Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character最新文献

{"title":"Oscillation period of MEPP frequency at frog neuromuscular junctions is inversely correlated with release efficacy and independent of acute Ca2+ loading.","authors":"P A Pawson,&nbsp;A D Grinnell","doi":"10.1098/rspb.1989.0061","DOIUrl":"https://doi.org/10.1098/rspb.1989.0061","url":null,"abstract":"<p><p>Periodic oscillations in miniature endplate potential (MEPP) frequency have been described at the frog neuromuscular junction. It is assumed that the periodic oscillations in MEPP frequency reflect cytosolic oscillations in intracellular Ca2+ concentration. In the course of a study related to describing the differences between weak and strong neuromuscular junctions by using the post-tetanic potentiation of MEPP frequency, we noted periodic oscillations in MEPP frequency in the first few minutes after a tetanus. The period of this oscillation (i.e. the time interval of one complete oscillation cycle) was inversely related to synaptic release efficacy, as measured by quantal content released per 100 microns of nerve terminal length. Junctions of high release efficacy have an oscillation period of 20 s or less whereas the oscillations in weaker junctions have periods of up to 60 s or longer. This relation is very similar during post-tetanic recovery in either a calcium containing Ringer solution or in a zero calcium-EGTA Ringer solution, indicating that external calcium is not necessary to express the phenomenon. We also found that the oscillations are apparent in resting junctions preceding a tetanus and that they are similar in period and show the same inverse relation to synaptic strength.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1289","pages":"489-99"},"PeriodicalIF":0.0,"publicationDate":"1989-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0061","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13717429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The morphology and topographic distribution of substance-P-like immunoreactive amacrine cells in the cat retina.","authors":"D I Vaney,&nbsp;G E Whitington,&nbsp;H M Young","doi":"10.1098/rspb.1989.0060","DOIUrl":"https://doi.org/10.1098/rspb.1989.0060","url":null,"abstract":"<p><p>In cat retinal wholemounts, substance-P-like immunoreactivity (SP-IR) was localized in a distinct population of amacrines whose cell bodies were normally placed in the ganglion cell layer. Although displaced amacrines accounted for 80-95% of the SP-IR amacrines in peripheral retina, this proportion decreased considerably within the area centralis, accounting for 50-80% of the labelled cells at maximum density. The SP-IR cells in both the inner nuclear and ganglion cell layers gave rise to well-defined varicose dendrites of uniform appearance that stratified around 60% depth (S3/S4) of the inner plexiform layer. In addition, sparse fine dendrites in stratum 1 (S1) could sometimes be traced to inner nuclear cells and occasionally to displaced amacrines. The combined SP-IR cell density ranged from less than 50 cells mm-2 in the far periphery to more than 500 cells mm-2 in the area centralis; the maximum density showed little individual variation despite wide differences in the proportion of displaced cells. The 39,000 SP-IR amacrines in a mapped retina had a triangular topographic distribution, with intermediate isodensity lines extending vertically in superior retina and horizontally along both arms of the visual streak. Colocalization experiments established that all SP-IR cells in cat retina showed GABA-like immunoreactivity, and that the SP-IR amacrines were quite distinct from the cholinergic amacrines identified by choline acetyltransferase immunohistochemistry.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1289","pages":"471-88"},"PeriodicalIF":0.0,"publicationDate":"1989-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0060","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13624918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vertical disparity, egocentric distance and stereoscopic depth constancy: a new interpretation.","authors":"P O Bishop","doi":"10.1098/rspb.1989.0059","DOIUrl":"https://doi.org/10.1098/rspb.1989.0059","url":null,"abstract":"<p><p>There has long been a problem concerning the presence in the visual cortex of binocularly activated cells that are selective for vertical stimulus disparities because it is generally believed that only horizontal disparities contribute to stereoscopic depth perception. The accepted view is that stereoscopic depth estimates are only relative to the fixation point and that independent information from an extraretinal source is needed to scale for absolute or egocentric distance. Recently, however, theoretical computations have shown that egocentric distance can be estimated directly from vertical disparities without recourse to extraretinal sources. There has been little impetus to follow up these computations with experimental observations, because the vertical disparities that normally occur between the images in the two eyes have always been regarded as being too small to be of significance for visual perception and because experiments have consistently shown that our conscious appreciation of egocentric distance is rather crude and unreliable. Nevertheless, the veridicality of stereoscopic depth constancy indicates that accurate distance information is available to the visual system and that the information about egocentric distance and horizontal disparity are processed together so as to continually recalibrate the horizontal disparity values for different absolute distances. Computations show that the recalibration can be based directly on vertical disparities without the need for any intervening estimates of absolute distance. This may partly explain the relative crudity of our conscious appreciation of egocentric distance. From published data it has been possible to calculate the magnitude of the vertical disparities that the human visual system must be able to discriminate in order for depth constancy to have the observed level of veridicality. From published data on the induced effect it has also been possible to calculate the threshold values for the detection of vertical disparities by the visual system. These threshold values are smaller than those needed to provide for the recalibration of the horizontal disparities in the interests of veridical depth constancy. An outline is given of the known properties of the binocularly activated cells in the striate cortex that are able to discriminate and assess the vertical disparities. Experiments are proposed that should validate, or otherwise, the concepts put forward in this paper.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1289","pages":"445-69"},"PeriodicalIF":0.0,"publicationDate":"1989-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0059","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13717428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The assembly of ionic currents in a thalamic neuron. III. The seven-dimensional model.","authors":"R M Rose,&nbsp;J L Hindmarsh","doi":"10.1098/rspb.1989.0051","DOIUrl":"https://doi.org/10.1098/rspb.1989.0051","url":null,"abstract":"<p><p>We replace our earlier three-dimensional ha-model of a thalamic neuron (Rose & Hindmarsh, Proc. R. Soc. Lond. B 237, 289-312 (1989b)) by a seven-dimensional ha-model. The stability and state diagrams for this seven-dimensional model are shown to be similar to those of the three-dimensional system with which it is compared. Two examples that illustrate how the seven-dimensional model can be related to experimental recordings are then discussed in detail. In each case we show the state and stability diagrams and the time courses of the different ionic currents during the burst response. We discuss how the various components of the state diagram could be determined experimentally. These experiments are illustrated by using our model to simulate the results of actual experiments. Finally the state and stability diagrams are transferred to a current-voltage diagram. This shows the advantage of the state diagram compared with the current-voltage diagram for representing the dynamics of the firing of a thalamic neuron.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"313-34"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The assembly of ionic currents in a thalamic neuron. II. The stability and state diagrams.","authors":"R M Rose,&nbsp;J L Hindmarsh","doi":"10.1098/rspb.1989.0050","DOIUrl":"https://doi.org/10.1098/rspb.1989.0050","url":null,"abstract":"<p><p>In the previous model of a thalamic neuron (R.M. Rose & J.L. Hindmarsh, Proc. R. Soc. Lond. B237, 267-288 (1989], which we referred to as the z-model, the burst response was terminated by the slow activation of a subthreshold outward current. In this paper we show that similar results can be obtained if the burst response is terminated by slow inactivation of the subthreshold inward current, Isa. We illustrate the use of this new model, which we refer to as the ha-model, by using it to explain the response of a thalamic neuron to a double ramp current. The main aim of the paper is to show how the stability and state diagrams introduced previously can be used to explain various types of firing pattern of thalamic and other neurons. We show that increasing the threshold for the fast action potentials leads to low threshold spikes of increased amplitude. Also, addition of a second subthreshold inward current adds a new stability region, which enables us to explain the origin of plateau potentials. In addition, various types of subthreshold oscillation are produced by relocating a previously stable equilibrium point in an unstable region. Finally, we predict a sequence of responses to current steps from different levels of background current that extends the burst, rest, tonic sequence of thalamic neurons. The stability and state diagrams therefore provide us with a useful way of explaining further properties of thalamic neurons and appear to have further applications to other mammalian neurons.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"289-312"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Osmotic flow equations for leaky porous membranes.","authors":"A E Hill","doi":"10.1098/rspb.1989.0055","DOIUrl":"https://doi.org/10.1098/rspb.1989.0055","url":null,"abstract":"<p><p>A basic set of equations describing the flows of volume (Jv) and solute (Js) across a leaky porous membrane, coupled to the differences of osmotic and hydrostatic pressures d pi and dP has been derived by using general frictional theory. Denoting the mean pore concentration of solute by c*s and the hydraulic and diffusive conductances by Lp and Ps/RT the equations take the form Jv = LpdP + sigma sLp d pi Js = c*s(1 - sigma f)Jv + Ps d pi/RT sigma s = theta (1 - DsVs/DwVw - Ds/Dos) sigma f = 1 - theta DsVs/DwVw - Ds/Dos in which Dw and Ds are the diffusion coefficients for water and solute in the pore and Dos that for free solution. The relation between the reflection coefficients sigma s and sigma f for osmosis and ultrafiltration is then given by sigma s = sigma f - (1- theta)(1 - Ds/Dos), where theta is the diffusive-driven:pressure-driven flow ratio. These equations follow from the fact that in leaky pores osmosis occurs by diffusion alone and that there cannot be any Onsager symmetry leading to sigma s = sigma f. Symmetry holds in the limits where either the pore is small, when sigma s = sigma f = 1, or where the pore is large when sigma s = sigma f = 0.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"369-77"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0055","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionic and charge-displacement currents evoked by temperature jumps in Xenopus oocytes.","authors":"I Parker","doi":"10.1098/rspb.1989.0056","DOIUrl":"https://doi.org/10.1098/rspb.1989.0056","url":null,"abstract":"<p><p>Membrane currents were recorded in voltage-clamped oocytes of Xenopus laevis. Currents were produced in response to temperature jumps imposed by a heating lamp. Responses were larger when the animal (pigmented) hemisphere of the oocyte was illuminated as compared to the vegetal hemisphere; they arose because of a thermal effect as they were attenuated by removal of infrared wavelengths. The temperature jump responses comprised two distinct components: (i) a slow maintained current, which inverted direction at a membrane potential of about -25 mV and, (ii) a fast transient current, which at all potentials examined (-160 to +30 mV), was inward at the onset of a light flash and outward at the offset. The slow component probably arises through temperature-dependent changes in the 'leakage' current of the oocyte, and measurements of reversal potentials in solutions of different ionic composition indicated that currents carried by Na+ and H+ ions contribute to the response. In contrast, the fast component was not altered by changes in composition of the bathing solution. This observation, together with the finding that the charge movements associated with the on and off transients were of similar magnitude, suggest that the fast current may arise because of the displacement of charges across the plasma membrane.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"379-87"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0056","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13714666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Osmosis in leaky pores: the role of pressure.","authors":"A E Hill","doi":"10.1098/rspb.1989.0054","DOIUrl":"https://doi.org/10.1098/rspb.1989.0054","url":null,"abstract":"<p><p>Osmosis in leaky pores is often considered to involve gradients of pressure that originate from concentration gradients at the pore wall. These postulated surface pressures are incompatible with the Boltzmann equation and result from an incorrect application of the Gibbs-Duhem equation to binary solutions near surfaces. Such pressures would give rise to tensions in the surface phase that are not observed experimentally. Application of the argument to the swelling of porous systems and gels shows that this phenomenon cannot involve internal pressures within the fluid phase.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"363-7"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0054","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fatty acid modifies Ca2+-dependent potassium channel activity in smooth muscle cells from the human aorta.","authors":"P D Bregestovski,&nbsp;V M Bolotina,&nbsp;V N Serebryakov","doi":"10.1098/rspb.1989.0048","DOIUrl":"https://doi.org/10.1098/rspb.1989.0048","url":null,"abstract":"<p><p>By using the patch-clamp technique the effect of 2-decenoic acid (DA) on Ca2+-activated potassium (K+) channels in the membrane of smooth muscle cells from the human aorta was studied. In the presence of 0.5 microM Ca2+ and 2 mM Mg2+ on the cytoplasmic side of the membrane, a more than tenfold elevation in the probability of the channels being open (po) was observed under the effect of DA. With divalent cation concentrations of less than 1 nM DA caused a more than twofold elevation in po. In the DA-treated membranes Mg2+ ions, which normally fail to activate the channels, brought about a nearly threefold increase in the channel activity when applied to the inner membrane surface. Channel sensitivity to the activating effect of cytoplasmic Ca2+ ions did not increase with the application of DA. Single-channel conductance was unchanged by DA exposure. We suggest that DA alters the Ca2+-binding mechanism of the channel, increasing its sensitivity to Mg2+ ions, presumably owing to membrane fluidization.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"259-66"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0048","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The assembly of ionic currents in a thalamic neuron. I. The three-dimensional model.","authors":"R M Rose,&nbsp;J L Hindmarsh","doi":"10.1098/rspb.1989.0049","DOIUrl":"https://doi.org/10.1098/rspb.1989.0049","url":null,"abstract":"<p><p>We have previously discussed qualitative models for bursting and thalamic neurons that were obtained by modifying a simple two-dimensional model for repetitive firing. In this paper we report the results of making a similar sequence of modifications to a more elaborate six-dimensional model of repetitive firing which is based on the Hodgkin-Huxley equations. To do this we first reduce the six-dimensional model to a two-dimensional model that resembles our original two-dimensional qualitative model. This is achieved by defining a new variable, which we call q. We then add a subthreshold inward current and a subthreshold outward current having a variable, z, that changes slowly. This gives a three-dimensional (v,q,z) model of the Hodgkin-Huxley type, which we refer to as the z-model. Depending on the choice of parameter values this model resembles our previous models of bursting and thalamic neurons. At each stage in the development of these models we return to the corresponding seven-dimensional model to confirm that we can obtain similar solutions by using the complete system of equations. The analysis of the three-dimensional model involves a state diagram and a stability diagram. The state diagram shows the projection of the phase path from v,q,z space into the v,z plane, together with the projections of the curves z = 0 and v = q = 0. The stability of the points on the curve v = q = 0, which we call the v, q nullcurve, is determined by the stability diagram. Taken together the state and stability diagrams show how to assemble the ionic currents to produce a given firing pattern.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"237 1288","pages":"267-88"},"PeriodicalIF":0.0,"publicationDate":"1989-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0049","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13713995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}