Study group discussion: Amantadine

Talking of antivirals... Amantadine is an antiviral used for Parkinson's disease! Anyone knowing it's mechanism in both these conditions?

Influenza is through M2 channel. Donno about Parkinsons.. Anticholinergic?

Amantadine increses the secretion of dopamine. Don't know the channels.

Mechanism of action of Amantadine: Prevents viral uncoating by binding to protein M2 (It's a protein which is a proton channel) that allows acidification of the viral core to activate viral RNA transcriptase.

Mnemonic: A man, to dine, takes off his coat!

Also, mutated M2 protein makes the virus resistant to the drug.

Woah! Thanks!

Amantadine MOA as a anti parkinsonian drug:
Increases release of DA
Increases synthesis of DA
Decreases reuptake of DA
Direct action NMDA receptors
*DA: Dopamine

Study group discussion: Why food doesn't taste good on high altitude, high pressure aeroplanes

I read an interesting article today, not very study related though.

It's why food tastes yucky in airplanes.

Wow! So they found out finally why food tastes bad in air planes!

Why is it yucky??

Change in pressure and altitude numbs 1/3 of our taste buds.

Haha nice!

And I blamed airlines!

Damn!!

Lack of humidity, noise and mass food production are contributory too but that's the main reason.

Interestingly, only salty and sweet sensation is affected. Bitter and spicy remain unaffected.

I wasted so many pleasurable gustatory senses by eating chocolates on the plane! I'll eat spicy next time!

Hahaha science rocks! Unfolding the mysteries of the world.

Yeah spicy in better than bitter!

So much better!

Study group discussion: Drugs that cause urinary calculi

Which diuretic agent is asociated with development of kidney stones?

Loop diuretics.
Potassium sparing diuretics.

So... Almost all of them?
Nope. Osmotic diuretics don't!

And thiazides are used for treating kidney stones!

Loop diuretics, carbonic anhydrase inhibitors and triamterene (Not all potassium sparing diuretics) are the ones that cause calculi.
Mechanism: Loops and CAI cause metabolic abnormalities.

Why only Triamterene?
The exact mechanism by which Triamterene promotes urinary calculus formation is unclear, although it is hypothesized that precipitation of triamterene and its metabolites provides a scaffold for nucleation and subsequent calculus growth.

Which carbonic anhydrase inhibitor cause renal stones? And what's the mechanism?

Prolonged use of carbonic anhydrase inhibitors may lead to a hyperchloremic metabolic acidosis, in which urinary pH is increased and urinary citrate is decreased.
Acidification of urine prevents calcium and phosphate stones but causes uric acid and cysteine stones. Link: http://medicowesome.blogspot.in/2012/12/acidification-of-urine.html

Speaking of stones, which antiretroviral drug causes nephrolithiasis?

Acyclovir?

I didn't know this. Just Googled and found that they cause crystalluria and obstructive nephropathy as well.

Indinavir was the drug I was asked about in a test.

A summary of drugs that cause stones (Source: ncbi)

Urinary calculi can be induced by a number of medications used to treat a variety of conditions.
Loop diuretics, carbonic anhydrase inhibitors, and abused laxatives can cause metabolic abnormalities that facilitate the formation of stones. Correction of the metabolic abnormality can eliminate or greatly attenuate stone activity

Magnesium trisilicate; ciprofloxacin; sulfa medications; triamterene; ephedrine, alone or in combination with guaifenesin; and indinavir may induce calculi via urinary supersaturation. Eliminating such calculi usually involves discontinuation of the medication or initiation of alternate therapy.

Thanks!

Study group experience #4

Discussions so far -

Histrionic personality disorder, Munchausen syndrome and MSBP  

Dissociative identity disorder, Post-Traumatic Stress Disorder and Shutter Island  

Migraine, aura and floaters  

Schizophrenia and Schizotypal disorder 

Malignant hypertension discussion 

Renal tubular acidosis types mnemonic 

How to do percussion (A clinically oriented topic) 

Cause of decreased glucose levels in CSF in bacterial meningitis  

Respiratory physiology (Interesting read for first years) 

Physiology books  

Transpulmonary pressure 

Case control and cohort study mnemonic  

Legionella confusion   

Compliance of the lungs  

Urinalysis  

Lateral spinothalamic tract mnemonic  

Trial of scar  

Management of ARDS 

Diagnostic tests for pulmonary embolism  

Amyloid  

Bone tumors 

Myocardial infarction markers  

Right ventricular infarction 

ECG sign of left ventricular aneurysm 

When I first thought of the group, negative thoughts poured in and everyone thought it was a bad idea: What if I get too many spam messages? All you'll receive is advertisements! You'll lose your Whatsapp privacy! It's too risky man! Why would you do something so stupid? Give your number to the internet?

But one person encouraged me: Eh? So what? Business men take risks all the time. Keep a verification so the spammers can't get it. Block people, duh! Why is that feature available on Whatsapp? You can always throw away your number or change it.

For everyone who benefits from the group discussions, you guys should totally thank that positive soul for this!

What I learnt by making the study group:

Don't be so negative, don't fear the bad stuff so much.

Be courageous. Take calculated risks.

Encourage people, no matter how crazy they sound.

It's takes just one person to make a life changing decision, make sure it's you.

*OMG I STILL CAN'T BELIEVE IT WORKED OUT SO WELL AND I'M TALKING TO YOU GUYS EVERYDAY*

-IkaN

Equilibrium potential value of an ion and how to apply it to action potential ?

The equilibrium potential value of an ion or the Em value.

I will try making some sense out of this confusing term.

1. Ions across a cell membrane have two forces acting on them, the concentration gradient and the electrical gradient. Since, Na,K and Cl are the most abundant of ions, it is only needed to know the Em of these three ions.

2. The Em is the value of the membrane potential at which both the concentration gradient force and the electrical gradient force are equal and opposite. This means that these two forces will cancel each other and there will be no net flow of ions across the membrane.

3. Also, remember whenever given the chance ( permeability ) the ion will try to reach a stability, that is it will try to achieve a membrane potential equal to its Equilibrium potential.

There is an equation called the Nernst equation to measure the Em value. When you solve this equation the values of Em are

Na- (+61Mv)
K   ( -94.1Mv)
Cl  (-70Mv)

Lets apply these terms, to the action potential

Study group discussion: ECG sign of left ventricular aneurysm

On ECG after an MI infarction..What is the sign for left ventricular aneurysm?

It's persistent ST segment elevation. After MI, the ST segment does rise, but it falls gradually too, reaching a normal. But if its elevated then its aneurysm.

In any specific leads?

The same leads where infarction shows up.

2, 3 and AVF leads.

So basically the ST segment doesnot fall back to normal right?

Yup.

Great didn't know that concept.

Study group discussion: Right ventricular infarction

Since it's MI..Review question.. Name a disease associated with right ventricular infarction?

Atherosclerosis?

I meant name a cause for right ventricular infarction, other than atherosclerosis.

It's pulmonary embolism.

The pulmonary embolus puts the right side of heart in strain and it dilates. This dilation obstructs the right coronary artery. This was my viva question on an ECG of right ventricular infarct.

So does not it lead to hypertrophy of the right ventricle?
In an acute setting, no.
If the pulmonary thromboembolism  is chronic it will cause pulmonary hypertension. Then it causes right ventricular failure.

So the acute pulmonary embolus should be the answer.

Ohh that makes some sense! Good one!

Study group discussion: Myocardial infarction markers

Which is the reinfarction cardiac marker?

It's CK MB. The levels fall in 3-4 days. So if you get a reinfarction and see your troponin you can't be sure if it's from last time.

CK MB falls in 36-48 hrs.

Why isn't it myoglobin? Myoglobin rises and falls the fastest.

Because myoglobin is not a specific cardiac marker.

No but in these cases, it is the most preferred. Cause it returns to normal within 24 hours.

Dunno.

I think the time after which re-infarction occurs also matters.

Do let us know.

These things are confusing. Good thing is we are trying to sort them out.

Yes, it is.

We had a confusion between myoglobin and CK MB in the diagnosis of re-infarction.

The answer is CK MB simply because it is cardiac specific and falls within 2 days.

The only use for myoglobin is ruling out a Myocardial Infarction, early. (Cause it's the first to rise and is very sensitive!)

If the levels are not up, it's not a MI.
If myoglobin levels are up - it could be a skeletal muscle injury or a MI, you don't know until you look at the other markers.

Even though myoglobin levels fall early, it is not used for the diagnosis of reinfarction because it's not specific and if the levels are up after an infarction, it could mean something else as well.

Harrison says both CK MB and myoglobin can be used for reinfarction. I would hate the question maker for asking us to choose between the two & go with CK MB because it's specific.

Woah... Awesome discussion... Thank you everyone for the cocepts... I so love this group.

Study group discussion: Amyloid

Does anyone have awesome things for amylodosis pathology?

Another concept you must understand is that the protein deposits in tissues depending upon where it was derived from.

For example, amyloid from immunoglobulins deposit in tissues of mesodermal origin like kidneys, heart, muscle, tongue.

When it's due to chronic inflammatory disease, it involves parenchymal organs like liver adrenals and pancreas.

Good concept.

Review question! Which amyloid protein is associated with Alzheimers disease?

Beta amyloid

Yes!

And why are patients with downs syndrome more susceptible to early Alzheimers?

Extra chromosome 21 which means extra copy of the presilline gene, I think.

Absolutely right!

Great.

Never knew that!

Oh oh one more!

Which condition is associated with amyloid deposition in the thyroid gland?

Are we talking about the medullary thyroid carcinoma?

Yep. The amyloid deposits are derived from calcitonin in that condition!

Which is the one in patients on dialysis?

Beta micro globulin?
B2 - microglobulin is seen in dialysis associated amyloid.
Derived from the MHC class 1 protein.

Yes. It's because the beta micro globulin is not filtered from the dialysis membrane.

Excellent stuff.

Study group discussion: Bone tumors

Osteoclastoma is a giant cell tumor, right?

And these giant cells can be differentiated from other giant cells on the basis of the number of nucleoli present?

 Yo

These giant cells will have about a 100 nucleoli

Osteogenic sarcoma is osteosarcoma. it is a malignant tumor

 names are confusing
 Osteosarcoma, osteoblastoma, osteoclastoma
 The other two are benign?

GCT(osteoclastoma) is a special variant bone tumor
Does not come under either benign or malignant
 Based on number of giant celss an osteoclastoma is loosely classified from typical to aggressive to malignant
 More giant cells and less stroma its benign, less giant cells more stroma its aggressive.

Osteoblastoma is a rare primary neoplasm of bone, categorized as a benign bone tumor that is closely related to osteoid osteoma. It differs from osteoid osteoma in its ability to grow larger than 2.0 cm in diameter and its aggressive behavior in bone.

Turner's syndrome mnemonic

Turner's syndrome mnemonic

Cystic hygroma, webbed neck: You can't turn your neck because of it.

Aortic coarction: Aorta takes a sharp turn.

Some toxicology mnemonics

Acetaminophen toxicity is treated with N acetyl cyteine.
Mnemonic: ACETaminophen ACETyl cysteine!

Ethylene glycol is metabolized to oxalic acid. Ethylene glycol is found in anti freeze.
Mnemonic: Freeze your EGO.
Anti freeze
Ethylene Glycol
Oxalic acid

Methanol is metabolized to formic acid by alcohol dehydrogenase which causes visual disturbances. It is treated with fomepizole.
Mnemonic: There's more to me (FoMEpizol) than what meets (Methanol) the eye (Blindness).

Study group discussion: Diagnostic tests for pulmonary embolism

What is the commonest sign on ecg for PE?

Nonspecific ST changes?
Nope.

SQ3 T3 something like that?
Nope.

Most common sign is sinus tachycardia. Most specific is S1q3t3 pattern..Positive only in 20-30% cases.

Ohhh!! Nice question.

Ooh.. We tend to forget common ones when looking out for rare signs!

What is the screening test for PE?

Screening test is d-dimer. If d-dimer is negative you virtually exclude the diagnosis of PE.

Which is the most specific diagnostic test for pulmonary embolism?

Pulmonary angiography.

Depends if the person is low risk or high risk! CT angiography is done though.

Which is the most preferred test for PE?

Spiral CT is preferred next to know location, size and blah blah.

What about VQ scan?

That's done if the patient is allergic to contrast.
Or has kidney failure.
Or CT isn't available.
Or the patient is pregnant.

In our hospital setting angiography would key since most patients can't afford CT.

Oh. But its invasive..and can be very harmful. It's only preferred when you are planning for thrombectomy..Or as a last resort to diagnose PE if all the other test are negative but d-dimer is positive.

Well money for a CT can feed a peasants family for a year.

True.

Venous doppler is preferred when CT or V/Q are inconclusive.

Whats d-dimer?
The clot thingy. It interlocks fibrin strands.

It is released from the thrombus.

Fibrin is non specific for clots
Because it is elevated in some other conditions as well. So d dimer to the rescue!
*Fibrin degradation products are.