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L D'Agostino S Pignata B Daniele R Ventriglia G Ferrari C Ferraro S Spagnuolo P E Lucchelli G Mazzacca 《Biochimica et biophysica acta》1989,993(2-3):228-232
Plasma diamine oxidase (DAO) values are enhanced by intravenous injection of heparin which releases the enzyme, synthesized in small bowel enterocytes, from binding sites located on endothelial cells of the intestinal microvasculature. Intestinal DAO, in analogy with lipoprotein lipase (another heparin-released enzyme), is believed to be electrostatically linked to endothelial binding sites composed of a glycosaminoglycan (GAG) which is presumably heparan sulphate, but the complete mechanism of enzyme release is not known. In this study we assayed in rats the DAO-releasing capability of heparan sulphate, dermatan sulphate, chondroitin sulphate A and hyaluronic acid, all heparin related compounds. Heparan sulphate, a compound with the same hexosamine as heparin but with a lower concentration of sulphated iduronic acid, induced a very high release of DAO (3-fold less than heparin), while the other tested GAGs, composed of higher proportions of non sulphated uronic acid and with galactosamine instead of glucosamine, induced a significantly lower release. In rats treated with 60 mg heparan sulphate the significant decrease in ileal mucosal DAO activity indicates that, in analogy with heparin, the high plasma enzymatic activity induced is of enterocytic origin. It is suggested that the high charge density of the compounds tested, due to the degree of sulphatation, is the decisive factor in promoting the release of intestinal DAO. 相似文献
3.
Feedback lighting provides illumination primarily during the subjective night (i.e., the photosensitive portion of the circadian cycle) in response to a given behavior. This technique has previously been used to test the nonparametric model of entrainment in nocturnal rodents. In three species (Rattus norvegicus, Mesocricetus auratus, and Mus musculus), the free-running period of the locomotor activity rhythm was similar whether the animals were exposed to continuous light or discrete light pulses occurring essentially only during the subjective night (i.e., feedback lighting). In the current experiments, feedback lighting was presented to squirrel monkeys so that light fell predominantly during the subjective night. Feedback lighting was linked to the drinking behavior in this diurnal primate so that when the animal drank, the lights went out. Despite the seemingly adverse predicament, the monkeys maintained regular circadian drinking rhythms. Furthermore, just as the period of the free-running activity rhythms of nocturnal rodents exposed to continuous light or feedback lighting were similar, the period of the drinking rhythms of the squirrel monkeys in continuous light and feedback lighting were comparable (25.6 +/- 0.1 and 25.9 +/- 0.1 hours, respectively), despite a substantial decrease in the total amount of light exposure associated with feedback lighting. The free-running period of monkeys exposed to continuous dark (24.5 +/- 0.1 hours) was significantly shorter than either of the two lighting conditions (P < 0.001). The results presented for the drinking rhythm were confirmed by examination of the temperature and activity rhythms. Therefore, discrete light pulses given predominately during the subjective night are capable of simulating the effects of continuous light on the free-running period of the circadian rhythms of a diurnal primate. The response of squirrel monkeys to feedback lighting thus lends further support for the model and suggests that the major entrainment mechanisms are similar in nocturnal rodents and diurnal primates. 相似文献
4.
In previous experiments two extreme modes of visual discrimination performance have been investigated by measuring small differences in pattern shape at points along a continuum of pattern shapes. These two modes, associated with discrete and continuous encoding processes, were obtained by simultaneously manipulating the number of pattern components in the display and the effective duration of the display. In this experiment, discrimination performance was measured for a fixed number of pattern components, namely three, and variable display time course. The stimuli used were curved lines drawn from a continuum with curvature parameter s. There were three stimulus time courses: (1) 2-s stimulus display, (2) 100-ms stimulus display, and (3) 100-ms stimulus display followed by a post-stimulus mask. Discrimination performance declined smoothly and monotonically with s for (1), but varied non-monotonically with s revealing a central peak for (3). Performance for (2) was intermediate between that for (1) and that for (3). A reduction in effective stimulus duration alone was thus sufficient to cause a transition from continuous to discrete modes of discrimination performance, a result which may be compatible with an explanation of variable discrimination modes based on a method of successive internal approximations of the stimulus. 相似文献
5.
Activation of human ribosomal genes by 5-azacytidine 总被引:2,自引:0,他引:2
Cultured human fibroblasts were exposed to 5-azacytidine which inhibits methylation of newly synthesized DNA. A significant increase in the mean number of Ag-stained active nucleolus organizers has been observed in treated cells. This suggests that DNA methylation is involved in modulation of human rRNA synthesis. 相似文献
6.
In peripheral blood lymphocytes of 12 nurses and 3 patients exposed to antineoplastic drugs we determined the ability to repair DNA after UV irradiation and DNA replicative synthesis after stimulation by PHA. In nurses the levels of unscheduled DNA synthesis and DNA replication were not different than in a control group, whereas in patients significant changes were observed during and after chemotherapy in the level of both types of DNA synthesis. 相似文献
7.
L. Ferraro S. Tanganelli L. Marani C. Bianchi L. Beani A. Siniscalchi 《Neurochemical research》1996,21(5):547-552
The effects of α-glycerylphosphorylcholine (α-GPC) on endogenous cortical GABA release were studied both in vivo and in vitro.
In freely moving rats, equipped with epidural cups, α-GPC (30–300 mg/kg i.p.) increased GABA release. This effect was potentiated
by atropine, both systematically administered (5 mg/kg i.p.) and locally applied (1.4 μM), but not by mecamylamine (4 mg/kg
i.p.). The α-GPC-induced increasein GABA release was abolished in rats pretreated with the α1 receptor antagonist prazosin (14 μg/kg i.p.). In cortical slices α-GPC (0.4 mM) increased the spontaneous GABA efflux. This effectwas abolished by tetrodotoxin (0.5 μM) and prazosin (1 μM), but not by atropine (0.15 μM) ormecamylamine (2.5μM). These results indicate that the facilitatory response by α-GPC on GABArelease does not depend on a direct activation of either muscarinic or nicotinic receptors, but suggest the involvement of the noradrenergic
system. 相似文献
8.
G Ghiazza G Zavarise G Ferraro A Barbero G Grillo 《Bollettino della Società italiana di biologia sperimentale》1984,60(3):673-678
The dangerous effects of phototherapy have been matter of discussion in recent years. In order to evaluate its in vitro action on the human DNA, the authors have performed the karyotypic analysis on 20 cultures of lymphocytes. In different times 16 cultures have been exposed to the action of a "blue light" fluorescent lamp, commonly used for the treatment of neonatal jaundice. The authors have not evidenced any morphological or numerical change of the karyotype in any of the cultures. 相似文献
9.
Summary The results of a detailed analysis of DNA replication in a late replicating tX/X chromosome (qter p221::p223 » qter) are reported. The chronology of DNA replication has been analyzed by comparing (a) the replication patterns of each of the two moieties of the translocation chromosome in different cells and (b) the two moieties with each other in the same cell. The study has been done on leukocyte and fibroblast cultures after BUdR incorporation. A comparison with the late replication pattern of the normal X chromosome has also been done. 相似文献
10.