QVCatullus t1_iycntuk wrote

It still goes exactly to what the post you're responding to said. They didn't claim that hydrogen had a low energy density, they said that a hydrogen tank that fit on a plane would either not have enough fuel (like, not even remotely enough -- the volumetric "energy density" of hydrogen is on the order of 1/3000 that of kerosene per atmosphere the hydrogen is stored at, so even with a high-pressure 700 bar tank you need 4ish times the fuel storage), or would have to be rated to such high pressures/low temperatures (for cryogenic storage, which is maybe not a good choice for air travel in any kind of near future) that it would be impractically heavy.

In other words, it seems like your comment is calling out a mistake in the post you're responding to, when really you're just restating it, since precisely the problem at hand the PP was referencing was the compression issue.


QVCatullus t1_ivttu6m wrote

It's worth pointing out that in this case, enzyme replacement therapy was used in utero to treat the disease, not cure it. The therapy hasn't changed that the patient still isn't able to manufacture the needed enzyme, and barring new developments will need to continue the infusions for life. What's important is that usually the therapy is not begun before the child is born, but that means that glycogen buildup has already had a chance to affect fetal development; in this case (some of) that damage was hopefully forestalled by beginning treatment before birth. The article also mentions that the hope is that the body's allergic reaction to the enzyme infusion will be ammeliorated by beginning the treatment early, which strikes me as reasonable enough but it looks like they'd like to start collecting data on that to see if it's a justified benefit.


QVCatullus t1_ivtoywn wrote

Tay-Sachs is famously much more prevalent among Ashkenazi Jews, not because it cares about your religion, but because it's a rare recessive disorder, so both of your parents have to happen to be carriers to pass it on. As a result, it will naturally be more prevalent in any smaller interbreeding population where it happens to become slightly more prevalent by chance. Historically, due both to internal and external pressure (i.e. religious encouragement to marry other Jewish persons as well as generations of Jews being cut off as outsiders from the majority populations in many places where the Ashkenazim have lived), Ashkenazim have been more likely to marry and reproduce with other members of the same closed group than with the wider population, so chance occurrence of Tay-Sachs somewhat above the norm dramatically increases the (still small, but the disease is so terrifying it's worth preparing around) chance of it appearing in offspring.

It's not only an "Ashkenazi disease"; other relatively closed groups have higher incidences, like French Canadians and Cajuns, and some Amish groups.

If the reference to Ashkenazim is what makes it sound remarkably specific, be aware that this simply means more or less "Jews of Germany" and in practice means even more broadly the Jewish diaspora population of most of Northern, Central, and Eastern Europe; the Jews whose ancestors likely spoke Yiddish -- as opposed to, say, the Jewish populations of Iberia, the Sepharadim, or the Mizrahim in the rest of the Mediterranean, sometimes grouped as part of the Sepharadim. As such, it means a very broad swath of the Jewish population, and in particular a group to which most Jews in the US belong, since so many emigrated from Central and Eastern Europe to the United States.

ETA: I worded the 2nd paragraph under the mistaken recollection that the Cajun population had inherited their propensity from French Canadian ancestors, but a bit of reading just now says that apparently the two are demonstrably not related, since the genetic mutations among the Canadian and Cajun groups are different. Apologies for being misleading, but that means that they should be considered two distinct semi-closed populations where prevalence is higher.