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The function of the external ear canal in cetaceans is still under debate and its morphology is largely unknown. Immunohistochemical (IHC) analyses using antibodies specific for nervous tissue (anti-S100, anti-NSE, anti-NF, and anti-PGP 9.5), together with transmission electron microscopy (TEM) and various histological techniques, were carried out to investigate the peripheral nervous system of the ear canals of several species of toothed whales and terrestrial Cetartiodactyla. This study highlights the innervation of the ear canal with the presence of lamellar corpuscles over its entire course, and their absence in all studied terrestrial mammals. Each corpuscle consisted of a central axon, surrounded by lamellae of Schwann receptor cells, surrounded by a thin cellular layer, as shown by IHC and TEM. These findings indicate that the corpuscles are mechanoreceptors that resemble the inner core of Pacinian corpuscles without capsule or outer core, and were labelled as simple lamellar corpuscles. They form part of a sensory system that may represent a unique phylogenetic feature of cetaceans, and an evolutionary adaptation to life in the marine environment. Although the exact function of the ear canal is not fully clear, we provide essential knowledge and a preliminary hypothetical deviation on its function as a unique sensory organ.

Objectives: To analyze the immunohistochemical profile of the human pancreatic pacinian corpuscles in comparison with that of the cutaneous pacinian corpuscles. In addition, we studied a Pacinilike corpuscle found in the adventitia of a pancreatic artery., Methods: We used immunohistochemistry to detect specific antigens for corpuscular constituents, specific antibodies for the identification of Adelta- and C-sensory fibers and for the detection of several growth factor receptors, and some members of the degenerin/epithelial Na channel superfamily of proteins., Results: Approximately 62% of pancreatic pacinian corpuscles have 2 to 10 axonic profiles each enclosed by its own inner core: 1 or 2 of these axonic profiles displayed RT-97 immunoreactivity (specific marker of mechanical axons). The cutaneous pacinian corpuscles showed not more than 2 axonic profiles with identical immunohistochemical characteristics. The expression of glial fibrillary acidic protein, epithelial membrane antigen, and tyrosine receptor kinase B was different between pancreatic and cutaneous pacinian corpuscles; the pattern of distribution of degenerin/epithelial Na channel proteins was identical in both cases. The arterial Pacinilike corpuscles displayed a specific immunohistochemical profile., Conclusions: Pancreatic pacinian corpuscles slightly differ from the cutaneous ones, and these differences could be related to topography, growth factor requirements, or function of pacinian corpuscles in the pancreas.

We used immunohistochemical techniques and confocal microscopy to study the morphometry of myelinated nerve endings in glabrous and hairy skin. A total of 30 healthy volunteers took part in this study designed to assess the possibility of obtaining reliable information on myelinated fibers using samples of hairy skin and to determine whether differences exist between myelinated terminations from different sites. We obtained consistent information on cutaneous myelinated terminations using hairy as well as glabrous skin samples. Myelinated endings from hairy and glabrous skin differ in density and distribution. However, from a comparison of our findings with data from nerve biopsy studies, we conclude that all cutaneous myelinated terminations are thinner terminal branches of large myelinated A beta fibers, whereas cutaneous terminations of small myelinated A delta fibers lose their myelin before entering the dermis and become indistinguishable from C-fiber terminations. The classic criteria, based on fiber size, used to distinguish myelinated fiber subgroups in sensory nerves are therefore not suitable for identifying myelinated terminations in the skin.

Eimer's organ is a small, densely innervated sensory structure found on the glabrous rhinarium of most talpid moles. This structure consists of an epidermal papilla containing a central circular column of cells associated with intraepidermal free nerve endings, Merkel cell neurite complexes, and lamellated corpuscles. The free nerve endings within the central cell column form a ring invested in the margins of the column, surrounding 1-2 fibers that pass through the center of the column. A group of small-diameter nociceptive free nerve endings that are immunoreactive for substance P surrounds this central ring of larger-diameter free nerve endings. Transmission electron microscopy revealed a high concentration of tonofibrils in the epidermal cells of the central column, suggesting they are more rigid than the surrounding keratinocytes and may play a mechanical role in transducing stimuli to the different receptor terminals. The intraepidermal free nerve endings within the central column begin to degrade 15 microm from the base of the stratum corneum and do not appear to be active within the keratinized outer layer. The peripheral free nerve endings are structurally distinct from their counterparts in the central column and immunocytochemical double labeling with myelin basic protein and substance P indicates these afferents are unmyelinated. Merkel cell-neurite complexes and lamellated corpuscles are similar in morphology to those found in a range of other mammalian skin., ((c) 2007 Wiley-Liss, Inc.)

The role of the capsule encasing the Pacinian corpuscle's (PC's) neurite, where mechanotransduction occurs, may be more than mechanical. The inner core of the PC's capsule consists of lamellar cells that are of Schwann-cell origin. Previously, we found both voltage-gated Na+ and K+ channels in these inner-core lamellae. Research on astrocytes and Schwann cells shows bidirectional signaling between glia and neurons, a major component of which is glutamate. Furthermore, Merkel cells show positive immunoreactivity for glutamate receptor mGluR5, and the glutamate-receptor antagonist kynurenate greatly decreases the static activity of the slowly adapting neurons of Merkel cell-neurite complexes. To investigate the possibility of glutaminergic interaction in PCs, we applied antibodies to glutamate, glutamate receptors, glutamate transporters, and SNARE proteins to cat mesenteric PC sections. Positive labeling was seen in the inner-core lamellae, at inter-lamellar connections, where the lamellae contact the membrane of the neurite and at the lamellar tips. The presence of these proteins on the lamellae and neurite membranes, demonstrated both with immunofluorescent light microscopy as well as immunogold electron microscopy, suggests a chemical, possibly bidirectional, interaction between the lamellar cells and the neurite. Thus, the capsule of the PC, apart from having a mechanical filtering function, may also provide an environment for lamellar-neurite interaction, perhaps acting as a neuro-modulator of the initiation, and/or continuation, of the mechanical-electrical transduction process. At the very least, the presence of the aforementioned proteins suggest some sort of "synaptic-like" activity in these mechanoreceptors, which up until now has not been considered possible.

Analysis of specimens taken from different areas of the deep fascia in 20 upper limbs was made in order to establish which kind of nerve fibres and endings are present in the deep muscular fascia. The flexor retinaculum and the lacertus fibrosus were also evaluated because they are anatomically hardly separable from the deep muscular fascia, although they have different functions. In particular, specimens were taken at the level of: (a) the expansion of pectoralis major onto the bicipital fascia, (b) the middle third of the brachial fascia, (c) the lacertus fibrosus, (d) the middle third of the antebrachial fascia, (e) the flexor retinaculum. This study demonstrated an abundant innervation of the fascia consisting in both free nerve endings and encapsulated receptors, in particular, Ruffini and Pacini corpuscles. However, differences in innervation were verified: the flexor retinaculum was resulted the more innervated element whilst lacertus fibrosus and the pectoralis major expansion the less innervated. These results suggest that the retinaculum has more a perceptive function whereas the tendinous expansions onto the fascia have mostly a mechanical role in the transmission of tension. The hypothesis that the fascia plays an important role in proprioception, especially dynamic proprioception, is therefore advanced. In fact, the fascia is a membrane that extends throughout the whole body and numerous muscular expansions maintain it in a basal tension. During a muscular contraction these expansions could also transmit the effect of the stretch to a specific area of the fascia, stimulating the proprioceptors in that area.

Pacinian corpuscles depend on either Aalpha or Abeta nerve fibers of the large- and intermediate-sized sensory neurons for the development and maintenance of the structural integrity. These neurons express TrkB and TrkC, two members of the family of signal transducing neurotrophin receptors, and mice lacking TrkB and TrkC lost specific neurons and the sensory corpuscles connected to them. The impact of single or double targeted mutations in trkB and trkC genes in the development of Pacinian corpuscles was investigated in 25-day-old mice using immunohistochemistry and ultrastructural techniques. Single mutations on trkB or trkC genes were without effect on the structure and S100 protein expression, and caused a slight reduction in the number of corpuscles. In mice carrying a double mutation on trkB;trkC genes most of the corpuscles were normal with a reduction of 17% in trkB-/-;trkC+/- mice, and 8% in trkB +/-;trkC -/- mice. Furthermore, a subset of the remaining Pacinian corpuscles (23% in trkB-/-;trkC+/- mice; 3% in trkB+/-;trkC-/- mice) were hypoplasic or atrophic. Present results strongly suggest that the development of a subset of murine Pacinian corpuscles is regulated by the Trk-neurotrophin system, especially TrkB, acting both at neuronal and/or peripheral level. The precise function of each member of this complex in the corpuscular morphogenesis remains to be elucidated, though.

Hypertrophy of Pacinian corpuscles is a condition that has been reported very infrequently. It was thought not to be connected with neurofibromatosis. A 24-year-old female with a lifelong history of neurofibromatosis type 1, who presented with left ring finger pain and decreased sensation for over 1 year is reported. Histopathology showed hypertrophy of Pacinian corpuscles. Hypertrophy of Pacinian corpuscles should be considered in the differential diagnosis of any patient with persistent pain localized to the distal palm or digits. This is the first case reported in a patient with neurofibromatosis. The finding of this lesion in a patient with neurofibromatosis is somewhat intriguing, though the relationship of these two entities is unclear.

Using electron microscope the receptors found in the zone of highest receptor sensitivity in the skin fold at the base of IV finger of rat hind limb were studied. These receptors are represented by complex incapsulated corpuscles consisting of a group of small endings similar to Pacinian corpuscles, which are densely packed and surrounded by a common connective tissue capsule. Each single primary receptor is provided with an unmyelinated receptor terminal, analogue of internal bulb, and a multilayered external bulb. Primary receptor differs from Vater-Pacinian corpuscle by a significantly smaller size, form of sensitive terminal in cross-section, small number of layers forming internal and external bulbs. Complex corpuscle is the derivative of n. tibialis myelinated sensory fiber. The later is divided after the loss of myelin forming a platform of division with several (up to 5) short sprouts and separate incapsulated receptors at their ends. The complex corpuscles described apparently are dermal mechanoreceptors.

The applied immunogold cytochemical technique in investigating the cytologic distribution of the laminin (LAM) molecule in the capsulated Pacinian and Herbst mechanoreceptors shows the presence of LAM around most elements of the receptor structures. The LAM immunoreactivity (LAM-IR) is best expressed in the vicinity of the perineural capsule cells of both receptor types, where it is primarily concentrated around the perinuclear regions as well as the cytoplasmic lamellae. Such a localization overlaps with the already known ultrastructural localization of a basal lamina (BL) around these cells. Laminin immunoreactivity is less well expressed around the modified Schwann cells. Even in these cells, however, there is an apparent immunoreaction around the cytoplasmic lamellae regardless of the lamellar location. In both receptor types, there is no LAM-IR in the cells of the subcapsular space. Of particular significance we consider the localization of gold particles (respectively the presence of a BL) between the innermost lamellae of the modified Schwann cells and the non-myelinated part of the receptor nerve fiber and their endings, as well as around the axoplasmic protrusions of the nerve endings. We discuss the role of the BL and LAM in the investigated rapidly adapting mechanoreceptors and their trophic influence upon the sensory regions. We also assume the arresting and selective effect of these membranes in building up the ion channels of the axolemma which probably has a certain importance in mechanotransduction.

It has long been accepted that action potentials arising from Pacinian corpuscles (PCs) originate at the first node of Ranvier located within the PC and that the mechanotransduction events (receptor potentials) are formed by stretch-activated channels selectively sensitive predominantly to Na+. Also, it has been shown previously that tetrodotoxin (TTX) affects the receptor potential suggesting that transduction may involve voltage-sensitive Na+ channels. To determine whether voltage-sensitive Na+ channels exist in the membrane thought to be responsible for transduction, immunocytochemical studies were performed using polyclonal antibodies raised in rabbit against the alpha subunit of rat type I and type II voltage-gated sodium channels. The results show the presence of label on the neurite and axolemma, as well as in the node regions. Interestingly, labeling is also found on the inner and outer lamellae that form the non-neural accessory structure surrounding the neurite. The presence of this label in the surrounding lamellae suggests that voltage-sensitive Na+ channels, that are involved in both transduction and action-potential generation, may be made available to the neurite via transport from the lamellae, a mechanism perhaps operating in parallel to axoplasmic transport.

During our systematic examination of the distribution of cytochrome P450 enzymes in the normal and diseased human pancreas, we observed a Pacinian corpuscle in a serial section of a tissue from a pancreatic cancer patient. We report the histologic and immunohistochemical patterns in this corpuscle and review the literature. The Pacinian corpuscle was situated within the pancreas of a 76-year-old woman with cancer in the head of the pancreas. We could demonstrate immunoreactivity within the corpuscle for the neurofilament protein. neuron-specific enolase, S-100 Protein, and for four cytochrome P450-isozymes. The possible function of Pacinian corpuscles in the mammalian and human pancreas is discussed.

The fortuitous finding of a complex Pacinian corpuscle within the lamina propria of the human urinary bladder is described. It consisted of a complex of encapsulated nerve endings within the areolar connective tissue of the lamina propria immediately adjacent to the inner aspect of the detrusor muscle. It showed no structural evidence of directional sensitivity and was associated on its outer aspect with small unmyelinated axons containing small clear and dense-cored vesicles. This appears to be the first report of an encapsulated nerve ending within the lining of the adult human urinary bladder.

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.

We studied carbohydrate residues of glycoproteins and proteoglycans (PGs) in peritoneal Pacinian corpuscles of five adult cats. Terminal monosaccharides of glycoproteins and related polysaccharides were identified by lectin histochemistry and the PGs and glycosaminoglycans (GAGs) by specific antibodies. The most intensive lectin staining reactions indicated an abundance of glycoconjugates with terminal mannose (Man) or sialic acid residues, but no complex-type oligosaccharides were detected within the corpuscles. Terminal fucose (Fuc) and galactose (Gal) residues typical for O-linked mucin-type glycoproteins generally associated with high water binding capacity were also absent. Antibodies against unsulfated chondroitin (C-0-S), chondroitin-4-sulfate (C-4-S), and decorin showed positive reactions in the interfibrillar spaces between the lamellae, around collagen fibers, and around the lamellae of the perineural capsule, especially in the outer parts known to contain Type II collagen. Biglycan showed a preference for the innermost part of the perineural capsule (intermediate layer), known to contain Type V collagen. Collagen V and biglycan are both linked to growth processes. Hyaluronic acid (HA), chondroitin-6-sulfate (C-6-S) chains, and a chondroitin sulfate proteoglycan (CSPG) were co-localized in the terminal glia. The study of carbohydrates with high water binding capacity may contribute to our understanding of the high viscoelasticity of Pacinian corpuscles.

The capsule and inner core are multilamellar auxiliary structures enveloping the axon terminal of the Pacinian corpuscle. The freezing injury of the rat interosseal Pacinian corpuscles induced the destruction of all cellular components while the extracellular matrix including the basal laminae survive the treatment. Simultaneous denervation and the freezing treatment of the Pacinian corpuscles discovered an ability of the basal lamina and other components of the extracellular matrix to stimulate a differentiation of migrated Schwann cells and fibroblasts into multilamellar auxiliary structures. The restoration of inner core and capsule in the Pacinian corpuscles was independent of the presence of sensory axon terminals. The restored lamellar structures of Pacinian corpuscles in long-term surviving rat (4 to 8 months) displayed atrophic changes. The results suggest that the extracellular matrix of rat Pacinian corpuscles may contain molecules that are produced by Schwann cells and fibroblasts during maturation of the multilamellar auxiliary structures. The molecules deposited into the extracellular matrix are able to influence the redifferentiation of multilamellar auxiliary structures from immature cells.

Light- and electron-microscopic immunocytochemistry (ICC) was performed on Pacinian corpuscles (PCs) obtained from cat mesentery to determine the presence and location of various proteins within the accessory capsule and the neurite. Antibodies to tubulin, neurofilament 200, actin, collagen II and V, glial fibrillary acidic protein (GFAP) and S-100 were used. Type II collagen was localized only in the outer core of the accessory capsule, which is composed of an inner core, an intermediate layer or growth zone, an outer core and an external capsule. Type V collagen was found only in the intermediate growth zone. Intermediate filaments labeled with anti-GFAP were only found in the inner core. The calcium-binding protein that was labeled by anti-S-100 was found only in the inner core. Diffuse and variable staining for actin is present throughout the accessory capsule. The differences in distribution of these various proteins within the capsule suggest different structural/functional properties of the various capsule regions. The neurite was found to contain microtubules (i.e., tubulin) and neurofilaments throughout, but these cellular inclusions were not found within the cytoplasmic extensions (filopodia) that project from the neurite into the hemilamellar clefts formed by the inner-core hemilamellae. The extensions, however, were found to contain actin in a much greater density than that seen in the neurite proper. The presence of actin, but apparent lack of other cytostructural elements within the extensions, is highly reminiscent of the composition of stereocilia found on vestibular and auditory hair cells. Since stereocilia have been shown to play a role in hair-cell mechanotransduction, it is possible that the cytoplasmic extensions are significantly involved with mechanotransduction within the PC.

The Pacinian corpuscle consists of a sensory axon terminal that is enveloped by two different structures, the inner core and the capsule. Since proteoglycans are extremely water soluble and are extracted by conventional methods for electron microscopy, the current picture of the structural composition of the extracellular matrix in the inner core and the capsule of the Pacinian corpuscle is incomplete. To study the structural composition of the extracellular matrix of the Pacinian corpuscles, cationic dyes (ruthenium red, alcian blue, acridine orange) and tannic acid were applied simultaneously with the aldehyde fixation. The interosseal Pacinian corpuscles of the rat were fixed either in 2% formaldehyde and 1.5% glutaraldehyde, with the addition of one of these cationic dyes or, in Zamboni's fixative, with tannic acid added. The cationic dyes and tannic acid revealed a different structural pattern of proteoglycans in the extracellular matrix in the inner core and in the capsule of the rat Pacinian corpuscles. The inner core surrounding the sensory axon terminal is a compartment containing proteoglycans that were distributed not only in the extracellular matrix but also in the cytoplasm of the lamellae. In addition, this excitable domain was separated from the capsular fluid by a thick layer of proteoglycans on its surface. An enlarged interlamellar space of the capsule contained large amounts of proteoglycans that were removed by digestion with chondroitinase-ABC. Ruthenium red and alcian blue provided only electron dense granules, probably corresponding to collapsed monomeric proteoglycan molecules. Acridine orange and tannic acid preserved proteoglycans very well and made it possible to visualize them as "bottlebrush" structures in the electron microscope. These results show that the inner core and the capsule of rat Pacinian corpuscles have different structural patterns of proteoglycans, which are probably involved in different functions.

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.

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.

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.

The ontogeny of cutaneous sensory nerve organs is described in higher vertebrates, and includes the lamellated corpuscles of Meissner, Pacini and Herbst, and the Merkel cell-neurite complex with bird Merkel and Grandry corpuscles, and mammalian Merkel cells. The main common feature is that for most corpuscles there is an inside-out order of assembly around the nerve ending which is present from the beginning of end-organ ontogeny. The exception is the mammalian Merkel cell which is present in the epidermis before the entrance of nerve fibers, and could play a promotional role in the development of skin innervation. The developmental origin of Herbst and Merkel corpuscles in birds is reported as demonstrated using embryological experiments with cell markers. Conclusions are that inner bulb cells of Herbst corpuscles and bird Merkel cells are of neural crest origin, whereas other cells (inner space and capsular cells for Herbst corpuscle and capsular cells for Merkel corpuscles) are provided by the local mesenchyme. The question of the ontogeny of mammalian Merkel cells is discussed in relation to the two debated hypothesis of epidermal and neural crest origins. Morphogenetic interactions during the development of cutaneous sensory end organs are also discussed.

The cutaneous sensory nerve formations belong to the structures which are studied intensely by the enzyme activity histochemistry since the early history of this technique. The histochemical localization of the activities of nonspecific cholinesterase, alkaline phosphatases, acid phosphatase, adenosine tri- and diphosphatases, adenylate cyclase, and dipeptidylpeptidase-IV in the cutaneous sensory nerve formations, mainly sensory corpuscles, is reviewed. The histochemical approach has brought new knowledge of both morphological building of these unique structures and their biochemical constituents. Taken together, the present results of enzyme histochemistry provide insight into the function of enzymes, and disclose new relationships between the sensory terminals and auxiliary structures in the cutaneous sensory nerve formations.

Electron-microscopic analyses of the mitochondrial organization within the neurite innervating the Pacinian corpuscle (PC) were performed to test the hypothesis that the sites of mechanotransduction are the filopodia projecting from the neurite's surface. Since high concentrations of mitochondria imply the need for metabolic energy, and since transduction mechanisms are heavily dependent on such energy, it was reasoned that the greatest concentration of mitochondria should occur near the filopodia if they are involved in mechanotransduction. The analysis that the mitochondria lie close to the terminal neurite's membrane, on average within 0.4 microns, and thus are ideally located for supplying energy for membrane mechanisms. Although they can be found in a ring-like array, as seen in cross-sections of the terminal neurite, their greatest concentration occurs where the filopodia project from the terminal neurite. A linear algebraic analysis of the data set confirmed a high probability of the joint occurrence of a filopodial base and an increased frequency (number) of mitochondria. Thus the results provide further circumstantial support for the hypothesis that transduction within the PC mechanoreceptors takes place at or near the filopodia.

The nerve endings of the human acetabular labrum were investigated. Twenty-three acetabular labra were obtained from 24 fresh human cadavers, stained with Suzuki's silver impregnation and an immunohistochemical technique for neurogenic specific protein S-100, and examined by light and electron microscopy. Ramified free nerve endings were seen in all specimens by silver staining, and also were observed by the immunohistochemical technique for S-100 protein. Sensory nerve end organs, such as a Vater-Pacini corpuscle, Golgi-Mazzoni corpuscle, Ruffini corpuscle, and articular corpuscle (Krause corpuscle), were observed by silver staining. Collagen fibers were scattered sparsely in the superficial layer of the labrum, and nerve endings were observed mostly in this region. Collagen fibers were sparse, and nerve endings also were observed in some regions among the collagen fiber bundles in the inner layer. Innervation of the acetabular labrum was confirmed in this study, suggesting that nerve endings in the labrum may be involved in nociceptive and proprioceptive mechanisms.

We have investigated the capacity of injured axons in the spinal dorsal columns of young adult rats to reinnervate grafted Pacinian corpuscles. A branch of the hindlimb interosseous nerve with a group of crural Pacinian corpuscles attached to it was autotransplanted to the surface of the spinal cord and the nerve stump was implanted into the dorsal column. Two to three months later 16 grafts were removed for examination by light and electron microscopy. By 3 months after transplantation almost all Schwann cell columns of the grafted nerve branch were occupied by regenerated myelinated and unmyelinated axons. Of 41 corpuscles examined by electron microscopy 24 were reinnervated by 1-3 myelinated fibres which gave rise to multiple terminals in the inner core. The remaining corpuscles appeared to be denervated. Only two of the reinnervated corpuscles contained regenerated endings which reiterated the distinct ultrastructure of normal presynaptic terminals of CNS axons, characterized by clusters of lucent vesicles and paramembranous densities. All other corpuscles were reinnervated by terminals which resembled peripheral mechanosensory endings as they contained mitochondria and very few vesicles. One such corpuscle was coinnervated by small terminals filled with large dense cored vesicles. We assume that the majority of grafted Pacinian corpuscles have been reinnervated by dorsal column axons and that the regenerated terminals with the ultrastructure of peripheral mechanosensory endings derive from central axons of primary sensory neurons, which are apparently capable of constructing mechanosensory-like terminals in response to signals from the Pacinian corpuscles. The vesicle-filled endings are probably formed by second order sensory neurons, corticospinal neurons and small peptidergic neurons unable to adjust their terminals to the new target.

1. Single fibre action potentials were recorded with 2 pairs of wire electrodes from human and dog lower sacral nerve roots and the rat nervus suralis. From the widths of single peaks of alpha 1 (FF), alpha 2 (FR), alpha 3 (S) (extrafusal) and gamma 1 and gamma 21-motoneurons (intrafusal) conduction velocity frequency distribution histograms were constructed and the limits of the velocity ranges determined. Distribution changes of conduction velocities in each group of alpha and gamma-motoneurons were used for recruitment analysis in the occasional firing mode. 2. In the dog, the rat and the human, the slower conducting fibres were recruited before the faster conducting ones in each group of motoneurons. In the dog, the slowly conducting gamma 1 and alpha 2-motoneurons were recruited directly following bladder catheter pulling, and the slowly conducting alpha 3-motoneurons were recruited 1 sec later. In the rat, the slowly conducting alpha 1-motoneurons were recruited directly following pin-pricking of the hindlimb, the slowly conducting alpha 2-motoneurons 0.2 sec later, and the slowly conducting alpha 3-motoneurons 1 sec later. In humans, the slowly conducting gamma 1 and alpha 2-motoneurons were recruited 2 sec following bladder catheter pulling, the slowly conducting alpha 3-motoneurons 4 sec following pulling. 3. In the dog, with no additional stimulation slowly (and fast) conducting gamma 21 and alpha 3-motoneurons showed repeated activation 3 to 4 sec later. A subgroup of the alpha 1-motoneurons showed repeated activation every 2 sec. In the rat, without stimulation, a slower conducting subgroup of the alpha 1-motoneurons showed preferential activation of the low and high conduction velocities every 2 sec. In the human, with no additional stimulation, the slowly and fast conducting alpha 2 and alpha 3-motoneurons were recruited repeatedly every 2 sec.

Nerve transection and immediate free nerve grafts using rat sciatic nerves were employed to observe the morphologic changes in periodical denervation and reinnervation of Pacinian corpuscles located on the interosseous membrane between the fibula and tibia. During periods of from 2 weeks to 20 months after the surgery, a total of 28 corpuscles were obtained under an operating microscope and processed for morphologic analysis using light and electron microscopes. Based on our morphologic findings, normal corpuscles were composed of an axon terminal and inner and outer cores. The axon terminal disappeared within 2 weeks after the nerve grafts, but the original inner and outer core cells remained for up to 20 months. In addition, a small number of collagen fibrils was observed between the inner and outer core cells. After 4 months, multiple axon terminals began to regenerate in the inner core. From 7 to 20 months, these axon terminals in some corpuscles developed a structure resembling that of normal terminals. Some of these terminals were located in the center of the inner core, but a few were in contact with the outside of the inner core. The production of collagen fibrils in denervated corpuscles was periodically activated in the intercellular spaces. These findings suggest that the morphologic changes in denervated corpuscles correspond to those in denervated nerves. Inner core cells, which are continuous with Schwann cells, remain in their original condition in denervated corpuscles until regenerating nerves enter the inner core and are essential for corpuscle regeneration, because they may produce some trophic substances that induce the regeneration of multiple axon terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

In the present paper the ultrastructural similarities among the terminal portions of Pacinian corpuscles, the nodes of Ranvier, and the initial segments of primary sensory neurons are pointed out. Our conclusion is based on our observations of cat Pacinian corpuscles and other general knowledge of the node of Ranvier and the initial segment published elsewhere. The morpho-functional similarities of three principal excitable regions of the sensory nerve fibres (the initial segments, the node of Ranvier, and the terminal portions of sensory nerve formations) are illustrated by identical distribution of the enzymes which are associated with ionic transport (alkaline phosphatase, Mg(2+)-ATPase), and non-specific cholinesterase. Furthermore, the polyanionic material revealed by Alcian blue staining in three excitable sites of the sensory axon confirms the supposition that excitable axolemma cannot be considered in the isolation of its surroundings produced by Schwann cells.

Pacinian corpuscles in the cat urinary bladder were studied using the hematoxylin and eosin staining, formaldehyde-induced fluorescence histochemistry, immunohistochemistry for tyrosine hydroxylase (TH) and immunoelectron microscopy. The existence of catecholaminergic nerve fibers penetrating into the corpuscles was clarified. (1) About 10 Pacinian corpuscles which were mainly located in the subserosa were found in the lower one-third portion of each urinary bladder. (2) One or two corpuscles containing blue-green fluorescent fibers were detected in each bladder. These fibers were equivalent to TH-immunopositive varicose fibers using the avidin-biotin-peroxidase complex method. (3) Thin nerve fibers containing dense-cored vesicles were found in the corpuscle by immunoelectron microscopy. These fibers spirally encompassed a swollen sensory terminal at a distance in the inner core. According to the above findings, we discuss a modulatory function of the catecholaminergic fibers in this mechanoreceptor.

Immunocytochemical demonstration of protein kinase C (PKC) subspecies (alpha, beta, gamma) was carried out in Pacinian corpuscles of rat hind feet using monoclonal or polyclonal antibodies against each of these subspecies. The inner core cells and lamellae and the Schwann cell cytoplasm of the nerve fiber innervating the corpuscle were strongly positive for PKC alpha-immunoreactivity (IR). In contrast, the axon terminal and the outer core did not display any positive alpha-IR. Very weak PKC beta-IR was detected in the ultraterminal region of the axon terminal, while the trunk region showed no immunoreactivity. Very faint PKC beta-IR was found also in the lamellar cells located at the periphery of the inner core and the endoneurial fibroblasts in the intermediate layer. PKC gamma-IR was not detected in any part of the corpuscle. The strong PKC alpha-IR in the inner core and the presence or absence of PKC alpha-, beta-, and gamma-IR in the axon terminal are discussed from the point of view of the functional aspects of each part.

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.

The authors studied the ultrastructure of axon processes in simple sensory corpuscles, Herbst and Pacinian corpuscles. They give a description of their shape, topographical localization and relation to organelles. They focused their attention to the incidence of various kinds of vesicles in the processes and at their bases, and the incidence and localization of of mitochondria. The most frequently occurring vesicles are those of medium electron density (clear vesicles), in small numbers there are also dense core vesicles and coated vesicles. The incidence of vesicles is predominantly polarized, i.e. they are situated at the bases of axon processes, opposite the so-called clefts of the inner core. In sporadic cases reach into the processes besides clear vesicles also mitochondria. Direct connection between axon processes and inner core lamellae was not observed. The authors are considering the possible importance of these processes in the transmission of stimuli to the axon. They are of the opinion that further studies are necessary to specify the morpho-physiological relations inside sensory corpuscles.

The ultrastructure of Pacinian corpuscles localized beneath the crural interosseous membrane was examined two weeks to 18 months after crushing the sciatic nerve in adult rats. The Pacinian inner core and capsule remained preserved during the transient period of denervation. Regenerating axons reached Pacinian corpuscles approximately three weeks after nerve crush. Up to 15 axonal sprouts entered a single corpuscle at the initial stage of reinnervation, but only 1-3 axons increased in size, myelinated and formed axon terminals in the inner core, the excess sprouts being eliminated. Most corpuscles of the crural group were reinnervated by the end of the first month. Three to 19 months after nerve crush, 10% of corpuscles examined were found to be monoaxonal and monoterminal as before the operation; 74% contained multiple terminals; 16% remained denervated. Over half the multiterminal corpuscles were supplied with a single myelinated axon that branched inside the corpuscles; the rest received two or three myelinated axons which formed several terminals. The terminals were distributed at random, usually in the axial region between the lamellae of the inner core. They were cylindrical, with an oval profile; the larger terminals were filled with mitochondria and microtubules at their circumference and contained a core of neurofilaments. Lateral processes of the terminals were filled with vesicles and had membrane specializations as in normal corpuscles. The mean number of terminals in reinnervated corpuscles was 4.07 +/- 0.37 (S.E.M.) at three months, and 3.26 +/- 0.49 (S.E.M.) 6-18 months after nerve crush. This small decrease was apparently the result of degeneration occasionally observed in some axon terminals at later stages of reinnervation. These experiments thus demonstrate that most rat Pacinian corpuscles become reinnervated with multiple terminals after nerve injury and maintain multiterminal innervation permanently.

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.

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.

High-threshold mechanoreceptors (mechanical nociceptors) with myelinated axons were electrophysiologically identified in hairy skin of the cat as described by Burgess and Perl ('67). Such elements possess receptive fields consisting of a number of punctate areas from which maximal firing can be elicited by intense (skin-damaging) mechanical stimuli. The spots of the receptive field are separated from each other by unresponsive regions, i.e., by skin areas from which responses cannot be evoked by stimuli effective at the spots. Fine steel pins were inserted to bracket closely a number of the spotlike responsive areas for each of several units. After aldehyde perfusion of the animal, osmification of the tissue and embedding in plastic, the marked skin zones were examined in semithin and ultrathin sections at the light and electron microscopic level. Near each delineated area, a thinly myelinated axon was found that could be traced to the papillary layer where it loses its myelin sheath. Unmyelinated axons accompanied by thin Schwann cell processes were then traced and found to penetrate the epidermal basal lamina in one of the papillae. At the epidermal penetration site, the axons contained both clear round, and large, dense core vesicles; at this level, the surrounding Schwann cell cytoplasm exhibited numerous pinocytotic vesicles. The zone of penetration may constitute the receptive apparatus. Some of these axons have been traced within the basal epidermal layer where they become surrounded by keratinocytes, lose their Schwann sheath, and apparently terminate. This overall morphological pattern was consistently present in the demarked areas of focal responsiveness, and was rare in the surrounding skin; this and its difference from other cutaneous neural endings suggest that the intraepidermal axon-Schwann cel complex constitutes the receptive structure for myelinated mechanical nociceptors. It is suggested that such complexes are the sense organs responsible for initiating the sensation of pricking pain produced by localized mechanical injury of the skin.

Healthy middle ear mucous membrane of newborns differs from the respiratory mucous membrane of the respiratory tract, in that it lacks a mucociliary epithelial pattern and because it has an absence of cells responsible for immunological resistance. Irritations over a short period of time and intensity cause a mucous membrane edema, which leaves behind, when the irritation disappeares, no permanent morphological changes in the structure of the mucous membrane. Severe irritations over a long period of time cause a characteristic change in the epithelium and submucosa: the single layered flat epithelium is replaced by respiratory epithelium; in the submucosa a proliferation of the connective tissue occurs simultaneously with the development of a local immunologically potent, cellular defense system. The actively secretive epithelial cells serve as the means whereby the antibodies are transported to the surface of the mucous membrane. Whereas at the time of mucous membrane edema, serum components (transsudate) are the primary source of the resulting "serotympanum", an increase in viscosity of the mucous allows one to recognize the active secretive work of the metaplastic epithelium. The biochemical composition of the various effusions givens a direct a direct indication of their origin: it is, however, no key to the cause! Only in the case of purulent secretions is it possible to recognize the cause by cellular or bacteriological identification. The same is valid for the norphological changes of the middle ear mucous membrane since the membrane will generally react in a similar manner, even though the types of irritation differ. When the stimulus which brought about the proliferation of the mucous membrane since the membrane will generally react in a similar manner, even though the types of irritation differ. When the stimulus which brought about the proliferation of the mucous membrane and the epithelial metaplasy disappears, the active production of mucous stops. However, a regression to the original condition does not take place: the mucous membrane remains ready to react!

The pacinian corpuscle is composed of an inner and an outer core or bulb. The former is formed by tightly packed and multi-layered thin cellular processes (lamellae) of lamellar cells which surround a centrally located axon terminal, and the latter, also called the capsule, is made up of very loosely piled layers of thin cells which encircle the inner core. Lamellar cells of the inner core are considered to be specialized Schwann cells, and the outer core cells are modified perineurial cells. In the present study, the matrix filling the extracellular spaces of the inner core consisted of basal lamina-like amorphous materials, sparce fine collagen fibrils, and the ground substance embedding these structural components. No definite basal laminae were found on the inner core lamellae except on the peripherally located ones which had distinct basal laminae. Outer-core cells were invested along the entire contour by distinct basal laminae. The interspace between the inner and outer cores was a continuation of the nerve endoneurium. The purpose of this investigation was to determine whether the extracellular matrix of the pacinian corpuscle, especially that of the inner core, has the ability to cause corpuscle regeneration, i.e. to make the regenerating axons and Schwann cells differentiate into corpuscular axon terminals and inner core cells, respectively. Pacinian corpuscles in the periosteum at the distal end of the fibula of mice were repeatedly frozen (3-5 times) in situ with forceps cooled with liquid nitrogen. Within 2-3 days, all the cellular constituents of the corpuscle had degraded, while the extracellular matrices of the inner and outer cores apparently remained undamaged. After 5-7 days, regenerating axons and accompanying immature Schwann cells entered these extracellular matrices of the inner cores. A remarkable finding was that these immature Schwann cells were detached from the axon, and sent thin cellular processes around the axon in a characteristic fashion, basically forming the same pattern as lamellae in a normal corpuscle. The regeneration of the inner core was completed by about 40 days after the freezing treatment. In the outer core, perineurial cells proliferated and extended through the basal lamina tubes of the old cells, becoming new outer core cells. These findings indicate that the extracellular matrix of the pacinian corpuscle has a specific property to cause the regeneration of the corpuscle.

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.