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Competition in the Crypt

By Hugo Snippert, Hubrecht Institute

Here is an image of the small intestine, zoomed in on the crypts. The “Confetti” gene was activated in all cells in the intestine, including stem cells. Once the Cre recombination process is over, each stem cell produces progeny that inherit the same fluorescent marking. The number of cells in the crypt is fixed. Thus, over time, stem cells (~14) compete each other out of this niche, and the crypt becomes clonal, visualized here by monochromatic crypts.

Image: This image was taken 4 months after Cre activation using a Leica Sp5 microscope. Clonal conveyor belts from the crypt base to the top of villi are imaged with four different colors at 40x magnification.

Nov 26

Dr. Jennifer L. Peters & Dr. Michael R. Taylor

St. Jude Children’s Research Hospital
Memphis, Tennessee, USA

Subject Matter:

The blood-brain barrier in a live zebrafish embryo

(20x)Technique:

Confocal

Dr. Jennifer Peters’ and Dr. Michael Taylor’s winning image of the blood-brain barrier in a live zebrafish embryo perfectly demonstrates the intersection of art and science that drives the Nikon Small World Competition.

The blood-brain barrier plays a critical role in neurological function and disease. Drs. Peters and Taylor, developed a transgenic zebrafish to visualize the development of this structure in a live specimen. By doing so, this model proves that not only can we image the blood-brain barrier, but we can also genetically and chemically dissect the signaling pathways that modulate the blood-brain barrier function and development.

Both Peters and Taylor have more than ten years of imaging experience. Peters is an imaging scientist in the St. Jude Children’s Research Hospital’s Light Microscopy Core Facility and Taylor is an Assistant Member in the Department of Chemical Biology and Therapeutics at St. Jude Children’s Research.

The head of a flower is made up of small seeds which are produced at the center, and then migrate towards the outside to fill eventually all the space (as for the sunflower but on a much smaller level). Each new seed appears at a certain angle in relation to the preceeding one. For example, if the angle is 90 degrees, that is 1/4 of a turn.

…

This angle has to be chosen very precisely: variations of 1/10 of a degree destroy completely the optimization. When the angle is exactly the golden mean, and only this one, two families of spirals (one in each direction) are then visible: their numbers correspond to the numerator and denominator of 2 consecutive numbers in the Fibonacci sequence, which is proved to converge toward the Golden Mean value of 1.6180339… (in the picture we have 21/34, the 7th and 8th terms of the Fibonacci sequence).

The Fibonacci sequence is named after Leonardo of Pisa, who was known as Fibonacci. Fibonacci’s 1202 book Liber Abaci introduced the sequence to Western European mathematics, although the sequence had been described earlier in Indian mathematics. (By modern convention, the sequence begins either with F₀ = 0 or with F₁ = 1. The Liber Abaci began the sequence with F₁ = 1, without an initial 0.)

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Seeking Next-Gen Probes

By Thomas Deerinck, NCMIR

For over 20 years, Tom has worked at UCSD’s Department of Neurosciences and the National Center for Microscopy and Imaging Research under the tutelage of Mark Ellisman, founder and director of NCMIR. Tom specializes in developing and applying new imaging techniques for biologists, including robotic serial blockface scanning EM (pioneered by Winfried Denk and others), which he believes will revolutionize EM imaging in biology. Tom is currently collaborating with Roger Tsien to develop the “next generation” of imaging probes for live-cell light and electron microscopies.

Image: Quadruple fluorescence image revealing the complexity of the optic fiber layer of a mouse retina. Optic nerve axons and glial cells are stained red and green, respectively while actin in the blood vessel-ensheathing endothelial cells are stained blue. DNA and RNA are in orange. The image was acquired by confocal microscopy.

Dec 14

LSD has been used in psychiatry for its perceived therapeutic value, in the treatment of alcoholism, pain and cluster headache relief, for spiritual purposes, and to enhance creativity. However, government organizations like the United States Drug Enforcement Administration maintain that LSD “produces no aphrodisiac effects, does not increase creativity, has no lasting positive effect in treating alcoholics or criminals, does not produce a ‘model psychosis’, and does not generate immediate personality change.”

Alcoholism

Some studies in the 1960s that used LSD to treat alcoholism reduced levels of alcohol misuse in almost 60% of those treated, an effect which lasted six months but disappeared after a year. A 1998 review was inconclusive. However, a 2012 meta-analysis of six randomized controlled trials found evidence that a single dose of LSD in conjunction with various alcoholism treatment programs was associated with a decrease in alcohol abuse, lasting for several months^.

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Filling the Dermis

By Tom Deerinck, NCMIR and UCSD

While the epidermis of mammalian skin contains primarily kerotinocytes, the dermis is composed largely of fibroblasts. The dermis is a type of connective tissue, and fibroblasts produce the two major structural components of its extracellular matrix: collagen fibers, which give the dermis strength and traction; and, elastin, which make the dermis stretchable and flexible. Unlike epithelial cells, fibroblasts do not form flat, monolayers but rather can migrate around the extracellular matrix. Thus, while epithelial cells line the body, fibroblasts are the ones to “sculpt it.”

Image: Fibroblast cells in culture imaged by multiphoton microscopy.

medicinenotes:

Protein Makes Sperm Flee

A compound that causes immature sperm cells to flee the testes early may provide new leads for contraceptives. Scientists pursuing a “male pill” have recently found multiple ways to disrupt sperm production, usually by shutting down genes and proteins unique to the testes. Now, a team led by C. Yan Cheng of the Population Council’s Center for Biomedical Research in New York City has identified a new way to stop spermatogenesis: disrupting the blood-testis barrier, a cellular firewall between the testes and blood circulation. When Cheng’s team injected a special protein fragment into rat testes, the blood-testis barrier broke down. This caused immature sperm to drift out of the testes early, before they were capable of fertilizing eggs. More importantly, these changes were reversible. The team reported their findings online today in Nature Communications. Any potential male contraceptive would be many years off and would require many more tests. Cheng’s team, for instance, has not tested whether rats injected with this protein fragment father fewer offspring. But Cheng says the advantage of this protein over other potential contraceptives is that the body produces it naturally in small amounts, so it’s likely to be well tolerated.

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