bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethanol consumption increases blood pressure and alters the responsiveness of the mesenteric vasculature in rats
Authors: Tirapelli Carlos R , Leone Andreia F C , Yogi Alvaro , Tostes Rita C , Lanchote Vera L , Uyemura Sergio A , Resstel Leonardo B M , Corrêa Fernando M A , Padovan Cláudia M , de Oliveira Ana M , Coelho Eduardo B 
Published: February 2008

Abstract
Chronic ethanol consumption and hypertension are related. In the current study we investigated whether changes in reactivity of the mesenteric arterial bed could account for the increased blood pressure associated with chronic ethanol intake. Changes in reactivity to phenylephrine and acetylcholine were investigated in the perfused mesenteric bed from rats treated with ethanol for 2 or 6 weeks and their age-matched controls. Mild hypertension was observed in chronically ethanol-treated rats. Treatment of rats for 6 weeks induced an increase in the contractile response of endothelium-intact mesenteric bed to phenylephrine, but not denuded rat mesenteric bed. The phenylephrine-induced increase in perfusion pressure was not altered after 2 weeks' treatment with ethanol. Moreover, acetylcholine-induced endothelium-dependent relaxation was reduced by ethanol treatment for 6 weeks, but not 2 weeks. Pre-treatment with indometacin, a cyclooxygenase inhibitor, reduced the maximum effect induced by phenylephrine (Emax) in endothelium-intact mesenteric bed from both control and ethanol-treated rats. No differences in the Emax values for phenylephrine were observed between groups in the presence of indometacin. l-NNA, a nitric oxide (NO) synthase (NOS) inhibitor, increased the Emax for phenylephrine in endothelium-intact mesenteric bed from control rats but not from ethanol-treated rats. Levels of endothelial NOS (eNOS) mRNA were not altered by chronic ethanol consumption. However, chronic ethanol intake strongly reduced eNOS protein levels in the mesenteric bed. This study shows that chronic ethanol consumption increases blood pressure and alters the reactivity of the mesenteric bed. Moreover, the increased vascular response to phenylephrine observed in the mesenteric bed is maintained by two mechanisms: an increased release of endothelial-derived vasoconstrictor prostanoids and a reduced modulatory action of endothelial NO, which seems to be associated with reduced post-transcriptional expression of eNOS.
Neuroprotective effects of breviscapine against apoptosis induced by transient focal cerebral ischaemia in rats
Authors: Yiming Liu , Wei He , Aihua Lin , Fandian Zeng 
Published: February 2008

Abstract
Breviscapine, a flavonoid isolated from the traditional Chinese medicinal herb Erigerin breviscapus, has been proved to be effective in protecting the brain against ischaemic damage, but the mechanisms remain unknown. In this study, we have demonstrated the effects of breviscapine on neuronal apoptosis in a rat model of transient focal cerebral ischaemia. Rats were administered with breviscapine (50 or 100 mg kg−1/day) intragastrically for seven successive days, then subjected to 2-h brain ischaemia induced by middle cerebral artery occlusion, followed by 24-h reperfusion. After reperfusion, the rats were killed and the brain samples were collected. Haematoxylin-eosin staining was used to evaluate the histopathological changes. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) and flow cytometry (FCM) analysis were used to detect the level of apoptosis. The expressions of bcl-2 and caspase-3 in the cortex were determined by Western blot. Significant increases in the number of haematoxylin-eosin- and TUNEL-positive staining cells and DNA fragmentation were observed at 24h after reperfusion, and the increases were inhibited by breviscapine (50 and 100 mg kg−1). Breviscapine at both doses markedly inhibited the expression and activation of caspase-3 and up-regulated the expression of bcl-2. These findings suggested that breviscapine attenuated neuroapoptosis and regulated the protein expression related to apoptosis after transient focal cerebral ischaemia, which may have contributed, in part, to the protective effects of breviscapine on cerebral ischaemic damage.
Quercetin does not alter lipopolysaccharide-induced fever in rats
Authors: Kanashiro Alexandre , Machado Renes R , Malvar David do C , Aguiar Fernando A , Souza Glória E P 
Published: February 2008

AbstractFever is considered an important component of the acute phase response of the body in defence against invading organisms such as bacteria. Quercetin, an important representative of the flavonoid class, has been extensively studied as an anti-inflammatory agent. In the present study, we investigated the effect of quercetin, administered orally (5, 25 and 50 mg kg−1) or intraperitoneally (50 mg kg−1), on the febrile response induced by either intraperitoneally (50 μg kg−1) or intravenously (5 μg kg−1) injected lipopolysaccharide (LPS from Escherichia coli) in rats. In contrast with the well known anti-inflammatory activity of quercetin, the results demonstrate that quercetin, at the doses used, did not alter the fever induced by LPS, regardless of the route of administration.
Transport ofSchisandra chinensisextract and its biologically-active constituents across Caco-2 cell monolayers — an in-vitro model of intestinal transport
Authors: Madgula Vamsi L M , Avula Bharathi , Choi Young W , Pullela Srinivas V , Khan Ikhlas A , Walker Larry A , Khan Shabana I 
Published: February 2008

AbstractWe have determined the intestinal transport of Schisandra chinensis extract and its lignans (gomisin A, gomisin N and schisandrin C) in the Caco-2 cell monolayer model. The transport across monolayers was examined for 2 h in absorptive and secretory directions. Quantitation of lignans was performed by HPLC. Out of the three lignans, gomisin A exhibited bi-directional transport, with Papp values in the range of 25–29 × 10−6 cm s−1, indicating a passive diffusion. Gomisin N, mixture and Schisandra extract displayed a higher transport in the secretory direction with efflux ratios in the range of 2.2–5.2. The efflux was decreased in the presence of inhibitors of multidrug resistance protein (MRP) transporter (MK-571) and P-glycoprotein (verapamil) indicating a possible involvement of an efflux pump and MRP in the transport of Schisandra lignans. Poor transport of schisandrin C was observed which could not be quantitated. The permeability of gomisin A in the isolated form was significantly different compared with the mixture or extract.
Thiolated chitosans: useful excipients for oral drug delivery
Authors: Werle Martin , Bernkop-Schnürch Andreas 
Published: February 2008

Abstract
To improve the bioavailability of orally administered drugs, formulations based on polymers are of great interest for pharmaceutical technologists. Thiolated chitosans are multifunctional polymers that exhibit improved mucoadhesive, cohesive and permeation-enhancing as well as efflux-pump-inhibitory properties. They can be synthesized by derivatization of the primary amino groups of chitosan with coupling reagents bearing thiol functions. Various data gained in-vitro as well as in-vivo studies clearly demonstrate the potential of thiolated chitosans for oral drug delivery. Within the current review, the synthesis and characterization of thiolated chitosans so far developed is summarized. Features of thiolated chitosans important for oral drug delivery are discussed as well. Moreover, different formulation approaches, such as matrix tablets and micro-/nanoparticles, as well as the applicability of thiolated chitosans for the oral delivery of various substance classes including peptides and efflux pump substrates, are highlighted.
Modeling of Permeability Impairment by Invasion of Solid Suspension During Waterflooding in Heterogeneous Porous Media
Authors: Moghadasi Jamshid 
Published: February 2008

Abstract
Waterflooding is one of the economically viable techniques for recovery of additional oil from mature fields. However, the brine used for it frequently contains suspended fine particles, which can deposit over the injection formation face and inside the adjacent wellbore formation to reduce the injectivity of the Waterflooding wells. In the state-of-the-art approaches of formation damage modeling by solid invasion, the heterogeneities of porous media should be considered. Sandstone invariably have small-scale heterogeneities, that may cause the effect of injected fluid carrying suspended particles on permeability alteration, to differ from what is predicted by a model based on a homogeneous formation.
The objective of this paper is to develop a mathematical model according to an overall mass balance, to investigate the effect of local heterogeneity of rock properties on permeability impairment by movement and deposition of solid particles instead of assuming a uniform porosity/permeability distribution as was used in the pervious models presented in the literature. The heterogeneous original porosity has been generated using standard geostatistical techniques.
Prediction of Influx Rate and Volume for Planning UBD Horizontal Wells To Reduce Formation Damage
Authors: Guo Boyun , Feng Yin , Ghalambor Ali 
Published: February 2008

Abstract
Underbalanced drilling (UBD) has been widely used as a means of reducing formation damage during drilling. The benefit of reduced formation damage results from the fact that the borehole pressure is intentionally maintained to be lower than formation pore pressure during drilling the pay zone.
UBD operations require additional surface equipment such as separators and reserve tanks to process and store the produced reservoir fluids. Selection of separators and reserve tanks for UBD involves using a method to predict reservoir fluid inflow rate and volume. Such a method is not available in the literature for UBD horizontal wells. This study filled the gap.
In this study, we derived an equation for pressure distribution in the borehole by rigorously coupling formation inflow and borehole hydraulics. A simple function for fluid influx rate distribution in the borehole was then developed. Fluid influx rate is predicted as a function of horizontal borehole length, which is time-dependent. The predicted fluid influx rate at the total depth is used for sizing separators. The total influx volume is predicted by integrating the influx rate over the total time for horizontal drilling. The predicted total influx volume is used for determining the required capacity of reserve tanks. A work procedure was developed for generating fluid inflow rate and influx volume profiles. Application of the procedure is illustrated in solving an example problem. This paper presents drilling engineers a mathematical tool that can be used for sizing separators and reserve tanks during horizontal UBD planning.
New Viscoelastic Surfactant Fracturing Fluids Now Compatible With CO2 Drastically Improve Gas Production in Rockies
Authors: Arias R. E. , Nadezhdin S. V. , Hughes K. , Santos N. 
Published: February 2008

Abstract
Historically, carbon dioxide (CO2)-foamed fracturing fluids were used to stimulate wells in the Waltman field in Wyoming—due to the low formation permeability and rock properties—and have been proven effective, but still not perfect. Limitations on the amount of proppant placed near water zones and formation damage from polymer residuals were the main drawbacks. A never ending quest for efficiency and higher production rates called for different options. One of those options was the recently developed CO2 viscoelastic surfactant (VES) fluid system. It has recently been employed to eliminate the disadvantages of the traditional polymer-based fluid. This VES-CO2 fluid system combines the benefits of viscoelastic surfactant-based fluid—such as low formation damage, superior proppant transport, and low friction pressures—with carbon dioxide advantages of enhanced cleanup and better hydrostatic pressure. This fluid was recently selected for the fracturing treatments on three wells. Initial production from these wells was observed in the range of 5 to 7 MMcf/D, significantly greater than neighboring wells' gas rates of 2 MMcf/D stimulated with polymer-based fluid.
Modeling Air and Water Perforator Swell for Better Risk Management
Authors: Han C. , Du Michael H. , Walton Ian C. 
Published: February 2008

Abstract
A detonated shaped charge fired from a perforating string or perforating gun will not only perforate its targets, but also possibly cause excessive damage or swell to its carrier. Comprehensive understanding of the post-perforating conditions of the perforator or perforator system is required if such damage and potential retrievability risks are to be avoided. In practice, the perforating design engineers do not have a well-established analytical tool to help them understand post-perforating behavior of perforators. They have to rely on their own experiences and previous perforating histories to roughly estimate the swell or damage conditions of similar perforators.
In this paper we analyze the failure modes of continuously phased perforators for both gas well and oilwell applications. Important factors concerning carrier serviceability are discussed. A method based on energy conservation is used to establish a swell model to predict the post-detonation conditions of the perforator. The model takes the total expendable energy from the explosives into account, relates it to the energy consumed by the functional and nonfunctional processes, and describes the relationship of energy distribution among them. A criterion is proposed to establish the serviceability of the perforators.
Analytical results from the model are compared with the data collected from surface tests. The results indicate that the model can reasonably predict the perforator swell and damage after detonation, and as such will be a useful tool that shortens the required time to develop future perforators.
New Effective Stress Law for Predicting Perforation Depth at Downhole Conditions
Authors: Grove B. , Heiland J. , Walton I. , Atwood D. 
Published: February 2008

Abstract
For natural completions, well productivity is proportional to the depth of the perforation tunnels. Perforation depth, in turn, is generally inversely related to the formation effective stress. Accurate productivity modeling, therefore, requires accurate knowledge of the relationship between the downhole stress environment and perforation depth.
A comprehensive experimental effort was recently conducted to evaluate the penetration performance of shaped charges into stressed Berea sandstone cores. Rock confining stress (σc) and pore fluid pressure (Pp) were varied from ambient to 10,000 psi, to simulate a range of downhole stress environments. This current work featured a broader and more systematic investigation of the influence of pore pressure than previous studies.
Our experiments yielded the expected inverse correlation between penetration depth and effective stress (σeff). However, the data suggest a new definition of effective stress. Historically, the perforating community has defined σeff = σc - Pp, but a new treatment (σeff = σc - aPp; a=0.5) better fits present data. Furthermore, this new effective stress law better fits published historical penetration results. Pore pressure's influence on penetration depth is therefore weaker than previously thought; for a given confining stress, increasing pore pressure does increase penetration, but to a lesser extent than conventional models would indicate. The present work suggests that all shaped charges would be similarly affected.
These findings are relevant to penetration modeling, and in turn to well productivity modeling and prediction. Further implications are to laboratory testing, regarding scaling of parameters to accurately simulate field conditions.
This work culminates an initial application of combined penetration mechanics and geomechanics analyses to the investigation of shaped charge penetration into geologic materials. Future work will address different rock types, additional poroelastic quantities, and dynamic effects as they contribute to pressure-induced strengthening of reservoir rock.
Determination of Optimum Perforation Design and Sanding Propensity in Long Horizontal Wells Based on Modified RP 19B Section IV Tests and Numerical Sand Prediction
Authors: Andrews J. S. , Bjørkesett H. , Djurhuus J. , Walton I. C. , Atwood D. C. , Heiland J. , Grove B. , Langseth B. 
Published: February 2008

AbstractGjøa is an oil and gas field located off the Norwegian Coast that is due to be developed with subsea infrastructure tied back to a floating production facility. Nine horizontal oil producers and four S-shaped gas producers are planned and all will require some form of sand prevention. Extensive rock mechanical work using Statoil's finite element modeling method suggests that oriented perforations can prevent sand production in the horizontal wells. This was offered as an alternative to mechanical sand control in the long horizontal wells due to traverse several shale and sand bodies of varying quality.Perforation tunnels with optimal "structural" stability for the given inherent material strength of the formation rock can be achieved by targeting perforations in the most stable direction with respect to the in-situ stress field. For high angle wells this normally equates to shooting in the vertical plane through the well path. Over a decade of production experience with this technique on the Norwegian Continental Shelf (NCS) confirms that oriented perforating can be a good sand prevention measure in suitable fields. Despite this track record and the rock mechanical analysis performed, the Gjøa project team wanted to conduct laboratory tests to confirm its applicability and also to optimize perforating parameters. An extensive laboratory test program was conducted on representative core and outcrop material. Five modified API RP 19B Section IV tests were performed to assess the influence of static and dynamic wellbore pressure conditions and wellbore fluid on perforation clean-up and PI. In addition, two tests were conducted on field core material in order to evaluate the sanding propensity of oriented perforations under conditions approximating those predicted during pressure depletion. The laboratory conditions required to induce sand production were quite extreme and vastly exceed the production scenario for the planned oil wells in the field. However, the cell geometry, boundary conditions and stress field in these experiments are not truly representative of the in-situ conditions around a true perforation in a well. In order to translate the sanding results into a conclusion relating to the validity of oriented perforating for the field, a finite element model was built to reproduce the lab conditions. This model correctly predicted the conditions required for sand failure as observed in the lab. This agreement provided validation of the operator's general sand prediction methodology and gave good confidence in the earlier rock mechanical predictions made for the field.
Effect of Basic Parameters on the Viscosity of Synthetic-Based Drilling Fluids
Authors: Ghalambor A. , Ashrafizadeh S. N. , Nasiri M. 
Published: February 2008

Abstract
In this study the effect of interactions among the ingredients of synthetic-based fluids (SBFs) on the rheology of the fluid at ambient temperature was investigated. It has been also attempted that through examination on the important variables affecting those interactions, the mechanism of viscosity building in SBFs be identified. Rheology measurements along with the microscopic observations from the invert emulsion structure of the SBFs can be utilized for such an examination. Viscosity building in the SBFs by means of organophilic clays is a function of several parameters including the type and amount of the clay, the synthetic based fluid, the composition of the internal dispersed phase, mixing time, and the type of emulsifier.
The impact of the synthetic-based fluid, i.e. an ester, olefin, or a paraffin, organophilic clays, water, calcium chloride, emulsifiers, and the mixing time on the rheological behavior of the produced mud was thoroughly investigated. Micrographs from scanning electron microscope (SEM) revealed that the presence of water has a vital role on the dispersion of clay in the fluid while presence of calcium chloride lowers both the stability of the fluid and the dispersion of the clay. Samples containing calcium chloride exhibited instability and phase separation within a 24-hours period. SEM micrographs and rheological measurements also revealed that the degree of clay dispersion depends on the polarity of the base fluid and the interaction of the polar groups in the fluid molecules with those of clays. The observations on the prepared samples at ambient temperature demonstrated that the minimum amount of clay content for a homogeneous and stable fluid is about 6 lb/bbl. The latter observation also confirmed the role of the organophilic clays on the stability of the invert emulsions.
Investigations on the effect of shear time on the viscosity of the fluids at ambient temperature resulted in a more appropriate thixotropic properties for esters in comparison with olefins and paraffins, e.g. ester based fluids reached the maximum viscosity after 20 minutes of mixing while that was about 60 minutes for the paraffin and olefin based fluids. The latter observation clearly demonstrates the superior dispersion behavior of the clays in esters. The occurrence of maximum viscosities shifted toward lower mixing times at elevated temperatures. This observation shows the favorable influence of the temperature on the thixotropic behavior of the SBFs.
The Experimental Study of Formation Damage During UBD Operation in the Fractured Carbonate Formations
Authors: Salimi S. , Ghalambor A. , Tronvoll J. , Alikarami R. 
Published: February 2008

Abstract
This paper describes an experimental investigation of formation damage during underbalanced drilling (UBD) conditions in a fractured carbonate core sample. A major portion of this study has concentrated on problems, which are often associated with UBD and the development of a detailed protocol for proper design and execution of an UBD program. Formation damage effects have been studied, which may occur even if the underbalanced pressure condition is maintained 100% of the time during drilling operation. One major concern to formation damage during UBD operations is the loss of the underbalanced pressure condition. Hence, it becomes vital to evaluate the sensitivity of the formation to the effect of an overbalanced pulse situation. The paper investigates the effect of short pulse overbalance pressure during underbalanced conditions in a fractured chalk core sample. Special core tests using a specially designed core holder are conducted on the subject reservoir core. Both overbalance and underbalanced tests are conducted with four UBD drilling fluids. Core testing is including the initial permeability measurement and return permeability after two different conditions of pressure (underbalanced and overbalance). Then the procedure is followed by applying a differential pressure on the core samples to mimic the drawdown effect to present capacity of the return permeability. In both UBD and short pulse OBP four mud formulation are used which are, lab oil, Brine (3% KCL), Based mud (Bentointe with XC polymer) and fresh water. The return permeability measurements show that a lab oil system performed fairly well during UBD and short OB conditions. The results indicate that short overbalance pressure provides significant reduction in permeability of the fractured carbonate formations. In most tests, even application of a high drawdown pressure during production cannot restore the initial permeability more than 40%.