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排序方式: 共有123条查询结果,搜索用时 15 毫秒
101.
Tenhagen BA Surholt R Wittke M Vogel C Drillich M Heuwieser W 《Animal reproduction science》2004,81(1-2):1-11
Ovsynch protocols are used to increase service rate and decrease days open and cullings for infertility. Recent reports have indicated better results after Ovsynch in primiparous than in older cows. However, this was not observed in all investigations on the subject. The objective of the study was to evaluate differences between primiparous and multiparous cows after synchronization of ovulation with an Ovsynch protocol in six trials. A total of 1584 cows (583 primiparous and 1001 multiparous cows, respectively) on three dairy farms were synchronized with an Ovsynch protocol consisting of a GnRH-analogue at Days 0 and 9, and a prostaglandin F(2alpha) analogue on Day 7. AI was carried out in all cows 16-20 h after the last treatment. Cows were categorized into primiparous and multiparous cows for analysis. Conception rate (CR) to timed AI, to further AI, overall conception rate and proportion of cows pregnant by 200 days in milk were compared between the age groups. Finally, two logistic regression models were calculated with conception to first service and conception by 200 DIM as the outcome variables. Independent variables were trial (categorical) and age group (primiparous versus multiparous). Conception rates to TAI were higher in primiparous than in older cows (37.9% versus 31.6%, P=0.015). Likewise pregnancy rates by 200 DIM were higher in primiparous cows (81.8% versus 75.4%, P=0.003). However, the extent of the difference varied between trials. Results indicate that Ovsynch protocols are more effective in primiparous than in older cows. 相似文献
102.
Lax JE Arteni AA Boekema EJ Pistorius EK Michel KP Rögner M 《Biochimica et biophysica acta》2007,1767(6):528-534
Iron deficiency triggers various processes in cyanobacterial cells of which the synthesis of an additional antenna system (IsiA) around photosystem (PS) 1 is well documented [T.S. Bibby, J. Nield, J. Barber, Iron deficiency induces the formation of an antenna ring around trimeric photosystem I in cyanobacteria, Nature 412 (2001) 743-745, E.J. Boekema, A. Hifney, A.E. Yakushevska, M. Piotrowski, W. Keegstra, S. Berry, K.P. Michel, E.K. Pistorius, J. Kruip, A giant chlorophyll-protein complex induced by iron deficiency in cyanobacteria, Nature 412 (2001) 745-748]. Here we show that PS2 also undergoes prominent structural changes upon iron deficiency: Prerequisite is the isolation and purification of a PS2-IdiA complex which is exclusively synthesized under these conditions. Immunoblotting in combination with size exclusion chromatography shows that IdiA is only bound to dimeric PS2. Using single particle analysis of negatively stained specimens, IdiA can be localized in averaged electron micrographs on top of the CP43 subunit facing the cytoplasmic side in a model derived from the known 3D structure of PS2 [B. Loll, J. Kern, W. Saenger, A. Zouni, J. Biesiadka, Towards complete cofactor arrangement in the 3.0 A resolution structure of photosystem II, Nature 438 (2005) 1040-4]. The presence of IdiA as integral part of PS2 is the first example of a new PS2 protein being expressed under stress conditions, which is missing in highly purified PS2 complexes isolated from iron-sufficient cells. 相似文献
103.
Elfriede Huber 《Protoplasma》1956,45(3):491-506
Ohne Zusammenfassung 相似文献
104.
B Surholt J M Van Doorn J Goldberg D J Van der Horst 《Biological chemistry Hoppe-Seyler》1992,373(1):13-20
The formation of low-density lipophorin (LDLp) in insect hemolymph, resulting from association of high-density lipophorin (HDLp) with both lipid and apolipophorin III, is considered to provide a reutilizable lipid shuttle for flight muscle energy supply. The changes in lipid and apolipoprotein composition of LDLp, isolated after flight activity, compared to that of HDLp in the hemolymph at rest, were studied in two evolutionary divergent insects, the hawkmoth Acherontia atropos and the migratory locust, Locusta migratoria. Using FPLC on Superose 6 prep grade as a novel technique to separate the apolipophorins of HDLp and LDLp, the ratio of apolipoprotein I, II, and III in HDLp of both species was demonstrated to be 1:1:1, whereas flight activity resulted in a ratio of 1:1:10 in LDLp. Injection of adipokinetic hormone into resting moths showed that, depending on the dose, the number of apolipophorin III molecules in LDLp can exceed that recovered after the physiological condition of flight. Analysis of the lipophorin lipids demonstrated that in addition to the considerable increase in diacylglycerol in the LDLp particle, which is consistent with the role LDLp in energy supply, particularly the hydrocarbons were increased compared to HDLp, rendering the mechanism of LDLp formation from HDLp even more complex. 相似文献
105.
106.
107.
Four Δ5-sterols and six Δ7-sterols were isolated from the seed oil of Trichosanthes kirilowii and identified as campesterol, sitosterol, stigmasterol, Δ7-campesterol, Δ7-stigmasterol, Δ7,22-stigmastadienol, 24-ethylcholesta-5,25-diene-3β-ol, 24-ethylcholesta-7,24(25)-diene-3β-ol, 24-ethylcholesta-7,25-diene-3β-ol, and 24-ethylcholesta-7,22,25-trine-3β-ol. 相似文献
108.
109.
Extraction with EDTA of lyophilized and lysozyme treated preparations of the blue-green algae Anacystis nidulans resulted in loss of the capacity for photoevolution of O2. Reactivation was achieved by the addition of both cations: Mn2+ and Ca2+ (or to a smaller extent by Mn2+ and Sr2+). The dual requirement for Mn2+ and Ca2+ could be demonstrated when the O2 evolution under short saturating light flashes and the variable chlorophyll fluorescence associated with the reduction of the primary acceptor of Photosystem II was examined. The fluorescence experiments in addition showed that incorporation of the cations was a light dependent step, since the fluorescence rise only started after a lag period. 相似文献