99 resultados para Frequency response


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Anthocyanins are the largest group of water-soluble pigments in the plant kingdom. A number of studies have demonstrated that anthocyanins present antioxidant capacity and show inhibitory effects on the growth of some cancer cells. Thus, the goal of this study was to evaluate both the antimutagenicity/antigenotoxicity and mutagenicity/genotoxicity of aqueous extract obtained from the Solanum melanogena, a possible novel source of anthocyanin, and its main purified anthocyanin extract (delphinidin), using the single cell (comet) assay and micronucleus test. Pretreatment with higher doses of the purified anthocyanin (10 and 20 mg/kg b.w.) led to a statistically significant reduction (p < 0.05) in the frequency of micronuclei in polychromatic erythrocytes induced by cyclophosphamide. The pattern of reduction ranged from 48% to 57% independent of concentration. No apparent: genotoxicity and mutagenicity was found for either the anthocyanin or delphinidin extracts. Taken together, these results suggest that mice pre-treated with specific compounds present in anthocyanins (delphinidin) displayed a lower incidence of mutations induced by cyclophosphamide. This finding emphasizes the potential of natural colorants to prevent mutations and also the applicability of genotoxic evaluation for improving health. Furthermore, the results presented here could be an additional argument to support the use of anthocyanins in the diet. (c) 2006 Published by Elsevier Ltd.

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Equine pituitary extract (EPE) has been reported to induce heightened follicular development in mares, but the response is inconsistent and lower than results obtained in ruminants undergoing standard superovulatory protocols. Three separate experiments were conducted to improve the ovarian response to EPE by evaluating: (1) effect of increasing the frequency or dose of EPE treatment; (2) use of a potent gonadotropin-releasing hormone agonist (GnRH-a) prior to EPE stimulation (3) administration of EPE twice daily in successively decreasing doses. In the first experiment. 50 mares were randomly assigned to one of four treatment groups. Mares received (1) 25 mg EPE once daily; (2) 50 mg EPE once daily (3) 12.5 mg EPE twice daily; or (4) 25 mg EPE twice daily. All mares began EPE treatment 5 days after detection of ovulation and received a single dose of cloprostenol sodium 7 days postovulation. EPE was discontinued once half of a cohort of follicles reached a diameter of greater than or equal to35 mm and hCG was administered. Mares receiving 50 mg of EPE once daily developed a greater number (P = 0.008) of preovulatory follicles than the remaining groups of EPE-treated mares, and more (P = 0.06) ovulations were detected for mares receiving 25 mg EPE twice daily compared to those receiving either 25 mg EPE once daily and 12.5 mg EPE twice daily. Embryo recovery per mare was greater (P = 0.05) in the mares that received 12.5 mg EPE twice daily than those that received 25 mg EPE once daily. In Experiment 2, 20 randomly selected mares received either 25 mg EPE twice daily beginning 5 days after a spontaneous ovulation. or two doses of a GnRH-a agonist upon detection of a follicle greater than or equal to35 mm and 25 mg EPE twice daily beginning 5 days after ovulation. Twenty-four hours after administration of hCG, oocytes were recovered by transvaginal aspiration from all follicles greater than or equal to35 mm. No differences were observed between groups in the numbers of preovulatory follicles generated (P = 0.54) and oocytes recovered (P = 0.40) per mare. In Experiment 3, 18 mares were randomly assigned to one of two treatment groups. Then, 6-11 days after ovulation, mares were administered a dose of PGF(2gamma) and concomitantly began twice-daily treatments with EPE given in successively declining doses, or a dose of PGF(2alpha), but no EPE treatment. Mares administered EPE developed a higher (P = 0.0004) number of follicles :35 mm, experienced more (P = 0.02) ovulations, and yielded a greater (P = 0.0006) number of embryos than untreated mares. In summary, doubling the dose of EPE generated a greater ovarian response, while increasing the frequency of treatment, but not necessarily the dose. improved embryo collection. Additionally, pretreatment with a GnRH-a prior to ovarian stimulation did not enhance the response to EPE or oocyte recovery rates. (C) 2002 Elsevier B.V. All rights reserved.

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Equine pituitary extract (EPE), has been reported to induce multiple ovulation in mares, however ovulation rates are poor in comparison to those obtained in other species. Attempts to improve the effectiveness of EPE for induction of superovulation in cyclic mares has focused on daily frequency of EPE treatment. Two experiments were performed to compare the ovarian response of cyclic mares given EPE once or twice-daily. Mares were assigned to one of two treatment groups 6 to 8 days after ovulation: prostaglandin was given once and EPE (25 mg) was given once daily (Group 1) or twice daily (Group 2). In Experiment 1, more (P < 0.05) follicles 35 mm were detected in mares treated with EPE twice daily (6.1 +/- 3.1) than in mares treated once a daily (2.0 +/- 0.6). In a second experiment, the embryo recovery rates of mares given the two EPE protocols used in Experiment 1 were compared. The number of ovulations per mare was higher (P < 0.05) for mares treated twice-daily (7.1 +/- 5.1, range 3 to 18) than for mares treated once daily (2.4 +/- 1.8, range 1 to 6). The number of embryos produced per mare was higher (P < 0.05) in mares in Group 2 (3.5) than in Group 1 (1.6).Although it is not clear whether the increased ovulation rate is due specifically to dose or frequency, twice-daily administration of a high dose of EPE significantly improved follicular development, ovulation and embryo recovery over the standard treatment of once-daily injection. (C) 2001 by Elsevier B.V.

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This study evaluated the effect of Matricaria chamomilla and vaccination frequency on cattle immunization against rabies. Four groups (n = 15/group) were treated with or without Matricaria chamomilla CH12 and vaccinated with one or two doses of rabies vaccine (30 day interval). No effect of chamomile was found on cattle immunization against rabies; however, antibody titers were protective in cattle vaccinated twice, while 93.3% of cattle vaccinated only once had titers under 0.5 UI/ml after 60 days. In conclusion, the use of chamomile did not alter the Immoral immune response in cattle, and two vaccine doses are suggested for achieving protective antibody titers.

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This study tested the use of ventilatory frequency (VF) as an indicator of stress in the Nile tilapia, Oreochromis niloticus (L.). Firstly, we tested the relationship between VF and plasma cortisol after confinement. Confined fish showed higher VF and plasma cortisol levels, but the latter continued to increase significantly for longer time than VF. Secondly, we conducted another experiment to test the use of VF as indicator of fish stress. In four out of six treatment, we confined the fish for different intervals (30 s, 5, 15 or 30 min). The others were used as control. In one, no handling was imposed. The other control consisted of introducing the partition (the same used to perform the confinement) into the aquarium for less than 4 s, without confinement and immediately removing the partition (partition control). Ventilatory frequency was increased for the partition control as much as for the longer duration of confinement. This clearly indicates that VF is a very sensitivity response to disturbance, but of limited use because this parameter does not reflect the severity of the stimulus. Thus, although VF is a non-invasive technique that does not require sophisticated recording equipment, its usefulness is limited. (C) 2004 Elsevier B.V. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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To study the effects of environmental hypercarbia on ventilation in snakes, particularly the anomalous hyperpnea that is seen when CO(2) is removed from inspired gas mixtures (post-hypercapnic hyperpnea), gas mixtures of varying concentrations of CO(2) were administered to South American rattlesnakes, Crotalus durissus, breathing through an intact respiratory system or via a tracheal cannula by-passing the upper airways. Exposure to environmental hypercarbia at increasing levels, up to 7% CO(2), produced a progressive decrease in breathing frequency and increase in tidal volume. The net result was that total ventilation increased modestly, up to 5% CO(2) and then declined slightly on 7% CO(2). on return to breathing air there was an immediate but transient increase in breathing frequency and a further increase in tidal volume that produced a marked overshoot in ventilation. The magnitude of this post-hypercapnic hyperpnea was proportional to the level of previously inspired CO(2). Administration of CO(2) to the lungs alone produced effects that were identical to administration to both lungs and upper airways and this effect was removed by vagotomy. Administration of CO(2) to the upper airways alone was without effect. Systemic injection of boluses of CO(2)-rich blood produced an immediate increase in both breathing frequency and tidal volume. These data indicate that the post-hypercapnic hyperpnea resulted from the removal of inhibitory inputs from pulmonary receptors and suggest that while the ventilatory response to environmental hypercarbia in this species is a result of conflicting inputs from different receptor groups, this does not include input from upper airway receptors.

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A introdução do mesilato de imatinibe como tratamento da leucemia mielóide crônica tem salvado muitos pacientes, mas o sucesso da terapia tem sido prejudicado pela resistência e possível não destruição do clone maligno. Este artigo descreve a resposta citogenética e padrões citogenéticos anormais envolvendo os genes ABL e BCR detectados por FISH em pacientes em uso exclusivo de imatinibe. Os resultados mostraram que outras alterações envolvendo os genes BCR e ABL não parecem estar relacionadas à resistência à droga, elas ocorrem em baixas freqüências e podem não estar associadas à resposta citogenética ou ao tempo de tratamento. Contudo, a resposta ao imatinibe parece ser individual e imprevisível, independente do tempo e do início do tratamento após o diagnóstico.

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Two lines of rainbow trout (Oncorhynchus mykiss) that exhibit divergent endocrine responsiveness to stressors also display disparate behavioral traits. To investigate whether the high-responding (HR) and low-responding (LR) fish also differ in cognitive function, the rate of extinction of a conditioned response was compared between the two lines. Groups of HR and LR fish were exposed to a paired conditioned stimulus (CS- water off) and unconditioned stimulus (US; confinement stressor). After exposure to 18 CS-US pairings, at least 70% of individuals of both lines acquired a conditioned response (CR) manifested as an elevation of blood cortisol levels on presentation of the CS only. Post-conditioning, the fish were tested by presentation of the CS at weekly intervals, for 4 weeks, with no further reinforcement, and the extinction of the CR in the two lines was compared. The decline in mean plasma cortisol levels after exposure to the CS over successive tests suggested that the CR was retained for a shorter period among the HR (<14 days) than LR fish (<21 days). The frequency of individuals within each line whose plasma cortisol levels indicated a stress response when exposed to the CS was significantly greater among the LR than HR fish at 14 and 21 days with no HR fish falling into this category at 21 days. At 28 days post-conditioning, there were no HR fish and only three LR fish were categorized as stressed. These results suggest that there are differences in cognitive function between the two lines. Possible mechanisms underlying these differences are discussed. (C) 2004 Elsevier B.V. All rights reserved.