Pathobiology Flashcards
What is a disease?
Any state in which the health of the human organism is impaired. Consequence of a failure of homeostasis.
What is Pathogenesis?
Biological mechanisms causing clinically evident diseases.
What is Atiology?
Specific cause of a disease
What is a risk factor?
A variable exposure or biological charactorisic that makes disease more likely e..g working in a building site with aspesdos.
Intrinisic factors for disease? (4 and examples)
-Genetic e.g. mutation- sickle cell anaemia
-Metabolic e.g. Diabetes, gall stones
-Cellular e.g. Autoimmune- Alzheimers, arthritis
-Structural
e.g. congenital- spina bifida, Ebsteins anomaly
or e.g. Aquired-atheroma
Extrinsic Factors for disease? (4 and examples)
- Physical e.g. trauma, bone fracture, radiation, temp= frost bite/ burns
- Chemical e.g. toxic substances- tobacco lung damage
- Biological e.g. Bacterial/ viruses/ fungi
- Nutritional- malnutrition.
What are the 4 stages of development of disease?
- Aetiological agent e.g. bacteria primary cause.
- Pathogenic mechanisms e.g. acute inflammation
- Pathological Process e.g. Morpholoical features- skin abscess,
- overt disease and secondary consequences-complications e.g. septicaemia
How were inherited diseases first indentified?
Garrod- noticed blackened urine and kidney stones was inherited in the disease Alkaptonuria 1901
Who started a catalogue of human diseases that exhibited Mendelian inheritance?
William Bateson 1909.
4 types of Mendelian patterns of inheritance?
- Autosomal recessive e.g. cystic fibrosis
- Autosomal dominant e.g. Huntingtons
- Autosomal co-dominant e.g. Sickle cell anaemia
- X linked e.g. Duchenne Muscular Dystrophy, Haemophilia (A and B)
Sickle cell anamia causes?
point mutation causing a change in AA 6 of B subunit from Glycine (charged) to Valine (uncharged) which when aggregates forms crystalline structures. HB^A to HB^s
Why is the proportion of carriers so high in Sub-sarharan Africa?
HB^s confers a resistance to milaria
What enables the chromosomes to be visuallised and abnormalities in banding to be seen? Decade found?
Karyotyping, 1970’s
What are the symptoms of Duchenne muscular dystrophy?
Muscle wasting away, progressive, lethal in childhood or early adult.
What are the causes of Duchenne Muscular Dystrophy?
Deletion of a DNA sequence on the gene Dystrophin- Dystrophin proteins link muscle fibres to the extracellular matrix maintaining tissue integrity.
What is Alkaptonuria?
Homogentisic acid accumulates in joints, causing cartilage damage & back pain; precipitates as kidney / prostate stones;
high levels are excreted, blackening urine
- allows diagnosis.
-Autosomal recessive
What is huntingtons disease? Year found?
1872, late onset disease caused by a repeat of CAG in the huntington gene increasing the size of the polyglutamate tract (QQQQ) 36+ glutamate have.
This makes the Huntinton protein toxic to neurones causing massive neuronal loss in the basal ganglia and dilation of lateral ventricles.
Example of cancer causing virus? Found when? (Retrovirus)
Rous Sarcoma Virus was found by Rous in 1911. DNA sequence was captured from the chicken and showed that the V-Src oncogene, which encodes an abnormal hyperactive version of a tyrosine kinase (now a C src Proto-oncogene)
Chromosomal rearrangements that disrupt the Proto- oncogenes cause cancer, Give an example?
Chronic Myelagenous Lukaemia caused by translocation “Philadelphia Chromosome” causing the ABL proto-oncogene to become a hyperactive version of tyrosine kinase BCR-ABL.
What is a V-oncogene?
A nucleic acid sequence in a virus responsible for the oncogenicity of the virus (proto to oncogene)
It is derived from the host cellular proto-oncogene and acquired from the host by recombination.
How does Retinoblastoma develop?
retinal tumour that can be unilateral (only one eye) which is typically non-heridatory or bilateral (both) which are always heridtory.
Why are bilateral retinalblastomas always hereditory?
Loss of function of a tumour supressor gene. Non hereditory needs to have two somatic mutations in the same cell to get bilateral hence very rare, else if inherited only needs one as there is already a germline mutation in every cell.
What are SNPS?
Single nucleotide polymorphisms. 3x10^7 across the human genome. They are a variation in the nucleotide in a specific location within the genome.
How are SNPs used?
They are markers used to tell people apart for profiling and seeing links to susceptibity for diseases.
Genome wide analysis Studies of SNPs:
-Genome wide SNPs collected.
-Case vs control comparison of specific SNPS.
-SNPS identified that increase susceptibilty to certain diseases.
If associated ‘locus is associated’
Can summarize results of a genome wide analysis study of SNPs on which graph?
Manhatten plot.
What is genome imprinting?
Structural modifications to specific regions of particular chromosomes that prevents the transcription of genes in these regions.
At what stages are genes imprinted?
DNA sequences can be methylated on the cytosine bases in the gametes and reappear in the somatic tissues of the progeny. (removed during germ line development in embryo) Happens during spermogenesis/oogenesis.Imprinting dependent on the sex of offspring.
If one gene is imprinted what will happen to expression?
If say the maternal gene is imprinted then this gene will not get expressed and therefore the Paternal gene will be.
What materal gene is always imprinted?
SNORD116 (small nuclear RNA)
What paternal gene is always imprinted?
UBE3A (ubiquitin protein ligase)
Disease linked to no function of SNORD 116 if paternal is mutated?
Prader Willi Syndrome
-low muscle tone, short stature, cognitive diability, obsese
Disease linked to no function of UBE3A if maternal is mutated?
Angelman Syndrome
-congititve disability,siezures, frequent smiling, sleep disturbance.
How are genes imprinted?
- Transcription activators are lost to make the gene off (but inducible)
- DNA Methylation
- Recruitment of Methyl- C binding proteins
- Recruitment of repressors to stabilise the switching off.
What is Epidemiology?
Science concerned with the pattern of disease frequency in humans. Time, distribution, place, person
What does Epidemiology presume..? (2)
Disease doesnt occur randomly there is a pattern.
Disease has an identifiable cause
Epidemiology triangle- three components that can constitute to disease?
Host e.g. genetic, age, sex, immunization, behaviour
Agent e.g. chemical, infectious,radiation
Environment e.g. socioeconomic conditions, temp
Who was the first to do a epidemiology study on Cholera in London and found the epicentre was a water source?
John Snow
How many a year die of diahrea?
6million
How many deaths in UK every day due to smoking? a year? Worldwide?
320+, 120,000 yr, 4 million worldwide a year, 1/5 of all deaths.
Why do smokers on average live 7.5 years less?
lung, mouth, throat, larynx, bladder, cervix, kidney and pancreas cancer. But also respiratory diseases suhc as COPD and vascular diseases such as stroke or cornory heart disease.
How does the tobacco lead to emphysema?
- Tobacco irritates the throat and lungs
- Interracts with resident macrophages n the lungs
- Neutrophils are recruited through chemotactic facors
- Protease is secreted.
- Proteins are digested-tissue damage =emphysema
How does the smoke’s oxidants and free radicals lead to emphysema?
- Smoke is ful of oxidants and free radicals
- Leads to lower levels of antitrypsin (tripsin inhibitor)
- Proteases such as trypsin become more active and digest protein =emphysema
How does the tar in cigarettes lead to emphysema?
- Cilia are destroyed by the sticky tar reducing cilia action.
- Excess mucus is not wafted away.
- Infections are cuaght.
- Leading to chronic bronchitus and emphysema due to tissue damage.
WHat did Robert Koch discover?
25 years after John Snow’s death the reactive agent fror Cholera, also TB and Anthrax.
How does smoking lead to birth complications? (5)
- Hypoxia- starved of Oxygen due to increase in carboxyhaeomoglobin.
- Disrupts signalling.
- Maternal endocrine/ parocrine changes (decreased progesterone, increased protoglandins)
- Restricted blood flow to placenta due to nicotine caused vasoconstriction.
- Increased risk of membrane rupture- decreased maternal immunity.
What are the two broad responses to extinsic factors?
- Allergic e.g. asthma, laryngitus
2. Pneumoconiosis e.g. from dust
Inhled antigen to response steps:
- Inhaled pathogen’s antigens are recognised as being foreign.
- Mast cells have specific IgE receptors which IgE binds to.
- The antigen then binds to these receptors,
- This causes the release of Hisamine by the mast cell by exocytosis.
- This causes bronchconstriction, mucus secretion and oedema (swelling)
The dust reactions may be: (4)
- Inert e.g. coal
- Allergic e.g. causing extrinsic allergic alveolitis
- Fibrous e.g. aspesdos, silicon
- Neoplastic e.g.Lung carcinoma (abnormal growth of tissue)
WHat diseases can aspestos cause? (4)
- Aspesosis
- Lung cancer,
- Mesothelioma
- cancer of stomach, colon or rectum
How is Aspesdos bad?
Aspesdos fibres often get coated by calcium and iron =ferruginous body. Microphages injest the fibre, which increases the fibrogenic response via release of growth factors that increase the deposition of collapgen by fibroblasts.
The average human contains … cells and ….microbial cells. e.g. gut microbiome not just pathogens.
10^13
10^14
1/5 deaths are caused by pathogens
What are the three types of pathogens?
- Obligate: can only survive in host usually very specific to host species.
- Faculative: Present in the environment(reservoir) waiting for host.
- Opportunistic: Normally benign but cause disease in comprimised host e.g. AIDS
What are virulence genes?
A few genes which enables the virus to become pathogenic.
How does Vibro Cholerae become virulent?
It needs to be infected by certain bacteriophages, which transfers the genes that encode cholera toxins to the bacteria, which cause the spread through diarrhoea etc.
The word to describe that fungi can change shape.
Dimorphism
Dimorphism is shown by Candida albicans how?
Consumed by macrophage in the yeast like state, but rapidly grows germ tubes to break the cell membrane and break free.
Dimorphism is shown by Histoplasma capsulatum how?
Changes state according to the temperature. In the soil grows as a mould with hyphae yet in a warm body changes to yeast morphology which can move better
Steps from sucking on an infected persons blood cycle of milaria?
- Anophilies mosquito sucks on an infected persons blood picking up the gametocytes of the plasmodium
- Fertilisation of the gametes and formation of a zygote.
- Invasion of gut and growth.
- Release of Sporozoits and migration to the siliviary glands.
- Mosquito sucks a persons blood and injects sporozoits.
- These replicate in the human liver
- These infect RBC’s
- Replicate and produce plasmodium gametes.
Three components that pathogens need to overcome?
Epithelium, flora and mucous.
How can come bacteria anchor themselves to the membrane?
With adhesins and P pili. These bind to receptor proteins on the cell surface (that are used for other functions)