clinical sciences 4 Flashcards
What are the four main types of membrane receptors?
Ligand-gated ion channel receptors
Tyrosine kinase receptors
Guanylate cyclase receptors
G protein-coupled receptors
What are examples of Ligand-gated ion channel receptors?
generally mediate fast responses
e.g. nicotinic acetylcholine, GABA-A & GABA-C, glutamate receptors
What are examples of tyrosine kinase receptors?
receptor tyrosine kinase: insulin, insulin-like growth factor (IGF), epidermal growth factor (EGF)
non-receptor tyrosine kinase: PIGG(L)ET: Prolactin, Immunomodulators (cytokines IL-2, Il-6, IFN), GH, G-CSF, Erythropoietin and Thromobopoietin
What are Guanylate cyclase receptors
contain intrinsic enzyme activity
e.g. atrial natriuretic factor, brain natriuretic peptide
What are G-protein coupled receptors?
generally mediate slow transmission and affect metabolic processes
activated by a wide variety of extracellular signals e.g. Peptide hormones, biogenic amines (e.g. adrenaline), lipophilic hormones, light
7-helix membrane-spanning domains
consist of 3 main subunits: alpha, beta and gamma
the alpha subunit is linked to GDP.Ligand binding causes conformational changes to receptor, GDP is phosphorylated to GTP,and the alpha subunit is activated
G proteins are named according to the alpha subunit (Gs, Gi, Gq)
Examples of Gs protein receptors?
Stimulates adenylate cyclase → increases cAMP → activates protein kinase A
- Beta-1 receptors (epinephrine, norepinephrine, dobutamine)
- Beta-2 receptors (epinephrine, salbuterol)
- H2 receptors (histamine)
- D1 receptors (dopamine)
- V2 receptors (vasopressin)
- Receptors for ACTH, LH, FSH, glucagon, PTH, calcitonin, prostaglandins
Examples of Gi protein receptors?
Inhibits adenylate cyclase → decreases cAMP → inhibits protein kinase A
- M2 receptors (acetylcholine)
- Alpha-2 receptors (epinephrine, norephinephrine)
- D2 receptors (dopamine)
- GABA-B receptor
Examples of Gq protein receptors?
Activates phospholipase C → splits PIP2 to IP3 & DAG → activates protein kinase C
- Alpha-1 receptors (epinephrine, norepinephrine)
- H1 receptors (histamine)
- V1 receptors (vasopressin)
- M1, M3 receptors (acetylcholine)
what is the structure of collagen?
Collagen is characterised by its triple-helix structure, which consists of three polypeptide chains wound around each other, forming a rope-like assembly that provides tensile strength to tissues.
What is involved in the synthesis of collagen?
Collagen synthesis involves several steps, starting with the translation of collagen mRNA to form preprocollagen, which contains extra peptide sequences.
what are the post translocation modifications involved in collagen synthesis?
Before forming the mature collagen, the procollagen undergoes extensive post-translational modifications such as hydroxylation of proline and lysine residues, crucial for stability and secretion.
what is involved in the assembly and secretion of collagen?
Hydroxylated procollagen forms a triple helix, is processed in the Golgi apparatus, and secreted into the extracellular matrix, where it forms collagen fibres.
What are the stages of sleep?
N1 → N2 → N3 → REM
Theta → Sleep spindles/K-complexes → Delta → Beta
The Sleep Doctor’s Brain
Parametric tests?
Student’s t-test - paired or unpaired
Pearson’s product-moment coefficient - correlation
Non-parametric tests?
Mann-Whitney U test
compares ordinal, interval, or ratio scales of unpaired data
Wilcoxon signed-rank test
compares two sets of observations on a single sample, e.g. a ‘before’ and ‘after’ test on the same population following an intervention
chi-squared test
used to compare proportions or percentages e.g. compares the percentage of patients who improved following two different interventions
Spearman, Kendall rank - correlation
What are the phases of the cardiac action potential ?
what are the conduction velocities in the heart?
What is the main function and properties of Neutrophils?
Primary phagocytic cell in acute inflammation
Granules contain myeloperoxidase and lysozyme
Most common type of white blood cell
Multi-lobed nucleus
What are the main function and properties of Basophil?
Releases histamine during allergic response
Granules contain histamine and heparin
Expresses IgE receptors on the cell surface
Bi-lobed nucleus
What is the main function and propeties of mast cell?
Present in tissues and are similar in function to basophils but derived from different cell lines
Releases histamine during allergic response
Granules contain histamine and heparin
Expresses IgE receptors on the cell surface
What is the main function and properties of eosinophil?
Defends against protozoan and helminthic infections
Bi-lobed nucleus
What is the main function and properties of monocyte?
Diffferentiates into macrophages
Kidney shaped nucleus
What is the main function and properties of macrophage?
Involved in phagocytosis of cellular debris and pathogens
Acts as an antigen presenting cell
Major source of IL-1
What is the main function and properties of natural killer cell?
Induce apoptosis in virally infected and tumour cells
What is the main function and properties of dendritic cell?
Acts as an antigen presenting cell
What is ion movement is responsible for th slurred upstroke of the R wave on an ECG (delat wave) in WPW ?
The presence of an R wave with a slurred upstroke on ECG suggests a delta wave, characteristic of Wolff-Parkinson-White (WPW) syndrome. This occurs due to an accessory pathway that conducts impulses faster than the normal conduction system through the atrioventricular (AV) node. This leads to impulses bypassing the AV node, leading to early ventricular depolarisation, resulting in a slurred upstroke in the R wave. The primary ion movement responsible for this early depolarisation is sodium ion influx through fast sodium channels during phase 0 of the action potential.
Tumour supressor gene vs oncogenes?
Tumour suppressor genes - loss of function results in an increased risk of cancer
Oncogenes - gain of function results in an increased risk of cancer
conditions associated with thiamine deficiency
Wernicke’s encephalopathy: nystagmus, ophthalmoplegia and ataxia
Korsakoff’s syndrome: amnesia, confabulation
dry beriberi: peripheral neuropathy
wet beriberi: dilated cardiomyopathy
Thiamine is a water soluble vitamin of the B complex group. One of it’s phosphate derivates, thiamine pyrophosphate (TPP), is a coenzyme in the following enzymatic reactions:
pyruvate dehydrogenase complex
pyruvate decarboxylase in ethanol fermentation
alpha-ketoglutarate dehydrogenase complex
branched-chain amino acid dehydrogenase complex
2-hydroxyphytanoyl-CoA lyase
transketolase
Thiamine is therefore important in the catabolism of sugars and aminoacids. The clinical consequences of thiamine deficiency are therefore seen first in highly aerobic tissues such as the brain (Wenicke-Korsakoff syndrome) and the heart (wet beriberi).
What is Abetalipoproteinaemia
Abetalipoproteinaemia is caused by vitamin E deficiency which can present with peripheral neuropathy and cerebellar ataxia.
What are the cell suface markers on Haematopietic stem cells?
CD34
What are the cell suface markers on helper T cells?
CD4, TCR, CD3, CD28
What are the cell surface markers on cytotoxic t cells?
CD8, TCR, CD3, CD28
What are the cell surface markers on regulatory t cells?
CD4, CD25, TCR, CD3, CD28
cell surface markers on B cells?
CD19, CD20, CD40, MHC II, B7
Cell surface markers on macrophages?
CD14, CD40, MHC II, B7
Cell surface markers on natural killer cells?
CD16, CD56
what are cluster of diferentitation molecules?
CD
cell surface markers, primarily found on immune cells, used to identify and characterize different types of immune cells and their subsets.
what are MHC molecules?
MHC (Major Histocompatibility Complex) molecules are cell surface proteins that play a crucial role in the immune system by presenting peptide fragments of proteins to T cells, enabling the body to recognize and respond to foreign substances and pathogens
What is the function of CD1?
MHC molecule that presents lipid molecules
What is is the function of CD2?
Found on thymocytes, T cells, and some natural killer cells that acts as a ligand for CD58 and CD59 and is involved in signal transduction and cell adhesion
is the function of what is CD3?
The signalling component of the T cell receptor (TCR) complex
is the function of What is CD4?
Found on helper T cells.
Co-receptor for MHC class II
Used by HIV to enter T cells
is the function of What is CD5?
Found in the majority of mantle cell lymphomas
What is is the function of CD8?
Found on cytotoxic T cells.
Co-receptor for MHC class I
Found on a subset of myeloid dendritic cells
What is the function of CD14?
Cell surface marker for macrophages
Where is CD15 expressed?
Expressed on Reed-Sternberg cells (along with CD30)
Where is the function of CD16?
Bind to the Fc portion of IgG antibodies
What is the function of CD21?
Receptor for Epstein-Barr virus
What is the function of CD28?
Interacts with B7 on antigen presenting cell as costimulation signal
What is the function of CD45?
Protein tyrosine phosphatase present on all leucocytes
What is the function of CD56?
Unique marker for natural killer cells
What is the function of CD95?
Acts as the FAS receptor, involved in apoptosis
X-linked recessive?
only males affected
Except patients with turners
Passed on through heterozygote females (carriers) and male-to-male transmission is not seen
Affected males can only have unaffected sons and carrier daughters.
Each male child of a heterozygous female carrier has a 50% chance of being affected whilst each female child of a heterozygous female carrier has a 50% chance of being a carrier.
Two main causes of Acute tubular necrosis?
There are two main causes of ATN; ischaemia and nephrotoxins:
ischaemia
shock
sepsis
nephrotoxins
aminoglycosides
myoglobin secondary to rhabdomyolysis
radiocontrast agents
lead
Features of acute tubular necrosis?
features of AKI: raised urea, creatinine, potassium
muddy brown casts in the urine
Histopathological features of acute tubular necrosis?
tubular epithelium necrosis: loss of nuclei and detachment of tubular cells from the basement membrane
dilatation of the tubules may occur
necrotic cells obstruct the tubule lumen
what are the three phases of acute tubular necrosis?
oliguric phase
polyuric phase
recovery phase
what is the chloride shift in respiratory physiology?
CO2 diffuses into RBCs
CO2 + H20 —- carbonic anhydrase -→ HCO3- + H+
H+ combines with Hb
HCO3- diffuses out of cell,- Cl- replaces it
What is the Bohr effect in respiratory physiology?
increasing acidity (or pCO2) means O2 binds less well to Hb
What is the haldane effect in respiratory physiology?
increase pO2 means CO2 binds less well to Hb
What is intention to treat analysis?
Intention to treat analysis is a method of analysis for randomized controlled trials in which all patients randomly assigned to one of the treatments are analysed together, regardless of whether or not they completed or received that treatment.
Intention to treat analysis is done to avoid the effects of crossover and drop-out, which may affect the randomization to the treatment groups.
What is the cell cycle regulated by?
The cell cycle is regulated by proteins called cyclins which in turn control cyclin-dependent kinase (CDK) enzymes.
What are the cell cycle phases?
- G0 (resting phase)
- G1(cell increases in size - under influence of p53)
- S (synthesis of DNA, RNA and histone, centrosome duplication)
- G2 (cells continue to increase in size)
- M (mitosis - cell devision, shortest phase of cell cycle)
What cell cycle phase determines the length of the cell cycle?
G1
What regulartory proteins are involved in G1 phase of cell cycle?
Cyclin D / CDK4, Cyclin D / CDK6 and Cyclin E / CDK2: regulates transition from G1 to S phase
What regulatory proteins are involved in S phase of the cell cycle?
Cyclin A / CDK2: active in S phase
What regulatory proteins are involved in the G2 phase of the cell cycle?
Cyclin B / CDK1: regulates transition from G2 to M phase
What immunoglobulin is involved in the activation of B cells?
IgD
Which complement deficiency predisposes to Neisseria meningitidis?
C5-9
What may linear regression do?
linear regression may be used to predict how much one variable changes when a second variable is changed
What is relative risk?
Relative risk (RR) is the ratio of risk in the experimental group (experimental event rate, EER) to risk in the control group (control event rate, CER). The term relative risk ratio is sometimes used instead of relative risk.
Relative risk is often used in cohort studies
What is a funnel plot?
A funnel plot is primarily used to demonstrate the existence of publication bias in meta-analyses.
Interpretation
a symmetrical, inverted funnel shape indicates that publication bias is unlikely
conversely, an asymmetrical funnel indicates a relationship between treatment effect and study size. This indicates either publication bias or a systematic difference between smaller and larger studies (‘small study effects’)
What is ascorbic acid?
vitamin C
Function of vitamin C?
Functions
antioxidant
collagen synthesis: acts as a cofactor for enzymes that are required for the hydroxylation proline and lysine in the synthesis of collagen
facilitates iron absorption
cofactor for norepinephrine synthesis
What is Scurvy?
Vitamin C deficiency (scurvy) leads to defective synthesis of collagen resulting in capillary fragility (bleeding tendency) and poor wound healing
Features vitamin C deficiency
gingivitis, loose teeth
poor wound healing
bleeding from gums, haematuria, epistaxis
How do you calculate standard error of the mean?
SEM = SD / square root (n)
How do you calculate confidence interval?
A 95% confidence interval:
lower limit = mean - (1.96 * SEM)
upper limit = mean + (1.96 * SEM)
The above formula is a slight simplification:
if a small sample size is used (e.g. n < 100) then it is important to use a ‘Student’s T critical value’ look-up table to replace 1.96 with a different value
if a different confidence level is required, e.g. 90% then 1.96 is replaced by a different value. For 90% this would 1.645
what is the confidence interval?
in simpler terms: a range of values within which the true effect of intervention is likely to lie
what is the normal size of the kidney ?
Each kidney is about 11cm long, 5cm wide and 3cm thick
where are the kidneys located?
They are located in a deep gutter alongside the projecting vertebral bodies, on the anterior surface of psoas major. In most cases, the left kidney lies approximately 1.5cm higher than the right.
On the left hand side the hilum is located at the L1 vertebral level and the right kidney at level L1-2. The lower border of the kidneys is usually alongside L3.
Anatomical relations of the kidneys?
What is the right kidney in direct contact with?
Right suprarenal gland
Duodenum
Colon
What is the left kiney in direct contact with?
Left suprarenal gland
Pancreas
Colon
Which interleukin is responsible for hypotension in sepsis ?
Sepsis triggers the release of IL-1 causing vasodilation → hypotension
By stimulating the release by the endothelium of vasoactive factors such as PAF, nitric oxide and prostacyclin it also causes vasodilation and increases vascular permeability. It is therefore one of the mediators of shock in sepsis. Along with IL-6 and TNF, it acts on the hypothalamus causing pyrexia.
Which interleukin is the key mediator in the immune response?
Interleukin 1 (IL-1) is a key mediator of the immune response. It is secreted mainly by macrophages and monocytes and acts as a costimulator of T cell and B cell proliferation.
What are examples of IL-1 inhibitors?
anakinra
IL-1 receptor antagonist
used in the management of rheumatoid arthritis
canakinumab
monoclonal antibody targeted at IL-1 beta
used systemic juvenile idiopathic arthritis and adult-onset Still’s disease
what clotting factors does heparin affect?
Prevents activation factors 2,9,10,11
What clotting factors does warfarin affect?
Affects synthesis of factors 2,7,9,10
If there is a isolated prolonged PT what is the most likely inherited cause?
Factor VII deficiency
An AR condition
Extrinsic pathway effected
APTT usually normal
Usually get mucocutaneous bleeding
Treat with Recombinant FVIIa, plasma-derived FVII
What occurs duing prophase?
Chromatin in the nucleus condenses
What occurs during prometaphase?
Nuclear membrane breaks down allowing the microtubules to attach to the chromosomes
What occurs during metaphase?
Chromosomes aligned at middle of cell
what occurs during anaphase?
The paired chromosomes separate at the kinetochores and move to opposite sides of the cell
What occurs during telophase?
Chromatids arrive at opposite poles of cell
What occurs during cytokinesis?
Actin-myosin complex in the centre of the cell contacts resulting in it being ‘pinched’ into two daughter cells
Fitness to fly - CV disease?
Cardiovascular disease
unstable angina, uncontrolled hypertension, uncontrolled cardiac arrhythmia, decompensated heart failure, severe symptomatic valvular disease: should not fly
uncomplicated myocardial infarction: may fly after 7-10 days
complicated myocardial infarction: after 4-6 weeks
coronary artery bypass graft: after 10-14 days
percutaneous coronary intervention: after 3 days
stroke: patients are advised to wait 10 days following an event, although if stable may be carried within 3 days of the event
Fitness to fly - respiratory disease?
Respiratory disease
pneumonia: should be ‘clinically improved with no residual infection’
pneumothorax: absolute contraindication, the CAA suggest patients may travel 2 weeks after successful drainage if there is no residual air. The British Thoracic Society used to recommend not travelling by air for a period of 6 weeks but this has now been changed to 1 week post check x-ray
Fitness to fly pregnancy?
Pregnancy
most airlines do not allow travel after 36 weeks for a single pregnancy and after 32 weeks for a multiple pregnancy
most airlines require a certificate after 28 weeks confirming that the pregnancy is progressing normally
Fitness to fly - surgery ?
Surgery
travel should be avoided for 10 days following abdominal surgery
laparoscopic surgery: after 24 hours
colonoscopy: after 24 hours
following the application of a plaster cast, the majority of airlines restrict flying for 24 hours on flights of less than 2 hours or 48 hours for longer flights
what is the major genetic susceptibility locus for rheumatoid arthritis?
The HLA-DRB1 gene is the major genetic susceptibility locus for rheumatoid arthritis (DRB104:01 and DRB104:04 hence the association with DR4)
Symtoms of Noonan syndrome?
As well as features similar to Turner’s syndrome (webbed neck, widely-spaced nipples, short stature, pectus carinatum and excavatum), a number of characteristic clinical signs may also be seen:
cardiac: pulmonary valve stenosis
ptosis
triangular-shaped face
low-set ears
coagulation problems: factor XI deficiency
what is noonan syndrome?
Often thought of as the ‘male Turner’s’, Noonan syndrome is an autosomal dominant condition associated with a normal karyotype. It is thought to be caused by a defect in a gene on chromosome 12
skewed distribution
Normal (Gaussian) distributions: mean = median = mode
Positively skewed distribution: mean > median > mode
Negatively skewed distribution mean < median < mode
To remember the above note how they are in alphabetical order, think positive going forward with ‘>’, whilst negative going backwards ‘
What is William’s syndrome?
William’s syndrome is an inherited neurodevelopmental disorder caused by a microdeletion on chromosome 7
What are the features of William’s syndrome?
Features
elfin-like facies
characteristic like affect - very friendly and social
learning difficulties
short stature
transient neonatal hypercalcaemia
supravalvular aortic stenosis
Diagnosis is made by FISH studies
when do you see subvalvular AS?
A subvalvular aortic stenosis is associated with hypertrophic obstructive cardiomyopathy
What is Niacin?
What are the features of Niacin deficiency?
Niacin is a water soluble vitamin of the B complex group. It is a precursor to NAD+ and NADP+ and hence plays an essential metabolic role in cells.
Biosynthesis
Hartnup’s disease: hereditary disorder which reduces absorption of tryptophan
carcinoid syndrome: increased tryptophan metabolism to serotonin
Consequences of niacin deficiency:
pellagra: dermatitis, diarrhoea, dementia
what chromosome are HLA antogen encoded by?
Chromosome 6
What stage in the cell cycle does vincristine act?
Vincristine, an antineoplastic agent, acts on the M phase of the cell cycle. It specifically inhibits tubulin polymerisation and spindle formation, thus preventing mitosis and causing cell death. This is crucial in cancer treatment as it halts the rapid proliferation of cancer cells.
what is responsible for haemolytic blood transfusion reactions?
Anti-A, B blood antibodies - IgM
when would you see red blood cell casts in the urine?
Glomerulonephritis
Renal ischaemia and infarction
When would you see white blood cell casts in the urine?
Acute pyelonephritis
Interstitial nephritis
when would you see granular - muddy brown - casts in the urine?
Acute tubular necrosis
When would you see Hyaline casts in the urine
Common and non-specific
May be seen following exercise or dehydration
When would you see Epithelial casts in the urine?
ATN
When would you see waxy casts in the urine?
Advanced CKD
when would you see fatty casts in the urine?
nephrotic syndrome
What would indicate that haematuria is glomerular in origin?
Dysmorphic red blood cells on microscopy
What are the effects of nitric oxide?
Nitrates
acts on guanylate cyclase leading to raised intracellular cGMP levels and therefore decreasing Ca2+ levels
vasodilation, mainly venodilation
inhibits platelet aggregation
clinical relevance of nitric oxide?
underproduction of NO is implicated in hypertrophic pyloric stenosis
lack of NO is thought to promote atherosclerosis
in sepsis increased levels of NO contribute to septic shock
organic nitrates (metabolism produces NO) is widely used to treat cardiovascular disease (e.g. angina, heart failure)
sildenafil is thought to potentiate the action of NO on penile smooth muscle and is used in the treatment of erectile dysfunctions
examples of tumour supressor genes?
What is anp broken down by?
ANP is broken down by neutral endopeptidases (also known as neprilysin).
What is hazard ratio?
The hazard ratio (HR) is similar to relative risk but is used when risk is not constant to time. It is typically used when analysing survival over time.
Properties of normal distribution ?
Properties of the Normal distribution
symmetrical i.e. Mean = mode = median
68.3% of values lie within 1 SD of the mean
95.4% of values lie within 2 SD of the mean
99.7% of values lie within 3 SD of the mean
this is often reversed, so that within 1.96 SD of the mean lie 95% of the sample values
the range of the mean - (1.96 *SD) to the mean + (1.96 * SD) is called the 95% confidence interval, i.e. If a repeat sample of 100 observations are taken from the same group 95 of them would be expected to lie in that range
What are the x-linked recessive conditions?
Androgen insensitivity syndrome
Becker muscular dystrophy
Colour blindness
Duchenne muscular dystrophy
Fabry’s disease
G6PD deficiency
Haemophilia A,B
Hunter’s disease
Lesch-Nyhan syndrome
Nephrogenic diabetes insipidus
Ocular albinism
Retinitis pigmentosa
Wiskott-Aldrich syndrome
What is the steps in atherosclerosis formation?
Initial endothelial dysfunction is triggered by a number of factors such as smoking, hypertension and hyperglycaemia this results in a number of changes to the endothelium including pro-inflammatory, pro-oxidant, proliferative and reduced nitric oxide bioavailability
fatty infiltration of the subendothelial space by low-density lipoprotein (LDL) particles
monocytes migrate from the blood and differentiate into macrophages.
These macrophages then phagocytose oxidized LDL, slowly turning into large ‘foam cells’. As these macrophages die the result can further propagate the inflammatory process.
smooth muscle proliferation and migration from the tunica media into the intima results in formation of a fibrous capsule covering the fatty plaque.
What is Alkaptonuria?
Alkaptonuria (ochronosis) is a rare autosomal recessive disorder of phenylalanine and tyrosine metabolism caused by a lack of the enzyme homogentisic dioxygenase (HGD) which results in a build-up of toxic homogentisic acid. The kidneys filter the homogentisic acid (hence black urine) but eventually it accumulates in cartilage and other tissues.
Alkaptonuria is generally a benign and often asymptomatic condition.
Possible features include:
pigmented sclera
urine turns black if left exposed to the air
intervertebral disc calcification may result in back pain
renal stones
Treatment for Alkaptonuria?
high-dose vitamin C
dietary restriction of phenylalanine and tyrosine
Which type of blood vessel vasoconstrict in response to hypoxia?
Pulmonary arteries vasoconstrict in the presence of hypoxia
A fall in the partial pressure of oxygen in the blood leads to vasoconstriction of the pulmonary arteries. This allows blood to be diverted to better aerated areas of the lung and improves the efficiency of gaseous exchange
What type of lab test is used to detect mutated oncogenes?
Polymerase chain reactions are used to detect mutated oncogenes
What are the different types of DNA mutations?
Which part of the renal tubule is impermeable to water?
The thin ascending limb of the loop of Henle is impermeable to water
Genetics of prader willi syndrome?
Prader-Willi syndrome is an example of genetic imprinting where the phenotype depends on whether the deletion occurs on a gene inherited from the mother or father:
Prader-Willi syndrome if gene deleted from father
Angelman syndrome if gene deleted from mother
Prader-Willi syndrome is associated with the absence of the active Prader-Willi gene on the long arm of chromosome 15. This may be due to:
microdeletion of paternal 15q11-13 (70% of cases)
maternal uniparental disomy of chromosome 15
features of prader willi syndrome?
hypotonia during infancy
dysmorphic features
short stature
hypogonadism and infertility
learning difficulties
childhood obesity
behavioural problems in adolescence
