How do we adjust to temperature?

[Ivan Seeking]

What happens when we acclimate to a new climate, over the long term? After fifteen years in Oregon, what once felt cold is quite comfortable. The N. California summer temperatures that were once enjoyable and still are to my father who lives there, now seem intolerable to me.

 

[pattylou]

I'd guess it is partly psychological. Id guess you have also changed your wardrobe and now may dress more warmly without realizing it.

We moved to southern California from Wisconsin. The weather is much nicer here. The biggest problem going back would be the winters - but that's because I got rid of all my winter clothes. I recall putting on four layers in the winter (longjohns, clothes, sweater, jacket) and I haven't had to wear more than 2 layers since moving here.

Has your wardrobe changed?

If there's a biological explanation for acclimating to different weather (there may well be) I haven't heard it.

 

[Ivan Seeking]

Has your wardrobe changed?

Absolutely but in just the opposite way. That's how it came up. The other day, while cleaning out the closet I realized that I have all sorts of heavy clothing that never gets used any more. When we first moved here I had to wear multiple layers of clothes and a heavy jacket when it was cold...and I was still freezing all the time. Now I find that a lightweight shirt and decent jacket almost always suffice. Likewise, now, anything over 75 degrees is getting too hot. But when I lived in N. California, with many days over 100 degrees F, it was common in the summer that it never got below that 75 or 80 degrees at night. And at the time, less the worst days when it would get up to and over 110F, it was mostly tolerable.

I thought of age, but my parents tolerate the high temps much better than I, and when they visit us, they're always cold. My weight has always varied a little but with no substantial change since moving here. It could be that we learn to ignore the cold, but then why do I feel too hot at such low temperatures. Seventy five degrees once seemed to be a very comfortable temp.

Edit: In my case, it could be a health issue of some sort, but this all seems to apply in many cases. When we first moved here, one of the first things that we noticed was how people dress; I looked like some kind of Eskimo compared to the other guys at work. And the idea that people were acclimated - a word commonly used - seemed to be obvious. But I have never really considered how it could be true.

 

[Moonbear]

I don't really know, but my first thought is thyroid hormones may be involved. Thyroid hormone concentrations can vary with photoperiod (light:dark cycle) in many mammals and birds, though I don't think that has ever been directly tested in humans, and can alter basal metabolic rate. At least in voles, it's reported to be associated with thermogenesis. Although, it seems any of the adiposity hormones (or all) may be involved according to another study. But, most of the studies I've come across seem to address short-term acclimation rather than the longer-term type of acclimation you're describing. I was hoping I might find some DOD-funded studies for you to address this; I was sure that would be of interest to them. I haven't come across any yet, but that doesn't mean they haven't been done. It might be that just too little is understood yet of the phenomenon.

Physiol Behav. 2005 Jun 2;85(2):143-9. Short photoperiod enhances thermogenic capacity in Brandt's voles.

Zhao ZJ, Wang DH.

Environmental cues play important roles in the regulation of an animal's physiology and behavior. In the present study, we examined the effects of short photoperiod (SD) on body weight as well as on several physiological, hormonal, and biochemical measures indicative of thermogenic capacity to test our hypothesis that short photoperiod stimulates increases in thermogenesis without cold stress in Brandt's voles. SD voles showed increases in basal metabolic rate (BMR) and nonshivering thermogenesis (NST) during the 4-week photoperiod acclimation. At the end, these voles (SD) had lower body weights, higher levels of cytochrome C oxidase (COX) activity and mitochondrial uncoupling protein-1 (UCP1) contents in brown adipose tissues (BAT), and higher concentrations of serum tri-iodothyronine (T3) and thyroxine (T4) compared to LD voles. No differences were found between male and female voles in any of the above-mentioned measurements. Together, these data indicate that SD experience enhances thermogenic capacity similarly in males and females of Brandt's voles.

Comp Biochem Physiol A Mol Integr Physiol. 2005 Feb;140(2):217-23. Epub 2005 Jan 27.
Role of adiposity hormones in the mouse during fasting and winter-acclimatization.

Korhonen T, Saarela S.

The influence of fasting and winter-acclimatization (cold and short-day acclimatization) on mouse plasma leptin, ghrelin, growth hormone (GH) and melatonin concentrations was determined from blood samples taken at mid-day and midnight. A 16-h fast decreased the plasma leptin but almost doubled the plasma ghrelin concentrations which contribute to energy saving, appetite stimulation and, in the case of leptin, to inhibition of reproduction. Winter-acclimatization did not affect plasma ghrelin concentrations, whereas leptin decreased to the same level as in fasting. The low leptin concentrations possibly enable an increased caloric intake for the purpose of thermogenesis. Fasting and winter-acclimatization seemed to abolish the diurnal leptin rhythm, but had no effect on that of ghrelin. Plasma melatonin concentration correlated negatively with ghrelin, suggesting a possible role for melatonin in the regulation of ghrelin concentration. SNS-activity and insulin appear to be the main regulators of leptin plasma concentration in the mouse, rather than melatonin as in some seasonal mammals. Interestingly, endogenous ghrelin did not stimulate GH secretion, which is a well-documented reaction to exogenous ghrelin injections.

 

[Ouabache]

I don't know the mechanism for how we adjust to temperature. But Ivan, I can vouch for you, it is a real sensation.

Just moving from east coast to the northern midwest in US, there is a noticable difference in seasonal temperatures and humidity. It took me 3 years to acclimate.

This helps explain something I've often wondered, how folks living in subartic, arctic, tropical and desert climates feel comfortable with their temperatures and humidity.

 

[Dr. Nick]

Key player: Brown Adipose Tissue feat. hipophysis.
Google it!
I have to run!

 

[Moonbear]

Key player: Brown Adipose Tissue feat. hipophysis.
Google it!
I have to run!

The abstract I already quoted for the article I cited already makes mention of BAT. Hypophysis is another name for the pituitary. The adenohypophysis is the anterior pituitary, which secretes thyroid hormone stimulating hormone (TSH), among many other hormones, which then signals thyroid hormone release from the thyroid gland.

Folks may be less familiar with the hormone leptin. It is one of the more recently discovered hormones and is secreted by fat cells and is believed to be one of the key players in feelings of satiety after meals. But all of its functions are still being sorted out.

Edit: I should note that I'm not sure how much BAT adult humans have and whether it would be sufficient to have such a function in humans. I know children have more BAT and small rodents have it, but my recollection is that there isn't much of it in adult humans...that could be really old, outdated information though.

 

[Ivan Seeking]

Last night, with a low temp of 65F, and muggy, it was the warmest night of the year so far. Even though the house was opened up I didn't sleep a wink all night - too hot. It seems that the changes in temp bother me sooner, as if there are seasonal adjustments with lower thresholds than before. But this is the thing that gets me: I'm probably less tolerant of hot weather now than most native Oregonians.

 

[selfAdjoint]

Wow, sounds uncomfortable there in Hilbert space. Have you considered "rigging"? :)

 

[Ivan Seeking]

Wow, sounds uncomfortable there in Hilbert space. Have you considered "rigging"? :)

Rigging; as in air conditioning?

 

[Moonbear]

Rigging; as in air conditioning?

That's how I best adjust to temperature; I push the buttons on the thermostat and flip the switch to either heat or cool depending on the time of year.

 

[Ivan Seeking]

I think that was intended as a Hilbert Space joke... As I said, I hadn't slept.

Yes, I think I can manage a solution. It was the science that interested me. So, as I know you already do, Moonbear, just think of me as a guinea pig.

 

[selfAdjoint]

Ivan got the point; there is something called a "rigged Hilbert space".

 

[Ivan Seeking]

Yes, rigged Hilbert spaces are great examples of how mathematicians can take a terribly difficult idea, and make it worse.

 

[Moonbear]

Yes, rigged Hilbert spaces are great examples of how mathematicians can take a terribly difficult idea, and make it worse.

Well, dagnabbit, this is biology, how do you expect me to understand math jokes over here?

 

[russ_watters]

Perhaps your body adjust it's reaction time? Ie, if you're used to hot weather, your body immediately starts sweating, opening capillaries, etc. when you feel the change in temperature and before it actually overheats? That's how programmable thermostats work - they actually anticipate based on past experience how long it takes to change the temperature and turn on the heat/ac before they sense the temperature is too high/low.

 

[Moonbear]

Perhaps your body adjust it's reaction time? Ie, if you're used to hot weather, your body immediately starts sweating, opening capillaries, etc. when you feel the change in temperature and before it actually overheats? That's how programmable thermostats work - they actually anticipate based on past experience how long it takes to change the temperature and turn on the heat/ac before they sense the temperature is too high/low.

I wish I had a real answer to your question, but it seems the consensus is none of us really knows why this happens. That is an interesting idea though. Since different temperature climates are also at different latitudes with the associated differences in photoperiod, it would be possible to predict to some degree seasonal temperature variation. At a higher latitude, you'd have slightly shorter days in summer than at a lower latitude, so the question would then be if those daylengths are sufficiently different and sufficiently detected by humans to predict temperature changes.

I think there would have to be some predictive cue such as photoperiod telling the body that it's the time of year when reaching 65 degrees at a particular phase of the circadian rhythm predicts it's going to be a hot day and you'll need to start cooling sooner. Sort of a predictive homeostatic mechanism rather than a reactive one.

Well, wait, (bear with me here, I'm thinking this through as I'm typing)...if that was the case, then by predicting changes, your body would begin adjusting to a predicted temperature before that temperature occurred, which would mean you wouldn't be maintaining proper homeostasis with the environment. If that happened, you'd expect that someone living in a hot climate who began cooling before the temperature got that hot would have a decrease in body temperature prior to a rise back to basal level when the cooling rate was appropriate for the ambient temperature. If that were the case, you would predict that the timing of diurnal changes in body temperature might be similar among groups of people at different latitudes, but the average temperatures at each time would differ between groups of people at different latitudes, or would correlate to latitude.

Now, where are those kids in need of science fair projects when you have an idea to give to them? This would be a fun science fair project that could be done online by getting volunteers to take their temperature a few times of day (morning, noon, evening, for example) for a few days and report in with their latitude, ambient temperature at the time they take their body temperature and see if there's a correlation. Of course, the differences might turn out to be too subtle to detect with the accuracy of your typical drug store thermometer. But, we'd be finding out if we react to or predict temperature changes. Oh, we'd have to get everyone to eat at the same time too, otherwise body temperature changes associated with mealtimes would screw up the results.

We can make this our first PF bio lab experiment.

 

[brewnog]

We can make this our first PF bio lab experiment.

Wolram will be gutted that he won't find out about the colour of belly button fluff though...

 

[Moonbear]

Wolram will be gutted that he won't find out about the colour of belly button fluff though...

I think that's more of a general science lab, so he can lay claim to the first PF lab, I'll just stick with the first PF bio lab.

BTW, what the heck is going on around here? I'm over answering questions in engineering, and the engineers are all over here in biology!

 

[Ivan Seeking]

Perhaps your body adjust it's reaction time? Ie, if you're used to hot weather, your body immediately starts sweating, opening capillaries, etc. when you feel the change in temperature and before it actually overheats? That's how programmable thermostats work - they actually anticipate based on past experience how long it takes to change the temperature and turn on the heat/ac before they sense the temperature is too high/low.

I never have trusted self tuning for PID loops.

 

[Ivan Seeking]

We can make this our first PF bio lab experiment.

That would be cool.

btw, you shouldn't ask people to bear with you; its very distracting.

 

[Ouabache]

most of the studies I've come across seem to address short-term acclimation rather than the longer-term type of acclimation.

I'd like to shed new light on this question. I experienced long term acclimation moving between two locations at the same latitude (maritime coastal climate to central U.S. temperate climate). It took several years for me to adjust in either location. I was exposed to the same photoperiod in both locations so can rule that out as a variable.

Here is a http://web.whrsd.org/faculty/Stephansky_Mark/pages/APBIO/AP_Notes/APN_19_Immune_Thermo.html that addresses long term acclimation[/color]. Here are some of the physiological responses.
Temperature Acclimation:
Adjusting to a new environmental temperature over a period of time.
Physiological acclimation to a new temperature has several aspects:
1) Cells may increase the production of certain enzymes.
2) They may produce the same enzyme but at a different temperature optima.
3) The cell membrane may change the properties of saturated and unsaturated lipids.
4) Cells can make rapid adjustments to temperature changes. In mammalian cells with a rapid increase in temperature (37 – 43 deg C), heat shock proteins are produced, which help maintain the shape of other proteins.

They also go into an interesting discussion about the hypothalamus' behavior as the body's thermostat. It monitors our temperature and can sense changes as small as 0.01 deg C. and regulates the body's heating and cooling mechanisms, using hormones. Sensory neurons on the skin are also sensitive to temperature and can trigger the hypothalamus to thermoregulate the body's reaction.