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T H Vu

Publications and source records attributed to T H Vu.

70 records · Page 4Linked to original sources
PubMed1995

Differential biallelic activation of three insulin-like growth factor II promoters in the mouse central nervous system.

Imprinting of the insulin-like growth factor II gene (IGF-II) is conserved in human, rat, and mouse. In human liver and chondrocytes, IGF-II transcripts from promoter hP1 are always derived from both parental alleles, while transcripts from promoters hP2-hP4 are from one parental allele. To examine the promoter-specific imprinting pattern of mouse IGF-II, we examined IGF-II expression in F1 generation mice derived from crossing M. spretus with M. musculus using a novel BsaA1 polymorphism in mouse IGF-II exon 6. There was maintenance of maternal IGF-II imprinting in all non-central nervous system (CNS) tissues in the F1 generation animals. However, there was biallelic expression of the IGF-II gene in CNS. Allelic expression of each IGF-II promoter transcript was examined by full-length cDNA amplification with promoter-specific primers. In every tissue in which IGF-II was imprinted, IGF-II transcripts were derived from paternal promoters mP1-mP3, while the maternal allele was suppressed. In the CNS, however, promoters mP1-mP3 of the imprinted maternal allele became activated, leading to the biallelic expression of IGF-II. Moreover, the expression of IGF-II from each parental allele differed in various CNS regions. In leptomeninges, mP1-mP3 drive IGF-II expression predominantly from the paternal allele, while in some CNS regions, the promoter transcripts were primarily from the maternal allele. The coordinate regulation of mouse IGF-II promoters suggests the presence of an upstream imprinting complex controlling IGF-II imprinting.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1994

Promoter-specific imprinting of the human insulin-like growth factor-II gene.

Genomic imprinting is a mechanism whereby only one of the two parental alleles is expressed. Loss or relaxation of genomic imprinting has been proposed as an epigenetic mechanism for oncogenesis in a variety of human tumours. Although the mechanism of imprinting is unknown, differential CpG methylation of the parental alleles has been implicated. The human insulin-like growth factor-II (IGF2) gene, which is transcribed from four promoters, P1-P4 (ref. 13), is imprinted in fetal liver but biallelic expression occurs in adult liver. Like most tissues, fetal liver uses primarily promoters P3 and P4 (ref. 17). Adult liver, however, transcribes IGF2 from promoter P1, and it has been suggested that the recruitment of P1 may be responsible for the absence of imprinting in human liver, and in choroid plexus and leptomeninges. We report here that in liver and chondrocytes, IGF2 transcripts from promoter P1 are always derived from both parental alleles, whereas transcripts from promoters P2, P3 and P4 are always from one parental allele. These findings demonstrate that imprinting and a lack of imprinting can both occur within a single gene in a single tissue, suggesting that regional imprinting factors may be important.

Adult↗
PubMed1994

TGF-beta 1 causes increased endothelial ICAM-1 expression and lung injury.

Neutrophil adherence to vascular endothelium is partially mediated by adhesion molecules, including intracellular adhesion molecule 1 (ICAM-1), on endothelial cells. We examined the effect of transforming growth factor-beta 1 (TGF-beta 1) on the expression of ICAM-1 in human umbilical vein endothelial cells (HUVEC). TGF-beta 1 (1 ng/ml) increased ICAM-1 and ICAM-1 mRNA expression in HUVEC, as assessed by flow cytometry and Northern blot analysis, respectively. In addition, we investigated whether exogenous recombinant TGF-beta 1 can cause neutrophil-mediated lung injury in guinea pigs. The plasma half-life of 125I-labeled TGF-beta 1 in guinea pigs was 4.6 +/- 0.1 min, and the 125I activity was 2.8 +/- 0.2% 8 h after injection. The ratio of 125I-labeled albumin concentration in lung tissue and bronchoalveolar lavage (BAL) fluid to that in plasma, lung wet-to-dry weight ratio, numbers of neutrophils in BAL fluid, and numbers of neutrophils per alveolus in fixed lung sections increased in guinea pigs that received a high dose of TGF-beta 1 (25 micrograms i.v. followed by 2 micrograms/h for 8 h) compared with the control group. These results suggest that TGF-beta 1 causes neutrophil-mediated lung injury, possibly through upregulation of ICAM-1 on endothelial cells, and might be important in the pathogenesis of lung injury.

Animals↗
PubMed1993

Insulin-like growth factor (IGF), IGF binding protein (IGFBP), and IGF receptor gene expression and IGFBP synthesis in human uterine leiomyomata.

Oestradiol is important in the growth of uterine leiomyomata and may act primarily or secondarily through mediators such as growth factors, including the insulin-like growth factors (IGF-I and IGF-II), mitogenic peptides. IGF binding proteins (IGFBPs) modulate IGF actions at their target cells. The objective of this study was to examine the possible steroid dependence of IGF, IGFBP and IGF receptor gene expression and IGFBP synthesis in uterine leiomyomata, using tissues from women cycling normally and made hypo-oestrogenic by a gonadtrophin-releasing hormone agonist (GnRHa). Using a solution hybridization ribonuclease protection assay, anti-sense RNA probes for IGF-I, IGF-II and beta-actin (control) were hybridized with total RNA isolated from leiomyomata exposed in vivo to a range of serum oestradiol (< 40-240 pg/ml) and progesterone (0-10 ng/ml) concentrations. IGF-I gene expression was most abundant in leiomyomata obtained during the late proliferative phase of the cycle and was undetectable in leiomyomata from hypo-oestrogenic patients. IGF-II gene expression was not dependent on endogenous steroid concentrations or cycle stage. IGFBP gene expression was investigated by Northern blotting. The order of relative abundance of IGFBP mRNAs was IGFBP-4 >>> IGFBP-3 >> IGFBP-5 > IGFBP-2 and was not dependent on the in-vivo oestrogen status. Type I and type II IGF receptor gene expression was investigated by polymerase chain reaction using gene-specific primers. Type I and type II IGF receptor mRNAs were detected in leiomyomata and were not dependent on cycle stage or in-vivo oestrogen status. Explant cultures of leiomyomata and myometrium synthesized IGFBP-3 (mol. wt = 38-43 kDa), IGFBP-4, and binding proteins of mol. wt = 34 and 31 kDa. Identification of IGFBP-2 was inconclusive, and IGFBP-1 was not detected. These data support the hypothesis that IGF-I, but not IGF-II, may be a mediator of oestradiol action in the growth of uterine leiomyomata, and that IGFBPs may further modulate, by an autocrine or paracrine mechanism, IGF-I action in this tissue.

Base Sequence↗
PubMed1993

Mechanisms of thyroid hormone action on the insulin-like growth factor system: all thyroid hormone effects are not growth hormone mediated.

Normal somatic growth requires that both the thyroid hormone axis and GH axis be intact. Thyroid hormone stimulates GH secretion, and many thyroid hormone actions on the insulin-like growth factor (IGF) system can be explained by this mechanism. We have previously described distinct changes in IGF binding protein (IGFBP) expression in experimental hypothyroidism in the rat; these changes could be completely corrected by thyroid hormone replacement. To see if the effects of thyroid hormone on IGFBP expression are, in fact, indirect GH effects, we rendered both newborn and adult rats hypothyroid with methimazole treatment, and investigated whether we could correct the resulting IGF and IGFBP changes with GH replacement. The prolonged high expression of serum IGFBP-2 and liver IGFBP-2 messenger RNA (mRNA) during the perinatal period in hypothyroid rat pups could not be normalized by GH therapy, although serum IGF-I values (reduced to 54% of control levels in the hypothyroid animals) were brought up to control level. In adult hypothyroid rats, serum IGF-I concentrations (51% of control levels), were increased up to 79% of control levels, but not totally corrected, by GH therapy. Reduced IGFBP-3 expression (80% of control serum and 50% of control liver mRNA levels) in adult hypothyroid animals was normalized by GH, but there was no correction of the reduced IGFBP-4 serum levels (50% of control levels). Hepatic mRNA levels for the type 1 and 2 IGF receptors were not altered by hypothyroidism, or by thyroid or GH replacement. Somatic growth in hypothyroid pups and adults was only partially corrected by GH therapy. We conclude that GH treatment of hypothyroid animals normalized serum IGF-I levels in the hypothyroid rat pup, but did not correct their prolonged IGFBP-2 expression. In the mature animal, serum IGF-I levels were partially corrected and IGFBP-3 levels were normalized by GH, but no change could be induced in the reduced serum IGFBP-4 levels. All the above changes were normalized by thyroid hormone replacement. Thus, the effects of thyroid hormone on serum IGF levels and IGFBP-3 expression seem to be mediated indirectly via GH. The effects on IGFBP-2 ontogeny, and IGFBP-4 expression in the mature animal, however, are either direct thyroid hormone effects, or mediated by some other route, independent of GH, IGFs, or IGF receptors.

Aging↗
PubMed1993

Differential expression of messenger ribonucleic acids encoding insulin-like growth factors and their receptors in human uterine endometrium and decidua.

During the menstrual cycle, the endometrium undergoes characteristic changes in response to circulating sex steroids. Intense mitotic activity of glands and stroma occurs in the proliferative (estradiol-dominant) phase, and glandular secretion and stromal differentiation in the secretory (progesterone-dominant) phase. The insulin-like growth factors (IGF-I and IGF-II) promote cellular growth and differentiation and have been proposed to participate in these cyclic endometrial events, acting as mediators of steroid hormones. The objective of this study was to determine whether the messenger RNAs (mRNAs) encoding the IGF peptides and the type I and type II IGF receptors are differentially expressed in human endometrium during the menstrual cycle and in early pregnancy. A solution hybridization ribonuclease protection assay, using 32P-labeled riboprobes for IGF-I, IGF-II, and beta-actin (control), revealed IGF-I gene expression primarily in proliferative and early secretory endometrium and abundant IGF-II gene expression in mid-late secretory endometrium and early pregnancy decidua. Northern analysis, using IGF-I and IGF-II complementary DNA probes, revealed multiple IGF-I mRNAs [2-7.6 kilobase (kb)], expressed primarily in proliferative and early secretory endometrium, and IGF-II mRNAs (1.4-6.0 kb), expressed primarily in secretory endometrium and in early pregnancy decidua. The 7.6-kb IGF-I mRNA and the 6.0-kb IGF-II mRNA were most abundantly expressed. IGF-IEa and IGF-IEb mRNA splicing variants were present in a ratio of about 9:1, respectively. Type I and type II IGF receptor gene expression in endometrium was investigated using specific riboprobes and the ribonuclease protection assay. Messenger RNAs encoding both receptors were more abundantly expressed in the secretory phase and during early pregnancy, compared to the proliferative phase. These results show that mRNAs encoding the IGF peptides and their receptors are differentially expressed in human endometrium, depending on the steroid hormone milieu. The preferential expression of IGF-I mRNA in the proliferative phase supports the hypothesis that IGF-I is an estromedin in human endometrium. The expression of endometrial IGF-II mRNA in the mid to late secretory phase and in early pregnancy supports a role for IGF-II in differentiative functions of the endometrium, perhaps including endometrial tissue shedding in the menstrual cycle or remodeling during early pregnancy.

Base Sequence↗
PubMed1992

Effect of NADPH oxidase inhibition on endothelial cell ELAM-1 mRNA expression.

Neutrophil adherence to endothelium is partially mediated by the expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) on endothelial cells activated by agents such as lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). To elucidate molecular mechanisms involved in the induction of ELAM-1 on endothelial cells, we investigated the effect of the NADPH oxidase inhibitor, apocynin (4-hydroxy-3-methoxyacetophenone), on ELAM-1 mRNA expression in human umbilical vein endothelial cells (HUVEC) by Northern blot analysis. Apocynin downregulated both LPS- and PMA-induced ELAM-1 mRNA expression in a dose-dependent manner. Our results suggest NADPH oxidase might play a key role in ELAM-1 mRNA expression in HUVEC.

Acetophenones↗
PubMed1992

Thrombin-induced events in non-platelet cells are mediated by the unique proteolytic mechanism established for the cloned platelet thrombin receptor.

We recently isolated a cDNA clone encoding a functional platelet thrombin receptor that defined a unique mechanism of receptor activation. Thrombin cleaves its receptor's extracellular amino terminal extension, unmasking a new amino terminus that functions as a tethered peptide ligand and activates the receptor. A novel peptide mimicking this new amino terminus was a full agonist for platelet secretion and aggregation, suggesting that this unusual mechanism accounts for platelet activation by thrombin. Does this mechanism also mediate thrombin's assorted actions on non-platelet cells? We now report that the novel thrombin receptor agonist peptide reproduces thrombin-induced events (specifically, phosphoinositide hydrolysis and mitogenesis) in CCL-39 hamster lung fibroblasts, a naturally thrombin-responsive cell line. Moreover, these thrombin-induced events could be recapitulated in CV-1 cells, normally poorly responsive to thrombin, after transfection with human platelet thrombin receptor cDNA. Our data show that important thrombin-induced cellular events are mediated by the same unusual mechanism of receptor activation in both platelets and fibroblasts, very likely via the same or very similar receptors.

Amino Acid Sequence↗
PubMed1990

Characterization of the molecular defects in the mouse E beta f and E beta q genes. Implications for the origin of MHC polymorphism.

The E beta f and E beta q genes have been isolated and sequenced to investigate the molecular basis for their defective expression. A previous study from this laboratory, which characterized the expression of these genes at the RNA level, showed both genes to have defects in posttranscriptional RNA processing. In this paper, the defect in the E beta q gene from the inbred mouse strain B10.G (Mus musculus domesticus) is shown to be a single base insertion in the RNA donor splice site of the first intron. This identical mutation was described previously for the E beta gene of the H-2w17 haplotype, which was derived from the Asian house mouse subspecies Mus musculus castaneus. Although it has been estimated that M. m. domesticus and M. m. castaneus separated from each other more than one million years ago, comparisons of genomic sequences reveal that the nonexpressed E beta q and E beta w17 alleles have not diverged significantly from one another; they are identical in their protein coding regions and have only minor differences elsewhere. In contrast, sequence comparisons of A beta q and A beta w17 show that these two expressed alleles differ by multiple amino acids. These findings provide evidence that selection, acting on expressed MHC proteins, plays a role in accumulation and maintenance of MHC polymorphism. The defective E beta f gene from the inbred strain B10.M has also been isolated. Sequence analysis has identified a mutation in the same RNA donor splice site as E beta q and E beta w17; however, in this gene the mutation is a single base substitution at position 5.

Amino Acid Sequence↗
PubMed1990

Pharmacological characteristics and distributions of sigma- and phencyclidine receptors in the animal kingdom.

The phylogenetic distributions of sigma- and phencyclidine receptors in neural tissues of 13 species and the pharmacological characteristics of these receptors in whole sea anemone and neural tissues of the guinea pig, chicken, and frog were studied. Specific binding of [3H]haloperidol and [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine, ligands that bind with high affinity to sigma- and phencyclidine receptors, respectively, was detected in all organisms examined. The order of potencies of various ligands to inhibit 1 nM [3H]haloperidol binding in brains of frogs and guinea pigs or 1 nM [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine in chicken or guinea pig brain homogenates was very similar. However, the characteristics and stereospecificity of binding of the two radioligands in sea anemone were different than in higher organisms. The results suggest that sigma- and phencyclidine binding sites are evolutionarily old, as the characteristics of the two sites are well preserved over a range of vertebrate phyla.

Animals↗
PubMed1989

Molecular defects in the non-expressed H-2 E alpha genes of the f and q haplotypes.

The expression and sequences of the mouse MHC class II genes, E alpha f and E alpha q, have been studied to determine the molecular basis for their defective expression. Previous work in our laboratory showed that H-2f and H-2q mice produce no detectable E alpha protein. Northern blot analysis confirms previous results showing normal amounts of E alpha f message and a 100-fold reduction in E alpha q mRNA. Despite that observation, the rates of transcription of both defective E alpha genes, measured by nuclear run-on transcription assays, are comparable to that of the normally expressed E alpha k gene. The nucleotide sequences of the E alpha f and E alpha q genes reveal mutations generating premature translation stop codons in both genes. A single base substitution has created the stop codon TGA at amino acid -2 in the E alpha f leader sequence. A nucleotide insertion at codon 64 in the second exon of the E alpha q gene results in a frame shift and a premature stop codon at amino acid residue 69 of a mature E alpha protein. The low steady state level of E alpha q mRNA may be correlated with the unusual size distribution of the RNA, possibly due to altered RNA processing.

Animals↗
PubMed1989

Developmentally regulated use of alternative promoters creates a novel platelet-derived growth factor receptor transcript in mouse teratocarcinoma and embryonic stem cells.

Embryonal carcinoma and embryonic stem cells expressed a novel form of platelet-derived growth factor receptor mRNA which was approximately 1,100 base pairs shorter than the 5.3-kilobase (kb) transcript expressed in fibroblasts and other cell types. The 4.2-kb stem cell transcript was initiated within the genomic region immediately upstream of exon 6 of the 5.3-kb transcript and therefore lacked the first five exons, which encode much of the extracellular domain of the receptor expressed in fibroblasts. In stem cells, the short form was predominant, although both forms were present at low levels. Following differentiation in vitro, expression levels of the long form increased dramatically. These findings suggest that during early embryogenesis, a stem cell-specific promoter is used in a stage- and cell type-specific manner to express a form of the platelet-derived growth factor receptor that lacks much of the extracellular domain and may function independently of ligand.

Animals↗
PubMed1988

Molecular basis for the defective expression of the mouse Ew17 beta gene.

Four of the eleven independent H-2 haplotypes of inbred mouse strains and approximately 15% of wild mouse chromosomes 17 fail to express the E alpha E beta class II histocompatibility (Ia) Ag. These E- haplotypes are defective in the expression of the E alpha and/or the E beta chain. None of the E beta defects has previously been described at the molecular level. In this study, we report the molecular basis for the defective expression of the E beta gene from the w17 haplotype of the H-2 congenic strain B10.CAS2, derived from wild Mus musculus castaneus. Comparison of the Ew17 beta genomic sequence to those of the functional Eb beta and Ed beta genes reveals a single base insertion in the RNA donor splice site of the first intron. By DNA shuffling, we have corrected the single base mutation, and we show by FACS analysis and 2-D PAGE of immunoprecipitates that the corrected Ew17 beta is expressed in L cells when co-transfected with an Ed alpha gene. Conversely, an Eb beta gene construct containing the mutant RNA splice site from Ew17 beta is not expressed. We conclude that the single base insertion in the first RNA splice donor site is the sole molecular defect in the Ew17 beta gene.

Amino Acid Sequence↗
PubMed1988

Prenatal and postnatal development of substance P immunocytochemistry within subnuclei of the rat interpeduncular nucleus.

In the present study, the temporal appearance and distribution of substance P within individual subnuclei has been examined during the development of the rat interpeduncular nucleus (IPN). The prenatal organization as well as migration pattern of individual IPN subnuclei are also described. The IPN was distinguishable on embryonic day (E) 19, near the ventral mesencephalon. At this age, the IPN was organized into individual subnuclei like the adult, except for a bilateral distribution of presumptive rostral neurons. Rostral neurons were merged into a single, midline subnucleus by the day of birth, thereby completing an adult pattern of subnuclear organization. SP immunoreactivity, restricted to the lateral subnuclei, was first detected at E20. The intensity of SP-positive fibers in the lateral subnucleus increased with age, and appeared to become selectively distributed along both the medial and lateral borders of this subnucleus. Additional SP-positive fibers became evident postnatally in a thin band overlying both central and intermediate subnuclei, and within the dorsal medial, central and apical subnuclei. SP-positive cell bodies were present in the rostral subnucleus on postnatal day 28, thereby completing the development of an adult pattern of SP immunoreactivity within the IPN.

Animals↗
PubMed1981

[Use of Doppler ultrasonic examination for per-operative checking of non surgical upper dorsal sympathectomy in the treatment of hyperhydrosis (author's transl)].

Doppler ultrasonic examination has been used as an indirect means of per-operative checking of sweat secretion after non surgical upper dorsal sympathectomy performed by percutaneous injection of hot saline into the upper dorsal sympathetic ganglions for the treatment of palmar hyperhydrosis. Their experience with pre, per and post-operative utilisation of Doppler effect in sixty cases has evidenced a full parallelism between the arterial vasodilation and the decrease in sweat secretion following the destruction of the sympathetic ganglions by hot saline. In the last series of thirty-five cases per-operative use of Doppler ultrasonic examination has spared them failures of the procedure. They consider Doppler ultrasonic examination as a precious help in classical open sympathectomy as well in their non surgical method.

Hand↗