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Archive - Mar 1, 2010

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Caddis Fly Silk May Be Useful Adhesive in Surgery

"Silk from caddis fly larvae may be useful some day as a medical bioadhesive for sticking to wet tissues," said Dr. Russell Stewart, an associate professor of bioengineering at the University of Utah and principal author of a new study of the fly silk's chemical and structural properties. "I picture it as sort of a wet Band-Aid, maybe used internally in surgery--like using a piece of tape to close an incision as opposed to sutures," he added. "Gluing things together underwater is not easy. Have you ever tried to put a Band-Aid on in the shower? This insect has been doing this for 150 million to 200 million years. There's just a fascinating diversity of these insects. Their adhesive is able to bond to a wide range of surfaces underwater: soft and hard, organic and inorganic. If we could copy this adhesive, it would be useful on a wide range of tissue types." Dr. Stewart hopes to make a synthetic version of the caddis fly silk for use as a surgical adhesive. There are thousands of caddis fly species worldwide in an order of insects named Trichoptera that is related to Lepidoptera, the order that includes moths and butterflies that spin dry silk. Because caddis flies are eaten by trout, fly fishermen often use caddis fly lures. Some species of caddis fly spend their larval stages developing underwater, and build an inch-long, tube-shaped case or shelter around themselves using sticky silk and grains of rock or sand (see photo). Some other species use silk, small sticks, and pieces of leaves. In these tube-dwelling species, each larva has a head and four legs that stick out from the tube. The larval case is often conical because it gets wider as the larva grows. A caddis fly larva eventually pupates, sealing off the tube as it develops into an adult fly, and then hatches.

Rapidly-Acting Antidepressant Shows Promise

In a recent issue of Biological Psychiatry, researchers from the NIH have reported that a medication called scopolamine appears to produce replicable rapid improvement in mood in patients with unipolar depression. Scopolamine temporarily blocks the muscarinic cholinergic receptor, thought to be overactive in people suffering from depression. Previously, the NIH team had demonstrated scopolamine’s anti-depressive effect in both unipolar and bipolar depression. The current study replicates these findings in an independent sample of unipolar depression patients. Conventional antidepressant treatments generally require three to four weeks to become effective, thus the discovery of treatments with a more rapid onset is a major goal of biological psychiatry. The authors noted that the first drug found to produce rapid improvement in mood was the synthetic NMDA glutamate receptor antagonist known as ketamine. Scopolamine is an alkaloid compound obtained from plants of the nightshade family (Solanaceae), such as henbane, jimson weed, Angel's Trumpets, corkwood, and belladonna (“deadly nightshade”). "Scopolamine was found to reduce symptoms of depression within three days of the first administration. In fact, participants reported that they experienced relief from their symptoms by the morning after the first administration of drug," explained Dr. Maura Furey, co-author of the new report. "Moreover, one half of participants experienced full symptom remission by the end of the treatment period. Finally, participants remained well during a subsequent placebo period, indicating that the antidepressant effects persist for at least two weeks in the absence of further treatment.”