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排序方式: 共有133条查询结果,搜索用时 218 毫秒
121.
M J Bogusky A M Naylor S M Pitzenberger R F Nutt S F Brady C D Colton J T Sisko P S Anderson D F Veber 《International journal of peptide and protein research》1992,39(1):63-76
The tripeptide sequence arginine-glycine-aspartic acid (RGD) has been shown to be the key recognition segment in numerous cell adhesion proteins. The solution conformation and dynamics in DMSO-d6 of the cyclic pentapeptides, [formula: see text], a potent fibrinogen receptor antagonist, and [formula: see text], a weak fibrinogen receptor antagonist, have been characterized by nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. 1H-1H distance constraints derived from two-dimensional NOE spectroscopy and torsional angle constraints obtained from 3JNH-H alpha coupling constants, combined with computer-assisted modeling using conformational searching algorithms and energy minimization have allowed several low energy conformations of the peptides to be determined. Low temperature studies in combination with molecular dynamics simulations suggest that each peptide does not exist in a single, well-defined conformation, but as an equilibrating mixture of conformers in fast exchange on the NMR timescale. The experimental results can be fit by considering pairs of low energy conformers. Despite this inherent flexibility, distinct conformational preferences were found which may be related to the biological activity of the peptides. 相似文献
122.
We investigated the quantitative relationships among pharyngeal resistance (Rph), genioglossal electromyographic (EMGge) activity, nasal resistance (Rna), and airflow in 11 normal men aged 19-50 while they were awake. We made measurements with subjects seated with the head erect, seated with the head flexed forward approximately 40 degrees, and supine. Each subject wore a face mask connected to a pneumotachograph to measure airflow. After topical anesthesia of the nose, two catheters for measuring nasal and pharyngeal airway pressures were passed through one nostril: the nasal pressure catheter was positioned at the nasal choanae, and the pharyngeal pressure catheter was positioned just above the epiglottis. We measured EMGge activity with an intraoral surface electrode. The subjects breathed exclusively through the nose while inhaling room air or rebreathing CO2. We measured Rph, Rna, airflow, and EMGge activity at approximately 90-ms intervals throughout each inspiration. Rph was invariant as head position was changed. At any given head position, EMGge activity rose as airflow increased, and Rph remained constant. In contrast, Rna increased as airflow increased. Because Rph was constant, EMGge activity was not correlated with Rph, but EMGge was positively correlated with Rna and airflow. On the basis of the stability of Rph in the face of marked changes in collapsing forces, we conclude that the dynamic interplay of posture, head and jaw position, and upper airway muscle activity quite effectively maintains pharyngeal patency, and interactions among these factors are subtle and complex. 相似文献
123.
Rebecca Chaplin-Kramer Emily Dombeck James Gerber Katherine A. Knuth Nathaniel D. Mueller Megan Mueller Guy Ziv Alexandra-Maria Klein 《Proceedings. Biological sciences / The Royal Society》2014,281(1794)
Pollinators contribute around 10% of the economic value of crop production globally, but the contribution of these pollinators to human nutrition is potentially much higher. Crops vary in the degree to which they benefit from pollinators, and many of the most pollinator-dependent crops are also among the richest in micronutrients essential to human health. This study examines regional differences in the pollinator dependence of crop micronutrient content and reveals overlaps between this dependency and the severity of micronutrient deficiency in people around the world. As much as 50% of the production of plant-derived sources of vitamin A requires pollination throughout much of Southeast Asia, whereas other essential micronutrients such as iron and folate have lower dependencies, scattered throughout Africa, Asia and Central America. Micronutrient deficiencies are three times as likely to occur in areas of highest pollination dependence for vitamin A and iron, suggesting that disruptions in pollination could have serious implications for the accessibility of micronutrients for public health. These regions of high nutritional vulnerability are understudied in the pollination literature, and should be priority areas for research related to ecosystem services and human well-being. 相似文献
124.
Keane Jared Guillaume Kenswil Paola Pisterzi Gonzalo Sánchez-Duffhues Claire van Dijk Andrea Lolli Callie Knuth Byambasuren Vanchin Adrian Christopher Jaramillo Remco Michiel Hoogenboezem Mathijs Arnoud Sanders Jacqueline Feyen Tom Cupedo Ivan G. Costa Ronghui Li Eric Moniqué Johannes Bindels Kirsten Lodder Bianca Blom Pieter Koen Bos Marc Hermanus Gerardus Petrus Raaijmakers 《Cell Stem Cell》2021,28(4):653-670.e11
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125.
S. Knuth L. G. Belyakova V. V. Velkov V. N. Dementyev H. J. Lommi R. A. L Harper H. G. Gyllenberg 《Engineering in Life Science》1984,4(3):195-208
Characteristics of genetic material: plasmids, vectors, recombinant DNA and DNA fragments were, studied from 235 patent documents. These documents were from the patent offices of the Federal, Republic of Germany (38), the German Democratic Republic (15), the European Patent Office (53), Finland (43), Great Britain (65), the Soviet Union (3), and the United States of America (18). Attention was paid also to the terminology used in the patent documents. According to this study the way in which the genetic material was characterized in patent documents of different countries was quite variable, and the terminology used was sometimes confusing. 相似文献
126.
Diaphragmatic electromyography using a multiple electrode array 总被引:1,自引:0,他引:1
Daubenspeck J. A.; Leiter J. C.; McGovern J. F.; Knuth S. L.; Kobylarz E. J. 《Journal of applied physiology》1989,67(4):1525-1534
We have developed a new technique for diaphragmatic electromyography using an array of seven sequential electrode pairs at 1.0-cm spacing on an esophageal catheter. This array provides information about the spatial distribution of the electrical field generated by the diaphragm and reveals a sharply peaked variation of electrical potential with distance along the esophagus. The rectified and integrated information from each of the seven pairs is summed to give an approximation to the total electrical activity over the span of the array, providing a signal that is relatively insensitive to the position of the array over approximately 4 cm of catheter movement and removes the requirement for balloon stabilization of the catheter. With our array, we have confirmed the artifact in the evoked compound muscle action potential that seems to be related to diaphragmatic shape as reported by others who used supramaximal phrenic nerve stimulation, but the magnitude of this artifact (compared with the functional residual capacity level) was modest near functional residual capacity, averaging 12 +/- 14% (SD) for lung volumes 1.0 l above and -4 +/- 15% for lung volumes 1.0 l below functional residual capacity along the rib cage-abdomen relaxation line. 相似文献
127.
Carita Lindholm Anna Acheva Sisko Salomaa 《Radiation and environmental biophysics》2010,49(2):133-138
A large number of studies have revealed that irradiated subjects produce soluble factors found in their blood plasma which,
when transferred into cell cultures from non-irradiated individuals, show clastogenic (chromosome breaking) activity. Increased
yields of chromatid-type aberrations have been characteristic in most of these studies. Exposed cohorts of various origins
have revealed to possess this feature: from A-bomb survivors to patients treated with radiotherapy. It is apparent that the
plasma factors are sustainable for long time periods. On the other hand, they seem to be produced very fast after exposure.
Considerable variation in the effect has been found between individuals with similar radiation exposure. Further, the phenomenon
is not restricted to irradiated populations. Clastogenic plasma has also been observed in patients with inflammatory diseases
or congenital chromosome breakage syndromes as well in subjects exposed to other agents than ionizing radiation. Chromosomal
aberration inducing substances have been detected not only in vivo, but also in vitro. A common feature to all the conditions
is that they are associated with oxidative stress. Studies on the biochemical nature of the clastogenic factor(s) have been
conducted, and tumor necrosis factor alpha and lipid peroxidation products, among others, have been suggested as good candidates.
The relevance of the plasma factors to health effects remains open. The aim of the paper is to give a short overview on the
phenomenon of clastogenic factors—their occurrence and formation as well as possible effectors. 相似文献
128.
Knuth Mark E.; Keith Brian; Clark Craig; Garcia-Martinez Jose L.; Rappaport Lawrence 《Plant & cell physiology》1983,24(3):423-432
Subjecting either cowpea or barley protoplasts to a combinedosmotic and pH shock provides the optimum conditions for theisolation of cowpea and barley vacuoles. Incubation of vacuolesin a defined medium resulted in 50% lysis after 30 min (cowpea)and 20 min (barley). The addition of 1 mM EDTA resulted in increasedstability of vacuoles with 50% lysis occurring after 50 min(cowpea) and 120 min (barley). Other compounds were tested fortheir effects on the stability of vacuoles. The longer life of vacuoles in the presence of EDTA allowedtransport studies to be carried out using radiolabeled tracers.The uptake of [14C]sucrose (10 mM) by cowpea vacuoles was stimulatedapproximately two-fold by the presence of MgATP (10 mM); theKm for [14G]sucrose uptake by cowpea vacuoles was 12.5 mM. Uptakeof [3H]GA1 ([3H]gibberellin A1) by cowpea vacuoles was alsostimulated two-to-four fold in the presence of 10 mM MgATP comparedto untreated vacuoles. No MgATP stimulation of [3H]GA1 or [14C]sucroseuptake could be observed in barley vacuoles. The effect of pHon uptake of [3H]GA1 was studied in both cowpea and barley vacuoles.Uptake was optimal at about neutral pH which also coincidedwith the optimum pH for maximum stability of vacuoles.
1 Dedicated to the memory of Prof. J. Ashida.
2 Present address: International Plant Research Institute, 853Industrial Road, San Carlos, CA 94070, U.S.A.
3 Present address: Institute de Agroquimica y Tecnológiade Alimentos, Jaíme Roig, 11, Valencia 10, Spain. (Received December 11, 1982; Accepted February 24, 1983) 相似文献
129.
130.
A characterization of the respiratory pattern of gasping 总被引:2,自引:0,他引:2