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Biomedical subjects

J C Byrne

Publications and source records attributed to J C Byrne.

At least 19 recordsLinked to original sources
PubMed1991

The state of the p53 and retinoblastoma genes in human cervical carcinoma cell lines.

Human cervical carcinoma cell lines that were either positive or negative for human papillomavirus (HPV) DNA sequences were analyzed for evidence of mutation of the p53 and retinoblastoma genes. Each of five HPV-positive cervical cancer cell lines expressed normal pRB and low levels of wild-type p53 proteins, which are presumed to be altered in function as a consequence of association with HPV E7 and E6 oncoproteins, respectively. In contrast, mutations were identified in the p53 and RB genes expressed in the C-33A and HT-3 cervical cancer cell lines, which lack HPV DNA sequences. Mutations in the p53 genes mapped to codon 273 and codon 245 in the C33-A and HT-3 cell lines, respectively, located in the highly conserved regions of p53, where mutations appear in a variety of human cancers. Mutations in RB occurred at splice junctions, resulting in in-frame deletions, affecting exons 13 and 20 in the HT-3 and C-33A cell lines, respectively. These mutations resulted in aberrant proteins that were not phosphorylated and were unable to complex with the adenovirus E1A oncoprotein. These results support the hypothesis that the inactivation of the normal functions of the tumor-suppressor proteins pRB and p53 are important steps in human cervical carcinogenesis, either by mutation or from complex formation with the HPV E6 and E7 oncoproteins.

Base Sequence↗
PubMed1991

Echocardiographic left ventricular wall thickness: a poor predictor of the severity of aortic valve stenosis.

Echocardiographic left ventricular hypertrophy is thought to be helpful in grading the severity of aortic stenosis. This study compared M-mode echocardiographic left ventricular wall dimensions with Gorlin aortic valve area. Good quality echocardiograms were obtained in 294 patients with aortic stenosis who also underwent cardiac catheterization. Patients with grade 3 or 4 aortic regurgitation were excluded. The correlation was calculated between the aortic valve area and the left ventricular wall dimensions. Correlation coefficients were poor; r = 0.13 for the septum, r = 0.15 for the posterior wall, and r = 0.17 for the mean wall dimension. Correlation was not improved significantly if patients with poor left ventricular function or systemic hypertension were excluded. Correlation with other hemodynamic parameters was better, peak left ventricular systolic pressure having r values of 0.36 and 0.30 for posterior wall and septum. Mean and peak aortic valve gradient had r values approaching 0.30 for both dimensions. If the peak gradient was included in multivariate analysis, the wall dimensions then had no predictive power for severity of aortic stenosis. This study demonstrates that the degree of left ventricular wall hypertrophy is not related to the severity of aortic outflow obstruction and therefore cannot be used to grade the severity of aortic stenosis.

Aortic Valve↗
PubMed1991

Comparison of Southern blot hybridization and polymerase chain reaction methods for the detection of human papillomavirus DNA.

A methodologic study was performed to compare the polymerase chain reaction (PCR) and Southern blot hybridization, two commonly used testing strategies for the detection of human papillomavirus (HPV) infection. Three laboratories tested masked aliquots of exfoliated cervical cell specimens obtained from 120 women by cervicovaginal lavage. The study population included 32 women with condylomatous atypia or cervical intraepithelial neoplasia and 88 control women with no known history of cervical neoplasia. Two laboratories used PCR with different sets of consensus primers for HPV detection. The third laboratory used low-stringency Southern blot hybridization to identify all HPV types, followed by high-stringency Southern and/or dot blot hybridization to confirm specific HPV types. One of the PCR primer sets detected HPV types with a differential efficiency that was not predicted by analysis of DNA sequences or direct testing of HPV-containing plasmids. In contrast, the second PCR primer set was shown to be a much broader consensus system, detecting the same HPV types as Southern blotting, though requiring much less clinical specimen. Over 80% of women with cervical intraepithelial neoplasia or condylomatous atypia were found to be HPV infected both by Southern blotting and by the second PCR primer set. Among the control women, 11% were HPV positive by Southern blotting, while 31% were positive with the second set of primers. Most of the HPV infections found only by PCR were not due to HPV type 6, 11, 16, 18, 31, 33, or 45. These known HPV types were uncommon among normal women in the study population, even as determined by the PCR method.

Base Sequence↗
PubMed1990

The effect of acute obstruction on ureteral function.

In an effort to understand the physiologic processes which contribute to, or hinder the transport of stones through the ureter, we examined the intraluminal ureteral pressures and peristaltic activity above and below the acutely obstructed site. Because of patient differences, variability in stone size, shape and composition, an in vivo animal model was developed to study acute ureteral obstruction. Five adult mongrel dogs were anesthetized. A midline celiotomy was made and an open-ended ureteral catheter was inserted through a distal ureterotomy and advanced up the ureter. An angiographic balloon catheter was inserted through a small nephrotomy and directed down the ureter. The experiment was divided into phases: control, ureteral obstruction (balloon inflation) and release of obstruction (balloon deflation). Compared to control values, peristaltic rate above the obstruction increased significantly (p less than 0.05), as well as baseline, peak, and delta (peak minus baseline) pressures. In contrast, the peristaltic rate below the obstructed site remained approximately the same as its control, despite the significant decreases in baseline, peak, and delta (p less than 0.05) pressures. Failure of transmission of effective peristalsis across the obstructed site may hinder stone passage; however, this remains to be proven. Moreover, the failure of transmission of the increased rate of peristalsis past the balloon and persistence of peristaltic activity below the site of obstruction despite absence of urine flow suggest segmental forces influence peristaltic activity.

Acute Disease↗
PubMed1989

Relation between interatrial shunts and decompression sickness in divers.

The prevalence of right-to-left interatrial shunts was determined by contrast echocardiography in a blind comparison of 61 divers who had had decompression sickness, divided into four predetermined clinical subgroups, and a control group of 63 who had not. The prevalence of shunt was 15/63 in the controls and did not differ significantly in 24 divers with onset of neurological symptoms more than 30 minutes after surfacing (4/24) or 6 with joint pain only (1/6). In divers who had neurological symptoms within 30 minutes of surfacing the prevalence of shunt was 19/29, significantly higher. Rashes soon after surfacing were related to shunts but late rashes were not.

Decompression Sickness↗
PubMed1989

E2 polypeptides encoded by bovine papillomavirus type 1 form dimers through the common carboxyl-terminal domain: transactivation is mediated by the conserved amino-terminal domain.

The E2 open reading frame (ORF) of bovine papillomavirus type 1 (BPV-1) encodes positive- and negative-acting factors that regulate viral gene expression. The full-length ORF encodes a transactivator, and two transcriptional repressors are expressed from the 3' half of the ORF. Previous analysis has shown that a conserved C-terminal region of 101 amino acids, which is shared by E2 transactivator and repressor proteins, contains the specific DNA binding activity. Further analysis of the E2 transactivator shows that a conserved N-terminal domain of approximately 220 amino acids is crucial for the transcriptional activation function, whereas the variable internal region is not required. The E2 proteins bind to a sequence, ACCGN4CGGT, several copies of which are sufficient to constitute an E2-dependent enhancer. By using a gel retardation assay and proteins derived by in vitro transcription and translation, we were able to show that the E2 polypeptides bind as dimers to a single DNA binding site. The dimeric E2 proteins are stable in the absence of DNA and dimerization is mediated through the DNA binding domain. This may reveal an additional mechanism of repression that could potentially result from the formation of inactive heterodimers between transactivator and repressor species.

Amino Acid Sequence↗
PubMed1988

Evidence for cooperativity between E2 binding sites in E2 trans-regulation of bovine papillomavirus type 1.

The long control region of bovine papillomavirus type 1 (BPV-1) can function in an orientation- and position-independent manner as an E2-dependent enhancer. Dissection of the long control region has revealed two E2-responsive elements, E2RE1 and E2RE2, which map, respectively, between nucleotides 7611 and 7806 and between nucleotides 7200 and 7386 of the BPV-1 genome. In this study, we have carried out a detailed analysis of E2RE1, which has previously been shown to be involved in the regulation of the BPV-1 promoters P89 and P7940. One characteristic of E2RE1 is the presence of a pair of ACCN6GGT motifs (E2 binding sites) at each end of the element. To determine the contribution of these sites, as well as other sequences within E2RE1, to enhancer function, specific mutations and deletions were generated by oligonucleotide reconstruction. The functional analysis of these mutations confirmed that a pair of E2 binding sites was essential for E2-dependent enhancer activity but also indicated that cooperativity between the motifs at each end of E2RE1 creates a highly responsive element. Isolated ACCN6GGT motif pairs could also act as E2-dependent enhancers but at a significantly reduced level in comparison to the intact element. The sequences between the E2 binding sites in E2RE1 were not required for enhancer function and could actually block the enhancer activity of an isolated pair of E2 binding sites when positioned between the binding sites and the enhancer-deleted simian virus 40 early promoter.

Animals↗
PubMed1987

Human cytomegalovirus (HCMV) enhances bovine papilloma virus (BPV) transformation in vitro.

Infection of NIH 3T3 cells with a combination of HCMV and BPV resulted in more foci than infection with BPV alone. Foci were microscopically apparent at 4 days in the mixed infection and did not appear until 2 days later in the cultures infected with BPV alone. The enhancement was abolished by heat inactivation of the HCMV and also when the HCMV was replaced by a "mock inoculum." Southern blot analysis of cellular DNA from transformed cells showed a similar amount of extrachromosomal BPV DNA in cells infected by BPV alone and in cells co-infected with HCMV. No HCMV antigens could be found in these cells by immunofluorescence. The mechanisms of the enhancement are not known. Stimulation of host DNA synthesis by HCMV could possibly increase the transforming efficiency of BPV. Alternatively, the increase in BPV transforming efficiency could be due to a transient increase in BPV-1 transcription by an HCMV transcriptional transactivation factor. Since both HCMV and human papillomaviruses are commonly found in the uterine cervix, HCMV may play a role in human cervical cancer by enhancing the carcinogenic potential of human papillomavirus.

Animals↗
PubMed1985

The bovine papillomavirus distal "enhancer" is not cis essential for transformation or for plasmid maintenance.

We constructed a mutant of bovine papillomavirus type 1 (BPV-1) DNA that lacked a transcriptional enhancer located 3' to the polyadenylation site of the early viral RNAs expressed in transformed cells. This mutant DNA, when separated from the procaryotic sequences, transforms mouse cells with an efficiency comparable to that of the full BPV-1 genome, and it exists as a stable multicopy plasmid in transformed cells. The BPV-1 distal enhancer suppresses the effects of a cis-inhibitory element in pML2 sequences but is not essential for the expression of the viral genes involved in cellular transformation or plasmid maintenance.

Animals↗
PubMed1985

Enhancer-dependent expression of the rat preproinsulin gene in bovine papillomavirus type 1 vectors.

The effect of position in a bovine papillomavirus type 1 (BPV-1) vector on foreign gene expression was assessed with the rat preproinsulin (rI1) gene. The rI1 gene was inserted at each of the BPV-1/pML2d junctions in either transcriptional orientation in derivatives of the pdBPV-1(142-6) vector which consists of the BamHI linear genome of BPV-1 DNA cloned into pML2d. Transformed lines of C127 cells were established and assayed for rI1 gene expression. Cells containing the rI1 gene at the 3' end of the BPV-1 transforming region expressed rat proinsulin, whereas cells with the gene at the 5' end of the nontransforming region did not. Variability in the plasmid copy number or in the extent of DNA rearrangement could not account for this difference. We conclude that the expression of the rat preproinsulin gene (which is normally tissue specific for pancreatic islet cells) in C127 cells depends on the transcriptional activation afforded by viral enhancer sequences located at the 3' end of the transforming region. Intervening BPV-1 or pML2d sequences appear to block this enhancer-mediated gene activation. In agreement with enhancer-dependent activation, a rat preproinsulin gene located in a blocked position (i.e., not adjacent to the BPV-1 enhancer) could be activated by the insertion of a DNA fragment containing the simian virus 40, Moloney murine sarcoma virus, or BPV-1 enhancer element adjacent to the rI1 gene. Thus, a gene which is normally not expressed in a particular cell may be activated when placed adjacent to a viral enhancer in a BPV-1 vector.

Animals↗
PubMed1984

Localization and analysis of bovine papillomavirus type 1 transforming functions.

Bovine papillomavirus type 1 (BPV-1) or cloned BPV-1 DNA can transform susceptible rodent cells, and the viral DNA remains as a stable extrachromosomal plasmid in the transformed cells. The transforming region of the BPV-1 genome has previously been localized to a specific fragment comprising 69% of the genome, which also contains the elements sufficient for extrachromosomal plasmid maintenance. To define more precisely the viral DNA sequences which are involved in cellular transformation, we have tested the ability of defined deletion mutants of BPV-1 DNA to morphologically transform mouse C127 cells. Cells containing the mutated DNAs have been examined for anchorage independence and tumorigenicity in nude mice. Several distinct regions of the BPV-1 genome were found to influence expression of the viral transformation functions. A transcriptional regulatory region located in the noncoding region 5' to the early open reading frames is essential for transcriptional activity and transformation. A transcriptional enhancer element, located 3' to the polyadenylation site for the viral RNAs expressed in transformed cells, has previously been shown to be essential for transformation (Lusky et al., Mol. Cell. Biol., 3:1108-1122, 1983). Deletion mutants affecting the E2 open reading frame, particularly the NH2 half, are significantly impaired in their ability to transform, suggesting that the E2 gene product is an important transforming protein of BPV-1. Mutants lacking the E6 and E7 open reading frames are still able to induce transformation but at a lowered efficiency, and the transformants have altered characteristics. Mutations localized within the E1 open reading frame do not significantly affect the transforming functions but result in the integration of the viral genome in the transformed cells, implicating the E1 gene product in stable plasmid replication and maintenance.

Animals↗
PubMed1982

Interferon induces morphologic reversion with elimination of extrachromosomal viral genomes in bovine papillomavirus-transformed mouse cells.

The effect of mouse L-cell interferon on bovine papillomavirus type 1 (BPV-1) transformation of murine cells was examined. Mouse interferon reduced the level of BPV-1-induced transformation of mouse C127 cells by 95%. Long-term treatment of established BPV-1-transformed mouse cell clones with mouse L-cell interferon led to a decrease in the average number of the plasmid viral genomes present in these cells to 1/3 to 1/8. Although revertant lines could not be isolated from these lines in the absence of treatment with interferon, flat revertants were easily selected from two independent clonal transformed lines carried for 60 generations in the continued presence of 200 units of interferon per ml. These flat revertants had the biological characteristics of nontransformed C127 cells and could be retransformed by BPV-1. Southern blot hybridization failed to detect BPV-1 DNA in any of eight independent revertant lines examined under conditions that could detect 0.2 copies per cell. We conclude that interferon treatment has resulted in a selective reduction of the amount of extrachromosomal BPV-1 DNA in transformed cells and has cured some treated cells completely of their viral DNA.

Bovine papillomavirus 1↗
PubMed1975

Physical map of the BK virus genome.

Two new human papovavirus isolates (JMV and MMV) from the urines of patients with Wiskott-Aldrich syndrome were morphologically and serologically identical to BK virus (BKV). The genomes of these two new isolates were found to be indistinguishable from prototype BKV DNA in a variety of nucleic acid hybridization experiments. Like BKV DNA, JMV and MMV DNAs share approximately 20% of their polynucleotide sequences with simian virus 40 DNA. The genome of JMV was indistinguishable from that of BKV by restriction endonuclease analysis; MMV DNA contained three instead of four R-Hind cleavage sites and one rather than no R-HpaII cleavage sites. Physical maps of the BKV and MMV genomes were constructed using restriction endonucleases, and these maps were oriented to the map of simian virus 40 DNA.

BK Virus↗