Patients with irritable bowel syndrome or constipation have an increased risk for ischaemic colitis

AIMS

To estimate the relative risk for ischaemic colitis in patients with and without irritable bowel syndrome or constipation, and to evaluate the role of irritable bowel syndrome and constipation as confounders in the relationship between commonly used gastrointestinal medications and ischaemic colitis.

METHODS

Patient cohorts were identified with the use of longitudinal MarketScan research databases from 1 January 1999 to 31 December 2002. Patients in each study cohort were matched 1:1 with comparable control patients using a propensity score. A Cox proportional hazards models were used to estimate relative risk for ischaemic colitis.

RESULTS

The relative risk for ischaemic colitis was 3.17 and 2.78 times higher for patients with irritable bowel syndrome and constipation, respectively, than for those without these disorders. Patients who were taking an antispasmodic, a proton pump inhibitor, or an H2-antagonist were at increased risk for ischaemic colitis [relative risk with 95% CI 2.73 (1.41-5.39), 2.00 (1.05-3.79), 2.75 (1.22-6.17) respectively]; however, when these results were adjusted for irritable bowel syndrome or constipation, the relative risks were attenuated and no longer statistically significant.

CONCLUSIONS

Patients with irritable bowel syndrome or constipation demonstrated a two- to threefold increased risk for ischaemic colitis. Moreover, irritable bowel syndrome and constipation strongly confounded the relationship between gastrointestinal drug use and the risk for ischaemic colitis, suggesting that etiologic studies of ischaemic colitis risk must account for the presence of irritable bowel syndrome or constipation.

Review of Reservoir Parameters to Optimize SAGD and Fast-SAGD Operating Conditions

Abstract

Although high recovery efficiency is expected from the SAGD process, high steam production costs and the substantial volumes of water required have made us focus on more effective recovery methods. One such method is the Fast-SAGD process which utilizes one or more offset horizontal wells parallel to the original SAGD well pair.

In these studies, simulations were used to examine the reservoir parameters and operating conditions that need to be in place to optimize the SAGD process. Based on the simulation of a typical Cold Lake reservoir in Alberta, the studies found that relatively clean sand reservoirs with a minimum thickness of 20 m and a vertical permeability of 2.5 Darcy are good candidates for the application of SAGD. Also, reservoirs in a fining upward depositional environment are ideally suited for a SAGD operation.

The results of our studies also showed that, for the same operating conditions, Fast-SAGD improved energy efficiency by 24% and productivity by 35% over SAGD. Fast-SAGD is therefore a more efficient recovery process requiring less steam and having lower operating costs to produce the same amount of bitumen.

The case of two offset wells located on either side of one SAGD well pair promises the most effective Fast-SAGD configuration, even if a total of six offset wells with a SAGD well pair is still economic compared to the conventional SAGD process. Cumulative bitumen production is increased and at the same time the cumulative steam-oil ratio is decreased as a result of higher thermal efficiency.

Introduction

Alberta's oil sands contain the largest crude bitumen resource in the world, having approximately 259 billion cubic metres of initial oil in-place and 27.7 billion cubic metres of remaining established reserves (see Tables 1a and 1b)(1). Over 80% of these reserves can be produced only by using in situ recovery methods; therefore, research to find more effective in situ recovery methods is encouraged.

The SAGD process has been tested in the field, and is now in a commercial stage of production in Western Canadian oil sands(2). The application of SAGD in various reservoir conditions has been studied, and recently research studies that can not only reduce the steam production cost but also enhance heat efficiency of the SAGD process have been conducted(3).

In our studies, the characteristics of the SAGD recovery method were reviewed. In addition, the proper reservoir conditions and optimized operating conditions for the SAGD process were researched by conducting numerical simulation. The possibility of applying the Fast-SAGD process, a modification of the SAGD process(4), was also investigated in comparison to conventional SAGD. Finally, the operating conditions for the optimization of the Fast-SAGD process were studied.

Variations of SAGD Process

Enhancements

The conventional SAGD process is a steam injection recovery method which uses two horizontal wells. In the Peace River area, a small pressure differential between adjacent pattern steam chambers was applied to enhance the SAGD process(5). A steam drive process can be applied to the SAGD operation once sufficient bitumen mobility has been obtained between steam chambers.

The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.

Fast-SAGD Application in the Alberta Oil Sands Areas

Abstract

Fast-SAGD, a modification of the SAGD process, makes use of additional single horizontal wells alongside the SAGD well pair to expand the steam chamber laterally. This method uses fewer wells and could reduce costs compared to a SAGD operation requiring paired parallel wells one above the other.

In this study, the Fast-SAGD process has been optimized through numerical reservoir simulations for the three typical oil sands areas in Alberta: Athabasca, Cold Lake, and Peace River. Two key reservoir parameters, reservoir thickness and vertical permeability, were screened under various operating conditions to characterize the optimal reservoir and operating conditions for the Fast-SAGD process. Economic analysis was then used for optimizing the Fast-SAGD operating conditions.

In most cases, the simulation results indicated improved energy efficiency and productivity for the Fast-SAGD process. In those cases, the project economics were enhanced compared to the SAGD process. Both Cold Lake- and Peace River-type reservoirs are good candidates for Fast-SAGD. In shallow Athabasca- type reservoirs, which are thick with high permeability, Fast-SAGD was shown to be almost as good as SAGD. This new process demonstrates improved efficiency and lower costs for extracting heavy oil from these important reservoirs.

Introduction

The steam assisted gravity drainage (SAGD) process was first implemented in Alberta and is now well established for the commercial production of bitumen from oil sands. Research studies(1–3) have found that the SAGD process is feasible for reservoirs thicker than 20 m with permeability in excess of 2 Darcies.

In the Fast-SAGD process, wells offset to the SAGD well pair, on either or both sides, are operated with cyclic steam stimulation (CSS) in order to accelerate the growth of the steam chamber Sideways(4). Moreover and consequent to such CSS, geomechanical stresses are larger than provided by industry's preferred relatively low-pressure SAGD to the extent that vertical drainage is enhanced significantly(5). Thus, Fast-SAGD uses fewer wells and achieves greater conformance and reduced costs compared to a SAGD operation.

Previous numerical studies(1, 5) of a typical Cold Lake-type reservoir have shown that the Fast-SAGD process enhances thermal efficiency, resulting in better production performance as compared to the conventional SAGD process.

In our study, Fast-SAGD operating conditions were optimized through numerical reservoir simulation for the three typical oil sands areas in Alberta: the shallow Athabasca (AB), the Cold Lake (CL), and the Peace River (PR). Two key reservoir parameters, reservoir thickness and permeability, were screened under various operating conditions to characterize the optimal reservoir for the Fast-SAGD process in each deposit.

A simple thermal efficiency parameter (STEP) was developed on the basis of three production performance parameters: cumulative steam-oil ratio (CSOR), calendar day oil rate (CDOR), and recovery factor (RF). It was validated as an economic indicator for optimizing SAGD performance(6, 7). This same economic indicator will also be used in this study to optimize the Fast-SAGD operating conditions.

Optimizing the Fast-SAGD Process

The Fast-SAGD process introduced by Polikar et al.(4) combines the SAGD and CSS processes. CSS helps the steam chamber formed by SAGD propagate sideways.

Induction chemotherapy with S-1 plus cisplatin in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN)

15501

Background: This study was to assess the efficacy and safety profiles of the combination treatment with S-1 and Cisplatin in patients with locally advanced SCCHN. Methods: Eligible patients were defined as histologically confirmed SCCHN, stage III or IV with no evidence of distant metastasis, evaluable lesions, adequate organ function, age of 20–80 years, and performance status 0,1 or 2. Cisplatin was infused over 1 hour on day 1 (75 mg/m2) and S-1 was administered orally for 14 consecutive days (day 2–15). The dosages of S-1 were assigned according to the patients’ body surface area (BSA): 50 mg twice a day (BSA < 1.5m2), 60 mg twice a day (BSA > 1.5m2). Each course was repeated every 3 weeks. After 2 course, tumor response were evaluated by CT scan and laryngoscopy. If the patients achieved a response (complete response: CR, or partial response: PR), they received one more course of chemotherapy before undergoing the radiotherapy or operation as a definitive local treatment. Results: All 22 patients were assessable for response and toxicity. The overall response was 80.9% (CR: 3, PR: 14). The adverse reactions occurred 120 times in 54 courses of 22 cases. The most common grade 3/4 adverse events were neutropenia, which occurred in 8 patients. Non-hematological toxicity of grade 3 and 4 included nausea and vomiting in 4 patients, fever in one patient and, fatigue in one patient. Since the observation period is short, the analysis about survival rate is not obtained so far. Conclusions: S-1 plus Cisplatin combination chemotherapy is effective against locally advanced SCCHN with mild toxicity.

No significant financial relationships to disclose.

Multicenter study of intravenous busulfan, cyclophosphamide, and etoposide (IV Bu/Cy/VP-16) as conditioning regimen for autologous stem cell transplantation in patients with non-Hodgkin’s lymphoma

17544

Background: The current study aimed to evaluate the efficacy and toxicity of the combination of intravenous busulfan, cyclophosphamide, and etoposide (IV Bu/Cy/VP-16) as a preparative regimen prior to autologous hematopoietic stem cell transplantation (ASCT) in patients with non-Hodgkin’s lymphoma (NHL). Methods: Forty patients with relapsed (n = 24) or high-risk (n = 16) lymphoma were enrolled into the study. High-dose chemotherapy consisted of intravenous busulfan (0.8 mg/kg i.v. q 6 hr from day-7 to day-5), cyclophosphamide (50 mg/kg i.v. on day-3 and day-2), and etoposide (400 mg/m2 i.v. on day-5 and day-4). Results: The median age of patients was 34 years (range, 17–63 years), and 21 (52.5%) patients were male. Pathologic subtypes were as follows: diffuse large B cell (n = 20), peripheral T cell, unspecified (n = 8), extranodal NK/T cell (n = 4), angioimmunoblastic T cell (n = 3), anaplastic large cell (n = 4), nodal marginal zone B cell (n = 2), and lymphoblastic (n = 3). The median dose of infused CD34+ cells and MNC was 3.95 (range, 0.7–20.6) × 106 and 8.12 (range, 3.0–13.6) × 108, respectively. WBC and platelet were successfully engrafted after ASCT in all patients, and the median days of engraftment of WBC and platelet was 12 (range, 9–48) and 27 (range, 8–263) days, respectively. After the ASCT, 34 complete responses (CR; 85.0%) and 4 partial responses (PR; 10.0%) were confirmed. Thirty-three (82.5%) patients experienced a fever without documented infection, while 2 patient developed fungal infection. However, there was no treatment-related death. After median follow-up duration of 360 (range, 83–639) days, 33 patients are in continuous complete remission, 4 patients are alive in relapse, and 3 patients died of disease. The estimated event-free and overall survival rate at 1.5-year was 80.9 ± 10.0 % and 92.5 ± 5.7 %, respectively. Conclusions: IV Bu/Cy/VP-16 was found to be well-tolerated and effective as a conditioning regimen in patients with NHL. Accordingly, this regimen can be regarded as an alternative high-dose treatment option in the ASCT for NHL.

No significant financial relationships to disclose.

Phase II study of capecitabine and irinotecan combination chemotherapy in patients with advanced gastric cancer

14037

Background: Several studies have shown the efficacy of capecitabine and irinotecan combination chemotherapy for advanced colorectal cancer, while no results have yet been reported for advanced gastric cancer. Accordingly, the current study evaluated the efficacy and safety of a combination regimen of capecitabine plus irinotecan in patients with advanced gastric cancer. Methods: Patients with previously untreated metastatic or recurrent, measurable gastric cancer received oral capecitabine 1000 mg/m2 twice daily from day 1 to 14 and intravenous irinotecan 100 mg/m2 on days 1 and 8, based on a 3-week cycle. Results: Forty-one patients were enrolled in the current study, among whom 38 were assessable for efficacy and 40 assessable for toxicity. Three complete responses and 16 partial responses were confirmed, giving an overall response rate of 46.3%. At a median follow-up of 269 days, the median time to progression and overall survival were 5.1 months and 8.6 months, respectively. Grade 3/4 neutropenia occurred in 4 patients and grade 3 febrile neutropenia was observed in 2 patients. Grade 3 diarrhea and grade 2 hand-foot syndrome occurred in 6 patients and 8 patients, respectively. Conclusions: The combination of capecitabine and irinotecan was found to be well tolerated and effective in patients with advanced gastric cancer. Accordingly, this regimen can be regarded as an important first-line treatment option for advanced gastric cancer.

No significant financial relationships to disclose.

CT-basierte Lebervolumetrie im Tiermodell: Bedeutung für die klinische Volumetrie im Rahmen der Leberlebendspende

PURPOSE

Exact preoperative determination of the liver volume is of great importance prior to hepatobiliary surgery, especially in living donated liver transplantation (LDLT). In the current literature, a strong correlation between preoperatively calculated and intraoperatively measured liver volumes has been described. Such accuracy seems questionable, primarily due to a difference in the perfusion state of the liver in situ versus after explantation. Purpose of the study was to asses the influence of the perfusion state on liver volume and the validity of the preoperative liver volumetry prior to LDLT.

METHODS

In an experimental study, 20 porcine livers were examined. The livers were weighted and their volumes were determined by water displacement prior and after fluid infusion to achieve a pressure physiologically found in the liver veins. The liver volumes in the different perfusion states were calculated based on CT-data. The calculated values were compared with the volume measured by water displacement and the weight of the livers.

RESULTS

Assessment of calculated CT volumes and water displacements at identical perfusion states showed a tight correlation and differed on average by 4 +/- 5 %. However, livers before and after fluid infusion showed a 33 +/- 8 % (350 +/- 150 ml) difference in volume.

CONCLUSION

CT-volumetry acquires highly accurate data as confirmed by water displacement studies. However, the perfusion state has major impact on liver volume, which has to be accounted for in clinical use.

Neurotrophin potentiation of iron-induced spinal cord injury

Previous studies have shown that pretreatment with neurotrophins can potentiate the vulnerability of cultured neurons to excitotoxic and free radical-induced necrosis, in contrast to their well known neuroprotective effects against apoptosis. Here we tested the hypothesis that this unexpected injury-potentiating effect of neurotrophins would also take place in the adult rat spinal cord. Fe(3+)-citrate was injected stereotaxically into spinal cord gray matter in adult rats in amounts sufficient to produce minimal tissue injury 24 h later. Twenty-four-hour pretreatment with brain-derived neurotrophic factor, neurotrophin-3, or neurotrophin-4/5, but not nerve growth factor, markedly enhanced tissue injury in the gray matter as evidenced by an increase in the damaged area, as well as the loss of neurons and oligodendrocytes. Consistent with maintained free radical mediation, the neurotrophin-potentiated iron-induced spinal cord damage was blocked by co-application of the antioxidant N-tert-butyl-(2-sulfophenyl)-nitrone. These data support the hypothesis that the overall neuroprotective properties of neurotrophins in models of acute injury to the spinal cord may be limited by an underlying potentiation of free radical-mediated necrosis.

Interactive PC-based volume rendering of CT datasets

In radiology, the reading of large CT volumes is a time consuming task. Interactive volume rendering (iVRT) is a promising new technique. Using dedicated hardware (VP1000, Terarecon Inc.) it can now be realized on a standard PC in a cost effective manner. For this purpose, a program built using the Visualization Toolkit with integrated functionality for the VP 1000 is used for almost real-time iVRT (8-9 frames/second). It is possible to embed opaque and translucent polygon surfaces (e.g., segmented structures). By interactively varying the opacity, color and gradient transfer functions as well as using freely placable cutting planes, the visualization can easily be adapted to different diagnostic needs.

Performance and membrane fouling in a pilot scale SBR process coupled with membrane

The performance of the pilot-scale submerged membrane coupled with sequencing batch reactor (SM-SBR) for upgrading effluent quality was investigated in this study. The reactor was operated with 3-hour cycle with alternating anoxic and aerobic conditions to treat organics, nitrogen and phosphate. Despite various influent characteristics, COD removal was always higher than 95%. Sufficient nitrification was obtained within a few weeks after start-up and during the stable period, complete nitrification occurred despite short aeration time. Total nitrogen (TN) removal efficiency was reached up to 85%. Membrane flux was critical for TN removal so that the decrease of flux by membrane fouling led to increase of HRT, and it caused the endogenous respiration of microorganisms such as nitrifying bacteria. The stirred cell test revealed the significant role of the soluble fraction in membrane permeability and dissolved solids played a major role in the short-term fouling mechanism. The cake resistance by the soluble COD fraction of supernatant or soluble microbial products (SMP) was investigated as a major part of total resistance.

Inhibitory effects of long-chain fatty acids on VFA degradation and beta-oxidation

The inhibitory effects of major long-chain fatty acids (LCFA), which have 16 or 18 carbons, not only on acetate degradation, but also on propionate degradation and beta-oxidation were examined in anaerobic serum bottle tests at 35 degrees C with the acclimated granular sludges. A modified Gompertz equation described cumulative methane production to assess the rates of VFA degradation and beta-oxidation, which were applied to a simplified noncompetitive model and a simplified substrate inhibition model, respectively. The specific methane production rates on acetate decreased as LCFA concentration increased, which was in good agreement with the noncompetitive inhibition model. Unsaturated oleate (C18:1) and linoleate (C18:2) were more inhibitory than saturated stearate (C18:0) and palmitate (C16:0) on acetate degradation. LCFA inhibition on propionate degradation was similar to that for acetate; however, propionate degradation was less inhibited than acetate degradation. Beta-oxidation was the rate-limiting step in LCFA degradation in most cases. As LCFA concentration increased, beta-oxidation rate reached the maximum value, and then decreased, which confirmed the substrate inhibition of LCFA. Oleate, the most abundant LCFA in wastewater, could be degraded more quickly than saturated LCFA containing the same or even less carbon in spite of relatively high toxicity on acetate degradation.

Modification of oligo(poly(ethylene glycol) fumarate) macromer with a GRGD peptide for the preparation of functionalized polymer networks

A novel macromer, oligo(poly(ethylene glycol) fumarate) (OPF), was synthesized by the reaction between poly(ethylene glycol) (PEG) of molecular weight 1000 (PEG 1.0K) and fumaryl chloride. The oligo(PEG fumarate) (OPF 1.0K) was modified with a peptide known to modulate cellular functions, Gly-Arg-Gly-Asp (GRGD), after being activated with 4-nitrophenyl chloroformate (NPC). The determined yield of the GRGD modification in 0.1 M sodium bicarbonate buffer of pH 8.3 was 83% as determined by NMR measurements. The OPF 1.0K and the OPF 1.0K modified with GRGD were cross-linked with an unsaturated biodegradable polyester, poly(propylene fumarate) (PPF), by photopolymerization. The cross-linked PPF was characterized by Fourier transform infrared (FT-IR) spectroscopy and contact angle measurements. The equilibrium contact angle of water on the cross-linked PPF surface decreased with the incorporation of OPF 1.0K and the OPF 1.0K modified with GRGD. The results suggest that the OPF macromer can be used for the preparation of functionalized networks incorporating cell adhesion specific sequences.