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Biomedical subjects

M L Freeman

Publications and source records attributed to M L Freeman.

At least 19 recordsLinked to original sources
PubMed2001

Dilation of high-grade pancreatic and biliary ductal strictures with small-caliber angioplasty balloons.

BACKGROUND: Pancreatic and bile duct strictures may be too stenotic to allow passage of conventional endoscopic dilators. METHODS: Four patients with strictures (3 pancreatic, 1 biliary) that could not be traversed with conventional endoscopic dilating devices, or in 1 case by a Soehendra stent extractor, underwent stricture dilation with a 3.3F peripheral angioplasty balloon to a maximum diameter of 6 mm. OBSERVATIONS: All strictures in the 4 patients were successfully traversed and dilated and stents were placed with resolution of the presenting clinical problem. CONCLUSIONS: Small-caliber angioplasty balloons are useful for dilation with subsequent stent placement of pancreatic and biliary strictures that are refractory to standard endoscopic approaches.

Adult↗
PubMed2001

Risk factors for post-ERCP pancreatitis: a prospective, multicenter study.

BACKGROUND: Post-ERCP pancreatitis is poorly understood. The goal of this study was to comprehensively evaluate potential procedure- and patient-related risk factors for post-ERCP pancreatitis over a wide spectrum of centers. METHODS: Consecutive ERCP procedures were prospectively studied at 11 centers (6 private, 5 university). Complications were assessed at 30 days by using established consensus criteria. RESULTS: Pancreatitis occurred after 131 (6.7%) of 1963 consecutive ERCP procedures (mild 70, moderate 55, severe 6). By univariate analysis, 23 of 32 investigated variables were significant. Multivariate risk factors with adjusted odds ratios (OR) were prior ERCP-induced pancreatitis (OR 5.4), suspected sphincter of Oddi dysfunction (OR 2.6), female gender (OR 2.5), normal serum bilirubin (OR 1.9), absence of chronic pancreatitis (OR 1.9), biliary sphincter balloon dilation (OR 4.5), difficult cannulation (OR 3.4), pancreatic sphincterotomy (OR 3.1), and 1 or more injections of contrast into the pancreatic duct (OR 2.7). Small bile duct diameter, sphincter of Oddi manometry, biliary sphincterotomy, and lower ERCP case volume were not multivariate risk factors for pancreatitis, although endoscopists performing on average more than 2 ERCPs per week had significantly greater success at bile duct cannulation (96.5% versus 91.5%, p = 0.0001). Combinations of patient characteristics including female gender, normal serum bilirubin, recurrent abdominal pain, and previous post-ERCP pancreatitis placed patients at increasingly higher risk of pancreatitis, regardless of whether ERCP was diagnostic, manometric, or therapeutic. CONCLUSIONS: Patient-related factors are as important as procedure-related factors in determining risk for post-ERCP pancreatitis. These data emphasize the importance of careful patient selection as well as choice of technique in the avoidance of post-ERCP pancreatitis.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed2001

Training and competence in gastrointestinal endoscopy.

Patients, physicians, and health care providers want assurances that individuals performing gastrointestinal endoscopic procedures are competent and adequately credentialed. Definition of competence, however, has been an elusive goal. Most organizations, including professional societies and hospital privileging committees, have relied on estimated numbers of procedures performed or subjective assessment by a proctor as a surrogate marker of competence. Increasingly, objective assessment of performance is recognized as important in determining competence. Recent data have shown that learning curves for trainees are substantially more gradual than generally thought, and that the number of procedures required to achieve basic technical proficiency is much higher. Emerging data demonstrate that there is substantial variation in outcomes of endoscopy in clinical practice, related in part to the prior training, subspecialty background, ongoing case volume, and the individual endoscopist. Outcome variations correlate with both technical success and complications. Strategies for assessing competence in trainees and those in practice include numbers of procedures performed, subjective or objective assessment by a proctor, and self-assessment by the trainee. In the future, it is hoped that computers will be increasingly used to document outcomes of endoscopy in training and clinical practice as a part of routine report generation.

Clinical Competence↗
PubMed2000

Inhibition of the 26S proteasome induces expression of GLCLC, the catalytic subunit for gamma-glutamylcysteine synthetase.

The majority of short- and long-lived cellular proteins are degraded by the activities of the 26S proteasome, a large multi-catalytic protease. Its unique function places it as a central regulatory activity for many important physiological processes. Lactacystin is a very specific 26S proteasome inhibitor and represents an excellent tool for demonstrating that a pathway exhibits proteasome-dependent biochemical regulation. Exposure of HepG2 cells to lactacystin resulted in robust elevation of GLCLC mRNA levels, followed by an increase in GSH concentrations. GLCLC is the gene that encodes the catalytic subunit for gamma-glutamylcysteine synthetase, the rate-limiting enzyme for the synthesis of glutathione (GSH). Inhibition of non-proteasome, protease activities did not induce GLCLC. Gel mobility shift assays and expression of CAT activity from heterologous reporter vectors identified Nrf2 mediation of the GLCLC antioxidant response element, ARE4, as the mechanism by which lactacystin induced GLCLC. These studies have identified 26S proteasome activity as a central regulatory pathway for glutathione synthesis.

Acetylcysteine↗
PubMed2000

Multi-faceted regulation of gamma-glutamylcysteine synthetase.

Glutathione is an important antioxidant that is involved in numerous cellular activities. gamma-Glutamylcysteine synthetase (gammaGCS) is a key regulatory enzyme in the synthesis of glutathione. It is a heterodimeric zinc metalloprotein that belongs to a unique class of proteins that gain activity due to formation of a reversible disulfide bond. The two subunits of gammaGCS exhibit differential and coordinate transcription regulation. In addition, the subunits are regulated at the posttranscriptional and posttranslational levels. These various levels of regulation allow numerous stimuli to induce or inhibit activity.

Amino Acid Sequence↗
PubMed2000

A randomized, controlled trial of transcutaneous carbon dioxide monitoring during ERCP.

BACKGROUND: Pulse oximetry, used to monitor oxygen saturation during endoscopy, does not directly measure hypoventilation. Study goals were to determine whether transcutaneous carbon dioxide (PtcCO(2)) monitoring during endoscopic retrograde cholangiopancreatography (ERCP) prevents severe hypoventilation and to assess the accuracy of clinical observation and pulse oximetry in detecting hypoventilation. METHODS: All patients received intensive clinical and electronic monitoring including pulse oximetry. Supplemental oxygen was administered for pulse oximetry < 90%. Patients were randomized to a treatment arm (group 1) where PtcCO(2) monitoring guided sedation or a control arm (group 2) where PtcCO(2) was recorded but unavailable for guiding sedation. RESULTS: Group 1 had significantly fewer episodes of severe carbon dioxide retention (rise in PtcCO(2) >/=40 mm Hg above baseline) than group 2 (0 of 199 versus 5 of 196, respectively, p = 0.03), as well a shorter mean duration of procedure discomfort (8.3% of procedure duration rated as "uncomfortable" versus 11.5%, p = 0.04). Correlations between clinical observation and objective measures of ventilation were poor: level of sedation versus PtcCO(2) (R = 0.3) or pulse oximetry (R = 0.06); slowest respiratory rate versus PtcCO(2) (R = 0.4) or pulse oximetry (R = -0.4). PtcCO(2) rises of greater than 20 mm Hg occurred without oxygen desaturation in 10.7% of patients receiving supplemental oxygen. CONCLUSIONS: Carbon dioxide retention during ERCP is not reliably detected by clinical observation or by pulse oximetry in patients receiving supplemental oxygen. The addition of PtcCO(2) monitoring prevents severe carbon dioxide retention more effectively than intensive clinical monitoring and pulse oximetry alone. The clinical relevancy of this observation needs to be determined in an appropriately designed outcome study.

Blood Gas Monitoring, Transcutaneous↗
PubMed2000

Value of stigmata in decision-making in gastrointestinal haemorrhage.

The stigmata of recent haemorrhage are endoscopically identified features that have a predictive value for the risk of further bleeding and thus help to determine which patients should receive endoscopic therapy. In conjunction with endoscopic features, clinical features related to the magnitude of bleeding and to patient co-morbidity have important independent effects on the risk of further haemorrhage. Stigmata have been best studied in the context of bleeding ulcers, the most common cause of upper gastrointestinal bleeding. Stigmata in ulcers are usually classified as active bleeding (spurting or oozing), a non-bleeding visible vessel, an adherent clot, a flat pigmented spot, or a clean base, in order of decreasing risk of further haemorrhage. Ulcer size and location may also affect the re-bleeding potential. Recent data suggest that both non-pigmented visible vessels and adherent clots have a higher risk of re-bleeding than was previously thought. The wide variation in prevalence and re-bleeding rates reported for various stigmata in the literature probably reflects variations in the definitions of stigmata and of re-bleeding, the vigour with which the ulcer bases are washed, the co-morbidity and ages of the patients, and the severity of bleeding encountered. Inter-observer agreement in the classification of stigmata is relatively poor and limits the utility of endoscopic features alone in making decisions regarding the management of patients with bleeding peptic ulcers. Imaging devices such as Doppler probes are being evaluated to refine the identification of underlying vessels and their re-bleeding potential, but the utility of these is currently uncertain. The findings of low-risk endoscopic stigmata in a haemodynamically and otherwise stable patient can in many cases allow out-patient management.

Decision Making↗
PubMed2000

Enhancement of radiation effects in vitro by the estrogen metabolite 2-methoxyestradiol.

2-Methoxyestradiol. 2-Methoxyestradiol (2-ME) is an endogenous estradiol metabolite that disrupts microtubule function, suppresses murine tumors, and inhibits angiogenesis. Since some microtubule inhibitors have been shown to alter radiosensitivity, we have evaluated 2-ME as a radiation enhancer in vitro. H460 human lung cancer cells were plated, treated with 2-ME for 24 h, and irradiated; then colony-forming ability was assessed. The radiation dose enhancement ratios (DERs) using this protocol were 1.3, 1.8 and 2.1 for 1, 1.5 and 2 microM 2-ME, respectively. Using a single-cell plating protocol, the respective DERs were 1.2, 1.5 and 1.8. The parent compound of 2-ME, beta-estradiol, did not enhance radiation effects at equally cytotoxic doses. Isobologram analysis showed that 1 microM 2-ME was additive with radiation, but that 1.5 and 2 microM were synergistic. Cell cycle analysis showed a dose-dependent increase in the percentage of cells in the radiosensitive G(2)/M phase after a 24-h treatment with 2-ME; a threefold increase in the percentage of cells in G(2)/M phase was observed using 2 microM 2-ME. Treatment with 2 microM 2-ME almost completely inhibited repair of sublethal damage (SLD) as shown using split-dose recovery. Radiosensitive, repair-deficient murine SCID (severe combined immunodeficient) cells did not show enhancement of radiation effects with 2 microM 2-ME, but enhancement was observed in the wild-type parental cells (CB-17). SCID cells complemented with human DNA-dependent protein kinase restored radioenhancement by 2-ME. In addition, MCF-7 breast cancer cells were also radiosensitized by 2 microM 2-ME (DER = 2.1). These data suggest that 2-ME is a potential radiation sensitizer, in addition to its previously reported antitumor and antiangiogenic properties. We have verified the antiangiogenic activity of 2-ME in vitro using human endothelial cells. Based on these results, we hypothesize that the mechanism of radiation enhancement may involve redistribution of cells into G(2)/M phase by 2-ME, and that the resulting population of cells is repair-deficient and thus radiosensitive.

2-Methoxyestradiol↗
PubMed1999

Radiopotentiation by the oral platinum agent, JM216: role of repair inhibition.

PURPOSE: To test for in vitro radiopotentiation by the orally-administered platinum (IV) complex, JM216; to compare these results to cisplatin and carboplatin; and to investigate whether the mechanism of radiopotentiation involves repair inhibition of radiation-induced DNA damage. METHODS AND MATERIALS: H460 human lung carcinoma cells were incubated with the drugs for 1 h at 37 degrees C, irradiated at room temperature, and returned to 37 degrees C for 20 min. Cells were then rinsed and colony forming ability was assessed. Wild-type V79 Chinese hamster cells and radiosensitive, DNA repair-deficient mutant cells (XR-V15B) were also studied along with H460 cells. Ku86 cDNA, which encodes part of a protein involved in DNA repair, was transfected into XR-V15B cells as previously described. The effect of JM216 on sublethal damage repair (SLDR) was also assessed using split-dose recovery. RESULTS: Using equally cytotoxic doses of JM216, cisplatin, and carboplatin, the radiation dose enhancement ratios (DER) were 1.39, 1.31, and 1.20, respectively; the DER with 20 microM JM216 was 1.57. JM216 (20 microM) did not significantly change the final slope of radiation survival curves, but greatly reduced the survival curve shoulder. V79 cells also showed radioenhancement using 20 microM JM216, but no enhancement occurred using XR-V15B cells. Transfection of Ku86 cDNA into XR-V15B cells restored radiopotentiation by JM216 to wild-type V79 levels. In addition, 20 microM JM216 completely inhibited sublethal damage repair in H460 cells. CONCLUSION: Our results show that JM216 can potentiate the effects of radiation in human lung cancer cells, and that the mechanism of this effect is probably inhibition of DNA repair by JM216.

Administration, Oral↗
PubMed1999

Same-day discharge after endoscopic biliary sphincterotomy: observations from a prospective multicenter complication study. The Multicenter Endoscopic Sphincterotomy (MESH) Study Group.

BACKGROUND: Same-day discharge after endoscopic biliary sphincterotomy (ES) is a common clinical practice, but there have been few data to guide appropriate selection of patients. Using a prospective, multicenter database of complications, we examined outcomes after same-day discharge as it was practiced by a variety of endoscopists and evaluated the ability of a multivariate risk factor analysis to predict which patients would require readmission for complications. METHODS: A 150-variable database was prospectively collected at time of ES, before discharge and again at 30 days in consecutive patients undergoing ES at 17 centers. Complications were defined by consensus criteria and included all specific adverse events directly or indirectly related to ES requiring more than 1 night of hospitalization. RESULTS: Six hundred fourteen (26%) of 2347 patients undergoing ES were discharged on the same day as the procedure, ranging from none at 6 centers to about 50% at 2 centers. After initial observation and release, readmission to the hospital for complications occurred in 35 (5.7%) of 614 same-day discharge patients (20 pancreatitis and 15 other complications, 3 severe). Of the same-day discharge patients, readmission was required for 14 (12.2%) of 115 who had at least one independently significant multivariate risk factor for overall complications (suspected sphincter of Oddi dysfunction, cirrhosis, difficult bile duct cannulation, precut sphincterotomy, or combined percutaneous-endoscopic procedure) versus 21 (4.2%) of 499 without a risk factor (odds ratio 3.1: 95% confidence interval [1.6, 6.3], p < 0.001). Of complications presenting within 24 hours after ES, only 44% presented within the first 2 hours, but 79% presented within 6 hours. CONCLUSIONS: Same-day discharge is widely utilized and relatively safe but results in a significant number of readmissions for complications. For patients at higher risk of complications, as indicated by the presence of at least one of five independent predictors, observation for 6 hours or overnight may reduce the need for readmission.

Adult↗
PubMed1999

On the path to the heat shock response: destabilization and formation of partially folded protein intermediates, a consequence of protein thiol modification.

This review discusses the initial events that occur during oxidative stress that induce the synthesis of heat shock proteins. The focus is on non-native oxidation or modification of protein thiols and the destablization that can result. Proteins that contain non-native modified thiols can become destablized such that they unfold into molten globule-like intermediates at or below 37 degrees C, relieving Hsf-1 negative regulation, and inducing Hsp transcription.

Animals↗
PubMed1999

Procedure-specific outcomes assessment for endoscopic retrograde cholangiopancreatography.

The outcome of therapeutic ERCP, or any other medical intervention, is a balance between technical success, avoidance of complications, and efficacy of the procedure in achieving its intended therapeutic goal. There is an increasing need for objective assessment of such outcomes to help physicians improve their quality of care, to enable patients to better select health care providers, and increasingly, because health care providers are demanding some kind of objective assessment. In this article, the author reviews methods for quantification of the three principal components of ERCP outcomes, and provides suggestions for data collection to facilitate quality assessment in clinical practice.

Biliary Tract Diseases↗
PubMed1999

Common human needs in the context of diversity: integrating schools of thought.

In this article we argue that effective social work practice which honors cultural diversity is best informed through an integration of the strengths associated with modern and postmodern schools of thought. This integration provides a lens for simultaneously seeing common human needs and individual differences, a vision that neither school of thought alone can provide. Aspects of Virginia Satir's growth model are presented as an example of a practice approach that incorporates this simultaneous attention to similarities and differences.

Cultural Diversity↗
PubMed1998

Expression of Bcl-2 increases intracellular glutathione by inhibiting methionine-dependent GSH efflux.

Overexpression of Bcl-2 and related anti-apoptotic gene products has been shown to increase the intracellular concentration of the antioxidant tripeptide glutathione in neuronal and hematopoietic cells. A similar examination of HeLa cells that stably overexpress Bcl-2 (Bcl-2/HeLa) demonstrated that the reduced form of glutathione (GSH) was increased by 60% compared to control cells (80 nmol GSH/mg protein compared to 50 nmol GSH/mg). Expression of gamma-glutamylcysteine synthetase, the rate limiting enzyme for glutathione synthesis was found to be independent of Bcl-2 overexpression, as determined by Northern blot analysis and immunoprecipitation of [35-S]-labeled enzyme. Bcl-2 overexpression did not alter the rate of GSH biosynthesis, measured under steady state conditions. Thus, the increase in GSH concentration was not the result of increased synthesis. Two activities have been described which govern efflux of reduced glutathione (GSH), RsGshT known as the sinusoidal transporter and RcGshT, known as the canalicular transporter. Both are low affinity, bidirectional, ATP and Na-independent. Consistent with expression of sinusoidal activity, DTT was found to stimulate GSH efflux while the amino acid methionine inhibited efflux in both HeLa and Bcl-2/HeLa cells. However, methionine-dependent inhibition of efflux was found to be significantly increased by expression of Bcl-2. To test the prediction that the increase in GSH observed in Bcl-2/HeLa cells was mediated by methionine; Bcl-2/HeLa cells were cultured for 24 hrs in methionine-free growth medium. Under these conditions, the GSH concentration of the Bcl-2/HeLa cells dropped to the level observed in HeLa cells (50 nmol GSH/mg protein). These studies suggest that overexpression of Bcl-2 increases GSH levels by altering methionine-dependent GSH efflux, an activity associated in HeLa cells with expression of the RsGshT transporter.

Culture Media↗
PubMed1998

Double-strand break repair deficiency and radiation sensitivity in BRCA2 mutant cancer cells.

BACKGROUND: The protein product of the BRCA2 gene mediates repair of double-strand breaks in DNA. Because a number of cancer therapies exert cytotoxic effects via the initiation of double-strand breaks, cancers comprised of cells carrying BRCA2 gene mutations may be more amenable to treatment with agents that cause such breaks. METHODS: We identified a human pancreatic adenocarcinoma cell line lacking one copy of the BRCA2 gene and containing a mutation (6174delT) in the remaining copy. In vitro and in vivo experiments were conducted with this cell line and with other carcinoma cell lines matched for similar genetic mutations, similar differentiation status, and/or similar carcinoma type to examine double-strand break repair, sensitivity to drugs that induce double-strand breaks, and radiation sensitivity. RESULTS: BRCA2-defective cells were unable to repair the double-strand DNA breaks induced by ionizing radiation. These cells were also markedly sensitive to mitoxantrone, amsacrine, and etoposide (drugs that induce double-strand breaks) (two-sided P = .002) and to ionizing radiation (two-sided P = .001). Introduction of antisense BRCA2 deoxyribonucleotides into cells possessing normal BRCA2 function led to increased sensitivity to mitoxantrone (two-sided P = .008). Tumors formed by injection of BRCA2-defective cells into nude mice were highly sensitive (>90% tumor size reduction, two-sided P = .002) to both ionizing radiation and mitoxantrone when compared with tumors exhibiting normal BRCA2 function. Histologic analysis of irradiated BRCA2-defective tumors showed a large degree of necrosis compared with that observed for control tumors possessing normal BRCA2 function. CONCLUSION: BRCA2-defective cancer cells are highly sensitive to agents that cause double-strand breaks in DNA.

Adenocarcinoma↗
PubMed1998

Enhanced gamma-glutamyl transpeptidase expression and selective loss of CuZn superoxide dismutase in hepatic iron overload.

Liver injury caused by iron overload is presumed to involve lipid peroxidation and the formation of products such as 4-hydroxynonenal (4HNE), which has been implicated in hepatic fibrogenesis. Cellular antioxidants that modulate the formation and detoxification of compounds such as 4HNE may represent important protective mechanisms involved in the response to iron overload. This study examines the relationship between 4HNE, collagen content, and antioxidant defenses in the livers of rats fed carbonyl iron for 10 weeks. Iron-loading resulted in significant increases in iron (8.8-fold), 4HNE (1.7-fold), and hydroxyproline (1.5-fold). Total glutathione content was unchanged by iron, but gamma-glutamyl transpeptidase activity (GGT) increased sixfold and CuZn superoxide dismutase (CuZnSOD) activity decreased >9%. GGT colocalized with iron deposition and was associated with increased GGT mRNA. Decreased CuZnSOD activity was paralleled by a reduction in CuZnSOD protein on Western blot and immunohistochemistry, but no decrease in CuZnSOD mRNA. Glutathione S-transferase (GST) and Mn superoxide dismutase (MnSOD) activities were also significantly increased by iron loading. These results demonstrate that iron overload significantly alters the expression of antioxidant enzymes associated with glutathione (GGT and GST) and superoxide metabolism (CuZnSOD and MnSOD). Furthermore, the localized induction of GGT may enhance detoxification of lipid peroxidation-derived aldehydes via glutathione-dependent pathways in iron-loaded hepatocytes. These alterations in antioxidant defenses may represent an adaptive response, limiting accumulation 4HNE, and thus, stimulation of collagen synthesis, accounting for the mild fibrogenic response seen in this model of iron overload.

Aldehydes↗