MDS PREP
Indirect chemical carcinogens differ from direct acting agents in those
indirect agents:
1. Induce carcinogenicity without chemical transformation
2. Induce carcinogenicity after chemical transformation
3. Don’t require metabolic conversion
4. None of the above
Pathology Answer: 2
Indirect chemical carcinogens differ from direct acting agents in that they
require metabolic activation to exert their carcinogenic effects. This means
that indirect carcinogens must undergo a chemical transformation within the body
before they can damage DNA and induce cancer. Direct acting carcinogens, on the
other hand, can interact directly with DNA without the need for metabolic
conversion. Therefore, the correct answer is:
2. Induce carcinogenicity after chemical transformation
1. Induce carcinogenicity without chemical transformation: This statement is
incorrect for indirect chemical carcinogens. Indirect carcinogens are typically
non-reactive or less reactive in their original form and must undergo metabolic
activation to become DNA-reactive. This metabolic conversion is crucial for
their carcinogenic potential.
2. Induce carcinogenicity after chemical transformation: This is the correct
explanation. Indirect carcinogens require metabolic activation by the body's
enzyme systems, particularly phase I enzymes such as cytochrome P450, to convert
them into electrophilic or reactive intermediates that can interact with DNA.
This activation process can occur in various tissues, often the liver, where
these enzymes are present. The reactive metabolites then form DNA adducts, which
can lead to mutations and ultimately cancer if not repaired properly by the
cell's DNA repair mechanisms.
3. Don’t require metabolic conversion: This statement is incorrect. Indirect
carcinogens do require metabolic conversion to become active carcinogens. It is
the direct acting carcinogens that can interact with DNA without the need for
such activation because they are already electrophilic or reactive in their
original form.
All of the following statements about an intraoral dental X-ray film are true except
1. It is composed of a cellulose acetate base coated with a silver bromide emulsion
2. It has a thin sheet of lead foil that lies in front of the film to prevent overexposure
3. It has an embossed dot on it which should be orientated towards the source of X-rays
4. It is exposed by the direct action of X-rays on the emulsion
Oral Pathology
Answer: 2
The statement about the lead foil is incorrect; it lies behind the film to prevent backscatter.
Letterer-Siwe disease is a disturbance of
1. Protein metabolism
2. Lipid metabolism
3. Mucopolysaccharide metabolism
4. Carbohydrate metabolism
Oral Pathology
Answer: 2
Letterer-Siwe disease is a disturbance of lipid metabolism.
Biochemical abnormality associated with osteogenesis imperfecta is increase in
1. Alkaline phosphatase
2. Acid phosphatase
3. Bicarbonate ion
4. Phosphorylase enzyme
The biochemical abnormality associated with osteogenesis imperfecta is an increase in acid phosphatase.
In a patient with MEN I, which of the following is NOT commonly found?
1) Gastrinomas
2) Insulinomas
3) Parathyroid adenomas
4) Oral and intestinal ganglioneuromatosis
Oral and intestinal ganglioneuromatosis is not commonly found in MEN I; it is associated with MEN II.
Penetration power of X-ray is measure of
1. Exposure time
2. Milliamperage
3. Kilovoltage
4. None of the above
Oral Pathology
Answer: 3
Penetration power of X-ray is primarily measured by kilovoltage.
Which of the following is responsible for autoimmunity in Epstein-Barr virus infection?
1) Molecular mimicry
2) Polyclonal B-cell activation
3) Upregulation of co-stimulatory molecules
4) Antigenic cross-reactivity
General Pathology
Answer: 2
Polyclonal B-cell activation is responsible for autoimmunity in Epstein-Barr virus infection, leading to various autoimmune manifestations.
Which of the following cell types show abnormal function when there is a history in a young adult of multiple arm and leg fractures following minor falls?
1) Granulocytic stem cells
2) Megakaryocytes
3) Plasma cells
4) Osteoclasts
Osteoclasts show abnormal function in conditions leading to multiple fractures, as they are responsible for bone resorption.