bioethics

stem cells

Embryonic stem cells, as their name suggests, are derived from embryos. Specifically, embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro � in an in vitro fertilization clinic � and then donated for research purposes with informed consent of the donors.

stem cells

Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics that will be explained in this document. Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago.

Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory.

Until recently, it had been thought that a blood-forming cell in the bone marrow � which is called a hematopoietic stem cell � could not give rise to the cells of a very different tissue, such as nerve cells in the brain.

In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease. It has been hypothesized by scientists that stem cells may, at some point in the future, become the basis for treating diseases such as Parkinson's disease, diabetes, and heart disease.

The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas. Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics that will be explained in this document.

stem cells in biomedicine

However, a number of experiments over the last several years have raised the possibility that stem cells from one tissue may be able to give rise to cell types of a completely different tissue, a phenomenon known as plasticity. Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, and hematopoietic stem cells that can develop into heart muscle.

When this occurs, they are removed gently and plated into several fresh culture dishes. The process of replating the cells is repeated many times and for many months, and is called subculturing.

Human embryonic germ cells, in contrast, are derived from a five- to ten-week-old fetus. Adult stem cells typically generate the cell types of the tissue in which they reside. A blood-forming adult stem cell in the bone marrow, for example, normally gives rise to the many types of blood cells such as red blood cells, white blood cells and platelets.

embryonic stem cells

Such information is critical for scientists to be able to grow large numbers of unspecialized stem cells in the laboratory for further experimentation. Stem cells can give rise to specialized cells.

The inner surface of the culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide.

The successful generation of an unlimited supply of dopamine neurons could make neurotransplantation widely available for Parkinson's patients at some point in the future. Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal: 1) why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and 2) what are the factors in living organisms that normally regulate stem cell proliferation and self-renewal? Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer.

embryonic stem cells

Over the course of several days, the cells of the inner cell mass proliferate and begin to crowd the culture dish. When this occurs, they are removed gently and plated into several fresh culture dishes.

stem cells in bioethics

These tests include. Growing and subculturing the stem cells for many months. This ensures that the cells are capable of long-term self-renewal. Scientists inspect the cultures through a microscope to see that the cells look healthy and remain undifferentiated. Using specific techniques to determine the presence of surface markers that are found only on undifferentiated cells. Another important test is for the presence of a protein called Oct-4, which undifferentiated cells typically make.

embryonic stem cells

They are not derived from eggs fertilized in a woman's body. The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst.