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PubMed1998

Calretinin-immunoreactive laminar nerve endings in the laryngeal mucosa of the rat.

The distribution of laminar nerve endings that contained immunoreactive calretinin was examined in the laryngeal mucosa of the adult rat. In whole-mount preparations, the immunoreactive laminar endings were distributed in the supraglottic region but not in the subglottic region. The laminar endings that arose from thick nerve fibers with or without swellings were identified as corpuscles with many variform terminal arborizations. They appeared to be located at the interface between the epithelium and the subepithelial connective tissue. The terminals were scattered under the basal lamina of the epithelium, and some of them were located within the epithelial layer. Immunoelectron microscopy revealed that both sub- and intraepithelial immunoreactive terminals that were filled with mitochondria were partly or totally ensheathed by Schwann cell processes. The denervation experiments, in which the superior laryngeal nerve was cut unilaterally or bilaterally, suggested that the laminar endings originate from the superior laryngeal nerve with strict ipsilateral innervation. The laminar endings might be associated with detection of changes in pressure in the laryngeal cavity or chemical stimuli.

Animals↗
PubMed1998

Effects of glutamate-induced excitotoxicity on calretinin-expressing neuron populations in the area postrema of the rat.

We mapped the distribution of calretinin-immunoreactive neuron populations in a circumventricular organ of the rat, the area postrema, and investigated their sensitivity to excitotoxic stimuli mediated by subcutaneously administered monosodium glutamate. We were specifically interested to ascertain whether the presence of calretinin can, per se, confer an in vivo intrinsic resistance for area postrema neurons to glutamate excitotoxicity. We found that dense populations of calretinin-positive neurons displayed a subregional compartmentation in coronal sections of the area postrema along its rostrocaudal axis. We demonstrated that calretinin-positive neurons differ in their sensitivities to monosodium glutamate depending on their position within the area postrema. Neurons in the caudal area postrema were the most sensitive ones, while those in the rostral area postrema were spared of degeneration. We conclude that calretinin-positive neurons in the area postrema are not uniformly protected against glutamate excitotoxicity. It is possible that differences in the local concentrations of monosodium glutamate due to regional heterogeneities in density and permeability of the capillary bed rather than neuronal expression of calretinin account for the observed effects.

Animals↗
PubMed1998

Enkephalin-immunoreactive subpopulations in the myenteric plexus of the guinea-pig fundus project primarily to the muscle and not to the mucosa.

Enkephalin (ENK) immunoreactivity was localised in different neuronal subpopulations of the myenteric plexus in the guinea-pig gastric fundus using immunohistochemistry for neurone-specific enolase (NSE), ENK, choline acetyltransferase (ChAT), substance P (SP), neuropeptide Y (NPY), calretinin (CALRET), and somatostatin (SOM). NADPH-diaphorase staining was used to label nitric oxide synthase (NOS)-containing neurones. ENK was observed in 44% of the myenteric neurones. The major ENK-positive subpopulations were ChAT/ENK (35% of ENK-positive neurones), ChAT/SP/ENK (26%), NOS/NPY/ENK (22%) and ChAT/SP/ENK/CALRET (9%). The projection pathways of these ENK-positive subpopulations to the circular muscle and the mucosa were determined using retrograde labelling with DiI in organ culture followed by immunohistochemistry. Of myenteric neurones retrogradely labelled from the mucosa and the circular muscle, 13% and 48% exhibited ENK immunoreactivity, respectively. Three major ENK-positive subpopulations innervating the mucosa or circular muscle were identified: ascending ChAT/SP/ENK (7% of all mucosa neurones; 24% of all circular muscle neurones), ascending ChAT/ENK (4%; 15%) and descending NOS/NPY/ENK (1%; 8%) neurones. Only very few CALRET- or SOM-positive neurones projected to the mucosa or circular muscle. ChAT/SP/ENK and ChAT/ENK neurones might function as ascending excitatory muscle motor neurones, whereas NOS/NPY/ENK neurones are most likely descending inhibitory muscle motor neurones. The relatively few ENK-positive mucosa neurones do not favour a major involvement of ENK-positive myenteric neurones in the control of gastric mucosa activity.

Animals↗
PubMed1999

Functional anatomy of the photoreceptor and second-order cell mosaics in the retina of Xenopus laevis.

Mosaics of photoreceptors, and horizontal and bipolar cells of the Xenopus laevis retina were studied in whole-mount preparations applying lectin-cytochemical, immunocytochemical and intracellular labeling techniques. The combined density of all photoreceptor types was about 13700/mm2, of which rods represented 53%. Of the cones, the large long-wavelength-sensitive (86% of all cones) and the miniature ultraviolet-wavelength-sensitive (4%) ones could be labeled with peanut agglutinin, whereas the large short-wavelength-sensitive (10%) cones remained unlabeled. There were no significant regional differences in photoreceptor distribution. Bipolar cells were selectively labeled with antibodies against calretinin. Their density was between 4000 and 6000 cells/cm2, with slightly elevated numbers in the superior nasal quadrant. Two types of horizontal cell were injected intracellularly. The luminosity-type cells were more frequent (approximately 1000 cells/mm2) than the chromaticity cells (approximately 450 cells/mm2). The dendritic field size of the latter cell type was threefold bigger than that of the luminosity cells. The coverage factors were estimated to be 3.3 for the luminosity cells and 5.2 for the chromaticity cells. The luminosity cells contacted all photoreceptor types, whereas chromatic horizontal cells received their inputs from the short-wavelength-sensitive cones and from some, but not all, rods. Luminosity cells encounter about 50-60 potential synaptic partners within their dendritic fields, whereas chromatic horizontal cells only about 20. Chromatic horizontal cells form multiple synaptic contacts with the short-wavelength-sensitive cones. The results indicate that the overall photoreceptor to bipolar and bipolar to ganglion cell convergence in Xenopus retina is similar to that in the central retinal specialized regions of mammals, predicting comparable spatial resolutions.

Animals↗
PubMed1999

Calretinin-immunoreactive nerves in the uterus, pelvic autonomic ganglia, lumbosacral dorsal root ganglia and lumbosacral spinal cord.

Nerves containing the calcium-binding protein calretinin have been reported in several organs but not in female reproductive organs and associated ganglia. This study was undertaken to determine if nerves associated with the uterus contain calretinin and the source(s) of calretinin-synthesizing nerves in the rat (are they sensory, efferent, or both?). Calretinin-immunoreactive nerves were present in the uterine horns and cervix where they were associated with arteries, uterine smooth muscle, glands, and the epithelium. Calretinin-immunoreactive terminals were apposed to neurons in the paracervical ganglia; in addition, some postganglionic neurons in this ganglion were calretinin positive. Calretinin perikarya were present in the lumbosacral dorsal root ganglia, no-dose ganglia, and lumbosacral spinal cord. Retrograde axonal tracing, utilizing Fluorogold injected into the uterus or paracervical parasympathetic ganglia, revealed calretinin-positive/Fluorogold-labeled neurons in the dorsal root and nodose ganglia. Also, capsaicin treatment substantially reduced the calretinin-positive fibers in the uterus and pelvic ganglia, thus indicating the sensory nature of these fibers. The presence of calretinin immunoreactivity identifies a subset of nerves that are involved in innervation of the pelvic viscera and have origins from lumbosacral dorsal root ganglia and vagal nodose ganglia. Though the exact function of calretinin in these nerves is not currently known, calretinin is likely to play a role in calcium regulation and their function.

Animals↗
PubMed2000

First appearance and distribution of calretinin-immunoreactive neurons in the early development of the chick central nervous system.

Silver impregnation studies in chick embryos have shown that, by the 2nd day of incubation, the earliest neurofibrillar differentiation occurred in neuroblasts located at the diencephalic-mesencephalic junction and in the rhombencephalon; some of these neuroblasts were believed to become reticular neurons. Since calretinin, a cytosolic calcium-binding protein of the "E-F hand" family, occurs in reticular neurons, the present study investigated immunohistochemically whether the early differentiating reticular neurons are also the first neurons to express this marker during chick embryo development. The first calretinin-immunoreactive neuroblasts appeared at stage 11 (40-45 h of incubation according to the series of Hamburger and Hamilton), and were located in the basal plate of the diencephalic-mesencephalic junction and of rhombomeres adjacent to the otic placode and in the alar plate and intermediate zone of the cervical spinal cord. In bromodeoxyuridine-injected embryos, these earliest calretinin-immunoreactive neurons were shown to express the calcium-binding protein 11-16 h after their last mitosis. By stage 11 up to the 14th day of incubation (stage 40), the calretinin-immunostained neurons increased in number and ultimately formed a chemically defined subset of neurons belonging to the tegmental reticular formation and raphe region of the brainstem. In the meantime, early calretinin-immunostained nerve processes were shown to form two conspicuous longitudinal bundles which run in the ventral and lateral margins of the brainstem and spinal cord.

Animals↗
PubMed1991

Calretinin-immunoreactivity in vagal and glossopharyngeal sensory neurons of the rat: distribution and coexistence with putative transmitter agents.

Immunoreactivity for the calcium binding protein, calretinin (calretinin-ir), was demonstrated in cell bodies of vagal and glossopharyngeal sensory ganglia (jugular, petrosal, and nodose ganglia) and in associated nerve fibers. In the jugular and petrosal ganglia, many calretinin-ir neurons were also immunoreactive for calcitonin gene-related peptide and substance P. In the nodose ganglion, most of the calretinin-ir neurons lacked these peptides. None of the calretinin-ir neurons in these ganglia were also immunoreactive for tyrosine hydroxylase.

Animals↗
PubMed1991

Identification and ultrastructural localization of a calretinin-like calcium-binding protein (protein 10) in the guinea pig and rat inner ear.

Calretinin has been identified as a brain specific calcium-binding protein which appears as a prominent protein in the cochlear nucleus. We identified and localized calretinin in the guinea pig and rat inner ear using polyclonal antibodies. Immunoblot analyses of guinea pig and rat auditory nerve homogenates revealed an immunoreactive band migrating with the same molecular weight as the purified protein, at Mr = 29 k. Immunocytochemistry was carried out at the light and electron microscope levels. In the guinea pig cochlea, inner hair cells, Deiters' cells, Hensen's cells and interdental cells of the spiral limbus were stained. Most of the cochlear ganglion cells were immunostained. In the guinea pig vestibular organs, the staining was exclusively neuronal and localized in large nerve fibers and nerve calices of the apex of the cristae. Only some vestibular ganglion cells were stained. In the rat cochlea, inner hair cells and most of the ganglion neurons were immunoreactive. In the rat vestibule, large nerve fibers and calices were stained as were some type II hairs cells. Only some vestibular ganglion cells were reactive. Electron microscopic observations of immunostained guinea pig cochlea and vestibule showed that the staining was cytosolic. In addition, specific sub-localization was also found in the apical portion of the nerve calices in association with microvesicles. These results describe the discrete localization of calretinin in the cochlea and in the vestibular receptors and suggest a function associated with biochemical regulations at the level of microvesicles in vestibular afferent neurons.

Animals↗
PubMed1992

Calretinin-immunoreactive neurons in the primary visual cortex of dolphin and human brains.

A new class of gamma-aminobutyric acid (GABA)ergic neurons immunoreactive to the calcium-binding protein calretinin (CR) was demonstrated in primary visual cortices of the bottlenose dolphin (Tursiops truncatus) and humans (Homo sapiens). Comparative analysis revealed several differences between dolphin and human visual cortex in the laminar distribution of CR-positive perikarya, although general typology of the immunoreactive CR-positive neurons was similar in both species. Thus, in both human and dolphin primary visual cortex almost all CR-positive neurons are non-pyramidal, either fusiform or bipolar cells, oriented with their long axis along the radial axis of the cortex. Large multipolar stellate cells were also observed in layers I and VI. The CR-positive neurons in the dolphin visual cortex are concentrated almost exclusively in layer I and, to a lesser extent, in layer II. In all other layers (IIIa, b, IIIc/V and VI) of the dolphin visual cortex CR-positive neurons were only rarely seen. In the human primary visual cortex CR-positive neurons are located mainly in layers II, III and IVa, b, c, with considerably lower densities of these cells observed in layers V and VI. CR-positive neurons in layer I of the human visual cortex are represented by Cajal-Retzius horizontal cells, whereas no such cells were seen in layer I of the dolphin neocortex. The numerical density of CR-positive neurons in the dolphin primary visual cortex is significantly lower than in the area of cortex in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Immunohistochemical localization of calretinin in the rat lateral geniculate nucleus and its retino-geniculate projection.

In the present study, we examined the distribution of calretinin-immunoreactive neuronal cell bodies and fibers in the lateral geniculate nucleus of the rat. In normal rats, clusters of immunoreactive cell bodies were found in: (i) the rostral portion of the ventral lateral geniculate nucleus pars medialis (VLGM), (ii) the intergeniculate leaflet (IGL), (iii) the intermediate region between the VLGM and the ventral lateral geniculate nucleus pars lateralis (VLGL), (iv) the caudomedial portion of the VLGM, and (v) the caudolateral portion of the VLGM. In the dorsal lateral geniculate nucleus (DLG), immunoreactive cell bodies were rarely observed. After uni- or bilateral eye enucleation, no significant alteration in the morphological features or distribution of immunoreactive cell bodies was detected in the lateral geniculate nucleus. In normal rats, immunoreactive fibers formed dense plexuses in: (i) the DLG, (ii) the external layer of the VLGL, (iii) the internal layer of the VLGL, (iv) the IGL, (v) the caudomedial portion of the VLGM, and (vi) the optic tract. After unilateral eye enucleation, immunoreactive fibers in the external layer of the VLG and in the optic tract almost totally disappeared on the contralateral side to the lesion. Unilateral eye enucleation caused a significant decrease of immunoreactive fibers in the DLG and in the internal layer of the VLGL, but a substantial number of immunoreactive fibers still remained there. In the IGL and the caudomedial portion of the VLGM, no observable alteration in the distribution of immunoreactive fibers was detected after uni- or bilateral eye enucleation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Distribution of calretinin mRNA in rat spinal cord and dorsal root ganglia: a study using non-radioactive in situ hybridization histochemistry.

Using non-radioactive in situ hybridization calretinin mRNA was detected in numerous small neurons within lamina II and IV of the dorsal horn. Many labelled cells are distributed over the whole ventral horn; however, no motoneurons contained the mRNA. In dorsal root ganglia 4.9 +/- 1.7% (mean +/- S.D., n = 5 animals) of the primary afferent neurons contained calretinin mRNA. Labelled cells were of intermediate and large size with diameters ranging from 36 to 68 microns indicating that calretinin is synthesized in neurons with myelinated afferent fibers and presumably a corpuscular ending.

Animals↗
PubMed1993

Calretinin-immunoreactive neurons in the trigeminal and dorsal root ganglia of the rat.

The cell body size of primary neurons were measured in the trigeminal (TG) and lumbar dorsal root ganglia (DRG) monochrome-stained for calretinin (CR)-like immunoreactivity. A trichrome stain for CR, carbonic anhydrase (CA) and tachykinin (TK) was also employed to estimate possible overlap of cellular distribution of these substances. In the DRG, the cell size spectrum of CR-positive cells was clearly bimodal; a greater proportion (84.1%) of CR-positive cells was distributed in the range > or = 800 microns2 with a mode between 1,500-1,600 microns2, while a smaller proportion (14.8%) < 700 microns2 with a mode of 400-500 microns2. They were evenly distributed throughout the DRG. Although CR-positive TG neurons were smaller than similar DRG neurons, a bimodal distribution pattern remained unchanged. 94.6% of CR-positive cells measured 100-1,400 microns2 with peak ranges of 200-300 microns2 and 400-500 microns2. Most of CR-positive cells in the ophthalmic division were 400 microns2 or larger and small CR-positive cells (< 400 microns2) were concentrated in the maxillary and mandibular divisions. Most of CR-positive DRG cells showed CA activity (76.5%), while those with TK-immunoreactivity were rare (7.2%). In the TG, 38.4% of CR-positive cells were TK-positive. They were mostly smaller than 800 microns2. On the other hand, CA was detected in 43.4% of CR-positive TG cells. Most of the TG cells co-expressing CR and CA were 400 microns2 or larger. Simultaneous co-expression of TK and CA by the CR-positive cells was negligible.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Ultrastructural localization of calretinin immunoreactivity in lobule V of the rat cerebellum.

Ultrastructural localization of a calcium-binding protein, calretinin, in the cerebellar cortex of the rat was examined with an immunoperoxidase method. The cerebellar lobule V was investigated in detail. In the molecular layer, calretinin immunoreactivity was found in parallel fibers and in their varicosities that formed synapses with unlabeled Purkinje cell dendritic thorns and Golgi cell dendrites. In the granular layer, most granule cells were immunostained for calretinin. Within immunostained granule cells, the labels were found in the cytoplasmic matrix of both the perikaryon and primary dendrite, and in euchromatin patches of the nucleus. Some mossy fiber terminals also stained for calretinin. In the white matter, a few axons were labeled for calretinin and surrounded by unstained myelin sheath. It is suggested that calretinin may play a role at the presynaptic sites of the parallel and mossy fiber terminals.

Animals↗
PubMed1993

Appearance of calretinin-immunoreactive neurons in the upper layers of the rat superior colliculus after eye enucleation.

The effects of retinal deafferentation on a calcium-binding protein, calretinin, in the upper layers (superficial gray layer and optic nerve layer) of the rat superior colliculus were examined. In intact rats and on the ipsilateral side of unilaterally eye-enucleated rats, the superficial gray layer and optic nerve layer contained a few dispersed calretinin-immunoreactive cells. On the contralateral side to the enucleation, the number of immunostained cells in the superficial gray layer and optic nerve layer was increased. These findings suggest that retinal deafferentation results in an increase in contents of calretinin in some cell bodies within the upper layers of the superior colliculus.

Afferent Pathways↗
PubMed1993

Calretinin-immunoreactivity in trigeminal neurons innervating the nasal mucosa of the rat.

Trigeminal primary neuronal cell bodies were labeled by retrograde transport of Fluoro-gold (FG) from the nasal mucosa of rats. The trigeminal ganglion containing the labeled cell bodies were processed for double stain for calretinin- and tachykinin-immunoreactivities (CR- and TK-irs). Except for a few contralateral cells, all the cells that innervated the nasal mucosa (NM cells) were confined to the ophthalmo-maxillary division of the trigeminal ganglion ipsilateral to the FG application. In the dorsal two-thirds of the ganglion, NM cells formed a cluster in the rostromedial part of ophthalmo-maxillary division (the rostromedial cluster). In the ventral third, the number of cells in the rostromedial cluster markedly decreased. Instead, numerous NM cells were found in the caudolateral part of the ophthalmo-maxillary division (the caudoventrolateral cluster). CR- and TK-irs were detected in 18% and 54% of overall population of NM cells, respectively. Virtually all of CR-immunoreactive (-ir) NM cells coexpressed TK. Although the proportion of TK-ir cells, irrespective of CR-ir, was similar for both clusters, CR-ir cells were more frequent in the caudoventrolateral cluster than in the rostromedial cluster. In the dorsal 1/3 of the ganglion where all the NM cells belonged to the rostromedial cluster, only 8.4% exhibited CR-ir. On the other hand, as much as 30.1% of NM cells expressed CR-ir in the ventral 1/3 where most NM cells were found in the caudoventrolateral cluster. Trigeminal cell bodies innervating the cornea and conjunctivum were located in the rostromedial part of the ophthalmo-maxillary division.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Calretinin-immunoreactive neurons are resistant to beta-amyloid toxicity in vitro.

The molecular pathways by which beta-amyloid protein (A beta) induces neurotoxicity in vitro are unknown. We report that cultured hippocampal neurons exhibiting immunoreactivity for the calcium binding protein calretinin are relatively resistant to degeneration resulting from exposure to either beta 25-35 or beta 1-42. These findings suggest that intrinsic characteristics of calretinin cells, possibly including enhanced calcium buffering capacity, underlie the resistance of these cells to A beta toxicity in vitro and perhaps similar insults in Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1994

Does the calcium binding protein calretinin protect dopaminergic neurons against degeneration in Parkinson's disease?

Parkinson's disease (PD) is characterized by a heterogeneous loss of dopaminergic neurons in the human mesencephalon affecting mainly the substantia nigra pars compacta (SNpc) and to a lesser extent the other dopaminergic cell groups. A rise in intracellular calcium concentrations represents one of the final events leading to nerve cell death. Calbindin D28k, a protein capable of buffering intracellular calcium concentrations is present in the dopaminergic neurons that are selectively preserved in PD but not in those that degenerate. To determine whether other calcium-binding proteins also represent putative protective factors of dopaminergic neurons in PD, we analyzed immunohistochemically the distribution of calretinin-containing (CR+) neurons, in the human mesencephalon of three control subjects and four patients with PD. No significant differences were observed between the number of CR+ neurons in the two subject groups. Sequential double immunostaining for calretinin and tyrosine hydroxylase showed a variable proportion of CR+ neurons among dopaminergic neurons: moderate co-localization was found in catecholaminergic cell group A8 and in the dorsal part of the ventral tegmental area (VTA) and low co-localization in the SNpc, the ventral part of the VTA and the central gray substance. This indicates that calretinin may only protect some dopaminergic neurons against degeneration in PD. Yet, in the SNpc a selective preservation of CR+ dopaminergic neurons was observed, suggesting a neuroprotective role in some dopaminergic cell groups only.

Aged↗
PubMed1994

Neural parvalbumin and calretinin in the tooth pulp.

Parvalbumin- and calretinin-immunoreactivities (CR-irs) were examined in the molar tooth pulp of the rat using immunohistochemical methods. CR-ir fibers were further classified based on the tachykinin-ir revealed by a double immunofluorescence method. The rat root pulp contained three types of nerve fibers; parvalbumin-ir smooth fibers, CR-ir (TK-negative) smooth fibers and CR-ir (TK-ir) varicose fibers. These fibers projected toward the roof of the pulp chamber and pulp horn without marked ramification. In the subodontoblastic layer at the roof of the pulp chamber and pulp horn, parvalbumin-ir smooth fibers repeatedly ramified and extended varicose terminals into the odontoblastic layer. CR-ir (TK-negative) smooth fibers reached the subodontoblastic layer without marked ramification and gave rise to varicose terminals that appeared to terminate within the subodontoblastic layer. On the other hand, CR-ir (TK-ir) varicose fibers proceeded to the subodontoblastic layer at the roof of the pulp chamber and pulp horn, where they ramified and penetrated the odontoblastic layer. The present study indicates that the rat tooth pulp contains myelinated parvalbumin-ir and CR-ir (TK-negative) fibers, and unmyelinated CR-ir (TK-ir) fibers, and that they project varicose terminals to the subodontoblastic and odontoblastic layers. The central projection sites of these sensory fibers have yet to be revealed.

Animals↗