摘要:

AbstractTwo cationic protein modification reagents, 1‐cyclohexyl‐3‐(2‐morpholinylethyl) carbodiimide (CMCD) and dimethyl (2‐hydroxy‐5‐nitrobenzyl) sulfonium bromide (HNB‐dmS), inhibit taste receptor cell stimulation by NaCl, sucrose, and HCl. Modified inactive derivatives of the reagents under the same conditions are ineffective. Inactivation by HNB‐dmS is essentially irreversible. The effects of inactivation by CMCD are reversible after about 10–15 minutes of a water rinse, however, when applied in the presence of glycine methyl ester, the inhibited response is stabilized and only recovers after about 1.5–3 hours. Glycine methyl ester alone has no inhibitory properties. The kinetics of inactivation by both HNB‐dmS and CMCD are consistent with a second‐order reaction with rate constants of 0.041 ± 0.001M−1sec−1and 0.121 ± 0.012M−1sec−1, respectively. The rate of inactivation by both compounds is independent of NaCl concentration as well as degree of receptor stimulation. This, together with the observation that the response to stimulation by all effectors examined is altered, suggests the inactivation occurs at an event which is common to the transduction of the response from all three stimuli. The ether:water partition coefficients, as well as previous results from inactivation byN–substituted maleimides, indicate that hydrophilic reagents do not cross the cell membrane in significant concentrations within the time period of application. This suggests the site of modification by the cationic protein modification reagents is at the surface of the cell membrane. Significant residual NaCl, sucrose, and HCl activity remains after total inactivation. To account for this, a two‐state

ISSN:0022-3034    

DOI:10.1002/neu.480080303

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

年代:1977

数据来源: WILEY

摘要:

AbstractNeurons in Ag‐B‐incompatible allografts of ganglia are acutely rejected while those in Ag‐B‐compatible grafts are able to survive the immune reaction directed against them. The present study was undertaken to determine the long‐term fate of neurons in allografts of ganglia in Ag‐B‐compatible rats. Isogenic strains of Ag‐B‐compatible adult Lewis (LE) and Fischer (FR) rats were used. The sensory nodose ganglia were reciprocally exchanged between normal LE and FR and between LE and FR animals rendered immunologically tolerant of each other's histocompatibity antigens. The findings were similar in both rat strains and revealed that although neurons and glial cells (i.e., satellite and Schwann cells) could survive for prolonged periods they were nevertheless eventually rejected by normal (nonimmunosuppressed) recipients. On the other hand, neurons and glial cells survived indefinitely in allografts in tolerant rats. Moreover, these neurons were functional because they regenerated nerve fibers into cotransplanted isografts of tongue and exerted the neurotrophic influence of inducing taste bud regeneration. The results demonstrate that, unlike kidney and heart, neurons in ganglia allografts cannot survive indefinitely without immunosuppression in Ag‐B‐compatible animals. Nevertheless, the permanent survival and function of neurons in Ag‐B‐compatible grafts can be achieved, as it is in Ag‐B‐incompatible ganglia grafts, by rendering the recip

ISSN:0022-3034    

DOI:10.1002/neu.480080304

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

年代:1977

数据来源: WILEY

摘要:

AbstractEmbryonic behavior of the chick is the product of spontaneous multiunit burst discharges within the ventral spinal cord. The present study describes the ontogeny of spinal cord burst discharges in embryos which were deprived of brain input by removing several neural tube segments of 2‐day embryos at cervical or mid‐thoracic levels. Characteristics of bioelectric activity present in both intact and chronically transected cords are: (a) the appearance of spike discharges; (b) the organization of unit discharges into synchronized multiunit bursts; (c) the establishment of intracord synchronization of burst discharges over wide expanses of cord tissue; (d) an increase in burst duration and complexity at 7 days due to the appearance of the burst afterdischarge; (e) an increase in the amount of burst activity from 6 to 13 days followed by a decline until hatching at 21 days; (f) a shift from periodic to irregular patterns of burst activity at 13 days; and (g) the existence of the cord burst discharge as a correlate of embryonic movement.Several differences were found between burst activity from chronic spinal and intact embryos: (a) cervical spinal embryos were significantly less active than controls from 15 through 19 days; and (b) long sequences of unusual repetitive burst afterdischarges appeared in chronic spinal embryos by 13 days.The results indicate that the transected embryonic spinal cord is remarkably autogenous in function, although patterns of activity unique to the transected cord appear and increase in prominence during later stages of incubat

ISSN:0022-3034    

DOI:10.1002/neu.480080305

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

年代:1977

数据来源: WILEY

摘要:

AbstractPrevious work has revealed that 4S RNA is the primary species of RNA in the axoplasm from the giant axons of the squid andMyxicola.This study shows that axoplasmic 4S RNA from the squid giant axon has the functional properties of tRNA. Axoplasmic RNA was charged with amino acids by aminoacyl‐tRNA synthetases prepared from squid brain. The aminoacylation was prevented by incubating the RNA with RNase prior to running the reaction. The amino acid‐RNA complex was labile at pH 9, which is characteristic of the acyl linkage between an amino acid and its tRNA. Aminoacyl‐tRNA synthetase activity was also present in the axoplasm, primarily in the soluble fra

ISSN:0022-3034    

DOI:10.1002/neu.480080306

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

年代:1977

数据来源: WILEY

摘要:

AbstractStop‐flow techniques were used to examine the rapid axonal transport of norepinephrine in rabbit sciatic nerves. When the midpoint of a nerve incubatedin vitrowas cooled to 2°C while the remainder was kept at 37°C, norepinephrine accumulated proximal to the cooled region at a rate corresponding to an average transport velocity between 5 and 6 mm/hr in a distal direction. Since only about half of the norepinephrine appeared to be free to move, the mean velocity of the moving fraction was probably twice as great. No norepinephrine accumulated distal to a broad cooled region under conditions in which there would have been a significant accumulation of dopamine‐β‐hydroxylase activity. Therefore, unlike dopamine‐β‐hydroxylase, norepinephrine may not be subject to rapid retrograde transport. When nerves that had been locally cooled for 1.5 hr were rewarmed uniformly to 37°C, a wave of norepinephrine moved exclusively in a distal direction. The peak of this wave moved at a velocity of 12.2 ± 0.5 mm/hr or 293 ± 12 mm/day; the front of the wave moved at about 18 mm/hr. or 430 mm/day; and the tail probably moved faster than 6 mm/hr. This spectrum of velocities was virtually identical to the one displayed by the wave of dopamine‐β‐hydroxylase activity that was generated under the same conditions. Our results are consistent with the conclusion that all axonal structures containing norepinephrine also contain dopamine‐β‐hydroxylase, but they are not co

ISSN:0022-3034    

DOI:10.1002/neu.480080307

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

年代:1977

数据来源: WILEY

摘要:

AbstractGlyoxylic acid was used to induce fluorescence in sections of rabbit sciatic nerve. In fresh nerves treated with this agent there were scattered finely beaded axons with a weak blue‐green fluorescence. During local cooling, blue—green fluorescence accumulated steadily at the proximal boundary of the cooled region but never at its distal boundary. This accumulation gave rise to dilated axons that often swelled into brilliantly fluorescent balloon‐like structures up to 10 μm in diameter. Axonal fluorescence was probably specific for norepinephrine, being enhanced by inhibition of the metabolism and diminished by inhibition of the synthesis or storage of this neurotransmitter. After local cooling of nerves for 1.5 hr, specific fluorescence was confined within 0.8 mm of the cooled region. Rewarming led to rapid removal of fluorescence from the cooled region and to disappearance of most of the balloon‐like swellings. Simultaneously, rewarming caused brightly fluorescent fibers that were neither dilated nor swollen to appear in distal regions of nerve. As this wave of fluorescence migrated distally with increasing duration of rewarming, it was spread over increasingly broad regions of nerve, which suggests that axonal transport of norepinephrine may involve some kind of dispersive

ISSN:0022-3034    

DOI:10.1002/neu.480080308

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

年代:1977

数据来源: WILEY

摘要:

AbstractConcentrations of cAMP (cyclic adenosine 3′,5′‐monophosphate) and cGMP (cyclic guanosine 3′,5′‐monophosphate), in ganglia from the garden snailHelix pomatia, vary considerably over the course of the day. There is a maximum in the concentration of both cyclic nucleotides between 08:00 and 12:00 (lights on 06:00 to 18:00), with the cAMP maximum occurring slightly later than that in cGMP. In addition there can be several smaller maxima in cAMP and cGMP levels; the timing of these can be markedly different from experiment to experiment, with cAMP and cGMP sometimes in and sometimes out of phase with each other. This pattern is observed inHelixwhich had been activated from the dormant state 4–6 days earlier, but is not present in dormant or in long‐active animals. The cyclic nucleotide rhythm can be seen in ganglia maintained in organ culture, and persists for at least 24 hours after removal of the tissue from the animal. There appears to be little change in the level of basal or Na Fstimulated adenylate cyclase activity inHelixganglia over the course of the day. On the other hand, both cAMP and cGMP phosphodiesterase activities exhibit rhythms which are consistent with the rhythms in cAMP and cGMP

ISSN:0022-3034    

DOI:10.1002/neu.480080309

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

年代:1977

数据来源: WILEY

摘要:

AbstractAn attempt was made to identify the neurophysiological processes involved in entrainment of the circadian rhythm of spontaneous optic nerve potentials from theAplysiaeye by determining whether pharmacological agents or ion substitutions could block phase shifts produced by single light pulses. Knowing which physiological processes are involved in entrainment should help define the morphological pathway traveled by entrainment information.A secretory step does not appear to be involved in the flow of entrainment information from the environment to the circadian oscillator. A treatment (HiMg LoCa) capable of inhibiting secretion did not interfere with phase shifting by light. Furthermore, treating eyes with putative transmitters or extracts of eyes did not phase shift the free running rhythm. Also, the phase shifting information is not translated into action potentials before reaching the oscillator since TTX–HiMg LoCa solutions did not block the light‐induced phase shift. The photoreceptor potential does seem to be important for light‐induced phase shifts. A correlation was found between the effects of treatments on the ERG and their effects on the light‐induced phase shift. Solutions which decreased the ERG by 90% or more blocked phase shifting whereas solutions which decreased the ERG by less than 74% had no effect on phase shifting by light.The results from these studies are consistent with two pathways for the flow of phase shifting information to the circadian oscillator. The circadian oscillator may be associated with receptor cells and the entrainment pathway would include a step involving the photoreceptor potential. Alternatively, the circadian oscillator may be associated with secondary cells and receive entrainment information via the photoreceptor potential and passive spread of current through a gap junction. Higher order cells than second‐order ones are probably not involved in the entrainmen

ISSN:0022-3034    

DOI:10.1002/neu.480080310

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

年代:1977

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480080302

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

年代:1977

数据来源: WILEY