NEET MDS Synopsis
ANTICHOLINERGIC DRUGS
Pharmacology
ANTICHOLINERGIC DRUGS
Blocks the action of Ach on autonomic effectors.
Classification
Natural Alkaloids - Atropine. Hyoscine
Semi-synthetic deriuvatives:- Homatropine, Homatropine methylbromide, Atropine methonitrate.
Synthetic compounds
(a) Mydriatics - Cyclopentolate. Tropicamide.
(b) Antisecretory - Antispasmodics - Propantha1ine. Oxy-phenonium, Pirenzipine.
c) Antiparkinsonism- Benzotopine, Ethopropazine, Trihexyphenidyl, Procyclidine, Biperiden
Other drugs with anticholinergic properties • Tricyclic Antidepressants • Phenothiazines • Antihistaminics • Disopyramide
MUSCARINIC RECEPTORS SUBTYPES & ANTAGONISTS
• M 1 Antagonists – Pirenzepine, Telenzepine, dicyclomine, trihexyphenidyl
• M 2 Antagonists – Gallamine, methoctramine
• M 3 Antagonists – Darifenacin, solifenacin, oxybutynin, tolterodine
Pharmacological Actions
CNS - stimulation of medullary centres like vagal. respiratory. vasomotor and inhibition of vestibular excitation and has anti-motion sickness properties.
CVS - tachycardia.
Eye - mydriasis
Smooth muscles - relaxation of the muscles receiving parnsympathetic motor innervation.
Glands - decreased secretion of sweat and salivary glands
Body Temperature - is increased as there is stimulation of temperature regulating centre.
Respiratory System- Bronchodilatation & decrease in secretions. For COPD or Asthma - antimuscarinic drugs are effective
GIT - Pirenzepine & Telenzepine - decrease gastric secretion with lesser side effects.
METAPLASIA
General Pathology
METAPLASIA
A reversible replacement of one type of adult tissue by another type of tissue. It is usually an adaptive substitution to a. cell type more suited to an environment, often at the cost of specialised function.
(1) Epithelial metaplasia:
Squamous metaplasia. This is the commoner type of metaplasia and is seen in:
Tracheobronchial lining in chronic smokers and in bronchiectasis.
In Vitamin A deficiency.
Columnar metaplasia:
Intestinalisation of gastric mucosa in chronic gastritis.
(2) Connective tissue metaplasia:
Osseous-Metaplasia in :
Scars.
Myositis ossificans
Myeloid metaplasia in liver and spleen.
Digit Sucking and Infantile Swallow
PedodonticsDigit Sucking and Infantile Swallow
Introduction to Digit Sucking
Digit sucking is a common behavior observed in infants and young children. It
can be categorized into two main types based on the underlying reasons for the
behavior:
Nutritive Sucking
Definition: This type of sucking occurs during
feeding and is essential for nourishment.
Timing: Nutritive sucking typically begins in the
first few weeks of life.
Causes: It is primarily associated with feeding
problems, where the infant may suck on fingers or digits as a substitute
for breastfeeding or bottle-feeding.
Non-Nutritive Sucking
Definition: This type of sucking is not related to
feeding and serves other psychological or emotional needs.
Causes: Non-nutritive sucking can arise from
various psychological factors, including:
Hunger
Satisfying the innate sucking instinct
Feelings of insecurity
Desire for attention
Examples: Common forms of non-nutritive sucking
habits include:
Thumb or finger sucking
Pacifier sucking
Non-Nutritive Sucking Habits (NMS Habits)
Characteristics: Non-nutritive sucking habits are often
comforting for children and can serve as a coping mechanism in stressful
situations.
Implications: While these habits are generally normal
in early childhood, prolonged non-nutritive sucking can lead to dental
issues, such as malocclusion or changes in the oral cavity.
Infantile Swallow
Definition: The infantile swallow is a specific pattern
of swallowing observed in infants.
Characteristics:
Active contraction of the lip musculature.
The tongue tip is positioned forward, making contact with the lower
lip.
Minimal activity of the posterior tongue and pharyngeal musculature.
Posture: The tongue-to-lower lip contact is so
prevalent in infants that it often becomes their resting posture. This can
be observed when gently moving the infant's lip, causing the tongue tip to
move in unison, suggesting a strong connection between the two.
Developmental Changes: The sucking reflex and the
infantile swallow typically diminish and disappear within the first year of
life as the child matures and develops more complex feeding and swallowing
patterns.
Mycobacterium leprae
General Pathology
Mycobacterium leprae
- tuberculoid type has intact cellular immunity
- forms granulomas and kill the organisms (very few present).
- evokes a positive lepromin skin test
- localized skin lesions that lack symmetry
- nerve involvement (organisms invade Schwann cells) that dominates the clinical picture and leads to skin anesthesia, muscle atrophy and autoamputation.
- lepromatous leprosy patients lack cellular immunity
- no granulomas
- organisms readily identified
- negative lepromin skin test
- Bacteremia disseminates to cooler areas like the digits.
- symmetrical, skin lesions that produce the classic leonine facies; biopsy reveals grentz zone in superficial dermis and then organisms in macrophages.
- neural involvement is a late feature of the disease.
- lepromin skin test is to determine host immunity; not a diagnostic test.
- treatment: dapsone + rifampin
Procoagulant Drugs
Pharmacology
Procoagulant Drugs:
Desmospressin Acetate
• Is a synthetic analogue of the pituitary antidiuretic hormone (ADH).
• Stimulates the activity of Coagulation Factor VIII
• Use for treatment of hemophilia A with factor VIII levels less than or equal to 5%, treatment of hemophilia B or in clients who have factor VIII antibodies. Treatment of severe classic von Willebrand's disease (type I) and when an abnormal molecular form of factor VIII antigen is present. Use for type IIB von Willebrand's disease.
Amino Acid Biosynthesis
Biochemistry
Amino Acid Biosynthesis
Glutamate and Aspartate
Glutamate and aspartate are synthesized from their widely distributed a-keto acid precursors by simple 1-step transamination reactions. The former catalyzed by glutamate dehydrogenase and the latter by aspartate aminotransferase, AST. Aspartate is also derived from asparagine through the action of asparaginase. The importance of glutamate as a common intracellular amino donor for transamination reactions and of aspartate as a precursor of ornithine for the urea cycle is described in the Nitrogen Metabolism page.
Alanine and the Glucose-Alanine Cycle
Role in protein synthesis,
Alanine is second only to glutamine in prominence as a circulating amino acid.. When alanine transfer from muscle to liver is coupled with glucose transport from liver back to muscle, the process is known as the glucose-alanine cycle. The key feature of the cycle is that in 1 molecule, alanine, peripheral tissue exports pyruvate and ammonia (which are potentially rate-limiting for metabolism) to the liver, where the carbon skeleton is recycled and most nitrogen eliminated.
There are 2 main pathways to production of muscle alanine: directly from protein degradation, and via the transamination of pyruvate by alanine transaminase, ALT (also referred to as serum glutamate-pyruvate transaminase, SGPT).
glutamate + pyruvate <-------> a-KG + alanine
Cysteine Biosynthesis
The sulfur for cysteine synthesis comes from the essential amino acid methionine. A condensation of ATP and methionine catalyzed by methionine adenosyltransferase yields S-adenosylmethionine
Tyrosine Biosynthesis
Tyrosine is produced in cells by hydroxylating the essential amino acid phenylalanine. This relationship is much like that between cysteine and methionine. Half of the phenylalanine required goes into the production of tyrosine; if the diet is rich in tyrosine itself, the requirements for phenylalanine are reduced by about 50%.
Phenylalanine hydroxylase is a mixed-function oxygenase: one atom of oxygen is incorporated into water and the other into the hydroxyl of tyrosine. The reductant is the tetrahydrofolate-related cofactor tetrahydrobiopterin, which is maintained in the reduced state by the NADH-dependent enzyme dihydropteridine reductase (DHPR).
Ornithine and Proline Biosynthesis
Glutamate is the precursor of both proline and ornithine, with glutamate semialdehyde being a branch point intermediate leading to one or the other of these 2 products. While ornithine is not one of the 20 amino acids used in protein synthesis, it plays a significant role as the acceptor of carbamoyl phosphate in the urea cycle
Serine Biosynthesis
The main pathway to serine starts with the glycolytic intermediate 3-phosphoglycerate. An NADH-linked dehydrogenase converts 3-phosphoglycerate into a keto acid, 3-phosphopyruvate, suitable for subsequent transamination. Aminotransferase activity with glutamate as a donor produces 3-phosphoserine, which is converted to serine by phosphoserine phosphatase.
Glycine Biosynthesis
The main pathway to glycine is a 1-step reaction catalyzed by serine hydroxymethyltransferase. This reaction involves the transfer of the hydroxymethyl group from serine to the cofactor tetrahydrofolate (THF), producing glycine and N5,N10-methylene-THF. Glycine produced from serine or from the diet can also be oxidized by glycine cleavage complex, GCC, to yield a second equivalent of N5,N10-methylene-tetrahydrofolate as well as ammonia and CO2.
Glycine is involved in many anabolic reactions other than protein synthesis including the synthesis of purine nucleotides, heme, glutathione, creatine and serine.
Aspartate/Asparagine and Glutamate/Glutamine Biosynthesis
Glutamate is synthesized by the reductive amination of a-ketoglutarate catalyzed by glutamate dehydrogenase; it is thus a nitrogen-fixing reaction. In addition, glutamate arises by aminotransferase reactions, with the amino nitrogen being donated by a number of different amino acids. Thus, glutamate is a general collector of amino nitrogen.
Aspartate is formed in a transamintion reaction catalyzed by aspartate transaminase, AST. This reaction uses the aspartate a-keto acid analog, oxaloacetate, and glutamate as the amino donor. Aspartate can also be formed by deamination of asparagine catalyzed by asparaginase.
Asparagine synthetase and glutamine synthetase, catalyze the production of asparagine and glutamine from their respective a-amino acids. Glutamine is produced from glutamate by the direct incorporation of ammonia; and this can be considered another nitrogen fixing reaction. Asparagine, however, is formed by an amidotransferase reaction.
Aminotransferase reactions are readily reversible. The direction of any individual transamination depends principally on the concentration ratio of reactants and products. By contrast, transamidation reactions, which are dependent on ATP, are considered irreversible. As a consequence, the degradation of asparagine and glutamine take place by a hydrolytic pathway rather than by a reversal of the pathway by which they were formed. As indicated above, asparagine can be degraded to aspartate
Keratinized Gingiva and Attached Gingiva
PeriodontologyKeratinized Gingiva and Attached Gingiva
The gingiva is an essential component of the periodontal tissues, providing
support and protection for the teeth. Understanding the characteristics of
keratinized gingiva, particularly attached gingiva, is crucial for assessing
periodontal health.
Keratinized Gingiva
Definition:
Keratinized gingiva refers to the gingival tissue that is covered by
a layer of keratinized epithelium, providing a protective barrier
against mechanical and microbial insults.
Areas of Keratinized Gingiva:
Attached Gingiva:
Extends from the gingival groove to the mucogingival junction.
Marginal Gingiva:
The free gingival margin that surrounds the teeth.
Hard Palate:
The roof of the mouth, which is also covered by keratinized
tissue.
Attached Gingiva
Location:
The attached gingiva is the portion of the gingiva that is firmly
bound to the underlying alveolar bone.
Width of Attached Gingiva:
The width of attached gingiva varies based on location and can
increase with age and in cases of supraerupted teeth.
Measurements:
Greatest Width:
Found in the incisor region:
Maxilla: 3.5 mm - 4.5 mm
Mandible: 3.3 mm - 3.9 mm
Narrowest Width:
Found in the posterior region:
Maxillary First Premolar: 1.9 mm
Mandibular First Premolar: 1.8 mm
Clinical Significance
Importance of Attached Gingiva:
The width of attached gingiva is important for periodontal health,
as it provides a buffer zone against mechanical forces and helps
maintain the integrity of the periodontal attachment.
Insufficient attached gingiva may lead to increased susceptibility
to periodontal disease and gingival recession.
Assessment:
Regular assessment of the width of attached gingiva is essential
during periodontal examinations to identify potential areas of concern
and to plan appropriate treatment strategies.
Lupus erythematosus
General Pathology
Lupus erythematosus
- chronic discoid lupus is primarily limited to the skin, while SLE can involve the skin and other systems.
- pathogenesis: light and other external agents plus deposition of DNA (planted antigen) and immune complexes in the basement membrane.
Histology:
- basal cells along the dermal-epidermal junction and hair shafts (reason for alopecia) are vacuolated (liquefactive degeneration)
- thickening of lamina densa as a reaction to injury.
- immunofluorescent studies reveal a band of immunofluorescence (band test) in involved skin of chronic discoid lupus or involved/uninvolved skin of SLE.
- lymphocytic infiltrate at the dermal-epidermal junction and papillary dermis.