Resistively loaded coplanar waveguide for microwave measurements of induced carriers

We describe the use of a coplanar waveguide (CPW) whose slots are filled with a resistive film, a resistively loaded CPW (RLCPW), to measure two-dimensional electron systems (2DESs). The RLCPW applied to the sample hosting the 2DES provides a uniform metallic surface serving as a gate to control the areal charge density of the 2DES. As a demonstration of this technique, we present measurements on a Si metal-oxide-semiconductor field-effect transistor and a model that successfully converts microwave transmission coefficients into conductivity of a nearby 2DES capacitively coupled to the RLCPW. We also describe the process of fabricating the highly resistive metal film required for fabrication of the RLCPW.

Proposed thresholds for pancreatic tissue volume for safe intraportal islet autotransplantation after total pancreatectomy

The simple question of how much tissue volume (TV) is really safe to infuse in total pancreatectomy-islet autotransplantation (TP-IAT) for chronic pancreatitis (CP) precipitated this analysis. We examined a large cohort of CP patients (n = 233) to determine major risk factors for elevated portal pressure (PP) during islet infusion, using bivariate and multivariate regression modeling. Rates of bleeding requiring operative intervention and portal venous thrombosis (PVT) were evaluated. The total TV per kilogram body weight infused intraportally was the best independent predictor of change in PP (ΔPP) (p < 0.0001; R(2) = 0.566). Rates of bleeding and PVT were 7.73% and 3.43%, respectively. Both TV/kg and ΔPP are associated with increased complication rates, although ΔPP appears to be more directly relevant. Receiver operating characteristic analysis identified an increased risk of PVT above a suggested cut-point of 26 cmH2O (area under the curve = 0.759), which was also dependent on age. This ΔPP threshold was more likely to be exceeded in cases where the total TV was >0.25 cm(3)/kg. Based on this analysis, we have recommended targeting a TV of <0.25 cm(3)/kg during islet manufacturing and to halt intraportal infusion, at least temporarily, if the ΔPP exceeds 25 cmH2O. These models can be used to guide islet manufacturing and clinical decision making to minimize risks in TP-IAT recipients.

Endoscopic ultrasound rendezvous for bile duct access using a transduodenal approach: cumulative experience at a single center. A case series

Endoscopic ultrasound (EUS)-assisted biliary access is utilized when conventional endoscopic retrograde cholangiopancreatography (ERCP) fails. We report a 10-year experience utilizing a transduodenal EUS rendezvous via a transpapillary route without dilation of the transduodenal tract, followed by immediate ERCP access. Patients included all EUS-guided rendezvous procedures for biliary access that were performed following ERCP failure. EUS-assisted bile duct puncture was performed via a transduodenal approach and a guide wire was advanced through the papilla without any dilation or bougienage of the tract; ERCP was performed immediately afterwards. EUS-assisted biliary rendezvous was attempted in 15 patients (mean age 66 +/- 18.2 years; malignant = 10, benign = 5). Mean diameter of measured bile ducts was 14.3 +/- 5.17 mm (range 4-23 mm). The reasons for initial ERCP failure were tumor infiltration or edema (n = 9), intradiverticular papilla (n = 2), pre-existing duodenal stent (n = 1), and anatomic anomalies (n = 3). Successful EUS-guided bile duct puncture and wire passage were achieved in all 15 patients (100 %), with drainage being successful in 12 / 15 (80 %). Failures occurred in three patients due to inability to traverse the biliary stricture (n = 2) or dissection of a choledochocele with the guide wire (n = 1); all were subsequently drained via percutaneous methods. Stents placed were metallic in eight patients and plastic in four. Complications consisted of moderate pancreatitis after a difficult ERCP attempt in one patient, and bacteremia after percutaneous biliary drainage in another. There were no instances of perforation, extraluminal air or fluid collections. EUS-assisted biliary drainage utilizing a transduodenal rendezvous approach demonstated a high success rate without any complications directly attributable to the EUS access. Advantages over percutaneous biliary and other methods of EUS biliary access include performance under the same anesthesia, and a very small-caliber needle puncture similar to EUS/fine-needle aspiration.

Endoscopic ultrasound rendezvous for bile duct access using a transduodenal approach: cumulative experience at a single center. A case series

Endoscopic ultrasound (EUS)-assisted biliary access is utilized when conventional endoscopic retrograde cholangiopancreatography (ERCP) fails. We report a 10-year experience utilizing a transduodenal EUS rendezvous via a transpapillary route without dilation of the transduodenal tract, followed by immediate ERCP access. Patients included all EUS-guided rendezvous procedures for biliary access that were performed following ERCP failure. EUS-assisted bile duct puncture was performed via a transduodenal approach and a guide wire was advanced through the papilla without any dilation or bougienage of the tract; ERCP was performed immediately afterwards. EUS-assisted biliary rendezvous was attempted in 15 patients (mean age 66 +/- 18.2 years; malignant = 10, benign = 5). Mean diameter of measured bile ducts was 14.3 +/- 5.17 mm (range 4-23 mm). The reasons for initial ERCP failure were tumor infiltration or edema (n = 9), intradiverticular papilla (n = 2), pre-existing duodenal stent (n = 1), and anatomic anomalies (n = 3). Successful EUS-guided bile duct puncture and wire passage were achieved in all 15 patients (100 %), with drainage being successful in 12 / 15 (80 %). Failures occurred in three patients due to inability to traverse the biliary stricture (n = 2) or dissection of a choledochocele with the guide wire (n = 1); all were subsequently drained via percutaneous methods. Stents placed were metallic in eight patients and plastic in four. Complications consisted of moderate pancreatitis after a difficult ERCP attempt in one patient, and bacteremia after percutaneous biliary drainage in another. There were no instances of perforation, extraluminal air or fluid collections. EUS-assisted biliary drainage utilizing a transduodenal rendezvous approach demonstated a high success rate without any complications directly attributable to the EUS access. Advantages over percutaneous biliary and other methods of EUS biliary access include performance under the same anesthesia, and a very small-caliber needle puncture similar to EUS/fine-needle aspiration.

Endoscopic ultrasound rendezvous for bile duct access using a transduodenal approach: cumulative experience at a single center. A case series

Endoscopic ultrasound (EUS)-assisted biliary access is utilized when conventional endoscopic retrograde cholangiopancreatography (ERCP) fails. We report a 10-year experience utilizing a transduodenal EUS rendezvous via a transpapillary route without dilation of the transduodenal tract, followed by immediate ERCP access. Patients included all EUS-guided rendezvous procedures for biliary access that were performed following ERCP failure. EUS-assisted bile duct puncture was performed via a transduodenal approach and a guide wire was advanced through the papilla without any dilation or bougienage of the tract; ERCP was performed immediately afterwards. EUS-assisted biliary rendezvous was attempted in 15 patients (mean age 66 +/- 18.2 years; malignant = 10, benign = 5). Mean diameter of measured bile ducts was 14.3 +/- 5.17 mm (range 4-23 mm). The reasons for initial ERCP failure were tumor infiltration or edema (n = 9), intradiverticular papilla (n = 2), pre-existing duodenal stent (n = 1), and anatomic anomalies (n = 3). Successful EUS-guided bile duct puncture and wire passage were achieved in all 15 patients (100 %), with drainage being successful in 12 / 15 (80 %). Failures occurred in three patients due to inability to traverse the biliary stricture (n = 2) or dissection of a choledochocele with the guide wire (n = 1); all were subsequently drained via percutaneous methods. Stents placed were metallic in eight patients and plastic in four. Complications consisted of moderate pancreatitis after a difficult ERCP attempt in one patient, and bacteremia after percutaneous biliary drainage in another. There were no instances of perforation, extraluminal air or fluid collections. EUS-assisted biliary drainage utilizing a transduodenal rendezvous approach demonstated a high success rate without any complications directly attributable to the EUS access. Advantages over percutaneous biliary and other methods of EUS biliary access include performance under the same anesthesia, and a very small-caliber needle puncture similar to EUS/fine-needle aspiration.

Significant clinical implications of prophylactic pancreatic stent placement in previously normal pancreatic ducts

Pancreatic duct stent placement is increasingly performed for the prevention of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP); however stents can result in injury especially in normal ducts. The clinical significance and outcomes of subsequent endoscopic therapy are unknown. This study was a retrospective review of the management of symptomatic stent-induced pancreatic duct injury following stent placement for prevention of post-ERCP pancreatitis in eight patients with previously normal pancreatic ducts. Subsequent treatment included pancreatic sphincterotomy, balloon dilation of stricture, and placement of multiple 3 - 5-Fr soft polymer pancreatic stents. All patients showed improvement or resolution of pancreatic strictures. Five patients had resolution or substantial improvement of pain, one patient showed a fair response with repeated ERCPs, and two patients failed to respond and underwent total pancreatectomy with islet autotransplantation. Pancreatic duct stent-induced ductal injury with significant clinical consequences can occur with conventional polyethylene stents. Endoscopic therapy is moderately effective but some patients develop irreversible damage. Caution should be used when placing standard polyethylene stents in normal ducts. Further research is required to identify safer materials and configurations of pancreatic stents.

Biliary cannulation during endoscopic retrograde cholangiopancreatography: core technique and recent innovations

Despite advances in imaging and device technology over the past decade, endoscopic retrograde cholangiopancreatography (ERCP) continues to be one of the most technically challenging interventions in endoscopy. The procedure remains compounded by two persistent problems: failure of successful biliary cannulation and post-ERCP pancreatitis (PEP). When performed outside expert high-volume centers, failed biliary cannulation may occur in up to 20 % of cases; repeated and prolonged attempts at cannulation increase the risk of pancreatitis, delay definitive therapy, and necessitate alternative therapeutic techniques with inferior safety profiles . Cannulation technique is believed to be a pivotal factor in the genesis of PEP and is obviously important for successful cannulation. This review will discuss some recent innovations in cannulation technique.

Recent advances and novel methods in pancreatic imaging

Traditional imaging studies for evaluating pancreatic disease including abdominal ultrasound (US) and computerized tomography (CT) are widely utilized due to their availability, non-invasiveness, and familiarity to practitioners. The addition of endoscopic ultrasound (EUS) and magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) has contributed significantly to the clinician's the ability to safely sample tissue, stage malignancy, evaluate the pancreatic ductal anatomy, and look for subtle parenchymal changes in the setting of chronic pancreatitis. The role of endoscopic retrograde cholangiopancreatography (ERCP) has diminished with the use of these less invasive modalities. Limitations in these conventional techniques include a lack of sensitivity and specificity in diagnosing early chronic pancreatitis, difficulties in differentiating malignancy from chronic or focal pancreatitis, and accuracy of staging pancreatic malignancy, particularly with regard to vascular involvement. Several recent advances in traditional imaging techniques have been described, which may improve our ability to accurately diagnose and stage pancreatic disease. Advances have been made in the standard modalities for imaging the pancreas such as multidetector CT, micro-bubble contrast enhanced ultrasound, and secretin stimulated MRCP. Other novel methods of pancreatic imaging have recently been described including EUS elastography, optical coherence tomography, diffusion weighted MRI, and MR spectroscopy. This article will review the recent advances in both traditional pancreatic imaging modalities as well as some of the emerging technologies for imaging evaluating diseases of the pancreas. As experience and clinical evidence accumulate, the role of these imaging techniques will continue to evolve.

The role of endoscopic retrograde cholangiopancreatography and endoscopic ultrasound in diagnosis and treatment of acute pancreatitis

Endoscopic retrograde cholangiopancreatography (ERCP) is an important tool for diagnosis and therapy in acute and recurrent pancreatitis. While treatment of biliary disorders leading to pancreatitis is common practice, over the past several years many specialized centers have been directing traditional biliary techniques such as sphincterotomy and stenting towards the pancreas. A justifiable fear of pancreatitis and other complications has caused many endoscopists to shy away from pancreatic endotherapy, but refinements in technique, extensive experience, and most notably the routine use of pancreatic stenting to prevent post-ERCP pancreatitis has opened up the field and allowed for endoscopists in specialized centers around the world to perform diagnostic and therapeutic ERCP of the pancreas safely and effectively. In acute gallstone pancreatitis, the benefit of therapeutic ERCP including biliary sphincterotomy has been proven in randomized controlled trials. There are also data to support the role of ERCP directed at the pancreatic sphincters and ducts in treatment of acute relapsing pancreatitis due to pancreas divisum, sphincter of Oddi dysfunction, smoldering pancreatitis, pancreatic ductal disruptions, and perhaps even in evolving pancreatic necrosis. Many causes of apparently idiopathic pancreatitis can be discovered after an extensive evaluation with endoscopic ultrasound (EUS), magnetic resonance cholangiopancreatography (MRCP) and ERCP with sphincter of Oddi manometry. ERCP often allows treatment of the underlying cause. Because of the inherent risks associated with ERCP, particularly when directed toward the pancreas, the role of ERCP in acute and especially recurrent pancreatitis should be primarily therapeutic with attempts to establish diagnosis whenever possible by less risky techniques including EUS and MRCP. With the added techniques, devices, skill-sets, and experience required, pancreatic endotherapy should preferably be performed in high volume tertiary referral settings. ERCP for diagnosis and treatment of severe or acute relapsing pancreatitis is also best performed using a multidisciplinary approach involving endoscopy, hepatobiliary-pancreatic surgery, and interventional radiology.

Endoscopic ultrasound-guided bile duct access for rendezvous ERCP drainage in the setting of intradiverticular papilla

Cannulation of an intradiverticular papilla during endoscopic retrograde cholangiopancreatography (ERCP) can be challenging. We present here a technique for endoscopic ultrasound-guided puncture of the common bile duct followed by rendezvous ERCP for biliary drainage through the native intradiverticular papilla.

Accurate diagnosis of pancreas divisum by linear-array endoscopic ultrasonography

BACKGROUND AND STUDY AIMS

During linear-array endoscopic ultrasonography (EUS), the main pancreatic duct can be followed continuously from the major papilla into the pancreatic body in most patients. Often, the duct can also be seen crossing a sonographic border between the ventral and dorsal pancreatic anlagen. It was hypothesized that the presence of either feature excludes pancreas divisum, whereas the absence of these features suggests complete pancreas divisum.

PATIENTS AND METHODS

Pancreas divisum was sought during all linear-array EUS examinations conducted between July 1999 and June 2003. Charts were reviewed retrospectively, and patients who underwent endoscopic retrograde pancreatography after, but not before, EUS were included in the study.

RESULTS

A total of 162 patients had EUS before ERCP. Adequate evaluation of the pancreatic duct was possible in 78 % of the patients. The prevalence of pancreas divisum was 13.6 %. In patients with adequate duct visualization, the sensitivity, specificity, and positive and negative predictive values for EUS were 95 %, 97 %, 86 %, and 99 %, respectively. The overall accuracy of EUS for identifying pancreas divisum was 97 % in this subgroup.

CONCLUSION

Adequate EUS evaluation of pancreas divisum was possible in most cases. Linear-array EUS is a promising diagnostic test for pancreas divisum.

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 implications of postsurgical adhesions

Adhesion development can have a major impact on a patient's subsequent health. Adhesions are a significant source of impaired organ functioning, decreased fertility, bowel obstruction, difficult re-operation, and possibly pain. Consequently, their financial sequelae are also extraordinary, with more than one billion dollars spent in the USA in 1994 on the bowel obstruction component alone. Performing adhesiolysis for pain relief appears efficacious in certain subsets of women. Unfortunately even when lysed, adhesions have a great propensity to reform. Adhesions are prevalent in all surgical fields, and nearly any compartment of the body. For treatment of infertility and recurrent pregnancy loss, lysis of intrauterine adhesions results in improved fecundability and decreased pregnancy loss.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Diamide-induced cytotoxicity and thermotolerance in CHO cells

Treatment with the sulfhydryl oxidant diamide denatures and aggregates cellular proteins, which prior studies have implicated as an oxidative damage that activates the heat shock transcription factor and induces thermotolerance. This study was initiated to further characterize cellular response to diamide-denatured proteins, including their involvement in diamide cytotoxicity. Cytotoxic diamide exposures at 37.0 degrees C denatured and aggregated cellular proteins in a manner that was proportional to cell killing, but this correlation was different than that established for heated cells. Diamide exposures at 24.0 degrees C were orders of magnitude less cytotoxic, with little additional killing occurring after diamide was removed and cells were returned to 37.0 degrees C. Thus, protein denaturation that occurred at 37.0 degrees C, after proteins were chemically destabilized by diamide at 24.0 degrees C [Freeman et al., J. Cell. Physiol., 164:356-366 (1995); Senisterra et al., Biochemistry 36: 11002-11011 (1997)], had little effect on cell killing. Thermotolerance protected cells against diamide cytotoxicity but did not reduce the amount of denatured and aggregated protein observed immediately following diamide exposure. However, denatured/aggregated proteins in thermotolerant cells were disaggregated within 17 h following diamide exposure, while no disaggregation was observed in nontolerant cells. This more rapid disaggregation of proteins may be one mechanism by which thermotolerance protects cells against diamide toxicity, as it has been postulated to do against heat killing. As with heat shock, nontoxic diamide exposures induced maximal tolerance against heat killing; however, there was no detectable, increased synthesis of heat shock proteins. Thus, diamide treatment proved to be a reproducible procedure for inducing a phase of thermotolerance that does not require new heat shock protein (HSP) synthesis, without having to use transcription or translation inhibitors to suppress HSP gene expression. These results complement those from studies with other stresses to establish the importance of protein denaturation/aggregation as a cytotoxic consequence of stress and a trigger for thermotolerance induction. The data also illustrate that differences in how proteins are denatured and aggregated can affect their cytotoxicity and the manner in which thermotolerance is expressed.

Clinical and economic outcomes of individuals with severe peptic ulcer hemorrhage and nonbleeding visible vessel: an analysis of two prospective clinical trials

OBJECTIVE

We report the clinical outcomes and direct medical costs of 155 patients with severe peptic ulcer hemorrhage and a nonbleeding visible vessel at emergency endoscopy treated with endoscopic hemostasis or medical-surgical therapy.

METHODS

In two consecutive, prospective, randomized, controlled trials, patients were randomly assigned to endoscopic hemostasis (heater probe, bipolar electrocoagulation, or injection sclerosis) or medical-surgical treatment. Study endpoints included the incidence of severe ulcer rebleeding and emergency surgery, length of hospital stay, blood transfusion requirements, mortality rate, and direct costs of utilized health care. Direct medical costs were estimated using combined fixed and variable institutional costs for consumed resources and Medicare reimbursement rates.

RESULTS

Compared with medical-surgical treatment, endoscopically treated patients had significantly lower rates of severe ulcer rebleeding (p = 0.004), emergency surgery (p = 0.002 and p = 0.019, 0.024), and blood transfusions (p = 0.025). Observed inter-trial differences in ulcer rebleeding rates may be partially explained in a multivariate model by covariates of comorbid disease and inpatient ulcer bleeding. In both trials, length of hospital stay, mortality rates, and treatment-related complications were similar. Estimated median direct costs per patient differed: The first trial had lower costs with endoscopic hemostasis ($4254, vs $4620 for electrocoagulation and $5909 for medical-surgical treatment), yet the second trial yielded lower costs with medical-surgical treatment ($3169, vs $3477 for injection sclerosis and $4098 for heater probe).

CONCLUSIONS

Compared with medical-surgical therapy, endoscopic hemostasis for severe ulcer hemorrhage and a nonbleeding visible vessel yielded significantly better patient outcomes and was safe. This procedure may or may not yield lower direct medical costs and cost savings.

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.

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.

Endoscopic intervention for biliary leaks after laparoscopic cholecystectomy: a multicenter review

BACKGROUND

Endoscopic therapy of biliary tract leaks was uncommon before laparoscopic cholecystectomy. Studies have demonstrated the efficacy of endoscopic drainage by endoscopic sphincterotomy or stent placement. Various endoscopic therapeutic modalities and long-term follow-up of this problem were studied.

METHODS

Members of the Midwest Pancreaticobiliary Group reviewed all patients referred for endoscopic therapy of biliary leaks after laparoscopic cholecystectomy from 1990 to 1994. Long-term follow-up was by direct patient contact.

RESULTS

Fifty patients were referred for endoscopic therapy of biliary leaks. Abdominal pain was present in 94%. The mean time from laparoscopic cholecystectomy to referral was 6.9 days. Therapy consisted of sphincterotomy only in 6 patients, stent only in 13, and sphincterotomy with stent in 31. Biliary leaks were healed in 44 patients at a mean of 5.4 weeks. A second or third endoscopic procedure was necessary to achieve healing in five patients. Two stent-related complications were noted. Percutaneous or surgical drainage of biliary fluid collections was required in 16 patients. The mean hospital stay for treatment of the leak was 11.1 days after endoscopic therapy. On follow-up (mean 17.5 months), all patients were well except two with mild abdominal discomfort.

CONCLUSIONS

Endoscopic sphincterotomy, stent placement, or sphincterotomy with stent are effective in healing biliary leaks after laparoscopic cholecystectomy. Despite prolonged treatment for the leak, patients did well on long-term follow-up.

PEST sequences in proteins involved in cyclic nucleotide signalling pathways

There is growing evidence that PEST sequences act as proteolytic recognition signals within polypeptides. PEST sequences are rich in proline (P), glutamic acid (E), serine (S), and threonine (T) and can be identified by the PEST-FIND program. Both the catalytic and regulatory subunits of the cAMP-dependent protein kinase have been shown to have conditional PEST sequences which are exposed upon cAMP binding to the enzyme. cAMP binding leads to rapid dissociation of C- and R-subunits, and both subunits have increased sensitivity to proteolysis. It is not known whether other proteins that participate in the cyclic nucleotide signalling pathway have PEST regions in their amino acid sequences. Therefore, we have screened amino acid sequences of proteins that are directly involved in cyclic nucleotide cascade, including cGMP-dependent protein kinases, anchoring proteins for cAMP-dependent protein kinase, cyclic nucleotide-gated ion channels, and cyclic nucleotide phosphodiesterases, for PEST sequences using the PEST-FIND program. Many PEST sequences with high scores have been identified in these proteins. The occurrence of the PEST sequences is very high in proteins involved in cyclic nucleotide signalling pathways (approximately 80%). This value is much higher than the percentage (10%) of PEST sequences that can be found in the primary structures of the proteins listed in the data bank. This frequent occurrence of PEST sequences in proteins involved in cyclic nucleotide action and metabolism suggests an important role of proteolysis of these key proteins of signal transduction.

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.

Stigmata of hemorrhage in bleeding ulcers

Models for predicting rebleeding after upper GI bleeding, and practice guidelines to determine management of these patients, must include not only endoscopic findings but clinical variables, such as severity of blood loss and the age and comorbidity of the patient. The importance of these variables in determining rebleeding risk, and the high degree of interobserver variability in identifying stigmata of hemorrhage, suggest that management strategies based too heavily on stigmata result in inappropriate discharge of some patients. The validity of various management strategies incorporating stigmata of hemorrhage needs to be prospectively assessed.

Destabilization of the Ca2+-ATPase of sarcoplasmic reticulum by thiol-specific, heat shock inducers results in thermal denaturation at 37 degrees C

A number of protein reactive compounds, including the thiol reagents diamide and arsenite, are known inducers of heat shock protein (HSP) synthesis and thermotolerance. These compounds are thought to damage cellular protein, which has been proposed to serve as the signal for induction. The specific mechanism of protein damage and its relation to thermal denaturation are unknown. The Ca2+-ATPase of sarcoplasmic reticulum, a membrane protein that contains 24 cys residues, was used to determine the effect of diamide, arsenite, N-ethylmaleimide (NEM), and the cys-specific probes Br-DMC and IAEDANS, which label one or two specific cys residues, respectively, on protein conformation and stability. The Ca2+-ATPase was chosen because diamide has been shown to affect the thermal properties of a class of membrane proteins of CHO cells (Freeman et al., 1995). The labeling of one or two thiols has no effect on activity or conformation, while more extensive reaction (but with less than approximately five to eight groups titrated) results in destabilization of the Ca2+-ATPase such that it denatures thermally at 37 degrees C. Higher levels of titration result in greater destabilization such that the protein is no longer stable at room temperature, with the production of a state similar to the thermally denatured state as assayed by activity, differential scanning calorimetry, ANS binding, and light scattering. The fractional denaturation induced by these thiol reagents, determined by the decrease in the heat absorbed during thermal denaturation, is directly proportional to inactivation of ATPase activity. Thus, inactivation of the Ca2+-ATPase by thiol reagents occurs because of denaturation not through oxidation of essential thiols. These results indicate that these thiol-specific heat shock inducers function by two mechanisms: (1) destabilization of proteins such that they thermally denature at 37 degrees C and (2) direct denaturation, apparently driven by thermal processes at room temperature, following more extensive reaction which results in extreme destabilization. We suggest that these are general mechanisms by which heat shock inducers damage proteins.

Destabilization and denaturation of cellular protein by glutathione depletion

This investigation tested the hypothesis that depletion of intracellular glutathione, in contrast to its oxidation could lead to non-native oxidation of protein thiols, thereby trapping proteins in an unstable conformation. Chinese hamster cells were exposed to the alpha, beta-unsaturated dicarboxylic acid diethylmaleate in order to produce rapid glutathione (GSH) depletion without oxidation. Measurement of the fluorescence of oxidized 2',7'-dichlorofluorescein diacetate indicated that reactive oxygen species accumulated in GSH depleted cells. Glutathione depletion was found to alter protein thiol/disulfide exchange ratios such that 17 to 23 nmol of protein SH/mg protein underwent oxidation. Differential scanning calorimetry (DSC) of glutathione depleted cells yielded a profile of specific heat capacity versus temperature that was characteristic of cells containing destabilized and denatured protein. In addition, cells depleted of glutathione exhibited a two-fold increase in NP-40 insoluble protein. These results indicate that depletion of intracellular glutathione caused oxidation of protein thiols, protein denaturation and aggregation and provide a mechanism to explain how GSH depletion can initiate stress responses.

An economic analysis of patients with active arterial peptic ulcer hemorrhage treated with endoscopic heater probe, injection sclerosis, or surgery in a prospective, randomized trial

BACKGROUND

There are no published, detailed assessments of the direct costs of endoscopic hemostasis for actively bleeding peptic ulcers. We compared the direct costs of care for patients with active ulcer hemorrhage treated with endoscopic or medical-surgical therapies and correlated these costs with patient outcomes.

METHODS

In a prospective, randomized, controlled trial, 31 patients with active ulcer hemorrhage at emergency endoscopy were randomly assigned to heater probe, injection, or medical-surgical treatment. For further ulcer bleeding, heater probe and injection patients were re-treated endoscopically and medical-surgical patients were referred for surgery. Direct costs were estimated using fixed and variable costs for resources consumed and Medicare reimbursement rates for physician fees.

RESULTS

Compared to medical-surgical treatment, the heater probe and injection groups had significantly higher primary hemostasis rates (100% and 90% vs 8%) and lower rates of emergency surgery (0% and 10% vs 75%), blood transfusions, and median direct costs per patient ($4153 and $5247 vs $11,149). Furthermore, compared to medical-surgical treatment, the heater probe group had a significantly lower incidence of severe ulcer rebleeding (11% vs 75%).

CONCLUSIONS

Heater probe and injection sclerosis are similarly efficacious treatments for active ulcer hemorrhage, and both treatments yield significantly lower direct costs of medical care and cost savings.

Expression of glutathione and gamma-glutamylcysteine synthetase mRNA is Jun dependent

The gene GLCLC encodes the catalytic subunit of gamma-glutamylcysteine synthetase (glutamate-cysteine ligase E.C. 6.3.2.2), the rate limiting enzyme for glutathione synthesis. When HepG2 cells were exposed to the serine/threonine phosphatase inhibitor okadaic acid (OA), increased expression of GLCLC was observed, as was the development of resistance to xenobiotic induced GSH depletion. Okadaic acid is known to activate both NF-kappaB and AP-1 activity. Inhibition of NF-kappaB activity by overexpression of an IkappaB alpha transdominant inhibitor or exposure to the protease inhibitor TLCK did not inhibit the OA mediated increase in GLCLC transcripts. Fibroblasts derived from a mouse containing a c-Jun null mutation exhibited diminished AP-1 binding activity, reduced levels of GLCLC message, and a correspondingly low GSH concentration compared to wild type cells. When the null cells, which express Jun B and Jun D, were exposed to OA, AP-1 binding activity increased, as did expression of GLCLC message. These results indicate that AP-1 transcription factors participate in the regulation of glutathione metabolism.

Alteration of transcriptional and post-transcriptional expression of gamma-glutamylcysteine synthetase by diethyl maleate

Gamma-glutamylcysteine synthetase (gamma-GCS), also known as glutamate-cysteine ligase (EC 6.3.2.2), is the rate-limiting enzyme in the synthesis of glutathione (GSH). The gene GLCLC encodes the catalytic subunit while GLCLR encodes the regulatory subunit. Although it has been shown that GLCLC can respond to a variety of stresses by increased transcription, it is not known whether a similar response occurs for GLCLR. Nor is it known whether post-transcriptional regulation of either gene product is altered during stress. The present investigation was undertaken to explore transcriptional and post-transcriptional regulation of GLCLC and GLCLR gene products when HepG2 cells were challenged with the radiation sensitizer diethyl maleate (DEM). Expression of steady-state GLCLC and GLCLR mRNA was enhanced 5-20-fold after DEM challenge. Nuclear run-off assays were performed on unstressed and stressed cells to determine whether the increased expression of GLCLC and GLCLR mRNA was due to altered transcriptional activity of these genes. The DEM treatment increased the transcription rates of both genes 2-5-fold. In unstressed HepG2 cells, the half-life of GLCLC mRNA transcripts was approximately 4 h. In contrast, the half-life of GLCLR transcripts was approximately 8 h. In cells treated with DEM, the half-lives of all transcripts were increased, indicating that message stabilization contributed to the increased expression of gene products. Finally, a PEST algorithm has identified a PEST (proline, glutamate, serine, threonine) motif within the catalytic subunit of gamma-GCS, suggesting that this subunit might exhibit conditional proteolytic regulation. These results imply that regulation of the products of the GLCLC and GLCLR genes may be altered at multiple levels during exposure to stress.