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Biomedical subjects

D Warburton

Publications and source records attributed to D Warburton.

At least 19 recordsLinked to original sources
PubMed2001

Complex cytogenetic rearrangement of chromosome 8q in a case of Ambras syndrome.

Ambras syndrome (AMS) is a unique form of congenital universal hypertrichosis. The syndrome has been found in association with rearrangements of chromosome 8 in two isolated cases. One of these patients was reported to have an apparently balanced paracentric inversion of chromosome 8, inv(8)(q12q22). Our cytogenetic analysis on this patient showed that the rearrangement of chromosome 8 is more complex than initially reported. We detected an insertion of the q23-q24 region into a more proximal region of the long arm of chromosome 8 as well as a large deletion in 8q23:46,XX, rea(8)(8pter-->8q13::8q23.2-->8q24.1::8q13-->8q23.1::8q24.1-->8qter). Given the large number of breakpoints and the presence of a substantial deletion, it is surprising that the proposita did not show anomalies other than these characteristic of Ambras syndrome.

Child, Preschool↗
PubMed2001

Nongenomic estrogen action in human lung myofibroblasts.

Recent studies have suggested that the antiproliferative effects of E2 may be mediated through a nongenomic action. Herein, we asked whether nongenomic estrogen action regulates phosphorylation of Raf1 and ERK1/2 mitogen-activated protein (MAP) kinase in lung myofibroblasts. We demonstrated that lung myofibroblasts, incubated in the presence of E2, showed a rapid phosphorylation on serine-259 of Raf1 and tyrosine-204 of ERK1/2 MAP kinase at 15 min, by approximately 3- and 5-fold, respectively. This phosphorylation was followed by dephosphorylation between 30 and 60 min. Western blot analysis showed that E2 regulates tyrosine phosphorylation of four main cytoplasmic proteins in lung myofibroblasts, of 42, 44, 70 and 100 kDa. Furthermore, our results indicated that E2 inhibits cell proliferation (BrdU index) in lung myofibroblasts by approximately 30% (P < 0.01). These data provide evidence that nongenomic action of E2, regulates both serine and tyrosine phosphorylation of cytoplasmic proteins in lung myofibroblasts, including Raf1 and ERK1/2 MAP kinase, which may regulate proliferation in lung myofibroblasts.

Binding Sites↗
PubMed2001

Pulmonary hypoplasia in mice lacking tumor necrosis factor-alpha converting enzyme indicates an indispensable role for cell surface protein shedding during embryonic lung branching morphogenesis.

Many membrane-bound protein precursors, including cytokines and growth factors, are proteolytically shed to yield soluble intercellular regulatory ligands. The responsible protease, tumor necrosis factor-alpha converting enzyme (TACE/ADAM-17), is a transmembrane metalloprotease-disintegrin that cleaves multiple cell surface proteins, although it was initially identified for the enzymatic release of tumor necrosis factor-alpha (TNF-alpha). Mammalian lung growth and development are tightly controlled by cytokines and peptide growth factors. However, the biological function of the cell shedding mechanism during lung organogenesis is not understood. We therefore evaluated the role of TACE as a "sheddase" during lung morphogenesis by analyzing the developmental phenotypes of lungs in mice with an inactive TACE gene in both in vivo and ex vivo organ explant culture. Neonatal TACE-deficient mice had visible respiratory distress and their lungs failed to form normal saccular structures. These newborn mutant lungs had fewer peripheral epithelial sacs with deficient septation and thick-walled mesenchyme, resulting in reduced surface for gas exchange. At the canalicular stage of E16.5, the lungs of TACE mutant mice were impaired in branching morphogenesis, inhibited in epithelial cell proliferation and differentiation, and delayed in vasculogenesis. Embryonic TACE knockout mouse lungs (E12) branched poorly compared to wild-type lungs, when placed into serumless organ culture. Gene expression of both surfactant protein-C and aquaporin-5 were inhibited in cultured TACE-mutant embryonic lungs, indicating defects in both branching and peripheral epithelial cytodifferentiation in the absence of TACE protein. Furthermore, both the hypoplastic phenotype and the delayed cytodifferentiation in TACE-deficient lungs were rescued by exogenous addition of soluble stimulatory factors including either TNF-alpha or epidermal growth factor in embryonic lung culture. Thus, the impaired lung branching and maturation without TACE suggest a broad role for TACE in the processing of multiple membrane-anchored proteins, one or more of which is essential for normal lung morphogenesis. Taken together, our data indicate that the TACE-mediated proteolytic mechanism which enzymatically releases membrane-tethered proteins plays an indispensable role in lung morphogenesis, and its inactivation leads to abnormal lung development.

ADAM Proteins↗
PubMed2001

Precise measurement of the positive muon anomalous magnetic moment.

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.

Journal Article↗
PubMed2001

Prenatal diagnosis of a familial Xq deletion in a female fetus: a case report.

X chromosome deletion is an infrequent finding in prenatal diagnosis and presents a difficult counseling challenge when it occurs. We present a case of a familial X chromosome long arm deletion discovered in a routine amniocentesis and subsequently in the mother. The pregnancy resulted in the birth of a normal girl, and X chromosome inactivation skewing was demonstrated in both mother and daughter. Xq deletion phenotypes and counseling issues are reviewed.

Adult↗
PubMed2001

Evidence that SPROUTY2 functions as an inhibitor of mouse embryonic lung growth and morphogenesis.

Experimental evidence is rapidly emerging that the coupling of positive regulatory signals with the induction of negative feedback modulators is a mechanism of fine regulation in development. Studies in Drosophila and chick have shown that members of the SPROUTY family are inducible negative regulators of growth factors that act through tyrosine kinase receptors. We and others have shown that Fibroblast Growth Factor 10 (FGF10) is a key positive regulator of lung branching morphogenesis. Herein, we provide direct evidence that mSprouty2 is dynamically expressed in the peripheral endoderm in embryonic lung and is downregulated in the clefts between new branches at E12.5. We found that mSprouty2 was expressed in a domain restricted in time and space, adjacent to that of Fgf10 in the peripheral mesenchyme. By E14.5, Fgf10 expression was restricted to a narrow domain of mesenchyme along the extreme edges of the individual lung lobes, whereas mSprouty2 was most highly expressed in the subjacent epithelial terminal buds. FGF10 beads upregulated the expression of mSprouty2 in adjacent epithelium in embryonic lung explant culture. Lung cultures treated with exogenous FGF10 showed greater branching and higher levels of mSpry2 mRNA. Conversely, Fgf10 antisense oligonucleotides reduced branching and decreased mSpry2 mRNA levels. However, treatment with exogenous FGF10 or antisense Fgf10 did not change Shh and FgfR2 mRNA levels in the lungs. We investigated Sprouty2 function during lung development by two different but complementary approaches. The targeted overexpression of mSprouty2 in the peripheral lung epithelium in vivo, using the Surfactant Protein C promoter, resulted in a low level of branching, lung lobe edges abnormal in appearance and the inhibition of epithelial proliferation. Transient high-level overexpression of mSpry2 throughout the pulmonary epithelium by intra-tracheal adenovirus microinjection also resulted in a low level of branching. These results indicate for the first time that mSPROUTY2 functions as a negative regulator of embryonic lung morphogenesis and growth.

Adenoviridae↗
PubMed2001

Prenatal exposure to nitrofen induces Fryns phenotype in mice.

Prenatal exposure to nitrofen is known to cause multiple malformations in mice. The reported malformations include lung hypoplasia, diaphragmatic hernia, cardiovascular defects, skeletal malformations, cleft palate, and renal abnormalities. The authors present detailed findings of craniofacial defects after prenatal exposure to nitrofen, and propose that together with the previously reported malformations, nitrofen exposure induces a Fryns phenotype in mice. Fryns syndrome is a rare human genetic syndrome that is an autosomal recessive disorder characterized by lung hypoplasia, diaphragmatic hernia, craniofacial malformations, skeletal malformations, cardiovascular malformations, and genitourinary malformations. Timed-pregnant Swiss Webster mice were gavage-fed 25 mg of nitrofen on day 8 of gestation. Control animals received olive oil. Osteogenesis and chondrogenesis were studied in fetuses recovered on day 17 after Alcian blue-Alizarin red staining. Approximately 26% of the nitrofen-exposed embryos had severe craniofacial defects, and there was generalized delay in chondrogenesis and osteogenesis throughout the skeleton. No such defects were noted in the control group. The authors propose that prenatal exposure to nitrofen induces a Fryns phenotype in mice, and thus speculate that nitrofen may target similar molecular mechanisms to those that lead to Fryns syndrome.

Abnormalities, Drug-Induced↗
PubMed2001

Gremlin negatively modulates BMP-4 induction of embryonic mouse lung branching morphogenesis.

Bone morphogenetic protein-4 (BMP-4) is a key morphogen for embryonic lung development that is expressed at high levels in the peripheral epithelium, but the mechanisms that modulate BMP-4 function in early mouse lung branching morphogenesis are unclear. Here, we studied the BMP-4 antagonist Gremlin, which is a member of the DAN family of BMP antagonists that can bind and block BMP-2/4 activity. The expression level of gremlin in embryonic mouse lungs is highest in the early embryonic pseudoglandular stage [embryonic days (E) 11.5-14.5] and is reduced during fetal lung maturation (E18.5 to postnatal day 1). In situ hybridization indicates that gremlin is diffusely expressed in peripheral lung mesenchyme and epithelium, but relatively high epithelial expression occurs in branching buds at E11.5 and in large airways after E16.5. In E11.5 lung organ culture, we found that exogenous BMP-4 dramatically enhanced peripheral lung epithelial branching morphogenesis, whereas reduction of endogenous gremlin expression with antisense oligonucleotides achieved the same gain-of-function phenotype as exogenous BMP-4, including increased epithelial cell proliferation and surfactant protein C expression. On the other hand, adenoviral overexpression of gremlin blocked the stimulatory effects of exogenous BMP-4. Therefore, our data support the hypothesis that Gremlin is a physiologically negative regulator of BMP-4 in lung branching morphogenesis.

Animals↗
PubMed2001

Novel mechanisms in murine nitrofen-induced pulmonary hypoplasia: FGF-10 rescue in culture.

We evaluated the role of the key pulmonary morphogenetic gene fibroblast growth factor-10 (Fgf10) in murine nitrofen-induced primary lung hypoplasia, which is evident before the time of diaphragm closure. In situ hybridization and competitive RT-PCR revealed a profound disturbance in the temporospatial pattern as well as a 10-fold decrease in mRNA expression level of Fgf10 but not of the inducible inhibitor murine Sprouty2 (mSpry2) after nitrofen treatment. Exogenous FGF-10 increased branching not only of control lungs [13% (right) and 27% (left); P < 0.01] but also of nitrofen-exposed lungs [23% (right) and 77% (left); P < 0.01]. Expression of mSpry2 increased 10-fold with FGF-10 in both nitrofen-treated and control lungs, indicating intact downstream FGF signaling mechanisms after nitrofen treatment. We conclude that nitrofen inhibits Fgf10 expression, which is essential for lung growth and branching. Exogenous FGF-10 not only stimulates FGF signaling, marked by increased mSpry2 expression, in both nitrofen-treated and control lungs but also substantially rescues nitrofen-induced lung hypoplasia in culture.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Migration and gelatinases in cultured fetal, adult, and hyperoxic alveolar epithelial cells.

Alveolar epithelial cell (AEC) migration mediated by matrix metalloproteinases (MMPs) is required for lung development and repair after injury such as hyperoxia. Of specific interest in lung remodeling are the gelatinases, which are upregulated in AEC after hyperoxia. We correlated migration and gelatinase production in AEC cultured from fetal, adult, and hyperoxic rats. Fetal AEC (19-20 days) had higher MMP-2 and MMP-9 gelatinase expression than adult AEC, with fivefold higher MMP-9 activity, and were migratory through gelatin, responding to epidermal growth factor, keratinocyte growth factor, and fibroblast growth factor-10. MMP-2 and MMP-9 expression and migratory activity could be detected from the time of plating. In contrast, adult AEC migrated and expressed MMP-2 and MMP-9 proteins only after 48 h of culture. AEC from hyperoxic rats were significantly more migratory through gelatin than control adult AEC, with significantly higher MMP-9 activity. Inhibition of MMPs with doxycycline reduced the migration of AEC from hyperoxic rats to the level of control adult AEC. Fibronectin-cultured "hyperoxic" AEC acquired a temporary capacity for migration similar to the A549 lung cancer cell line, which is both highly migratory and invasive and is derived from the AEC type 2 lineage. These data suggest that MMP activity is associated with a migratory phenotype in fetal, hyperoxic, and transformed AEC in vitro, and we speculate that MMPs may play a key mechanistic role in AEC migration in vivo during lung development and repair.

Aging↗
PubMed2001

Bradykinin B1 receptor up-regulation by interleukin-1beta and B1 agonist occurs through independent and synergistic intracellular signaling mechanisms in human lung fibroblasts.

Bradykinin B1 receptors (B1R) are rapidly induced after tissue trauma and are thought to be involved in maintaining the inflammatory response. Little is known about the intracellular signaling pathways mediating B1R induction in response to stress and inflammation. Here, we show that up-regulation of B1R by B1R agonist and interleukin-1beta (IL-1beta) occur through distinct but synergistic pathways in IMR-90 human lung fibroblasts. Incubation of cells with the B1R agonist desArg10kallidin (desArg10KD; 100 nM) and IL-1beta (500 pg/ml) resulted in a 3- and 4-fold increase, respectively, in B1R by 6 h, whereas coincubation of these factors produced up to a 20-fold increase. Furthermore, coincubation increased the potency of IL-1beta by 2-fold. Both the individual and the synergistic responses were sensitive to genistein, a general tyrosine kinase inhibitor. On the other hand, only the desArg10KD response and the synergistic response were sensitive to the p38 mitogen-activated protein kinase inhibitor SB 203580. Furthermore, only the synergistic response was sensitive to the nuclear factor-kappaB inhibitor pyrrolidine dithiocarbamate. Despite B1R up-regulation in A549 human lung epithelial cells by desArg10KD or IL-1beta individually, these factors did not act synergistically in this cell line. In conclusion, our results reinforce the view that kinins act in concert with proinflammatory cytokines to enhance selectively the inflammatory response of certain lung cells to kinins through distinct but synergistic intracellular signaling mechanisms. Thus, kinins may exert a pivotal role in maintaining and modulating feed-forward inflammatory processes in the lung.

Cells, Cultured↗
PubMed2001

Impaired left ventricular systolic function after a half-ironman race.

OBJECTIVE: To assess the effects of prolonged strenuous exercise in the form of a half-ironman (HI) race (2 km swim, 90 km bike ride and a 21 km run) on left ventricular systolic function. METHODS AND RESULTS: The study participants consisted of nine male triathletes (mean age +/- SD 32+/-5 years) who competed in the Great White North HI race. Two-dimensional transthoracic echocardiograms were obtained two to three days before the HI (prerace), immediately after completion of the HI (postrace) and 24 h after cessation of exercise. Compared with before the race, performing an HI was associated with a decline in systolic blood pressure (prerace 127.2+/-15.0 mmHg compared with after the race 116.1+/-10.2 mmHg, P<0.05), the systolic blood pressure to end-systolic cavity area ratio (a surrogate for left ventricular contractility - prerace 14.3+/-3.0 mmHg/cm(2) compared with postrace 11.0+/-2.2 mmHg/cm(2), P<0.05) and the fractional area change (prerace 54.1+/-3.8% compared with postrace 47.4+/-5.5%, P<0.05). There was also a concomitant increase in heart rate (prerace 56.3+/-9.4 beats/min compared with postrace 74.1+/-10.7 beats/min, P<0.05), the end-systolic cavity area (prerace 9.2+/-2.2 cm(2) compared with postrace 10.8+/-1.9 cm(2), P<0.05) and the end-systolic cavity area to end-systolic myocardial area ratio (prerace 0.39+/-0.08 compared with postrace 0.51+/-0.1, P<0.05), which returned toward baseline values 24 h after cessation of the HI. CONCLUSIONS: Performing an HI appears to be associated with a transient impairment in left ventricular contractility and a subsequent decline in left ventricular systolic function that tends to return toward normal values within 24 h after cessation of exercise.

Adult↗
PubMed2001

Abrogation of tumor necrosis factor-alpha converting enzyme inhibits embryonic lung morphogenesis in culture.

TNF-alpha converting enzyme (TACE)-mediated cell surface protein ectodomain cleavage constitutes an important cellular regulatory mechanism during mammalian lung development. Herein, we have found that TAPI, a synthetic inhibitor of TACE, inhibits embryonic mouse lung branching morphogenesis in culture. To further investigate the biological significance of TACE as a shedding enzyme during early lung organogenesis, we have devised an antisense oligonucleotide to specifically block endogenous TACE gene expression at both transcriptional and translational levels in embryonic mouse lung explant culture. Addition of TACE antisense oligonucleotide resulted in a concentration-dependent reduction in lung branching morphogenesis in culture, whereas both scrambled and sense control oligonucleotides showed no adverse effects on lung growth. Furthermore, both aquaporin-5 (Aqp5) and surfactant protein-C (SP-C) mRNA expression and protein immunoreactivity were significantly inhibited in cultured mouse lungs treated with TACE antisense oligonucleotide, indicating defective epithelial cell differentiation in embryonic lungs with decreased TACE expression. TACE is known to be involved in the proteolytic release of TGF-alpha, an EGF family stimuli critical for lung growth and maturation. We therefore tested the possibility that a lack of diffusable TGF-alpha, due to TACE deficiency, contributes to the inhibitory lung morphogenesis in the presence of TACE antisense oligonucleotide in lung culture. Soluble TGF-alpha, when included in the lung culture, rescued the TACE antisense oligonucleotide-treated lungs from inhibition of both lung branching morphogenesis and lung epithelial cell differentiation, suggesting an impaired release of circulating regulators necessary for lung development in the absence of TACE gene expression. Our findings provide evidence that TACE-mediated membrane protein shedding is indispensable for normal lung branching morphogenesis and cytodifferentiation, probably through regulating the availability of positive cytokines/growth factors essential for lung organogenesis such as TGF-alpha.

ADAM Proteins↗
PubMed2000

Smad7 and Smad6 differentially modulate transforming growth factor beta -induced inhibition of embryonic lung morphogenesis.

Transforming growth factors beta (TGF-beta) are known negative regulators of lung development, and excessive TGF-beta production has been noted in pulmonary hypoplasia associated with lung fibrosis. Inhibitory Smad7 was recently identified to antagonize TGF-beta family signaling by interfering with the activation of TGF-beta signal-transducing Smad complexes. To investigate whether Smad7 can regulate TGF-beta-induced inhibition of lung morphogenesis, ectopic overexpression of Smad7 was introduced into embryonic mouse lungs in culture using a recombinant adenovirus containing Smad7 cDNA. Although exogenous TGF-beta efficiently reduced epithelial lung branching morphogenesis in control virus-infected lung culture, TGF-beta-induced branching inhibition was abolished after epithelial transfer of the Smad7 gene into lungs in culture. Smad7 also prevented TGF-beta-mediated down-regulation of surfactant protein C gene expression, a marker of bronchial epithelial differentiation, in cultured embryonic lungs. Moreover, we found that Smad7 transgene expression blocked Smad2 phosphorylation induced by exogenous TGF-beta ligand in lung culture, indicating that Smad7 exerts its inhibitory effect on both lung growth and epithelial cell differentiation through modulation of TGF-beta pathway-restricted Smad activity. However, the above anti-TGF-beta signal transduction effects were not observed in cultured embryonic lungs with Smad6 adenoviral gene transfer, suggesting that Smad7 and Smad6 differentially regulate TGF-beta signaling in developing lungs. Our data therefore provide direct evidence that Smad7, but not Smad6, prevents TGF-beta-mediated inhibition of both lung branching morphogenesis and cytodifferentiation, establishing the mechanistic basis for Smad7 as a novel target to ameliorate aberrant TGF-beta signaling during lung development, injury, and repair.

Animals↗
PubMed2000

A cysteine residue in the helix-loop-helix domain of Id2 is critical for homodimerization and function.

Id proteins are negative regulators of basic helix-loop-helix (bHLH) transcription factors. In this study, we compared the expression of Id2 mRNA in proliferating (fetal) and nonproliferating (adult) alveolar epithelial cells (AECs). The expression of Id2 was higher in adult AECs than in the corresponding fetal cells, suggesting that Id2 might play a functional role in developmental regulation of lung epithelial cell proliferation. By screening a mouse embryo cDNA library in the yeast two-hybrid system, Id2 was identified as a self-associating protein. Structural analysis by deletion and site-directed mutagenesis demonstrated that the HLH domain and a cysteine residue within the HLH domain are essential for Id2 homodimerization. Furthermore, in vitro synthesized Id2 homodimers became monomers under reducing conditions, indicating that the formation of an intermolecular disulfide bond is critical for Id2 homodimerization. Transient transfection assays in A549 cells showed that wild-type Id2 down-regulated the activity of the cyclin A promoter by 70%, while mutating the cysteine critical for Id2 homodimerization abolished the inhibitory effect of wild-type Id2.

Animals↗
PubMed2000

Trisomic pregnancy and earlier age at menopause.

We tested the hypothesis that the connection between advanced maternal age and autosomal trisomy reflects the diminution of the oocyte pool with age. Because menopause occurs when the number of oocytes falls below some threshold, our hypothesis is that menopause occurs at an earlier age among women with trisomic pregnancies than it does among women with chromosomally normal pregnancies. To determine their menstrual status, we interviewed women from our previous study of karyotyped spontaneous abortions who, in 1993, were age >/=44 years. Premenopausal women completed interviews every 4-5 mo, until menopause or until the study ended in 1997. The primary analyses compare 111 women whose index pregnancy was a trisomic spontaneous abortion with two groups: women whose index pregnancy was a chromosomally normal loss (n=157) and women whose index pregnancy was a chromosomally normal birth (n=226). We used a parametric logistic survival analysis to compare median ages at menopause. The estimated median age at menopause was 0.96 years earlier (95% confidence interval -0.18 to 2.10) among women with trisomic losses than it was among women with chromosomally normal losses and chromosomally normal births combined. Results were unaltered by adjustment for education, ethnicity, and cigarette smoking. Our results support the hypothesis that trisomy risk is increased with decreased numbers of oocytes. Decreased numbers may indicate accelerated oocyte atresia or fewer oocytes formed during fetal development.

Abortion, Spontaneous↗
PubMed2000

Cloning and characterization of DIP1, a novel protein that is related to the Id family of proteins.

Using human cyclin D1 as the "bait" in a yeast two-hybrid system, together with a HL60 cDNA library, we identified a novel human nuclear protein designated DIP1. This protein is expressed in a variety of cell types, and in fibroblasts its level remains constant throughout the cell cycle. However, the level of this protein increases severalfold during the differentiation of HL60 cells. The DIP1 protein can be phosphorylated in vitro by a cellular kinase and this activity reaches its maximum in extracts obtained from cells in the G1 phase of the cell cycle. DIP1 contains a helix-loop-helix motif but lacks an adjacent basic DNA-binding domain, thus resembling the Id family of proteins. The dip1 gene is located on human chromosome 16p11.2-12, a locus that is amplified in several types of human cancer. These results suggest that DIP1 may be involved in the control of gene expression and differentiation, but its precise function remains to be determined.

Amino Acid Sequence↗