In two common infections of the vagina, bacterial vaginosis (and sometimes in trichomonas vaginalis) your doctor may do a “whiff” test, where he or she takes some discharge, drops some potassium hydroxide on it (a base, KOH) and smells it for a fishy, foul odor. The base causes some foul-smelling amines to be released: cadaverine and putrescine . What great names.

Interestingly, some women will complain of foul odor after intercourse, and the reaction is the same: semen is basic, and when it mixes with the discharge, you get the same release of cadaverine and putrescine. Cool.

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Okay medical blogosphere, let’s figure this one out (comments are open!). Is there a physiologic mechanism to “breaking the seal,” or is it just a drinking myth? ( Breaking the seal, if you’re not familiar with the term, refers to the idea that if you’re out drinking, once you start peeing, then you’re going to have to go urinate every 10-20 minutes after that. “Don’t break the seal!” means don’t start peeing, ’cause then you’ll never stop! )

From Goodman and Gillman’s Pharmacology:

Alcohol inhibits the release of vasopressin (antidiuretic hormone; see Chapter 29) from the posterior pituitary gland, resulting in enhanced diuresis (Leppaluoto et al., 1992). The volume loading that accompanies imbibing complements the diuresis that occurs as a result of reduced vasopressin secretion. Alcoholics have less urine output than do control subjects in response to a challenge dose with ethanol, suggesting that tolerance develops to the diuretic effects of ethanol (Collins et al., 1992). Alcoholics withdrawing from alcohol exhibit increased vasopressin release and a consequent retention of water, as well as dilutional hyponatremia.

Vasopressin (ADH, antidiuretic hormone) causes your kidneys to reabsorb free water molecules, to maintain your sodium osmolality, so knock that out and you’re going to be peeing lots of dilute urine, making you hypernatremic. Combine that with ethanol’s peripheral vasodilation, making your kidneys think you’re hypovolemic (even though you’ve been drinking lots of fluid), and they’re going to try to clamp down to reabsorb all the possible sodium they can… aaand that’s all I’ve got. Maybe it’s just a feed-forward positive feedback relationship with the continued filtering of the kidneys, since they don’t realize ADH isn’t being released? I don’t think it really matters if you stop drinking or not.

I swear I experience this all the time, but maybe it’s just the drunkness and rapid passage of time. I’m stumped.

(Excuse: Was reviewing phys today for Anesthesia which starts on Monday, and boy can my mind wander.)

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Not a whole lot of interest in blogging right now–in the middle of GI and wanting to do a 1,000 things, and blogging’s 1,001. Although 2nd year is a pain in the ass, and information overload, I actually feel like I’m becoming a doctor. It’s kinda cool. I know some of the most common drugs, I know most of the organ systems. What a great feeling.

Try to beef up on my auscultation (stethescope) skills, which is proving quite challenging, but here’s a couple of excellent tutorials for any students out there reading: Blaufuss Multimedia’s Heart Sounds and The Auscultation Assistant .

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Farting-I mean, flatulence -is due to poor absorption of carbohydrates.

Beans contain raffinose and stachyose, tri- and quadrupe saccharides, and cannot be digested by humans. They get passed along through your large intestine, where your normal flora (bacteria living in your colon) feast on them. (They do this anaerobically, fermenting the carbs, so that’s where the gas comes from.)

This is clearly why I went to med school.

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Yes, that’s right. Eat too much black licorice, and your heart can stop.

(Okay, okay, it’s a bit of a dramatic extreme, but it’s true. I swear .)

Black licorice contains a compound called glycyrrhizic acid, which mimics a hormone in your body (aldosterone), which causes you to lose potassium through your urine. This causes what’s called hypokalemia , which can lead to abnormal heart rhythms. (Maintaining the right level of potassium in your body is vitally important. Too much or too little can cause abnormal heart rhythms. Luckily your kidneys usually keep everything juuuuust right.)

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In the spirit of summer and pools and swimming, a quick little physiology lesson, since I just finished my exercise physiology and autonomic nervous system studies. Ever curious why you’re supposed to wait an hour after eating before you jump in the pool? When you start exercising, your body reroutes blood from your digestive system (which is activated by eating food) to your muscles. It clamps off a lot of your circulation from your stomach to the muscles you’re using. And when your digestive system still has food in it that it’s trying to digest, it needs blood flow to get the energy to digest it all. It’s not getting that flow, so it keeps working, without oxygen, and you get acid buildup because of it. And voila. Acid buildup equals pain, pain equals cramp.

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Props to the placenta. If you remember your Health 101 course from high school, the placenta allows woman and fetus to share nutrients, immune cells, and even oxygen without sharing the same blood. (It also can make almost every hormone the rest of the body’s organs can make, but that’s for another day.) Oxygen floats around your blood inside a molecule called hemoglobin (one part of the hemoglobin molecule complex contains iron, which is what makes your blood red). But how does the oxygen get transfered from one blood system to the other? Simple. As the woman’s hemoglobin starts to dump off her oxygen, the fetus’s hemoglobin scoops it up.

Take a look at the graph to the right. (Don’t run away! Please!) On the Y-axis, you’ve got hemoglobin O2 saturation (ie: the percentage of hemoglobins that are still carrying oxygen, and haven’t released it yet). On the X-axis, you’ve got the pressure of oxygen in your blood (ie: how much oxygen’s in your blood at a certain spot in your body – it decreases the further you get from the heart). Now take a look at the blue line–that’s the adult line. At 40% pressure, about half of the hemoglobins still have their oxygen. But as you get further from the heart, hemoglobins start dumping their oxygens more rapidly.

Now look at the fetal, red line. It’s above the blue one. So, at the same pressure, more of the fetal hemoglobin still has its oxygen. Sum it all up: when the adult is starting to dump off its oxygen, the fetus is still holding tighter to its oxygen, so it collects any oxygen that the woman’s hemoglobin is releasing.

Here’s the trick– fetal hemoglobin is just slightly different from adult hemoglobin. At birth, the baby stops producing its fetal hemoglobin, and starts producing adult hemoglobin, since it’s ready to start breathing on its own.

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