Acquired Gastric Dieulafoy-Like Lesion due to Aberrant Blood Supply Diverted From the Left Phrenic Artery to an Enlarged Splenule

Dieulafoy lesion is an aberrant submucosal vessel that can erode into the overlying tissue leading to hemorrhage. It is a rare but important cause of gastrointestinal bleeding. We present a case of a patient who developed an acquired Dieulafoy lesion 39 years after splenectomy. Abdominal computed tomography showed an aberrant vessel from a branch of the left phrenic artery, coursing through the gastric fundus to supply a splenule. Angiography with embolization of the aberrant vessel resulted in no further bleeding.

Long-term follow-up of branch-duct intraductal papillary mucinous neoplasms with No change in first 5 Years of diagnosis

BACKGROUND

Discontinuation of branch-duct intraductal papillary mucinous neoplasm (BD-IPMN) surveillance after 5 years of no change remains controversial. Long-term outcomes of BD-IPMN without significant changes in the first 5 years were evaluated.

METHODS

We performed a multi-center retrospective analysis of patients with BD-IPMN diagnosis from 2005 to 2011 (follow-up until 2017). Significant changes were defined as pancreatic cancer (PC), pancreatectomy, high-risk stigmata (HRS), worrisome features (WF) and worrisome EUS features (WEUS).

RESULTS

Of 982 patients who had no significant changes, 5 (0.5%), 7 (0.7%), 99 (10.1%), 4 (0.4%) patients developed PC, HRS, WF, WEUS, respectively, post-5 years. PC and HRS/WF/WEUS incidences at 12 years were 1.0% and 29.0%, respectively. Patients that developed HRS/WF/WEUS had larger cyst size in first 5 years compared to those that did not [16 (12-23) vs. 12 (9-17) mm, p = 0.0001], cyst size of >15 mm having higher cumulative incidence of HRS/WF/WEUS. PC mortality was 0.8%; all-cause mortality was 32%. Incidence of mortality due to PC was higher in HRS/WF/WEUS group, p < 0.0001. The mortality rate at 12 years for ACCI (age-adjusted Charlson Comorbidity Index) of ≤3, 4-6, and ≥7 were 3.5%, 19.9%, and 57.6% (p < 0.0001), respectively.

CONCLUSIONS

Incidence of PC in patients with BD-IPMN without significant changes in first 5 years of diagnosis remains low at 1.0%. Incidence of HRS/WF/WEUS was higher at 29.0%. PC-related mortality was higher in HRS/WF/WEUS group. These risks should be weighed against patients' overall mortality (utilizing scoring systems such as ACCI) when making surveillance decision of BD-IPMN beyond 5 years.

The effect of prophylactic hemoclips on the risk of delayed post-endoscopic mucosal resection bleed for upper and lower gastrointestinal lesions: a retrospective cohort study

Background

Endoscopic mucosal resection (EMR) is a minimally invasive procedure used for the treatment of lesions in the gastrointestinal (GI) tract. There is increased usage of hemoclips during EMR for the prevention of delayed bleeding. This study aimed to evaluate the effect of hemoclips in the prevention of delayed bleeding after EMR of upper and lower GI tract lesions.

Method

This is a retrospective cohort study using the Kaiser Permanente Southern California (KPSC) EMR registry. Lesions in upper and lower GI tracts that underwent EMR between January 2012 and December 2015 were analyzed. Rates of delayed bleeding were compared between the hemoclip and no-hemoclip groups. Analysis was stratified by upper GI and lower GI lesions. Lower GI group was further stratified by right and left colon. We examined the relationship between clip use and several clinically-relevant variables among the patients who exhibited delayed bleeding. Furthermore, we explored possible procedure-level and endoscopist-level characteristics that may be associated with clip usage.

Results

A total of 18 out of 657 lesions (2.7%) resulted in delayed bleeding: 7 (1.1%) in hemoclip group and 11 (1.7%) in no-hemoclip group (p = 0.204). There was no evidence that clip use moderated the effects of the lesion size (p = 0.954) or lesion location (p = 0.997) on the likelihood of delayed bleed. In the lower GI subgroup, clip application did not alter the effect of polyp location (right versus left colon) on the likelihood of delayed bleed (p = 0.951). Logistic regression analyses showed that the clip use did not modify the likelihood of delayed bleeding as related to the following variables: use of aspirin/NSAIDs/anti-coagulants/anti-platelets, pathologic diagnoses (including different types of colon polypoid lesions), ablation, piecemeal resection. The total number of clips used was 901 at a minimum additional cost of $173,893.

Conclusion

Prophylactic hemoclip application did not reduce delayed post-EMR bleed for upper and lower GI lesions in this retrospective study performed in a large-scale community practice setting. Routine prophylactic hemoclip application during EMR may lead to significantly higher healthcare cost without a clear clinical benefit.

Percutaneous Endoscopic Necrosectomy of Complex Walled-Off Lateral Necrosis of the Pancreas with the Aid of Laparoscopic Babcock Forceps: A Case Report of an Endoscopic and Radiologic Team Approach

INTRODUCTION

The initial therapeutic intervention for infected necrotizing pancreatitis usually begins with endoscopic cystogastrostomy for drainage, followed by endoscopic necrosectomy. Endoscopic pancreatic necrosectomy is commonly performed transluminally through transgastric or transduodenal routes. This case describes necrosectomy via a transcutaneous route for laterally located walled-off pancreatic necrosis and the novel use of Babcock forceps for an obstructed fully covered metal stent.

CASE PRESENTATION

A 62-year-old woman presented with abdominal pain, nausea, and vomiting. After multiple admissions and repeated abdominal imaging, she was found to have laterally located, infected, walled-off pancreatic necrosis. Initially, a drainage catheter was placed by an interventional radiologist and was eventually upsized to a 28F catheter. Subsequently, a fully covered metal stent was placed in the gastroenterology suite under fluoroscopic guidance and was used to gain access for percutaneous sessions of necrosectomy. A percutaneous sinus tract endoscopic necrosectomy was performed under direct endoscopic view. However, difficulties occurred with removing necrotic debris even through this large covered stent. Thus, laparoscopic Babcock forceps were used under fluoroscopy to remove lodged debris from the midstent. Repeat abdominal computed tomography scan 3 days after necrosectomy showed near resolution of the walled-off pancreatic necrosis.

DISCUSSION

This Babcock technique with endoscopic necrosectomy has not been previously described in the literature, to our knowledge. Babcock forceps were an ideal tool in our case because they were able to gain access to the obstruction in the stent, but the "teeth" are small and dull enough to prevent from catching onto the metal stent mesh.

Effect of a region-wide incorporation of an algorithm based on the 2012 international consensus guideline on the practice pattern for the management of pancreatic cystic neoplasms in an integrated health system

AIM

To examine the practice pattern in Kaiser Permanente Southern California (KPSC), i.e., gastroenterology (GI)/surgery referrals and endoscopic ultrasound (EUS), for pancreatic cystic neoplasms (PCNs) after the region-wide dissemination of the PCN management algorithm.

METHODS

Retrospective review was performed; patients with PCN diagnosis given between April 2012 and April 2015 (18 mo before and after the publication of the algorithm) in KPSC (integrated health system with 15 hospitals and 202 medical offices in Southern California) were identified.

RESULTS

2558 (1157 pre- and 1401 post-algorithm) received a new diagnosis of PCN in the study period. There was no difference in the mean cyst size (pre- 19.1 mm vs post- 18.5 mm, P = 0.119). A smaller percentage of PCNs resulted in EUS after the implementation of the algorithm (pre- 45.5% vs post- 34.8%, P < 0.001). A smaller proportion of patients were referred for GI (pre- 65.2% vs post- 53.3%, P < 0.001) and surgery consultations (pre- 24.8% vs post- 16%, P < 0.001) for PCN after the implementation. There was no significant change in operations for PCNs. Cost of diagnostic care was reduced after the implementation by 24%, 18%, and 36% for EUS, GI, and surgery consultations, respectively, with total cost saving of 24%.

CONCLUSION

In the current healthcare climate, there is increased need to optimize resource utilization. Dissemination of an algorithm for PCN management in an integrated health system resulted in fewer EUS and GI/surgery referrals, likely by aiding the physicians ordering imaging studies in the decision making for the management of PCNs. This translated to cost saving of 24%, 18%, and 36% for EUS, GI, and surgical consultations, respectively, with total diagnostic cost saving of 24%.

Merkel cell carcinoma of unknown primary with lymph node and mesenteric metastasis involving the pancreas and duodenum

Merkel cell carcinoma (MCC) of skin is a rare, aggressive cutaneous malignancy of neuroendocrine origin. MCC predominantly affects elderly Caucasians and has high predilection for sun exposed areas. Histologic exam and immunohistochemical profile is required to establish the diagnosis. It has high propensity for local recurrence and metastasis, and carries poor prognosis. However, metastasis to mesentery involving the duodenum is very uncommon and rarely reported in literature. We hereby describe a patient with lymph node and mesenteric metastasis invading duodenum and pancreas with unknown primary origin of MCC.

Coached practice using ERCP mechanical simulator improves trainees' ERCP performance: a randomized controlled trial

BACKGROUND AND STUDY AIMS

Preliminary data suggested that simulation practice using an endoscopic retrograde cholangiopancreatography (ERCP) mechanical simulator (EMS) improved trainees' skill. The aims of the current study were to confirm the impact of coached EMS practice at the beginning of ERCP training and to investigate whether subsequent uncoached EMS practice provides additional benefit.

METHODS

Trainees entering ERCP training in 2008 (n = 8) and 2009 (n = 8) at two referral medical centers were randomized to receive a coached EMS practice either with (2009) or without (2008) subsequent uncoached practices or only routine training (controls). The outcome measures were successful deep biliary cannulation by the trainee and overall performance score as rated by blinded trainers, during the subsequent 3 months of clinical practice.

RESULTS

Trainees undergoing single and multiple EMS practices were more likely than controls to achieve successful biliary cannulation (single: adjusted odds ratio [aOR] 2.89, 95 % confidence interval [CI] 2.21 - 3.80 [P < 0.001]; multiple: 3.09, 95 %CI 1.13 - 8.46 [P = 0.028]) and to have superior overall performance scores (aOR 3.29, 95 %CI 1.37 - 7.91 [P = 0.008] and 6.92, 95 %CI 3.77 - 12.69 [P < 0.001], respectively). The benefit of single and multiple EMS practices on overall performance score remained significant after adjustment for success or failure of deep biliary cannulation (aOR 2.98, 95 %CI 1.38 - 6.43 [P = 0.005] and 6.09, 95 %CI 2.40 - 15.45 [P < 0.001], respectively). The benefits of single vs. multiple EMS practices were not statistically different.

CONCLUSIONS

Coached simulation using EMS improved novice trainees' success of biliary cannulation and overall ERCP performance. Additional uncoached practices did not appear to provide further benefit. Trainees should undergo a coached EMS practice at the beginning of ERCP training.

A Retrospective Clinical Study of Cervical Restorations: Longevity and Failure-Prognostic Variables

The aim of this retrospective clinical study was to compare the longevity of cervical restorations between resin composite (RC) and glass ionomer (GI) and to investigate variables predictive of their outcome. The clinical performance of the two restorative materials in function was compared using the ratings of the modified United States Public Health Service (USPHS) criteria. A total of 479 cervical restorations were included in the study. Ninety-one already-replaced restorations were reviewed from dental records. The other 388 restorations still in function were evaluated according to the modified USPHS criteria by two investigators. Longevity and prognostic variables were analyzed with the Kaplan-Meier survival analysis and multivariate Cox proportional hazard model. The clinical performances of the two materials were evaluated according to the ratings of the USPHS criteria and compared using the Pearson chi-square test and Fisher exact test. The longevity was not significantly different between RC and GI (median survival time, 10.4 ± 0.7 and 11.5 ± 1.1 years, respectively). The main reasons for failure were loss of retention (82.2%) and secondary caries (17.8%). The longevity of cervical restoration was significantly influenced by tooth group and operator group (Wald test, p&lt;0.05), while material, gender, presence or absence of systemic diseases, arch, and reason for treatment did not affect the longevity. Contrary to the longevity, the clinical performance of RC was superior to GI in the criteria of retention, marginal discoloration, and marginal adaptation, but similar in secondary caries, wear, and postoperative sensitivity.

Correction of severe thoracolumbar spondylolisthesis (grade 4) secondary to neurofibromatosis with posterior spinal instrumented fusion alone. A case report

A 15-year-old teenager with Type 1 Neurofibromatosis presented with grade 4 spondylolisthesis over T12/L1 junction resulting paraparesis (Frankel D). Radiograph showed a Cobb angle of 88 degrees. Computed tomography scan showed dysplastic vertebral bodies, pedicles and facet joints of T11, T12 and L1 vertebra with complete T12/L1 facets dislocation. Magnetic resonance imaging confirmed presence of spinal cord compression. He underwent posterior instrumentation and posterolateral fusion (T8 to L4) using hybrid instrumentation. Extensive corticotomy of the posterior elements was followed by the use of large amount of bone graft. Post operatively, his neurology improved markedly back to normal. Radiographs showed a good correction of the deformity. He was immobilized in a thoracolumbar orthosis for six months. A solid posterior fusion was achieved at six months follow up. At 36-month follow up, he remained asymptomatic. This case report illustrates a successful treatment of a grade 4 thoracolumbar spondylolisthesis secondary to neurofibromatosis with posterior spinal fusion alone.

Effect of ERCP mechanical simulator (EMS) practice on trainees' ERCP performance in the early learning period: US multicenter randomized controlled trial

OBJECTIVES

The impact of endoscopic retrograde cholangiopancreatography (ERCP) mechanical simulator (EMS) practice on trainee clinical performance is unknown. The hypothesis that trainees with EMS practice (study group (SG)) have improved clinical outcomes compared with those without such practice (control group (CG)) is tested.

METHODS

This was a randomized controlled trial involving six US academic centers. Sixteen trainees were randomized after ERCP didactic teaching. SG (n=8) participated in two sessions of EMS practice on selective cannulation; CG (n=8) did not undergo EMS practice. All participants' clinical performances were monitored in the subsequent 16 weeks. Intervention effects were assessed in multivariable regression models using generalizing estimating equations (GEE) to account for cluster randomization of trainees. The primary outcome was successful biliary cannulation, and secondary outcomes were cannulation time and competency score.

RESULTS

Cannulation success rate was 47.1% for CG and 69.6% for SG. SG had higher odds of successful cannulation (adjusted odds ratio=3.01, P=0.021). SG trainees achieved faster cannulation time (min) (4.7±4.2 vs. 10.3±14.1, P<0.001). Trainee competency scores given by supervising physicians were comparable confirming adequate blinding of the trainers. Limitations included short observation period, small number of ERCPs performed by individual trainees, and variation in the number of ERCPs between trainees.

CONCLUSIONS

In a prospective multicenter randomized controlled trial during early training, a significantly higher proportion of the biliary cannulations performed by trainees with EMS practice were successful and with faster cannulation time compared with those performed by trainees without such practice. The results provide objective evidence to support the continued evaluation of EMS practice to augment clinical training.

Synthesis of Cu-CNT nanocomposite powder by ball milling

In this paper, to improve the poor wettability between the Carbon nanotubes (CNTs) and metal matrix, the mechanical alloying (MA) technique by the ball milling method was employed. Also, the CNTs were pre-coated to improve the agglomeration of the CNTs with copper powder. The main aim of this work is the fabrication of Cu-CNT nanocomposite powder using the MA by ball milling. The as-received dendritic copper powders change their shape sequentially to flaky, disk-typed particles and finally, to globular type particles. Also, the tendency of globular formation was prominent in the milled Cu-Cu coated MWNTs (multi-walled carbon nanotubes) powder and the grain size of the sintered Cu coated MWNTs specimen decreased more than that of the pure copper specimen. Finally, the homogeneous Cu-CNT nanocomposite intermetallic particles having fine grains was produced by the MA method of ball milling.

Comparison of accessory performance using a novel ERCP mechanical simulator

BACKGROUND AND STUDY AIMS

There is a paucity of in vitro methods for evaluating ERCP accessories. We hypothesize that the time taken to perform a simulated single stent or multiple stents placement is different for stenting systems with or without the capability of intraductal ductal release (IDR) of the guide wire.

PATIENTS AND METHODS

We conducted an un-blinded in vitro comparison of ERCP accessories using a mechanical simulator during hands-on ERCP practice workshops. A total of 21 U.S. participants and 20 Chinese participants with various level of ERCP experience took part in the different practice workshops. Accessories with and without the capability of intraductal release of guide wire were compared. Total time required for completing a simulated stenting procedure with single or multiple stents and the respective simulated fluoroscopy time were recorded.

RESULTS

There was no significant difference in the time taken for placement of a single stent using either stenting systems. Stenting system capable of intraductal release of the guide wire required significantly shorter time to complete placement of three stents.

CONCLUSIONS

Using time required to complete a specific task, i. e. biliary stenting, the mechanical simulator permits the performance of different accessories by the same group of operators to be evaluated objectively.

The cost-effectiveness and budget impact of intravenous versus oral proton pump inhibitors in peptic ulcer hemorrhage

BACKGROUND & AIMS

The most cost-effective route of administering proton pump inhibitor (PPI) therapy in peptic ulcer hemorrhage remains uncertain. Oral (PO) PPI therapy may be less effective than intravenous (IV) PPI therapy, but is less expensive and does not mandate a 72-hour posthemostasis hospital stay to complete a full therapeutic course. Because there are currently no published head-to-head clinical trials comparing IV vs PO PPIs, we used decision analysis with budget impact modeling to measure the clinical and economic outcomes of these competing modes of administration.

METHODS

We compared 3 postendoscopic strategies for high-risk peptic ulcer hemorrhage: (1) PO PPI therapy, (2) IV PPI therapy, and (3) IV histamine(2) receptor antagonist therapy. The primary outcomes were cost per quality-adjusted life-year gained, and per-member per-month cost in a hypothetical managed care organization with 1,000,000 covered lives.

RESULTS

Compared with the PPI strategies, the histamine(2) receptor antagonist strategy was more expensive and less effective. Of the 2 PPI strategies, using IV instead of PO PPI cost an incremental 708,735 US dollars per year to gain 1 additional quality-adjusted life-year. Substituting IV in lieu of PO PPI cost each member 2.86 US dollars per month to subsidize. The IV PPI strategy became dominant when the rebleed rate with PO PPIs exceeded 24% (base case = 13%), and when the hospital stay on IV PPIs decreased to less than 72 hours.

CONCLUSIONS

The higher effectiveness of IV PPI therapy may not offset its increased costs vs PO PPI therapy in ulcer hemorrhage. The managed care budget impact of IV PPIs exceeds most benchmarks.

Improvement of existing nightsoil treatment plant for nitrogen removal

This study was performed to increase the treatment efficiency and to reduce operation and maintenance costs of the existing nightsoil treatment plant. The existing nightsoil plant was not established by the nitrogen removal process, and was operated ineffectively with deterioration of treatment efficiency rate, and according to the demand of many operators, the expenses of operation and maintenance have become excessive. Modified plant has been changed through two steps. The first step, liquid decayed tank using closed oxidation ditch is operated to increase retention time only for nitrification. The second step, modified liquid decayed tank including anoxic tank is operated, it has an excellent nitrogen removal rate. In first step, when HRT was increased from 10 days to 13 days in liquid decayed tank including aeration tank using closed oxidation ditch, TN concentration of effluent appeared below 51 mg/L less than discharge limit, 60 mg/L. In second step, when anoxic tank and oxic tank were installed, HRT has been increased to 13 days and 26 days, respectively. Then average TN concentration of effluent was detected less than 13 mg/L for over one year. The simple process modified the existing two processes resulted in the reduction of costs for operation and maintenance in the personnel, chemical, and filter change sphere.

Color characteristics of low-chroma and high-translucence dental resin composites by different measuring modes

The objective of the described research was the evaluation of the effects of the differences in the color-measuring geometry (SCE, SCI) and the standard illuminant on the color and color change after polymerization and thermocycling of resin composites. White, translucent, and conventional shades of two brands of resin composites were measured before and after polymerization and after thermocycling according to the CIE L*a*b* color scale on a reflection spectrophotometer with SCE and SCI geometry under the standard illuminants A, D65, and C. Under both SCE and SCI modes, the color differences (DeltaE*) of specimens between the values measured under illuminants A and D65 or A and C were larger than those between D65 and C in unpolymerized, polymerized, and thermocycled conditions. With SCE geometry, DeltaE* after polymerization of the white shade group was 8.7-9.8 under D65, and was higher than the conventional shade group (p < 0.05) in both materials. With SCE geometry, DeltaE* between polymerized and thermocycled white, translucent shade was 4.4-7.1 under D65. With SCI geometry, the results were in general agreement with those of SCE mode. After polymerization, DeltaE* measured under illuminant A was generally higher than that under D65 or C (p < 0.01). After thermocycling, the color change was different depending on the color-measuring geometry and standard illuminant.

Design parameters of high rate algal ponds using filamentous algae matrix for treating rural stream water

High rate algal ponds (HRAP) with a filamentous algae matrix (FAM) as the predominant species, were operated to evaluate the characteristics of FAM and the basic design parameters for treating polluted rural stream water. The porous and gelatinous FAM was formed like a sponge, which functions to prevent excessive loss of the algae in the effluent and can easily be retrieved from the ponds. The organic fraction of harvested FAM was about 88%, which is suitable for use as fertilizer. The HRAP system using FAM was found to be an effective nutrient removal process not requiring any artificial carbon sources for nitrification. At HRT 4 days, the T-N and T-P removal efficiencies were 85.9% and 65.8%, respectively. When the pH and water temperature were maintained above 9 and 15 degrees C, HRT required for achieving a 70% T-N removal efficiency could be reduced by about 3 days. The oxygen production rate by FAM was calculated as 1.45 mgO2/L/m2. The design surface area of HRAP needed per rural inhabitant was about 2.72 m2.

Unexpected difficult intubation in a patient with normal airway on assessment

Routine preoperative assessment of the patient's airway includes an assessment of mouth opening and a grading of the view according to the Mallampati scale. This is carried out with the patient sitting and actively opening the mouth without phonation. This case report illustrates that the temporomandibular joint is a complex joint and that certain pathologies may prevent passive depression of the mandible after induction of anaesthesia.

Comparison of color of resin composites of white and translucent shades with two shade guides

PURPOSE

The purpose of this study was to compare the color of resin composites of white, translucent, and conventional shades with shade guides, based on the analysis of the color distribution of shade guides. The influence of color measuring mode, specular component included (SCI) or excluded (SCE), was also determined.

MATERIALS AND METHODS

The labial portions of shade guide tabs (Vita and Chromascop) were polished flat with up to 2400-grit SiC paper. Color coordinates were measured according to CIE L*a*b* color scale on a reflection spectrophotometer with both the SCE and SCI modes. The color coordinates of white, translucent, and conventional shades of two brands of resin composites were measured and compared with those of the shade guides.

RESULTS

There was no logical order in the color distribution of the two shade guides. The color of white and translucent shades of resin composites was located on the low CIE a* and CIE b* value area. The CIE L*, a*, b* values of resin composite with the same color designations were different, depending on the brand of material. The color difference (deltaE*) of shade guides by the measuring mode (SCE vs. SCI) was between 3.2 and 6.5.

Monodithiolene molybdenum(V, VI) complexes: a structural analogue of the oxidized active site of the sulfite oxidase enzyme family

The active sites of the xanthine oxidase and sulfite oxidase enzyme families contain one pterin-dithiolene cofactor ligand bound to a molybdenum atom. Consequently, monodithiolene molybdenum complexes have been sought by exploratory synthesis for structural and reactivity studies. Reaction of [MoO(S(2)C(2)Me(2))(2)](1-) or [MoO(bdt)(2)](1-) with PhSeCl results in removal of one dithiolate ligand and formation of [MoOCl(2)(S(2)C(2)Me(2))](1-) (1) or [MoOCl(2)(bdt)](1-) (2), which undergoes ligand substitution reactions to form other monodithiolene complexes [MoO(2-AdS)(2)(S(2)C(2)Me(2))](1-) (3), [MoO(SR)(2)(bdt)](1-) (R = 2-Ad (4), 2,4,6-Pr(i)(3)C(6)H(2) (5)), and [MoOCl(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)](1-) (6) (Ad = 2-adamantyl, bdt = benzene-1,2-dithiolate). These complexes have square pyramidal structures with apical oxo ligands, exhibit rhombic EPR spectra, and 3-5 are electrochemically reducible to Mo(IV)O species. Complexes 1-6 constitute the first examples of five-coordinate monodithiolene Mo(V)O complexes; 6 approaches the proposed structure of the high-pH form of sulfite oxidase. Treatment of [MoO(2)(OSiPh(3))(2)] with Li(2)(bdt) in THF affords [MoO(2)(OSiPh(3))(bdt)](1-) (8). Reaction of 8 with 2,4,6-Pr(i)(3)C(6)H(2)SH in acetonitrile gives [MoO(2)(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)](1-) (9, 55%). Complexes 8 and 9 are square pyramidal with apical and basal oxo ligands. With one dithiolene and one thiolate ligand of a square pyramidal Mo(VI)O(2)S(3) coordination unit, 9 closely resembles the oxidized sites in sulfite oxidase and assimilatory nitrate reductase as deduced from crystallography (sulfite oxidase) and Mo EXAFS. The complex is the first structural analogue of the active sites in fully oxidized members of the sulfite oxidase family. This work provides a starting point for the development of both structural and reactivity analogues of members of this family.

Nickel dithiolenes revisited: structures and electron distribution from density functional theory for the three-member electron-transfer series [Ni(S2C2Me2)2]0,1-,2-

The complexes [Ni(S2C2Me2)2](z) (z = 0, 1-, 2-) have been isolated for the purpose of investigating their electronic structures in a reversible three-member electron-transfer series. Members are interrelated by reversible redox reactions with E(1/2)(0/1-) = -0.15 V and E(1/2)(1-/2-) = -1.05 V versus SCE in acetonitrile. The three complexes have nearly planar structures of idealized D(2)(h) symmetry. As the series is traversed in the reducing direction, Ni-S and C-S bond lengths increase; the chelate ring C-C bond length decreases from the neutral complex to the monoanion and does not change significantly in the dianion. Structural trends are compared with previous results for [Ni(S2C2R2)2)](1-,2-). Following the geometrical changes, values of nu(Ni)(-)(S) and nu(C)(-)(S) decrease, while the value of nu(C)(-)(C) increases with increased reduction. Geometry optimizations at the density functional theory (DFT) level were performed for all members of the series. Geometrical parameters obtained from the calculations are in good agreement with the experimental findings. The 5b(2g) orbital was identified as the LUMO in [Ni(S2C2Me2)2], the SOMO in [Ni(S2C2Me2)2](1-), and the HOMO in [Ni(S2C2Me2)2]2-. Unlike in the situation in the [M(CO)2-(S2C2Me2)2]z series (M = Mo, W; z = 0, 1-, 2-), the apparent contribution from the metal d orbital in the electroactive orbital is not constant. In the present series, the d(xz) contribution increases from 13 to 20 to 39% upon passing from the neutral to the monoanionic to the dianionic complex. Accurate calculation of EPR g-values of [Ni(S2C2Me2)2]1- by DFT serves as a test for the reliability of the electronic structure calculations.

Color stability of glass-ionomers and polyacid-modified resin-based composites in various environmental solutions

PURPOSE

To evaluate the degree of color stability of glass-ionomers (GIs) and polyacid modified resin-based composites (PMRBCs) in various environmental solutions.

MATERIALS AND METHODS

Seven polyacid-based esthetic restorative materials were used: three chemical-cured GIs, one resin-modified GI and three polyacid-modified RBCs. A light-cured resin-based composite (RBC) (Z 100) was used as a control. Disk type specimens were prepared and were aged in four different solutions (deionized water, 0.1 mole acetic acid solution, 75% ethanol, and 10% hydrogen peroxide solution) for 1, 7, 14, 21, 28, and 56 days. The specimens were kept at 37 degrees C throughout the study. Color coefficients (CIE L*a*b*) were measured by a reflection spectrophotometer with SCE mode, and the surface of specimens was examined by a stereo zoom microscope.

RESULTS

In deionized water, all specimens showed an acceptable color stability. All of the GIs and PMRBCs showed significant color change in 0.1 mole acetic acid solution. The light-cured resin-modified GI showed a significant color change in 75% ethanol solutions. 10% hydrogen peroxide solution resulted in degradation and a high degree of color change for chemical-cured GIs. The light-cured resin-modified GI and PMRBCs showed high color change in 10% hydrogen peroxide solution. The light-cured RBC (Control), showed excellent color stability in all experimental solutions.

Bis(dithiolene)molybdenum analogues relevant to the DMSO reductase enzyme family: synthesis, structures, and oxygen atom transfer reactions and kinetics

A series of dithiolene complexes of the general type [Mo(IV)(QR')(S(2)C(2)Me(2))(2)](1)(-) has been prepared and structurally characterized as possible structural and reactivity analogues of reduced sites of the enzymes DMSOR and TMAOR (QR' = PhO(-), 2-AdO(-), Pr(i)()O(-)), dissimilatory nitrate reductase (QR' = 2-AdS(-)), and formate dehydrogenase (QR' = 2-AdSe(-)). The complexes are square pyramidal with the molybdenum atom positioned 0.74-0.80 A above the S(4) mean plane toward axial ligand QR'. In part on the basis of a recent clarification of the active site of oxidized Rhodobacter sphaeroides DMSOR (Li, H.-K.; Temple, C.; Rajagopalan, K. V.; Schindelin, H. J. Am. Chem. Soc. 2000, 122, 7673), we have adopted the minimal reaction paradigm Mo(IV) + XO right arrow over left arrow Mo(VI)O + X involving desoxo Mo(IV), monooxo Mo(VI), and substrate/product XO/X for direct oxygen atom transfer of DMSOR and TMAOR enzymes. The [Mo(OR')(S(2)C(2)Me(2))(2)](1)(-) species carry dithiolene and anionic oxygen ligands intended to simulate cofactor ligand and serinate binding in DMSOR and TMAOR catalytic sites. In systems with N-oxide and S-oxide substrates, the observed overall reaction sequence is [Mo(IV)(OR')(S(2)C(2)Me(2))(2)](1)(-) + XO --> [Mo(VI)O(OR')(S(2)C(2)Me(2))(2)](1)(-) --> [Mo(V)O(S(2)C(2)Me(2))(2)](1)(-). Direct oxo transfer in the first step has been proven by isotope labeling. The reactivity of [Mo(OPh)(S(2)C(2)Me(2))(2)](1)(-) (1) has been the most extensively studied. In second-order reactions, 1 reduces DMSO and (CH(2))(4)SO (k(2) approximately 10(-)(6), 10(-)(4) M(-)(1) s(-)(1); DeltaS(double dagger) = -36, -39 eu) and Me(3)NO (k(2) = 200 M(-)(1) s(-)(1); DeltaS(double dagger) = -21 eu) in acetonitrile at 298 K. Activation entropies indicate an associative transition state, which from relative rates and substrate properties is inferred to be concerted with X-O bond weakening and Mo-O bond making. The Mo(VI)O product in the first step, such as [Mo(VI)O(OR')(S(2)C(2)Me(2))(2)](1)(-), is an intermediate in the overall reaction sequence, inasmuch as it is too unstable to isolate and decays by an internal redox process to a Mo(V)O product, liberating an equimolar quantity of phenol. This research affords the first analogue reaction systems of biological N-oxide and S-oxide substrates that are based on desoxo Mo(IV) complexes with biologically relevant coordination. Oxo-transfer reactions in analogue systems are substantially slower than enzyme systems based on a k(cat)/K(M) criterion. An interpretation of this behavior requires more information on the rate-limiting step(s) in enzyme catalytic cycles. (2-Ad = 2-adamantyl, DMSOR = dimethyl sulfoxide reductase, TMAOR = trimethylamine N-oxide reductase)

Electron distribution in the nonclassical bis(dithiolene) electron transfer series [M(CO)2(S2C2Me2)2]0/1-/2- (M = Mo, W): assessment by structural, spectroscopic, and density functional theory results

The electron-transfer series [M(CO)2(S2C2Me2)2]0/1-/2- (series 2) have been established, and the previously reported series [M(S2C2Me2)3]0/1-/2- (series 3) confirmed, by voltammetry (M = Mo, W). Redox reactions are reversible with EMo > EW, and all members of each series have been isolated. Members of a given series have very similar distorted trigonal prismatic structures; isoelectronic complexes are isostructural. The existence of these series with structurally characterized members facilitates examination of geometric and electronic properties over three consecutive oxidation states. Upon traversing the series in the reducing direction, M-S, S-C, and C-O bond distances increase, and M-C, chelate ring C-C, and vCO values decrease. Density functional calculations identify the electroactive orbital, which is well separated in energy from other orbitals. Trends in bond lengths and vibrational frequencies in a given series are fully accountable in terms of increasing population of this orbital, whose composition is roughly constant across the series and is dominantly ligand (ca. 80%) in character. Consequently, redox reactions in the two series are essentially ligand-based. The noninnocent nature of dithiolene ligands in oxidized complexes has been long recognized. The results of DFT calculations provide a contemporary description of the delocalized ground states in the two series. The trends in parameters involving the carbonyl groups provide a particularly clear indication of the classical behavior of a pi-acceptor ligand in isostructural molecules subject to consecutive reductions over three oxidation states.

X-ray spectroscopy of enzyme active site analogues and related molecules: bis(dithiolene)molybdenum(IV) and -tungsten(IV,VI) complexes with variant terminal ligands

The X-ray absorption spectra at the molybdenum and selenium K-edges and the tungsten L2,3-edges are acquired for a set of 14 Mo(IV) and W(IV,VI) bis(dithiolene) complexes related to the active sites of molybdo- and tungstoenzymes. The set includes square pyramidal [MoIVL(S2C2Me2)2]- (L = O2-, R3SiO-, RO-, RS-, RSe-) and [WIV(OR)(S2C2Me2)2]-, distorted trigonal prismatic [MoIV(CO)(SeR)(S2C2Me2)2]- and [WIV(CO)L(S2C2Me2)2]- (L = RS-, RSe-), and distorted octahedral [WVIO(OR)(S2C2Me2)2]-. The dithiolene simulates the pterin-dithiolene cofactor ligand, and L represents a protein ligand. Bond lengths are determined by EXAFS analysis using the GNXAS protocol. Normalized edge spectra, non-phase-shift-corrected Fourier transforms, and EXAFS data and fits are presented. Bond lengths determined by EXAFS and X-ray crystallography agree to < or = 0.02 A as do the M-Se distances determined by both metal and selenium EXAFS. The complexes [MoIV(QR)(S2C2Me2)2]- simulate protein ligation by the DMSO reductase family of enzymes, including DMSO reductase itself (Q = O), dissimilatory nitrate reductase (Q = S), and formate dehydrogenase (Q = Se). Edge shifts of these complexes correlate with the ligand electronegativities. Terminal ligand binding is clearly distinguished in the presence of four Mo-S(dithiolene) interactions. Similarly, five-coordinate [ML(S2C2Me2)2]- and six-coordinate [M(CO)L(S2C2Me2)2]- are distinguishable by edge and EXAFS spectra. This study expands a previous XAS investigation of bis(dithiolene)metal(IV,V,VI) complexes (Musgrave, K. B.; Donahue, J. P.; Lorber, C.; Holm, R. H.; Hedman, B.; Hodgson, K. O. J. Am. Chem. Soc. 1999, 121, 10297) by including a larger inventory of molecules with variant physiologically relevant terminal ligation. The previous and present XAS results should prove useful in characterizing and refining metric features and structures of enzyme sites.

Synthesis and structures of bis(dithiolene)molybdenum complexes related to the active sites of the DMSO reductase enzyme family

Structural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes are sought. These sites usually contain two pterin-dithiolene cofactor ligands and one protein-based ligand. Reaction of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R = Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum-(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to [MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes [Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- affordthe trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1- (Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]- (9, 10). In contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1-(14, 15), which have not been successfully decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(mu-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(mu-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3-5, 7-10, 12-14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations. Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)

The antiemetic and dysphoric effects of droperidol in the day surgery patient

The incidence of side-effects of two doses of droperidol used as a prophylactic antiemetic were compared (10 vs 20 micrograms/kg). Two hundred and twenty-eight women for day case laparoscopy were recruited. Pain and nausea scores were collected in the recovery area and in the Day Surgery Unit prior to discharge. A telephone follow-up questionnaire was administered. Incidences of anxiety, restlessness and dysphoric reactions were similar in both groups (29.2% vs 29.0%). The incidence of postoperative vomiting varied from 4.4 to 7.7%. There were no significant differences between the two groups when nausea scores, incidences of vomiting and pain after discharge were compared. An unexpected finding was the significantly higher incidence of pain in the 10 micrograms/kg group. We conclude that there is no advantage in lowering the dose of droperidol below 20 micrograms/kg in this group of patients.

Intracorporeal ligation of the cystic duct during laparoscopic cholecystectomy

During laparoscopic cholecystectomy, the cystic duct (CD) is ligated in one of two ways: by clipping or by creating a knot outside the abdominal cavity and then introducing it into the cavity. A new technique allows safe ligation of the CD intracorporeally before its division by tying the knot at the site with absorbable tie material. To build the knot, a loosely constructed surgeon's square knot encircling the CD is converted to a slip knot, which is then cinched and tightened. The tightening process of the slip know is executed by winding the long tail clockwise around the left-hand needle holder (traction) While the right-hand needle holder winds the short tail counterclockwise (countertraction). The endpoint of the tightening is determined by feeling the amount of torque to both hands and by visual confirmation of the knot integrity. To prevent reverse slippage, three single, flat knots are tied in square fashion. The cystic artery has also been ligated intracorporeally during laparoscopic cholecystectomy using the same technique with the same positive results and without complications.

Comparison of a wipe and a vacuum collection method for the determination of lead in residential dusts

Lead-containing house dust is an important source of childhood lead exposure. Standard methods for collection of settled dust for evaluation of lead content have not been established. Little is known about the relationships between the various wipe and vacuum-based methods employed in past studies, preventing meaningful comparisons of results. This study characterized the relationship between a frequently used wipe dust collection method and a vacuum-based in-line filter method used to collect dust in a national survey of lead in paint and dust in U.S. housing. The correlation coefficient was 0.82 for estimates of lead loadings (PbD, mg/m2) from 71 pairs of side-by-side wipe and vacuum dust samples collected from uncarpeted floors, window sills, and exterior window wells in six dwellings. Geometric mean (GM) wipe PbD estimates exceeded those for vacuum samples by a factor of 3.9 and 5.7 for floors and window sills, respectively, findings consistent with the multiple sources of sample loss associated with the vacuum sampler. For window wells, the GM vacuum PbD estimate exceeded the GM wipe PbD estimate by a factor of 3.4, possibly due to the use of an alternative vacuum nozzle. The resulting increase in the estimated prevalence of U.S. homes with elevated dust lead loadings had wipe-sampling instead of vacuum-sampling methods been used in the national survey is discussed.