Unit I Deck 3 Flashcards
What is the major obstacle in eradicating tuberculosis?
AIDS.
Why does M. tuberculosis gram stain poorly?
Mycolic acid in its cell wall
Mycobacteria are gram __1__ and acid-fast __2__.
- Negative
2. Positive
What is the process by which M. tuberculosis infects?
It gets eaten by naive macrophages to use them as a trojan horse. Then the CD8 cells kill the macrophages creating granulomas, where the TB is hidden. TB then travels to the lymph nodes and attacks.
In what places can you get extrapulmonary TB?
- Neck - scrofula
- GI (rare)
- CNS - abscesses
- Genitourinary
- Skeletal
What is miliary?
Millet-like non-calcified foci of infection of liver, lung and spleen, evidence of hematogenous spread of TB throughout body, fatal if untreated
What are two main hallmarks of TB tx?
- Observed dosing
2. Isoniazid
What vaccine is used for TB abroad, but not here in the US?
BCG vaccine, live attenuated M. Bovis, effective against about 70% of TB
True or False: Latent cases of TB remain contagious.
False. Latent TB is not contagious.
What are atypical mycobacteria?
Neither M. TB nor M. leprae. Live in environment, cause infections in humans rarely, usually a cutaneous infection.
What kind of infection could be respinsible for scrofula in children?
Most likely an atypical mycobacteria, M. scrofulaceum. Scrofula is usually evidence of s re-infection, so the likelihood of a reinfection of TB in a child is low. But it could still be TB.
True or False: M. Leprae has no in vitro culture system.
True! A few labs keep armadillos as reservoirs.
What is another term for Hansen’s disease?
Leprosy
What are the treatments of choice for Hansen’s disease?
- Dapsone
2. Rifampin
What does the Lepromin PPD test for?
The Lepromin PPD tests for anti-leprosy response and position on the TB-lepro spectrum. It cannot determine exposure.
What is the most common atypical mycobacterial infection? How is it treated?
M. Marinum, found in fresh and salt water, creates lesions where it came into contact with previously broken skin. Treat with tetracycline.
What is the difference between the M. Leprae PPD and the M. tubercolosis PPD?
M. Leprae is a hypersensitivity test, while M. TB is an antibody test.
Name 2 instances of normal apoptosis.
- Normal development (adult or embryonic)
2. In response to an error found at a cell growth checkpoint
What is the source of syndactyly?
Syndactyly occurs when, during development, cells that should have apoptosed to produce fingers/toes, do not.
Give an example of apoptosis in an adult.
In mammary glands post-lactation
Lining of gut
What are trophic factors?
Trophic factors are “survival factors,” without which a cell will initiate apoptosis, ie at birth, when there are many more neurons than target cells, the lack of trophic factors to certain neuronal cells prunes them out
Why does apoptosis not initiate an immune response? How is this different from necrotic cells?
Intracellular contents are not released, controlled waste disposal, whereas necrotic cells swell and burst, initialting an immune response to the foreign contents.
What are the steps leading up to apoptosis, beginning with the lack of trophic factors?
Trophic factors normally phosphorylate Bad and inactivate it.
- Without trophic factos, Bad is free to to interact with apoptotic proteins Bcl2 and Bcixi in the mitochondrial membrane
- Bcl2 and Bcixi are now not doing their job of inhibiting the Bax ion channel in the mitochondrial membrane.
- Bax opens and releases cytochrome c into the cytosol
- Cytochrome c initiates a caspase cascade (a series of cytosine proteases) that go around cleaving and being bad
- Result is a proteolytic amplification cascade
Name 2 types of cells that have reached terminal differentiaion.
- Neuronal cells
2. Cardiac cells
What stage do cells enter when they run out of telomerase?
Senescence
What is telomerase made of?
Telomerase is a ribozyme, part protein, part RNA
Where does telomerase add its GGGTTA?
To the parental strand, so that during replication, no terminal genes are lost AND the chromosomes don’t anneal
True or False: Most adult tissues lack telomerase.
True.
When telomeres get too short, what is activated, leading to senescence?
p53, which blocks cells in G1. p53 is an important tumor suppressor gene.
What are the 2 main goals of senescence?
- To limit unwanted proliferation
2. To protect cells from replicating incomplete or unstable chromosomes.
Name a locally-acting growth factor and its function.
PDGF - platelet-derived growth factor, stimulates would repair and epidermal/epithelial cell migration.
Name a systemically-acting growth factor.
EPO - erythropoietin, made in kidney, stimulated RBC synthesis
What is anoikis?
Anoikis, from the Greek for “without a home,” refers to anchorage-dependent regulation of cell growth and describes how a cell floating in a medium, with nowhere to adhere, or call home, will apoptose.
Anchorage-dependent cell growth refers to what specific tissue?
Epidermal tissue, where only the cells in contact with the basal lamina will proliferate.
Describe a situation influences by contact inhibition of cell proliferation.
Wound repair. When cells meet each other, they exert contact inhibition one another and normally do not proliferate. When a wound occurs, the cells regrow to fill the gap.
What does GEF stand for?
Guanine-nucleotide exchange factor
What does GAP stand for?
GTPase activing protein
What is the normal proliferation of skin epidermis?
- As long as stem cells are attached to the basal lamina, they will continue to proliferate.
- When cells detach, they stop proliferating and start differentiating
- Increase in cadherins and keratins –> increase in desmosomes
- After 2-4 weeks, skin is sloughed off and replaced
Name 4 situations that cause cancerous activity of cells.
- Upregulation of telomerase, or downregulation of p53
- Stop needing growth factors to initiate replication
- No cell-cell contact inhibition –> form foci when cells pile up on top of each other
- No more anchorage-dependence for growth
What is an oncogene?
An oncogene is a disregulated (mutated or overexpressed) version of a gene normally found in the cellular genome.
Conversion of a proto-oncogene to an oncogene is usually the result of:
A somatic mutation, not inherited
What are the functions of p53?
Induces synthesis of inhibitor cdk21
Blocks Rb phosphorylation
May induce apoptosis or senescence
DNA viruses carry genes within their normal genome that encode proteins that block ___1___ and ___2___ function, thereby leading to hyperproliferation and transformation of infected cells.
- Rb
2. p53
Name 2 viruses known to cause cancer.
- SV40
2. HPV virus
True or False: Mutation of a single proto-oncogene cannot alone cause cancer.
False. It only takes one!
Name 2 notable tumor suppressor genes.
- Rb - Retinoblastoma
2. p53
Can a heterozygote with 1 mutant tumor suppressor gene produce adequate function to inhibit genes?
Yes
Mutations in tumor suppressor genes tend to be ___1___ while mutations in proto-oncogenes tend to be ___2___.
- inherited (ie retinoblastoma)
2. acquired somatic mutations
Give an example or a proto-oncogene where 1 small mutation in the gene creates a hyperactive protein.
pp60Src - tyrosine kinase protein in Rat sarcoma (Ras)