ISSN:0022-3034    

DOI:10.1002/neu.480070302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe sympathetic adrenergic ground plexus of the rat iris is able to innervate whole embryonic hearts transplanted to the anterior eye chamber. The transplants beat continuously from the time of transplantation and for at least five months, initially at 150–200 beats/min, and later approximately 250 beats/min. From seven days postoperatively onwards increased light to the eye produced deceleration while decreased light produced acceleration of the transplants. The rate changes coincided with changes in pupil diameter. Topical atropine reduced the light dependent rate variations of the transplants, especially the dramatic decrease in rate at white light.Waking stress caused a large rate increase. The “waking‐effect” was strongly reduced by sympathetic decentralization and completely abolished by propranolol. The high rate seen in red light was decreased to the low rate of white light by decentralization. Isoprenaline restored red light rate levels in the decentralized transplant.The intraocular heart thus receives a dual functional autonomic input from the host iris and becomes a sensitive monitor of an autonomic nervous activity that can easily be varied at will in a physiological way by changing the light influx to

ISSN:0022-3034    

DOI:10.1002/neu.480070303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA method to prepare suspensions of taste bud cells is described. Bovine circumvallate papillae, which contain most of the taste buds in this animal, are incubated in collagenase‐containing medium and the epidermal sidewall tissue is then dissected from the inner gelatinous dermis. The sidewall tissue, which contains the taste buds, is gently homogenized by manual operation of an all‐glass homogenizer with a loose‐fitting pestle. The suspended material is separated on a discontinuous Ficoll gradient (2%, 8%, 10%, 12% w/w). The material banding at the 8–2% interface is greatly enriched in spindle‐shaped cells that are morphologically similar to taste bud cells as they appearin situ. These cells are not seen when the procedure is done with tissues devoid of taste buds, namely the upper surface of the circumvallate papilla or epithelium from the intermolar eminence.Fluorescence analysis indicates that the hydrophobic probe, 8‐anilino‐1‐naphthalenesulfonate (ANS), binds to relatively nonpolar sites in the suspension. It is postulated that the probe is adsorbing onto the surface membrane of the cell.These preparations may be useful in studying specificity and transduction in

ISSN:0022-3034    

DOI:10.1002/neu.480070304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractMembrane potentials, cable parameters, and component resting conductances were measured in extensor digitorum longus (EDL) muscle fibers from adult ratsin vitroat 24°C, after 15 to 18 days of denervation by nerve section, and at seven to ten days following epineural injection of 100 to 450 μg of colchicine in the peroneal nerve. The denervated muscles were paralyzed throughout the experimental period, whereas the colchicine‐treated preparations showed no clinical paralysis except for the first day or two. The EDL from the untreated side served as a control.Both the denervated and colchicine‐treated fibers were depolarized, showed signs of fibrillation, had tetrodotoxin‐resistant action potentials, and membrane resistance was increased two‐ to sevenfold. In the denervated fibers, mean chloride conductanceGCldropped from a control value of 3196 to 596 μmhos/cm2while mean potassium conductanceGKshowed a tendency to rise from 260 to 332 μmhos/cm2. Colchicine‐treated fibers while showing a similar fall in meanGClfrom 2993 to 1066 μmhos/cm2, also showed a significant fall in meanGKfrom 213 to 116 μmhos/cm2.It was concluded that factors transported by the microtubular system are important for the maintenance of the high restingGClof mammalian skeleta

ISSN:0022-3034    

DOI:10.1002/neu.480070305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractMembrane potentials, cable parameters, and component resting ionic conductances of gastrocnemius fibers from normal goats were measuredin vitroat six to 32 days following denervation by section of the tibial nerve.Denervated fibers were depolarized an average of 11.6 ± 1.5 mV (six preparations) from the control mean of 62.1 ± 1.0 mV (124 fibers) over the period studied. Fibrillation, tetrodotoxin‐resistant action potentials, and anodebreak excitation were present in the denervated preparations after 13 days. The control cable parameters from 124 fibers (13 preparations) were membrane resistance, 1052 ± 70 ω·cm2and membrane capacitance, 6.2 μF/cm2. In denervated fibers membrane resistance increased two to three times in the 13 to 32 day period; membrane capacitance increased about 50% in normal solution at eight to nine, 27–28, and 32 days. Myoplasmic resistivity was assumed to be 112 Ωcm. Measurements were made at 38°C.Component resting conductances were determined from the cable parameters in normal and chloride‐free solution. Mean chloride conductanceGCland mean potassium conductanceGKof control fibers were 776 ± 49 μmhos/cm2and 175 ± 15 μmhos/cm2(92 fibers), respectively. Following denervationGClincreased slightly at six to nine days then fell to low values at 16 to 32 days that were close to or indistinguishable from zero.GKincreased significantly to 372 ± 40 μmhos/cm2and 499 ± 90 μmhos/cm2at 16 to 20 and 32 days, respectively.It was concluded from these findings thatGClandGKof mammalian skeletal muscle are controlled by factors from the nerve and/or muscle action potentials. Goat muscle is different from frog muscle in whichGCldoes not change andGKdecreas

ISSN:0022-3034    

DOI:10.1002/neu.480070306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractLarger axons usually have faster conduction velocities, lower thresholds, and larger extracellular action potentials than smaller axons. However, it has been shown that the largest fiber, R2, in the right pleurovisceral connective of the marine mollusc,Aplysia, has a higher threshold and a slower conduction velocity than does the smaller axon of cell R1, even though the amplitude of R2's spike is larger than R1's spike. One explanation of this apparent paradox is that the two axons have different “intrinsic membrane and axoplasmic constants” (Goldman, L. (1961),J. Cell Comp. Physiol.57:185–191). However, the deep infolding of R2's axonal membrane suggested that differences in the shape of the two axons might also account for the paradox. Accordingly, we measured the conduction velocities of the two axons and then examined the same axons in the electron microscope in order to measure their volumes and surface areas. Our morphological observations indicate that the extensive infolding of surface membrane causes R2 to have a smaller volume to surface area ratio than R1. Thus, since conduction velocity is proportional to the square root of the volume to surface area ratio (Hodgkin, A. L. (1954),J. Physiol.125:221–224), it is predictable that the smaller axon would have a faster conduction velocity. The results suggest that the paradoxical conduction velocities can be explained largely as resulting from differences in the shapes of the two axons. However, certain discrepancies between the measured and the predicted values suggest that other factors are contributing

ISSN:0022-3034    

DOI:10.1002/neu.480070307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractDNA content of cerebellar basket and Purkinje cells of four month, one year, and two year old albino rats was determined by Feulgen cytophotometry. DNA content per nucleus remained essentially constant during aging although there was a slight shift to lower Feulgen‐DNA values occurring in the one year age group. Purkinje cells of all three age groups were found to contain tetraploid amounts of DNA as compared to diploid basket cell

ISSN:0022-3034    

DOI:10.1002/neu.480070308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractWe have used anin vitropreparation of the frog arachnoid membrane to study the role of this membrane in the maintenance of the “blood‐cerebrospinal fluid (csf) barrier.” Electron microscopy showed that the membrane was made up of 10–15 layers of flat epithelial cells joined together by numerous cell junctions. The electrical resistance of the preparation was about 2000 ohms cm2. The steady‐state transmural potential difference (pd) ranged up to 45 mV, csf positive, and this was eliminated by either the addition of ouabain to the csf, or by replacing the NaCl with TEA Cl. The pd across the membrane increased when bicarbonate was added to the external bathing solutions. We conclude that this pd is due to the active transport of sodium from the subural fluid to the csf. In some preparations the transmural pd was reversed, i.e., csf negative, and this was also abolished by the addition of ouabain to the csf, or by replacing chloride with isethionate. We conclude that this pd is related to active chloride transport. These, and other experiments, lead us to the conclusion that the arachnoid membrane is involved in the production of the cerebrospinal fluid and the maintenance of the blood‐cerebrospinal fl

ISSN:0022-3034    

DOI:10.1002/neu.480070309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA long‐lasting birefringence change (the delayed response) was found to be produced in a tetanically stimulated squid giant axon. The change was independent of the concurrent membrane potential change, summated on repetitive stimulation, and always had a sign representing a decrease in resting birefringence. The axon was placed between a polarizer and an analyzer with their polarizing axes crossed, making an angle of 45° with the longitudinal direction of the axon. The light beam that passed through the axon and the other optical elements was received by a photodiode. The change in light intensity evoked by repetitive stimulation was composed of brief initial responses, which took place in response to individual stimuli, and a delayed response, which developed gradually and lasted for several hundred msec. It was necessary to differentiate the effect of birefringence change from that of turbidity change. Formulas were derived on the assumption that the optical properties of the axon could be represented by a model of a uniaxial crystal that was not only birefringent but also dichroic, its extinction coefficients and the angle of retardation being changed independently on excitation. Calculations with them yielded the resting retardation, which agreed well with those obtained by the Sénarmont's method, and the change in birefringence, which agreed well with the other calculated value derived from experiments using a quarter‐wave plate. The results of the calculation confirmed the existence of the long‐lasting birefringence change in the tetanically stimulat

ISSN:0022-3034    

DOI:10.1002/neu.480070310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY