BBB

Question 1

What is the purpose of the blood-brain-barrier?
▪ It protects the peripheral nervous system.
▪ It supplies nutrients while preventing hazardous chemicals from reaching the brain.
▪ It transmits electrical signals between neurons.
▪ It provides another layer of CSF.
▪ It transmits potentially hazardous chemicals into the brain safely.

Answer 1

It supplies nutrients while preventing hazardous chemicals from reaching the brain.

Question 2

How do amino acids enter the brain?
▪ amino acids are lipophilic and therefore pass via diffusion across cells
▪ amino acids bind to receptors on endothelial cells and pass the BBB via receptor-mediated transcytosis
▪ amino acids can pass transcellularly like water and chloride
▪ amino acids enter via carrier-mediated transport proteins

Answer 2

amino acids enter via carrier-mediated transport proteins

Question 3

Which of the following is not considered as site of CNS barrier?
▪ Brain parenchymal vessel endothelium
▪ Arachnoid epithelium
▪ Ventricular septum endothelium
▪ Choroid plexus epithelium

Answer 3

Ventricular septum endothelium

Question 4

Which of the following statements is false regarding the blood-brain-barrier?
▪ The ways of the capillaries supplying the brain have tight fitting cells making it difficult for polar drugs to leave the capillaries.
▪ The capillaries in the brain have a fatty coating making it more difficult for drugs to enter the brain.
▪ The walls of the capillaries supplying the brain are made up of several layers of cells, which act as a barrier to the release of drugs.
▪ Hydrophobic drugs pass through the blood brain barrier more easily than hydrophilic drugs.

Answer 4

The capillaries in the brain have a fatty coating making it more difficult for drugs to enter the brain.

Question 5

Which of the following statements regarding microglia is false?
▪ Mikroglia are the resident immunocompetent cells of the brain
▪ Mikroglia are derived from monocytes and macrophages
▪ Resting state microglia act similarly to antigen-presenting-cells and recruit lymphocytes in the case of inflammation
▪ excessively activated microglia can cause inflammation and neurotoxicity

Answer 5

Resting state microglia act similarly to antigen-presenting-cells and recruit lymphocytes in the case of inflammation

Question 6

Which statement correctly describes how O2 and CO2 cross the BBB?
▪ O2 and CO2 cross the BBB through direct diffusion as both are non-polar gaseous molecules.
▪ O2 can cross the BBB through direct diffusion, but CO2 is transported via facilitated diffusion as CO2 is a polar molecule.
▪ The tight junctions between endothelial cells do not allow for the passage of CO2 or O2 paracellularly or transcellularily – the molecules pass soley as solutes dissolved in water through Aquaporins.
▪ None of the above.

Answer 6

O2 and CO2 cross the BBB through direct diffusion as both are non-polar gaseous molecules.

Question 7

Mast cells
▪ are glial cells that provide neurotropic factors to damaged neurons
▪ are essential in regulating ion homeostatis in extracellular fluid
▪ release several vasoactive, anticoagulant and chemotactic factors
▪ are not present in the CNS, only in the PNS

Answer 7

release several vasoactive, anticoagulant and chemotactic factors

Question 8

o Which of the following statements regarding astrocytes is false?
▪ Astrocytes originate from the neuroectoderm
▪ Their morphology is highly variable and depends on the location in the brain and state of activation
▪ Astrocytic end feet exhibit contractile properties and can regulate blood flow based on neuronal activity
▪ Astrocytes form part of the so-called “gliovascular unit”

Answer 8

Astrocytic end feet exhibit contractile properties and can regulate blood flow based on neuronal activity

Question 9

Smooth muscle cells
▪ are of neuroectodermal origin
▪ are primarily localized in veins and regulate vessel tone
▪ are under the influence of nerve terminals and astrocytes
▪ are not present in the BBB-regulation of vessel tone only occurs through Pericytes

Answer 9

are under the influence of nerve terminals and astrocytes

Question 10

What important role do Pericytes play in the developing brain?
▪ Migrating Pericytes produce angiogenic factors, thereby guiding endothelial cells in the organization of vessel walls
▪ In the developing brain, Pericytes serve as stem cells from which endothelial cells originate.
▪ In the developing brain, Pericytes have immunological properties and regulate inflammation caused by apoptosis.
▪ Pericytes have no association to endothelial cells in the developing brain, they only later migrate to endothelial walls later in development.

Answer 10

Migrating Pericytes produce angiogenic factors, thereby guiding endothelial cells in the organization of vessel walls

Question 11

Which of the following statements regarding pericytes is false?
▪ Pericytes are enclosed by the basement membrane
▪ Pericytes stabilize capillaries
▪ Pericytes exhibit contractile properties and play a roll in regulating cerebral blood flow
▪ Pericytes have immunological functions within the capillary lumen

Answer 11

Pericytes have immunological functions within the capillary lumen

Question 12

Microglia cells
▪ take on an amoeboid form when activated in response to inflammation or neuronal damage
▪ only reside in the brain perivascular space in close association with endothelial cell
▪ contain granules with vasoactive histamine
▪ induce transporter expression on endothelial cells to increase glucose influx following tissue damage

Answer 12

take on an amoeboid form when activated in response to inflammation or neuronal damage

Question 13

The term “phenotypic sculpting” refers to:
▪ the mutual induction (regulation of gene expression) between endothelium and perivascular astrocytes causing changes in BBB permeability and transporter expression
▪ angiogenesis in the developing brain which is then greatly reduced due to induction of apoptosis by perivascular astrocytes
▪ the mutual induction (regulation of gene expression) between astrocytes and neurons in order to maintain interstitial neurotransmitter concentrations in a state of homeostasis
▪ astrocytic induction of angiogenesis in the brain following acute tissue damage via secretion of VEGF and other neurotrophic factors

Answer 13

the mutual induction (regulation of gene expression) between endothelium and perivascular astrocytes causing changes in BBB permeability and transporter expression

Question 14

What is believed to be the purpose of the astrocyte-neuron lactate shuttle?
▪ fast glycolytic metabolism of glucose in astrocytes decreases interstitial glucose concentrations, which increases the driving force of glucose transport via GLUT1 into neurons.
▪ fast glycolytic metabolism of glucose increases lactate concentrations in the interstitial fluid which is essential for pH regulation in the brain.
▪ fast glycolytic metabolism of glucose in neurons decreases intracellular glucose concentrations, thus increasing the driving force of glucose transport via GLUT1 into neurons.
▪ Glycolysis is the main metabolic pathway in neurons and the astrocyte-neuron-shuttle allows for an efficient elimination of pyruvate and lactate out of neuronal cells.

Answer 14

fast glycolytic metabolism of glucose in astrocytes decreases interstitial glucose concentrations, which increases the driving force of glucose transport via GLUT1 into neurons.

Question 15

Which of the following statements is true regarding the glucose transport into the brain within the neurovascular unit?
▪ Glucose transport into the brain is independent from neuronal activity
▪ In areas of the brain that exhibit increased neuronal activity, higher densities of glucose transporters have been observed on BBB endothelial cells
▪ Glucose transport into the train is very constant. Since the glucose extraction ratio is only 15%, there is a substantial subtraction reserve for glucose.

Answer 15

In areas of the brain that exhibit increased neuronal activity, higher densities of glucose transporters have been observed on BBB endothelial cells

Question 16

What is the main difference between GLUT1 and GLUT3 transporters?
▪ GLUT1 transporters are located on the BBB and have a higher affinity to glucose than GLUT3 transporters located on neurons
▪ GLUT1 transporters are located on the BBB and have a lower affinity to glucose than GLUT3 transporters located on neurons
▪ GLUT3 transporters are located on the BBB and have a higher affinity to glucose than GLUT1 transporters located on neurons
▪ GLUT3 transporters are located on the BBB and have a lower affinity to glucose than GLUT1 transporters located on neurons

Answer 16

GLUT1 transporters are located on the BBB and have a lower affinity to glucose than GLUT3 transporters located on neurons

Question 17

Glucose crosses the blood-brain-barrier
▪ by receptor-mediated transcytosis
▪ transcellularly as Glucose is lipophilic
▪ facilitated diffusion through the GLUT1 transporter
▪ primary active transport by the GLUT1 transporter

Answer 17

facilitated diffusion through the GLUT1 transporter

Question 18

What is the average brain extracellular glucose concentration?
▪ 5mM
▪ 10mM
▪ 1mM
▪ 20nM

Answer 18

1mM

Question 19

Which of the following statements accurately describes the astrocyte-neuron lactate shuttle?
▪ In case of enhanced brain activation and reduced oxygen supply, glucose is taken up by neurons via GLUT3 transporter, metabolized into lactate via anerobic glycolysis, and then lactate is shuttled to astrocytes for elimination.
▪ Brain activation stimulates glycolysis in astrocytes, followed by conversion of pyruvate to lactate. Lactate is then shuttled to the neurons, where it is further metabolized oxidatively.
▪ In case of enhanced brain activation and reduced oxygen supply, glucose is taken up by neurons via GLUT1 transporter, metabolized into lactate via anerobic glycolysis, and then lactate is shuttled to astrocytes for elimination.
▪ Brain activation stimulates glycolysis in neurons, followed by conversion of pyruvate to lactate. Lactate is then shuttled to the astrocytes, where it is further metabolized oxidatively.

Answer 19

Brain activation stimulates glycolysis in astrocytes, followed by conversion of pyruvate to lactate. Lactate is then shuttled to the neurons, where it is further metabolized oxidatively.

Question 20

The term neurovascular unit
▪ refers to the minimal functional assembly including BBB endothelial cells, astrocytes, neurons, and other glial and non-glial cells.
▪ refers to the minimal functional assembly including BBB endothelial cells, pericytes and astrocyte end feet.
▪ is misleading because neurons have no anatomical association with the BBB endothelial cells – neurons only communicate with the BBB through astrocytes
*refers to the territorial brain parenchyma perfused by a specific cerebral artery.

Answer 20

refers to the minimal functional assembly including BBB endothelial cells, astrocytes, neurons, and other glial and non-glial cells.

Question 21

Neurovascular coupling refers to the increase in cerebral blood flow in response to increased neuronal activity
▪ via arteriole vasodilation i.e. functional recruitment.
▪ via transporter density increase.
▪ via capillary recruitment i.e. capillaries which were previously not perfused, open and can contribute to enhanced blood flow.
▪ via secretion of VEGF from astrocytes which leads to vasculogenesis.

Answer 21

via arteriole vasodilation i.e. functional recruitment.

Question 22

Which of the following statements accurately describes glucose transport in the brain?
▪ the glucose concentration gradient across the BBB (from blood to interstitial fluid) is very low (1mM – 0.7mM), therefore the glucose transporter must have a low Km to ensure sufficient glucose transport into the brain
▪ the glucose concentration gradient across the BBB (from blood to interstitial fluid) is higher than the concentration gradient from interstitial fluid to intracellular concentrations (1mM – 0.7mM), therefore the glucose transporters on neurons must have a low Km
▪ glucose concentration gradients are irrelevant in terms of glucose transport in the brain because blood, interstitial and intracellular glucose concentrations are similar (approximately 1mM)
▪ glucose concentration gradients are irrelevant in terms of glucose transport in the brain because GLUT transporters are active transporters and concentration-independent.

Answer 22

the glucose concentration gradient across the BBB (from blood to interstitial fluid) is higher than the concentration gradient from interstitial fluid to intracellular concentrations (1mM – 0.7mM), therefore the glucose transporters on neurons must have a low Km

Question 23

The BBB regulates ion concentration in the brain. Which of the following statements is true?
▪ Na is secreted into the brain via abluminal Na/K/ATPase and luminal Na-K-2CL, while K is absorbed via luminal K-channels from brain into blood.
▪ Na is absorbed from brain into blood via lumbinal Na/K/ATPase and abluminal Na-K-2CL, while K is secreted into the brain via ablumbinal K-channels.
▪ Na and K can pass the BBB paracellularly because the tight junctions have pores that allow for passive ion flow.
▪ Na/K/ATPase transporters are present on luminal and abluminal endothelial membranes allowing for the secretion and absorption of Na and K in and out of the brain, regulated by astrocytes.

Answer 23

Na is secreted into the brain via abluminal Na/K/ATPase and luminal Na-K-2CL, while K is absorbed via luminal K-channels from brain into blood.

Question 24

o Astrocytes in close association with the endothelial cells of the BBB play an important role in regulating BBB function. Which of the following statements is false?
▪ Astrocytes release BBB phenotype-inducing factors i.e. can increase tight junction formation and electrical resistance
▪ Astrocytes can induce expression of enzymes and transporters in the endothelial cells altering ion secretion and absorption across the BBB
▪ Astrocyte end feet cover capillaries in the brain and are essential for the regulation of composition and volume of interstitial fluid in brain parenchyma
▪ Astrocyte end feet associated with the BBB have contractile properties and can regulate blood flow through capillaries similar to pericytes

Answer 24

Astrocyte end feet associated with the BBB have contractile properties and can regulate blood flow through capillaries similar to pericytes

Question 25

Cerebral edema is a major contributing factor to disability and death following ischemic stroke, partly because progression of swelling in the brain reduces flow in additional vessels, expanding the ischemic zone. Which of the following statements is false?
▪ The breakdown of the BBB occurs approximately 4-6h following ischemic stroke.
▪ There is an enhanced secretion of Na and water into the brain due to an activation of NaK2Cl luminal transporters.
▪ Astrocytes swell due to membrane-bound NaK2Cl channel activation and high concentration of aquaporins on astrocyte end feet.
▪ No water crosses the blood brain barrier in the early hours of stroke – it is purely astrocyte swelling that causes initial edema.
*None of the above statements are false.

Answer 25

No water crosses the blood brain barrier in the early hours of stroke – it is purely astrocyte swelling that causes initial edema.

Question 26

Which two BBB ion transporters are believed to be involved in pH regulation?
▪ Na/K/ATPase and inward rectifying K channels
▪ Multiple K channel types are known to be involved in pH regulation
▪ ClHCO3 and Na/H Exchange
▪ Na/Ca exchange directly coupled with Na/H channels

Answer 26

ClHCO3 and Na/H Exchange

Question 27

Experimental inhibition of astroglial calcium signaling may have what effect on the neurovascular unit?
▪ inhibit the functional link between neuronal activation and vascular tone
▪ inhibit COX1 in endothelial endfeet and therefore lead to a constitutively dilated vessel tone
▪ inhibit postsynaptic neurotransmitter release from neurons – in turn astrocytes would not release vasoactive substances
▪ astrocytes could no longer secrete Ca-dependent neurontransmitters such as acetylcholine from their endfeet and this would lead to extensive vasodialation of all surrounding vessels

Answer 27

inhibit the functional link between neuronal activation and vascular tone

Question 28

o The so-called astrocyte-neuron lactate shuttle provides additional metabolic substrate to functionally active neuronal synapses. How is glycolysis stimulated in the astrocyte in response to neuronal activity?
▪ adjacent astrocytes have neurotransmitter receptors, which upon activation lead to an intracellular signaling cascade ultimately stimulating phosphoglycerate kinase (PGK) activity within the astrocyte
▪ adjacent neuronal activity leads to an influx of sodium into the astrocyte which then activates phosphoglycerate kinase (PGK) and stimulates glycolysis within the astrocyte
▪ adjacent neuronal activity leads to decreased extracellular K concentrations which are detected by astrocytes – in response phosphoglycerate kinase (PGK) is activated and glycolysis initiated
▪ even in resting state, there is synaptic activity in neurons, therefore the phosphoglycerate kinase (PGK) in astrocytes is constitutively active in order to ensure a constant lactate shuttle to all surrounding neurons.

Answer 28

adjacent neuronal activity leads to an influx of sodium into the astrocyte which then activates phosphoglycerate kinase (PGK) and stimulates glycolysis within the astrocyte

Question 29

Acute and chronic inflammation and stress can have detrimental effects in the brain. What have studies shown regarding the role of the BBB in disease?
▪ the release of neurotransmitters and cytokines lead to alterations in tight junction expression and thus ultimately increasing BBB permeability
▪ the release of neurotransmitters and cytokines does not effect the BBB due to the high coverage of endothelial cells by astrocytic end feet, thereby protecting BBB from endogenously released factors
▪ the release of neurotransmitters and cytokines lead to alterations in tight junction expression and thus ultimately decreasing BBB permeability
▪ the release of neurotransmitters and cytokines lead to an increased expression of BBB basolateral aquaporins, thereby leading to massive edema

Answer 29

the release of neurotransmitters and cytokines lead to alterations in tight junction expression and thus ultimately decreasing BBB permeability

Question 30

A common method used to investigate the integrity of the BBB in the development of drugs with ZNS targets is:
▪ the delivery of radioactively labeled sucrose into the CNS because its molecular weight is similar to common CNS drugs (i.e. antidepressants, antiepileptic drugs etc)
▪ the delivery of radioactively labeled sucrose into the CNS because its molecular weight is much larger than common CNS drugs (i.e. antidepressants, antiepileptic drugs etc)
▪ the delivery of a glucose analog with a tracer in order to measure BBB integrity as well as metabolic activity of cells
▪ the delivery of a glucose analog with a tracer in order to measure metabolic activity of endothelial cells which is an accurate indicator of BBB permeability

Answer 30

the delivery of radioactively labeled sucrose into the CNS because its molecular weight is similar to common CNS drugs (i.e. antidepressants, antiepileptic drugs etc)

Question 31

-glycoprotein (Pgp) transporters
▪ are present on the apical/luminal side of the BBB and are so-called “efflux transporters” that move toxic substances out of the cell and into the blood
▪ are particular ion antiporters on the apical/luminal side of the BBB and are essential for regulation drug concentrations in the brain
▪ are also known as “organic anion transporting polypeptides” that mediate the transport of organic anion across the cell membrane
▪ are only present in the peripheral nervous system – on fenestrated endothelial cells

Answer 31

are present on the apical/luminal side of the BBB and are so-called “efflux transporters” that move toxic substances out of the cell and into the blood

Question 32

Which of the following drug modifications does not enhance BBB uptake?
▪ lipidization to increase bioavailability
▪ structural modifications to increase Pgp receptor affinity
▪ prodrug development for entry into the cell via luminal transporters, followed by intracellular cleavage into an active metabolite
▪ glycosylation to alter biodegradation and increase bioavailabilty

Answer 32

structural modifications to increase Pgp receptor affinity

Question 33

What have many in vitro and in vivo studies shown to be one of the main causes of the increased BBB permeability during ischemic stroke and hypertension?
▪ The release of chemokines and cytokines lead to the trafficking of tight junction associated proteins away from the tight junction, thereby increasing paracellular passage of solutes
▪ Mechanical stress caused by continuous hypertension and stoke edema leads to the phosphorylation of ion transporters causing increased functional BBB permeability, while TJ proteins remain intact
▪ The release of chemokines and cytokines paradoxically lead to an increased expression of ZO-1 and occludin, therefore it remains unknown as to why there is an increase in BBB permeability
▪ The release of chemokines and cytokines lead to an endocytosis of ZO-1, claudin and occluding proteins, leading to complete loss of TJ functionality and break down of the BBB

Answer 33

▪ The release of chemokines and cytokines lead to the trafficking of tight junction associated proteins away from the tight junction, thereby increasing paracellular passage of solutes

Question 34

Which of the following is not a disadvantage of delivering drugs through so-called “non-vascular routes”, i. e. intra-cerebral injection?
▪ it is an invasive procedure
▪ drugs diffuse only to a limited area
▪ it can cause systemic toxicity as drugs are transported through the spinal cord through CSF
▪ side effects are often reported

Answer 34

it can cause systemic toxicity as drugs are transported through the spinal cord through CSF

Question 35

Lipidization is a technique used to increase transcellular diffusion across the BBB for drugs with CNS targets. Which of the following statements regarding lipidization of drugs/solutes is true?
▪ Lipidization strategies increase the non-specific distribution of the drug in all organ
▪ Lipidization is only applicable to biopharmaceuticals and cannot be applied to small molecules
▪ Lipidization not only increases transcellular diffusion of a solute across the BBB, but also inhibits efflux via anatgonization of Pgp transporters, hence increasing bioavailability in the brain
▪ Lipidization is only applied to enhance diffusion of macromolecules because modification of small molecules to cross the BBB via specific transporters is easier

Answer 35

Lipidization strategies increase the non-specific distribution of the drug in all organ

Question 36

The term “molecular Trojan horses” used to describe a drug deliver system refers to genetically modified proteins that cross the BBB
▪ via absorptive endocytosis
▪ via carrier-mediated transport
▪ via endogenous receptor-mediated endocytosis
▪ via lipidization and paracellular diffusion

Answer 36

via endogenous receptor-mediated endocytosis

Question 37

Which of the following is not an applied method to achieve brain delivery of large hydrophilic molecules?
▪ osmotic BBB disruption via injection of hypertonic solutions (i.e. manitol) in order to allow for paracellular diffusion of larger molecules
▪ local BBB disruption using focal ultrasound or electromagnetic fields in order to allow for paracellular diffusion of larger molecules
▪ co-application of drug with bradykinin receptor agonists to decrease tight junction tightness to enhance paracellular diffusion of larger molecules
▪ Lipidization is typically used to enhance paracellular diffusion of large hydrophilic molecules across the BBB

Answer 37

Lipidization is typically used to enhance paracellular diffusion of large hydrophilic molecules across the BBB

Question 38

Absorptive endocytosis of solutes/drugs across the BBB
▪ Refers to the cationization of solutes which consequently leads to neutralization of the negatively charged luminal glycocalyx, thereby decreasing BBB tightness and enhancing transcellular transport
▪ is used to facilitate transport of positively charged solutes across the BBB by non-specific binding to negatively charged luminal glycocalyx on endothelial cells
▪ refers to receptor-mediated endocytosis of solutes that have been modified to increase ligand-receptor affinity of luminal transports on endothelial cells
▪ is used to facilitate transport of negatively charged solutes across the BBB by specific binding to cation-amino-acid transporters (CAT1) present on lumen of endothelial cells

Answer 38

▪ is used to facilitate transport of positively charged solutes across the BBB by non-specific binding to negatively charged luminal glycocalyx on endothelial cells

Question 39

So-called PEGylation of drugs is often used in order to
▪ increase receptor-affinity to endogenous carrier transporters
▪ increase drug stability and thereby extend the circulating life of the drug
▪ decrease drug solubility if the half-life of a substance is too long and thereby reducing systemic toxicity to the organism
▪ fluorescently mark molecules in order to investigate in vivo distribution of newly developed drugs with CNS targets

Answer 39

increase drug stability and thereby extend the circulating life of the drug

Question 40

Dynamic in vitro models for investigating the BBB refers to
▪ a flow-based in vitro BBB model that applies a “flow” to simulate shear stress of blood flow which may influence the high tightness of the BBB in vivo which was previously difficult to reproduce in vitro
▪ the co-culture of astrocytes and endothelial cells to simulate the neurovascular unit as accurately as possible
▪ an in vitro BBB model including neurons that allows for neuronal electrical stimulation which may influence the high tightness of the BBB in vivo which was previously difficult to reproduce in vitro
▪ the co-culture of pericytes and endothelial cells to simulate the vasoactive properties of the neurovascular unit as accurately as possible

Answer 40

a flow-based in vitro BBB model that applies a “flow” to simulate shear stress of blood flow which may influence the high tightness of the BBB in vivo which was previously difficult to reproduce in vitro

Question 41

o What is the main disadvantage of almost all in vitro methods used to investigate the BBB?
▪ only a single cell culture of endothelial cells is possible, therefore investigation of the interaction of endothelial cells with astrocytes is nearly impossible in in vitro models
▪ all in vitro models tend to show reduced barrier function and higher paracellular permeability which does not accurately represent the tightness of the BBB in vivo
▪ it can take up to months for endothelial cell cultures to develop before analysis can be done, therefore the cost of these experiments is extremely high
▪ the use of dye in fluorescence microscopy disrupts tight junction proteins and therefore microscopy of in vitro systems is nearly impossible

Answer 41

all in vitro models tend to show reduced barrier function and higher paracellular permeability which does not accurately represent the tightness of the BBB in vivo

Question 42

Transendothelial electrical resistance
o is a useful indicator of the viability of neurons in a co-culture of endothelial cells and neurons as neurons often undergo apoptosis in cell culture and their viability needs to monitored
o is a useful indicator of ion flux and hence functional permeability as it reflects the impedance to the passage of small ions through a physiological barrier
o is a useful indicator of the passage of gaseous molecules such as O2 and CO2 across the BBB as it reflects the impedance to the passage of such polar molecules across the BBB
o is a useful indicator of the passage of water across the BBB and hence paracellular permeability since in vitro endothelial cells have no aquaporins

Answer 42

is a useful indicator of ion flux and hence functional permeability as it reflects the impedance to the passage of small ions through a physiological barrier

Question 43

BBB breakdown has been observed hours following ischemic stroke. Which of the following statements is true?
▪ early contrast agent leakage (suggestive of BBB breakdown) is predictive of subsequent hemorrhage following treatment
▪ early contrast agent leakage (suggestive of macrophage infiltration) is predictive of a good outcome following treatment
▪ larger perfusion deficits surrounding the lesion suggest intact BBB and therefore is predictive of a good outcome following treatment
▪ BBB and ischemic stroke have never been investigated via MRI

Answer 43

early contrast agent leakage (suggestive of BBB breakdown) is predictive of subsequent hemorrhage following treatment

Question 44

Cellular MRI involves in vivo and in vitro labeled cells with contrast agent, for the in vivo labeling for cells, USPIOs (ultra-small-paramagnetic iron oxide) are intravenously injected and taken up by macrophages. How can this method aid in investigating the BBB following cerebrovascular injury?
▪ this method not only shows extravasation of macrophages following inflammation, but may also be an indicator of BBB breakdown and leakage
▪ this method is able to completely differentiate between BBB breakdown from controlled extravasation of macrophages and monocytes and is therefore much more specific than perfusion imaging
▪ Macrophages can never enter the BBB (immune-privilege) and therefore, entry of labeled macrophages into the brain suggests complete BBB breakdown
▪ Macrophages enter the brain via the ventricular system through the choroid plexus, therefore contrast-filled ventricles in MRI are suggestive of enhanced permeability

Answer 44

this method not only shows extravasation of macrophages following inflammation, but may also be an indicator of BBB breakdown and leakage

Question 45

Which technique is most commonly used in the clinic to detect BBB breakdown using MRI?
▪ permeability BBB in which intravenously injected contrast agents that extravasate and accumulate in surrounding tissue indicate BBB breakdown
▪ cellular MRI in which in vitro labeled cells are injected and extravasation of labled macrophages into inflammted tissue indicate BBB breakdown
▪ so far no MRI sequence can detect BBB breakdown, only infarcted tissue and hypoperfused area are visible on MRI
▪ molecular MRI showing CAM upregulation is the gold standard for investigating BBB breakdown in the clinic

Answer 45

permeability BBB in which intravenously injected contrast agents that extravasate and accumulate in surrounding tissue indicate BBB breakdown

Question 46

Which of the following magnetic resonance (MR) modalities does NOT correctly correlate correctly to the property of the neurovascular unit that it investigates?
o Perfusion MRI – cerebral blood flow
o Molecular MRI - adhesion molecules
o Permeability MRI – BBB breakdown
o Diffusion MRI – tight junction upregulation
o Cellular MRI - Leukocyte extravasation

Answer 46

Diffusion MRI – tight junction upregulation

Question 47

What is the main pitfall of using functional MRI for neurovascular imaging following cerebrovascular injury?
o indirect method to investigate neuronal activation and is dependent on intact neurovascular coupling and vascular reactivity, this could result in false negative activation
o imaging with functional MRI takes over 2 hours therefore neurovascular structures may change rapidly over the course of measuring one subject
o functional MRI can only be performed in small rodents because the magnetic strength is too high for human subjects (7T vs. 1.5T)
o functional MRI is the gold standard for neurovascular imaging and therefore is applied in many studies investigating the BBB following cerebrovascular injury

Answer 47

indirect method to investigate neuronal activation and is dependent on intact neurovascular coupling and vascular reactivity, this could result in false negative activation

Question 48

Which tight junction proteins are down-regulated in oxidative stress such as in hypoxia or in stroke? (multiple answers)
▪ tricellulin
▪ claudin-1, -3, -12
▪ ZO-1

Answer 48

claudin-1, -3, -12

Question 49

Tight junctions are formed by the following tretraspanin molecules, except:
▪ claudins
▪ occludin
▪ tricellulin
▪ ZO-2

Answer 49

ZO-2

Question 50

Main characteristics of tight junctions
▪ electron dense material between endothelial or epithelial cells
▪ close paracellular cleft for any molecule
▪ electron dense material between pericytes and astrocytes
▪ open paracellular cleft for any molecule

Answer 50

▪ electron dense material between endothelial or epithelial cells
▪ close paracellular cleft for any molecule

Question 51

Which is considered to be the main tight junction protein of the BBB maintaining the paracellular tightening?
▪ Tricellulin
▪ Occludin
▪ Claudin-3
▪ Claudin-5

Answer 51

▪ Claudin-5

Question 52

Where are tight junction proteins localized at the blood-brain barrier?
▪ In the cell-cell contacts between the plasma membrane of pericytes, astrocytes and brain capillary endothelial cells
▪ In the cell-cell contacts between the plasma membrane of neurons and brain capillary endothelial cells
▪ In the cell-cell contacts between the plasma membrane of brain capillary endothelial cells and end feet of astrocytes
▪ In the cell-cell contacts between the plasma membrane of brain capillary endothelial cells

Answer 52

In the cell-cell contacts between the plasma membrane of brain capillary endothelial cells

Question 53

Which are the most common Claudins found and studied in the BBB?
▪ claudin-1, -3, -5, -15
▪ claudin-1, -2, -5, -11
▪ claudin-1, -3, -4, -10
▪ claudin-1, -3, -5, -12

Answer 53

claudin-1, -3, -5, -12

Question 54

Molecular size sealed by Claudin-5
▪ >800 Da
▪ >400 Da
▪ <400 Da
▪ <800 Da

Answer 54

<800 Da

Question 55

The following are tight junction-associated marvel proteins (TAMPs) except:
▪ occludin
▪ ZO-1
▪ tricellulin
▪ marvelD3

Answer 55

▪ ZO-1

▪ tricellulin