Search PubMed⌕ Search

Biomedical subjects

J Sylvester

Publications and source records attributed to J Sylvester.

At least 19 recordsLinked to original sources
PubMed2006

Inhibition of interleukin 1-induced matrix metalloproteinase 13 expression in human chondrocytes by interferon gamma.

BACKGROUND: Despite well-documented immunomodulation by interferon gamma (IFNgamma), its role and mechanism of regulation of matrix metalloproteinase 13 (MMP13) gene expression in human chondrocytes is unknown. OBJECTIVE: To investigate the ability and mechanism of IFNgamma to suppress interleukin 1 (IL1)-induced MMP13 expression in articular chondrocytes. METHODS: Human chondrocytes were treated with IFNgamma or IL1beta alone or in combination. MMP13 mRNA was analysed by semiquantitative reverse transcriptase-PCR. MMP13 protein, phospho-signal transducer and activator of transcription 1 (STAT1) and p44/42 mitogen-activated protein kinase levels were measured by western blotting. MMP13 promoter luciferase, cytomegalovirus cyclic AMP response element-binding protein (CBP)/p300 plasmids and STAT1 small interfering RNA (siRNA) were transfected by the calcium phosphate method. IFNgamma receptor was also neutralised. Activator protein (AP) 1 activity was monitored by the TransAM transcription factor kit. STAT1-CBP/p300 interaction was studied by immunoprecipitation. RESULTS: IFNgamma potently suppressed IL1-induced expression of MMP13 and promoter activity. Blockade with neutralising IFNgamma R1 antibody revealed that MMP13 inhibition by IFNgamma is mediated by the IFN receptor. IFNgamma-stimulated activation of STAT1 was directly correlated with MMP13 suppression. Knockdown of the STAT1 gene by specific siRNA or its inhibition with fludarabine partially restored the IL1beta induction of MMP13 expression and promoter activity. IFNgamma did not alter AP1 binding ability but promoted physical interaction of STAT1 and CBP/p300 coactivator. p300 overexpression reversed IFNgamma inhibition of endogenous MMP13 mRNA expression and exogenous MMP13 promoter activity. CONCLUSION: IFNgamma, through its receptor, activates STAT1, which binds with CBP/p300 coactivator, sequesters it from the cell system, and thus inhibits transcriptional induction of the MMP13 gene in chondrocytes. IFNgamma and its signalling pathways could be targeted therapeutically for diminishing IL1-induced cartilage degradation by MMP13 in patients with arthritis.

Blotting, Western↗
PubMed2003

Molecular mechanisms of N-acetylcysteine actions.

Oxidative stress generated by an imbalance between reactive oxygen species (ROS) and antioxidants contributes to the pathogenesis of arthritis, cancer, cardiovascular, liver and respiratory diseases. Proinflammatory cytokines and growth factors stimulate ROS production as signaling mediators. Antioxidants such as N-acetylcysteine (NAC) have been used as tools for investigating the role of ROS in numerous biological and pathological processes. NAC inhibits activation of c-Jun N-terminal kinase, p38 MAP kinase and redox-sensitive activating protein-1 and nuclear factor kappa B transcription factor activities regulating expression of numerous genes. NAC can also prevent apoptosis and promote cell survival by activating extracellular signal-regulated kinase pathway, a concept useful for treating certain degenerative diseases. NAC directly modifies the activity of several proteins by its reducing activity. Despite its nonspecificity, ability to modify DNA and multiple molecular modes of action, NAC has therapeutic value for reducing endothelial dysfunction, inflammation, fibrosis, invasion, cartilage erosion, acetaminophen detoxification and transplant prolongation.

Acetylcysteine↗
PubMed2001

Factors predicting the use of breast-conserving therapy in stage I and II breast carcinoma.

PURPOSE: To define patterns of care for the local therapy of stage I and II breast cancer and to identify factors used to select patients for breast-conserving therapy (BCT). PATIENTS AND METHODS: A convenience sample of 16,643 patients with stage I and II breast cancer treated in 1994 was obtained from hospital-based tumor registries. Histologic variables were determined from original pathology reports. RESULTS: BCT was performed in 42.6% of patients. Multivariate analysis demonstrated that living in the Northeast United States (odds ratio [OR], 2.48; 95% confidence interval [CI], 2.16 to 2.84), having a clinical T1 tumor (OR, 2.51; 95% CI, 2.27 to 2.78), and having a tumor without an extensive intraductal component (OR, 2.07; 95% CI, 1.81 to 2.37) were the strongest predictors of breast-conserving surgery. Radiation therapy was given to 86% of patients who had breast-conserving surgery. Age less than 70 years was the most significant predictor of receiving radiation (OR, 2.11; 95% CI, 1.77 to 2.25). Tumor variables did not correlate with the use of radiation, but favorable tumor characteristics were associated with the use of breast-conserving surgery. CONCLUSION: Despite strong evidence supporting the use of BCT, the majority of women continue to be treated with mastectomy. Predictors of the use of BCT do not correspond to those suggested in guidelines.

Adult↗
PubMed2001

The role of androgen ablation in patients with biochemical or local failure after definitive radiation therapy: a survey of practice patterns of urologists and radiation oncologists in the United States.

To identify therapeutic patterns for putative prostate cancer treatment failures and the role played by androgen ablation therapy in these patients, a questionnaire study was undertaken with urologists and radiation oncologists who had attended a brachytherapy forum at the Seattle Prostate Institute (SPI). Hypothetical questions were asked about recommendations the physicians would give to a patient demonstrating biochemical or local failure after external-beam radiation therapy. Most of the physicians queried were in private practice; 53% were radiation oncologists and 47% were urologists. The respondents' recommendations for a hypothetical patient, who was 45 to 65 years of age, with a biopsy-proven local recurrence was treatment with androgen ablation (35% of respondents), radical prostatectomy (25%), interstitial brachytherapy (20%), and observation (19%). In the 65- to 75-year-old patient with a local recurrence, the respondents recommended observation (43%), androgen ablation (35%), interstitial brachytherapy (17%), and radical prostatectomy (4%). In patients receiving androgen ablation for a biochemical failure alone, there was no consensus on whether to use luteinizing hormone-releasing hormone agonist alone, total androgen ablation, orchiectomy, or intermittent androgen ablation. Criteria that prompted physicians to initiate androgen ablation were based on the rate of prostate-specific antigen (PSA) increase (67%), an absolute PSA number (24%), or clinical failure (9%). In the younger patient with a local recurrence, local intervention with radical prostatectomy or interstitial brachytherapy was recommended most often, followed by androgen ablation, then by observation. In the older patient, observation was recommended most often, followed closely by androgen ablation. Overall, there was a lack of consensus on how to deliver androgen ablation. However, there was remarkable agreement between urologists and radiation oncologists on virtually all issues queried.

Age Factors↗
PubMed2001

Tripterygium wilfordii Hook F extract suppresses proinflammatory cytokine-induced expression of matrix metalloproteinase genes in articular chondrocytes by inhibiting activating protein-1 and nuclear factor-kappaB activities.

The major pathologic manifestations of rheumatoid arthritis (RA) and osteoarthritis (OA) are joint inflammation and articular cartilage resorption by proinflammatory cytokine-stimulated matrix metalloproteinases (MMPs) and aggrecanases. The Chinese herbal remedy Tripterygium wilfordii Hook F (TWHF) is effective for treatment of various types of arthritis. However, mechanisms and targets of its actions are poorly understood. Anti-inflammatory activities of the extracts of this plant were previously attributed to inhibition of cyclooxygenase-2 mRNA and prostaglandin E(2) synthesis. Here, we show that in primary human femoral head osteoarthritic and normal bovine chondrocytes, TWHF partially or completely inhibited mRNA and protein expression of tumor necrosis factor-alpha, interleukin (IL)-1, and IL-17-inducible MMP-3 and MMP-13. This agent also inhibited cytokine-stimulated MMP-3 protein expression in human synovial fibroblasts. A dose range of 2.5 to 10 ng/ml of TWHF was effectively inhibitory for IL-1. Pretreatment for 30 min or 1 h (but not 2-10 h) after IL-1 treatment with TWHF inhibited MMP-3 RNA induction. The inhibitory doses had no adverse effect on the viability of chondrocytes. Mechanistic studies revealed no impact on the activation of extracellular signal-regulated kinase, p38, and c-Jun N-terminal kinase mitogen-activated protein kinases. Instead, TWHF partially inhibited DNA binding capacity of cytokine-stimulated activating protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) transcription factors. Therefore, besides its anti-inflammatory activity, this agent may also be effective in blocking cartilage matrix resorption by MMPs by impairing AP-1 and NF-kappaB binding activities. Thus, TWHF extract contains novel inhibitors of MMP expression that may be of therapeutic potential in arthritis and other conditions associated with increased MMPs.

Animals↗
PubMed2000

Hippocampal sulcal cavities on MRI: relationship to age and apolipoprotein E genotype.

Hippocampal sulcal cavities are usually considered incidental findings on brain MRI. In a group of 92 elderly volunteers, the authors graded the number and size of hippocampal sulcal cavities with brain MRI to obtain a cavity score. Cavity scores increased with age, and were higher in subjects carrying the APOE epsilon4 or epsilon2 alleles than in subjects with the epsilon3/3 genotype. Age-related morphologic changes in the hippocampus may be mediated by the APOE genotype.

Age Factors↗
PubMed2000

Short-course androgen ablation combined with external-beam radiation therapy and low-dose-rate permanent brachytherapy in early-stage prostate cancer: a matched subset analysis.

BACKGROUND AND PURPOSE: In order to evaluate the effect of short-term androgen blockade on biochemical control rates for high-risk patients receiving a combination regimen of external-beam radiation therapy and low-dose-rate permanent seed implant brachytherapy, a retrospective matched subset analysis was performed. PATIENTS AND METHODS: Inclusion in the high-risk cohort required at least two of the following poor prognostic factors: serum prostate specific antigen (PSA) concentration > or = 10.0 ng/mL, Gleason score > or = 7, or clinical stage T(2c) or T(3a) disease. Twenty-one patients who underwent androgen ablation between June 1991 and December 1995 in addition to combined-modality radiation therapy qualified as high risk, as did 77 patients who underwent combined-radiation therapy only. There was no statistically significant difference between the two groups in terms of follow-up (mean 44.6 v 47.8 months, respectively), pretreatment PSA, clinical stage, biopsy Gleason score, or the presence of all three poor prognostic factors. RESULTS: The overall rates of freedom from biochemical failure at 5 years were 77% in the hormonally treated group and 58% in the nonhormonally treated group. The difference was not statistically significant by log rank test (P = 0.08). CONCLUSION: Longer follow-up with larger patient numbers is needed to define the role of adjuvant androgen ablation combined with radiation therapy.

Androgen Antagonists↗
PubMed1999

Neoadjuvant Androgen Ablation Combined with External-Beam Radiation Therapy and Permanent Interstitial Brachytherapy Boost in Localized Prostate Cancer.

Androgen ablation therapy has been combined with permanent interstitial brachytherapy in order to downsize the gland prior to seed implantation. It also has been employed in an attempt to improve the effectiveness of therapy in patients with a poor prognosis. We report on 50 patients consecutively treated and prospectively followed. All received neoadjuvant hormonal therapy (NHT) and 45 Gy of external-beam therapy to a limited pelvic field, followed by permanent implantation of (125)I or (103)Pd seeds. The median follow-up is 42.1 months (range 9.0-90.8 months). The prostate specific antigen (PSA) progression-free survival rate (<1.0 ng/mL) was 76% at 5 years (Kaplan-Meier method). Local control was achieved in 100% of the patients and distant disease-free survival in 85%. High-risk patients treated contemporaneously with these patients, who received external-beam radiation and a seed boost without NHT, had a 62% rate of 5-year PSA progression-free survival. Although the modest improvement in PSA progression-free survival is not statistically significant at 5 years (P = 0.5), the patients treated with NHT in addition to combined radiotherapy presented with significantly higher serum PSA concentrations (mean 21.0 ng/mL; median 17.0 ng/mL) than those treated with combination radiotherapy alone (mean 15.6 ng/mL; median 10.6 ng/mL) and thus had a worse prognosis.

Journal Article↗
PubMed1998

Reduction of radioactive seed embolization to the lung following prostate brachytherapy.

PURPOSE: Ultrasound-guided interstitial implantation of radioactive seeds is a common treatment for early stage prostate cancer. One of the risks associated with this therapy is seed embolization to the lung. This paper reports on the incidence and possible adverse effects of seed migration. METHODS AND MATERIALS: Two hundred ninety consecutive patients were treated with permanent radioactive seed brachytherapy for prostate cancer between January 1 and December 31, 1995. One hundred fifty-four patients were treated with iodine-125 (I-125), and 136 patients were treated with palladium-103 (Pd-103). All but one patient had a routine post implant chest radiograph (CXR), leaving 289 evaluable patients. RESULTS: Twenty radioactive seed pulmonary emboli were identified in 17 patients; 3 patients had two emboli each. The radioactive seed pulmonary embolism rate for the entire group of patients was 5.9%. Acute pulmonary symptoms were not reported by any patient in this series. One hundred forty-six study patients were implanted with free seeds alone (136 Pd-103 and 11 I-125), and 143 were implanted with linked seed embedded in a vicryl suture for the peripheral portions of their implants. The radioactive seed embolization rate by patient was 11% (16/146) versus 0.7% (1/143) for free seed implants and implants utilizing linked seeds, respectively. The difference was statistically significant, p = 0.0002. No patient had detectable morbidity as a consequence of seed emboli. CONCLUSION: The use of linked seeds embedded in vicryl sutures for the peripheral portion of permanent radioactive seed prostate implants significantly reduced the incidence of pulmonary seed embolization in patients treated with the Seattle technique.

Brachytherapy↗
PubMed1997

Results of hospital cancer registry surveys by the American College of Surgeons: outcomes of prostate cancer treatment by radical prostatectomy.

BACKGROUND: The number of prostate cancer patients treated by radical prostatectomy has increased. Different data sources have yielded various estimates of the outcomes of this treatment and the need for additional therapy. To provide additional perspective on these issues, the American College of Surgeons conducted surveys of cancer registries and reviewed related data. METHODS: In 1993, in the first phase of the study, hospital cancer registries and programs were sent survey forms and instructions requesting data on up to 5 patients treated by radical prostatectomy at their institutions in 1990. In 1996, in the second phase of the study, additional data were requested on treatment administered to the 1990 patients up to 5 years after surgery, and hospitals were also invited to submit new data on patients diagnosed in 1993. Responses were received from 482 hospitals concerning 2122 patients for 1990, and 265 hospitals provided data on 1304 patients diagnosed in 1993. Follow-up data on 1076 of the 1990 patients were provided by 258 hospitals. Kaplan-Meier survival curves were calculated to determine the probability of additional treatment after radical prostatectomy. RESULTS: Similar surgical pathology outcomes were reported for the 1990 and 1993 patients. For 1990 and 1993, respectively, it was reported that 27.5% and 29.7% of patients maintained erectile function adequate for intercourse after surgery. For 1990 and 1993, respectively, complete control or only occasional urinary incontinence requiring no pads was reported for 81.3% and 79.8% of patients. The surgical mortality rates were less than 1% for both the 1990 and the 1993 patients. The 5-year cumulative probability of any additional treatment after radical prostatectomy was 10.5%. Seminal vesicle involvement, positive surgical margins, lymph node involvement, capsular penetration, high Gleason score, and high prostate specific antigen were significantly associated with greater probability of additional treatment. CONCLUSIONS: Hospital cancer registries are valuable sources of data on patterns of care and outcome for prostate cancer patients. Continuing evaluation of the outcomes of prostate cancer treatments is needed to reconcile the differences in outcomes reported from different data sources.

Erectile Dysfunction↗
PubMed1997

Interstitial implantation techniques in prostate cancer.

Brachytherapy is a radiotherapeutic technique that allows the physician to implant radioactive isotopes into a body cavity or directly into tissue. Different radioisotopes have unique characteristics that the brachytherapist may utilize for a particular situation. The use of brachytherapy is part of standard radiation oncology practice in gynecological and head and neck cancer management. The prostate is approachable for interstitial implantation due to its close proximity to the perineum. Over 20 years ago, primitive methods of brachytherapy were utilized in the treatment of prostate cancer. However, poor results due to inconsistency in achieving adequate coverage of the entire prostate and poor patient selection caused this treatment modality to fall out of favor. Technological advances over the last decade have restored attention to brachytherapy for prostate cancer. Particularly important has been the development of transrectal ultrasound, new radioisotopes such as palladium-103, computer tomography, computerized dosimetry systems, and earlier diagnosis. Modern interstitial implantation utilizing transperineal template and transrectal ultrasound guidance has resulted in improved consistency in radiation dose delivery to the entire prostate. Early results are encouraging in terms of the relatively low morbidity of the procedure, improved local control rates, and biochemical progression free survival. This has resulted in an outpatient treatment that has high patient acceptance.

Aged↗
PubMed1996

Does brachytherapy have a role in the treatment of prostate cancer?

The goal of radiation therapy is to deliver a high dose to the tumor while preserving normal surrounding tissue. For early-stage prostate cancer, the ultimate conformal irradiation is to place radioactive sources directly into the gland either as permanent or temporary seeds. Permanent seed implantation is capable of delivering two times the radiobiologically equivalent dose of external beam irradiation to the prostate and tumor. In the past, the results of prostate brachytherapy were likely poor owing to the technical difficulty in accurately placing the radioactive seeds uniformly throughout the prostate. The use of low-dose-rate I-125 to treat high-grade cancers probably also contributed to the poorer results as compared with external beam irradiation. Over the last 10 years, however, technologic advances in transrectal ultrasonography, computer dosimetry, and template-based transperineal techniques have dramatically improved the accuracy and consistency of the brachytherapist to place radioactive sources directly into the prostate gland. Transperineal ultrasound or CT directed seed implantation has replaced the older retropubic method. Brachytherapists are now able to accurately map out the gland prior to the implant and carefully evaluate preoperatively seed placement. The availability of such radioactive sources as iodine-125, palladium-103, and iridium-192 has also given the brachytherapist isotopes that can be more carefully matched to the biology and stage of the tumor. More sensitive definitions of failure have prompted radiation oncologists and urologists to carefully evaluate the efficacy of external beam irradiation and surgery. Accurate comparison of the efficacy of brachytherapy to surgery and to external beam radiation requires a randomized study. Comparisons of retrospective studies are fraught with the problems of the heterogeneous nature of early-stage prostate cancer. Imbalances in stage, grade, initial PSA extraprostatic disease, and nodal status of patient groups make comparisons difficult. Most of the long-term data for permanent seed implantation are the result of work at a single institution. These results will need to be repeated at other institutions treating patients in a similar manner. Because techniques vary from institution to institution, permanent implant results will need to be carefully evaluated for technique as well as stratified for pretreatment variables. Pretreatment PSA and grade appear to be more sensitive variables than stage in predicting failure after radiation. As more patients are diagnosed with very early and nonpalpable disease, future studies will need to stratify patients based on these pretreatment factors. Patients with early-stage disease but identified as high risk for extraprostatic disease will require more intensive regimens. The treatment outcomes based on biopsy results are inconclusive. A lack of consensus on the definition of a truly positive biopsy remains forthcoming. The value of a positive prostate biopsy as an outcome predictor for clinical failure is still unclear. The use of prostate nuclear cell antigen staining may help clarify the issue. Comparison of treatment outcome based on absolute PSA is also difficult. The Seattle series suggest that brachytherapy by permanent seed implantation is as efficacious as external beam irradiation for early-stage disease in patients with a low PSA (< 10 ng/mL). As the PSA value rises above 10 ng/mL, the probability of failure after external beam rises substantially. Results from the Seattle series suggest an advantage to seed implant alone or the judicious application of seed implant boost to external beam radiation for these patients with more advanced cancer. The most sensitive measurement of therapeutic outcome is progression-free survival. Few studies to date have evaluated progression-free survival.

Biopsy↗
PubMed1996

Spatial distribution of sex chromosomes and ribosomal genes: a study on human lymphocytes and testicular cells.

The location of the sex chromosomes in relation to the rRNA genes in the nuclei of human lymphocytes and testicular cells was examined. Sex chromosomes were found to be located closer to ribosomal genes than would be expected assuming a random arrangement of these chromosomes with respect to rRNA genes. This proximity could be observed irrespective of the transcriptional activity of ribosomal genes indicating that the chromosomal material and not transcriptional activity is responsible for the intranuclear order of these chromosomes.

Adult↗
PubMed1995

In vivo 31P-NMR studies of age and energy metabolism in an animal flap model.

Changes in phosphate energy metabolism with time in a rat flap model were followed noninvasively with in vivo 31P-NMR. The influence of age on high-energy phosphate metabolites in perfused and ischemic ends of 3 x 10 cm dorsal flaps was noted from 30 minutes to 7 days after closure in 6-, 12-, and 24-month-old (n = 4, 7, and 8, respectively) male Fischer 344 rats. Phosphocreatine to inorganic phosphate ratios showed younger animals exhibiting significant returns to preinjury energy status in 2- and 3-mm ischemic layers. This behavior, 24 to 72 hours after closure, coincides with neovascularization of the flap tissue. By contrast, 12- and 24-month-old animals experienced statistically significantly lesser high-energy rebound, developing greater necrosis in the ischemic regions. Early intracellular pH lowering, indicative of lactate production, was somewhat greater in the flaps of younger animals. The in vivo 31P-NMR methods thus provide metabolic insights into flap behavior correlating with physiologic influences of aging.

Aging↗
PubMed1993

Staging procedures, clinical management, and survival outcome for ovarian carcinoma.

OBJECTIVE: To evaluate the relationship between survival and patterns of clinical management for ovarian carcinoma. DESIGN: Retrospective analysis of cancer registry data including follow-up, operative reports, and pathology reports. SETTING: Seventy-seven Illinois hospitals with active cancer registries. PATIENTS: A total of 2669 women with newly diagnosed ovarian carcinoma from 1983 through 1988. MAIN OUTCOME MEASURES: Frequency of use of specific staging procedures and treatment options. Survival was estimated using the Kaplan-Meier product-limit method. RESULTS: Thirty percent of 632 stage I patients, 31% of 233 stage II patients, and 45% of 516 stage III patients underwent hysterectomy, bilateral salpingo-oophorectomy, omentectomy, sampled peritoneal washings, and node biopsy. Five-year survival for those receiving this extensive surgery (who were therefore pathologically staged) was as follows: stage I, 80%; stage II, 63%; and stage III, 28%. For those not receiving this extensive surgery (who were therefore clinically staged), the 5-year survival at these stages was 76%, 62%, and 21%, respectively. The overall survival curves were not significantly different between those who were pathologically staged and those who were clinically staged for stage I patients (P = .27) or stage II patients (P = .47), but were for stage III patients (P = .01). Platinum-based combination chemotherapy was given to 76% of 221 patients with pathological stage III disease. Their 5-year survival--50% for the group with no residual disease and 20% for the group with residual disease--was better than for those receiving regimens without platinum--37% and 5%, respectively, for the two groups--and the overall survival curves were significantly better for those receiving platinum (P < .0005 for both groups). The groups receiving platinum had younger patients. CONCLUSIONS: Extensive surgery for pathological staging was not usually done for management of ovarian cancer, while platinum-based chemotherapy was commonly used. Failure to undergo extensive surgery had little impact on survival for stage I and II patients. However, use of extensive surgery and platinum-based chemotherapy improved survival for stage III patients. The improved survival for this group receiving platinum-based chemotherapy may be explained in part by selection of younger patients for this treatment.

Female↗
PubMed1993

In vitro replication of plasmids containing human ribosomal gene sequences: origin localization and dependence on an aprotinin-binding cytosolic protein.

We previously investigated the role of an aprotinin-binding protein (ADR) in the initiation of DNA replication in isolated quiescent nuclei. In the present study, we have used a cell-free DNA replication system to test the ability of plasmid vectors which contain sequences from the human ribosomal RNA gene to serve as replicative templates in vitro when exposed to ADR-containing preparations. Significant dTTP incorporation was seen using DNA from either a 7-kb sequence in the 5' spacer region (CHE) or a 7-kb sequence which begins near the end of the 28S coding region and extends into the 3' spacer region (ADBB), while sequences from other regions of the rRNA gene mediated little or no dTTP incorporation. The characteristics of plasmid-directed dTTP incorporation indicate that most incorporation is due to DNA replication and not repair or damage-initiated processes. To conclusively demonstrate origin-dependent replication in the plasmid system and to further map replication origins, an approach was developed using ddGTP to restrict the length of daughter strands followed by hybridization of these replication products to restriction fragments spanning the putative origin region. This approach allowed us to identify replication origin activity apart from parent strand repair or synthesis initiated at random damaged sites. One of the origins was localized to a 1375-bp fragment within the 5' spacer region, and this fragment contains sequences homologous to those found in other replication origins.

Aprotinin↗
PubMed1993

A study on nucleolar DNA: isolation of DNA from fibrillar components and ultrastructural localization of different DNA probes.

The nature and localization of DNA contained in the fibrillar centres and the dense fibrillar component (the fibrillar complex) in the nucleoli, was studied in human LEP cells, Sertoli cells, spermatogonia A and in mitotic chromosomes of stimulated lymphocytes. A novel procedure for isolating the intact fibrillar complex from LEP cells was used; the complex contains DNA that hybridizes to secondary constrictions of mitotic chromosomes and to 28 S rDNA sequences, on Southern blots. Electron microscopic DNA-DNA in situ hybridization was performed, with (a) a probe prepared from DNA extracted from the fibrillar complex of LEP cells, (b) a probe for human total genomic DNA, and (c) a probe for the transcribed part of human rDNA. On the basis of the results obtained we conclude that the ribosomal RNA genes in human Sertoli cells and spermatogonia A are predominantly associated with the dense fibrillar component, including the border region between fibrillar centres and the dense fibrillar component. The ribosomal RNA genes are the main, if not exclusive, DNA type present in the fibrillar complex in the studied cell types.

Adult↗