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Biomedical subjects

J H Chang

Publications and source records attributed to J H Chang.

At least 91 records · Page 5Linked to original sources
PubMed1999

Kinematics of cervical spine discectomy with and without bone grafting: quantitative evaluation of late fusion in a sheep model.

OBJECTIVE: This study was conducted to evaluate the kinematic response of late fusion results for cervical spine discectomies with and without bone grafting. MATERIALS AND METHODS: Fifteen Barbados Black Belly sheep underwent sham operations (Group A, n = 5), C2-C3 discectomies only (Group B, n = 5), and C2-C3 discectomies with autologous iliac bone grafting (Group C, n = 5). Ten months after surgery, the animals were killed. Fresh ligamentous spines (C1-C5) were subjected to the relevantly applied loads through a loading frame attached to the C1. Each vertebra (from C2 to C4) was attached with a set of three infrared light-emitting diodes to record the spatial location relating to each load application using a Selspot II system (Selcom Selective Electronics, Inc., Valdese, NC). The load-deformation data of the C2-C3 and C3-C4 motion segments were recorded and analyzed for the three groups. RESULTS: At the C2-C3 motion segment, the results indicated that Group B displayed larger motion ranges of rotation and lateral bending loads than did the other two groups. Significantly larger motion ranges of rotation loads were found in Group B than in Group C (P<0.05, for both comparisons). In contrast, Group C had the smallest motion ranges of flexion, lateral bending, and rotation loads. At the C3-C4 motion segment, both groups that had undergone discectomies had a significantly larger motion range of flexion load compared with Group A (P<0.05, for both comparisons). A significant increase in the motion range of right axial rotation was found in Group B (P<0.05), but not in Group C, compared with Group A. Group B exhibited larger motion ranges responding to all six tested loads than did Group C. CONCLUSION: The results indicate that anterior fusion after C2-C3 cervical discectomies, regardless of the presence or absence of bone grafting, decreases the motion range of flexion load at the C2-C3 motion segment, and contrary data were seen at the C3-C4 motion segment. For axial rotation loads, discectomies without bone grafting resulted in increased motion ranges of both C2-C3 and C3-C4 motion segments whereas discectomies with bone grafting did not. The data may have clinical relevance regarding the role of bone grafting in cases of cervical spine disease.

Animals↗
PubMed1999

Molecular cloning and characterization of the Helicobacter pylori fliD gene, an essential factor in flagellar structure and motility.

Helicobacter pylori colonizes the human stomach and can cause gastroduodenal disease. Flagellar motility is regarded as a major factor in the colonizing ability of H. pylori. The functional roles of flagellar structural proteins other than FlaA, FlaB, and FlgE are not well understood. The fliD operon of H. pylori consists of flaG, fliD, and fliS genes, in the order stated, under the control of a sigma(28)-dependent promoter. In an effort to elucidate the function of the FliD protein, a hook-associated protein 2 homologue, in flagellar morphogenesis and motility, the fliD gene (2,058 bp) was cloned and isogenic mutants were constructed by disruption of the fliD gene with a kanamycin resistance cassette and electroporation-mediated allelic-exchange mutagenesis. In the fliD mutant, morphologically abnormal flagellar appendages in which very little filament elongation was apparent were observed. The fliD mutant strain was completely nonmotile, indicating that these abnormal flagella were functionally defective. Furthermore, the isogenic fliD mutant of H. pylori SS1, a mouse-adapted strain, was not able to colonize the gastric mucosae of host mice. These results suggest that H. pylori FliD is an essential element in the assembly of the functional flagella that are required for colonization of the gastric mucosa.

Animals↗
PubMed1999

Simultaneous analysis of urinary 2-thiothiazolidine-4-carboxylic acid and thiocarbamide as a biological exposure index for carbon disulfide exposure.

The objectives of this study were to develop optimal analytic methods for detecting urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) and thiocarbamide simultaneously and to evaluate the usefulness of these metabolites to a biological exposure index (BEI) for carbon disulfide (CS2) exposure. For this experiment, synthesized TTCA and thiocarbamide were used. The synthesized TTCA was identified by infrared spectrophotometer, nuclear magnetic resonance spectrometer and thin layer chromatography. The recovery rates of both metabolites were calculated to find the optimum analytical method. The amounts of urinary TTCA and thiocarbamide were measured by using an ultraviolet detector connected to high performance liquid chromatography (HPLC) after the administration of CS2 (350, 700 mg/kg) into Sprague-Dawley rats intraperitoneally. The maximum absorbance wave lengths for TTCA and thiocarbamide were 272 and 236 nm, respectively. Ethyl acetate extraction with NaCl as a salting-out reagent was used as a simultaneous extraction method for these metabolites. HPLC conditions for these metabolites included using a NH2 column, 50 mM KH2PO4: acetonitrile (85:15) and pH 3. Excreted amounts of urinary TTCA and thiocarbamide were increased significantly following CS2 administration. TTCA, which was already adopted as a BEI for CS2 by the American Conference of Governmental Industrial Hygienists (ACGIH), seems to be a more useful BEI for CS2 exposure than thiocarbamide. However further studies are needed to increase analytical efficiency before thiocarbamide can be adopted as a BEI and to apply this analytic method for simultaneous analysis of these metabolites in workers exposed to CS2.

Animals↗
PubMed1999

Subcutaneous sparganosis--a case report and a review of human sparganosis in Taiwan.

Human sparganosis is a rare parasitic disease infected by plerocercoid larva (sparganum) of Spirometra species. It was usually diagnosed accidentally and has long been underestimated. In this report, we describe a 53-year-old woman presenting as an enlarging subcutaneous nodule in the right thigh for 3 months, which was excised in the belief that it was a lipoma. Characteristic sparganum accompanied by granulomatous inflammation, eosinophilic infiltrate and sinus tract in the subcutaneous tissue were discovered under microscopic examination of the excised tissue. Contaminated drinking water was presumed to be the infectious source. Complete excision is a curative treatment. We also review previously documented 19 human sparganosis in Taiwan to provide the clinical context for this report.

Female↗
PubMed1998

Polymorphism of the CYP1A1 and glutathione-S-transferase gene in Korean lung cancer patients.

The levels of expressions and catalytic activities of cytochrome P450 (CYP1A1) and glutathione-S-transferase class mu (GSTM1) enzymes in lungs and their metabolic balance may be an important determinant host factor underlying lung cancer. Genetic differences in metabolism, MspI restriction sites, Ile-Val polymorphism of CYP1A1 gene, and the null genotype of GSTM1 have been reported to be associated with susceptibility to lung cancer. The present studies were undertaken to establish frequencies of the polymorphic genotypes of CYP1A1 and GSTM1 in Koreans, and to evaluate linkage disequilibrium of the genotypes associated with higher lung cancer risks among Koreans. GSTM1(-) genotype was found in 52% of control subjects, whereas it was found in 55% of lung cancer patients. The allelic variants in CYP1A1 were distributed differently in lung cancer patients and controls. The heterozygous genotype frequency of the MspI site in lung cancer patients (53%) was higher than in controls (49%). The frequency of Ile/Val genotype of CYP1A1 was low in lung cancer patients, which are mostly squamous cell carcinoma.

Adenocarcinoma↗
PubMed1998

Evidence for the ability of nucleophosmin/B23 to bind ATP.

By taking advantage of its ability to be retained by ATP-agarose, we have demonstrated that nucleophosmin/B23 is capable of binding ATP. The specificity of the binding was confirmed by the absence of significant binding to AMP-agarose and by its loss when nucleophosmin/B23 in nuclear extracts was preincubated with ATP. Preincubation of the nuclear extracts with other ribonucleotide triphosphates (GTP, CTP, UTP) did not compete for the binding of nucleophosmin/B23 to ATP-agarose. The purified recombinant nucleophosmin/B23 was also able to be retained by ATP-agarose. The Kd for binding of ATP to the purified recombinant nucleophosmin/B23, on the basis of retention on a nitrocellulose membrane, was 86.5+/-8.3 microM; the number of binding sites was 0.68 per nucleophosmin/B23 protein molecule. To determine the possible ATP-binding site of nucleophosmin/B23, various deletion clones including the two mutants in which the putative ATP-binding sequence had been deleted were constructed. Deletion of the portions of the molecule (residues 83-152 and 185-240) had little effect on the ATP binding. The C-terminal deleted mutant (residue 242 to the C-terminus deleted) lost most of its ability to be retained by ATP-agarose and to bind [alpha-32P]ATP on a nitrocellulose membrane. The results indicate that the C-terminal portion (residues 242-294) contains the essential ATP-binding site of nucleophosmin/B23.

Adenosine Triphosphate↗
PubMed1998

Effects of synthetic inhibitor of metalloproteinase and cyclosporin A on corneal haze after excimer laser photorefractive keratectomy in rabbits.

To evaluate the effects of synthetic inhibitor of metalloproteinase (SIMP) and cyclosporin A (CsA) on corneal haze after excimer laser photorefractive keratectomy (PRK) in rabbits, PRK was performed on 60 rabbits. They were randomized to one of four groups: group A which received topical SIMP, group B which received topical CsA, group C which received both SIMP and CsA, and group D which received vehicles. Another 16 rabbits did not undergo PRK and were randomized to one of four groups: group E which received topical SIMP, group F which received topical CsA, group G which received both SIMP and CsA, and group H which received vehicles. SIMP solution (1 mm) was instilled every two hours and 2% cyclosporin was instilled four times a day, this was carried out for as long as 6 weeks after surgery. At one, two, four, and six weeks after surgery, slit lamp examination was performed with haze gradings recorded, and corneal specimens were obtained from groups A, B, C, and D. In groups E-H, all rabbits were killed after six weeks of eyedrops instillation. Light microscopy and immunohistochemistry for collagen types III, IV, and VI were performed on the specimens obtained. Slit lamp examination and light microscopy revealed that SIMP significantly reduced corneal haze after PRK, but CsA did not. Immunohistochemistry revealed that deposition of types III and IV collagen was detected in ablated area in groups A-D, and SIMP reduced the frequency of positive staining for type III collagen. In groups E-F, corneas were normal. These findings suggest that SIMP significantly reduced corneal haze and the synthesis of type III collagen after excimer laser PRK in rabbits.

Animals↗
PubMed1998

Experience with minimally invasive surgery in infants.

BACKGROUND: This study evaluates the feasibility, safety, and efficacy of performing advanced endoscopic procedures in infants under 5 kg. METHODS: Over a 51-month period 183 infants weighing 1.3 to 5.0 kg underwent 195 procedures using minimally invasive techniques. The majority of the procedures were performed using 3.5-mm instruments and 2.7-mm scopes. Procedures include Nissen fundoplication, pyloromyotomy, colon pull-through, patent ductus arteriosus closure, Ladd's procedure, colon resection, congenital diaphragmatic hernia repair, ovarian cyst excision, and exploration. RESULTS: All but two procedures were completed successfully endoscopically. There were two intraoperative complications and no mortality. Days to discharge for patients admitted for their specific procedure were Nissen 2.1, patent ductus arteriosus 2, pyloromyotomy 1, and pull-through 3.4. CONCLUSIONS: This study demonstrates that advanced endosurgical techniques in infants is safe, effective, and associated with the same benefit as that seen in older patients.

Endoscopy↗
PubMed1998

Laparoscopic Ladd's procedure in infants with malrotation.

PURPOSE: This clinical study was undertaken to examine the feasibility of a laparoscopic approach for the treatment of documented malrotation. METHODS: From May 1994 through January of 1997, 12 patients, aged 5 days to 4 months, weighing 3 to 7 kg, underwent laparoscopic Ladd's procedure for malrotation. All patients had symptoms of intermittent upper intestinal obstruction, and malrotation was documented by an upper gastrointestinal contrast study. None of the patients had acute volvulus or compromised bowel. The procedure was performed using 3 trocars of 3.5 mm diameter. Ports were placed in the infraumbilical ring, and the right and left mid to lower quadrants. A standard Ladd's procedure with appendectomy was performed in all cases. RESULTS: All procedures were completed successfully through the laparoscope. Operative times averaged 58 minutes (35 to 120 minutes). One patient with Pierre-Robin underwent a laparoscopic Nissen fundoplication and gastrostomy tube placement at the same time requiring 120 minutes. Feedings were started on postoperative day (POD) 1 in 10 cases and POD 2 in two cases. Hospital stay ranged from 2 to 4 days (average, 2.2) in the patients with isolated malrotation. The patient with Pierre-Robin had a prolonged hospitalization because of chronic respiratory problems not associated with surgery. There were no complications. All patients had resolution of their symptoms. CONCLUSIONS: Laparoscopic Ladd's procedure is a safe and effective technique. It can be performed in neonates in times equivalent to standard open techniques, and it appears to allow for earlier feeds and decreased hospital stays.

Congenital Abnormalities↗
PubMed1998

T-lymphocyte responses to plicatic acid-human serum albumin conjugate in occupational asthma caused by western red cedar.

BACKGROUND: T cells are known to play a major role in the pathogenesis of atopic allergic asthma, but it is less clear whether they are involved in occupational asthma caused by low molecular weight chemicals such as plicatic acid. OBJECTIVES: We sought to determine whether peripheral blood T cells from patients with western red cedar asthma (WRCA) recognize plicatic acid (PA) conjugated to human serum albumin (HSA) as judged by proliferation or cytokine production and to analyze the response to PA inhalation with flow cytometry. RESULTS: Significant proliferative responses to PA-HSA were observed in eight of 33 patients with WRCA, none of 10 exposed nonasthmatic cedar workers, and one of 18 nonasthmatic control subjects. Two of 25 patients with WRCA also showed proliferative responses to unconjugated PA. All the WRCA responders were either currently exposed to cedar or had ceased exposure within the preceding 2 years. None of the four patients receiving oral steroids responded, but inhaled steroids did not seem to influence responsiveness. No correlations were found between the maximum stimulation response and any of the current FEV1 values, the current PC20 methacholine values, or the magnitude of the late asthmatic response to PA. Peripheral blood T-cell subset proportions and their degree of activation were similar in patients with WRCA and exposed control subjects. There was no change in T-cell phenotypes or their activation markers after PA inhalation challenge. In vitro, PA-HSA stimulation did not affect subset ratios but led to release of small amounts of IL-5 and IFN-gamma, with no detectable increase in IL-4. CONCLUSIONS: PA-HSA-specific T lymphocytes seem to be present in small numbers in the peripheral blood of patients with WRCA and may respond to antigenic exposure by producing IFN-gamma and IL-5. However, the proportion of responding cells would appear to be lower than in comparable studies of atopic asthma.

Adult↗
PubMed1998

Isolation of a strain of Bacillus thuringiensis ssp. kurstaki HD-1 encoding delta-endotoxin Cry1E.

A strain of Bacillus thuringiensis, STB-1, toxic against Spodoptera exigua, was isolated. Bacillus thuringiensis STB-1 produced bipyramidal inclusions and reacted with the H antiserum of B. thuringiensis ssp. kurstaki. The plasmid and protein profiles of B. thuringiensis STB-1 were compared with those of its reference strains, ssp. kurstaki and ssp. kenyae. To verify the gene type of B. thuringiensis STB-1, PCR analysis was performed with Spodoptera-specific cry gene primers. The result showed that B. thuringiensis STB-1, unlike its reference strains, had crylAa, crylAb, crylAc and crylE, suggesting that B. thuringiensis STB-1 was a unique strain with respect to gene type. In addition, B. thuringiensis STB-1 showed a high level of toxicity against both S. exigua and Bombyx mori, whereas B. thuringiensis ssp. kurstaki HD-1 or ssp. kenyae showed a high level of toxicity against only Bombyx mori or S. exigua, respectively.

Animals↗
PubMed1998

The two-stage mutation model in retinal hemangioblastoma.

BACKGROUND: The two-stage mutation model involving successive inactivation of both alleles of a tumor suppressor gene was originally proposed by Knudson, who analyzed the age incidence curves for unilateral and bilateral retinoblastoma, and suggested that hereditary tumors arise by a single somatic event superimposed on a defective genetic background and sporadic tumors by a two-stage somatic process. In this study, the age-incidence curve of patients with retinal hemangioblastoma with and without associated von Hippel-Lindau disease were analyzed. METHODS: We reviewed the literature between 1964 and 1998 to find all reported cases of retinal hemangioblastoma and classified patients in a type A group (n = 223) when associated with von Hippel-Lindau disease and a type B group (n = 30) when not associated with von Hippel-Lindau disease. We analyzed and compared the age incidence of these two groups. RESULTS: There was a statistically significant difference between the mean age at diagnosis of retinal hemangioblastoma in the two groups, i.e., 48.4 +/- 16.6 years for type B patients and 24.9 +/- 12.0 years for type A patients (p < 0.0001). The age incidence curve for type A retinal hemangioblastoma fit a first-order equation (log S = 0.411-0.034t) with r = 0.97, indicating a single somatic mutation, whereas the age incidence curve for type B retinal hemangioblastoma fit a second-order equation (log S = 0.184-2.25 x 10(-4)t2) with r = 0.97, indicating two somatic mutations. CONCLUSIONS: Type B (sporadic) retinal hemangioblastoma may arise from two separate somatic mutations inactivating both alleles at the von Hippel-Lindau locus, whereas patients with von Hippel-Lindau disease (type A) inherit a defective allele and require only one additional somatic mutation.

Adolescent↗
PubMed1998

The small GTP-binding protein Rho potentiates AP-1 transcription in T cells.

The Rho family of small GTP-binding proteins is involved in the regulation of cytoskeletal structure, gene transcription, specific cell fate development, and transformation. We demonstrate in this report that overexpression of an activated form of Rho enhances AP-1 activity in Jurkat T cells in the presence of phorbol myristate acetate (PMA), but activated Rho (V14Rho) has little or no effect on NFAT, Oct-1, and NF-kappaB enhancer element activities under similar conditions. Overexpression of a V14Rho construct incapable of membrane localization (CAAX deleted) abolishes PMA-induced AP-1 transcriptional activation. The effect of Rho on AP-1 is independent of the mitogen-activated protein kinase pathway, as a dominant-negative MEK and a MEK inhibitor (PD98059) did not affect Rho-induced AP-1 activity. V14Rho binds strongly to protein kinase Calpha (PKCalpha) in vivo; however, deletion of the CAAX site on V14Rho severely diminished this association. Evidence for a role for PKCalpha as an effector of Rho was obtained by the observation that coexpression of the N-terminal domain of PKCalpha blocked the effects of activated Rho plus PMA on AP-1 transcriptional activity. These data suggest that Rho potentiates AP-1 transcription during T-cell activation.

Amino Acid Sequence↗
PubMed1998

Effects of retinal laser photocoagulation on photoreceptor basic fibroblast growth factor and survival.

PURPOSE: In an unpublished study, the authors found that immunoreactivity for basic fibroblast growth factor (bFGF) is increased in rod photoreceptors adjacent to long-standing laser burns in human diabetic retinas. The goal of this study was to determine whether laser photocoagulation produces a similar increase in photoreceptor bFGF and promotes survival of these cells in dystrophic rodent retinas. METHODS: Threshold (whitening) and subthreshold (nonwhitening) laser burns were made in retinas of normal and Royal College of Surgeons (RCS) rats and normal and rds mice. The retinas were processed for immunocytochemical and morphometric analyses. RESULTS: In nonlasered normal rat and mouse retinas, bFGF immunoreactivity was prominent in the nuclei of Müller cells and astrocytes. Photoreceptors were bFGF negative except for a zone of bFGF-immunoreactive rods near the ora serrata. Some photoreceptors in nonlasered retinas of RCS rats and rds mice became bFGF immunoreactive. After laser treatment, bFGF immunoreactivity was markedly increased in all photoreceptors flanking the threshold burns and within the subthreshold burns in normal and mutant rats and mice. In RCS rat retinas, photoreceptor bFGF immunoreactivity remained elevated within subthreshold burns and flanking the threshold burns, and photoreceptor survival was prolonged. In rds mouse retinas, increased bFGF immunoreactivity in photoreceptors was not sustained and their degeneration was not retarded. CONCLUSIONS: Laser treatment of RCS rat retinas produced a sustained increase in bFGF immunoreactivity in photoreceptors and prolonged their survival, but laser treatment of rds mouse retinas did not have a long-term effect on photoreceptor bFGF immunoreactivity or survival. Although species differences in laser effects on photoreceptor bFGF and survival are apparent, the finding that rods flanking laser burns in human retinas have sustained increases in bFGF immunoreactivity suggests that laser treatment may be useful for prolonging survival of mutant photoreceptors in retinas of patients with retinitis pigmentosa.

Adult↗
PubMed1998

Rhodopsin transgenic pigs as a model for human retinitis pigmentosa.

PURPOSE: To further characterize the retinas of Pro3471Leu rhodopsin transgenic pigs, a model for human retinitis pigmentosa. METHODS: Retinas from normal and transgenic pigs, newborn to 20 months old, were processed for light and electron microscopic immunocytochemical examination. RESULTS: At birth, rod numbers were normal in the transgenic retinas, but their outer segments were short and disorganized and their inner segments contained stacks of rhodopsin-positive membranes. The newborn rod synapses lacked synaptic vesicles and ribbons and had numerous rhodopsin-positive, filopodia-like processes that extended past the cone synapses into the outer plexiform layer. Rod cell death was apparent by 2 weeks and was pronounced in the mid periphery and central regions by 6 weeks. Far peripheral rods were initially better preserved, but by 9 months virtually all rods had degenerated. Cones degenerated more slowly than rods, but by 4 weeks the cone synapses were shrunken and some mid peripheral cones had lost their immunoreactivity for phosphodiesterase-gamma, arrestin, and recoverin. From 9 months to 20 months, the cone outer segments shortened progressively, and more cones lost immunoreactivity for these proteins. CONCLUSIONS: The rhodopsin transgenic pig retina shares many cytologic features with human retinas with retinitis pigmentosa and provides an opportunity to examine the earliest stages in photoreceptor degeneration, about which little is known in humans. The finding of abnormal rhodopsin localization in newborn rods is consistent with misrouting of mutant rhodopsin as an early process leading to rod cell death. Novel changes in the photoreceptor synapses may correlate with early electrophysiological abnormalities in these retinas.

Animals↗
PubMed1997

Novel fluoroquinolone antibacterial agents containing oxime-substituted (aminomethyl)pyrrolidines: synthesis and antibacterial activity of 7-(4-(aminomethyl)-3-(methoxyimino)pyrrolidin-1-yl)-1-cyclopropyl-6- fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid (LB20304).

New pyrrolidine derivatives, which bear an alkyloxime substituent in the 4-position and an aminomethyl substituent in the 3-position of the pyrrolidine ring, have been synthesized and coupled with various quinolinecarboxylic acids to produce a series of new fluoroquinolone antibacterials. These fluoroquinolones were found to possess potent antimicrobial activity against both Gram-negative and Gram-positive organisms, including methicillin resistant Staphylococcus aureus (MRSA). Variations at the C-8 position of the quinolone nucleus included fluorine, chlorine, nitrogen, methoxy, and hydrogen atom substitution. The activity imparted to the substituted quinolone nucleus by the C-8 substituent was in the order F (C5-NH2) > F (C5-H) > naphthyridine > Cl = OMe = H against Gram-positive organisms. In the case of Gram-negative strains, activity was in the order F (C5-NH2) > naphthyridine = F (C5-H) > H > Cl > OMe. The advantages provided by the newly introduced oxime group of the quinolones were clearly demonstrated by their comparison to a desoximino compound 30. In addition, the oxime moiety greatly improved the pharmacokinetic parameters of the novel quinolones. Among these compounds, compound 20 (LB20304) showed the best in vivo efficacy and pharmacokinetic profile in animals, as well as good physical properties. The MICs (microgram/mL) of LB20304, compound 30, and ciprofloxacin against several test organisms are as follows: S. aureus 6538p (0.008, 0.031, and 0.13), methicillin resistant S. aureus 241 (4, 16, and 128), Streptococcus epidermidis 887E (0.008, 0.016, and 0.13), methicillin resistant S. epidermidis 178 (4, 32, and 128), Enterococcus faecalis 29212 (0.063, 0.13, and 1), Pseudomonas aeruginosa 1912E (0.25, 0.5, and 0.13), Escherichia coli 3190Y (0.008, 0.016, and 0.008), Enterobacter cloacae P99 (0.008, 0.031, and 0.008), Actinobacter calcoaceticus 15473 (0.063, 0.13, and 0.25). On the basis of these promising results, LB20304 was selected as a candidate for further evaluation.

Animals↗
PubMed1997

Mechanism of E1A-induced transforming growth factor-beta (TGF-beta) resistance in mouse keratinocytes involves repression of TGF-beta type II receptor transcription.

Cellular transformation driven by the E1A oncogene is associated with the development of cellular resistance to the growth inhibitory effects of transforming growth factor-beta (TGF-beta). We demonstrate that development of resistance occurs simultaneously with decreased expression of TGF-beta type II receptor (TGF-beta RII) mRNA and protein. To determine whether changes in transcriptional regulation are responsible for the decreased receptor expression in E1A-transformed cells, a series of mobility shift assays was performed utilizing nuclear extracts from E1A-transformed and untransformed murine keratinocytes using radiolabeled positive regulatory elements (PRE1 and PRE2) of the TGF-beta RII promoter. The results from these assays suggest that E1A-transformed cells express markedly lower levels of nuclear proteins that bind specifically to PRE1 and PRE2. Transfection of both E1A-transformed and untransformed cell lines with a series of mutant promoter constructs confirmed that both PREs contribute significantly to basal expression of TGF-beta RII and that inactivation of either element leads to markedly reduced promoter activity. We conclude that development of TGF-beta resistance in E1A-transformed cells is achieved in part through transcriptional down-regulation of the TGF-beta RII gene and that this down-regulation is the result of decreased expression of unidentified transcription factor complexes that interact with PRE1 and PRE2.

Adenovirus E1A Proteins↗