Stem Cells, Genetic Engineering, and Infectious Diseases

Posted on Dec 13, 2024 in Biology

Stem Cells and Transplants

ITEM 5. Who can donate? Usually, a person in a situation of brain death, or *encephalic* death. A person who has died and whose brain has stopped functioning, but whose heart is still beating artificially, can have their organs transplanted, as they are in perfect condition. In some types of transplants, the donor may be a living person (skin, bone marrow, kidney, etc.).

Immune Rejection

Our immune system can distinguish self from foreign. If white blood cells detect something strange, they try to destroy it. This capability is important when it comes to a virus. It is important that the receptor and donor are as similar as possible, *compatible*, but this will still cause rejection. To help, drugs called immunosuppressants are used. These reduce the ability of the immune response, but once these are stopped, the body is left exposed to many infections.

The Technical Impossibility of Obtaining Certain Organs and Tissues

Some organs (brain, nervous tissue) are impossible to obtain and transplant. Regenerative medicine is based on the use of stem cells and aims to regenerate any tissue or organ that does not work without harming the patient.

Fertilization

The union of egg and sperm occurs within the female genital tract, the fallopian tube. The result is the formation of a *zygote*. The fallopian tube connects the ovary, where ovules are produced, to the *uterus*.

Development

The joint changes that occur in any living being during life. It begins with the formation of the first *zygote*. The part of the development that ends with birth is called *embryonic* development. Postnatal development begins at birth and continues throughout life.

Stages of Embryonic Development

  1. A sperm tries to cross to an egg in the fallopian tube. Fertilization ends when the nuclei of sperm and egg fuse, since we are developing an embryo here.
  2. The zygote moves into the uterus and begins to divide. At the end of the second day, it consists of two cells.
  3. Cells keep dividing to form an embryo of 32 cells, the *morula*.
  4. A cavity is formed in the morula, and this structure is called an *early blastocyst*.
  5. A group of cells is formed in the blastocyst, called a *late blastocyst*.
  6. The embryo is implanted in the uterine wall, which has been prepared for this by coating a layer called the *endometrium*.

Assisted Reproduction

Artificial Insemination

It is the introduction of sperm, previously obtained, artificially inside the female genital tract.

In Vitro Fertilization and Embryo Transfer (IVF)

Consists of fertilizing an egg with a sperm outside the body of the woman. This technique is used when the female genital tracts are blocked by the abnormal proliferation of tissue. It is developed in these stages:

a) Egg Retrieval: It stimulates the production of eggs in the ovaries of the woman. The ova are retrieved from the ovaries before they are released to the tubes.

b) Fertilization: The extracted eggs are fertilized by spermatozoa. The embryos are left to develop until they reach the morula state.

c) Transfer of Embryos: The embryos are inserted into the uterus of the woman. When they reach the late blastocyst stage, they nest and are implanted in the endometrium.

Types of Stem Cells

  • Totipotent: These are cells capable of generating a complete individual. Besides the zygote, the first 8 cells resulting from their division remain totipotent. This means that if the group divides into two cells, each group would lead to a complete individual.
  • Pluripotent: They cannot cause a complete individual but retain the ability to originate all types of cells that make it up.
  • Multipotent: Even in adults, there are cells that retain some capacity to cause some types of cells; they are called adult stem cells.
  • Oligopotent: Some adult stem cells can only cause some types of cells. They are referred to as oligopotent stem cells, for example, skin stem cells or nerve tissue stem cells.

Regenerative Medicine

A new branch of biomedicine that aims to produce a functional organ or tissue to replace the affected one.

  • Embryonic Stem Cells: Coming from early embryos. They are more likely to be pluripotent and can cause any tissue type.
  • Adult Stem Cells: Found in all human tissues. Except for the cells of the bone marrow and the umbilical cord blood, they are multipotent.
  • Induced Pluripotent Cells (iPS): They are specialized adult cells that dedifferentiate and transform back into pluripotent embryonic stem cells.

Stages of Therapeutic Cloning

  1. A biopsy is taken from the patient who needs a transplant, and the nucleus of the obtained cells is extracted.
  2. The nucleus is introduced into the egg of a donor from which its own nucleus has been derived.
  3. It is left to develop to the blastocyst stage, obtaining embryos called *somatic*.
  4. Embryonic stem cells are obtained from the blastocyst and cultured in vitro to increase their number.
  5. When the number of stem cells is sufficient, they are available in means for their differentiation.

Emerging and Reemerging Diseases

ITEM 3. Emerging Diseases: Germs are transmitted by unknown factors. Some of them have been confined to their place of origin before coming into contact with people.

Reemerging Diseases: The major infectious diseases of the past continue with us. This is the case of cholera, dengue, tuberculosis, or malaria.

Infectious Agents

  • Viruses: They are cellular parasites that need to be introduced into cells to reproduce. They are smaller, and examples include influenza, AIDS, and common colds.
  • Bacteria: Unicellular prokaryotic organisms that can be reproduced without invading other cells. Examples include tuberculosis, cholera, and anthrax.
  • Protozoa and Fungi: Protozoa are unicellular, and fungi are unicellular or pluricellular. These are also called parasites.

Antibiotics

Chemicals, synthetic or of biological origin, that kill bacteria or prevent their multiplication. The first antibiotic was penicillin.

Antivirals

They are used for infectious bacterial diseases. The first problem is that viruses are not cells. There are few antiviral drugs to prevent the virus from entering the cells.

Reproduction of Influenza Virus

  1. The virus attaches to a cell membrane.
  2. The virus enters the cell by endocytosis through the formation of a vesicle that contains it inside.
  3. Once inside, the vesicle membranes bind, freeing fragments of RNA (genetic information of the virus).
  4. The cell machinery makes copies of the genetic information of the virus and builds new capsules.
  5. The new viruses leave the cell and infect new cells.

Genes, Chromosomes, and Genetic Engineering

ITEM 6. A gene is a portion of DNA with a particular base sequence that determines the appearance of a character. A chromosome is the structure that DNA forms in the nucleus or in the cells. DNA molecules are very long but are formed by the repetition of only four basic subunits, nucleotides. Each of these has a different molecular base that can only mate in one way, A with T and G with C.

Genetic Engineering

The set of techniques used by biologists to provide living cells with new properties, to manipulate the DNA molecule where genes are made.

Genetically Modified Organisms (GMOs)

For example, a plant or animal that has been modified by genetic engineering.

How to Get a Transgenic Organism

In the first step, introduce the gene into the genome of a cell of the body you want to modify:

  1. Extract all DNA.
  2. Locate and remove the gene.
  3. Clone the gene.
  4. Modify the exogenous gene.
  5. Introduce the transgene into the nucleus of the cell to be modified.
  6. Test that the transgene has been incorporated.

In the second stage, obtain a plant or animal from the cell whose genome has been modified.