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91.
92.
An experiment was made to determine the absorption of purine metabolites in dietary nucleic acids through the digestive tract, and also to determine the utilization of nucleic acids absorbed in the body, using growing lambs. Two pairs of 120‐ and 180‐day‐old twin female lambs with a bodyweight of 18.2–19.0 kg were kept in metabolism crates and fed on purine‐free milk replacement (MR) with supplements of exogenous purine (purine base or purine nucleoside) at a level of 0.2 mmol/BW0.75/d for 5 consecutive days, and thereafter they were maintained in the crates for 4 days. The daily amount of exogenous purine supply was calculated based on the urinary excreted purine derivatives (PD) in lambs fed on milk replacement alone. A urine sample was collected daily for 9 consecutive days, and the urinary excretion of PD was determined daily. Urinary PD excretion opened to increase within 24 h after the dose of purine bases, and the level was recovered on 3 days after ceasing the exogenous purine supply. The recovery of PD in the urine was about 70% of the purine supplement. When purine nucleosides were added to the feed, urinary PD excretion was initiated within 24 h after dosing, and the values were recovered after ending the purine nucleoside supply. The recovery rate of PD in the urine was only 30% of the supplemented purine. The plasma allantoin levels were almost similar after feeding purine bases and purine nucleosides, and the values were mostly in the range (40–60 µmol/L). These findings indicate that an exogenous purine can be directly incorporated into the body, and the purine as nucleoside is more effectively utilized for the synthesis of nucleic acids than as a purine base in the body of growing lambs. 相似文献
93.
Land use changes operate at different scales. They trigger a cascade of effects that simultaneously modify the composition
or structure of the landscape and of the local vegetation. Mobil animals, and birds in particular, can respond quickly to
such multi-scalar changes. We took advantage of a long term study on the response of songbirds to land-use changes on four
Mediterranean islands in Corsica and Sardinia to explore the benefits of a multi-scale analysis of the relationships between
songbird distribution, vegetation structure and landscape dynamics. Field data and aerial photographs were used to describe
the vegetation at three different scales. Birds were censused by point counts. We used statistical variance decomposition
to study how bird distribution and vegetation at various scales were linked. We analysed multi-scale vegetation changes (floristic
composition, plot vegetation type, and landscape structure) and their consequences on bird distribution with multivariate
and non-parametrical tests. The distribution of most species was linked to at least two spatial scales. The weight of a given
scale was consistent with life-history traits for species whose biology was well-known. In the examples studied, vegetation
composition, vegetation type and landscape changes that resulted from land abandonment negatively affected birds depending
on open or heterogeneous areas. Our results emphasize that multi-scale analyses can greatly enhance our understanding of bird
distribution and of their changes. Management of these populations should take into account measures at various spatial scales
depending on the sensitivity of the species. 相似文献
94.
Michael J. Murray Fabio del Piero Stuart C. Jeffrey Michael S. Davis Martin O. Furr Edward J. Dubovi John A. Mayo 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(1):36-41
Of 17 foals born on a Thoroughbred breeding farm between March and April 1995, infection with equine herpesvirus type 1 (EHV-1) was associated with neonatal morbidity in 5 foals, 3 of which died or were euthanized. Morbidity and mortality were associated with pulmonary inflammation, and EHV-1 was identified in the lungs of the 3 foals that died. All neonatal EHV-1 infections occurred in foals of mares housed in the same pasture and barn. No other clinical manifestations of EHV-1 infection (eg, abortion, neurologic disease, or respiratory disease) occurred during this outbreak. Three foals were treated with acyclovir (1 died, 2 survived), which may have influenced the clinical outcome in the surviving foals. 相似文献
95.
Perennial ryegrass and meadow fescue were grown alone and in association in field plots, to gain an idea of the nature and importance of the competitive interactions between them, and their relative contributions to the yield of the newly-established sward.
Experiments over 10 weeks and 9 months both showed that the contribution by fescue to the overall dry-matter yield was severely restricted by perennial ryegrass. There were no deaths of fescue plants during the experimental period (which included an overwintered treatment). The depression in yield was rather a result of a marked decrease in size and weight of the individual plants, brought about by competition for light and nutrients from the faster-growing ryegrass. 相似文献
Experiments over 10 weeks and 9 months both showed that the contribution by fescue to the overall dry-matter yield was severely restricted by perennial ryegrass. There were no deaths of fescue plants during the experimental period (which included an overwintered treatment). The depression in yield was rather a result of a marked decrease in size and weight of the individual plants, brought about by competition for light and nutrients from the faster-growing ryegrass. 相似文献
96.
Intercropping of Corn with Soybean and Lupin for Silage: Effect of Seeding Date on Yield and Quality
B. Prithiviraj K. Carruthers Q. Fe D. Cloutier R. C. Martin D. L. Smith 《Journal of Agronomy and Crop Science》2000,185(2):129-136
Intercropping of corn with legumes is an alternative to corn monocropping and has a number of advantages, for example, lower levels of inputs, lower costs of production and better silage quality than the monocrop system. An experiment was carried out at two sites in 1993 and 1994 to investigate the effects of seeding date (simultaneous with corn or 3 weeks later) and number of rows of large‐seeded legumes (one or two) seeded between the corn rows. The intercrop plots received 90 kg ha?1 less nitrogen fertilizer than the monocrop plots, which received 180 kg ha?1. Silage yields were sometimes decreased by the simultaneous seeding of corn and large‐seeded legumes. Protein content and concentration were not affected by most treatments and provided reasonable quality silage, despite a reduction in the amount of nitrogen fertilizer used. 相似文献
97.
In well-aerated culture solutions Ca-montmorillonite at 0.25% concentration markedly accelerated and increased growth, glucose consumption and CO2 evolution by various Streptomyces, Micromonospora and Nocardia species. The montmorillonite was a little more active than Ca-humate and was usually still but somewhat less effective when confined to dialysis tubing. Ca-exchange resin, Na2SiO3 and finely powdered CaCO3 exerted very little or no effect. In many cultures the relation of glucose consumption to biomass formation indicated a more efficient use of the glucose C for cell synthesis in the presence of clay. In other cultures the greater biomass formation was associated with a more rapid and complete utilization of the glucose present. 相似文献
98.
Axenic cultures of Anacystis, Microcoleus, Plectonema and Synechococcus isolated from Greenfield sandy loam and of Anabaena flos-aquae, Nostoc muscorum and Chlorella pyrenoidosa from other sources were cultured under light and constant aeration and with [U-14C]-glucose in the nutrient medium. Whole cells, cell walls, cytoplasm and extracellular polysaccharides of selected species readily decomposed in the soil and after 22 weeks between 61 and 81% of the added C had evolved as CO2. Complexing of cell wall and cytoplasmic preparations from A. flos-aquae and N. muscorum with model humic acid-type phenolic polymers reduced decomposition of the cell walls by 40% and of the cytoplasm by 70%. Over 50% of the residual 14C activity in the soil amended with whole algal cells remained in the 0.5% NaOH-extracted soil. With exception of Microcoleus sp. more of the residual 14C from cell walls, cytoplasm and polysaccharide fractions was present in the humic acid or fulvic acid fractions. 相似文献
99.
100.
Observations on the cooling and cryopreservation of pig oocytes at the germinal vesicle stage 总被引:9,自引:0,他引:9
B A Didion D Pomp M J Martin G E Homanics C L Markert 《Journal of animal science》1990,68(9):2803-2810
This study examined the viability of pig oocytes at the germinal vesicle stage following cooling or cryopreservation. Cumulus-intact oocytes (n = 641) were collected from slaughterhouse pig ovaries and used in two experiments. In Exp. I the viability of 1) control, 2) cryoprotectant control (CC, 1.5 M glycerol/.5 M sucrose), 3) cooled (0 degrees C) and 4) cryopreserved (-196 degrees C) oocytes was assessed after no incubation or a 24-h incubation. Survivability was judged by morphological appearance, trypan blue exclusion and fluorescein diacetate staining. Survival rate of control oocytes (90%; based primarily on morphological appearance of the cumulus) incubated 0 h was greater (P less than .05) than that of all other groups, whereas survival rate of -196 degrees C oocytes (57%) was less (P less than .05) than that of all other groups. However, vital staining of 0 degrees C and -196 degrees C oocytes showed 0% survival rate as evidenced by trypan blue uptake and lack of fluorescence. The cumulus cells surrounding oocytes that were stored at 0 degrees C or -196 degrees C survived freezing as evidenced by trypan blue exclusion and intense fluorescence. Similar differences among treatment groups were found for oocytes incubated 24 h. Exp. 2 examined the temperature at which oocytes became sensitive to cooling. Oocyte death occurred when oocytes were cooled to 15 degrees C or lower. These results demonstrate that pig oocytes at the germinal vesicle stage did not survive cooling to 15 degrees C or below. When assessing the viability of cryopreserved cumulus enclosed oocytes it is important to use vital stains in conjunction with morphological appearance. 相似文献