排序方式： 共有19条查询结果，搜索用时 15 毫秒
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M. A. A. Paalman C. H. Van Der Weijden J. P. G. Loch 《Water, air, and soil pollution》1994,73(1):49-60
Sorption of Cd at low concentrations onto river Rhine suspended matter was examined in terms of sorption rate, reversibility and factors such as competition and complexation with major inorganic sea-water ions. More than 90% of the final amount of Cd is sorbed within the first few hours. Desorption experiments show that the process is virtually reversible. In experiments with diluted sea water the sorption of Cd strongly decreases even at low salinity. Sorption isotherms show that the sorption of Cd in NaNO3 solutions is regulated by the free Cd2+ activity. In a Ca(NO3)2 environment the Cd sorption decreases with increasing Ca2+ concentrations, which implies competition between Ca2+ and Cd2+ for the different sorption sites. In different electrolyte solutions of similar ionic strength the sorption of Cd decreases in the solution order NaNO3 > NaCl > NaCl+MgCl2+CaCl2 > diluted sea water. Although inorganic speciation calculations show that even at low salinities dissolved Cd is dominated by Cd-chloro complexes, chloride accounts for only about one third of the increased mobility of Cd. As a result of addition of Ca2+ and Mg2+ the sorption capacity of suspended matter for Cd is further reduced by a factor three. 相似文献
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JF Pycock S. Dieleman P. Drifjhout Y. van der Brug C. Oei GC van der Weijden 《Reproduction in domestic animals》1995,30(4):224-227
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Inchaisri C Jorritsma R Vernooij JC Vos PL van der Weijden GC Hogeveen H 《Reproduction in domestic animals》2011,46(6):1043-1049
The objective of this research was to determine the contribution of cow factors to the probability of successful insemination accounting for the serial number of inseminations in analysis. The investigation was performed with 101,297 insemination records in 51,525 lactations of different cows from 1368 herds obtained from the Dutch milk production recording database. Cows that had a first insemination (AI) between 40 and 150 days post-partum with one or more inseminations (≤6 inseminations) were selected. An insemination was defined successful when not followed by another insemination and when the cow calved between 267 and 295 days after insemination, or when the cow was culled between 135 and 295 days after the last insemination. Breed, parity, days in milk, lactation curve characteristics, milk production traits, moment of AI related to peak milk yield time (before or after peak milk yield), the last calf (female, male, twin or stillbirth) and season of insemination were selected as independent parameters for a model with successful rate of insemination as dependent parameter. A multivariable logistic regression model was used within cow and farm as a random effect. The probability of successful insemination was the highest in the first insemination and decreased in the following inseminations. However, the success rate of all inseminations increased in a later stage of lactation. The improvement in the successful inseminations in a later stage of lactation was better in multiparous cows than in first parity cows. Insemination in summer and before peak milk yield time reduced the success of insemination. The success rate was the lowest in 100% Holstein Friesian cows compared with other breeds and was the highest when the last calf was a female calf compared to a male calf, twin or stillbirth. In conclusion, the success of first and following inseminations depended on parity, breed, season of insemination, last calf status, daily milk yield at insemination date, serial insemination number and days in milk at insemination date. 相似文献
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Bajcsy AC Kindahl H Szenci O van der Weijden GC Bartyik J Taverne MA 《Reproduction in domestic animals》2012,47(2):208-212
Various parenteral treatment forms of oxytocin, as often used under praxis circumstances, may act differently on contractility of the uterus during the first days of the puerperium. Various patterns of such induced uterotonic responses may lead to alterations in the emptying characteristics of the uterine lumen, thus influencing, as a late consequence, the process of involution. Therefore, this study was designed to test whether two different parenteral administration forms of oxytocin induce changes in peripheral plasma concentrations of 15-ketodihydro-prostaglandin F(2α) (PGF(2α) metabolite) in early post-partum cows. Between 13 and 15 h after uncomplicated calving, healthy dairy cows without retained foetal membranes were treated with 50 IU oxytocin, either intramuscularly (OT-IM group; n = 15) or intravenously (OT-IV group; n = 16). Saline solution was administered intramuscularly as controls (CON group; n = 15). Jugular blood samples were taken at 10-min intervals from 1 h before to 2 h after treatment. Plasma PGF(2α) metabolite levels were measured by radioimmunoassay. No significant differences in peripheral plasma PGF(2α) metabolite concentrations occurred in the OT-IM and CON groups, but mean values significantly increased in the OT-IV group, peaking at 20 min after treatment and reaching pre-treatment baseline values again at 120 min. Although the source of prostaglandins was not investigated in this study, our results suggest that exogenous oxytocin may enhance secretion of prostaglandins by the uterus during the first day after normal calving. These prostaglandins might contribute, by an endocrine or paracrine route, to the stimulation of myometrial contractility when exogenous oxytocin is given during this early post-partum stage. 相似文献
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MAM Taverne NCM de Schwartz M Kankofer MM Bevers HA van Oord D Schams St Gutjahr & GC van der Weijden 《Reproduction in domestic animals》2001,36(5):267-272
The aim of this study was to test the functional status of uterine oxytocin receptors in cows in vivo around parturition. The animals received consecutive, intra‐arterial injections of 800, 1600 and 3200 mU of oxytocin at three different stages: during late gestation (days 260–274), at 12 h and at 24 h after intramuscular injection of a prostaglandin F2α analogue at day 275 to induce parturition. Cows (n=6) had been provided with myometrial electrodes and a catheter had been installed in the aorta and in a branch of the uterine vein (UV). Regular blood samples were obtained from the UV from 5 min before until 45 min after each oxytocin injection to measure plasma levels of prostaglandin F2α (PGF2α) and oxytocin. Uterine electromyographic (EMG) activity was registered continuously during each experiment. The increase of oxytocin levels in UV plasma after intra‐arterial injections was dose dependent (p < 0.02). Pre‐ and post treatment oxytocin levels at 24 h after induction of parturition were significantly increased (p=0.0313). Both during late pregnancy and at 12 h after induction of parturition, oxytocin caused a significant increase in EMG activity (p=0.022). After the 3200 mU dose the increase was significantly higher than with the other 2 doses (p=0.004). After each dose, EMG activity returned to baseline levels within some 15 min. At 24 h after induction of parturition, the pre‐treatment level of EMG activity had increased. Doses of 800 mU and 1600 mU of oxytocin produced a significant (p=0.022) increment of EMG activity, which was of the same magnitude as during the preceding stages; after 3200 mU of oxytocin the response was significantly higher than before (p=0.008). No significant increases of PGF2α levels in UV plasma could be measured after oxytocin injections at any of the three stages. It is concluded that the myometrium of the pregnant cow responds in vivo to physiological doses of oxytocin. At 24 h after induction of parturition, when luteolysis has occurred and a parturient pattern of parturient myometrial activity has already started to develop, the response is enhanced. Physiological doses of oxytocin did not evoke a spurt release of PGF2α in uterine venous blood during the peripartal period. 相似文献
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Roads may effect animal communities in various ways. One such way is ‘di sturbance’, i.e. emission of stimuli to which animals may respond by avoiding the vicinity of the road. The extent, intensity and mechanism of this effect is almost entirely unknown. Veen (1973), studying the bird species lapwing Vanellus vanellus, black-tailed godwit Limosa limosa, oystercatcher Haematopus ostralegus, redshank Tringa totanus and ruff Philomachus pugnax in open grassland areas, found disturbance over surprisingly long distances, ranging from 500–600 m for a quiet rural road to 1600–1800m for a busy highway. However, his approach has met with serious methodological criticism.The validity of Veen's conclusions was tested by critically reanalysing bird distribution in one of his study plots. It is inferred that his conclusions do hold for the lapwing, the godwit and possibly the redshank, though not for the oystercatcher. An additional field study in four areas yielded similar results, with comparable disturbance distances. The total population loss over this distance may amount to 60%. Rough indications were obtained that the distance-density graph is a logistic one, while the relation between traffic volume and total population loss is possibly logarithmic. In addition confirmation was obtained of the general impression that, apart from roads, disturbance may also be caused by farms, other buildings and plantations, suggesting that disturbance caused by a road is not easily eliminated by planting trees alongside.It is recommended that extra care be taken in planning new roads, while impact statements concerning roads which disregard disturbance and other long-distance effects on the fauna should be rejected. 相似文献
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