fish – GOLLYGEE!

Chemical structure of oxazepam

Traces of drugs are floating around rivers and streams all across the country. They are introduced to the ecosystem when we take medication, metabolize them and flush them down the toilet. Because they are present in low amounts in the environment they have not been thought to be of huge concern to the species that inhabit waterways. But, a new study shows that traces of oxazepam, a benzodiazepine and antianxiety medication, can alter behavior in wild Euorpean perch, making them more active than normal. From The New York Times:

Researchers then took baby fish hatched from the roe of wild perch in what they considered a drug-free waterway, and divided them into three groups of 25. One group had no exposure to Oxazepam; the other two were placed in water with what researchers called a low concentration, at three times higher than the Fyris River, or an extremely high concentration, at 1,500 times higher.

The more Oxazepam they ingested the more active the fish were, measured by the number of swimming motions in a 10-minute period. They were also less social, spending less time near a section of the tank with other fish and more time near an empty compartment. And they were quicker to grab and eat zooplankton. At the highest Oxazepam concentration, fish were also bolder, measured by how long it took them to leave a box in the tank and explore new territory.

“Basically, no one left the box before they were subjected to the drug,” said Dr. Brodin, who said he saw the difference when he entered the room each day. The non-exposed fish “were hiding basically,” while the others “were out there, greeting me. They were totally different fish.”

It should be noted that the lowest concentration that the researchers measured is above the concentration usually observed in waterways. Fish in real world conditions may not have any altered behavior at all.

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.

GOLLYGEE!

Tag: fish

oxazepam and fish behavior

RNA probing