woah, you're totally right. my professor screwed that one up. we were taught that PDE5 cleaves both cAMP and cGMP, but it looks like only PDE1, 2, and 3 cleave both.

the downstream effects would be almost identical though. both cAMP and cGMP cause myosin light chain kinase to be phosphorylated by their respective kinases (PKA and PKG), leading to lower myosin activity and thus relaxation.

nice catch!

that's semantics.

in the context of what the poster was saying, i was pointing out that it is arteries that serve as conduits for blood that is flowing toward the penis (and all other tissues of the body), and veins are what serve as conduits for blood flowing away from the tissues.

thanks for your deep insight though.

/medical student

1) veins don't deliver blood, arteries do

2) the relaxation I was referring to was of the smooth muscle in the walls of the arteries leading to the penis

3) there isn't much regulation of bloodflow that takes place on the venous side (ie venous drainage is relatively constant). thus if you increase flow inward it will necessarily lead to pooling (ie erection)

the classic ED drugs all work by relaxing the arteries that flow toward the penis by inhibiting PDE5, a phosphodiesterase predominantly found in penis arteries. this increases cAMP levels, leaving to vasodilation and an erection. unfortunately these drugs aren't perfectly specific, and cause small amount of vasodilation throughout the body, along with a corresponding drop in blood pressure. this is why they tell you not to take the ED pills if you take other vasodilators like nitroglycerin.

if you could engineer a Gs (i was wrong in my earlier post when I said Gi, you want more cAMP not less) receptor that was light sensitive, and get it to express only in the penis artery smooth muscle.... and shine light through your skin to activate these receptors, it would work the same way.

obviously not an ideal way to treat a disorder. these light gated channels are probably only good for basic scientific research.

actually, it totally could work. erections occur because certain smooth muscle in the penis relaxes, allowing blood to flow in the right places. ED drugs block the degradation of a chemical that promotes this relaxation. a light gated receptor of the proper type (Gi) could be designed to do the same thing.

Please note that we have added a consequence for failure. Any contact with the chamber floor will result in an unsatisfactory mark on your official testing record, followed by death.

I have to ask... what made you want to pursue a PhD if you weren't acquainted with papers and research? General interest?

I'm not shocked he doesn't have an advisor. I'm shocked that he thought going to university websites would be the way to go.

excellent point. these days, a given professor's field is usually pretty small. they only want to talk shop with people who both understand their niche and show actual intellectual curiosity in it.

If you are trying to find a mentor in any scientific field, you don't go looking for "lists" of interests. I don't even know what that refers to. You find recently published primary literature in areas you have interest in, and speak to those authors. This helps you find people who are actively working in the field you seek to be a part of. Even if the authors themselves aren't right for you, they are more likely to know other people in the field than anyone else.

Frankly, I'm kind of shocked. You are applying to PhD programs, but don't currently know any scientists in the field? What about at your undergraduate institution? How did you get interested in social science without reading any papers?

I would recommend looking into supernova searching. As an undergraduate, I worked in a lab that used a robotic telescope high in the mountains to automatically search for these extremely bright and relatively common phenomena. Given their brightness and longevity, it is relatively simple (in astronomical terms) to design and build a system to look for these objects. check out KAIT, the telescope I worked on.

I took a high-level bio class at UC Berkeley this past semester that concerned exactly this type of genetic therapy. someone brought up the idea of doing this to normals with the pit viper IR heat-sensitive ionic channel gene, tie it to some downstream color of choice.

sign me up.

after a quick look at the paper linked in the article (Identifying photoreceptors in blind eyes caused by RPE65 mutations: Prerequisite for human gene therapy success), it is clearly not about gene therapy in humans. it is a study of the thickness of the retina in humans homozygous for a mutation in a specific retinal gene. as the title says, it is a prerequisite for gene therapy.

the actual paper, Human gene therapy for RPE65 isomerase deficiency activates the retinoid cycle of vision but with slow rod kinetics, can be found here. It concerns the same gene, incidentally.

i don't think they would film anything before the person died either way.

planet earth took years and years to film. i'm not suggesting this will be anywhere near as good as planet earth, just that production companies have plenty of time on their hands. it's not like someone is going to scoop them.