Human genetic in psy Flashcards
Phenotype
•Observable properties of an organism produced by the genotype and environmental influences
Down syndrome phenotype
–Sloping forehead –Protruding tongue –Short stubby limbs –Slightly flattened nose –Almond-shaped eyes –May have congenital eye, ear and heart defects
Chromosomes
•Most of our cells contain 46 chromosomes
•The 46 chromosomes are actually 23 pairs
–1 set from mother, 1 set from father
–except gametes: each contain only 23 chromosomes
–Gametes are the sex cells - sperm from male and ova from female
•Each chromosome pair carries genes of the same type
•These chromosome pairs match in size and the functions they serve
Karyotype
- The karyotype is a description of the chromosomal content of a cell
- The autosomes (non-sex chromosomes) are numbered 1 to 22
- The sex chromosomes are either X or Y
Variations in karyotype
47, X Y + 21 Down (cause mild to severe intellectual disability and physical abnormality) treat by surgery, specila intervention and education program. at 20, 1/1900, at 35 1/300 at 45 1/30
47, X X + 21 Down
47, X X Y Klinfer Extra X chromosome cause physical abnormality, treat by hormone therapy. one in 600
45, X Turner cause severe hormonal and intellectual issue, hormone therapy, 1/2500 female
47, X Y Y sydrome above averageheight, no treatment, 1/1000
Klinefelter syndrome
•XXY condition can affect development in 3 ways:
–Physical development: weak muscles and reduced strength. Lagging in physical development.
–Language development: Between 25 and 85% of XXY males have some language difficulties
–Social development: XXY males tend to be quieter and undemanding compared with XY males
Chromosomes role
- A chromosome carries the genetic information of the body
- Information is arranged in a linear sequence
- Chromosomes are made up of chromatin. Chromatin constitutes nucleic acids (DNA and RNA) and proteins (histones and non-histones)
- Chromosomes are only visible during cell division processes, called mitosis and meiosis. Otherwise, they unfold and uncoil into a diffuse network within the nucleus
Deoxyribonucleic acid
DNA
- Primary structure (sequence) of DNA is described by the order of the bases in a 5’ to 3’ direction
- Humans have ~ 3.3 x 109 bases
- The locus is used to describe a sequence of DNA situated on a specific region on a chromosome
- DNA is a double-stranded structure consisting of 2 nucleotides held together by hydrogen bonds between the bases in opposing strands
- DNA molecules are organized into stretches of sequence called genes
Genes
•Each gene has one or more specific effects upon the phenotype of the
organism.
•A gene can recombine with another gene
•A gene can mutate into different forms
•Genes are expressed at different time points in life
•A gene can only influence development when it is turned on and is
expressed
•For the DNA to impart information, it must first be transcribed
Transcription and
Translation
- The strand of DNA acts as a template for the synthesis of ribonucleic acid (RNA)
- Like DNA, RNA forms stable structures by base-pairing
- DNA information can be copied to RNA for transcription and translation and carried to other areas of the cell to create proteins
- Messenger RNA carries the instructions specifying sequences of amino acids
- Groups of three bases of mRNA serially code for each amino acid
- These groups of 3 bases are called codons
- There are potentially 64 possible codons, but in nature there are only 20 different amino acids
Areas of DNA
ORF: open reading frame
UTR: un-translated region
RBS: ribosome binding site
Promoter: region of DNA that initiates transcription of the gene
Operon: is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter
Polycistronic: codes for more than one protein
Proteins`
•20 different amino acids •Proteins are the end product of gene expression •Protein types: –Enzymes –Haemoglobin –Insulin –Collagen –Keratin –Histones –Actin and myosin –Immunoglobulins
Alleles
- About one-third of human genes have two or more different forms, called alleles
- An allele is one of two or more forms (or variations) of a gene
- The alleles of a given gene influence the same trait or characteristic
- E.g. eye colour
- The different allele forms result in different eye colours (green, brown, hazel, grey etc)
Gene Expression
- The dominant allele is the form of the gene that is expressed if present.
- The recessive allele is expressed if a dominant allele is absent.
Polygenic Inheritance
•When traits are governed by more than one
gene
•Applies to most traits and behaviors of interest
to behavioral scientists
Mutations
•Mutation is the process of change in the sequence of DNA
•Mutations are the source of genetic variation and the basis for natural selection
•Mutations have a wide range of effects on organisms, depending on the type and location of mutation
•They can occur spontaneously or be induced by external factors such as exposure to chemicals and radiation
•There are four main types of mutations
–Base substitutions
–Deletions of DNA
–Insertions of DNA
–Whole or partial chromosomal abnormalities
Genetic origins of disease
•Over 5,000 human diseases and disorders are mpresently known to have genetic origins
Recessive gene: PKU, sickle-cell anemia, Tay-Sachs mdisease, cystic fibrosis
Single dominant gene: Huntington’s disease, neurofibromatosis
Polygenic inheritance: cancer, heart disease, asthma, mpsychiatric disorders, behavior disorders
Sex-Linked inheritance: red-green color blindness, hemophilia, Duchenne muscular dystrophy, fragile-X syndrome
Chromosomal anomalies: Down syndrome (trisomy 21), Klinefelter syndrome (XXY), Turner syndrome (XO)
Regulator gene defects: genetic male with female genitalia
Tay-Sachs disease
- A fatal, autosomal recessive neurodegenerative disease of infancy and early childhood
- Rare in most populations
- Caused by mutations of HEXA gene on chromosome 15q23-q24.
- First identified in 1969
Tay-Sachs disease vunerable pop
•Population studies and pedigree analyses suggest that mutations may have arisen from small founder populations:
–Carrier frequency is 1:25 in Ashkenazi Jews
–Same mutation is found in Cajun population in southern Louisiana
–Two different mutations are common in French Canadians
–Higher carrier frequency in Irish-American and Pennsylvania Dutch communities compared with general population
•Incidence in unscreened Jewish populations is 1 in 3,900 births
•Internationally, screening has reduced the incidence of Ashkenazi Jews with TSD-affected children by more than 90%
Tay-Sachs disease education in australia
•Australian high-school-based preconception genetic screening programs help young people through screening and education
–Choosing a partner not at risk
–IVF, donor gametes, adoption
–Selective terminations
–Child-free
•Aim is to optimize reproductive and life choices for participants.
Huntington’s disease
- Progressive neurodegenerative disorder
- Autosomal dominant
- Huntington gene isolated in 1993, on chromosome 4 at 4p16.3
- > 40 repeats of CAG (cytosine, adenine, guanine) trinucleotide in coding region of gene
- Mean onset ~40 yrs, death 12-15 years afterwards
- Prevalence 5-10 per 100,000 people
- Symptoms include cognitive deterioration, personality change, memory loss and depression, and choreic and slow movement
- The gene contains an expanded trinucleotide repeat (CAG) that ranges from 9-35 in healthy adults, and from 36 to 180 in Huntington’s disease.
- Alleles with 36-39 repeats show “reduced penetrance”- only some individuals will go on to develop clinical symptoms.
- Individuals with juvenile-onset (Westphal variant) usually have expansions >55 repeats and develop Huntington’s disease before 20 years.
- Onset appears to be earlier when the transmission is from the father.
Chorea and bradykinesia
characterise movement
control in HD
Voluntary
• Bradykinetic
• Inconsistent and inefficient movement
-Abnormal co-contractions of muscles
-Prolonged EMG bursts
-Less efficient and more variable movements in handwriting
• Sequential and simultaneous movement difficulties
Involuntary
• Involuntary ‘dance-like’ choreic movement
• Abates in advance stages of disease, when akinetic and mbradykinetic movements become mclearer
Broad sub-cortical and cortical damage in HD
- Neuronal and astrocyte loss in the basal ganglia (caudate, putamen, global pallidus and other areas)
- Selective degeneration of GABAergic neurons of striatum
- As disease progresses, greater cortical atrophy occurs
Schizophrenia
•Fundamental and characteristic distortions of thinking, perception and affect that are inappropriate or blunted
•Psychopathological thoughts
–Hallucinations, paranoid or bizarre delusions, and disorganised speech and thinking leading to significant social and occupational dysfunction
•Onset typically occurs in young adulthood
•Affects ~ 0.5% of population
•Course of schizophrenic disorders can be continuous or episodic
•Not due to depression or manic symptoms unless it is clear that schizophrenic symptoms antedate the affective disturbance; not due to drug intoxication or withdrawal
Genetic risk of Schizophrenia
•Genetic risk for schizophrenia is more likely to be continuous
than categorical.
•The last 5 years of genetic research has produced evidence
that genetic risk for schizophrenia is largely polygenic.
Fragile-X syndrome
- FXS is the most common inherited form of intellectual disability
- Expansion mutation of a CGG repeat sequence in the FMR1 gene at the locus Xq27.3
- Leads to silencing of the gene and absence of the gene product - the FMR1 protein product
- This protein is essential for synaptic plasticity, development of the shape of the brain, and cognitive development
- Boys are typically more severely affected than girls
Phenylketonuria
- Children with phenylketonuria (PKU) are unable to metabolize phenylalanine.
- Phenylalanine is an amino acid found in high-protein foods (e.g., meats, eggs, fish, nuts) and in some artificial foods (e.g., diet drinks, artificial sweeteners).
- PKU is a disorder that is related to a defective gene on chromosome 12, in which the body cannot break down this amino acid. It builds up in the body and can cause problems with brain development.
- With early diagnosis and a properly restricted (phenylalanine-free) diet, however, mental retardation resulting from PKU can be avoided.
How gene regulation affect development
- Normal human development will only occur if a given gene is turned on and off at the correct time, in the right place and for the right length of time
- Some genes are only turned on in a few cells and for only a few hours and then are switched off permanently (e.g., during development of the embryo)
- Other genes are involved in the basic functioning of almost all cells almost all of the time
- Regulator genes control the switching on and off of genes
- External factors can affect the switching on and off of genes;
- There is a continuous interaction between the environment and the genotype;
- The range of reaction refers to all the phenotypes that could theoretically result from a given genotype, given all the environments in which it could survive and develop…
Phenotype and Genotype of children
•A child with a given genotype would likely develop quite differently in a loving, supportive family compared with growing up in an alienated, abusive family.
•The child actively creates and explores the environment in which they live.
•By virtue of their nature, they evoke different responses from
others.
•Children actively seek out things that they inherently enjoy.
•This increases as they age – so children at school will become friends with people who have similar energy levels and interests.
Epigenetics
•Heritable (but reversible) changes in gene expression that are not coded in the DNA sequence but by post-translational modifications in DNA, histone proteins and in microRNA
•Environment can produce persistent alterations in the phenotype through altering gene expression
•There are three different mechanisms involved in the regulation of genes
–Histone modification
–DNA methylation
–microRNA
Autoimmune disorders
Autoimmune diseases encompass more than 80 disorders, affecting ~7% of population
–E.g., Rheumatoid arthritis, Lupus, Type 1 diabetes, Multiple sclerosis
•Monozygotic twin studies often show discordance of these diseases, suggesting a role for environmental factors contributing to disease development
•Interplay between genetic and environmental factors may predispose and progress autoimmune diseases
–E.g., Exposure to UV radiation, infections, tobacco smoke, pollutants,
alcohol consumption
–Gender bias (females), age, latitude of country point towards environmental factors contributing to disease predisposition
•Circulating immune cells are in constant exposure to environmental factors
•Currently, the precise epigenetic mechanisms involved in autoimmune disorders is unclear
Genetics and environment
- The interplay between genes and experience is very complex
* This model of hereditary and environmental influences can help to simplify this interplay
Phylogenetic continuity
- We are just another type of animal.
- Due to our shared evolutionary history, we share many characteristics and developmental processes with other living things.
- The size of human brain is markedly larger and more complex than other mammals
- Principles of cortical development and physiology are shared
Cell reproduction: Meiosis
- Cell reproduction: Meiosis
- Meiosis is a special type of cell division, necessary for sexual reproduction.
- Meiosis produces gametes
- The DNA is replicated, recombined, and the cell divides twice
Sperm
• Ejaculation – 500 million sperm
• Sperm physiology
• Sperm’s travel ~ 6 hours (6-7 inches) vagina,
uterus, fallopian tube
• Only about 200 ever get close to the ovum
Why does the amount of sperm aarrive at the tube isl ow
– Tangles
– Wrong fallopian tube
– Abnormal shapes
Three phases of prenatal
development
• Period of the zygote
– 0 to 14 days
– From conception to implantation into the wall of the uterus
• Period of the embryo
– 3 to 8 weeks
– Virtually all the major organs are formed
• Period of the fetus
– 9th week until birth
– All the major organs begin to function and the developing organism grows
The zygote
- sperm Penetration
- Sealing of the membrane
- Tail of sperm falls off, contents of head gush into ovum
- Within hours the nuclei of the two gametes merge, producing the zygote
- Within 12 hours of fertilisation, the zygote splits into two equal parts, each containing a full set of genetic material. This process is called…..mitosis
Cell reproduction: Mitosis
- Mitosis is a process of cell replication and division, in which the cell separates the chromosomes in the cell nucleus into two identical sets, in two separate nuclei
- These two daughter cells are genetically identical to each other and their parent cell
Blastocyst
Ball-like structure that contains 60-80 cells, within 4 days of conception
• Implantation occurs between 8 and 14 days from conception
• Rates of success
– Only half of all fertilised ova are firmly implanted
– Perhaps as many as half of all such implants are genetically abnormal or fail to develop, or burrow into a site incapable of sustaining them
– ¾ of zygotes fail to survive this initial phase of development
Embryo
- Cell differentiation
* The inner cell mass will become the embryo and the rest of the cells will become the amniotic sac and placenta
Four major support structures in an embryo
• Amnion is a watertight sac that fills with fluid, acting as a cushion, regulating temperature and providing a weightless environment
-yolk sac is a structure that develops inside uterus during early pregnancy. It provides an embryo with nourishment
• Chorion is a membrane surrounding the amnion, and it eventually becomes the lining of the placenta
• Allantois forms the umbilical cord
Inner cell mass has 3 layers
- The top layer (ectoderm) becomes the nervous system, the nails, teeth, inner ears, lens of the eyes and outer layer of skin
- The middle layer (mesoderm) becomes the bones, muscles, circulatory system, inner layers of skin and other internal organs
- The bottom layer (endoderm) develops into the digestive tract, lungs, urinary tract and glands
Neural tube
- A U-shaped groove forms down the centre of the top layer and these tops of the U move together and fuse creating the neural tube
- One end of the neural tube will swell and develop into the brain, and the rest will become the spinal cord
Twin development
- Monozygotic twin, come from a single egg that divide itself
- dizygotic twin, a women ovulated two egg, both of them are impregnated
Embryo/Fetal behaviour ( Movement)
- From 5-6 weeks after conception, the organism moves spontaneously
- By 12 weeks, most movements that are present at birth are able to be performed by the fetus
- Different activity levels of fetuses
Fetal experience
• The fetus receives: – Tactile stimulation – Taste stimulation – Smell stimulation – Hearing stimulation
Fetal Learning
• In the last 3 months of pregnancy, the central nervous system has developed enough to support fetal learning
• Fetal learning:
– Habituation studies measuring heart rate in utero
– Preference for familiar sounds, smells and tastes antenatally
• Neonate association learning:
– Oral motor patterns and altered milk flow
– Cross-sensory learning
– Conditioning to tactile and taste stimuli
Teratogens
- ~45% of pregnancies fail within the first 3 weeks
- Teratogens are external environmental agents that can cause damage or death during the prenatal period
- Sensitive periods
Alcohol as a Teratogens
- Ability of foetus to metabolise alcohol is very low
- The risks of Fetal Alcohol Effects are greatest if a pregnant woman binges occasionally (5 or more standard drinks in a session)
- No well-defined sensitive period for alcohol
- Drinking can also affect the male reproductive system – reduced sperm motility, lower sperm count and abnormally formed sperm
Fetal Alcohol Syndrome
Microencephaly (small head) and malformations of the heart, limbs, joints and
face
• FAS babies are likely to display excessive irritability, hyperactivity, seizures and tremors
• Smaller and lighter than normal and their physical growth lags behind that of
normal age-mates. Many display a lower IQ
Thalidomide
• Drug used in the late 1950s and early 1960s to treat morning sickness or as a sedative
• Sensitive period - major limb deformities if the mother took the drug between the 4th and 6th week after conception
– At 21-24 days after conception, the baby was likely to be born without ears
– Between 25 and 27 days, these babies had no arms or grossly deformed arms
– Between the 28th and 36th days, the child might have deformed legs or no legs
– If taken at 40 days or after, there was usually no effect.
• Most mothers who took thalidomide, however, had no apparent birth defects – a finding that illustrates the dramatic differences that individuals display in response to teratogens
Effects of Teratogens deepenmd on
- Timing of teratogen and structure formation
- Genetics and environment
- Same defect can be caused by different teratogens
- A variety of defects can result from a single teratogen
- The longer the exposure or higher the dose, the greater the harm
- Father and mother exposure effects
- Long-term effects often depend on postnatal environment
- Sleeper effects
Rubella
- In 1941, Australian doctor McAllister Gregg noticed a link between rubella and babies who were born blind.
- Sensitive period at 8 weeks of pregnancy.
- Studies suggesting that 60-85% of babies whose mothers had rubella in week 8 had a birth defect, compared with about 50% of those infected in week 9 to 12, and 16% of those infected in weeks 13 to 20.
- Rubella epidemic in 1964 – evidence suggesting higher risk of psychotic disorders for those exposed to rubella in- utero.
The adult human brain
• Most complex system of which we know of
• Human brain and CNS consist of trillions of highly m specialized cells that work in synchrony
– Chemical signals
– Electrical signals
• Larger and more complex than brains of other mammals
The first and second brains
- Human brain makes up about 2/3 of the neuronal mass of the body and contains almost ¾ of all of our synapses
- Enteric nervous system (gut) consists of sheaths of neurons embedded in the walls of the gut
- It contains ~100 million neurons (more than the spinal cord or the peripheral NS)
- Brain outsources the digestion process to this nervous system
- 90% of fibers in the vagus nerve carry information from the gut to the brain
- ENS uses more than 30 neurotransmitters
- 95% of the body’s serotonin is found in the bowels
Brain growth
- The brain grows at an astounding rate early in life
- Between the 7th prenatal month and the 1st birthday, the brain increases in weight by ~1.7 grams per day
- “Brain growth spurt” - last 3 months prenatally and first 2 years after birth
Definitions • Central nervous system (CNS) • Peripheral nervous system • Soma • Dendrite
– Brain and spinal cord
– Nerves attached to the CNS that lie outside of the CNS
– The cell body of a neuron, which contains the nucleus
– A branched, tree-like structure attached to the soma. It receives information from terminals of other neurons
Definitions • Synapse • Axon • Multipolar neuron • Neurotransmitter
– A junction between the terminal of the axon and the membrane of another neuron
– Long thin cylindrical structure that conveys information from the soma of a neuron to its terminal
– A neuron with one axon and many dendrites attached to its soma
– A chemical released by the nerve terminal that has an excitatory
or inhibitory effect on another neuron
Neurons
• Basic unit of the brain
• Three basic types
– Sensory neurons
– Motor neurons
– Interneurons
All neurons have…
1. Cell body - (soma), which contains all the information needed to keep the
cell functioning
2. Dendrites - fibres that receive information from other cells and conduct
that information towards the cell body in the form of electrical impulses
3. Axon - the fibre, any where from a few micrometers to over a meter in
length, that conducts electrical signals away from the cell body to
connections with other neurons
Neurons migration
- Neurons migrate along pathways laid down by a network of guiding cells to form the major parts of the brain
- Peak at end of second trimester of pregnancy
- Scientists established in 1998 that formations of new neurons occur in the hippocampus (an area of the brain important for learning and memory) and these new neurons occur throughout life
Neuron types and specialization
- Different neuron types
- Neurons assume specialised functions depending on where they migrate
- Any neuron has the potential to serve any neural purpose (pluripotency)
Glial cells
• Glial perform a variety of critical functions
• There are five key types of glial cells
• Glial cells play a major role in communication within the brain by
– influencing the formation and strengthening of synapses
– Producing myelin, that helps neurons conduct electrical messages along the neural network
– communicating among themselves in a network separate from the neural network
• Some evidence suggesting people with schizophrenia or bipolar disorder may have a defect in a gene that regulates the production of myelin
• Astrocytes
– Most common of the glial cells
– Mop up excess neurotransmitters emitted from synapses
– Feed neurons by supplying nutrients and neurotransmitter precursors
– Control where and when neurons will make new synapses
• Oligodendrocytes
– Wraps tips around the axons of neurons and extrudes myelin, creating sheaths that help speed conduction of electrical activity along the axon
– Myelin is the “white matter” of the brain
• Schwann cells
– These cells form a layer around the axon, helping conduct electrical impulses
– They are the only glial cells found in the peripheral nervous system, so they also act like astrocytes
• Microglia
– Serve as the immune system in the brain
• NG2+ cells
– Precursor cells to oligodendrocytes, astrocytes, and neurons
Myelination
- Myelin (80% lipid and 20% protein)
- Oligodendrocytes
- Sheath acts as an insulator to speed up the transmission of neural impulses
- Myelination begins at 7 months of gestation
the result of mylination
• Allow for increasingly complex movement
• Myelination continues into early adulthood
– The reticular formation and the frontal cortex are not fully myelinated at puberty. These are areas of the brain that allow us to concentrate and make good decisions etc. This may explain the lengthening of attention span as one grows up
– Myelination enhances the efficiency of processing between the more primitive emotional subcortical areas of the brain and the more regulatory prefrontal cortical area.
• An infant’s ability to process emotional expressions on another person’s face may improve as this myelination occurs
– Thus, may also underpin the development of Theory of Mind in the child
Brain development in the fetus (neurogenesis)
- The brain starts to develop in weeks 2 and 3, with the folding and fusion of the ectoderm to form the neural tube.
- Following on is a sequence of events that are genetically determined, and environmentally influenced via epigenetics.
6mth and 9mth central nervous
system
at 6m the brain is smooth at 9 mont able to develop gyri and sulci
Growth of dendrites
The growth of dendrites of the neurons and arborization rapidly accelerate around the time of the 28th week of gestation onwards
Synaptogenesis
- A synapse is a specialized junction between two cells through which they communicate
- Synaptogenesis is the formation of synapse connections between mneurons
- Synaptogenesis proceeds rapidly during the brain growth spurt
- The peak of synaptogenesis occurs at the 34th week of gestation in humans at the rate of 40,000 new synapses per second
- Synaptogenesis continues in postnatal life
Different types of synapses
Neuron to neuron synapse
Neuron to glia synapse
NG2+ glia are relatively newly
described glial cells.
Apoptosis and synaptic pruning
• The brain has evolved so that it produces an excess of neurons and synapses in preparation for receiving information from the world – sensory and motor stimulation
• Neurons that successfully interconnect with other neurons crowd out those that do not, so that about half the neurons produced early in life also die early
• If neurons are not used, then they will die via the process known as
apoptosis and their connections with other neurons will die – this process is called synaptic pruning.
• Surviving neurons form hundreds of synapses, many of which will disappear if the neuron is not properly stimulated
• Neurons and their synapses that receive the most stimulation continue to function.
• The young infant’s brain is highly plastic
Importance of early experiences
on brain development
Austin Reisen (1913-1996), US researcher
• Noted that when people had congenital cataracts removed, they had difficulties with recognising and interacting with forms (circles, squares, triangles)
• Reisen reared infant chimps in the dark for periods of up to 16 months. He showed that dark-reared chimps experienced atrophy of the retina and the neurons of the optic nerve
• If the chimp was exposed to light before 7 months then the atrophy was reversed. But if not, then the chimp’s atrophy was irreversible and often led to total blindness if the deprivation lasted longer than one year
• Neurons that are not properly stimulated will die
Environmental stimulation
effects on neuron
mouse in enriched cage have highly developed neuron compare to those in the standard cage
Brain areas develop at different
rates
- Not all parts of the brain grow at the same rate
- At birth, the most highly developed areas are the lower (subcortical) brain centres – these areas control states of consciousness, inborn reflexes, vital biological functions such as respiration, digestion of food and elimination of wastes
- Surrounding these structures are the cerebrum (outer grey matter aka cerebral cortex and white matter) and the cerebral cortex (outer grey matter), the areas involved in voluntary movements, perception, higher intellectual activities like learning, thinking, language etc
Method for Investigation of Brain Development
Different methods used to investigate typical and atypical brain development
Examples:
• electroencephalographic (EEG) recordings
• magnetoencephalography (MEG)
• functional magnetic resonance imaging (fMRI)
• positron emission tomography (PET)
• near-infrared spectroscopy (NRIS)
A Study Investigating Structure
• First longitudinal tractography study of brain development from childhood to adulthood
• Diffusion Tensor Imaging (DTI) tractography method used with data
– from 103 healthy subjects
– 221 scans from childhood to young adulthood (5-32 years)
• 92 people with 2 scans; 7 with 3 scans; 4 with 4 scans
• Mean age between first and second scan was 4.0 years
– Assessed 10 white matter tracts
• Brain volume – total brain, gray and white matter volumes
• Tract volume – fractional anisotropy (FA) reflects axon packing and myelination; mean diffusivity (MD) reflects water content and density of white matter
Brain volume:
White matter volume increased significantly across the age range.
Gray matter volume decreased across the age range.
White matter increases were offset by gray matter decreases, so there was no overall change in total brain volume with age.
Conclusions from this study of brain st
• Development occurs for most children across all 10 major white matter tracts studied
• This development continues during the twenties in several association tracts
– Inferior and superior longitudinal and fronto-occipital fasciculi
• These tracts support complex cognitive processing – inhibition, executive functioning, attention
• White matter increases and gray matter decreases in most subjects across age
• Increase in white matter presumably reflects myelination…whilst the decrease in gray matter presumably reflects synaptic pruning and myelination
Growth over time of children
- Very rapid growth during first 2 years of life
- Prolonged period of physical development
- Pubertal growth spurt
Hormones influence growth
the hypothalamus control the pituitary galnd which release different hormone
World Health Organisation growth
charts
- The WHO has growth charts available from a sample of 8,500 children from widely different ethnic backgrounds and cultural settings (Brazil, Ghana, India, Norway, Oman, USA).
- The WHO growth charts represent a single international standard that represents the best description of physiological growth for all children from birth to 18 years
- Over 140 countries have adopted the WHO growth standards
Growth monitoring
Regular measuring of weight and length of child
• Plotting information on a growth curve
• Take action steps if required
• Child’s health should then improve
Why is growth monitoring important
In developing nations, the United Nations Children’s Fund recommends monthly growth monitoring of all children up to 18 months of age.
• Growth monitoring often co-occurs with complex development programs aimed at improving nutrition and it is perceived to mobilize communities.
• In developed countries, growth monitoring is conducted far less frequently. The purpose is different and the outcomes that are anticipated are more modest.
Abnormal growth causes and solution
• Growth monitoring helps to detect:
- Feeding difficulties -Take a more detailed history and offer the mother advice
- Chronic ill health-Take a longer medical history and the child may need to be treated or referred to a specialist
- Social deprivation- A mix of inputs will be commonly applied – more intensive monitoring, home visits and targeting by health visitors and community health workers
Environmental factors that influences on child growth
Three main types of environmental influences on physical growth of children:
- Nutrition
- Illness
- Quality of care that child receives
Nutrition
- Diet is perhaps the most important environmental influence on human growth
- Children who are inadequately nourished grow very slowly, if at all
- If undernutrition is neither prolonged nor especially severe, children usually recover from any growth deficits by having a growth spurt once their diet becomes adequate
- Children are able to catch up with short term growth spurts in order to regain their genetically programmed growth trajectories
Malnutrition
- Prolonged malnutrition has a more serious impact especially in the first 5 years of life.
- In many developing nations, as many as 85% of all children aged under 5 experience some form of malnutrition
- One out of every four children aged under five (~146 million children) is underweight for his or her age, and at increased risk of an early death
- There are two types of nutritional disease related to under-nutrition – Marasmus and Kwashiorkor
Marasmus
- Marasmus affects babies who receive insufficient protein and too few calories.
- This can happen if the mother is malnourished and does not have the resources to provide her child with a substitute for breast milk or if the child is separated from his/her mother
- Babies with marasmus become very frail and wrinkled in appearance as growth stops and the body tissues begin to waste away.
- If these children survive, they may remain small in stuture and often suffer from impaired social and intellectual development
Kwashiorkor
- Kwashiorkor affects children who receive enough calories but not enough protein
- In many poor nations, one of the few high- quality sources of protein readily available is breast milk
- So breast-fed infants do not ordinarily suffer from marasmus unless their mothers are severely malnourished
- They may develop kwashiorkor when they are weaned from the breast but then have no other source of protein
- As the disease progresses, the child’s hair thins, the face, legs and abdomen swell with water and severe skin lesions may develop.
Overnutrition
- Dietary excess is another form of poor nutrition.
- Increased risks of obesity, type 2 diabetes, high blood pressure, heart, liver and kidney disease.
- Difficulties with friendships.
- Habits.
Obesity epidemic
- 1 billion overweight adults in world - 300 million are obese
- Obesity and overweight pose major risks for chronic illness
- Combination of increased consumption of energy-dense foods and reduced physical exercise
Nutrition in gestation
- Field of nutrigenomic research – how nutritional factors can impact the regulation of genes and therefore their functions without altering the genetic code – has advanced massively in the last few years
- Cohort and epidemiological studies provide information about the role and timing of differences in nutrition on health, from an epigenetics perspective
Netherland food famine
• During the Nazi occupation in Winter 1944, food supply was extremely shortened in parts of the Netherlands
– Daily rations were < 700 cals = 2,929 kj
• Lasted for a short period of time and had a major impact on ongoing pregnancies
• Dutch cohort studies have analyzed the outcome of pregnancies during this period of famine and consequences of massive maternal under-nutrition on offspring over time
result of the famine
• Prenatal exposure to the famine was associated with adverse metabolic and mental phenotypes later in life
– Higher BMI
– Elevated plasma lipids
– Increased risks of schizophrenia
– Increased risk of cardiovascular disease
• Many of these associations were dependent on the sex of the fetus and the timing of exposure during gestation (first trimester in particular)
Measles
- Highly contagious viral infection
- Spread by respiratory droplets or direct contact by infected saliva
- Vaccinated individuals have immunity to measles
- No treatment
- People in Australia still die from measles today
- Major epidemic can be averted by large scale vaccinations
- Massive increase in measles cases across the world in 2019
Rubella/German measles
- Viral infection
- Spread by respiratory droplets or direct contact with infected saliva
- No treatment
- Major complications with pregnant women
Mumps
- Contagious viral infection
- Spread by respiratory droplets or direct contact with infected saliva
- Painful swelling in salivary glands and testes for men (can lead to sterility)
- Can occur at any time point in a person’s life
- No treatment
Wakefield big fuck up
• In 1998, Wakefield and colleagues published a paper
suggesting a link between the measles, mumps and rubella (MMR) vaccine and autism.
• The work was discredited and retracted.
• Other studies found no evidence
• Resulted in MMR vaccine rate dropping particularly for children born in late 90s and early 2000s.
• Still used as an argument now for non-vaccination
WHO data on vaccinations
• Immunization prevents illness, disability and death from vaccine-preventable diseases including
– cervical cancer, diphtheria, hepatitis B, measles, mumps, pertussis (whooping cough), pneumonia, polio, rotavirus diarrhoea, rubella and tetanus
• Immunization currently averts an estimated 2 to 3 million deaths every year. An additional 1.5 million deaths could be avoided, however, if global vaccination coverage improves
• An estimated 19.4 million infants worldwide are still missing out on basic vaccines
– Around 60% of these children live in 10 countries: Angola, the Democratic Republic of the Congo, Ethiopia, India, Indonesia, Iraq, Nigeria, Pakistan, the Philippines, and Ukraine
