检索结果-内蒙古大学图书馆

A phylogenetic analysis of the tropidurine lizards (Squamata: Tropiduridae), including new characters of squamation and epidermal micro structure

引用

ZOOLOGICAL JOURNAL OF THE LINNEAN SOCIETY 2000年第2期128卷 189-233页

作者： Harvey, MB Gutberlet, RL Univ Texas Dept Biol Arlington TX 76019 USA

Characters of scale surface microstructure are combined with 'traditional' morphological characters in a phylogenetic analysis of the Tropidurini. Tropidurid lizards show variation in types of coarse and fine scale surface microstructure, in the anatomical distribution of different scale surface features, and in scale organ morphology and distribution. The morphology of the inner surface zone of scales is here described for the first time using scanning electron microscopy. Our phylogeny differs considerably from those proposed in earlier studies. New characters and frequency coding of polymorphic characters help resolve the problematic relationships of several species. Statistical confidence supports recognition of one large cis-Andean and one large trans-Andean clade of species. Based on our results, we synonymize Plesiomicrolophus with Microlophus and Uranoscodon with Tropidurus. The phylogenetic relationships of newly discovered Tropidurus are resolved: T. callathelys is the sister species of I: melanopleurus;I:xanthochilus is the sister species of T. spinulosus. Tropidurus spinulosus is found to be more closely related to I strobilurus and a clade of Amazonian species than to I: melanopleurus. The species previously placed in Uracentron are more closely related to species previously placed in Plica than to T. strobilurus as previously thought. (C) 2000 The Linnean Society or London.

关键词： Tropidurus Uranoscodon Microlophus Plesiomicrolophus microdermatoglyphics epidermis frequency coding systematics

来源：评论

学校读者我要写书评

暂无评论

PROTEIN-PHOSPHORYLATION DRIVEN BY INTRACELLULAR CALCIUM OSCILLATIONS - A KINETIC-ANALYSIS

引用

BIOPHYSICAL CHEMISTRY 1992年第3期42卷 257-270页

作者： DUPONT, G GOLDBETER, A Faculté des Sciences Université Libre de Bruxelles Belgium.

Given the ubiquitous nature of signal-induced Ca2+ oscillations, the question arises as to how cellular responses are affected by repetitive Ca2+ spikes. Among these responses, we focus on those involving protein phosphorylation. We examine, by numerical simulations of a theoretical model, the situation where a protein is phosphorylated by a Ca2+-activated kinase and dephosphorylated by a phosphatase. This reversible phosphorylation system is coupled to a mechanism generating cytosolic Ca2+ oscillations;for definiteness, this oscillatory mechanism is based on the process of Ca2+-induced Ca2+ release. The analysis shows that the average fraction of phosphorylated protein increases with the frequency of repetitive Ca2+ spikes;the latter frequency generally rises with the extent of external stimulation. Protein phosphorylation therefore provides a mechanism for the encoding of the external stimulation in terms of the frequency of signal-induced Ca2+ oscillations. Such a frequency encoding requires precise kinetic conditions on the Michaelis-Menten constants of the kinase and phosphatase, their maximal rates, and the degree of cooperativity in kinase activation by Ca2+. In particular, the most efficient encoding of Ca2+ oscillations based on protein phosphorylation occurs in conditions of zero-order ultrasensitivity, when the kinase and phosphatase are saturated by their protein substrate. The kinetic analysis uncovers a wide variety of temporal patterns of phosphorylation that could be driven by signal-induced Ca2+ oscillations.

关键词： CALCIUM REGULATION KINASE CALMODULIN frequency coding BIOCHEMICAL OSCILLATIONS

来源：评论

学校读者我要写书评

暂无评论

Response properties of single neurons in higher level auditory cortex of adult songbirds

引用

JOURNAL OF NEUROPHYSIOLOGY 2019年第1期121卷 218-237页

作者： Bottjer, Sarah W. Ronald, Andrew A. Kaye, Tiara Univ Southern Calif Sect Neurobiol Los Angeles CA USA

The caudomedial nidopallium (NCM) is a higher level region of auditory cortex in songbirds that has been implicated in encoding learned vocalizations and mediating perception of complex sounds. We made cell-attached recordings in awake adult male zebra finches (Taeniopygia guttata) to characterize responses of single NCM neurons to playback of tones and songs. Neurons fell into two broad classes: narrow fast-spiking cells and broad sparsely firing cells. Virtually all narrow-spiking cells responded to playback of pure tones, compared with approximately half of broad-spiking cells. In addition, narrow-spiking cells tended to have lower thresholds and faster, less variable spike onset latencies than did broad-spiking cells, as well as higher firing rates. Tonal responses of narrow-spiking cells also showed broader ranges for both frequency and amplitude compared with broad-spiking neurons and were more apt to have V-shaped tuning curves compared with broad-spiking neurons, which tended to have complex (discontinuous), columnar, or O-shaped frequency response areas. In response to playback of conspecific songs, narrow-spiking neurons showed high firing rates and low levels of selectivity whereas broad-spiking neurons responded sparsely and selectively. Broad-spiking neurons in which tones failed to evoke a response showed greater song selectivity compared with those with a clear tuning curve. These results are consistent with the idea that narrow-spiking neurons represent putative fast-spiking intemeurons, which may provide a source of intrinsic inhibition that contributes to the more selective tuning in broad-spiking cells. NEW & NOTEWORTHY The response properties of neurons in higher level regions of auditory cortex in songbirds are of fundamental interest because processing in such regions is essential for vocal learning and plasticity and for auditory perception of complex sounds. Within a region of secondary auditory cortex, neurons with narrow spikes exhibited hi

关键词： auditory cortex frequency coding intensity coding vocal learning

来源：评论

学校读者我要写书评

暂无评论

frequency AND LOCATION SPECIFICITY OF THE HUMAN VERTEX N1-WAVE

引用

ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1988年第6期69卷 523-531页

作者： NAATANEN, R SAMS, M ALHO, K PAAVILAINEN, P REINIKAINEN, K SOKOLOV, EN UNIV HELSINKI DEPT PSYCHOL RITARIKATU 5 SF-00170 HELSINKI 17 FINLAND MOSCOW STATE UNIV DEPT PSYCHOPHYSIOL MOSCOW USSR

Test tones of 1000 Hz subjectively located in the middle of the head were randomly presented with equiprobable intervening tones. The latter stimulus was constant within a stimulus block. The frequency of the intervening stimulus varied between different blocks from 578 Hz to 1728 Hz and its location varied in parallel with the frequency along the left-right dimension through 7 different locations. The constant inter-stimulus interval was 460 msec. The EEG was recorded at Cz and Fz. The N1 wave elicited by the test stimuli was smaller the smaller was the separation between the two stimuli in frequency or location. These results were interpreted in terms of stimulus-specifically adapted detector activity. The more the test and intervening stimuli resemble each other the greater is the overlap between the respective feature-detector populations activated and, therefore, the smaller is the N1 amplitude. Thus the sensory-specific component of the N1 wave generated in the primary auditory areas at least in part reflects detector activity. The selective frequency adaptaiton was much more specific in the present study than in the previous ones and suggested that the N1 component recorded was generated by highly frequency-specific neurons. The frequency and location effects were independent, i.e., the frequency effect was rather similar for different location separations, and vice versa. Thus, evidence for separate detectors for frequency and location of an auditory stimulus was obtained.

关键词： Audition Detector Event-related potential Evoked potential N1 N100 frequency coding

来源：评论

学校读者我要写书评

暂无评论

THE EFFECT OF SIGNAL DURATION ON frequency DISCRIMINATION AT LOW SIGNAL-TO-NOISE RATIOS IN DIFFERENT CONDITIONS OF INTERAURAL PHASE

引用

HEARING RESEARCH 1990年第3期48卷 201-208页

作者： HENNING, GB WARTINI, S TECH UNIV MUNICH INST ELECTROACOUST W-8000 MUNICH 2 GERMANY

frequency discrimination in noise at low signal-to-noise ratios where the signals to be discriminated are equally well detected but only faintly audible is better when the signals are in-phase at the ears than when they are out-of-phase. In spite of the difference in discriminability, however, the form of the dependence of the just-noticeable frequency difference on signal duration is the same in both cases.

关键词： Binaural masking Duration frequency coding

来源：评论

学校读者我要写书评

暂无评论

Optimal signal in sensory neurons under an extended rate coding concept

引用

BIOSYSTEMS 2007年第1-3期89卷 10-15页

作者： Lansky, Petr Greenwood, Priscilla E. Acad Sci Czech Republ Prague 14220 4 Czech Republic Arizona State Univ Dept Math & Stat Tempe AZ 85287 USA

We define an optimal signal in parametric neuronal models on the basis of interspike interval data and rate coding schema. Under the classical approach the optimal signal is located where the frequency transfer function is steepest. Its position coincides with the inflection point of this curve. This concept is extended here by using Fisher information which is the inverse asymptotic variance of the best estimator and its dependence on the parameter value indicates accuracy of estimation. We compare the signal producing maximal Fisher information with the inflection point of the sigmoidal frequency transfer function. (C) 2006 Elsevier Ireland Ltd. All rights reserved.

关键词： interspike interval Fisher information optimal signal frequency coding

来源：评论

学校读者我要写书评

暂无评论

Time-patterned drug administration: Insights from a modeling approach

引用

CHRONOBIOLOGY INTERNATIONAL 2002年第1期19卷 157-175页

作者： Goldbeter, A Claude, D Free Univ Brussels Fac Sci Unite Chronobiol Theor B-1050 Brussels Belgium Hop Paul Brousse INSERM EPI 0118 Villejuif France Univ Paris 11 Ctr Sci Orsay France INRIA Rocquencourt France

The physiological effects of a drug depend not only on its molecular structure but also on the time-pattern of its administration. One of the main reasons for the importance of temporal patterns in drug action is biological rhythms-particularly those of circadian period. These rhythms affect most physiological functions as well as drug metabolism, clearance, and dynamic processes that may alter drug availability and target cell responsiveness with reference to biological time. We present an overview of the importance of time-patterned signals in physiology focused on the insights provided by a modeling approach. We first discuss examples of pulsatile intercellular communication by hormones such as gonadotropin-releasing hormone, and by cyclic adenosine monophosphate (cAMP) signals in Dictyostelium amoebae. Models based on reversible receptor desensitization account in both cases for the existence of optimal patterns of pulsatile signaling. Turning to circadian rhythms, we examine how models can be used to account for the response of 24h patterns to external stimuli such as light pulses or gene expression, and to predict how to restore the physiological characteristics of altered rhythms. Time-patterned treatments of cancer involve two distinct lines of research. The first, currently evaluated in clinical trials, relies on circadian chrono-modulation of anticancer drugs, while the second, mostly based on theoretical studies, involves a resonance phenomenon with the cell-cycle length. We discuss the implications of modeling studies to improve the temporal patterning of drug administration. Copyright (C) 2002 by Marcel Dekker, Inc.

关键词： chronobiology chronopharmacology chronotherapy circathan rhythms frequency coding pulsatile signaling

来源：评论

学校读者我要写书评

暂无评论

THE EFFECT OF INTERAURAL PHASE ON frequency DISCRIMINATION WITH BROAD-BAND AND NARROW-BAND MASKERS

引用

HEARING RESEARCH 1990年第3期48卷 195-200页

作者： HENNING, GB UNIV OXFORD DEPT EXPTL PSYCHOL S PARKS RD OXFORD OX1 3UD ENGLAND

With both broad-band and narrow-band noise maskers there is a small range of signal-to-noise ratios where, with the maskers in-phase and signals ***. out-of-phase at the ears, detection performance growth with increasing signal-to-noise ratio but frequency discrimination performance does not. The observation may have significant consequences for our understanding of the way in which frequency is coded at low signal-to-noise ratios.

关键词： Binaural masking-level differences frequency coding

来源：评论

学校读者我要写书评

暂无评论

DENDRITIC MORPHOLOGY OF CENTRAL AUDITORY NEURONS CORRELATES WITH THEIR TONOTOPIC POSITION

引用

JOURNAL OF COMPARATIVE NEUROLOGY 1990年第3期294卷 443-454页

作者： SANES, DH GOLDSTEIN, NA OSTAD, M HILLMAN, DE NYU SCH MED DEPT OTOLARYNGOL NEW YORK NY 10016 USA NYU SCH MED DEPT PHYSIOL & BIOPHYS NEW YORK NY 10016 USA

We have investigated the morphology of dendritic arbors in a central auditory nucleus, the lateral superior olive, of the Mongolian gerbil. Morphometric observations were obtained directly from Golgi-impregnated material by using a microcomputer-based three-dimensional data acquisition system. In particular, measurements were made to determine the dendritic arborization across each of these axes: the tonotopic axis, the rostrocaudal axis, and the isofrequency axis (i.e., perpendicular to the tonotopic axis). The tonotopic position of each cell was computed on the basis of a topographic map that has been constructed for the gerbil LSO (Sanes et al.: J. Comp. Neurol. 279:436-444, 1989). It was found that the span of a dendritic arbor along the tonotopic axis was directly correlated with the neuron''s tonotopic position: Low frequency neurons had much broader arborizations than high frequency neurons. Moreover, the distibution of frequency bandwidths to which single LSO neurons responded showed a striking similarity to dendritic arborizations across the tonotopic axis. Lower frequency neurons responded to a larger number of octaves than higher frequency neurons. There was no correlation between tonotopic position and dendritic arborization in the isofrequency or rostrocaudal axis. Nor was there any correlation between frequency and total dendritic length, number of priamry dendrites, or soma area. However, there was a small but significant difference between the primary dendrite diameter of low and high frequency neurons. Low frequency neurons had significantly greater diameters. These reuslts suggest that the frequency selectivity of central auditory neurons may employ, as one morphological substrate, the distance over which their dendrites arborize along the tonotopic axis.

关键词： auditory pathways lateral superior olive morphometry dendrites frequency coding cytoarchitecture

来源：评论

学校读者我要写书评

暂无评论

Neural coding in antennal olfactory cells of tsetse flies (Glossina spp.)

引用

CHEMICAL SENSES 1998年第5期23卷 521-530页

作者： Voskamp, KE Noorman, N Mastebroek, HAK Van Schoot, NEG Den Otter, CJ Univ Groningen Dept Anim Physiol NL-9750 AA Haren Netherlands Univ Groningen Dept Biophys NL-9750 AA Haren Netherlands

Spike trains from individual antennal olfactory cells of tsetse flies (Glossina spp.) obtained during steady-state conditions (spontaneous as well as during stimulation with 1-octen-3-ol) and dynamic stimulation with repetitive pulses of 1-octen-3-ol were investigated by studying the spike frequency and the temporal structure of the trains. In general, stimulation changes the intensity of the spike activity but leaves the underlying stochastic structure unaffected. This structure turns out to be a renewal process. The only independently varying parameter in this process is the mean interspike interval length, suggesting that olfactory cells of tsetse flies may transmit information via a frequency coding. In spike records with high firing rates, however, the stationary records had significant negative first-order serial correlation coefficients and were non-renewal. Some cells in this study were capable of precisely encoding the onset of the odour pulses at frequencies up to at least 3 Hz. Cells with a rapid return to pre-stimulus activity at the end of stimulation responded more adequately to pulsed stimuli than cells with a long increased spike frequency. While short-firing cells process information via a frequency code, long-firing cells responded with two distinctive phases: a phasic, non-renewal response and a tonic, renewal response which may function as a memory of previous stimulations.

关键词： M-morsitans Pheromone Adaptation Receptors Responses Neurons Diptera Moths Diptera Moth Pheromones octenol frequency coding spikes Cells Smell spike cells Stimuli Stimulation Glossina Spike Neurons

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：