1,721,023 research outputs found
Quantifying Bird Migration by a High-Resolution Weather Radar
No full textWe propose a bird detection and count algorithm designed to work with radar maps of PPI type. The spatial arrangement of birds is modeled according to the Poisson distribution. It is possible to handle a non-uniformtarget distribution both on the vertical and on the horizontal plane. The method is applied to measurements carried out by an S-band Doppler weather radar located on the South side of the Alps. Quantitative estimates are given for the distribution of bird volume density with height,
for the cumulative density (integrated over height), and finally for the daily migration traffic rate of nocturnal migrants over an area of about 2000 square kilometers
Effects of pinealectomy on the circadian rhythms of the activities of polyamine biosynthetic decarboxylases and tyrosine adminotransferase in different organs of the rat
No full textThe circadian rhythms of the activities of some enzymes were compared in liver, kidneys, and thymus of sham-pinealectomized and pinealectomized rats. Ornithine decarboxylase and tyrosine aminotransferase were chosen because of the well known fluctuations of their activities during the day. The diurnal behavior of S-adenosyl-L-methionine decarboxylase activity was first ascertained to display circadian rhythm in all of the above-mentioned organs of sham-pinealectomized rats and then was compared with that of pinealectomized rats. Before the operation and until killed, all of the animals were kept under rigidly standardized conditions. They were killed at 6-h intervals during the day. Chronobiologically in pinealectomized animals, the acrophase of the circadian rhythm of ornithine decarboxylase activity was markedly shifted in liver and, to a lesser degree, in kidneys. For the same enzyme, pinealectomy modified the amplitude in thymus and, even more so in kidneys. As for the circadian rhythm of S-adenosyl-L-methionine decarboxylase activity, pinealectomy induced an increase of the amplitude only in kidneys. No chronobiological parameter of the circadian rhythm of tyrosine aminotransferase activity was changed by pinealectomy in any of the chosen organs. The results of chronobiological analyses are supported by and in agreement with the results of analyses of variance of the effects of pinealectomy on the circadian rhythms tested. Two conclusions seem to be justified: 1) the pineal gland plays a part in the rat time-keeping machinery regulating enzyme circadian rhythms; and 2) in the circadian organization of the rat, the pineal gland plays the role of a coupling device, rather than that of master oscillator
Pineal gland and polyamines
No full textThe activity of ornithine decarboxylase was assayed in several organs (thymus, testes, prostate gland, liver, kidneys, adenohypophysis, anterior hypothalamus, and adrenals) taken from adult male rats killed at seven day interval up to six weeks after pinealectomy. The absence of the pineal gland particularly influences the ornithine decarboxylase activity in the thymus, in which the level of the enzyme is decreased irreversibly by the fourth week after the operation. In other organs the ornithine decarboxylase activity was often significantly different from that of corresponding shampinealectomized controls at various weeks after the surgical removal of the gland. Moreover, these differences between operated and sham-operated animals are sometimes positive, sometimes negative. Thus, the polyamine biosynthetic pathway in different organs appears to be regulated, directly or indirectly, by a new neuroendocrine centre, the pineal gland, and this pineal gland has thus been shown to be active in adult life in correlating endocrine-enzymatic functions
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