Term
What is generic descriptor of Vit A |
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Definition
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Term
Retinoids exhibit biological activity for retinOL or retinAL? |
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Definition
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Term
Beta-ionine ring, isopreponoid units and conjugated double bond system are characteristics of what vitamin? |
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Definition
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Term
Which three types of forms of does vit A come in? |
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Definition
Retinoid, Precursors or provitamins, synthetic form |
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Term
What are examples of retinoids and their chemical formula? |
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Definition
- all trans- retiNOL (R- CH2OH) - RetiNAl (R-CHO) - Retinoic Acid ( R-COOH) |
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Term
Parent compounds have all cis or all trans configuration? |
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Definition
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Term
What are examples of precursors or provitamins? |
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Definition
- β-carotene - other carotenoids |
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Term
What is Tretinoin and what is it used for? |
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Definition
Tretinoin is all –trans retinoic acid used to treat PSORASIS (skin condition that causes skin redness and irritation) and APL (acute promyelocytic leukemia) |
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Term
What is Etretinate or Accutane and what is it used for? |
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Definition
It is a 13- cis retinoic acid used to treat ACNE |
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Term
What carotenoids are MOST prevalent in diet? (six) |
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Definition
alpha carotene beta carotene Lycopene Lutein Zeaxanthin beta-cryptozanthin |
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Term
Which carotenoids are Provitamin A carotenoids? (3) |
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Definition
a-carotene b-carotene b-cryptoxanthin |
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Term
Natural occurring are carotenoids in which form? |
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Definition
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Term
What is dietary source of beta carotene? |
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Definition
- green leafy vegetables, carrots, red palm oil. Fruits: peaches, apricots, mango, papaya - yellow orange veggies: sweet potato, squash, cassava - High carotenoid rice |
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Term
What are dietary sources of alpha carotene? |
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Definition
- green leafy vegetables, carrots, red palm oil. Fruits: peaches, apricots, mango, papaya - yellow orange veggies: sweet potato, squash, cassava - High carotenoid rice |
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Term
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Definition
Green leafy vegetables, peas, pepper, egg yolk |
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Term
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Definition
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Term
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Definition
tomato, watermelon, pink grapefruit |
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Term
In the conversion of beta carotene to retiNOL,what enzymes are present and their function? |
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Definition
Cleavage enzyme: 15,15- dioxygenase (in cytosol of mucosal cells- intestines)
Reduction enzyme: retinaldehyde reductase |
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Term
15,15 dioxygenase and retinaldehyde reductase are involved in which reaction? |
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Definition
Conversion of beta carotene to retoNOL |
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Term
1 μg retoNOL= how many IU |
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Definition
3.33 IU vit A from retinol |
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Term
1 RE = how many μg of all trans retinol? |
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Definition
1 RE = 1 μg of all trans retinol |
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Term
1 RE = how many μg of beta carotene? |
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Definition
1 RE= 6 μg of beta carotene |
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Term
1 RE = how many μg of other provitamin A carotenoids? |
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Definition
1 RE = 12 μg of other provitamin carotenoids |
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Term
1 RAE = ___ μg all trans retinol |
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Definition
1 RAE = 1 μg all trans retinol |
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Term
1 RAE= ____ μg of all trans beta carotene in OIL |
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Definition
1 RAE = 2 μg of all trans beta carotene in OIL |
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Term
1 RAE= ____ μg of FOOD BASED all trans beta carotene |
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Definition
1 RAE = 12 μg of FOOD BASED all trans beta carotene |
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Term
1 RAE = ___ μg of other food based pro vitamin A carotenoids |
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Definition
1 RAE= 24 μg of other food based pro vitamin A carotenoids |
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Term
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Definition
1 μg all trans retinol 6 μg beta carotene 12 μg of other provitamin A carotenoids 1-6-12 |
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Term
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Definition
1 μg all trans 2 μg all trans beta carotene in OIL 12 μg FOOD BASED all trans beta carotene 24 μg of other food based PROVITAMIN A carotenoids
1-2-12-24 |
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Term
The RDA vit A for Male is? |
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Definition
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Term
The RDA Vit A for Female is? |
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Definition
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Term
Daily value for Vit A is? |
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Definition
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Term
10 IU of beta carotene =____ IU retinol |
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Definition
10 IU of beta carotene = 3.33 IU of retinol |
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Term
When converting from IU beta carotene from fruits to vegetables to μg RAE, IU is divided by ___? (page 7 notes) |
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Definition
IU is divided by 20 (2x10) |
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Term
Compare Preformed vit A (retiNOL) with provitamin A? |
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Definition
Preformed: - animal food as retinol and retinyl ester - toxic - highly absorptive (70-90%)
Provitamin A: - plant food as beta carotene and other carotenoids - limited conversion to vit A - carotenodermia is benign - low absorptive efficiency |
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Term
What are some of the chemical properties of retinoids? |
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Definition
Color: light yellow to redding - soluble in organic solvents - sensitive to oxidation, isomerization and polymerization by light, oxygen, and high temperatures - stable in crystalline form and as an OIL stored in dark, cool place - characteristics UV absorption spectrum |
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Term
What is REH and what role does it play in metabolism of retinoids? |
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Definition
REH is Retinyl Ester Hydrolase, it is found in pancreatic juices and it hydrolyzes retinyl esters |
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Term
Which enzymes are required to release proteins from vit A? |
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Definition
Release from protein requires PEPSIN and PROTEOLYTIC enzymes |
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Term
Which complex carries retinoids to different parts of the body? |
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Definition
TTR RBP 1:1 ratio (transthyretin or prealbumin) binds thyroxin |
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Term
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Definition
Re-esterification of retinol LRAT (lecithing: retinol acyl transferase) |
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Term
Once retinol is re-esterified, it gets packaged into chylomicrons. T or F |
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Definition
True. its called Chylo RE (p 10) |
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Term
How are Chylo RE carried to the liver? |
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Definition
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Term
How are Chylo RE taken up by the liver? |
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Definition
Chylo RE taken up by the liver in association with chylomicron remnant by RECEPTOR-MEDIATED ENDYCYTOSIS |
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Term
Where does hydrolysis and esterification of retinoids occur? |
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Definition
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Term
What are two (2) esterificaton enzymes for retinoids and give brief description. |
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Definition
1. LRAT - uses ACYL groups from phosphotidylcholine - high affinity - involves retinol complexed to CRBP II 2. ARAT - uses acyl groups from CoA - low affinity - non specific binding |
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Term
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Definition
LRAT: lecithin - esterification enzyme - uses ACYL groups from phosphotidylcholine - high affinity - involves retinol complexed to CRBP II |
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Term
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Definition
ARAT - esterification enzyme - uses acyl groups from CoA - low affinity - non specific binding |
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Term
ARAT vs LRAT a. Which one is high affinity enzyme? b. Which one uses acyl group from CoA? c. Which one envolves renitol complexed to CRBP II? |
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Definition
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Term
Where is most (50-85 %) of Vit A stored? In what form? |
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Definition
Mostly as RE stored in LIVER hepatic stellate cells |
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Term
Vit A is excreted in bile but only after _______ and _______ ? |
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Definition
hydroxylation and glucoronidation |
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Term
Vit A is excreted in bile but only after _______ and _______ ? |
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Definition
hydroxylation and glucoronidation |
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Term
Vit A is excreted in bile but only after _______ and _______ ? |
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Definition
hydroxylation and glucoronidation |
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Term
Where is apo-retinol binding protein (apo- RBP) synthesized and what does it combine with to form a 1:1 complex? |
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Definition
apo-RBP is synthesized by hepatocytes and apo RBP combines with retinOL to form 1:1 complex called holo-RBP |
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Term
Draw diagram of transport and cellular metabolism in intestine, liver and target organs (VIt A) (p 10) |
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Definition
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Term
Where is RBP- TTR complex formed? |
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Definition
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Term
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Definition
Transthyretin is a tetrameric protein whihc strongly binds four thyroxine molecules |
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Term
What is RBP (retinold binding protein) function in plasma? |
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Definition
to solubilize retinol and deliver it to cells |
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Term
Which protein limit "free" retinoid? |
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Definition
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Term
Which protein channels retinoids to specific enzymes responsible for metabolic transformation and limits 'free' retinoids? |
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Definition
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Term
In the nuclei, specific retinoid-receptor proteins have what function? |
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Definition
To regulate the activity of retinoid- responsive genes |
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Term
Retinoid- binding protein and receptors? a. in PLASMA b. in CELLS c. in NUCLEI |
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Definition
1. in plasma RPB functions to solubilize retinOL and deliver it to cells 2. in CELLS: cellular retinoid binding protein limit "free" retinoid and channel retinoids to specific enzymes responsible for metabolic transformation 3. in NUCLEI: specific retinoid receptor protein regulate the activity of retinoid responsive genes |
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Term
Draw retinoid conversion reactions. Vit a (page 13) |
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Definition
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Term
What are functions of vit A? |
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Definition
a. 11-cis retinAL fucntions in retina. Convert light into neural signals necessary for vision b. Ret. Acid maintains normal differentiation of the conjuctival membranes, cornea, and other cells to prevent xerophthalmia. - cellular differentiation - Development - Immunity |
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Term
11-cis-retiNAL (function in vision) |
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Definition
11-cis retinAL fucntions in retina. Convert light into neural signals |
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Term
Retinoic Acid (function in vision) |
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Definition
Ret. Acid maintains normal differentiation of the conjuctival membranes, cornea, and other cells to prevent xerophthalmia. |
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Term
Function of Vit A in vision |
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Definition
Light absorbing unit (chromophore): 11 cis retinal bound to opsin - disk contain "visual pigment" or rhodopsin (in rods) and iodopsins (in cones) -absorption of a photon light catalyzes the isomerization of 11-cis-retinal to all trans retinal and its release from opsin. - this triggers a neuronal signaling cascase - regeneration occurs in RPE (retinal pigment epithelium) |
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Term
Draw visual cycle . Vit A page 14 |
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Definition
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Term
+ or - Vitamin A in Basal Cells: cell differention |
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Definition
+ A: Cuboidal, columnar, and goblet cells - A: squamous (scale like) cells |
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Term
Role of Vit A (RA) in gene expression? |
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Definition
1. Binding of RA to its nuclear receptor 2. Activation of receptor 3. Binding of the receptor to a RARE 4. Regulation of the expression of genes downstream |
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Term
Retinoic Acid: RAR, RXR: what do they bind? |
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Definition
RAR: binds RA and 9-cis-RA RXR: binds 9-cis-RA |
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Term
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Definition
Skin(keratin) Matrix (laminin) Enzymes( alcohol dehydrogenatse, etc) |
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Term
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Definition
Drying and ulceration of cornea - night blindness - conjuctival xerosis - bitot's spots - corneal xerosis - ulceration - necrosis/keratomalacia |
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Term
Immune function and Vit A |
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Definition
Effects on the immune system - infection - morbidity - growth - mortality (Inf and Children, women of reproductive age) |
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Term
Follicular hyperkeratosis |
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Definition
in deficiency of Vit A, mucous secreting epithelial cells become keratinized |
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Term
Xerophthalamia: clinical deficiency and progression |
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Definition
Clinical deficiency: conjuctival xerosis, bitot spots progression: corneal xerosis, ulceration, keratomalacia, blindness |
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Term
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Definition
Beta carotene: - 18 % incr. lung cancer - 8 % incre in lung cancer mortality - more heart disease
Vit E: - no effect in lung cancer mortality - decrease death from eschemic heard disease and stroke - increase death from hemorrhagic stroke |
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Term
Vit A deficiency? Who's at risk? Consequences? |
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Definition
125,000 to 250,000 million children (pre-school) and pregnant and lactating women Consequences: Leading cause of preventable childhood blindness - night blindness and xerophthalmia - 250,000-500,000 per year Increase risk of mortality and morbidity in pre school children, and most likely in pregnant women - Incresse risk of dying from childhood infections |
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Term
Where is Vit A deficiency in pre school children most prevalent *region |
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Definition
south east asia . 127 million |
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Term
What are contributing factors to Vit A deficiency? |
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Definition
Low intake in diet or breast milk High demand during infection High losses with diarhhea |
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Term
How does immune responce changes due to Vit A deficiency? |
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Definition
Lymphoid cellularity - thymic atrophy - reduced number of spleen cells - reduced lymphocytes etc
Antibody responses - reduced T cell dependent antigens
Cell mediated immunity - reduced cytoxicity - alterations in cytokine production
Innate Immunity - decreased number of natural killer cells - Reduced phagocytosis by macrophages |
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Term
What are risk factors of Vit A deficiency? |
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Definition
Age Gender Physiological status Diet Socioeconomic conditions Clusterin |
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Term
Evaluation of Vit A status: Clinical Histological Biochemical |
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Definition
Clinical - night blindness - dark adaptaion tests Histological - conjuctival impression cytology
Biochemical: Retinol levels in serum Relative Dose Response (RDR) Modified Relative Dose Response (MRDR) |
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Term
Relative Dose Response Test *Vit A assessment status |
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Definition
Relative Dose Response Test:
As liver reserves of Vit A become low, conservation starts to increase efficiency of Vit A. - At critical threshhold , rate of release is dimineshed and blood levels are low - BUT, synthesis of carier protein RBP continues - SO accumulation of a pool of preformed RBP
Procedure: - Fasting blood sample is taken - oily solution w/450-1000 micrograms of RETINYL PALMITATE is given orally - Small meal with some fat is given - After 5 hours, second blood test - Blood analyzed and RDR is calculated: RDR= ret (5 hr)- ret (0 hr)/ ret (5 hr)
RDR > 20% indicates of INAdequate hepatic stores |
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Term
Modified Relative dose response: Vit A assessment |
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Definition
- uses DEHYDRO- RETINOL for dosing and a single blood sample at 5 hours post dosing |
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Term
Public Health Measures to correct Vit A deficiency (3) |
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Definition
Food Fortification Supplementation Dietary Diversificaton |
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Term
Supplement of Vit A (+ and -) |
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Definition
+: easy to implement fast improvement in Vit A status Easy to target vulnearable pop low cost easy to do -: short term approach distribution every 6 months requires heaby logistics |
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Term
What children are at high risk of deficiency of vit A? |
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Definition
measles diarrhea chicken pox protein energy malnutrition severe infection |
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Term
Food Fortification of Vit A (+, -, main issues) |
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Definition
+ : - wide coverage - easy to implement - does not depend on active participation - inexpensive
- : - entire pop exposed - target pop may not be reached - requires a centralized food industry - need effective surveillance
Main issues:
- selection of appropriate food vehicle - Selection of appropriate level of fortification - need for regulation - sustanability - economic implications |
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Term
What are clinical indicators to assess vit A deficiency? |
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Definition
Clinical: pre school: night blindress < 6 yo: >1 % bitot spots (<6 yo: >0.5 %)
Pregnant women: night blindness (> 6%)
Sub clinical: pre school: serum retinol <6 yo >20 % |
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Term
Draw deficiency to toxicity curve of Vit A page. 28 |
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Definition
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Term
Toxicity and Vit A (symptoms) |
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Definition
Hypervtiaminosis A - bright red marginal discoloration of the gingiva - Retinoid Embryopathy (during 1st trimester) - malformation (limb) - craniofacial defects in bones and oral clef - cardiac, thymic, CNS defect - microtia/anotia (ear) - |
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Term
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Definition
Excess intake of Vit A leads to incrased risk of osteoporosis.
- May impair the ability of vit D to promote calcium absorption - 1500 mcg/day --> reduced bone mineral density compare with who consumed <500 mcg - effect of retinols is decresed with use of estrogens - High vit A does not equal to high blood levels of retinol - beta carotene intake is ok, esp from fruits and veggies - only problems with retiNOL |
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