Biomedical subjects

B M Moats-Staats

Publications and source records attributed to B M Moats-Staats.

8 recordsLinked to original sources

PubMed1992

Tissue-specific developmental regulation of the messenger ribonucleic acids encoding the growth hormone receptor and the growth hormone binding protein in rat fetal and postnatal tissues.

Tissue responsiveness to growth hormone is likely to be regulated by local concentrations and availability of the membrane-bound growth hormone receptor (GHR) and perhaps by the actions of the soluble growth hormone binding protein (GHBP). To determine whether the developmental regulation of the GHR and GHBP might vary among tissues, we have measured the relative abundance of the 4.3-kb GHR and 1.3-kb GHBP mRNA in rat fetal and postnatal liver, kidney, lung, and ileum by Northern hybridization of polyadenylated RNA with a 32P-labeled antisense riboprobe prepared from a rat GHR cDNA. The GHR and GHBP mRNA were both present in the four tissues studied at fetal age 19 d (E19). In postnatal liver, both transcripts increased in abundance 3- to 4-fold after 14 d to mature levels at 42 d (p = 0.0001). Similar changes were seen in postnatal kidney for GHR mRNA abundance; however, GHBP mRNA abundance increased only 2- to 3-fold to mature levels by 28 d (kidney GHR versus GHBP mRNA profile, p = 0.0001). In lung, a 2-fold linear increase in GHR mRNA abundance was observed (p = 0.0019), but the GHBP mRNA did not change (GHR versus GHBP mRNA profile, p = 0.0006). Both transcripts decreased in abundance by 2- to 3-fold from E19 to 42 d in ileum (p less than 0.05). The abundance of both transcripts was three to 10 times greater in 60-d liver than in the other three tissues at 60 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1992

Gene expression of insulin-like growth factors (IGFs), the type 1 IGF receptor, and IGF-binding proteins in dexamethasone-induced fetal growth retardation.

Altered gene expression and/or actions of the insulin-like growth factors (IGFs) have been implicated in the mediation of both pre- and postnatal growth retardation secondary to glucocorticoid excess. To investigate this possibility, we assessed the gene expression of the IGFs, the type I IGF receptor, and IGF-binding proteins (IGFBPs) in 20-day gestation liver and lung of growth-retarded fetuses whose mothers were treated with dexamethasone (DXM; 100 micrograms, ip, daily) on gestation days 15-19 (gestation = 21-22 days). DXM treatment in dams produced fetal growth retardation without decreasing litter size (32% decrease in fetal body weight). Both fetal liver and lung demonstrated decreased wet weight (48% and 47%, respectively) and DNA content (65% and 51%, respectively) compared to control animals. Our results suggest that increased expression of IGFBP-1, and possibly IGFBP-2, is involved in mediating the marked growth retardation. As assessed by solution hybridization assays and Northern blot analysis, there was an 8.5-fold increase in IGFBP-1 mRNA expression in the livers of DXM-treated fetal animals compared to that in sham-injected controls (P less than 0.002). IGFBP-2 mRNA expression was also increased (60%) in fetal liver, whereas IGFBP-3 was decreased (57%). In fetal lung, IGFBP-1 transcript abundance was also higher in DXM-treated fetal animals. Serum concentrations of IGFBP-1, but not those of IGFBP-2, were increased (approximately 4-fold) in the DXM-treated fetuses, as quantified by [125I]IGF-I ligand blotting and IGFBP-2 immunoblotting. Because hypoinsulinemia increases the expression of IGFBP-1 and -2, serum insulin concentrations were measured and found to be decreased in the DXM-treated fetuses (24 microU/ml) compared to control values (72 microU/ml). Analysis of mRNA expression for IGF-I, IGF-II, and the type 1 receptor transcripts did not support a role for decreased IGF or IGF receptor expression in the etiology of DXM-mediated growth retardation. IGF-I was unchanged in both liver and lung, and IGF-II transcripts were increased by 31% in liver and unchanged in lung of DXM-treated fetal animals. Northern analysis of hepatic and lung poly(A) RNA demonstrated no evidence for independent regulation of specific-sized IGF transcripts. Further, type 1 IGF receptor RNA abundance increased 42% in fetal liver and was unchanged in lung. Because IGFBPs may modulate IGF action, these results suggest that increased IGFBP-1, and possibly IGFBP-2, expression may be of importance in the etiology of DXM-induced fetal growth retardation.

Animals↗

PubMed1991

Evidence that pretranslational and translational defects decrease serum insulin-like growth factor-I concentrations during dietary protein restriction.

Dietary protein restriction causes GH resistance and decreases serum insulin-like growth factor-I (IGF-I) concentrations. To determine whether pretranslational or translational defects are involved in the decline of serum IGF-I concentrations during protein restriction, we measured hepatic IGF-I mRNA abundance together with the serum IGF-I peptide response to exogenous GH after 1 week of protein restriction (5% casein in diet; P5) in hypophysectomized rats. We compared these responses with those of hypophysectomized rats fed a protein-sufficient diet (15% casein in diet; P15) and given exogenous GH. A single injection of rat GH (200 micrograms/100 g BW) produced a comparable IGF-I mRNA increment in both groups (at 6 h, 7.8 +/- 1.1 arbitrary units in P5 vs. 8.2 +/- 1.1 in P15), but failed to raise serum IGF-I normally in the P5 group (at 6 h, 90 +/- 15 ng/ml in P5 vs. 216 +/- 63 in P15; P less than 0.01). The post-GH decline of the 7.5-kilobase (kb) IGF-I mRNA abundance was faster in P5 than in P15 animals. In another experiment in intact rats subjected to protein restriction, injections of pharmacological doses of rat GH (400 micrograms/100 g BW.day) for 1 week restored liver IGF-I mRNA abundance to normal without normalization of serum IGF-I (403 +/- 91 vs. 713 +/- 53 ng/ml; P less than 0.01). Our data suggest that 1) the machinery involved in the transcription of the liver IGF-I gene is intact in protein-restricted rats, because these animals retain the ability to muster normal IGF-I mRNA responses to high doses of exogenous GH; 2) the stability of the 7.5-kb IGF-I mRNA is probably decreased by the protein restriction, as suggested by the faster decline of the 7.5-kb transcript in P5 than in P15 hypophysectomized rats; and 3) the discrepancy between normal liver IGF-I mRNA abundance and low serum and liver IGF-I peptide concentrations suggests that translational stalling of the IGF-I mRNAs or increased serum IGF-I clearance is involved in the low serum IGF-I concentrations during dietary protein restriction.

Animals↗

PubMed1991

Reduced serum concentrations of insulin-like growth factor-I (IGF-I) in protein-restricted growing rats are accompanied by reduced IGF-I mRNA levels in liver and skeletal muscle.

The serum concentration of insulin-like growth factor-I (IGF-I) is reduced in growing rats fed a low-protein diet, and this decrease is age-dependent, being more pronounced in younger animals. To determine whether this decrease in serum IGF-I is related to a decrease in IGF-I mRNA, growing female rats were given free access to either a 15% protein-sufficient or a 5% protein-deficient diet for 1 week. Protein restriction in 4-week-old rats decreased body weight gain by 44% (P less than 0.001 compared with 4-week controls), serum IGF-I concentration by 67% (P less than 0.001) and liver IGF-I mRNA abundance by 51% (P less than 0.001). During week 6, protein restriction for 1 week resulted in a 20% increase in food intake with no change in weight gain, a 38% reduction in serum IGF-I (P less than 0.001 compared with 6-week controls) and a 39% decrease in liver IGF-I mRNA (P less than 0.001). The serum IGF-I concentration was highly correlated (r = 0.80; P less than 0.001) with the hepatic IGF-I mRNA concentration. Skeletal muscle IGF-I mRNA abundance was also decreased significantly by protein restriction (37% at week 4, P less than 0.001, and 24% at week 6, P less than 0.01) and was closely correlated (r = 0.71; P less than 0.001) with body weight gain. Liver GH-binding protein and GH receptor mRNA abundance were reduced by 1 week of protein deprivation at week 6 but not at week 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Canine tracheal epithelial cells express the type 1 insulin-like growth factor receptor and proliferate in response to insulin-like growth factor I.

Disaggregated airway epithelial cells replicate in serum-free media containing supraphysiologic concentrations of insulin. To examine the hypothesis that the type 1 insulin-like growth factor (IGF) receptor mediates the mitogenic action of insulin on these cells, we studied the mitogenic effects of IGF-I and insulin, and the expression of type 1 IGF receptors in primary cultures of adult canine tracheal epithelial cells. Isolated tracheal epithelial cells were grown in varying concentrations of IGF-I or insulin in Ham's F12 medium supplemented with transferrin, cholera toxin, and endothelial cell growth supplement. Both IGF-I and insulin increased DNA synthesis (measured as [3H]thymidine incorporation into DNA) and cell number in a concentration-dependent fashion, but IGF-I was at least 20 to 60 times more potent than insulin in its mitogenic effects. No additive or synergistic effect was observed with the simultaneous addition of IGF-I and insulin in maximally effective doses. A monoclonal antibody directed against the type 1 IGF receptor (alpha IR3) blocked the mitogenic activity of both IGF-I and insulin. Affinity labeling of type 1 IGF receptors by covalent cross-linking with disuccinimidyl suberate demonstrated the tracheal epithelial cell IGF-I binding moiety to have a relative molecular weight of 130,000 D. Binding of [125I]IGF-I to this protein was inhibited by low concentrations of IGF-I, relative to insulin, and by alpha IR3. An 11-kb transcript characteristic of mRNA for the type 1 IGF receptor was recognized in poly(A+) RNA derived from cultured canine tracheal epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Production and action of insulin-like growth factor I/somatomedin C in primary cultures of fetal lung fibroblasts.

Production of insulin-like growth factor I/somatomedin C (IGF-I) by 19-day-gestation fetal rat lung fibroblasts was studied, and a paracrine (local production and action) mitogenic activity of this growth factor was explored. Specific IGF-I mRNAs were demonstrated in these cells, consistent with production of IGF-I. Using an IGF-I monoclonal antibody, IGF-I-like material was isolated from fetal lung fibroblast conditioned medium (FCM) and separated by molecular weight. Several molecular weight species were identified, including an 8,000 to 10,000 molecular weight species, a weight similar to purified IGF-I. IGF-I binding proteins elaborated by these cells were also demonstrated. The possibility of a paracrine mitogenic activity of the fetal lung fibroblast-produced IGF-I in cultures was suggested by demonstrating a reduction in DNA synthesis in cultures incubated with either the IGF-I monoclonal antibody or an IGF-I receptor antibody. These findings indicate that 19-day-gestation fetal rat lung fibroblasts produce IGF-I that acts in a paracrine fashion and suggest that this growth factor is biologically active during fetal lung development.

Animals↗

PubMed1989

Dietary protein restriction in artificially reared neonatal rats causes a reduction of insulin-like growth factor-I gene expression.

To determine in neonates the effects of protein restriction on growth, serum IGF-I, and IGF-I gene expression, we adapted a technique for rearing neonatal rats (days 6-18 of life) artificially by continuous infusion of milk through a gastrostomy. The artificially reared (AR) animals were given isocaloric diets containing 8%, 13.5%, or 18% lactalbumin protein. The AR rats were compared to rats reared by their mothers (MR) for 18 days. The growth of AR rats was related to the amount of dietary protein, with the pups given 18% protein having the best growth (25.55 g gained during the 12 days of the study) and those given 8% protein having the worst (13.42 g). The 13.5% protein-fed animals were intermediate in weight gain (18.39 g). The weight gains of the 18% and 8% protein-fed pups were significantly different from that of the MR animals (18.37 g). An identical pattern of tail length growth was noted among the groups. Mean serum IGF-I concentrations followed the same pattern (MR, 1.66 U/ml on day 18 of life; 18% AR, 2.53; 13.5% AR, 1.52; 8% AR, 1.31). Liver IGF-I mRNA was rank-ordered identically with weight gain and serum IGF-I [MR, 23.10 pg/micrograms poly(A+) RNA; 18% AR, 27.66; 13.5% AR, 21.02; 8% AR, 18.76]. Unexpectedly, the 7.5-kilobase IGF-I mRNA size class showed a 2- to 3-fold higher abundance in all groups of AR rats compared to that in MR controls (P less than 0.01), suggesting that this IGF-I size class is regulated independently of the other species. The reductions in serum IGF-I and IGF-I mRNA during protein restriction of neonatal rats suggest that these responses are mediated by decreased IGF-I gene expression at the level of transcription or RNA stabilization.

Animals↗

PubMed1985

Nucleotide sequence analysis of a cDNA encoding human ubiquitin reveals that ubiquitin is synthesized as a precursor.

Ubiquitin is a 76-amino acid protein whose sequence is highly conserved throughout evolution from invertebrates to mammals. It is both a cytoplasmic and nuclear protein. In the cytoplasm it is involved in ATP-dependent nonlysosomal proteolysis. In the nucleus, ubiquitin is conjugated to histone 2A and may play a role in regulation of chromatin structure and/or regulation of transcriptional activity. During attempts to identify a cDNA encoding somatomedin-C (insulin-like growth factor I) we screened a fetal human liver cDNA library with a mixture of 17 base oligonucleotides corresponding to a portion of the B chain of somatomedin-C. One oligonucleotide of the mixture hybridized to two cDNAs encoding ubiquitin despite a 2-base pair mismatch. Nucleotide sequence analyses of the 350- and 516-base pair cDNAs revealed that they correspond to the same ubiquitin mRNA. The coding sequence of the 516-base pair cDNA begins at amino acid 5 of the ubiquitin sequence and encodes amino acids 5 through 76 of ubiquitin, an 80-amino acid carboxy-terminal extension, a 3' untranslated region, and a poly(A) tail. The finding that ubiquitin is synthesized as a precursor raises the possibility that the precursor sequence may be important in compartmentalization of ubiquitin or ubiquitin precursors. Analyses of ubiquitin mRNAs in poly(A) RNA extracted from human liver and various rat tissues reveals that there are three distinct mRNAs encoding ubiquitin in humans and four mRNAs in the rat.

Amino Acid Sequence↗