:)) Flashcards
where is type 4 collagen found?
* basal membrane *
where do u find reticular connective tissue?
role?
- found at boundary of connective tissue and epithelium
- supporting stroma for highly cellular organs (like liver).
function: wound healing and scar tissue.
what do u stain to see elastic fibres
orcein
what is ECM made of?
- proteoglycans
- collagens
- noncollagenous glycoproteins (fibronectin and laminin)
what is special about myofibroblast - what do they do?
myofibroblasts:
(- appear similar to fibriblasts)
- express alpha smooth muscle actin.
- differ from smooth muscle cells bc lack external basal lamina
where are mast cells not found? where found tho
- NOT found in: brain and spinal cord ( remember this!!)
- found in: CT of skin and mucous (and other places too)
what is the name of the thick layer of dense irregular connective tissue in the skin?
what is the layer find above this?
- *above:** papillary
- *thick =** reticular layer
where are viral replication sites for viruses?
which type go where?
- *cytoplasm**: most RNA viruses
- *nucleus**: most DNA viruses
(some do both e.g. retroviruses)
what are the subunits of viral capsids called?
capsomere: usually associate with, or are found close to, the virion nucleic acid.
what are normal 4 strucutres of viruses?
name a virus that is an exceptions to the normal 4 structural categories of viruses?
exception: pox virus
what is the baltimore classification system?
dsDNA viruses
ssDNA viruses
dsRNA viruses
(+)ssRNA viruses
(-)ssRNA viruses
ssRNA-RT viruses
dsDNA-RT viruses
what type of virus (from baltimore classification) is:
- coronavirus
- influenza
- HIV?
- coronavirus: (+)ssRNA viruses
- influenza:(-)ssRNA viruses
- HIV: ssRNA-RT viruses
explain how oral and oespophageal cancers are caused by excess alchohol intake
- *ethanol:**
- reaction: ethanol –> acetaldeyde
- acetaldeyde reacts with deoxyguanosine = weak mutagen. further reaction -> stronger mutagen (DNA adduct)
- *UV**
- p53 implicated
- formation of cylobutane pyrmindine dimers (CPD) covalent bonds form between 2 adjacent pyrimidines in same DNA strand. VERY STRONG BOND
what is the mutation that occurs in ras gene to make it mutagenic?
- single nucleotide exchange GGC TO GTC in bladder cancers (glycine -> valine)
which cancers does XPA gene increase chance of?
a) Non-melanoma (basal cell and squamous cell) skin cancer at UV exposed sites
- patients with XPA mutation have 10, 000 x increased risk*
- median age onset 9 years (c.f. 60 in general pop)*
b) cutaneous melanoma (melanocytes)
- patients with XPA mutation have 2000x increased risk*
- median age: 22 years (c.f. 30 years)*
- what are the three main mechanism of gene alterations that activate oncogenes?
- point mutations: single base change in DNA (e.g. Ras oncogene)
- chromsomal rearrangements: translocation of chr activates oncogene by using regulatory elements from a highly transcribed gene to drive expression of oncogene
- gene amplification (e.g HER2)
where is c-myc normally encoded?
where is IgH normally encoded?
explain cancer that occurs when the above translocate
- c-myc: found on chr 8
- on chromsome 14, there is a gene that codes of IgH - has a very strong promoter
- translocation of region of chr 8 and 14: myc gets translocated near to promoter of IgH
- results in strong promoter driving the expression of myc: Burkitt lymphoma
what is a cause of lymphoma?
- strong promoter of IgH on chromosome 14 translocates to chromsome 18
- switches ON bcl-2 gene (anti-apoptotic protein) in active B-lymphocytes (is normally switched off)
- cells that harbour mutations do not go into apoptosis
- causes lymphoma
describe how DNA methylation can lead to tumour suppression (epigenetics) in promoter region
- methylation moves from lysine 4 of the histone 3 (H3) (normal function) to lysine 9 of H3
- leads to transcriptional repression & loss of tumour suppressor gene expression
what type of gene is hudsons two hit hypothesis about?
tumour supressor genes
how does DNA damage occur by formation of DNA adducts in lung cancer?
how does DNA damage occur by UV radation ? and where
- *smoking**
- (benzopryene (BP) from smoke is oxidised (x2))- results in BPDE (ultimate carcinogen)
- BPDE forms adduct with guanosine residues in lung epithelial cells
- occurs often in tumour suppressor genes, such as p53
- *UV**:
- damage in basal cells of melansomes (particularly keratinocytes)
- p53 implicated
- formation of cylobutane pyrmindine dimers (CPD) covalent bonds form between 2 adjacent pyrimidines in same DNA strand. VERY STRONG BOND
what does HPV cause?
HPV: cervical cancer
how do cancer cells become insensitive to anti growth signals?
Insensitivity to anti-growth signals:
There are genes that normally express growth suppressing signals e.g. TP53 and RB involved in the cell cycle, but can be mutated in cancer
Therefore there are no longer gatekeeping mechanisms to keep cell cycle progression in check.
what do cancer cells express to maintain telomere length?
So, in normal cells, when the telomeres are short enough, it looses its protective ability and the cell is triggered into apoptosis.
In cancer cells, telomerase (not normally expressed in healthy cells) is expressed which counters the erosion to telomeres and therefore removes a barrier to proliferation and the cell will achieve immortality.