only, e.g. ADBC. (A) Sustained endogenous expression of Oct4 (B) Gain of embryonic marker protein (C) Loss of fibroblast-specific marker protein (D) OSKM overexpression

If a hematopoietic cell is deprived of colony-stimulating factors, it typically …

Indicate true (T) and false (F) statements below regarding differentiation of blood cells. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTT. ( ) Most blood cells are derived from the pluripotent stem cells by a few cell divisions. ( ) Commitment to a specific differentiation path is a stepwise process. ( ) Upon contacting connective-tissue cells of the bone marrow, hematopoietic stem cells lose their stem-cell character and differentiate. ( ) Committed hematopoietic progenitor cells typically divide rapidly.