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1.
This paper is concerned with the nature of the transmembrane potential induced in an inactive nerve fiber lying in an impressed potential field within a nerve trunk. The impressed potential field is assumed to be produced by the synchronous activity of other fibers within the trunk; an expression for the induced transmembrane potential is obtained utilizing the principles of electromagnetic field theory. The results strongly indicate that membrane capacitance is the main determinant of the induced transmembrane potential wave form. 相似文献
2.
By treating a nonmyelinated nerve fiber as a continuous cable consisting of three distinct zones (Resting, transitional, and excited), the following mathematical expression was derived: (formula: see text) where v is the conduction velocity, d the diameter of the fiber, R the resistance of the membrane of unit area at the peak of excitation, rho the resistivity of the medium inside the fiber, and C the capacity of membrane per unit area. The validity of this expression was demonstrated by using squid giant nerve fibers intracellularly perfused with dilute salt solutions. The relationship between these results and previous theories and experiments on conduction velocity is discussed. 相似文献
3.
The extracellular potential field of the single active nerve fiber in a volume conductor 总被引:4,自引:0,他引:4
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The potential field of an active fiber in a uniform medium of infinite extent and within a nerve trunk is calculated from transmembrane potential data. The resulting distributions are given quantitatively. A comparison of both magnitude and field pattern in the nerve trunk and infinite medium environments is made and the effect of interstitial conductivity and nerve trunk diameter on potential magnitudes is considered. 相似文献
4.
Summary The development of a synthetic medium that supports growth and differentiation of insect embryonic tissues afforded the possibility
of studying the interactions between nerve and other cell types in long term cultures. The mechanical dissociation of embryonic
nerve tissues results in survival of nerve cells but not of glial cells. The dissociated glial-free neurons produce a dense
fibrillar network in the presence, but not in the absence, of foregut explants or other tissues from same donors. Nerve fiber
bundles outgrowing from dissociated neurons enter foregut segments and establish synaptic connections with muscle cells. Foregut
explants undergo differentiation and become contractile in long term cultures when innervated by dissociated nerve cells.
The progressive deterioration of similar foregut tissues cultured alone contrasts with the excellent condition of innervated
explants and suggests that this is due to trophic factors released by nerve fibers. The same in vitro systems provided the
opportunity of studying the interaction between nerve fibers produced by the autonomic ingluvial ganglion, which adheres to
the surface of the alimentary tract, and muscle cells. Multiple esophagus explants from cockroach embryos become interconnected
by fibers emerging from ingluvial ganglia, when the explants are combined in vitro at short distance from each other. Muscle
cells migrating from the esophagi line up on axons branching out in the medium, or form contractile ribbons which, in turn,
establish connections with nerve fibers. The thigmotropism of muscle cells and strong affinity for nerve fibers reveal a new
aspect of muscle cells-to-fibers interaction, amenable to further analysis in vitro.
This work was supported in part by United States Public Health Service grant NS-03777 and grant GB-16330 X from the National
Science Foundation 相似文献
5.
1. Strength-duration data for the giant fiber of the great stellar nerve of the squid (Loligo pealii) can be approximately described by several mathematical formulations. 2. Excitation time constants for isolated giant fibers are essentially the same as constants of the giant fibers in the intact nerve. 3. The strength-duration curves of the fibers in the intact nerve lie higher on the voltage axis than those of the isolated fibers. It is concluded that the principal effect of other fibers upon the excitation of one fiber in a nerve trunk is that of shunting the stimulating current. 4. Deterioration of the nerve shifts the curve upward and to the left, resulting in shorter time constants. 5. Decreasing interelectrode distance also shifts the curve upward and to the left. 6. Excitation time constants of the giant fibers are larger with plate electrodes than with wire or pore electrodes. 7. The strength-duration curves of the smaller fin nerve fibers lie consistently to the right of, and the time constants are longer than those of the giant fibers. 相似文献
6.
S Aizu 《Tissue & cell》1975,7(3):433-452
The cardiac ganglion trunk of prawn, Peneaus japonicus Bates, is on the middle line of ventral wall of the cardiac tube and consists of nine ganglion cells, many nerve fibers and neuropils. These neuronal elements are insulated by supporting cells and connective tissue fibers. The peripheral area of the perikaryal cytoplasm of the ganglion cell is separated into many compartments by deep invaginations of the cell membrane. Each compartment is packed with a tight network of the agranular endoplasmic reticulum. Among nerve fiber bundles are many small areas of neuropil. Most of the synapses in the ganglion trunk are observed in the neuropil, but there are a few nerve terminals which form synapses with the somata of ganglion cells. 相似文献
7.
Volume Control by Muscle Fibers of the Blue Crab : Volume readjustment in hypotonic salines 总被引:1,自引:1,他引:0
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Single isolated muscle fibers from the walking legs of the blue crab, Callinectes sapidus act as Boyle-van't Hoff osmometers with an osmotically inactive volume of 33 %. Fibers in hypotonic salines undergo a spontaneous volume readjustment toward the initial volumes of the cells found in isotonic salines. The volume readjustment is initiated by the increase in cell volume in hypotonic salines and appears to be dependent on the duration of exposure of the fiber to external sodium, the sodium concentration, and the pH of the external medium. The volume-readjusted cells continue to behave as osmometers, but with an increased relative osmotically inactive volume and a decreased internal resistivity. The decreases in cell volumes appear to be, in large part, due to losses of osmotically active nonelectrolytes from the cells. 相似文献
8.
The influence of subthreshold depolarizing prepulses on the threshold current-to-distance and the threshold current-to-diameter
relationship of myelinated nerve fibers has been investigated. A nerve fiber model was used in combination with both a simple,
homogeneous volume conductor model with a point source and a realistic, inhomogeneous volume conductor model of a monofascicular
nerve trunk surrounded by a cuff electrode. The models predict that a subthreshold depolarizing prepulse will desensitize
Ranvier nodes of fibers in the vicinity of the cathode and thus cause an increase in the threshold current of a subsequent
pulse to activate these fibers. If the increase in threshold current of the excited node is large enough, the excitation will
be accompanied by a strong hyperpolarization of adjacent nodes, preventing the propagation of action potentials in these fibers.
As fibers close to the electrode are more desensitized by prepulses than more distant ones, it is possible to stimulate distant
fibers without stimulating such fibers close to the electrode. Moreover, as larger fibers are more desensitized than smaller
ones, smaller fibers have lower threshold currents than larger fibers up to a certain distance from the electrode. The realistic
model has provided an additional condition for the application of this method to invert nerve fiber recruitment, i.e., real
or virtual anodes should be close to the cathode. When using a cuff electrode for this purpose, in the case of monopolar stimulation
the cuff length (determining the position of the virtual anodes) should not exceed twice the internodal length of the fibers
to be blocked. Similarly, the distance between cathode and anodes should not exceed the internodal length of these fibers
when stimulation is to be applied tripolarly.
Received: 15 May 2000 / Accepted in revised form: 9 February 2001 相似文献
9.
1. Cultured neurons from embryonic chick sympathetic ganglia or dorsal root ganglia grow nerve fibers extensively on simple substrata containing fibronectin, collagens (types I, III, IV), and especially laminin. 2. The same neurons cultured on substrata containing glycosaminoglycans grow poorly. Glycosaminoglycans (heparin) inhibit nerve fiber growth on fibronectin substrata. 3. Proteolytic fragments of fibronectin support nerve fiber growth only when the cell attachment region is intact. For example, a 105 kD fragment, encompassing the cell attachment region, supports growth when immobilized in a substratum, but a 93 kD subfragment, lacking the cell attachment region, is unable to support fiber growth. When it is added to the culture medium, the 105 kD fragment inhibits fiber growth on substrata containing native fibronectin. 4. In culture medium lacking NGF, DRG neurons extend nerve fibers only on laminin and not on fibronectin, collagen or polylysine. Studies with radioiodinated laminin indicate that laminin binds with a relatively high affinity (kd approximately equal to 10(-9) M) to DRG neurons, and to a variety of other neural cells (NG108 cells, PC12 cells, rat astrocytes, chick optic lobe cells). We have isolated a membrane protein (67 kD) by affinity chromatography on laminin columns and are characterizing this putative laminin receptor. 5. Dissociated DRG neurons or ganglionic explants cultured on complex substrata consisting of tissue sections of CNS or PNS tissues extend nerve fibers onto the PNS (adult rat sciatic nerve) but not CNS (adult rat optic nerve) substrata. Other tissue substrata which support fiber growth in vivo (embryonic rat spinal cord, goldfish optic nerve) support growth in culture. While substrata from adult CNS, which support meager regeneration in vivo (adult rat spinal cord) support little fiber growth in culture. 6. Ganglionic explants cultured in a narrow space between a section of rat sciatic nerve and optic nerve grow preferentially onto the sciatic nerve suggesting that diffusible growth factors are not responsible for the differential growth on the two types of tissues. 7. Dissociated neurons adhere better to sections of sciatic nerve than optic nerve. Laminin, rather than fibronectin or heparan sulfate proteoglycan, is most consistently identifiable by immunocytochemistry in tissues (sciatic nerve, embryonic spinal cord, goldfish optic nerve) which support nerve fiber growth. Taken together, these data suggest that ECM adhesive proteins are important determinants of nerve regeneration. 相似文献
10.
11.
George W. Schmidt 《Bulletin of mathematical biology》1953,15(4):489-500
A mathematical theory is developed which permits the determination of certain parameters of an inhomogenous tissue, such as
a nerve trunk without its epineurium. The parameters are the permeability coefficients for entrance into an exit of a substance
from the nerve fibers, and the diffusion coefficient of the interstitial material. The experimental data required are the
dimensions of the cross-section, the average diameter of the fibers, and the ratio of the cross-sectional are of the fibers
to the total cross-section, as well as the time course of the decrease of the fraction of the substance left in the nerve
trunk, when the trunk is immersed in a bathing solution containing none of it. 相似文献
12.
Evidence for GABAergic fibers entering the superior cervical ganglion of rat from the preganglionic nerve trunk 总被引:2,自引:0,他引:2
The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk. 相似文献
13.
E. Dobó P. Kása R. J. Wenthold F. Joó J. R. Wolff 《Histochemistry and cell biology》1989,92(2):133-136
Summary The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk. 相似文献
14.
A Shimozawa 《Acta anatomica》1978,100(2):185-192
An electron-microscopic analysis of the mouse facial nerve near the geniculate ganglion shows that there are, on the everage, 603 more nerve fibers in the portion of the nerve distal to the geniculate ganglion than there are in the part proximal to the ganglion. The average distal increase in the number of unmyelinated fibers is 444 and that in the myelinated fibers is 165. The somatic motor nerve fibers and the parasympathetic fibers in the mouse facial nerve may not contribute to the distal excess. It is possible that the increase in the number of unmyelinated fibers distal to the geniculate ganglion is mainly due to the presence of postganglionic sympathetic fibers in the facial trunk distal to the geniculate ganglion and the greater petrosal nerve. The distal increase in the number of myelinated fibers may be mainly contributed by the sensory fibers. 相似文献
15.
Abstract– Embryonic sensory neurons have an absolute requirement for the nerve growth factor to survive and grow fibers, at least in vitro . We have now shown that the inorganic cations, magnesium and potassium are also necessary for the survival of these cells. On the other hand, calcium is not needed for the survival of the sensory neurons, but is needed for the neurons to grow fibers. Therefore, by changing the concentration of calcium ions in the culture medium it is possible to separate the two actions (survival and fiber outgrowth) of the nerve growth factor on sensory neurons. 相似文献
16.
In experiments on rats, we studied 4-aminopyridine (4-AP)-induced modifications of the excitability of peripheral nerve fibers in an efferent trunk, the ventral root (VR), and in a mixed trunk including both afferent and efferent fibers, the sciatic nerve (SN). For this purpose, we examined how 4-AP influenced the parameters of integral action potentials recorded from the VR and SN in three experimental modes. These were: (i) stimulation of the SN and recording of antidromic action potentials from the VR in vivo after systemic injections of 4-AP into the animal, (ii) stimulation of a preparation of the SN dissected from the animal after systemic injection of 4-AP and recording of action potentials from another segment of the same preparation in vitro, and (iii) stimulation of an SN preparation and recording of action potentials from another region of this preparation in vitro, but after direct application of the solution of 4-AP to this preparation. It was found that 4-AP significantly increased the threshold for generation of action potentials and enhanced their amplitude, decreased the duration of action potentials recorded from the VR, and shortened the refractory period following these responses. The drug also significantly increased the amplitude and decreased the duration of action potentials recorded from the SN in vitro after systemic injections of the agent, but the threshold for response generation in this preparation noticeably dropped; the post-response refractory period in this case showed no changes. Modifications of action potentials recorded from the SN in vitro after direct applications of 4-AP were in general similar to the described above. Other examined parameters of action potentials (chronaxia and dynamics of an increase in the amplitude related to intensification of stimulation) showed no significant changes under the influence of 4-AP. We conclude that 4-AP increases the excitability of nerve fibers in the nerve trunks under study, but not to the point where the electrical interaction between excited and nonexcited fibers in the fiber conductors under study (VR and SN) overcomes the threshold. 相似文献
17.
Chafika Zenjari Bénoni Boilly Hubert Hondermarck Yolande Boilly-Marer 《Development, growth & differentiation》1997,39(1):15-22
Previous studies have shown that both fibroblast growth factor (FGF)-1 and nerves play an important function during limb regeneration, but no correlation between these two regeneration factors has yet been demonstrated. In the present study we first establish that exogenous FGF-2, a member of the FGF family that binds to the same high-affinity receptors as FGF-1, is able to stimulate both [3 H]-thymidine incorporation and the mitotic index in the mesenchyme and the epidermal cells of denervated blastemas. We then use cocultures of spinal cord and blastema on heparin-coated dishes, an in vitro system mimicking the in vivo interactions during limb regeneration, to show that interactions between nerve fibers from the spinal cord and the blastema enhance the release of bioactive FGF-1. Release of this growth factor seemed to correlate with nerve fiber regeneration, as it decreased in the presence of the dipeptide Leu-Ala, known to inhibit neurite outgrowth, while the inverse dipeptide Ala-Leu was inactive. Therefore, these results support our hypothesis that the interaction between nervous tissue and blastema is permissive for the release of FGF-1, which in turn stimulates blastema cell proliferation. 相似文献
18.
LORENTE R DE NO R 《The Journal of general physiology》1951,35(2):183-201
The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers. 相似文献
19.
The Absence of CD47 Promotes Nerve Fiber Growth from Cultured Ventral Mesencephalic Dopamine Neurons
Franziska Marschinke Sanaz Hashemian Takashi Matozaki Per-Arne Oldenborg Ingrid Str?mberg 《PloS one》2012,7(9)
In ventral mesencephalic organotypic tissue cultures, two timely separated sequences of nerve fiber growth have been observed. The first appearing nerve fiber pattern is a long-distance outgrowth that occurs before astrocytes start to proliferate and migrate to form an astrocytic monolayer that finally surrounds the tissue slice. These long-distance growing nerve fibers are retracted as the astrocytes migrate, and are followed by a secondary outgrowth. The secondary outgrowth is persistent in time but reaches short distances, comparable with outgrowth seen from a dopaminergic graft implanted to the brain. The present study was focused on the interaction between the astrocytes and the long-distance growing non-glial associated nerve fibers. Cross talk between astroglia and neurite formation might occur through the integrin-associated protein CD47. CD47 serves as a ligand for signal regulatory protein (SIRP) α and as a receptor for the extracellular matrix protein thrombospondin-1 (TSP-1). Embryonic day 14 ventral mesencephalic tissue from CD47+/+ and CD47−/− mice was used to investigate astrocytic migration and the tyrosine hydroxylase (TH) –positive outgrowth that occurred remote from the astrocytes. TH-immunohistochemistry demonstrated that the non-glial-associated nerve fiber outgrowth in CD47−/− cultures reached significantly longer distances and higher density compared to nerve fibers formed in CD47+/+ cultures at 14 days in vitro. These nerve fibers often had a dotted appearance in CD47+/+ cultures. No difference in the astrocytic migration was observed. Further investigations revealed that the presence of CD47 in control culture did neither hamper non-glial-associated growth through SIRPα nor through TSP-1 since similar outgrowth was found in SIRPα mutant cultures and in CD47+/+ cultures treated with blocking antibodies against the TSP-1, respectively, as in the control cultures. In conclusion, long-distance growing nerve fiber formation is promoted by the absence of CD47, even though the presence of astrocytes is not inhibited. 相似文献
20.
V M Nikulin 《Arkhiv anatomii, gistologii i émbriologii》1985,88(4):29-33
In serial electively stained transversal sections of the vagus nerve trunk taken at the levels beginning from its exit out of the brain, up to terminal branches in the abdominal cavity (10 corpses of mature persons) myelin fibers of three classes have been counted. Along the course of the nerve trunk in the craniocaudal direction the total number of the myelin fibers decreases. Only about 10% of the initial amount of the myelin conductors revealed at the level of the intracranial part of the vagus nerve get into the abdominal cavity. Simultaneously, the ratio of the myelin fibers belonging to different classes changes: the part of the fine conductors increases, and that of the fibers having middle and large diameters decreases. The most important in the dynamics of the whole amount of myelin fibers and in the number of the conductors belonging to different classes at all the levels of the nerve trunk is the getting off the organs' branches with various functional specialization. 相似文献