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排序方式: 共有128条查询结果,搜索用时 31 毫秒
1.
The biosynthesis of volatile esters by Red Delicious apples was investigated by incubating fruit tissue with deuterated flavor precursors at various times after controlled atmosphere (CA) storage and measuring deuterium incorporation into branched-chain ester volatiles. 2-Methylbutyl acetate was the only volatile not significantly reduced by CA storage. Conversion of 2-methylbutanol to 2-methylbutyl acetate and of 2-methylbutanoic acid to ethyl 2-methylbutanoate and to hexyl 2-methylbutanoate was limited by the availability of 2-methylbutyl substrates but not by acetyl-CoA, ethanol, or hexanol, respectively. The enzymatic activity required for these reactions declined during CA storage. The conversion of 2-methylbutanoic acid to 2-methylbutanol was also substrate limited, but enzymic activity appeared stable in storage. Biosynthesis of both 2-methylbutanoic acid and 2-methylbutanol, from isoleucine, was severely depressed under CA storage. The reduced metabolism of isoleucine to 2-methylbutanoyl-CoA may be the primary reason for reduced branched-chain ester synthesis in CA-stored Red Delicious apples. Enantioselective gas chromatography-mass spectrometry confirmed that the chirality of (S)-2-methylbutyl acetate derives from l-isoleucine with the other enzymes in this pathway not being enantiospecific. Treatment of tissue samples with 2-methylbut-2E-enal gave only (S)-2-methylbutyl acetate, indicating that biosynthesis was not via tiglyl-CoA. 相似文献
2.
3.
Warnick LD Nydam D Maciel A Guard CL Wade SE 《Journal of the American Veterinary Medical Association》2002,221(2):273-276
OBJECTIVE: To determine prevalence of udder cleft dermatitis in a dairy herd that was experiencing an outbreak of sarcoptic mange. DESIGN: Clinical survey. ANIMALS: 1,597 Holstein cows and late-gestation heifers. PROCEDURE: Animals were examined for udder cleft dermatitis and for skin lesions consistent with sarcoptic or chorioptic mange. Skin scrapings were collected from 56 cows and examined for ectoparasites. The herd was revisited 1 year later, and prevalences of udder cleft dermatitis and lesions consistent with mange were determined in 506 cows. RESULTS: Of the 1,597 cattle examined, 280 (18%) had udder cleft dermatitis, and 1,397 (87.5%) had lesions consistent with mange. In 43 of 56 (77%) cows, skin scrapings revealed Sarcoptes mites. Udder cleft dermatitis was significantly more common in older than in younger cows. In first-lactation cows, udder cleft dermatitis was less common during the first 4 months of lactation than in the later stages of lactation, but udder cleft dermatitis was identified in cows in all stages of lactation and in cows that were not lactating. The herd was treated with eprinomectin to control mites, and prevalence of lesions consistent with mange 1 year later was only 2.8%. However, prevalence of udder cleft dermatitis was still 12%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cows in any stage of lactation and cows that are not lactating can have udder cleft dermatitis but that lesions are more common in older cows. Control of sarcoptic mange was accompanied by a moderate reduction in the prevalence of udder cleft dermatitis but did not eliminate the condition. 相似文献
4.
Air space within a compost material can be measured using several methods. This project, focusing on bulking materials, compared five air space (AS) test methods: particle density (PD) method, modified PD (MPD) method, air pycnometer (AP) method, modified air pycnometer (MAP), and a quick method. There were significant differences between results obtained using the different tests. PD and MAP methods yielded results representing total air space (TAS), while the AP and MPD methods yielded values which were thought to represent free air space (FAS). The Quick method resulted in AS values dramatically different from the other methods, and further development and validation of the method was recommended. The MPD was found to be unsuitable for samples containing fine material, such as biosolids. Both the PD and the MAP tests were precise; however, results were biased to TAS values. This was illustrated through the similarity between AS values measured by the two tests and the predicted TAS. The MAP was the simplest method and was recommended for use with compost samples. Strong linear correlations were observed between TAS and bulk density (BD; kg m?3: TAS = 100 – 0.096*BD (R2=0.98) for PD and 100 – 0.090*BD (R2=0.90) for MAP. The effect of storage time on FAS, TAS, and moisture content was examined in this study. Straw samples were stored for a month and showed no change in the physical properties. Woodchip samples were stored for over 5 months. A slight change in both FAS and TAS was observed, but the differences were minor compared to variations induced by different particle sizes and moisture levels. 相似文献
5.
麦谷蛋白亚基Clu-1和Glu-3位点基因等位变异对小麦品质特性的影响 总被引:6,自引:0,他引:6
甲单向一步SDS-PAGE方法分析表明亲本品种Suneca和Cook在麦谷蛋白亚基的5个位点(Glu-B1,Glu-D1,Glu-A3,Glu-B3和Glu-D3)均含不同等位基因。本研究重点对Suneca×Cook的F_4代群体中在麦谷蛋白亚基位点均为纯合基因的60个系的出粉率(FY),面粉蛋白质含量(FP)及和面时间(PTM)进行了分析,以研究麦谷蛋白各亚基位点等位基因变异及位点间互作对小麦品质特性的影响。结果表明,不同基因型间出粉率无显著差异,Glu-D1位点等位基因d和a对FP的效应存在显著差异,Glu-Dld基因(编码5 10亚基)的正效应显著高于Glu-Dla基因(编码2 12亚基);Glu-D1、Glu-A3和Glu-B3位点上基因的等位变异对PTM有显著和极显著影响,含Glu-Dld、Glu-A3b和Glu-B3b基因的系分别比含Glu-Dla,Glu-A3d和Glu-B3h基因的系有较长的和面时间;Glu-B1位点上等位变异i和u以及Glu-D3位点等位基因b和e分别对PTM无明显影响。在这种遗传背景下,麦谷蛋白亚基位点对PTM的效应大小依次排列为Glu-D1>Glu-B3>Glu-A3>GIu-B1=Glu-D3。Glu-1位点和Glu-3位点间对和面特性的影响存在累加效应和互作效应。 相似文献
6.
Vicentini CB Forlani G Manfrini M Romagnoli C Mares D 《Journal of agricultural and food chemistry》2002,50(17):4839-4845
Some pyrazolo[3,4-d]pyrimidin-4(5H)-thione, pyrazolo[3,4-d][1,3]thiazin-4-one/thione, and pyrazolo[1,5-c][1,3,5]thiadiazine-4-one/thione derivatives were synthesized and screened for antifungal activity against the causal agent of rice blast disease, Magnaporthe grisea. In all cases a remarkable inhibition of fungal growth was found in the range from 10 to 200 microg x mL(-1). Several compounds were able to control mycelium growth at a rate of 10 microg x mL(-1), a concentration at which the reference compound tricyclazole was completely ineffective. At least in the case of the most active substance, at the same dose the growth of seedlings or cultured cells of rice was substantially unaffected. Results allowed definition of structural requirements either to maintain or to enhance mycotoxic activity. 相似文献
7.
Daryl P. Domning 《Biological conservation》1982,22(2):101-126
All available published statistics on the exploitation of the Amazonian manatee Trichechus inunguis are collected and analysed to determine the major trends in exploitation and, if possible, their effects on the species. The manatee's role in the Amazonian economy has traiditionally been on the level of subsistnce hunting for local consumption; export of surplus manatee products has been limited and sporadic, and keeping of records has been even more so. Unknown quantities of manatee meat were shipped to the Guianas and West Indies in the 17th century, At least from the 1780s to about 1925, the only manatee product common in Amazonian commerce was mixira (fried meat packed in lard). From 1935 to 1954, manatee hides were exported to southern Brazil and elsewhere for the manufacture of heavy-duty leather. From 1954 to the legal banning of manatee hunting in 1973, manatees were again heavily exploited for meat. At no time did manatee products make up more than a small fraction of a percent of the Amazon region's trade. Numbers of animals killed per year cannot be determined with any precision, but early statistics on mixira reflect no more than 1000/year, while the peak years of hide and meat production probably required 4000–7000 manatees/year, exclusive of unrecorded subsistence hunting. Taking the latter into account, it is likely that actual mortality ran to several thousand animals per year throughout the past two centuries. Decline of meat production in the 1960s may reflect overexploitation. Evidence was also found of some exploitation for meat of West Indian manatees T. manatus in the states of Alagoas and Bahia, Brazil, the latter constituting the southernmost record of the species since the early 19th century. 相似文献
8.
Genetic impacts under selective breeding of agricultural crops have been frequently investigated with molecular tools, but
inadequate attention has been paid to assess genetic changes under long-term genetic improvement of plant traits. Here we
analyzed allelic changes with respect to wheat trait improvement in 78 Canadian hard red spring wheat cultivars released from
1845 to 2004 and screened with 370 mapped SSR markers. The improvements in quality, maturity, yield, disease, stem rust, leaf
rust, sawfly resistance, and agronomy were considered. A total of 154 (out of 370) loci with significant allelic changes across
21 chromosomes were detected in the 78 wheat cultivars separated into improved versus non-improved groups for eight traits.
The number of significant loci for improving a trait ranged from four for quality to 68 for yield and averaged 35. Many more
loci with significant allelic reduction for improving a trait were detected than those with significant allelic increase.
Selection for early maturity introduced more alleles, but improving the other traits purged more alleles. Significantly lower
numbers of unique alleles were found in the cultivars with improved traits. The distributions of unique allele counts also
varied greatly across the 21 chromosomes with respect to trait improvement. Significant SSR variation between two cultivar
groups was observed for improvement in seven traits, but not in stem rust. The proportional SSR variation residing between
two groups ranged from 0.014 to 0.118. The proportional SSR variations within the improved cultivar groups consistently were
much lower than those within the non-improved groups. These findings clearly demonstrate the association between allelic changes
and wheat trait improvements and are useful for understanding the genetic modification of the wheat genome by long-term wheat
breeding. 相似文献
9.
A physical map of the 1-gigabase bread wheat chromosome 3B 总被引:2,自引:0,他引:2
Paux E Sourdille P Salse J Saintenac C Choulet F Leroy P Korol A Michalak M Kianian S Spielmeyer W Lagudah E Somers D Kilian A Alaux M Vautrin S Bergès H Eversole K Appels R Safar J Simkova H Dolezel J Bernard M Feuillet C 《Science (New York, N.Y.)》2008,322(5898):101-104
As the staple food for 35% of the world's population, wheat is one of the most important crop species. To date, sequence-based tools to accelerate wheat improvement are lacking. As part of the international effort to sequence the 17-billion-base-pair hexaploid bread wheat genome (2n = 6x = 42 chromosomes), we constructed a bacterial artificial chromosome (BAC)-based integrated physical map of the largest chromosome, 3B, that alone is 995 megabases. A chromosome-specific BAC library was used to assemble 82% of the chromosome into 1036 contigs that were anchored with 1443 molecular markers, providing a major resource for genetic and genomic studies. This physical map establishes a template for the remaining wheat chromosomes and demonstrates the feasibility of constructing physical maps in large, complex, polyploid genomes with a chromosome-based approach. 相似文献
10.
Gardner RB Nydam DV Mohammed HO Ducharme NG Divers TJ 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2005,19(5):761-764
The purpose of this study was to test the hypothesis that horses with right dorsal displacement of the large colon (RDDLC) have elevations in serum gamma glutamyl transferase (GGT) activity when compared with horses with left dorsal displacement of the large colon (LDDLC). Medical records from 37 horses with RDDLC and 48 horses with LDDLC were reviewed. Horses were included for study if the RDDLC or LDDLC was confirmed by exploratory laparotomy or postmortem examination and if a serum GGT measurement was obtained within 24 hours before surgery. The proportion of horses with GGT activity within or above the reference range was determined. Of 37 horses, 18 (49%; exact binomial 95% confidence interval, 32-66%) with RDDLC and, of 48 horses, 1 (2%; 95% CI, 0-11%) with LDDLC had GGT above the reference range. Horses with RDDLC had higher serum GGT than did horses with LDDLC. Of 37 horses, 36 (97%) with RDDLC were discharged with a good prognosis and none returned as a result of hepatic disease. Evaluation of surgical and postmortem examinations revealed that positioning of the colon in horses with RDDLC results in compression of the bile duct, which can cause extrahepatic bile duct obstruction and a subsequent elevation in serum GGT activity. 相似文献