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Narotam S. Bhandal Robert L. Ramsey Robert J. Harvey Mark G. Darlison Peter N. R. Usherwood 《Invertebrate neuroscience : IN》1995,1(3):267-272
We have previously described the isolation of a complementary DNA (cDNA) from the freshwater molluscLymnaea stagnalis encoding a polypeptide that exhibits 50% identity to the ß-subunits of vertebrate -aminobutyric acid (GABA) type A (GABAA) receptor. When expressed inXenopus laevis oocytes fromin vitro-transcribed RNA, the snail subunit forms functional homo-oligomeric receptors possessing chloride-selective ion channels. In recordings from voltage-clamped oocytes held at –60 mV, GABA induced an inward current, whereas application of the chloride-channel blocker picrotoxin (in the absence of agonist) elicited an apparent outward current. Single channel recordings obtained from cell-attached patches have revealed a single population of 20 pS channels, with an open probability greater than 90% (at a pipette potential of –100 mV) in the absence of GABA. The relationship between single channel current and pipette potential was linear over the studied range (–100 mV to +60 mV), but the open probability was less for hyperpolarizations than for depolarizations. The spontaneous channel openings were blocked by micromolar concentrations of picrotoxin. Functional hetero-oligomeric receptors were formed when the molluscan subunit was co-expressed in oocytes with the bovine GABAA receptor 1-subunit, but the channels gated by these receptors did not open spontaneously. 相似文献
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Background
The statistical modeling of biomedical corpora could yield integrated, coarse-to-fine views of biological phenomena that complement discoveries made from analysis of molecular sequence and profiling data. Here, the potential of such modeling is demonstrated by examining the 5,225 free-text items in the Caenorhabditis Genetic Center (CGC) Bibliography using techniques from statistical information retrieval. Items in the CGC biomedical text corpus were modeled using the Latent Dirichlet Allocation (LDA) model. LDA is a hierarchical Bayesian model which represents a document as a random mixture over latent topics; each topic is characterized by a distribution over words. 相似文献4.
Estimating the rate of evolution of the rate of molecular evolution 总被引:35,自引:13,他引:22
A simple model for the evolution of the rate of molecular evolution is
presented. With a Bayesian approach, this model can serve as the basis for
estimating dates of important evolutionary events even in the absence of
the assumption of constant rates among evolutionary lineages. The method
can be used in conjunction with any of the widely used models for
nucleotide substitution or amino acid replacement. It is illustrated by
analyzing a data set of rbcL protein sequences.
相似文献
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Vipond C Mulloy B Rigsby P Burkin K Bolgiano B;the MenC IS Working Group 《Biologicals》2012,40(5):353-363
Meningococcal group C (MenC) plain polysaccharide (PS) and conjugate vaccines are primarily evaluated by physicochemical methods to ensure that batches are consistently manufactured. As different assays are employed to quantify the MenC PS content of final formulations and bulk intermediaries, there is a need for an International MenC PS Standard to calibrate internal references used in the different laboratories. Twelve laboratories from nine different countries participated in a collaborative study to determine the MenC PS content of a candidate International Standard MenC PS preparation (08/214) and to assess its suitability. On the basis of the results from this study the candidate standard 08/214 was established as an International Standard for the quantification of MenC PS content in vaccines and components. It has a content of 1.192 ± 0.192 mg MenC PS/ampoule (expanded uncertainty with coverage factor of k = 2.365 corresponding to a 95% level of confidence), as determined by the resorcinol assays carried out by eight of the participating laboratories. The standard is available from The National Institute of Biological Standards and Control who act as guardians and distributors of the material under the auspices of WHO. 相似文献
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Background
Ensemble attribute profile clustering is a novel, text-based strategy for analyzing a user-defined list of genes and/or proteins. The strategy exploits annotation data present in gene-centered corpora and utilizes ideas from statistical information retrieval to discover and characterize properties shared by subsets of the list. The practical utility of this method is demonstrated by employing it in a retrospective study of two non-overlapping sets of genes defined by a published investigation as markers for normal human breast luminal epithelial cells and myoepithelial cells. 相似文献7.
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INDRIK IS KRAMS 《Ibis》2001,143(4):476-481
This paper tests the hypothesis that foraging site selection reflects a trade-off between the various needs for concealment from predators, to find food, and for the individual to maintain some view of its surroundings. After removal of Crested Tits Parus cristatus (the dominant species in mixed flocks), Willow Tits P. montanus did not decrease their foraging heights as expected but remained in the most exposed parts of young pines. In contrast, after removal of Willow Tits, Crested Tits increased their foraging height from the sheltered lower canopy to sites previously occupied by Willow Tits. When flock size was reduced, the birds maintained the same high levels of vigilance without concealing themselves in dense vegetation. I suggest that flock members may benefit from foraging in sites that afford good anti-predator vigilance. 相似文献
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Trehalose as cryoprotectant for the freeze preservation of carrot and tobacco cells 总被引:5,自引:0,他引:5
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Suspension cultures of carrot (Daucus carota, line C1), tobacco (Nicotiana tabacum, line TX1), and Nicotiana plumbaginifolia (line NP) were frozen under controlled conditions with trehalose as the sole cryoprotectant. Maximal post-thaw viability (71-74%), measured by phenosafranin dye exclusion, was obtained with the C1 cells following a 24hour pretreatment with 5 or 10% trehalose and with 40% trehalose as the cryoprotectant during freezing. TX1 cells pretreated for 24 hours with 10% trehalose and cryoprotected with 40% trehalose during freezing showed 47% viability following thawing as determined by phenosafranin dye exclusion. The NP cells required a 3 to 6 day pretreatment with 10% trehalose and 40% trehalose as a cryoprotectant at the time of freezing for the recovery of viable cells. Growing cells were recovered when the C1 and NP cells treated as described were plated on agar-solidified medium following thawing. 相似文献
10.
Ninety ejaculates from a total of 76 AI boars were extended in Beltsville Thawing Solution (BTS). Boar identity, breed, weight
of the ejaculate and sperm concentration were registered. Motility and acrosome integrity were assessed after storage at 16–18°C
for 6, 30, 54, 78, and 102 h. Storage time had a significant influence on both motility (p < 0.01) and acrosome integrity
(p < 0.001). The Least Square Means for percentage of motility showed a small decline from 79.8% after 6 h of storage to 78.4%
at 102 h. Motility at 78 and 102 h was significantly different from motility at 6 h (p < 0.05). The percentage of sperm cells
with normal acrosomes declined throughout the experiment. The Least Square Means for 6, 30, 54, 78, and 102 h of storage were
93.9%, 90.6%, 88.0%, 84.8%, and 78.2%, respectively. The decrease in acrosome integrity from one storage time to the next
was highly significant throughout the trial (p < 0.001). There was a significant influence of boar (p < 0.001) and sperm concentration
(p < 0.01) on motility, while acrosome integrity was affected only by boar (p < 0.001). Breed of the boars and weight of the
ejaculate did not influence the dependent variables. 相似文献