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Prenatal development of calbindin D-28K in human visual cortex.

The distribution of the calcium-binding protein calbindin D-28K (CB) was investigated in human fetal primary visual cortex. CB is present in Cajal-Retzius cells of layer I, in sparse neurons of the ventricular and intermediate zones (VZ, IZ), and in tangential fibres in IZ by 15 weeks (W) of gestation. Cajal-Retzius cells lose their staining by 30W. CB appears in layers II-VI mainly from 26W, following an inside-outside sequence. Until 34W, CB labelling is in somata and neuropil located primarily in layers IVA, IVC and V. Then reactive perikarya and puncta increase in layers II-IVA and deep IVB and C, but are reduced in infragranular layers from 34W to term. From 30W positive somata form clusters in the cell-rich bands in layers IV and V and labelled neuropil in layers III and IV has a periodic pattern from 34W. Also from 34W, numerous lightly reactive pyramidal cells are present in layers II to IVA in primary, but not secondary, visual cortex. Our results show precocious expression of CB before full laminar differentiation of the cortex and that some of this expression is transient.

Calbindins↗

Postnatal development of calcium-binding proteins calbindin and parvalbumin in human visual cortex.

In adult primate visual cortex, the calcium-binding proteins calbindin (CB) and parvalbumin (PV) are localized in different subsets of GABAergic neurons with a characteristic laminar distribution. However, the emergence and development of CB and PV in relation to the periods of functional maturation of the human visual cortex are not known. Therefore, we examined (i) postnatal changes in the distribution of immunoreactivity (ir) for CB and PV in the visual cortex; (ii) the pattern of changes in immunoreactivity in relation to the synaptic maturation; and (iii) differences in the maturation of CB and PV immunoreactivity between areas 17 and 18. We found a consistently high expression of CB in neonatal visual cortex, particularly in layer IV and infragranular layers. However, despite an early appearance of PV, its peak in development occurred only after 2 months of age, characterized by a transient overexpression in the thalamo-recipient layer IV and a continuous inside-out maturation in supragranular layers. The neonatal pattern of high CB-ir in layers IV-VI was transformed during infancy and childhood into an adult pattern of high CB-ir in layer II, but low CB-ir in layer IV and infragranular layers. There was no difference in pattern and tempo of maturation of calcium-binding proteins between area 17 and 18, indicating simultaneous development of cortical inhibitory circuits among cytoarchitectonically and functionally distinct cortical areas. In addition, the reorganization of CB/PV expression temporally and spatially coincides with the course of cortical synaptogenesis, and delineates the major stages of maturation of the human visual cortex.

Adolescent↗

1,25-Dihydroxycholecalciferol regulates rat intestinal calbindin D9k posttranscriptionally.

To determine whether calbindin D9k (CaBP) is subject to posttranscriptional control, 6-wk-old Sprague Dawley-derived rats were fed one of three purified diets, 1.5% Ca and 3.0% Ca, mostly as carbonate, and 2.9% Ca, mostly as gluconate. Two weeks later, 5-cm segments of duodenum, jejunum, ileum, cecum and colon were obtained and analyzed for CaBP and CaBP-mRNA. Analysis of the steady-state distribution of CaBP-mRNA and of CaBP revealed a statistically significant (r = 0.95; P < 0.01) linear relationship between CaBP-mRNA and CaBP. When, however, animals that had been fed the 1.5% Ca diet received by intrajugular injection 1.2 nmol 1,25-dihydroxycholecalciferol [1.25-(OH)2-D3] and their CaBP-mRNA and CaBP were analyzed as a function of time after 1,25-(OH)2-D3 administration, the kinetic response of the two molecules differed. The CaBP-mRNA increased linearly by approximately 68% for 4 h after administration and then declined over the next 6 h to a concentration below the preinjection value. Thus, appearance and disappearance of CaBP-mRNA approximated 17% x h(-1). The CaBP, however, increased steeply to 80% above preinjection concentration until 2 h postinjection, i.e., at a rate of 40% x h(-1). Thereafter, CaBP decreased to 35% above the preinjection value between 5 and 10 h postinjection (2.5% x h(-1)). These findings are consistent with a 1,25-(OH)2-D3-mediated posttranscriptional regulation of CaBP concentrations, because the 1,25-(OH)2-D3-mediated increase in CaBP-mRNA is not reflected in an immediately changed CaBP level.

Animals↗

Vitamin D receptor (VDR) knockout mice reveal VDR-independent regulation of intestinal calcium absorption and ECaC2 and calbindin D9k mRNA.

To study the role of calbindin D(9k) (CaBP) and epithelial calcium channel ECaC2 in intestinal calcium (Ca) absorption, vitamin D receptor knockout (KO) and wild-type (WT) mice were fed either 0.5% Ca or a 2.0% Ca rescue diet starting at 21 d of age. Ca absorption and parameters involved in this process were measured at 60 or 90 d of age. Compared with WT, KO mice fed the 0.5% Ca diet had higher plasma parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], and lower plasma Ca and insulin-like growth factor-I (IGF-I). Duodenal Ca absorption (% Ca absorbed) in KO mice was reduced 71% relative to WT mice and was associated with 55% lower CaBP mRNA, 47% lower CaBP protein and 95% lower ECaC2 mRNA levels. Compared with WT mice, the percentage of Ca absorbed in KO mice fed the 0.5% Ca diet was inappropriately low for the level of duodenal CaBP. The 2% Ca rescue diet normalized plasma Ca, prevented osteomalacia, increased growth and plasma IGF-I levels, but did not normalize plasma PTH or 1,25(OH)(2)D(3) in KO mice. In addition, the relationship between CaBP protein and the percentage of Ca absorbed was normalized, whereas ECaC2 mRNA fell to near zero. Our data demonstrate that higher CaBP levels do not ensure high rates of duodenal Ca absorption and that transcellular Ca absorption can occur even when ECaC2 gene expression is very low. In addition, our data suggest that the 2% Ca diet promotes a vitamin D receptor-independent anabolic effect on bone formation and calcium absorption, leading to improved calcium balance even in the presence of high PTH levels.

Animals↗

Selective proton labelling of amino acids in deuterated bovine calbindin D9K. A way to simplify 1H-NMR spectra.

A technique for proton labelling of selected amino acids in deuterated calbindin D9K, heterologously expressed in E. coli, was developed in order to simplify and obtain higher resolution in 1H-NMR spectra. The spectra from two double-labelling experiments, Val plus Ser and Val plus Leu, when compared to the uniformly protonated protein showed a dramatically simpler pattern with low background signals and gave considerably sharper resonances due to reduced relaxation rates in the deuterated proteins. The selective proton labelling technique will enable detailed and rapid analysis of interesting domains of proteins and will also make the analysis of larger proteins feasible.

Amino Acids↗

Effect of genistein as a selective estrogen receptor beta agonist on the expression of Calbindin-D9k in the uterus of immature rats.

Genistein, a phytoestrogen possessing a high affinity for estrogen receptor beta (ERbeta), is of increasing interest because of its possible influence on the physiology of mammalian reproductive tracts. Although estrogen has been demonstrated to regulate Calbindin-D9k (CaBP-9k) in the rat uterus as with other calcium binding proteins, the role of ERbeta on the modulation of CaBP-9k remains to be elucidated. To elucidate the effect of genistein as a selective ERbeta agonist on uterine expression of CaBP-9k mRNA and protein, immature female rats were injected with genistein daily for three consecutive days in a dose-dependent (0.4, 4, and 40 mg/kg/day) and time-dependent (40 mg/kg/day; 3, 6, 12, 24, 48, and 72 h) manner. Then, the expression of CaBP-9k mRNA and protein was analyzed by Northern hybridization and Western blot, respectively, in the absence or presence of ICI 182,780 (ICI), an estrogen antagonist. In addition, the protein levels of ERalpha and ERbeta and mRNA level of progesterone receptor (PR) were further measured following genistein treatment to elucidate which of ERs is involved in CaBP-9k modulation. In a dose-dependent experiment, the highest dose of genistein (40 mg/kg/day) for 3 days significantly induced uterine CaBP-9k protein as 17beta-estradiol (E2) did. In addition, its maximal mRNA expression was observed at 3 and 6 h, and it returned to control level at 24 h in a time-dependent experiment. In parallel with its mRNA level, the protein level of CaBP-9k was significantly induced by genistein at 3 h and sustained up to 48 h. The pretreatment with ICI, followed by genistein or E2, completely blocked genistein- and E2-induced CaBP-9k protein in the uterus of immature rats. Interestingly, genistein was demonstrated to induce ERalpha protein, but not ERbeta and PR mRNA, an E2-responsive gene, in this tissue. These results imply that genistein, an ERbeta ligand, may regulate CaBP-9k gene through ERalpha pathway. Taken together, the present study demonstrated that genistein enhanced CaBP-9k gene via ERalpha in the uterus of immature rats, suggesting that ERalpha may be a key mediator in uterine CaBP-9k gene induction in immature rats.

Animals↗

Novel progestogenic activity of environmental endocrine disruptors in the upregulation of calbindin-D9k in an immature mouse model.

Endocrine disruption is a major global health concern in the industrialized world. The induction of uterine calbindin-D9k (CaBP-9k), which belongs to a large family of intracellular calcium binding proteins, was used to assess the exposure of endocrine disruptors (EDs) in an immature mouse model. Sex steroid hormones have been demonstrated to regulate uterine CaBP-9k expression in the uterus of rats and mice. In particular, the mouse CaBP-9k gene was predominantly regulated by progesterone (P4), whereas rat CaBP-9k was mainly induced by 17-beta-estradiol (E2) in the uterus. In the present study, immature (14-day-old) female mice were injected with 4-tert-octylphenol (OP), nonylphenol (NP), bisphenol A (BPA), E2, or P4 to determine their effects on uterine CaBP-9k mRNA and protein expression. In addition, to specify estrogenic or progestogenic activity of EDs in the regulation of CaBP-9k, the mice were co-treated with ICI 182,780, an estrogen receptor (ER) antagonist, or RU486, a progesterone receptor (PR) antagonist,. Treatments with OP, NP, or BPA resulted in an increase in CaBP-9k mRNA and protein in the uterus of immature mice in a dose-dependent and time-dependent manner. The EDs-induced expression of CaBP-9k mRNA and protein was reversed or abolished by pretreatment with RU486 or ICI 182,780, suggesting that these synthetic chemicals may have both progestogenic and estrogenic properties by acting through PR or ER in the induction of uterine CaBP-9k mRNA and protein in this model. These results describe a novel in vivo model for detection of both estrogenic and progestogenic activities of EDs in the induction of CaBP-9k mRNA and protein in the uterus of immature mice.

Animals↗

Estrogen receptor alpha pathway is involved in the regulation of Calbindin-D9k in the uterus of immature rats.

It has been demonstrated in our previous studies that Calbindin-D9k (CaBP-9k) is a potent biomarker for screening estrogen-like chemicals in the rat model. Although treatments with 17beta-estradiol (E2) and endocrine disrupting compounds resulted in the up-regulation of uterine CaBP-9k, the mechanism of CaBP-9k induction by these compounds through two subtypes of estrogen receptors (ERalpha and ERbeta) is unclear. Thus, in the present study, immature rats were treated with propyl pyrazole triol (PPT, an ERalpha-selective ligand), diarylpropionitrile (DPN, an ERbeta-selective ligand), E2, or dimethyl sulfoxide (DMSO, a vehicle control) for three days in order to clarify which subtype of ER is involved in the uterine CaBP-9k induction. Following injection with these ER ligands, uterine CaBP-9k expression was analyzed by Northern blot and immunoblot assays. Uterine CaBP-9k expression is mainly mediated by PPT in a dose- and time-dependent manner in immature rats, whereas no significant alteration of the uterine CaBP-9k gene was observed after DPN treatment. In addition, an estrogenicity of PPT in inducing CaBP-9k expression was completely blocked by the anti-estrogen ICI 182,780, implying that uterine CaBP-9k is solely induced by ERalpha. A single treatment with PPT rapidly increased the protein levels of ERalpha and PR, an E2-mediated gene, in these tissues. Taken together, these results indicate that uterine CaBP-9k is induced by E2 and endocrine disrupting chemicals via the ERalpha pathway, but not ERbeta, in the uterus of immature rats.

Animals↗

Induction of calbindin-D9k messenger RNA and protein by maternal exposure to alkylphenols during late pregnancy in maternal and neonatal uteri of rats.

Environmental chemicals are proposed to possess hormone-like properties, such as mimicking natural hormones, inhibiting the action of hormones, and inducing abnormal gene expression. Among environmental chemicals, the alkylphenol products (APs), octylphenol (OP) and nonylphenol (NP), are derived from alkylphenol ethoxylates and have been reported to be environmentally persistent. Thus, in the present study, we examined the effect of two APs, OP and NP, on the expression of Calbindin-D(9k) (CaBP-9k) following maternal exposure during late pregnancy in maternal and fetal uteri. Treatment with a high dose (600 mg/kg body weight [BW]) of OP and NP resulted in an induction of CaBP-9k mRNA at Day 5 of lactation, as did a single treatment with diethylstilbestrol (DES) and 17beta-estradiol (E2) in maternal uteri. The expression of CaBP-9k mRNA was also induced following treatment with a high dose (600 mg/kg BW) of OP, transferred from the mother, exposed to fetuses during late pregnancy, and persisted through Day 5 of lactation. It is of interest that treatments with high doses of OP (400 and 600 mg/kg BW) reduced the expression of maternal estrogen receptor alpha (ERalpha) mRNA, as E2 did. However, all doses of NP resulted in an inhibition of neonatal ERalpha, while only the high does of OP (600 mg/kg BW) induced the reduction of neonatal ERalpha mRNA expression, as E2 did. Parallel to mRNA, the expression of CaBP-9k protein was significantly induced by treatment with a high dose of OP and NP. In conclusion, maternal exposure to APs, OP and NP, during late pregnancy increased the expressions of CaBP-9k mRNA and protein in maternal and neonatal uteri. These results suggest that the absorption and distribution of environmental estrogenic compounds in maternal and neonatal uteri are extremely rapid, and these chemicals can easily pass though the placenta during pregnancy to affect functions of neonatal reproductive tissues.

Animals↗

Cloning of the porcine Calbindin-D9k complementary deoxyribonucleic acid by anchored polymerase chain reaction technique.

The Calbindin-D9k (CaBP-9k) is a cytosolic calcium binding protein expressed in the mammalian intestine, placenta, and uterus. The protein is probably involved in calcium transport across the intestinal and placental epithelia. In uterus, a function in controlling myometrial activity involving intracellular calcium has been postulated. The amino acid sequence of the porcine CaBP-9k has been determined from intestine. The cDNAs for the bovine, murine, and rat CaBP-9k have been cloned. The objective of this study was the cloning of the porcine cDNA encoding the CaBP-9k. We performed the anchored polymerase chain reaction (PCR) technique using rat and bovine cDNA sequence-derived primers for amplification of intestinal cDNA. Both 5' and 3' amplification products were cloned and sequenced. The sequences revealed the full-length cDNA encoding the porcine CaBP-9k, coding region for 79 amino acids, 57 nucleotides 5' and 149 nucleotides 3' noncoding region. The inferred amino acid sequence is identical to the published amino acid sequence, except for one residue. The porcine CaBP-9k cDNA is 82.8% and 69.1% homologous with the bovine and rat sequences, respectively. Both bovine and porcine cDNAs contain a stretch of approximately 50 nucleotides not found in the rat sequence. Northern analysis showed a 600 nucleotide transcript in intestine, kidney, and uterus.

Amino Acid Sequence↗

Porcine calbindin-D9k gene: expression in endometrium, myometrium, and placenta in the absence of a functional estrogen response element in intron A.

The expression of Calbindin-D9k (CaBP-9k) in the pig uterus and placenta was measured by Northern blot analysis and reverse transcription polymerase chain reaction (PCR), respectively. Progesterone (P4) administration to ovariectomized pigs decreased CaBP-9k mRNA levels. Expression of endometrial CaBP-9k mRNA was high on pregnancy Days 10-12 and below the detection limit on Days 15 and 18. On Day 60, expression could be detected at low levels. In myometrium and placenta, CaBP-9k mRNA expression was not detectable by Northern analysis using total RNA. Reverse-transcribed RNA from both tissues demonstrated the presence of CaBP-9k transcripts by means of PCR. The partial CaBP-9k gene was amplified by PCR and cloned to determine the sequence of intron A. In contrast to the rat CaBP-9k gene, the pig gene does not contain a functional estrogen response element (ERE) within this region. A similar ERE-like sequence located at the identical location was examined by gel retardation analysis and failed to bind the estradiol receptor. A similar disruption of this ERE-like sequence has been described in the human CaBP-9k gene, which is not expressed at any level in placenta, myometrium, or endometrium. It is concluded that the pig CaBP-9k gene is regulated in these reproductive tissues in a manner distinct from that in rat and human tissues. The regulation is probably due to a regulatory region outside of intron A, which in the rat gene contains the key cis element for uterine expression of the CaBP-9k gene.

Animals↗

Dopaminergic neurons expressing calbindin in normal and parkinsonian monkeys.

In cynomolgus monkeys, midbrain neurons immunoreactive (IR) for the calcium-binding protein calbindin D-28k (CaBP) occur principally in the dorsal tier of substantia nigra pars compacta (SNc) and in the ventral tegmental area (VTA), and most of these neurons co-express tyrosine hydroxylase (TH). In monkeys rendered parkinsonian (PD) after MPTP injections, CaBP-IR neurons are much less severely affected than TH-IR neurons in SNc and in VTA, and most spared neurons in SNc/VTA display both CaBP and TH immunoreactivity. These results reveal that, in contrast to the situation in other neurodegenerative diseases, CaBP may be used as a marker for a specific neuronal population that is less prone to degeneration in Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Compartmental distribution of parvalbumin and calbindin D-28k in rat globus pallidus.

The cellular localization of parvalbumin (PV) and calbindin D-28k (CB) in the globus pallidus (GP) of rats was studied with double-immunohistochemical methods applied to single sections. The two calcium-binding proteins were found to be differentially distributed in GP. PV-positive cells were largely concentrated in the lateral part of GP where CB immunostaining was minimal. Their number and location varied along the rostrocaudal axis of GP. Pallidal PV cells were either large and multipolar or small and fusiform. In contrast, the medial part of GP was markedly enriched with CB neuropil but largely devoid of PV-positive cells. This spatial segregation indicates the existence of at least two different functional domains in the rat GP.

Animals↗

Calbindin-D28K cells in the hamster SCN express light-induced Fos.

Although the suprachiasmatic nuclei (SCN) have been intensively analyzed, they contain a population of cells that has not yet been characterized. In this study, we examined the distribution of cells immunoreactive (ir) for calbindin-D28K (CaBP), calretinin (CR), parvalbumin, vasopressin-associated neurophysin (NP), substance P (SP), vasoactive intestinal peptide (VIP), and light-induced Fos-like protein. Previously unidentified cells in the core of the hamster SCN contained CaBP. Photic stimulation during the night induced Fos expression in about 75% of the CaBP-positive SCN cells, and about 50% of the Fos-positive cells in the core region expressed CaBP. These findings provide new information in the search for the cellular localization of pacemaker cells in the SCN, as photic input entrains the circadian system, and cells that receive photic input must be either part of the clock itself, or an upstream component of the clock.

Animals↗

Co-localization of glycine and calbindin D-28k in the vestibular ganglion of the rat.

Bipolar neurons of the vestibular ganglion (VG) are biochemically heterogeneous. The calcium-binding protein calbindin D-28k (Calb) is present only in a subset of particularly large neurons, and the amino acid glycine (Gly) has been immunocytochemically detected in a group of similarly sized cells. The close correspondence in size and number of cells in these two subgroups suggests that the Calb- and Gly-positive populations may be identical. In order to test this hypothesis, we performed direct and indirect double-labeling for Calb and Gly in the VG of the rat. The results confirm the existence of a distinct subpopulation of Calb-immunoreactive neurons, consisting of the largest cells in the VG. In contrast, the vast majority of neurons in the VG display some degree of Gly immunoreactivity, which gradually decreases from intense to almost unlabeled. Direct evidence is provided that the fraction of cells most heavily labeled by Gly antibodies is not identical with the Calb-positive subpopulation. Although some correlation between soma diameter and labeling intensity exists, Gly immunoreactivity is clearly not restricted to large neurons. The findings imply that the functional mechanisms in which Gly is potentially involved may be shared by a large spectrum of primary vestibular afferents with a broad range of physiological properties.

Animals↗

Unipolar brush cells in marmoset cerebellum and cochlear nuclei express calbindin.

Unipolar brush cells (UBCs) are excitatory neurons in the mammalian cerebellum and cochlear nuclei (CN), including the CN of primates, as shown only recently. UBCs are readily identified by their expression of the calcium-binding protein calretinin (CR), except for those of the primate CN that hardly immunostain for CR. The present findings corroborate the existence of UBCs in the CN of a primate, Callithrix. Furthermore, evidence is presented for UBCs, in the cerebellum and a small subpopulation of UBCs in the CN of Callithrix to express the calcium-binding protein calbindin (CB). This may be unique for Callithrix as CB-expressing UBCs have not been recognized in any other mammal. Presence of CB but not CR in UBCs of the Callithrix CN may indicate a certain interchangeability between these two calcium-binding proteins.

Animals↗

No decrease of 1,25(OH)2D3 receptors and duodenal calbindin-D9k in uraemic rats.

In parathyroids of uraemic patients or animals, decreased specific binding of 1,25(OH)2D3 has been observed and implicated in the genesis of secondary hyperparathyroidism of renal failure. We re-examined binding of 1,25(OH)2D3 using chromatin preparations for receptor characterization which differed from previous studies (a) by inclusion of protease inhibitors (PMSF, aprotinin) and molybdate in the extraction buffer and (b) by omitting the K-extraction step. With this method, the Nmax in the intestinal mucosa and parathyroids of uraemic animals was significantly higher, while the receptor sedimentation constant (S), DNA affinity and KD were all unchanged. The ratio of occupied to total receptors was not significantly altered. The regulation of 1,25(OH)2D3 receptors in response to acute injection of 1,25(OH)2D3 was abnormal. Calbindin-D9k concentration in the intestines of uraemic and control rats was comparable both before and after administration of 1,25(OH)2D3. The present data demonstrate (a) increased 1,25(OH)2D3 receptors and (b) unchanged 1,25(OH)2D3-dependent synthesis of calcium binding protein (CaBP) in experimental uraemia.

Animals↗

Immunological characterization, developmental pattern and vitamin-D-dependency of calbindin D-28 K in rat teeth ameloblasts.

It has been suggested that vitamin D is involved in the process of cell differentiation and extracellular mineralization during tooth development. One of the best-defined molecular markers of the action of vitamin D is a calcium-binding protein of Mr 28,000 called calbindin D-28 K (CaBP 28 K). Since this protein is present in growing teeth, we have examined its synthesis in teeth from vitamin D-replete and -deplete rats by Western blotting and immunocytochemistry with an antiserum to CaBP 28 K purified from rat kidney. The CaBP 28 K present in the enamel organ is a single molecular species migrating near 30 k Da, similarly to the kidney protein. The differentiation and maturation of odontogenic cells were followed during early postnatal development (2-12 days) in rat molars. At the light-microscope level, CaBP 28 K was only found in a single cell-type, the ameloblasts. The expression of this protein appeared to be developmentally controlled, since its distribution varied with the cell stage and the functional steps of amelogenesis. The protein was localized in the basal compartment of ameloblasts from the presecretory stage. During the early secretory stage, the concentration of cytoplasmic CaBP 28 K formed a gradient from the apical to the basal pole of the ameloblasts. Staining appeared homogeneous in the cytoplasm of later secretory ameloblasts. CaBP 28 K was discontinuously distributed during the maturation stage. This discontinuity might be related to cyclical changes in mature ameloblasts. In all stages, ameloblasts from vitamin-D-deficient rats appeared depleted of CaBP 28 K.

Ameloblasts↗