Developmental Biology
grrlscientist | March 12, 2010tags: evolution, evolutionary biology, gynandromorph, bilateral gynandromorph bird, half-sider, mixed-sex chimaera, sex determination, molecular biology, genetics, developmental biology, endocrinology, birds, chicken, Gallus gallus, ornithology, researchblogging.org,peer-reviewed research, peer-reviewed paper, journal club
Half-sider.
Almost exactly one year ago, hundreds of American birders
were thrilled by sightings and photographs of this remarkable
Northern Cardinal, or Redbird, Cardinalis cardinalis,
photographed in Warrenton, VA.
Image: DW Maiden, 2 March 2009.
I'll never forget…
neurophilosophy | February 19, 2010
Click to enlarge
THIS cartoon by Dwayne Godwin, a professor of neurobiology at Wake Forest University School of Medicine, and Jorge Cham, the former researcher and cartoonist who created PhD Comics, has won first place in the informational graphics category of the 2009 International Science and Engineering Visualization Challenge.
The New York Times has a slide show of the winning entries, and today's issue of Science contains a special feature about the competition. To see the full size infographic, click on the image above, or visit Godwin's public engagement page, where it, and others…
grrlscientist | May 21, 2009tags: book review, Why Evolution is True, evolution, creationism, religion, scientific method, Jerry Coyne
Considering the plethora of books about evolution out there, is it really necessary to publish yet another one? What can another book about evolution have to offer that previous books have not provided? This new book not only presents the latest information about evolution to come to light, but it also responds to the most recent attacks made upon this branch of scientific knowledge. The book, Why Evolution is True (NYC: Viking; 2009) by Jerry Coyne, is the most up-to-date and one of the…
neurophilosophy | February 24, 2009Alzheimer's Disease is the most common form of dementia, affecting more than 400,000 people in the U.K. and some 5.5 million in the U.S. The disease has a characteristic pathology, which often appears first in the hippocampus, and then spreads to other regions of the brain. This is accompanied by impairments in cognition, with cell death and loss of connections leading first to deficits in memory and spatial navigation, and then to global dysfunction.
The exact cause of Alzheimer's is not known, but a number genes have been implicated. One of these encodes a protein called amyloid precursor…
neurophilosophy | January 19, 2009The brains of vertebrates are asymmetrical, both structurally and functionally. This asymmetry is believed to increase the efficiency of information processing - one hemisphere is specialized to perform certain functions, so the opposite is left free to perform others. In the human brain, for example, the left hemisphere is specialized for speech. This has been known since the 1860s, when the French physician Paul Broca noted that the aphasia (or inability to speak) which is a common symptom of stroke is associated with damage to a discrete region of the left frontal lobe.
Very little is…
neurophilosophy | November 19, 2008
This beautiful image of the brain of a 5-day-old zebrafish larva, which was created by Albert Pan of Harvard University, has just won 4th place in the 2008 Olympus BioScapes Digital Imaging competition. (See a larger version here.)
It was created using the Brainbow technique, a genetic method for labelling neurons, with which individual cells can be made to express a random combination of fluorescent proteins. An image of a mouse brainstem labelled using the same method was awarded 1st prize in last year's competition.
neurophilosophy | November 10, 2008A team of Japanese researchers has demonstrated that embryonic stem cells obtained from mice and humans can spontaneously organize themselves into cortical tissues when grown in a culture dish under special conditions.
Reporting in the journal Cell Stem Cell, the researchers show that the neurons generated form functioning short-range and long-range connections, and can be effectively integrated into existing neuronal circuits following transplantation into the brains of experimental animals.
Yoshiki Sasai, head of the Organogenesis and Neurogenesis Group at RIKEN's Center for…
neurophilosophy | October 10, 2008
This reconstruction, produced by researchers from the European Molecular Biology Laboratory in Heidelberg, Germany using a technique called digital scanned laser light sheet fluorescence microscopy, shows the movements of all 16,000 cells in an 18-hour-old zebrafish embryo.
To make the film, the researchers injected a fluorescent protein into an embryo at the one cell stage. They began imaging at the 64-cell stage and recorded 370 images, each less than 3 thousandths of a millimeter apart, in multiple directions at 1,226 time points separated by 90 second intervals. The recording was…
neurophilosophy | August 8, 2008The classic Nobel Prize-winning studies of David Hubel and Torsten Weisel showed how the proper maturation of the developing visual cortex is critically dependent upon visual information received from the eyes. In what would today be considered highly unethical experiments, Hubel and Weisel sewed shut one eye of newborn kittens. They found that this monocular deprivation had dramatic effects on the visual part of the brain: the columns of cortical tissue that normally receive inputs from the closed eye failed to develop, while those that receive inputs from the other eye were significantly…
neurophilosophy | June 17, 2008
The winners of the first Kavli Prize were announced a couple of weeks ago. One of the three recipients of the prize for neuroscience was Pasko Rakic, a professor of neurobiology and neurology at the Yale School of Medicine.
Rakic has spent most of his career investigating the development of the cerebral cortex of man and other mammals, and it is for his outstanding contribution to this area of research that he has been awarded the Kavli Prize for Neuroscience.
Cortical development (or corticogenesis) is a highly dynamic and complex process, involving the tightly orchestrated movements of…
neurophilosophy | December 13, 2007The word "wOOt" - spelt with zeros instead of the letter 'o' - has just been voted as Merriam-Webster Online Dictionary's Word of the Year. Coined by internet users, and defined as an interjection "expressing joy", it's quite apt today, because my axon guidance essay was returned with a mark of 80%.
I posted the essay in 4 parts while I was away in Egypt. Here it is again:
Part 1: The growth cone.
Part 2: A novel axon guidance mechanism.
Part 3: The turning point.
Part 4: New directions.
wOOt!
neurophilosophy | November 22, 2007[Introduction|Part 2|Part 3]
The three studies discussed here make important contributions to our understanding of axon guidance. Lopez-Bendito et al describe a novel guidance mechanism involving tangentially migrating GABAergic interneurons. These cells migrate ventrally from the LGE to form a permissive corridor through the MGE, a region that is otherwise non-permissive for TCAs.
The corridor is fully formed by the time TCAs reach the ventral aspect of the MGE. This is therefore a means by which the presentation of guidance cues can be regulated both spatially and temporally. This may be…
neurophilosophy | November 21, 2007[Introduction|Part 2|Discussion]
Tojima et al (2007) find that the growth cone's response to attractive guidance cues requires asymmetrical vesicle transport and exocytosis. They cultured dorsal root ganglion (DRG) cells from embryonic chicks, and produced localized elevations in calcium ion concentration on one side of the growth cone by photolytic release of the caged calcium ion compound DMNT-EDTA. In cells cultured on a substrate of cell adhesion molecule L1, this causes calcium-induced calcium release (CICR), and elicits a turning response in the direction of the calcium signal. In…
neurophilosophy | November 20, 2007[Introduction|Part 3|Part 4]
Lopez-Bendito et al (2006) show that pathfinding of thalamocortical axons (TCAs) requires the formation of a permissive corridor through non-permissive territory, and that this corridor is generated by cells which undergo a tangential migration from the lateral ganglionic eminence (LGE).
TCAs arise in the dorsal thalamus, and follow a stereotyped pathway into the developing neocortex. Initially, they are repelled by Slit 1 and Slit 2 expressed in the hypothalamus. They extend rostrally into the telencephalon and turn sharply before extending dorsolaterally to…
neurophilosophy | November 19, 2007
Dylan T. Burnette/ Nikon Small World.
The remarkable specificity of neuronal connectivity depends on accurate axon pathfinding during development. Pathfinding involves the detection of guidance cues in the environment by the growth cone, a motile chemotactic structure at the leading tip of the extending axon.
The growth cone was discovered over 100 years ago by Santiago Ramon y Cajal, the father of modern neuroscience. Cajal's description of the growth cone (or cono de crecimiento) has not been bettered:
From the functional point of view, one might say that the growth cone is like a…
gregladen | November 6, 2007This is interesting:
Doctors began operating today on a 2-year-old girl born with four arms and four legs in an extensive surgery that they hope will leave the girl with a normal body, a hospital official said.
Lakshmi is joined to a "parasitic twin" who stopped developing in the mother's womb. The surviving fetus absorbed the limbs, kidneys and other body parts of the undeveloped fetus.
[source]
It is believed that in utero, this girl had a twin whom she absorbed, reportedly after that twin's "death." (I'm not so sure about the death part... that sounds like an assumption.)
Various parts…
neurophilosophy | October 5, 2007Below is the PowerPoint I presented in the journal club this morning. It's a summary of a recent paper about laterality in the nematode worm:
Poole, R. J. & Hobert, O. (2006). Early embryonic programming of neuronal left/right asymmetry in C. elegans. Curr. Biol. 16: 2279-2292. [PDF]
I mentioned this study in yesterday's post about asymmetry in the nervous system, without going into too much detail. I'm sharing the presentation here because, although the paper is quite complex, the experiments described in it are very elegant.
When it comes to using PowerPoint, I'm a minimalist. I…