Biomedical subjects

L Cancela

Publications and source records attributed to L Cancela.

At least 19 recordsLinked to original sources

PubMed1994

Chronic restraint attenuates the immunosuppressive response induced by novel aversive stimuli.

The exposure to a novel aversive event, such as foot shock, induced a decrease in the percentage of T lymphocytes and a clear reduction in the delayed-type hypersensitivity reaction (DTH). This immunosuppressive response to an acute stressor was absent in rats that were previously exposed to a chronic immobilization stress regime (2 h daily during 7 consecutive days), but was still present in animals with prior exposure to only one or three restraint sessions. No stress effect was observed in other immunologic parameters, such as the percentage of B lymphocytes or the hemagglutinin titer, in any of the experimental treatments. The possible involvement of central adaptive mechanisms in the attenuation of the immunosuppressive response induced by an acute stress is discussed.

Animals↗

PubMed1993

Seven-day variable-stress regime alters cortical beta-adrenoceptor binding and immunologic responses: reversal by imipramine.

Rats were submitted daily to a variable stressor for 1 week with or without concurrent imipramine (IMI) administration. One day after the last injection or stressful event, binding of cortical beta-adrenoceptors was determined in all experimental groups. Another group of chronically stressed animals with or without concurrent IMI administration were sacrificed 24 h following the last stress or injection treatment, and several immunologic parameters were evaluated. Chronically stressed rats showed an enhanced number of cortical beta-adrenergic sites without changes in their affinity. This effect was not present following concurrent administration with the antidepressant. In addition, a decreased percentage of T lymphocytes and a reduced delayed-type hypersensitivity reaction was also observed in stressed animals. Both responses were no longer evident when stressed rats were previously administered IMI. A possible link between behavioral, neurochemical, and immunologic alterations due to the stress regime is discussed.

Animals↗

PubMed1992

Local chromatin changes accompany the expression of the calbindin-D28K gene: tissue specificity and effect of vitamin D activation.

The high affinity calcium-binding protein calbindin-D28K is one of the known proteins transcriptionally up-regulated by the hormonally active form of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. This regulation is tissue specific, since in the absence of 1,25-(OH)2D3, the expression of calbindin-D28K is virtually abolished in intestine, whereas it is decreased, but clearly detectable, in kidney, and it remains present at its highest level in cerebellum. Several studies have shown that there is a strong correlation between an increase in the sensitivity to nuclease digestion of a given gene locus and its potential for transcription. Furthermore, hypersensitive sites have often been mapped to regions of DNA including or surrounding sequences known to be important for the regulation of gene transcription. In this study we have scanned the 5'-end and flanking DNA of the calbindin-D28K gene for the presence of DNase-I-hypersensitive (DH) sites in order to localize possible regulatory regions involved in the tissue-specific and hormone-dependent regulation of this gene. We have found that in tissues where calbindin is not expressed, such as liver, no DH sites could be detected. In cerebellum, the same set of DH sites was observed in the presence or absence of 1,25-(OH)2D3 treatment, reflecting the vitamin D-independent expression of the calbindin gene in this tissue. A more complex pattern of DH sites was found in intestine, independently of the vitamin D status of the animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Molecular structure, chromosome assignment, and promoter organization of the human matrix Gla protein gene.

Matrix Gla protein (MGP) is an 84-residue vitamin K-dependent protein initially isolated from bovine bone. MGP is also expressed at high levels in heart, kidney, and lung and is up-regulated by vitamin D in bone cells. To characterize the genomic sequences responsible for the regulated expression of this gene, we screened a human genomic library using a MGP cDNA probe and obtained two clones containing the MGP locus. The human MGP gene spans 3.9 kilobases of chromosomal DNA and consists of four exons separated by three large intervening sequences which account for more than 80% of the gene. Southern analysis of total human genomic DNA indicated the presence of a single copy of the MGP gene. Hybridization of the hMGP cDNA to a series of Chinese Hamster x human hybrid clones assigned this gene to the short arm of the human chromosome 12 (12p). The N-terminal sequences of the known vitamin K-dependent vertebrate proteins reveal a transmembrane signal peptide, followed by a putative gamma-carboxylation recognition site and a Gla-containing domain. Each of these regions correspond to a separate exon in MGP. MGP also contains a fourth exon of unknown function which codes for 11 residues and lies between the transmembrane signal peptide and the putative recognition site for the gamma-carboxylase. This four-exon organization is essentially identical to that of bone Gla protein and is quite different from the two exon organization encoding this region in the other known vitamin K-dependent proteins. Analysis of the MGP gene promoter revealed, in addition to the typical TATA and CAT boxes, the presence of a number of putative regulatory sequences homologous to previously identified hormone and transcription factor responsive elements. In particular, two regions of the promoter were delineated containing possible binding sites for retinoic acid and vitamin D receptors.

Amino Acid Sequence↗

PubMed1990

Opioid involvement in the adaptive change of 5-HT1 receptors induced by chronic restraint.

Rats immobilized for 2 h daily for 7 days showed an increased behavioral response (forepaw treading and hind-limb abduction) to 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) 24 h after the last stress session. An injection of naloxone before each stress session fully antagonized the increased behavioral reactivity to 5-MeODMT. Treatment with morphine or beta-endorphin associated with each immobilization session for 3 days produced a response to 5-MeODMT higher than that of animals subjected to immobilization only. Chronic immobilization for 7 days did not affect the shaking behavior induced by 5-hydroxytryptophan (5-HTP) 24 h after the last restraint session. These findings suggest that chronic stress may induce a selective adaptive change of the 5-HT1 site and activate an opioid mechanism that is most likely to be involved in the development of this adaptive change.

5-Hydroxytryptophan↗

PubMed1990

Effect of chronic variable stress on monoamine receptors: influence of imipramine administration.

Adult male rats were exposed to a series of unpredictable stressors, a paradigm considered to be a model of experimental depression, with or without concurrent administration of imipramine. One day after the last stress event of the chronic regime, binding of cortical beta-adrenoreceptors and the behavioral serotonin (5-HT) syndrome induced by 5-methoxy-N,N,dimethyltryptamine (5-MeODMT) were determined in all the experimental groups. Stressed rats showed an "up-regulation" of cortical beta-adrenergic sites, while similar values to control rats were observed when stressed animals were administered imipramine. Regarding the behavioral 5-HT syndrome, comparable behavioral scores were observed between controls and chronically stressed rats. The combination of chronic exposure to different stressors with imipramine treatment resulted in a significant increase of forepaw treading and Straub tail scores. The probable facilitation of behavioral deficits induced by this scheme of chronic stress and the recovery following concurrent administration of imipramine are discussed.

Animals↗

PubMed1988

1 alpha,25(OH)2 vitamin D3: a steroid hormone capable of producing pleiotropic receptor-mediated biological responses by both genomic and nongenomic mechanisms.

Vitamin D3 is now considered a pro-hormone and its biological activities are in a great majority due to its hormonally active derivative 1 alpha,25-dihydroxyvitamin D3. The actions of vitamin D3 have been extensively studied both in vivo and in vitro using different animal models as well as a diversity of cell types including intestinal epithelial cells, kidney cells, lymphocytes, macrophages and a number of malignant cell lines. Results thus obtained have considerably extended the number of target tissues for this vitamin and hormone far beyond its classical target organs, parathyroid gland, kidney, intestine and bone. Studies performed at the cellular, subcellular and molecular levels have led to the establishment of new concepts on the mode of action of vitamin D3 which is not believed to act through receptor-mediated genomic and nongenomic events leading to the expression of the full biological response.

Animals↗

PubMed1988

Time course studies on phosphate transfer in frog urinary bladder.

Unidirectional 32P-phosphate and 3H-mannitol fluxes were simultaneously measured, at two minutes intervals, in frog urinary bladders. The spontaneous or externally imposed transepithelial potential (PD) and short circuit current (SCC) were also recorded in most experiments. It was observed that: (1) Phosphate transfer was rapidly and reversibly modified by changes in mucosal sodium concentration in open circuit conditions. (2) Between four and six minutes after changing mucosal NaCl concentration, phosphate fluxes reached a new steady-state value. (3) The observed correlation between the Na-dependent phosphate flux and the Na-dependent transmembrane potential was high (r = 0.99, N = 12). (4) In open circuit conditions, the mucosa-to-serosa unidirectional phosphate fluxes were inhibited by 10(-5) M amiloride, while the serosa-to-mucosa movements were increased. (5) On the contrary, no effects of mucosal NaCl concentration or amiloride on the mucosa-to-serosa phosphate fluxes were detected in short circuit conditions. (6) The transepithelial phosphate transfer was linearly related to phosphate concentration and insensitive to arsenate (10(-3) M) action. (7) An externally imposed PD was less effective for driving a phosphate movement than the one depending on Na, suggesting some type of coupling between Na+ and phosphate transports. (8) The mucosa-to-serosa phosphate fluxes were reduced by parathyroid hormone and oxytocin. Maximum inhibition was observed four minutes after the hormonal action. It is concluded that the transepithelial PD plays a major role in phosphate handling in frog urinary bladder.

Animals↗

PubMed1988

Calcium-transport in quiescent and 1,25-dihydroxycholecalciferol-stimulated human osteosarcoma cells. Role in 24 hydroxylase enhancement.

The present study evaluates in osteosarcoma cells, the effects of a calcium channel inhibitor nicardipine in 24-hydroxylase activity and 45Ca desaturation curve in presence of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). This sterol induced an increase in 24-OHase activity and 45Ca fluxes. Nicardipine reversed the effect of 1,25(OH)2D3 on 45Ca fluxes but reinforced the enhancement of the 24-OHase activity. The fact that the effects of 1,25(OH)2D3 were reduced by cycloheximide support the hypothesis of a de novo protein synthesis. Our study has allowed us to dissociate the effects of 1,25(OH)2D3 on 24-OHase enhancement from those on Ca2+ transport.

Calcitriol↗

PubMed1988

Influence of adrenocorticotrophic hormone on the behaviour in the swim test of rats treated chronically with desipramine.

Chronic desipramine (DMI) administration induced a dose-dependent reduction in the immobility time of the swim test in rats. A combined treatment of ACTH (50 iu kg-1 s.c.) and DMI (5 or 10 mg kg-1 i.p.) for 7 days potentiated the anti-immobility effect of DMI. ACTH 4-10, a fragment peptide with little corticotrophic activity, mimicked ACTH-induced potentiation. No stimulating effect on locomotor activity was observed following seven daily co-administrations of ACTH or ACTH 4-10 and DMI (10 mg kg-1). This behavioural evidence indicates that ACTH potentiation involves a central mechanism and demonstrates a functional interaction between ACTH and DMI at the behavioural level.

Adrenocorticotropic Hormone↗

PubMed1988

Molecular structure of the chicken vitamin D-induced calbindin-D28K gene reveals eleven exons, six Ca2+-binding domains, and numerous promoter regulatory elements.

The seco-steroid hormone 1,25-dihydroxyvitamin D3 is known to induce the expression of a calcium binding protein termed calbindin-D28K in a variety of target tissues. In order to comprehend the mechanism of induction we have cloned and sequenced the chicken calbindin-D28K gene. The gene spans some 18.5 kilobases (kb) of chromosomal DNA from the putative Cap site to the polyadenylation site of the 2.8 kb mRNA. It is split into 11 coding exons by 10 intervening sequences. The promoter region of this gene is markedly G + C-rich (60-80%) extending from -225 to +400. Within this region we find 70 CpG dinucleotides, four G-C boxes, and numerous known promoter regulatory signals. These putative regulatory signals include a TATA box (ATAAATA) at -30 and a CAT box (CCAAT) at -326. Ten additional variant CAT boxes are found in the upstream promoter region (-218 to -770) of this gene. Furthermore we have identified a glucocorticoid-like responsive element at -410 (TCTACACACTGTTCC) and this element overlaps a metal responsive element (TGCACTC) and a variant CAT box (CCAAAT) and juxtaposes an enhancer-like core element (AAATGGT) on its 3'-side. In addition, the calbindin-D28K promoter is composed of a variety of simple repeated sequences, some of which are components of putative regulatory signals. All splice junctions were found to conform to the GT-AG rule. A consensus sequence of the 5'-splice junction reads AG/GTAAG-TTATA. A consensus sequence of the 3'-splice site consists of two elements: a pyrimidine track (mainly T) followed by ACAG/G-T. A two-dimensional model of calbindin-D28K was constructed which projects the existence of 6 alpha-helix-loop-alpha-helix regions characteristic of calcium binding domains. The 3'-end of the gene consists of a single large (2039 base pair) uninterrupted exon, an organizational feature common to other members of the calcium binding protein gene family which include calmodulin, parvalbumin, Spec I, myosin light chains, etc. Another feature common to the gene family is the presence of the repeated sequence ATTT or TTTA located in the 3'-untranslated exons. These simple repeat sequences could be involved in regulating mRNA degradation by serving as a ribonuclease recognition signal.

Amino Acid Sequence↗

PubMed1988

[Primary hyperparathyroidism seen in rheumatology. Clinical symptoms and the relation between bone histologic signs and biological parameters].

We report the clinical and biological picture of 34 primary hyperparathyroidism (PHT) cases, diagnosed in rheumatology. It concerned 25 women and 9 men, aged 61 + 11 years. The PHT was often asymptomatic (47 p. cent of cases) at the time of diagnosis. The clinical manifestations were dominated by asthenia (50 p. cent) and renal lithiasis (47 p. cent). We found a chondrocalcinosis in 29 p. cent of patients. No patient presented any bony manifestations of cystic osteitis; 7 out of 34 patients (including 6 women between 57 and 74 years) presented vertebral compression. The mean calcemia was 117 +/- 9 mg/l. There were no hypercalcemic attack. The dosage of PTH and cyclic AMP were elevated in 29 out of 32 and 28 out of 31 patients respectively. In all patients, the level of either of these two tests was increased. The chloremia/phosphoremia ratio was also extremely predictive of HBP, since it was increased, exceeding 3.3 in 33 out of 34 patients. The 25-hydroxyvitamin D levels (25 (OH) D) were normal. The levels of 1,25 (OH) 2D were markedly spread (37 +/- 16 pg/ml) and not significantly different from the reference group. Patients with lithiasis did not present a higher level of 1,25 (OH) 2D. A bone histomorphometry carried out in 15 patients showed a bone trabecular volume similar to that of the reference with the same age. The osteoclastic resorption was increased in all cases and was not correlated with the PTH level, but was significantly correlated with the level of 1,25 (OH) 2D (r = 0.79 p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1987

Regulation of 24-hydroxylase activity in mouse skin fibroblast by cholecalciferol derivatives, triamcinolone acetonide and a calcium modulating agent, nicardipine.

Mouse skin fibroblasts in culture were used to study the regulation of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) induced 24 hydroxylase (24-OH-ase) under the influence of 3 agents: (1) 24,25-Dihydroxycholecalciferol (24,25(OH)2D3), 62.5 10(-9) M, which led to a significant decrease in the 1,25(OH)2D3-induced 24-OH-ase, probably acted through a nuclear effect mediated by the 1,25(OH)2D3 receptor protein. (2) Triamcinolone acetonide (10(-6)M) which was found to increase the 24-OH-ase enhancement induced by 1.25 and 6.25 nM 1,25(OH)2D3 whereas it did not alter the effect of 31.2 nM 1,25(OH)2D3. (3) A factor which is likely to induce changes in the cell calcium transport or in the Ca pool sizes, i.e. a calcium channel blocker, nicardipine. The effect of 1.25 nM 1,25(OH)2D3 on 24-OH-ase activity was increased by nicardipine (20 microM) which was found to reduce the effect of 6.25 nM 1,25(OH)2D3. The rate of DNA synthesis (measured by [3H]thymidine incorporation) was increased after incubation of fibroblasts with 1,25(OH)2D3 (1.25 nM) plus triamcinolone acetonide (10(-6) M), although it was reduced by nicardipine in comparison with 1,25(OH)2D3 alone. So the effects of these agents on the 1,25(OH)2D3 induced 24-hydroxylase were shown to be independent of the rate of DNA synthesis.

Animals↗

PubMed1987

Lack of biological activity of vitamin D3-3 beta sulfate during lactation in vitamin D-deficient rats.

Sulfoconjugated vitamin D has been claimed to have an important antirachitic activity and to be present at higher amounts than free vitamin D in maternal milk. We have previously shown that vitamin D3-3 beta sulfate (SD3) administration has little effect on calcium and bone metabolism during pregnancy in rats. In the present work, we have compared the biological activity of free vitamin D3 (D3) and SD3 during the lactation period. After delivery, D-depleted (-D) female rats were orally treated with D3 or SD3 (1,300 pmoles/every two days) during 20 days of lactation. Vitamin D status was determined before, during and at the end of the treatment for mother rats and at days 1 and 20 of life in suckling pups. Both mothers and pups were sacrificed at day 20 of lactation and subjected to hormonal and mineral determinations and to histomorphometric analysis of bone metabolism. After 12 days of SD3 treatment, mother rats showed a slight but significant elevation in plasma concentrations of calcium phosphorus and vitamin D metabolites. This effect was reversed at the end of lactation; at this time most maternal plasma parameters did not differ from those observed in -D non-treated mothers. By contrast, 20 days of D3 administration in mothers normalized plasma biochemical parameters. These results were confirmed by analysis of both static and dynamic parameters of bone formation. Maternal SD3 treatment did not improve either plasma biochemical or histological parameters of bone formation and resorption in suckling pups which remained comparable to that of D-deficient pups; by contrast, pups from D3-treated mothers normalized most biochemical plasma parameters although bone metabolism remained abnormal. In conclusion, the biological activity of SD3 on bone and mineral metabolism during lactation in rats is as low as in the nonreproductive stages.

Animals↗

PubMed1986

Assessment of vitamin D sulphate in human milk using desorption chemical ionization mass spectrometry.

Vitamin D3 sulphate (SD3) identification in human milk was obtained using Desorption Chemical Ionization (DCI). The chemical ionization reagent gas used was nitrogen, molecules were ionized when the emitter was heated. SD3 was obtained from lactarium human milk and purified by high-performance liquid chromatography (HPLC). A selected ion monitoring (SIM) measurement was carried out with typical ions, m/z 366 for SD3 and m/z 384 for parent vitamin D3, the intensity ratio (I366/I384) greater than 1 being related to the presence of the sulphoconjugated form of vitamin D3 in the sample analysed. The detection of small quantities of SD3 in human milk is possible using this technique.

Chemical Phenomena↗

PubMed1986

Bone changes due to pregnancy and lactation: influence of vitamin D status.

The effects of pregnancy and lactation on endosteal bone formation and resorption were evaluated in vitamin D-depleted (-D) and vitamin D-repleted (+D) rats. Pregnancy induced a marked stimulation of osteoclastic bone resorption and of static and dynamic parameters of bone formation and mineralization. Bone resorption increased independently of vitamin D status and did not correlate with plasma 1,25-dihydroxyvitamin D3 [1,25(OH)2D] levels, but it was associated with increased plasma immunoreactive parathyroid hormone (iPTH) concentrations. Stimulation of the endosteal bone formation rate was mainly impaired in D-depleted rats, resulting in trabecular bone loss, which, in -D mother rats, was associated with decreased bone ash and total bone calcium. Lactation further stimulated bone resorption and reduced the trabecular bone volume; ash weight and bone calcium content were also decreased independently of the vitamin D status and changes in plasma iPTH levels. In presence of vitamin D, the bone formation rate increased fourfold during lactation but was unchanged in -D lactating rats. During lactation, vitamin D-depleted rats lost twofold more calcified bone than +D rats because of impaired mineralization. Thus, the present study shows that both the endosteal bone resorption and formation are stimulated by pregnancy and lactation and that vitamin D is required for normal bone mineralization during the reproductive period.

Animals↗

PubMed1986

Relationship between the vitamin D content of maternal milk and the vitamin D status of nursing women and breast-fed infants.

This work was designed to study the effect of the vitamin D content of human milk on the vitamin D status of exclusively breast-fed infants, and the relation between milk and maternal serum concentrations of vitamin D during the first month of lactation. Serum levels of calcium (Ca), phosphorus (P), magnesium (Mg) and 25-hydroxyvitamin D (25-OH-D) were determined in a racially heterogeneous population of nursing women, between days 3 and 5 (L3), 15 and 18 (L15) and 30 and 45 (L30) post partum. The same parameters were determined in the serum of 1-month-old breast-fed infants. Maternal milk samples were obtained at L3, L15 and L30 and analysed for Ca, P, Mg, vitamin D and 25-OH-D content. Milk levels of Ca, P and Mg were found to be within the range previously described by other authors. No correlation was found between serum and milk levels of vitamin D and 25-OH-D in nursing mothers. The 25-OH-D concentration in milk was related to its vitamin D content and strongly correlated (P less than 0.001) with the 25-OH-D levels in the serum of exclusively breast-fed infants. No significant changes were observed in maternal serum levels of 1,25-dihydroxyvitamin D (1,25-(OH)2D3) measured at L3 and L30, or between maternal and infant levels of 1,25-(OH)2D3 at L30. This study emphasizes the importance of the 25-OH-D content of maternal milk, in being primarily responsible for the vitamin D concentrations found in the serum of exclusively breast-fed infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Feeding↗

PubMed1986

Calcidiol in human milk. The effect of prohormone on vitamin D status of breast fed unsupplemented infants.

Vitamin D, free or sulfoconjugated, and calcidiol (25(OH)vitamin D) levels were measured by competitive binding assay in breast milk samples of nursing mothers. Vitamin D status of their unsupplemented breast fed infants was determined. A strong correlation was established during the first month of the infant life only between calcidiol mother milk content and breast-fed infant serum. Calcidiol seems to be the vitamin D derivative mainly responsible for the maintainance of the vitamin D status of the newborn infant.

24,25-Dihydroxyvitamin D 3↗