Vitamins Organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.
Types-There are 13 vitamins A, C, D, E, K, B12, and 7 grouped under the vitamin B complex.
Human body can synthesize vitamin B(niacin) and vitamin D on their own.
Vitamins are categorized into two groups;
1. Fat soluble Vitamins - A, D, E and K . Lipids such as triglycerides contain these vitamins, which are absorbed from the intestine into the bloodstream and then stored in fatty tissue such as liver.
2. Water soluble Vitamins - Vitamin C, B complex and B 12. only small amounts of Vitamin C and B complex are stored by the body and hence, regular intake of these vitamins is necessary.
Vitamin A Functions: normal growth, formation of bones and teeth, maintenance of night vision, and protecting the linings of the respiratory, digestive, and urinary tracts against infection.
Vitamin A is absorbed by the body in the form of retinol . Carotene, the precursor of retinol , is found in various vegetables(carrots) and fruits. Dietary sources: liver, fish-liver oils, egg yolk and dairy products. Deficiency diseases: Night blindness, Xerophthalmia, Keratomalacia , and complete blindness.
Excessive intake leads to loss of appetite, reduced resistance to infection, skin peeling, stunted growth, hair loss and irregular menstruation. Excessive intake during pregnancy may cause birth defects. In infants, excessive intake may cause skull deformities, which disappear if the diet is corrected.
Vitamin B12 (cyanocobalamin)
Functions: production of the genetic material, production of red blood cells in bone marrow, utilization of folic acid and carbohydrates in the diet, and functioning of the nervous system.
Dietary sources: liver, kidney, chicken, pork, fish, eggs, and dairy
Vitamin B complex
products.
Deficiency diseases: Megaloblastic anaemia , sore mouth and tongue, numbness and tingling in the limbs, depression and memory loss. High intake of vitamin B12 has no known harmful effects.
1. Thiamine(vitamin B1)(Aneurin)
Functions: Essential for various enzymes involved in the utilization of carbohydrates, functioning of nerves, muscles, and the heart.
Dietary sources: whole-grain cereals, wholemeal breads, brown rice, pasta, liver, kidney, pork, fish, beans, nuts, and eggs.
Mild deficiency results in tiredness, irritability, and loss of appetite. Severe deficiency causes abdominal pain, constipation, depression, memory impairment, and beriberi .
In alcoholics, it causes Wernicke–Korsakoff syndrome , which leads to loss of memory for recent events although long term memory is intact.
Vitamin B1 is lost in polished rice.
2. Riboflavin(vitamin B2)
Functions: necessary for enzymes involved in the breakdown and utilization of carbohydrates, fats, and proteins; the production of energy in cells; the utilization of other B vitamins; and hormone production by the adrenal glands.
Dietary sources: Liver, whole grains, milk, eggs, and brewer’s yeast. Deficiency disorders: soreness in and around tongue and mouth, eye disorders such as amblyopia and photophobia.
3. Niacin(Nicotinic acid)
Functions: needed by enzymes involved in the metabolism of carbohydrates and fats, the functioning of the nervous and digestive systems, the manufacture of sex hormones, and the maintenance of healthy skin.
Dietary sources: liver, lean meat, fish, nuts, and dried beans.
Deficiency disorders: Pellagra - causes gastrointestinal disturbances and erythema, dermatitis, diarrhoea, and nervous or mental disorders. Pellagra is often linked to over-dependence on maize as a staple food.
4. Pantothenic acid
Functions: essential for the enzymes involved in metabolism of carbohydrates and fats, manufacture of corticosteroids and sex hormones, utilization of other vitamins, functioning of the Ascorbic acid
nervous system and adrenal glands, and growth and development. Dietary sources: vegetables, cereals, and animal foods.
Deficiency leads to fatigue, headache, nausea, abdominal pain,
numbness and tingling, muscle cramps, and susceptibility to respiratory infections. Prolonged deficiency leads to peptic ulcer .
5. Pyridoxine(vitamin B6)
Functions: needed by enzymes and hormones involved in the utilization of carbohydrates, fats, and proteins, manufacture of red blood cells and antibodies, functioning of the digestive and nervous systems, and maintenance of healthy skin.
Dietary sources: liver, chicken, pork, fish, whole grains, wheat germ, bananas, potatoes, and dried beans.
Pyridoxine is also synthesised by intestinal bacteria.
Deficiency may cause weakness, irritability, depression, skin disorders, inflammation of the mouth and tongue, anaemia, and, in infants, seizures. In very large amounts, pyridoxine may cause neuritis .
6. Biotin(vitamin H)
Functions: essential for enzymes involved in the breakdown of fatty acids and carbohydrates and for the excretion of the waste products of protein breakdown.
Dietary sources: liver, peanuts, dried beans, egg yolk, mushrooms, bananas, grapefruit, and watermelon.
Biotin is also synthesised by intestinal bacteria.
Deficiency causes weakness, tiredness, poor appetite, hair loss, depression, inflammation of the tongue, enteritis and eczema.
7. Folic acid
Functions: necessary for enzymes involved in the manufacture of nucleic acids and consequently for growth and
reproduction, production of red blood cells, and functioning of the nervous system.
Dietary sources: green vegetables, mushrooms, liver, nuts, dried beans, peas, egg yolk, and wholemeal bread.
Deficiency disorders: anaemia , sores around the mouth, and, in children, poor growth.
Severe deficiency may occur during pregnancy or breastfeeding.
Functions: growth and maintenance of healthy bones, teeth, gums, ligaments, and blood vessels; production of certain neurotransmitters and adrenal gland hormones; immunity against infection and wound healing and absorption of iron.
Dietary sources: citrus fruits and vegetables.
Mild deficiency leads to weakness, general aches, swollen gums, and nosebleeds.
Serious deficiency leads to scurvy and anaemia . Excessive consumption forms kidney stones(calculi).
Vitamin C is lost when foods are processed, cooked, or kept warm.
Vitamin D Vitamin D2 - Calciferol
Vitamin D3 - Cholecalciferol
Function: regulates the balance of phosphate and calcium in the body, aids calcium absorption in the intestine, and promote strong bones and teeth.
Dietary sources: oily fish, liver, and egg yolk.
Vitamin D is synthesized by the action of ultraviolet light on a particular chemical in the skin.
Deficiency leads to: rickets in children; long-term deficiency in adults leads to osteomalacia .
Excessive intake of vitamin D may lead to hypercalcaemia and abnormal calcium deposits in the soft tissues, kidneys, and blood vessel walls. In children, it may cause growth retardation.
Vitamin E
Tocopherol
Functions: essential for normal reproduction, maintaining the activities of certain enzymes and formation of red blood cells.
Vitamin E also protects the lungs and other tissues from damage by pollutants and slows aging of cells by neutralizing free radicals. Dietary sources include vegetable oils, nuts, meat, green vegetables, cereals, and egg yolk.
Deficiency leads to anaemia.
Vitamin K Functions: aids in formation of substances that promote blood clotting.
Dietary sources: green vegetables, vegetable oils, egg yolk, cheese, pork, and liver.
Vitamin K is also synthesised by intestinal bacteria.
Deficiency leads to nosebleeds and bleeding from the gums, intestine, and urinary tract. Severe cases lead to brain haemorrhage.
Vitamin P Bioflavonoid(citrin)
Regulates the permeability of the capillary walls, found in citrus fruit, blackcurrants and rosehips.
Other facts Vitamin was first discovered by F.G. Hopkins but the term 'vitamin' was coined by Casimir Funk. Vitamin F is obsolete.
Vitamin G is another name for Vitamin B2.
Vitamin B complex was formerly regarded as single vitamin.
Medical
preparations
Scientific
innovations
Vitamin D - used to treat osteomalacia. Vitamin A - used to treat severe acne.
Golden rice - variety of rice (Oryza sativa) produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A , in the edible parts of rice.
In 2005, a new variety called Golden Rice 2 , which produces up to 23 times more beta-carotene than the original golden rice, was announced. Although golden rice was developed as a humanitarian tool, it has met with significant opposition from environmental and anti-globalization activists.
Proteins
A protein is a biologically functional molecule made up of polymers of amino acids. Proteins may also contain sugars (glycoproteins) and lipids (lipoproteins).
Proteins are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies. Proteins account for more than 50% of the dry mass of most cells.
Types There are 2 main types of proteins.
Fibrous proteins - insoluble form of proteins which form the structural basis of many body tissues.
Globular proteins - soluble form of proteins which include all enzymes, hormones, etc…
Based on function, proteins are classified into 8 groups: Enzymes - act as catalysts in biochemical reactions. e.g. Digestive enzymes.
Receptors - these proteins mediate between a chemical agent that acts on nervous tissue and the physiological response. All organs having nerve endings, which respond to stimuli with the help of receptors.
Hormones - These are regulatory proteins which control the physiological processes such as growth and development, metabolic rates(insulin) etc… Defensive proteins - These are components of immune system which protect the organism from external agents such as virus and bacteria. e.g. antibodies
Transport proteins - these are special type of proteins capable of transporting substances throughout the circulatory system. e.g. Haemoglobin carries oxygen, lipoprotein carries lipids etc…
Structural proteins - These proteins form a structural part of organism and provide protection along with response and stimuli against external agents.
e.g. Keratin(hair, horns, feathers), connective tissues(Collagen, elastin) etc…
Storage proteins - Proteins stored for consumption of offspring. e.g. protein in eggs(albumin), milk(casein), seeds etc…
Contractile and motor proteins - These proteins are essential for locomotion. e.g. Actin and myosin.
Metabolism Before absorption, proteins are broken down into their constituent amino
acids. In the absence of carbohydrates, proteins are consumed for energy. Human body requires a mixture of eight amino acids to maintain nitrogenous equilibrium. These amino acids are also known as
essential(indispensable) amino acids. These include isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In addition, infants require histidine.
Dietary sources
Deficiency diseases
Meat, nuts, legumes, egg, milk etc…
Marasmus:
Cause: malnutrition or semi-starvation conditions. It normally affects the children below 3 years.
Effects: stunted growth, emaciation, brittle hair, dehydration and loose folds of skin on the limbs and buttocks due to loss of muscle and fat. Persistent marasmus can cause mental handicap and impaired growth. Treatment: providing a high-energy, protein rich diet.
Kwashiorkor: It is one of the most important causes of ill health and death among children in the tropics. It affects typically the small child weaned from the breast and not yet able to cope with an adult diet, or for whom an adequate amount of first-class protein is not available. Cause: malnutrition.
Effects: stunted growth and a puffy appearance due to oedema, enlargement of liver, dehydration, and the child loses resistance to infection, which may have fatal consequences. The more advanced stages are marked by jaundice, drowsiness, and a fall in body temperature.
Treatment: Child is kept warm and frequently fed with first-class proteins such as small amounts of milk, and vitamin and mineral tablets. A
nutritious diet is then gradually introduced. Most treated children recover, but those less than 2 years old may suffer from permanently stunted growth.
Lipids
Lipids are organic compounds insoluble in water but soluble in organic solvents. Lipids form essential structural component of living cells. Biologically important lipids include fats, phospholipids, and steroids.
Fats in human beings are a form of body tissue that serves as a source of energy. It also function as cushion and insulates vital organs. Each gram of fat can produce 9·3 Calories. An enzyme called lipase secreted in the digestive tract, catalyses the breakdown of fats into individual fatty acids before they are absorbed into the bloodstream.
Composition Fats are made up of two types of molecules namely, glycerol and fatty acids.
Fats are hydrophobic due to the nonpolar nature of C-H bonds in fatty acids.
Types Fats are divided into 2 main groups, saturated and unsaturated, depending on the proportion of hydrogen atoms. Saturated fats:
Fatty acids whose carbon chain cannot absorb any more hydrogen atoms are called saturated fatty acids.
Animal fats are saturated fats. Excessive consumption of these fats is not good for health.
Unsaturated fats:
A fatty acid whose carbon chain can absorb additional hydrogen atoms are called unsaturated fatty acids.
Unsaturated Fats are abundant in fish and vegetable oils such as soya, bean, maize, sunflower etc…
Monounsaturated fatty acids(MUFA) are unsaturated fats with only one vacant site in carbon chain that could take an extra hydrogen.
Poly Unsaturated Fatty Acids(PUFA): fatty acid whose carbon chain can absorb relatively high number of additional hydrogen atoms are called polyunsaturated fats.
Essential fatty acids: Essential fatty acids are a form of unsaturated fatty acids, which our body cannot synthesise on its own . e.g. linoleic acid, linolenic acid, omega-3 fatty acids etc..
Diseases
Atherosclerosis : Major cause of heart strokes and high blood pressures.caused by fats Cause: excessive consumption of saturated fats.
Formation: fatty deposits inside the arterial walls narrows the arteries and impede the blood flow.
FAQ What is body fat?
Fat stored beneath the skin and around various internal organs to serve as a source of energy and provide insulation to vital organs are called body fats or Adipose tissue. Excessive accumulation of adipose tissue as a result of eating more food than is metabolized by exercise and the body’s basic energy needs leads to obesity.
Why fats doesn't mix with water?
Fats separate from water because the hydrogen in water molecules bond with each other and exclude the fats. What are hydrogenated vegetable oils?
Hydrogenated vegetable oils are unsaturated fatty acids synthetically converted to saturated fats by adding hydrogen to prevent them from becoming rancid.
What are trans-fats?
As a result of hydrogenation, unsaturated fatty acids form trans arrangement of the carbon atoms adjacent to its double bonds. Trans fats contribute more to atherosclerosis(cardiovascular disease) by increasing the ratio of LDL to HDL.
Carbohydrates
Carbohydrates Essential structural components of living cells and source of energy for animals. Carbohydrates are essential in formation of amino acids and fatty acids.
Composition Carbohydrates are composed of Carbon, Hydrogen and Oxygen.
Hydrogen and Oxygen are composed in the same ratio as water(2:1).
Types Carbohydrates are broadly classified into two groups, 1. Monosaccharides(Simple carbohydrates or simple sugars) with small molecules. Major monosaccharides:
Sugar Source
Glucose Occurs naturally in several forms in many food
sources. e.g. dextrose.
Galactose Milk .
Fructose Found in honey and in many ripe fruits.
Glucose is absorbed directly by the body, without any breakdown. Galactose and fructose are converted into glucose by liver, before their utilization by body cells.
Surplus glucose is converted and stored in the form of glycogen and fat by liver, muscles, and fat cells.
Hydrolysis breaks glycogen to form glucose monomers.
2. Polysaccharides(Complex carbohydrates or Starches) are polymers formed by combination of monosaccharides through covalent bonds. Polysaccharides are insoluble in water.
Polysaccharides either serve as storage material(glycogen) or forms building material(cellulose, chitin etc..) for organisms' structures. Oligosaccharides: carbohydrates containing between two and ten monosaccharide units linked together.
Disaccharides(double sugars) - formed by combination of two monosaccharides joined by a covalent bond. Major disaccharides:
Dietary sources
Disaccharide Source
Sucrose Cane, Beet and many other plants.
Maltose Formed by the action of malt or diastase on starch.
Lactose One glucose molecule linked to a galactose molecule. Found only in milk.
These complex sugars are broken down into simple sugars before their absorption.
Fruits, cereals and all starch foods.
Composition of elements in human body
Essential elements:
Element Characteristics % of
Body mass
Oxygen Oxygen is essential for life. It is absorbed by the lungs and ransported by haemoglobin within the erythrocytes to the tissues. Within the individual cell it is involved in the production of adenosine triphosphate(ATP) , a compound that stores chemical energy for muscle cells, by the oxidative metabolism of fats and carbohydrates.
Hypoxia causes anaerobic metabolism with a resulting build-up in Lactic acid, the result of muscle cell activity. If severe enough, the lack of ATP causes a breakdown in cellular function and the death of the individual.
Indications for oxygen therapy include high altitude, heart failure, anaemia, pulmonary hypertension, carbon monoxide poisoning, anaesthesia and post-operative recovery.
Carbon Carbon forms an essential part in all compounds found in living tissues.
Two isotopes of carbon, C11 and C14, are used in medicine. Carbon-11 is used in positron-emission tomography(PET). Carbon-14 is used as a tracer element in studying various aspects of metabolism.
Hydrogen Universal element present in most of the organic compounds.
Nitrogen Essential for all organic compounds involving amino
65.0%
18.5%
9.5%
3.3%
functional group. Especially amino acids which are essential in formation of protein.
Trace elements:
Element Characteristics % of
Body mass
Calcium It is the most abundant mineral in human body.
1.5%
Calcium is essential for cell function, muscle contraction, the transmission of nerve impulses, and blood clotting. Calcium is especially needed by the growing child and the pregnant and nursing mother. The uptake of calcium by the baby is helped by vitamin D.
Chief sources of calcium are dairy products, eggs, and green, leafy vegetables.
Hypocalcaemia: Tetany - Clinical neurological syndrome characterized by muscular twitching and cramps and (when severe) seizures.
Hypercalcaeima: Calculi(stones) in the kidneys or gallbladder.
Recommended daily intake:
500 mg for children.
700 mg for adolescents.
500–900 mg for adults and
1,200 mg for pregnant or nursing mothers.
Medicinal preparations: Calcium carbonate(chalk)
Calcium chloride - used as dehydrating agent.
Calcium gluconate - used to prepare calcium injections. Calcium hydroxide(slaked lime)
Liquor of calcium hydroxide (lime-water)
Calcium lactate - used as supplementary calcium. Calcium phosphate
Chlorine 0.2%
Magnesium Magnesium is essential for formation of bones and teeth,
0.1%
muscle contraction, nerve impulse transmission, and activation of many enzymes. The adult body contains around 25 grams of magnesium, the greater part of which is in the bones.
Dietary sources include cereals, nuts, soya beans, milk, and fish. More than two-thirds of our daily supply comes from cereals and vegetables.
Antibiotics
Antibiotics Literally antibiotics are chemical substances extracted from a mould or bacterium that can kill or inhibit the growth of microorganisms. Antibiotics - substances from one microorganism that can kill or inhibit the growth of another microorganism.
Semisynthetic antibiotics - antibiotic substances derived from a substance produced by a microorganism.
First
antibiotic
Drug
mechanism
Penicillin(derived from the mould Penicillium notatum). Discovered by: Sir Alexander Fleming in 1928.
Antibiotics destroy the cell wall, inhibits protein and nucleic acid synthesis and synthesis of other essential metabolites. Antibiotics,
such as penicillin and its derivatives, prevent the synthesis of bacterial cell wall called peptidoglycan.
Since gram-positive cells are composed of more peptidoglycan, these antibiotics are most effective against gram-positive bacteria.
Types Narrow spectrum antibiotics:
Antibiotics capable of working on limited types of bacteria, such as penicillin are called narrow spectrum antibiotics. Wide spectrum antibiotics:
Antibiotics that work on many types of bacteria by preventing cell wall synthesis, without affecting the host cells are called wide spectrum antibiotics. These include cephalosporins, bacitracin, isoniazid, and vancomycin.
Inhibitors of protein synthesis:
Antibiotics that work on many types of bacteria by interfering with ribosome function such as chloramphenicol, erythromycin, tetracycline, streptomycin, and gentamicin. Inhibitors of nucleic acid synthesis:
Antibiotics that inhibit nucleic acid synthesis either interfere with DNA replication or transcription, may also harm the host. Some of the DNA replication inhibiting antibiotics include Rifampin, quinolones , nalidixic acid, nofloxacin, and ciprofloxacin. Competitive inhibitor antibiotics such as Sulfanilamide , a sulfa drug , mimics the structure of Para Amino Benzoic Acid(PABA) and competes to bind with the enzyme that normally binds PABA, inhibiting the synthesis of folic acid.
Humans are not affected, since, humans obtain folic acid through diet rather than synthesizing it.
Important antibiotics
Bacitracin Effective against several types of Gram-positive organisms.
Cephalosporins Broad spectrum antibiotics.
Chloramphenicol Used against serious infections such as typhoid fever.
Ciprofloxacin Used against anthrax infections.(Tradename: Cipro)
Erythromycin Used to treat infections caused by gram positive bacteria.
Gentamicin Used to treat urinary tract infections.
Isoniazid Used to treat tuberculosis
Penicillin Used in the treatment of various infections.
Quinolones Used against gram negative organisms
Rifampin Used to treat tuberculosis.
Streptomycin Used to treat Tuberculosis
Sulfa drugs Used to inhibit the growth of bacteria that require PABA.
Tetracycline Used to treat infections.
Vancomycin Used against resistant strains of streptococcus and staphylococcus.
Algae
Algae Aquatic photosynthetic eukaryotic organisms.
Kingdom Protista
Characteristics Cell structure: Eukaryotic. Categories: Algae are grouped into seven categories.
Phototrophic: uses energy from sunlight to synthesize organic compounds for nutrition.
Pigments: Chlorophyll a, Chlorophyll b, Chlorophyll c, Carotenoids(β- carotene), Phycobilins and other accessory pigments that absorb light of different wavelengths. Reproduction:
Asexual reproduction: some employ mitosis, while others undergo fragmentation of cells from colonies or from multicellular aggregates or by produce spores that develop into mature organisms.
Sexual reproduction: involves meiosis, they produce haploid gametes that combine to form diploid zygotes, a process that results in greater genetic variation.
Important Algae types
Golden algae: contains Chlorophyll c and carotenoid called fucoxanthin that give them a yellowish brown color.
Fire algae: consists of the dinoflagellates, unicellular algae that also possess chlorophyll c. This algae have capability to produce oil droplets , but also store energy as starch. Dinoflagellates are known for their tendency to form algal blooms.
Yellow green Algae(Xanthophyta): They are unicellular and contain chlorophyll c.
Red algae: Phycobilins a form of photosynthetic pigments can capture green and blue light that penetrates deep into the water, allowing the red algae to survive at greater depths than other algae. Some red algae have cell walls made of calcium carbonate and play a role in building coral reefs.
Brown and red algae together constitute seaweed. Some brown algae can reach up to 100 feet in length.
Niche Aquatic system: Plays the prominent role as primary
producers.
Ecological
Significance
Ecosystem: They produce most of the planet’s oxygen.
Human food chain: Major source of iodine and protein for many
human societies.
Imbalances Sudden increase in nutrients leads to overgrowth of algae in
waterbodies (eutrophication) and disturbs the food webs.
Increased decomposition of algae results in overconsumption of oxygen in the waterbodies, resulting in the death of
other microorganisms in the ecosystem and increase in BOD. Red tide: A phenomenon of discoloration of seawater caused by a bloom of toxic red dinoflagellates called Gymnodinium breve . During the spring and fall, the waters of the shores of the Pacific, Gulf Coast, and New England states churn, carrying an abundance of nutrients to the surface. These conditions allow Gymnodinium breve to thrive, giving the water a reddish appearance. The algae secrete products that are toxic to fish and other marine organisms and that concentrate in shellfish. Though the toxin is harmless to shellfish, it can be harmful to humans who ingest it, causing neuromuscular problems such as numbness.
Economic significance
Algae Benefits
Gelidium and Gracilaria
Important sources of agar , a substance that microbiologists use to thicken culture
media and also to produce the gelatin capsules that contain drugs or vitamins.
Purple seaweed Produces Carrageen , a substance used in food production, cosmetics, and pharmaceutical industries.
Red and Brown algae
Used as food source. Kelps(brown algae) - a good source of Iodine . Also produces algin , a gelling agent used in many foods such as ice cream and in substances such as toothpaste. Seaweeds also contain many vitamins and minerals.
Acquired Immuno Deficiency Syndrome |: AIDS
AIDS Acquired Immuno Deficiency Syndrome
First reported 1981
Etiology AIDS is caused by the retrovirus called Human
Immunodeficiency Virus(HIV) of Lentivirus family. There are two genetic but antigenically different variants of HIV noted among AIDS patients.
1. HIV-1 - commonly found in U.S., Europe, and Central Africa.
2. HIV-2 - commonly found in West Africa. AIDS also occur in other species such as
1. Felines or cats - Feline Immunodeficiency Virus(FIV) of Lentivirus family.
2. Monkeys - Simian Immunodeficiency Virus(SIV) of Lentivirus
family.
Epidemiology HIV transmission occurs broadly through exchange of blood or body
fluids contaminated by the virus or virus-infected cells.
Sexual transmission is responsible for more than 75% of all cases of HIV transmission and especially heterosexual transmission
accounts for most infections. Transmission among intravenous drug abusers occurs through shared needles, syringes etc… contaminated with HIV. About 1% of all AIDS cases in infants results from vertical transmission of virus from infected mother to the fetus or newborn. Mother-to-infant vertical transmission occurs in three modes
1. In utero - through placental infection 2. Intrapartum - during delivery and 3. Breast feeding.
HIV cannot transmit through normal day-to-day personal contacts and there is no evidence of infection through insect bites.
Structure of HIV
HIV-1 virion is spherical in shape. The virus core contains:
1. Capsid protein p24
2. Nucleocapsid protein p7/p9
3. Two copies of genomic RNA and
4. Three viral enzymes(protease, reverse transcriptase, and
integrase).
Capsid protein or p24 is the most readily detected viral antigen and is therefore the target for the antibodies used to diagnose HIV infection in blood screening. Extreme variability in antigen structure poses a formidable barrier for vaccine development.
Symptoms Initial stage symptoms include fever, headache, sore throat, and
swollen lymph nodes.
Symptoms post clinical latency include swollen lymph nodes, fever, diarrhea, weight loss, and fatigue.
Pathogenesis HIV is a retrovirus , which has the ability to reproduce by
synthesizing DNA from the RNA genome . It mainly infects immune system and CNS.
Infection and progression of virus occurs through following stages,
1. The retrovirus inserts the synthesized DNA into a host chromosome.
2. The enzyme called reverse transcriptase in the capsid reads the RNA template and synthesize the DNA from it.
3. After the penetration of virus into the host cell, the genome gets converted into DNA.
4. This DNA enters into the host genome and reside dormant for a long time.
5. Future stimulation of immune system by an unknown cause activates the replication of virus.
6. Newly assembled virions(a complete virus particles) are released which subsequently affect other cells and destroys the T cells having CD4 receptors.
7. B and T lymphocytes attack and destroy the virus from circulation, but the virus persists in the lymph nodes.
8. Virus replicates at a faster rate than the body can replenish its T cells and infects other immune system components such as monocytes, macrophages, and B cells but does not kill these cells, so they serve as an additional and continual source of new virions.
9. The person gradually loses the ability to fight infections and begins to develop opportunistic infections (Diseases caused by a microorganism that is pervasive in the environment and to which people are generally resistant, but that affects someone
an impaired immune system).
10. When CD4 T cell count reduces to less than 200 per cubic millimeter of blood(normal range is between 500 and 1,800), common opportunistic infections such as toxoplasmosis, histoplasmosis, Pneumocystis pneumonia, cervical cancer, herpes, hepatitis C, candidiasis, bacterial diarrheas, and tuberculosis attacks easily.
11. Successive suppression and inactivity of immune system leads to the proliferation of diseases and gradual deterioration of the body.
Diagnosis Two types of diagnosis are common, which includes screening a blood sample for the presence of antibodies against the virus.
1. Enzyme-Linked ImmunoSorbent Assay(ELISA) - detects antibodies specific for viral proteins . The test takes a few weeks to get results. The production of a detectable level of antibodies by the specific immune system can take up to eight weeks after the initial exposure to the virus, so this test is not much accurate when performed immediately after infection. 2. Western Blot Analysis - detects the presence of HIV proteins in the blood and is used toconfirm a positive antibody screen result. Results from these tests can be obtained within 20 minutes.
Treatments There is no cure for AIDS. The drugs are expensive and causes serious side effects. All contemporary drugs can either slow or stop viral replication but cannot inactivate all viral particles, which makes eradication impossible.
Also the problem of the rapid mutation rate exacerbates the situation to formulate a vaccine for the virus.
Antiviral therapy effectively reduces mother-to-child transmission, but only 5 percent of women receive this therapy.
Drugs Reverse transcriptase inhibitors:
Reverse transcriptase inhibitor drugs work by inhibiting the enzyme and halting the life cycle of the virus.
e.g. Azidothymidine(AZT) was the first drug approved for treating HIV infection. Protease inhibitors:
Protease inhibitor drugs work by interfering with a viral protein called HIV protease. Without this protein the viral particles cannot assemble properly and become inert.
Fusion inhibitors inhibit the viruses from fusing with the host cell membranes and stops the replication of virus.
e.g. Selzentry a drug that works by blocking a receptor CCR5 , that the virus often uses to gain entry into the host’s white blood cells. Highly Active Antiretroviral Therapy(HAART) uses Cocktail drugs( a combination of three or more drugs with different mechanisms of action) to overcome potential resistance. HIV mutates very rapidly and quickly becomes resistant to a once-effective drug.
Statistics Around 95% of HIV infections are recorded in developing countries.
AIDS is the fifth major cause of death in adults between the ages of 25 and 44.
Africa alone carries more than 50% of the HIV patients.
Around 90 percent of the children infected with HIV belong to sub-Saharan Africa.
Liable factors.Injected drug use.
Commercial prostitution.
Refusal of men to wear a condom during sex. Forced sex.
Extramarital sex affairs.
Govt. Schemes Govt. has setup State AIDS bodies in 25 states and 7 union territories in 1992.
India’s first National AIDS Control Programme NACP-I was launched in 1992 National AIDS Control Organization (NACO) was put into operation.
The National AIDS Committee was formed in the Ministry of Health and Family Welfare.
Helpful information. Indications for oxygen therapy include hypoxemia, increased working of breathing, and hemodynamic insufficiency. Thanks for sharing
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