Stem Cells

most important aspect of mitosis

"parent" cell and the "daughter" cells (producedthroughthistypeofcelldivision)aregeneticallyidentical. Inorderforthis to occur, the DNA of the "parent" cell must be duplicated before the cell divides

Women may be infertile for several reasons.

- Hormonal imbalances may result in inability to ovulate or maintain the endometrium properly for pregnancy to proceed -A blocked fallopian tube (oviduct) may result in an inability for the zygote to reach the uterus where it should implant. -Ovarian cysts may prevent proper ovulation of the egg. -Endometriosis and uterine cysts may impair the ability of the blastocyst to implant in the endometrium of the uterus

stem cells in treatment for spinal injuries

>250,000 people have spinal injuries 11,000newinjurieseachyear No cure or even treatment until 1998 (stem cells found to regrow nerve tissue) Human embryonic stem cells injected directly into the spinal column of the mouse

Human embryos created by IVF can be frozen and used later

Couplescaneitheruse them, donate them to infertile couples, discard them of let them be used for stem cell research. costs $2,000/yr to store

This slide shows the development of male and female anatomies

It is a good illustration of the different morphologies that can develop from a common plan and how cell differentiation and migration produce organs with different functions

Cell differentiation

involves genetic changes within the DNAof the cells. DNA directschangesinthechromosomeswhich"switchesoff"muchoftheDNA. Thecell then only uses a portion of the DNA and begins to take on a specialized function

Cell differentiation

involves genetically controlled changes which causes the cells to take on different characteristics. It is through cell differentiation that the 210 different tissue types of the body are produced

Growth

involves mitosis increasing the number of cells from the original zygote to the adult body composed of trillions of cells

Men may be infertile for several reasons

low sperm count or weak sperm that may reduce the chances of fertilization of the egg, impotence, and hormone imbalances that impair the ability of the man to produce sperm adequately for reproduction Side effects to medication can also cause men to produce inadequate amounts of sperm cells or be unable to perform sexually resulting in the inability to deliver sperm to the egg

stem cells

non-specialized cells that can differentiate into other specific types of cells human embryonic stem cell growing on a layer of supporting cells (fibroblasts) Signals that direct stem cells to become a particular cell (220 types in humans) are currently largely unknown

Mitosis consists of the following steps

prophase(not shown above), metaphase, anaphase,and telophase Emphasisisgiven to how the doubled chromosomes split apart into the two sides of the cell and how the cell then divides into two distinct "daughter" cells that have the identical chromosomes as the original cell. Toaccomplishthedivisionofthechromosomes, the doubled chromosomes line up in the center of the cell during metaphase and then split apart during anaphase. Telophase is the stage in which the cell separate into two distinct cells

mitosis of body cells

All 46 chromosomes in the "parent" cell replicate and then the chromosomes divide to oppositesidesofthecell. Mitosisisresponsibleforincreasinginthenumberofcells (growth) and in tissue repair and replacement

where do embryonic cells come from?

Embryonic stem cells come from a Blastocyst (4 or 5 days after fertilization, 50 to 150 cells), not a fetus or even an embryo as most people think of them

idea behind stem cells

The stem cells used for research came from frozen embryos that were going to be discarded

During interphase, the chromosomes are doubled.

Then during mitosis the chromosomes are separated and the cell splits into two distinct cells. This results in daughter cells with the same number of chromosomes as the parent cell

Two major steps are involved in human development

growth and differentiation

This slide depicts the life cycle of humans. Adults are composed of cells with 46 chromosomes which are referred to as diploid (2n)

Through meiosis (reduction division), the adult cells divide into gametes which have 23 chromosomes and are referred to as haploid (n). The human gametes are sperm (produced by the male) and the egg (produced by the female). When an egg is fertilized by a sperm, the complete number of 46 chromosomes is restored and the resulting zygote is again diploid (2n). The zygote then undergoes mitosis (increasing in number of cells identical to the zygote) and differentiation (in which the cells specialize into the 210 different tissue types of the human body) as it undergoes development

Dr. James Thomson discoverer" of stem cells in 1998 has found a way to convert adult skin cells to human embryonic stem cells (or at least stem cells with ESC capabilities) "Inducing" adult stem cells to be pluripotent

University of Wisconsin, was the first to cultivate stem cells. He collected stem cells from surplus embryos from fertility clinics. He stopped the cells from differentiating, but kept them dividing producing large quantities of undifferentiated cells

In vitro fertilization

a technique that has been widely used to help infertile couples 5 mil born from this

human development involves

addition of more cells-mitosis creation of adult cells with special functions through cell differentiation, creating 210 dif tissues in the body

blastocyst

characterizedbyahollowinteriorwith aninnercellmass. Theinnercellmassiswhereembryonicstemcellsarelocated. The cells of the inner cell mass have the potential to differentiate into any of the 210 tissuetypesoftheadultbody. The blastocyst stage is the stage of development the implants into the endometrium

two types of stem cells

embryonic- most potential for differentiation b/c can become nearly any type of cell in the body adult- usually can be become only a particular type of cell- ex. adult stem cells in bone marrow can differentiate into red blood cells, white blood cells, or platelets

adult stem cells Remind them of skin cells constantly dying and being remade. True for most cell types... Adult Stem cells are more specialized already - not as plastic (flexible) as embryonic Stem cells in even a newborn baby are considered "adult"

responsible for tissue repair and regeneration birth = 'adult' found throughout the body cells constantly die and must be replenished not as flexible as embryonic

Louise Brown

the first human born through "test-tube" technology (in vitro fertilization)in1978. Whenthiswasoriginallydone,therewasmuchcontroversy oversuchmanipulationofhumanlife. Todaythousandsofchildrenhavenowbeen born to couples using in vitro fertilization

Fertilization

theovumbythespermoccursintheoviduct. Thisiswherethediploid number is restored (2n) in the zygote. The zygote then undergoes mitotic division which increases it's number of cells, but no differentiation is occurring Eventuallya blastocyst stage is reached

why the controversy

those who oppose - embryonic stem cell research requires destruction of embryos -many believe life begins at conception and find it morally wrong to destroy embryo that could develop into a human in favor - embryos destined for incineration - stem cells have the potential to cure many diseases and conditions

adult stem cells Much of the research using adult stem cells comes from umbilical cord blood because these cells are pluripotent (less differentiated - able to become a cell in any one of the three germ layers)

treatment in humans- bone marrow transplant, stem cells to make new blood cells umbilical cord blood- banking cord blood, almost as flexible as embryonic stem cells, future uses