basic science Flashcards
what transcription factor direct mesenchymal stem cells to be osteoblasts
Runx2
WNT effects on osteoblasts
promote osteoblast survival and proliferation
what does sclerostin do to osteoblasts?
produces DKK-1 which inhibits WNT/B-catenin which decreases stimulation of osteoblasts
nitrogen-containing bisphosphonate mechanism
inhibit protein prenylation within mevalonate pathway, blocking farnesyl pyrophosphate synthase. causes loss of GTP formation that’s needed for ruffle border
non-nitrogen containing bisphosphonate mechanism
metabolized into a non-functional ATP analogue inducing apoptosis
wolff’s law
remodeling occurs in response to mechanical stress
Hueter-Volkmann law
compression inhibits growth, tension stimulates growth
what zone of the physis do lysosomal storage diseases affect?
reserve zone
what is the precursor cell to osteoclasts?
hematopoietic cells in macrophage lineage
osteoblast precursor
undifferentiated mesenchymal stem cells
bone graft resorption rates, fastest to slowest
calcium sulfate -> tricalcium phosphate -> hydroxyapatite
what synthetic bone graft has the highest compressive strength?
calcium phosphate
what properties does DBM have as a bone graft?
osteoconductive, osteoinductive
what properties does autograft have as a bone graft?
osteoconductive, osteoinductive, osteogenic
what properties do synthetic allografts have as bone graft?
osteoconductive only
what properties do BMPs have as bone graft?
osteoinductive only
how does calcium affect PTH?
decreased calcium levels stimulate parathyroid chief cells to increase PTH, acts to increase resorption of calcium
defect in type 1 hereditary vitamin-D dependent rickets
defect in renal 25(OH)-vitamin D 1a-hydroxylase, inhibits conversion of vitamin D to active form
inheritance of type 1 and type 2 hereditary Vitamin-D dependent rickets
autosomal recessive
defect in type 2 hereditary Vitamin-D dependent rickets
defect in intracellular receptor for 1,25(OH)2-vitamin D3
inheritance of Vitamin D-resistant/familial hypophosphatemic rickets
x-linked dominant mutation in PHEX gene
labs in familial hypophosphatemic rickets/Vitamin-D resistant
low phosphate, normal calcium, vitamin D, and PTH, high alk phos
what lab value distinguishes type 1 from type 2 hereditary vitamin-D dependent rickets?
type 1 has low Vitamin D (can’t be converted to active form), type 2 has really high Vitamin D (receptor defect)
what type of collagen is the disc annulus?
type 1
what type of cartilage is the nucleus pulposus?
type 2
what disease causes black urine and black cartilage?
alkpatonuria, accumulation of homogentisic acid causes cartilage destruction
inheritance of alkaptonuria
autosomal recessive defect of homogentisic acid oxidase
most sensitive and specific lab test for RA
anti-CCP
mechanism of methotrexate
folate analogue, inhibits purine metabolism and T-cell activation
mechanism of leflunomide
inhibits pyrimidine synthesis
mechanism of hydroxychloroquine
blocks activation of toll-like receptors (TLR9) which decreases activity of dendritic cells
mechanism of etanercept
TNF-a receptor fusion protein that binds to TNF-a
mechanism of infliximab
anti TNF-a monocolonal antibody
mechanism of adalimumab
anti TNF-a monoclonal antibody
mechanism of golimumab
anti TNF-a monoclonal antibody
mechanism of anakinra
recombinant IL-1 receptor antagonist
mechanism of rituximab
monoclonal antibody to CD20 antigen (inhibits B cells)
mechanism of abatacept
selective co-stimulation modulator that binds to CD-80 and CD-86 (inhibits T cells)
mechanism of ustekinumab
monoclonal antibody targeting IL-12 and IL-23
mechanism of tocilizumab
IL-6 receptor inhibitor
what DMARDs target TNF-a?
etanercept, adalimumab, infliximab
lab in ankylosing spondylitis
HLA-B27
what kind of arthritis is DIP involvement associated with?
psoriatic
crystals seen in gout
monosodium urate, yellow needle-shaped, negatively birefringent
crystals seen in pseudogout
calcium pyrophosphate, rhomboid-shaped, blue, weakly positively birefringent
order of zones at direct bone-tendon insertion
tendon > fibrocartilage > mineralized fibrocartilage > bone
what changes on SSEPs are concerning?
50% decrease in amplitude, 10% increase in latency
characteristic of MRSA that makes it resistant
PBP2A (penicillin binding protein 2A) coded by mecA gene on SCCmecIV
GPCs in clusters
staph
GPCs in pairs/chains
strep
most common cause of septic arthritis after chickenpox/varicella
Group A strep (GPCs in chains)
p acnes
gram positive anaerobic rod
where is coccidiomycosis found
southwestern US to central America
where is histoplasmosis found
Ohio and Mississippi river valleys
where is blastomyces found
africa and southeast/central US
where is cryptococcus found
pacific northwest, british columbia, subtropics
risk of HIV transmission from contaminated needlestick
0.3%
risk of HIV transmission from blood transfusion
1/500,000
risk of HCV transmission from needle stick
3%
examples and mechanism of B-lactam antibiotics
penicillin, cephalosporin, vancomycin.
inhibit cross-linking of polysaccharides in the cell wall by blocking transpeptidase enzyme
examples and mechanism of aminoglycosides
gentamycin, tobramycin
inhibit protein synthesis (30S-ribosomal subunit)
examples and mechanism of clindamycin and macrolides
clinda, erythromycin, clarithromycin, azithromycin
inhibit dissociation of peptidyl-transfer RNA from ribosomes (50S-ribosomal subunit)
mechanism of tetracylcines
inhibit protein synthesis (30S ribosomal subunit)
mechanism of rifampin
inhibits DNA-dependent RNA polymerase F
examples and mechanism of quinolones
ciprofloxacin, levofloxacin
inhibits DNA gyrase
best measures of adequate resuscitation in shock
urine output > 30 ml/hr, lactate < 2.5
mechanism of aspirin
irreversibly binds COX in platelets
mechanism of warfarin
inhibits VitK-2,3-epoxide reductase to prevent vitamin-K carboxylation in liver, inhibits factors 2, 7, 9, 10, proteins C and S
mechanism of heparin
activates antithrombin III which then inhibits factors 2a, 3, 10a
mechanism of LMWH/lovenox
activates antithrombin III which then inhibits factors 2a, 3, 10a
mechanism of fondaparinux
indirect Xa inhibitor (through AT3). fondaparINux - INdirect inhibition
mechanism of rivaroxaban, apixaban
direct Xa inhibitor
mechanism of dabigatran and argatroban
direct thrombin (IIa) inhibitor
mechanism of TXA
synthetic lysine analogue, competitive inhibitor of plasminogen activation
risk of HCV transmission from blood transfusion
1 in 2 million
active form of Vitamin D
1,25-dihydroxycholecalciferol
material with a linear stress-strain curve up to failure, little to no plastic deformation
brittle
material that undergoes large plastic deformation before failure
ductile
anisotropic material
mechanical properties vary with the direction of the applied load
what metal is most susceptible to galvanic and crevice corrosion
stainless steel
the risk of galvanic corrosion is highest between what two metals?
stainless steel and Co-Cr alloy
what is Hooke’s law?
stress is proportional to strain when a material is loaded in the elastic zone
galvanic corrosion
dissimilar metals leads to electrochemical destruction
crevice corrosion
occurs in fatigue cracks due to differences in oxygen tension, titanium least prone
fretting corrosion
mode of destruction at the contact site from relative micromotion of two materials/components
what non-organic component gives bone its compressive strength?
hydroxyapatite (makes up 60% of dry weight). Ca10(PO4)6(OH)2
which organic components of bone are made by osteoblasts?
collagen 1, osteocalcin, osteonectin, alk phos
what conditions stimulate human mesenchymal stem cells to convert to osteoblasts?
low strain, high oxygen
what conditions stimulate human mesenchymal stem cells to convert to fibroblasts?
high strain
what conditions stimulate human mesenchymal stem cells to convert to chondroblasts?
med strain, low oxygen
what molecules do osteoclasts use to break down bone?
MMP, cathepsin K, TRAP
what inflammatory markers activate osteoclasts?
IL-1, IL-6, TNFa, PG-E2
what indirectly stimulates osteoclasts via stimulating osteoblasts?
Vitamin D, PTH, PTHrP
what directly inhibits osteoclasts?
calcitonin, TGF-B, IL-10. (OPG and estrogen indirectly via osteoblasts)
what cell produces sclerostin?
osteocyte
what does calcitonin do to osteocytes?
stimulates production of sclerostin
what does PTH do to osteocytes?
inhibits (indirectly stimulates osteoblasts)
inheritance of cleidocranial dysplasia
autosomal dominant mutation in CBFA-1/RUNx2
what causes osteopetrosis?
osteoclast malfunction causing decreased osteoclast activity/remodeling (due to proton pump/Cl channel or carbonic anhydrase-2 malfunction, or OPG overexpression)
what causes pyknodysostosis?
cathepsin K deficiency (causes acro-osteolysis of terminal phalanges)
what is the treatment for paget’s disease?
bisphosphonates and calcitonin
what is the treatment for paget’s disease secondary sarcoma?
chemo and wide resection
labs in paget’s disease
high urine N- and C-telopeptides
which bisphosphonates are non-nitrogen containing?
the low TEC ones (tiludronate, etidronate, clodronate)
what condition is teriparatide contraindicated in?
paget’s, increases risk of secondary sarcoma
what 2 receptors are on osteoblasts?
PTH receptor and Vitamin D receptor
which growth factors promote cartilage/early tendon and ligament healing?
TIP - TGF-B, IGF-1, PDGF
what type of collagen is present in initial tendon/ligament healing?
type 3
what type of collagen is involved in ehlers-danlos?
type 5
what type of collagen is involved in multiple epiphyseal dysplasia?
type 9
what type of collagen is present in initial bone healing?
type 10
what type of collagen is involved in schmid chondrodysplasia?
type 10
what happens to water and collagen in OA?
water increases, collagen quantity, quality/cross linking, and proteoglycan synthesis decreases, no change in chondrocyte number
what happens to cartilage in aging?
water decreases, collagen cross linking increases, keratan sulfate increases, chondroitin sulfate, proteoglycan synthesis, and chondrocyte number decrease
what happens to collagen in a healed ligament?
increased number of fibers, lower cross linking, diameter, and mass
which collagen type is increased in early OA?
type 10
which conditions affect the reserve zone of the physis?
PKGD (packaged), pseudoachondroplasia (COMP), kniest syndrome (col 2A1 defect), gaucher (b-glucocerebrosidase), diastrophic dysplasia (AR mutation in DTDST sulfate transport gene)
which conditions affect the proliferative zone of the physis?
MEGA - MHE (AD mutation in ext gene), gigantism, achondroplasia (AD mutation in FGFR3)
which conditions affect the hypertrophic zone of the physis?
3S’s - SCFE, salter harris fx, Schmid
what controls proximal to distal limb growth? what is the gene product?
AER, FGF
what controls radial to ulnar limb growth? what is the gene product?
ZPA, sonic hedgehog
what controls dorsal to ventral limb growth? what is the gene product?
WNT, wnt
effects of PTH
activate osteoclasts, increase calcium (kidney resorption) and Vitamin D production, decrease phosphate (kidney resorption)
effects of Vitamin D
activate osteoclasts, increase calcium and phosphate
what zone of the physis is affected in nutritional Vitamin D deficient rickets?
hypertrophic/zone of provisional calcification
labs in vitamin D deficient rickets
low Vitamin D, calcium, phosphate. high PTH (compensatory for low calcium) and alk phos
treatment for x-linked hypophosphatemic rickets
phosphate and Vitamin D
labs in renal osteodystrophy
low calcium, high phosphate (kidney malfunction leads to phosphate retention), high PTH and alk phos
psoriatic arthritis HLA
HLA B27+
what is overexpressed in psoriatic arthritis?
cathelicidin
what gene is associated with CA-MRSA?
PVL gene
mechanism of corticosteroids
inhibit phospholipase A2 (converts phospholipids to arachidonic acid which gets converted to prostaglandins)
genetic hypercoagulable states
M35CS - MTHFR gene mutation, AT3 deficiency, Factor V Leiden, Protein C and S deficiency
order of muscle fiber recruitment
slow-twitch fatigue resistant type 1, type IIa fast-twitch fatigue resistant, type IIb fast-twitch easily fatigable