NBME 19

Question 1

How does water get reabsorbed in the kidney?

Answer 1

It diffuses across- no energy needed

Question 2

What does histone acetyltransferase do?

Answer 2

Decreases the affinity of histones for DNA, so it weakens the DNA-histone bond and makes DNA segments more accessible for transcription factors and RNA polymerases

Question 3

In a viral infection, what is critical for the initial establishment of the infection?

Answer 3

Presence of viral receptor molecules on epithelial cells

Question 4

Sildenafil mechanism of action

Answer 4

Inhibits PDE5 => increases cGMP => smooth muscle relaxation

Question 5

HOX gene products and retinoic acid bind to specific DNA sequences on different chromosomes. What is the function of these?

Answer 5

They act as transcription factors

Question 6

Antibodies associated with Graves disease?

Answer 6

Thyrotropin receptor autoantibodies

Question 7

Antibodies associated with Hashimoto’s?

Answer 7

Antithyroid peroxidase (antimicrosomal) autoantibodies. 
Antithyroglobulin autoantibodies

Question 8

In hyperparathyroidism, mechanism of how it causes osteopenia?

Answer 8

Paracrine stimulation of osteoclasts by osteoblasts

Question 9

Dereased lysosomal hydrolase activity in occurs in what diseases?

Answer 9

Lysosomal storage disorders (e.g. Neimann-Pick disease

Question 10

Patient has a problem with the respiratory burst mechanism. Dx?

Answer 10

NADPH oxidase deficiency

Question 11

Patient with weakness of her left leg, decreased muscle strength, no other abnormalities. When her eyes are closed, she can’t tell whether her left great toe is raised or depressed. Which vessel is affected?

Answer 11

Right anterior cerebral artery.
Because weakness of left leg is motor and/or sensory, the left great toe symptom is a distractor because everything else is normal. so the area affected is motor, sensory area of right frontal and parietal lobes => Right ACA

Question 12

A mutant form of a voltage gated sodium channel inactivates more rapidly than normal. What property will the neuron have?

Answer 12

Decreases the amplitude of the action potential

Question 13

In a damaged lung, what does the cell that is responsible for repair produce?

Answer 13

Surfactant ( because it’s type 2 pneumocytes)

Question 14

If you upregulate bcl-2, what will happen?

Answer 14

Apoptosis is inhibited- e.g. decreased cell death in the thymic cortex

Question 15

Xeroderma pigmentosa causes what type of DNA damage?

Answer 15

Formation of pyrimidine dimers

Question 16

What is Marcus Gunn pupil?

Answer 16

Also called- relative afferent pupillary defect
When you shine light in to the normal eye, both eyes constrict.
And then when you swing the light to the affected eye, both pupils dilate instead of constricting. This is because of injury to the optic nerve ipsilaterally.

Question 17

What makes the blood-testis barrier?

Answer 17

Tight junctions between adjacent Sertoli cells

Question 18

Morphine adverse effect- facial flushing cause?

Answer 18

Histamine release

Question 19

Picture frame vertebrae is seen in what?

Answer 19

Paget’s disease of bone

Question 20

Lab values of Paget’s

Answer 20

Increased Alk. phos

Ca, phosphorous, PTH- normal

Question 21

What is psychogenic polydipsia?

Answer 21

When a person drinks excessive water without being thirsty.

Lab- urine osmolarity increases during water deprivation

Question 22

Features of polio

Answer 22

Destruction of anterior horn of spinal cord- LMN weakness. Decreased reflexes

Question 23

Features of West Nile Encephalitis

Answer 23

Meningitis
Flaccid paralysis
Seizure
Coma

Question 24

What is vascular conductance?

Answer 24

The flow of a volume of blood through the vasculature

Question 25

What is confined placental mosaicism?

Answer 25

It's when the chorionic villus sampling testing comes back showing trisomy in some cells. And all the subsequent tests show normal chromosomal counts. This is due to trophoblastic mutation, or trisomic rescue. This is when the trisomic cells that were supposed to be in the fetus confined to the placenta, so fetus is normal

Question 26

In an elderly pregnant patient, at 11 weeks of gestation, what test can you do to test for chromosomal abnormalities?

Answer 26

Chorionic villous sampling

Question 27

What are dysplastic nevi?

Answer 27

Pigmented skin lesions that occur in sun exposed and nonsun exposed areas

Question 28

Nephrotic syndrome- Uniformly thickened glomerular capillary basement membrane. Immunofluorescence- granular deposits of IgG and C3. Dx?

Answer 28

Membranous nephropathy

Question 29

68 y/o patient with 2 month history of inability to maintain an erection. Has fatigue and difficulty sleeping and concentrating. What happens to libido and nocturnal erections?

Answer 29

Patient has depresssion. Libido- decreased Nocturnal erections- normal

Question 30

Patient with diarrhea. Colonoscop- multiple ulcers that have undermined and destroyed large areas of the intestinal epithelium. What parasite is causing this?

Answer 30

Entamoeba histolytica

Question 31

Histological changes you see in a biopsy of an ulcer of the vulva of syphilis?

Answer 31

Obliterative endarteritis with lymphocytes and plasma cells

Question 32

Patient given penicillin. What kind of anemia do you see? Labs?

Answer 32

Direct Coombs positive hemolytic anemia

Question 33

What does AMP do to breakdown of skeletal muscle glycogen phosphorylase?

Answer 33

AMP is an allosteric activator

Question 34

What drugs cause photosensitivity?

Answer 34

``` SAT For Photo Sulfonamides Amiodarone Tetracycline 5-FU ```

Question 35

Advantage of randomized controlled trial versus prospective cohort study

Answer 35

Better control for confounding variables

Question 36

For PPD skin test, positive is usually 10 mm. If you change the induration to 5mm, what happens to incidence and prevalence of a positive PPD skin test?

Answer 36

They would both increase

Question 37

75 y/o patient with Alzheimer's, he has aspiration penumonia with compromised swallowing function. He has no advance directives. How should you address the feeding tube issue?

Answer 37

Encourage the family to come to a consensus based on their perception of the patient's wishes

Question 38

13 year old girl, comes to the doctor with her mother for general check up. You want to ask the patient about sexual activity. How do you do that?

Answer 38

Ask the mother to leave the room before asking the patient any questions

Question 39

8 year old girl, unconscious. They were traveling in a truck overnight. She slept in the back, in an enclosed cabin. In the morning, she was hard to wake up, and had a severe headache and nausea. She has cherry red skin around the mouth. Dx? Tx?

Answer 39

Carbon monoxide posioning. | 100% O2

Question 40

Patient with dryness of skin, excessive freckling and keratoses with exposure to sun. What's defective?

Answer 40

Nuclear excision repair of pyrimidine dimers