TH-sea

When I was in Japan recently I had the chance to try sea urchin sushi, which were delicious if you don't mind the texture. I hadn't eaten sea urchin since being a kid, when we used to collect them from the local beach in Spain and eat them fresh out of the sea with a dash of lemon. Now I was amused to find out in this article that sea urchin ovaries (the part you eat), has non trivial amounts of anandamide. Anandamide, which is derived from the word bliss in Sanskrit, is the endogenous canabinoid our body secretes. This may explain why some biologists waste their time with invertebrate zoology. More interestingly, the company described in the articles is trying to develop a THC - anadamide hybrid mollecule that would be even more potent against pain.

When thinking about it a little more it didn't surprise me that reproductive organs would contain the ligand, since they are known to express the receptors:

"With respect to reproductive organs, cannabinoid receptors and/or endocannabinoids have been detected in the pituitary gland, testis, Leydig cells, epididymis, prostate, sperm cells, ovary, uterus, oviduct, preimplantation embryo, placenta, embryo, fetus and neonates"

It is thought that in sperm, the anandamide prevents the acrosome reaction, therefore preventing the sperm from activating before it reaches the female tract and also preventing polyspermy during fertilization. The question is, how much anadamide (AEA) is there in reproductive biological fluids?




"We detected AEA, OEA, and PEA in human seminal plasma, mid-cycle oviductal fluid, and follicular fluid analyzed by HPLC/MS"

And the sequela, how much of that stuff do you need to feel a buzz?

"Oral administration of AEA and 2-AG to mice can produce psychotropic effects, suggesting that these endocannabinoids reach the brain ( Di Marzo et al., 1998)."

A quick survey of the literature suggest that 5.8mg/kg is the ED50 of AEA to impair working memory performance (i.e. get a mouse high). So a rough approximation of the dose of milk for an infant to feel the effects is 20,209 L of milk, or for a woman to get high of seminal fluid she would need to chug a good 62,142 L. Notice that calculating the converse would be morally reprehensible.

I suppose the fact that it's so dilute is a good thing for the baby since: "Newborn humans, that had been exposed to marijuana prenatally, exhibit increased tremors, exaggerated responses to stimulation, and spend less time sleeping quietly ( Fried and Smith, 2001).".... but it fails to explain why babies have such munchies...

The gender bending urbisexuals

No I'm not talking about metrosexual urbanites but of the hypothetical ancestor of animals with bilateral symmetry (as opposed to radial symmetry like sea urchin). The urbilateria is one of my favorite ideas in evo-devo. I like it because this mystical beast is purely a construct of inference, much like particle physic's Higgs Boson. The idea is that by looking at existing clades and phyla of protostomes and deuterostomes we can imagine what the common ancestor might have looked like. For example, maybe it had segments, and antennae, a mouth, two eyes. But what I really wonder is how did it have sex? Was the urbilateria a hermaphrodite? did it have external or internal fertilization? But the question I'm most interested in, is how his germ cells and stem cells operated. See there are two ways of making germ cells: preformation and epigenesis. In the former it is the asymetric distribution of germ plasm (coming from the oocyte) during cell division that makes the germ cell, while in the latter it is signals (BMPs) coming from the epiblast which directs dedifferentiation into germ cells. Extavour and Akam think that our ancestor used epigenesis, and that preformation reevolved several times, by simply maintaining maternal expression of germ cell genes like nanos and vasa in the zygote.

There must however be a tradeoff in keeping totipotent stem cell genes expressed in germ cells such as nanog, sox2, oct4. Quite likely that tradeoff is the risk of teratocarcinoma, which is the bizarre cancers deriving from germ cells. Great measures are taken to control germ cells and stop them from either differentiating into somatic cells or turning into cancers. Primordial Germ Cells (PGCs) are mostly transciptionally silent. They have vast changes in their chromatin structure, and very specific changes in histone and DNA methylation. In fact their embryonic precursors don't even express the stemness genes, those need to be reactivated by the BMP signal. To simplify, the stemness of the ES cell is a great liability and is quickly erased by down regulating master genes, only later does the germ cell regain this ability but at the cost of becoming transcriptionally silent. Futhermore, the migration of PGCs to the gonadal ridge acts as a second barrier to weed out potentially defective germ cells. Many germ cells get lost and die during that process. They must get there to be rescued by paracrine signals within a very narrow time. Futhermore even within the adult most female germ cells remain transcriptionally silent. Male germ cells which must remain active and divide have evolved a special DNA methylation system to keep retrotransposons in check, and they are particularly prone to apoptosis at pachytene if anything goes wrong, which means males are more susceptible to acute environmental exposure to sterilizing substances. Interrestingly germ cells also lack interferon sensitivity which has led to the evolution of a whole gamut of non-coding RNA regulation. There are about 50 000 piRNAs which regulate germ cells and we know almost nothing about. I've been looking at a possible link between large scale changes in chromatin that occur in germ cells and piRNA as a potential comprehensive exam topic. It really blows my mind.

So where does that leave our poor urbilateria. Well perhaps it had only one type of stem cell interspersed through its body and those stem cells were mostly silently waiting for an injury, but also capable of producing germ cells. We wont know for sure until synthetic biology as grown enough for us to recreate hypothetical ancestors...

Underpants science

This morning while I was perusing my drawers for a fresh pair of boxers i noticed that all my white boxers had holes, while all my black boxers were intact. Considering I bought them on the same day, I wash them together, they are the same model, why would that be? I have two theories: the color theory and the textile theory. Perhaps I wear white more often, perhaps because subconsciously they look cleaner or something like that meaning that colour influences my decision, not all that surprising considering the colour of a placebo pill influences its efficacy. Fake blue sleeping pills for example are better than red ones. The other possibility is that the textile on the white underpants was treated differently, for example in the manufacture it may have been bleached, leaving the fibers more vulnerable and weaker.

Speaking of underpants, we all know that tighty whities are bad for sperm count, but there is good research out there about the effect of textile on sperm count. So stay away from polyester, apparently the static may be harmful to your swimmers. If you're really paranoid about your underpants, you may also cook them for 30 min in the microwave to get rid of fungus, as it obliterates any candida spores. I was terrified of candida as a kid after my friend who was infected was denied any type of sweets. don't take that chance, nuke your boxers...

Finally I came across this disturbing pubmed abstract about dogs chewing on testes. So avoid to putting treats in your underpants.