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M Thomasset

Publications and source records attributed to M Thomasset.

At least 37 records · Page 2Linked to original sources
PubMed1993

Estrogen-induced calbindin-D 9k gene expression in the rat uterus during the estrous cycle: late antagonistic effect of progesterone.

Progesterone modulates estrogen-stimulated responses in the uterus. Calbindin-D 9k (CaBP9k), a 17 beta-estradiol-responsive gene expressed in the uterus, was used as a marker to examine the interactions between endogenous progesterone and estradiol in the rat. The variations in uterine CaBP9k messenger RNAs (mRNAs) during the rat estrous cycle indicated that CaBP9k gene expression was greatest during the estrogen-dominated phases (proestrus and estrus) and became totally repressed during diestrus, when progesterone predominates. Estradiol was found to be the major controlling factor of CaBP9k gene expression in vivo, progesterone antagonizing estrogen-induced CaBP9k gene expression. The inhibitory role of progesterone was further examined in two experiments. Mature cyclic rats were injected with the progesterone antagonist RU486 before the progesterone surge of proestrus, and the estrous cycle was mimicked in ovariectomized rats by sequential injections of estrogen and progestin. Progesterone did not appear to be involved in the rapid decrease in CaBP9k mRNA during estrus but was implicated in the down-regulation of the estrogen-stimulated CaBP9k gene expression at the end of estrus and during diestrus. This delayed effect of progesterone was confirmed in the ovariectomized rat model. CaBP9k mRNA accumulation in estrogen-primed ovariectomized rats was suppressed by estrogen followed 1 h later by the progesterone agonist R5020. This effect occurred more than 24 h after progestin treatment. The inhibition of the estrogen-induced CaBP9k gene expression in the rat uterus by progesterone is certainly mediated by the progesterone receptor, because progesterone had no effect without estrogen priming or when the antagonist RU486 was used. The delayed progesterone effect probably does not involve depletion of nuclear estrogen receptors, the major rapid mechanism proposed for estrogen inhibition by progesterone in the rodent uterus, or control of estrogen receptor synthesis, as shown by Northern blot analysis of estrogen receptor mRNA.

Animals↗
PubMed1992

Development of the olivocerebellar projection in the rat: I. Transient biochemical compartmentation of the inferior olive.

In the present study the early phases of the development of the inferior olive were examined by using immunocytochemical techniques. We observed that, from embryonic day 16 onward, antibodies against the calcium binding proteins parvalbumin and calbindin and the calcitonin gene related peptide stain partially overlapping territories of the inferior olive. This staining delimits a biochemical zonation of the inferior olive which is combinatory and transient. We have previously observed a biochemical parcellation of the cerebellar Purkinje cells which, like that of the inferior olive, is first observed at E16, involves the combined expression of marker proteins and is also transient. In order to know whether the biochemical compartmentations of the cerebellum and inferior olive arise independently, the time course of the development of the olivocerebellar projection was studied by anterograde and retrograde in vitro axonal tracing by using the fluorescent carbocyanine dye DiI. The olivocerebellar axons were found to reach the limit of the cerebellar plate at E16 and to enter it at E17. Even at this age the great majority of the climbing fibers are tightly fasciculated, which minimizes their interactions with the PC clusters. These observations indicate that the topographical heterogeneity of Purkinje cells and inferior olive neurons arise independently. The transient biochemical individualization of subgroups of neurons during development could contribute to recognition mechanisms.

Animals↗
PubMed1992

Calbindin-D28K and ischemic damage of pyramidal cells in rat hippocampus.

An antibody against rat calbindin-D28K, a calcium-binding protein present at high concentration in certain neurons of the central and peripheral nervous systems, was used to determine the progression of the pathological events in the rat hippocampus following experimental cerebral ischemia. Calbindin-D28K immunoreactivity is present in dentate granule cells and in the CA1-CA2 pyramidal cells. CA1 subfield contains a higher proportion of calbindin-D28K-positive pyramidal cells than does the CA2 subfield and CA1 cells are more immunoreactive than the CA2 cells. The pyramidal cells of the CA1 and CA2 subfields are vulnerable to ischemia. The cells in the CA1 became necrotic within 3-4 days after ischemia while those of the CA2 became necrotic within 2 days. There was a concomitant decrease in calbindin-D28K immunoreactivity in the whole hippocampal regio superior after ischemia which peaked 3 days postischemia. The difference in CA2 and CA1 vulnerability seemed to be inversely correlated with the calbindin-D28K contents of the CA2 and CA1 pyramidal cells. The decrease in the calbindin-D28K contents of these neurons was accompanied by cell damage. We therefore suggest that calbindin-D28K is an important factor for the survival of pyramidal cells in the hippocampal formation after ischemia.

Animals↗
PubMed1992

Calbindin-D9K gene expression in the lung of the rat. Absence of regulation by 1,25-dihydroxyvitamin D3 and estrogen.

Calbindin-D9K (CaBP9K) is classically considered to be the molecular expression of 1,25-dihydroxyvitamin D3. The hormone is known to regulate the rat CaBP9K gene in duodenal tissue at transcriptional and posttranscriptional levels. This study shows that the CaBP9K gene is expressed in the rat lung, and that this expression is probably not vitamin D- or estrogen-dependent. The CaBP9K gene is not expressed in alveolar macrophages, but CaBP9K messenger RNA (mRNA) was localized by in situ hybridization in alveolar epithelial cells. CaBP9K mRNA was detected as early as the 20th day of gestation. The quantity of CaBP9K mRNA gradually increased during growth, from 1-77 days after birth, whereas the CaBP9K concentration dramatically increased from day 19 to day 20 of gestation. Vitamin D-deficient male rats (8 weeks old) were given a single injection of 1,25-dihydroxyvitamin D3 (650 pmol/100 g body wt) and killed 1 h and 24 h after injection. The hormonal treatment resulted in a rise in duodenal CaBP9K mRNA, but no significant change in lung extracted CaBP9K mRNA. Mature ovariectomized rats were injected with 17 beta-estradiol (0.5 microgram/100 g body wt) and killed 24, 48, and 72 h later. The CaBP9K mRNA concentration in the uterus was markedly dependent on estrogen; that of the lung was not. The factors regulating the CaBP9K gene expression in the lung remain to be determined.

Aging↗
PubMed1991

DNase I-hypersensitive sites are associated, in a tissue-specific manner, with expression of the calbindin-D9k-encoding gene.

We have examined the chromatin structure of a 28-kb chromosomal region containing the gene (CaBP9k) encoding calbindin-D9k in different rat tissues. DNase I-hypersensitive sites (HSs) were probed with DNase I using an indirect end-labeling technique. Duodenal chromatin, where the gene is strongly expressed, contained one major HS (HS4) and three minor HSs (HS2, HS3 and HS5) near the promoter region. The HS4 was mapped just upstream from the promoter region and had the characteristics of a tissue-specific HS. The HS5 was located at the transcription start point, it included the TATA box and its presence was correlated with a promoter function. The duodenal chromatin contained two additional HSs, a major HS (HS1) located approx. 3.5 kb upstream from the cap site and a minor HS (HS6) in the second intron at +0.5 kb. Despite the marked effect of 1,25-dihydroxyvitamin D3 (DHD3) on the CaBP9k mRNA level, the pattern of HSs in duodenal chromatin was unchanged after stimulation with DHD3. The liver chromatin contained one major HS (HS1) identical to the duodenum HS1 (although this tissue does not express CaBP9k). It also contained a liver-specific HS (HS0) 0.1 kb upstream from HS1. The interaction of HS0 with HS1 could explain the absence of CaBP9k expression in the liver. Thus, specific sets of HSs are associated with various functional states of CaBP9k in a tissue-specific manner.

Amino Acid Sequence↗
PubMed1991

The immunocytochemical distribution of calbindin-D28k and parvalbumin in identified neurons of the pulvinar-lateralis posterior complex of the cat.

The calbindin-D28k and parvalbumin immunoreactivities of the neurons of the pulvinar-lateral posterior complex (Pul-LP) were studied in the cat. The neurons of the Pul-LP projecting to the cerebral cortex were identified by a retrogradely transported tracer injected in the suprasylvian gyrus. Two populations of cells were found, a calbindin-D28k-immunoreactive, large-diameter population and a parvalbumin-immunoreactive, small-diameter group. The two kinds of cells are closely intermingled. The former includes the neurons retrogradely marked, and therefore projecting to the suprasylvian gyrus. The latter includes neurons which were not retrogradely marked, and therefore presumably intrinsic elements.

Animals↗
PubMed1991

Differential expression of calbindin-D 28 kDa in rat incisor ameloblasts throughout enamel development.

Calbindin-D 28 kDa (CaBP 28 kDa), a vitamin D-dependent calcium-binding protein, has been associated with calcium handling by cells. We have investigated the expression of this protein in the rat incisor enamel organ, an epithelium interposed between a mineralizing matrix and connective tissue rich in blood vessels, by radioimmunoassay (RIA), Western blotting, and quantitative protein A-gold immunocytochemistry with antibodies to rat kidney CaBP 28 kDa. RIA of cytosolic extracts showed that enamel organs contained relatively high concentrations of CaBP 28 kDa (compared to kidney; see review by Christakos S., C. Gabrielides, and W.B. Rhoten 1989 Endocr. Rev., 10:3-25). Immunoblotting of proteins extracted from enamel organ strips revealed an intensely-stained band near 28 kDa throughout amelogenesis following ameloblast differentiation. Immunocytochemically, CaBP 28 kDa was localized exclusively within ameloblasts. The density of labelling increased from the presecretory stage to the secretory stage and fluctuated across the maturation stage in relation to ameloblast modulation. Ruffle-ended ameloblasts consistently showed the most intense immunoreaction. Gold particles were present throughout the cytoplasm and nuclei of ameloblasts but regions rich in rough endoplasmic reticulum or cell webs showed a higher immunolabelling. Some gold particles were also associated with the external face of the rough endoplasmic reticulum. Multivesicular bodies in maturation stage ameloblasts were occasionally immunoreactive. These data suggest that the intracellular concentration of CaBP 28 kDa is regulated throughout amelogenesis reflecting a stage-specific control of calcium homeostasis in ameloblasts.

Ameloblasts↗
PubMed1991

Effects of 1,25(OH)2D3 on compensatory renal growth in the growing rat.

Renal compensatory growth after uninephrectomy (UNX) was examined in vitamin D replete male 100 g Sprague-Dawley rats. Five days after UNX, the contralateral kidney wet weight increased by 25% with the kidney weight/body weight ratio reaching a plateau by day 7 after UNX. The early weight increase was primarily due to an increased cell number, as evaluated by a stereological technique in perfusion-fixed kidneys. Twenty pmol 1,25(OH)2D3 by daily s.c. injection increased time-averaged 1,25(OH)2D3 concentrations 3.3-fold and reduced the increment in the kidney weight of UNX pairfed rats compared to solvent UNX controls. The number of mitoses (whole kidney and different nephron segments) were significantly reduced by giving 1,25(OH)2D3 to UNX animals at different levels of food intake. The effect was also demonstrable in PTX animals on a constant infusion of exogenous PTH (100 ng/kg/hr 1,34 bPTH by osmotic minipump). The data suggest that changes of 1,25(OH)2D3 concentration within a physiologically relevant range modulate compensatory (and possibly basal) growth of the kidney.

Animals↗
PubMed1991

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↗
PubMed1991

Abnormal intestinal regulation of calbindin-D9K and calmodulin by dietary calcium in genetic hypertension.

Using isolated duodenal cells from spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto rats (WKY), we previously showed that cellular calcium flux was decreased in SHR and that increasing dietary calcium (from 1 to 2%) eliminated strain differences in Ca2+ fluxes. The present study was carried out to investigate the role of calbindin-D9K and calmodulin in the flux difference and dietary calcium effects. Calbindin-D9K and calmodulin were separated by sodium dodecyl sulfate (SDS) gel electrophoresis in duodenal protein extracts of SHR and WKY (12-14 and 24-26 wk old) fed either a 1 or 2% calcium diet and measured by a ligand blotting (45Ca) technique. Young SHR had a significantly lower calbindin-D9K (P less than 0.001) than did WKY on either diet. Calmodulin was significantly lower in young SHR than in WKY (P less than 0.002). There was no strain difference in calmodulin in older rats fed the normal calcium diet. Calbindin-D9K was significantly decreased by the high-calcium diet in both strains at both ages. There was a significant correlation between duodenal calbindin-D9K and plasma levels of calcitriol (r = +0.80, P less than 0.001) in WKY but not in SHR. Calmodulin was significantly decreased by dietary calcium in mature WKY (4.8 +/- 0.2 vs. 3.7 +/- 0.4 micrograms/mg cell protein, P less than 0.03), demonstrating a potential regulation by dietary calcium of this protein. Finally, there was a significant correlation between calbindin-D9K and calmodulin (r = 0.59, P less than 0.001) in WKY but not in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Expression of compartmentation antigen zebrin I in cerebellar transplants.

The mammalian cerebellum is divided into multiple parasagittal compartments as defined by the organization of afferent and efferent projections and by the pattern of expression of several biochemical markers. One such marker is the antigen zebrin I, a 120 kD polypeptide of unknown function that is expressed differentially by a subset of Purkinje cells. Zebrin I+ Purkinje cells are grouped into an array of 14 parasagittal bands interposed by zebrin I- compartments. This Purkinje cell compartmentation corresponds to compartments in the olivocerebellar projection. The afferent axon compartments are present prior to the expression of the mature zebrin I phenotype, thus raising the possibility that differential afferent input regulates the zebrin I phenotype of the target of that input. Lesion studies in the neonate preclude a role for afferent inputs in the regulation of zebrin I expression postnatally, but a prenatal role in commitment still remains open. To explore this possibility, cerebellar anlagen were dissected from embryos at embryonic days 12-15, that is, prior to any contact with afferents, and transplanted ectopically into adult hosts. In the first series of experiments, the grafts were placed into the anterior chamber of the eye, and in the second series, into cavities prepared in the neocortex. Grafts were allowed to mature and then were immunoperoxidase or immunofluorescence stained for zebrin I immunoreactivity. Zebrin I was expressed by grafted Purkinje cells in cortico and in oculo. Double-labelling experiments confirmed that both the zebrin I+ and the zebrin I- phenotypes were present. The zebrin I immunoreactivity revealed that the zebrin I+ Purkinje cells resemble those in situ with an extensive dendritic arborization that extends through the molecular layer perpendicular to the long axes of the folia. In conclusion, the present data suggest that afferent input does not play a role in the determination of the zebrin I phenotype of Purkinje cells.

Animals↗
PubMed1990

Colocalization of calbindin and GABA in medial nucleus of the trapezoid body of the rat.

Using immunocytochemical methods, both calbindin and GABA were found to be colocalized in the somas of all the cells of the medial nucleus of the trapezoid body (NMTB) of the rat auditory system. In the lateral superior olive (LSO), calbindin was also found in the terminals but not in the cells. Some terminal labelling was found in the medial superior olive (MSO). GABA was also found in the somas of some cells in both LSO and MSO, but most of the labelling was in terminals. In the rat, calbindin appears to be more involved in a pathway that detects interaural intensity differences.

Animals↗
PubMed1990

Ultrastructural and functional abnormalities of intestinal and renal epithelium in the SHR.

Intestinal calcium transport, renal tubular calcium reabsorption, and plasma 1.25 (OH)2 vitamin D3 (calcitriol) levels have all been reported to be diminished in the spontaneously hypertensive rat (SHR) compared with its genetic control the Wistar Kyoto rat (WKY). In the present study, absorptive duodenal and renal tubular epithelia of 12- to 14-week-old male SHR and WKY were examined by electron microscopy to determine whether such disturbances could be related to structural abnormalities. Patchy loss of microvilli in both duodenal and proximal tubular epithelia was observed in the SHR, whereas brush border membrane was entirely normal in the WKY. Irregular spaces were observed between the basal aspects of SHR intestinal epithelial cells and their basement membrane. In addition, the average height of duodenal and renal microvilli was reduced in the SHR. Two specific markers of the brush border membrane, alkaline phosphatase and villin, as well as the cytoplasmic vitamin-D dependent calcium-binding proteins, CaBP9K and CaBP28K were determined. Duodenal alkaline phosphatase activity was reduced in the SHR, compared with the WKY: 0.145 +/- 0.002 vs. 0.186 +/- 0.002 IE/min.microns 3 x 10(3) brush border, mean +/- SEM, N = 10 pairs, P less than 0.001. However, duodenal villin expression was not different from that of the WKY. Duodenal CaBP9K and renal CaBP28K content was diminished in the SHR: 21.0 +/- 0.80 vs. 29.9 +/- 2.19 micrograms/mg protein, N = 6 pairs, P less than 0.01 for duodenum, and 4.47 +/- 0.39 vs. 7.67 +/- 0.54 micrograms/mg protein, N = 6 pairs, P less than 0.001 for kidney. These data showing structural and functional abnormalities of intestinal and kidney cells in the SHR appear to reflect a disorder of transporting epithelia which may be either intrinsic or related to reduced circulating calcitriol.

Alkaline Phosphatase↗
PubMed1990

Epithelial abnormalities in intestine and kidney of the spontaneously hypertensive rat.

A variety of perturbations of calcium metabolism are reported to occur in the spontaneously hypertensive rat (SHR) compared to its genetic control the Wistar-Kyoto rat (WKY), including significant dysfunction of calcium handling by the proximal renal tubule of the SHR, resulting in impaired active calcium transport in the gut and an apparent renal calcium leak. We explored the intestinal and renal epithelia of 12- to 14-week-old SHR and WKY using electron microscopy. Biochemical comparisons of these transport epithelia included measurements of three vitamin D dependent cellular proteins and one structural protein: alkaline phosphatase, intestinal CaBP9K, renal CaBP28K, and villin expression. Electron microscopy demonstrated a patchy loss in microvilli in the SHR, accounting for approximately 10 to 15% of the total microvillar surface. In the kidney, morphological abnormalities were observed only in the proximal renal tubule. Again, there was patchy loss of microvilli from the brush border membrane. In SHR duodenal alkaline phosphatase activity was significantly reduced compared to the WKY (0.145 +/- 0.002 v 0.186 +/- 0.002 integrated extinction/min/micron 3 X 10(3) brush border (P less than .001). Duodenal CaBP9K and renal CaBP28K were significantly reduced in SHR compared to WKY. There were no differences in villin expression. These data are consistent with the previously characterized disturbances of active calcium transport in the intestine and inappropriate renal calcium leak in the SHR. While a possible link between these disturbances and hypertension remains to be determined, this study provides supportive evidence for a primary disturbance in cell calcium handling and transporting epithelia in this form of genetic hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Developmental changes of Ca2+, PO4, and calcitriol metabolism in spontaneously hypertensive rats.

We have measured Ca and P balance, serum calcitriol, and vitamin D-dependent intestinal calcium-binding protein (CaBP9k) in the spontaneously hypertensive rat (SHR) and its normotensive control, the Wistar-Kyoto rat (WKY) at 4-5 and again at 13-14 wk of age. In rats on a 1% Ca diet, P balance was significantly more positive in the 5-wk-old SHR than WKY (P less than 0.01); Ca balance tended to be greater in the 5-wk-old SHR. In contrast, in the 14-wk-old SHR, P and Ca balance were less positive than in the WKY (P was 5.8 +/- 1.3 vs. 13 +/- 1.7 mg/day, P less than 0.01, and Ca was 53 +/- 4.6 vs. 67 +/- 2.7 mg/day, P less than 0.05). On the 1% Ca diet, plasma calcitriol levels of the 5-wk-old SHR were higher than those of the WKY (58 +/- 3.2 vs. 40 +/- 2.1 pg/ml, P less than 0.002), whereas at 12 wk there was no difference. On Ca-deficient (0.1%) diets, plasma calcitriol was increased in 5-wk-old and 12-wk-old SHR and WKY, compared with the 1% Ca diet (P less than 0.001). Calcitriol metabolic clearance rate was the same in the 13-wk-old SHR and WKY on either Ca diet. Intestinal CaBP9k content of the 5-wk-old (38 +/- 2.6 vs. 40 +/- 3.9 micrograms/mg) and the 12-wk-old (11 +/- 1.6 vs. 14 +/- 1.4 micrograms/mg) SHR and WKY were similar on the 1% Ca diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Stimulation of calbindin-D9K (CaBP9K) gene expression by calcium and 1,25-dihydroxycholecalciferol in fetal rat duodenal organ culture.

We have used organ cultures of 18-day fetal rat duodena to study the regulation of calbindin-D9K (CaBP9K) gene expression by 1,25-dihydroxycholecalciferol (1,25(OH)2D3) and calcium. The epithelium of the fetal rat duodena maintained in culture for 10 days in a defined serum-free medium with no exogenous 1,25(OH)2D3 contains differentiated enterocytes. Treatment with 10(-8) M 1,25(OH)2D3 resulted in a 2-fold increase in CaBP9K messenger RNA (mRNA) after 1 h; CaBP9K content was increased 2.5-fold in 24 h. Simultaneous treatment of cultures with 1,25(OH)2D3 and 1 microM actinomycin D selectively blocked 1,25(OH)2D3-stimulated CaBP9K mRNA and protein synthesis. Fifty micromolars of cycloheximide significantly decreased CaBP9K protein accumulation but not mRNA. These findings indicate that 1,25(OH)2D3 controls CaBP9K gene transcription. Enterocytes exhibit some CaBP9K gene expression after 10 days under basal culture conditions, suggesting that CaBP9K synthesis is not dependent on 1,25(OH)2D3 alone. This basal expression drops after 24 h in a calcium free medium with 1 mM EGTA, suggesting that extracellular calcium is involved in the control of this gene. Increasing the calcium concentration to 1.2 mM resulted in a 6-fold increase in CaBP9K mRNA after 3 h and a 10-fold increase in CaBP9K protein content after 24 h. Calcium may increase CaBP9K gene transcription, since simultaneous addition of 1 microM actinomycin D and calcium blocked the calcium effect on CaBP9K mRNA. Therefore, this in vitro study demonstrates that both calcium and 1,25(OH)2D3 stimulate CaBP9K gene expression in the rat duodenum.

Animals↗