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排序方式: 共有269条查询结果,搜索用时 15 毫秒
1.
Myrian Megumy Tsunokawa Hidalgo Ana Beatriz Marques de Almeida Fábio Lucas Zito de Moraes Rodrigo Yudi Palhaci Marubayashi Fabiana Ferreira de Souza Thales Ricardo Rigo Barreiros Maria Isabel Mello Martins 《Reproduction in domestic animals》2021,56(8):1117-1127
This study aimed to study the characteristics and subpopulations of spermatozoa from bulls with low and high reproductive performance based on pregnancy rates. Based on historical records of pregnancy rate from four farms, 24 bulls were selected. Two groups were established, with low pregnancy rates (n = 12; LOW), including bulls that presented pregnancy rates <52.27% (33.33% to 51.81%); and a group with high pregnancy rates (n = 12; HIGH), with pregnancy rates >52.27% (52.27% to 69.64%), after fixed-time artificial insemination (FTAI). The thawed sperm straws were analysed to sperm kinetics, morphology, plasma membrane integrity and sperm subpopulations. The LOW group exhibited a higher proportion of static cells (p < .05). In contrast, the HIGH group showed greater percentages for membrane integrity and total and progressive motility, and cells with fast and medium velocity (p < .05). In the cluster procedures, four sperm subpopulations were established. The low-fertility bulls presented the highest percentage of subpopulation 2 (41.46%), characterized by slow and progressive spermatozoa. The high-fertility bulls exhibited the highest percentage of subpopulation 3 (37.17%), characterized by fast and nonlinear spermatozoa. Results from this study indicated that bulls with greater percentages of fast and nonlinear spermatozoa seem to have greater fertilization capacity and the subpopulations analysis can be considered a tool to identify ejaculates with high fertility. 相似文献
2.
The reaction of 2,4-decadienal and methyl 13-oxooctadeca-9,11-dienoate with phenylalanine was studied to determine if alkadienals and ketodienes are able to produce the Strecker-type degradation of amino acids to the corresponding Strecker aldehydes. When reactions were carried out at 180 degrees C, both carbonyl compounds degraded phenylalanine to phenylacetaldehyde, among other compounds. The yield of the phenylacetaldehyde produced depended on the reaction pH and increased linearly with both the amount of the lipid and the reaction time. The yield of this conversion was approximately 8% when starting from decadienal and approximately 6% when starting from methyl 13-oxooctadeca-9,11-dienoate, and the reaction rate was lower for the ketone than for the aldehyde. Simultaneous to these reactions, the lipid was converted into pyrrole, pyridine, or aldehyde derivatives as a result of several competitive reactions. In particular, 9-14% of the decadienal was converted into hexanal under the assayed conditions. All these reactions are suggested to be produced as a consequence of the oxidation of the alkadienal or the ketodiene to the corresponding epoxyalkenal or unsaturated epoxyketone, which were identified in the reaction mixtures by GC-MS. All these results suggest that alkadienals and ketodienes, which are quantitatively important secondary lipid oxidation products, can degrade amino acids to their corresponding Strecker aldehydes. Therefore, under appropriate conditions, these products are not final products of the lipid oxidation and can participate in carbonyl-amine reactions analogously to other lipid oxidation products with two oxygenated functions. 相似文献
3.
Acanthocephalan and spargana parasites were identified within a body wall mass during exploratory surgery in a wild green tree snake. Acanthocephalan parasites have not previously been reported in this species. Surgical excision, the treatment of choice, could not be achieved because of the extensive infiltration of the coelomic cavity. 相似文献
4.
5.
Díaz-Maroto MC Díaz-Maroto Hidalgo IJ Sánchez-Palomo E Pérez-Coello MS 《Journal of agricultural and food chemistry》2005,53(13):5385-5389
Volatile oil extracts of fennel seeds (Foeniculum vulgare Mill.) and thyme leaves (Thymus vulgaris L.) were obtained by simultaneous distillation-extraction (SDE) and supercritical fluid extraction (SFE) and analyzed by gas chromatography-mass spectrometry (GC-MS). In general, fennel oil extracted by SDE and SFE showed similar compositions, with trans-anethole, estragole, and fenchone as the main components. In contrast, thymol and p-cymene, the most abundant compounds in thyme leaves, showed big differences, with generally higher amounts of monoterpenes obtained by SDE. However, in this case, the differences between the extracts were higher. Key odorants of fennel seeds determined by gas chromatography-olfactometry (GC-O) showed similar patterns when applying SDE and SFE. trans-Anethole (anise, licorice), estragole (anise, licorice, sweet), fenchone (mint, camphor, warm), and 1-octen-3-ol (mushroom) were the most intense odor compounds detected in fennel extracts. Thymol and carvacrol, with oregano, thyme, and spicy notes, were identified as key compounds contributing to the aroma of thyme leaves. 相似文献
6.
The oxidation of methyl linoleate (LMe) in the presence of bovine serum albumin (BSA) was studied to analyze both the processes involved when lipid oxidation occurs in the presence of proteins and the relative progression of the several reactions implicated. The disappearance of LMe, the formation of primary and secondary lipid oxidation products, the loss of essential amino acids, and the production of oxidized lipid/amino acid reaction products (OLAARPs) were studied as a function of incubation time. During the first steps of lipid oxidation, LMe was converted quantitatively to methyl linoleate hydroperoxides, which were very rapidly degraded to either secondary products of lipid oxidation or OLAARPs. No significant differences were identified in the major lipid oxidation products formed in incubations with or without proteins, indicating that mechanisms for formation of these compounds are similar in both cases. In addition, no significant differences were observed between the time-courses of formation of secondary oxidation products and OLAARPs, suggesting that hydroperoxide decomposition and OLAARP formation occur simultaneously when the lipid oxidation process takes place in the presence of proteins. Furthermore, OLAARP formation seems to be an unavoidable process that should be considered as a last step in the lipid peroxidation process. 相似文献
7.
Contribution of pyrrole formation and polymerization to the nonenzymatic browning produced by amino-carbonyl reactions 总被引:1,自引:0,他引:1
Recent studies have hypothesized that pyrrole formation and polymerization may be contribute to the nonenzymatic browning produced in both oxidized lipid/protein reactions and the Maillard reaction. To develop a methodology that would allow investigation of the contribution of this browning mechanism, the kinetics of formation of color, fluorescence, and pyrrolization in 4, 5(E)-epoxy-2(E)-heptenal/lysine and linolenic acid/lysine model systems were studied. In both cases similar kinetics for the three measurements were observed at the two temperatures assayed (37 and 60 degrees C), and there was a high correlation among color, fluorescence, and pyrrolization measurements obtained as a function of incubation time. Because the color and fluorescence production in the 4,5(E)-epoxy-2(E)-heptenal/lysine system is a consequence of pyrrole formation and polymerization, the high correlations observed with the unsaturated fatty acid also suggest a contribution of the pyrrole formation and polymerization to the development of color and fluorescence observed in the fatty acid/lysine system. Although the contribution of other mechanisms cannot be discarded, all of these results suggest that when the pyrrole formation and polymerization mechanism contributes to the nonenzymatic browning of foods, a high correlation among color, fluorescence, and pyrrolization measurements should be expected. 相似文献
8.
The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra. 相似文献
9.
DR Link G Natale R Shao JE Maclennan NA Clark E Korblova DM Walba 《Science (New York, N.Y.)》1997,278(5345):1924-1927
A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and molecular tilt. These instabilities combine to form a chiral layer structure with a handedness that depends on the sign of the tilt. The bulk states are either antiferroelectric-racemic, with the layer polar direction and handedness alternating in sign from layer to layer, or antiferroelectric-chiral, which is of uniform layer handedness. Both states exhibit an electric field-induced transition from antiferroelectric to ferroelectric. 相似文献
10.
PM Lundquist R Wortmann C Geletneky RJ Twieg M Jurich VY Lee CR Moylan DM Burland 《Science (New York, N.Y.)》1996,274(5290):1182-1185
The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties. 相似文献