Biology In Human Welfare Human Health And Disease 3

AIDS: A Sequential Overview#

1. Definition: AIDS (Acquired Immuno Deficiency Syndrome) is a syndrome (group of symptoms) resulting from a deficiency in the immune system, acquired during an individual’s lifetime (not congenital).

2. Discovery and Spread: First reported in 1981, AIDS has spread globally, causing over 25 million deaths.

3.Causative Agent: AIDS is caused by the Human Immunodeficiency Virus (HIV), a retrovirus with an RNA genome enclosed in an envelope.

4. Transmission: HIV transmission occurs through: - Sexual contact with an infected person. - Transfusion of contaminated blood and blood products. - Sharing infected needles (e.g., intravenous drug users). - Transmission from an infected mother to her child via the placenta.

5. High-Risk Groups: Individuals with multiple sexual partners, intravenous drug users, those requiring repeated blood transfusions, and children born to HIV-infected mothers are at higher risk. (Note: The text prompts the reader to consider situations requiring repeated blood transfusions.)

6. Important Note: HIV/AIDS is not spread through casual touch or physical contact; transmission occurs only through body fluids. Social isolation of those infected is harmful.

7. Incubation Period: A time lag exists between infection and the appearance of AIDS symptoms, ranging from a few months to many years (typically 5-10 years).

8. Viral Replication: After entering the body, HIV enters macrophages. Using reverse transcriptase, the viral RNA genome replicates into viral DNA, which integrates into the host cell’s DNA. The infected macrophages produce new viruses, acting as “HIV factories.” HIV also infects helper T-lymphocytes (TH cells), leading to their destruction and a progressive decline in their numbers.

9. Symptoms and Progression: During the infection, individuals may experience fever, diarrhea, and weight loss. The decrease in helper T-lymphocytes weakens the immune system, making individuals susceptible to opportunistic infections (bacteria like Mycobacterium, viruses, fungi, and parasites like Toxoplasma). Severe immunodeficiency ensues.

10.Diagnosis: A widely used diagnostic test is the enzyme-linked immunosorbent assay (ELISA).

11. Treatment: Anti-retroviral drugs offer partial effectiveness, prolonging life but not preventing eventual death.

12. Prevention: Since there is no cure, prevention is crucial. HIV infection often results from conscious behaviors. Exceptions include infections from blood transfusions or mother-to-child transmission due to inadequate monitoring.

13. Prevention Strategies: National AIDS Control Organisation (NACO), other NGOs, and WHO implement various prevention programs, including: * Ensuring safe blood supplies. * Using disposable needles and syringes. * Free distribution of condoms. * Controlling drug abuse. * Promoting safe sex practices. * Regular HIV testing for at-risk populations.

Cancer: A Comprehensive Overview#

I. Introduction:

• Cancer is a leading cause of death globally, affecting millions annually.
• It’s characterized by uncontrolled cell growth and differentiation due to a breakdown of regulatory mechanisms.
• Extensive research focuses on understanding cancer development, treatment, and control.

II. Cellular Mechanisms:

• Normal cells exhibit contact inhibition, preventing uncontrolled growth.
• Cancer cells lose this property, leading to continuous division and tumor formation.
• Tumors are classified as benign (localized) or malignant (invasive and metastasizing).
• Malignant tumors’ rapid growth invades and damages surrounding tissues, competing for nutrients.
• Metastasis, the spread of cancer cells to distant sites via blood, is a defining characteristic of malignant tumors.

III. Causes of Cancer (Carcinogens):

• Cancer can be induced by physical, chemical, or biological agents.
• Physical carcinogens include ionizing (X-rays, gamma rays) and non-ionizing (UV) radiation causing DNA damage.
• Chemical carcinogens, such as those in tobacco smoke, are linked to cancers like lung cancer.
• Oncogenic viruses possess viral oncogenes that contribute to cancer development.
• Cellular oncogenes (proto-oncogenes) in normal cells can become activated, leading to oncogenic transformation.

IV. Cancer Detection and Diagnosis:

• Early detection is crucial for successful treatment.
• Methods include biopsy and histopathological studies of tissues.
• Blood and bone marrow tests are used to detect increased cell counts (leukemias).
• Radiography (X-rays), CT scans, and MRI are employed to detect internal organ cancers.
• Antibodies against cancer-specific antigens aid in detection.
• Molecular biology techniques identify genes linked to inherited cancer susceptibility, aiding prevention through informed carcinogen avoidance.

V. Cancer Treatment:

• Common approaches include surgery, radiation therapy, and immunotherapy.
• Radiotherapy uses irradiation to lethally target tumor cells while sparing surrounding tissues.
• Chemotherapy employs drugs to kill cancer cells, some specific to certain tumors, but often with side effects (hair loss, anemia).
• Combined treatments (surgery, radiotherapy, chemotherapy) are often used.
• Immunotherapy utilizes biological response modifiers (e.g., α-interferon) to activate the immune system and enhance tumor destruction, addressing the immune system evasion often displayed by tumor cells.