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101.
The temporal and spatial scales employed by foraging bees in sampling their environment and making foraging decisions should depend both on the limits of bumble bee memory and on the spatial and temporal pattern of rewards in the habitat. We analyzed data from previous experiments to determine how recent foraging experience by bumble bees affects their flight distances to subsequent flowers. A single visit to a flower as sufficient to affect the flight distance to the next flower. However, longer sequences of two or three visits had an additional effect on the subsequent flight distance of individual foragers. This suggests that bumble bees can integrate information from at least three flowers for making a subsequent foraging decision. The existence of memory for floral characteristics at least at this scale may have significance for floral selection in natural environments. 相似文献
102.
103.
The purpose of this work was to test whether induction of massive -carotene synthesis in the alga Dunaliella bardawil is triggered by oxygen radicals. The following results were obtained: (i) The induction of -carotene synthesis is preceded by a lag period of about 4 h during which the cells swell and photosynthesis is partially inhibited, (ii) Addition of promoters of oxygen radicals or of azide (an inhibitor of catalase and superoxide dismutase) during the induction period, under conditions which are suboptimal for massive -carotene accumulation, greatly enhances -carotene synthesis, photodegradation of chlorophyll and inhibition of photosynthesis, (iii) High irradiance, which induces massive -carotene accumulation, also induces a high catalase activity. It is suggested that photosynthetically produced oxygen radicals are involved in triggering massive -carotene accumulation in D. bardawil. 相似文献
104.
Inherent asymmetry of the structure of F1-ATPase from bovine heart mitochondria at 6.5 A resolution. 总被引:2,自引:0,他引:2
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J P Abrahams R Lutter R J Todd M J van Raaij A G Leslie J E Walker 《The EMBO journal》1993,12(5):1775-1780
ATP synthase, the assembly which makes ATP in mitochondria, chloroplasts and bacteria, uses transmembrane proton gradients generated by respiration or photosynthesis to drive the phosphorylation of ADP. Its membrane domain is joined by a slender stalk to a peripheral catalytic domain, F1-ATPase. This domain is made of five subunits with stoichiometries of 3 alpha: 3 beta: 1 gamma: 1 delta: 1 epsilon, and in bovine mitochondria has a molecular mass of 371,000. We have determined the 3-dimensional structure of bovine mitochondrial F1-ATPase to 6.5 A resolution by X-ray crystallography. It is an approximately spherical globule 110 A in diameter, on a 40 A stem which contains two alpha-helices in a coiled-coil. This stem is presumed to be part of the stalk that connects F1 with the membrane domain in the intact ATP synthase. A pit next to the stem penetrates approximately 35 A into the F1 particle. The stem and the pit are two examples of the many asymmetric features of the structure. The central element in the asymmetry is the longer of the two alpha-helices in the stem, which extends for 90 A through the centre of the assembly and emerges on top into a dimple 15 A deep. Features with threefold and sixfold symmetry, presumed to be parts of homologous alpha and beta subunits, are arranged around the central rod and pit, but the overall structure is asymmetric. The central helix provides a possible mechanism for transmission of conformational changes induced by the proton gradient from the stalk to the catalytic sites of the enzyme. 相似文献
105.
Transformation of pecan and regeneration of transgenic plants 总被引:5,自引:0,他引:5
Gale H. McGranahan Charles A. Leslie Abhaya M. Dandekar Sandra L. Uratsu Ida E. Yates 《Plant cell reports》1993,12(11):634-638
A gene transfer system developed for walnut (Juglans regia L.) was successfully applied to pecan (Carya illinoensis [Wang] K. Koch). Repetitively embryogenic somatic embryos derived from open-pollinated seed of Elliott, Wichita, and Schley were co-cultivated with Agrobacterium strain EHA 101/pCGN 7001, which contains marker genes for beta-glucuronidase activity and resistance to kanamycin. Several modifications of the standard walnut transformation techniques were tested, including a lower concentration of kanamycin and a modified induction medium, but these treatments had no measurable effect on efficiency of transformation. Nineteen of the 764 viable inoculated embryos produced transgenic subclones; 13 of these were from the line Elliott6, 3 from Schley5/3, and 3 from Wichita9. Transgenic embryos of Wichita9 germinated most readily and three subclones were successfully micropropagated. Three transgenic plants of one of these subclones were obtained by grafting the tissue cultured shoots to seedling pecan rootstock in the greenhouse. Gene insertion, initially detected by GUS activity, was confirmed by detection of integrated T-DNA sequences using Southern analysis. 相似文献
106.
Catherine A. Vandevoort Laurie E. Neville Theodore L. Tollner Leslie P. Field 《Zoo biology》1993,12(3):257-265
Preservation of the genetic diversity of the captive orangutan, especially the wild-caught founders, is critical in maintaining a long-term population in zoological parks. One solution to the problem of maintaining maximum genetic diversity would be to initiate a program of artificial insemination for genetically underrepresented individuals through the banking and interinstitutional use of cryopreserved semen. However, little is known about basic orangutan semen characteristics, and current methodology is inadequate to support such a program. In this paper, we report the results of semen collection from an adult Sumatran orangutan (Pongo pygmaeus abelli), using an artificial vagina without anesthesia or electrical stimulation. A total of 27 ejaculates were evaluated during a 1-year period. The total and liquid volumes of the ejaculates at 1 h following collection were 6.1 ± 0.6 ml and 2.6 ± 0.4 ml, respectively (mean ± SEM). The liquid portion continued to exude semen for 2 h; however, 90% of the motile sperm was exuded within the first 30 min. The total number of sperm in the ejaculate was 164 ± 106 ± 16.5, and the percentage of motile cells was 60 ± 2.7%. We conclude that the artificial vagina provides a promising technique for semen collection in the orangutan, and view these results as an initial step in developing methods for in vitro sperm capacitation, sperm cryopreservation, and artificial insemination. © 1993 Wiley-Liss, Inc. 相似文献
107.
Continuous culture experiments with identical experimental designs were run with a mixed microbial community of activated sludge origin and an axenic bacterial culture derived from it. Each culture received 2-chlorophenol (2-CP) at a concentration of 160 mg/L as COD and L-lysine at a concentration of 65 mg/L as COD. A factorial experimental design was employed with dilution rate and media composition as the two controlled variables. Three dilution rates were studied: 0.015, 0.0325, and 0.05 h–1. Media composition was changed by adding four biogenic compounds (butyric acid, thymine, glutamic acid and lactose) in equal COD proportions at total concentrations of 0, 34, 225, and 1462 mg/L as COD. The measured variables were the effluent concentrations of 2-CP as measured by the 4-aminoantipyrene test and lysine as measured by the o-diacetylbenzene procedure. The results suggest that community structure and substrate composition play important roles in the response of a microbial community to mixed substrates. The addition of more biogenic substrates to the axenic culture had a deleterious effect on the removal of both lysine and 2-CP, although the effect was much larger on lysine removal. In contrast, additional substrates had a positive effect on the removal of 2-CP by the mixed community and much less of a negative effect on the removal of lysine. The dilution rate at which the cultures were growing had relatively little impact on the responses to the additional substrates.Abbreviations COD
chemical oxygen demand
- 2-CP
2-chlorophenol
- DOC
dissolved organic carbon
- MDL
method detection limit
- SS
suspended solids 相似文献
108.
Holly L. Neibergs Daniel S. Gallagher Michel Georges Leslie S. Sargeant Allan B. Dietz James E. Womack 《Mammalian genome》1993,4(6):328-332
The gene for the -A subunit of inhibin (INHBA) was assigned to bovine syntenic group U13 by bovine x rodent hybrid somatic cells and the polymerase chain reaction (PCR). A 482-bp PCR fragment was used to clone a 37-kb cosmid. This cosmid was assigned to bovine Chromosome (Chr) 4 (BTA 4) by fluorescence in situ hybridization (FISH). This is the first assignment of a U13 marker to a bovine chromosome. A restriction fragment length polymorphism (RFLP) was detected with PstI within the INHBA cosmid. 相似文献
109.
Linkage map of seven polymorphic markers on rat Chromosome 18 总被引:8,自引:0,他引:8
Elaine F. Remmers Ellen A. Goldmuntz Hongbin Zha Leslie J. Crofford Joseph M. Cash Peter Mathern Ying Du Ronald L. Wilder 《Mammalian genome》1993,4(5):265-270
A genetic linkage map of seven polymorphic markers was created with F2 intercross progeny of F344/N and LEW/N rats and assigned to rat Chromosome (Chr) 18. Five of the markers described were defined by simple sequence length polymorphisms (SSLPs) associated with five genes: transthyretin (TTR), trypsin inhibitor-like protein (TILP), 2 adrenergic receptor (ADRB2), olfactory neuron-specific G protein (OLF), and gap junction protein (GJA1). One marker was defined by a restriction fragment length polymorphism (RFLP) detected with a probe for the human colony stimulating factor 1 receptor (CSF1R) gene. The D18N1R locus was defined by an anonymous DNA fragment amplified by the randomly amplified polymorphic DNA (RAPD) technique with a single short primer. These seven DNA loci formed a single genetic linkage group 30.4 cM in length with the following order: TTR-6.8 cM-D18N1R-9.1 cM-TILP-4.3 cM-CSF1R-0 cM-ADRB2-10.2 cM-OLF-0 cM-GJA1. The five SSLP markers were highly polymorphic. In a total of 13 inbred rat strains analyzed (F344/ N, LEW/N, LOU/MN, WBB1/N, WBB2/N, MR/N, MNR/N, ACI/N, SHR/N, WKY/N, BN/SsN, BUF/N, and LER/N), three to six alleles were detected for each marker. Remarkable linkage conservation was detected between the region of rat Chr 18 mapped and a region of mouse Chr 18. However, genes associated with these markers have been mapped to three different human chromosomes (Chrs 5, 6, and 18). The markers described here should be useful for genetic mapping studies and genetic monitoring of inbred rat strains. 相似文献
110.
The presentation by antigen-presenting cells of immunodominant peptide segments in association with major histocompatibility complex (MHC) encoded proteins is fundamental to the efficacy of a specific immune response. One approach used to identify immunodominant segments within proteins has involved the development of predictive algorithms which utilize amino acid sequence data to identify structural characteristics or motifs associated with in vivo antigenicity. The parallel-computing technique termed ‘neural networking’ has recently been shown to be remarkably efficient at addressing the problem of pattern recognition and can be applied to predict protein secondary structure attributes directly from amino acid sequence data. In order to examine the potential of a neural network to generalize peptide structural feature related to binding within class II MHC-encoded proteins, we have trained a neural network to determine whether or not any given amino acid of a protein is part of a peptide segment capable of binding to HLA-DR1. We report that a neural network trained on a data base consisting of peptide segments known to bind to HLA-DR1 is able to generalize features relating to HLA-DR1-binding capacity (r = 0.17 and p = 0.0001). 相似文献