A general idea of carbohydrates in the eye, Glycemic Index and different classifications of carbohydrates based on chemical nature their digestion and absorption, carbohydrate metabolism in the eye and its transport
Types of fat, transportation of fat in the blood, FUnction of fat in the diet, DHA accumulation in the eye, Disc shedding in the retina, DHA conservation in eye, Role of DHA in the eye
Lens is a transparent, biconvex, crystalline structure placed between iris and the vitreous in a saucer-shaped depression, the patellar fossa. The lens is a crystalline structure that is avascular and is devoid of nerves and connective tissue
It consists of three distinct part:
Lens capsule
Anterior lens epithelium, and
Lens substance or lens fibres
Vitamin A, Digestion, absorption, transport, Functions and requirement and deficiency ad eye relate problems.
Vitamin C, Functions, requiremnts, deficiency
Vitamin E, defciency and eye
Types of fat, transportation of fat in the blood, FUnction of fat in the diet, DHA accumulation in the eye, Disc shedding in the retina, DHA conservation in eye, Role of DHA in the eye
Lens is a transparent, biconvex, crystalline structure placed between iris and the vitreous in a saucer-shaped depression, the patellar fossa. The lens is a crystalline structure that is avascular and is devoid of nerves and connective tissue
It consists of three distinct part:
Lens capsule
Anterior lens epithelium, and
Lens substance or lens fibres
Vitamin A, Digestion, absorption, transport, Functions and requirement and deficiency ad eye relate problems.
Vitamin C, Functions, requiremnts, deficiency
Vitamin E, defciency and eye
Corneal metabolism
1. o Cornea requires energy for normal metabolic activities as well as for maintaining transparency and dehydration o Energy is generated by the breakdown of glucose in the form of ATP o Most actively metabolizing layer are epithelium and endothelium o Sources of nutrients : o Oxygen : mainly from atmosphere through tear film , with minor amount supplied by the aqueous and limbal vasculature o Glucose , amino acid, vitamins and other nutrients supplied to cornea by aqueous humor o Glucose also derived from glycogen stores in corneal epithelium o Epithelium consumes O2 10 times faster then stroma
2. o Three process or pathways – o Pentose shunt (Hexose monophosphate shunt) –occurs both in hypoxic and normoxic condition o Glycolysis (Embden meyerhof pathway) –anaerobic process , glucose / glycogen converted to pyruvate yeilding 2 ATPs o TCA or krebs or citric acid cycle- aerobic condition pyruvate is oxidized to yield 36 ATP, water, CO2.
3. o In normal conditions all the glucose consumed by the cornea o Glucose mostly come from aqueous humor o The rate of glucose consumption by the whole cornea is approx. 100 microgram/hr/cm2. o 1 mol. of glucose will be converted to the pyruvic acid and produced 2 molecules lactic acid and 2 mol. of ATP o In the krebs cycle, 1 mol. of glucose will utilize the pyruvic acid and O2 to produced 36 mol. ATP o Epithelium and endothelium will consume the oxygen
4. o The pentose phosphate pathway is used to metabolize five carbon sugars; one ATP and 2 NADH molecules are produced from oxidation of one glucose molecule o Produced intermediates for nucleic acid synthesis and some amino acids o This process will happen in hypoxic or normoxic condition o The purpose of glucose metabolism through the pentose shunt is the production of NADPH
Every component of the eye is vulnerable to damage from ROI, particularly retina. There are several reasons for the vulnerability of the retina, including high concentrations of polyunsaturated fatty acid (PUFA), constant exposure to visible light, high consumption of oxygen, an abundance of photosensitisers in the neurosensory retina and the RPE, the process of phagocytosis by the RPE which is known to generate hydrogen peroxide.
Physiology of cornea in which you will get all the details about corneal functions, corneal metabolism, wound healing and information about contact lenses
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power.
Corneal metabolism
1. o Cornea requires energy for normal metabolic activities as well as for maintaining transparency and dehydration o Energy is generated by the breakdown of glucose in the form of ATP o Most actively metabolizing layer are epithelium and endothelium o Sources of nutrients : o Oxygen : mainly from atmosphere through tear film , with minor amount supplied by the aqueous and limbal vasculature o Glucose , amino acid, vitamins and other nutrients supplied to cornea by aqueous humor o Glucose also derived from glycogen stores in corneal epithelium o Epithelium consumes O2 10 times faster then stroma
2. o Three process or pathways – o Pentose shunt (Hexose monophosphate shunt) –occurs both in hypoxic and normoxic condition o Glycolysis (Embden meyerhof pathway) –anaerobic process , glucose / glycogen converted to pyruvate yeilding 2 ATPs o TCA or krebs or citric acid cycle- aerobic condition pyruvate is oxidized to yield 36 ATP, water, CO2.
3. o In normal conditions all the glucose consumed by the cornea o Glucose mostly come from aqueous humor o The rate of glucose consumption by the whole cornea is approx. 100 microgram/hr/cm2. o 1 mol. of glucose will be converted to the pyruvic acid and produced 2 molecules lactic acid and 2 mol. of ATP o In the krebs cycle, 1 mol. of glucose will utilize the pyruvic acid and O2 to produced 36 mol. ATP o Epithelium and endothelium will consume the oxygen
4. o The pentose phosphate pathway is used to metabolize five carbon sugars; one ATP and 2 NADH molecules are produced from oxidation of one glucose molecule o Produced intermediates for nucleic acid synthesis and some amino acids o This process will happen in hypoxic or normoxic condition o The purpose of glucose metabolism through the pentose shunt is the production of NADPH
Every component of the eye is vulnerable to damage from ROI, particularly retina. There are several reasons for the vulnerability of the retina, including high concentrations of polyunsaturated fatty acid (PUFA), constant exposure to visible light, high consumption of oxygen, an abundance of photosensitisers in the neurosensory retina and the RPE, the process of phagocytosis by the RPE which is known to generate hydrogen peroxide.
Physiology of cornea in which you will get all the details about corneal functions, corneal metabolism, wound healing and information about contact lenses
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power.
Biochemistry of musculoskeletal system. biochemistry of MSS prepared by Fikad...fikaduseyoum1
biochemistry of MSS prepared by Fikadu Seyoum Tola. This ppt essentially discuss about collegen biosnthesis, defect and muscle energy metabolism with its regulations.
An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes
The aqueous humour is a transparent, watery fluid similar to plasma, but containing low protein concentrations. It is secreted from the ciliary epithelium, a structure supporting the lens
Small amounts of vitamins are required in the diet to promote growth, reproduction, and health. Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats.
Water soluble vitamins include Vitamin C and the vitamin B complex: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), Vitamin B6, biotin (B7), folic acid (B9), Vitamin B12. Vitamin A in its Beta-Carotene form is also water-soluble.
The tear film is a complex mixture of substances secreted from multiple sources on the ocular surface, including the lacrimal gland, the accessory lacrimal glands, the meibomian glands, and the goblet cells.
A picornavirus is a virus belonging to the family Picornaviridae, a family of viruses in the order Picornavirales. Vertebrates, including humans, serve as natural hosts. Picornaviruses are nonenveloped viruses that represent a large family of small, cytoplasmic, plus-strand RNA viruses with a 30-nm icosahedral capsid.
Poxviruses are brick or oval-shaped viruses with large double-stranded DNA genomes. Poxviruses exist throughout the world and cause disease in humans and many other types of animals. Poxvirus infections typically result in the formation of lesions, skin nodules, or disseminated rash.
Leptospirosis is a bacterial disease that affects humans and animals. It is caused by bacteria of the genus Leptospira. In humans, it can cause a wide range of symptoms, some of which may be mistaken for other diseases. Some infected persons, however, may have no symptoms at all.
The human immunodeficiency virus (HIV) is a lentivirus (a subgroup of retrovirus) that causes HIV infection and over time acquired immunodeficiency syndrome (AIDS).
Treponema is a genus of spiral-shaped bacteria. The major treponeme species of human pathogens is Treponema pallidum, whose subspecies are responsible for diseases such as syphilis, bejel, and yaws.
Haemophilus is the name of a group of bacteria. There are several types of Haemophilus. They can cause different types of illnesses involving breathing, bones and joints, and the nervous system. One common type, Hib (Haemophilus influenzae type b), causes serious disease. It usually strikes children under 5 years old
Moraxella is a genus of Gram-negative bacteria in the Moraxellaceae family. It is named after the Swiss ophthalmologist Victor Morax. The organisms are short rods, coccobacilli, or as in the case of Moraxella catarrhalis, diplococci in morphology, with asaccharolytic, oxidase-positive, and catalase-positive properties
Pseudomonas is a type of bacteria that can cause infections. Pseudomonas is a common genus of bacteria, which can create infections in the body under certain circumstances. There are many different types of Pseudomonas bacteria
Neisseria gonorrhoeae is the obligate human pathogen that causes the sexually transmitted disease (STD) gonorrhea. This Gram-negative diplococci/gonococci does not infect other animals or experimental animals and does not survive freely in the environment. The gonococcal infection occurs in the upper or lower tract, pharynx, ophthalmic area, rectum, and bloodstream. During the 1980’s gonorrhea was also referred to as “the clap” when public awareness was quite minimal. This was one of the venereal diseases prostitutes hoped to contract since it resulted in infertility by pelvic inflammatory disease (PID). As documentation, diagnostic testing, and public awareness improved, there has been a decline in incidence reports, however, it is still considered a very common infectious disease.
Meningococci are a type of bacteria that cause serious infections. The most common infection is meningitis, which is an inflammation of the thin tissue that surrounds the brain and spinal cord. Meningococci can also cause other problems, including a serious bloodstream infection called sepsis. In its early stages, you may have flu-like symptoms and a stiff neck. But the disease can progress quickly and can be fatal. Early diagnosis and treatment are extremely important. Lab tests on your blood and cerebrospinal fluid can tell if you have it. Treatment is with antibiotics. Since the infection spreads from person to person, family members may also need to be treated.
A vaccine can prevent meningococcal infections.
Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Diphtheria causes a thick covering in the back of the throat. It can lead to difficulty breathing, heart failure, paralysis, and even death. CDC recommends vaccines for infants, children, teens and adults to prevent diphtheria. The presentation consists of basic concepts regarding the bacteria and its infection. It has explanation in detail about signs and symptoms of Diptheria
Contraindications, Adverse reactions and ocular nutritional supplementsArun Geetha Viswanathan
utritional supplements comprise a great deal of the products available over the counter in most pharmacies. Although most vitamin supplements are relatively harmless—except for the fat soluble ones A, D, E, and K—they are not the only supplements available to patients. Some of these other, non-vitamin supplements can actually be harmful to patients and often they have been proven to be ineffective. This doesn’t mean that patients will stop taking them though, which in turn leaves the potential for contraindications of nutritional supplements with prescription-based drugs wide open.
Ageing is a gradual process that takes place over many decades. Most theories of ageing relate to impaired DNA replication and loss of cell viability and hence the viability of the body’s organs. Ageing is often accompanied by socioeconomic changes that can have a great impact on the nutritional needs and status of elderly individuals. The incidence of disability increases with ageing, with over a third of the elderly population limited by chronic conditions and unable to carry on normal daily living activity
Carotenoids are class of fat soluble coloured pigments, found primarily in plants, where they play a critical role in the photosynthetic process. Two xanthophylls, lutein (L) and zeaxanthin (Z) accumulate at the macula where they make up macular pigment (MP). In the human eye, the MP optical density (MPOD) is not uniformly distributed across the retina
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
3. Glycosaminoglycans
• The cornea and vitreous contain a macromolecular structure composed of collagen
proteins, which form fibres (with diameters which are thinner than half the
wavelength of light)
• interfibrillar spaces filled with polysaccharides known as glycosaminoglycans
(GAGs) -reduce the effects of diffraction.
• These polysaccharides consist of repeating disaccharide units forming long
polysaccharide chains.
4. Glycosaminoglycans
• The major GAG of the vitreous is hyaluronic acid – made of disaccharide unit of
glucuronate and N-acetyl glucosamine.
• The cornea contains four different types of GAG:
(1) keratan sulphate
(2) Chondroitin
(3) chondroitin sulphate
(4) dermatan sulphate
5. Proteoglycans
• Proteoglycans (mucoproteins) are proteins which contain one or more GAG
covalently linked to it
• these proteins are usually non-collagenous proteins, some GAGs have been found
to be linked to certain collagen types and are referred to as ‘part-time’
proteoglycans
• proteoglycans in ocular matrices interact with collagen in a functional manner and
(1) Regulates collagen fibril diameter
(2) Maintains the fibril distance in the collagen network
7. Corneal Stroma
• Types of collagen in stroma.
Stromal Collagen
Type I (60%) Type V (10%) Type VI (30%)
Type III
(low conc.)
8. Corneal Stroma
• The collagen fibrils are 25–35 nm in diameter
• transparency of the corneal stroma is due to the organised lattice structure of the
collagen fibrils
• The structure is responsible for destructive interference, where light scattered by
neighbouring fibrils in predictable and opposing directions cancels each other out,
except in the primary visual axis
• fibril size and interfibrillar space play important roles in maintaining transparency
of this tissue.
9. Corneal Stroma
• Light-scattering occurs when the regional fluctuation in refractive index exceeds
the dimension equal to one-half the wavelength of light (200 nm) (>200 nm in case
of corneal swelling)
• proteoglycans are responsible for maintaining the relative positions of the fibrils
and for restricting fibril lateral growth
• proteoglycans control fibril diameter which both play an important role in ensuring
correct fibrillogenesis and corneal transparency.
10. The Vitreous
• The vitreous is highly hydrated ( >98% Water ) and transparent ( 90% of visible of
light)
• It is composed of hydrogel structure maintained by a network of thin unbranched
collagen fibrils with GAGs (hyaluronan) filling the spaces of the network.
• This is needed for maintaining corneal transparency.
• The peripheral or cortical vitreous contains hyalocyte cells(believed to originate
from blood Macrophages)
• The hyalocytes are secretory cells responsible for the synthesis of hyaluronan and
collagen which then move toward the central vitreous for matrix assembly.
12. Hyaluronan
• The concentration of adult vitreous hyaluronan has been estimated between 65
and 400 mg/ml.
• subject to age dependent concentration changes, involving an initial increase in the
first 20 yrs - relatively constant concentration up to 70 yrs - then further increase
• Its high molecular mass and numerous mutually repelling anionic groups give rise
to a highly hydrated viscous matrix
• at high concentrations they form hydrodynamic interactions which give rise to
networks which can act as a molecular sieve, excluding cells and large molecules,
thereby contributing to transparency
15. Age-Related Change in Vitreal Connective Tissue
• The human vitreous is subject to age-related changes, and morphologically two
distinct but simultaneous structural alterations occur:
(1) collapse of the collagen network (syneresis)
(2) formation of collagen free, liquid-filled spaces (synchysis)
• The vitreous undergoes liquefaction with age
• The liquefaction is due to a decrease in gel volume, believed to occur by syneresis
(contraction) of the collagen fibrillar network.
• The collagen fibrils aggregate into large bundles
• These structural changes occur by the time the eye has reached adult size- 14–15
yrs (20% liquefied) - 40–50 years - 80–90 years ~50% of the vitreous is liquefied
16. Age-Related Change in Vitreal Connective Tissue
• If the hyaluronic acid (HA) molecules are no longer attached or associated with the
collagen, it will clump, and stick to itself squeezing water molecules out.
• With age, there is a depolymerisation of hyaluronic acid, causing these molecules
to release their water and form lacunae i.e., pockets of liquefied vitreous.
• The collagen 'filaments' aggregate to form larger 'fibrils', causing further collapse
of the vitreous gel structure.
• This process is known as vitreous degeneration and 'syneresis’.
• The collagen fibrils may 'float' within the liquid vitreous pockets, giving the patient a
sensation of floaters.
18. Age-Related Change in Vitreal Connective Tissue
• The posterior border of the vitreous base separates from the retina as the gel-like
structure of the vitreous collapses, leading to posterior vitreous detachment (PVD)
• PVD is common with ageing, and usually makes a clean break away from the retina.
• the vitreous adheres tightly to the retina in certain places and a small, horseshoe-
shaped tear in the retina can result from persistent tugging by the vitreous, leading
to retinal detachment
19. Glucose Metabolism in Cornea
• much of the glucose is metabolised by the hexose monophosphate pathway (the
pentose shunt) with no production of ATP.
• The products are ribose-5-phosphate and NADPH (2)
• The corneal epithelium is permeable to oxygen - give rise to reactive oxygen species
- oxidise the sulfhydryl (-SH) groups of proteins
20. Glucose Metabolism in Lens
• Three main pathways :
(1) glycolysis (80–85%)
(2) TCA (Krebs) cycle (~5%)
(3) hexose monophosphate (pentose shunt) (10– 15%)
• Glucose yields – 2 ATP under aerobic condition and 36 ATP under anaerobic
condition
• The maintenance of the lens structural integrity requires:
(1) osmotic balance provided by Na+,K+-ATPase
(2) redox balance provided by glutathione (and GSH reductase)
(3) protein synthesis necessary for growth and maintenance of the tissue.
21. Glucose Metabolism in Lens
• GSH maintains unaggregated state of lens proteins by reducing or reversing
oxidative damage by UV
• HMP in the lens provides the NADPH required by GSH reductase, which is
important in maintaining GSH and redox balance
22. NADPH NADP+
Glucose Metabolism in Lens
• Glucose can be converted to sorbitol by auto-oxidation or enzymatically by aldose
Reductase which utilises NADPH supplied by HMP
• Sorbitol can be converted to fructose by sorbitol dehydrogenase;
• the ratio of the two enzymes in the human lens favours sorbitol production
• Less than 5% of glucose is converted to sorbitol
• it slowly diffuses out to the aqueous humour and doesn't accumulate in the lens
23. Glucose Metabolism in Lens
• high external glucose concentrations lead to increased lens glucose, which saturates
the normal metabolic pathways, leading to increased sorbitol synthesis
• Sorbitol accumulation leads to increased osmolarity of the lens - affects the
structural organisation of crystallins and promotes denaturation and aggregation,
leading to increased scattering of light and cataract
Sorbitol accumulation
↑ Glucose accumulation ↑ Osmolarity
Changes in
crystallin
organization
Cataract
↓ Glucose accumulation
(infantile hypoglycemia)
↓ NADPH ↑ ROS
24. Glucose Metabolism in Lens
• one of the most metabolically active tissues
• The blood–retinal barrier is overcome by carrier-mediated facilitated diffusion
through specific plasma membrane glycoproteins, the glucose transporters GLUT 1
and GLUT 3.
GLUT1
GLUT3
Glucose
BloodRetinalBarrier
Pigmented epithelium
26. Glucose Metabolism in Lens
• In the absence of glucose (hypoglycemia, aglycemia) the retina can metabolise
exogenous lactate or pyruvate
• The hexose monophosphate pathway (HMP) is also active in the retina: produce
NADPH for Glutathione and Ribose phosphate for DNA and RNA
Sorbitol accumulation
↑ Glucose accumulation ↑ Osmolarity
Fluid
retention
and hypoxia
Retinopathy
27. Glycemic Index (GI)
• A relative ranking of carbohydrate in foods
according to how they affect blood glucose
levels.
• Carbohydrates with a low GI value (55 or less)
are more slowly digested, absorbed and
metabolised and cause a lower and slower rise
in blood glucose and, therefore insulin levels
• Foods with a high GI are those which are rapidly
digested, absorbed and metabolised and result
in marked fluctuations in blood sugar (glucose)
levels.
28. Glycemic Index (GI)
• There are three classifications for GI:
• Individual food portion:
• Low: 55 or less
• Moderate: 56 – 69
• High: 70+
• Low GI carbohydrates – is one of the secrets to long-term health, reducing your risk
of type 2 diabetes and heart disease. It is also one of the keys to maintaining
weight loss
29. GI to Age-Related Macular Degeneration
• In the first study published in 2006, women with high dietary GI compared had an
approximately 2.7-fold increased risk for early AMD, mainly pigment abnormality
• Consuming lower GI diets appears to provide ophthalmic benefit in addition to that
gained from currently known dietary factors.
• Under hyperglycemia, aldose reductase (AR) reduces glucose to sorbitol which is
later oxidized to fructose.
• In this process, the AR consumes cofactor NADPH.
• Therefore, the hyperglycemic polyol pathway consumes NADPH and hence results
in the depletion of reduced glutathione (GSH).
• This increases intracellular oxidative stress.
31. GI to Age-Related Macular Degeneration
Hyperglycemia
• Oxidative stress
• Angiogenesis
• Capillary occlusion
• Blood flow abnormalities
• Inhibition of cell division of retinal associated cells
• Induces inflammation and apoptosis
32. Diabetic eye disease
• Diabetic retinopathy affects blood vessels in the retina that lines the back of the eye. It
is the most common cause of vision loss among people with diabetes and the leading
cause of vision impairment and blindness among working-age adults.
• Diabetic macular edema (DME). A consequence of diabetic retinopathy, DME is
swelling in an area of the retina called the macula.
• Cataract is a clouding of the eye’s lens. Adults with diabetes are 2-5 times more likely
than those without diabetes to develop cataract. Cataract also tends to develop at an
earlier age in people with diabetes.
• Glaucoma is a group of diseases that damage the eye’s optic nerve—the bundle of
nerve fibers that connects the eye to the brain. Some types of glaucoma are associated
with elevated pressure inside the eye. In adults, diabetes nearly doubles the risk of
glaucoma..
33. Carbohydrates
Carbohydrates are polyhydroxy aldehydes, ketones, alcohols, acids, their simple
derivatives and their polymers having linkages of the acetal type. They may be
classified according to their degree of polymerization and may be divided initially into
three principal groups, namely sugars, oligosaccharides and polysaccharides
Carbohydrates
Monosaccharides Disaccharides Polysaccharides
Complex
polysaccharides
34. Classification on the basic of degree of polymerization
• Monosaccharides: consisting of single unit of sugar and also known as simple
sugars (DP: 1)
• Disaccharides: consisting of (2) monosaccharide's (DP: 1-2)
• Oligosaccharides: each moleculeconsisting of (3-9) monosaccharide units (DP: 3-9)
• Polysaccharides: each molecule containing more than 9 but usually several
monosaccharaides units (DP: >9)
35. Monosaccharides
Biose (C2H4O2)
• Glycolic aldehyde is the only member of this group
• Crystalline and is easily soluble in water
• Sweet in taste
Trioses (C3H6O3)
• Two compounds of this category are: Glyceraldehyde and dihyroxyacetone
• They occur in plant and animal tissue in small amounts and are derived from
breakdown of glucose
36. Monosaccharides
Tetroses (C4H8O4)
• Two compounds belonging to this category are known: erythrose and threose
Pentoses (C5H10O5)
• Pentoses occurring commonly in nature are: 1) Arabinose, 2) Xylose, 4) Ribose
• Deoxyribose which occur free deoxyribonucleic acid contains one oxygen atom less
than ribose
• Arabinose: It does not occur free in nature. The polysaccharide Xylan present in
cherry gum or gum arabic is formed is formed by combination of a large number of
arabinose molecules
37. Monosaccharides
Pentoses (C5H10O5)
• Xylose: Xylose doesn’t occur free in nature. Polysaccharide xylan present in wood
gum and straws is formed by combination of a large number of arabinose
molecules.
• Ribose: It is present in adenylic acid and ribonucleic acid (RNA) occurring in plant
and animal tissues
• Deoxyribose: It is constituent of deoxyribonucleic acid (DNA) which is present in
the nucleus of plant and animal cells
38. Monosaccharides
Hexoses (C6H12O6)
• Divided into two groups:
• 1) Aldoses or sugar containing aldehyde group, e.g. glucose, galactose and
mannose
• 2) Ketose or sugars containing a ketone group, e.g. fructose and sorose
• Glucose – main source of energy. Normal human blood contains 80-100mg of
glucose
• Fructose: occurs in free state in many fruits. Readily utilized by body
• Galactose: present in milk
39. Disaccharides
Formed by combination of two monosaccharides
Sucrose
• Cane sugar, Formed by condensation of one molecule of glucose and one molecule
of fructose. Readily hydrolyzed by sucrase present in intestinal juice
Sucrose Glucose + Fructose
Sucrase
40. Disaccharides
Maltose
• Malt Sugar is present in malt made from barley, ragi, jowar etc.
• Formed from two molecules of glucose
Maltose 2 Glucose
Maltase
41. Disaccharides
Lactose
• Milk Sugar
• Formed by condensation one molecule of glucose and one molecule of galactose
• Digested by lactase in intestinal juice
Lactose Glucose + Galactose
Lactase
42. Polysaccharides
Starch
• Important source of starch are: cereals and millets, roots and tubers
• It consists of mixture of two polymers amylose and amylopectin
• Starch is hydrolyzed by dilute acids to glucose
• Amylase present in saliva or pancreatic juice convert starch to maltose
Starch Glucose
Acids
Starch Maltose
Amylase
43. Polysaccharides
Dextrins
• Polysaccharides formed y the partial hydrolysis of starch by acids or amylase
• They composed of a large number of glucose molecules
• They are soluble in water
Glycogen
• Is the reserve carbohydrate found in liver (3-7 %) and muscle (0.5-1%) of animal
and man
• It is made of large number of glucose molecules
44. Functions of Carbohydrates in the diet
1. They supply energy for body functions and for doing work
2. They are essential for the oxidation of fats, production of ribose sugar, ATP and
NAD(P)H
3. They exert a sparing action on proteins
4. They provide carbon skeleton for the synthesis of some non essential amino
acids
5. Carbohydrates are present in all tissues and cells
6. Its is needed for production and functioning of glycoproteins
7. They add flavor to the diet
8. Starch which forms the main source of carbohydrates in the average diets has a
land taste and is non-irritant and hence can e consumed in large amounts to
provide major part of the energy requirements of the body
45. Important source of carbohydrate in diet
Food item Carbohydrate in g/100g
Cereals and Millets 63-79
Pulses 56-60
Nuts an Oil seeds 10-25
Roots and Tubers 22-39
Arrow root flour 85-87
Cane sugar 99
Sago 87-89
Honey 79-80
Jaggery 94-95
Milk 4-5
Dried Fruits 67-77
Fresh Fruit 10-25
46. Carbohydrate Requirements
• The percentage calories derived from carbs in diets consumed by a vast majority
of people in developing countries is as high as 60-70%
• The carbohydrate calories should be at least 40% in well balanced diets
• The level of carbohydrate calories in the diet will also depend on the availability
of fat and the economic conditions of the people as the fat is about twice as
costly as cereals and millets in developing countries
Age group Optimal level of carbohydrate calories
as per cent of total calories
Adults 50-70
Expectant and Nursing Mothers 40-60
Infants (1-12 months) 40-50
Preschool children (1-5 yrs. ) 40-60
Older children and adolescents 50-70