Immunohistochemical study of sensory nerve formations in human glabrous skin.

The sensory nerve formations (or corpuscles) of normal human glabrous skin from hand and fingers, obtained by punch biopsies, were studied by the streptavidin-biotin method using monoclonal antibodies directed against neurofilament protein (NFP), S-100 protein, glial fibrillary acidic protein (GFAP), cytokeratins, and vimentin. NFP immunoreactivity (IR) was observed in the central axons of most sensory formations, while S-100 protein IR was restricted to non-neuronal cells forming the so-called inner cells core or lamellar cells. Furthermore, vimentin IR was found in the same cells of Meissner's and glomerular corpuscles. None of the sensory nerve formations were stained for GFAP or keratin. The present results suggest that the main nature of the intermediate filaments of the non-neuronal cells of sensory nerve formations from human glabrous skin is represented by vimentin and not by GFAP. Thus, our findings suggest that lamellar and inner core cells of SNF are modified and specialized Schwann cells and not epithelial or perineurial derived cells.     

Survival of Pacinian corpuscles after denervation in adult rats

Summary The ultrastructure of Pacinian corpuscles located on the crural interosseous membrane was studied in adult rats 6 h to 10 months after transection of the right sciatic nerve. Axon terminals degenerated one day after transection and were engulfed and resorbed by cells of the inner core within one week. The axial space left after removal of the axonal debris was closed by the lamellae of the inner core. The main structural features of the inner core and capsule remained preserved after denervation throughout the period of study. The denervated inner cores, however, became atrophic 10 months after neurotomy, their mean diameter being reduced by 17.5% compared with that of contralateral control corpuscles. The number of capsular lamellae was unaltered, and perineurial pathways of the peripheral nerve stump remained preserved. Schwann cells proliferated and formed Büngner bands during the first month after denervation, but retracted their processes and became atrophic at later stages after neurotomy.Survival of Pacinian corpuscles after long-term denervation in adult rats is in contrast to their rapid degeneration within several days after nerve section in neonates.     

Electron microscopic observations of degeneration of human Pacinian corpuscles in amputated fingers.

Amputated human fingers were used to observe the morphologic changes in degeneration of Pacinian corpuscles, and postoperative moving two-point discrimination of the replanted fingers was examined to analyze sensory recovery after replantation. Normal corpuscles are composed of an axon terminal and inner and outer cores, resembling a sliced onion. The inner core is composed of thin, multilayered lamellar cells, and the outer core consists of multiple layers of thin perineurial cells. Based on our morphologic findings, following mitochondrial degeneration in the axon terminal, the terminal and inner core cells disappeared within 9 to 16 hours, but the outer core did not lose its structure until more than 24 hours after amputation. Collagen fibrils in the corpuscles appeared from 5 hours after amputation and periodically increased their amount up to 27 hours after amputation. Postoperative sensory recovery of the replanted fingers was significantly poorer with 9 hours or more of cold ischemia. These findings suggest that the inner core cells originating from Schwann cells degenerate at over 9 hours after amputation, and this may be related to the poor sensory recovery of replanted fingers. It also appears that the outer core cells originating from the perineurial cells in the amputated fingers survive even up to 27 hours after amputation and produce collagen fibrils in the extramatrix spaces of the outer core cells.     

A fine structural localization of the non-specific cholinesterase activity in glomerular nerve formations (endings)

Snout glabrous skin (rhinarium) of the cat is innervated not only by typical simple lamellar corpuscles but also glomerular formations. In contrast to simple lamellar corpuscles, glomerular nerve formations are located away the dermal papillae. In cross sections, glomerular nerve formation consists of several axonal profiles enveloped by 1-2 cytoplasmic lamellae of Schwann cells. The space among them is filled by collagenous microfibrils and the basal lamina-like material. Capsule was composed from fibroblast-like cells without definite basal lamina. An electron-dense reaction product due to non-specific cholinesterase activity was associated with Schwann cells and their processes surrounding unmyelinated terminal portion of the sensory axons. Abundant reaction product was bound to the collagenous microfibrils and was deposited in extracellular matrix between Schwann cell processes. These results are further evidence for the presence of the non-specific cholinesterase molecules as integral component of the extracellular matrix in sensory corpuscles. On the basis of histochemical study two possible explanation are considered for functional involving of this enzyme in sensory nerve formations.     

Ultrastructure of Merkel corpuscles and so-called "transitional" cells in the white Leghorn chicken

In the chicken Merkel corpuscles are located in the dermis and consist of specialized Merkel cells, discoid nerve endings and lamellar cells. Merkel cells contain characteristic membrane-bound dense-core granules and bundles of microfilaments. Asymmetric junctions, synapse like, with thickened membranes and clusters of dense-core vesicles were observed between the Merkel cells and the nerve endings. The nerve ending is derived from myelinated nerves and sometimes contains clusters of clear vesicles. A laminar system formed by lamellar cells of the Schwann cell type encloses the Merkel cells and the nerve endings. So called "transitional" cells, showing some of the morphological features of both keratinocytes and Merkel cells, were observed in the basal layer of the epidermis. One was located partly in the epidermis and partly in the dermis. The structure of Merkel corpuscles is compared with that of Merkel cells in other tetrapods. The developmental significance of "transitional" cells and the origin of Merkel cells are discussed.     

The ultrastructure of sensory corpuscles in the skin in the hedgehog snout

The ultrastructure of sensory nerve endings was examined in the snout skin in 3 adult hedgehogs (Erinaceus europaeus). The material was taken intravitally under total anaesthesia and processed in a usual way for the electron microscopy. The corpuscles were evaluated in the individual sections and series sections made through the whole corpuscle. In the superficial layers of the dermis simple sensory corpuscles and free endings were found. The simple sensory corpuscles can be divided into three types. a) Corpuscles containing a greater number of lamellae in the inner core, the lamellae are arranged regularly and are separated by two opposite clefts. The capsule is formed by only several lamellae undoubtedly of fibrocytic origin. b) Corpuscles containing a smaller number of wider lamellae in the inner core situated often at random. The clefts are also irregular and are often closed in the superficial layers of the inner core. The capsule is quite simple mostly formed by a single lamella of fibrocyte which often fails to form a continuous coat of the corpuscle. c) The third type is typical of its inner core being formed by few lamellae arranged irregularly. These corpuscles have no connective tissue capsule and are separated from the environments only by the basement membrane of superficial lamellae of the inner core. The corpuscles of the second type resemble considerably the developmental stages of simple sensory corpuscles as described in the literature in the cat. They are the same in size or smaller than the corpuscles of the first type. The free nerve endings occurred in two forms. a) Flattened (lanciform) nerve terminals. The axon is rich in mitochondria. The sides of the flattened terminal is lined with one to three wide lamellae while the axon reaches as far as the surface of the formation which is covered only with the basement membrane. b) Typical free endings rich in mitochondria which are embedded in the cytoplasm of Schwann cells or occasionally are covered only with the basement membrane. The lanciform endings which are not linked up with the hairs here may represent a transition from free endings to simple sensory corpuscles.     

Protein kinase C (alpha, beta, gamma) in Pacinian corpuscle.

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.     

Innervation of the synovial membrane of the cats joint capsule

Summary Results of investigations on the occurrence of nerve fibres and endings in the synovial membrane of the knee and elbow joint in the cat are reported. The stratum synoviale contains only autonomic fibres, running in the adventitia of arteries.Free nerve endings are lacking in the stratum synoviale. Simple Pacinian corpuscles with an inner core are occasionally observed in the border zone between the stratum synoviale and fibrosum. The ultrastructure of these endorgans resembles that of Pacinian corpuscles in the hairless and hairy skin of the cat.     

Specificity of membrane specializations in mechanoreceptors of birds--A freeze-etching study

The detailed knowledge of the molecular process of mechanotransduction is still an unsolved question. The investigation of the intramembranous structure of the cutaneous mechanoreceptors may play an important role in elucidating this problem. In this relation, Herbst sensory corpuscles in ducks were studied for the first time using the freeze-etching and thin sectioning techniques. Herbst corpuscles have the basic structural components valid for most of the encapsulated mechanoreceptors in mammals: a capsule made of perineural cells, a lamellar complex of modified Schwann cells, surrounding the non-myelinated part of the receptor nerve fiber and its ending. Freeze-etching replicas reveal that the plasmalemmae of the capsule cells, modified Schwann cells and axolemmae of parts of the nerve fiber differ in both density and pattern of distribution of intramembranous particles (IMPs) as well as IMP size. On all the plasmalemmae the IMP density is higher on the P-face (2000-3300 microm(-2)) than the respective E-face (800-1500 microm(-2)). The axolemma of the ending of the receptor nerve fiber expresses higher density of IMPs than its shaft. The mean IMP size for all the plasmalemmae varies between 5.5 and 7.5 nm. Many tight junctions occur between the capsule cells. These results indicate that the non-myelinated axolemma as well as the plasmalemmae of other components of Herbst corpuscles are specialized in terms of content and distribution of IMPs. The IMPs may represent various kinds of mechanosensitive channel proteins or related membrane-bound proteins participating in the process of mechanotransduction.     

The effect of long-term denervation on the ultrastructure of Pacinian corpuscles in the cat

Summary The ultrastructure of Pacinian corpuscles of the cat located in the crural region and innervated by the interosseous nerve was studied 1 to 14 months after denervation. Both the Pacinian inner core and capsule remained well preserved one month after denervation. However, the denervated inner cores underwent progressive atrophy and wasting, which resulted in a gradual reduction of the amount of inner-core cells and lamellae, widening of interlamellar clefts, formation of empty spaces in the axial region and a considerable increase in the number of collagen fibrils. In spite of the wasting, the inner core still survived 14 months after denervation, but at least half of its volume became occupied by collagen fibrils which surrounded the remaining inner-core cells and lamellae. Collagen fibrils assembled in the denervated core were markedly thinner than those found in the capsule, as is also the case in normal Pacinian corpuscles. In the capsule, discrete focal degeneration, occasional pyknosis of the innermost capsular cells and macrophage infiltration were observed from the first month after nerve section onward, but the number of capsular layers remained within the normal range (30–40) up to 14 months after denervation.     

Intrinsic innervation of the rat knee joint articular capsule and ligaments

In spite of the practical importance of having a detailed knowledge of knee joint innervation to understand the pathophysiologic aspects, little information is now available concerning the density and pattern of the nerve fibres which are distributed to it. The present study has been designed to investigate the density and distribution of nerve fibres and receptor corpuscles in the knee joint articular capsule, cruciate and collateral ligaments in the rat, using the acetylcholinesterase (AChE) histochemical in toto staining technique. The investigation was performed on male Wistar rats of 3 months of age, some of which had been treated with capsaicin to deplete their afferent 'C' fibres of their content of neuropeptides. AChE-positive nerve fibres and different types of receptor corpuscle endings were found within articular capsule and ligaments. The highest density of AChE-positive nerve fibres was noticeable in the fibular collateral ligament followed by the tibial collateral ligament, the posterior cruciate ligament, the anterior cruciate ligament and the articular capsule. In the articular capsule the number of type I endings was higher than in the ligaments. The opposite is true for the other type of receptor corpuscles found as well as for nerve endings. Capsaicin treatment significantly reduced the density of AChE-positive nerve fibres in knee joint ligaments but did not affect nerve fibres in the articular capsule. Moreover, it caused the disappearance of some kind of receptor corpuscles within the collateral and cruciate ligaments. The above data collectively suggest that the AChE in toto staining technique may represent a good method for investigating joint innervation and that a significant percentage of nerve fibres supplying knee joint ligaments is represented by C fibre afferents.     

Quantitative evaluation of sensory nerve endings in hypertrophy of labia minora pudendi in women.

The authors studied the types of sensory nerve endings in hypertrophic labia minora pudendi in women aged between 18 and 69. The nervous tissue was impregnated with silver nitrate by Lavrentyev's modification of the Bielschowski-Gross method. The sensory nerve endings were divided into the following groups: free endings and arborizations, spray-like endings, seven types of clew-like nerve endings, and Pacinian corpuscles. It is the clew-like endings that absolutely predominate, they were 2,027 in number. The arborizations and spray-like endings found were 105 in number and only 4 of Pacinian corpuscles were found. As compared with normal labia there are no principal differences among the types of sensory nerve endings. The main difference consists in the rate of occurrence (89.6 as against 57.8) and in the thickness of the capsule, while the nerve clew proper does not grow in diameter. Therefore, we are of theopinion that a more frequent occurrence and larger size of the capsule is associated with local changes in the organ (especially with hypertrophy of the connective tissue). We observed no differences due to age either in the occurrence of the individual types or in the thickness of the capsule. Great individual variability in both directions was seen. The findings corroborated again the rare occurrence of meissner's endings in the labia minora in woman. Therefore it may be assumed that it is rather a random finding and that it is a type of clew-like nerve ending. Finally, we presume that the individually varying rate of occurrence of the nerve endings in the external genitals could also affect general sensitivity in this region, including sexual sensitivity.     

Specificity of membrane specializations in mechanoreceptors of birds—A freeze-etching study

The detailed knowledge of the molecular process of mechanotransduction is still an unsolved question. The investigation of the intramembranous structure of the cutaneous mechanoreceptors may play an important role in elucidating this problem. In this relation, Herbst sensory corpuscles in ducks were studied for the first time using the freeze-etching and thin sectioning techniques. Herbst corpuscles have the basic structural components valid for most of the encapsulated mechanoreceptors in mammals: a capsule made of perineural cells, a lamellar complex of modified Schwann cells, surrounding the non-myelinated part of the receptor nerve fiber and its ending. Freeze-etching replicas reveal that the plasmalemmae of the capsule cells, modified Schwann cells and axolemmae of parts of the nerve fiber differ in both density and pattern of distribution of intramembranous particles (IMPs) as well as IMP size. On all the plasmalemmae the IMP density is higher on the P-face (2000–3300?µm^?2) than the respective E-face (800–1500?µm^?2). The axolemma of the ending of the receptor nerve fiber expresses higher density of IMPs than its shaft. The mean IMP size for all the plasmalemmae varies between 5.5 and 7.5?nm. Many tight junctions occur between the capsule cells. These results indicate that the non-myelinated axolemma as well as the plasmalemmae of other components of Herbst corpuscles are specialized in terms of content and distribution of IMPs. The IMPs may represent various kinds of mechanosensitive channel proteins or related membrane-bound proteins participating in the process of mechanotransduction.     

Developmental origin of the Herbst cutaneous sensory corpuscle. Experimental analysis using cellualr markers

The development of Herbst cutaneous sensory corpuscles can be obtained in homoplastic and xenoplastic associations of frontal bud and sensory ganglion between different species of birds. Two different techniques of cellular marking were used in the present investigation: (1) Labeling of all cells of one of the components of the association by tritiated thymidine and histoautoradiographic analysis. (2) Xenoplastic recombinations of frontal bud and sensory ganglion between the quail and the duck and between the quail and the chick, and characterization of the origin of the cells by Feulgen staining of the characteristic large-sized nuclear granule of the quail.From a study of the constitution of the chimeric Herbst corpuscles found in the grafts the following findings emerged: (a) The vast majority of the inner bulb cells—if not all of them (which are located along the axial nerve ending) as well as probably some cells of the inner space originate from cells that accompany the nerve during its outgrowth. These cells are present in the spinal ganglion and in the Gasserian ganglion of 5- to 7-day embryos. (b) All other cell categories of corpuscle, namely the capsular cells and the majority of the inner space cells, are provided by the dermal mesenchyme.These results are discussed in relation with what is known about the origin of the various categories of cells in the sheaths of peripheral nerves.     

Degeneration and regeneration of some mechanoreceptors. An ultrastructural study. III. Ultrastructure of reinnervated Herbst corpuscles

The ultrastructure of reinnervated Herbst corpuscles shows that the regenerating nerve branches appear in the inner zone of the receptors at the end of the first month after nerve crush. The nerve branches are accompanied by the Schwann receptor cells. Two periods of regeneration can be established. During the first period the changes reflect mainly the quantitative relations between the regenerating nerve branches and the Schwann receptor cells, whereas during the second period the intracytoplasmic and intraaxoplasmic renewal of the organelles take place. The final regeneration of the receptors finishes at the end of the fifth month after nerve crush and one month later after nerve transection. Also, after transection the number of reinnervated receptors is less encountered.     

Fine Structure of the Adrenocortical Homolog and the Corpuscles of Stannius of Amia calva L.

A comparison is made between the fine structure of yellow corpuscles and white corpuscles located within the kidneys of the holostean fish, Amia calva L. The yellow corpuscles are composed of epithelial cells possessing all the features of steroid-producing tissues, namely an abundance of vacuoles, tubular smooth endoplasmic reticulum, and mitochondria with tubular cristae. The Golgi apparatus is also a conspicuous component of their cytoplasm. These cells are homologous to adrenocortical cells of higher vertebrates and they have cytoplasmic projections which extend into the lumina of surrounding sinusoids. The white corpuscles possess epithelial cells of variable appearance but all cells contain secretory granules and an extensive rough endoplasmic reticulum. The secretory granules appear to originate at the Golgi apparatus and occasionally are observed intact in the intercellular space. However the method of release of these granules was not clearly defined. These corpuscles are similar to the corpuscles of Stannius which have been described in modern bony fish. The presence of multivesicular bodies and smooth endoplasmic reticulum in some cells may reflect the origin of the corpuscles of Stannius from the tubular nephron. A. calva appears to be a suitable organism for comparative studies into the function of the adrenocortical homolog and corpuscles of Stannius in “primitive” fish.     

Ultrastructural and carbohydrate histochemical study of the Vater-Pacini corpuscles in the digital pads of the North American raccoon (<Emphasis Type="Italic">Procyon lotor</Emphasis>), with special regard to basic function

Numerous and very large Vater-Pacini corpuscles were observed in the forefoot digital pads of the North American raccoon (Procyon lotor). In addition to ultrastructure, the distribution and selectivity of complex glycoconjugates in this sensory corpuscle type were examined by carbohydrate histochemical techniques, in particular lectin histochemistry. The Vater-Pacini corpuscles present showed the typical lamellar structure known for mammals and contained high amounts of neutral and acidic glycoconjugates with various saccharide residues (α-l-fucose, β-d-galactose, sialic acid) in a specific intracorpuscular distribution pattern, including variations between the outer lamellae and the inner core. The results obtained are discussed with regard to possible functions of the Vater-Pacini corpuscles found in the raccoon forefoot pads. The corpuscular glycoconjugate components may furnish a high and differentiated viscoelasticity for rapid pressure transmission within the large Vater-Pacini corpuscles. Thus, the digital pads of the forepaws can be considered as part of a specific mechanoreceptor system related to excellent object manipulation properties in this mammalian species.     

A re-evaluation of the cytology of cat Pacinian corpuscles

Summary The ultrastructure of cat mesenteric Pacinian corpuscles in cross and longitudinal sections has been examined. The terminal ends of lamellar cells of the inner core have been identified in longitudinal sections through the proximal portion of the inner core. These terminal bulbous expansions contain characteristic concentric membranes of rough endoplasmic reticulum and in some cases masses of oval membranous inclusions. The central axon as seen in cross section is oval in profile, having X-(short) and Y-(long) axes, and each axonal face is characterized by specializations of the axolemma. At the X-axis, the inner lamellae of the inner core tightly abut a smooth axolemma, with no intervening connective tissue matrix, in a manner reminiscent of a neuroepithelium. The axolemma of the Y-axis has numerous axonal spines (microspikes) that project into the cleft in the inner core. The extent of the axolemma having axonal spines can only be appreciated in longitudinal sections. The clefts contain a specialized connective tissue with elastic and collagen fibrils. The connective tissue compartment of fibers and matrix separating individual inner core lamellae is unique, in that it contains extremely thin collagen fibrils measuring approximately 15 nm in diameter. The diameter of collagen fibrils increases as the cleft is approached. Here the fibrils resemble typical endoneural collagen.     

The corpuscles of Stannius in arawana (Osteoglossum bicirrhosum), an ancient teleost

The corpuscles of Stannius of arawana (Osteoglossum bicirrhosum), an ancient teleost, were examined by routine light and electron microscopy and following their immunoreactivity to salmon and trout stanniocalcin antisera. Periodic acid-Schiff positive cells of the corpuscles of Stannius had a follicular arrangement and demonstrated a strong immunohistochemical reaction with both stanniocalcin antisera. Fine structural analysis of the paired, posteriorly located, and perirenal ovoid glands revealed two morphologically distinct cell types the basal laminae of which were ramified by nerve terminals. Immunocytochemistry demonstrated that osmiophilic secretory granules in both cell types were immunoreactive to the stanniocalcin antisera. When extracts of arawana corpuscles of Stannius were subjected to sodium dodecyl sulphate electrophoresis and Western blot analysis a diffuse molecular weight band was evident ( approximately 68 kDa) in the non-reduced condition. In all cases, immunoreactivity was abolished by preabsorption of the antisera with salmon stanniocalcin or with a crude extract of arawana corpuscles of Stannius. The corpuscles of Stannius of arawana are similar to those in more recent teleosts with respect to cell structure and their anatomical distribution but their stanniocalcin is more similar in molecular weight to that present in at least one other non-teleost actinopterygian (the gar) which has an ancient lineage.     

A morphological study of the peri- and epineurium in the compression zone of the median nerve in carpal tunnel syndrome

The structure of the peri- and epineurium of the median nerve in the carpal tunnel syndrome was studied by light and transmission electron microscopy. Electron microscopy confirms the flattened lamellar arrangement of the perineurial cells, but in contrast to the normal architecture the perineurial component of the median nerve in carpal tunnel syndrome consists of 20-25 layers of ramified squamous-type cells, each layer being separated from the adjacent one by a wide space containing thick bundles of collagen fibrils. The perineurial cells are bounded on both sides by a basement membrane which is of substantial thickness. A prominent feature is the occurrence of multiple pinocytotic vesicles and caveolae opening on both the internal and external aspects of the flattened cells. They also contain bundles of closely aggregated filaments. In the spaces between the perineurial cells we find, in some places, extremely disoriented and individually abnormal fibrils and fine filaments arranged in form of a spider web. Matrix vesicles can also be seen. The epineurium of the median nerve in the carpal tunnel syndrome is also considerably thickened, and the attachment is solid, so that the median nerve is relatively immobile constricted like an hourglass. The thick collagen fibers are orientated predominantly parallel to the axis of the nerve, but circular fibers can also be seen. Apart from fibroblasts, the outer layer of the epineurium contains mast cells and vasa nervorum as well as myelinated nervi nervorum. Variable quantities of fat are also present, particularly in the surrounding loose connective tissue.