NUTRITION in human beings

Date: December 09, 2014

 

                                                                                                                 Nutrition

The sum total of all the processes starting from taking the food upto its utilization is called nutrition.

Depending upon the made of nutrition, the organisms can be classified as autotrophs and heterotroph.

Organisms- (1) Autotrophs                                     (2) Heterotrophs

(1) Autotrophs – (Auto = self  ;   Troph = nutrition)

In autotrophic nutrition the organism prepares or synthesizes its own food utilizing only the inorganic raw material.

  1. Green plants & autotrophic bacteria. These organisms contain chlorophyll pigment, which is capable of trapping & fixing the solar energy. This energy is utilized for synthesizing nutrients like glucose from the raw materials like carbon dioxide, water & few minerals.

Process of Photosynthesis             6CO2 + 12H2O  Sunlight                  C6H12O6 + 6H2O +6O2

                                                                                       Chlorophyll

(2) Heterotrophs – (Hetero = different   ;   Troph = nutrition)

It is a type of nutrition in which energy is derived from the intake and digestion of the organic substances, normally of plant or animal source. In this type of nutrition, organic substances after intake are first digested into simple forms. Then these simple molecules are utilized by the organism.

e.g. All animals, bacteria & fungi.

Heterotrophs – Three types of Heterotrophic Nutrition

(A) Saprophytic Nutrition                              (B) Parasitic Nutrition                     (C) Holozoic Nutrition

Nutrition in Animals

Depending upon food, nutritionally animals are:

  1. Herbivores feeding on plant food g. Goat, Cow, Rabbit
  2. Carnivores feeding on other animals g. Lion, Tiger
  3. Omnivores feeding on all types of food g. Human
  4. Detrivores feeding on detritus or organic remains g. Earthworm
  5. Scavengers feeding on carrions g. Vulture
  6. Frugivorous feeding on Fruits g. Parrot
  7. Sarguivores taking meal of blood g. Leach, female
  8. Insectivores eating insects g. Common bats.
  9. Cannibals eating other members of own species g. many snakes

Digestive system

It is a system of alimentary canal and digestive glands.

Alimentary Canal

It is a tube of variable diameter having muscular wall and glandular epithelia. Alimentary canal is made of mouth vestibule, Buckle Cavity, pharynx, Esophagus, Stomach, Small Intestine, Large Intestine and Anus.

  1. Mouth:
  2. Vestibule: Space between gums and lips
  3. Buccal Cavity (Oral cavity): Large space bounded by palate above. Throat with tongue below and jaws with teeth on the sides. The superior of tongue bears papillae (vallate, fungi form and fill form) having taste buds.

There are different areas for different tastes:-

Sweet (tips), salt (tip and sides), sour (sides) and bitter (base).

The basal region also contains two tonsils or lingual tonsils. There are other two types of tonsils – pharyngeal and palliative. Tonsils contain lymphoid tissue. Tonsillitis is inflammation,  of tonsils.

Teeth: A tooth has three parts: crown (exposed part), neck (surrounded by gum) and root (embedded in socket).

Tooth is mainly made of ivory like substance called dentine. In root region dentine is covered by bone – like cement and periodontal membrane. In crown part, dentine is covered by enamel (hardest, white shining). Internally tooth has a pulp cavity with connective tissue, nerve fibres, lymph and blood vessels. On the outside it contains odontoblasts (dentine producing).

In humans milk, deciduous or temporary teeth begin to appear at the age of 6-11 moths. They are completed by the age of two years. There are 20 milk teeth.

Dental formula is the no. of teeth in one half of upper jaw divided by teeth of one half of the lower jaw.

Dental formula for milk teeth is

  

Permanent teeth begin to appear between the age of 6-12 years. Milk teeth are lost. Last molars come out late after 18 years of age. They are called wisdom teeth.

Dental formula for permanent teeth is-

                

Caries:- Decay of teeth due to degeneration of enamel and formation of cavities

Pyorrhoea :- Infected gums and tooth sockets.

  1. Pharynx:- it lies between soft palate and sixth cervical vertebra. Pharynx is distinguishable into 3 parts: nasopharynx, oropharynx and laryngopharynx.
  2. Oesophagues: - A muscular tube of 25-40 cm length which connects pharynx with stomach.
  3. Stomach: - It is the widest and distensible J-shaped part of alimentary canal which is on the left side of the body. Empty stomach has folds called gastric rugae

Function: - Stomach stores food, churns and breaks it, adds gastric juice, Produces an intrinsic gastrin, factor for absorption of B 12, Secretes hormone Gastrin absorbs alcohol, some drugs, small quantity of sugar and water. Gastrin, histamine and vagal activation stimulate secretion of gastric juice and churning movement of stomach.  

Ruminant Stomach: - In ruminants the stomach is differentiated into chambers –Rumen, Reticulum, Omasum and Abomasum.

  1. Small Intestine: - It is the longest part of alimentary canal. Small intestine is differentiated into three parts-

Duodenum, Jejunum and Ileum. Small intestine has circular folds (Plicae circulares) and villi. Crypts of Lieberkuhn occur throughout.

Duodenum:- 20-25 cm long duodenum has an ampulla (ampulla of vater) where women bile duct and pancreatic duct open jointly. Sphincter of oddi juards the opening. Brunners glands occur in it.

Jejunum :- 0.80-1.5m

Ileum:- 1.8-2.5m – characterized by club shaped villi and peyers patches. Villi increase the iternal surface of ileum by about 10 times. Peyers patches are lymphoid tissue Patches scattered along the intestinal wall that protect the intestine from infection. Major digestion and absorption occur in small intestine. It also produces a no. of hormones like cholecystokinin pancreozymin, secretin, enterogastrone, duocrinin, enterocrinin, and villikinin.

Large Intestine:- it is known so because of its large diameter (4-6 cm) as compared to small intestine (3.5-4.5cm). Length 1.5m long. Differentiated into four parts caecum, colon, rectum and anal canal.

Caecum :- Externally it bears a blind tube, having lymphoid tissue, called vermiform appendix (7-9cm long) infection of the latter is called appendicitis.

Colon:- Largest part of large intestine

Rectum:- 12-15cm long tube. Enlargement of rectal veins causes piles or haemorrhoids.

Anal Canal:- connects rectum with anus. 3cm long

Anus:- Terminal inferior opening of alimantary canal

Digestive Glands

They include salivary glands gastric glands, liver, pancrease and intestinal glands

Salivary Glands:- 3 pairs of salivary gland-

  1. Parotid – below and in front of ears. Mumps is a viral infection of parotid glands
  2. Submaxillary or submandibular- Angles of lower jaw.
  3. Sublingual – below the tongue

About 1.0 – 1.5 litres of saliva is produced daily. Saliva contains 99% water, some salts, lysozyme and Ptyalin.  (PH is 6.7)

Ptyalin or salivary amylase converts starch and glygcogen into limit dextrins, maltose and is maltose making the food sweet. Lysozyme is antibacterial

Gastric Glands :-              (1) Cardiac glands secrete mucus

                                             (2) Pyloric glands secrete mucus

                                             (3) fundic glands

Fundic glands:- (i) Peptic cells (chief or zymogen cells) secrete pepsinogen and gastric lipase (proenzyme) In calf another proenzyme called prorennin is also produced.

(ii) Oxyntic cells (parictal cells) yield HCL and intrinsic factor HCL makes the gastric juice acidic (PH = 2.0-3.7)

(iii) Mucous (goblet) cells secrete mucus

(iv) Argentaffin cells

Secretion of gastric glands is called gastric juice. Mucus protects stomach wall against HCL action and protein digesting enzyme HCL changes pepsinogen and prorennin into active enzymes pepsin and rennin.

Pepsin functions in acidic medium and changes protein into peptones. Milk protein casein is coveted into calciun paracaesinate for curdling it. In calf this is done by rennin

  1. Liver:- Largest gland lies on right side below the diaphragm. It is differentiable into small left lobe and large right lobe. Gall bladder lies on the inferior surface of right lobe. Certain mammals like Horse and Rat do not have gall bladder. The two lobes of liver produce right and left hepatic ducts. They join to form common hepatic duct. A cystic duct comes from gall bladder. The two join to form bile duct that attaches with pancreatic duct before opening in duodenum. The opening of bile duct into pancreatic duct is controlled by sphincter of Boyden. When not passing into duodenum bile from liver lobes enters cytic duct and enters gall bladder for concentration and storage. Amount of bile produced per day is about 600ml. Bile is yellowish green alkaline solution with 89-98% water no digestive enzymes but four types of chemicals and some non-digestive enzymes

(a) inorganic salts:- Bicarbonates chlorides, carbonates and phosphates of sodium, potassium and calcium.

(b) Bile Salts:- sodium taurocholate and sodium glycocholate.

(c) Fatty Substances:- cholesterol lectithin and other phospholipids.

(d) Bile Pigments:- Bilirubin (yellowish) and biliver din (greenish). Bile salts emulsify fat and activate lipases. Bile helps in absorption of iron calcium fatty acids carotene fat soluble vitamins. It has an excretory role as well. Accumulation of bile pigments in the body causes jaundice.

Pancreas:- Heterocrine gland lies posterior to stomach. The exocrine part of pancreas consist of lobules lobule of acini or alveoli and acinus of pyramidal cells that secrete pancreatic juice. Pancreatic duct joins the bile duct before opening into duodenum. And accessory duct of Santorini may take pancreatic juice directly into duodenum. Pancreatic juice is alkaline (PH= 73.5-8.5) having four types of enzymes.

(a) proteolytic proenzymes:- trypsinogen chymotrypsinogen and procarboxypeptidase.

(b) nucleases:- like DNA ase and RNA ase.

(c) Steapsin:- or pancreatic lipase

(d) pancreatic:- amylase. Proenzyme trypsinogen is changed to trypsin by enteropeptidase or enterokinase of intestine.

Intestinal Glands:- They occur as crypts of Lieberkuhn and Brunner’s glands Brunner’s glands mostly occur in duodenum and open into crypts of Lieberkuhn. They secrete mucus. Goblet cells secrete mucus. The digestive juice of intestinal glands is called intestinal juice or succus entericus slightly alkaline (PH=7.5) contains mucin inorganic salts and many enzymes - enterokinase aminopeptidases dipeptidase nucleotidases (nucleotides into nucleosides and phosphate), nucleosidases (cucleosides into nitrogen bases and pentose sugars) intestinal lipase (fat into fatty acids glycerol monoglycerides) isomaltase (limit dextrin and isomaltose into glucose) maltase (maltose to glucose) lactase (lactose to glucose and galactose) sucrase (=invertase sucrose to glucose and fructose) argentafin cells produce secretin and peristaltic stimulant called 5-hydroxytryptamine (serotonin). Crypts have different types of enzyme secreting cells, paneth cells for lysozyme and argentaffin cells for hormones.

 

Glands

Enzyme

pH

Site of Action

Substrate

Product

 

 

 

 

Carbohydrate

Fat

Protein

N. Acid

 

Salivary Glands (Saliva)

i. Ptyalin

6.7

Buccal cavity, Oesophagus & Part of Stomach

Starch Glycogen

-

-

-

Limit dextrins Maltose, Isomaltose

                   

Gastric Glands (Gastric juice)

i. Prorennin-Rennin (Calf)

2.0-3.7

Stomach

-

-

Casein

-

Calcium Paracaseinate

ii. Pepsinogen – Pepsin

2.0-3.7

Stomach

-

-

(a) Protein

(b) Calcium

-

Peptones

iii. Gastric Lipase (Infants)

2.0-3.7

Stomach

-

Milk Fat

Paracaseinate

-

Fatty Acids & Glycerol

Liver (Bile)

No Enzyme

Makes food alkaline emulsifies fat and helps in its absorption.

Pancrease (Pancreatic juice)

i. Chymotrypsinogen-chymotrypsin

7.5-8.5

Small Intestine

-

-

Casein

-

Calcium Paracaseinate

ii. Trypsinogen-Trypsin

7.5-8.5

Small Intestine

-

-

(a) Protein (b) Calcium Paracaseinate

 

Peptones & Peptides

iii.Procarboxy peptidases-carboxypeptidases

7.5-8.5

Small Intestine

-

-

Larger Peptides

 

Smaller Peptides

iv. pancreatic Lipase

7.5-8.5

Small Intestine

-

Fat

-

-

Fatty acids

Monoglycerides Glycerol

v. Pancreatic Amylase

7.5-8.5

Small Intestine

Starch Glycogen, Dextrins

-

-

-

Limit dextrins maltose, Isomaltose

vi. DNA-ase

7.5-8.5

Small Intestine

-

-

-

DNA

Deoxyribonucleotides

vii. RNA-ase

7.5-8.5

Small Intestine

-

-

-

RNA

Ribonucleotides

Small intestine (Succus Entericus)

i. Aminopeptidases

7.0-7.5

Small Intestine

-

-

Peptides

-

Amino Acids and smaller peptides

ii. Dipeptidases

7.0-7.5

Small Intestine

-

-

Dipeptides

-

 Amino acids

iii. Necleotidases

7.0-7.5

Small Intestine

-

-

-

Nucleotide

Nucleosides, Phosphates

iv. Nucleosidases

7.0-7.5

Small Intestine

-

-

-

Nucleotides

Nitrogen base, Pentose sugars

v. Intestinal Lipase

7.0-7.5

Small Intestine

-

Fat

-

-

Fatty acids glycerol Monoglycerides

vi. Isomaltase

7.0-7.5

Small Intestine

Limit Dextrins, Isomaltose

-

-

-

Glucose

vii. Maltase

7.0-7.5

Small Intestine

Maltose

-

-

 

Glucose

viii. Lactase

7.0-7.5

Small Intestine

Lactose

-

-

-

Glucose, Galactose

ix. Sucrase (Invertase)

7.0-7.5

Small Intestine

Sucrose

-

-

-

Glucose, Gructose

                             

Peristalsis is a series of waves of contraction that pass from one end to the other and is meant for pushing the food. It consists of a slight expansion of alimentary canal in front of food and contraction behind the food. In stomach Gastric pepsin further softens the food. The pulpy food is now called chime. The soluble food is absorbed by villi. Food in small intestine is in the form of liquid emulsion called chyle. Undigested food with lot of water enters large intestine. Water is absorbed in the region of colon. Colon has bacteria that feed on undigested food. Some of them produce B-vitamins, small quantities of vitamin K and odoriferous cases like phenols and hydrogen sulphide.

Basal Metabolic Rate (BMR):- It is the minimum energy requirement for maintenance of body as during rest or sleep. 1600 kcal/day BMR per unit weight decreases with increases in size and vice-varsa, i.e. a rat will have higher BMR than lion.

Routine Metabolic Rate (RMR):- It is the energy requirement of a moderately active person. 2800 kcal for adult males and 2200 kcal for adult females.

Active Metabolice Rate (AMR):- energy requirement of a person doing heavy physical work.

Balanced Diet:- it is the diet that contains all the components in optimum proportions and quantity required for maintaining the body in perfect state of health activity and development. Various components of balanced diet are carbohydrates (60%), fats (25%), Proteins (15%), vitamins (traces), minerals (traces) and roughage.

Carbohydrates:- Carbohydrates or hydrates of carbon are compounds of C, H and O general formula of Cn H2n On. They can be Monosaccharides (e.g.; glucose), disaccharides (e.g.; sucrose, lactose, maltose), polysaccharides (e.g.; glycogen, starch, ccellulose), they supply energy at the physiological rate of 4 kcal/gm (caloric value 4.1) Living cells receive carbohydrates from blood mostly as glucose. Glucose is absorbed from alimentary canal. Excess is stored in liver and muscles as glycogen. The process of formation of glycogen from glucose is called glycogenesis. When level of blood glucose falls glycogen of liver is hydrolysed to produce it. The phenomenon is called glycogenolysis. Excess carbohydrate of food is changed to fat through the process of lipogenesis.

Lipids:- Lipids or esters of fatty acids and alcohols are of two types simple or compound. They are a source of energy with a physiological rate of 9kcal/gm. Fat is the major stored food kept in adipose tissue. Subcutaneous fat noyu only provides body form but also functions as insulating layer. Phospholipids are constituents of cell membranes. Medullary sheath of nerve fibres contains glycolipids. Human diet should have more unsaturated fat because some unsatureated fatty acids cannot be synthesized from other. They are called essential fatty acids e.g. linoleci acids linolenic acid arachidonic acid.daily requirement of adult is 50gm.

Proteins:- Proteins are amino acid polymers. They build up various protoplasmic structures including the cell membranes (structural proteins). Matrix of connective tissue (fibres) cartilage and bone keratin of outer dead skin hair and nail are proteinaceous. All enzymes are made of proteins. Aminal proteins are called first class proteins because they supply all the amino cids required for building various proteinaceous substances. Plant proteins often lack one or more amino acids which human beings cannot build from others. The amino acids which cannot be formed by humans from other amino acids are called essential amino acids. They are eight in number - methionine, threonine, tryptophan, valine, leucine, isoleucine, lysine and phenylalanine. Two amino acids are slow to be formed. They are known as semi-indispensible arginne, histidine.

Vitamis (Funk 1912):- They are accessory food factors which are required in small quantity for controlling metabolism and body functioning. Vitamins are of two types – fat soluble (A, D, E and K) and water soluble (B and C). B Vitamins are of several types viz, thiamine, riboflavin, pantothenic acid, nicotinamide, pyridoxine, biotine, folic acid and cobalamine


 

Vitamin

Function

Deficiency

Source

1.

A (Retinol) Yellow viscous oil

Antixerophthalmic, synthesis of retinal pigments, maintenance of epithelia (prevention of keratinisation), anti-infective

Xerophthalmia, night blindness, keratomalacia (dermatosis, toadskin) stunted growth

Carotene in vegetables mango, orange and as such in milk, butter, ghee, egg, yolk, liver oil

2.

D (Steroi-Calciferol) ten types common D2 and D3

Antirachitic, absorption and retention of Ca and P.

Rickets in children, osteomalacia in adults

Sunshine

3.

E (Tocopherol) Colourless oil a and b

Antisterility factor, antioxidative for membrane lipids, skin and hair

Erythrocyte breakdown (Anaemia) muscular dystrophy (cramps) miscarriage and reduced fertility

Green vegetables, oils, milk, cheese, butter, egg.

4.

K (Phylloquinone) Yellow oil and fat K1 and K2

Antihaemorrhagic factor, synthesis of prothrombin (hence essential for blood coagulation), electron carrier, liver functioning

Prolonged bleeding (bleeding disease) or haemorrhages, liver malfunctioning.

Green vegetables, Tomato, colon bacteria

5.

 Thiamine (B1) vitamin G

Antineuritic, Antiberberi, functioning of muscles and nerves

Ancrexia, muscular atrophy, Beriberi in humans and polyneuritis in animals

Yeast, whole, grains egg, yolk, liver

6.

Riboflavin (B2)

Maintenance of skin and oral mucosa antimigraine

Cheilosis, giossitis, intolerance to light

Yeast, green vegetables, milk, curd, cheese egg.

7.

Pantothenic Acid (B3 also B5)

Formation of CoA, required in cell respiration, functioning of skin and nerves

Gastro intestinal disorders graying of hair burning feet syndrome

Yeast, milk, wheat, bran, pulses, liver, colon, bacteri.

8.

Nicotinamide (Niacine, Nicotinic Acid) N6, also B5, B7 Vitamin P-P (Pellarge preventive)

Antipellagra component of NAD+, NADP+, energy transfer and nervous system

Pellagra

Yeast, pulses, green vegetables cereals, milk, egg, yolk, liver

9.

Pyridoxine (B6)

Component of coenzyme pyridoxal phosphate

Anaemia, neuritis, pain convulsions, skin lesions

Yeast, green vegetables, egg, yolk, wheat, germ liver

10.

Biotin (B4) vitamin H

Prosthetic group of some enzymes in energy liberation, and fat systhesis. Avidin of raw egg white prevents biotin absorption

Dermatitis, anorexia, muscular pain, rise in blood cholesterol

Yeast, green vegetables, egg, yolk, colon bacteria

11.

Folic Acid (Be) Vitamin M

Required in erythrocyte maturation DNA and RNA synthesis transfer of methyl groups

Megablastic anaemia, gastrointestianal disorders, glossitis

Leafy Yeast, vegetables, egg, yolk, colon bacteria liver

12.

Cobalamine B12

Required for erythrocyte maturation. DNA synthesis, myelin formation

Pernicious anaemia, glossitis loss of peripheral sensation

Milk, egg, liver, fish, colon, Bacteria

13.

C (Ascorbic Acid) Heat Labite

Absorption of iron, formation of dentine collagen and bone matrix, amino acid oxidation

Scurvy, stiff sore joints, fragile blood vessels and bones delayed wound healing

Citrus fruits, Guava, Tomato, Amla, ,Mango

Inositol, lipoic acid and para-amino benzoic (PABA) are also considered to be components of vitamin B-complex.

 

Nutritonal Disorders

  1. Marasmus:- It is a disorder caused by deficiency of food or protein energy malnutrition
    (PEM). Marasmus occurs in infants (1-2 years) when they do not get sufficient mother’s milk and weaning diet. Such infants are often provided with very diluted cow or buffalo milk. Marasmus babies have shirvelled appearance with thin face, sunken eyes, wrinkled and dry skin, protruding ribs, reduced digestion and frequent diarrhea, low weight little growth and poor mental abilities.
  2. Kwashiorkor:- It is a protein energy malnutrition that occurs in children of 1-4 years (weaning and post weaning) due to constant reduced protein availability. This can be due to (i) early stoppage of breast milk (ii) late supply of supplementary food (iii) over diluted milk (iv) maintaining children on cooking water of cereals. A kwashiorkor chkild has match stick legs protruded belly blotchy skin, anaemia, oedema of certain parts and repeated diarrhea.
  3. Obesity:- Obesity is a luxury nutritional disorder caused by greater intake of food than the requirement of body. It is quite common in persons having higher intake of sweets, carbohydrate rich food fried articles fat rich food and absence of roughage in food. Obese persons are overweight with excessive accumulation of fat. Movements are reduced. There is a risk of diabetes osteoarthritis, gall bladder stones high blood pressure and cardiac probiems. The reasonjs for novereating are psychogenic physiological genetic and developmental.
  4. Hyper-cholesterolemia:- It is characterized by high blood cholesterol due to higher intake of cholesterol rich eggs, red meat, butter and ghee or reduced biotin intake. Cholesterol gets deposited on the walls of blood vessels making their lumen narrow and walls stiffer. Thus increases blood pressure or hypertension. It leads to other cardio-vascular disorders.
  5. Rickets:- The disorder is due to deficient ossification of bone ends leading to their bending and swelling of joints. It occurs in children of 6 months to 2 years when their diet is deficient in vitamin D, calcium or phosphorus.
  6. Osteomalacia:- The disorder occurs in adults when their food is deficient in vitamin D1 calcium or phosphorus. Bones of vertebral column become weak. Pelvic and other bones bend and become soft.
  7. Xerophthalmia:- It is a vitamin A deficiency disorder which is caused by stoppage of lachrymal activity. Cornea and eye lids become dry and ulcerated. It leads to swelling of dry eye lids and opacity of cornea. Xerophthalmia, if untreated leads to blindness.
  8. Night Blindness (Nyctalopia):- Dietary deficiency of vitamin A results in deficiency of rhodopsin or visual purple. The latter impairs the ability to see in dim light or night.
  9. Beriberi:- Beriberi is a debility produced by deficiency of thiamine as during excessive intake of polished rice. It results in loss of appetite, weakening of muscles, fatigue, poor digestion, palpitation, slow reflexes, body rigidity and neuritis. There is inflammation of peripheral nerves, weakening of muscles, paralysis and progressive edema. Depending upon the system affected, beriberi is of five type- dry, wet, mixed, cardiac and corporal.
  10. Pellagra:- The disorder is due to deficient vitamin nicotinamide. It is charactered by extra-pigmentation, thickening cracks and eruption in exposed regions of skin (Dermatitis), glossitis (swollen toungue), swollen lips peripheral neuritis and dementia.
  11. Scurvy:- Vitamin C deficiency leads to scurvy characterized by bleeding gums, falling of teeth, fragile blood vessels, fragile bones and slow healing of injuries.
  12. Cheilosis:- Inflammation and cracking of mouth corners due to riboflavin (B2) deficiency.
  13. Anaemia:- It is disorder in which hemoglobin content of the blood is low due to either few red blood corpuscles or their hemoglobin content. It is of three types (a) Microcytic (most common) due to iron deficiency leading to fewer and smaller erythrocytes with reduced hemoglobin. (b) Megablastic due to fewer abnormal red blood cells caused by deficiency of folic acid or B12 (c) Pernicious due to production of hemoglobin free immature RBCs caused by B12 deficiency as a result of deficient intrinsic factor. Sickle cell anemia and thalasemia are genetically controlled. Anemia also occurs due to excessive blood loss. The same is called post haemorrhagic anemia.

 


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