Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Calbindin 1”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1994

Specific binding to vitamin D response elements of chicken intestinal DNA-binding activity is not related to the vitamin D receptor.

In this report we confirm that the putative vitamin D response element (VDRE), located between -320 and -306 in the chicken calbindin-D28K gene, is not a binding site for the vitamin D3 receptor (VDR). In examining the ability of chicken intestinal nuclear extracts (CINE) to bind known VDREs, we observed a specific VDRE-binding activity, which is distinct from VDR. In fact, VDR-depleted CINE retains the ability to bind the rat osteocalcin VDRE. The VDRE-binding activity binds DNA with high affinity and contacts it at the same guanine residues as VDR. Its specificity in binding structural variants of the AGGTCA repeat is broader than that of VDR, as direct repeats spaced by 3, 4, and 5 base pairs are almost equally effective competitors when added to the probe in molar excess. Palindromic arrangements of the same motif are lower affinity competitors. The retinoid-X receptor is involved in the binding complex, as incubation of CINE with antibody to retinoid-X receptor results in a quantitative supershift. Antibodies to retinoic acid receptors (RAR alpha and -beta), T3 receptor, or chicken ovalbumin up-stream promoter-transcription factor had no apparent effect. These data suggest that species specificity is a relevant aspect of VDR/VDRE recognition, and that a novel factor(s), different from VDR, might be involved in the effect of vitamin D on gene expression.

Animals↗
PubMed1992

Ontogeny of calbindin-D28K and calbindin-D9K in the mouse kidney, duodenum, cerebellum and placenta.

The appearance of the calcium-binding proteins (CaBP-D28K and CaBP-D9K) in embryonic mice tissues was determined using a sensitive immunohistochemical assay. CaBP-D28K first appears in myenteric nerve plexuses of the duodenum on day E15, in duodenal villus cells on day E16, in Purkinje cells of the cerebellum on day E19, in cells of the mesonephric duct on day E11 and in the metanephric duct on day E12. CaBP-D9K first appears in enterocytes of the duodenum on day E18, in trophoblastic giant cells (TGC) of the placenta on day E10, and in the metanephric duct on day E15. A differential time of appearance and colocalization of the two CaBPs is demonstrated in the embryonic mouse kidney, suggesting either that vitamin D does not control both CaBPs in the foetus or that the vitamin D control is unequal. The early appearance and location of CaBP-D9K in TGCs may suggest that these cells play an important role in transplacental transfer of calcium.

Animals↗
PubMed2002

Intracellular calcium ion response to glucose in beta-cells of calbindin-D28k nullmutant mice and in betaHC13 cells overexpressing calbindin-D28k.

This article describes studies on the glucose-induced responses of intracellular Ca2+ concentration ([Ca2+]i), insulin release, and redistribution of calbindin-D28k, a calcium-binding regulatory protein, in beta-cells of pancreatic islets of calbindin-D28k knockout (KO) and wild-type mice (C57BL6) as well as in betaHC-13 control cells and betaHC-13 CaBP40 cells (beta-cell line overexpressing calbindin-D28k). Upon increasing the glucose concentration from 2.8 to 30 mM, islets of KO mice showed a significantly greater increase in [Ca2+]i (mean increase in [Ca2+]i, i.e., delta[Ca2+]i, was 296 nM) compared with wild-type mice (delta[Ca2+]i = 97 nM). betaHC-13 CaBP40 cells showed little change in [Ca2+]i upon elevation of glucose from 5.5 to 32.7 mM, whereas betaHC-13 control cells exhibited significant increases in [Ca2+]i, (delta[Ca2+]i = 510 nM). Similarly, upon addition of 30 mM glucose, the rate of insulin release increased from 25.2 (basal rate) to 145.2 pg/mL/min in betaHC-13 control cells, whereas in betaHC-13 CaBP40 cells the rate of insulin release was only 27.5 pg/mL/min in high glucose. Thus, levels of calbindin-D28k in beta-cells affect both [Ca2+]i and insulin secretion in response to glucose. The three-dimensional reconstruct of confocal immunofluorescent images showed that glucose caused redistribution of calbindin-D28k resulting in co-localization in the region of L-type voltage-dependent calcium channels (VDCC). This co-localization may be an important regulatory function concerning Ca2+ influx via L-type VDCC and exocytosis of insulin granules.

Animals↗
PubMed2005

Endogenous Ca2+ buffer concentration and Ca2+ microdomains in hippocampal neurons.

Ca2+-binding proteins are ubiquitously expressed throughout the CNS and serve as valuable immunohistochemical markers for certain types of neurons. However, the functional role of most Ca2+-binding proteins has to date remained obscure because their concentration in central neurons is not known. In this study, we investigate the intracellular concentration of the widely expressed Ca2+-binding protein calbindin-D28k in adult hippocampal slices using patch-clamp recordings and immunohistochemistry. First, we show that calbindin-D28k freely exchanges between patch pipette and cytoplasm during whole cell patch-clamp recordings with a time constant of approximately 10 min. Substituting known concentrations of recombinant calbindin-D28k in patch pipettes enabled us to determine the endogenous calbindin-D28k concentration by postrecording immunohistochemistry. Using this calibration procedure, we find that mature granule cells (doublecortin-) contain approximately 40 microm, and newborn granule cells (doublecortin+) contain 0-20 microm calbindin-D28k. CA3 stratum radiatum interneurons and CA1 pyramidal cells enclose approximately 47 and approximately 45 microm calbindin-D28k, respectively. Numerical simulations showed that 40 microm calbindin-D28k is capable of tuning Ca2+ microdomains associated with action potentials at the mouth of single or clustered Ca2+ channels: calbindin-D28k reduces the increment in free Ca2+ at a distance of 100 and 200 nm by 20 and 35%, respectively, and strongly accelerates the collapse of the Ca2+ gradient after cessation of Ca2+ influx. These data suggest that calbindin-D28k equips hippocampal neurons with approximately 160 microm mobile, high-affinity Ca2+-binding sites (kappa(S) approximately 200) that slow and reduce global Ca2+ signals while they enhance the spatiotemporal fidelity of submicroscopic Ca2+ signals.

Aging↗
PubMed2006

Expression of a familial Alzheimer's disease-linked presenilin-1 variant enhances perforant pathway lesion-induced neuronal loss in the entorhinal cortex.

Alzheimer's disease (AD) is characterized by neuronal loss in the hippocampus and entorhinal cortex that is manifested by progressive memory impairment and cognitive decline. Autosomal-dominant, familial forms of AD (FAD) are caused by mutations in genes encoding amyloid precursor protein, presenilin-1 (PS1), and presenilin 2. Although it is established that expression of mutant PS1 variants leads to increased production of highly fibrillogenic amyloidbeta42 (Abeta42) peptides that deposit in the brains of patients with AD, the mechanism(s) by which Abeta deposition and expression of mutant genes induce lamina- and region-specific vulnerability of neuronal populations is not known. We have examined the hypothesis that expression of transgene-encoded FAD-linked mutant PS1 variants in entorhinal cortex neurons exacerbates the vulnerability of these cells to lesion-induced neuronal loss. To test this notion, we transected the perforant pathway (PP) of transgenic mice harboring either wild-type human PS1 (PS1HWT) or the FAD-linked mutant PS1DeltaE9 variant and examined neuronal survival in layer II of the entorhinal cortex (ECL2). Remarkably, PP transections lead to marked reductions in the numbers of ECL2 neurons in the ECL2 of mice expressing mutant PS1, compared with ECL2 neurons in PP-lesioned PS1HWT mice. Finally, and in contrast to studies in nontransgenic mice and in mice expressing PS1HWT, ECL2 neurons that express mutant PS1 and the calcium binding protein calbindin-D28k in ECL2 are also susceptible to lesion-induced neuronal loss. We conclude that expression of FAD-linked mutant PS1 variants enhances the vulnerability of neurons in the entorhinal cortex to PP lesion-induced cytotoxicity.

Alzheimer Disease↗
PubMed1994

Subterranean mole-rats naturally have an impoverished calciol status, yet synthesize calciol metabolites and calbindins.

Mole-rats (Family Bathyergidae) have no obvious source of calciol. They live in an environment devoid of sunlight and consume a herbivorous diet. Calciol status, metabolism and expression were examined in six species of Bathyergids. Serum levels of calcidiol in all species were < 5 micrograms/l and those of calcitriol were low (18.0 +/- 11.0 (SD) ng/l, N = 57) when compared to other rodents. Within 72 h of injecting animals with tritium-labelled calciol, most of the labelled prohormone had been metabolized to more polar metabolites. Three times more tritium-labelled calcitriol (19.3 +/- 2.9%) was present than (24R)-hydroxycalcidiol (6.2 +/- 10%). The natural absence of detectable circulating concentrations of calcidiol and the threefold greater amount of calcitriol to (24R)-hydroxycalcidiol produced indicate that calciol naturally is in short supply. Calciol-dependent calbindins were absent in the duodenum. Calbindin-D28k was present in the Purkinje cells of the cerebellum and in some collecting ducts and proximal and distal convoluted tubules of the kidney. Calbindin-D9k also was present but was localized uniquely in the juxtaglomerular cells of the five southern African species. These data confirm that Bathyergid mole-rats naturally have an impoverished calciol status. Despite the presence of calbindins in renal tissues, the functional importance of this hormone in calbindin synthesis and other normal mole-rat physiology is not known.

Animals↗
PubMed2004

Endometrial expression of calbindin (CaBP)-d28k but not CaBP-d9k in primates implies evolutionary changes and functional redundancy of calbindins at implantation.

The endometrium is hostile to embryo implantation except during the 'window of receptivity'. A change in endometrial gene expression is required for the development of receptivity. Calbindin-d9k (CaBP-d9k) and calbindin-d28k (CaBP-d28k) are proteins possessing EF-hand motifs which have high affinity for Ca2+ ions. Previously, it has been demonstrated that, in mouse endometrium, the expression of both calbindins is highly regulated during implantation and that both proteins play critical but functionally redundant roles at implantation. This study was the first to determine the expression of these two calbindins in the human and rhesus monkey endometrium. Initial RT-PCR analysis demonstrated that CaBP-d28k but not CaBP-d9k mRNA expression is detectable in the endometrium of both species. Western blot analysis confirmed the presence of immuno-reactive CaBP-d28k protein in the primate endometrium. Furthermore, the endometrial expression pattern of CaBP-d28k mRNA and protein was examined by Northern blot analysis and immunohistochemistry respectively in both species across the menstrual cycle and during early pregnancy. Semi-quantitative statistical analysis of the immunohistochemistry results revealed that, in the human, CaBP-d28k protein expression was maximal in luminal and glandular epithelium during the mid-secretory phase, coinciding with the time when the endometrium is receptive to embryo implantation. Expression in rhesus monkey showed a similar trend. These results suggest that, in the primate endometrium, only CaBP-d28k is expressed and that the specific regulation of this calbindin is potentially important for the establishment of uterine receptivity.

Animals↗
PubMed2003

Analyses of beta-1 syntrophin, syndecan 2 and gem GTPase as candidates for chicken muscular dystrophy.

Despite intensive studies of muscular dystrophy of chicken, the responsible gene has not yet been identified. Our recent studies mapped the genetic locus for abnormal muscle (AM) of chicken with muscular dystrophy to chromosome 2q using the Kobe University (KU) resource family, and revealed the chromosome region where the AM gene is located has conserved synteny to human chromosome 8q11-24.3, where the beta-1 syntrophin (SNTB1), syndecan 2 (SDC2) and Gem GTPase (GEM) genes are located. It is reasonable to assume those genes might be candidates for the AM gene. In this study, we cloned and sequenced the chicken SNTB1, SDC2 and GEM genes, and identified sequence polymorphisms between parents of the resource family. The polymorphisms were genotyped to place these genes on the chicken linkage map. The AM gene of chromosome 2q was mapped 130 cM from the distal end, and closely linked to calbindin 1 (CALB1). SNTB1 and SDC2 genes were mapped 88.5 cM distal and 27.6 cM distal from the AM gene, while the GEM gene was mapped 18.5 cM distal from the AM gene and 9.1 cM proximal from SDC2. Orthologues of SNTB1, SDC2 and GEM were syntenic to human chromosome 8q. SNTB1, SDC2 and GEM did not correspond to the AM gene locus, suggesting it is unlikely they are related to chicken muscular dystrophy. However, this result also suggests that the genes located in the proximal region of the CALB1 gene on human chromosome 8q are possible candidates for this disease.

Amino Acid Sequence↗
PubMed1985

Cerebellar Purkinje cell-specific protein-like immunoreactivity in noradrenaline-chromaffin cells and ganglion cells but not in adrenaline-chromaffin cells in the rat adrenal medulla.

By means of immunohistochemistry combined with fluorescence microscopy, a cerebellar Purkinje cell-specific protein, also named spot 35 protein, was found to occur in all noradrenaline-chromaffin cells and some ganglion cells of the rat adrenal medulla. The immunoreactivity was localized in the chromaffin granules as well as the cytoplasmic matrix. The nucleus as well as the interior of the membranous organelles, were free of immunoreaction. No immunoreactivity was found in most of the intra-adrenal nerve fibers except for a few nerve fibers derived from the immunoreactive ganglion cells. Neither Schwann, satellite cells nor cortical cells were immunoreactive. It is suggested that some intracellular phenomenon possibly relating to the regulation of intracellular Ca-ion concentration is common to noradrenaline-chromaffin cells, medullary ganglion cells and cerebellar Purkinje cells.

Adrenal Medulla↗
PubMed1989

Immunohistochemistry of neuron-specific and glia-specific proteins.

This paper reviews the immunohistochemical distribution of four brain-derived proteins, NSE, NFP, spot 35 and S-100 protein, in neuronal and paraneuronal tissues, concentrating on the results of our own research group. Neuron-specific enolase (NSE), a brain-specific isozyme of the glycolytic enzyme enolase, is characterized by its consistent occurrence in the cytoplasm of mature neurons. Immunoreactivity for NSE has been found in almost all paraneurons of both sensory and endocrine nature, suggesting that a unique system of intracellular energy metabolism may be shared by neurons and paraneurons. Neurofilament protein (NFP), a neuronal cytoskeletal protein, is immunohistochemically recognized in only a part of neurons, apparently due to the scarcity in neurofilaments in some neurons or to a decreased antigenicity for NFP in the cell. Similarly, only small populations of cells in restricted types of paraneurons, including gut endocrine cells and thyroid C cells, are immunoreactive for NFP. However, the potentiality for paraneurons to express NFP is given credence by the fact that its immunoreactivity is rather frequently found in the neoplasmas of paraneurons which normally do not show this immunoreactivity. Spot 35 protein which is a cerebellar Purkinje cell-specific protein, has displayed immunohistochemical localization in sensory and endocrine paraneurons as well as some neurons including a specific type of intramural nerve cells in the gut. The selective localization of this calcium-binding protein may be correlated with the secretory function and calcium-dependent excitable membrane property in those cells. S-100 protein, another brain-derived calcium-binding protein, is contained in sustentacular cells of paraneuronal organs as well as glial elements of nervous systems. Although it is now widely accepted that S-100 protein is not "glia-specific" but contained in a variety of non-glial cells, its beta subunit protein is still a useful marker for a series of glial and sustentacular cells.

Animals↗
PubMed1989

Olfactory receptor cells: immunocytochemistry for nervous system-specific proteins and re-evaluation of their precursor cells.

The immunohistochemical localization of nervous system-specific proteins and cytokeratin in the olfactory mucosa is described mainly in humans and guinea pigs. Immunoreactivity for neuron-specific enolase (NSE) was demonstrated in olfactory receptor cells including their dendrite and axon. Immunoreactivity for neurofilament protein (NFP) was contained in the dendrite and perikaryon of the olfactory cells, but not in the axon. Immunoreactivity for spot-35 protein, a kind of neuron-specific proteins was selectively localized in several flask-shaped cells of the olfactory epithelium only in the guinea pig. These spot-35 protein-positive cells were suspected of being microvillar cells, considered the second type of receptor cells dispersed in the olfactory epithelium. Immunoreactivity for glia-specific S-100 protein was demonstrated in the Bowman's glands as well as Schwann cells associated with the olfactory nerves in the lamina propria. Supporting cells were not immunolabelled with any antisera against nervous system-specific proteins. Cytokeratin, a useful marker for epithelial cells, was expressed exclusively in basal cells. Axotomy of olfactory nerves induced the disappearance of the olfactory receptor cells with NSE immunoreactivity 3 days after the operation. Regenerating cells showing NSE immunoreactivity were first recognized in the lower portion of the epithelium within 7 days. The epithelium was completely repaired 3-4 weeks later and came to contain many NSE-reactive mature receptor cells. Bromodeoxyuridine (BrdU), administered during regeneration of the olfactory epithelium, was immunohistochemically detected in the cells of the layer above the basal cell layer, but not in the latter itself. This result does not support the general contention that the receptor cells originate from the basal cells.

Animals↗
PubMed1989

Immunocytochemistry of neuron-specific proteins and neuropeptides in taste buds and associated nerves.

The taste buds and associated nerves in the guinea pig, rat, cat, and mouse were investigated by immunocytochemistry and formaldehyde-induced fluorescence histochemistry. The antisera used were against spot 35 protein, neuron-specific enolase (NSE), neurofilament protein (NFP), and substance P. The spot 35 protein immunoreactivity was confined to taste bud cells in the guinea pig and rat; the immunoreactive cells, slender in shape, comprised half the number of the total taste bud cells in the guinea pig but were fewer in the rat. For NSE, on the other hand, taste bud cells as well as neural elements localized in both the taste bud and the subepithelial connective tissue were immunoreactive in all the species investigated. Furthermore, all of the spot 35 protein-immunoreactive cells proved to be NSE-immunoreactive in the guinea pig and rat. For NFP, neither the bud cells nor the nerves in the taste bud were reactive, whereas a part of nerves in the connective tissue was immunostained in all the species. The antiserum against substance P exclusively detected some parts of nerves in and out of the taste buds in the cat, rat, and mouse. The aminergic innervation was rather meager and appeared in the nerve fibers localized in the taste buds and connective tissue of the cat and mouse.

Animals↗
PubMed1990

Localization of spot 35-calbindin (rat cerebellar calbindin) in the anterior pituitary of the rat: developmental and sexual differences.

Spot 35 protein is identical to rat brain calbindin, as based on the complete homology of their nucleotide sequence, and is named here as spot 35-calbindin. The immunoreactivity for this protein was first detected on embryonic Day 16 (E16) in the anterior pituitary anlages. As the development proceeded, spot 35-immunoreactive cells increased in number in the pars distalis, especially in its antero-ventral portion, and also pars tuberalis. No sex difference was noticed in the population density of the immunoreactive cells until postnatal Week 3. At postnatal Week 5 and thereafter through adulthood, spot 35-immunoreactive cells were much more numerous in the male anterior pituitary than in the female organ. All immunopositive cells for spot 35-calbindin contained secretory granules, and no folliculo-stellate cells were immunopositive. Any of the anterior pituitary hormones including ACTH, GH, LH, PRL and TSH could be simultaneously expressed with spot 35-calbindin in the granulated cells. Based on the ultrastructure of the secretory granules, spot 35-immunoreactive cells were classified into four types: cells containing round granules, 350 nm; those containing granules of irregular contour larger than 350 nm; those containing small granules, up to 150 nm; and those containing a mixture of the round large and small granules. Cells containing large round granules were dominant in males, while cells containing small granules were dominant in females. The functional significance of spot 35-calbindin in the anterior pituitary is briefly discussed.

Animals↗
PubMed1991

Differential changes in expression of the neurofilament triplet protein-immunoreactivity in Purkinje cells of the cerebellum during the postnatal development of rats.

By means of peroxidase-anti-peroxidase (PAP) immunohistochemistry with both the neurofilament (NF) triplet (small: 68 K, medium: 150 K, high: 200 K) antisera and the antiserum against spot 35-calbindin, developmental changes in expression of the immunoreactivity for the NF triplet proteins in different domains of the Purkinje cells was examined in the cerebella of postnatal rats. From birth till the postnatal day 6 (P6) the somata and dendrites exhibited moderately positive immunoreaction for small and medium NF subunits. In contrast, the incubation for the high NF subunit resulted in a negative immunoreaction for the somata and dendrites of the Purkinje cells at those stages. On P8 and P10 they were weakly immunoreactive for all NF triplet. Thereafter the intensity of their immunoreaction decreased progressively and the Purkinje cell somata and dendrites were immunonegative for all NF triplet proteins on P21, when the Purkinje cell attained an adult appearance in morphology. On the other hand, the Purkinje cell axons, which can be identified selectively by the positive immunoreaction for the spot 35-calbindin throughout the course of the postnatal development, exhibited positive immunoreactivity for all the NF triplet on the 9th, 21th and 50th postnatal days in the cerebellar white matter. The development of the slow axoplasmic transport and the posttranslational modification of the NF triplet proteins are discussed as possible mechanisms underlying the differential expression of the immunoreactivity for the NF triplet proteins in different domains of the Purkinje cells during postnatal development.

Animals↗
PubMed1992

Reticular endings of Purkinje cell axons in the rat cerebellar nuclei: scanning electron microscopic observation of the pericellular plexus of Cajal.

The pericellular plexus of Purkinje cell axons in the cerebellar nuclei was first recorded by Cajal (1911), using the Golgi method. The present study observed the axonal plexus in the rat by scanning electron microscopy after the plexus' detachment from the soma of target neurons by NaOH maceration. The pericellular plexus revealed numerous axons with ellipsoidal and moniliform swellings. They branched and crossed with each other to form, as a whole, a reticulum which enveloped the target neuron instead of multiple isolated boutons. Some axon terminals were separated from each other by thin glial processes, while others lacked such septa, thus being directly juxtaposed. Immunohistochemistry for spot 35 protein, a Purkinje cell-specific protein, detected similar beaded and reticular axons terminating on the neuronal somata, confirming their identification as Purkinje cells. Transmission electron microscopic observation showed that most of the axon terminals in question contained elliptical vesicles, characteristic for Purkinje cells. The vesicles were not accumulated toward small patchy areas of synaptic specialization but disseminated along the entire length of the terminal portion of axons.

Animals↗
PubMed1999

Alteration in the expression level of calbindin D28k in the periodontal ligament of the rat molar during experimental tooth movement.

The present immunohistochemical study was designed to investigate changes in the distribution and expression level of calbindin D28k in the periodontal ligament during experimental tooth movement in the rat molar to clarify the physiological role of this protein in the ligament. In normal animals, calbindin D28k-like immunoreactivity appeared sparsely in spindle-shaped cells in the alveolar half of the periodontal ligament. Electron microscopic observations showed that these immunoreactive cells were characterized by well-developed rough-surfaced endoplasmic reticulum and phagosomes--which often contained collagen fibers--suggesting that these cells could be categorized as periodontal fibroblasts. Twelve hours following the onset of the experimental tooth movement, cells positive for calbindin D28k increased in number in the periodontal ligament, especially in the alveolar half of the pressured side. Immunoelectron microscopy showed that the calbindin D28k-immunopositive cells had morphological features similar to those of fibroblasts in the normal ligament, and that these cells occasionally made contact with immunonegative macrophage-like cells. Immunopositive cells gradually decreased in number, and the distribution of the cells and intensity of the immunoreactivity returned to normal levels by 14 days following the induction of the experimental tooth movement. The present results suggest that calbindin D28k plays an important role in the homeostasis and cyto-protection of fibroblasts in the periodontal ligament at the initial phase of experimental tooth movement.

Animals↗
PubMed2004

Taste buds and nerve fibers in the rat larynx: an ultrastructural and immunohistochemical study.

We investigated the rat laryngeal taste buds and their innervation by electron microscopy and immunohistochemical methods. Taste buds were densely arranged in the surface facing the laryngeal cavity of the epiglottis, the aryepiglottic fold, and the cuneiform process of the arytenoid cartilages. The cells of the buds were classified into types I, II, III, and basal cells, the ultrastucture of which was almost the same as that previously reported in lingual taste buds. The type III cells that had synaptic contacts with nerve fibers were considered to be sensory cells. Immunohistochemical analysis revealed thick calbindin D28k-immunoreactive fibers and thin varicose fibers immunoreactive for calcitonin gene-related peptide or substance P in and around the taste bud. Serotonin-immunoreactive cells were also observed here. The results revealed the innervation pattern of laryngeal taste buds to be the same as that in lingual taste buds. Carbonic anhydrase (CA) is known to catalyze the hydration of CO2 and dehydration of H2CO3, and seems to be essential in CO2 reception. Immunoreactivity for CAI was detected in slender cells and that for CAIII was observed in barrel-like cells in the laryngeal taste buds. The pH-sensitive inward rectifier K+ (Kir) channel in the cell membrane may be involved in CO2 reception as well. CAII-reactive cells were also reactive to Kir4.1, PGP 9.5 and serotonin. Our results indicated that CAII and Kir4.1 are located in type III cells of the laryngeal taste buds, and supported the idea that the buds may be involved in the recognition of CO2.

Animals↗
PubMed2006

Expression of the ammonia transporter, rh C glycoprotein, in normal and neoplastic human kidney.

Recent studies have identified the presence of a novel Mep/Amt/Rh glycoprotein family of proteins that may play an important role in transmembrane ammonia transport. One of the mammalian members of this family, Rh C glycoprotein (RhCG), transports ammonia, is expressed in distal nephron sites that are critically important for ammonia secretion, exhibits increased expression in response to chronic metabolic acidosis, and originally was cloned as a tumor-related protein. The purpose of our studies was to determine the localization of RhCG in the normal and neoplastic human kidney. Immunoblot analysis of human renal cortical protein lysates demonstrated RhCG protein expression with a molecular weight of approximately 52 kD. Immunohistochemistry revealed both apical and basolateral Rhcg expression in the distal convoluted tubule, connecting segment, and initial collecting tubule and throughout the collecting duct. Co-localization with calbindin-D28k, H(+)-ATPase, aquaporin-2, and pendrin showed that distal convoluted tubule and connecting segment cells, A-type intercalated cells, and non-A, non-B cells express RhCG and that B-type intercalated cells, principal cells, and inner medullary collecting duct cells do not. In renal neoplasms, RhCG was expressed by chromophobe renal cell carcinoma and renal oncocytoma but not by clear cell renal cell carcinoma or by papillary renal cell carcinomas. These studies suggest that RhCG contributes to both apical and basolateral membrane ammonia transport in the human kidney. Furthermore, renal chromophobe renal cell carcinoma and renal oncocytoma seem to originate from the A-type intercalated cell.

Adenocarcinoma, Follicular↗