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Dregus M Schmarr HG Takahisa E Engel KH 《Journal of agricultural and food chemistry》2003,51(24):7086-7091
The enantiomeric compositions of 2-methylbutanol (1), 4-methylhexanol (2), 2-methylbutanoic acid (3), and 4-methylhexanoic acid (4) present in rhubarb (Rheum rhabarbarum L.) stalks were determined. Enantiodifferentiation was achieved via multidimensional gas chromatography using heptakis(2,3,6-tri-O-ethyl)-beta-cyclodextrin as a chiral stationary phase. For all compounds the enantiomeric ratios were in favor of the (R)-enantiomers. The alcohols (1 and 2) exhibited generally high excesses of the (R)-enantiomers, the ratios varying slightly from batch to batch. For the acid (3) a rather narrow range averaging 65% (R):35% (S) was observed. The procedure applied to isolate the volatiles (vacuum headspace technique, simultaneous distillation--extraction, liquid--liquid extraction) had no significant impact on the enantiomeric ratios. The study describes for the first time a plant used as food material in which 2-methyl-branched volatiles are not nearly exclusively present as (S)-enantiomers. This information enlarges the current regulatory knowledge regarding the classification of these important flavor compounds as "natural" on the basis of their enantiomeric ratios. 相似文献
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This field study investigated whether the administration of a single dose of gonadotropin‐releasing hormone (GnRH) to dairy cows without a corpus luteum (CL) 4 weeks after calving can improve reproductive performance. Holstein dairy cows underwent ultrasonography to assess the presence of ovarian structures at 29.2 ± 5.2 days post‐partum, and cows were divided into two main groups based on the presence (CL group, n = 230) or absence (non‐CL group, n = 460) of a CL. The non‐CL group was further randomly divided into two subgroups based on the administration of GnRH (non‐CL GnRH group, n = 230) or no GnRH (non‐CL control group, n = 230). Subsets of cows from non‐CL control (n = 166) and non‐CL GnRH (n = 175) groups received a second ultrasonography at 44.5 ± 5.4 days post‐partum to assess CL formation. The percentage of cows with CL at the second ultrasonography was greater in the non‐CL GnRH group (70.9%) than in the non‐CL control group (53.0%, p = 0.0006). The hazard of the first post‐partum insemination by 150 days in milk (DIM) was higher in the CL group than in the non‐CL control group (hazard ratio [HR]: 1.36, p = 0.001). The probability of a pregnancy to the first insemination was higher in non‐CL GnRH (odds ratio [OR]: 1.50, p = 0.04) and CL groups (OR: 1.55, p = 0.03) compared to the non‐CL control group. Furthermore, the hazard of pregnancy by 210 DIM was higher in non‐CL GnRH (HR: 1.30, p = 0.01) and CL (HR: 1.51, p = 0.0001) groups than in the non‐CL control group. In conclusion, administration of GnRH to dairy cows without a CL 4 weeks after calving was associated with an increase in ovulation and improved reproductive performance. 相似文献
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M Dorsch B Meehan WP Michalski HG Heine AJ Foord G Carlile J Wang S McCullough K Zuelke 《Australian veterinary journal》2016,94(3):64-66
In this study, we explored the potential utility of the human‐focused FilmArray® Respiratory Panel for the diagnosis of a broad range of influenza viruses of veterinary concern as compared with the standard portfolio of recommended TaqMan®‐based diagnostic tests. In addition, we discuss some potential operational advantages associated with the use of such integrated sample extraction, amplification and analysis devices in the context of a future long‐term, dual‐role strategy for the detection of emergency diseases of both human and veterinary concern. 相似文献
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H G Schmarr W Eisenreich K H Engel 《Journal of agricultural and food chemistry》2001,49(12):5923-5928
Cis- and trans-3-methyl-4-octanolide (1, whiskey lactones) were converted into their thio- (2), thiono- (3), and dithio- (4) derivatives by reaction with phosphorus pentasulfide. The reaction products were characterized by GC-mass spectrometry, (1)H NMR spectroscopy, and GC-olfactometry. Two-dimensional NOESY spectra showed that sulfur is incorporated into the ring with reversal of the absolute configuration at C-4, whereas substitution of the keto-oxygen atom by sulfur occurs with retention of ring configuration. The cis- and trans-pairs of 2, 3, and 4 were separated into enantiomers by GC on heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin as chiral stationary phases. GC-olfactometry revealed a sweet coconut-like odor for the cis-thio- and pleasant mushroom-like flavors for the cis-thiono- and trans-dithio-derivatives of whiskey lactone. 相似文献
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The mare provides a unique experimental model for studying follicle development in monovular species. Development of antral follicles in horses is characterized by the periodic growth of follicular waves which often involve the selection of a single dominant follicle. If properly stimulated, the dominant follicle will complete development and eventually ovulate a fertile oocyte. Regulation of follicular wave emergence and follicle selection involves an interplay between circulating gonadotropins and follicular factors that ensures that individual follicles are properly stimulated to grow (or to regress) at any given stage of follicular wave development. Periodic development of follicular waves continuously occurs during most of post-natal life in the mare and is influenced by factors such as stage of oestrous cycle, season, pregnancy, age, breed and individual so that different types of follicular waves (minor or major, ovulatory or anovulatory) and different levels of activity within waves may develop under different physiological conditions. Changes in gonadotropin levels and/or in the sensitivity of follicles to circulating gonadotropins seem to account largely for these physiological variations in follicle development. 相似文献