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R D Zachman

Publications and source records attributed to R D Zachman.

At least 19 recordsLinked to original sources
PubMed2001

Prenatal ethanol consumption increases retinol and cellular retinol-binding protein expression in the rat fetal snout.

Fetal exposure to ethanol disrupts normal craniofacial development, resulting in characteristic features of fetal alcohol syndrome (FAS). One mechanism that could result in some anomalies of this syndrome is through ethanol disrupting the regulatory role played by vitamin A in fetal development, thereby inducing morphological alterations which manifest as FAS. This work begins to explore a possible interaction of ethanol with vitamin A in craniofacial development. Retinoid levels and the expression of cellular retinol-binding protein (CRBP) and retinoic acid receptor (RAR) mRNA were determined in snouts of 20-day fetuses exposed to ethanol throughout gestation, compared to controls. Snout retinol and retinyl palmitate levels were elevated in fetuses of ethanol-treated rats, but retinoic acid levels were unaffected. The expression of CRBP mRNA, as determined by Northern analysis, was greater in snouts of fetuses exposed to ethanol, but there was no change in RAR alpha, beta, gamma or retinoid X receptor beta mRNA. These results demonstrate that prenatal ethanol consumption can alter certain markers of vitamin A metabolism and function in the fetal snout.

Animals↗
PubMed2000

Effect of retinoic acid and ethanol on retinoic acid receptor beta and glial fibrillary acidic protein mRNA expression in human astrocytoma cells.

This work explores the hypothesis that perturbations caused by ethanol on the regulatory role of retinoids in brain development may be a mechanism involved in the neuropathology of fetal alcohol syndrome. The interaction of ethanol and retinoic acid (RA) on RA receptor (RAR) beta and glial fibrillary acidic protein (GFAP) mRNA expression is evaluated. In the U-373 MG astrocytoma, mRNA expression of RAR beta was increased and GFAP was decreased by RA. Ethanol decreased the expression of RAR beta mRNA, but increased that of GFAP. The RA-stimulated increase in RAR beta was not affected by the presence of ethanol. RA prevented the ethanol-induced increase in GFAP mRNA. Cycloheximide abolished only the GFAP response to ethanol. This work shows that an interrelationship between ethanol and RA exists in the astrocyte.

Astrocytoma↗
PubMed1998

Retinoic acid and dexamethasone affect RAR-beta and surfactant protein C mRNA in the MLE lung cell line.

Lung development and surfactant biosynthesis are affected by retinoic acid (RA) and dexamethasone (Dex). Using a mouse lung epithelial cell line, we are exploring RA-Dex interactions through the study of RA and Dex effects on RA receptor (RAR) and surfactant protein (SP) C mRNA expression. RA increased expression of RAR-beta (5.5 times) and SP-C (2 times) mRNA, with maximal effects at 24 h and at 10(-6) M. The RA induction was not inhibited by cycloheximide, suggesting RA affects transcription. With added actinomycin D, RA did not affect the disappearance rate of RAR-beta mRNA, but SP-C mRNA degradation was slowed, indicating an effect on SP-C mRNA stability. Dex decreased RAR-beta and SP-C expression to 75 and 70% of control values, respectively, with greatest effects at 48 h and at 10(-7) M. There was no effect of Dex on either RAR-beta or SP-C mRNA disappearance with actinomycin D. However, cycloheximide prevented the effect of Dex. Despite Dex, RA increased both RAR-beta and SP-C mRNA. This work suggests that RA and Dex affect RAR-beta and SP-C genes by different mechanisms.

Animals↗
PubMed1998

Effect of maternal/fetal vitamin A deficiency on fetal rat lung surfactant protein expression and the response to prenatal dexamethasone.

The purpose of this work was to determine whether maternal/fetal vitamin A deficiency in vivo had an effect on fetal lung surfactant protein expression and its response to antenatal maternal dexamethasone (DEX). Weanling female rats at 21 d (30-35 g) were fed control (C) (4 mg of vitamin A/kg of diet) or a vitamin A-deficient (D) (0.06 of mg vitamin A/kg) diet. These females were mated, and at selected pregnancy dates fetal and maternal tissues were obtained. Control mothers had liver retinyl palmitate (RP) concentrations of 246 +/- 32 nmol/g of wet weight; those in the D group had 6.1 +/- 2.9 nmol/g of wet weight. Control fetal liver RP was 12-fold higher and control fetal lung RP was 3-fold higher than in the D group (liver: 18.5 +/- 0.4 nmol/g versus 1.5 +/- 0.25 nmol/g; lung: 1.8 +/- 0.98 nmol/g versus 0.6 +/- 0.2 nmol/g). Neither fetal lung surfactant protein (SP)-C mRNA nor SP-A mRNA was affected by vitamin A deficiency. In a second experiment, pregnant rats from both C and D groups were injected with either DEX (1 mg/kg) or an equal volume of saline on d 15-17, and killed on d 18. DEX increased fetal lung SP-C mRNA 2-fold over the level found in the saline-injected group (saline, 1.0 +/- 0.2 versus DEX, 2.1 +/- 0.2, p < 0.02). This increase in SP-C mRNA also occurred in fetal lungs from the D group (saline, 1.8 +/- 0.4 versus DEX 3.7 +/- 0.2, p < 0.01). Retinoic acid receptor-beta mRNA, which responds to vitamin A levels and DEX in many systems, was lower in fetal lungs of the D group that had been treated with DEX. We conclude that fetal rat lung development, as measured by SP-C mRNA and SP-A mRNA, and the SP-C mRNA response to DEX, was not affected by vitamin A deficiency.

Animals↗
PubMed1998

The interaction of ethanol and vitamin A as a potential mechanism for the pathogenesis of Fetal Alcohol syndrome.

The mechanism of the fetal embryopathology resulting from ethanol ingestion during pregnancy is not established. This review summarizes recent research on the interaction of ethanol and vitamin A in models that explore if an interaction between these two compounds might potentially be the mechanism for fetal alcohol syndrome. The rationale for this hypothesis includes the known facts that: (1) in adults, ethanol ingestion alters vitamin A metabolism and tissue distribution; (2) there are many phenotypic similarities between fetal alcohol syndrome and malformations of both vitamin A toxicity and deficiency; and (3) the vitamin A metabolite, retinoic acid (RA), is a potent mediator in embryogenesis and differentiation. One interaction that could possibly alter fetal development is that the synthesis of RA from retinol, catalyzed by alcohol dehydrogenase, might be competitively inhibited by ethanol leading to RA deficiency. Controversy over this hypothesis continues. Another model demonstrates in vivo effects of pregnant rat mother's ethanol consumption on retinol, retinyl ester, RA content, RA receptor (RAR) binding, and the levels of RAR expression in developing fetal organs. The variable responses in this model still need clarification, and specific defects resulting from specific RAR changes have not yet been identified. In a quail embryo model, ethanol treatment mimics vitamin A deficiency, and RA appears to prevent the adverse effects of ethanol. Finally, RA and ethanol reverse or block each other's effects in studies on isolated neuroblastoma cells. Taken together, these experiments show definite interactions between ethanol and vitamin A. Further studies are needed to determine if any of these mechanisms significantly contribute to prenatal ethanol consumption embryopathy; but, clearly this hypothesis is gaining experimental support.

Adult↗
PubMed1996

Use of the intramuscular relative-dose-response test to predict bronchopulmonary dysplasia in premature infants.

We tested the hypothesis that an intramuscular relative dose response (IM-RDR) on day 1 of life would more accurately predict which premature infants would develop bronchopulmonary dysplasia (BPD) than single measurements of retinol, retinyl palmitate (RP), or retinol binding protein (RBP). Seventy-five premature infants < or = 32 wk gestation had the IM-RDR on day 1 of life. An RDR > or = 25% occurred in 6 of 37 infants who did not develop BPD compared with 15 of 38 infants who developed BPD (P = 0.025). Retinol, RP, and RBP on day 1 were not different between the groups. BPD infants who received postnatal dexamethasone during their hospital course had a higher day-28 baseline retinol concentration (1.19 +/- 0.15 mumol/L) than did the group with no BPD (0.82 +/- 0.06 mumol/L) (P = 0.03). However, the effect of postnatal dexamethasone on serum retinol was biphasic, rising initially, and then declining after 8-12 d. RP values at time 0 and 5 h on day 28 were higher than day 1 values in both infants without BPD and infants with BPD who did not receive dexamethasone. Retrospective analysis also revealed a significant correlation between a day-1 RDR > or = 25% and the incidence of intraventricular hemorrhage in these premature infants. Because the IM-RDR is more helpful in predicting the development of BPD than single serum retinol and RP analyses, this test could be useful in determining which premature infants might benefit from supplemental vitamin A for BPD.

Bronchopulmonary Dysplasia↗
PubMed1995

Postnatal rat lung retinoic acid receptor (RAR) mRNA expression and effects of dexamethasone on RAR beta mRNA.

Retinoids exert multiple effects upon lung differentiation and growth. Although the mechanisms involved are presently poorly understood, increasing evidence points to a central role of nuclear retinoic acid receptors (RAR). The purpose of this study was to determine RAR mRNA expression profile during postnatal alveolarization, compared with the expression in prenatal and adult rat lung, and to describe the effects of dexamethasone (DEX) and oxygen on postnatal lung RAR gene expression. Total RNA was isolated from lungs of Sprague-Dawley rats on prenatal day 19, on postnatal days 1, 3, 7, 10, and 14 of life, and from adults. One subgroup of littermate pups was treated with DEX daily for 3 or 7 days. In a second experiment, rats were exposed to room air or to 95% oxygen for 72 hours, and received either DEX or saline. Northern hybridization showed that the levels of all RAR subtypes in fetal lung were 45% or less of levels at postnatal day 1. The 3.7 kb RAR alpha transcript levels were lower than day 1 on days 10 and 14 (relative to day 1, day 10 = 0.54 +/- 0.05; day 14 = 0.54 +/- 0.08), but there was no change in a 2.7 kb RAR alpha transcript over this time period. By contrast, RAR beta mRNA levels were significantly higher at days 3, 10, and 14 compared with day 1 (day 3 = 1.79 +/- 0.19; day 10 = 1.41 +/- 0.14; day 14 = 1.53 +/- 0.05). Similarly, RAR gamma mRNA expression levels were higher on day 10 (1.45 +/- 0.09), but by day 14 there was no difference from day 1. Adult lung 3.7 kb RAR alpha, 2.7 kb RAR alpha, and RAR gamma were lower than day 1, but RAR beta was significantly greater (3.7 alpha = 0.52 +/- 0.05; 2.7 alpha = 0.49 +/- 0.26; gamma = 0.74 +/- 0.06; beta = 1.63 +/- 0.22). Treatment with DEX prevented the rise in RAR beta mRNA occurring on day 3 and significantly lowered (0.65 +/- 0.06) the amount of RAR beta mRNA in day 7 lung. Exposure of rat pups to oxygen caused an increase in RAR beta mRNA (1.21 +/- 0.03). DEX treatment again decreased RAR beta mRNA in both control (0.55 +/- 0.06) and oxygen-exposed pups (0.67 +/- 0.12). In addition, 2.7 kb RAR alpha mRNA was decreased with the combination of DEX and oxygen exposure (0.63 +/- 0.06). The differential gene expression profiles and the response to DEX and oxygen of the various members of the RAR family suggest that each subtype may have a specific role during the period of alveolarization in rat lung.

Air↗
PubMed1995

Role of vitamin A in lung development.

There is good rationale for presuming a role for vitamin A in lung development. In situ studies have demonstrated that certain retinoic acid (RA) receptor proteins are localized in a specific fashion during fetal lung branching and airway growth. Vitamin A stores are high in fetal lung and decrease toward term, possibly being utilized for changes in lung morphogenic remodeling. The binding activity, levels and expression of the cytosolic and nuclear receptor proteins for vitamin A undergo changes before and after birth in rat lung. RA slows fetal Type II cell proliferation in culture but stimulates choline incorporation into phosphatidylcholine. RA can regulate several other factors involved in lung development such as homeobox genes, matrix molecules and certain growth factors. Further study is needed on this potential functional role of RA in lung. Retinol deficiency results in lung histopathology that is similar to bronchopulmonary dysplasia, which occurs frequently in human premature neonates. Clinical trials are attempting to define the role of supplementation of vitamin A in the prevention and treatment of that condition.

Animals↗
PubMed1995

Prenatal ethanol consumption alters the expression of cellular retinol binding protein and retinoic acid receptor mRNA in fetal rat embryo and brain.

The mechanism by which prenatal ethanol ingestion causes fetal alcohol syndrome (FAS) is unknown. We hypothesize that ethanol disrupts the normal function of retinoids in embryogenesis and differentiation, resulting in FAS. The present work was designed to determine if prenatal ethanol ingestion affects the expression of cellular retinol binding protein (CRBP) and nuclear retinoic acid receptors (RARs). Paired timed pregnant rats were fed a liquid diet, one group treated with 36% of carbohydrate calories replaced with ethanol. Maternal serum retinol concentrations during pregnancy peaked on the 6th day of pregnancy, but no difference was noted between the ethanol and control group. At the 12th and 20th day of gestation, embryos or fetal brain were removed, and RNA was isolated for Northern hybridization. The abundance of CRBP mRNA was significantly elevated by ethanol consumption. In both the 12-day embryo (relative density of control: 1.00 +/- 0.10; vs. ethanol: 1.87 +/- 0.30, p < 0.05) and 20-day fetal brain (relative density of control: 1.00 +/- 0.09; vs. ethanol: 1.46 +/- 0.09, p < 0.01). In the embryo, ethanol ingestion resulted in a decrease in the level of RAR-beta mRNA (control: 1.00 +/- 0.05; vs. ethanol: 0.71 +/- 0.07, p < 0.01), but had no effect on RAR-alpha or RAR-gamma mRNA. In contrast to the embryo, the expression of both the 3.7- and 2.7-kb RAR-alpha transcripts was significantly greater in day 20 fetal brain of ethanol-treated rats (3.7-kb RAR-alpha control: 1.00 +/- 0.11; vs. ethanol: 1.65 +/- 0.06; p < 0.001; 2.7-kb RAR-alpha control: 1.00 +/- 0.14; vs. ethanol: 1.74 +/- 0.27, p < 0.05), whereas RAR-beta and RAR-gamma expression were not altered. These observations suggest that altered vitamin A function is a potential factor in the embryopathy of prenatal ethanol exposure.

Animals↗
PubMed1995

The effect of maternal ethanol ingestion on fetal rat heart vitamin A: a model for fetal alcohol syndrome.

Ethanol consumption during pregnancy can cause fetal alcohol syndrome (FAS). Although the exact mechanism is unknown, nutritional alterations caused by ethanol exposure may be an etiologic factor in FAS. The congenital heart defects seen in FAS are similar to those found in vitamin A teratogenesis. Because ethanol ingestion alters vitamin A metabolism, we hypothesized that the cardiac manifestations seen in FAS result from an alteration in vitamin A metabolism or function in the developing fetus. Twenty-day gestation fetal rat hearts from ethanol-exposed and control pregnancies were analyzed for 1) levels of endogenous retinol, retinyl palmitate, and retinoic acid by quantitative HPLC; 2) binding activity levels of both retinol by cellular retinol binding protein and retinoic acid by cellular retinoic acid binding protein using specific competitive binding assays; and 3) relative abundance of cellular retinol binding protein and retinoic acid receptor alpha, beta, and gamma subtype message as expressed in mRNA. Levels of retinol and retinyl palmitate were significantly higher (p < 0.01) and the level of retinoic acid was significantly lower (p < 0.02) in the ethanol-exposed fetal hearts. Binding activity levels of cellular retinol binding protein and cellular retinoic acid binding protein were not different in the two groups. The message for retinoic acid receptor alpha (3.7 kb) was increased (p < 0.01) and the message for retinoic acid receptor beta was decreased (p < 0.05) in the ethanol-exposed hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Expression of retinoic acid receptor genes in fetal and newborn rat lung.

Lung differentiation and development are affected by vitamin A and its metabolites. One mechanism through which retinoids might exert their effects is through nuclear retinoic acid receptors (RAR). The gene expression profile of the RAR family (alpha, beta, gamma) has previously been determined in both the developing mouse embryo to 14.5 days gestation, and in the adult lung. The purpose of this study was to determine the expression of the RAR genes during the period of gestation that results in the formation of the saccular lung stage. Total RNA was extracted from fetal lungs of Sprague-Dawley rats at gestational days 17, 19, 20, 21, and 22, and from 12-hour-old newborns for Northern hybridization. Two transcripts of RAR alpha mRNA (3.7 and 2.7 kb) were found at each time point. At day 17, the 2.7 kb RAR alpha mRNA was increased two-fold or more than at any other time studied. At days 19-22 the levels of the 3.7 kb RAR alpha species were also lower than day 17 and newborn levels. One RAR beta mRNA transcript (3.4 kb), present at all time points, was significantly higher in the newborn than on days 17-22. Expression of RAR gamma mRNA could only be demonstrated by reverse transcriptase-polymerase chain reaction. We speculate that the higher RAR alpha species at day 17 indicates a role for RAR alpha in the maintenance of the columnar epithelial cells of the glandular phase of lung development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of dexamethasone and oxygen exposure on neonatal rat lung retinoic acid receptor proteins.

Retinol deficiency in animal models results in histopathologic airway changes that appear similar to those found in human premature infants with bronchopulmonary dysplasia (BPD). Dexamethasone (DEX), a steroid now often used in the treatment of BPD, might potentially affect lung vitamin A homeostasis since it alters serum and liver retinoid stores in certain models. Our objective was to determine the effect of DEX on neonatal rat lung retinoid status and the binding of retinoic acid (RA) to cytosolic and nuclear receptor proteins. We examined this effect both in room air and when the animals breathed 95% oxygen (O2). Twenty-four 1-day-old rat pups received either 1 microgram/g DEX subcutaneously, an equal volume of normal saline (NS) subcutaneously at 0 (start experiment time), 24, and 48 hours, or no injection at all, and were sacrificed at 72 hours. Twelve rats in each treatment group were housed in room air and 12 in each group were exposed to > 95% O2 for the 3 day period. Lung and liver were analyzed for retinyl palmitate (RP). Nuclear retinoic acid receptor (RAR) and cellular retinoic acid binding protein (CRABP) were measured by specific binding assays. DEX decreased liver RP by 33-55% and rat pup lung RP by over 60%; it also decreased lung RAR binding (mean dpm/microgram protein +/- SEM) in both room air and oxygen groups: Air (11.2 +/- 1.0) vs. Air/DEX (4.6 +/- 1.3, n = 6; P < 0.01), and O2 (18.2 +/- 0.6) vs. O2/DEX (3.2 +/- 0.6, n = 6; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Maternal ethanol ingestion effects on fetal rat brain vitamin A as a model for fetal alcohol syndrome.

Fetal embryo, head, and brain tissue from different gestational ages were analyzed for retinol content, nuclear retinoic acid receptor and cytosolic retinoic acid binding protein levels after maternal ethanol ingestion and compared with fetal levels in control diet pregnancies. Retinol levels in fetal embryo and brain of ethanol-ingesting pregnancies were 2- to 3-fold higher than fetal embryo and brain retinol of control pregnancies. Nuclear retinoic acid receptor was lower in 10-day embryo of ethanol pregnancies and apparently unaffected in fetal head and brain by maternal ethanol consumption at other days of gestation. In fetal head there was a significant overall ethanol effect on cytosolic retinoic acid binding protein, with increased levels in fetal tissue from ethanol-consuming pregnancies. These observations of altered embryo, fetal head, and fetal brain retinol and receptor protein levels support the hypothesis of a possible role of vitamin A in fetal alcohol syndrome.

Alcohol Drinking↗
PubMed1993

Effect of gestational age and retinol (vitamin A) deficiency on fetal rat lung nuclear retinoic acid receptors.

Retinol, or one of its metabolites such as retinoic acid (RA), is an important factor in the differentiation and maintenance of integrity of lung epithelium. Retinol deficiency in rats induces morphologic changes in respiratory tract epithelial cells that are histologically similar to those found in human premature infants with bronchopulmonary dysplasia. The exact mechanism of retinoid action in cellular growth and differentiation is not understood, but recently investigators have focused on mechanisms mediated by nuclear RA receptors (RAR). The role of these RAR as regulators of retinoid function is being studied in adult animal tissues and malignant cell lines, but little is known about RAR in developing fetal lung tissue. The purpose of this study was to determine the effect of gestational age and vitamin A deficiency on fetal rat lung nuclear RAR. RAR were also assayed in vitamin A control and vitamin A-deficient adult rat lung. A competitive binding assay and size exclusion HPLC separation were used to quantitate total RAR-specific binding. Binding analysis revealed a single class of receptor binding sites with high affinity (kd approximately 10(-9) M) for RA and RAR saturation at 2-5 nM RA. Specific binding of lung RAR in rat fetuses at 18 d gestation was two to three times greater than in fetuses at 20-21 d gestation, newborn pups, or adults. Western blot analysis revealed a predominance of RAR-beta receptors in fetal lung. Lungs from vitamin A-deficient fetuses demonstrated up-regulation of nuclear RAR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Use of quantitative amniotic fluid phosphatidylglycerol as a criterion for fetal lung maturation.

Phosphatidylglycerol (PG) in amniotic fluid was quantitatively measured by thin-layer chromatography (TLC) in 941 amniotic fluid samples and related to the presence or absence of respiratory distress syndrome (RDS) in neonates born within 7 days of the amniocentesis. In 639 case tests with PG 1 nmol/ml or more of amniotic fluid, there was no RDS. However, there were six cases of RDS associated with 109 tests of PG from 0 to less than 1 nmol/ml. These 109 tests would all have been reported as PG positive if PG were only qualitatively assessed on the TLC plate by the naked eye. The highest incidence of RDS occurred when PG was absent (23 RDS of 193 patients). Hence, this study suggests that quantitative analysis of PG determines a cutoff point of PG that eliminates false-positive PG assessments (1 nmol/ml in our laboratory). There was no difference in the levels of PG between males and females at equal gestational ages, but the incidence of RDS among male neonates was 2.4 times higher (p less than 0.05) than female neonates in the group with an immature amniotic fluid lecithin to sphingomyelin ratio and PG less than 1.0 nmol/ml.

Amniotic Fluid↗
PubMed1992

Expression of retinoic acid nuclear receptors and tissue transglutaminase is altered in various tissues of rats fed a vitamin A-deficient diet.

The effects of vitamin A nutritional status on the levels of expression of retinoic acid nuclear receptors (RAR), and the retinoic acid-responsive gene, tissue transglutaminase, were determined in rats. Weanling male Sprague-Dawley rats fed a vitamin A-deficient diet for approximately 7 wk developed vitamin A deficiency, as confirmed by the depletion of liver retinol and retinyl palmitate. Controls were fed the same diet supplemented with 24 mg/kg retinyl acetate. The levels of expression of RAR beta mRNA were approximately 80% lower in bladder, brain, liver, lung and trachea and those of RAR gamma mRNA were approximately 50% lower in bladder, lung and trachea of rats fed the vitamin A-deficient diet than in controls. The levels of expression of RAR alpha mRNA were approximately 90% lower in brain and approximately 30% greater in liver, kidney, intestine and lung of rats fed the vitamin A-deficient diet. Vitamin A deficiency also resulted in reduced expression of tissue transglutaminase in the bladder, lungs and trachea, which paralleled the effects observed for RAR beta and RAR gamma. When vitamin A-deficient rats were subsequently fed a retinol-deficient diet supplemented with retinoic acid for 4 wk, the expression of RAR (beta and gamma) and tissue transglutaminase returned to the control levels. These results indicate that vitamin A nutritional status in rats influences the expression of both RAR and tissue transglutaminase in certain tissues.

Animals↗