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61.
Edda T?pfer-Petersen Andrea Wagner Julia Friedrich Anna Petrunkina Mahnaz Ekhlasi-Hundrieser Dagmar Waberski Wolfgang Drommer 《The Journal of experimental zoology》2002,292(2):210-215
Sperm are stored in the isthmic region of the oviduct under conditions that maintain sperm viability and suppress motility. This region is also the site in which essential steps of the capacitation process are coordinated with the appearance of the ovulated egg. The influx of Ca(2+) and phosphorylation of sperm proteins are features of the ongoing capacitation process. Using a cell-culture system of oviductal epithelial cells, it was found that sperm bound to the epithelial cells showed a reduced Ca(2+) uptake and almost no tyrosine phosphorylation as shown by indirect immunofluorescence. Furthermore, sperm viability, measured as membrane integrity with propidium iodide, is significantly prolonged as compared to sperm in suspension. The formation of the sperm reservoir appears to be mediated by carbohydrate-protein interaction. In the pig, it has been found that mannosyl-oligosaccharides exposed by the epithelial cells are high-affinity ligands for sperm-associated lectins. Ovalbumin and mannopentaose are effective inhibitors of sperm binding to explants of oviductal epithelium. Spermadhesins, a new class of animal lectins and the major secretory products of the porcine seminal vesicle, associate with the sperm surface at ejaculation and are candidate molecules for the receptors of the epithelial carbohydrates. 相似文献
62.
Edda Krmer Karl-Artur Kovar 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,731(2):5636
The concentration effect of automated on-line solid-phase extraction (SPE) in combination with HPLC and very sensitive electrochemical detection was employed for the determination of N-ethyl-4-hydroxy-3-methoxy-amphetamine (HMEA, the main metabolite of the ecstasy analogue MDE), Δ9-tetrahydrocannabinol (THC) and 11-nor-Δ9-tetrahydrocannabinol-carboxylic acid (THC-COOH) in plasma and urine in comparison to a previously published psilocin assay. For the SPE either CBA (functional group: carboxypropyl)- or CH (functional group: cyclohexyl)-sorbent was used. The following separation was carried out on a reversed-phase column (LiChroCart, Superspher 60 RP select B from Merck). Depending on the hydrodynamic voltammogram of the analyzed substance the oxidation potential varied from 920 mV up to 1.2 V. In spite of using high potentials, precision and accuracy were always within the accepted statistical requirements. The limits of quantitation were between 5 ng/ml (THC, THC-COOH in plasma) and 20 ng/ml (HMEA in plasma). Advantages of on-line SPE in comparison with off-line methods were less manual effort, evidently smaller volumes (≤400 μl) of plasma or urine and almost always higher recovery rates (>93%). The assays have been successfully proven with real biological samples and found suitable for use in routine analysis. 相似文献
63.
Fragmentation and destruction of natural habitats is currently considered to be the major threat to wildlife populations.
We here perform a comprehensive analysis of the demographic effects of habitat fragmentation and destruction on 14 populations
of the root vole. The experiment was divided into two consecutive periods. During the first period, we contrasted populations
with the same initial size and structure in continuous and fragmented habitat. During the second period, we fragmented the
continuous habitat into the same configuration as the permanently fragmented habitat so that the effect of habitat destruction
could be evaluated. We estimated survival and fecundity parameters and combined them into population projection matrices to
evaluate their relative impact on population growth. In the first period of the experiment there was no difference in population
growth rate between fragmented and continuous populations, although litter size was significantly higher in the continuous
populations. In the second period, we found higher population growth rates in populations that had experienced habitat destruction.
By applying the transition matrix model to empirical estimates of demographic parameters, we demonstrate that the difference
in population growth rate in the second period of the experiment was the result of a nonsignificant difference in adult survival.
Movements out of the habitat patches were significantly lower in populations that had experienced habitat destruction. We
conclude that predator-caused mortality of animals moving out of the habitat patches was the main determinant of demographic
variation in this system.
Received: January 31, 2002 / Accepted: March 25, 2003 相似文献
64.
Javadi M Hofstätter E Stickle N Beattie BK Jaster R Carter-Su C Barber DL 《The Journal of biological chemistry》2012,287(31):26223-26234
Gene targeting experiments have shown that the cytokine erythropoietin (EPO), its cognate erythropoietin receptor (EPO-R), and associated Janus tyrosine kinase, JAK2, are all essential for erythropoiesis. Structural-functional and murine knock-in experiments have suggested that EPO-R Tyr-343 is important in EPO-mediated mitogenesis. Although Stat5 binds to EPO-R phosphotyrosine 343, the initial Stat5-deficient mice did not have profound erythroid abnormalities suggesting that additional Src homology 2 (SH2) domain-containing effectors may bind to EPO-R Tyr-343 and couple to downstream signaling pathways. We have utilized cloning of ligand target (COLT) screening to demonstrate that EPO-R Tyr(P)-343 and Tyr(P)-401 bind to the SH2 domain-containing adaptor protein SH2B1β. Immunoprecipitation and in vitro mixing experiments reveal that EPO-R binds to SH2B1 in an SH2 domain-dependent manner and that the sequence that confers SH2B1 binding to the EPO-R is pYXXL. Previous studies have shown that SH2B1 binds directly to JAK2, but we show that in hematopoietic cells, SH2B1β preferentially associates with the EPO-R. SH2B1 is capable of constitutive association with EPO-R, which is necessary for its optimal SH2-dependent recruitment to EPO-R-Tyr(P)-343/Tyr(P)-401. We also demonstrate that SH2B1 is responsive to EPO stimulation and becomes phosphorylated, most likely on serines/threonines, in an EPO dose- and time-dependent manner. In the absence of SH2B1, we observe enhanced activation of signaling pathways downstream of the EPO-R, indicating that SH2B1 is a negative regulator of EPO signaling. 相似文献
65.
Bing He Anne-May
sterholm Anna Hoverflt Carol Forsblom Eyrún Edda Hjrleifsdttir Ann-Sofie Nilsson Maikki Parkkonen Janne Pitkniemi strdur Hreidarsson Cinzia Sarti Amy Jayne McKnight A. Peter Maxwell Jaakko Tuomilehto Per-Henrik Groop Karl Tryggvason 《American journal of human genetics》2009,84(1):5-13
Diabetic nephropathy (DN) is the primary cause of morbidity and mortality in patients with type 1 diabetes mellitus (T1DM) and affects about 30% of these patients. We have previously localized a DN locus on chromosome 3q with suggestive linkage in Finnish individuals. Linkage to this region has also been reported earlier by several other groups. To fine map this locus, we conducted a multistage case-control association study in T1DM patients, comprising 1822 cases with nephropathy and 1874 T1DM patients free of nephropathy, from Finland, Iceland, and the British Isles. At the screening stage, we genotyped 3072 tag SNPs, spanning a 28 Mb region, in 234 patients and 215 controls from Finland. SNPs that met the significance threshold of p < 0.01 at this stage were followed up by a series of sample sets. A genetic variant, rs1866813, in the noncoding region at 3q22 was associated with increased risk of DN (overall p = 7.07 × 10−6, combined odds ratio [OR] of the allele = 1.33). The estimated genotypic ORs of this variant in all Finnish samples suggested a codominant effect, resulting in significant association, with a p value of 4.7 × 10−5 (OR = 1.38; 95% confidence interval = 1.18–1.62). Additionally, an 11 kb segment flanked by rs62408925 and rs1866813, two strongly correlated variants (r2 = 0.95), contains three elements highly conserved across multiple species. Independent replication will clarify the role of the associated variants at 3q22 in influencing the risk of DN. 相似文献
66.
Edda S. Oddsdottir Jørgen Eilenberg Robin Sen Gudmundur Halldorsson 《Agricultural and Forest Entomology》2010,12(3):319-324
- 1 Weevil larvae of the genus Otiorhynchus are a serious problem in agriculture and forestry, causing damage to a wide range of plant species, primarily by larval feeding on roots. Otiorhynchus larvae are a serious pest in forest plantations in Iceland, causing 10–20% mortality of newly‐planted seedlings.
- 2 We studied the effects of soil fungi on the survival of Otiorhynchus sulcatus larvae. The larvae were introduced into pots with birch seedlings grown in: (i) nursery peat; (ii) nursery peat inoculated with three different species of ectomycorrhizal fungi; (iii) nursery peat inoculated with insect pathogenic fungi; (iv) nursery peat inoculated with ectomycorrhizal fungi and insect pathogenic fungi; and (v) nursery peat inoculated with natural forest soil from Icelandic birch woodland.
- 3 Larval survival was negatively affected by inoculation of: (i) the ectomycorrhizal fungus Laccaria laccata; (ii) the ectomycorrhizal fungus Cenococcum geophylum; (iii) the insect pathogenic fungus Metarhizium anisopliae; and (iv) forest soil. Inoculation with the ectomycorrhizal fungus Phialophora finlandia did not have any significant effect on larval survival. No significant synergistic effect was found between insect pathogenic and ectomycorrhizal fungi.
- 4 It is concluded that ectomycorrhizal and insect pathogenic fungi have a significant potential in biological control of Otiorhynchus larvae in afforestation areas in Iceland. Further studies are needed to establish the effect of these fungi in the field and to analyse how mycorrhizal fungi affect root‐feeding larvae.
67.
68.
This study compared domestic guinea pigs (Cavia aperea f. porcellus; DGP) and two different populations of the wild cavy (Cavia aperea), its ancestor, to examine whether rearing of wild mammals in captivity affects their behavior and physiological stress responses. One population of wild cavies consisted of wild-trapped animals and their first laboratory-reared offspring (WGP-1). The animals of the other population were reared in captivity for about 30 generations (WGP-30). The spontaneous behavior of each of six groups of WGP-1 and WGP-30 and nine groups of DGP, each consisting of one adult male and two adult females, was analyzed quantitatively. Blood samples of the males were taken to determine cortisol, epinephrine, and norepinephrine concentrations. In addition, the exploratory behavior of 60-day-old male WGP-1, WGP-30, and DGP was investigated in an exploration apparatus. The domesticated animals displayed significantly less aggression, but significantly more sociopositive and male courtship behavior than their wild ancestors. In addition, DGP were much less attentive to their physical environment. Surprisingly, no behavioral difference was found between WGP-1 and WGP-30. Basal cortisol concentrations did not differ between wild and domestic guinea pigs. Catecholamine concentrations, however, as well as the challenge values of cortisol, were distinctly reduced in the DGP. WGP-1 and WGP-30 did not differ with respect to their endocrine stress responses. In the exploration apparatus both forms of wild cavies were much more explorative than the domestic animals. These data suggest that the long-term breeding and rearing of wild guinea pigs in captivity do not result in significant changes in behavior and hormonal stress responses. It appears to take much longer periods of time and artificial selection by humans to bring about characters of domestication in wild animals. 相似文献
69.
70.
The multidrug transporters belonging to major facilitator superfamily in Mycobacterium tuberculosis 总被引:2,自引:0,他引:2
De Rossi E Arrigo P Bellinzoni M Silva PA Martín C Aínsa JA Guglierame P Riccardi G 《Molecular medicine (Cambridge, Mass.)》2002,8(11):714-724
BACKGROUND: Both intrinsic and acquired multidrug resistance play an important role in the insurgence of tuberculosis. Detailed knowledge of the molecular basis of drug recognition and transport by multidrug transport systems is required for the development of new antibiotics that are not extruded or of inhibitors that block the multidrug transporter and allow traditional antibiotics to be effective. MATERIALS AND METHODS: We have undertaken the inventory of the drug transporters subfamily, included in the major facilitator superfamily (MFS), encoded by the complete genome of Mycobacterium tuberculosis (MTB). These proteins were identified on the basis of their characteristic stretches of amino acids and transmembrane segments (TMS) number. CONCLUSIONS: Genome analysis and searches of homology between the identified transporters and proteins characterized in other organisms revealed 16 open reading frames encoding putative drug efflux pumps belonging to MFS. In the case of two of them, we also have demonstrated that they function as drug efflux proteins. 相似文献