Download Apoptosis of tail muscle during amphibian metamorphosis

Apoptosis of tail muscle during amphibian metamorphosis
Apoptosis is a form of programmed cell death. Unlike necrosis, which is a form of
traumatic cell death that results from cell injury, apoptosis has many advantages.
Programmed cell death occurs in a variety of organs during amphibian
metamorphosis and is usually identified, using electron microscopes, as
apoptosis. Amphibians are an ideal organism to study programmed cell death
because there is a massive cell death in such a short period.
It is well known that cell death occurs during amphibian metamorphosis (more
specifically, the metamorphosis of a tadpole into an adult frog). This is under
control of the thyroid hormone (TH), which is a hormone released by the thyroidand affects protein synthesis. Many tissues, organ systems, and muscles are made
of proteins. As the aquatic tadpole develops into a terrestrial adult, cells in the tail
die. Cells in the gut also die to form tissues and organs, such as lungs.
The climax of metamorphosis from a tadpole into an adult frog is marked by the
disappearance of its tail.
Prior to apoptosis, the amphibian is in a larval (think, like an infant) state, where
the tail is very prominent. Tadpoles are also aquatic, not needing oxygen from
the air. After apoptosis, the tail is no longer visible and limbs have taken its
place. Apoptosis also plays a crucial role in the development of the lungs, other
internal organs, limbs (arms or legs), and digits (fingers or toes). If apoptosis did
not occur in the development of limbs, there would be no definition between
each finger. Likely, if apoptosis did not occur in tadpoles, adult frogs may never
be formed, or they may look very different than they do now.
The development of neural connections in the human brain
Brain cells divide and grow, migrate to new locations, and make neurological
connections. These cells consist of glia (non-neuronal cells that aid in support,
nutrition, and homeostasis) and neurons (responsive cells that process and
transmit chemical signals). Programmed cell death is essential for the
development of neural tissue, including the human brain. The role of apoptosis
(genetically programmed cell death) in the development of the human brain is
widely recognized. Massive cell death occurs in the nervous system from the
earliest stages of development.
Apoptosis is a complex process, characterized by biological and chemical
changes in the nucleus and cytoplasm of cells. Because of this, many more
changes occur in more cells, and even brain tissue. Transformations can be seen
starting in the nucleus, and then in the components that lie in the cytoplasm. The
chromatin begins to clump, splitting the nuclear envelope, spilling in to the
cytoplasm. The mitochondria change shape, from long, bean shaped to a
condensed form. The cell ultimately dies. These cells then get consumed by
phagocytes (cells that “eat” other dead cells).
Ultimately, apoptosis gets rid of extra neurons and glial cells. If this fails, the brain
may not develop properly. This could lead to many other disorders or even death.
Apoptosis in the development and maintenance of the
immune system
Programmed cell death (apoptosis) is essential for the development and
maintenance of cellular homeostasis of the immune system.
The immune system is the body system that fights off infections or pathogens
(infectious agent, or germ). Just as a castle has several lines of defense, or armies,
so does your body. The immune system relies on the physical barriers to keep
pathogens out. However, when pathogens get past the physical barriers, the
warrior cells of the immune system come into help the body cells.
When humans get sick, a virus or bacteria will attack cells in the body. These cells
then send signals to the helper cells, T cells and B cells to help defend the body. T
cells destroy body cells that are infected with pathogens. B cells produce proteins
that deactivate pathogens that have not yet infected a body cell. When the body
is under attack, T cells and B cells grow and divide very rapidly to fight off the
pathogens (these are like your body’s army). Once the body maintains its
homeostasis and fights off the pathogens, apoptosis kills the extra T cells and B
cells. Only a small amount of the cells remain in case of another infection.