Wikipedia:Reference desk/Archives/Science/2013 December 12

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December 12

Why don't all viruses cause cancer ?

After all, they all mess with our DNA or RNA. StuRat (talk) 00:41, 12 December 2013 (UTC)

I'm pretty sure they do, or can. Carcinogen says Certain viruses such as Hepatitis B and human papilloma virus have been found to cause cancer in humans and later on Certain viruses can also act as carcinogens by interacting with DNA. Oh sorry you said all, I missed that. OK well oncovirus says The vast majority of human and animal viruses do not cause cancer, probably because of long-standing coevolution between the virus and its host. That would be part of the general phenomenon of diseases evolving to be non-fatal over time - if you're dead you can't spread the disease, so it's not adaptive to kill the host. I guess that leaves the question "how do they avoid it?".  Card Zero  (talk) 00:54, 12 December 2013 (UTC)

Yes, I had the same thought about evolution, although I'm not sure if the small portion of hosts which die from getting cancer put a significant evolutionary pressure on the virus. And yes, I'm interested in the specific cancer-causing and not-cancer-causing mechanisms of viral replication. StuRat (talk) 01:26, 12 December 2013 (UTC)

I really don't know why you would expect them to. As a general rule, anything that causes random changes to your genetic material, can also cause cancer. Most of the time, a cell that suffers the change probably doesn't become cancerous (I'm guessing a little here; maybe someone has more precise information). My guess is, most of the time, the change either has no real effect on the cell, or else it kills it. However, the few (maybe very few?) cells that do become cancerous are the ones that get noticed.

But viruses don't cause random changes; they cause a very specific set of changes directed at reproducing the virus. If, for a particular virus, that particular set of changes doesn't cause cancer, then why should the virus cause cancer? --Trovatore (talk) 01:13, 12 December 2013 (UTC)

Why are some viruses more likely to cause cancer than others ? I've never heard of the flu virus causing cancer, for example, even though it's widespread. So what do they do differently, than, say, HPV, which causes cancer fairly often ? StuRat (talk) 01:24, 12 December 2013 (UTC)

Well, let me start out by saying I'm just guessing here. But I would note that HPV, almost by definition, causes cell proliferation (warts), which I imagine is its strategy for spreading. It might be a fine balance between causing a benign tumor like a wart, and causing a malignant one. --Trovatore (talk) 01:29, 12 December 2013 (UTC)

It seems like it might have to do with the location of the infection, as HPV that causes plantar wart does not cause cancer, AFAIK. Is that the same strain of HPV ? StuRat (talk) 01:24, 12 December 2013 (UTC)

There are dozens, if not hundreds of strains of HPV, and it is quite easy to catch more than one. μηδείς (talk) 03:47, 12 December 2013 (UTC)

Many viruses do not actually alter the host cell DNA; they just use the "machinery" of the host cell to produce more virus particles. Retroviruses do actually alter the host cell DNA, though. --Dr Dima (talk) 01:30, 12 December 2013 (UTC)

Is it as simple as only retroviruses being carcinogenic then ? StuRat (talk) 01:34, 12 December 2013 (UTC)

No. Epstein-Barr or HPV cause cancer by different means (namely, by turning off some of the cell's natural tumor suppression mechanisms, as far as I remember. Not sure, though). --Dr Dima (talk) 01:44, 12 December 2013 (UTC)

You are right. I have answered this twice at length and lost the response. So, basically, there are thousands of viruses, not all related, nor all working by the same mechanism. There are hundreds of types of cancers, which simply means cell-types reproducing out of control by the normal regulatory mechanisms. Some cancers either suppress those regulatory mechanisms (HPV) or accidentally affect them. Some viruses, like HIV, which overwrites DNA, weaken the immune system, allowing normally "weak" cancers like Kaposi's Sarcoma to overwhelm it. There's not just one type of virus or cancer or mechanism, but hundreds or thousands. Asking why all viruses don't cause cancers is like asking why all bacteria don't cause sores, given that some of them do. It's a fatally broad overgeneralization. μηδείς (talk) 03:45, 12 December 2013 (UTC)

You're just saying "It's complicated, so I don't know the answer". If so, let others answer. There must be some commonalities between those viruses which are carcinogenic. If you don't know, hopefully others will. StuRat (talk) 13:39, 12 December 2013 (UTC)

Medeis's answer is actually pretty good. Looie496 (talk) 18:08, 12 December 2013 (UTC)

There's no necessary commonality between all viruses that cause cancer, because causing a cancer is not a goal of the virus's action. (Keep in mind that "cancer" is a general term covering hundreds of different types of diseases all having unregulated growth as a common factor, just like diabetes is not just one disease, but a host of syndromes of different types and causes, all having unregulated blood sugar as a common factor.)

Some viruses like HPV cause initially benign tumors. Every time cells reproduce (which is what happens when tissues grow, as they do in tumors) they acquire mutations. If, at some point, a cell acquires a mutation that turns off a major regulatory gene, voilà, cancer. Retroviruses can cause cancer if they cause a mutation in a regulatory gene when they insert their own code into the host DNA. HIV doesn't cause Kaposi's Sarcoma directly at all, but allows it to flourish by weakening the immune system. (It turns out KS is actually caused by another virus, human herpes virus 8.)

There are so many different types of viruses, and they are so diverse (they are usually considered the equivalent to a phylum, if not a kingdom, taxonomically--virus classification) it is not even known if they have just one common origin, or if they have arisen separately from differing origins--virus origins. Cancers can even be caused by simple repeated mechanical injury causing scarring, such as found in animals with harness sores. Other than the factor of unregulated growth, there's no single marker (i.e., molecule) unique to cancers not also shared by healthy tissue. The issue is indeed complicated, and admitting it is not saying we don't know the answer, it's the first step in finding the answer. μηδείς (talk) 18:43, 12 December 2013 (UTC)

There are a few different ways for a virus to cause cancer. The most direct is by an integrase to take viral DNA and put it into the genome. As a rule, this is always trouble - gene therapy researchers have hopes on particular vectors that are particularly scrupulous, but so far getting any virus, however carefully chosen and modified, to modify DNA without cancer is hard to guarantee with any confidence.

Another way to cause cancer is by producing compounds that interfere with the body's anticancer mechanisms. Large T antigen is a classic. A virus like this can mess with multiple cell safety mechanisms (p53, pRb) at the same time. (random paper: [1]) Growths like genital warts don't always stop growing.

HIV has two more ways to cause cancer: make the immune system keep growing at a frenetic pace until AIDS-related lymphoma develops, or interfere with immune surveillance so that something like Kaposi's sarcoma gets started (thanks to a second virus, KSHV). The former is not that dissimilar from the idea of hepatitis C causing cancer by increasing liver cell replication.

Viruses can have a really indirect role on cancer sometimes, like an alleged viral cause of diabetes;^[2] having diabetes then increases the risk of cancer somewhat.

Yet despite all these things, there are still plenty of viruses that only produce RNA in the cell, and usually result in a rapid lytic infection that destroys the cells they mess with, or else the immune system destroys them, and the infection is brief enough that the wear and tear on the body is minimal. Wnt (talk) 07:24, 13 December 2013 (UTC)

Thanks, Wnt, that's more of the type of answer I'm looking for. So, if a virus only changes RNA, doesn't suppress the immune system, and doesn't remain for long (probably as a result of not suppressing the immune system), then it's not carcinogenic, right ? StuRat (talk) 14:26, 13 December 2013 (UTC)

Hmmmm.... I know any statement like that in biology has to have a big glaring exception, but I'm drawing a blank right now. :) Wnt (talk) 14:41, 13 December 2013 (UTC)

HPV s just such an exception, it's not a retrovirus, and does not suppress the immune system. Now, if Wnt will repeat that, perhaps Stu will find Wnt's comment helpful. μηδείς (talk) 01:26, 14 December 2013 (UTC)

It's perhaps also worth remembering that non retroviral DNA viruses can sometimes integrate into the genome and when they do so can sometimes also contribute to cancer. Our oncovirus article includes a few examples I think, such as Merkel cell polyomavirus. Probably more at [3]. Unlike retroviruses, DNA viruses aren't usually intentionally integrated in to the genome AFAIK, but it can happen anyway. In fact, I think this is actually one of the problems, because DNA viruses aren't generally really evolved to integrate, when they integrate they usually stop spreading which is bad for the virus but also also may be bad for the host since the mechanisms to help them spread may be integrated and contribute to the cell trying to spread (instead of just the virus). P.S. Yes this is a somewhat simplified explaination but it sounds like this is all that is wanted. Nil Einne (talk) 00:37, 15 December 2013 (UTC)

Actually, the HPV article explains that the virus tends to cause cancer when persistent, not otherwise, so it is well in accordance with the rule. But it's a good point about "accidental" integration of DNA viruses without a specific integrase. Wnt (talk) 04:57, 15 December 2013 (UTC)

Urine as a fertilizer

I have read that urine should be diluted 1/20 to be used as a fertilizer. Is it better to allow the urine to ferment first, or can it be used to full effect from the spigot? μηδείς (talk) 03:38, 12 December 2013 (UTC)

Have you read Urine? The article discusses use as a fertilizer and typical dilutions to avoid damage from the concentrated nitrogen. The nitrogen is very useful as fertilizer, but the salt content can be a negative. Edison (talk) 03:49, 12 December 2013 (UTC)

Yes, I have read it, and you seem to have ignored my question. Does letting the urine sit to ferment have any effect, positive or negative? μηδείς (talk) 04:23, 12 December 2013 (UTC)

Note that your stated dilution is way weaker than those given in the article. That's why I pointed to the article. If you're going to water the plants a lot anyway, it probably all evens out. There seems to be a tradeoff, in that fermented urine loses nitrogen as ammonia is emitted as vapor, but some "Organoponic" projects let aerobic processes operate to produce microorganisms they think are useful, per "Plant & Soil Science: Fundamentals & Applications: Fundamentals and Applications" (2010) by Rick Parker (page 182). Edison (talk) 20:21, 12 December 2013 (UTC)

Thanks, that's an interesting link. The topic came up when the last snowstorm led from discussion of purchasing a generator to what to do if you couldn't get fertilizer for the vegetable garden. I vaguely remember having read some book that recommended using fermented urine. μηδείς (talk) 20:55, 12 December 2013 (UTC)

Just remember Don't Eat the Yellow Snow Richerman (talk) 23:27, 12 December 2013 (UTC)

Perhaps it depends on what you're fertilising. The film The World's Fastest Indian includes references to a reasonably common New Zealand and Australian custom of peeing on (or more accurately, under) a lemon tree. It is believed, in its obviously undiluted form, to be good for the tree. I'm certainly not aware of it ever doing any harm. HiLo48 (talk) 00:57, 13 December 2013 (UTC)

I believe I actually have seen a lemon in NJ, but that's not the sort of vegetable we'd be growing if the electric grid crashed. Small plants won't tolerate a direct peeing upon. My underlying question is, is there a difference between urea and bacterial produced ammonia so far as the plant is concerned. μηδείς (talk) 01:13, 13 December 2013 (UTC)

Softening of the brain

Can softening of the brain, by itself, cause death, or does it facilitate death by some other means? According to the report of the event in the New York Times, Richard Upjohn died of this cause, but everything I'm finding about it as a cause of death (like the Times story) is quite old, generally 19th century or earlier. I'm not particularly inclined to trust 19th-century sources on questions like this. Nyttend (talk) 04:17, 12 December 2013 (UTC)

Paresis was once referred to as "softening of the brain". ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:09, 12 December 2013 (UTC)

Yikes! The brain in its normal state is already pretty soft -- something like the texture of pudding. If it got much softer, it would liquefy. Looie496 (talk) 18:02, 12 December 2013 (UTC)

What flavor of pudding does monkey brains resemble? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:14, 12 December 2013 (UTC)

Brains are largely made of fat. Looie is probably using pudding in the British sense, which includes things like scrapple--although one would assume brains don't have so much salt and peeper unless added. μηδείς (talk) 01:29, 13 December 2013 (UTC)

So even Einstein was a fathead, ja? ...and... "peeper"? Like confusing the eyeballs with hard-boiled eggs? ...and... This stuff is expensive, hence the term "puddin' on the ritz". ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:03, 13 December 2013 (UTC)

Appropriate shower length

How long exactly should one stay in the shower after a normal day at work or at school? Admiral Caius (talk) 17:54, 12 December 2013 (UTC)

Five minutes and 37.34 seconds. Seriously, how do you expect to get an answer to a question like this? --Trovatore (talk) 17:58, 12 December 2013 (UTC)

Actually, the 5 minute, 37 and ³⁴/₁₀₀ths of a second shower is quite standard in the West and its former colonies. In the Netherlands they have a timer set to that length by law for all home and hotel showers. There were riots in Indonesia just after Indonesian independence from the Dutch when President Sukarno tried to institute a 333¹/₃rd second standard. The Left supported Sukarno's rounder number, while the Right would not abide by the 4 second shortening. His second attempt to switch to the new standard in 1965 is seen as a major factor in Sukarno's 1967 overthrow. μηδείς (talk) 18:11, 12 December 2013 (UTC)

That joke was 99 and ⁴⁴/₁₀₀ths percent pure. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 12 December 2013 (UTC)

Unilever did a survey and found that 8 minutes is popular. I can't tell you whether this is morally right, but it's normal (in the UK).  Card Zero  (talk) 21:36, 12 December 2013 (UTC)

One would have thought that normality in the UK consisted in a bath, rather than a shower. Insofar as this question is capable of a serious answer, though, "until you're clean, but no longer" is the only possibility. Tevildo (talk) 21:57, 12 December 2013 (UTC)

"Until you're clean, but no longer" is as storied a principle of the Magna Carta as "a man's home is his castle". We American's assume it as an inheritance from common law. (In addition to the 8 minute shower, there're the 16-min New York Strip shower, the 24-min Texas Deluge, and the 27-min Kramer Special.) But the trend is toward the worldwide 05:37.34 standard of the Napoleonic Code. It's only a matter of time until, as with the Imperial unit system, the Anglosphere nations drop the irrational 8-or-so-minutes and adopt the metric 05:37.34 per shower douchelitre system. μηδείς (talk) 22:11, 12 December 2013 (UTC)

Medies, that apostrophe is too far below the belt for it not to be deliberate. See also decimal time. :) Tevildo (talk) 22:24, 12 December 2013 (UTC)

Hahahaha! LOL! That was for Jack's enjoyment, I really didn't expect anyone else to notice. μηδείς (talk) 22:32, 12 December 2013 (UTC)

Ahh, the essence of these things is subtilty. I would recommend a 'rediculous' at some point, which I expect to see in the dictionaries before I meet my maker. Tevildo (talk) 23:02, 12 December 2013 (UTC)

I pronounce ridiculous as if it were spelt riddickulous, so it's unlikely it would occur to me to put an 'e' in there. But anything to please Jack, if I can remember. (I do say turrible though. μηδείς (talk) 01:19, 13 December 2013 (UTC)

"Anything to please Jack" - I will certainly hold you to that, Medeis. Oh wait ... you couldn't have been referring to me, since I've taken no part in this thread up till now, and I know you're well-mannered enough not to talk about editors behind their backs, so to speak. You're off the hook, it seems. Damn. I was so looking forward to being pleased on a regular basis. I don't suppose you'd care to please me in your spare time ...? -- Jack of Oz ^{[pleasantries]} 08:50, 14 December 2013 (UTC)

Well, getting clean is not always the sole purpose of a shower. For example, some people sing. Do you know what they sing? I didn't think so. --Trovatore (talk) 22:23, 12 December 2013 (UTC)

Beethoven's Ninth Symphony, on a good day. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:28, 12 December 2013 (UTC)

In the original German? Learning the Ode to Joy was actually a big factor in my deciding to skip lunch in HS so I could study German in addition to French. My 2 y/o niece sings Freude schoene Goetterfunken, Tochter aus Elysium, but to the unfortunate lyrics her brother taught her, "I hate mommy, I hate mommy, I hate mommy, I hate mom." μηδείς (talk) 01:26, 13 December 2013 (UTC)

The omitted other option in the setup to that joke is what makes it funny. DMacks (talk) 02:29, 13 December 2013 (UTC)

Call it an enthymeme. --Trovatore (talk) 03:01, 13 December 2013 (UTC)

From experience, I would say that a female teenagers need to be in the shower from the moment they get home from school, until the moment they need to get dressed up for their date. Male teenagers on the other hand, seem genetically prone, to shun soap, water, shower gels and are far happier if they they liberally coat themselves and clothes in motorcycle grease, before they go out to pick up their date. So I suspect the time period you are requesting is between two hours showering (for females) and a 1/10 of a second brief glance of a shower-head for boys. --Aspro (talk) 22:02, 12 December 2013 (UTC)

On a school camp a few years ago to an area experiencing drought and subsequent water shortages, the showers had a timer which turned off the water after three minutes. To get it going again the person showering had to leave the shower booth and press a button on the wall on the other side of the bathroom. Apparently the girls organised friends to repeatedly press the button for them. The boys coped. HiLo48 (talk) 22:45, 12 December 2013 (UTC)

The correct length of a shower is until the hot water runs out. --Carnildo (talk) 01:54, 13 December 2013 (UTC)

Resolved

Unless you have a tankless water heater. (Which means I lose track of time all the time when I shower.) Hot Stop 05:49, 13 December 2013 (UTC)

Or unless you turn off the shower halfway through to raise steam (believe it or not, there are people who do that!) 2601:9:3200:467:1830:AF9B:D09C:6497 (talk) 07:10, 13 December 2013 (UTC)

:It seems like winter itch is a constraint^[4] - at least, in the winter. Unless you want to fool with bath oils, anyway. Wnt (talk) 07:31, 13 December 2013 (UTC)

I wonder if I'm the only one to do this: I take a hybrid bath/shower (a bower ?). That is, if I have sufficient time, I first take a bath and even shave my face and use a pumice stone on my foot calluses in the tub. However, the bathwater is then dirty and sudsy, so not good for rinsing. I then take a short shower to rinse off, and also clean the tub.

In this setup, the shower is shorter than a normal shower, as the washing has already been done. I also find this setup is good if your water heater isn't up to par, as it then spreads out when the hot water is generated, between when the bath is run and when the shower is taken, allowing hot water time to regenerate in between. Of course, this approach is not so good if others need to use the bathroom or hot water, and doesn't conserve water or energy (try a whore bath for that: [5]). StuRat (talk) 14:39, 13 December 2013 (UTC)

It's a shath, not a bower. Bowers are dry and woody. See wikt:bower. μηδείς (talk) 18:09, 13 December 2013 (UTC)

Sometimes when I have a cold or other mild illness I will turn on the shower head, stop the plug, and sit in the bath while the shower fills it, like sitting in a warm pool during a rainstorm. That's less about washing than comfort. μηδείς (talk) 17:44, 13 December 2013 (UTC)

While there can't be a proper answer as to how long any individual should spend in the shower there are possible answers. This shows how much a shower is going to cost, while this discusses ways to conserve water as does this. CambridgeBayWeather (talk) 19:31, 13 December 2013 (UTC)

Taking showers is actually not healthy for the skin. So, I think the correct (but socially incorrect) answer is 0 seconds per day. Humans obviously have not evolved the need to take showers, we are just animals and the processes in the skin are optimalized for some dirt and dried out sweat to have build up on your skin. Removing that dirt layer may make it necessary for you to use all sorts of skin care products that will then only partially undo the damage done by showering. Count Iblis (talk) 10:27, 14 December 2013 (UTC)

I'm fond of the idea that human ancestors spent substantial time in the Okavango Delta and a larger similar environment that existed in the region at the time, so I'm fond of the notion that humans were often exposed to water for prolonged periods (not an "aquatic ape hypothesis" so much as a part-time wading ape, part-time mud ape, part-time desert ape, part-time walking behind the wildfires and eating cooked meat ape. Whether that's true or not, certainly such environments were a part of their travels and travails and the selection will have responded to it to some degree. Wnt (talk) 05:02, 15 December 2013 (UTC)

Yes, in a tropical setting, I think frequent bathing might have had advantages. Here's a few:

1) Cool off on hot days to prevent hyperthermia.

2) Drown fleas, lice, etc.

3) Reduce human odor. This is important both for hunting and avoiding being found by wild animals and enemy tribes.

4) There's a social aspect to communal bathing which helps to cement important relationships.

5) Might be a good way to find a mate, assuming they found clean mates more attractive. StuRat (talk) 06:36, 15 December 2013 (UTC)

I doubt reducing odor was a priority - otherwise, why are humans (and other primates) so smelly? Predators are famous for avoiding humans; man-eating lions are famous exceptions, and even sharks spit us out more often than not. With tissues soaked in uric acid, not only do we smell bad... odds are we taste like pee. By and large we won't even eat each other. I'm inclined to put humans down in the "unpalatable" column. Wnt (talk) 14:40, 15 December 2013 (UTC)

I suspect that predators avoiding humans is a recent thing, which evolved after we became dangerous to them. Back when we were easy prey, there would have been no reason to avoid eating humans. (Yes, individual humans may not seem dangerous, but the fact that if one is killed we will likely track down and kill the animal that did it, quite possibly along with all of it's relatives, makes us collectively quite dangerous, and puts evolutionary pressure on predators to avoid us.)

As far as other primates, most have the good sense to stay up in trees most of the time, where they are relatively safe from many predators, so their odor giving them away is not as much of a problem. StuRat (talk) 12:06, 16 December 2013 (UTC)

Blood disorders

I am looking for a definition of Philadelphia G. It was diagnosed in 1975 by a doctor in Philadelphia. It is also called ASG. Where do I look to get an accurate definition?© — Preceding unsigned comment added by 2600:1013:B007:553E:C99E:DACF:C58F:DA74 (talk) 22:59, 12 December 2013 (UTC)

See Hemoglobinopathy for what we have on the issue. Hb G-Philadelphia is redlinked from that article - I'm fairly sure that's what you're looking for. Tevildo (talk) 23:07, 12 December 2013 (UTC)

I think this might be the actual article you want. Apologies for the decidedly non-PC language. Tevildo (talk) 23:46, 12 December 2013 (UTC)