An evaluation of the role of identified interneurons in triggering kicks and jumps in the locust

1989 ◽  
Vol 61 (1) ◽  
pp. 45-57 ◽  
Author(s):  
I. C. Gynther ◽  
K. G. Pearson
Keyword(s):  
High Frequency ◽  
Locusta Migratoria ◽  
Motor Program ◽  
Additional Mechanism ◽  
Leg Extension ◽  
Current Pulses ◽  
Staining Techniques ◽  
Triggering Process ◽  
Made In

1. We have used intracellular recording and staining techniques to examine the importance of certain identified interneurons within the system responsible for triggering kicks and jumps in the locust, Locusta migratoria. In particular, our study focused on a pair of metathoracic interneurons called the M-neurons. These cells make strong inhibitory connections to hind-leg flexor motoneurons and are thought to play a key role in the termination of flexor activity which causes kicks and jumps to be triggered (8, 20, 24). 2. Simultaneous recordings from M-neurons and flexor motoneurons during bilateral hindleg kicks revealed that in most cases the onset of the M-neuron's high-frequency discharge coincided precisely with the start of the flexor's rapid repolarization. This result demonstrated that M's activity had the correct timing to be involved in the triggering process and so confirmed suggestions made in previous studies. At times, however, the flexor motoneurons began to repolarize slowly prior to the first spike in the M-neuron, indicating that triggering must involve other neurons and perhaps also an additional mechanism such as a reduction of flexor excitation. 3. The sufficiency and necessity of the M-neurons for triggering kicks were tested by experiments involving intracellular current injections. The application of a brief pulse of depolarizing current to an M-neuron, in order to evoke a burst of spikes in the cell prior to the time it would normally have become active, caused extension of the ipsilateral leg to be triggered prematurely but did not influence the motor program in the contralateral leg. This effect was only observed when the discharge frequency evoked artificially in the M-neuron was greater than that seen during natural performance of the behavior. Even then, the repolarization produced in the flexor motoneurons by the current pulses was not the same as occurs normally. We conclude that under natural circumstances the M-neurons, by themselves, are not sufficient to trigger kicks. 4. When the usual discharge in an M-neuron was prevented by the injection of hyperpolarizing current, both legs were still able to kick. This lack of necessity of the M-neurons confirms that additional neurons must be involved in the triggering process. The rate of repolarization of the flexor motoneurons during kicks in which M activity had been abolished was slower and more variable than is seen in normal kicks but this did not appear to alter the timing of leg extension.(ABSTRACT TRUNCATED AT 400 WORDS)

Flight-initiating interneurons in the locust

1985 ◽  
Vol 53 (4) ◽  
pp. 910-925 ◽  
Author(s):  
K. G. Pearson ◽  
D. N. Reye ◽  
D. W. Parsons ◽  
G. Bicker
Keyword(s):  
High Frequency ◽  
Discharge Rate ◽  
Locusta Migratoria ◽  
Motor Program ◽  
Flight Activity ◽  
Neuronal System ◽  
Cellular Mechanisms ◽  
Closely Related Species ◽  
Staining Techniques ◽  
Frequency Burst

We have used intracellular recording and staining techniques to investigate the cellular mechanisms for the initiation and maintenance of flight in the locust, Locusta migratoria. In particular, we examined the properties of a small group of interneurons in the mesothoracic ganglion. We refer to these interneurons as 404 neurons. Their structure has been described, in a closely related species, by Watson and Burrows (21). Using a preparation in which intracellular recordings could be made from the main neurite of a 404 neuron during the generation of flight activity, we observed that the 404 neurons discharged tonically throughout flight episodes elicited by a constant wind stimulus on the head and by a sudden dimming of the lights. Their discharge rate was linearly related to the frequency of the flight activity. Depolarization of individual 404 neurons often initiated flight activity in quiescent preparations, and the application of hyperpolarizing currents during a flight episode either slowed or stopped flight activity. Hyperpolarizing currents also prevented the initiation of flight activity in some preparations. Individual 404 neurons were not always necessary for the generation of flight activity, since flight activity sometimes persisted when all spiking in a 404 neuron was prevented by the application of a hyperpolarizing current. We conclude that the 404 neurons function to initiate and maintain flight activity in response to wind stimulation of the head, but we have not yet established that they are the only thoracic neurons with this function. The 404 neurons discharged with a high-frequency burst at the time of triggering of a kick. Since the motor program for a jump is similar to that for a kick, the 404 neurons may also be involved in linking the initiation of flight activity to the jump. None of our data indicate that the 404 neurons receive input from the central rhythm generator. Thus the neuronal circuitry for flight appears to be hierarchically organized with at least one distinct neuronal system providing a tonic drive to initiate and maintain activity in the system that patterns activity in flight motoneurons.

Experimental Observation of Inertia-Dominated Squeeze Film Damping in Liquid

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Antoine Fornari ◽  
Matthew Sullivan ◽  
Hua Chen ◽  
Christopher Harrison ◽  
Kai Hsu ◽  
...  
Keyword(s):  
Drag Force ◽  
High Frequency ◽  
Power Laws ◽  
Plane Motion ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Made In

We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit.

ASPECTS IN BUILDING A COMPANY WEB-SITE AND ITS ROLE FOR THE DEVELOPMENT OF BUSINESS

2018 ◽  
pp. 117-124
Author(s):  
Petar Halachev ◽  
Victoria Radeva ◽  
Albena Nikiforova ◽  
Miglena Veneva
Keyword(s):  
Life Cycle ◽  
Web Site ◽  
The Internet ◽  
A Company ◽  
The Web ◽  
Design Construction ◽  
Made In ◽  
Site Types

This report is dedicated to the role of the web site as an important tool for presenting business on the Internet. Classification of site types has been made in terms of their application in the business and the types of structures in their construction. The Models of the Life Cycle for designing business websites are analyzed and are outlined their strengths and weaknesses. The stages in the design, construction, commissioning, and maintenance of a business website are distinguished and the activities and requirements of each stage are specified.

Aboutness

2014 ◽  
Author(s):  
Stephen Yablo
Keyword(s):  
Subject Matter ◽  
Philosophy Of Language ◽  
Mental States ◽  
Library Science ◽  
Philosophical Methodology ◽  
Major Advance ◽  
Truth Conditions ◽  
Ways Of Being ◽  
Made In

Aboutness has been studied from any number of angles. Brentano made it the defining feature of the mental. Phenomenologists try to pin down the aboutness features of particular mental states. Materialists sometimes claim to have grounded aboutness in natural regularities. Attempts have even been made, in library science and information theory, to operationalize the notion. However, it has played no real role in philosophical semantics, which is surprising. This is the first book to examine through a philosophical lens the role of subject matter in meaning. A long-standing tradition sees meaning as truth conditions, to be specified by listing the scenarios in which a sentence is true. Nothing is said about the principle of selection—about what in a scenario gets it onto the list. Subject matter is the missing link here. A sentence is true because of how matters stand where its subject matter is concerned. This book maintains that this is not just a feature of subject matter, but its essence. One indicates what a sentence is about by mapping out logical space according to its changing ways of being true or false. The notion of content that results—directed content—is brought to bear on a range of philosophical topics, including ontology, verisimilitude, knowledge, loose talk, assertive content, and philosophical methodology. The book represents a major advance in semantics and the philosophy of language.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

The Role of the Endothelium in Premature Atherosclerosis: Molecular Mechanisms

2020 ◽  
Vol 27 (7) ◽  
pp. 1041-1051 ◽  
Author(s):  
Michael Spartalis ◽  
Eleftherios Spartalis ◽  
Antonios Athanasiou ◽  
Stavroula A. Paschou ◽  
Christos Kontogiannis ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Low Density Lipoprotein ◽  
Critical Role ◽  
Density Lipoprotein ◽  
Number Of Genes ◽  
Causes Of Mortality ◽  
Artery Disease ◽  
Genetic And Environmental Factors ◽  
Made In

Atherosclerotic disease is still one of the leading causes of mortality. Atherosclerosis is a complex progressive and systematic artery disease that involves the intima of the large and middle artery vessels. The inflammation has a key role in the pathophysiological process of the disease and the infiltration of the intima from monocytes, macrophages and T-lymphocytes combined with endothelial dysfunction and accumulated oxidized low-density lipoprotein (LDL) are the main findings of atherogenesis. The development of atherosclerosis involves multiple genetic and environmental factors. Although a large number of genes, genetic polymorphisms, and susceptible loci have been identified in chromosomal regions associated with atherosclerosis, it is the epigenetic process that regulates the chromosomal organization and genetic expression that plays a critical role in the pathogenesis of atherosclerosis. Despite the positive progress made in understanding the pathogenesis of atherosclerosis, the knowledge about the disease remains scarce.

Conclusions

2018 ◽  
Author(s):  
Amy Strecker
Keyword(s):  
International Law ◽  
Eu Law ◽  
World Heritage Convention ◽  
State Practice ◽  
The World ◽  
State Obligations ◽  
Made In ◽  
Landscape Protection

The final chapter of this book advances four main conclusions on the role of international law in landscape protection. These relate to state obligations regarding landscape protection, the influence of the World Heritage Convention and the European Landscape Convention, the substantive and procedural nature of landscape rights, and the role of EU law. It is argued that, although state practice is lagging behind the normative developments made in the field of international landscape protection, landscape has contributed positively to the corpus of international cultural heritage law and indeed has emerged as a nascent field of international law in its own right.

scholarly journals Simultaneity and Precise Time in Rotation

Universe ◽  
2019 ◽  
Vol 5 (12) ◽  
pp. 226 ◽  
Author(s):  
Don Koks
Keyword(s):  
Time Coordinate ◽  
Near Future ◽  
Precise Time ◽  
Made In

I analyse the role of simultaneity in relativistic rotation by building incrementally on its role in simpler scenarios. Historically, rotation has been analysed in 1 + 1 dimensions; but my stance is that a 2 + 1 -dimensional treatment is necessary. This treatment requires a discussion of what constitutes a frame, how coordinate choices differ from frame choices, and how poor coordinates can be misleading. I determine how precisely we are able to define a meaningful time coordinate on a gravity-free rotating Earth, and discuss complications due to gravity on our real Earth. I end with a critique of several statements made in relativistic precision-timing literature, that I maintain contradict the tenets of relativity. Those statements tend to be made in the context of satellite-based navigation; but they are independent of that technology, and hence are not validated by its success. I suggest that if relativistic precision-timing adheres to such analyses, our civilian timing is likely to suffer in the near future as clocks become ever more precise.

The Role of Histones and Heparin in Sepsis: A Review

2021 ◽  
pp. 088506662199232
Author(s):  
Xiaojuan Zhang ◽  
Xin Li
Keyword(s):  
Septic Shock ◽  
Multiple Organ ◽  
Clinical Settings ◽  
The Past ◽  
Life Saving ◽  
Extracellular Histones ◽  
Sepsis And Septic Shock ◽  
Development And Management ◽  
Made In

Septic shock with multiple organ failure is a devastating situation in clinical settings. Through the past decades, much progress has been made in the management of sepsis and its underlying pathogenesis, but a highly effective therapeutic has not been developed. Recently, macromolecules such as histones have been targeted in the treatment of sepsis. Histones primarily function as chromosomal organizers to pack DNA and regulate its transcription through epigenetic mechanisms. However, a growing body of research has shown that histone family members can also exert cellular toxicity once they relocate from the nucleus into the extracellular space. Heparin, a commonly used anti-coagulant, has been shown to possess life-saving capabilities for septic patients, but the potential interplay between heparin and extracellular histones has not been investigated. In this review, we summarize the pathogenic roles of extracellular histones and the therapeutic roles of heparin in the development and management of sepsis and septic shock.

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