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91.
92.
Secretory granules containing primarily growth hormone and prolactin were isolated from bovine anterior pituitaries. Marker enzyme analysis and electron microscopy indicated that the secretory granule fraction did not contain measureable amounts of other intracellular organelles. Such isolated granules were resistant to a variety of chemical and physical challenges including variations in osmolarity, ionic strength, EGTA, sonication, boiling, etc. The only treatments that were found to routinely result in granules lysis were alkaline pH and 0.5% SDS. Nonspecific leakage of both growth hormone and prolactin was less than 9% of total hormone pool even after a 60-min incubation. The release of prolactin but not growth hormone could be increased by lowering the free calcium concentration. Conversely, 10(-5) M ionophore A23187 caused a decrease in nonspecific hormone leakage. This raises the possibility that a nonexocytosis secretory pathway might be involved in pituitary hormone release. The initial secretory granule fraction was further purified using discontinuous sucrose gradient ultracentrifugation to yield a subfraction highly enriched in prolactin granules. These granules had the same stability characteristics as the original secretory granule fraction. The use of such granules should prove useful in our efforts to understand how calcium regulates cellular secretion. 相似文献
93.
Michael K. Dowd Jing Zeng Alfred D. French Peter J. Reilly 《Carbohydrate research》1992,230(2):223-244
Energy surfaces were computed for relative orientations of the relaxed pyranosyl rings of the two anomeric forms of kojibiose, nigerose, and maltose, the (1 → 2)-, (1 → 3)-- and (1 → 4)--linked
-glucosyl disaccharides, respectively. Twenty-four combinations of starting conformations of the rotatable side-groups were considered for each disaccharide. Optimized structures were calculated using MM3 on a 20° grid spacing of the torsional angles about the glycosidic bonds. The energy surfaces of the six disaccharides were similar in many respects but differed in detail within the low-energy regions. The maps also illustrate the importance of the exo-anomeric effect and linkage type in determining the conformational flexibility of disaccharides. Torsional conformations of known crystal structures of maltosyl-containing molecules lie in a lower MM3 energy range than previously reported. 相似文献
94.
P. F. Dowd H. R. Burmeister R. F. Vesonder 《Entomologia Experimentalis et Applicata》1992,63(1):95-100
The antiinsectan properties of the Fusarium graminearum-derived novel sterol sulfate, 4,4,24-trimethylcholesta-8,14,24(28)-trien-2,3,11,12-tetrol 12 acetate, 3-sulfate were tested on the corn earworm (Heliothis zea (Boddie), the fall armyworm (Spodoptera frugiperda (J. E. Smith), and the driedfruit beetle (Carpophilus hemipterus L.). The sterol sulfate could not be used as a sterol source by any of the insects. The sterol sulfate inhibited growth of S. frugiperda and C. hemipterus larvae at 2500 and 4000 ppm, respectively. Defensive implications of this compound are discussed. 相似文献
95.
96.
31P NMR and saturation transfer studies of the effect of Pb2+ on cultured osteoblastic bone cells 总被引:1,自引:0,他引:1
The mechanism of lead toxicity at the cellular level remains unknown, although an effect of lead on intracellular Ca2+ has been described. Since bone is a major target for lead, we have investigated the effect of lead on bioenergetic rates and on the intracellular free Mg2+ concentration in cultured osteoblastic bone cells. Using 31P NMR and the saturation transfer technique we have detected a sizable (18%) transfer of saturation from gamma ATP to Pi in a perfused osteoblastic osteosarcoma bone cell line, Ros 17/2.8, and have found a large (greater than 82%) reduction in the Pi----ATP rate upon treatment with 10 microM Pb2+. The NMR-measured unidirectional rate was much greater than the net rate of ATP synthesis through glycolysis and oxidative phosphorylation. By using iodoacetate we investigated the mechanism of the saturation transfer and found that it is catalyzed by the glycolytic enzyme couple glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase. The net rate of glycolysis as measured by lactate production and that of oxidative phosphorylation as measured by O2 consumption were found to be significantly decreased by 18 and 74%, respectively, with lead treatment. In addition, from the chemical shifts of intracellular ATP resonances, we found a significant reduction of 21% in the intracellular free Mg2+ concentration upon Pb2+ treatment. The observed lead-induced reduction in ATP synthesis/utilization and the decrease in intracellular free Mg2+ may contribute to the impairment of bone formation during lead intoxication. 相似文献
97.
Phillips CD Phelan G Dowd SE McDonough MM Ferguson AW Delton Hanson J Siles L Ordóñez-Garza N San Francisco M Baker RJ 《Molecular ecology》2012,21(11):2617-2627
Metagenomic methods provide an experimental approach to inform the relationships between hosts and their microbial inhabitants. Previous studies have provided the conceptual realization that microbiomes are dynamic among hosts and the intimacy of relation between micro- and macroorganisms. Here, we present an intestinal microflora community analysis for members of the order Chiroptera and investigate the relative influence of variables in shaping observed microbiome relationships. The variables ranged from those considered to have ancient and long-term influences (host phylogeny and life history) to the relatively transient variable of host reproductive condition. In addition, collection locality data, representing the geographic variable, were included in analyses. Results indicate a complex influence of variables in shaping sample relationships in which signal for host phylogeny is recovered at broad taxonomic levels (family), whereas intrafamilial analyses disclosed various degrees of resolution for the remaining variables. Although cumulative probabilities of assignment indicated both reproductive condition and geography influenced relationships, comparison of ecological measures among groups revealed statistical differences between most variable classifications. For example, ranked ecological diversity was associated with host phylogeny (deeper coalescences among families were associated with more microfloral diversity), dietary strategy (herbivory generally retained higher diversity than carnivory) and reproductive condition (reproductively active females displayed more diverse microflora than nonreproductive conditions). Overall, the results of this study describe a complex process shaping microflora communities of wildlife species as well as provide avenues for future research that will further inform the nature of symbiosis between microflora communities and hosts. 相似文献
98.
Arick Brown Charity Bechtel Jerome Bill Hui Liu Jun Liu Dan McDonald Satyan Pai Asha Radhamohan Ryan Renslow Brooke Thayer Stefan Yohe Chris Dowd 《Biotechnology and bioengineering》2010,106(4):627-637
Pre‐filtration using ion exchange membrane adsorbers can improve parvovirus filter throughput of monoclonal antibodies (mAbs). The membranes work by binding trace foulants, and although some antibody product also binds, yields ≥99% are easily achieved by overloading. Results show that foulant adsorption is dependent on pH and conductivity, but independent of scale and adsorber brand. The ability to use ion exchange membranes as pre‐filters is significant because it provides a clean, well defined, chemically stable option for enhancing throughput. Additionally, ion exchange membranes facilitate characterization of parvovirus filter foulants. Examination of adsorber elution samples using sedimentation velocity analysis and SEC‐MALS/QELS revealed the presence of high molecular weight species ranging from 8 to 13 nm in hydrodynamic radius, which are similar in size to parvoviruses and thus would be expected to plug the pores of a parvovirus filter. A study of two identical membranes in‐series supports the hypothesis that the foulants are soluble, trace level aggregates in the feed. This study's significance lies in a previously undiscovered application of membrane chromatography, leading to a more cost effective and robust approach to parvovirus filtration for the production of monoclonal antibodies. Biotechnol. Bioeng. 2010;106: 627–637. © 2010 Wiley Periodicals, Inc. 相似文献
99.
α,α-Trehalose is of interest because of its cryoprotective and antidessicant properties, and because it possesses various technical anomalies such as 13C NMR spectra that give misleading indications of intramolecular structural symmetry. It is a non-reducing disaccharide, with the glycosidic oxygen atom shared by the anomeric carbon atoms of the two glucose rings, and is therefore subject to a proposed ‘overlapping’ exo-anomeric effect. We report here a study of the electron density of trehalose with X-ray diffraction and quantum mechanics calculations, similar to a recent study of sucrose, also a non-reducing molecule. In particular we studied the electron density around the glycosidic linkage and the hydrogen bonding with both deformation density and Atoms in Molecules (AIM) analyses. A total of 129,952 single crystal X-ray intensity measurements were collected on α,α-trehalose dihydrate to a resolution of sin θ/λ = 1.18 Å−1 at 100 K and refined with an aspherical multipole model to a final agreement factor of R1 = 0.0160. Wavefunctions were calculated at three levels of theory. Redistribution of electron density due to anomeric effects was reduced in trehalose, compared to sucrose. Five new C-H?O hydrogen bonds were confirmed with bond critical points and bond paths from AIM analyses, as were the previously proposed O-H?O hydrogen bonds. 相似文献
100.
Evangelia Morou Andrew J. Dowd Shavanti Rajatileka Andrew Steven Janet Hemingway Hilary Ranson Mark Paine John Vontas 《PLoS neglected tropical diseases》2010,4(8)