排序方式： 共有70条查询结果，搜索用时 31 毫秒
61.
62.
One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites. 相似文献
63.
We examined effects of nutrient availability and changing root zone temperature (RZT) on growth, gas exchange and plasma membrane H(+)-ATPase (PM-ATPase) activity of roots of 1-year-old Scots pine (Pinus sylvestris L.) seedlings during spring flushing. The 6-week growth-chamber experiment was carried out in hydroponic cultures that supplied the seedlings with low (0.5 mM N) or high (3 mM N) nutrient concentration and two rates of increase in RZT were simulated: slow warming (SW-treatment) and fast warming (FW-treatment). Air temperature, humidity, and light conditions were similar in all treatments. Growth of roots and shoots was retarded at low RZT, and fresh mass increment of roots was closely correlated with RZT sum. High nutrient availability increased nitrogen concentrations of needles and stems, but only at RZTs >13 degrees C. Low RZT and low availability of nutrients suppressed gas exchange of the seedlings. Real PM-ATPase activity was highly dependent on RZT. At high RZTs, real PM-ATPase activity was affected by nutrient availability but this effect was related to root growth. We conclude that, under conditions of high nutrient availability, Scots pine seedlings can compensate for the suppressive effects of long-term exposure to low RZT by rapidly accelerating growth, gas exchange and root metabolism, but only when RZT has increased above a threshold value, which was 13 degrees C in this study. 相似文献
64.
KL Goularte EM Madeira CER Ferreira EH Duval AD Vieira RG Mondadori T Lucia Jr 《Reproduction in domestic animals》2015,50(6):972-979
Bull semen production centres (SPC) generally present satisfactory quality control for sperm processing, but non‐standardized hygiene procedures. This study describes a Hazard Analysis and Critical Control Points (HACCP) system developed for bull SPC and subsequently implemented in a commercial SPC. After the identification of hazards at each step of semen processing and the determination of their risk and severity, monitoring and corrective procedures were designed to assess the system's efficiency. The HACCP system identified six microbiological hazards, 10 physical hazards, four chemical hazards and three critical control points. After the establishment of Good Processing Practices, Standard Operating Procedures and Standard Sanitizing Operating Procedures, the system was validated through an audit, to identify eventual failures and to define measures to correct them. 相似文献
65.
SUMMARY Two cases of abnormal accumulation of foetal fluids in sheep are described. In the first case, a ewe, at 64 days of pregnancy, had 2 sacs of fluid, one at each of the tips of the pregnant and non-pregnant horns. Neither sac contained a foetus. The composition of the fluids differed from those of the amniotic and allantoic fluids associated with a single foetus. The composition resembled that of foetal plasma. We conclude that the 2 sacs were amniotic sacs from conceptuses that had been resorbed, and that at this early (0.4) stage of pregnancy, amniotic fluid can accumulate in the absence of a viable foetus.
The second case was a rare case of hydrallantois in a ewe at 100 days of pregnancy. The volume of allantoic fluid (1800 mL) was more than 10 times normal. The composition was normal, except for high chloride and calcium concentrations and a very low creatinine concentration. The foetus and the volume and composition of the amniotic fluid were normal. The hydrallantois might have occurred as a result of some alteration in function of the allantoic membrane, perhaps as a result of altered hormonal status of the ewe. 相似文献
The second case was a rare case of hydrallantois in a ewe at 100 days of pregnancy. The volume of allantoic fluid (1800 mL) was more than 10 times normal. The composition was normal, except for high chloride and calcium concentrations and a very low creatinine concentration. The foetus and the volume and composition of the amniotic fluid were normal. The hydrallantois might have occurred as a result of some alteration in function of the allantoic membrane, perhaps as a result of altered hormonal status of the ewe. 相似文献
66.
Riikonen J Kets K Darbah J Oksanen E Sober A Vapaavuori E Kubiske ME Nelson N Karnosky DF 《Tree physiology》2008,28(2):243-254
Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO(2) ([CO(2)]) or O(3) ([O(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. The trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwintering buds and early leaf development during the 8th-9th year of free-air CO(2) and O(3) exposure at the Aspen FACE site located near Rhinelander, WI. Net photosynthesis was enhanced 49-73% by elevated [CO(2)], and decreased 13-30% by elevated [O(3)]. Elevated [CO(2)] delayed, and elevated [O(3)] tended to accelerate, leaf abscission in autumn. Elevated [CO(2)] increased the ratio of monosaccharides to di- and oligosaccharides in aspen buds, which may indicate a lag in cold acclimation. The total carbon concentration in overwintering buds was unaffected by the treatments, although elevated [O(3)] decreased the amount of starch by 16% in birch buds, and reduced the size of aspen buds, which may be related to the delayed leaf development in aspen during the spring. Elevated [CO(2)] generally ameliorated the effects of elevated [O(3)]. Our results show that both elevated [CO(2)] and elevated [O(3)] have the potential to alter carbon metabolism of overwintering buds. These changes may cause carry-over effects during the next growing season. 相似文献
67.
TM Tamminen L Sahlin B Masironi J Taponen O Laitinen‐Vapaavuori T Katila 《Reproduction in domestic animals》2017,52(1):153-159
The aim of the study was to localize oxytocin receptors (OTR) and measure mRNA expression of OTR in the canine uterus with and without the influence of progesterone. Uterine samples were taken from nine anoestrous and eight dioestrous bitches during ovariohysterectomy. Histological changes were evaluated in haematoxylin and eosin (HE)‐stained samples. Purified polyclonal antibody for OTR was used in immunohistochemistry to localize receptors in uterine layers. Relative mRNA concentration of OTR was evaluated with real‐time PCR from full‐thickness uterine samples taken from the middle horn and the body. Myometrial smooth muscle cells, endometrial luminal epithelium (LE) and deep and superficial glandular epithelium were positively stained for oxytocin receptors in non‐pregnant animals. No significant difference in staining intensity was detected between uterine middle horn and body. However, the staining intensity of LE was significantly higher in dioestrous than in anoestrous uteri (p < .05). Leucocytes and endothelium of blood vessels were also positively stained for OTR. Real‐time PCR showed no significant differences in OTR mRNA expression between the middle horn and the body of the uterus, or between anoestrous and dioestrous uterus. No correlation was noted between OTR mRNA expression and blood progesterone concentration. In conclusion, despite the apparent inactivity, the uterus of the non‐pregnant bitch expresses OTR. The distribution or relative expression of OTR does not differ between uterine horn and body in dioestrus or anoestrus except in LE. LE may have more oxytocin‐dependent activity during dioestrus than anoestrus. 相似文献
68.
An ultrasound assessment of follicle turnover following two different protocols for synchronization of oestrus and ovulation, as well as an assessment of achieved synchronization between ovulation and AI and conception rates in nulliparous and pluriparous buffaloes were carried out during months of increasing day length. Nulliparous buffaloes (n = 30) were subjected only to Ovsynch protocol whereas pluriparous buffaloes (n = 31) were assigned to Ovsynch (n = 14) or to PRID-pregnant mare serum gonadotrophin (PMSG) (n = 17) protocol according to the presence of functional CL confirming cyclic and acyclic conditions. Ultrasound examination of ovarian follicular dynamics at critical days in the course of synchronization treatments was employed to monitor the fate of the largest available follicles at the beginning of treatments. Such available dominant follicle would persist throughout the protocol as ovulating follicle (no-follicle shift) or would regress giving way to a new follicle to become dominant and ovulate (follicle shift). Furthermore, ultrasound monitoring would determine the degree of synchronization of ovulation and final outcome represented by pregnancy rates. Pregnancy rate following Ovsynch protocol was 40% (12/30) and 42.8% (6/14) in nulliparous and pluriparous buffaloes respectively (p = 0.8575). Most ovulations were synchronized and recorded at AI and the following day in nulliparous (24/30; 80%) and pluriparous (12/14; 85.7%) buffaloes respectively (p = 1.000). A follicle shift was recorded in 14 of 30 (46.6%) and 11 of 14 (78.5%) in nulliparous and pluriparous buffaloes respectively (p = 0.0466). Among established pregnancies: eight derived from follicle shift (66.6%) and four from no-follicle shift (33.3%) in nulliparous buffaloes, p = 0.0729 whereas in pluriparous buffaloes five (83.3%) derived from follicle shift and one from no-follicle shift (16.6%), p = 0.6154. Collectively, from 18 pregnancies in nulliparous and pluriparous buffaloes following Ovsynch protocol, 13 derived from follicle shift (72.2%) and five from no-follicle shift (27.7%), p = 0.0860. Pregnancy rate in pluriparous buffaloes following PRID-PMSG protocol was 70.5% (12/17). The majority of ovulations were synchronized and recorded at first, second AI and following day (13/17; 76.4%). A follicle shift occurred in 15/17 buffaloes (88.2%) and among the 12 recorded pregnancies, 11 derived from follicle shift (91.6%), p = 0.5147. In conclusion, pregnancy rates following Ovsynch protocol were similar in nulliparous and pluriparous cyclic buffaloes. A progestagen treatment on acyclic buffaloes but still displaying some ovarian follicular dynamics, resulted in significantly higher pregnancy rate compared with Ovsynch (p = 0.0376). According to the time of scheduled AI, a high degree of synchronized ovulations were recorded following the implementation of both protocols. 相似文献
69.
70.
RA Satrapa EM Razza ACS Castilho RAL Simões CF Silva T Nabhan MF Pegorer CM Barros 《Reproduction in domestic animals》2013,48(6):1043-1048
The IGF system is related to embryo quality. We aim to determine the effect of the heat stress on the mRNA expression of IGF1 and IGF2, IGFR1 and IGFR2, IGFBP2 and IGFBP4, and PAPPA in in vitro production (IVP) blastocysts from Nelore and Holstein after ovum pick up (OPU) to better understand the differences between these breeds. Oocytes from four Nelore and seven Holstein were collected in six OPU sessions. Following in vitro maturation and fertilization using six Nelore or Holstein sires, embryos were divided into control (cultured at 39°C) and heat stress (HS; exposed to 41°C for 9 h). Blastocysts were submitted to RNA extraction. The IGF1 expression was higher in blastocysts under HS in both breeds, and the expression of IGFBP2 and IGFBP4 was higher in Holstein blastocysts under HS. The high PAPPA expression and the low expression of IGFBP2 and IGFBP4 are associated with a more efficient degradation of IGFBPs, which results in greater IGF bioavailability in Nelore blastocysts and may contribute to the superior HS tolerance in Nelore, when compared to Holstein. 相似文献