摘要:

AbstractTransmitted light interference microscopy is shown to be a sensitive technique for detecting email transient changes in optical path differences of axons during and following electrical stimulation. It is tentatively concluded that water enters the axon during and following tetanizing stimulation and that this event is in accord with earlier findings concerning opacity changes under similar experimental conditions. It was further demonstrated that the membrane of the axon is normally under a hydrostatic pressure difference of approximately 2 cm of H2O and this may be a contributing factor to the optical properties of the axon during the excitation process.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04405.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractFive different types of exfoliated cells, representing different stages of cornification, have been observed in daily urethral smears from male mice. The frequencies of the cells belonging to two of these types vary cyclically. The mean duration of the cycles is about 3.5 days.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04406.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractCatechol‐o‐methyltransferase (COMT) activity was determined in normal and preganglionically denervated sympathetic ganglia as well as in parasympathetic and sensory ganglia of the cat by means of the micro‐radiochemical method of McCaman (1965). Low levels of COMT activity were found to be present in all three types of investigated ganglia. In the sympathetic ganglia the COMT activity was almost evenly distributed. No correlation could be demonstrated between COMT activity, monoamine oxidase (MAO) activity and the reported catecholamine content in the various sympathetic ganglia. Preganglionic denervation of sympathetic ganglia did not significantly change the enzyme activity. The results indicate that in the autonomic ganglia COMT is confined neither to presynaptic structures nor to “adrenergic

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04407.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractIn a study of the response of single units in the cochlear nucleus of the white rat it was found that all the units which responded to pure tones showed a selectivity with regard to tone frequency. Responses were obtained in the tone frequency range from 200 to 34,000 Hz. Most of the units responded to pure tones with a sustained train of discharges. The threshold in these units was found to rise abruptly when the tone frequency was increased above that of the unit's characteristic frequency (CF). A much more gradual increase in threshold was noted when the tone frequency was decreased below the unit's CF. The slope of the high frequency part of the tuning curves varied between 0 and 50 Hz per dB increase in threshold, when measured 20—30 dB above the unit's threshold at its characteristic frequency. The slope measured in that way showed no apparent dependence of on the CF of the units. Many units with a high CF had tuning curves with a second peak located at a lower frequency. A few units had almost symmetrical tuning curves with a slope of the same order of magnitude as that recorded for the low frequency part of the common type units. The maximal obtainable firing rate of common type units was found to decrease rapidly when the frequency of the stimulus tone was increased above the unit's CF. Conversely the maximal discharge rate was almost constant for tones below the unit's CF. Iso‐rate functions based on stimulus response curves, were found to be similar to tuning curves when a discharge rate of about 20 per cent about the unit's spontaneous rate was used as a criterion of respo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04408.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe response patterns are described of cochlear nucleus units (termed rat transient units) which only responded to a tone burst with a single discharge evoked immediately after the onset. When these cells were stimulated with bursts of repetitive clicks such units showed a marked selectivity to the click repetition rate. At a low click repetition rate one discharge was evoked for each click but this one to one relationship failed rapidly when the click rate was increased slightly above a given click repetition rate. Any additional increase in click rate resulted in only a single discharge fired immediately after the onset of a click burst and thus resembling these units' response to tone bursts. By replacing the click sounds by short bursts of pure tones presented repetitively it was shown that rat transient units were not selective to repetition rateper se, but rather, to the duration of silent interval between successive sounds. The activity of these units to click stimulation could be inhibited by broad band noise or by pure tones within certain frequency limits. Furthermore, these units showed a spectral selectivity which appeared when the stimulation was pure tones or band‐pass filtered clicks. The spectral region of highest sensitivity varied among the individual units in the range from 5 to 20 kHz and was thus widely different from the critical repetition rate for click stimulation. The latter rate was found to vary from 200 to 800 clicks per second in different units.These findings may thus explain why, in psychoacoustic experiments, repetitive presentation of short sounds results in a pitch perception which is dependent on the length of the silent periodbetweensuccessive sound

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04409.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe effects of hind‐limb ischemia on the concentrations of adrenaline and noradrenaline in the adrenals, heart and spleen, on the excretion of these compounds and their 3‐0‐methylated metabolites in the urine and on the uptake of (°)‐noradrenaline‐7‐3H by the adrenals, kidneys. spleen and heart have been studied in 20° C and 3° C acclimated rats at an environmental temperature of 20° C. The adrenals of uninjured 3° C acclimated rats contained more adrenaline and noradrenaline than those from 20° C acclimated rats. In a 20° C environment both types of rat excreted the same amounts of these compounds. Hind‐limb ischemia increased the rate of secretion of adrenaline and noradrenaline since the adrenal contents of these compounds were reduced, their excretion and that of two of their metabolites was increased and tissue uptake was not reduced. The response was the same in 20° C and 3° C acclimated rats after a 4 hr period of bilateral hind‐limb ischemia. According to the assay methods used adrenaline secretion preceded that of noradrenaline and the secretion of both continued for up to 26 hrs after the injury. The possible factors in the injury leading to the increase in catecholamine secretion are discussed and also the relation between these changes and some of the biochemical s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04410.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractPupil diameter and refractive state were measured in cynomolgus monkeys under pentobarbital before and after i.m. administration of reserpine, 2 and 5 mg/kg. Reserpine was found to cause only a small miotic response and no accommodation at all.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04411.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe diaphragm, which previously has been shown to contain relatively few proprioceptors and to lack autogenetic facilitation, was found to be under reflex control from intercostal afferents. Electrical stimulation of the intercostal nerves of the lowest thoracic segments elicited a polysynaptic reflex excitation of phrenic motoneurones followed by a depression of ‘spontaneous’ phrenic motor activity. No phrenic responses were elicited from the upper thoracic segments. Increased phrenic activity was also elicited by mechanical stimulation of the trunk wall; the receptive area of these effects was similarly limited to the region of the insertion of the diphragm. Alike reflex effects were obtained from both the internal and the external intercostal nerves. In the internal nerve both group Ib and II afferents were found to contribute to the reflex whereas in the external nerve it was mainly the secondary muscle spindle endings which gave rise to the response. In contrast to the intercostal‐to‐intercostal reflexes cutaneous afferents proved to be without effect in the intercostal‐to‐phr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04412.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe reflex connections between the lower intercostal segments and the phrenic motor pool, described in a preceding paper, has been studied further. It was found that the diaphragm on contraction could exert enough mechanical force on the lower part of the rib cage to provoke a reflex discharge in the phrenic motoneurones. The intercostal‐to‐phrenic reflex arch thus constitutes a link in a loop for self‐excitation of the phrenic nucleus which may make up for its lack of autogenetic facilitation. Up to five synchronized reverberating phrenic volleys could be recorded in response to a single diaphragmatic jerk. These were abolished by paralyzing doses of gallamine. Conduction times and excitability cycles for the loop have been studied. Examination of reflex firing probality for phrenic motoneurones has revealed considerable individual differencies in their responsiveness to each of the three afferent input parameters: a) nerve stimulated, b) strength and c) frequency of stimulation. The order of reflex recruitment of phrenic motoneurones followed the same order as found for their respiratory engagement: small spikes always appeared earlier than bigger s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04413.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe supraspinal and reflex control of γ‐motoneurones has been studied with intra‐ and extracellular recording from lumbosacral γ‐motoneurones in the cat. Monosynaptic EPSPs were recorded in some γ‐motoneurones on stimulation of the brain stem. These effects were evoked from the Deiters' nucleus and from fibres descending in the medial longitudinal fascicle probably originating in the pontine reticular formation. Previous investigations have revealed monosynaptic connections to α‐motoneurones from these regions and our results suggest parallel effects to α‐ and part of the γ‐motoneurone population supplying one muscle. Indirect evidence suggests that this monosynaptic effect is exerted only on static γ‐motoneurones, thus implying a linkage between the descending monosynaptic control of α‐ and static γ‐motoneurones via these pathways. The reflex effects to γ‐motoneurones have been studied with graded electrical stimulation of ipsi‐ and contralateral hindlimb nerves. Five γ‐motoneurones, presumably all belonging to extensor motor nuclei, were found to receive IPSPs from group I afferents and it is suggested that only static γ‐motoneurones are influenced. It has not been possible to decide if these IPSPs are evoked from Ib or Ia afferents. The reflex effects from group II and III muscular afferents, joint and cutaneous afferents seem to conform to the effects evoked

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04414.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY