1. To better understand the potential of adult stem cells to differentiate into
ID: 210611 • Letter: 1
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1. To better understand the potential of adult stem cells to differentiate into various cell types, the following studies were performed Bone marrow was harvested from adult male mice and then transplanted into isogeneic female recipient mice that had been treated with a level of irradiation sufficient to destroy their own hematopoetic stem cells (see the figure). Although the dose of irradiation given was lethal to mice that did not receive a transplant, the majority of the recipient mice receiving the transplant survived. After 4 weeks, was analyzed. The composition of the blood was normal with respect to all blood cell types. Every blood cell examined was determined to be positive for the presence of the Y peripheral blood from the recipient mice Male mouse Harvest marrow . Bone lsogeneic female mouse transplant Lethal irradiation Labeled" mouse a.What was the purpose of using male mice as the bone marrow donors and female mice as the recipients? Would the converse experiment (female donors, male recipients) have worked? b.What was the purpose of irradiating the recipient mice prior to transplantation? What outcome might you expect if bone marrow cells were transplanted to nonirradiated mice After 8 weeks, some of the recipient mice were sacrificed and histochemical analysis was performed on tissue sections of various organs. Occasional Y chromosome-positive cells were found in the liver, skeletal muscle, and brain. Furthermore, the Y chromosome- positive cells were positive for markers of liver hepatocytes, skeletal muscle cells, and neurons (albumin, dystrophin, and NeuN, respectively) What does the appearance of Y chromosome-positive cells in multiple organs and the expression of organ-specific markers indicate about the localization of cells derived from bone marrow? About their differentiation potential? About their function?Explanation / Answer
Answer to question 1 - part a)
there is a very important fact, which has been found in many researches over the time that :
there is an impact of DONOR and RECIPIENT sex, in certain situations and cases,remember not always :
what can happen is if we use a female donor mice , it can result in increased risk of chronic graft versus host disease ( that is there can be a incompatibility between both types of tissues and can turn in severe affects), in all recipients (male or female)situations like this can ruin the experiment .
2. male mouce stem cells will only contain a Y chromosome , that was going to be analyzed later for our studies .
3. so male donors are preferred in such cases particularly.
also YES, the vice versa could have been possible too, but then there always remains a risk of GVHD in the recipient (male or female).
Answer to part b)
if irradiation would have been done , after the transplantation , it would have killed the freshly transplanted stem cells.
if bone marrow cells would have been transplanted to an non irrdiated mice, the mice would have been surviving normal , but now start dividing and then differentiating in new cells, with the donor genome and Y chromosome, a chimeric mice could have been observed. with two types of blood cells . half cells having female sex chromosome , and half having Y chromosome .
Answer to part c)
the shape and expression of organ specific markers in different cell type locations indicate few things:
1. these stem cells , divide and then get differentiated according to there particular locations , this happens by a great contribution of a microenvironment of that loaction or organ , that is if we will place a stem cell in heart cells after some time, it will start looking and expressing just as heart muscle cells beacause it is exposed to the microenvironment or all the factors and proteins of the heart muscles, a similar thing happens , so in all these locations it has been specically differentiated to form a particular type of cell even genetically it starts expressing only those particular genes which are required in that organ , AND REST OF GENES WILL BE SWITCHED OFF, this is how DIFFERENTIATION OF STEM CELLS OCCURS.
REMEMBER stem cells only divide when there is a stress or injury and does not divide in an uncontrolable manner.
answer question 2.
TOTOPOTENT STEM CELLS.- CAN DIFFERENTIATE IN ANY FORM AND TYPE OF CELL TYPE.
PLURIPOTENT STEM CELLS- CAN divide in almost all types of cell types
MULTIPOTENT STEM CELLS- can divide in two or three types of cell types.
UNIPOTENT STEM CELLS.- can divide in only one type of cell.
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