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* NBME 7 Block 3__________plz help
 #502800  
  iqbalian01 - 04/28/10 22:11
 
  5) A normal woman is a carrier of an X-linked recessive disorder that is lethal in utero (spontaneously aborted). Which of the following is the expected ratio of her viable female to male children?

a) 1:1
b) 1:2
c) 2:1
d) 2:3
e) 3:2

isn’t it, 1:1 (a)?


21) A 14 year old girl is admitted to the hospital after sustaining injuries in a house fire. Her temp is 37.2 C (99 F), pulse is 115/min, respirations are 9/min, & bp is 100/65 mmHg. Physical examination shows second-degree burns over 40% of her body surface area. Labs show:

Serum:
Na+ : 138 mEq/L
K+ : 4 mEq/L
Urea nitrogen: 90mg/dL
Creatinine: 3.5mg/dL

Urine:
Na+ : 3 mEq/L
Osmolarity: 1220 mOsmol/kg
Excreted fraction of sodium: 2 ------B--- > 3 ----C----> 4 ----D---> 5
……………………l
……………………l
……………………l
……………………E
……………………l
……………………l
…………………...Ѵ
……………………6 -----F--- > 7

There is suppose to be a downward arrow from 2 to 6 with the letter in the reaction pathway being ‘E’ and then from 6 to 7 with the letter being ‘F’.

Answer is which one: A, B, C, D, E, F ?


Q31) a 16 month old girl is brought to the physician for a routine examination. Physical examination shows hypertension, rapid eye movements, and a firm, nodular midline abdominal mass. Lab studies show increased urine concentration of homovanillic & vanillymandelic acids. Which of the following is the most likely cause of the findings in this patient?

a) Aldosterone-secreting adenoma
b) Hepatoblastoma
c) Medulloblastoma
d) Nephroblastoma (wilms tumor)
e) Neuroblastoma

I believe it’s ‘e’, but besides the location, how do you differentiate between Wilm’s tumor and neurblastoma, because they can both occur in this age group and present with hypertension?


Q43) A previously healthy 32 year old man is unconscious after an overdose of a sedative drug. His pulse is 90/min, respirations are 6/min, and bp is 80/40 mmHg. Arterial blood gas analysis on room air shows:

pH : 6.8
PCO2 : 80mmHg
PO2 : 40 mmHg
HCO3- : 12 mEq/L

Which of the following best describes this patient’s acid-base status?

a) Metabolic acidosis with resp compensation
b) Resp acidosis & metabolic acidosis
c) Resp acidosis with metabolic compensation
d) Uncompensated metabolic acidosis

Wouldn’t the answer be ‘b’, because the HCO3- is too low for it to just be option ‘d’, right?
 
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* Re:NBME 7 Block 3__________plz help
#2092579
  iqbalian01 - 04/28/10 22:20
 
  sorry, it didnt come up right for 2 questions...

21) A 14 year old girl is admitted to the hospital after sustaining injuries in a house fire. Her temp is 37.2 C (99 F), pulse is 115/min, respirations are 9/min, & bp is 100/65 mmHg. Physical examination shows second-degree burns over 40% of her body surface area. Labs show:

Serum:
Na+ : 138 mEq/L
K+ : 4 mEq/L
Urea nitrogen: 90mg/dL
Creatinine: 3.5mg/dL

Urine:
Na+ : 3 mEq/L
Osmolarity: 1220 mOsmol/kg
Excreted fraction of sodium:
 
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* Re:NBME 7 Block 3__________plz help
#2092582
  iqbalian01 - 04/28/10 22:21
 
  dont know why it's not coming up right. :(

21) A 14 year old girl is admitted to the hospital after sustaining injuries in a house fire. Her temp is 37.2 C (99 F), pulse is 115/min, respirations are 9/min, & bp is 100/65 mmHg. Physical examination shows second-degree burns over 40% of her body surface area. Labs show:

Serum:
Na+ : 138 mEq/L
K+ : 4 mEq/L
Urea nitrogen: 90mg/dL
Creatinine: 3.5mg/dL

Urine:
Na+ : 3 mEq/L
Osmolarity: 1220 mOsmol/kg
Excreted fraction of sodium: less than 1 percent

A decrease in which of the following is the most likely explanation for this patient’s lab findings?

a) Collecting duct free water reabsorption
b) Distal tubule potassium secretion
c) Distal tubule sodium reabsorption
d) Glomerular filtration
e) Proximal tubule sodium reabsorption

It’s ‘d’, right because the BUN:creatinine ratio is increase, meaning that the GFR has decreased..right?



 
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* Re:NBME 7 Block 3__________plz help
#2092593
  iqbalian01 - 04/28/10 22:23
 
 
Q27) A diagram of a pathway of amino acid biosynthesis is shown. Enzymes are indicated by letters, & intermediates of the pathway are indicated by numbers. Compound 5 most likely regulates which of the following labeled enzymes?

1 ----A ----- >2 ------B--- > 3 ----C----> 4 ----D---> 5
……………………l
……………………l
……………………l
……………………E
……………………l
……………………l
…………………...Ѵ
……………………6 -----F--- > 7

There is suppose to be a downward arrow from 2 to 6 with the letter in the reaction pathway being ‘E’. then an arrow from 6 to 7 with the letter 'F' as the enzyme in that pathway.


 
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* Re:NBME 7 Block 3__________plz help
#2092786
  yeabiruh - 04/29/10 00:40
 
  hi iqbalian01 can u do me a favor ? please send me NBME 7 my email is yeabiruh@yahoo.com....

Q 31 to differentiate between neuroblastoma and nephroblastoma(wilms )

Neuroblastoma is a tumor of adrenal medula(postganglionic sympathetic neurons),it might occur in the posterior abdominal wall,causes childhood hypertension and is associated with opsoclonus -myoclonus syndrome(paraneeoplastic syndrome,myoclonic jerks of the extremities,chaotic eye movements in all directions) and lab shows increased VMA and HVA
mean age 18 months

Wilms tumor is a tumor of Kidney(derived from mesonephric mesoderm..which gives the nephrons),hypertension due to renin,on lab no VMA and HVA ,mean age of onset 2-5 years
 
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* Re:NBME 7 Block 3__________plz help
#2092799
  yeabiruh - 04/29/10 01:11
 
  for Q 5..

-The woman is a carrier of lethal x linked recessive disorder (let us designate normal X and abnormal X'....) ...so she is XX'

-Which means this condition is lethal only for male fetus not for female fetus( as she is alive) given that the female fetus doesn't have two abnormal X'X'

-For this condition to be lethal to female fetus ,the female fetus should recieve one abnormal X' from father ..however in the question we are told tha male who has this recessive condition is already dead in the utero....which means we can forget father factor in our calculation

-Hence when we use the 2 by 2 table we can focus only on the mother

-The mother is XX' ...and she can give normal X and Abnormal X'

-Let us start ...this mother gives the normal X ...5O% chance of making normal XX(Viable female) and 50 % chance of making normal XY (viable male)
...........this mother gives the abnormal X' ...50% chance of making carrier XX'(viable female) and 50 % chance of making abnormal X'Y (non viable male )...

- Out of the Maximum four possibilities ...
1-2 viable female fetus...
2-1 viable male fetus...
3-1 nonviable male fetus

in the question we are asked the ratio between viable female and viable male ...so it is 2 : 1
 
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* Re:NBME 7 Block 3__________plz help
#2092818
  yeabiruh - 04/29/10 02:01
 
  for q 21...the patient is pressented with Azotemia .....and we have to find it whether it is prerenal ,renal and postrenal ...
-As a burn victim she is prone to get prerenal azotemia ....and this loss of of fluid can also

cause renal azotemia(acute tubular necrosis) ...so to differentiate this two we use the urine

osmolarity....in the patient it is 1220 mosm ,which means the renal tubules are ok to

concentrate urine(especially the loop of henle)...so renal azotemia is out and post renal

azotemia is out also as there is no clue in the question....

And prerenal azotemia is the presentation in this patient....normally to calculate excreted

fraction of sodium...we need urine creatinine which is not in the question...but as the kidney

is intact and able to Reabsorb Na ...the fractional ecretion is usually less than 1% ...from

golijan...and if there is less than 2 %in the choice that is my answer....
 
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* Re:NBME 7 Block 3__________plz help
#2092826
  yeabiruh - 04/29/10 02:07
 
  Sorry Folks for Q 21....
I thought the question is to calculate fractional excretion of Na

As u said iqbalian01...the cause for these abnormal lab findings is ...
A decrease in GFR due to decreased Glomerular Blood Hydrostatic Pressure due to decreased renal blood flow due to a decrease in Cardiac Output due to the Burn..........
 
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* Re:NBME 7 Block 3__________plz help
#2092834
  yeabiruh - 04/29/10 02:15
 
  for Q 43...I agree with u...i should be both metabolic and respiaratory acidosis...and the

answer is not D because to compensate metablic acidosis the PCO2 should be less than 40

and Respiratory should be at least greater than 20(in the patient PCO2 is 80 and RR is 9)...

Thank u iqbalian01....for making me read....
 
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* Re:NBME 7 Block 3__________plz help
#2092838
  yeabiruh - 04/29/10 02:31
 
  for q 27...The question is about feedback inhibition, in which the committed step is

allosterically inhibited by the final product....Usually the final product is the one which inhibits

(negative feedback ) the enzyme (rate limiting one).....but the question is about an

intermediate(5) feed back inhibition...so my assumption is if intermediate 5 is produced in

excess it allosterically inhibits(regulates) the enzyme above it ..which is Enzyme D....

But this is my assumption ...the answer can be another enzyme....
 
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* Re:NBME 7 Block 3__________plz help
#2093193
  iqbalian01 - 04/29/10 13:52
 
  thanks so much yeabiruh. i'm extremely thankful for your detailed explanations...very very helpful.
check your email too. :)
 
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