SciBlogs

Archive January 2012

motivating tomorrow’s biologists Alison Campbell Jan 31

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That’s the title of Susan Musante’s paper in the latest issue of Bioscience (& many thanks to David Winter for sending it on). It’s a summary of some key points made by speakers at an NAS convocation called “Thinking evolutionarily: evolution education across the life sciences.”

Now, I find science fascinating, exciting, & endlessly interesting, & I’m sure my colleagues feel the same. The thing is, how to pass all that on to our students? As I’ve said before, simply providing them with quantities of facts is not going to do it. At the convocation, several speakers stressed that

[simply] regurgitating the biological knowledge generated by the scientific community or conducting “cookbook” laboratory experiments does not result in genuine understanding or excitement on the part of students… Instead, the nature and process of science, the unifying concepts and connections to the real world, and the problems encountered and discoveries made by scientists are what make biology come alive.

Biologists, of course, recognise the complexity of their subject all too well. However, I suspect that our desire to ‘get the facts across’ obscures that complexity and at the same time works against – rather than for – student engagement. So, how can biology educators motivate their students as they come to understand our fascinating subject?

One part of the equation is how it’s taught, something I’ve discussed before (here, for example). While those lecture-room techniques can make a real difference to student understanding and mastery, there are other learning environments to consider. Beginning to move away from ‘cookbook’ labs is part of it. Yes, there are practical skills that students need to learn, but why not look for ways to deliver those skills in contexts that are more meaningful and relevant to the students? For example, in the B semester our first-years practice a lot of those skills in the context of solving a ‘whodunnit’, finding out who disposed of the paper coordinator (me!). (OK, we chose that one because of the generally high interest in shows like CSI; other contexts would work as well. Anything to move away from following a recipe to get a result that most in the class probably realise is a ‘given’.)

Another tool – and an important one, if we’re hoping to give our students a feel for what scientists actually do, is to give them a chance to work with primary data – something that is in ready supply in universities :-)  There are some great resources for educators in the BioQUEST database, such as the Beagle Investigations Return with Darwinian Data, or BIRDD, to use in giving students that experience. Musante also quotes David Mindell (of the California Academy of Sciences) on the benefits of field trips:

We have a real disconnect between students and the natural environment

he says, and we should recognise that

allowing students to explore the outdoors through research projects is a proven way to encourage them to inquire deeply about the world in which they live.

This is something that the University of Sydney’s Pauline Ross uses to great effect with her undergraduate students.

We can use well-designed assessment tools to provide some extrinsic motivation to students, but giving the opportunity to gain personally-relevant experiences through such activities may well be more effective in the long run. Letting students gain those relevant experiences seems to be particularly important

for students that are under-represented in the sciences and students that initially have low expectations for success,

according to another speaker at the convocation, Paul Beardsley. This is something that deserves much closer attention here in NZ, especially when the Tertiary Education Commission’s funding priorities are taken into consideration.

Musante’s thoughtful summary provides links to a range of databases that teachers should find useful, and ends with a reminder that educators need to be students as well – not only adding to their own subject knowledge, but continuing to learn

about what motivates students and works to engage them, [so that] their students will be able to take ownership of their own learning. And that is essential if we are to increase the biological literacy of today’s students, who are tomorrow’s politicians, school board members, precollege teachers, and voters.

S.Musante (2012) Motivating tomorrows biologists. Bioscience 62(1): 16 doi: 10.1525/bio.2012.62.1.5

critical thinking – a classroom resource Alison Campbell Jan 29

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I joined Facebook about a year ago – primarily to access the NZIBO pages, but subsequently I found I quite enjoyed keeping up with what friends & family are up to. More recently I’ve added ‘entities’ like ScienceAlert, & through that particular link I’ve just found an excellent series of short videos on critical thinking. With the new NZ school year coming up, I thought it might be good to share them more widely.

So, here we go :-)

The first video in the series – produced by techNyou & funded by the Australian government – looks at basic logic & faulty arguments, & talks in passing about things like confirmation bias.

The second in the series discusses the structure of logical arguments & introduces the idea of logical fallacies.

Video #3 explains the ‘straw man’ logical fallacy:

The fourth clip reminds us that it’s not a good idea to accept arguments simply on the basis of whether or not we like someone – ask for the facts & evidence, & base decisions on that:

Number 5 reminds us that our brains are all too ready to ‘see’ patterns that aren’t really there, & brings in the idea of the ‘gambler’s fallacy’.

And the last one in the series so far is entitled ‘the precautionary principle’, and goes on to explain the nature of a scientific theory. (The precautionary principle needs to be used with care – you could say, with caution, lol – if we always waited for a 100% guarantee that all risks were identified, we might never act at all. Nor can science ever provide such a guarantee.

These videos are all clear, to the point, & brief – an excellent resource & basis for ongoing classroom discussion :-)

why things got bigger (rpt) Alison Campbell Jan 27

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ResearchBlogging.org

One of my tasks at the moment it the revision/rewriting of the study guide (along with my actual lecture notes etc) for my A semester first-year biology class. As part of that I’m reviewing some of the material I give the students to read & came across a previous post of mine on the relationship between atmospheric oxygen and the size of eukaryote organisms. And I liked it (still), so thought I’d repost it here :-)

The earliest fossils we have are of prokaryotes – a major taxonomic grouping that includes both bacteria and members of the Archaea (things like blue-green algae, aka cyanobacteria). And like modern prokaryotes, those early life-forms were tiny. Most of us are far more familiar with some of the eukaryotes, and perhaps a major reason for this is that we can see them: they are orders of magnitude bigger than microbes. And an interesting question is: what sort of trajectory took some forms of life from the tiny to the ginormous? Was there a smooth upward trend in the maximum size of living things? Or did things progress like a learner driver – by bunny-hops?

Well, what you see when you look at the fossil record is not a smooth upwards progression. Instead there are two points where the maximum size of organisms increases rapidly, both followed by  periods of relative stasis. This is something I’ve talked about in my first-year lectures for quite a while, but it’s been documented very thoroughly in a recent paper (Payne et al. 2009). Here’s the relevant figure from their article.

trends in maximum size of living things.png

You can see from this that there was a big jump in maximum size about 2 billion years ago, & then another leap about a billion years later. What was going on?

Well, part of the answer’s given in the figure’s legend: those marked increases in size happened around the time when atmospheric oxygen levels increased as a result of photosynthesis, an environmental change that supported more active metabolisms and bigger living things.

The first jump marks the appearance of eukaryote fossils. Remember that one of the characteristics of eukaryotes is the presence of mitochondria, organelles that carry out aerobic respiration (a process that releases more chemical energy than the anaerobic respiration typical of most prokaryotes). All the evidence points to mitochondria having originated by the process of endosymbiosis: they were once free-living aerobic bacteria that entered into a symbiotic relationship within other prokaryote cells, and over time lost the ability to survive outside their hosts, This was an ancient event indeed – but a significant one, because when the levels of available oxygen had reached a certain level, these new hybrid organisms, the early eukaryotes, were at an advantage. They could generate more ATP than their prokaryote competitors, & some of the extra energy made available by aerobic respiration supported an increase in cell size and complexity.

Maximum body size leapt up again a billion years later, after another surge in atmospheric oxygen levels. This timeframe sees the appearance of Ediacaran and Cambrian organisms – multicellular organisms. Some of those evolutionary experiments – the Ediacarans – died out, but many of the others are still with us today. And the evolution of multicellularity opened a new door for upward changes in body size: a single cell can be only so big before it encounters punishing difficulties with obtaining food & oxygen and disposing of waste. This is because single-celled organisms must carry out these processes across their body surfaces. But relative to volume, surface area increases more slowly as organisms get bigger, & this places an upper limit on the size of single-celled organisms. (Ostrich eggs aside, one of the largest single-celled organisms I can think of is the alga Caulerpa, which can be several metres long with hundreds of large flat fronds. It can do this because, while long, the cell is also broad & extremely thin, giving a high surface area: volume ratio.) Whereas with multicellular organisms we see the evolution of guts, gas exchange surfaces, circulatory and excretory systems.

And there hasn’t been a lot of movement since then. We might like to think of ourselves as large animals, who share the Earth with even larger animals (blue whales, anyone?) and plants (such as the sequoia), & are much larger (& more sophisticated ;-) ) than those Cambrian critters. Yet that second growth spurt levels off about 450 million years ago, when the largest things around were big cephalopods (with shells up to 5m long!). As Payne et al. comment, [the] maximum size of animals has increased by only 1.5 orders of magnitude since the Ordovician; the giant sauropods of the Mesozoic and even the extant blue whale add comparatively little to the size range of animals. The largest living individual organism, the giant sequoia, is only 3 orders of magnitude bigger than the largest Ordovician cephalopod and one and a half orders of magnitude bigger than the blue whale.

Payne, J., Boyer, A., Brown, J., Finnegan, S., Kowalewski, M., Krause, R., Lyons, S., McClain, C., McShea, D., Novack-Gottshall, P., Smith, F., Stempien, J., & Wang, S. (2008). Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity Proceedings of the National Academy of Sciences, 106 (1), 24-27 DOI: 10.1073/pnas.0806314106

And if you’re interested in the evolution & significance of mitochondria, you can’t go past Nick Lane’s excellent book:

N. Lane (2005) Power, sex, suicide: mitochondria and the meaning of life. Oxford.

should universities offer courses in ‘alternative & complementary therapies’? Alison Campbell Jan 26

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An article in the Sydney Morning Herald tells its readers: Scientists urge unis to axe alternative medicine courses. According to the article,

[a]lmost one in three Australian universities now offer courses in some form of alternative therapy or complementary medicine, including traditional Chinese herbal medicine, chiropractics, homeopathy, naturopathy, reflexology and aromatherapy.

We were talking about it & my friend Aimee said, “I think the key question to ask here is whether universities are scientific bastions, educational institutes, or organisations geared towards making money.” And I agree with her. While alternative therapies/complementary medicines are certainly popular, & there’s wide public interest in them (as evidenced by stories in the NZ Heraldhere, & here) – universities surely teach critical thinking (within & beyond their science programs), & there’s little evidence of either in many CAM modalities. Nor should the hoary old argumentum ad populum carry weight in scientific circles: just because an idea is popular, doesn’t mean it’s correct.

In other words, universities are educational institutions offering research-based, evidence-based programs in science & other disciplines, & subjects that lack that strong basis should have no place in their curricula. As the newly formed Australian lobby group, Friends of Science in Medicine, said in its letter to Australian vice-chancellors,

by giving “undeserved credibility to what in many cases would be better described as quackery” and by “failing to champion evidence-based science and medicine”, the universities are trashing their reputation as bastions of scientific rigour.

Hear, hear! After all, it’s not enough to put on a course because of actual or perceived student demand. The program also needs to be academically rigorous. And applying that rigour to an examination of the content should enough to see offerings such as homeopathy out the door. After all, claims that the homeopathic treatment for burns is more heat, or that homeopathic plutonium is a valid treatment for anything, are easy to test (& to find wanting). And explanations for its mode of action fly in the face of all we know od how the world works. The same is true for many other CAMs (& don’t get me started on leeches!).

chris stringer talks about human origins Alison Campbell Jan 26

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Just a heads-up for teachers & students: next month Chris Stringer will be giving public lectures on human evolution in Auckland, Wellington, Christchurch & Dunedin. (No Hamilton talk! I am sad :-( I’ve got an all-day meeting that means I’d never get up to the Auckland  event in time.) From the latest Royal Society “Alert”:

Professor Chris Stringer: ‘Origin of our species, Neanderthals and the Early Human Occupation of Britain and Europe’, February 2012

Professor Chris Stringer answers some of the big questions:  How can we define modern humans, and how can we recognise our beginnings in the fossil and archaeological record? How can we accurately date fossils, including ones beyond the range of radiocarbon dating? Has human evolution stopped, or are we still evolving? What can we expect from future research on our origins?

Professor Chris Stringer is in New Zealand by invitation of the Allan Wilson Centre for Molecular Ecology and Evolution and his public talks are supported by the Royal Society of New Zealand.  Details for booking tickets are available at http://www.royalsociety.org.nz/events/origin-of-our-species/

  • Auckland, 6.00 pm, 22 February, Auckland War Memorial Museum;
  • Christchurch, 6.00 pm, 23 February, C1 Central Lecture Theatre, University of Canterbury;
  • Dunedin, 6.00 pm, 24 February, St David Lecture Theatre, University of Otago;
  • Wellington, 6.00 pm, 25 February, Embassy Theatre, Courtenay Place.

web 2.0, postmodernism, & attitudes to science Alison Campbell Jan 25

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A new post by Orac discusses various tactics of the anti-vaccine movement, with reference to a new paper published in the journal Vaccine. (Link is to a pdf - apologies if this isn’t accessible to all as it’s well worth the time spent reading.) In the paper (entitled Anti-vaccine activists, Web 2.0, and the postmodern paradigm — An overview of tactics and tropes used online by the anti-vaccination movement), Anna Kata comments on how the combination of ready access to information via internet search engines, combined with a post-modern attitude to science as a means of viewing the world, have enhanced the spread and uptake of anti-vaccination messages.

In fact, you could argue that this combination enhances the spread of pseudoscience per se. For that reason I found Anna’s concluding statement particularly valuable & (like Orac) have reproduced it here (with bolding for emphasis):

… [F]inding common ground with those who question, fear or crusade against vaccines** is no easy task. Their arguments are constantly shifting and evolving – this has been furthered by the fluidity of the Internet and social media. While acknowledging and correcting flawed arguments is important, an approach that moves beyond providing “the facts” is likely needed. With the anti-vaccination movement embracing the postmodern paradigm, which inherently questions an authoritative, science-based approach, “facts” may be reinterpreted as just another “opinion”. This issue is as much about the cultural context surrounding healthcare, perceptions of risk, and trust in expertise, as it is about vaccines themselves. For these reasons it is possible the minds of deeply invested anti-vaccination activists may never be changed; therefore it is for both the laypersons with genuine questions or worries about vaccines and the healthcare professionals who work to ease their fears that keeping abreast of the methods of persuasion discussed here is essential. Recognising anti-vaccine tactics and tropes is imperative, for an awareness of the disingenuous arguments used to cajole and convert audiences gives individuals the tools to think critically about the information they encounter online. It is through such recognition that truly informed choices can then be made.

** or in favour of other modalities

Kata A. Anti-vaccine activists, Web 2.0, and the postmodern paradigm — An overview of tactics and tropes used online by the anti-vaccination movement. Vaccine (2011), doi:10.1016/j.vaccine.2011.11.112

scientists have cured cancer! – or have they? Alison Campbell Jan 21

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The other day my friend Renee sent through this link, & her thoughts. ”This article (& website) set my woo-ometer off big time,” she said. The article’s entitled Scientists cure cancer, but no one takes notice, and begins thusly:

Canadian researchers find a simple cure for cancer, but major pharmaceutical companies are not interested. Researchers at the University of Alberta, in Edmonton, Canada, have cured cancer last week, yet there is a little ripple in the news or on TV.

“The comments make fascinating and infuriating reading,” Renee commented, citing one in particular:

Cancer is a VERY hyped up misunderstood disease, Im gunna look into this this is very interesting, but cannabis, mdma, turmeric, milk thistle, and many other natural herbs & super foods, a diet rich in real nutrition & super foods will prevent it, so will using cannabis, our endocannabinoids are our natural defense ageist [against] caner also which is why cannabis cures cancer, cannabis supplements our endocannabinoids with its own the only 2 sources found naturally with a system tied into just about every system in our body’s.

Let’s deal quickly with our commenter, who seems to have a rather strong focus on the use of cannabis, along with channelling people like Mike Adams. (I did wonder if s/he was one of Orac’s very few banned commenters, who had a similar one-track mind.) Their statements about cannabis preventing or curing cancer are easily checked by looking at whether regular users have a lower incidence of cancer than the rest of the population. And this has been done. This study (PubMed is our friend) found that use of marijuana/cannabis didn’t increase the risk of cancer overall, & “was not associated with tobacco-related cancers”, but that there was some indication that it might increase the risk of “site-specific cancers” (prostate & cervical). Other studies have similar findings, but our commenter needs to remember that ‘no increased risk’ is not the same as ‘no risk’.

Now, on to the original article, which was posted on May 15 last year. Scirus & Google Scholar are also our friends – and neither of them turn up any 2011 press releases from the University of Alberta, Edmonton, let alone a scientific paper from that year demonstrating that DCA cures cancer. This is a rather large red flag, although going back a year or so we do find that University of Alberta (UofA from now on) researchers published some preliminary work back in 2007 (the link’s to a popular article based on a university press release). The American Cancer Society treated this release with a certain level of skepticism.

And there are other red flags. First up, cancer is not a single disease, and it is highly unlikely that there will be one single, unitary cure. (If you’re interested in learning more, I highly recommend Siddhartha Mukherjee’s superb book The Emperor of all Maladies: a biography of cancer.) And the article contains some rather basic biological errors: for example, its author describes mitochondria as “natural cancer fighting human cells”, & of glycolysis as being less effective at fighting cancer. None of this gives me any confidence in the accuracy or veracity of the article.

What the UofA researchers actually said was that cancer cells seem to suppress the action of their mitochondria (the site of aerobic respiration in our cells), moving to glycolysis for ATP release. This makes them extremely hungry for glucose, because the cells need energy to grow but can gain only a little ATP from each molecule of glucose. Drugs that target this abnormal metabolism could be a signficant tool in treating cancer. In the UofA research, when isolated (in vitro)cells from a number of different human cancers were exposed to dichloroacetate (DCA), the chemical seemed to switch the mitochondria back to normal metabolic pathways & reduce the proliferation of tumour cells. It also appeared to shrink tumours in rats – all rather promising, you’d think. But that’s all it is, a potential treatment that has so far undergone a phase I clinical trial, discussed here by Orac. (Interestingly, the article Renee sent me doesn’t mention this trial at all, suggesting it’s simply a re-hash of an even earlier posting.)

Orac notes that this trial involved two aspects – looking at the effect of DCA on excised glioblastomas (a type of brain cancer), & examining its effects on 5 patients with glioblastoma. He also points out a shortcoming of the trial – that the patients were also receiving other chemotherapeutic drugs, together with surgery &/or radiation. This means that it’s very hard to tease out any impact of DCA alone, which makes claims about its efficacy rather premature.

I’m afraid I do have a tendency to cynicism, & my cynical side wonders if the post that Renee came across was written in order to increase sales of DCA… Certainly there are a number of purveyors of this chemical, many of whom would have us believe that doctors & pharmaceutical companies have a vested interest in preventing people from gaining access to this ‘miracle cure’. Which is a long way from reality. Here, to wrap up, is Orac’s take on it:

Balancing harms versus benefits, risks and rewards, all the while doing the best for each patient that we can is very, very hard. One has to remember that cancer is not just one disease. Not only that, but even a single type cancer is often not just one disease. As I have written extensively about before, cancer is incredibly complex. Because of that complexity, it’s incredibly unlikely that any one drug will be any sort of “magic bullet” to cure cancer. Worse, simply using a drug like DCA outside the auspices of well-designed clinical trials will virtually guarantee that we will never know for sure whether the drug actually works. Because of that, as frustrating as it is, as slow as it is, letting science take its course to determine if DCA works, how it works, and for what cancers it works is the best method to make sure that the most patients are helped and the fewest are harmed. I don’t say this because I want DCA to fail; I say it because I want DCA to be shown to be an efficacious treatment for cancer.

We need all the good treatments we can get.

(After I wrote this I found that PZ also blogged about the story when it first came out. For those who are interested, he explains in some detail why DCA’s ability .)

it must be the silly season Alison Campbell Jan 16

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… not only do we have at least one homeopath using heat to treat burns (yes, really! That piece of burning stupid – to use an Oracian aphorism – is admirably covered here by Grant), but we also have the Daily Mail announcing that scientists have discovered – ta-daah! – a hangover cure (hat-tip to David Winter for passing the story on):

New drug lets you enjoy a drink without getting drunk, and wake up without a hangover – at least if you’re a rat

Well, at least they mention that the work’s been done in rats, which is a step up from many such reports (although I suspect that the first clause is what most readers will remember). What else do they have to say? From the sub-header we learn that the drug

  • [was] extracted from [an] ancient Chinese remedy
  • stops hangovers, prevents rats passing out

and that

  • rats given [the equivalent of] 20 beers in two hours…. recovered their balance in 15 minutes [when given the drug].

The drug is “now moving to tests in humans.”

O-Kay…

The drug in question is called dihydromyricetin, or DHM, “a flavonoid component of herbal medicines.” It’s not unknown for ‘ancient remedies’ to turn out to actually have some pharmaceutical benefits. Think willow bark, for example. So we can go with that. But this ‘stops hangovers’ bit – how on earth would they know? (Hint: the research was done on rats, which I seriously doubt go round groaning “oh my aching head” the morning after.)

Anyway, what was the actual scientific study about? The full article is behind a paywall but you can read the abstract for free here. It turns out that the researchers weren’t looking for a hangover cure, & in fact were not looking at hangovers at all. They were instead looking at potential means of treating ‘alcohol use disorders’ (AUDs), which they describe as “the most common form of substance abuse” & characterise thusly:

The development of AUDs involves repeated alcohol use leading to tolerance, alcohol withdrawal syndrome, and physical and psychological dependence, with loss of ability to control excessive drinking.

In other words, they’re talking about alcoholism.

It seems that when rats were injected with DHM they didn’t develop “acute alcohol intoxication”; nor did they suffer from withdrawal symptoms. The drug also cut back on the animals’ drinking. It seems to do this through its effects on particular receptor molecules in the brain, some of which are inhibited and others enhanced. Identifying some of the key molecules in the brain that are involved in addictive responses to alcohol, and of a compound that seems to block the development of this addiction, opens the way for the possibility of developing a pharmacological means of treating alcoholism.

But a hangover cure, it ain’t.

Y.Shen, A.K.Lindemeyer, C.Gonzalez, X.M.Shao, I.Spigelman, R.W.Olsen & J.Liang (2012) Dihydromyricetin as a novel anti-alcohol intoxication medication. The Journal of Neuroscience 32(1): 390-401. doi: 10.1523/JNEUROSCI.4639-11.2012

Steve Novella’s BS detector Alison Campbell Jan 12

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This week I’ve found myself becoming quite frustrated with the way alternative ‘therapies’ are being presented in the NZ Herald. Two of the three described to date are – as described – essentially massage therapies (as Michael Edmonds has noted here) & hardly need the overlay of pseudoscientific claims (unless, perhaps, to gain wider acceptability?). The third, so-called hirudotherapy, has the potential to do real harm – as Siouxsie and I have both pointed out – and lacks any evidence for several of its claims. And I’m left wondering why the journalists concerned don’t appear to be querying any of the claims made for & about these various modalities.

Which leads me to think that Steve Novella‘s BS** detector needs to be very widely read & discussed. There’s a full article about this in last September’s The Skeptic magazine, but the key points are summarised below. Useful in science classrooms – heck, in any classroom! – and in newsrooms as well. As Steve notes, “raising the red flag or activating your BS detector doesn’t mean it’s going to be BS in the end”, but what follows is a a list of questions that we should all ask when presented with a new claim where we can’t be sure whether or not it’s actually legit:

  • How extraordinary are the claims?
  • How many different conditions are claimed to be treated by one modality?
  • What is the mechanism?
  • What is the plausibility?
  • Is the treatment generally accepted or promoted by a single individual or group?
  • Are there claims for a conspiracy of suppression?

It would be a useful ‘nature of science’ classroom exercise to revisit the Herald‘s articles with these questions in mind.

** BS = bovine excrement

Steve Novella (2011) The BS Detector. The Skeptic 31(3):11-15 (the magazine of the Australian Skeptics, www.skeptics.com.au)

leeches & health – asking some questions Alison Campbell Jan 10

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This morning’s Herald ran an article on ‘alternative therapies’ - New Zealanders’ beliefs about their effectiveness, & a Herald reporter’s experience of one such ‘therapy’. (Apparently there will be more to come over the next few days.) The article presented some results from a recent UMR research poll – as it was provided ‘exclusively to the Herald’ I wasn’t able to read the whole thing – which apparently show that around 75% of those surveyed believe that arnica reduces bruising (which it may well do, provided we’re talking therapeutic & not homeopathic concentrations), while 51% believe that homeopathy has been scientifically proven. Sigh. (The article also cited a 2008 Massey University study, which I wrote about at the time it came out.)

So I suppose I shouldn’t have been surprised to read on & find that the reporter who tried hirudotherapy (ie blood-letting using medicinal leeches) didn’t actually question any of the claims made for this particular treatment modality.

Apparently, ‘leech therapy’

has “gone global” since Greek physician Nicander in Colophon was recorded as using them in 200 BC.

Well, yes – leeches have a long history of medical use. Much of this was at a time when people believed things such as health being a matter of balancing the four ‘humors’, and that imbalances could be dealt with by bleeding the patient. This could be done using either a scalpel, or a leech. Given that the germ theory of disease was well in the future & standards of surgical hygiene rather limited, I would have gone for the leech every time. Although – there would still be the risk of picking up a real blood-borne illness from the last patient to be sucked on (see below). However, leeches have come back into favour & are used in some aspects of mainstream medical practice.

The practitioner featured in this article told the reporter that

medical leeches can treat problems ranging from arthritis, diabetes, endometriosis, hepatitis and high blood pressure to bronchitis.

“Their saliva has enzymes that helps break blood clots, and widens blood vessels to stop bacteria growth and present inflammation. It also helps blood circulation and flow,” he said.

Leech saliva does contain a rich mix of chemicals, as you’d expect in a blood-sucker. After all, the last thing a leech needs is for your body’s normal blood-clotting cascade to kick in while it’s dining, nor does it need local inflammatory responses as these would slow the flow of blood to the wound site. These constituents are listed in a 2007 article by Dr Karen Dente (emphasis mine)

  • Hirudin, a direct thrombin inhibitor;
  • Hyaluronidase, which increases the local spread of leech saliva through human tissue at the site of the would and also has antibiotic properties;
  • A histamine-like vasodilator that promotes local bleeding; and
  • A local anaesthetic.

Note the use of the word ‘local’. This is not the same as the systemic effects claimed above. Hirudin is used clinically as an anticoagulant – in controlled, measurable doses, which is not what you’re going to get by using individual leeches.

What about these claims of the problems leeches can be used to treat? (It would have been nice to see the reporter asking this!) While it’s possible that a leech’s kiss might have some impact on circulatory issues, what about bronchitis? Hepatitis? Diabetes?

I can actually think of a potential mechanism for their use in treating some of the sequelae of diabetes, where peripheral circulation may be reduced. But how on earth is leech saliva going to address the root problem with diabetes ie the body’s inability to produce (Type 1) or to respond to (Type 2) insulin? Certainly a PubMed search turned up nothing for ‘leeches + diabetes’ (or ‘hirudo + diabetes’, come to that).

As for hepatitis, the various types are due to viral infections that target the liver. Off we go to PubMed again. It turns out that the virus that causes hepatitis B can persist in a leech’s gut for up to 15 weeks. This alone should rule out the use of leeches in anything other than controlled, use-once-and-discard circumstances. And again, there is nothing on PubMed relating to therapeutic uses of leeches for people with hepatitis. (Nothing, also, for bronchitis or endometriosis…)

The medicinal hirudo leeches, which are used at his clinic, can help reduce wrinkles and stimulate circulation in reattachment operations for organs with critical blood flow, he claims. “These creatures are God’s gift to nature, and nature’s gift to mankind to keep us in good health.”

That’s a really strange juxtaposition – a minor cosmetic issue and a major surgical problem! Anyway, while it is indeed correct that leeches are used in reattachment operations where circulation is an issue (for example, reattachment of an ear), unless these leeches are used on a ‘once only & then discard’ basis, there’s the potential for bad health outcomes too, if a prior customer was carrying hepatitis…

NB neither antiquity nor popularity are, by themselves, a good indication that something actually works.

________________________________________________________________________________

Over at Respectful Insolence, commenter lilady tells me that an Austrian version of hirudotherapy involves “bathing in turpentine, shaving certain areas of [the] body, and then letting the leeches suck your blood.” One celebrity endorsing this ‘treatment’ says that “These are not swamp leeches, they are ‘highly trained’ medical leeches.

I suspect the humour in this statement was not intentional.

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