Exam 2 Correlation Boxes Flashcards
DNA building block
deoxyribonucleotide
Deoxyribonucleotide
Composed of 2-deoxyribose with base (purine/pyrimidine) at 1’ position & phosphate at 5’ position
(Deoxy)ribonucleoside
Base plus (deoxy)ribose
(Deoxy)ribonucleotide
(Deoxy)ribonucleoside with 1 to 3 phosphate groups Base plus (deoxy)ribose with 1 to 3 phosphate groups
Nucleoside analog inhibitors (blue, p. 324)
Lack 3’-OH –> converted to dNTPs –> inhibit DNA replication
Examples: ara-C, acyclovir, AZT
Ara-C (arabinosylcytosine, cytarabine)
Nucleoside analog inhibitor containing the sugar arabinose
Animal cells convert to ara-CTP –> comp inh of DNA pol
Treats leukemia
Acyclovir (acyloguanosine)
Nucleoside analog inhibitor
Herpesvirus-encoded thymidine kinase catalyzes phosphorylation –> host enzymes convert mono-P –> tri-P
Lacks 3’-OH group, acts as chain terminator in DNA synth
AZT (azidothymidine)
Nucleoside analog inhibitor used in HIV therapy
Taken up by HIV-infected cells –> activated –> utilized by viral reverse transcriptase (RNA-dependent DNA pol)
Lacks 3’-OH group, acts as chain terminator in DNA synth
Xeroderma Pigmentosum (p 333)
Defect in NER complex (DNA repair process)
Skin extremely sensitive to sunlight, prone to developing melanomas & squamous cell carcinomas
UV light –> cyclobutane thymine dimers form in DNA (easily repaired in normal people by NER)
Hereditary nonpolyposis colorectal cancers (p 333)
Increased risk w/MER complex gene mutations (MSH2, MLH1)
Mutation in good copy of MER complex gene –> non-functional MER complex –> tumor allowed to develop
Cockayne syndrome (p 334)
Rare autosomal recessive, congenital disorder
Mutations in genes (ERCC6 & ERCC8) that are involved in TCR of DNA; if DNA not repaired –> cell dysfunction and cell death
Developmental and neurologic delay, photosensitivity, progeria; hearing loss/eye abnormalities; death occurs w/in first 20 yrs of life
Type A: ERCC 8, Type B: ERCC 6 (70% of cases)
BRCA associated Breast Cancer (p334)
Mutations in tumor suppressor genes (BRCA1 & BRCA2) –> 5x risk increase in women for breast/ovarian cancer before menopause (inc for men too)
BRCA1: Ass w/higher risk of cervical/uterine/pancreatic/colon cancer in women; pancreatic, testicular, & early prostate cancer in men
BRCA2: inc risk of developing melanoma & pancreatic, stomach, gallbladder, & bile duct cancer in women; pancreatic, testicular, & early prostate cancer in men (more often than BRCA1)
Transcription Factors (p. 341)
Trans-acting proteins that regulate gene transcription across chromosomes
Proteins that bind to many lipophilic hormones (steroid/thyroid hormones, vitamin D)
TF Deregulation (p. 348)
Causes inappropriate in/activation of cell growth genes –> oncogenesis/cancer
Can occur by aberrant increase in expression level or by coding sequence mutations that alter TF activity
TF homo/heterodimers
Can promote/repress transcription of target genes
Bind target sequences on DNA –> recruit other proteins (like RNA Pol)
TF regulatory hydrophilic molecules
Hydrophilic molecules that act at surface of cell via GPCR/receptor tyrosine kinase/receptor-ass kinase
Regulate gene expression, usually involving regulated phosphorylation
DNA-binding domains
Enable transcription factors to bind specific DNA sequences (response elements) in promoter/regulatory gene region
Promoter regions
Located immediately upstream of transcription start site
Regulatory sequences
May resides thousands of kb up/downstream from transcribed gene
Aberrant DNA methylation (p. 348)
Exemplified by FMR1: CGG expansion –> cytosine methylation –> region extends into promoter area –> transcription turned off
Oncogenes
Significantly represented by mutated TF genes
Increased TF expression level
Result of TF misregulation exemplified by an increase in number of gene copies
TF coding sequence mutations
Result of TF misregulation exemplified by loss of phosphorylation site required for regulated shutdown of TF activity
Preproinsulin to mature insulin (p. 363)
20-residue signal peptide cleaved in ER lumen –> pro insulin –> folds to form 2 intramolecular disulfide bridges –> passes through Golgi into beta granules –> cleaved to 33-residue C peptide (leaves behind mature insulin)
Fragile X Mental Retardation Syndrome
Gene encodes a protein involved in neurologic function
CGG expansion –> cytosine methylation –> region extends into promoter area –> transcription turned off
Gene is silent (even though triplet expansion occurs upstream of protein-coding region)
FMR1 gene
Encodes a protein involved in neurologic function
DNA sequence contains 30 repeats of CGG
Mutated DNA sequence contains >200 repeats of CGG
Preproinsulin
Made in pancreatic beta cells (single polypeptide w/104 AA’s)
PT collagen modification (p 364)
Inside cell: some lysines on precollagen –> 5-hydroxylysines –> some glycosylated w/gal & glc
Outside cell: some lysines/hydroxylysines oxidatively deaminated to aldehydic residues, some prolines on procollagen hydroxylated –> 4- & 3-hydroxyprolines
Essential to assembly/cross-linking of collagen helices
Need ascorbic acid
Mature insulin
Contains two peptides of 30 & 21 residues linked by 2 disulfide linkages
Stored in beta granules as Zn-bound hexamer until secretion
Produced/released in equimolar amounts to C peptide
Circulating C peptide
Produced/released in equimolar amounts to mature insulin
Immunoassay to assess pancreatic beta cell function (particularly in patients w/circulating anti-insulin antibodies)
Distinguish b/w hypoglycemic disorders due to islet cell tumors & facetious hypoglycemia
Islet cell tumors
Due to overproduction of insulin
Cause hypoglycemic disorders
Facetious hypoglycemia
Due to exogenous insulin infusion
Heterotrimeric type I collagen
Most abundant structural protein in vertebrates
Lysyl hydroxylase
Part of PT collagen modification, needs ascorbic acid
Mutations –> skin/bone/joint disorders (Ehlers-Danlos syndrome type VI, Nevo syndrome, Bruck syndrome type 2, epidermolysis bullosa simplex)
Prolyl hydroxylase
Part of PT collagen modification, needs ascorbic acid
Karyotyping (p 385)
Allows determination of the number, size & gross structure of metaphase chromosomes
Traditional gold standard cytogenetic method in identifying chromosomal abnormalities ass w/genetic disorders
Does not provide info at molecular level
Chromosomal Mutations (p 328)
Involve large segments of DNA (millions of bp’s)
4 types: inversion, deletion, duplication, translocation
Meiosis (p 368)
Process by which a diploid (2N) germline cell divides into haploid (1N) gametes
Occurs in 2 stages
Inversion
Type of chromosomal mutation in which a segment of chromosomal DNA is present in its reverse orientation
Deletion
Type of chromosomal mutation in which a segment of chromosomal DNA is lost
Duplication
Type of chromosomal mutation in which a segment of chromosomal DNA is copied, resulting in amplification of genes contained in that region
Translocation
Type of chromosomal mutation in which two different chromosomes exchange segments of their DNA
Can be either balanced or unbalanced
Balanced Translocation
Type of chromosomal mutation in which resultant hybrid chromosomes are similar in length to their normal counterparts
Unbalanced Translocation
Type of chromosomal mutation in which resultant hybrid chromosomes are dissimilar in length to their normal counterparts
Mitosis
Process by which a diploid (2N) somatic cell divides to produce 2 identical daughter cells, each of which also contains 2N amounts of DNA
Meiosis I
Following interphase, chromosomes divide as in mitosis
During prophase, duplicated homologous chromosomes pair up to form a bivalent (which has 4 chromatids, 1 for each chromosome), allowing homologous recombination
Cell division proceeds to generate 2 daughter cells (each has 1 unmodified parental chromosome and one recombinant chromosome)
Homologous recombination
Exchanging of fragments of maternal and paternal chromatids
Occurs in Meiosis I
Leads to genetic variation
Bivalent
Structure with 4 chromatids, 1 for each chromosome
Formed during prophase I when duplicated homologous chromosomes pair up to allow homologous recombination
Meiosis II
Sister chromatids in each cell separate to produce 4 gametes (each with 1N amount of DNA)
Does not involve any further DNA synthesis
Uniparental disomy (p 319)
Phenomenon when an individual receives 2 copies of a chromosome or part of a chromosome from 1 parent and no copies from the other parent
May occur as a random error in meiosis during the formation of egg or sperm cells or in early fetal development
Often asymptomatic because the individual has at least one copy of each gene
If in imprinted genes, there may be delayed development, mental retardation, and other medical issues (most well known is Prader-Willi syndrome w/chromosome 15)
Mosaicism (p 319)
Condition in which cells from an individual who has developed from a single fertilized egg have different genotypes
Caused by an error in cell division early in embryonic life
Percentage of normal to abnormal cells determines disease severity/symptoms/treatment, high %age mosaicism results in similar presentation to typical nonmosaic form of disease
Diagnosed with chromosomal or microarray analysis
Ex: Down, Klinefelter, & Turner syndrome
Prader-Willi syndrome
Involves the imprinting gene on the long arm of chromosome 15
Paternal gene is silenced
Dysfunction leads to uncontrolled eating and obesity
Mosaic Down syndrome
chromosome 21 trisomy in a %age of cells
Mosaic Klinefelter syndrome
some cells are normal/46XY, some have an extra chromosome/47XXY
Mosaic Turner syndrome
some cells are normal/46XX, some have a missing chromosome/45XO
Congenital disorders of glycosylation (p 365)
Caused by defects in assembly of 14-sugar oligosaccharide on phosphorylated dolichol (Type I) or in processing of to complex types of glycoproteins in Golgi (Type II)
1a (70%) caused by phosphomannomutase defect
1b caused by phosphomannose isomerase defect
CDG1a
Phosphomannomutase defect (mannose-6P –> mannose-1P) –> defective assembly of 14-sugar oligosaccharide on phosphorylated dolichol
CDG1b
Phosphomannose isomerase defect (fructose-6P –> mannose-6P) –> defective assembly of 14-sugar oligosaccharide on phosphorylated dolichol
Ascorbic acid
Essential for lysyl and prolyl hydroxylase activity
DNA content (p 366)
Resting mammalian cells in the G1 phase: DNA content of 2N
S phase: DNA content varies b/w 2N & 4N
G2 & M phase: DNA content doubled to 4N
After cytokinesis: back to 2N
Proteolysis of cyclins (p 368)
regulated mechanism to degrade transiently expressed cyclin proteins in order terminate activity of cyclin-CDK complexes
cyclins targeted by polyubiquitination
RAS and cancer (p104)
Mutant forms of mammalian RAS (or its GEFs & GAPs) have been implicated on a wide range of cancers (30-50% of lung/colon cancers, 90% pancreatic cancers)
Point mutations decrease intrinsic GTPase activity-> lock in active/GTP-bound state
Ex- neurofibromatosis (NF-1 gene encodes a GAP for RAS)
RB protein (p 371)
Discovered through examination of microdeletions in chromosome 13 in individuals with retinoblastoma
Hereditary form: 1 copy of gene mutated or lost in every cell & cells become predisposed to cancer (if good second copy is damaged by mutation, cells lose control of G1 checkpoint)
Nonhereditary form: cancerous cells contain different somatic mutations in both copies of the RB gene
Recognition domains (p 105)
SH2 or PTB domains on adaptor proteins that recognize and bind to receptor motifs that have phosphorylated Tyr residues
Ex- GRB-2, IRS-1
Small G proteins (p 105)
Transduce signals from plasma membrane receptors -> effector proteins (ex- kinases)
Intrinsic GTPase activity (mutations lead to cancer)
Control cell prolif, intracellular vesicular traffic, survival/apoptosis, cell shape/polarity, membrane transport, secretion
Monomeric
RAS superfamily w/>150 members, 20-25 kDa
Subfamilies: RAS, RAB, RHO, ARF, RAN
Fibrosarcomas in chickens (p 376)
Caused by Rous sarcoma retrovirus (RSV)
Transforming factor: v-src (Tyr kinase, oncogenic form of normal host Porto-oncogene c-SRC)
Replicative cell senescence (p 371)
Type of aging in somatic cell cultures
Due to progressive shortening of telomeres w/each cell division (especially if cells lack telomerase)-> DNA damage–> p53-mediated cell cycle arrest at G1 checkpoint
Ex- human skin fibroblasts in cell culture stop dividing after 30-50 population doublings, even when abundant growth factors are present in the culture medium
germline cells
contain 23 chromosomes (unpaired)
haploid
also known as gametes
ubiquitin ligases
catalyze targeting of cyclins for proteolysis
ubiquitinate CKIs to target for degradation, releasing the inhibition of S phase cyclin-CDK complexes
p53 and cancer (p 371)
More than 50% of all cancers exhibit mutations in p53
Examples of failed p53 activation: Li-Fraumeni syndrome, ataxia telangiectasia
Metabolic activation of benzo(a)pyrene–> potent mutagen
Activated benzopyrene & Aflatoxin–> p53 mutations by G->T transversions
Aflatoxin
fungal metabolite present as contaminant in moldy grain & peanuts
induces G->T transversions in p53
carcinogen (mutation caused leads to cancer)
Li-Fraumeni syndrome
example of failed p53 activation due to gene mutation
Ataxia telangiectasia
example of failed p53 activation due to gene mutation
Retinoblastoma
childhood disease of retinal development
unchecked division of precursor cells in immature retina–> tumor development
Incidence Rate: 1/20,000
Hereditary form: affects BOTH eyes
Nonhereditary form: affects only affects one eye
telomerase
needed to maintain telomeres
Preserves their length & protects from damage by promoting end cap structures
Neurofibromatosis
Condition marked by growth of tumors by nerve tissue
Caused by an inactivation in neurofibromin (NF-1) gene (encodes GTPase-activating protein (GAP) for RAS
Absence of NF-1 –> RAS allowed to uncontrollably activate pathways that promote nerve tissue growth
aging-induced DNA damage
leads to p53-mediated cell cycle arrest at G1 checkpoint
involved in replicative cell senescence
could be mediated by accumulation of reactive oxygen species (ROS)
v-src
Tyr kinase, oncogenic form of normal host Porto-oncogene c-SRC
Transforming factor in RSV
Causes fibrosarcoma in chickens
Early pregnancy factor (EPF)
immunosuppressive protein secreted by trophoblast to prevent rejection of embryo
measured by expensive, early pregnancy tests
chorionic gonadotropin (hCG)
initial pregnancy signal secreted from syncytiotrophoblast
measured by OTC pregnancy tests
Hypatidiform Mole
Tumor in uterus caused by fertilization of empty or normal oocyte by 2 sperm
Can lead to choriocarcinoma
Symptoms: vaginal bleeding, pelvic pressure/pain, enlarged uterus, hyperemesis gravidarum
Choriocarcinoma
Malignant tumor formed from hypatidiform mole that can spread to lungs, vagina, bone, brain, liver, & intestines
In vitro fertilization & embryo transfer
Assisted reproductive technology in which administered hormones stimulate ovulation, egg is fertilized in petri dish, & cells are implanted back in uterus as early blastocysts
Other cells can be frozen
Cryopreservation of embryos
Assisted reproductive technology in which fertilized eggs are frozen between 8-cell and blastocyst stage
Intracytoplasmic sperm injection
Assisted reproductive technology in which sperm are injected into egg & the blastocyst is implanted back in uterus after 1 week
Ectopic Pregnancy
Embryo implants somewhere besides the uterus (usually uterine tubes)
Symptoms: normal hCG, cramping/pain
Increased risk of hemorrhage
Placenta Previa
Placenta covers all or part of cervix opening
Vaginal bleeding after 20 wks gestations
Teratoma
Mass of all 3 germ layers
May be remnant of primitive streak or due to abnormal migration of germ cells
Chordomas
Rare, slow-growing, aggressive neoplasms of bone in axial skeleton (sacral ragions & spheno-occipital region of skull)
Arise from notochord remains
Developmental verbal dyspraxia (DVD)
Results from mutation in FoxP2 (under positive selection)
Fox genes regulate cell growth/prolif/diff/longevity
Aniridia
Results from absence of iris due to mutation in Pax6 (makes protein for eyes, CNS, & pancreas
Lim proteins
Proteins that play role in formation of all body segments
Absence–> headless embryos
Msx genes
Overexpression leads to premature fusion of skull joints and unnatural brain growth (craniosynostosis)
Genes that inhibit cell diff prenatally and promote tissue proliferation and face/limb formation postnatally
Craniosynosytosis
premature fusion of skull joints that prevents natural brain growth due to overexpression of Msx genes
Campomelic dysplaxia
Results from mutation in Sox9, affecting skeleton, reproductive system, resp sys, & face
Symptoms: short legs, dislocated hips, underdeveloped shoulder blades, 11 pairs of ribs, neck bone abnormalities, clubfeet, ambiguous genitalia, & softened resp cartilage
DHH
Desert Hedgehog ligand-receptor complex that can cause partial gonadal dysgenesis and polyneuropathy
Accutane
Retinoid that leads to increased levels of retinoic acid, causing Hox overexpression and leading to birth defects in CNS & axial skeleton (b/w 2nd & 5th week of gestation)
Used to treat severe acne
Basal cell carcinoma
Results from mutations in PTCH receptor for SHH that cause uncontrolled SMO activity (cell growth/rep)
HIV diagnosis technique
Utilizes indirect ELISA (detects HIV antibodies) and PCR (uses reverse transcriptase to detect viral RNA)
Need multiple forms of testing b/c indirect ELISA gives many false pos/neg results
MI diagnosis technique
Utilizes sandwich ELISA (detects troponin antigen isoforms)
Troponin I & T inc week after AMI
Pregnancy diagnosis technique
Utilizes sandwich ELISA (detects hCG antigen, shows color band)
Glucose metabolism (glucagon+epinephrine+cortisol+insulin)
Starved: Glucagon increases glc by stimulating glycogenolysis in liver & inhibiting glycogenesis
Epinephrine -> stimulates Glucagon secretion
Depleted glycogen stores -> Cortisol stimulates gluconeogenesis (induces transcription of gluconeogenic enzymes)
Fed: Insulin lowers glc by glycogenesis (storage) and glycolysis (catabolism) and inhibition of gluconeogenic enzymes
Glucose metabolism: Glucagon
Starved: Glucagon increases glc by stimulating glycogenolysis in liver & inhibiting glycogenesis
Stimulated by epinephrine
Glucose metabolism: Epinephrine
stimulates Glucagon secretion (stimulation of glycogenolysis and inhibition of glycogenesis)
Glucose metabolism: Cortisol
Depleted glycogen stores -> stimulates gluconeogenesis (induces transcription of gluconeogenic enzymes)
Glucose metabolism: Insulin
Fed: lowers glc by stimulating glycogenesis (storage) and glycolysis (catabolism) and inhibiting gluconeogenic enzymes
Lipophilic and hydrophilic medications
Lipophilic: oral contraceptives contain lipophilic signaling molecules that have long half-lives (hrs-days), so are often taken daily; ex- Ethinyl Estradiol
Hydrophilic: short half-lives (mins-secs) taken as needed; ex- Epinephrine for severe acute allergic rxns to prevent anaphylactic shock
Lipophilic medication example
Ethinyl Estradiol (oral contraceptive, long half-life -> taken daily)
Hydrophilic medication example
Epinephrine (contained w/in epinephrine autoinjectors)- short half-life, taken during severe acute allergic rxn to prevent anaphylactic shock
GPCR signaling diversity
Same hormone in diff cells may produce diff physiological responses
Epinephrine binds beta-adrenergic receptors -> smooth muscle relaxation (bronchial and intestinal) AND heart muscle contraction
Produces same 2nd messenger (cAMP), but downstream signaling causes diff physiological effects based on tissue
Epinephrine can be used to relieve bronchospasms during an asthma attack AND to restore cardiac rhythms after shock/cardiac arrest
Epinephrine signaling in smooth muscle
Binds beta-adrenergic receptors -> smooth muscle relaxation (bronchial and intestinal)
Can be used to relieve bronchospasms during an asthma attack
Epinephrine signaling in cardiac muscle
Binds beta-adrenergic receptors -> cardiac muscle contraction
Can be used to restore cardiac rhythms after shock/cardiac arrest
Beta-Agonists
Beta-agonist albuterol is a hydrophilic molecule that binds to and activates beta2-adrenergic receptors
Beta-Agonists relax bronchial smooth muscles and stimulate heart muscle contraction
Side effect: tachycardia (rapid heart rate)
Administered directly to the lungs (inhaler or nebulizer) to treat airway-constricting conditions (asthma, bronchitis, COPD)
Patients unresponsive to albuterol are given epinephrine
Nitric oxide
Endothelium-derived agent responsible for relaxation of smooth muscle
Generated from Arg in endothelial cells (rxn promoted by Ca-calmodulin)
Diffuses to neighboring smooth muscle -> activates guanylate cyclase -> cGMP production -> activates protein kinase G -> smooth muscle relaxation and vasodilation
Ex- nitroglycerin (should not be taken w/Viagra because the latter inhibits cGMP phosphodiesterase, leading to extreme vasodilation and possibly fatal drops in BP)
Nitroglycerin
Decomposes in the body to NO -> diffuses to neighboring smooth muscle -> activates guanylate cyclase -> cGMP production -> activates protein kinase G -> smooth muscle relaxation and vasodilation
Should not be taken w/Viagra because the latter inhibits cGMP phosphodiesterase, leading to extreme vasodilation and possibly fatal drops in BP
Antihistamines
Lipophilic compounds that block histamine binding to H1 GPCR -> decrease allergic symptoms
Some are anti-emetics and can inhibit motion sickness symptoms
Ex- centirizine, loratadine, diphenhydramine hydrochloride
Histamine
Hydrophilic signaling molecule derived from His that causes allergic symptoms (sneezing, runny nose, itchy/watery eyes)
It is a ligand that binds to 4 histamine receptors (H1-4)
RAS GAP
GTPase-activating protein for RAS
Deactivates RAS by stimulating GTP hydrolysis, releasing GTP from RAS (RAS+GTP=active, RAS+GDP=inactive)
In NF-1 gene mutation (encodes for GAP), absence allows RAS to uncontrollably activate pathways to promote nerve tissue growth
RAS GEF
Guanine nucleotide exchange factor
Activates RAS GTPases by stimulating GTP -> GDP and release of GDP (RAS+GTP=active, RAS+GDP=inactive)
SH2 and PTB domains
Special recognition domains on adaptor proteins GRB-2 and IRS-1
Recognize and bind to motifs on the receptor that contain phosphorylated Tyr residues
Insulin resistance
Loss of insulin stimulation of glc uptake by GLUT4 in adipose and skeletal muscle
Obese subjects: reduced insulin activation of PKB (IRS-1/2 in signaling pathway likely impaired)
Tyr phosphorylation of IRS-1/2 needed to recruit PI-3 kinase
Ser/Thr phosphorylation inactivates IRSs -> degradation
Multiple kinases may be involved in Ser/Thr IRS-1/2 phosphorylation (stimulated by cytokines/free FAs/hyperinsulinemia)
stem cells (p 319)
2 types: embryonic & adult
Differentiate into specialized cells in stages involving multiple factors that combine to produce epigenetic markers in the cell’s DNA that restrict DNA expression & the type of cell the stem cell will differentiate into
DNA expression can be passed on to daughter cells through cell division, or daughter cells can retain their status as stem cell-> capable of long-term renewal
Embryonic stem cells
ES cells
Derived from embryo
Pluripotent
May be used to treat spinal cord injuries, heart failure, Parkinson disease, Type I diabetes, arthritis, osteoporosis, liver failure
Adult stem cells
Undifferentiated cells that generate cell types in the tissues in which they reside
iPS cells (p 397)
Induced pluripotent stem cells
Recombinant DNA technology being utilized to develop iPS cells from differentiated adult cells (instead of ES cells)
May be possible w/genes for 4 TFs: Oct4, Sox2, Nanog, Lin28
May be possible to make patient-specific iPS cells to treat many currently incurable diseases
Totipotent
Describes the cells in the zygote right after fertilization
Have ability to form an entire new organism (twins, quadruplets, etc.)
Pluripotent
Describes the cells in the blastocyst ~4 days after fertilization
Can give rise to many types of cells but not all types necessary for fetal development
Bilirubin conjugation
Unconjugated: fairly insoluble in aqueous media, made soluble by 50% methanol & then reacted with Diazo reagent to form indirect bilirubin
Conjugated to glucuronate: relatively soluble, reacts with Diazo reagent to form direct bilirubin (absorbs 540 nm light)
Total bilirubin in adult serum: .2-1.2 mg/dL
Total bilirubin in infant serum: 1-12 mg/dL
Direct bilirubin
Pink/red-purple product formed by reaction of soluble bilirubin with Diazo reagent that absorbs light at 540 nm
Normal serum in adults: .1-.3 mg/dL
Infants have negligible amounts
Indirect bilirubin
Formed by mixing unconjugated bilirubin with 50% methanol in order to make soluble, then reacting with Diazo reagent
Measured by total bilirubin minus direct dilirubin
Diazo reagent
In presence of 50% methanol: measures total bilirubin
In absence of 50% methanol: measures direct bilirubin
Can also be done with sodium acetate & caffeine-benzoate
Sodium acetate causes alkaline pH
Caffeine benzoate accelerates coupling of Diazo reagent with unconjugated bilirubin, creates blue product (absorbs at 600 nm)
Congenital erythropoietic porphyria
Results from deficiency of uroporphyrinogen III cosynthase
Key intermediates diverted to nonfunctional uroporphyrinogen I isomer, producing red color in urine, red fluorescene of the teeth, premature destruction of erythrocytes, & skin photosensitivity
Uroporphyrinogen III cosynthase
Deficiency causes congenital erythropoietic porphyria
Body tries to use nonfunctional uroporphyrinogen I isomer
Color changes in bruises
Bruise is type of hematoma due to pooling of blood caused by capillary damage
Cleanup by macrophages leads to Hb degradation to heme (red), biliverdin (green), & bilirubin (red-yellow)
Released iron trapped as hemosiderin (red-brown)
Neonatal jaundice
Due to low levels of conjugating enzyme at birth
Hemolysis (blood group incompatibility) or liver dysfunction can lead to pathological jaundice
Premature birth exacerbates
Excess unconjugated bilirubin can diffuse into basal ganglia-> toxic encephalopathy (kernicterus)
Treatment: babies placed under fluorescent blue light to convert bilirubin to polar, water-soluble isomers
Intramuscular administration of tin-mesoporphyrin (SnMP: heme oxygenase inhibitor)
Neonatal bilirubin
Total bilirubin goes from 1 mg/dL to 10-12 mg/dL at 3 days, then back to normal after a week
SnMP
Potent heme oxygenase inhibitor
Administered intramuscularly to treat neonatal jaundice
Excess unconjugated bilirubin
Causes neonatal jaundice due to low levels of conjugating enzyme at birth
Can diffuse into basal ganglia and cause toxic encephalopathy (kernicterus)
Fluorescent blue light can convert bilirubin to polar, water-soluble isomers
UDP-glucuronyl transferase-related disorders
Crigler-Najjar syndrome (UDP-glucuronyl transferase deficiency)
Type 1: complete absence of the gene
Type 2: benign partial deficiency of gene (Arias syndrome)
Gilbert syndrome: common, benign, results from decreased UDP-glucuronyl transferase activity, total bilirubin
Kernicterus
Encephalopathy in newborns caused by hyperbilirubinema
Excess unconjugated bilirubin diffuses into basal ganglia
Crigler-Najjar syndrome
Type 1: complete absence of the gene for UDP-glucuronyl transferase, severe hyperbilirubinemia that accumulates in the brain of affected newborns, causing kernicterus
Type 2: benign form, results from mutation causing partial deficiency of gene for UDP-glucuronyl transferase (Arias syndrome), enzyme activity decreased to 10%
Crigler-Najjar syndrome, Type 1
Complete absence of the gene, severe hyperbilirubinemia that accumulates in the brain of affected newborns, causing kernicterus
Treatment: transfusions in the immediate neonatal period, phototherapy, heme oxygenase inhibitors (reduce transient worsening of hyperbilirubinemia), oral calcium phosphate/carbonate (complex with bilirubin in gut), liver transplantation (before brain damage and phototherapy)
Gilbert syndrome
common (2-10% of population), benign, results from decreased UDP-glucuronyl transferase activity (25%), total bilirubin
Crigler-Najjar syndrome Type 2
benign form, results from mutation causing partial deficiency of gene for UDP-glucuronyl transferase (Arias syndrome), enzyme activity decreased to 10%
Hepatitis
Inflammation of the liver, sometimes caused by viral infections, that leads to hepatic dysfunction
Causes increased conjugated and unconjugated bilirubin, conjugated bilirubin accumulates in skin and sclera (eyes), causing yellow coloration
May accumulate in urine, causing it to be tea-colored
Celebrity porphyrias
King George III: variegate porphyria- abdominal pain, delirium, port-colored urine, hallucinations, convulsions (arsenic poisoning from medications)
King George IV, Queen Anne, Vincent van Gogh
Disorders related to collagen defects
Scurvy: deficient vitamin C leads to defective prolyl hydroxylase-> can’t form collagen, abnormal integrity of connective tissues and skin-> easy bruising
Ehlers Danlos: inherited disorders caused by genetic defects in fibril-forming collagen (Type I/III), in its synthesizing enzymes (lysyl oxidase), or in copper availability
Symptoms: thin, stretchy skin w/abnormally loose/bendy joints
Osteogenesis imperfecta: inherited disorders marked by deficiencies in Type I collagen, varying severity
Symptoms: brittle bones, loose joints, blue sclera
Macrophages and iron
Phagocytic WBCs engulf and digest aged RBCs, allowing iron to be extracted from degraded Hb and loaded onto transferrin for transport to appropriate sites
Scurvy
Deficient vitamin C leads to defective prolyl hydroxylase-> can’t form collagen, abnormal integrity of connective tissues and skin-> easy bruising
Osteogenesis imperfecta
Locus heterogeneity
Inherited disorders marked by deficiencies in Type I collagen, varying severity
Symptoms: brittle bones, loose joints, blue sclera
Ehlers Danlos
Inherited disorders caused by genetic defects in fibril-forming collagen (Type I/III), in its synthesizing enzymes (lysyl oxidase), or in copper availability
Symptoms: thin, stretchy skin w/abnormally loose/bendy joints
Hydrolysis of cyclic nucleotides
Phosphodiesterases reduce cyclic NTs-> noncyclic NTs
Ex: cAMP -> AMP by cAMP phosphodiesterase
Phosphodiesterase inhibitors prolong cyclic NT effects
Ex: Viagra, caffeine
Inhibition of G proteins by Bacterial Toxins
Covalently modify (ADP ribosylation) alpha subunits of Gs and Gi, decreasing GTPase activity -> remains active (GTP-bound)-> continued stimulation of AC and overproduction of cAMP
Ex: Cholera (ADP ribosylation of Cys on Gialpha)-> CFTR stays open-> loss of electrolytes and water
Ex: Pertussis -> loss of fluids, excessive mucous secretion (whooping cough)
Phosphodiesterase inhibitors
Prolong cyclic NT effects (NTs can’t be broken down)
Ex: Viagra inc cGMP-> smooth muscle relaxation/vasodilation
Ex: caffeine-> cAMP accumulates-> tachycardia
Cholera toxin
Inhibits G protein Covalently modifies (ADP ribosylation) Cys on alpha subunits of Gi, decreasing GTPase activity -> remains active (GTP-bound)-> continued stimulation of AC and overproduction of cAMP-> CFTR stays open-> loss of electrolytes and water
Hereditary spherocytosis (HS)
autosomal dominant disorder involving a deficiency in spectrin that causes spheroidal RBCs that are less rigid and subject to destruction in the spleen
Alteration caused by cytoskeletal abnormalities at sites of interaction b/w spectrin 𝛂 and 𝛃 and protein 4.1
Symptoms: anemia, jaundice, splenomegaly
Treatment: splenectomy
Elliptocytosis
Autosomal dom disorder in which defective self-association of spectrin subunits, defective spectrin binding to ankyrin, protein 4.1 defects, and abnormal glycophorin result in oval-shaped RBCs
Symptoms: anemia, jaundice, splenomegaly
Treatment: splenectomy
Sickle cell anemia
Results from point mutation (Glu→ Val in 𝛃-globin chain of hemoglobin) Hb S (defective hemoglobin) tetramers aggregate→ polymerize in deoxygenated RBCs→ biconcave disk changes into rigid/less deformable sickle-shape→ severe chronic hemolytic anemia & obstruction of postcapillary venules
Thalassemia syndrome
Heritable anemias characterized by defective synth of 𝛂 or 𝛃 chains of normal hemoglobin tetramer (𝛂2𝛃2)
Symptoms: anemia (defective Hg synth & hemolysis)
Erythroblastosis fetalis
Ab-induced hemolytic disease in newborns caused by blood group incompatibility b/w mother & fetus (ABO & Rh antigens) in the last trimester of pregnancy
Possible combos: Rh+ fetus in Rh- mother; A/B/AB fetus in O mother
Symptoms: hemolytic anemia→ hypoxic injury to heart/liver→ generalized edema; jaundice (hyperbilirubinemia→ unconjugated bilirubin take up by brain tissue)→ CNS damage
Rh antigen does not cause issues in 1st pregnancy b/c IgM is produced but cannot cross the placenta; smaller IgG produced in next pregnancies which can cross placenta
Treatment: give mother anti-D globulin soon after delivery of Rh+ baby, preventing long-lasting Rh antigen sensitization
Leukocyte adhesion deficiencies
Defects in wound healing, recurrent infections, marked leukocytosis (inc # of leukocytes)
LAD I: defect in 𝛃 subunit of integrin→ prevents diapedesis→ inflammatory cell infiltrates devoid of neutrophils
LAD II: absent fucosyl-containing ligands for selectins due to congenital defect of endogenous fucose metabolism
Selectin-carb interactions help roll leukocytes on endothelial cell surface for diapedesis to inflamed areas
Asthma
Mast cell-eosinophil interaction
Mast cells degranulate→ release chem mediators→ eosinophils/neutrophils attracted from blood vessels into connective tissue in respiratory mucosa
Eosinophils release additional mediators→ enhance bronchoconstriction & edema
Eosinophil cationic protein & major basic protein→ damages epithelial cell lining, disturbs mucociliary function
Thrombocytopenia
Decrease in platelets to 20,000/µL of blood)
Can be caused by dec in platelet production, inc in platelet destruction, & platelet aggregation in microvasculature (result of pathologic changes in endothelial cell production of procoagulant substances)
Thrombocytosis
increase in platelets circulating in blood
Bernard-Soulier syndrome
congenital bleeding disorder caused by deficiency of glycoprotein 1b-factor IX complex
Platelets unable to attach to vascular subendothelial surfaces (relevant for platelet aggregation after exposure to injured tissue)
Von Willebrand’s disease
Congenital bleeding disorder caused by deficiency in von Willebrand’s factor (protein ass w/factor VIII)
Platelets unable to attach to vascular subendothelial surfaces (relevant for platelet aggregation after exposure to injured tissue)
Most freq bleeding disorder
Hemophilia
common hereditary disease ass w/serious bleeding due to deficiency of factor VIII or IX
Gene on X chromosome, mutation→ hemophilia A & B (X-linked rec: affected males, female carriers)
Hemophilia A: reduction in amt/activity of factor VIII (protein synth in liver)
Hemophilia B: reduction in amt/activity of factor IX
Treatment: plasma-derived or engineered recombinant factors
Gray platelet syndrome
Autosomal dominant disease involving macrothrombocytopenia due to reduction in content of 𝛂 granules
Thrombocytopenia + inc platelet volume
MYH9 (myosin heavy chain 9)-related disorders
Ass w/macrothrombocytopenia MYH9 mutation (normally encodes nonmuscle myosin heavy chain IIA- isoform in platelets & neutrophils) → defective production of platelets during proplatelet formation
Arrhythmogenic right ventricular cardiomyopathy (ARVC)
Ass w/missense mutations in Desmocollin-2→ desmocollin not properly inserted into membrane (lack of tight cell-cell contact)
Common cause of sudden cardiac death in young
Blistering disorders
Autoimmune response
Pemphigus foliaceus: abs against desmoglein 1→ loss of adhesion of keratiniocytes in the superficial layers of the epidermis
Listeria
invades intestinal cells, divides into new cells, then mimics ARPs to use human actin to push through
Surface protein ActA activates Arp ⅔ complex→ growing filaments push cell through cytoplasm
Marfan’s Syndrome
mutated fibrillin (microfibrils in elastin fibers)
Hypochromic microcytic anemia
Deficiency: Insufficient diet, menstruation, aspirin abuse, GI ulcers
(smaller, less color on smear)
Hemochromatosis
malregulated iron uptake/export by enterocyte
Autosomal rec incidence: 1/250
Symptoms: cirrhosis, skin pigmentation, manifests ~60 y/o
Treat w/blood letting
Overload: Genetics can affect Fe overload in a patient
megaloblastic macrocytic anemia
B12/Folate needed for DNA synthesis→ can’t make RBCs in bone marrow
Large RBCs→ high mean corpuscular volume (MCV)
Normal Hb in relation to size
Smear: macrocytic, normochromic (normal Hb), oval cells
Large RBCs in bone marrow (megaloblasts)
Hypersegmented neutrophils (lots of lobes)
Pernicious Anemia
B12 Deficiency due to lack of intrinsic factor
Type of megaloblastic macrocytic anemia
Results from failure to absorb vitamin B12 (lack of intrinsic factor)
Gastric mucosa destruction (auto-immune) or hereditary low levels of IF
Occurs in elderly
