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Some strains of Rhizobium japonicum can use hydrogen as an energy source for growth under microaerophilic conditions. Mutant strains have been selected that use hydrogen in the presence of high partial pressures of oxygen. The mutants contain more hydrogenase than the parent strain, both as free-living cells and as bacteroids in nitrogen-fixing soybean root nodules. 相似文献
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Effects of Body Condition and Protein Supplementation on LH Secretion and Luteal Function in Sheep 总被引:1,自引:0,他引:1
CA Meza-Herrera T Ross D Hallford D Hawkins A Gonzalez-Bulnes 《Reproduction in domestic animals》2007,42(5):461-465
In ruminants, nutrition is one of the exogenous inputs affecting reproductive function at different levels of the hypothalamic-hypophyseal-gonadal axis. However, the exact mechanisms or even the identification of the signalling metabolic compounds by which nutrition affects reproductive function still need further clarification. The role of static body condition (BC) and its interaction with a short-term protein supplementation (PL), on secretion of metabolic hormones [growth hormone (GH), insulin and insulin-like growth factor-1 (IGF-1)], as well as on secretion of LH and progesterone (P4) was evaluated in sheep. Twenty-four Rambouillet ewes divided into two groups, with lower (LBC) and higher body condition (HBC), were randomly assigned within BC to one of two PL levels: low (LPL, 24% of crude protein; 14 g/animal/day), and high (HPL, 44% of crude protein; 30 g/animal/day). The secretion of GH, insulin, IGF-1 and LH was evaluated on day 10 of the oestrous cycle; appearance and timing of oestrous behaviour were previously detected using rams. Progesterone secretion was evaluated on day 13 of the same cycle. No differences were found (p > 0.05) between PL groups on serum GH concentrations during the sampling period (overall mean of 4.0 +/- 0.3 ng/ml), but a trend for lower values in HBC sheep was found (3.6 +/- 0.4 vs 4.4 +/- 0.4 ng/ml, p = 0.06). A BC effect was observed (p < 0.05) on serum IGF-1 level, with higher values in HBC sheep (p < 0.05). Neither BC nor PL affected (p > 0.05) secretion of LH and the number of corpora lutea, nor serum P4 and insulin concentrations. Results indicate a predominance of the static component of nutrition on sheep metabolic hormone responses, GH and IGF-1, with no effect of short-term PL on secretion of pituitary and ovarian hormones as well as luteal number and activity. 相似文献
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Follicular Dynamics in Heifers during Pre-pubertal and Pubertal Period Kept under Two Levels of Dietary Energy Intake 总被引:1,自引:0,他引:1
MA Romano VH Barnabe JP Kastelic CA de Oliveira RM Romano 《Reproduction in domestic animals》2007,42(6):616-622
The objective of this study was to characterize follicular dynamics in pre-pubertal, pubertal and post-pubertal periods, as well as the effect of high-energy intake on follicular development and age at puberty in heifers. Thirty-one Nelore (Bos indicus) heifers, 6 months old, were randomly assigned to receive two different diets: one of low (GI) and other of high dietary energy intake (GII). Animals were evaluated in relation to body weight gain by being weighed every 21 days. Heifers were evaluated every other day by real-time linear ultrasonography to characterize ovarian structures development from weaning to post-pubertal period. Blood samples were collected to determine plasmatic concentrations of progesterone by RIA method. The ovulation was determined when progesterone concentrations were >1 ng/mL in three consecutive samples, and by ultrasound images of corpus luteum; and oestrous behaviour in some animals. Age at puberty differed among heifers of GII (17.00 +/- 0.46 months) compared with heifers of GI (19.87 +/- 0.47 months; p < or = 0.05). Maximum size of the dominant follicles at pre-pubertal period was greater in GII heifers than in GI (10.52 +/- 0.33 and 9.76 +/- 0.15 mm, respectively; p < or = 0.05). As heifers approached first ovulation time, size of dominant follicle increased (11.75 +/- 0.37 mm for GI and 12.52 +/- 0.91 mm for GII; p < or = 0.05). Body weight at puberty was not different in both groups (302.33 +/- 27.31 kg for GI and 326.19 +/- 27.78 kg for GII heifers; p > 0.05). We conclude that animals receiving high dietary energy intake attained the puberty earlier and the development of follicles were different than in low dietary energy intake. 相似文献
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We measured dormant season (November through February) maintenance respiration rates (R(m)) in stems and branches of 9-year-old loblolly pine (Pinus taeda L.) growing in plots under conditions of controlled nutrient and water supply in an effort to determine the relationships between R(m) and tissue size (surface area, sapwood volume, sapwood dry weight), tissue nitrogen content and temperature. Dormant season R(m) per unit size (i.e., surface area, &mgr;mol m(-2) s(-1); sapwood volume, &mgr;mol m(-3) s(-1); or sapwood dry weight, nmol g(-1) s(-1)) varied with tissue size, but was constant with respect to tissue nitrogen content (&mgr;mol mol(-1) N s(-1)). Cambium temperature accounted for 61 and 77% of the variation in stem and branch respiration, respectively. The basal respiration rate (respiration at 0 degrees C) increased with tissue nitrogen content, however, the Q(10) did not. Improved nutrition more than doubled stem basal respiration rate and increased branch basal respiration by 38%. Exponential equations were developed to model stem and branch respiration as a function of cambium temperature and tissue nitrogen content. We conclude that failure to account for tissue nitrogen effects on respiration rates will result in serious errors when estimating annual maintenance costs. 相似文献
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Maier NR 《Science (New York, N.Y.)》1938,87(2263):439-441
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