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Calbindin-D28K-immunoreactive cells and fibres in the human amygdaloid complex.

The distribution of calbindin-D28k-immunoreactive cells and fibres in five human amygdalae was analysed from sections that had been stained immunohistochemically with a monoclonal antibody raised against calbindin-D28k. The highest density of calbindin-D28k-positive neurons were found in the anterior cortical, medial, posterior cortical and accessory basal nuclei, in the parvicellular division of the basal nucleus and in the amygdalohippocampal area. The lowest densities of immunopositive neurons were found in the paralaminar nucleus, in the periamygdaloid cortex (PAC1 and PACo) and in some of the intercalated nuclei. The deep nuclei (lateral, basal and accessory basal nuclei) contained a high density of calbindin-D28k-immunoreactive fibres and terminals. The cortical nuclei and the central nucleus were characterized by intense neuropil labelling. Morphologically, a large majority of the calbindin-D28k-immunoreactive neurons were aspiny or sparsely spiny and resembled inhibitory local circuit neurons. A small population of lightly-stained, pyramidal-shaped neurons was also observed. In most of the amygdaloid nuclei, calbindin-D28k-immunoreactive fibres travelled close to each other and formed bundles, which suggests that some of the immunostained neurons were double-bouquet cells. In the paralaminar nucleus, the calbindin-D28k-immunoreactive axons formed tortuous plexus (100-200 microns in diameter) that surrounded several unstained somata. This study provides baseline information on the morphology and distribution of calcium-binding protein-containing inhibitory cells and fibres immunoreactive for calbindin-D28k in the human amygdaloid complex. This information can be used in future studies on the pathogenesis of diseases known to damage the amygdala, such as Alzheimer's disease and temporal lobe epilepsy.

Adult↗

Parvalbumin- and calbindin D28k-immunoreactive neurons in the superficial layers of the spinal cord dorsal horn of rat.

Immunohistochemical techniques were utilized to investigate the distribution and morphology of neurons containing the calcium binding proteins parvalbumin (PV) and calbindin D28k (CaBP) in the superficial layers of rat spinal cord. Most PV-immunoreactive (PV-IR) neurons were restricted to a 25 to 60 microns thick band straddling the border between lamina II and III. Positive somata had long rostrocaudally oriented dendrites confined to narrow sagittally arranged sheets within this band and axons that entered lamina II or the superficial portions of lamina III. Long varicose axons, presumed to originate from these cells, were moderately distributed in Lissauer's tract and lamina II. CaBP-immunoreactive (CaBP-IR) neurons were found within lamina I and throughout lamina II. Large calibre PV-IR and CaBP-IR axons were seen in the dorsal column and the lateral funiculus. Dorsal rhizotomy or neonatal capsaicin treatment appeared to have no effect on PV-IR and CaBP-IR elements in the superficial lumbar dorsal horn. However, dorsal rhizotomy reduced the number of positive axons in the dorsal column and in deeper lamina of the dorsal horn. These results add to the known lamination patterns of the superficial dorsal horn and point to the existence of a lamina defined by PV-positive neurons at the lamina II/III border. These neurons may have electrophysiological characteristics attributed to PV- or CaBP-containing neurons elsewhere in the CNS.

Animals↗

Distribution of calretinin, calbindin-D28k, and parvalbumin in the rat thalamus.

The localization of three calcium-binding proteins, calretinin, calbindin-D28k, and parvalbumin, in the rat thalamus was immunohistochemically examined. a) Some thalamic regions revealed cells almost exclusively containing one of the calcium-binding proteins. For example, almost only calretinin-stained cells were found in the central medial and paraventricular nuclei. Calbindin-D28k-stained cells were mostly found in the centrolateral, interanteromedial, anteromedial, and posterior nuclei. Only parvalbumin-positive cells were found in the central part of the reticular nucleus. b) Other regions expressed overlap between the distributions of two cell components composed of different calcium-binding proteins. For example, both calretinin-stained cells and calbindin-D28k-labeled cells were found in the lateroposterior, intermediodorsal, rhomboid, and reuniens nuclei. c) Other regions showed no cells stained for any of the calcium-binding proteins. For example, generally no calcium-binding protein was detected in neurons of the anterodorsal, anteroventral, ventrolateral, ventral posterolateral, ventral posteromedial, or gelatinosus nuclei, or of the central part of the mediodorsal nucleus. These three proteins serve as useful marker for localizing subpopulations of neurons within the thalamus.

Animals↗

The chemical heterogeneity of cortical interneurons: nitric oxide synthase vs. calbindin and parvalbumin immunoreactivity in the rat.

Neurons that contain nitric oxide synthase (NOS) type I and the calcium binding proteins calbindin D28k or parvalbumin were simultaneously visualized by means of double immunohistofluorescence in the cerebral cortex of Wistar and Sprague-Dawley rats. All the three immunoreactive cell populations were primarily represented by nonpyramidal neurons. NOS-immunoreactive cells were less numerous than the calbindin- or parvalbumin-immunoreactive ones, and were intermingled with the neurons containing these calcium binding proteins. NOS-immunoreactive cells were separate from the parvalbumin-immunoreactive ones, whereas a minor proportion of them was found to be colocalized with calbindin. The cortical neurons in which NOS and calbindin coexisted were more numerous in the Sprague-Dawley than in the Wistar rats, and displayed an anteroposterior gradient of density, with the highest concentration in the medial prefrontal, frontal, and cingulate cortices. Double NOS-calbindin-immunoreactive neurons prevailed in the deep cortical layers and they were relatively numerous in the cingulate cortex. The present data indicate a selectivity in the expression of NOS vs. calbindin and parvalbumin in cortical cells, and further support the chemical heterogeneity of GABAergic interneurons in the cerebral cortex.

Animals↗

Cloning and analysis of calbindin-D28K cDNA and its expression in the central nervous system.

The vitamin D-dependent calcium-binding protein (CaBP), calbindin-D28K (CaBP28K), is present in the central nervous system (CNS), the sensory system, and kidneys of mammals and birds. Recent studies have indicated that several other CaBPs of very similar Mrs are also present in the CNS. This study was carried out to establish the relationship between CaBP28K and other CaBP, particularly spot 35, to provide a basis for further studies on the tissue-specific regulation and distribution of CaBP28K. A cloned pC28 cDNA was isolated from a rat brain expression library using synthetic oligodeoxyribonucleotides (oligos) complementary to rat spot-35 mRNA. This pC28 cDNA had an open reading frame (ORF) of 783 nucleotides (nt) coding for a 261-aa, 30-kDa protein. There was 100% homology between the pC28 sequence and that of the CaBP28K isolated from rat brain cDNA library using a chicken intestinal CaBP28K probe (Hunziker and Schrickel, 1988). Thus the aa and nt sequences of rat CaBP28K and spot 35 are identical. Primer extension studies and Northern analyses show that the major species of CaBP28K mRNA contains a 5'-untranslated region of 132 nt, a coding region of 261 codons and a 3'-untranslated region of 804 nt without the poly(A) tail. The rat CaBP28K probe hybridizes to one major RNA species (1.9 kb) and two minor ones (2.8 and 3.2 kb) in the cerebellum, hippocampus, retina and kidney. This distribution correlates well with the distribution of CaBP28K itself in these organs. Comparison of the genomic organization of the CaBP28K gene with that of other members of the 'EF-hand' CaBP family emphasizes that the CaBP28K gene diverged from the others at the first duplication of the gene encoding one CaBP domain. All the members of the 'EF-hand' gene CaBP family evolved by exon shuffling and specific genomic rearrangements.

Amino Acid Sequence↗

Up regulation of calbindin-D28K mRNA in the rat hippocampus following focal stimulation of the perforant path.

Calbindin-D28K is a constitutive Ca2(+)-binding protein expressed in hippocampal neurons that are resistant to various forms of excitotoxic injury. However, the local factors controlling calbindin-D28K expression within the central nervous system are unknown. We report that neuronal excitation via the perforant path leads to an increased expression of calbindin-D28K mRNA within dentate granule cells. This response is related specifically to stimulation that induces prolonged periods of bursting afterdischarges and precedes cellular injury. The up regulation of calbindin-D28K mRNA occurs during the type of neuronal activation associated with elevated cytosolic Ca2+ and suggests that the maintenance of Ca2+ homeostasis includes a system of feedback control at the level of gene expression.

Animals↗

Evidence for calcium-reducing and excito-protective roles for the calcium-binding protein calbindin-D28k in cultured hippocampal neurons.

Neuronal systems for calcium homeostasis are crucial for neuronal development and function and may also contribute to selective neuronal vulnerability in adverse conditions such as exposure to excitatory amino acids or anoxia, and in neurodegenerative diseases. Previous work demonstrated the presence and differential distribution of calcium-binding proteins in the CNS. We now report that a subpopulation of neurons in dissociated cell cultures of embryonic rat hippocampus expresses calbindin-D28k (Mr 28,000 calcium-binding protein) immunoreactivity and that these neurons are relatively resistant to neurotoxicity induced by either glutamate or calcium ionophore. Direct comparisons of dynamic aspects of intracellular calcium levels and calbindin-D28k immunoreactivity in the same neurons revealed that calbindin-D28k-positive neurons were better able to reduce free intracellular calcium levels than calbindin-D28k-negative neurons. These findings indicate that the differential expression of calbindin-D28k in hippocampal neurons occurs early in development and may be one determinant of selective neuronal vulnerability to excitotoxic insults.

Animals↗

Cellular targets and trophic functions of neurotrophin-3 in the developing rat hippocampus.

The expression of the neurotrophins and trk receptors in the hippocampus has directed attention toward their roles in the development and maintenance of this region. We have examined the effects of the neurotrophins NT-3, BDNF, and NGF in cultures of developing rat hippocampal cells by two criteria: rapid induction of c-fos and neurotrophic responses. The selective induction of c-fos mRNA suggests the presence of functional receptors for NT-3 and BDNF, but not NGF, in embryonic hippocampal cultures. The NT-3-responsive cells were localized in pyramidal neurons of areas CA1 through CA3 and dentate granular and hilar cells of postnatal organotypic slices, as detected by c-Fos immunocytochemistry. In addition to immediate early responses, NT-3 caused a 10-fold increase in the number of cells expressing the neuronal antigen calbindin-D28k. This increase was dose dependent, with maximal stimulation at 10 ng/ml. In contrast, BDNF elicited small but significant calbindin responses. These results indicate biological responses to NT-3 in the CNS and suggest roles for for this neurotrophin during hippocampal neurogenesis.

Animals↗

Stable transfection of calbindin-D28k into the GH3 cell line alters calcium currents and intracellular calcium homeostasis.

Previous work demonstrating the presence and differential distribution of Ca(2+)-binding proteins in the CNS has led to the proposal that cytosolic proteins, such as calbindin-D28k (CB), may play a pivotal role in neurons. We have used a retrovirus containing the full-length cDNA for CB to transfect the pituitary tumor cell line GH3, to generate CB-expressing GH3 cells and to investigate whether ionic channel activities as well as the concentration of intracellular free Ca2+ ([Ca2+]i) homeostasis could be altered by the presence of this Ca(2+)-binding protein. We show that CB-transfected GH3 cells exhibited lower Ca2+ entry through voltage-dependent Ca2+ channels and were better able to reduce [Ca2+]i transients evoked by voltage depolarizations than the wild-type parent cell line. These observations provide a mechanism by which CB may protect tissues against Ca(2+)-mediated excitotoxicity.

Animals↗

Opposing effects of ethanol and nicotine on hippocampal calbindin-D28k expression.

Long-term ethanol exposure produces multiple neuroadaptations that likely contribute to dysregulation of Ca(2+) balance and neurotoxicity during ethanol withdrawal. Conversely, nicotine exposure may reduce the neurotoxic consequences of Ca(2+) dysregulation, putatively through up-regulation of the Ca(2+)-buffering protein calbindin-D(28k). The current studies were designed to examine the extent to which 10-day ethanol exposure and withdrawal altered calbindin-D(28k) expression in rat hippocampus. Further, in these studies, we examined the ability of nicotine, through action at alpha(7)(*)-bearing nicotinic acetylcholine receptors (nAChRs), to antagonize the effects of ethanol exposure on calbindin-D(28k) expression. Organotypic cultures of rat hippocampus were exposed to ethanol (50-100 mM) for 10 days. Additional cultures were exposed to 500 nM (-)-nicotine with or without the addition of 50 mM ethanol, 100 nM methyllycaconitine (an alpha(7)*-bearing nAChR antagonist), or both. Prolonged exposure to ethanol (>/=50 mM) produced significant reductions of calbindin-D(28k) immunolabeling in all regions of the hippocampal formation, even at nontoxic concentrations of ethanol. Calbindin-D(28k) expression levels returned to near-control levels after 72 h of withdrawal from 10-day ethanol exposure. Extended (-)-nicotine exposure produced significant elevations in calbindin-D(28k) expression levels that were prevented by methyllycaconitine co-exposure. Co-exposure of cultures to (-)-nicotine with ethanol resulted in an attenuation of ethanol-induced reductions in calbindin-D(28k) expression levels. These findings support the suggestion that long-term ethanol exposure reduces the neuronal capacity to buffer accumulated Ca(2+) in a reversible manner, an effect that likely contributes to withdrawal-induced neurotoxicity. Further, long-term exposure to (-)-nicotine enhances calbindin-D(28k) expression in an alpha(7)* nAChR-dependent manner and antagonizes the effects of ethanol on calbindin-D(28k) expression.

Animals↗

Functionally improved bone in calbindin-D28k knockout mice.

In vitro studies indicate that Calbindin-D28k, a calcium binding protein, is important in regulating the life span of osteoblasts as well as the mineralization of bone extracellular matrix. The recent creation of a Calbindin-D28k knockout mouse has provided the opportunity to study the physiological effects of the Calbindin-D28k protein on bone remodeling in vivo. In this experiment, histomorphometry, microCT, and bend testing were used to characterize bones in Calbindin-D28k KO (knockout) mice. The femora of Calbindin-D28k KO mice had significantly increased cortical bone volume (60.4% +/- 3.1) compared to wild-type (WT) mice (45.4% +/- 4.6). The increased bone volume was due to a decrease in marrow cavity area, and significantly decreased endosteal perimeters (3.397 mm +/- 0.278 in Calbindin-D28k KO mice, and 4.046 mm +/- 0.450 in WT mice). Similar changes were noted in the analysis of the tibias in both mice. The bone formation rates were similar in the femoral and tibial cortical bones of both mice. microCT analysis of the trabecular bone in the tibial plateau indicated that Calbindin-D28k KO mice had an increased bone volume (35.2% +/- 3.1) compared to WT mice (24.7% +/- 4.9) which was primarily due to increased trabecular number (8.99 mm(-1) +/- 0.94 in Calbindin-D28k KO mice compared to 6.75 mm(-1) +/- 0.85 in WT mice). Bone mineral content analysis of the tibias indicated that there is no difference in the calcium or phosphorus content between the Calbindin-D28k KO and WT mice. Cantilever bend testing of the femora demonstrated significantly lower strains in the bones of Calbindin-D28k KO mice (4135 micro strain/kg +/- 1266) compared to WT mice (6973 micro strain/kg +/- 998) indicating that the KO mice had stiffer bones. Three-point bending demonstrated increased failure loads in bones of Calbindin-D28k KO mice (31.6 N +/- 2.1) compared to WT mice (15.0 N +/- 1.7). In conclusion, Calbindin-D28k KO mice had increased bone volume and stiffness indicating that Calbindin-D28k plays an important role in bone remodeling.

Animals↗

Excessive testosterone treatment and castration induce reactive astrocytes and fos immunoreactivity in suprachiasmatic nucleus of mice.

The suprachiasmatic nucleus (SCN) has long been recognized as the central mammalian circadian pacemaker that controls behavioral and physiological processes. The role of the SCN in circadian rhythms has been the subject of a wide range of physiological and behavioral studies, although the influence of homeostasis rhythms (such as fluctuating hormone levels) on the SCN of the hypothalamus is not entirely clear. The present study was undertaken to examine the morphological interactions between astroglial and neuronal elements in the SCN of mice after either a short-term excessive testosterone treatment (ETT) or castration, using glial fibrillary acidic protein (GFAP), and immediate early gene c-fos as well as calbindin-D28k (CB) immunohistochemistry. Both ETT and castration resulted in a significant increase in the accumulation of reactive astrocytes and Fos-imunoreactivity (IR), especially in the dorsomedial (DM) sub-region of the SCN. However, CB-IR neurons in the examined brain regions showed little change. These findings indicate that the DM sub-region of the SCN may be a possible center of hormonal regulation via a hypothalamic neuroendocrine circuit, and that a non-photic stimuli mechanism might play a role in circadian rhythm regulation.

Animals↗

Calbindin-D28k content and firing pattern of hippocampal granule cells in amygdala-kindled rats: a perforated patch-clamp study.

The dentate gyrus is believed to play an important pathophysiological role during experimentally induced kindling. In this study, we investigated whether an altered content of the calcium binding protein calbindin-D(28k) or an increased intrinsic excitability of hippocampal granule cells contribute to the induction of the kindling phenomenon. We determined the firing pattern of granule cells in hippocampal slices using perforated patch-clamp recordings in current clamp mode. The expression of calbindin-D(28k) and glutamic acid decarboxylase (GAD(67)) by granule cells was analyzed immunohistochemically. Rats developed secondarily generalized limbic seizures within approximately 11 days of twice-daily stimulation of the amygdala. As reported for other kindling paradigms, this protocol induced a clear up-regulation of GAD(67) in granule cells, indicating their involvement in the induced neuronal activity. However, when comparing kindled and control rats, we could not detect any differences in intrinsic excitability: Firing frequency, after-hyperpolarisations, action potentials, input resistance and membrane potentials were nearly identical between both groups. Furthermore, we did not observe any differences in the calbindin-D(28k) immunoreactivity between groups. In every slice, virtually all granule cells were found to be strongly calbindin-D(28k) positive, and there was no apparent reduction in the general level of calbindin-D(28k) expression. We conclude that changes in intrinsic membrane properties or in the calbindin-D(28k) content of granule cells are not necessary for the development of amygdala kindling.

Action Potentials↗

Calbindin D28k-containing neurons in the paratrigeminal nucleus receive convergent nociceptive information and project to nucleus of the solitary tract in rat.

The paratrigeminal nucleus (PTN) receives orofacial somatic and visceral afferent fibers and contains many calbindin-D28k neurons (CB-containing neurons) that project to nucleus of the solitary tract (NTS). In the present study, retrograde and transganglionic tracing methods combined with immunofluorescence histochemistry and confocal laser scanning microscopy were used. After Fluoro-gold (FG) injection into the unilateral NTS, 74.4% FG-labeled neurons of ipsilateral PTN were double-labeled with CB. Furthermore, 41.0% and 32.5% FG/CB double-labeled neurons co-existed with Fos induced by nociceptive stimulation of the lips and the upper alimentary tract, respectively. In the PTN unilateral to FG injection site, 26.6% CB-LI neurons were double-labeled with PAG, 61.5% and 79.0% CB/PAG double-labeled neurons were triple-labeled with FG and Fos, and 22.9% FG/CB double-labeled neurons were triple-labeled with PAG, 84.3% FG/PAG double-labeled neurons expressed Fos induced by the upper alimentary tract stimulation. In the intact animals, 62.8% CB-LI neurons and 88.3% PAG-LI neurons co-existed with GABA(B)R, respectively. In addition, some terminals from the inferior alveolar nerve (IAN) were closely apposed to CB/Fos double-labeled or CB single-labeled neurons. These results suggested that CB-containing neurons in the PTN receive the nociceptive information converge from the orofacial area and visceral organs, and comprising the glutamatergic excitatory transmission pathway from the PTN to the NTS. This pathway might be modulated by GABA via the GABA(B) receptor.

Animals↗

Dystonin deficiency reduces taste buds and fungiform papillae in the anterior part of the tongue.

The anterior part of the tongue was examined in wild type and dystonia musculorum mice to assess the effect of dystonin loss on fungiform papillae. In the mutant mouse, the density of fungiform papillae and their taste buds was severely decreased when compared to wild type littermates (papilla, 67% reduction; taste bud, 77% reduction). The mutation also reduced the size of these papillae (17% reduction) and taste buds (29% reduction). In addition, immunohistochemical analysis demonstrated that the dystonin mutation reduced the number of PGP 9.5 and calbindin D28k-containing nerve fibers in fungiform papillae. These data together suggest that dystonin is required for the innervation and development of fungiform papillae and taste buds.

Animals↗

Firing pattern and calbindin-D28k content of human epileptic granule cells.

In the hippocampus of chronic temporal lobe epilepsy, many abnormalities in structure and function have been described but their pathophysiological relevance often is poorly understood. In this study, we asked whether there may be a link between changes in the firing pattern and the loss of the calcium binding protein calbindin-D28k in epileptic hippocampal granule cells. Using the perforated patch-clamp technique, we investigated granule cells in slices prepared from human hippocampi removed for the treatment of pharmacoresistant temporal lobe epilepsy. Granule cells in hippocampi without significant signs of structural damage (lesion group) displayed a firing pattern indistinguishable from that of rodent granule cells and were strongly labeled with anti-calbindin-D28k antibodies. In contrast, half of granule cells in sclerotic hippocampi (HS group) showed an altered firing pattern and a severe loss of calbindin-D28k. While these cells show passive membrane properties comparable to cells of the rodent and lesion group, they lack the medium afterhyperpolarization and display only a weak spike frequency adaptation. On the other hand, granule cells in the HS group have an increased action potential threshold and an enlarged fast afterhyperpolarization. Applying post-recording immunohistochemistry to individual electrophysiologically characterized granule cells, we show that the loss of calbindin-D28k is not causally related to any of the changes in firing pattern. Both alterations seem to occur during the course of temporal lobe epilepsy, with the firing pattern being affected earlier than the calbindin-D28k content. In conclusion, we propose that it is the combination of the altered intrinsic excitability of granule cells with the amplified and prolonged synaptic input from perforant path fibers previously described in the epileptic dentate area which promotes tonic, non-adapting, high frequency firing of granule cells and thereby strongly augments the excitability of the hippocampus.

Action Potentials↗

Odontoblast primary cilia: facts and hypotheses.

Odontoblasts, the cells responsible for the dentine formation, are organized as a single layer of highly polarized and differentiated post-mitotic cells along the interface between the dental pulp and the mineralized tubules. They lay down the physiological secondary dentine throughout the life of the teeth. Odontoblasts play a central role in the transportation of calcium to the dentine and they possibly mediate early stages of sensory processing in teeth. A primary cilium, 9+0 configuration, have been regularly identified in a supra nuclear location. Calbindin D28k has been detected at the base of the cilium membrane. The cilium structure was positive with detyrosinated alpha tubulin antibodies in vivo and in cultured human odontoblasts. Transcripts of tektin, a protein involved in ciliogenesis, were expressed in vitro. The putative role of the primary cilium constituting a critical link between external teeth stimuli and odontoblast responses is extensively discussed.

Calbindin 1↗

Changes in expression of P2X purinoceptors in rat cerebellum during postnatal development.

Changes in expression of P2X receptors (P2X1-7) during postnatal development of the rat cerebellum are described. At P3, immunoreactivity (ir) to all the P2X receptors, except for P2X3 receptors, was found in Purkinje cells and deep cerebellar nuclei, P2X5-ir being most prominent. Granular and microglial cells were labeled for P2X5 (weakly) and P2X4 receptors, respectively. At P7, expression of all the P2X receptors (with the exception of P2X3) was up-regulated, P2X5 and P2X6 receptors being most prominent. Scattered P2X receptor-ir in unipolar brush cells in the granular cell layer and P2X1- and P2X7-ir of microglial cells was also present. At P14, the dendritic trees of Purkinje cells were intensely labeled by P2X1-7 receptor antibodies, except for P2X3, while P2X1, P2X4 and P2X7 receptor immunostaining in microglial cells and P2X5 receptor immunostaining in granular cells was up-regulated. At P21, expression of all P2X receptors (except P2X3) was down-regulated in the Purkinje cells and deep cerebellar nuclei; P2X1, P2X4 and P2X7 receptors-ir was present in microglial cells. In contrast, expression of P2X5-ir in granular cells was up-regulated. At P60, expression levels of all the P2X receptors (except P2X3) were similar with those at P21. In double-labeling experiments, almost all the P2X-ir Purkinje cells were immunoreactive for calbindin-D28k, while 60-80% of P2X-ir cells in the granular cell layer were immunoreactive for calretinin. The possible short- and long-term functional significance of the changes in expression of P2X receptors during postnatal development is discussed.

Age Factors↗