Musings -- January 2018 to ?? (current posts)

Musings is an informal newsletter mainly highlighting recent science. It is intended as both fun and instructive. Items are posted a few times each week. See the Introduction, listed below, for more information.

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   January 17 (Current e-mail)
   January 10    January 3

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New items

Posted since most recent e-mail; they will be announced in next e-mail, but feel free...


Monkey malaria in humans?

January 19, 2018

If we are going to keep track of diseases, and try to reduce them, it would help if we really knew what caused them.

A recent article illustrates the problem. It shows that an outbreak of malaria was not caused by the usual suspects, but by a distinct pathogen: a monkey malaria parasite, Plasmodium simium.

The common human malaria pathogens are P falciparum and P vivax. About twenty other malaria parasites are known for primates, eight of which are known to be able to infect humans. P knowlesi, whose primary host is macaque monkeys, causes considerable human malaria in Southeast Asia. Except for that, it is thought that most human malaria is transmitted (by mosquitoes) from other humans. Transmission of malaria from non-humans to humans -- so-called zoonotic transmission -- is considered uncommon.

What now? The short version of the story is that (human) malaria recently reappeared in a region of Brazil from which it had been eliminated. It appeared to be vivax malaria. However, the new work shows that it was actually simium malaria, which is known to be in the area. Why the confusion? The two parasites are hard to tell apart -- except by using modern molecular techniques. In the new work, the scientists used sequencing of the mitochondrial genome.

Does it matter? Well, it may not matter to those who got sick. But it does matter to those who want to understand disease transmission. In this case, the two diseases are transmitted differently. One is transmitted between humans, whereas the other is transmitted from monkeys to humans. (In both cases, transmission is by a mosquito vector.)

As you read this story... What really matters is the source of the infection. It matters whether the disease is being transmitted only from humans or from monkeys. It isn't the name of the bug that matters, but the transmission pattern.

If the new malaria is indeed monkey malaria from the reservoir in the forest, it means that the disease had never really been eliminated from the region. It was merely held in check. The re-emergence may well be due to changing patterns of forest use, including for tourism.

Disease is complicated.


News stories:
* Malaria parasite spreads from howler monkeys to humans. (S Boseley, Guardian, September 1, 2017.)
* Zoonotic Malaria: Back in Southern Brazil, or Did It Never Leave? -- Potential wildlife reservoirs could threaten public health. (M Walker, MedPage Today, September 1, 2017.)

* "Comment" article accompanying the article. Freely available: Plasmodium simium: a Brazilian focus of anthropozoonotic vivax malaria? (M J Grigg & G Snounou, Lancet Global Health 5:e961, October 2017.)
* The article, which is freely available: Outbreak of human malaria caused by Plasmodium simium in the Atlantic Forest in Rio de Janeiro: a molecular epidemiological investigation. (P Brasil et al, Lancet Global Health 5:e1038, October 2017.)

You will encounter the word autochthonous in this story, especially in the article itself. It means native. In context, an autochthonous case is one that has not been imported (say by someone who had been in a region with malaria). Therefore, there must be a local (native) source.

There is apparently some uncertainty whether the vivax and simium are really distinct species, or just different strains; it doesn't matter.

* * * * *

A recent post on malaria: Malaria and bone loss (September 10, 2017).

A recent post exploring other zoonoses -- diseases transmitted to humans from other animals: Bats and the coronavirus reservoirs (July 25, 2017). Also check the linked item there on "One health".

There is a section of my page Biotechnology in the News (BITN) -- Other topics on Malaria. It includes a list of Musings posts on malaria, and on mosquitoes in general.



January 17, 2018 (Current e-mail)


A new species of orangutan?

January 16, 2018

There are three species of orangutans, not two, according to a new article.

It's not that the scientists found a new animal, but that they examined the knowns more carefully, and concluded that one population is sufficiently distinct that it deserves species status.



Pongo tapanuliensis, the Tapanuli orangutan.

Tapanuli refers to three districts in Sumatra (such as South Tapanuli).


   This is trimmed and reduced from a figure in the Mongabay news story.

Determining species is not easy. The common separation of orangutans into two species, Bornean and Sumatran, was established only in 2001. It required genome analysis to make the distinction clear.

In the new work, a team of scientists reports that one population of orangutans in Sumatra is morphologically and genetically distinct from the other orangutan species.

The work began with a single specimen of a dead animal. Features of the head, including the teeth, seemed quite distinct from what is considered normal for Sumatran orangutans. Genetic analyses, including animals from all three groups, confirmed the differences, and suggested that the new species split off from the others about 3.4 million years ago (mya). For comparison, the split between the other two orangutan species is dated at only 0.7 million years ago.

There is very limited data behind the proposal to designate a new species here. The article makes the case, but it needs confirmation, probably including more data, and discussion. The population of the proposed new species is only about 800 individuals, in a limited area -- as best they understand it now. Whether the species designation holds up or not, the work is a call for further investigation of the Sumatran orangs. The Tapanuli orangutans are at least an endangered population; they may be an endangered species.


If you are struck by the hair of the animal shown above... The authors note that the hair of this species is "frizzier" than for the others. (I doubt that any orangs use combs.)


News stories:
* Anthropologists describe third orangutan species. (Phys.org, November 2, 2017.)
* The Eighth Great Ape: New orangutan species discovered in Sumatra. (M Erickson-Davis, Mongabay, November 2, 2017.) Eight great ape species? That refers to living species. Three orangs, as discussed here; two gorilla species; chimps; bonobos; humans.

The article: Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species. (A Nater et al, Current Biology 27:3487, November 20, 2017.)

More orangs... Re-introducing captive animals into the wild: an orang-utan mix-up (June 27, 2016).

More from Sumatra... Does the moon affect earthquakes? (October 21, 2016).

More about dividing things up among species: An interesting skull, and a re-think of ancient human variation (November 12, 2013).



How long does a supernova event last?

January 14, 2018

A nova is a new object appearing in the sky. A supernova is an unusually bright nova. It is now understood that supernovae are due to stars exploding as they die. As one might expect in some general sense for an explosion, a supernova rapidly becomes much brighter; it then decays.

Here are some supernova data, from a recent article...

That's a complex figure, but we can summarize it and get the main message.

The figure shows data for the brightness of two supernova events over time. The data for one event are shown by the big colored points over the top part of the graph. The data for the other event are shown by the dashed lines at the lower left.

The big picture... The brightness for one event (iPTF14hls; top) remained high over at least the first 400 days shown here. It declined slowly after that. The brightness for the other event (SN1999em; lower left) declined dramatically over about 100-150 days.

SN1999em is a typical supernova of this type. In fact, it was thought that such supernova events could not last more than about 150 days. And that's the point: the event shown across the top lasted far longer. iPTF14hls is an unusual supernova event.

A new article presents this recent unusual supernova event. The data for SN1999em are shown for comparison.


Don't try to compare the brightness of one supernova with the other here. They are plotted on different scales -- though this is not very clear in the article. Since the spacing of magnitude units is the same on both scales, we can compare the rates of decline; that's what we want here.

And yes, the bigger the magnitude number, the less bright the object is.

The big gap at around 300 days? The object was behind the Sun during that time.

The various colors for the data are for different spectral bands. The various symbols are for different observing stations.

This is slightly modified from Figure 1 of the article. I added the label identifying the supernova for the top data set. Also, I removed some stuff at the top of the full figure that I did not want to get into.


Not only is the new event extended, but there seem to be increases in brightness along the way. For example, there is a substantial increase in brightness at about 100 days, and there is a small peak at about 200 days.

It's probably not hard to look at the new data and suggest that this is a more complex event, with multiple explosions along the way. It is as if the star is exploding one piece at a time. That's fine, but astronomers have not seen such a complex supernova event before. Further, the authors are unable to provide any simple explanation in terms of current understanding of how stars collapse and explode.

Interestingly, there is evidence that this star may have exploded a little about 60 years ago, though one cannot connect the earlier event to the current one with certainty. "Exploded a little"? That's an interesting idea in itself.

The new supernova may be an example of a pulsational pair-instability supernova. But what that really means -- what really happened here -- is not at all clear. It is something new, something that cannot be explained at this point. It is truly a scientific discovery.


News stories:
* Zombie star' cheats death again and again, dumbfounding scientists. (T Puiu, ZME Science, November 9, 2017.)
* Supernova Discovery Challenges Theories of How Certain Stars End Their Lives. (Sci-News.com, November 9, 2017.)

* News story accompanying the article: Astronomy: The star that would not die. (S Woosley, Nature 551:173, November 9, 2017.)
* The article: Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star. (I Arcavi et al, Nature 551:210, November 9, 2017.)

More supernovae...
* The major source of positrons (antimatter) in our galaxy? (August 13, 2017).
* Could you find debris from a supernova in your backyard? (April 27, 2016).



Pumping tin

January 12, 2018

You know how to pump water? You could pump tin the same way, right? Well, you would have to melt it first. And that creates a new problem: the pump must be able to operate at high temperature.

The melting point of tin is actually fairly low, only 232 °C. However, being able to pump it at much higher temperature (T) could facilitate its use in heat transfer systems. That is actually the big motivation behind the current work, besides simply demonstrating a high-T pump. In a new article, scientists develop a pump that can operate at over 1200 °C. Maybe even at 1400 °C.

Here is the plan for the pump...

Most of the figure is a diagram of the pump. In general, it looks fairly normal at this level.

At the lower left is a photo of part of the pump in action. The color is due to the heat. That's the main point of showing the figure. (The color in the upper part, which is a diagram, is artistry.)

This is trimmed from Figure 1 of the article. (I have removed one part of the figure, at upper right. The two lines going up from the gears go to the part I cut out.)


The secret to operating a pump at such a high T? The materials, of course. Ceramics. Graphite. The chemical inertness of such materials at high T is known, but ceramics can be brittle. What is novel is making a functioning pump out of them.

How well did the pump survive? The following figure shows the gears after 72 hours of operation...

Look at the gear on the right. The black line shows the original shape. You can see that there is significant wear.


   This is Figure 5 from the article.


It works, but needs improvement.

The authors note plans for such improvement. For example, they note that the gear material used here was chosen partly for convenience for initial testing; better materials are available.

The article claims that this is the highest temperature at which pumping has been demonstrated. It shows that ceramics can be used to make a high-T pump; the scientists plan work to make it practical. They even envision going on to pump silicon. The melting point is 1420 °C, and they would hope to pump it at over 2000 °C. Pumping molten tin or silicon could be a good way to transfer energy.


Video: Pumping Liquid Metal (Tin) at 1200C (~2200F). (YouTube, 2 minutes.) Interesting, but not well labeled. Background music, but no useful narration. Some of it is too fast to follow at a single viewing.


News stories:
* Pumping liquid metal at 1,400 °C opens the door for better solar thermal systems -- A ceramic pump can handle the heat; careful engineering prevents it from cracking. (M Geuss, Ars Technica, October 13, 2017.)
* Ceramic pump moves molten metal at a record 1,400 degrees Celsius. (Phys.org, October 11, 2017.)

* News story accompanying the article: Engineering: Liquid metal pumped at a record temperature . (K Lambrinou, Nature 550:194, October 12, 2017.)
* The article: Pumping liquid metal at high temperatures up to 1,673 kelvin. (C Amy et al, Nature 550:199, October 12, 2017.)

Posts about pumping include...
* Lamb-in-a-bag (July 14, 2017).
* pH and the color of petunias (March 26, 2014).
* Caltech engineer turns rat into jellyfish (September 22, 2012).

Previous posts about tin: none.



January 10, 2018


A look at Chopin's heart

January 9, 2018

That's it.

It's in a jar of a brown fluid, which is probably cognac.


   This is the Figure from the article.


Frederic Chopin died in 1849. His heart was removed from his body, according to his wishes. It was put in a bottle, as shown above, and given to his sister. The heart is now at a church in Warsaw, and is examined from time to time.

Chopin was only 39 when he died, and the cause of his death has never been clear.

A new article reports briefly on the most recent examination of Chopin's heart, in 2014 -- 69 years after the previous examination.

Among the prominent findings are three lesions near arrow A in the figure. The authors note that these are most likely from tuberculosis.

Arrow B points to stitching to the left ventricle, following its opening during the autopsy.

There is more, but not much more. It's a two-page article, with observations and some interpretation -- and much uncertainty. Heart specialists may enjoy the detail. But the big story here is the big picture: the preservation and examination 165 years later of Chopin's heart.


News stories, both of which provide good overviews:
* Chopin's Preserved Heart May Offer Clues About His Death -- Scientists who recently examined the organ have suggested that Chopin died of complications from tuberculosis. (B Katz, Smithsonian, November 9, 2017.)
* Examination of Chopin's pickled heart solves riddle of his early death -- Scientists diagnose rare complication of tuberculosis following analysis of heart stored in jar of cognac for 170 years. (R McKie, Guardian, November 4, 2017.) Overstates the conclusions, but still, a useful story.

The article: A Closer Look at Frederic Chopin's Cause of Death. (M Witt et al, American Journal of Medicine, in press.)

Previous heart post: Heart regeneration? Role of MNDCMs (November 10, 2017).

Another examination of an old specimen for possible TB... A new approach for testing a Llullaillaco mummy for lung infection (August 17, 2012).

There is more about music on my page Internet resources: Miscellaneous in the section Art & Music. It includes a list of related Musings posts.



In the aftermath of gun violence...

January 8, 2018

Guns are a political issue in the United States.

In December 2012 a gunman went into the Sandy Hook Elementary School in the US state of Connecticut and killed 20 children (and six adults). Such a mass killing, especially of children, provokes debate about gun laws -- a least for a while.

A new scientific article reports some data about guns, in the context of the Sandy Hook incident.

The question the authors examined is... What is the effect of a major shooting, which becomes a major news event, on subsequent gun events?

The following figure summarizes some of the main findings...

The graph plots data for two gun-related phenomena over time. One is shown as blue bars; the other is shown as a black line.

A quick inspection of the graph shows that both phenomena reached a peak in early 2013 -- immediately after the Sandy Hook event.

What are these two phenomena? The graph labels them well. The black line shows sales of guns in the US (left-hand y-axis). The blue bars show accidental gun-related deaths of children (right-hand y-axis). (The death data is given as deaths per 100,000 population per month.)

In both cases, the data is shown in a way that emphasizes the variation from "average". Zero is the average value over the time period. There is nothing of particular interest except for the peak values already mentioned. The magnitudes of the values at that peak were the largest magnitudes found, whether positive or negative.

   This is Figure 2 from the article.


That is, the Sandy Hook event, with its news coverage, was quickly followed by a burst of gun sales and accidental gun-deaths of children.

The data above for accidental deaths of children is given as a rate, and compared to the average. We can add that the blue bar for that peak period represents 18 deaths above the average -- an increase in the absolute death rate of about 60%. (There were also 39 extra deaths of adults. The overall increase in the gun-death rate was about 20%.) Note that these numbers are all for accidental deaths from guns, not criminal activity.

The graph shows a correlation; it does not show there is a causal connection. However, if we assume, for the moment, a causal connection... It may be good to note that most people who responded to Sandy Hook had no direct connection with the original event itself. The results shown above are national data. Most who responded -- if indeed the data shown are a "response" -- knew of the story only through the news media, including the political discussion.

I will just leave it at that: an example of collecting evidence about the effect of guns. There is no claim that we understand what is behind the data shown here, or that this is the complete story. And it is not for me to get into the political issues.


News stories:
* Sandy Hook shooting aftermath: Increased gun sales, more accidental deaths by firearms. (EurekAlert!, December 7, 2017.) Includes some general discussion of gun issues, including the importance -- and difficulty -- of collecting data.
* After a Mass Shooting, a Surge in Accidental Deaths -- Research on the Sandy Hook massacre shows public focus on firearms after a massacre leads to more tragedy, particularly among children. (P Mosendz, Bloomberg, December 7, 2017.) An example of coverage by the general news media.
* Sandy Hook mass shooting triggers weapons purchase. (K Jaramillo, LatinAmerican Post, December 17, 2017.) A view from outside the US.
* Wellesley Faculty Find that a Jump in Gun Sales and Accidental Gun Deaths Followed the 2012 Sandy Hook Shootings. (Wellesley College, December 8, 2017.) From the lead institution -- a two-hour drive from Sandy Hook. Links to several news stories in the mainstream general media.

* "Policy forum" accompanying the article: Gun-violence research: Saving lives by regulating guns: Evidence for policy. (P J Cook & J J Donohue, Science 358:1259, December 8, 2017.) This is a broader discussion of gun violence and gun laws. The emphasis is on right-to-carry laws. There is only minimal discussion of the current article,
* The article: Firearms and accidental deaths: Evidence from the aftermath of the Sandy Hook school shooting. (P B Levine & R McKnight, Science 358:1324, December 8, 2017.)

More about human violence...
* Violence within the species -- in various mammals; implications for the nature of humans (December 6, 2016).
* Human violence (November 28, 2011).

The previous mention of a gun was in the post What happens when a lithium ion battery overheats? (February 19, 2016). It was a heat gun in this case.



A "greener" way to make acrylonitrile?

January 6, 2018

Acrylonitrile, for use in making polymers and carbon fiber, is made from petroleum. A new article offers a possible new way to make it from a biological product.

The following figure outlines the process, and shows some data for an early version.

Start with Part B, on the right. This shows the new process, at two levels of detail. It's not important to follow all the detail, especially at the start, but we will use some of it as we go along.

The bottom section of Part B shows the overall process (equation 4). Compound 5 is converted to compound 7. Compound 7 is acrylonitrile, the desired product. Compound 5 is the ethyl ester of 3-hydroxypropanoic acid. Previous work had established a bacterial fermentation to make compound 5 from sugar; it is the starting material here.

The top two sections of Part B show the two steps -- one on each end of the starting compound. The first step is dehydration: removing the -OH group and an -H from the next C, leading to a double bond (equation 1). That gives compound 6, an intermediate here. The second step is to remove the ester group, and replace it with a nitrile group (equations 2-3). That gives compound 7, the desired product.


Part A shows an example of how this works. In this case, the overall process was run at various temperatures (T). The graph shows what happened as a function of T. For example, at the lowest T (150 °C), the process led to about 90% of the original compound 5, and 10% of the intermediate 6. There was essentially none of the desired product 7. That is, not much happened at this low T. With higher T, more and more 7 was obtained, reaching over 50% at the highest T shown here. The level of 6, the intermediate, first rises with T, then falls -- as more is converted to the final product.

The top line in the graph (labeled "8")? It's pretty much flat, at 100%. That's good; that's the sum of all the chemicals they analyzed. It's a test to see that the analyses make sense; all of the material is accounted for.

This is slightly modified from parts of Figure 1 in the article. I added more numbers for labeling. The authors numbered reactions 1-3 in part B. I added the numbers 4-8 for various equations, chemicals, and lines.


That's the idea, but the best yield is not very good. The authors went further, and did the two steps separately. The first step is done at a fairly low T, making the intermediate, compound 6. That product stream is passed on to a second reactor, at a higher T. Doing the two steps separately, at different T, leads to an overall yield of the desired product of about 98%. Excellent!

In addition to avoiding petroleum and having a high yield, the proposed process is actually simpler than the current process. And it avoids the release of hydrogen cyanide (HCN), so it may be safer, too. Nevertheless, we emphasize that the article is a presentation of something new, with only small-scale testing.

The article summarizes an economic projection for the process, suggesting that the product cost would be competitive with current prices, based on petroleum. These numbers are encouraging. However, the current price fluctuates, depending on market forces, and the projected prices have considerable uncertainty. Further, cost projections for new processes are usually optimistic. If nothing else, it takes a while to get a new process running efficiently.


News stories:
* A Sweet Approach to Renewable Acrylonitrile Production. (S Himmelstein, Engineering 360 (IEEE), December 8, 2017.) Includes a flow chart of the overall proposed process, as shown in Figure 3 of the article.
* NREL Develops Novel Method to Produce Renewable Acrylonitrile. (National Renewable Energy Laboratory (NREL), December 7, 2017.) From the lead institution.

The article: Renewable acrylonitrile production. (E M Karp et al, Science 358:1307, December 8, 2017.) Check Google Scholar for a freely available copy.

A post about acrylonitrile polymers: Fixing the heart with some glue and light (July 27, 2014). Acrylonitrile is called cyanoacrylate in this earlier post. As usual in organic chemistry, the prefix cyano and the suffix nitrile are interchangeable.

Another post proposing an improved way to make a chemical used in plastics: A simpler way to make styrene (July 10, 2015).

A post about use of titanium dioxide as a catalyst: Photocatalytic paints: do they, on balance, reduce air pollution? (September 17, 2017).

A broad view of plastics... History of plastic -- by the numbers (October 23, 2017).



Treating obesity: A microneedle patch to induce local fat browning

January 5, 2018

This post ties together several issues that have come up before. They include...
- brown fat, especially the more specific issue of beige fat;
- the implications of developing beige fat for obesity, and also for diabetes;
- the use of microneedle patches to deliver a drug through the skin.

There are some background links about those issues at the end, but the key biology issue is the beige fat. Our traditional view of fat is that it is an energy reserve. We store fat for later use, when food is scarce. Of course, if we don't use it later, we get obese. We now recognize a second type of fat cell, which actively burns fat molecules -- without collecting the energy in any useful form, except heat. This "thermogenic" fat is called brown fat. (Its brown color is due to a high level of mitochondria, with their brown cytochromes.) Beige fat is a type of brown fat; more specifically it is brown fat made from the ordinary storage (or "white") fat. Since brown fat burns food without collecting the energy, it seems logical that it might be useful in preventing weight gain. Since the brown fat affects energy metabolism, perhaps it would have an impact on diabetes.

The stories of brown -- and especially beige -- fat are fairly new. We are beginning to understand them, but still have little idea how we might make use of the information.

A new article explores a way to exploit beige fat. The scientists have a drug that stimulates the conversion of ordinary white fat calls to beige fat cells. They deliver the drug, locally, through the skin by use of a microneedle patch. They then observe what happens.

The study is done with mice, with diet-induced obesity.

Here is the idea...

Start with the layer of skin. Below it are some fat cells (adipocytes). Above it is a microneedle patch, labeled "browning agent patch", with three of the needles penetrating the skin.

The patch contains a drug called rosiglitazone (Rosi), which is packaged in nanoparticles (NP) in the patch. The drug is slowly released under the skin. It then converts some of the white fat cells to beige fat cells.

   This is the Figure from the abstract of the article.


Here is an example of the results...

This is a glucose tolerance test. A big dose of glucose is given; the blood sugar level is measured over time. You can see that it rises rapidly due to the glucose that was given. It then falls.

The two main curves here are "EV" (blue, top) and "Rosi" (red, bottom). Rosi is the drug; EV stands for empty vehicle -- a mock needle patch without any drug.

You can see that the mock EV treatment shows a high peak glucose level, but the Rosi treatment results in a lower peak.

There is a third curve, labeled "CL" (green). It is for a different drug. The results for the two drugs, Rosi and CL, are similar.

   This is Figure 5c from the article.


The results show that the drugs improved glucose tolerance in this mouse model. Other data show that the drugs reduced weight gain. Overall, the article shows that induced browning of fat can be of practical benefit, and that the microneedle patch is an effective delivery tool. The patch allows local slow-but-sustained delivery; it may be a "gentle" way to provide the drug. Thus it may minimize some of the problems that have been observed with systemic delivery of such drugs.

We noted at the outset that our understanding of brown and beige fat is new and limited. That holds, too, for steps toward treatment. The current article is an interesting step, but it is important to understand how early it is.


News stories:
* Microneedle skin patch that delivers fat-shrinking drug locally could be used to treat obesity and diabetes. (Phys.org, September 15, 2017.)
* Nanoparticle Drug Delivery Patch for Obesity Treatment. (B Cuffari, AZoNano, September 21, 2017.)

The article: Locally Induced Adipose Tissue Browning by Microneedle Patch for Obesity Treatment. (Y Zhang et al, ACS Nano 11:9223, September 26, 2017.)

Background posts include ...
* Beige fat, with a connection to obesity: An obesity gene: control of brown fat (October 2, 2015).
* A post on diabetes, including glucose tolerance tests: Making a functional mouse pancreas in a rat (February 17, 2017).
* Microneedle patches: Clinical trial of self-administered patch for flu immunization (July 31, 2017).

More on diabetes is on my page Biotechnology in the News (BITN) -- Other topics under Diabetes. That includes a list of related Musings posts.



January 3, 2018


Diagnosing diabetes in people of African ancestry: a race-dependent variable

January 3, 2018

Diabetes is a disorder that affects the level of glucose in the blood. Of course, blood sugar level varies. A single measurement of the level is just one snapshot.

One way to diagnose diabetes is to measure a stable change that accumulates over time depending on the blood sugar. A useful example is glycated hemoglobin, a product of the hemoglobin reacting with the sugar. A single measurement of glycated hemoglobin integrates the entire history of the person's blood glucose level over the lifetime of the red blood cells (RBC).

It is known that there are factors other than diabetes that can affect the level of glycated hemoglobin, but doctors still find the measurement useful. for both diagnosis and monitoring.

A recent article reports a special problem with the glycated hemoglobin measurement in people of African ancestry.

The following graph summarizes some of the key results. We'll work through it slowly; it takes a while to get to the important data.

The y-axis shows the amount of glycated hemoglobin found in the blood of various groups of people. All the people studied here were thought to be free of diabetes.

The x-axis is labeled by ancestry and GS. The GS is the genetic score, a measure of how many genetic variants the person has that seem to have some effect on the glycation level.

To get the idea of the graph, look at the first group of measurements, at the left. These are for people of European ancestry. The three points are for the lowest 5% of the distribution, the middle 90%, and the top 5%. The values for glycated hemoglobin range from about 5.2 to 5.6 for these points. This shows that genetic variation does affect the level of glycation.

The second group of three points is for a sub-population of those of European ancestry. The results are similar.

The next two groups of data are for people of Asian ancestry. For these people, the range of values is smaller.

And now, the "important" part... The next two data sets are for people of African ancestry. There is a now a very wide range of values. In particular, the scores for the lowest 5% of those of African ancestry are very low compared to the scores for the other groups.

   This is Figure 5 from the article.


That is, some people of African ancestry have an unusually low level of glycated hemoglobin. This is shown on the graph by the average value for the lowest 5%. It is about 5.0 for Africans, over 5.2 for the other groups.

What is it due to? A particular mutation in the gene for the enzyme glucose-6-phosphate dehydrogenase (G6PD). This is a gene on the X chromosome, so men have only one copy. Look at the last (right-most) set of data on the graph above. It is for African-ancestry men ("AA men"). Those who have the base T at this site have a glycated hemoglobin level of about 5.0. Those who have C at that site have about 5.8.

Next to that data set are the results for AA women. They have two copies of the gene, of course, so the situation is a little more complicated. But the general pattern is the same. T leads to low glycation.

What does this mutation do? It affects the lifetime of the RBC. The allele with T leads to short-lived RBC. If the RBC don't live as long, they don't accumulate as much modified hemoglobin. That is, we understand how the T allele leads to low glycation.

The point is that the T allele could interfere with the diagnosis of diabetes, by leading to a low level of glycation that is not reflecting the actual blood sugar level. The authors note that this T allele is almost unique to people of African ancestry. About 11% of African Americans have a T; "almost no one of any other ancestry" [author summary, p7] has it. It thus seems clear that this is a race-related variable that could bias the detection of diabetes.


The current article does not provide specific information on how the newly discovered mutation affects glycation level in diabetics. That remains for future work, as does then working out what an appropriate response should be. For example, it might be appropriate to check for the G6PD mutation as part of diabetes screening, at least for those of African ancestry.


News story: Type 2 diabetes is being misdiagnosed in African-Americans, genetic study suggests. (EurekAlert!, September 12, 2017.)

The article, which is freely available: Impact of common genetic determinants of Hemoglobin A1c on type 2 diabetes risk and diagnosis in ancestrally diverse populations: A transethnic genome-wide meta-analysis. (E Wheeler et al, PLoS Medicine 14:e1002383, September 12, 2017.)

Other posts about race differences include...
* Alcohol consumption, an "ethnic" mutation, and a possible new drug (October 28, 2014).
* Why African-Americans have a high rate of kidney disease: another gene that is both good and bad (August 17, 2010).

Previous post on diabetes... Making a functional mouse pancreas in a rat (February 17, 2017).

There is a section of my page Biotechnology in the News (BITN) -- Other topics on Diabetes. It includes a list of related Musings posts.

Another effect of some mutations in the G6PD gene: Genes that protect against malaria (January 19, 2010).



The spider with the mostest ... (and such)

January 2, 2018


Most mass... Specimens of this spider as heavy as 170 grams have been found.

It is Theraphosa blondi, the Goliath bird-eater.

170 grams is more than 1/3 of a pound. More than an ordinary hamburger patty.

This spider is also one of the "Most delicious." Roasted.

   This is reduced from the first figure in the news story by Moscato. Figure 3A of the article shows a specimen of this spider, but the figure here is better for sense of scale.


And at the right...


Most web... As much as 2.8 square meters.

Made by a Caerostris darwini, Darwin's bark spider.

The creature at the bottom is presumably about 2 meters tall -- or at least was before the photographer truncated him. The spider? Don't know if it is visible in there. However, there is one featured in part e of the full figure in the article.


   This is Figure 3f from the article.


There are 96 more spider records in the article. Some are quantitative, some qualitative or subjective (such as "most delicious", mentioned above). Some are the biggest for some feature, some the smallest. Most are about the spiders themselves from nature. A few are about odd things from the lab (such as a ten-legged spider); a few are about those who study spiders.

Let's end this with a quiz... The spider Dipoena santaritadopassaquatrensis. What record does it hold? You may be able to guess from the information given here. You can check yourself in the article.


News stories:
* Only the very best make it into the 'spider world records'. (D Moscato, Earth Touch News, November 6 2017.)
* Ninety Nine World Records. (A Reis, Lab Times, November 16, 2017.)

The article, which is freely available: Record breaking achievements by spiders and the scientists who study them. (S Mammola et al, PeerJ 5:e3972, October 31, 2017.) It's fun to browse. The authors' purpose is to promote interest in spiders. There are many pictures, though perhaps not enough.

The article says that the spider records will be maintained -- and updated -- as a web page at the site for the International Society of Arachnology. I don't see it there, so maybe it is just a plan for now. If anyone finds it, let me know.

* * * * *

Among spider posts in Musings...
* How a spider can help you do better microscopy (September 9, 2016). Most recent spider post.
* What to do if your brain won't fit in your head (February 18, 2012). The spider discussed in this post is noted under "largest central nervous system."
* How to seat a spider in front of the computer (September 28, 2010). The purpose here is to give the spider an eye exam. That's not easy with a spider, especially one that has eight eyes. The article notes various things about spider vision -- and hearing. Also, jumping spiders (a large group) are often mentioned.
* Spiders (December 21, 2009). Peacock spiders. The winner for "most elaborate courtship." This post also notes (with pictures) the happy-face spider. It's relative, the Caribbean smiley-faced spider, is the winner for "genus with most species named after celebrities."
* The vegetarian spider (October 21, 2009). The winner for "strangest diet."

The last time Musings started a new year with a post on arthropods... A new year (January 1, 2010).



Older items are on the archive pages, starting with 2017 (September-December).


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Last update: January 19, 2018