1. VITAMIN A The fat soluble vitamin A, as such is present only in foods of animal origin. However, its provitamins carotenes are found in plants. Hippocrates (about 500 B.C.) cured night blindness. Rx ox liver (in honey)

2. Chemistry RETINOL The term retinoids is often used to include the natural and synthetic forms of vitamin A Beta IONON ring

3. Retinol: A primary alcohol containing a β-ionone ring with an unsaturated side chain, retinol is found in animal tissues as a retinyl ester with long-chain fatty acids Retinal: This is the aldehyde derived from the oxidation of retinol. Retinal and retinol can readily be interconverted Retinal: This is the aldehyde derived from the oxidation of retinol. Retinal and retinol can readily be interconverted Retinoic acid: This is the acid derived from the oxidation of retinal. Retinoic acid cannot be reduced in the body, and, therefore, cannot give rise to either retinal or retinol Retinoic acid: This is the acid derived from the oxidation of retinal. Retinoic acid cannot be reduced in the body, and, therefore, cannot give rise to either retinal or retinol

4. DIETARY SOURCES The best sources are liver, kidney, egg yolk, milk, cheese, butter. Fish (cod or shark) liver oils are very rich in vitamin A. Animal sources contain (preformed) vitamin A.

5. Vegetable sources contain the provitamin A-carotenes Yellow and dark green vegetables and fruits are good sources of carotenes e.g., Yellow and dark green vegetables and fruits are good sources of carotenes e.g., carrots spinach pumpkins mango

6. ABSORPTION Transport & Storage OF VITAMIN A Retinyl Ester Retinol AND FFA

7. Intestinal Cell Beta Carotene RETINAL RETINOL FFA Retinyl Ester Chylomicron Retinyl Ester RETINOL Retinyl Ester Retinol AND FFA Retinyl Ester Di-oxygenase NADH or NADPH dependent retinalreductase

11. RODS AND CONES 10 Million Rods and 5 Million Cones Rods are involved in dim light vision whereas cones are responsible for bright light and colour vision.

13. Rhodopsin (mol. wt. 35,000) is a conjugated protein present in rods. lt contains11-cis retinal and the protein opsin. The aldehyde group (of retinal) is linked to e-amino group of lysine (of opsin). Rhodopsin (mol. wt. 35,000) is a conjugated protein present in rods. lt contains11-cis retinal and the protein opsin. The aldehyde group (of retinal) is linked to e-amino group of lysine (of opsin). Rhodopsin Bleaching of rhodopsin : When exposed to light, the colour of rhodopsin changes from red to yellow, by a process known as bleaching. Bleaching occurs in a few milliseconds and many unstable intermediates a re formed during this process. Bleaching of rhodopsin : When exposed to light, the colour of rhodopsin changes from red to yellow, by a process known as bleaching. Bleaching occurs in a few milliseconds and many unstable intermediates a re formed during this process.

16. Wald's Visual Cycle A. Generation of Nerve Impulse Wald was awarded Nobel Prize in 1967, for identifying the role of vitamin A in vision. Rhodopsin (mol. wt. 35,000 Daltons) plays the pivotal role in vision. Wald was awarded Nobel Prize in 1967, for identifying the role of vitamin A in vision. Rhodopsin (mol. wt. 35,000 Daltons) plays the pivotal role in vision. It is a membrane protein found in the photoreceptor cells of the retina. Rhodopsin is made up of the protein opsin and 11-cis-retinal

20. Dark adaptation time : For his work on dark adaptation, Torsten Wiesel was awarded Nobel prize in 1981. i. Bright light depletes stores of rhodopsin in rods. Therefore when a person shifts suddenly from bright light to a dimly light area, there is difficulty in seeing, for example, entering a cinema theater. After a few minutes, rhodopsin is resynthesized and vision is improved. This period is called dark adaptation time. However, within a few minutes, known as dark adaptation time, rhodopsin is resynthesized and vision is improved. Dark adaptation time is increased in vitamin A deficient individuals. Dark adaptation time : For his work on dark adaptation, Torsten Wiesel was awarded Nobel prize in 1981. i. Bright light depletes stores of rhodopsin in rods. Therefore when a person shifts suddenly from bright light to a dimly light area, there is difficulty in seeing, for example, entering a cinema theater. After a few minutes, rhodopsin is resynthesized and vision is improved. This period is called dark adaptation time. However, within a few minutes, known as dark adaptation time, rhodopsin is resynthesized and vision is improved. Dark adaptation time is increased in vitamin A deficient individuals.

21. Colour vision Color vision is the ability of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. The colour vision is governed by colour sensitive pigments Porphyropsin (red) Iodopsin (green) Cyanopsin (blue). All these pigments are retinalopsin complexes. When bright light strikes the retina, one or more of these pigments are bleached, depending on the particular colour of light. The colour vision is governed by colour sensitive pigments Porphyropsin (red) Iodopsin (green) Cyanopsin (blue). All these pigments are retinalopsin complexes. When bright light strikes the retina, one or more of these pigments are bleached, depending on the particular colour of light. Splitting of these three pigments in different proportions results in the perception of different colours by the brain Splitting of these three pigments in different proportions results in the perception of different colours by the brain

22. Other Biochemical Functions of Vitamin A  Retinoic acid has a role in the regulation of gene expression and differentiation of tissues. All-trans-retinoic acid and 9-cisretinoic acid act like steroid hormones Vitamin A function like steroid hormone

23. Retinol is necessary for the reproductive system. Retinol acts like a steroid hormone in controlling the expression of certain genes. This may account for the requirement of vitamin A for normal reproduction. In vitamin deficiency, miscarriages are noticed in female rats while atrophy of germinal epithelium and sterility are seen in male rats. Retinol acts like a steroid hormone in controlling the expression of certain genes. This may account for the requirement of vitamin A for normal reproduction. In vitamin deficiency, miscarriages are noticed in female rats while atrophy of germinal epithelium and sterility are seen in male rats. Anti-oxidant property: There is a correlation between the occurrence of epithelial cancers and vitamin A deficiency. The anticancer activity has been attributed to the natural antioxidant property of carotenoids. Anti-oxidant property :

24. Beta carotenes may be useful in preventing heart attacks. Those who were given beta carotene supplements suffered half as many heart attacks as in the group taking. Beta carotenes may be useful in preventing heart attacks. Those who were given beta carotene supplements suffered half as many heart attacks as in the group taking.

25. Vitamin A is necessary for the maintenance of normal epithelium and skin.

26.  Retinyl phosphate synthesized from retinol is necessary for the synthesis of certain glycoprotein which are required for growth and mucus secretion  Retinol and retinoic acid are involved in the synthesis of transferrin, the iron transport protein.  Vitamin A is considered to be essential for the maintenance of proper immune system to fight against various infections.  Retinyl phosphate synthesized from retinol is necessary for the synthesis of certain glycoprotein which are required for growth and mucus secretion  Retinol and retinoic acid are involved in the synthesis of transferrin, the iron transport protein.  Vitamin A is considered to be essential for the maintenance of proper immune system to fight against various infections.

27. ( Nyctalopia) is one of the earliest symptoms of vitamin A deficiency. The individuals have difficulty to see in dim light since the dark adaptation time is increased. Prolonged deficiency irreversibly damages a number of visual cells. Deficiency manifestations of Vitamin A

28. SEVERE DEFICIENCY OF VITAMIN A LEADS TO XEROPHTHALMIA XN = Night Blindness X1 = Conjunctival Xerosis (X1A) with Bitot spot (X1B) X2 = Corneal Xerosis X3 = Corneal Ulceration, less than one-third (X3A); more than one-third (X3B) XS = Corneal Scar XF = Xerophthalmic Fundus XN = Night Blindness X1 = Conjunctival Xerosis (X1A) with Bitot spot (X1B) X2 = Corneal Xerosis X3 = Corneal Ulceration, less than one-third (X3A); more than one-third (X3B) XS = Corneal Scar XF = Xerophthalmic Fundus

29. Conjuntival Xerosis Dirty white or slivery gray, foamy, triangular in shape patches seen in conjunctiva Bitot’s spots

30. Corneal xerosis Corneal ulceration

31. XF = xerophthalmic fundus

32. Preventable Blindness The deficiency of vitamin A is the most common cause of blindness in Indian children below the age of 5. One-third of the world's blind population are residing in India. About 40% of blindness is preventable. Vitamin A deficiency is a major public health problem. A single dose of vitamin A is given, as a prophylactic measure, to children below 1 year age. Preventable Blindness The deficiency of vitamin A is the most common cause of blindness in Indian children below the age of 5. One-third of the world's blind population are residing in India. About 40% of blindness is preventable. Vitamin A deficiency is a major public health problem. A single dose of vitamin A is given, as a prophylactic measure, to children below 1 year age.

33. 6. Skin and Mucous Membrane Lesions Follicular hyperkeratosis or phrynoderma results from hyperkeratinization of the epithelium lining the follicles. The skin becomes rough.

34. Keratinizing metaplasia of the epithelium of the respiratory, gastrointestinal and genitourinary tract have been observed. Epithelium is atrophied. Keratinization of urinary tract epithelium may lead to urinary calculi. Keratinizing metaplasia of the epithelium of the respiratory, gastrointestinal and genitourinary tract have been observed. Epithelium is atrophied. Keratinization of urinary tract epithelium may lead to urinary calculi. The alterations in skin may cause increased occurrence of generalized infections. The alterations in skin may cause increased occurrence of generalized infections.

35. i. Decreased intake. ii. Obstructive jaundice causing defective absorption. iii. Cirrhosis of liver leading to reduced synthesis of RBP. iv. Severe malnutrition, where amino acids are not available for RBP synthesis v. Chronic nephrosis, where RBP is excreted through urine. Causes for Vitamin A Deficiency

36. Daily Requirement of Vitamin A The recommended daily allowance (RDA) for The RDA of vitamin A for adults is around 1000 retinol equivalents( 3,500 lU) for man and 800 retinol equivalents (2,500 lU) for woman. i. Children = 400-600 microg/day. ii. Men = 750-1000 microg/day iii. Women = 750 microg/day iv. Pregnancy = 1000 microg/day One international unit = 0.3 mg of retinol. One retinol equivalent = 1 microgram of retinol or 6 microgram of beta carotene. = 3.33 lU of vitamin A activity from retinol Daily Requirement of Vitamin A The recommended daily allowance (RDA) for The RDA of vitamin A for adults is around 1000 retinol equivalents( 3,500 lU) for man and 800 retinol equivalents (2,500 lU) for woman. i. Children = 400-600 microg/day. ii. Men = 750-1000 microg/day iii. Women = 750 microg/day iv. Pregnancy = 1000 microg/day One international unit = 0.3 mg of retinol. One retinol equivalent = 1 microgram of retinol or 6 microgram of beta carotene. = 3.33 lU of vitamin A activity from retinol

37. Hypervitaminosis A or Toxicity Excessive intake can lead to toxicity since the vitamin is stored. It has been reported in children where parents have been overzealous in supplementing the vitamins.

38. Retinoid Cream for Acne Retino-A 0.025% or 0.05% are the types of tubes available, and contain the derivatives of vitamin A.

39. f) A 10 year old child in ophthalmology OPD was found to be suffering from xeropthalmia. i) Which vitamin deficiency is this ? ½ ii) What are the functions of this vitamin ?1 1 / 2 iii) Which are the other deficiency manifestations of this vitamin1 1 / 2 iv) Give RDA of this vitamin ½ f) A 10 year old child in ophthalmology OPD was found to be suffering from xeropthalmia. i) Which vitamin deficiency is this ? ½ ii) What are the functions of this vitamin ?1 1 / 2 iii) Which are the other deficiency manifestations of this vitamin1 1 / 2 iv) Give RDA of this vitamin ½