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排序方式: 共有467条查询结果,搜索用时 10 毫秒
81.
Settivari RS Spain JN Ellersieck MR Byatt JC Collier RJ Spiers DE 《Journal of dairy science》2007,90(3):1265-1280
The responses of lactating Holstein cows to daily administration of bovine somatotropin (bST) were measured at thermoneutrality (Tn) and under both constant and cycled heat-stress conditions to determine the relationship between thermal status and bST-induced shifts in milk production. All tests included a 5-d acclimation period at Tn (18°C), followed by a 2-d increase in ambient temperature to 28.5°C. After d 3, ambient temperature was cycled between 28.5 (day) and 25.5°C (night) for 4 d. Daily injections with either 31 mg of bST or saline began on d 1 of the experiment. Milk production, feed intake, and respiratory rate (RR) were measured daily. Intraperitoneal, telemetric temperature transmitters were used for a continuous measure of core body temperature (Tcore). Blood samples were collected during each phase to evaluate the changes in serum chemistry in response to bST and heat stress. Following a 15-d recovery, cows were switched across injection treatments and the study was repeated. Milk production decreased by ∼18.4% below the initial yield at Tn by the end of 7 d of heat challenge. Although a reduction in milk production occurred during heat stress in both groups, milk production was higher in bST-treated cows compared with control cows during periods of constant and cyclic heat. Likewise, bST treatment during the entire period increased the milk-to-feed ratio over the control level by ∼11.3%. Plasma insulin-like growth factor 1 and serum nonesterified fatty acids accompanied the increased growth hormone level with bST treatment (∼122.0 and 88.8%, respectively), whereas plasma urea nitrogen was reduced by ∼13.3% to reflect the shift to lipid metabolism. There was no difference in Tcore of the treatment and control groups at Tn. Both bST and control cows increased RR and Tcore above the Tn level by ∼94.8 and 2.9%, respectively, during constant heat, with a greater increase in Tcore of bST-treated compared with control cows (∼0.6%). The increase in RR during heat stress preceded Tcore by 1 d for both groups. During cyclic heat, Tcore decreased by ∼0.4% compared with constant heat in both the control and bST-treated groups. Bovine somatotropin treatment increased milk production similarly during the Tn and heat-stress periods, ∼8.3% over the control; however, the bST-induced increase in milk-to-feed ratio was greatest during the continuous and cyclic heat-stress phases, ∼16.2%. This increase occurred together with the elevation in Tcore. 相似文献
82.
Subclinical hypocalcemia,plasma biochemical parameters,lipid metabolism,postpartum disease,and fertility in postparturient dairy cows 总被引:1,自引:0,他引:1
W.G. Chamberlin J.R. Middleton J.N. Spain G.C. Johnson M.R. Ellersieck P. Pithua 《Journal of dairy science》2013
A study was conducted to evaluate the potential association between Ca status at calving and postpartum energy balance, liver lipid infiltration, disease occurrence, milk yield and quality parameters, and fertility in Holstein cows. One hundred cows were assigned to 1 of 2 groups based on whole-blood ionized Ca concentration ([iCa]) on the day of calving [d 0; hypocalcemic [iCa] <1.0 mmol/L (n = 51); normocalcemic [iCa] ≥1.0 mmol/L (n = 49)]. Cows were blocked based on calving date and parity. Blood samples were collected approximately 14 d from expected calving date (d −14), the day of calving (d 0), and on d 3, 7, 14, 21, and 35 postpartum for measurement of plasma nonesterified fatty acid, iCa, total Ca, glucose, and total and direct bilirubin concentrations, and plasma aspartate aminotransferase and gamma glutamyl transferase activities. Liver biopsies were obtained from a subset of cows on d 0, 7, and 35 for quantification of lipid content. Milk samples were collected on d 3, 7, 14, 21, and 35 postpartum for measurement of somatic cell count and percentages of protein, fat, and solids-not-fat. Data for peak test-day milk yield, services per conception, and days open were obtained from Dairy Herd Improvement Association herd records. Disease occurrence was determined based on herd treatment records. Hypocalcemic cows had significantly higher nonesterified fatty acids on d 0. Hypocalcemic cows also had significantly more lipid in hepatocytes on d 7 and 35 postpartum. However, no statistically significant differences were observed between groups for plasma aspartate aminotransferase and gamma glutamyl transferase activities or total and direct bilirubin concentrations. Milk protein percentage was lower in hypocalcemic cows on d 21 and 35. However other milk quality variables (somatic cell count, milk fat percentage, and solids-not-fat) and milk yield variables (peak test-day milk yield and 305-d mature-equivalent 4% fat-corrected milk yield) did not differ between groups. No differences were observed between groups in the occurrence of clinical mastitis, ketosis, displaced abomasum, dystocia, retained placenta, metritis, or fertility measures (percentage cycling at 50–60 d postpartum, services per conception, or days open). These data suggest that early lactation fatty acid metabolism differs between cows with subclinical hypocalcemia and their normocalcemic counterparts. 相似文献
83.
Bhushan B Halasz A Spain J Thiboutot S Ampleman G Hawari J 《Environmental science & technology》2002,36(14):3104-3108
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) can be efficiently mineralized with anaerobic domestic sludge, but the initial enzymatic processes involved in its transformation are unknown. To test the hypothesis that the initial reaction involves reduction of nitro group(s), we designed experiments to test the ability of a nitrate reductase (EC 1.6.6.2) to catalyze the initial reaction leading to ring cleavage and subsequent decomposition. A nitrate reductase from Aspergillus niger catalyzed the biotransformation of RDX most effectively at pH 7.0 and 30 degrees C under anaerobic conditions using NADPH as electron donor. LC/MS (ES-) chromatograms showed the formation of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and methylenedinitramine as key initial products of RDX, but neither the dinitroso neither (DNX) nor trinitroso (TNX) derivatives were observed. None of the above detected products persisted, and their disappearance was accompanied by the accumulation of nitrous oxide (N20), formaldehyde (HCHO), and ammonium ion (NH4+). Stoichiometric studies showed that three NADPH molecules were consumed, and one molecule of methylenedinitramine was produced per RDX molecule. The carbon and nitrogen mass balances were 96.14% and 82.10%, respectively. The stoichiometries and mass balance measurements supported a mechanism involving initial transformation of RDX to MNX via a two-electron reduction mechanism. Subsequent reduction of MNX followed by rapid ring cleavage gave methylenedinitramine which in turn decomposed in water to produce quantitatively N2O and HCHO. The results clearly indicate that an initial reduction of a nitro group by nitrate reductase is sufficient for the decomposition of RDX. 相似文献
84.
M.B. SÁNCHEZ‐ILÁRDUYA C. SÁNCHEZ‐FERNÁNDEZ M. VILORIA‐BERNAL D.M. LÓPEZ‐MÁRQUEZ L.A. BERRUETA B. GALLO F. VICENTE 《Australian Journal of Grape and Wine Research》2012,18(2):203-214
Background and Aims: During wine ageing, a great variety of reactions take place, resulting in an immense variety of products whose structure sometimes remains unknown. The aim of this work is the study of different fragmentation patterns of flavanol‐anthocyanin derivatives formed along the wine ageing; these patterns are useful for elucidating the different structures of these compounds and other new related ones. Methods and Results: Several wines from the Protected Denomination of Origin Rioja have been studied by an analytical method that combines column chromatography and high‐performance liquid chromatography with diode array and mass and tandem mass spectrometric detections. Thirty‐five coloured flavanol‐anthocyanin compounds formed by direct reaction or by acetaldehyde‐mediated condensation have been identified. For direct reaction derivatives, two different fragmentation patterns (one of them not previously reported) have been observed depending on the position of flavanol in the coloured derivative. Several compounds have been identified in aged wines for the first time to the authors' knowledge, like (+)‐gallocatechin‐cyanidin‐3‐glucoside and (+)‐catechin‐cyanidin‐3‐glucoside Conclusions: The developed analytical procedure has allowed the identification of some compounds for the first time, and two different fragmentation patterns have been observed depending on the position of flavanol in the pigment. Significance of the Study: The establishment of different fragmentation patterns allows the structural elucidation of unknown compounds. 相似文献
85.
We report a new form of congenital muscular dystrophy (CMD) in 4 patients from three unrelated families with probable autosomal-recessive inheritance. All patients had the clinical characteristics of merosin-positive congenital muscular dystrophy, but had marked mental retardation. The disease was slowly progressive and 1 patient died from dilated cardiomyopathy at the age of 13 years. In addition to dystrophic changes with necrosis and regeneration in muscle, the most striking finding was mitochondrial depletion in the center of the sarcoplasm. Mitochondria at the periphery of fibers were markedly enlarged ("megaconial" appearance) with complicated cristae, and contained a normal amount of mitochondrial DNA by in situ hybridization. Mitochondrial enlargement may represent functional compensation for mitochondrial depletion in the central sarcoplasm, where myofibrillar degeneration occurred. 相似文献
86.
87.
Oxygen uptake (VO2) was determined in 10 males during the following types of maximal exercise (work time: about 5 min): uphill running, bicycling, arm work (cranking), and combined arm work and bicycling (A + L). The A + L exercise was performed in four different ways, the arms doing 10%, 20%, 30%, or 40% of the same total rate of work; and also with the maximal bicycle work load plus either maximal or submaximal arm work. VO2 was the same in running as in all types of A + L exercise, except when the arm work load was 10% and 40% of the total rate of work, where VO2 was 2.5% (P less than 0.05) and 9.4% (P less than 0.001) lower, respectively. Bicycle VO2 was lower than VO2 in running but equal to A + L VO2 when arm work intensity was 40% of the total rate of work. It is concluded that VO2 during maximal exercise a) to a certain extent depends on the exercising muscle mass, b) is lower than the oxygen-consuming potential of the muscles involved in A + L exercise, and c) in A + L exercise is influenced by the ratio of arm work to total rate of work and the subject's fitness for arm work and bicycling. 相似文献
88.
89.
WR Sanborn JF Vieu S Komalarini Sinta R Trenggonowati IL Kadirman Sumarmo A Aziz T Sadjimin Triwibowo Atas S Ayam 《Canadian Metallurgical Quarterly》1979,82(1):143-153
The distribution of phage types was studied among 577 strains of Salmonella typhi from Indonesia. Chemotype, colicinogeny, and tetrathionate reductase activity were also studied for most of these strains. The current phage type formula for Java was determined to be: A, D2, D6, E1a, E2, M1, and 46, but two other large groups of strains were also found, I + IV and degraded Vi+ strains. Significant differences in S. typhi strain distributions were noted between two localities on Java with respect to phage type and tetrathionate reductase activity. Comparisons were made with past phage typing studies in Jakarta as well as with more recent studies in other parts of south-east Asia. Phage types A, D1, D2, and E1 persisted at a rather steady level in Jakarta for 28 years. Evidence was found for epidemiological links to European and Asian areas. Antibiotic resistance among these Indonesian S. typhi strains was rare. 相似文献
90.