Bull influences on conception percentage and calving date in Angus Hereford, Brahman and Senepol single-sire herds

Bull breeding soundness parameters, semen characteristics and sexual behavior were evaluated for effects on reproductive performance in single-sire beef herds. A total of 155 cow herds (Angus, 50 herds; Hereford, 40 herds; Brahman, 46 herds; and Senepol, 19 herds) bred to bulls of the same breed were observed for 8 yr. All bulls produced adequate quality semen and had scrotal circumference (SC) >/= 30 cm. Reproductive performance was evaluated by the conception rate (CON), conception rate during the first 21 d of the breeding season (21dCON), mean calving date (MCD), and mean calving date of the first half of the herd to calve (HHCD). Correlations were determined between breeding soundness parameters and reproductive performance for all bulls combined, by breed, and by age. The Cp statistic was used to select models for the effects of parameters on CON, 21dCON, MCD and HHCD. Breeding season length and breed had significant effects. The percentages of normal cells, proximal droplets, detached heads and the semen score (motility plus percentage of normal cells) had a significant effect on CON when all bulls were considered. After the effect of season was deleted, the most significant parameter affecting CON in the Brahman was the percentage of detached sperm heads. In the Angus, motility was significantly correlated with all reproductive performance indices. In the Hereford, breeding soundness examination score (BSE) was positively correlated with 21dCON.     

Nitrogen Fixation in Continuous Culture with NH(4)Cl-Containing Media

N balance and N dilution were determined from growth of Azospirillum brasilense Sp7 and two unidentified gram-negative nitrogen-fixing microorganisms in continuous culture supplied with NH(4)Cl. At the 1.1 and 2.2 mM NH(4)Cl steady states (N-to-C ratios of 1:68 and 1:34, respectively), the organisms grew with NH(4)Cl and N(2) as N sources simultaneously under carbon limitation. No ammonium could be detected in the supernatant of these cultures.     

Inverse Diauxy in the Yeast Hansenula anomala: Mutants Derepressed for Malic Acid Utilization in the Presence of Glucose

Utilization of l-malic acid by yeast strain Hansenula anomala IGC 4380 is subject to glucose repression. Derepressed mutants were obtained with UV light by use of the nonmetabolizable glucose analog 2-deoxyglucose as a selective agent. Three mutant strains degraded l-malic acid in the presence of up to 30% (wt/vol) glucose and are of potential interest for the biological deacidification of grape must. The mutant strains, as compared with the parent strain, displayed inverse diauxy in glucose-malate medium, glucose being metabolized only after malate consumption had been completed.     

固氮酶铁钼辅因子FeMo-co在水与非水体系内重组活力与催化活力的比较研究

 本文提出一种测定FeMo-co催化活力的反应体系,用此反应体系,在测定FeMo-co催化活力的过程中,FeMo-co与变种UW45抽提液的重组活性始终保持不变。讨论了水含量、还原剂对FeMo-co催化活力和重组活力的影响。     

过量硼对猕猴桃产量和采后贮藏的影响

在新西兰,美味猕猴桃(Actinidia deliciosa var. deliciosa)植株普遍存在营养失调问题,而缺钾最为广泛。但对主产区进行广泛调查表明,有极为大量的植株受过量硼的影响。大多数情况下,硼过量发病率高与灌溉含硼量高的水或施用过量硼(通常,每公顷施2公斤以上硼)有关。 近年来,猕猴桃在商品性生产上颇获成功,但有关其栽培技术要求,尤其是营养失调对产量和釆后贮藏的影响了解甚少。本研究旨在检测过量硼对商品性果园猕猴桃植株生长的影响。 试验设在新西兰北岛Edgecumbe附近的果园。土壤为新冲积土,粉砂壤土。株冠     

Gravitropism of maize and rice coleoptiles: dependence on the stimulation angle

Gravitropism of maize and rice coleoptiles was investigated with respect to its dependence on the angle of displacement or the initial stimulation angle (ISA). Close examination of curvature kinetics and the response to a drop in stimulation angle (SA) indicated that the gravtropic response during an early but substantial part of the curvature development is directly related to the ISA, there being no effect of the reduction of SA resulting from the curvature response itself. On the basis of this finding, the relationship between the steady SA and the curvature rate was determined. In maize, the curvature rate increased linearly with the sines of SAs up to an SA of 90 degrees. Rice coleoptiles, however, showed a saturation curve in the same range of SAs. The saturation profile was nearly identical between coleoptiles grown in air and those submerged in water, although the latter elongated much faster. Rice coleoptiles appeared to be far more sensitive to gravity than maize coleoptiles. It is concluded that the sensitivity to gravity, assessed through dependence on ISA, is a property inherent to a given gravitropic organ. Long-term measurements of curvature indicated that the coleoptiles bend back past the vertical. This overshooting was marked in submerged rice coleoptiles.     

Binding of Bacillus thuringiensis Cry1 Toxins to the Midgut Brush Border Membrane Vesicles of Chilo suppressalis (Lepidoptera: Pyralidae): Evidence of Shared Binding Sites

Binding and competition among Cry1Aa, Cry1Ac, and Cry1Ba toxins were analyzed quantitatively in vitro by using (sup125)I-labeled activated toxins and brush border membrane vesicles isolated from Chilo suppressalis larval midguts. The three toxins bound specifically to the midgut brush border membrane vesicles. Direct binding experiments showed that Cry1Aa and Cry1Ba recognized a single class of binding sites with different affinities, whereas Cry1Aa recognized two classes of binding sites, one with a high affinity and a low concentration and the other with a lower affinity but higher concentration. Competition experiments showed that toxins Cry1Ac and Cry1Ba shared a binding site in the C. suppressalis midgut membranes and that this site was also the low-affinity binding site for Cry1Aa.     

The BIORACK facility and its performance during the IML-2 Spacelab mission

The configuration and performance of the Biorack facility during the Second International Microgravity Laboratory mission (IML-2; 8-23 July 1995) is described in detail. During this Spacelab mission, Biorack flew with two incubators (22 degrees C and 37 degrees C), glovebox, cooler (5 degrees C) and four passive thermal conditioning units (PTCU; 5 degrees C and 10 degrees C) in the stowage. The crew worked more than 40 h to perform 19 Biorack experiments originating from seven European countries. Almost 200 Biorack experiment containers had to be translocated in about 1500 predetermined steps before the Space Shuttle Columbia returned after nearly 14 days: 18 h or 236 orbits in space to Kennedy Space Center, Florida.