1,852 research outputs found

    Seasonal Variation in Birds

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    Wild birds show cyclical alternation between breeding seasons and seasons of sexual inactivity. During the latter the sex glands are at rest and are very small. With the approach of the breeding season they start to grow rapidly, -- increasing in volume up to one thousand times. Accompanying this growth of the gonads many secondary sex characters also show a characteristic development. This is true in first respect for the sperm- and oviducts, but also external secondary sex characters often show striking changes. The bill color of the sparrow is light brown during the resting period and becomes blue black in the breeding season. In some birds, as the Rose-breasted Grosbeak, a remarkable change also takes place in the plumage. Experiments have been performed and will be presented to show the external and hormonal factors that control these seasonal changes

    Subtype-selective GABAA receptor mimetics—novel antihyperalgesic agents?

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    Agonists at the benzodiazepine-binding site of ionotropic Îł-aminobutyric acid (GABAA) receptors are in clinical use as hypnotics, anxiolytics, and anticonvulsants since the early 1960. Analgesic effects of classical benzodiazepines have occasionally been reported in certain subgroups of patients suffering from chronic pain or after spinal delivery through intrathecal catheters. However, these drugs are generally not considered as analgesics but should in fact be avoided in patients with chronic pain. Recent evidence from genetically modified mice now indicates that agents targeting only a subset of benzodiazepine (GABAA) receptors should provide pronounced antihyperalgesic activity against inflammatory and neuropathic pain. Several such compounds have been developed recently, which exhibit significant antihyperalgesia in mice and rats and appear to be devoid of the typical side-effects of classical benzodiazepine

    A Study of the Gonadotropic Potency of Bird Pituitary (Domestic Turkey)

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    Pituitary glands were collected from domestic turkeys and assayed on immature rats and on non-breeding adult sparrows. Various dosages were given. In the rat 25 milligrams of the dry powdered gland produces a minimal reaction. Smaller amounts gave little or no effect while larger amounts gave greater reactions. Daily injections of 5 to 10 milligrams of the powdered gland cause a striking development of the sex glands of sparrows within two weeks
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