Category: Chemistry (page 10 of 15)

dioxin causes reproductive problems

2,3,7,8-Tetrachlorodibenzo-p-dioxin, referred to as dioxin, is a contaminant in Agent Orange. It is toxic and known to cause developmental defects and cancer.

From Science Daily:

 Since the 1960s, when the defoliant Agent Orange was widely used in Vietnam, military, industry and environmental groups have debated the toxicity of one of its ingredients, the chemical dioxin, and how it should be regulated.

But even if all the dioxin were eliminated from the planet, Washington State University researchers say its legacy would live on in the way it turns genes on and off in the descendants of people exposed over the past half century.

Writing in the journal PLoS ONE, biologist Michael Skinner and members of his lab say dioxin administered to pregnant rats resulted in a variety of reproductive problems and disease in subsequent generations. The first generation of rats had prostate disease, polycystic ovarian disease and fewer ovarian follicles, the structures that contain eggs. To the surprise of Skinner and his colleagues, the third generation had even more dramatic incidences of ovarian disease and, in males, kidney disease.

“Therefore, it is not just the individuals exposed, but potentially the great-grandchildren that may experience increased adult-onset disease susceptibility,” says Skinner.

RNA probing

Each red dot is a single probe bound to the RNA target. The cell nucleus is stained blue. Note the increase of fluorescence over time.

Scientists have developed a probe to bind and fluoresce in the presence of a single copy of viral RNA. Up until now, probes fluoresced nonspecifically to other nucleotides limiting their usefulness. A group of scientists use the FISH (fluorescence in situ hybridization) technique to improve things. From CEN:

Yong Chen, at the University of California, Los Angeles, and his colleagues wanted to design a more sensitive assay. They built a long single-stranded DNA containing about 1,000 copies each of two sequences: one complementary to a portion of the RNA that makes up the influenza A virus and another complementary to a fluorescently labeled strand of DNA. They designed the sequences so that they didn’t complement sequences found in their target cells.

To test their new probe, the scientists added it to dog kidney cells infected with influenza A. They had chemically frozen the cells’ biomolecules before adding the probe. After washing away unbound probe, they added the fluorescently labeled strand of DNA.

When the researchers looked at the cells under a microscope, single molecules of viral RNA appeared as bright red dots. They assumed their probes bound a single RNA molecule because the viral nucleic acid concentrations early in the infection were much smaller than that of their DNA probe. The scientists didn’t see the glowing spots in uninfected cells, indicating very little off-target binding, Chen says. His team repeated the experiment with infected cells treated with the antiviral drug ribavirin. Six hours after infection, the amount of viral RNA in those cells was one-twelfth that of untreated cells.

light activated muscle

Scientists have been hard at work designing artificial muscle that gets activated when exposed to light:

Sakar and colleagues at MIT teamed up with scientists at the University of Pennsylvania to genetically engineer mouse muscle cells that twinge in response to light. The researchers loaded the cells with a light-activated protein, let the cells fuse into fibers, and mixed them with a special gel to form 3-D strips smaller than the width of a grain of rice. Then, they hit the strips with narrow beams of blue light.

Only the light-zapped fibers jumped; those in the dark stayed still. “I was hoping it would work, but the first time I saw it, it was amazing,” Sakar says. “I was very, very excited.”

Sakar and colleagues even got the muscle fibers to show off a bit of brawn. Tissue strips stretched between two tiny elastic posts pulled the structures together when scientists switched on the light.

Read more at Science News. The full report is on line Lab on a Chip The MIT press release is here with a neat video.

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