Avian flu! Swine flu! Now, bat flu?
Last week I sent you a news article on the recent coronavirus, first described in Wuhan, China, that was emerging as a 'new' human virus, one not previously detected in humans or known to cause human disease. A week later, as you know, this remains the top health news story, and rightly so - the virus has now killed many dozens, and infected many thousands, around the globe.
Viruses are a bit of an evolutionary quandary. They are tiny objects, composed of protein and nucleic acid. They are not considered to be cells, and they are not considered to be 'alive'. They are parasitic 'replicating devices' - they can only replicate when they have successfully infected the cell of a host species. And, they are designed to take-over the protein machinery of their host's cell, causing it to make many more virus particles, and to spread them.
Mammals have evolved with viruses throughout our history, and our immune systems contain some viral defenses, just as our genomes contain bits and pieces of DNA that may have been viral in origin. In recent years and decades, we have increasingly been aware of 'new' viruses, not previously seen in humans, that are suddenly causing human disease. Swine flu, avian flu, MERS, SARS, and others - and now, the Wuhan coronavirus.
Why are viruses so common in mammals? Because we are really good hosts for them - lots of cellular protein machinery, warm-blooded cells which promote high rates of viral replication, dense social structure which promotes transmission. From rats to cats, bats, camels and more, each mammalian group bears its own viral load.
Why do viruses move between mammal species? Two words: mutation and opportunity. As viruses mutate, they can gain or lose features that make them better, or worse, suited for particular host species (e.g., cats versus dogs). As species co-mingle, the odds improve that a virus can successfully 'make the leap' to a host of a different species, one to which it is newly well-suited.
Why are so many of these novel viruses originating in Asia? Population density and food production practices. On the global scale, the U.S. is relatively sparsely populated (save our largest cities). Across the globe, it is very common for population densities to be much higher than those found here. And, high human densities require ramped-up food production. Much of food production here is commercialized and removed from the public, but again, this is a global exception. Across most of the world, food production tends to be on a smaller scale, and it tends to be much more personal - individuals tending their own animals, working with their tissues and bringing their own products to open market. Together, this density and close contact ups the risk of transmission of animal viruses to human hosts.
What can we do? Addressing the inequities of education and opportunity that put some more at risk of public health diseases than others is a global problem, one that is daunting in scale. Can we immediately correct it? No, of course not. We can, however, be careful consumers, paying attention to the kinds of products we purchase, their degree of commercialization, the level of exploitation that may be attached to them. We can pay attention to climate issues, which seem to exacerbate many emerging diseases. And personally, we can practice good public health ourselves - stay up-to-date with vaccinations, follow good hand hygiene protocols, cover our coughs and our sneezes. And, we can stay informed, and help others to be informed - that is perhaps the best defense of all.
I hope that, by this time next week, the spread of this coronavirus has been contained.
Good morning all,
Hot off of the presses this morning is a news report about sustainable "forest farms", efforts to use environmentally-friendly propagation methods, in naturalistic-type settings, to commercially produce native plants that are of economic value. It's an interesting idea, and one that is quite different (by necessity) from the mass-production, highly-intensive, large-scale format of most of our modern agricultural production.
Many find these small scale, low-impact 'farming' methods attractive for their reduced reliance upon chemicals and their shortened supply chains, with products often moving from producer to consumer with few or no intermediaries. As these authors note, these practices may provide a bit of 'social justice' as well, by providing more-direct benefits and controls to producers. As such, these methods could represent a 'win-win' situation: valued and sustainable production, and well-served consumers. This ties in very nicely with the concepts in our last chapter, including the adoption of sustainable agricultural practices.
Good morning all,
In the news this weekend is a report about nitrogen pollution from farming and industrial activities, topics we discussed just this past week. These are global problems, but the problems are worse in some areas than in others. And, the political will to address them is equally uneven in its distribution.
I suspect that we will see more of these 'crises', as industries are shut down or face temporary moratoriums when pollution reaches dangerous levels. These are not easy problems to fix - it's very hard to change communities that have been operating in a given way toward newer/better methods, especially when much has been invested in current technologies and practices. Big solutions, integrating social reform, advanced engineering, and education are likely to be required.
See you this afternoon for review -
Nobel Prize for Medicine jointly awarded to William Kaelin Jr, Sir Peter Ratcliffe and Gregg Semenza - CNN
Good morning all,
In recent weeks we have considered the role of the circulatory and respiratory systems in collecting and delivering oxygen to our tissues, and just last week I sent you a long article about altitude-induced hypoxia and the physiological challenges that it stimulates. We've also discussed the kidney hormone EPO, and its role in stimulating the production of RBCs.
Fresh on the heels of those discussions and reading, this week's science news included the awarding of this year's Nobel Prize in Medicine, to a group of three researchers who study this very phenomenon, the physiological responses to oxygen. Their work is crucial to an understanding of how cells adapt to changing oxygen levels.
Nobel Prizes in science fields are awarded to researchers who have long, established careers and who have made discoveries that defined their fields. This year's winners are no exception - these scientists are well-established and highly respected. And, not surprisingly, they are still active. They also are likely to follow another tradition in that they most likely will use the award not to enrich themselves personally, but to support the work of their research groups. It's a great example of the selflessness that drives much of science: exploration and discovery for the greater good.
There are plenty of other news stories on these awards, including
Breakthroughs in science normally come after long, hard work, built from many small steps of progress - and informed by many failed experiments, a lot of trial-and-error, and requiring much patience. One prize winner (of years past) said that 'if I have seen further than others, it is only because I have stood on the shoulders of those who came before me'. They say that 'no man is an island', and in science that is certainly true - modern science is a highly collaborative venture, and today's advances are built upon the progress of earlier investigators.
When you contribute to a project, no matter how small or insignificant your part may seem, it's important to remember that it adds to our collective knowledge and capability. Who knows? Future Nobel Prizes may depend on you!
Have a great weekend -
Good morning everyone,
In the recent science news are articles related to several of the topics we have considered recently - this is a nice confirmation that our course topics are 'up-to-date'!
Early in the term we considered the behavior of parasitic wasps, that stun prey and then oviposit eggs within them so that their larvae have a ready food supply during early growth. In the news this week is description of a different kind of parasitic wasp, one which parasitizes other wasps.
Here, the form of parasitism is less direct, in that the parasite deposits its eggs into the same plant gall that its host occupies. The parasite larvae then can attack the host, and in doing so, they accomplish a form of behavioral and physiological 'hypermanipulation'. Not only do they use the host tissues for their own nourishment, but they actually trigger a malformed version of the hosts normal escape behavior, which ensures that the host itself doesn't escape the gall but which provides the parasite an escape route.
The degree to which parasites manipulate their hosts can be extraordinary. We are used to thinking that parasites can make use of host tissues, but examples like this reveal more complicated interactions, with some parasites hijacking host behavior as well. There are plenty of examples, such as these:
All are good reminders that host behavior, as well as host tissues, can be exploited by parasites.
Even more recently, I sent you some information about humans who have developed some ability to perform echolocation. Just this week came a report on this topic, suggesting real, functional remapping of the brain's visual cortex to support this new capability:
At some level, neural plasticity is responsible for all that we can learn, but to have whole-scale re-functioning of a part of the brain from one sense to another is very impressive.
Have a good weekend -
Good evening all,
As we remain caught-up on our lecture schedule, we do not need to meet in person on Friday (04 Oct) for lecture. Instead, I'd like to you to consider a recent science news article that bears on our lecture material.
In recent weeks, we have considered the properties of our blood, its red blood cells and hemoglobin, as well as the ways in which the circulatory and respiratory systems interact to deliver oxygen to our tissues. We've also described how erythropoietin (EPO, a hormone released from the kidneys in response to low blood oxygen levels) can stimulate the production of more RBCs.
The article I am sending you considers these same phenomena in a human population that lives (but not thrives) in perhaps the highest-elevation city in the world, La Rinconada, Peru. La Rinconada sits at an elevation of 5,100 m (more than 16,500 ft) above sea level, and has a regular population of >50,000 at this very high altitude, there to work in gold mines.
The air at this elevation contains only half as much oxygen as the air at sea level. Persons not accustomed to living at high altitude can become very ill (sometimes fatally) at elevations above 9,000 ft. To give you an idea of how high in the Andes this city is, consider that 'mountain climbing' here is the US is typically considered to be very technical above 12,000 ft in elevation, and not for amateurs. At La Rinconada, people may spend their entire lives above 16,000 ft in elevation.
The physiological challenges of life at this altitude are many and severe. The low oxygen levels stimulate extremely high levels of RBCs and hemoglobin, as much as 3x those considered to be normal. This, in turn, causes blood viscosity to rise dramatically, which causes abnormally high blood pressures. These elevated blood pressures place extra strain on the heart, causing it to enlarge, often dramatically. Despite these adjustments, many suffer from chronic hypoxia, termed 'chronic mountain sickness', or CMS. Blue-ish skin, fatigue, and low endurance all are common symptoms of CMS, and all stem from low levels of blood oxygen.
Curiously, populations long adapted to life at high altitudes (including some populations in these South American Andes mountains, and others in the Himalayas of Southern Asia) seem to have evolved at least some protections against chronic hypoxia and the challenges it poses. This suggests that there may be genetic tools that can be put to use in helping others who suffer from hypoxia not because of altitude, but because of diseases related to cardiac or respiratory function.
This article describes one team of physiologists and their efforts to assess human physiology and health at this altitude. Their initial focus was on CMS and body responses to it, but they quickly became caught-up in the socio-economic plight of the people there - life is brutal for the residents of this city, and the researchers felt, in many ways, helpless to help them. They certainly could not improve the economic status of the town's residents, nor could they offer a cure for CMS. There, as in many parts of the world (including our own country), the working class are too easily exploited, too easily marginalized. Lack of access to basic health care is often one of the first signs of a population that is short of options and resources. When that combines with dangerous forms of employment for the un- or under-educated, health issues rise and life expectancy falls.
There is a companion podcast for this article as well:
As you review these materials, I'd like you to think about the basic physiological mechanisms at play: how low blood oxygen levels can stimulate RBC responses, and, in turn, how these can contribute to blood pressure, which itself can trigger responses (remember ANF, when blood pressure rises?). Keeping ourselves in homeostatic conditions is complex even under typical environmental conditions; life under extreme conditions only amplifies the challenge.
I hope that you enjoy this article, and I hope that you enjoy the Homecoming weekend. Please be safe, and I will see you on Monday.
Good morning all,
We recently considered bat echolocation as a model for sensory coevolution. During our discussions, we noted that many animals have sensory capabilities outside of the range of humans.
How about humans who can perform echolocation?
There are a small number (few dozen) people in the world who have developed some level of proficiency at echolocation for navigation. Daniel Kish is the most famous person with these abilities (but there are others):
In all of these cases, the ability came about after a loss of vision. Our human visual cortices make up a huge part of our brains, and once they are freed from visual responsibilities, it seems that they can be co-opted (at least in part) for other uses. This neural flexibility is well-known, as it is the basis for the recovery that is possible from brain trauma, including stroke. Blind persons who read Braille are known to have some expanded touch sensitivity in visual areas of the brain, and sensory re-mapping is known to occur in persons with high-levels of musical training, or in new mothers nursing infants. Still, the development of echolocation as a sensory capability is quite different, in that it adds to the human sensory repertoire, not simply expands upon an existing sense.
There are lots of interesting articles about human echolocation, including:
Next time you find yourself in a dark room, you might be tempted to give it a try! I think that I will stay close to the light switch...
Have a great weekend -
Good evening everyone,
At the end of this week we find ourselves in the midst of a discussion of immune function, first with our lecture yesterday on the immune system (Chapter 7), to be followed by our next lecture on infectious disease (Chapter 8), scheduled for next Monday.
Recall that for tomorrow's class (Friday 20 Sept), we will not meet in person. Instead, I'd like you to read/digest a news article on a current and very relevant immune topic, that of environmental exposure to antigens.
For much of the history of our species, human life and society was based around agriculture, including exposure to domesticated animals. In the last hundred years, of course, that has changed for many, as populations became more urban. During this same period, the use of cleansing and sanitizing products in the household has increased dramatically, culminating recently in the explosion of "anti-bacterial" products, such as soaps, wipes, and tissues.
Most immunologists believe that we have taken cleanliness a bit too far. According to the "hygiene hypothesis", natural exposure to antigens keeps the immune system primed for action, and enables it to make robust responses to actual disease agents. In our ultra-clean worlds, however, many (especially the young children of cleaning-obsessed parents) are coming into contact with fewer and fewer natural antigens, and increasingly their immune systems are ill-equipped to respond to them when they do, leading to a rash (no pun intended) of allergies, sensitivities, or, at worst, autoimmune disorders.
This article explores the "hygiene hypothesis" and some of its implications. As you go through it, I'd like you to consider a few key questions:
- what happens to our immune system when we are exposed to naturally-occurring antigens?
- why should exposure to non disease-causing antigens enable us to better respond to more serious antigens?
- do you personally use anti-bacterial products in your household?
- does this article make you want to reconsider their use, in any way?
Our immune system is wonderfully complicated and powerful, but some think that our social behaviors have evolved faster than is good for it. Perhaps a nice walk outdoors, a swim in a lake, or a picnic in the grass is just what we need...
Have a great weekend - see you on Monday.
Good morning all,
Just passing along here an interesting news article, linking behavior and conservation.
Human have long associated with animals, and in doing so have shaped many of their behaviors. Here's an example of a detrimental effect: a semi-domestication that changes foraging behavior and seed dispersal in endangered New Zealand weka:
This kind of change illustrates the behavioral flexibility many species employ, particularly for adapting their own ecology to exploit the humans around them. In the long run, these sorts of associations can cause evolutionary change in brain and behavior (https://www.nationalgeographic.com/animals/2019/09/humans-shaped-dog-brains/), in ways that can dramatically alter the natural ecology of species. This is also an important reminder that interacting too much with endangered species can endanger them ever more if they imprint too strongly on humans - hence the need for 'panda suits' (https://www.youtube.com/watch?v=GaLP6S9ZHQ4 - how's that for a day job?).
See you tomorrow for review of the material for our first exam. I'm not planning a formal lecture; instead, I will review any material on which you have questions.