Analysis of Immiscible Water-Alternating-Gas (WAG) Injection Using Micromodel Tests

Abstract

In waterflooded reservoirs, it is possible to recover a significant amount of residual oil by enhanced oil recovery. Immiscible water-alternating-gas (WAG) injection is one of the well-established methods for improving oil recovery. However, the mechanism of three-phase flow in the process has not been well understood and prediction of the three-phase permeability has been highly uncertain.

This paper presents the results of immiscible WAG injection in a water-wet micromodel. During immiscible gas injection after an initial waterflood, gas moved through the residual oil paths, and residual oil was pushed either toward the production end of the model or into previously waterflooded channels. Breakthrough of gas occurred at about 0.25 PV for the micromodel used in this work. Further gas injection beyond the breakthough volume increased oil recovery only very slightly. When water was injected following gas injection, it flowed through channels that were created in the initial waterflood. Most of the residual oil that had been pushed into these waterflooded channels by the previous gas injection was produced. The mechanism of gas, oil, and water flow during immiscible WAG injection was analyzed. The observations and analysis provide insight into the flow behaviour of a three-phase system in the immiscible WAG process, which is important in the modelling of the process.

Introduction

A problem with gas injection (both miscible and immiscible) is the inherently unfavourable mobility ratio and the resulting poor volumetric sweep in reservoirs. Injection of gas as slugs alternated with water slugs, or water-alternating-gas (WAG), is the common practice presently used for controlling gas mobility. The WAG technique is indeed a combination of two oil recovery processes: gas injection and waterflood. However, the use of the combination of the two processes has resulted in some problems that have perplexed the industry since the pilot test studies were implemented in the early 1970s.

In the immiscible gas injection process, the portion of the injected gas dissolved in the oil reduces the oil viscosity. In addition to reducing viscosity, the dissolved gas also swells the oil, so for a given fixed residual oil saturation, less stock tank oil remains after a waterflood. These two mechanisms have been demonstrated by numerous laboratory PVT and coreflood tests. Laboratory coreflood experiments also showed that the free gas displacement is a very important mechanism for immiscible gas injection. Analysis of results from a tertiary CO2 injection field test revealed that incremental oil production by immiscible CO2 injection has two components(1). The first is an instantaneous response, probably resulting from gas displacing oil that was not being displaced by water. The second component is the long-term effect caused by viscosity reduction, swelling, and relative permeability alteration. The mechanism of instantaneous response, i.e., a sharp increase in the oil production rate during a CO2 slug injection, is still not well understood. Spival et al.(1) also realized that N2 contained in the CO2 stream is a complicating factor that reduces the solubility of CO2 in the oil and, on the other hand, may decrease the residual oil saturation by being trapped in the reservoir.

Determining the Most Profitable ASP Flood Strategy for Enhanced Oil Recovery

Abstract

While chemical floods have proven technically successful, the high cost of chemicals makes it challenging to develop a costeffective tertiary process. If high interfacial tension (IFT) exists between the oil and water phases, the resulting capillary forces will resist externally applied viscous forces. This could cause the injected water and chemicals to bypass the residual oil and go to waste.

The experimental studies presented here include reservoir fluid characterization, IFT measurements, and coreflood tests; all critical elements in designing a cost-effective alkaline/surfactant/ polymer (ASP) injection strategy. Coreflood tests used either sandpacks or composite reservoir cores with a selected medium crude oil. Injected surfactant concentration, slug size, chasing fluid, and residual oil saturation were the varied parameters. The optimal surfactant concentration of 0.15 wt% and slug size of 0.5 pore volume (PV) obtained relatively high oil recovery while maintaining a favourably high displacement efficiency ratio. Incremental recovery was 23 – 41% initial oil-in-place (IOIP) in sandpack tests and about 16% IOIP with reservoir cores. Overall, these coreflood results indicate that ASP flooding is a suitable enhanced oil recovery method for medium oil if the right chemical concentration and slug size are selected.

Introduction

The use of ASP flooding to recover oil left behind by waterflooding has become more common in recent years. Several significant developments have made ASP flooding a viable option for field enhanced oil recovery (EOR) projects and more attractive than polymer or micellar/polymer flooding. First, because world oil consumption continues to grow while production in many mature fields continues to decline, oil prices are predicted to stabilize above US$20/bbl. Second, newly developed cheaper surfactants have reduced the cost of EOR formulations by 40 to 60%, while maintaining the same high oil recoveries obtained using more expensive surfactants. The incremental cost per barrel of oil produced has been reduced to a reasonable level, between US$1.44 and $5.83(1). Third, chemical flooding can be evaluated in the oil field faster and more economically than in the past using the single-well EOR pilot test and field-scale numerical simulations. Fourth, waterfloods in most mature reservoirs have experienced early water breakthrough and have reached their economic limit. Therefore, oil companies have to consider applying new EOR technologies to increase recovery factors in such fields.

The proven medium oil resource in southwest Saskatchewan, estimated at 534.5 × 106 m3, is located in reservoirs characterized by thin pay and shaly sand. Primary and secondary methods have recovered an estimated 25% IOIP from these reservoirs(2) and are nearing their economic limit. There has been little development of this resource by EOR technologies.

The Saskatchewan Research Council (SRC) has conducted extensive studies to develop ASP flooding for a selected reservoir- Instow-with reserves of about 22.1 × 106 m3 of medium oil originally in place. Instow field is located in Ranges 18 and 19 of Townships 9 and 10 in southwest Saskatchewan. This moderate- permeability sandstone reservoir (Upper Shaunavon sand at a depth of 1,370 m) was discovered in 1954 and has been waterflooded since 1959.

Alkaline/Surfactant/Polymer (ASP) Flood Potential in Southwest Saskatchewan Oil Reservoirs

Abstract

Most of the medium oil reservoirs in southwest Saskatchewan are in thin pay zones of less than 8 m. Primary and waterflood methods have reached more than 80% of their estimated oil recovery potential. These medium oil reservoirs are basically untouched by enhanced oil recovery techniques.

An initial study was conducted to assess the suitability of Alkaline/Surfactant/Polymer (ASP) flooding for southwest Saskatchewan reservoirs. On the basis of screening criteria in the literature, the region's reservoir conditions, except for some of the formation types, are favourable for ASP flooding. If only sandstone formations are considered for this process, about 49% of the pools in the region are good candidates for ASP flooding. Extensive oil/water interfacial tension and viscosity measurements were taken using screening criteria for surfactant, alkaline, and polymers. A series of sandpack flood tests were conducted in sandpacks to evaluate ASP flooding for the oil. A tertiary oil recovery of 39% IOIP (72% ROIP) was obtained for the test using all three chemicals. These sandpack flood test results showed that a synergistic enhancement among the chemicals did occur in the ASP system for the medium oil with a very low acid number. The results also indicated that, for a medium oil, mobility control was essential and selection of the right surfactant was important.

Introduction

Oil reservoirs located in southwest Saskatchewan, with 3.1 billion barrels of proven oil, are characterized by thin pay (2 to 8 m in thickness) and shaley sand. The estimated oil recovery by primary and secondary methods from these reservoirs is about 25% initial oil in place (IOIP)(1). Waterfloods in most of these reservoirs have experienced early water breakthrough and high water cut due to the high oil-to-water viscosity ratio. For some of these reservoirs, waterfloods have nearly reached their economic limit. For achieving additional oil recovery and subsequent financial benefits, the development of an enhanced oil recovery technique is essential.

Chemical-enhanced oil recovery methods mainly include micellar/polymer flooding, alkaline flooding, polymer flooding, and combinations of two or all of the three methods. Extensive studies of these processes have found that successful chemical flooding needs to be able to efficiently lower the oil/water interfacial tension and to have very good mobility control.

The displacement mechanism of an ASP flood is similar to that of micellar/polymer flooding except that much of the surfactant is replaced by low-cost alkali. Therefore, the overall cost is lower even though the chemical slugs can be larger. Polymer is usually incorporated in the larger, dilute slug. It has been recognized that oil recovery can be greatly improved by the synergism of chemicals used in the ASP formulations.

ASP processes are also being tested in the field. A field-wide project in Wyoming reports costs of US$10 to $22/tonne (US$1.6 – 3.5/bbl) of incremental oil produced(2). The economic analysis of two ASP pilot tests in the Daqing oil field, China, showed that the chemical cost was US$21 to $28/tonne (US$3 – 4/bbl) of incremental oil produced(3).

An experimental investigation of retention of liquids in corners of a square capillary

The retention of liquids in the corners of a 0.03-cm square capillary after the passage of a gas slug was studied experimentally as a function of capillary number in the range from 10(-3) to 10(-6). In gas-wetting liquid systems, for capillary number greater than 5 x 10(-4), the retention of a wetting liquid in the corners showed a strong dependence on the capillary number; i.e., the retention of the liquid decreased with decreasing capillary number. For capillary number less than 10(-4), the retention of a wetting liquid was found to be determined by the capillary forces and the rate (or viscous) effect was negligible. In gas-oil-water systems involving double displacements--gas was displacing oil which was in turn displacing water--the total retention of water and oil vs capillary number curve showed the same trend as the retention of a wetting phase in a gas-wetting liquid system. However, because of the viscous effect, the water retention showed a continuous decrease with decreasing capillary number and could be lower than the capillary equilibrium value at very low capillary numbers. As a result of this, the oil retention vs capillary number curve in the double displacement process showed a minimum; i.e., oil retention increased with decreasing capillary number in the range of very low capillary numbers.

Steroidal saponins from Dioscorea panthaica and their cytotoxic activity

A new steroidal saponin, dioscoreside E (1), and a known compound, protodioscin (2), were isolated from an ethanol extract of the rhizomes of Dioscorea panthaica. The structure of 1 was established as 3-O-[bis-alpha-L-rhamnopyranosyl-(1 --> 2 and 1 --> 4)-beta-D-glucopyranosyl]-26-O-beta-D-glucopyranosyl-20(R)-methoxy-25(R)-furosta-5,22(23)-diene-3beta,26-diol, on the basis of spectral and chemical evidence. Compounds 1 and 2 showed cytotoxic activity against a panel of tumor cell lines.

Oil Layer Flow Along the Corners of Non- Circular Capillaries by Gravity Drainage

Abstract

The fundamentals of oil layer drainage along the corners of non-circular capillaries in two-phase (gas-oil) and three-phase (gas-oil-water) systems were studied. Experiments of oil layer flow along the corners of square capillaries were carried out to investigate the saturation dependency of oil phase relative permeability in single layer drainage. The quadratic behaviour of oil relative permeability in the gas injection process reported in the literature was explained. For double-layer flow (water layer and oil layer) in a three-phase system, numerical analysis showed that the lubricating effect of a water layer on the relative permeability of oil phase in layer drainage was significant. The dependency of oil layer flow by gravity drainage on oil saturation, water saturation, and oil-to-water viscosity ratio was investigated numerically. The experimental results confirmed the mathematical analysis.

Introduction

Both laboratory experimental results and oil field performance analysis have demonstrated that very high oil recoveries of residual oil can be achieved if gravity drainage is the dominant production mechanism(1–4). Because of the importance of the oil relative permeability in the process of gravity drainage, extensive studies have been conducted on the measurement and analysis of threephase relative permeability.

Numerous measurements have been carried out to determine the three-phase relative permeability during the gravity drainage process(4). It was found that a quadratic change of oil relative permeability with respect to the oil saturation is followed if:the porous medium is water-wet;oil flows in layers; andwater flow is negligible.

Oil layer drainage is an important recovery mechanism in a gravity assisted gas injection process and other enhanced oil recovery methods such as steam assisted gravity drainage (SAGD) and vapour extraction process (VAPEX). To develop physically sound modelling capabilities for these processes, a better understanding of the fundamentals of oil layer flow is necessary at both the microscopic level and the macroscopic level. The results of this study can help improve the understanding and modelling of the oil phase flow in porous media in SAGD, VAPEX, and other gravity assisted gas injection processes.

Single Layer Drainage

In this instance, the procedure to measure the accumulation of wetting liquid by gravity drainage was essentially that of Chatzis, et al.(3) The oils used were heptane and Soltrol 170. At experimental temperature (23 ° C), heptane had a viscosity of 1.0 mPa.s and a density of 0.69 g/cm3, whereas Soltrol 170 had a viscosity of 3.0 mPa.s and a density of 0.70 g/cm3.

The flow rate of liquid in single layer drainage along the four corners of a square capillary under steady-state condition is expressed as follows(5):

Equation 1 (available in full paper)

where S is the saturation of the liquid in the tube, D is the size of the square capillary, and β?is the dimensionless resistance coefficient. If the saturation of the wetting liquid in two square capillaries of different sizes is the same, the layer drainage rate is proportional to the tube size raised to the fourth power.

Coreflood Studies of Tertiary CO2 Flood in Naturally Fractured Midale Formation in Southeast Saskatchewan

Abstract

The distinctive geology of the Weyburn and Midale reservoirs has important implications for the design of a CO2 injection process for these fields. They are contained within two distinct zones of the Mississippian Carbonate formation; the tight, high-porosity Marly zone sits on top of the low-porosity Vuggy zone. The latter zone has a higher permeability, and is more extensively fractured vertically, than the Marly zone. These geological features result in a relatively unswept Marly zone after waterflooding. The Marly/Vuggy sequence presents an opportunity for a CO2 flood to take advantage of gravity segregation to recover the large remaining oil target in the Marly zone.

A series of coreflood tests were conducted to simulate tertiary CO2 injection in the Marly/Vuggy zones in the Weyburn and Midale reservoirs. Berea cores with different permeabilities were split lengthwise. The halved segments of the core were butted together to represent the Marly and Vuggy zones. Water (in waterflood mode) and CO2 (in tertiary CO2 flood mode) were injected into the bottom high-permeability section of the dualpermeability core. The coreflood results showed that, in the tertiary CO2 flood, CO2 could migrate to and recover the oil from the top low-permeability zone which was poorly swept by the waterflood. Also, the effects on tertiary oil recovery of operating pressure, injection rate, and permeability contrast could be significant.

Introduction

The Weyburn and Midale reservoirs in southeast Saskatchewan hold light and medium gravity oil in fractured, low permeability Midale Beds. These reservoirs are contained within two distinct zones of the Mississippian Carbonate formation: the tight, highporosity Marly zone sits on top of the low-porosity Vuggy zone. The latter zone has a higher permeability, and is more extensively fractured vertically than the Marly zone. These geological features result in a relatively unswept Marly zone after waterflooding.

It is believed that the distinctive geology of these reservoirs has important implications for the design of a CO2 injection process for these fields, i.e., the Marly-Vuggy arrangement of the reservoir offers potential to utilize gravity segregation effects to enhance oil recovery. Numerical analyses(1, 2) of tertiary CO2 injection in these naturally fractured reservoirs showed that CO2 injected into the lower, more permeable Vuggy zone can contact and mobilise a large amount of oil in the Marly, which has remained relatively unaccessed by waterflooding.

A coreflood program was designed at Saskatchewan Research Council (SRC) to address the CO2 injection process in Weyburn reservoir and comparable fields. Laboratory core displacement tests were conducted with a dual permeability split Berea core representing the Marly and Vuggy zones of a reservoir. Some preliminary results reported in a previous paper(3) showed that CO2 injected into the Vuggy zone could rise to the upper Marly zone, and that the potential to recover incremental oil by a tertiary CO2 slug flood is high. After the technique of butting the core halves was improved, the several additional tertiary CO2 coreflood tests reported here were performed with Weyburn reservoir fluid at 63 ° C (reservoir temperature) to confirm the previous finding.

Apoptosis, proliferation and p53 gene expression of H. pylori associated gastric epithelial lesions

AIM: To study the relationship between Helicobacter pylori (H. pylori) and gastric carcinoma and its possible pathogenesis by H. pylori.

METHODS: DNEL technique and immunohistochemical technique were used to study the state of apoptosis, proliferation and p53 gene expression. A total of 100 gastric mucosal biopsy specimens, including 20 normal mucosa, 30 H. pylori-negative and 30 H. pylori-positive gastric precancerous lesions along with 20 gastric carcinomas were studied.

RESULTS: There were several apoptotic cells in the superficial epithelium and a few proliferative cells within the neck of gastric glands, and no p53 protein expression in normal mucosa. In gastric carcinoma, there were few apoptotic cells, while there were a large number of proliferative cells, and expression of p53 protein significantly was increased. In the phase of metaplasia, the apoptotic index (AI, 4.36% ± 1.95%), proliferative index (PI, 19.11% ± 6. 79%) and positivity of p53 expression (46.7%) in H. pylori-positive group were higher than those in normal mucosa (P < 0.01). AI in H. pylori-positive group was higher than that in H. pylori-negative group (3.81% ± 1.76%), PI in H. pylori-positive group was higher than that in H. pylori-negative group (12.25% ± 5.63%, P < 0.01). In the phase of dysplasia, AI (2.31% ± 1.10%) in H. pylori-positive group was lower (3.05% ± 1.29%) than that in H. pylori-negative group, but PI (33.89% ± 11.65%) was significantly higher (22.09% ± 80.18%, P < 0.01). In phases of metaplasia, dysplasia and gastric cancer in the H. pylori-positive group, AIs had an evidently graduall decreasing trend (P < 0.01), while PIs had an evidently gradual increasing trend (P < 0.05 or P < 0.01), and there was also a trend of gradual increase in the expression of p53 gene.

CONCLUSION: In the course of the formation of gastric carcinoma, proliferation of gastric mucosa can be greatly increased by H. pylori, and H. pylori can induce apoptosis in the phase of metaplasia, but in the phase of dysplasia H. pylori can inhibit cellular apoptosis. And H. pylori infection can strengthen the expression of mutated p53 gene.

Two new steroidal saponins from the rhizomes of Dioscorea panthaica and their cytotoxic activity

Two new steroidal saponins, dioscoresides C (1) and D (2), along with a new natural product, pregnadienolone 3-O-beta-gracillimatriose (3), and two known compounds, pregnadienolone 3-O-beta-chacotrioside (4) and pseudoprotodioscin (5), were isolated from the rhizomes of Dioscorea panthaica Prain et Burkill. On the basis of extensive NMR studies and chemical evidence, dioscoresides C and D were determined to be 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-23(S)-methoxy-25(R)-furosta-5,20(22)-dien-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside and 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-20,22-seco-25(R)-furosta-5-en-20,22-dine-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1--> 4)]-beta-D-glucopyranoside. These compounds showed mild cytotoxicity against the cancer cell lines, A375, L929, and HeLa, in a dose-dependent manner.

Increased nitric oxide in peritoneal fluid from women with idiopathic infertility and endometriosis

OBJECTIVE

To verify whether nitric oxide in peritoneal fluid is associated with endometriosis and infertility.

STUDY DESIGN

Twenty-five women with idiopathic infertility and 38 with endometriosis were recruited, and 18 cases of uterine myomata and 2 cases of ovarian cyst served as controls. Peritoneal fluid samples were aspirated from the pouch of Douglas during laparoscopy or laparotomy. Metabolites of nitric oxide (nitrite and nitrate) in peritoneal fluid were determined by a method using nitrate reductase and the Griess reaction.

RESULTS

Peritoneal concentrations of nitrate/nitrite in both infertile women (42.02 +/- 12.98 mmol/L) and patients with endometriosis (41.75 +/- 16.42 mmol/L) were significantly higher than that in controls (33.96 +/- 13.07, P < .05 for both). No significant difference in peritoneal nitrate/nitrite level was found between infertile women and patients with endometriosis (P > .5). Peritoneal levels of nitrate/nitrite were comparable among patients with endometriosis at different stages (P > .5). Patients with endometriosis had more peritoneal fluid than controls and idiopathic infertile women, while controls and idiopathic infertile women had comparable amounts of peritoneal fluid.

CONCLUSION

An increased peritoneal level of nitric oxide is a common alteration in endometriosis, endometriosis-associated infertility and idiopathic infertility and may be associated with the pathogenesis of these diseases.

Identification of peptide ligand-binding domains within the human motilin receptor using photoaffinity labeling

The cDNA encoding the human motilin receptor was recently cloned and found to represent a G protein-coupled receptor that is structurally related to the growth hormone secretagogue receptors. Together, these represent a new Class I receptor family. Our aim in the present work is to gain insight into the molecular basis of binding of motilin to its receptor using photoaffinity labeling. To achieve this, we developed a Chinese hamster ovary cell line that overexpressed functional motilin receptor (CHO-MtlR; 175,000 sites per cell, with K(i) = 2.3 +/- 0.4 nm motilin and EC(50) = 0.3 +/- 0.1 nm motilin) and a radioiodinatable peptide analogue of human motilin that incorporated a photolabile p-benzoyl-l-phenylalanine (Bpa) residue into its pharmacophoric domain. This probe, [Bpa(1),Ile(13)]motilin, was a full agonist at the motilin receptor that increased intracellular calcium in a concentration-dependent manner (EC(50) = 1.5 +/- 0.4 nm). This photolabile ligand bound specifically and with high affinity to the motilin receptor (K(i) = 12.4 +/- 1.0 nm), and covalently labeled that molecule within its M(r) = 45,000 deglycosylated core. Cyanogen bromide cleavage demonstrated its covalent attachment to fragments of the receptor having apparent M(r) = 6,000 and M(r) = 31,000. These were demonstrated to represent fragments that included both the first and the large second extracellular loop domains, with the latter representing a unique structural feature of this receptor. The spatial approximation of the pharmacophoric domain of motilin with these receptor domains support their functional importance as well.

Influence of growth hormone-insulin-like growth factor I axis on normal pregnancy

OBJECTIVE

To investigate the role of growth hormone-insulin-like growth factor I (IGF-I) axis in normal pregnancy.

METHODS

Totally, 116 normal pregnant women were recruited from January 1997 to June 1998, with 20 normal nonpregnant women as controls. Maternal growth hormone (GH) and IGF-I concentrations were assayed by RIA and enzyme-linked immunosorbent assay, respectively.

RESULTS

Maternal serum levels of GH increased throughout gestation, reached a peak at 25 weeks of pregnancy and remained fairly high (chi 2 = 40.458, P < 0.0001). There was a significant difference between samples at 5-9 week gestational age and the controls (3.45 micrograms/L vs 1.61 micrograms/L, P < 0.05). The maternal serum levels of IGF-I increased rapidly throughout gestation from 29-week gestation and reached a peak of 188.86 micrograms/L at term delivery (chi 2 = 50.224, P < 0.0001).

CONCLUSIONS

Maternal GH levels increased progressively throughout gestation, which correlated with fetal growth. Maternal GH may regulate nutrition supply among mother, placenta and the fetus and play an important role in transporting nutritional substrates by the placenta. The maternal IGF-I in the third trimester may promote fetal growth and placental functions.

Inoculation of human interleukin-17 gene-transfected Meth-A fibrosarcoma cells induces T cell-dependent tumor-specific immunity in mice

OBJECTIVE

The biological activities of interleukin-17 (IL-17), a newly cloned cytokine, have not been fully elucidated. The present study was designed to assess the in vitro and in vivo effect of transfecting the IL-17 gene into tumor cells.

METHODS

A complementary DNA (cDNA) encoding human IL-17 (hIL-17) was obtained by polymerase chain reaction amplification from the human CD4+ T cell cDNA library and inserted into the plasmid pRc/cytomegalovirus to construct an expression vector for the hIL-17 gene. Murine Meth-A fibrosarcoma cells were transfected with the hIL-17 gene using the lipofectin method. The hIL-17 gene-expressing clone (Meth-A/IL-17) was selected and analyzed for cytokine expression by Northern blot.

RESULTS

There was no significant difference in the in vitro proliferation rate among parent Meth-A, cells transfected with vector alone and Meth-A/IL-17 cells. When the tumor cells were transplanted subcutaneously into BALB/c nude (nu+/nu+) mice, there was no difference in in vivo growth rates among the three cell lines. Challenge with tumor cells in conventional BALB/c mice, however, resulted in the rejection of Meth-A/IL-17 cells, but the other two lines did grow. After immunization with Meth-A/IL-17 cells, the mice were rechallenged by parent Meth-A or syngeneic MOPC-104E plasmacytoma cells; the immunized mice rejected the Meth-A cells, but not the MOPC-104E cells. Injecting the anti-thy 1,2 (CD90), anti-CD4 or anti-CD8 monoclonal antibody into conventional BALB/c mice resulted in the resumption of in vivo growth of Meth-A/IL-17 cells, but injecting the anti-asialo GM1 antibody did not. Furthermore, flow cytometric analysis demonstrated a significant increase in the expression of major histocompatibility complex (MHC) class I and class II antigens and lymphocyte function-associated antigen-1 on Meth-A/IL-17 cells.

CONCLUSION

Meth-A cells transfected with the hIL-17 gene can induce tumor-specific antitumor immunity by augmenting the expression of MHC class I and II antigens, and both CD4+ and CD8+ T cells may play important roles in inducing antitumor immunity, suggesting the possibility of developing a tumor vaccine incorporating IL-17-transfected tumor cells.

Effects of pioglitazone on adipose tissue remodeling within the setting of obesity and insulin resistance

Obesity and dysfunctional energy partitioning can lead to the development of insulin resistance and type 2 diabetes. The antidiabetic thiazolidinediones shift the energy balance toward storage, leading to an increase in whole-body adiposity. These studies examine the effects of pioglitazone (Pio) on adipose tissue physiology, accumulation, and distribution in female Zucker (fa/fa) rats. Pio treatment (up to 28 days) decreased the insulin-resistant and hyperlipidemic states and increased food consumption and whole-body adiposity. Magnetic resonance imaging (MRI) analysis and weights of fat pads demonstrated that the increase in adiposity was not only limited to the major fat depots but also to fat deposition throughout the body. Adipocyte sizing profiles, fat pad histology, and DNA content show that Pio treatment increased the number of small adipocytes because of both the appearance of new adipocytes and the shrinkage and/or disappearance of existing mature adipocytes. The remodeling was time dependent, with new small adipocytes appearing in clusters throughout the fat pad, and accompanied by a three- to fourfold increase in citrate synthase and fatty acid synthase activity. The appearance of new fat cells and the increase in fat mass were depot specific, with a rank order of responsiveness of ovarian > retroperitoneal > subcutaneous. This differential depot effect resulted in a redistribution of the fat mass in the abdominal region such that there was an increase in the visceral:subcutaneous ratio, as confirmed by MRI analysis. Although the increased adiposity is paradoxical to an improvement in insulin sensitivity, the quantitative increase of adipose mass should be viewed in context of the qualitative changes in adipose tissue, including the remodeling of adipocytes to a smaller size with higher lipid storage potential. This shift in energy balance is likely to result in lower circulating free fatty acid levels, ultimately improving insulin sensitivity and the metabolic state.

A new triterpenoidal saponin from Ixeris sonchifolia and its cytotoxic activity

A new triterpenoidal saponin, echinocystic acid 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside (1), was isolated from Ixeris sonchifolia. Its structure was elucidated on the basis of full spectral data analysis and chemical methods. The cytotoxic activity of compound 1 was evaluated using the tumor cell lines of A375, Hela, and L929 in vitro.

DNA binding of TEA/ATTS domain factors is regulated by protein kinase C phosphorylation in human choriocarcinoma cells

Transcription enhancer factor 1 (TEF-1) controls the expression of a diverse set of genes. Previous studies implicated protein kinase C (PKC)-mediated signal transduction in modulating TEF function. We demonstrate that in human choriocarcinoma BeWo cells, the PKC activator 12-O-tetradecanoyl phorbol 13-acetate and PKC inhibitor bisindolylmaleimide reciprocally down- and up-regulate, respectively, TEF-mediated GGAATG core enhancer activity. In vitro TEF-1 phosphorylation with several PKC isozymes and phosphoamino acid analysis confirmed that TEF-1 is a potential PKC substrate. TEF-1.DNA complexes formed by BeWo nuclear extracts are supershifted by phosphoserine- and phosphothreonine- but not phosphotyrosine-specific antibodies, indicating that TEF-1 is phosphorylated in vivo at serine and threonine residues. The TEF-1 phosphorylation domain was localized to the third alpha-helix of the DNA binding domain and adjacent hinge region by phosphopeptide analysis. TEF-1 phosphorylation significantly reduced its DNA binding activity both in vitro and in vivo, providing a possible mechanism for the inhibitory action of PKC. Finally, BeWo cells contained abundant levels of gamma and delta PKC isoforms, and their overexpression resulted in even greater inhibition of GGAATG core enhancer activity after 12-O-tetradecanoyl phorbol 13-acetate treatment. These data strongly suggest that PKC-mediated phosphorylation is a key factor controlling TEF function.

[Placental expression of epidermal growth factor receptor in pregnancy induced hypertension]

OBJECTIVE

To clarify the expression of epidermal growth factor receptor (EGFR) in placenta from women with pregnancy induced hypertension (PIH).

METHODS

EGFR of placenta was determined by immunohistological method and compared between normal pregnancies (34 cases) and pregnancies accompanied by PIH (30 cases).

RESULTS

Positive immunostain of EGFR was located on cytoplasm, and membrane of syncytiotrophoblast and a small part of cytotrophoblast. Compared with that of normal pregnancy, the expression of EGFR in placenta from pregnancies complicated with PIH decreased significantly (P < 0.05). No significant differences of EGFR expression in placenta were found among women with mild, moderate and severe PIH (P > 0.5). No significant correlation was found between expression of EGFR and neonatal birthweight, placental weight (P > 0.01, for both).

CONCLUSION

Decreased expression of placental EGFR was found in women with PIH, and that may play a role in the pathogenesis of PIH.

The transmembrane domain of syntaxin 1A is critical for cytoplasmic domain protein-protein interactions

Assembly of the plasma membrane proteins syntaxin 1A and SNAP-25 with the vesicle protein synaptobrevin is a critical step in neuronal exocytosis. Syntaxin is anchored to the inner face of presynaptic plasma membrane via a single C-terminal membrane-spanning domain. Here we report that this transmembrane domain plays a critical role in a wide range of syntaxin protein-protein interactions. Truncations or deletions of the membrane-spanning domain reduce synaptotagmin, alpha/beta-SNAP, and synaptobrevin binding. In contrast, deletion of the transmembrane domain potentiates SNAP-25 and rbSec1A/nsec-1/munc18 binding. Normal partner protein binding activity of the isolated cytoplasmic domain could be "rescued" by fusion to the transmembrane segments of synaptobrevin and to a lesser extent, synaptotagmin. However, efficient rescue was not achieved by replacing deleted transmembrane segments with corresponding lengths of other hydrophobic amino acids. Mutations reported to diminish the dimerization of the transmembrane domain of syntaxin did not impair the interaction of full-length syntaxin with other proteins. Finally, we observed that membrane insertion and wild-type interactions with interacting proteins are not correlated. We conclude that the transmembrane domain, via a length-dependent and sequence-specific mechanism, affects the ability of the cytoplasmic domain to engage other proteins.

Heterogeneic distribution of thymidine phosphorylase between primary tumors and metastatic lesions of human pancreatic ductal carcinoma: implications for the efficacy of chemotherapy with 5-FU or its derivatives

PURPOSE

It has been suggested that the expression of thymidine phosphorylase (TdRPase) correlates with the malignant potential of various cancers, but its involvement in human invasive ductal carcinoma (IDC) of the pancreas has not been reported. In the present study, the distribution and clinical significance of TdRPase in IDCs and benign diseases of the pancreas were assessed, especially in relation to the efficacy of chemotherapy with 5-FU or its derivatives.

METHOD

The expression of TdRPase in 148 specimens of pancreatic IDCs (66 primary lesions, 46 nodal lesions and 36 distant metastases from 126 patients) and in 24 specimens of benign diseases (4 cystadenomas, 3 hyperplasias, and 17 chronic pancreatitises) was examined by immunohistochemical staining with anti-TdRPase monoclonal antibody and evaluated in terms of three grades of immunoreactivity: negative 0, low 1, or high 2.

RESULTS

Positive TdRPase staining (low and high immunoreactivity) was detected in 71% (47/66) of the primary lesions, in 46% (21/46) of the involved nodes, in 53% (19/36) of various lesions of distant metastasis, and in 37% (9/24) of the benign diseases. The staining intensity was significantly higher in the IDC tissues than in the benign disease tissues, and significantly lower in the metastatic lesions than in the primary lesions. TdRPase reactivity did not correlate with the survival rate in both resectable and unresectable IDCs. In patients with both primary tumor and nodal involvement, however, high TdRPase activity in involved nodes was significantly associated with a poor prognosis. On the other hand, although adjuvant chemotherapy was found to improve the survival of patients, TdRPase activity in the tumor did not show any significant relationship with the efficacy of chemotherapy with 5-FU or its derivatives.

CONCLUSIONS

The present study suggested that in pancreatic IDC the activity of TdRPase in primary lesions is different from that in metastatic lesions, and that DNA is synthesized mainly through the salvage pathway in primary lesions and through a de novo pathway in metastatic lesions. This may be one of the reasons for the heterogeneity in chemosensitivity of human pancreatic IDC.