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Biomedical subjects

D S Goodman

Publications and source records attributed to D S Goodman.

At least 19 recordsLinked to original sources
PubMed1995

Regulation of adipocyte gene expression by retinoic acid and hormones: effects on the gene encoding cellular retinol-binding protein.

Our laboratory has reported that adipose tissue and adipocytes are importantly involved in retinoid storage and metabolism. To gain further insight, we examined factors that may regulate CRBP mRNA levels in primary cultures of rat epididymal and murine BFC-1 beta adipocytes. Northern blot analysis revealed that retinoic acid is a potent inducer of CRBP mRNA, causing a 7.5-fold rise in mRNA levels in primary adipocytes and a 9.5-fold rise in BFC-1 beta adipocytes. This induction of CRBP mRNA was dose-dependent at retinoic acid concentrations ranging between 10(-8) and 10(-5) M. Retinoic acid induction of CRBP mRNA levels showed a short lag period (6 h) and reached a maximal level of induction by 12 h in BFC-1 beta adipocytes and by 48 h in primary epididymal adipocytes. Nuclear run-on transcription assays of retinoic acid-induced BFC-1 beta adipocytes indicated that the rate of CRBP gene transcription is enhanced 3.6- to 4.3-fold by retinoic acid. In contrast, dexamethasone markedly down-regulated CRBP expression in a dose-dependent manner at concentrations ranging between 10(-9) and 10(-6) M. CRBP mRNA levels in primary and BFC-1 beta adipocytes declined, respectively, by 90% and 80% when adipocytes were exposed to 10(-6) M dexamethasone for 24 h. Studies of mRNA half-life indicated that dexamethasone acts to lessen CRBP expression through the specific destabilization of CRBP mRNA. Treatment of both primary and BFC-1 beta adipocytes with triiodothyronine alone had no effect on CRBP mRNA levels; however, when adipocytes were treated with a mixture of triiodothyronine and retinoic acid, the induction of CRBP mRNA levels by retinoic acid was reduced. In summary, these studies indicate that CRBP gene expression is regulated by retinoic acid, dexamethasone, and triiodothyronine; thus suggesting that retinol uptake, intracellular transport, and metabolism are dynamically regulated in adipocytes.

Adipocytes↗
PubMed1992

Differentiation-dependent expression of retinoid-binding proteins in BFC-1 beta adipocytes.

Recently, we demonstrated that adipose tissue plays an important role in retinol storage and retinol-binding protein (RBP) synthesis. Our data suggested that RBP expression in adipose tissue is dependent on the state of adipocyte differentiation. To examine this possibility, we explored the differentiation-dependent expression of RBP using BFC-1 beta preadipocytes, which can be stimulated to undergo adipose differentiation. Total RNA was isolated from undifferentiated (preadipocytes) and differentiated (adipocytes) BFC-1 beta cells and analyzed by Northern blotting. RBP mRNA was not detected in the preadipocytes, but considerable RBP mRNA was present in differentiated BFC-1 beta cells. In BFC-1 beta cells, induced to differentiate with insulin and thyroid hormone, RBP mRNA was first detected after 4 days, reached a maximum level by day 10, and remained at this maximum level for at least 2 more days. Cellular retinol-binding protein was expressed at low levels in the BFC-1 beta preadipocytes and the level of expression increased for 6 days after induction to differentiate and slowly declined on later days. Neither the maximum level of RBP expression nor the day on which this level was reached was influenced by the level of retinol provided in the BFC-1 beta culture medium. BFC-1 beta cells secreted newly synthesized RBP into the culture medium at a rate of 43 +/- 14 ng RBP/24 h/10(6) adipocytes. When the BFC-1 beta adipocytes were provided 1.0 microM retinol in the medium, they accumulated the retinol and synthesized retinyl esters. These studies with BFC-1 beta cells confirm that RBP synthesis and secretion and retinol accumulation are intrinsic properties of differentiated adipocytes. Furthermore, they suggest that RBP and cellular retinol-binding protein gene expression are regulated as part of a package of genes which are modulated during adipocyte differentiation.

Adipose Tissue↗
PubMed1992

Retinoids and retinoid-binding protein expression in rat adipocytes.

Adipose tissue has been reported to contain relatively high levels of the specific mRNA for retinol-binding protein (RBP) (Makover A., Soprano, D.R., Wyatt, M. L., and Goodman, D.S. (1989) J. Lipid Res. 30, 171-180). Studies were conducted to explore retinoid and retinoid-binding protein storage and metabolism in adipose tissue. In these studies, we measured RBP and cellular retinol-binding protein (CRBP) mRNA levels and retinoid levels in 6 adipose depots in male rats. Total RNA was isolated from inguinal, dorsal, mesenteric, epididymal, perinephric, and brown adipose tissue, and average RBP and CRBP mRNA levels were determined by Northern blot analysis. The relative levels of RBP mRNA in these 6 anatomically different adipose depots averaged, respectively, 6.3, 6.7, 16, 34, 37, and 21% of the level in a rat liver RNA standard. Retinoid levels in the 6 depots were similar and averaged approximately 6-7 micrograms of retinol eq/g of adipose tissue. Since adipose tissue contains several cell types, the cellular localizations of RBP and CRBP expression and retinoid storage were examined. RNA was prepared from isolated rat adipocytes and stromal-vascular cells. Cellular levels of the mRNAs for RBP, CRBP, apolipoprotein E (apoE), lipoprotein lipase, adipocyte P2, and adipsin were measured by Northern blot analysis. RBP was expressed almost exclusively in the adipocytes and only weakly in the stromal-vascular cells. Both CRBP and apoE mRNA levels were relatively high in the stromal-vascular cell preparations and only very low mRNA levels were found in the adipocytes. Lipoprotein lipase, adipsin, and adipocyte P2 mRNAs were found in substantial levels in both the adipocytes and stromal-vascular cells, but with higher levels present in the adipocytes. Cultured adipocytes synthesized RBP protein and secreted it into the medium. Only adipocytes (not stromal-vascular cells) contained retinol, at levels between 0.65-0.8 micrograms of retinol eq/10(6) cells. These studies demonstrate that adipocytes store retinoid and synthesize and secrete RBP, and suggest that rat adipocytes may be dynamically involved in retinoid storage and metabolism.

Adipose Tissue↗
PubMed1992

Transfer and metabolism of retinol by the perfused human placenta.

The transfer and metabolism of retinol by human placenta was investigated using an in vitro perfusion system with independent maternal and fetal circulations. 3H-retinol bound to albumin added to the maternal perfusate was rapidly taken up and concentrated by the placenta to levels 16.5 +/- 5.28 times the maternal perfusate. Approximately 8% of the retinol retained in the placenta was esterified. No metabolites were detected in the perfusates. Perfusion of placenta with retinol bound to retinol-binding protein (RBP) reduced the placental concentration to 4.4 +/- 1.72 times the maternal concentration and eliminated evidence of metabolism. The transfer rate of RBP:3H-retinol was less than that of albumin:14C-retinol when measured concurrently in three experiments (clearances 0.11 versus 0.75 mL/min, 0.21 versus 1.7 mL/min, and 0.29 versus 0.48 mL/min, respectively). Transfer of the radioactive retinol was more rapid than 125I-RBP or albumin, indicating that retinol was transferred independently of the proteins. The transfer index of retinol (clearance retinol:clearance L-glucose) was 0.73 +/- 0.085 compared to 2.1 +/- 0.36 for thiamin and 3.4 +/- 0.95 for riboflavin, both water-soluble vitamins with active transport systems. The retinol transferred to the fetal perfusate is not bound to RBP, as demonstrated by gel filtration chromatography and chromatography on a transthyretin affinity column, despite the availability of RBP in the cord serum added to the perfusate. The endogenous retinol in the cord serum is bound to RBP.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport, Active↗
PubMed1992

A new transthyretin mutation associated with amyloid cardiomyopathy.

In transthyretin (TTR) a new mutation (TTR-Thr45) has been identified in a patient with familial amyloidosis characterized clinically by prominent cardiomyopathy and the absence of peripheral neuropathy. Comparative peptide mapping by high-performance liquid chromatography of the patient's plasma TTR together with normal TTR showed the presence of an abnormal tryptic peptide in the patient's TTR. The sequence of this peptide (peptide 6, residues 36-48) demonstrated the presence of a threonine-for-alanine substitution at position 45. This change can be explained by a single base change of adenine for guanine in the Ala-45 codon and was demonstrated directly by DNA sequence analysis of PCR-amplified exon 2 of the TTR gene; allele-specific oligonucleotide hybridization both in the patient and in fixed heart tissue from his aunt confirmed the base change. The TTR-Thr45 mutation is a new variant TTR found associated with cardiomyopathy.

Amino Acid Sequence↗
PubMed1991

The National Cholesterol Education Program: guidelines, status, and issues.

The 1987 report of the Adult Treatment Panel (ATP) of the National Cholesterol Education Program (NCEP) was concerned with who should be treated for high blood cholesterol levels and how they should be treated. Total cholesterol levels were classified for identification of cases. Low-density lipoprotein cholesterol levels were classified for decisions about treatment. The ATP guidelines emphasize diet as the primary approach to treating patients with high blood cholesterol levels. The recommendations of the report are being widely publicized through physician and patient educational programs and the mass media. The report of the Population Panel of the NCEP provides recommendations and guidelines for the public health approach to the problem of high cholesterol levels. When the recommendations of both reports are fully implemented, it is expected that substantial reductions in the incidence of coronary heart disease will be achieved.

Adult↗
PubMed1991

Selenium, retinol, retinol-binding protein, and uric acid. Associations with cancer mortality in a population-based prospective case-control study.

Using a prospective case-control study design, baseline levels of plasma selenium, retinol, and retinol-binding protein, and baseline blood uric acid levels were compared in 136 case patients who subsequently died from cancer and 238 matched control subjects. Subjects were followed for an average of 8 1/2 years. In matched analyses, selenium levels were lower in case patients with gastrointestinal or prostate cancer; retinol levels, lower in those with gastrointestinal or breast cancer; retinol-binding protein levels, lower in case patients with gastrointestinal cancer; and uric acid levels, lower in a group with "other" cancers. However, only the uric acid association with "other" cancers and the retinol-binding protein association with gastrointestinal cancer were statistically significant (P < or = .02) in conditional logistic regression analyses controlling for multiple potential covariates. Relationships for each of the substances varied by cancer site, and although some relationships were suggestive, our results point to the need for larger studies with adequate numbers for site-specific analyses.

Adult↗
PubMed1991

Cellular retinoic acid-binding protein messenger RNA: levels in rat tissues and localization in rat testis.

Studies were conducted to explore the tissue- and cell-specific regulation of cellular retinoic acid-binding protein (CRABP) expression in the rat. Two studies were carried out. The first explored the regulation of CRABP mRNA levels in selected rat tissues by dietary retinoid status, and the relationship between CRABP mRNA and protein levels in different tissues. The second examined the cellular localization of CRABP expression in the testis. In order to conduct these experiments, a cDNA encoding CRABP was isolated and characterized. The DNA sequence of the coding region had 96% identity with that of the mouse CRABP cDNA and encodes a protein identical to mouse and bovine CRABP. CRABP mRNA and protein levels were quantified in five tissues from normal, retinoid-deficient, and retinol-repleted rats. Tissue CRABP and CRABP mRNA levels were highly correlated (P less than 0.01) indicating that inter-tissue variability of CRABP levels mainly results from regulation of CRABP mRNA levels. Neither CRABP protein nor mRNA levels were affected by retinol deficiency, in marked contrast with results previously demonstrated with cellular retinol-binding protein (CRBP) (J. Lipid Res. 1990. 31: 821-829). 35S-labeled CRABP cRNA probes were used to localize CRABP mRNA within the testis of adult rats by in situ hybridization. CRABP mRNA was localized selectively in the periphery of the seminiferous tubules, primarily in type A spermatogonia. The localization of CRABP mRNA differs from that of CRABP protein, which is known to be enriched in maturing and more mature germinal cells. This difference suggests that CRABP in germ cells may be highly stable, remaining in the maturing germ cells without degradation long after CRABP mRNA levels have declined to very low levels. The specific localization of CRABP mRNA and protein presumably reflects the biological roles of retinoic acid in the development and/or later function of germinal cells.

Amino Acid Sequence↗
PubMed1990

Distribution of transthyretin in the rat eye.

We reported previously synthesis of transthyretin (TTR), or prealbumin, a transport protein for thyroxine and retinol, in the eyes of rats and cows and showed that in the rat eye, TTR mRNA is localized exclusively in the retinal pigment epithelium (RPE). We now demonstrate by immunohistochemistry that TTR has a more widespread distribution in the rat eye than does its mRNA. Intense immunoreactivity for TTR was found in the RPE, ciliary epithelium, iris epithelium, corneal endothelium, optic nerve fiber layer of the retina, and lens capsule. Depending on the method of processing, immunoreactivity of varying intensity was found also in other ocular structures. In particular, the retinal ganglion cells were strongly immunoreactive on frozen sections but not on paraffin sections. Although vitreous humor was not included in the sections of adult rat eye, sections of a 25-mm rat embryo showed intense immunoreactivity in the vitreous humor. Since plasma TTR does not cross Bruch's membrane into the retina, our findings suggest that ocular TTR is synthesized, at least in part, in the RPE and is transported to specific locations within the eye. Although the physiologic role of ocular TTR is unknown, it is possible that it participates in retinol cycling within the eye. The widespread ocular distribution of TTR may account for the occurrence of various forms of ocular amyloidosis in the familial amyloidotic polyneuropathies, a group of dominantly inherited disorders caused by point mutations in the TTR gene.

Animals↗
PubMed1990

Localization of cellular retinol-binding protein mRNA in rat testis and epididymis and its stage-dependent expression during the cycle of the seminiferous epithelium.

Anatomical localization of cellular retinol-binding protein (CRBP) mRNA was examined in normal rat testis and epididymis and also in retinoid-deficient rat testis. In situ hybridization was performed with 35S-labeled rat CRBP cRNA probes on frozen tissue sections. In normal testis, CRBP mRNA was mainly localized in the Sertoli cells and to some extent in peritubular cells. A distinct cyclic variation of the relative levels of hybridizable CRBP mRNA was observed during the spermatogenic cycle. The peak of CRBP mRNA content was seen in the stages of the cycle that preceded those in which peak CRBP protein content had been observed previously in our laboratory by immunohistochemistry. No appreciable amount of CRBP mRNA was observed in the interstitial space or in the lumen of the tubules. CRBP mRNA displayed the same anatomical localization in the retinoid-deficient testis, but the level of hybridizable CRBP mRNA was substantially reduced. A strong hybridization signal for CRBP mRNA was seen in proximal epididymis and was strikingly localized in the ductular epithelium. CRBP mRNA was not detectable in the distal portion of the epididymis. These studies provide information about the cell-specific expression of CRBP synthesis within the testis and epididymis and about its cyclic variation and regulation.

Animals↗
PubMed1990

Lack of effect of lovastatin therapy on the parameters of whole-body cholesterol metabolism.

UNLABELLED: The effects of lovastatin therapy on the parameters of body cholesterol metabolism were explored in nine hypercholesterolemic patients. Long-term cholesterol turnover studies were performed before therapy, and were repeated after 15 mo of lovastatin therapy (40 mg/d) while continuing on therapy. The major question addressed was whether a reduction in plasma cholesterol level with lovastatin would be associated with a reduction in the whole-body production rate of cholesterol or with the sizes of exchangeable body cholesterol pools as determined by the three-pool model of cholesterol turnover. The mean plasma cholesterol level decreased 19.4% (from 294 to 237 mg/dl), and low-density lipoprotein cholesterol decreased 23.8% (from 210 to 159 mg/dl) with lovastatin therapy. Changes in high-density lipoprotein cholesterol level were not significant. The cholesterol production rate did not change significantly with therapy (1.09 +/- 0.10 [mean +/- S.D.] vs. 1.17 +/- 0.09 g/d). By comparison, colestipol and niacin treatment in three other subjects more than doubled the cholesterol production rate (1.14 +/- 0.28 vs. 2.42 +/- 0.34 g/d). Thus, hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibition by lovastatin at the therapeutic dose used here did not change the steady-state rate of whole-body cholesterol synthesis. Despite the changes in plasma cholesterol levels, no significant changes were seen in the values of M1, of M3 or of Mtot, the sizes of the pools of rapidly, of slowly, and of total body exchangeable cholesterol. CONCLUSION: lovastatin therapy to lower plasma cholesterol does not lead to corresponding reductions in body cholesterol pools or to a reduction in the rate of whole-body cholesterol synthesis. In the new steady state that exists during long-term lovastatin therapy, along with increased expression of the genes for HMG-CoA reductase and the LDL receptor, the body compensates for the effects of the drug so that cholesterol production rate and tissue pool sizes are not changed from pretreatment values.

Adult↗
PubMed1990

Cellular retinol-binding protein messenger RNA levels in normal and retinoid-deficient rats.

A study was conducted to determine the levels of cellular retinol-binding protein (CRBP) mRNA and protein in various tissues of the rat, to explore relationship between CRBP mRNA and protein levels in different tissues, and to examine the effects of changes in retinol nutritional status on the tissue distribution and levels of CRBP mRNA. Previous studies have shown that tissue CRBP protein levels are reduced in totally retinoid-deficient rats, but are otherwise minimally affected by changes in retinoid status. Three groups of male rats were compared: normal controls, retinoid-deficient, and retinol-repleted deficient rats. CRBP mRNA levels were measured by RNase protection assay and CRBP protein levels by radioimmunoassay in seven tissues. High levels of both CRBP mRNA and CRBP protein were found in the proximal epididymis, kidney, and liver; lower levels were seen in lung, testis, spleen, and small intestine. Tissue CRBP mRNA and protein levels were highly correlated (P less than 0.01) with each other. Retinoid deficiency did not alter the levels of CRBP mRNA found in the proximal epididymis, kidney, and liver. In contrast, CRBP mRNA levels in the lung, testis, spleen, and small intestine were reduced substantially in retinoid-deficient rats, to values that were only 23% to 50% of the corresponding values in the tissues of control rats. After oral repletion with retinol (4-18 h earlier), CRBP mRNA levels for these latter four tissues were found to have risen to control or near-control levels. The suggestion is raised that retinol repletion may have directly induced the expression of the CRBP gene in these particular tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of irradiation on the release of growth factors from cultured bovine, porcine, and human endothelial cells.

The effects of radiation on the release of mitogenic factors into the media of cultured endothelial cells of bovine, porcine, and human origins were studied. Although unirradiated controls revealed a significant background activity, single doses of irradiation (20-60 Gy) resulted in a dose-related increased release of growth factor activity, measured by the mitogenic effects of the conditioned media on both 3T3 mouse fibroblasts and unirradiated endothelial cells serving as target cells. Receptor binding competition assays for the platelet-derived growth factor receptor revealed that 12-28% of the total mitogenic activity was due to platelet-derived growth factor-like mitogens. Mitogenic assays using endothelial cells and specific antibody mediated inhibition assays suggested that another component of the mitogenic activity was due to a fibroblast growth factor-like factor. Although radiation resulted in a significant increase in cell death, the enhanced growth factor activities did not appear to result from cell lysis-related leakage of intracellular stores of growth factor. Instead, our data suggest that the growth factors were synthesized de novo and secreted at elevated levels by the cells which maintained postradiation a high level of metabolic activity. Time course studies demonstrated that the growth factors accumulation in the conditioned media started within the first 24 h after radiation and reached a plateau within 72 h after treatment. Radiation-induced release of endothelial cell-derived growth factors may be involved in the pathogenesis of both early vascular damage and the late fibrosis which represents a prominent feature of late radiation damage in normal tissues.

Animals↗
PubMed1989

An in situ-hybridization study of the localization of retinol-binding protein and transthyretin messenger RNAs during fetal development in the rat.

The patterns, and the cellular sites, of expression of the genes for retinol-binding protein (RBP) and transthyretin (TTR) were studied during early- to mid-stages of rat embryogenesis. In situ hybridization of single-stranded RNA probes to rat embryo sections revealed specific sites at which RBP messenger RNA (mRNA) and TTR mRNA were localized in rat conceptuses from 7 to 13 days of gestation. RBP and TTR mRNAs were both observed in the visceral endoderm as early as at 7 days of gestation. The transcripts were not expressed in the parietal endoderm. At 9 days of gestation, TTR mRNA was strongly detected in the visceral extraembryonic endoderm and in the foregut endoderm, whereas RBP mRNA was detected only in the visceral extraembryonic endoderm. From the 10th day to the 13th day of gestation, both transcripts were increasingly expressed in the visceral yolk sac endoderm and in the developing fetal liver, and gradually decreased in the foregut. At 11 days of gestation, TTR mRNA was first detected in the tela choroidea of the fourth ventricle in the brain; and at 13 days, the TTR mRNA was strongly evident in the developing choroid plexus of the fourth and lateral ventricles. These in situ hybridization studies with embryos at different developmental stages show that RBP and TTR mRNAs are transcribed quite early during embryogenesis. The protein products of these transcripts may play important roles in vitamin A and thyroid hormone metabolism, and in the functions that these regulatory compounds play, in the developing rat embryo.

Animals↗