Different intrafusal fiber composition of spindles in sheep and pig extraocular muscles.

Histochemical profiles of intrafusal fibers have been examined in muscle spindles of extraocular muscles of sheep and pig. Results show that in the sheep the intrafusal content presents, in addition to chain fibers, at least one bag1 and one bag2 fiber, whereas in the pig almost all the spindles are one-bag-fiber [corrected] spindles.

Nerve endings in palm skin grafts.

We examined regeneration of Meissner corpuscles in palm skin grafts. In only one of the specimens (split-thickness skin graft from the sole of the foot), numerous regenerated Meissner corpuscles were found in the dermal papilla. This suggests that the nerve pattern of the graft depends on reinnervation from the recipient site and the regeneration of encapsulated nerve endings contained in the graft. It is recommended that skin grafts containing the encapsulated nerve endings be used in digits to obtain a satisfactory recovery of the sensory function.

Immunohistochemical study of Pacinian corpuscles using monoclonal antibodies for neurofilament protein, glial fibrillary acidic protein and S-100 protein.

The presence of neurofilament protein (NFP), glial fibrillary acidic protein (GFAP) and S-100 protein has been investigated in Pacinian corpuscles from cat's mesentery by means of immunohistochemical methods. The NFP-like positivity was found in the central axon of the corpuscles; the GFAP- and S-100 protein-like immunoreactivities were shown in the innermost layers of the differentiated cell of the inner core. No positive reaction was detected in the capsule. The authors discuss these findings.

Nasal 'flow' receptors of the rat.

This study was performed to identify trigeminal nasal 'flow' receptors and to investigate their firing characteristics. For this purpose, single unit afferent activity was recorded from the anterior ethmoidal nerve in anesthetized rats breathing through the nose or a tracheostomy. In fourteen rats breathing through the nose, 40 of 73 endings tested were identified as 'flow' receptors for the following characteristics: their spontaneous activity had an inspiratory modulation that disappeared during nasal occlusions, they were markedly stimulated by exposure to cold air and inhibited by warm air. In eleven rats breathing through a tracheostomy, 85 endings were identified as 'flow' receptors being stimulated by a constant nasal airflow (100-300 ml/min) with room air (22-26 degrees C) or cold air (0-15 degrees C), but inhibited with warm air (30-45 degrees C). Fifty-five 'flow' receptors (Type R1 and R2) exhibited a dynamic response to the constant airflow, while the other 30 receptors (Type S) showed a static response. A large proportion of 'flow' receptors (more than 52%) were responsive to tactile stimuli. For all the flow receptors, a decrease in intranasal temperature was the primary factor to excite them. These results suggest that the trigeminal nerve has a number of 'flow' receptors which operate as thermoreceptors.

Localization of mechanoreceptors in the protozoan, Stentor coeruleus.

Mechanoreceptor channels were localized by using the ligands, tubocurarine (TC), decamethonium (Deca), and gallamine (Gall), which have been shown to bind specifically to these channels. The binding of radioactively labeled TC (TC*) was found to be directly proportional to the cell surface area suggesting that the channels are uniformly distributed over the cell surface. Intracellular TC and Gall injections did not depress mechanical stimulus sensitivity though these drugs did depress sensitivity when applied extracellularly at the same concentrations; therefore, the ligand binding sites are on or near the external surface of the cell. Autoradiographs revealed that radioactively labeled Deca (Deca*) bound to the pigmented stripes but not to the ciliary stripes or membranellar band. Further, Stentor induced to shed their membranellar band through exposure to 8% urea were more sensitive to mechanical stimuli than were controls; therefore, the membranellar cilia do not appear to contain mechanoreceptor channels. Collectively, these data indicate that the mechanoreceptor channels are located in the somatic surface covering the pigmented stripes. The density of mechanoreceptor channels in the plasma membrane covering the somatic surface is tentatively estimated to be between 5500 and 14,500 microns-2 based on the density of TC* binding, the apparent number of TC molecules binding per mechanoreceptor channel, and data suggesting that only one fifth to one fourth of the bound TC* is bound to structures in the plasma membrane.

Membrane heterogeneity in sensory receptors of rat vibrissae: Merkel receptors differ from other nerve endings.

The cupric/ferrocyanide reaction was used to analyse cation-binding sites in rat vibrissae. The heminode of the last myelinated segment had moderate staining. No staining of any complex receptor was found except for Merkel receptors. Both the Merkel cell and associated nerve ending were stained except for their apposed cell membranes, suggesting either reciprocal membrane specialization at that site, or prevention of cupric/ferrocyanide penetration into the space between the two cells.

Calcitonin gene-related peptide- and substance P-immunoreactive nerve fibers in Meissner's corpuscles of rats: an immunohistochemical analysis.

The present study demonstrates that about 15% of the Meissner's corpuscles (MCs) of the rat glabrous skin of the feet contain one to two fibers immunoreactive for calcitonin gene-related peptide (CGRP), and that these fibers originate from the dorsal root ganglion. Double immunofluorescent cytochemical investigation has revealed that almost all the CGRP-immunoreactive (CGRPI) fibers in the MCs were immunoreactive for substance P. Subsequent immunoelectron microscopic analysis has demonstrated that the CGRPI fibers in the MCs are unmyelinated. In the course of passage through the MCs, no synaptic contact between the CGRPI fibers and underlying cells or non-CGRPI fibers was found.

Localization of proprioceptive neurons innervating the muscle spindles of pig extraocular muscles studied by horseradish peroxidase labelling.

Each muscle of the extraocular muscles, containing abundant muscle spindles, was exposed to horseradish peroxidase (HRP) on 8 young pigs (2-month-old, 20-30 kg in body weight, both sexes). The results obtained are follows: The HRP-labelled neurons innervating the superior rectus muscle were always found in a crescent ventro-medio-dorsal fashion in the most medial position of the contralateral oculomotor nucleus. The HRP-labelled cells for the medial rectus muscle appeared close to the superior rectus group in the ipsilateral nucleus. The labelled cells for the inferior rectus muscle appeared in the ventrolateral position of the ipsilateral nucleus and those for the inferior oblique muscle in the area between the medial rectus and inferior rectus muscle groups. The labelled cells for the superior oblique muscle were found in the contralateral trochlear nucleus and those for the lateral rectus muscle bilaterally in the abducens nuclei, predominantly on the ipsilateral side and poorly on the contralateral side. The HRP-labelled cells were composed of large (alpha) and small (gamma) multipolar cells and of bipolar, oval or round (proprioceptive) cells, all intermingled together within the nucleus. The bipolar cells have been also identified in the 3 nuclei by means of Nissl staining technique. On this basis, they should be considered as the proprioceptive neurons. In the shrew-moles, the cell bodies of the proprioceptive neurons innervating the snout muscle spindles have been found close to the ipsilateral glossopharyngeal ganglion and those of the somatic sensory neurons in the ipsilateral trigeminal ganglion. In the pigs, no HRP-labelled cells were found in the trigeminal mesencephalic tract nucleus, but the HRP-labelled cells were found in the ipsilateral trigeminal and the superior cervical sympathetic ganglia. From the results, it could be emphasized that the proprioceptive neurons innervating the pig extraocular muscle spindles are located within the nuclei of the IIIrd, IVth and VIth cranial nerves.

Immunocytochemical evidence for the GABAergic innervation of the stretch receptor neurons in crayfish.

The GABAergic innervation of the stretch receptor neurons of the crayfish Orconectes limosus has been investigated by means of light- and electron microscope immunocytochemistry using an antibody to GABA. Both whole-mount preparations and post-embedding semithin sections revealed a massive GABAergic innervation of both the slowly and the fast adapting receptor neurons. The stretch receptor organ is supplied by one principle GABA-immunoreactive axon, which gives off several branches that innervate the receptor neurons. Cell body, initial axon segment and dendritic region of the sensory neurons are covered by numerous GABA-immunoreactive varicose fibers. Electron microscopy revealed that the GABA-immunoreactive varicosities establish specialized synaptic contacts with the sensory neurons. The functional significance of the occurrence of GABA-immunoreactive varicosities on the different parts of the sensory neurons is discussed. The results support the physiological and pharmacological evidence that GABA is a transmitter substance of the efferent inhibitory neurons which innervate the crayfish stretch receptor neurons.

Location-dependent characteristics of pulmonary stretch receptor activity in the rabbit.

In anaesthetized, thoracotomized and artificially ventilated rabbits, the location of pulmonary stretch receptors (SR) was established by means of local mechanical stimulation as well as by micro-injections of the local anaesthetic cinchocaine. Differences in SR activity were analyzed in relation to the receptor site during specific stimulation by lung inflation, as well as during nonspecific activation by ammonia inhalation. Out of 107 SR, 55% were located in larger airways, i.e., in the trachea, main bronchus and lobar bronchi ("central SR"), whereas 45% were found to lie more peripherally ("peripheral SR"). There were several differences with respect to the discharge pattern evoked by lung inflation and by ammonia inhalation between SR of different locations. The increase of discharge rate evoked by lung inflation and by ammonia inhalation was significantly greater in peripheral than in central SR. Significantly more central than peripheral SR discharged throughout the whole respiratory cycle, i.e., even at end-expiratory lung volume. Furthermore, a delayed inspiratory recruitment as well as a transient cessation of firing after the initial increase of activity, which followed ammonia inhalation, occurred more frequently in central than in peripheral SR.

Mechanoreceptive neurons in an insect brain.

Staining deutocerebral nerves in locusts with cobalt chloride revealed a connective tissue strand innervated by the first side branch of the nervus scapalis medialis. The strand spans the joint between the basal segment of the antenna (scapus) and the head capsule (tentorium), parallel to the levator scapi muscle. It is shortest with the antenna completely elevated and becomes stretched during depression. The four to five neurons innervating the strand near its distal insertion are activated by mechanical stimuli such as direct elongation of the strand or depression of the antenna. As revealed by centripetal staining these neurons have their central arborizations in the posterior deutocerebrum, but their perikarya are located in the protocerebrum, close to the pars intercerebralis and the central body. These morphological and physiological characteristics identify the structure as a mechanoreceptive sense organ of the strand receptor class.

Single unit sensory activity in free walking crabs: force sensitive mechanoreceptors of the dactyl.

Activities of individual, force-sensitive mechanoreceptors (funnel canal organs) of the terminal segment (dactyl) of the crab leg have been recorded in freely moving animals. During the stance phase of walking receptors discharge in regular bursts that are closely correlated with activity of the opener muscle of the propodite when the leg is used on the trailing side in lateral locomotion. Individual funnel canal organs also show sustained discharges to imposed cuticular strains and strains resulting from resisted muscle contractions. These receptors thus can monitor both internal and external forces that are applied to the leg in locomotion.

Comparison by electrophoresis of proteins characteristic of the lateral line and skin of Xenopus laevis.

In experiments aimed at determining acousticolateralis marker proteins, fractions of lateral-line organs and skin of Xenopus laevis were analyzed by one- and two-dimensional polyacrylamide-gel electrophoresis. A protein fraction of approximately 44K mol. wt (K = 1000 daltons) and isoelectric pH 6.3, consisting of at least two components, was enhanced in lateral-line neuromast tissue (containing hair cells) and was decreased in tactile organs and skin (lacking hair cells). This "neuromast-marker-protein" fraction had a mol. wt close to that of actin but was shown to be different from actin. Two other major proteins, at mol. wts 16 and 28K, were present in gels of skin and absent in gels of lateral-line tissue. These proteins were shown to be due to secretion of the amphibian granular glands and were designated "negative marker proteins".

Tactile-like corpuscles in neurofibromas: immunohistochemical demonstration of S-100 protein.

Tactile-like corpuscles in neurofibroma tissues were examined by the indirect immunoperoxidase method using rabbit anti-S-100 sera. In all five cases examined, positive staining was observed in their constituent cells, both in the flattened cytoplasm and nuclei. On examination of the normal peripheral nervous system, positive staining was exclusively confined to Schwann cells in the nerve bundles and Schwann-related cells such as lamellar cells in the Meissner corpuscle, whereas staining was negative in perineurial cells. Electron-microscopic examination showed ultrastructural similarity between constituent cells of the tactile-like corpuscles in neurofibroma and lamellar cells in the Meissner corpuscle. These findings may indicate Schwannian nature of the tactile-like corpuscles.

[Water-soluble proteins of Pacinian corpuscles]. / Vodorastvorimye belki telets Pachini.

The composition of water soluble proteins has been investigated in different parts of Pacinian corpuscles. The Pacinian corpuscles fluid proteins have been compared with the receptor homogenate proteins and blood serum of a cat. It is supposed that proteins of the Pacinian corpuscle fluid are produced from the blood system on the whole. The composition of the Pacinian corpuscle fluid as well as a great variety of glycoproteins in it allows to suppose that the Pacinian corpuscles fluid perform a transport function.

[Characteristics of soluble proteins of Pacinian corpuscles]. / Nekotorye kharakteristiki rastvorimykh belkov telets Pachini.

The paper describes some characteristics of water- and salt-soluble proteins from tissue mechanoreceptors (Pacini's corpuscles). The proteins were divided into fractions with different molecular weights with a purpose of determining fraction wise the content of nucleotides and protein-carbohydrate complexes. Possibilities of performing metabolic functions by soluble proteins and of creating a specific tissue mechanoreceptor microenvironment are discussed.

Magnets in guitarfish vestibular receptors.

Black magnetic particles are intermixed with white crystalline otoconia in the inner ear gravity receptors of a saltwater ray. Their size and composition suggest that they are multidomains of magnetite-ilmenite.

Ultrahistochemical demonstration of cations in the guinea pig organ of Corti.

The distribution of cations in the guinea pig organ of CORTI was studied by means of the ultrahistochemical pyroantimonate method. In the outer hair cells precipitates were localized at the cell membrane, at stereocilia, in the subplasmalemmal cisterns, in the the nucleus, in mitochondria and within the ground plasm. Coarse precipitates at the cell membrane may consist mainly of cations other than calcium ions. The subplasmalemmal cisterns are suggested to sequester cations in the outer hair cells. The mechanism of the trapping reaction and factors injuring this histochemical method are discussed.