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F Chytil

Publications and source records attributed to F Chytil.

At least 19 recordsLinked to original sources
PubMed1992

A retinoic acid response element from the rat CRBPI promoter is activated by an RAR/RXR heterodimer.

The expression of the rat cellular retinol binding protein I (rCRBPI) can be upregulated in vivo by retinoic acid (RA). Here we have analyzed the rCRBPI promoter region and compared it to the corresponding mouse sequence. We find that the CRBPI 5' flanking region has been highly conserved between rat and mouse, including a RA response element (RARE) approximately 1 kb upstream of the start of transcription. The RARE is of the direct repeat type with a two nucleotide spacer. Like other direct repeat RAREs, this response element is activated by RAR alpha and beta but not by RAR gamma 1. Furthermore, the rCRBPI-RARE is most effectively activated when both RAR and RXR are present. In addition RAR/RXR heterodimers are required for efficient binding to the rCRBPI-RARE, while RARs or RXR alone do not interact effectively with this response element. The rCRBPI gene is therefore most likely activated in vitro by a RAR/RXR heterodimer.

Animals↗
PubMed1992

The lungs and vitamin A.

Evidence is reviewed supporting the view that vitamin A (retinol) and its metabolite, retinoic acid, called natural retinoids, are major factors involved in differentiation and in maturation of the lungs. This conclusion is based on morphological observation that lack of this dietary micronutrient causes keratinizing squamous metaplasia of the bronchopulmonary tree that can be reversed by refeeding the animal with retinol. In addition to these observations suggesting an indirect participation of retinol and/or retinoic acid in the differentiation of this organ, more direct evidence is presented that this vitamin is involved in pulmonary gene expression. Adult as well as fetal lungs accumulate retinyl esters, the storage form of vitamin A, contain specific retinol- and retinoic acid-binding proteins and, more importantly, express several isoforms of nuclear retinoic acid receptors. These proteins are involved in activation and repression of specific genes regulated by retinoic acid. That retinol and/or retinoic acid may be involved in lung maturation is suggested by experimental results showing depletion of lung retinyl esters at birth, by significant alterations in the levels of the cellular retinoic acid-binding protein during lung maturation and, more importantly, by reduction in the morbidity of prematurely born human neonates who are given vitamin A because they are susceptible to bronchopulmonary dysplasia.

Animals↗
PubMed1992

Effect of retinoids on nuclear retinoic acid receptors mRNA in adipose tissue of retinol-deficient rats.

In this study, we examined effects of retinol deficiency and three retinoids, all-trans-retinoic acid, 13-cis-retinoic acid, and etretin, the aromatic derivative of retinoic acid on nuclear retinoic acid receptor isoforms alpha, beta, and gamma mRNA in rat adipose tissue. Retinol deficiency caused an almost 50% decrease in isoform beta mRNA levels of adipose tissue, whereas little change occurred in the abundance of alpha and gamma isoforms transcripts in this tissue. Intragastric administration of all-trans-retinoic acid to retinol-deficient rats increased the adipose tissue retinoic acid receptor isoforms beta and gamma mRNA levels sixfold and twofold, respectively, in 4 h as compared to adipose tissue of retinol-deficient rats that were administered cottonseed oil. In contrast to this, 13-cis-retinoic acid and etretin at equimolar doses were not effective in inducing beta or gamma isoforms mRNA in retinol-deficient rats. These results show that adipose tissue isoform beta responds to retinol deficiency, and all-trans-retinoic acid rapidly induces beta and gamma mRNA isoforms in this tissue. Thus, retinoic acid may regulate expression of specific genes through its interaction with retinoic acid receptors in adipocytes.

Adipose Tissue↗
PubMed1991

Differential effects of all-trans and 13-cis-retinoic acid on mRNA levels of nuclear retinoic acid receptors in rat lung and liver.

The effects of three retinoids, all-trans-retinoic acid (all-trans-RA), 13-cis-RA, and etretin were examined on mRNA abundance of nuclear retinoic acid receptors (RAR-alpha, beta, and gamma) in lung and liver of retinol deficient and chow fed rats. All-trans-RA increased lung RAR-beta mRNA levels 5 or 11-fold in chow fed and retinol deficient rats, respectively. Similarly to lung, liver RAR-beta mRNA levels were 3-fold higher in retinol deficient rats fed all-trans-RA than the rats fed cottonseed oil. Lung RAR-gamma mRNA levels were also induced 2-fold by all-trans-RA. In contrast to this, 13-cis-RA and etretin at equimolar doses failed to enhance lung or liver RAR-beta or lung RAR-gamma mRNA levels in retinol deficient rats. These data for the first time show that all-trans-RA is more effective than its 13-cis-isomer in regulating the expression of RAR-beta and gamma transcripts in adult animal.

Animals↗
PubMed1991

Retinoic acid affects the expression of nuclear retinoic acid receptors in tissues of retinol-deficient rats.

The multitude of biological effects of the vitamin A metabolite, retinoic acid, are mediated by nuclear retinoic acid receptors (RARs), which are members of the steroid/thyroid hormone receptor superfamily. RAR-alpha, -beta, and -gamma are encoded by three genes from which multiple isoforms can be generated. Recent studies suggest that the expression of at least some RAR isoforms can be regulated by retinoic acid in certain cell lines. Here we examined regulation of RAR expression in the adult animal. RARs were analyzed by Northern blots from lung, liver, and testes of retinol-deficient rats. Retinol deficiency caused a 65-70% decrease in the mRNA levels of lung and liver RAR-beta, whereas no change was observed in RAR-alpha and -gamma mRNA levels in these organs. In the testes of retinol-deficient animals, two transcripts, RAR-alpha 1 (3.7 kb) and RAR-alpha 2 (2.8 kb), were detected as compared with one RAR-alpha 1 (3.7 kb) transcript in retinol-sufficient testes. When retinol-deficient rats were orally administered 1 dose of retinoic acid (100 micrograms per rat), lung RAR-beta mRNA levels started to increase after 1 hr and reached a 16-fold higher level after 4 hr; after 4 hr these retinoic acid-fed rats also showed a 7-fold increase in liver RAR-beta mRNA levels as compared with levels in the retinol-deficient rats. In contrast, liver, lung, and testes RAR-alpha transcripts remained either unchanged or showed only a slight increase in response to retinoic acid. RAR-gamma was constitutively expressed in lung, and its mRNA levels were induced 2-fold by retinoic acid. These results show tissue diversity in the rapid induction of RAR-beta and RAR-gamma by retinoic acid in the adult animal and suggest distinct roles for the various receptor isoforms in the control of the retinoid response.

Animals↗
PubMed1991

Expression of nuclear retinoic acid receptors in rat adipose tissue.

Expression of nuclear retinoic acid receptors (RAR-alpha, beta and gamma) was examined by Northern blots in rat lung, liver, and adipose tissue. Three transcripts of approximate sizes 7.3, 3.7, and 2.8 Kb were detected in adipose tissue. In contrast to adipose tissue only 3.7 and 2.8 Kb mRNA species were detected in liver and lung. Two RAR-beta gene transcripts (3.3 and 3.0 Kb) were expressed in adipose tissue, liver, and lung. RAR-gamma mRNA (3.36 Kb) was detected in adipose tissue and lung. The distribution of three RARs in adipose tissue suggests the physiological role of retinoic acid in the regulation of specific genes via RARs in adipocytes.

Adipose Tissue↗
PubMed1991

Site-directed mutagenesis of rat cellular retinol-binding protein. Alteration in binding specificity resulting from mutation of glutamine 108 to arginine.

Cellular retinol-binding protein (CRBP) is a retinol-specific binding protein. A rat cDNA clone of CRBP was expressed in Escherichia coli. In order to determine amino acid residues in CRBP which may be important for the binding of all-trans-retinol, comparative model-building studies were performed in which strong sequence similarities were identified between CRBP and several other binding proteins. Based on this analysis, specific amino acids were predicted to be important in retinol binding, and these predictions were tested using the technique of site-directed mutagenesis to subtly alter the protein's structure and function. Specifically, site-directed mutagenesis was performed to alter the Gln-108 to Arg-108 (Q108R). Making use of fluorescence, Q108R was found to have a 3-fold lower affinity for all-trans-retinol, and the fine structure of the excitation spectrum of the Q108R.all-trans-retinol complex was also different than for the wild type.all-trans-retinol complex. The mutant bound 13-cis-retinol with an excitation spectrum identical to wild type bound to 13-cis-retinol, but with only one-half of the fluorescence intensity. In competition binding experiments, the Q108R mutant was found to have similar binding affinities for all-trans-retinol, all-trans-retinoic acid, 13-cis-retinoic acid, and retinal, while wild type CRBP was only able to bind to all-trans-retinol. Thus, altering a single amino acid in CRBP (Gln-108 to Arg-108) caused a significant change in the ligand binding specificity of the protein.

Animals↗
PubMed1991

Opposing effects of retinoic acid and dexamethasone on cellular retinol-binding protein ribonucleic acid levels in the rat.

Cellular retinol-binding protein (CRBP) is a potential mediator of vitamin A action. To determine whether retinoic acid and dexamethasone administration, alone and in combination, influence CRBP gene expression, adult female vitamin A-sufficient Sprague-Dawley rats randomly received 1) all-trans retinoic acid (100 micrograms) by intragastric intubation, 2) dexamethasone (2 micrograms/g BW) by ip injection, or 3) both all-trans retinoic acid and dexamethasone in the same doses. Control animals received either cottonseed oil by intragastric intubation or saline by ip injection. Six hours after treatment, lung and liver tissue were collected for Northern blot analysis with the radiolabeled cDNA specific for rat CRBP. Retinoic acid administration increased the amount of lung CRBP mRNA only, whereas dexamethasone decreased both lung and liver CRBP mRNA abundance. In animals treated with both retinoic acid and dexamethasone, CRBP mRNA abundance was also reduced. We conclude that CRBP gene expression can be modulated by both retinoic acid and dexamethasone in the vitamin A-sufficient animal. In the whole animal, our findings indicate that dexamethasone not only represses CRBP gene expression, but also opposes the effect of retinoic acid.

Animals↗
PubMed1990

Plasma retinol-binding protein response to vitamin A administration in infants susceptible to bronchopulmonary dysplasia.

We hypothesized that changes in plasma retinol-binding protein (RBP) concentration in response to vitamin A administration might be useful for evaluating vitamin A status of very low birth weight infants susceptible to bronchopulmonary dysplasia. We prospectively studied 24 consecutively admitted neonates (birth weight less than 1350 gm, gestational age less than 31 weeks, ventilator dependent for greater than 24 hours after birth), who were eligible to receive 2000 IU supplemental vitamin A by intramuscular injection on postnatal day 1 and on alternate days thereafter for 28 days. In addition to serial assessment of vitamin A status, we measured plasma RBP just before and 1, 3, and 6 hours after an intramuscular injection of vitamin A (2000 IU/kg retinyl palmitate) on days 1 and 28. The percent increase in plasma RBP (delta-RBP) was high (mean +/- SD: 61 +/- 37%) and plasma vitamin A and RBP values were low on day 1, indicative of vitamin A deficiency. Supplemental vitamin A improved vitamin A status of all infants as shown by low delta-RBP (mean +/- SD: 8 +/- 9%) and normal plasma vitamin A and RBP values on day 28. Bronchopulmonary dysplasia was diagnosed in 12 of 24 infants. Infants with bronchopulmonary dysplasia had a higher mean (+/- SD) delta-RBP on day 28 than those without bronchopulmonary dysplasia (13 +/- 10% vs 3 +/- 3%, p less than 0.01), indicative of persistence of low vitamin A status in infants with lung disease despite supplementation. We conclude that the plasma RBP response to vitamin A is a useful indicator of vitamin A status in very low birth weight infants. Although vitamin A supplementation at the dosage used in this study normalizes conventional plasma indexes of vitamin A in very low birth weight infants, the plasma RBP response to vitamin A may continue to reflect persistence of low vitamin A status in the more immature infants with significant lung disease. We suggest that the plasma RBP response to vitamin A may be a useful functional test in such infants.

Bronchopulmonary Dysplasia↗
PubMed1990

Vitamin A storage in lungs during perinatal development in the rat.

We examined the ontogeny of vitamin A storage in fetal and neonatal lungs during perinatal development in the rat. High-performance liquid chromatography was used to measure concentrations of vitamin A and its esters, retinyl palmitate and stearate, in various fetal and neonatal tissues at times ranging from gestational day 14 through 21, and from postnatal day 1 through 21. The data show that significant vitamin A storage occurs in the fetal lung during the latter one-third of prenatal life. Depletion of these stores that begins before birth and continues into the early postnatal period suggests that the developing lung may be dependent on these local vitamin A stores during active growth and differentiation. The utilization of vitamin A stores in the developing lung appears to be independent of the liver stores of vitamin A.

Animals↗
PubMed1990

Effect of maternal vitamin-A administration on fetal lung vitamin-A stores in the perinatal rat.

Vitamin A (retinol) is essential for normal differentiation and integrity of developing respiratory epithelium and its deficiency has been linked to an increased susceptibility to lung injury. Because significant vitamin-A storage occurs in the fetal lung near term in the perinatal rat, prematurely born animals deprived of adequate stores in their lungs may be susceptible to the adverse effects of vitamin-A deficiency. It would be desirable if lung vitamin-A stores could be augmented with maternal administration, but the feasibility of this strategy has not been reported. We therefore conducted this study in rats to determine whether maternal administration of vitamin A could increase the lung stores of vitamin A in the offspring. Vitamin-A-sufficient pregnant rats were given a single dose of either vitamin A (50,000 IU retinyl palmitate) or 0.9% saline solution on gestational day 16 (term = 21 days) by the intragastric route. High-performance liquid chromatography was used to measure concentrations of vitamin A and its esters in fetal and neonatal lungs and livers at times ranging from gestational day 17 through 21, and from postnatal day 1 through 14. The concentrations of vitamin-A esters in the lungs of fetuses and newborn pups of the vitamin-A-treated animals were significantly (1.7- to 7.1-fold) higher than those of the control group. This increase in the lung vitamin-A ester concentrations was seen within 24 h of maternal administration and persisted throughout the 14-day postnatal period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Retinoid-binding protein distribution in the developing mammalian nervous system.

We have analysed the distribution of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) in the day 8.5-day 12 mouse and rat embryo. CRBP is localised in the heart, gut epithelium, notochord, otic vesicle, sympathetic ganglia, lamina terminalis of the brain, and, most strikingly, in a ventral stripe across the developing neural tube in the future motor neuron region. This immunoreactivity remains in motor neurons and, at later stages, motor axons are labelled in contrast to unlabelled sensory axons. CRABP is localised to the neural crest cells, which are particularly noticeable streaming into the branchial arches. At later stages, neural crest derivatives such as Schwann cells, cells in the gut wall and sympathetic ganglia are immunoreactive. An additional area of CRABP-positive cells are neuroblasts in the mantle layer of the neural tube, which subsequently appear to be the axons and cell bodies of the commissural system. Since retinol and retinoic acid are the endogenous ligands for these binding proteins, we propose that retinoids may play a role in the development and differentiation of the mammalian nervous system and may interact with certain homoeobox genes whose transcripts have also been localised within the nervous system.

Animals↗
PubMed1989

Cellular retinoic acid-binding protein and the role of retinoic acid in the development of the chick embryo.

The distribution of cellular retinoic acid-binding protein (CRABP) in four stages of chick development is described using an affinity-purified antibody against rat CRABP. CRABP is the protein to which retinoic acid (RA) binds when it enters cells and may reflect the requirement of those cells for RA. We found several discrete cell populations which showed high levels of immunoreactivity. Some were in the neural tube such as the commissural neurons and the dorsal roof plate. Some were of neural crest origin such as the dorsal root ganglia, sensory axons, sympathetic ganglia, and enteric ganglia. The remaining populations were certain connective tissue cells, limb bud cells, and the myotome. These results suggest that certain organ systems, particularly the nervous system, have a requirement for RA during development and they may further our understanding of the teratogenic effects of retinoids on the embryo.

Age Factors↗
PubMed1989

The role of retinoid-binding proteins in the generation of pattern in the developing limb, the regenerating limb and the nervous system.

We summarize existing data and describe new information on the levels and distribution of cellular retinoic acid-binding protein (CRABP) and cellular retinol-binding protein (CRBP) in the regenerating axolotl limb, the developing chick limb bud and the nervous system of the chick embryo in the light of the known morphogenetic effects of retinoids on these systems. In the regenerating limb, levels of CRABP rise 3- to 4-fold during regeneration, peaking at the time when retinoic acid (RA) is most effective at causing pattern duplications. The levels of CRBP are low. The potency of various retinoids in causing pattern respecification correlates well with the ability of these compounds to bind to CRABP. In the chick limb bud, the levels of CRABP are high and the levels of CRBP are low. Again the binding of various retinoids to CRABP correlates well with their ability to cause pattern duplications. By immunocytochemistry, we show that CRABP is present at high levels in the progress zone of the limb bud and is distributed across the anteroposterior axis in a gradient with the high point at the anterior margin. In the chick embryo, CRABP levels are high and CRBP levels are low. By immunocytochemistry, CRABP is localised primarily to the developing nervous system, labelling cells and axons in the mantle layer of the neural tube. These become the neurons of the commissural system. Also sensory axons label intensely with CRABP whereas motor axons do not and in the mixed nerves at the brachial plexus sensory and motor components can be distinguished on this basis. In the neural tube, CRBP only stains the ventral floor plate. Since the ventral floor plate may be a source of chemoattractant for commissural axons, we suggest on the basis of these staining patterns that RA may fulfill this role and thus be involved morphogenetically in the developing nervous system.

Ambystoma↗
PubMed1988

Retinoic acid rapidly induces lung cellular retinol-binding protein mRNA levels in retinol deficient rats.

Retinol deficiency resulted in decreased mRNA levels for cellular retinol-binding protein (CRBP) in the lungs and the testes. The level of lung CRBP mRNA increased 2.3-fold one hour after oral administration of retinoic acid to retinol deficient rats. In contrast, testicular CRBP mRNA level was not influenced. Our data indicate that retinoic acid regulates CRBP mRNA level in the whole animal and this rapid effect suggests a role for CRBP in the mechanism of vitamin A action at genomic level.

Animals↗