The document discusses the absorption, transport, metabolism, and excretion of vitamin A. It notes that vitamin A is absorbed in the small intestine and transported to the liver via chylomicrons. In the liver, it is stored as retinyl esters and then mobilized as retinol bound to retinol-binding protein for transport to tissues. Vitamin A undergoes various metabolic conversions including esterification and isomerization. It is excreted in both urine and feces, with a high efficiency of absorption under normal conditions.
VITAMIN B3
GUL MUNEER
Niacin
Niacinamide 0R Nicotinamide
Vitamin P OR PP (pellagra preventive)
Pellagra preventive factor
Anti black tongue factor
Nicotinic acid
Vitamin G (after Goldberger’s death, vitamin B3 was some times called in his honor)
Structure of Vitamin B3
Function of Vitamin B3
DISCOVERY of Vitamin B3
PROPERTIES of Vitamin B3
Nicotinic Acid (Plant form)
CHEMISTRY of Vitamin B3
Sources of Vitamin B3
RECOMMENDED DAILY ALLOWANCE (RDA) of Vitamin B3
BIOCHEMICAL FUNCTIONS of Vitamin B3
Digestion and Absorption of Dietary Niacin
Metabolism of B-3
Deficiency of B3
VITAMIN B3
GUL MUNEER
Niacin
Niacinamide 0R Nicotinamide
Vitamin P OR PP (pellagra preventive)
Pellagra preventive factor
Anti black tongue factor
Nicotinic acid
Vitamin G (after Goldberger’s death, vitamin B3 was some times called in his honor)
Structure of Vitamin B3
Function of Vitamin B3
DISCOVERY of Vitamin B3
PROPERTIES of Vitamin B3
Nicotinic Acid (Plant form)
CHEMISTRY of Vitamin B3
Sources of Vitamin B3
RECOMMENDED DAILY ALLOWANCE (RDA) of Vitamin B3
BIOCHEMICAL FUNCTIONS of Vitamin B3
Digestion and Absorption of Dietary Niacin
Metabolism of B-3
Deficiency of B3
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.
Vitamin A, Digestion, absorption, transport, Functions and requirement and deficiency ad eye relate problems.
Vitamin C, Functions, requiremnts, deficiency
Vitamin E, defciency and eye
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.
Vitamin A, Digestion, absorption, transport, Functions and requirement and deficiency ad eye relate problems.
Vitamin C, Functions, requiremnts, deficiency
Vitamin E, defciency and eye
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.
CDSCO and Phamacovigilance {Regulatory body in India}NEHA GUPTA
The Central Drugs Standard Control Organization (CDSCO) is India's national regulatory body for pharmaceuticals and medical devices. Operating under the Directorate General of Health Services, Ministry of Health & Family Welfare, Government of India, the CDSCO is responsible for approving new drugs, conducting clinical trials, setting standards for drugs, controlling the quality of imported drugs, and coordinating the activities of State Drug Control Organizations by providing expert advice.
Pharmacovigilance, on the other hand, is the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problems. The primary aim of pharmacovigilance is to ensure the safety and efficacy of medicines, thereby protecting public health.
In India, pharmacovigilance activities are monitored by the Pharmacovigilance Programme of India (PvPI), which works closely with CDSCO to collect, analyze, and act upon data regarding adverse drug reactions (ADRs). Together, they play a critical role in ensuring that the benefits of drugs outweigh their risks, maintaining high standards of patient safety, and promoting the rational use of medicines.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Muktapishti is a traditional Ayurvedic preparation made from Shoditha Mukta (Purified Pearl), is believed to help regulate thyroid function and reduce symptoms of hyperthyroidism due to its cooling and balancing properties. Clinical evidence on its efficacy remains limited, necessitating further research to validate its therapeutic benefits.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
2. Absorption of vitamin A
I.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
3. Absorption of retinoids
• Most of the preformed vitamin A in the
diet is in the form of retinyl esters.
• Retinyl esters are hydrolyzed in the
lumen of the small intestine to yield
retinol.
• This step is catalyzed by hydrolases
produced by the pancreas and situated
on the mucosal brush border or intrinsic
to the brush border itself.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
4. Absorption of retinoids
• The retinyl esters, as well as the carotenoids,
are hydrophobic and, thus, depend on
micellar solubilization for their dispersion in
the aqueous environment of the small
intestinal lumen.
• Vitamin A is poorly utilized from low-fat diets!
• The micellar solubilization of vitamin A
facilitates access of soluble hydrolytic
enzymes to their substrates.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
5. Absorption of retinoids
The overall absorption of retinol from retinyl
esters appears to be fairly high (about 75%).
This process appears to be minimally affected by
the level and type of dietary fat, although the
absorption is appreciably less efficient at very
high vitamin A doses .
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
6. Absorption of retinoids
Vitamin A can also be absorbed via non
lymphatic pathways.
In mammals, the portal system may be an
important alternative route of vitamin A
absorption when the normal lymphatic pathway
is blocked.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
8. Carotenoid metabolism linked
to absorption
• Some carotenoids can be provitamins A because they
can be metabolized to yield retinal due to the action
of retinal-forming carotene dioxygenases.
• Most of this bioconversion occurs via the central
cleavage of the polyene moiety by a predominantly
cytosolic enzyme, β-carotene 15,15′-dioxygenase, found
in the intestinal mucosa, liver and corpus luteum.
• The enzyme requires iron as a cofactor.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
9. Retinoid metabolism linked to
absorption
• Retinal produced by at least the central cleavage step
is reduced in the intestinal mucosa to retinol.
• This step is catalyzed by another enzyme, retinaldehyde
reductase, which is also found in the liver and eye.
• The reduction requires a reduced pyridine nucleotide
(NADH/NADPH) as a cofactor.
• This step can be catalyzed by a short-chain alcohol
dehydrogenase/aldehyde reductase.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
10. Mucosal metabolism of retinol
• Retinol, formed either from the hydrolysis of
dietary retinyl esters or from the reduction of
retinal cleaved from β-carotene, is absorbed
by facilitated diffusion via a specific
transporter.
• Then, retinol is quickly re-esterified with long-
chain fatty acids in the intestinal mucosa.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
11. Mucosal metabolism of retinol
• Vitamin A is transported to the liver mainly (80 to 90% of
a retinol dose) in the form of retinyl esters.
• The composition of lymph retinyl esters is independent
of the fatty acid composition of the most recent meal.
• Retinyl palmitate typically comprises about half of the
total esters.
• Retinyl stearate comprises about a quarter.
• Retinyl oleate and retinyl linoleate are present in small
amounts.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
12. Two pathways for the enzymatic reesterification of
retinol are:
A low-affinity route involves uncomplexed retinol.
• It is catalyzed by acyl-CoA: retinol
acyltransferase.
A high-affinity route involves retinol complexed
with a specific binding protein, cellular retinol-
binding protein type II.
• It is catalyzed by lecithin–retinol acyltransferase.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
14. Retinyl esters
Retinyl esters are secreted from the
intestinal mucosal cells in the hydrophobic
cores of chylomicron particles, by which
absorbed vitamin A is transported to the
liver through the lymphatic circulation,
ultimately entering the plasma
compartment through the thoracic duct.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
15. Transport of carotenoids
Carotenoids that are not
metabolized at the intestinal mucosa
are transported from that organ by
chylomicra via the lymphatic
circulation to the liver, where they
are transferred to lipoproteins.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
16. Transport of carotenoids
The hydrocarbon carotenoids are
transported primarily in low-density
lipoproteins (LDLs).
The more polar carotenoids are transported
in a more evenly distributed manner among
LDLs and high-density lipoproteins (HDLs).
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
17. Transport of carotenoids
β-carotene is retained by the
chylomicron remnants to be
internalized by the liver for
subsequent secretion in very low
density lipoproteins (VLDLs).
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
18. Impact of abetalipoproteinemia
• The absorption of vitamin A (as well as the other fat soluble
vitamins) is a particular problem in patients
with abetalipoproteinemia.
• These patients lack apo B and can not synthesize any of the
apo B-containing lipoproteins: LDLs, VLDLs, chylomicra.
• Having no chylomicra, they show hypolipidemia and low
plasma vitamin A levels.
• When given oral vitamin A supplementation, their plasma
levels are normal.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
19. Storage of vitamin A in the liver
• Newly absorbed retinyl esters are taken up by the
liver in association with chylomicron remnants by
receptor-mediated endocytosis on the part of liver
parenchymal cells.
• Within those cells, remnants are degraded by
lysosomal enzymes.
• Retinol can be transferred from the parenchymal
cells to stellate cells, where it is re-esterified.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
20. Retinyl ester hydrolysis
• Vitamin A is mobilized as retinol from the liver by
hydrolysis of hepatic retinyl esters.
• This mobilization accounts for about 55% of the
retinol discharged to the plasma (the balance
comes from recycling from extrahepatic tissues).
• The retinyl ester hydrolase involved in this
process shows extreme variation between
individuals.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
21. Retinol-binding protein
Once mobilized from liver
stores, retinol is transported to
peripheral tissues by means of a
specific carrier protein, plasma
retinol-binding protein (RBP).
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
22. Transport of retinoids
The transport, storage, and
metabolism of the retinoids involve
their binding to several other binding
proteins, such as cellular retinol-
binding protein types I and II, and
cellular retinoic acid-binding protein
types I and II.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
23. Cellular uptake of retinol
• Due to their hydrophobic character, the
plasma membranes do not present a barrier
to retinol uptake.
• Retinol can enter target cells by nonspecific
partitioning into the plasma membrane from
RBP, but most of the vitamin appears to enter
cells through specific RBP (receptor-mediated
mechanisms).
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
24. Retinol recycling
The majority of retinol
that leaves the plasma
appears to be recycled.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
25. Plasma retinol homeostasis
In healthy individuals,
plasma retinol is maintained
within a narrow range:
40–50 mg/ml in adults.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
26. Vitamin A in adipose tissue
Appreciable amounts
of vitamin A are stored
in adipocytes: 15–20%
of total body store.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
27. Milk retinol
Retinol is transferred
from mother to
infant through milk.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
28. Metabolism of vitamin A
III.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
29. Metabolism of vitamin A
The metabolism of vitamin A centers
around the transport form, retinol, and the
various routes of conversion available to it:
•esterification
•conjugation
•oxidation
•isomerization
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
30. Excretion of vitamin A
IV.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
31. Excretion of vitamin A
• Vitamin A is excreted in various forms in
both the urine and feces.
• Under normal physiological conditions,
the efficiency of enteric absorption of
vitamin A is high (80–95%), with 30–60%
of the absorbed amount being deposited
in esterified form in the liver.
4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
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4/7/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.