bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forcing neural progenitor cells to cycle is insufficient to alter cell-fate decision and timing of neuronal differentiation in the spinal cord
Authors: Lobjois Valérie , Bel-Vialar Sophie , Trousse Françoise , Pituello Fabienne 
Published: February 2008

Abstract
Background
During the development of the nervous system, neural progenitor cells can either stay in the pool of proliferating undifferentiated cells or exit the cell cycle and differentiate. Two main factors will determine the fate of a neural progenitor cell: its position within the neuroepithelium and the time at which the cell initiates differentiation. In this paper we investigated the importance of the timing of cell cycle exit on cell-fate decision by forcing neural progenitors to cycle and studying the consequences on specification and differentiation programs.

Results
As a model, we chose the spinal progenitors of motor neurons (pMNs), which switch cell-fate from motor neurons to oligodendrocytes with time. To keep pMNs in the cell cycle, we forced the expression of G1-phase regulators, the D-type cyclins. We observed that keeping neural progenitor cells cycling is not sufficient to retain them in the progenitor domain (ventricular zone); transgenic cells instead migrate to the differentiating field (mantle zone) regardless of cell cycle exit. Cycling cells located in the mantle zone do not retain markers of neural progenitor cells such as Sox2 or Olig2 but upregulate transcription factors involved in motor neuron specification, including MNR2 and Islet1/2. These cycling cells also progress through neuronal differentiation to axonal extension. We also observed mitotic cells displaying all the features of differentiating motor neurons, including axonal projection via the ventral root. However, the rapid decrease observed in the proliferation rate of the transgenic motor neuron population suggests that they undergo only a limited number of divisions. Finally, quantification of the incidence of the phenotype in young and more mature neuroepithelium has allowed us to propose that once the transcriptional program assigning neural progenitor cells to a subtype of neurons is set up, transgenic cells progress in their program of differentiation regardless of cell cycle exit.

Conclusion
Our findings indicate that maintaining neural progenitor cells in proliferation is insufficient to prevent differentiation or alter cell-fate choice. Furthermore, our results indicate that the programs of neuronal specification and differentiation are controlled independently of cell cycle exit.
Differentiation of naive CD4+ T cells into CD4+CD25+FOXP3+ regulatory T cells by continuous antigen stimulation
Authors: Mahic Milada , Yaqub Sheraz , Bryn Tone , Henjum Karen , Eide Dag M , Torgersen Knut M , Aandahl Einar M , Taskén Kjetil 
Published: February 2008

AbstractHuman CD4+CD25+ regulatory T (TR) cells express the transcription factor forkhead box p3 (FOXP3) and have potent immunosuppressive properties. While naturally occurring TR cells develop in the thymus, adaptive TR cells develop in the periphery from naive CD4+ T cells. Adaptive TR cells may express cyclooxygenase type 2 (COX-2) and suppress effector T cells by a PGE2-dependent mechanism, which is reversible with COX inhibitors. In this study we have characterized the differentiation of naive CD4+ T cells into adaptive TR cells in detail during 7 days of continuous antigen stimulation. After 2 days of stimulation of CD4+CD25– T cells, the cells expressed FOXP3 and COX-2 and displayed potent immunosuppressive properties. The suppressive phenotype was present at all observed time-points from Day 2, although suppression was merely present at Day 7. The adaptive TR cells expressed cell surface markers consistent with an activated phenotype and secreted high levels of TGF-β, IL-10, and PGE2. However, the suppressive phenotype was found exclusively in cells that proliferated upon activation. These data support the notion that activation of naive CD4+ T cells leads to concomitant acquisition of effector and suppressive properties.
A Prospective Study of Gastric Carcinoids and Enterochromaffin-Like Cell Changes in Multiple Endocrine Neoplasia Type 1 and Zollinger-Ellison Syndrome: Identification of Risk Factors
Authors: Berna Marc J. , Annibale Bruno , Marignani Massimo , Luong Tu Vinh , Corleto Vito , Pace Andrea , Ito Tetsuhide , Liewehr David , Venzon David J. , Delle Fave Gianfranco , Bordi Cesare , Jensen Robert T. 
Published: February 2008

Abstract
Context: Multiple endocrine neoplasia type 1 (MEN1) patients frequently develop Zollinger-Ellison syndrome (ZES). These patients can develop proliferative changes of gastric enterochromaffin-like (ECL) cells and gastric carcinoids (ECL-cell tumors). ECL-cell changes have been extensively studied in sporadic ZES patients and can be precursor lesions of gastric carcinoids, but little is known about factors influencing their severity or development of carcinoids in MEN1/ZES patients.
Objectives: Our objective was to prospectively analyze ECL-cell changes and gastric carcinoids (ECL-cell tumors) in a large series of MEN1/ZES patients to detect risk factors and deduct clinical guidelines.
Setting and Patients: Fifty-seven consecutive MEN1/ZES patients participated in this prospective study at two tertiary-care research centers.
Interventions and Outcome Measures: Assessment of MEN1, gastric hypersecretion, and gastroscopy with multiple biopsies was done according to a fixed protocol and tumor status. ECL-cell changes and α-human chorionic gonadotropin staining were assessed in each biopsy and correlated with clinical, laboratory, and MEN1 features.
Results: ECL-cell proliferative changes were universally present, advanced changes in 53% and carcinoids in 23%. Gastric nodules are common and are frequently associated with carcinoids. Patients with high fasting serum gastrin levels, long disease duration, or a strong α-human chorionic gonadotropin staining in a biopsy are at higher risk for an advanced ECL-cell lesion and/or gastric carcinoid.
Conclusions: Gastric carcinoids and/or advanced ECL-cell changes are frequent in MEN1/ZES patients, and therefore, regular surveillance gastroscopy with multiple routine biopsies and biopsies of all mucosal lesions are essential. Clinical/laboratory data and biopsy results can be used to identify a subgroup of MEN1/ZES patients with a significantly increased risk for developing gastric carcinoids, allowing development of better surveillance strategies.
Pharmacokinetics of the sequential metabolites of loteprednol etabonate in rats
Authors: Wu Whei-Mei , Huang Fenglei , Lee Yangsuk , Buchwald Peter , Bodor Nicholas 
Published: February 2008

Abstract
Pharmacokinetics, metabolism and excretion of two sequential inactive metabolites of the soft corticosteroid loteprednol etabonate (LE), Δ1-cortienic acid etabonate (AE) and Δ1-cortienic acid (A), have been investigated in rats. Pharmacokinetic studies (two-compartment model, 10 mg kg−1 intravenous bolus of AE or A) found the elimination of both AE (t1/2(β), 12.46 ± 1.18 min; CLtotal, 101.94 ± 5.80 mL min−1 kg−1; and Kel, 0.24 ± 0.02 min−1) and A (t1/2(β), 14.62 ± 0.46 min; CLtotal, 53.80 ± 1.40 mL min−1 kg−1; and Kel, 0.18 ± 0.02 min−1) to be significantly faster than that previously determined for the parent LE (t1/2(β), 43.41 ± 7.58 min; CLtotal, 67.40 ± 11.60 mL min−1 kg−1; and Kel, 0.071 ± 0.024 min−1). For metabolism and excretion evaluations, 1 and 10 mg kg−1 of either AE or A were intravenously administered, and the urine and bile were collected. AE and A rapidly reached their peak concentrations in the bile and urine, and most of them were eliminated within one hour. Total cumulative excretions at 4 h after 1 and 10 mg kg−1 injections were 85.51 ± 3.38% and 67.50 ± 2.67% for AE, and 71.90 ± 3.72% and 37.73 ± 2.69% for A in bile; and 4.84 ± 1.87% and 13.85 ± 3.27% for AE, and 24.28 ± 8.44% and 22.35 ± 1.12% for A in urine, respectively. After AE administration, the excretion of AE was &gt; 90%, and A was &lt; 10% in all cases, indicating that the elimination of AE was much faster than its metabolism (to A). In a manner similar to that seen for LE, dose-dependent elimination was observed both in AE and A. These results suggested that both AE and A were ideal leads for the design of soft steroids based on the inactive metabolite approach.
Spermicidal activity of sulfonylureas and meglitinide analogues: role of intrasperm Ca2+ elevation
Authors: Kumar Naveen , Jain Subheet , Gupta Anshu , Tiwary Ashok Kumar 
Published: February 2008

Abstract
Intrasperm calcium concentration ([Ca2+]is) is known to play a vital role in regulating motility and viability of ejaculated spermatozoa. KATP channel blockers are reported to block KATP channels, leading to depolarization of the cell membrane. This activates the voltage-gated calcium channels, resulting in enhanced Ca2+ influx, which eventually elevates the intracellular [Ca2+] level. Hence, it can be hypothesized that drugs acting on KATP channels could possess the ability to elevate [Ca2+]is. Sulfonylureas such as glibenclamide or gliclazide, as well as meglitinide analogues such as repaglinide, produced a dose- and time-dependent decrease in viability, each requiring 7.5 mm, 10 mm and 6.5 mm, respectively, to produce death of all sperm cells immediately upon addition to ejaculated human semen samples. The reduction in sperm viability was accompanied by an elevation of [Ca2+]is and was affected by removal of extracellular Ca2+. Significantly (P &lt; 0.05) less time was required to elevate [Ca2+]is and produce complete loss of sperm viability when any of these drugs were added to sperm cells simultaneously with selected agents affecting Ca2+ homeostasis. Thus, the spermicidal activity of these drugs attributed to elevation of [Ca2+]is and their synergism can be potentially exploited for developing contact spermicidal formulations.
Pharmacological profile of an essential oil derived from Melissa officinalis with anti-agitation properties: focus on ligand-gated channels
Authors: Abuhamdah Sawsan , Huang Liping , Elliott Mark S J , Howes Melanie-Jayne R , Ballard Clive , Holmes Clive , Burns Alistair , Perry Elaine K , Francis Paul T , Lees George , Chazot Paul L 
Published: February 2008

Abstract
A dual radioligand binding and electrophysiological study, focusing on a range of ligand-gated ion channels, was performed with a chemically-validated essential oil derived from Melissa officinalis (MO), which has shown clinical benefit in treating agitation. MO inhibited binding of [35S] t-butylbicyclophosphorothionate (TBPS) to the rat forebrain gamma-aminobutyric acid (GABA)A receptor channel (apparent IC50 0.040±0.001 mg mL−1), but had no effect on N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropianate (AMPA) or nicotinic acetylcholine receptors. Electrophysiological analyses with primary cultures of rat cortical neurons demonstrated that MO reversibly inhibited GABA-induced currents in a concentration-dependent manner (0.01–1 mg mL−1), whereas no inhibition of NMDA- or AMPA-induced currents was noted. Interestingly, MO elicited a significant dose-dependent reduction in both inhibitory and excitatory transmission, with a net depressant effect on neurotransmission (in contrast to the classical GABAA antagonist picrotoxinin which evoked profound epileptiform burst firing in these cells). The anti-agitation effects in patients and the depressant effects of MO in in-vitro we report in neural membranes are unlikely to reflect a sedative interaction with any of the ionotropic receptors examined here.
Foolproof Completions for High-Rate Production Wells
Authors: Ehlig-Economides C. A. , Tosic S. , Economides M. J. 
Published: February 2008

Abstract
Operators, especially those managing production from deepwater reservoirs, are striving to produce hydrocarbons at higher and higher rates without exposing the wells to completion failure risk. To avoid screen failures, recent studies have favored high rate water pack (HRWP) completions over high-permeability fracturing (HPF), known in the vernacular as a frac&pack (FP) for very high rate wells. While a properly designed gravel pack (GP) completion may prevent sand production, it does not stop formation fines migration, and, over time, fines accumulation in the GP will lead to increasing completion skin. Although, and not always, the skin can be removed by acidizing, it is not practical to perform repeated acid treatments on deepwater wells, particularly those with subsea wellheads, and the alternative has been to subject the completion to increasingly high drawdown, accepting a high skin effect. A far better solution is to use a HPF completion. Of course the execution of a successful HPF is not a trivial exercise, and frequently, there is a steep learning curve for such a practice.
This paper explains the importance in HPF completions of the well trajectory through the interval to be hydraulically fractured, for production, not execution, reasons. A new model quantifies the effect of the well inclination on the connectivity between the fracture and the well via perforations both in terms of the total skin and the screen flow velocity. Guidelines are provided based on the maximum target production rate, including forecasts of multiphase flow, to size the HPF completion to avoid common completion failures that may result from high fluid rate and/or fines movement. Once the HPF is properly designed and executed, the operator should end up with a long term low skin good completion quality well that can be safely produced at the maximum flow rates, with no need for well surveillance and monitoring.
Innovative Water-Shutoff Solution Enhances Oil Recovery From a West Venezuela Sandstone Reservoir
Authors: Andersson Goran , Molesworth Gregg , González Belkis , Al-Harthy Salah , Lian Eric 
Published: February 2008

Abstract
With the discovery of new fields becoming less common and the continued development of brownfields, water control is becoming increasingly essential to enhancing oil recovery. Water control operations are especially challenging in under-pressured reservoirs with openhole completions, such as in the Boscan field in West Venezuela. Gravel-packed slotted liners and standalone premium screens are common completion methods in this field.
Dual injection, combined with permanent water shutoff (WSO) gels or relative permeability modifiers to control water production in these completions has traditionally produced inconsistent results. This method can fail to change the well production profile and possibly damage oil-producing layers.
This paper will discuss the development, implementation, and results of an innovative solution for water shutoff that was engineered for the complex completion methods mentioned. The solution involves three key stages; the temporary isolation of the producing layers, the permanent shutoff of the water zones, and the effective cleanup of the isolated producing layers.
The results of ten water control treatments are presented here. The average water cut was reduced to 30% from 88% and oil production was increased by an average of 300 BOPD per well through the application of this water shut-off solution.
In one particular well, two previous water control treatments using a conventional water shutoff technique, including a relative permeability modifier (RPM), had left the well producing 100% water. The new solution reduced the water cut to 25%, resulting in a gain in oil production of 300 BOPD. This innovative solution was established as a standard practice for water shutoff in the Boscan field.
Water Hammer Effects on Water Injection Well Performance and Longevity
Authors: Wang Xiuli , Hovem Knut , Moos Daniel , Quan Youli 
Published: February 2008

Abstract
Water hammer effects resulting from the shutting in of water injection wells are an often ignored issue in petroleum production operations but they have considerable impact on injection well performance and longevity. Mismanaged, they can result in substantial and perhaps irreparable damage. This paper presents a study on the creation and propagation of water hammer due to rapid shut-in of water injectors.
Water hammer1-4 or pressure surge, is a pressure transient phenomenon which has long been known to occur as a result of a sudden change in fluid flow velocity. In water injectors, rapid shut-in creates a water hammer. Over time, injectors that undergo repeated rapid shut-ins often have significantly reduced injectivity and show evidence of sanding and even failure of the down-hole completion5. It is therefore critical to understand the nature of water hammer including the magnitude, frequency, and energy dissipation.
To study the water hammer in water injectors, a field trial was conducted to record pressure pulses generated from rapid shut-ins, at different well depths, in a soft formation, cased and perforated (C&P) water injector. Modeling work was conducted to understand the data.
The results of the field trial and model work demonstrated that:
The magnitude of the first pressure pulse due to abrupt shut-in can be estimated by using the equation: Δp = V×ρ×c, where V is the flow velocity, ρ is the fluid density, and c is the speed of propagation of a pressure signal along the well. High rate sampling (up to 100 samples/second) is required to capture subtle details of the water hammer signal. Water hammer can be modeled as a low-frequency pressure wave similar to the higher frequency Stoneley waves produced during VSP and by acoustic logging tools. Models of water hammer propagation in a synthetic analog of the test well reproduced most of the details of the signals recorded during the tests.
Manganese-Tetraoxide-Weighted Invert Emulsions as Completion Fluids
Authors: Moroni L. P. , Fraser J. R. , Somerset R. , Jones A. , Guarneri A. 
Published: February 2008

Abstract
Traditionally, completion equipment has been run in clear fluids, brines, or base oils, to minimize the potential for solids to plug equipment, preventing tools from being set correctly or setting prematurely. However, both brines and base oils have limitations. Base oils typically have densities around 0.8 sg which has well control implications and brines can become prohibitively expensive where high densities are required.
In the North Sea, many wells are either highly deviated or require extended reach to access compartmentalised reservoirs. Consequently, the reservoir often comprises a significant proportion of shales. The use of brine as a completion fluid can therefore lead to significant wellbore instability and reservoir impairment issues.
A novel approach has been employed by a UK operator to address these problems by compromising between the shale stability provided by oil and the density achievable with brine. The fluid employed is a low-solids, invert emulsion formulated with a high-density internal phase brine. Due to the density limit of the base solids-free brine, additional density is achieved through the use of manganese tetraoxide (Mn3O4). Manganese tetraoxide has a very small, sub-micron, particle size which allows a degree of self suspension thus allowing a fluid with low viscosities to be utilized. The use of this type of formulation provides a fluid which gives good wellbore stability while running completions screens but allows the completion fluid to be produced back in the testing phase of the well without plugging the screens due to the extremely fine particle size of the manganese tetraoxide. This fluid was designed to exhibit excellent sag performance while minimizing the gellation potential of the fluid. The physical characteristics of manganese tetraoxide (small spherical particles) were an important factor in the design of the fluid due to the very tight clearances expected when setting downhole tools.
This paper presents laboratory design data and case histories from the UK sector of the North Sea and in Kazakhstan where this type of high-density fluid has been used to run the lower completions while successfully maintaining wellbore stability.
Successful Combination of an Organically Crosslinked Polymer System and a Rigid-Setting Material for Conformance Control in Mexico
Authors: Deolarte Carlos , Vasquez Julio , Soriano Eduardo , Santillan Arturo 
Published: February 2008

Abstract
The Cantarell field, a mature reservoir offshore Mexico, presents significant water management problems because the hydrocarbon production comes from a naturally fractured carbonate reservoir. Controlling water production in the Cantarell field becomes more critical because of its limited water-handling facilities. This paper presents the field application of two systems widely used in the petroleum industry for water control: (1) an organically crosslinked polymer (OCP) system and (2) a rigid-setting material (RSM) system.
The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). To date, more than 100 jobs have been performed in Mexico with this system to address conformance problems such as water coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and casing-leak repair. This system can penetrate deep into the matrix of the rock or fractures to provide a more efficient water shutoff. The RSM system is a rigid "cement-like" setting material that has a right-angle set. Unlike cement, the RSM system is capable of rapidly developing high compressive strength to avoid losing the treatment to the formation before setting and will not invade the formation. The RSM system is for near-wellbore applications.
Several case histories are presented in this paper to show the application of these two water-shutoff systems together. The OCP system was used for deep matrix/fracture penetration while the RSM system was used as a tail-in because of its fast-setting properties and its capability to stop gas migration. These advanced water-control technologies have extended the well life and profitability of the treated wells. In the past, many of these wells were abandoned because of the limited water-handling facilities.
Removal of Filter Cake Formed by Manganese Tetraoxide Based-Drilling Fluids
Authors: Al Moajil A. , Nasr-El-Din H. A. , Al-Yami A. , Al-Aamri A. , Al-Aqil A. 
Published: February 2008

Abstract
Manganese tetraoxide (Mn3O4) has been recently used as a weighting material for water-based drilling fluids (Al-Yami et al., 2007). Mn3O4 particles are spherical, 1-2 µm in diameter, and have a specific gravity of 4.8 g/cm3. A mud (102 ± 5 pcf) was developed to drill deep gas wells. The filter cake formed by this fluid contained polymers (starch, XC-polymer, and polyanionic cellulose polymers), Mn3O4 and a small amount of CaCO3. Unlike CaCO3, Mn3O4 is a strong oxidizer and, as a result, HCl not recommended to be used to remove the filter cake. The objective of this work is to develop a new cleaning fluid to effectively and safely remove the filter cake that contains large amounts of Mn3O4.
Various organic acids, chelating agents, enzymes, and a combination of these chemicals were tested up to 300 °F. Characterization of filter cake before and after soaking in several cleaning fluids were conducted using XRD/XRF/SEM techniques. Solubility of Mn3O4 was conducted using various acids and chelating agents at different temperatures up to 284 °F and 200 psi. The concentration of manganese in spent chemicals was measured using Inductivity Coupled Plasma (ICP).
Extensive lab testing indicated that Mn3O4 particles in the filter cake were coated by polymeric materials that acted as a barrier. The coating material reduced the ability of cleaning fluids to remove filter cake. The efficiency of cleaning fluid was improved by soaking filter cake in a starch specific enzyme, and then applying the cleaning fluids. HCl, citric, and in-situ lactic acid were found to be the most effective fluids in dissolving Mn3O4 particles. This paper will discuss the characteristics of filter cake and the effectiveness of various cleaning fluids. New cleaning fluids were designed to remove Mn3O4 filter cake, while maintaining the integrity of the formation and well tubulars.