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[Cholinesterase activity in the Pacinian corpuscles in denervation and the application of colchicine to the nerve].

In the Pacinian corpuscles, cholinesterase activity was predominantly revealed along the plasma membrane and in the cytoplasm of the inner core cells. A faint quantity of histochemical end product was detected in the axis cylinder. An increased cholinesterase activity was found after the nerve transection. This change coincides in time with phagocytosis of degenerated axis cylinder by the inner core cells. A decrease in cholinesterase activity was observed in the Pacinian corpuscles after colchicine application to the nerve. This effect may be due to either the blockade of axoplasmic transport of cholinesterase in afferent nerve or/and to the elimination of the trophic influence exerted by the nerve on the cholinesterase activity in the inner care cells.

Animals↗

The effect of Mg2+ and Ca2+ on the excitability of Pacinian corpuscles.

The effect of altering extracellular Ca2+ and Mg2+ levels on electrical properties of Pacinian corpuscles of adult cat has been examined. High Mg2+ solution (5--15 mM) increased the excitability of the receptors and the amplitude of the receptor potential. Ca2+-free EDTA solution caused an increase in the amplitude of the receptor potential in the first 60 min and then its decrease. Mg2+ ions slow down or prevent the depressant effect of the Ca2+ lack on the receptor potential. The phase of the receptor potential amplitude increase in Ca2+-free media was reversibly blocked by tetraethylammonium ions. Treatment with 2,4-dinitrophenol produced a transient increase in the receptor potential amplitude. The threshold of the mechanosensitive receptor membrane was unaffected in Ca2+-free or Mg2+-rich solution. The results suggest that divalent cations are not directly involved in the process of mechanoelectric transformation in Pacinian corpuscles.

Animals↗

Immunocytochemical localization of the neural cell adhesion molecules L1, N-CAM, and J1 in Pacinian corpuscles of the mouse during development, in the adult and during regeneration.

The immunocytochemical localization of the neural cell adhesion molecules L1, N-CAM and J1/tenascin was investigated by light and electron microscopical techniques in murine Pacinian corpuscles during development, in the adult and in the regenerating state. In adult corpuscles, L1 was present only at contact sites between the sensory axon and inner core lamellae. From birth, the earliest stage tested, until day 7, L1 was additionally expressed on lamellar processes of the inner core cells. N-CAM was expressed in developing and adult corpuscles on lamellae and somata of the inner and outer core cells at their contact sites but was hardly detectable at contact sites between axolemma and inner core lamellae. J1/tenascin was found only in association with the extracellular material of the inner core, especially with the two radial clefts and the boundary space between inner and outer core. In developing corpuscles, J1/tenascin became detectable on extracellular material with the onset of inner core differentiation at approximately day 2. After transection or crush of the sciatic nerve, L1 disappeared from the corpuscles but reappeared with regrowing axons at contact sites between axonal membranes and inner core cells. At any regenerative stage inner core cells remained L1-negative. In denervated and reinnervated corpuscles the expression pattern of N-CAM and J1/tenascin did not differ from the normal adult. These observations suggest that a sensory organ, the Pacinian corpuscle, differs from the sciatic nerve and the neuromuscular junction in that its expression of adhesion molecules remains the same in the denervated state as in the innervated adult. Furthermore, in the denervated Pacinian corpuscle, adhesion molecule expression does not resemble that of any developmental stage tested. Thus, other cures than regulation of adhesion molecule expression patterns might be involved in the successful reinnervation of sensory corpuscles.

Aging↗

Pacinian corpuscles in rats with carbon disulphide neuropathy.

Adult Wistar rats were exposed to carbon disulphide vapours at a concentration of 2.4 mg/l of air for 5 days a week (6 h a day), and the ultrastructure of Pacinian corpuscles and their nerve supply was investigated after 6 months of exposure. Both degenerative and regenerative changes were observed in sensory axons and the corpuscles. In a sample of corpuscles examined, 30% were denervated and about 60% showed clear signs of reinnervation. Some of the reinnervated corpuscles were supplied by unmyelinated axons. In others, one to three myelinated axons were already found at the nerve entry. The axons branched and formed three to eight terminals in the inner core. Due to continuous intoxication, most regenerated terminals were again undergoing degeneration. In peripheral nerves, the evidence of axonal regeneration has been reported in various toxic distal axonopathies. However, the reinnervation of Pacinian corpuscles has not been described before. It can be expected that reinnervation of Pacinian corpuscles and other end-organs also occurs in other axonopathies, if not during continuous poisoning, then at least after its cessation.

Animals↗

Transplantation of pacinian corpuscles of the rat into the brain.

In adult inbred rats of the AVN strain, branches of the crural interosseous nerve were dissected out from donors and transplanted into the brain of recipients, together with a cluster of Pacinian corpuscles, (either into a suction cavity or the cerebral cortex) into a slit 1-2 mm deep. The grafts were fixed and processed for electron microscopy 10 days to 6 months after the operation, and their ultrastructure was examined. Sporadic axons of small diameter grew into the nerve branches of some of the grafts from 11 days onward, and became myelinated during the 2nd month after the operation, but none of the transplanted Pacinian corpuscles became reinnervated. The corpuscles, however, survived denervation and grafting. Most of them retained a well-preserved inner core and an intact capsule, consisting of a normal complement of 29.2 +/- 1.0 (mean +/- SE) capsular layers (n = 8), as did the corpuscles previously examined after denervation in situ. Some of the corpuscles underwent degenerative changes, presumably due to a delayed or restricted revascularization. In this group of corpuscles, the inner core underwent disintegration and was gradually replaced by collagen fibrils, whereas the capsule remained preserved but the number of its layers eventually reduced by 40%. It is assumed that the lack of reinnervation of the grafted Pacinian corpuscles was due to the paucity of regenerating axons, and their failure to form correct projections along those Schwann cell columns connected with the corpuscles.

Animals↗

Distribution of pacinian corpuscles in the cat forefoot.

The distribution of pacinian corpuscles in the cat forefoot was investigated using celloidin sections stained with haematoxylin and eosin. The corpuscles were oval or elliptical, their longitudinal and transverse diameters being 590.0 +/- 207.6 microns and 320.0 +/- 119.6 microns. There were 667 corpuscles (mean value for 4 feet) in each forefoot, 80% of which were in the toe region and the remainder in the palmar region. The number of corpuscles was similar in both forefeet. There was no difference in light microscopic structure. Corpuscles were located (1) in the dermis and subcutaneous tissue of the skin folds covering the claw, (2) between the flexor digitorum tendon and middle phalanx, (3) in the subcutaneous adipose tissue of the metacarpal pad and (4) in short digital muscle of the carpal pad. Scattered corpuscles were found in contact with the periosteum of distal and middle phalanges and with flexor tendon sheath, and in the dermis of the palm. Corpuscles were observed to be clustered in the skin folds of the toes. Skin folds, made of dorsal hairy skin, covered the claw on both sides, with most corpuscles in contact with hair follicles and others scattered between hair follicles. Forefoot corpuscles were often in proximity with blood vessels. Corpuscles in the palmar region were seen to be arranged along the superficial palmar metacarpal nerve.

Adipose Tissue↗

Degeneration and regeneration of some mechanoreceptors. An ultrastructural study. IV. Ultrastructure of reinnervated Pacinian corpuscles.

The first signs of reinnervation of the Pacinian corpuscles have been established at the middle of the second month after nerve crush. The regenerative process pass through two periods. During the first period the progressive increase of the Schwann receptor cells has been observed parallel to the reduction of the regenerating nerve branches. During the second period the reorganization and renewal of the regenerated organelles takes place. Some organelles as dense core vesicles, coated vesicles and microtubules of the receptor nerve fibre show noticeable dynamics. The regeneration has been established only in the preexisting after denervation capsulated remnants of the receptors. After nerve transection the regeneration is prolonged one month later and the less of quantity reinnervated receptors have been observed.

Animals↗

Ultrastructural study of the Pacinian corpuscles in the newborn and adult dog forefoot.

Pacinian corpuscles (PC) of the newborn and adult dog forefoot were studied by electron microscopy. The PC of newborn dog forefoot show a rare development: they exhibit a lamellar arrangement, although the lamellar compartments do not surround completely the fiber. The outer core cells show a well-developed perinuclear endoplasmic reticulum. They are surrounded by a discontinuous basal lamina. Mast cells between the lamellae of the outer core are observed. Desmosome-like and zonula adherens junctions, as well as pinocytotic vesicles, are shown in the inner core cells. Intermediate filaments are also observed in the glial cells of the inner core. In PC of adult dog forefoot a general organization of a concentrically arranged capsule, outer core, intermediate layer and inner core around a nerve ending is always present. In the intermediate layer, lamellar cells (specialized fibroblast) do not surround completely the inner core. The inner core lamellae possess numerous pinocytotic vesicles, an extensive network of filaments, special cell junctions (gap, desmosome) and a discontinuous basal lamina. The present results show a conservative structural organization in PC, although differences among species are discussed.

Age Factors↗

Electron microscopical localization of non-specific cholinesterase activity in three principal parts of cat Pacinian corpuscles.

Non-specific cholinesterase (nCHE) activity was demonstrated histochemically on electron microscope level in 3 parts of Pacinian corpuscles from the cat mesenterium. The reaction product was abundant on the plasmic membrane of the inner core lamellae. Schwann cells of a myelinated portion of a sensory axon in Pacinian corpuscles were devoid of positive reaction to nCHE activity. These results are in agreement with those obtained in other sensory nerve endings. Therefore, the cells investing the terminal portion of an unmyelinated sensory axon are considered to be specialized Schwann cells. Furthermore, the amount of end product was lower on the specialized Schwann cells around ultraterminal than terminal portion of a sensory axon. A significantly higher nCHE activity confined to the inner core around the terminal portion of a sensory axon suggests the participation of this enzyme in the maintenance of ionic milieu in periaxonal microenvironment.

Animals↗

Grafts of pacinian corpuscles reinnervated by dorsal root axons.

In adult rats, a piece of the crural interosseous nerve with several Pacinian corpuscles attached was removed from the crural region, autotransplanted onto the surface of the lumbar spinal cord and connected with the peripheral stump of a transected dorsal root. From 10 days up to 6 months after the operation, the grafts were investigated by light and electron microscopy. The regenerating dorsal root axons grew along the grafted nerves into the attached Pacinian corpuscles. By 1-2 months after the operation, the nerves and their branches became almost completely reinnervated by myelinated and unmyelinated dorsal root axons. In a sample of corpuscles examined 2-6 months after grafting, 75% of corpuscles were found reinnervated; each of them was supplied by 1-5 large myelinated axons that formed multiple axon terminals in the inner core. The maximal number of axonal profiles found in a transverse section through different levels of the inner core varied, in individual corpuscles, from 3 to 17 axons and terminals. The dorsal root terminals formed in the grafted corpuscles were mainly filled with mitochondria and resembled peripheral sensory endings. In some instances, the newly formed endings developed lateral processes and membrane specializations characteristic for peripheral Pacinian terminals. Thus regenerating dorsal root axons recognize a grafted peripheral mechanoreceptor as their target and reinnervate it with axon terminals, most of them structurally transformed into peripheral sensory endings.

Animals↗

Immunohistochemical localization of some extracellular molecules and their integrin receptors in the rat Pacinian corpuscles.

The present results suggest that laminin-1 and 3 are localized in the specialized Schwann cells of Pacinian corpuscles, in spite of incomplete deposition of the basal lamina on the surface of their cytoplasmic processes. In addition, laminin-3 is concentrated and probably function as a stop protein not only in the neuromuscular junction, but also in the specialized Schwann cells enveloping the dendritic zone of the afferent axon. No significant changes of immunostaining for both laminins and their integrin receptors following denervation of Pacinian corpuscles indicate that their synthesis is independent to afferent axon as a prerequisite for successful reinnervation.

Animals↗

The capsule structure of Pacinian corpuscles from the cat mesentery.

Using the electronograms of Pacinian corpuscle capsule of the cat mesentery the authors have studied in details the structure of its layers and lamellae. The thickness of the capsule lamellae ranged between 30 nm-320 nm, the mean width being 150 nm. On the surface they are overlaid by means of lamina basalis. The capsule is formed by circular layers composed, most often, by 1-2 lamellae, less frequently, by larger number of lamellae. The width of the space between the layers of lamellae is 150-820 nm. A number of lamellae is provided with longer or shorter processes. They are directed more often to the adjacent lamella with which they can be also connected by means of membrane specialization. However, they are also directed into the space between individual layers of the capsule. The importance of these processes has not been known. Furthermore, the authors have studied the reciprocal link-up of the lamellae within one layer. The lamellae are connected either side-to-side, by inserting the end of one lamella into the infolding of the other, end-to-side or end-to-end. Rich pinocytotic activity (rich occurrence of caveolae) was observed in the lamellae of the capsule. Therefore the authors are of the opinion that the capsule and its lamellae have not only mechanical significance or the function of the transfer system and filter, but they form an important component (subsystem) of the whole metabolic system in the sensory corpuscle.

Animals↗

Painful hyperplasia and hypertrophy of pacinian corpuscles in the hand: report of two cases with immunohistochemical and ultrastructural studies, and a review of the literature.

Hypertrophy and hyperplasia of pacinian corpuscles in the hand are very rare, with only 29 cases previously published. We describe two new cases in middle-aged patients whose chief complaint was progressive digital pain. Immunohistochemical and electronmicroscopic investigations indicated that the lump replicates the structure of enlarged pacinian corpuscles and should not be considered as a real tumor, nor connected to neurofibromatosis. No recurrence was observed after surgical excision. Although local trauma was encountered in 55% of the reported cases, the pathogenesis of such a lesion is still speculative.

Adult↗

[Study of individual Pacinian corpuscle mechanoreceptors following application of colchicine to a nerve].

Colchicine application to the cat caudal mesenteric nerve containing sensory fibers for single mechanoreceptors (Pacinian corpuscles) causes degeneration of the axis cast of the nerve endings. Ultrastructural changes in the receptors showed no difference from the axonal degeneration after the nerve section but the rate of degeneration was considerably slower. Ultrastructural, electrophysiological, and biochemical changes occurring in the Pacinian corpuscles were not the result of direct action of colchicine, but appeared to be realized through the nerve by the axoplasmic transport block. It is suggested that the receptor's structure is under the sensory neuron neurotrophic control.

Alkaline Phosphatase↗

Denervation of Pacinian corpuscles: electron microscopic observations in the rat following nerve transection.

Nerve transection using rat sciatic nerves was employed to observe morphologic changes in the periodic denervation of Pacinian corpuscles. During periods of from 1 to 20 weeks after surgery, a total of 15 corpuscles were obtained under the operating microscope and processed for morphologic analysis using light and electron microscopes. Based on the morphologic findings, normal corpuscles were composed of an axon terminal and inner and outer core cells. Following nerve transection, the axon terminal immediately disappeared at 1 week, but the original inner and outer core cells were preserved, with macrophage migration occurring in the outer core. After 8 weeks, the circular regularity of the inner and outer core lamellae was occasionally broken. The lamellae had wavy courses and there were many empty spaces in the inner core. Even at 20 weeks after denervation, there was interruption in the continuity of the outer core cells; the membranous structure of the outer core and the lamellar structure of the inner core were well-preserved; the outer and inner core cells were still present. Simultaneously, a small number of collagen fibrils were observed between the inner and outer core cells from the earliest postoperative stage. These fibrils increased in number in later stages. The results suggest that, immediately after destruction of axon terminals, macrophages migrate into the interlamellar spaces where they engulf the debris of the degenerated axon terminals. The degeneration of the corpuscles seems to be similar to that of denervated nerve axons; therefore, the inner core cells, which are continuous with the Schwann cells, maintain their original condition for at least 20 weeks after corpuscle denervation. The outer core cells, which are continuous with the perineurial nerve cells, are assumed to be the main cells producing the collagen fibrils in the denervated Pacinian corpuscles.

Animals↗

Fine structure of Pacinian corpuscles in the mesentery of the cat.

Pacinian corpuscles in the mesentery of adult cats were fixed with either glutaraldehyde, osmium tetroxide or permanganate solutions by close intra-arterial injection through the mesenteric artery, and were processed, after electron staining and Epon embedding, for electron microscopy. Better resolution of the corpuscle's ultrastructure was obtained than available heretofore. The myelinated segment of the corpuscle contains blood vessels separated from the axon by collagen fibers and 3 to 4 layers of lamellae. No blood vessels are found in the central core, though access from the vessels is afforded by diffusion through the "cleft" of the inner core. Two cell types are discernible in the inner core hemilamellae; the "clear cells" in which pinocytotic vesicles and organelles abound and reflect the greater metabolic activity of these cells, in contrast to the "dark cells." The ultraterminal is ellipsoidal in form with projections into the "cleft" which give this portion an irregular appearance in section. The terminal and ultraterminal are packed with mitochondria, and "synaptic" vesicles are seen in the ultraterminal. The innermost laminae of the inner core cells are in close apposition to the terminal and break their regular pattern of hemilamellation to surround the small ultraterminal projections at the apical part of the corpuscle.

Animals↗

Development of a receptor on a foreign nerve fiber in a Pacinian corpuscle.

When the sensory fiber of a Pacinian corpuscle (in cat mesentery) is transected (at the inferior mesenteric nerve) transduction fails within 30 hours: the nerve ending produces no generator potentials in response to mechanical stimulation. Electrically elicited nerve impulse conduction continues for at least another 18 hours. A transducer mechanism develops on a regenerating nerve fiber when this fiber enters the denervated corpuscle. Such transducer development takes place on myelinated fibers from the inferior mesenteric nerve, which normally supplies corpuscles, as well as on myelinated hypogastric nerve fibers, which normally do not go to corpuscles, including fibers larger than the original corpuscle afferents.

Action Potentials↗

Nerve compression by pacinian corpuscles.

Compression of nerves of the hand by hyperplasia of pacinian corpuscles is a rare occurrence. Six cases with previous history of trauma in the hand in four of them have been reported in the literature. We present two cases of nerve compression of the two varieties reported, both with previous histories of trauma. In these two cases, surgical excision of the tumor determined the disappearance of clinical symptoms.

Adult↗