Tuesday, March 08, 2005
Mine eyes have been opened. I've always liked histology—much of my thesis work involved fixing, slicing, and staining tissues to characterize the cells therein—but I've always viewed it with a vertebrate bias. Most histology classes (the relative few you can find any more, at least…it's a discipline that isn't as well represented in the undergrad curriculum as it used to be) are packed full of pre-meds, and they focus almost entirely on characterizing vertebrate and especially mammalian tissues.
So it was a pleasant surprise to find a paper by Cole and Hall on comparative histology, with an extensive reference list that's leading me to all kinds of stuff I've neglected before. This is one of the joys of studying science—that you can stumble across an interesting question that you hadn't considered before, and surprise, you find the library and the labs are full of interesting data. And even better, much of the data is just beautiful.
The paper is focused on just one tissue, cartilage, and seeks to characterize its distribution across different animal groups. Here's the abstract:
Tissues similar to vertebrate cartilage have been described throughout the Metazoa. Often the designation of tissues as cartilage within non-vertebrate lineages is based upon sparse supporting data. To be considered cartilage, a tissue should meet a number of histological criteria that include composition and organization of the extracellular matrix. To re-evaluate the distribution and structural properties of these tissues, we have re-investigated the histological properties of many of these tissues from fresh material, and review the existing literature on invertebrate cartilages. Chondroid connective tissue is common amongst invertebrates, and differs from invertebrate cartilage in the structure and organization of the cells that comprise it. Groups having extensive chondroid connective tissue include brachiopods, polychaetes, and urochordates. Cartilage is found within cephalopod mollusks, chelicerate arthropods and sabellid polychaetes. Skeletal tissues found within enteropneust hemichordates are unique in that the extracellular matrix shares many properties with vertebrate cartilage, yet these tissues are completely acellular. The possibility that this tissue may represent a new category of cartilage, acellular cartilage, is discussed. Immunoreactivity of some invertebrate cartilages with antibodies that recognize molecules specific to vertebrate bone suggests an intermediate phenotype between vertebrate cartilage and bone. Although cartilage is found within a number of invertebrate lineages, we find that not all tissues previously reported to be cartilage have the appropriate properties to merit their distinction as cartilage.
Another of the joys of science is the delight we take in feeling ignorance spall and flake away as we hammer at our brains with new information. This was one of those papers where I was constantly thinking, "I did not know that—neat!" as I read it.
Cartilage is a connective tissue: that means that it consists of scattered cells imbedded in a matrix of extracellular material. In the case of cartilage, that matrix is a hydrophilic mucopolysaccharide (chondroitin sulfate) interlaced with collagen and/or elastin fibers. A kind of fiber-reinforced, dense snot, in other words. The matrix has characteristic staining properties, and the tissue is easily recognized in sections; the image to the left is a slice through a piece of vertebrate cartilage, and what you see is pinkish-purple stained cells called chondrocytes within the smooth, grayish-blue matrix. You can also see the purplish, collagen-rich connective tissue sheath that envelops the cartilage, the perichondrium. I've often used simple Alcian Blue staining to visualize cartilage, which turns the matrix a strong, bright blue color.
Cole and Hall developed their own pentachromatic staining protocol, which labels multiple common properties of cartilage in one procedure, and allows them to more accurately determine whether a tissue actually is appropriately called a cartilage. The protocol stains the tissues with the following colors:
|purple||cell nuclei, cytoplasm|
|green||low tensile collagen fibers|
|red||high tensile collagen fibers|
They applied these stains to a regular zoo of invertebrates, and found cartilage and chondroid tissues (like cartilage, but lacking the chondrocytes) all over the place…and made some very pretty pictures, too. Here, for instance, are the feeding tentacles of a couple of sabellid polychaete worms, which possess a core of cartilage:
(d) Feeding tentacle from the sabellid polychaete Potamilla. The cartilage is composed of two distinct regions: an inner cellular region (cc) and an outer acellular matrix (arrows). (e) Tentacle from the sabellid polychaete Myxicola showing similar organization as in (d). The large vacuolar chondrocytes (*) are more apparent than in Potamilla.
And here's a lovely example of convergent evolution. At the top is a piece of funnel cartilage from a cuttlefish; at the bottom is a piece of cartilage from the skull of a salmon.
(j) Funnel cartilage from a juvenile cuttlefish, Sepia officinalis, showing newly formed ECM with low mucopolysaccharide content (arrows) at the periphery. Chondrocytes within the interior are large and spherical, similar to vertebrate chondrocytes. (k) Cartilage undergoing endochondral ossification from the head of the Atlantic salmon Salmo salar. Zone of calcification (arrows) retains higher mucopolysaccharide staining than the adjacent hyaline cartilage (hc).
The similarities are impressive. Both have rounded chondrocytes nested in the mucopolysaccharide matrix, with a bounding region rich in collagen, the perichondrium.
Perhaps it isn't too surprising that cephalopods have evolved a tissue similar to our cartilage. One of the points of this paper is that the universality of cartilage-like tissues in the metazoa suggests that this is one of those properties that we inherited from a common ancestor—that using these mucopolysaccharides to build a more rigid framework was a useful feature found in early metazoans.
The data on invertebrate cartilaginous endoskeletons presented here offer unique insights into the evolution of vertebrate skeletal tissues. The ability to form cellular connective tissues structurally similar to cartilage without type II collagen is a feature that appeared before the evolution of vertebrates, supporting the notion that cartilage is not simply an embryonic adaptation (as per Romer), but was present in vertebrates before calcification evolved. Vertebrate cartilage and bone may have arisen from the same ancestral chondroid connective tissue that gave rise to the invertebrate cartilages, as evidenced by the fact that invertebrate cartilages share features not only with vertebrate cartilage but also with bone, such as cell-cell connections, use of type I collagen and possibly osteonectin and bone sialoproteins.
Cole AG, Hall BK (2004) The nature and significance of invertebrate cartilages revisited: distribution and histology of cartilage and cartilage-like tissues within the Metazoa. Zoology 107:261-273.
Science • EvoDevo • (6) Comments • (0) Trackbacks • Other weblogs
Since it is International Women's Day, I thought I'd shut up for at least one post and let a woman speak. But first, a little masculine context…
I listen to feminists and all these radical gals -- most of them are failures. They've blown it. Some of them have been married, but they married some Casper Milquetoast who asked permission to go to the bathroom. These women just need a man in the house. That's all they need. Most of the feminists need a man to tell them what time of day it is and to lead them home. And they blew it and they're mad at all men. Feminists hate men. They're sexist. They hate men—that's their problem.
Reverend Jerry Falwell
The feminist agenda is not about equal rights for women. It is about a socialist, anti-family political movement that encourages women to leave their husbands, kill their children, practice witchcraft, destroy capitalism, and become lesbians.
Let's let one of my favorite feminists, Elizabeth Cady Stanton, have the last words.
The whole tone of Church teaching in regard to women is, to the last degree, contemptuous and degrading.
Elizabeth Cady Stanton
The bible teaches that women brought sin and death into the world, that she precipitated the fall of the race, that she was arraigned before the judgment seat of Heaven, tried, condemned and sentenced. Marriage for her was to be a condition of bondage, maternity a period suffering and anguish, and in silence and subjection, she was to play the role of a dependent on man's bounty for all her material wants, and for all the information she might desire... Here is the Bible position of woman briefly summed up.
Elizabeth Cady Stanton
My heart's desire is to lift women out of all these dangerous, degrading superstitions, and to this end will I labor my remaining days on earth.
Elizabeth Cady Stanton
The Bible and the Church have been the greatest stumbling blocks in the way of women's emancipation.
Elizabeth Cady Stanton
The religious superstitions of women perpetuate their bondage more than all other adverse influences.
Elizabeth Cady Stanton
Godlessness • Politics • (76) Comments • (1) Trackbacks • Other weblogs
Monday, March 07, 2005
As long as I'm guilty of rampant promiscuity, I might as well go all out and apply for that job as a stripper at the Sugar Shack Lounge. The only requirement is a name change, using the name of your first pet plus the name of the street you lived on.
Snoop Willis, that's me. I'm down with it, fo' shizzle.
(I'm glad I'm a first-born, too—some of my siblings would be stuck with "Pooh Titus.")
BurningBird has a hilarious post that starts off as a comment on Google's AutoLink feature, and then somehow seques into a riff on the clueless male weblogger cliche, and then comes this shocking revelation:
"Oh, I don’t mean that men and women’s brains are wired so differently that men are naturally more adept at linking then women. No, the difference between men and women lies in how men perceive links, not their ability to use them."
She leaned closer to me, even though no one else was in the place.
"You see, guys see links as an extension of themselves. "
Extensions of themselves? Extensions? Slowly, understanding dawned.
"You always were a bright girl, mores the pity." She said, winking at me. "You got it in one. To you and me, a link is just a link. To a guy, however, a link is something special, a part of himself. The most,um, important part of himself."
I feel so forward, all of a sudden. And all of those links in the blogroll to the right are looking like notches on the bedpost.
Hey, wait…and all those people linking to me? Oh, uh, say…I'm feeling all transgressed, and a bit faint. This is a troubling metaphor.
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This story of armadillos, cockroaches, and gun-totin' frat boys sounds awfully urban-legendish, but it's set in Texas, so I suppose it could have happened.
(via BMW for Peace, another Morris weblog!)
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Weblogs • Weirdness • (8) Comments • (0) Trackbacks • Other weblogs
I'm looking at the endocast scans that Dean Falk did of the Homo floresiensis specimen (as reported by Carl Zimmer), and I'm reasonably well convinced that this is not a microcephalic. Here are some very nice comparative images. The H. floresiensis specimen is in the center, with H. sapiens above it, a chimpanzee below it, a microcephalic to the left, and H. erectus to the right. Here's a view from the left of a computer reconstruction:
And this is the frontal view:
There's also a whole series of quantitative plots of various parameters of relative brain dimensions, and in every case, the microcephalic is the odd man out, as you might expect of a pathology. H. floresiensis looks to have had a brain that was normal in its gross organization, just small.
Science • EvoDevo • Organisms • (6) Comments • (0) Trackbacks • Other weblogs
Sean Carroll asks the question every scientist who attends a humanities talk asks: why are they reading a paper out loud?
Here's a simple way that academia could be greatly improved: humanities professors should stop reading their papers out loud, and start talking from notes like normal people. I will never understand why they do this in the first place. There is no reason why humanists, trained in the arts of rhetoric and communication, should be even worse at giving talks than scientists are. It's certainly not because it's easier to read a pre-written paper word for word; I tried it at an humanities conference once and found it to be utterly awkward and unnatural. I thought the Western tradition was supposed to valorize speech over writing. Does this go back to Plato's battle vs. the Sophists or something?
Yeah, what's up with that? I try to attend our campus faculty lecture series here, which is a mix of people from various disciplines, and that's the most striking difference. The humanities people put up a stack of papers on a lectern, stand behind it, and basically don't move much at all while reading aloud. The science people move the lectern out of the way, clearing the podium, and fire up the projector—then they talk informally while flipping through data and waving their arms a lot.
To put it in grossly unfair terms that favor my side of the divide, the humanities people sound formal and stilted and don't show their evidence and put me to sleep, while the scientists are dynamic and invite questions and interaction. In the Senior Seminar are students are required to give in their final year, we explicitly tell them they shouldn't read a prepared script, and we dock 'em points if they do. So why do you humanities people out there put yourselves in this formal straightjacket when you give talks?
Here's another weird academic difference, from Inside Higher Ed:
The other day I had my composition students in groups, ready to "peer edit," according to the latest pedagogy. Suddenly one student just got up, and started for the door. I glared at her. "Just going to the bathroom," she airly explained. I did not reply.
Wrong. I should have said or done something. We cannot have students wandering out of our classrooms at will. That way lies -- what? High school? Or do they ask permission from the teacher first in high school? Elementary school? This is where they are presumably taught to ask, and certainly where they must learn to discipline their bodily functions.
Most likely my student did not have to go to the bathroom. She just wanted to stroll a bit before bending to the task at hand. Another student might have been more aggressive, in order to demonstrate her dislike of the task, if not school itself. But in any case, what to do? If doing nothing seems wrong, shouting at the student to sit down does not seem right.
I have always thought of the bathroom as marking the moment of discipline in the college classroom. Any student mention of the bathroom, whether in good faith or not, becomes as impossible to deal with as it is inescapable. When students do anything in the classroom that merits the exercise of faculty discipline, professors are on their own. The easiest thing for everybody to do is to look the other way. There are few rules, unlike those in place for elementary, middle, and high school teachers.
There's more, but that had me gaping in disbelief. Why so much concern for enforcing the attention of his students? I consider my students to be adults, and if they have to leave during class, I'm going to trust that they are only doing what is necessary. As long as they aren't disruptive, I don't mind at all. He actually has it backwards, I think: grade school is where teachers are often anal retentive and police the behavior of students more closely, and require silly things like hall passes to use the bathroom. In college, we assume they are all big boys and girls. I thought.
It's also a rather snide article. He seems a bit dismissive of this "latest pedagogy" (peer editing is new?) and assumes that the student dislikes the classwork. I get the distinct impression that someone likes to keep his sphincter tightly puckered.
Am I just more laid back than most, or do other faculty avoid treating their classroom like an EST seminar?
Academics • (41) Comments • (2) Trackbacks • Other weblogs
Ohio is shooting itself in the head: reducing funding to higher education, forcing tuition hikes that turn our best students away (and to the vocationally oriented schools that Bush visits every time he comes to our area), preventing universities from extending partner benefits to faculty members, and what might seem insignificant in a list like this, the ABOR. But the ABOR is not insignificant. It's one of those things that leaves anyone who thinks about it slack-jawed with disbelief. Don't mistake that disbelief with fear. The ABOR together with these other developments creates a working environment that most of us will work to flee in the coming years.
And don't forget Ohio's dalliance with Intelligent Design creationism! These are all reflections of extremist insanity: the people who are getting elected to state offices include increasing numbers of just plain ignorant yahoos (not just in Ohio, but also here in Minnesota—I don't understand how Michele Bachmann can be a viable candidate). They are consistently anti-intellectual, anti-science, anti-gay, anti-abortion, and anti-reason. Horowitz and his goons fit right in, since what they want is the destruction of diversity and the reconstruction of the American university system as madrassas of the right.
I picked up a couple of pamphlets from Horowitz's talk last week. The double-speak is amazing. There is a handbook titled "Students for Academic Freedom"—it's all about building a network of informers to monitor faculty. They are instructed to "research the party registration of faculty members," to "interview students" and make a list of "politically influenced grades," to research commencement speakers and invited lecturers for the past ten years, to "identify any lack of diversity." Then they are to go straight to the highest levels possible—the president, the board of trustees—to report it.
It's an interesting tactic. I'm sure that if you looked through a list of invited speakers to our science department, there's a noticeable deficiency of creationists, perpetual motion machine inventors, and anti-environment crackpots. This is discrimination, in the sense of discernment, since they simply aren't worth taking seriously. In the same sense, the kind of hysterical know-nothing extremists that reside on Horowitz's side of the political spectrum are discriminated against, with good reason: they are the antithesis of the spirit of learning that should be present at any decent university. We tend to avoid inviting shrill speakers who are going to ignorantly accuse their hosts of horrible crimes. It happens—Horowitz spoke at St. John's, for instance—but no one should be surprised if significantly less than half the speakers at any university are members of the wingnut fringe. Or even significantly less than one percent.
And Horowitz certainly does accuse universities of terrible crimes. Alongside his little red book, "Students for Academic Freedom," that claims to demand tolerance and respect for diversity, he had another charming pamphlet: "Campus Support for Terrorism." This book starts by blaming the Left for WWII and the rise of Hitler, and claims that campus Leftists are an "imminent threat…to the nation." That's right, we're all evil appeasers and friends of Adolf, plotting to destroy the country. Next to that was another book, "The Shadow Party," which demonizes the Democrats and, ironically enough, expresses shock and dismay that MoveOn had some commercials submitted to it that compared Bush to Hitler.
Horowitz made it clear that he thinks every Democrat anywhere to the left of Joe Lieberman and Zell Miller is literally a traitor to the country and ought to be locked up or deported or worse…and this is the guy we're supposed to believe wants to promote diversity on campus?
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Sunday, March 06, 2005
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I was thinking of writing something on this when I saw the recent article, but Sya has beaten me to it so I don't have to. It's cool stuff; another cellular organelle, the hydrogenosome (which functions like mitochondria to generate ATP, but uses the anaerobic rather than aerobic metabolic pathway) has been identified as an endosymbiont, with its own genome.
Science • EvoDevo • (4) Comments • (0) Trackbacks • Other weblogs
Hey, gang, Wednesday is my birthday! I'm sure many of you have already made your reservations and are planning to show up at my house with armfuls of gifts and bottles of champagne for an evening of wild partying, but if you can't make it, no worries: there's another way you can celebrate. Write something, anything about science or the natural world and post it to your weblog, and then send a link to it to grrlscientist, me, or email@example.com. Then, on 9 March, after all the champagne has been drunk and the revelers have toddled home or passed out on the floor, I'll be able to pull up the laptop, aim my browser at Living the Scientific Life, and spend some pleasant time seeing what smart people say about science on The Tangled Bank.
C'mon. As a favor to an old man getting older.
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Saturday, March 05, 2005
Really, when I started this site I did not imagine that people would ever write odes to it. I hope that when Pharyngula: The Musical opens on Broadway, that someone will send me tickets.
Weblogs • Weirdness • (6) Comments • (0) Trackbacks • Other weblogs
And that concludes our little tour of Christian wingnuttery for today. I hope that you found it helpful, and that you now know that dinosaurs existed as recently as 1966, that Darwin was the worst mass murderer in the history of the world, and that God cares more about your kisses than you do.
Wait! I've heard the first two often enough, but that business about kisses is new! God is such a prevert.
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No, I'm not going to do it (my stomach isn't that strong), but I'm happy to see that some people are. Here's What's Left catches them approving of a lie by Ann Coulter, and sends them a little polite fact-check—you know, that stuff blogs are supposed to be good for. You can guess what their response has been.
At least it's a step up from their usual foul-mouthed strategy of siccing their mob of thuggish readers on their critics. But bravo for the people who do try to keep Power Line honest.
The operative word up there is "try". You definitely can't succeed. There has been an update to the attempt; Power Line responded to the pressure with a faint and intrinsically dishonest disclaimer.
Their commitment to untruth is impressive.
Politics • Rethuglicans • (12) Comments • (0) Trackbacks • Other weblogs