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PubMed2001

Topography of corpuscular mechanoreceptors in the shoulder joint region of monodelphis domestica.

The topography and structure of corpuscular mechanoreceptors in the shoulder joint capsule and periarticular connective tissue of a small laboratory marsupial (monodelphis domestica) were studied using light and electron microscopy. This animal is known to use its upper extremities for a wide range of activities like climbing and manipulating food. Thus, the shoulder joint of this animal species has a similar wide range of movement as the human shoulder joint, but is small enough for serial sectioning in its entirety. Silver stained serial paraffin sections were examined under the light microscope and the distribution of the different types of mechanoreceptors was reconstructed using three-dimensional image processing. In addition, selected mechanoreceptors were studied electron microscopically. Approximately 100 small lamellated corpuscles were found in the dense connective tissue of the joint capsule close to the insertion on the scapula and in the thickening of the joint capsule close to the glenoid labrum. Ruffini corpuscles were found in much smaller numbers in the moderately dense connective tissue of the axillary region. Only very few Vater-Pacinian corpuscles were seen in the soft periarticular connective tissue. The large number and localization of mechanoreceptor corpuscles in the shoulder joint capsule especially close to the glenoid labrum suggests, that these specialized nerve endings are likely to play an important role in control of joint movement. They can induce protective reflexes during extreme movements in the shoulder joint preventing shoulder luxation by increasing the tone of muscles pressing the humerus head into the glenoid cavity.

Animals↗
PubMed1997

The effects of neonatal median nerve injury on the responsiveness of tactile neurones within the cuneate nucleus of the cat.

1. The capacity of cuneate neurones to attain normal functional properties following neonatal median nerve injury was investigated with single neurone recording in anaesthetized cats, 12-24 months subsequent to a controlled crush injury. Effectiveness of the peripheral nerve injury was confirmed by the abolition of the median nerve compound action potential following the crush. 2. Cuneate recording was carried out after denervation of the forearm, apart from the median nerve, to ensure that neurones studied had receptive fields within the distribution zone of the regenerated median nerve. Controlled and reproducible tactile stimuli were used to evaluate the functional capacities of neurones to determine whether they were consistent with those reported earlier for cuneate neurones in cats that had normal peripheral nerve development. 3. Twenty-two cuneate neurones with well-defined tactile receptive fields within the distribution zone of the regenerated median nerve were classified according to their adaptation characteristics and functional properties. Slowly adapting neurones responded throughout static skin indentations and had graded and approximately linear stimulus-response relations over indentation ranges up to 1.5 mm. Rapidly adapting neurones responded to the dynamic phases of skin indentations and could be divided into two broad classes, one most sensitive to vibrotactile stimuli at 200-400 Hz which appeared to receive a predominant input from Pacinian corpuscle receptors, and a non-Pacinian group that included neurones most sensitive to skin vibration at 5-50 Hz which appeared to receive glabrous skin input from the rapidly adapting class of afferent fibres. 4. Based on the stimulus-response relations and on measures of phase locking in the responses to vibrotactile stimuli, it appears that the functional properties of cuneate neurones activated from the field of a regenerated median nerve subsequent to a neonatal nerve crush injury were consistent with those reported previously for 'control' cuneate neurones. The results indicate that cuneate neurones can acquire normal tactile coding capacities despite the disruption caused by prior crush injury to their peripheral nerve source.

Animals↗
PubMed1980

On- versus off-responses of raccoon glabrous skin rapidly adapting cutaneous mechanoreceptors.

1. The on- and off-responses of 50 raccoon median nerve fibers associated with rapidly adapting cutaneous mechanoreceptors in glabrous skin were examined under experimental conditions designed to allow comparable opportunities for on- and off-responses to occur. Trapezoidal stimuli were utilized, providing for equal stimulus indentation and retraction velocities and equal static displacement times and intertrial intervals. Principal findings were as follows: 2. At stimulus levels well above displacement and velocity thresholds for on-responses, 80% of units yielded a more vigorous on-response than off-response (as measured by the total number of ramp impulses); in 6%, the reverse was true; while in the remaining 14%, the off-discharge was absent. 3. On and off displacement thresholds were approximately equal (on median, 43 micron; off median, 42 micron). However, on velocity thresholds were significantly lower than off velocity thresholds (on median, 1.0 micron/ms; off median, 3.8 micron/ms). 4. Exponents (b) of power functions relating discharge rate to ramp velocity (frequency = a x velocityb) were consistently greater for on-responses than for off-responses, but intercept constants (a) were consistently greater for off-responses than for on-responses. 5. Previous findings that mammalian rapidly adapting (RA) mechanoreceptors possess a "linear directionality" generally favoring on-responses were confirmed. 6. Results are discussed in relation to the role of viscoelastic properties of RA mechanoreceptors and neighboring skin. It is suggested that, when considerations is also given to the mechanical properties of surrounding tissues, the Loewenstein and Skalak (18) analysis of the mode of operation of Pacinian corpuscles might also apply, at least qualitatively, to the simple dermal (rapidly adapting) corpuscle of raccoon glabrous skin.

Afferent Pathways↗
PubMed1986

The ventroposterior inferior nucleus in the thalamus of cats: a relay nucleus in the Pacinian pathway to somatosensory cortex.

The ventroposterior region of the thalamus of mongrel cats was searched to locate zones activated by somatic stimuli. By using stimuli that selectively excited Pacinian corpuscles, areas activated by this class of afferent fibers were differentiated from regions activated by other classes of cutaneous mechanoreceptors. The results showed that Pacinian inputs excite neurons in the ventroposterior inferior nucleus (VPI) of the thalamus, whereas other more dorsal zones within the ventroposterior thalamus receive inputs from other mechanoreceptor classes. This definition of the VPI tended to be larger and to extend further lateral than some published descriptions. Horseradish peroxidase (HRP) was injected into ventroposterior zones shown by electrophysiological recordings to receive inputs from Pacinian afferents. Subsequently, labeled cell bodies were observed in the caudal poles of the dorsal column nuclei, a region previously shown to be activated by Pacinian afferents. Very few labeled cells were found in the central region of these nuclei, a region previously shown to be activated by other classes of cutaneous mechanoreceptors. Electrophysiological recordings were used to locate a small portion of the second somatosensory cortex driven by Pacinian stimuli. When HRP was injected into this region cell bodies in the VPI and the lateral part of the posterior group were labeled, but few or no labeled cells were found in ventroposterior lateral nucleus. We hypothesize that the VPI receives Pacinian information from a cytoarchitecturally distinct region in the caudal poles of the dorsal column nuclei. Further, we suggest that a major cortical target for the VPI is a subdivision of the second somatosensory cortex. These studies do not exclude the possibility that Pacinian inputs have other thalamic and cortical targets.

Afferent Pathways↗
PubMed1975

Ultrastructure of the joint receptors of the tortoise (Testudo graeca. Emys orbicularis).

The ultrastructure of the spray-like ramified encapsulated corpuscles with the primitive inner core from the joint capsules of the large limb joints of the tortoise (Testudo graeca and Emys orbicularis) was examined. Each of the branches of the receptor consists of three components. Through the middle of the receptor branche runs the nerve terminal, containing in the receptor matrix numerous mitochondria, tiny light vesicles and neurofilaments and neurotubules running in the axial way. The nerve terminal gives off on some places among the inner core cells tiny finger-like processes. The axon is surrounded by the inner core cells and their irregular plasmatic processes. Among the inner core cells and their irregular plasmatic processes there is a labyrinth of spaces, connected centrally with the periaxonal space and with the boundary space on the periphery. The inner core cells are covered on the surface, turning to the boundary space by the basal membrane. The inner core has a very primitive structure, it still lacks the typical lamellar structure. The capsule of the receptor is formed by flat cells, which surround the inner core in 1--3 layers. Between the capsule of the receptor and the inner core is the boundary space, containihg sporadical collagenous fibrils. The structure of the spray-like ramified encapsulated corpuscles with the primitive inner core from the joint capsules of the tortoise is analogous to the simple lamellar receptors from the skin of some reptiles (Von Düring 1973, 1974). The primitive structure of the inner core of the joint receptors in the tortoise reminds of the structure of the inner core of the developing simple (paciniform) corpuscles (Poláĉek and Halata 1970) and Pacinian corpuscles (Malinovský 1974). The observed nerve endings represent a primitive, early stage in phylogeny development of the lamellar mechanoreceptors.

Animals↗
PubMed1994

The effect of stimulus duration on frequency-response functions in the Pacinian (P) channel.

Psychophysical experiments on human observers and physiological measurements on Pacinian corpuscles (PCs) isolated from cat mesentery were performed to explain certain discrepancies in the psychophysical-physiological model (Bolanowski et al., 1988) for the sense of touch in the vibrotactle Pacinian (P) channel. The model was based on correlations among the psychophysical frequency response obtained on human glabrous skin and physiological frequency-response functions measured on two PC preparations: PC fibers innervating human glabrous skin (Johansson et al., 1982) and PCs isolated from cat mesentery. The three frequency-response functions were qualitatively similar. However, the low-frequency slope for the human PC fibers differed from the slopes for the psychophysical and cat mesentery PC functions by being 3 dB/octave less steep. This discrepancy can be explained theoretically by differences in methodology involving the effect of stimulus duration and the property of temporal summation known to exist in the P channel (i.e., a 3-dB increase in sensitivity per doubling of stimulus duration). To test this, experiments were performed using two methods of stimulation: (1) a constant stimulus duration for different test frequencies, as generally used in this laboratory; and (2) a constant number of stimulus cycles (n = 5) for each test frequency as used by Johansson et al. The method of least squares was used to calculate the low-frequency (50 to 150-Hz) slopes of individual psychophysical and physiological functions. The mean slopes that resulted from using the two methods of stimulation were consistent with the theoretical expectations.

Animals↗
PubMed1980

Sacrococcygeal paciniomas.

Two well differentiated pure Paciniomas, bearing no resemblance to neurofibromas, were resected from infants with spinal deformities. Each was in the form of a thick cord running from a sacral dimple through a low occult spina bifida to the spinal dura. The lesions are considered to be a malformation or hamartomatous overgrowth. Control sacrococcygeal regions from necropsies on 15 infants were examined histologically, and Pacinian corpuscles were found in 7, usually near the tip of the coccyx, and never numerous.

Female↗
PubMed1986

Envelope detection of amplitude-modulated high-frequency sinusoidal signals by skin mechanoreceptors.

High-frequency (1000-2000 Hz) sinusoidal vibrations of the skin, which are normally imperceptible, induce distinct sensations when amplitude modulation is applied in the frequency region around 200 Hz. This phenomenon appears to be initiated in the mechanoreceptor, as a result of rectification in the mechanoelectrical transduction process. The curve for sensitivity to modulation frequency resembles the frequency-sensitivity curve of the Pacini receptor system. The low-frequency slope is flatter than that of comparable psychophysical frequency-threshold curves for sinusoidal stimuli. This finding suggests that mechanical filtering (in the capsule of the Pacinian corpuscle and the surrounding skin tissue) contributes to the detection threshold. The characteristics of such a mechanical filter are estimated.

Fingers↗
PubMed1977

Pacinian neurofibroma.

At rare intervals in the literature, reports have appeared of a skin tumour containing structures resembling Pacinian corpuscles. Four such tumours collected over the course of 20 years are described and the literature reviewed.

Adolescent↗
PubMed1994

Hairy skin: psychophysical channels and their physiological substrates.

Experiments were conducted in which threshold-frequency characteristics were measured on the hairy skin of the forearm of human observers. Thresholds were measured with two stimulus probe areas (2.9 and 0.008 cm2) at three skin-surface temperatures (15 degrees, 30 degrees, and 40 degrees C). The results suggest that whereas glabrous skin uses four distinct channels of information, only three channels may be involved in mediating the sense of touch for hairy skin. The three channels are defined as Ph, (Pacinian, hairy skin), NPh low (non-Pacinian, hairy skin, low frequencies) and NPh mid (non-Pacinian, hairy skin, middle frequencies). In addition, it is proposed that the neural substrates for the three psychophysically characterized channels are, respectively, the Pacinian corpuscle (PC) nerve fibers, the slowly adapting type II (SAII) fibers, and the rapidly adapting (RA) fibers.

Afferent Pathways↗
PubMedDate not supplied

Does sympathetic activity modify afferent inflow at the receptor level in man?

Results from animal experiments have indicated that the normal sensory input into the central nervous system can be modulated by sympathetic nervous outflow at the receptor level. Preliminary data obtained with a new type of percutaneous electrode suggest that there may be a linkage between ongoing activity in Pacinian corpuscle (PC) afferents and skin sympathetic activity in conscious humans. Further studies attempting to evaluate the possible linkage between afferent and sympathetic nerve functions in man may be of substantial physiological and clinical interest.

Afferent Pathways↗
PubMedDate not supplied

[The cytoskeleton and mechanoreception thresholds].

In order to analyse the mechanisms of high sensitivity of mechanoreceptors the role of cytoskeleton in the deformation of receptor membrane was considered. The later was considered as an elastic plate. Local relative deformations epsilon s near the attachment points of cytoskeleton filaments to the membrane were calculated. It is shown that at different types of deformation for small regions of the membrane with the size R of several scores of nm the epsilon s values are L/R where L is absolute displacement of the region under the effect of the force applied. For the hair cells of the corti organ the model including neighbor stereocilia connected by the skeleton filaments shows the values epsilon s approximately 10(-4). The latter by several orders exceed the values characteristic of the single stereocilium deflection. On the basis of the model calculations of epsilon s a hypothesis is advanced for Pacinian corpuscle concerning the existence of a bond between the membrane sensitive ending and the inner capsula via cytoskeleton filaments, which suggests high epsilon s values of this receptor. The cytoskeleton elements should be considered an intrinsic part of the sensitive centre.

Animals↗
PubMed1975

Mesenteric baroreceptors.

Occlusion of the mesenteric vessels in the cat and injection of catecholamines produced significant changes in skin and muscle blood flows. These were abolished by cutting the mesenteric nerves. The occurrence of systemic pressure and peripheral resistance changes in cross-perfused mesenteric preparations indicates that hemodynamic factors alone, such as might result from occlusion of a large vascular region, were not initiating the reflex. This also excludes extramesenteric receptors within the heart and large vessels from the reflex. Since both intravascular pressure and catecholamines have been shown to modify Pacinian receptor discharge in vivo, the evidence suggests that the mesenteric Pacinian corpuscle is the baroreceptor probably initiating the vasomotor reflexes in skin and muscle. The net effect of mesenteric receptor activity appears to be an inhibition of vasomotor neurons supplying skin and muscle.

Animals↗
PubMed1995

Lumbosacral spinal intradural extramedullary paciniomyolipoma: magnetic resonance imaging, computed tomography, and pathology findings.

This report describes a paciniomyolipoma as an intradural tumor of the lumbar spinal cord composed of adipose tissue, striated skeletal muscle, and pacinian corpuscles. Simple lipomas, myolipomas, and other variant lipomas of the spinal cord have been described in the literature; to the authors' knowledge, however, this is the first report of this unusual and unique lipoma.

Adipose Tissue↗
PubMed1986

Mechanoreceptors in the human anterior cruciate ligament.

This study was undertaken to identify and quantitate mechanoreceptors in the human anterior cruciate ligament (ACL). Ligaments from six human subjects were obtained at autopsy, cut into cross-sectional segments 1.0-1.5 cm thick, and kept oriented as to the femoral and tibial attachments. The segments were stained in bulk by using a modified gold chloride method, frozen, and sectioned on a sliding microtome at 100 microns. The sections were floated in alcoholic gelatin, mounted on slides, dehydrated, and coverslipped. Serial sections were studied with the light microscope and receptors were photographed. Cross-sectional maps of every tenth section were made outlining the periphery of the ACL and the receptors within that section. With these maps, a computerized, morphometric analysis of the ACL was done, thus obtaining the percentage of receptors in each section and in each ACL. In addition to free nerve endings, two morphologically distinct mechanoreceptors were identified: (1) Ruffini end organs and (2) Pacinian corpuscles. Preliminary morphometric analyses show that populations of mechanoreceptors are greater at the femoral and tibial ends of the ligament and constitute approximately 2.5% of the ligament. Based on these findings the human ACL has the anatomic basis for a discriminating afferent outflow to the central nervous system.

Humans↗
PubMed2000

Developmental and lesion-induced changes in the distribution of the glucose transporter Glut-1 in the central and peripheral nervous system.

The active transport of D-glucose from the vascular to the neural compartment requires the presence of a carrier molecule at the blood-brain and the blood-nerve barrier. The glucose transporter 1 (Glut-1) seems to be the main carrier in blood-tissue barriers of endothelial and perineurial type. The distribution of Glut-1 was assessed in the normal central and peripheral nervous system of young and adult animals and compared with changes after nerve injury. Immuno-histochemistry, in situ hybridization, and perfusions with Evans Blue were carried out. Glut- I was not expressed in the perineurium of peripheral nerves at birth, but appeared in the perineurium of peripheral nerves, spinal roots, in the capsule of dorsal-root ganglia, and in the pia mater of adult animals. The perineurium of peripheral nerves subjected to Wallerian degeneration presented a faint Glut-1 immunoreaction, which was restored after regeneration. Glut-1 was expressed in capillaries of the gray substance of the spinal cord. Perineurial-derived lamellar cells of Pacinian corpuscles exhibited a strong Glut-1-like immunoreactivity in response to denervation and during development. Merkel cells and Meissner corpuscles were found to be Glut-1 negative. Glut-1 seems to reflect the quality of an adult, mature perineurial and blood-nerve barrier.

Adult↗
PubMed2000

Innervation of the metacarpophalangeal and interphalangeal joints: a microanatomic and histologic study of the nerve endings.

Six pairs of fresh human cadaver hands were dissected under the surgical microscope at x28 to x32 and selectively silver stained. In addition, 18 proximal interphalangeal and metacarpophalangeal joints of fresh cadaver hands were processed with protein gene product 9.5 for measurement and analysis of nerve endings in those joints. The results demonstrated that the proximal interphalangeal joints are innervated by 2 palmar articular nerves (mean diameter, 0.21-0.53 mm). Each metacarpophalangeal joint of the second through fifth fingers is predominantly supplied by 1 palmar articular nerve (mean diameter, 0.41-0.59 mm), which comes from the deep branches of the ulnar nerve, as well as by 2 dorsal articular nerves (mean diameter, 0.11-0.24 mm). The metacarpophalangeal joint of the thumb also had 2 dorsal articular nerves (mean diameter, 0.18-0.24 mm) and 2 palmar joint nerves (mean diameter, 0.29-0.31 mm). The mean densities of the type IV free nerve endings and the mean numbers of the encapsulated endings in the palmar capsules were consistently much greater than in the dorsal or lateral capsules. The majority of encapsulated endings were pacinian corpuscles. The anatomic and histologic information may help the surgeon avoid damaging these small joint nerves during operative procedures and to reconstruct or de-innervate them if necessary. (J Hand Surg 2000; 25A:128-133.

Finger Joint↗
PubMed1994

The effects of aging on information-processing channels in the sense of touch: II. Temporal summation in the P channel.

Thresholds for detecting 250-Hz vibrotactile signals of variable duration applied to the thenar eminence of the hand were measured in 16 subjects ranging in age from 19 to 81 years. Detection thresholds were higher in older than in younger subjects. Correlation coefficients for the relation between threshold and age ranged from 0.94 to 0.96, depending on signal duration. In addition, the amount of temporal summation was negatively correlated with age. Both the elevated detection thresholds and the reduced amount of temporal summation in elderly subjects may be partially due to the decrease in the number of Pacinian corpuscles in the hand that occurs with aging. Another factor that could be responsible for reduced temporal summation in older as compared to younger subjects is impairment of the temporal integrator.

Adult↗