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R D Burk

Publications and source records attributed to R D Burk.

At least 19 recordsLinked to original sources
PubMed1995

Stable inducible expression of a functional rat liver organic anion transport protein in HeLa cells.

Recently we expression cloned a rat liver organic anion transport protein in Xenopus laevis oocytes (Jacquemin, E. Hagenbuch, B, Stieger, B., Wolkoff, A.W., and Meier, P.J.,(1994) Proc. Natl. Acad. Sci. U.S.A. 91, 133-137). In the present study, we have stably transfected the cDNA encoding this protein into HeLa cells by using a vector containing a zinc-inducible promoter. The parent cells have virtually no baseline transport of [35S]sulfobromophthalein, whereas the induced transfected cells express a novel 74-kDa protein and avidly transport this ligand. Transport by these cells is saturable (Km = 3.3 microM, Vmax = 257 pmol/min/mg protein), bidirectional, and highly temperature-dependent. In the presence of albumin, uptake of [35S]sulfobromophthalein requires the presence of extracellular Cl, whereas in the absence of albumin, this C1- dependence is not seen. These studies indicate that cellular uptake of sulfobromophthalein does not result from direct interaction with the plasma membrane lipid bilayer but rather requires the presence of a specific plasma membrane transporter.

Albumins↗
PubMed1995

Persistent genital human papillomavirus infection as a risk factor for persistent cervical dysplasia.

BACKGROUND: Cervical dysplasia, also referred to as squamous intraepithelial lesion (SIL) in cytology or cervical intraepithelial neoplasia in histopathology, is thought to have the potential to advance in progressive stages to cervical cancer. However, not all cases of SIL progress, and most of the mild lesions spontaneously regress. Factors that govern regression, persistence, and progression of SIL are poorly understood. PURPOSE: Our analysis sought to identify factors that determined persistence or regression of SIL. METHODS: Seventy subjects with histopathologically confirmed cervical dysplasia were followed at 3-month intervals for 15 months. At each visit, the cervix was evaluated by Pap smear and colposcopy, and exfoliated cervicovaginal cells were analyzed for human papillomavirus (HPV) DNA. For each subject, data from every two consecutive visits were grouped as a pair. Persistent SIL was considered present if a lesion was detected at a visit (t) as well as at the next visit (t + 1) and absent if a lesion was detected at visit t but not at visit t + 1. A statistical model for time-dependent data correlated persistent SIL with various risk factors. RESULTS: Age, ethnicity, education, sexual behavior, smoking, and the use of oral contraceptives did not correlate with persistent SIL. The risk of persistent SIL was associated with continual HPV infection in visits t and t + 1 (HPV positive by Southern blot analysis: odds ratio [OR] = 3.91, and 95% confidence interval [CI] = 1.58-9.65; HPV positive by polymerase chain reaction [PCR]: OR = 2.42, and 95% CI = 1.03-5.67) and a persistent high viral load (OR = 4.07, and 95% CI = 1.35-12.30). When typed by PCR, individuals with type-specific persistent infection in visits t and t + 1, and particularly those with a continual high viral load (OR = 4.97; 95% CI = 1.45-17.02), had the highest risk for persistent SIL compared with those with a low level of type-specific persistent infection or non-type-specific persistent infection. The presence of persistent HPV infection in visits t-1 (the preceding time interval) was also predictive of persistent SIL in visits t and t + 1, although the strength of association was weaker, suggesting that persistent HPV and SIL occur synchronously. CONCLUSION: HPV infection and its associated cervical lesions tend to occur concurrently, and type-specific persistent HPV infection, particularly with a high viral load, produces chronic cervical dysplasia. IMPLICATIONS: The natural history of genital HPV infection directly influences the prognosis of cervical dysplasia as measured by persistence of the lesion. Testing for HPV infection may be valuable in the clinical management of women with cervical dysplasia.

Adult↗
PubMed1992

Loss of heterozygosity on chromosome 17p and mutant p53 in HPV-negative cervical carcinomas.

Inactivation of the protein product of the wild-type tumour suppressor gene p53 through complexing of the protein with the E6 oncoprotein of human papillomaviruses (HPV) in HPV-infected cells is thought to be important in the aetiology of cervical carcinoma. Mutations of p53 have also been reported in HPV-negative carcinomas, and we now demonstrate loss of heterozygosity (LOH) of chromosome region 17p13 (in which p53 is located) in such tumours. Immunocytochemical staining with monoclonal antimutant-p53 antibody revealed that the carcinomas with LOH on 17p and completely lacking HPV DNA sequences had mutant p53. Thus the LOH had apparently resulted in the loss of the wild-type allele. Consequently, in both HPV-positive and HPV-negative tumours there is loss of function of wild-type p53, in the former because the protein product of the p53 gene complexes with that of the viral E6 gene, in the latter because the protein is altered, presumably as a result of a direct alteration of the p53 gene but possibly because of other post-translational changes. That this mutant allele of the tumour suppressor gene may sometimes behave like an oncogene is suggested by the presence of more than the expected number of copies of the remaining chromosome 17 homologue in some carcinomas.

Chromosome Aberrations↗
PubMed1992

Human papillomavirus type 13 and pygmy chimpanzee papillomavirus type 1: comparison of the genome organizations.

Human papillomavirus type 13(HPV-13) is associated with oral focal epithelial hyperplasia (FEH) in humans. A recent epidemic of a FEH-like disease in a pygmy chimpanzee (Pan paniscus) colony allowed us to clone a novel papillomavirus genome. To assess the homology between HPV-13 and the pygmy chimpanzee papillomavirus type 1 (PCPV-1), the complete nucleotide sequences of both FEH-related viruses were determined. In both viruses, all eight major open reading frames were located on one strand and the genomic organization was similar to that of other mucosal papillomaviruses. The genomes of PCPV-1 and HPV-13 showed extensive overall sequence homology (85%). They could be classified, using phylogenetic analysis, together with HPV types 6, 11, 43, and 44 in a group associated with benign orogenital lesions. These data indicate that two phylogenetically related papillomaviruses can elicit similar pathology in different primate host species, reflecting viral genomic similarities.

Animals↗
PubMed1992

Biologic characteristics of specific human papillomavirus types predicted from morphology of cervical lesions.

Human papillomavirus (HPV) DNA was detected by Southern blot hybridization in cervicovaginal lavage samples from 199 of 329 (60.5%) women attending a municipal hospital colposcopy clinic. Human papillomavirus was identified in 195 of 264 (73.9%) patients with a squamous intraepithelial lesion or cancer on biopsy or Papanicolaou smear (Bethesda system) compared with 11 of 65 (16.9%) without squamous intraepithelial lesion (P < .0001). The most common HPV type identified was HPV 16 (20.6% of positive samples), and 36.7% of isolates contained uncharacterized HPVs. Of women with cervical intraepithelial neoplasia (CIN) grade III or cancer, 23.4% were infected with HPV 16 compared with less than 4% with any other single HPV type. Based on biopsy diagnosis in patients infected with specific HPV types, HPVs 6 and 11 had low oncogenic potential; HPVs 18, 31, 35, and 45 had intermediate oncogenic potential; and HPVs 16 and 33 had high oncogenic potential. Hyperchromatic, unusually enlarged nuclei ("meganuclei"), and/or abnormal mitoses were found significantly more often in lesions infected with HPVs 16, 33, and 35 than in those infected with HPVs 6, 11, 18, 31, and 45, even in low-grade lesions, and may represent a histologic marker for HPVs with significant oncogenic potential. Human papillomavirus capsid protein was detected significantly less often by immunocytochemical staining in CIN I and CIN II lesions infected with HPVs 16 and 33 (8.3%) than in those infected with HPVs 6, 11, 18, and 31 (60%; P = .007), suggesting early abnormalities in cellular differentiation in lesions infected with highly oncogenic HPVs.

Antigens, Viral↗
PubMed1992

Self-administered home cervicovaginal lavage: a novel tool for the clinical-epidemiologic investigation of genital human papillomavirus infections.

OBJECTIVE: Our objective was to evaluate a self-administered cervicovaginal irrigation apparatus (MY-PAP, Medtech, Bohemia, N.Y.) for the detection of cervicovaginal human papillomavirus infection. STUDY DESIGN: Twenty-five women referred to a colposcopy clinic because of a recent abnormal Papanicolaou smear were studied. Human papillomavirus infection test results detected by Southern blot hybridization and polymerase chain reaction from physician-administered and MY-PAP self-administered cervicovaginal lavage were paired for comparison. RESULTS: Seventeen (68%) patients returned home samples by mail a mean of 13 days after the clinic visit. All clinic samples and 16 of 17 (94%) home samples yielded adequate deoxyribonucleic acid for human papillomavirus infection analyses. Human papillomavirus infection was detected by polymerase chain reaction in 14 of 16 (88%) samples with complete concordance of viral detection in paired samples from the clinic and home. Southern blot detected human papillomavirus infection in 13 of 25 clinic samples (52%) and 7 of 16 home samples (44%), with concordance in 12 of 16 paired samples (75%). Specific viral type was the same in all positive paired samples (6/6). Concordance was high when the initial sample had a strong (2+ to 4+) human papillomavirus infection signal (5/6, 83%) or a negative result (5/6) or when a dysplastic (cervical intraepithelial neoplasia grade 1 to 3) lesion (9/11, 82%) was seen on cervical biopsy. CONCLUSION: Self-administered lavage represents an extremely promising technique for obtaining cervicovaginal lavage samples for human papillomavirus infection analyses.

Blotting, Southern↗
PubMed1992

Follow-up evaluation of cervicovaginal human papillomavirus infection in adolescents.

We performed a second examination for human papillomavirus (HPV) DNA on 51 sexually experienced 13- to 21-year-old (mean = 17.8 years) female patients seen at an urban teaching hospital. Cervicovaginal lavages were performed 6 to 36 months apart (median = 13.3 months) to collect cells for HPV DNA detection and typing by Southern blot hybridization. At the first and second visits, 39.2% (20/51) and 25.5% (13/51) of patients, respectively, were infected with HPV. Collectively, 56.9% (29/51) of patients had at least one positive HPV test result. Although 7.8% (4/51) were infected with HPV at both visits, only one patient had infection with the same HPV type. These findings suggest that although HPV infection is a common sexually transmitted disease, genotype-specific HPV infection detected by Southern blot at two visits was rare.

Adolescent↗
PubMed1992

Immune tolerance to a defined heterologous antigen after intrasplenic hepatocyte transplantation: implications for gene therapy.

Development of a host immune response against gene products expressed by genetically modified cells could be a serious limitation for gene therapy. During examination of whether site-specific differences in antigen presentation could regulate the host immune response, we observed an absence of antibodies against hepatitis B virus surface antigen (HBsAg) when HBsAg producing transgenic hepatocytes were transplanted into the spleen. Intrasplenic transplantation resulted in translocation of a large number of cells into the portal vascular bed and liver sinusoids. In these recipients, HBsAg secreted by the transplanted hepatocytes circulated indefinitely in the blood. In contrast, subcutaneous or intraperitoneal transplantation of the transgenic hepatocytes induced an anti-HBs response, followed by clearance of serum HBsAg. Rechallenge with HBsAg in a highly immunogenic form failed to break the tolerance in intrasplenic hepatocyte recipients even though these animals responded to another antigen (keyhole limpet hemocyanin). Immunization with HBsAg in intraperitoneal recipients of HBsAg producing hepatocytes further elevated anti-HBs titers. Our results indicate that hepatocyte transplantation into the portal vascular bed via injection into the spleen can confer immune tolerance to secreted heterologous antigens. This finding should have important implications for human gene therapy as well as for analyzing the mechanisms of immune tolerance.

Animals↗
PubMed1992

Phylogenetic classification of human papillomaviruses: correlation with clinical manifestations.

Human papillomaviruses (HPVs) are a heterogeneous group of small dsDNA viruses which cause a variety of proliferative epithelial lesions at specific anatomical sites. Although more than 65 different virus types have been cloned and characterized, no uniform classification system exists. In order to classify HPV DNA types, phylogenetic trees were constructed based on nucleotide sequence alignments using parsimony and distance matrix algorithms. The resulting phylogenetic trees provide a classification of the HPVs into specific groups encompassing the known tissue tropism and oncogenic potential of each HPV type. The implications of a phylogenetic taxonomy on the diagnostic detection of HPVs and the concept of different HPV species are discussed.

Algorithms↗
PubMed1992

Polymerase chain reaction detection of human papillomavirus: quantitation may improve clinical utility.

A case-control study compared detection by polymerase chain reaction (PCR) specific for human papillomavirus (HPV) type 16 with restriction enzyme analysis and Southern blot hybridization detection of HPV type 16. Cervicovaginal lavage samples from 64 women with histopathologic evidence of a cervical squamous intraepithelial lesion and 55 samples from cytologically healthy women were studied. Several methods of PCR product analysis, including radioactive and nonradioactive probing, were compared. The sensitivity of HPV detection by PCR when the amplified DNA fragment was visualized on a gel was equivalent to those of detection by restriction enzyme and Southern blot analyses. Hybridization of the PCR product with radioactively or nonradioactively labeled oligonucleotide probes increased the sensitivity of HPV detection by 100-fold. However, an increase in the sensitivity of the assay preferentially identified low levels of the virus in cytologically healthy women. Therefore, the value of HPV detection in identifying women with cervical neoplastic disease was greater, and the odds ratio for the presence of a cervical squamous intraepithelial lesion was higher when the less sensitive modalities were used. These results suggest that quantitation of HPV by PCR may maximize the clinical significance of a positive test result. Further studies will be needed to determine the optimal level of virus detection which has the highest positive predictive value of clinical disease.

Base Sequence↗
PubMed1991

Human papillomavirus infection and other risk factors for cervical neoplasia: a case-control study.

A case control design has been used to investigate risk factors associated with the development of cervical squamous intraepithelial lesions (SIL) in a population of urban women in which non-affluent minority groups were heavily represented. Eighty-five women with histologically confirmed SIL were compared to a control group of 70 cytologically normal women. HPV infection was determined using both Southern blot hybridization and polymerase chain reaction (PCR) amplification specific for HPV types 16, 18, and 33. When Southern blot was used to detect HPV, logistic regression analysis identified HPV infection (odds ratio (OR) = 17.9, 95% confidence interval (CI) = 6.2-51.6) and low educational achievement (OR = 3.4, 95% CI = 1.2-10.1) as major independent risk factors. When PCR was employed to detect HPV, the logistic regression model suggested that HPV infection (OR = 10.4, 95% CI = 3.6-30.4) and Hispanic ethnicity (OR = 5.0, 95% CI = 1.2-20.5) represented independent risk factors; low educational achievement and Black ethnicity were risk factors of borderline significance. PCR detection of simultaneous co-infection with more than one HPV type was associated with a very high risk of SIL (OR for one type = 7.2, 95% CI = 2.4-21.9; OR for greater than I type = 43.0, 95% CI = 6.9-266.6). Furthermore, increased viral load determined by either method carried an increased risk of disease. HPV infection with viral types previously reported to be related to neoplastic or dysplastic lesions carried the highest risk of SIL. The association of HPV detected by Southern blot and SIL in women less than 35 years old had an OR of 10.1, whereas in women greater than or equal to 35 the OR was 74.5 (p = 0.09 for homogeneity of ORs). We conclude that infection with HPV is the major risk factor for cervical SIL and suggest that targeted HPV screening of women over age 35 may represent an innovative strategy to detect women at high risk of cervical neoplasia.

Age Factors↗
PubMed1991

Permanent engraftment and function of hepatocytes delivered to the liver: implications for gene therapy and liver repopulation.

To examine the distribution of intrasplenically transplanted hepatocytes, we used HBsAg-producing G7 HBV transgenic hepatocytes or cells labeled with 111In. Most hepatocytes translocated to the liver (55% +/- 7%; mean +/- S.D.); the spleen retained a smaller fraction (15% +/- 3%); and some transplanted cells localized in lungs (3%) or pancreas (1%). Transplanted hepatocytes were rapidly assimilated into the liver lobule. Morphometrical quantitation indicated that the numbers of transplanted hepatocytes in the liver at 48 hr and at 9 mo after transplantation were similar. Serum HBsAg was detected in recipients of the G7 HBV hepatocytes during the 1-yr experiment. These results indicate that a large number of hepatocytes can be reproducibly delivered to the liver by transplantation into the spleen. Transplanted hepatocytes engraft rapidly, assimilate into host liver, maintain normal function and survive permanently. Systems for safe delivery and localization of hepatocytes in the liver represent a critical step toward successfully accomplishing hepatocyte-directed gene therapy and repopulation of the acutely devastated liver.

Animals↗
PubMed1991

High risk of human papillomavirus infection and cervical squamous intraepithelial lesions among women with symptomatic human immunodeficiency virus infection.

We investigated the relationship of human papillomavirus (by cervicovaginal lavage and Southern blot), human immunodeficiency virus, and squamous intraepithelial lesions in 96 high-risk women in the Bronx, New York. Antibodies for human immunodeficiency virus were detected in 51 (53%) women. Of the 33 women with symptomatic human immunodeficiency virus infection, 23 (70%) had human papillomavirus infection compared with 4 of 18 (22%) asymptomatic women who were human immunodeficiency virus seropositive and 10 of 45 (22%) uninfected women (p less than 0.0001). The rate of squamous intraepithelial lesions was 52% (14 of 27) for women with both viruses detected, 18% (6 of 34) for women with either virus detected, and 9% (3 of 35) for uninfected women. Among symptomatic human immunodeficiency virus-infected women, a strong association between human papillomavirus infection and squamous intraepithelial lesions was demonstrated (odds ratio, 12; 95% confidence interval, 1.3 to 108). Risk was highest for younger women from ethnic or racial minority groups. Advanced human immunodeficiency virus-related disease, with its associated immunosuppression, seems to exacerbate human papillomavirus-mediated cervical cytologic abnormalities. Public health measures are needed to provide Papanicolaou smear screening and appropriate clinical follow-up and treatment for women at high risk for human immunodeficiency virus infection.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Type-specific and cross-reactive epitopes in human papillomavirus type 16 capsid proteins.

Genital human papillomavirus (HPV) 16 infection is frequently associated with cancer of the uterine cervix, as well as with precancerous lesions. In order to generate serologic reagents which might be useful in the diagnosis of HPV 16 infection, rabbit polyclonal and mouse monoclonal antisera were raised to carboxy terminal peptides from the HPV 16 L1 and L2 open reading frames (ORFs). Anti-L1 and -L2 peptide sera recognized HPV 16 L1 and L2 fusion proteins in Western blots and by immunoprecipitation. In Western blot analysis of L1 proteins from different HPV types, antisera to the L1 peptide reacted only with HPV 16, thus identifying an HPV 16 type-specific linear epitope. Anti-L2 peptide sera reacted with L2 fusion proteins from HPVs 6 and 16, but not from BPV, thus identifying a partially cross-reactive epitope in the HPV 16 L2. Computer analysis of carboxy terminal amino acid sequences of the L1 and L2 ORFs of multiple HPV types supported the Western blot findings. Despite the HPV 16 type specificity found in Western blots, anti-L1 peptide sera identified nuclear antigen by immunocytochemistry in cervical biopsies infected with HPV 16, as well as other genital HPV types. Anti-L2 peptide sera failed to recognize antigen in infected tissue.

Amino Acid Sequence↗
PubMed1991

Cervicovaginal human papillomavirus infection in suburban adolescents and young adults.

To investigate the prevalence rates of and risk factors for genital human papillomavirus (HPV) infection in white, middle-class adolescents, we obtained specimens for HPV from 107 patients undergoing pelvic examination at a suburban adolescent health service. Specimens were obtained by means of cervicovaginal lavage and were analyzed for HPV DNA by Southern blot analysis. The subjects' mean age was 18.5 (+/- 2.0 SD) years; 47% of the subjects were seen for contraception, 36% for possible pregnancy, 12% for a gynecologic complaint, and 5% for a general examination. We detected HPV in 32% of patients; HPV types included 6/11 (6%), 16 (3%), 18 (15%), 31 (3%), 42 (6%), 45 (18%), and 56 (6%). The DNA type was classified as uncharacterized in 47%, and 3% had more than one type. Univariate analysis revealed that patients found to have HPV were more likely to have more than two sexual partners, to have been sexually active for more than 2 years, to have had menarche before 12 years of age, and to have a history of sexually transmitted disease; logistic regression multivariate analysis demonstrated that number of partners and age at menarche were independent risk factors for HPV. These data indicate that HPV is common among sexually active teenagers regardless of ethnicity or socioeconomic status. The association of cervicovaginal HPV infection with sexual activity further supports the notion of the sexual transmission of this agent.

Adolescent↗
PubMed1991

Human papillomavirus, gonorrhea, syphilis, and cervical dysplasia in jailed women.

We assessed the prevalence of human papillomavirus (HPV) by cervicovaginal lavage and Southern blot and inquired about behavioral risk factors for cervical disease and sexually transmitted diseases by interview in 114 female detainees at a large New York City jail. Of the women screened, 8% had abnormal Pap smears, 35% had HPV, 7% had gonorrhea, and 22% had serologic syphilis. Given the high rates of HPV infection and cervical cytology, Pap smears should be a routine intake procedure for incarcerated women.

Adult↗