Important Points! Website: http://play.psych.mun.ca Course outline Course lectures Study questions Course info (i.e. change of exam date, class cancelled, assignment info, etc) Not time in class to cover all material in text, but students are responsible for text and class material for midterms and exams. Students are responsible for all material covered in class (but not in text). Chapter 15: Neurological Disorders Preview Tumors Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders Tumors Mass of cells whose growth is uncontrolled and that serves no useful function. Malignant Tumor – a cancerous tumor; lacks distinct border and may metastasize. Benign Tumor – a noncancerous tumor; has a distinct border and cannot metastasize. Glioma – a cancerous brain tumor composed of one of several types of glial cells. Meningioma – a benign brain tumor composed of the cells that constitute the meninges. Seizures Partial seizures– does not involve the whole brain Generalized seizures – involves the entire brain, widespread. Simple Complex Grand mal – generalized, tonic/clonic Absence (Petit mal) – generalized, absence of behavior Causes: Injury, stroke, developmental abnormality, effect of a growing tumor Febrile seizures Infantile fever Alcohol or barbiturate withdrawal Genetic factors Treatment - Anticonvulsant drugs, surgery, diet Cerebrovascular Accidents Hemorrhagic Stroke - rupture of a cerebral blood vessel Obstructive Stroke – occlusion of a blood vessel Thrombus – blood clot that forms within a blood vessel Embolus – piece of material that forms in one part of the vascular system, breaks off, carried by blood stream until it reaches a smaller artery Treatment Clot dissolving drugs Hypothermia Constraint-induced movement therapy Preview Tumors Seizure Disorders Cerebrovascular Accidents Disorders of Development Toxic chemicals Inherited metabolic disorders Down Syndrome Degenerative Disorders Disorders Caused by Infectious Diseases Disorders of Development Toxic Chemicals During pregnancy, impairs fetal development Mother contracts rubella (German measles) Mother ingests alcohol during pregnancy Inherited Metabolic Disorders Phenylketonuria (PKU) Tay-Sachs disease Inherited Metabolic Disorders Tay-Sachs disease Causes brain to swell and damage itself against the inside of the skull and dura mater Metabolic “storage” disease 1 or more enzymes are missing, waste products cannot be destroyed by lysosomes, accumulation Lysosomes get larger, cells get larger, brain swells Symptoms begin around 4 months Exaggerated startle response, listlessness, irritability, spasticity, seizures, dementia, death Down Syndrome Genetic accident ~0.15% of births Usually occurs during ovulation Extra chromosome 21 is created in the egg 3 chromosome 21s in the zygote Down Syndrome Probability increases with advancing maternal age Genetics of DS Trisomy 21 Caused by a nondisjunction event. a gamete (a sperm or egg cell) is produced with an extra copy of chromosome 21 Cause of approximately 95% 88% from nondisjunction in the maternal gamete 8% from nondisjunction in the paternal gamete. Nondisjunction is the failure of chromosome pairs to separate properly during cell division The result of this error is a cell with an imbalance of chromosomes Down Syndrome Mosaicism When some of the cells in the body are normal and other cells have trisomy 21 This can occur in one of two ways: 1. Nondisjunction event during early cell division in a normal embryo leads to a fraction of the cells with trisomy 21 2. Down syndrome embryo undergoes nondisjunction and some of the cells in the embryo revert to the normal chromosomal arrangement. Variability in the fraction of trisomy 21, both as a whole and among tissues. Cause of 1–2% Down Syndrome Robertsonian translocation The long arm of chromosome 21 is attached to another chromosome, often chromosome 14 or itself (called an isochromosome) A person with such a translocation is phenotypically normal. During reproduction, there is a significant chance of creating a gamete with an extra chromosome 21 Cause of 2–3% of observed cases of Down syndrome. No maternal age effect, and is just as likely to have come from fathers as mothers. Down Syndrome Duplication of a portion of chromosome 21 Region of chromosome 21 will undergo a duplication (rare) Leads to extra copies of some, but not all, of the genes on chromosome 21 If the duplicated region has genes that are responsible for Down syndrome physical and mental characteristics, such individuals will show those characteristics Very rare Down Syndrome Consequences Disfigurement Flattened skull and nose Folds of skin over the inner corners of the eyes Short fingers Retarded intellectual development Often serious medical complications Preview Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders variant Creutzfeldt-Jackob (BSE) Parkinson’s Disease Huntington’s Disease Alzheimer’s Disease Multiple Sclerosis Disorders Caused by Infectious Diseases Degenerative Disorders: vCJD Transmissible Spongiform Encephalopathies Contagious brain disease whose degenerative process gives the brain a sponge-like appearance. Bovine Spongiform Encephalopathy (BSE) Creutzfeldt-Jakob Disease (CJD) Fatal familial insomnia Kuru (humans) Scrapie (sheep) Prions – protein that can exist in two forms that differ only in their 3-D shape. Stanley Prusiner (discovered 1986) Nobel Prize (1997) Normal prion protein (synaptic protein) Development and learning and memory Accumulation of misfolded prion protein is responsible for TSE. PRION DISEASES PrPc (normal) and PrPsc (prion infected) PrPC PrPSC PrPSC -protease-resistant (prion protein also heat resistant) Abnormal protein taken up into neuron by retrograde transport Transmissible Spongiform Encephalopathies Encephalopathies Encephalopathy gives the brain a ‘swiss cheese’-like appearance Once introduced into the cell the PrPsc can cause the PrPc (normal) to become misfolded APOPTOSIS: programmed cell death Caspases: enzymes generated by the cell initiating cell death BSE: caspase 12 Transmissable Spongiform Encephalopathy Creutzfeldt-Jakob Disease (CJD) NEURODEGENERATIVE DISEASE Rapidly progressive dementia, memory loss, personality changes and hallucinations Physical problems such as speech impairment, jerky movements, balance and coordination dysfunction (ataxia), changes in gait, rigid posture, and seizures Death Creutzfeldt-Jakob Disease (CJD) Three recognized methods of affliction Familial Sporadic Acquired Iatrogenic Variant (a.k.a. New Variant) Long incubation periods (4-40 years) Species Barrier and multiple exposures FOOD FOR THOUGHT 50,000 BSE-infected cattle are estimated to have entered the human food chain before its recognition in 1986 “You’re sick, Jessy!…Sick, sick, sick!” vCJD: Age of Onset British Medical Journal 2001; 322 : 841 Preview Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders variant Creutzfeldt-Jackob (BSE) Parkinson’s Disease Huntington’s Disease Alzheimer’s Disease Multiple Sclerosis Degenerative Disorders Lewy Body Parkinson’s Disease A disease caused by degeneration of the nigrostriatal system – the dopamine-secreting neurons of the substantia nigra (send axons to BG) Lewy Body – abnormal circular structures with a dense core consisting of -synuclein protein (presynaptic protein); found in dopaminergic nigrostriatal neurons of Parkinson’s patients. DA pathways Parkinson’s Disease 1% of people over 65 Symptoms: Muscular rigidity Slowness of movement Resting tremor Postural instability Difficulties with handwriting or making facial expressions Genetic causes of PD Gene mutations Mutation on chromosome 4 Gene that codes for alpha-synuclein (SNCA) – located in presynaptic terminal of DA cells Toxic gain of function Dominant Abnormal SNCA becomes misfolded, forms aggregations - make up lewy bodies Toxic gain of function – genetic disorder caused by a dominant mutation that involves a faulty gene that produces a protein with toxic effects Genetic causes of PD Mutation on chromosome 6produces an abnormal Parkin protein Recessive disorder Loss of function Normal Parkin plays a role Trafficking defective/misfolded proteins to proteasomes for destruction (recycling) Defective Parkin: Allows abnormally high levels of defective proteins to accumulate in dopaminergic neurons Fails to ubiquinate abnormal proteins Ubiquitination – targets the abnormal proteins for destruction by the proteasomes Kills the cell Fig. 15.16 Sporadic PD ~95% of cases are sporadic (occur in the absence of family history) Causes: Toxins present in environment Insecticides Faulty metabolism Unidentified infectious disorder Toxic chemicals inhibit mitochondrial functions which leads to the aggregation of misfolded alpha-synuclein, in DA neurons, kills the cell Why the Nigrostriatal Pathway? • Ca2+ channels – regulate spontaneous activity of DA cells in NGS pathway • Na+ channels – regulate spontaneous activity of DA cells in other pathways • Animal models – SNCA, increased Ca2+, increased DA = kill cells • DA cells in other pathways don’t contain increased Ca2+, neurons are spared Treatment for PD L-DOPA – precursor of DA Increased level of L-DOPA in brain causes remaining DA neurons to secrete more DA, alleviates symptoms Short-term Number of nigrostriatal DA neurons decline – symptoms become worse High levels of L-DOPA produce side effects – acting on DA systems other than nigrostriatal Hallucinations and delusions Treatment for PD http://www.youtube.com/watch?v=d64iAcaK69M MPTP – 1-methyl-4-phenyl-1,2,3-6-thrahydropyridine Nonhuman primates respond to MPTP the same as humans Cell loss in substantia nigra Level of DA is greatly reduced Gross motor symptoms Deprenyl (monamine agoinst) – blocks the effects of MPTP in the animal model Inhibits the activity of the enyzme MAO-B Intracellular breakdown of DA by MAO-B causes the formation of H202 – damages the cell Increases mitochondrial function in the brains of mice Administration in early Parkinson’s slows the progression of the disease Treatment for PD Stereotaxic surgery Transplantation of fetal tissue/neural stem cells Pallidotomies – surgical destruction of the internal division of the globus pallidus Electric stimulation or lesion of subthalamic nucleus Genetically modified virus into the subthalamic nucleus, delivered a gene for GAD (synthesis of GABA) Causes some of the glutamate neurons into GABA-producing neurons Symptoms improved Treatment for PD Transplantation of fetal tissue Re-establish the secretion of DA in the neostriatum Tissue is obtained from the SN of aborted human fetuses and implanted into the caudate nucleus and putamen Fetal cells grow in their new host and secrete DA, reducing symptoms (initially) Develop severe dyskinesias (involuntary movements) Misfolded SNCA is transferred from the recipient's own neurons to the grafted neurons No longer recommended Treatment of PD Transplantation of neural stem cells – undifferentiated cells with potential to develop into DA neurons Transplantation of large number of cells – increasing the numbers of surviving cells Remond et al., 2007 MPTP injections in monkeys destroyed nigrostriatal DA neurons Implanted neural stem cells in the caudate Stem cells differentiated into DA neurons, astrocytes and other cells that protect and repair neurons Motor behavior improved GPi - Output of BG Output, directed through the thalamus to motor cortex, is inhibitory Decrease in activity of DA input to caudate nucleus and putamen causes an increase in activity of GPi Damage to GPi might relieve the symptoms of PD Treatment of PD Pallidotomies MRI to determine location of GPi low intensity, high-frequency stimulation through electrode GPi, temporarily disabling it If patients rigidity stopped (patient is awake) Metabolic activity in premotor and supplementary motor areas returns to normal levels Release the motor cortex from inhibition Treatment of PD Lesions of subthalamic nucleus Subthalamic nucleus has an excitatory effect on GPi Damage to subthalamus decreases the activity of this region and removes some of the inhibition on motor output Normal people – damage to subthalamus causes involuntary jerking and twitching PD patients – damage to subthalamus causes normal motor activity (normally depressed) Treatment of PD Stimulation of subthalamus (deep brain stimulation) Implant electrodes in subthalamic nucleus and attach a device that permits PD patient to electrically stimulate the brain Fewer side effects (compared to surgery) How can stimulation and lesions of the same area produce the same effect??? Gene Therapy as a Treatment of PD Genetically modified virus into the subthalamic nucleus of PD patients Delivered a gene for GAD (enzyme that makes GABA) Production of GAD turned some of the glutamate neurons into inhibitory, GABA neurons Activity of GPi decreased, activity of supplementary motor area increased, symptoms improved Preview Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders variant Creutzfeldt-Jackob (BSE) Parkinson’s Disease Huntington’s Disease Alzheimer’s Disease Multiple Sclerosis Huntington’s Disease Degeneration of caudate nucleus and putamen Uncontrollable movements, jerky limb movements Progressive, cognitive and emotional changes Death (10-15 years) HD The disease can affect both men and women. HD is caused by an autosomal dominant mutation in either of an individual's two copies of a gene called Huntingtin, which means any child of an affected person typically has a 50% chance of inheriting the disease. Physical symptoms of Huntington's disease can begin at any age from infancy to old age, but usually begin between 35 and 44 years of age. About 6% of cases start before the age of 21 years with an akinetic-rigid syndrome; they progress faster and vary slightly. Huntington’s Disease Neurodegeneration in the putamen First: Inhibitory neurons (GABAergic) Removes inhibitory control of motor areas in cortex (hyperkinetic) As the disease progresses, neural degeneration occurs in many other regions Huntington’s Disease GENETICS Dominant gene on chromosome 4 Gene that codes the huntingtin protein (htt) Repeated sequence of bases that code for the amino acid glutamine Abnormal htt becomes misfolded and forms aggregates in nucleus Cell death: apoptosis Huntington’s Disease Normal Huntingtin (htt) Forms complex with clatherin, Hip1 and AP2 Involved in endocytosis and neurotransmitter release Huntington’s Disease Htt protein has abnormally long glutamine tract May lead to abnormal endocytosis and secretion of neurotransmitters Nature 415, 377-379 (2002) Striatal death by apoptosis Another study: Li et al. 2000 Caspase-3 HD mice with caspase inhibitor lived longer Inhibits apoptosis Huntington’s Disease Normal htt facilitates the production and transport of brain derived neurotropic factor (BDNF) BDNF: neurotropic factor critical for the survival of neurons BDNF produced in cortex and transported to basal ganglia Abnormal htt interferes with BDNF in 2 ways: Inhibits the expression of the BDNF gene Interferes with the transport of BDNF from the cerebral cortex to the BG Huntington’s Disease Fig. 15.20 (artist’s rendition): Huntington’s Disease, Inclusion Bodies Inclusion bodies: Role is unclear in Huntington’s Disease Tissue infected with abnormal htt produces inclusion bodies Neurons with inclusion bodies had lower levels of abnormal htt elsewhere in the cell, cell lived longer than cells without inclusion bodies Neuroprotective? Treatment of HD None Happ1 - Antibody that acts intracellularly (intrabody) Targets a portion of the Htt protein Mouse models of HD, insertion of the Happ1 gene into brain suppressed production of mutant Htt and improved symptoms Preview Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders variant Creutzfeldt-Jackob (BSE) Parkinson’s Disease Huntington’s Disease Alzheimer’s Disease Multiple Sclerosis Alzheimer’s Disease Degenerative brain disorder of unknown origin; causes progressive memory loss, motor deficits, and death. 10% of the population over 65 years old and 50% of the population over 85 Severe degeneration of the hippocampus, entorhinal cortex and neocortex (prefrontal and temporal association areas), Locus coeruleus, Raphe nucleus Signs of Alzheimer’s Disease 1. Memory loss that disrupts daily life 2. Challenges in planning or solving problems 3. Difficulty completing familiar tasks at home, at work or at leisure 4. Confusion with time or place 5. Trouble understanding visual images and spatial relationships 6. New problems with words in speaking or writing 7. Misplacing things and losing the ability to retrace steps 8. Decreased or poor judgment 9. Withdrawal from work or social activities 10. Changes in mood and personality Alzheimer’s Disease Amyloid Plaque – Extracellular deposit containing a dense core of -amyloid protein surrounded by degenerating axons and dendrites and activated microglia and reactive astrocytes. Alzheimer’s Disease Neurofibrillary Tangle – a dying neuron containing intracellular accumulations of abnormally phosphorylated tau-protein filaments that formerly served as the cell’s internal skeleton. XS amounts of phosphate ions become attached to strands of tau, changing its molecular structure Transport is disrupted, cell dies Alzheimer’s Disease Amyloid plaques formed by defective β-amyloid protein (Aβ) Gene encodes the production of the β-amyloid precursor protein (APP; ~700 a.a. long) APP is then cut in 2 places by secretases to produce β-amyloid protein β-secretase γ-secretase Results in Aβ-40 or Aβ-42 Normal brain ~95% of Aβ is short AD brain Aβ-42 is as high as 40% Folds improperly and form aggregates System cannot ubiquinate the high amounts of long Aβ proteins Fig. 15.23 Alzheimer’s Disease Some forms of AD are familial APP gene – chromosome 21 Gene for the amyloid beta precursor protein (APP) is located on chromosome 21, and people with trisomy 21 (Down Syndrome) who thus have an extra gene copy almost universally exhibit AD by 40 years of age. Netzer, W.J., Powell, C., Nong, Y., Blundell, J., Wong, L., Duff, K., Flajolet, M., Greengard, P. (2010). Lowering beta-amyloid levels rescues learning and memory in a Down syndrome mouse model. PLoS One. 5(6):e10943. Two presenilin genes found on chromosomes 1 and 14 Subunits of γ-secretase Apolipoprotein E (ApoE) – glycoprotein that transports cholesterol in the blood and also plays a role in cellular repair ApoE4 – interfers with removal of long form of Aβ Other causes: Traumatic brain injury Alzheimer’s Disease Aβ inside cell (not plaques) is the cause of neural degeneration Aggregated forms of amyloid (Aβ oligomers) interact with microglia, causing an inflammatory response that triggers the release of toxic cytokines (chemicals produced by the immune system that destroy infected cells) trigger XS release of glutamate by glial cells, causes excitotoxicity (increased inflow of Ca2+ through neural NMDA receptors Cause synaptic dysfunction and suppress the formation of LTP AD and protective effects of “intellectual activity” The Religious Orders Study Positive relationship b/w increased number of years of formal education and cognitive performance Billings et al., (2007) AD mice – contain mutant human gene for APP that leads to development of AD Training on water maze every 3 months from age 2 and 18 months Training delayed the accumulation of Aβ and led to a slowed decline of the animals’ performance Treatment Decline in Ach levels Cholingeric agonists (acetylcholinesterase inhibitors) NMDA receptor antagonist (memantine) Immunotherapeutic approach Amyloid vaccine to reduce plaque deposits and improve performance on memory tasks in a transgenic mouse model Mixed results Dangerous side effects Preview Tumors Seizure Disorders Cerebrovascular Accidents Disorders of Development Degenerative Disorders variant Creutzfeldt-Jackob (BSE) Parkinson’s Disease Huntington’s Disease Alzheimer’s Disease Multiple Sclerosis Multiple Sclerosis Autoimmune demyelinating disease Sclerotic plaques Multiple Sclerosis Epidemiology More women then men Late twenties-thirties Childhood in colder climates Canada has amongst the highest MS incidence estimates in the world 55,000 – 75,000 Prairie provinces and Atlantic Canada highest (2005; University of Calgary) Multiple Sclerosis TREATMENTS: Interferon β Modulates the responsiveness of the immune system Treatment slows the progression and severity of the attacks Glaterimer acetate (copaxone) Peptides composed of random sequences of glutamate, alanine and lysine May stimulate anti-inflammatory responses