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Lipid
Lipids are a group of fat-like substances that are insoluble in water but soluble in organic compounds. They include true fats, lipids, sterols, and hydrocarbons. Lipids are classified based on their solubility into simple lipids like fats and oils, compound lipids containing other groups, and derived lipids formed by hydrolysis. Their physical state determines how they behave in staining. Hydrophilic lipids are water-miscible while hydrophobic lipids are not. Special fixation and sectioning are required to demonstrate lipids histochemically. Stains like Oil Red O and Sudan dyes are used to identify lipids in tissues and smears. The distribution and accumulation of lipids are diagnostically important in several body systems and
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Lipid
- 1. Lipids Mr:Mahmoud Ibrahim MSc ofHistopathology and Cytology
- 2. Lipids •group of fator fat like substances characterized by their insolubility in water, it can be dissolved in organic compounds.
- 3. These fat wouldinclude: 1. True fats :esters of fatty acids and glycerol 2 .Lipids : phospholipids and wax. 3. Sterols :cholesterol. 4. Hydrocarbons: carotene.
- 4. Classification •Lipids are classifiedaccording to their solubility in organic solvents •1. Simple lipids: ester of fatty acids with alcohol and include fats, oils and waxes
- 5. Fats are neutralesters of glycerol with saturated or un saturated fatty acids. Oil are similar to fat but are liquid in room temperature . • .
- 6. •Waxes are estersof higher alcohol with long chains of fatty acids
- 7. •2. Compound lipids: consist of fatty acids and alcohol and one more of the other group such as phosphorous or nitrogen, these can be found in the brain and CNS.
- 8. •3. Derived lipids:fatty acids that can originated from simple and compound lipids by hydrolysis. Cholesterol .bile acids, and sex hormones are examples.
- 9. Physical properties • Thephysical state of particular lipids is necessary in determining it’s behavior in the staining reactions. • According to surface properties and their permeability either to aqueous or to organ tropic reagents, lipid are classified to
- 10. 1. Hydrophilic groups. 2.Hydrophobic groups.
- 11. Hydrophilic groups •These iswater miscible like phospholipids which are contain phosphor and basic group make it miscible with water.
- 12. Hydrophobic groups •Which arenot contain polar group that make it not miscible with water. •These can demonstrated with organo tropic solutions.
- 13. Fixation of lipids •The most common method for demonstration lipids in tissue is frozen section (cryostat). • The only reagents that truly fix lipid are osmium tetra oxide and chromic acid for short time.
- 14. •Prolonged fixation canalter the reactive group. •Formaldehyde can chemically alter certain group ,to avoid this this disadvantage we use formal calcium.
- 15. Microtomy •Frozen or cryostatsection are required for lipid histochemical..
- 16. Demonstration •Control Sections: •Control sectionare important in lipid demonstration to exclude interference from cross-reacting non lipid compound.
- 17. Positive control •Suggest theuse of cryostat section obtained from rat or human brain (phospholipids ),fatty liver (fatty acids) ,adrenal (cholesterol).
- 18. Negative control •Treating sectionat 56c for 30 minutes with chloroform- methanol mixture.
- 19. Extraction method •Lipids aretotally extracted by chloroform- methanol mixture if hydrochloric acid is included in the solvent to release bounds of lipids ,the addition of water is facilitating the extraction of phospholipids
- 20. Medical important oflipids 1. Lipids have vital role in normal cell membrane. 2. Myelin sheath is particularly rich in lipids. 3. Simple lipids are usually found in the body as energy stores
- 21. •4. Compound lipidis very important in brain and CNS.
- 22. Diagnostic importance 1. Nervoussystem: a. Demyelination occurs when myelin sheath damaged by infections agents, toxins and allergic reactions. b. Multiple sclerosis.
- 23. •c. Sphingolipidosis isgroup of storage disorders due to enzyme defect
- 24. •2. Cardiovascular system:Deposition of cholesterol in arterial wall leading to atherosclerosis, also lipid can accumulate in heart muscles of patient with cardiomyopathies
- 25. •included by bacteriainfections, alcohol ,toxins ,or due to chronic anemia.
- 26. 3. Skeletal muscles:Detect excess of neutral fat in muscles biopsies in case of primary and secondary lipid storage, due to deficiency in acyl coenzyme A dehydrogenases.
- 27. Fat stains • Theoil red O (ORO) stain can identify lipids (fat) in smears and tissues. Fresh smears or cryostat sections of tissue are necessary because fixatives containing alcohols, or routine tissue processing with clearing, will remove lipids.
- 28. •The ORO isa rapid and simple stain. •Uses: It can be useful in identifying fat emboli in lung tissue or clot sections of peripheral blood.
- 29. Oil red Ostain of fat emboli in lung.
- 30. • Oil redO - Fat Embolism - Fat stain
- 31. Lipid Staining: Oilred O and Hematoxylin.
- 32. Lipid in skin,demonstrated by Oil Red O method.
- 33. Sudan Dye •Sudan stainingis a simple physical process, in that dye is more soluble in fats than their dye solvents . However there are some evidence that staining may be by a process of adsorption.
- 34. •The first dyeused was Sudan III (Daddi 1896)
- 35.