Identification of the intimin-binding domain of Tir of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) attaches intimately to mammalian cells via a bacterial outer membrane adhesion molecule, intimin, and its receptor in the host cell membrane, Tir. Tir is a bacterial protein translocated into the host cell membrane and tyrosine phosphorylated after insertion. Tir-intimin binding induces organized actin polymerization beneath the adherent bacteria, resulting in the formation of pedestal-like structures. A series of Tir deletion derivatives were constructed to analyse which Tir domains are involved in intimin binding. We have localized the intimin-binding domain (IBD) of Tir using a yeast two-hybrid system and a gel-overlay approach to a region of 109 amino acids that is predicted to be exposed on the surface of the plasma membrane. A truncated Tir protein lacking this domain was translocated to the host cell membrane and tyrosine phosphorylated, but failed to bind intimin or to induce either actin polymerization or Tir accumulation beneath the bacteria. These results indicate that only a small region of Tir is needed to bind intimin and support the predicted topology for Tir, with both N- and C-terminal regions in the mammalian cell cytosol. They also confirm that Tir-intimin interactions are needed for cytoskeletal organization. We have also identified N-terminal regions involved in Tir stability and Tir secretion to the media.

[A novel Lp(a) assay not affected by apo(a) size polymorphism]

Apo(a), the protein moiety of Lp(a), has size polymorphism that derives from the variable number of K4 type 2 repeats. We have developed three ELISA method with using monoclonal antibodies against the K4 type 2 repeats, the K4 type 5-protease domain, and the K5 protease domain of the apo(a) molecule. The commercial assay kits were correlated with the results from ELISA that utilized a monoclonal antibody against the K4 type 2 but indicated poor correlation with an ELISA method using anti Lp(a) K4 type 5-protease domain monoclonal antibody. Serum Lp(a) values were 1.8-fold overestimated by the commercial assay kits in samples with S4 type of the largest isoform, but our ELISA method in which the apo(a) K4 type 5-protease domain is used as labeled antibody and capture antibody was not affected by size polymorphism.

Enteropathogenic Escherichia coli: a pathogen that inserts its own receptor into host cells

Enteropathogenic Escherichia coli (EPEC) is a major cause of infant diarrhea, killing hundreds of thousands of children per year worldwide. Intimate attachment to the host cell leading to the formation of actin-rich pedestals beneath the adhering bacteria is an essential feature of EPEC pathogenesis. EPEC attaches to host cells via the outer membrane adhesin, intimin. It was recently shown that EPEC inserts its own receptor for intimate adherence, Tir (translocated intimin receptor) into the host cell membrane. The focus of this review is on the discovery and characterization of this novel receptor, and our current understanding of its role in pedestal formation. Gram-negative bacterial secretion systems, including type III secretion systems, are reviewed and discussed in the context of Tir delivery into the host cell membrane. The relationship and relevance of in vitro models compared to the actual in vivo situation is essential to understanding disease. We have critically reviewed the use of animal models in studying EPEC infection. Elucidating the function of Tir will contribute to our understanding of how EPEC mediates disease.

Improved inhibitors of glucosylceramide synthase

Previous work has led to the identification of inhibitors of glucosylceramide synthase, the enzyme catalyzing the first glycosylation step in the synthesis of glucosylceramide-based glycosphingolipids. These inhibitors have two identified sites of action: the inhibition of glucosylceramide synthase, resulting in the depletion of cellular glycosphingolipids, and the inhibition of 1-O-acylceramide synthase, resulting in the elevation of cell ceramide levels. A new series of glucosylceramide synthase inhibitors based on substitutions in the phenyl ring of a parent compound, 1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (P4), was made. For substitutions of single functional groups, the potency of these inhibitors in blocking glucosylceramide synthase was primarily dependent upon the hydrophobic and electronic properties of the substituents. An exponential relationship was found between the IC50 of each inhibitor and the sum of derived hydrophobic (pi) and electronic (sigma) parameters. This relationship demonstrated that substitutions that increased the electron-donating characteristics and decreased the lipophilic characteristics of the homologues enhanced the potency of these compounds in blocking glucosylceramide formation. A novel compound was subsequently designed and observed to be even more active in blocking glucosylceramide formation. This compound, D-threo-4'-hydroxy-P4, inhibited glucosylceramide synthase at an IC50 of 90 nM. In addition, a series of dioxane substitutions was designed and tested. These included 3',4'-methylenedioxyphenyl-, 3',4'-ethylenedioxyphenyl-, and 3'4'-trimethylenedioxyphenyl-substituted homologues. D-threo-3', 4'-Ethylenedioxy-P4-inhibited glucosylceramide synthase was comparably active to the p-hydroxy homologue. 4'-Hydroxy-P4 and ethylenedioxy-P4 blocked glucosylceramide synthase activity at concentrations that had little effect on 1-O-acylceramide synthase activity. These novel inhibitors resulted in the inhibition of glycosphingolipid synthesis in cultured cells at concentrations that did not significantly raise intracellular ceramide levels or inhibit cell growth.

Enterohemorrhagic Escherichia coli O157:H7 produces Tir, which is translocated to the host cell membrane but is not tyrosine phosphorylated

Intimate attachment to the host cell leading to the formation of attaching and effacing (A/E) lesions is an essential feature of enterohemorrhagic Escherichia coli (EHEC) O157:H7 pathogenesis. In a related pathogen, enteropathogenic E. coli (EPEC), this activity is dependent upon translocation of the intimin receptor, Tir, which becomes tyrosine phosphorylated within the host cell membrane. In contrast, the accumulation of tyrosine-phosphorylated proteins beneath adherent EHEC bacteria does not occur, leading to questions about whether EHEC uses a Tir-based mechanism for adherence and A/E lesion formation. In this report, we demonstrate that EHEC produces a functional Tir that is inserted into host cell membranes, where it serves as an intimin receptor. However, unlike in EPEC, in EHEC Tir is not tyrosine phosphorylated yet plays a key role in both bacterial adherence to epithelial cells and pedestal formation. EHEC, but not EPEC, was unable to synthesize Tir in Luria-Bertani medium but was able to secrete Tir into M9 medium, suggesting that Tir synthesis and secretion may be regulated differently in these two pathogens. EHEC Tir and EPEC Tir both bind intimin and focus cytoskeletal rearrangements, indicating that tyrosine phosphorylation is not needed for pedestal formation. EHEC and EPEC intimins are functionally interchangeable, but EHEC Tir shows a much greater affinity for EHEC intimin than for EPEC intimin. These findings highlight some of the differences and similarities between EHEC and EPEC virulence mechanisms, which can be exploited to further define the molecular basis of pedestal formation.

Enteropathogenic E. coli interactions with host cells

Enteropathogenic E. coli (EPEC) interacts with intestinal epithelial cells, causing diarrhea and associated diseases. This pathogen binds to epithelial cells using sophisticated mechanisms that exploit existing epithelial signal transduction pathways and host cytoskeletal components, ultimately resulting in the bacterium resting upon a pedestal on host cell surfaces. Recent data indicates that similar mechanisms occur in vivo. EPEC interactions with host cells illustrate several principles of pathogenesis that are used by bacteria that interact with mammalian host cells.

CD4- and CD56-positive T-cell line, MTA, established from natural killer-like T-cell leukemia/lymphoma

We have established a T-cell line, MTA, from the peripheral blasts of a patient with natural killer (NK)-like T-cell leukemia/lymphoma. The MTA cell displays a T-cell and NK-cell phenotype (CD2+, CD3+, CD4+, CD56+) identical to freshly isolated leukemic blasts from the patient. This cell line shows clonal T-cell receptor rearrangement and a distinguishable character by light microscopy with May-Grünwald Giemsa staining. G-banding analysis showed that the MTA cells had a karyotype of 94(4N), XXXX, add (1) (p36), del (5) (q14q23), add (17) (p11), add (19) (q13). However, unlike NK malignancy, we could not show a direct pathogenic role for Epstein-Barr virus (EBV) with EBV-encoded small RNA and polymerase chain reaction analysis. The MTA cell line is a novel cell line with which to study NK-like T-cell ontogenecity.

Successful culture and sustainability in vivo of gene-modified human oral mucosal epithelium

Human oral mucosal cells are an attractive site for tissue engineering because they are the most accessible cells in the body and easy to manipulate in vitro. They thus have possibilities for targeting by somatic gene therapy. We examined the efficiency of retrovirus-mediated gene transfer and the construction of mucosal epithelium in vivo. Human oral mucosal cells were transduced with a retroviral vector carrying the lacZ gene at high efficiency and constructed epithelium after G418 selection with 3T3 cells in vitro. The cultured oral mucosal epithelium membrane was then grafted onto immunodeficient mice. Beta-Gal expression was detected histochemically in vivo 5 weeks after grafting. Furthermore, we transduced factor IX cDNA into the mucosal epithelium membrane, and it was then transplanted into nude mice. Between 0.6 and 1.8 ng of human factor IX per milliliter was found in mouse plasma, and the production was continued for 23 days in vivo. These results confirmed that the oral mucosal epithelium is an ideal target tissue for gene therapy or tissue engineering.

Real-time detection system for quantification of hepatitis C virus genome

BACKGROUND & AIMS

For diagnosis of hepatitis C virus infection and monitoring of viral load in patients, a highly sensitive and accurate hepatitis C virus quantification system is essential.

METHODS

Hepatitis C virus genome was detected by real/time detection system using an ABI Prism 7700 sequence detector (Perkin Elmer Corp./Applied Biosystems, Foster City, CA).

RESULTS

As few as 10 copies of the genome were detected, and the quantification range was between 10(1) and 10(8) copies (r > 0.99). This system was 10-100-fold more sensitive than an Amplicor monitor (Roche Diagnostic Systems, Branchburg, NJ). The coefficient of variation values for both intra-assay precision and interassay reproducibility of identifying the genome quantification ranged from 0.37% to 2.00% and 0.88% to 4.66%, respectively. The system could detect the genome in 98% of patients with chronic hepatitis, 95.8% of patients with liver cirrhosis, and 100% of patients with hepatocellular carcinoma who had the antibody to hepatitis C virus, but could not detect the genome in patients without the antibody.

CONCLUSIONS

The establishment of a real-time detection system enables more accurate diagnosis of infection and monitoring of viral load in interferon-treated patients via quantification of viral genome.

Distribution of 1,4-dioxane in relation to possible sources in the water environment

The distribution of 1,4-dioxane was investigated in surface and groundwater in relation to possible sources. Water samples from river, coastal sea, and groundwater were collected and examined in Kanagawa Prefecture, Japan, from 1995 to 1998. Almost all samples were contaminated by 1,4-dioxane. On annual changes, the concentrations did not vary significantly in river water. However, some samples were still heavily polluted in groundwater. The highest correlation was between the concentration of 1,4-dioxane and 1,1,1-trichloroethane in the polluted groundwater samples. Soil and groundwater that was polluted by 1,1,1-trichloroethane in the past is still a possible source of 1,4-dioxane. In regard to a survey of other sources, effluents from the combined collection treatment from apartment houses, river basin sewage systems, and chemical plants were examined. The load unit of 1,4-dioxane from the treated effluent of domestic wastewater was assumed to be approximately 0.25 mg/person/day. This was derived from commonly used household chemicals, which contained 1,4-dioxane as a by-product. In river basin sewage systems, the concentrations in effluents varied significantly. High concentration inflows were probably not degraded and released. Although 50-60% of removal was recognized in acclimatized activated sludge from a chemical plant, 1,4-dioxane was easily desorbed with water from sludge.

Immune response of post-transplant peripheral lymphocytes against the patient pre-B cell line, NAGL-1

We have established a pre-B acute lymphoblastic leukemia (ALL) cell line, NAGL-1, from the bone marrow of a patient diagnosed with pre-B ALL. The patient has been disease-free for the 4 years since allogeneic bone marrow transplantation from her HLA-genotypically identical sister. NAGL-1 showed a pre-B cell phenotype (CD19+, CD10+, c mu+, s mu-) mostly identical to freshly isolated leukemic cells from the patient. This cell line strongly expressed HLA class I and HLA-DR molecules, as well as the costimulatory molecules CD54, CD40, and CD86. Cytotoxic T-lymphocyte (CTL) lines were generated by stimulating the donor-derived peripheral blood mononuclear cells with either irradiated leukemic cells or NAGL-1. Both CTL lines showed specific lysis against NAGL-1 in 51Cr release assays. Lytic activity was partially inhibited by anti-CD8 and anti-HLA class I monoclonal antibodies. Treatment of NAGL-1 with TNF-alpha increased its susceptibility to the CTL line. One CD8+ T cell clone derived from the CTL line killed both the patient phytohemagglutinin (PHA) blasts and NAGL-1 but not the donor PHA blasts, suggesting that the clone recognized the patient-specific minor antigen presented on both PHA blasts and NAGL-1. Utilization of leukemic cell lines could be a useful model for the development of CTL lines and clones for immunological study and potential immunotherapy.

Clinical evaluation of serum and immunohistochemical expression of SCC and CA19-9 in radiation therapy for cervical cancer

The prognostic significance of serum level of SCC and CA19-9 (i.e. sr-SCC and sr-CA19-9) and tumor expression of SCC and CA19-9 (i.e. im-SCC and im-CA19-9) were investigated in patients undergoing radiation therapy for cervical cancer. A total of 103 patients comprising 95 squamous cell carcinomas, 3 adenosquamous cell carcinomas and 5 adenocarcinomas, were studied. The tumor expression of SCC and CA19-9 were determined immunohistochemically. The positivity of the patients with abnormal sr-SCC levels for squamous cell carcinoma, adenosquamous cell carcinoma and adenocarcinoma were 87.7%, 50.0% and 40.0%, respectively The 5-year-survival rates of sr-SCC positive and negative patients were 71.1% and 100%, respectively (P > 0.1). The survival rates of im-SCC positive and negative patients were 70.0% and 80.7%, respectively (P > 0.1). The positivity of patients with im-CA19-9 in squamous cell carcinoma, adenosquamous cell carcinoma, im-CA19-9 adenocarcinoma were 29.1%, 66.6%, and 100%, respectively. The 5-year-survival rates of sr-CA19-9 positive patients was 62.5%, poorer than the 77.6% of negative ones (P < 0.1). The survival rate of im-CA19-9 expression positive patients was 92.0%, significantly better than the 70.7% in negative patients (P < 0.05). Although the sr-SCC level just at the end of radiation therapy was not correlated with local control, re-elevation of the SCC was highly associated with early relapse. These results suggested that follow-up of patients by periodical serum examination for these tumor markers is highly useful for the early detection of tumor relapse.

Two enteropathogenic Escherichia coli type III secreted proteins, EspA and EspB, are virulence factors

Enteropathogenic Escherichia coli (EPEC) belongs to a family of related bacterial pathogens, including enterohemorrhagic Escherichia coli (EHEC) O157:H7 and other human and animal diarrheagenic pathogens that form attaching and effacing (A/E) lesions on host epithelial surfaces. Bacterial secreted Esp proteins and a type III secretion system are conserved among these pathogens and trigger host cell signal transduction pathways and cytoskeletal rearrangements, and mediate intimate bacterial adherence to epithelial cell surfaces in vitro. However, their role in pathogenesis is still unclear. To investigate the role of Esp proteins in disease, mutations in espA and espB were constructed in rabbit EPEC serotype O103 and infection characteristics were compared to that of the wild-type strain using histology, scanning and transmission electron microscopy, and confocal laser scanning microscopy in a weaned rabbit infection model. The virulence of EspA and EspB mutant strains was severely attenuated. Additionally, neither mutant strain formed A/E lesions, nor did either one cause cytoskeletal actin rearrangements beneath the attached bacteria in the rabbit intestine. Collectively, this study shows for the first time that the type III secreted proteins EspA and EspB are needed to form A/E lesions in vivo and are indeed virulence factors. It also confirms the role of A/E lesions in disease processes.

Surgical indication for congenital heart disease with extremely thickened media of small pulmonary arteries

BACKGROUND

Nineteen patients (mean age, 7.6 months) with a percent wall thickness of more than 33% in the small pulmonary arteries were found to have extremely thickened media. Based on our findings, a criterion of operative indication is proposed.

METHODS

The percentage of extremely thickened media of small pulmonary arteries for all pulmonary arteries was determined on microscopic lung sections and was introduced as an index for operative indication.

RESULTS

Operative repair was performed in 16 patients: 9 died intraoperatively and 7 survived more than 12 months. In 4 of 5 patients that had pulmonary artery banding, medial hypertrophy remained despite pulmonary artery banding. Operative repair also had no positive effect. In operative and late deaths and in survivors without a decrease of pulmonary arterial pressure, the percentage of extremely thickened media of small pulmonary arteries was shown to be more than 10%, whereas in 5 survivors and 1 operative death with a significant postoperative decrease of pulmonary arterial pressure, the value was less than 7%.

CONCLUSIONS

If a patient has less than 7% of small pulmonary arteries with extremely thickened media, operative repair is likely to be effective. When the value is higher than 10%, not only operative repair but also pulmonary artery banding cannot be recommended because of ineffectiveness and hazard.

[Actual situation and problems in the information office of clinical laboratories; questionnaire surveys of central laboratories of university hospitals]

The laboratory tests supplied by clinical laboratory comprise an increasing volume in most hospitals. Consultation and effective utilization of laboratory data are important aspects of evidence-based medicine. Effective utilization of laboratory data will also contribute to the efficiency of hospital practice. Questionnaire surveys were conducted to investigate the actual situation in the information office of clinical laboratories in national, public and private facilities of 80 medical universities in Japan. Few facilities demonstrated efficient functioning, although information offices had been opened in six national, one public, and four private universities. The office staff received many questions on specimen handling and analytical methods. In the future, the office will be expected to be actively involved in mutual communications with clinical physicians and an information system such as computerized web is anticipated. Furthermore, a full-time laboratory physician and technicians are expected to provide support as experts in patient diagnosis.

Inoperable pulmonary vascular disease in infants with congenital heart disease

BACKGROUND

Among 120 infants less than 12 months of age who had lung biopsy and autopsy, 20 were inoperable because of severe irreversible pulmonary vascular disease.

METHODS

The infants were classified into three groups. Group 1 comprised 6 patients who showed complete obstruction of the small pulmonary arterial lumen and atrophy of the peripheral arterial media and who were considered to have absolute operative contraindications. Group 2 comprised 6 patients who had no pathologic findings of absolute operative contraindication and had an index of pulmonary vascular disease of more than 2.2. They were isolated as having advanced plexogenic pulmonary arteriopathy. Group 3 comprised 8 patients who had extremely thickened media of small pulmonary arteries, with abnormally thickened media extending into the small peripheral arteries characterized by extremely narrow lumina and medial thickness exceeding luminal diameter.

RESULTS

Six of the 9 patients in whom operative repair was abandoned on the basis of preoperative or intraoperative lung biopsy are still alive. Of the 11 patients who underwent operation without biopsy, none survived.

CONCLUSIONS

Preoperative or intraoperative lung biopsy and assessment of arteriopathy based on the above criteria are recommended in all patients in whom fatal pulmonary vascular disease is suspected.

Thieno[2,3-d]pyrimidine-3-acetic acids. A new class of nonpeptide endothelin receptor antagonists

On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan.

Vascular responsiveness in alloxan-induced diabetes-susceptible (ALS) and resistant (ALR) mice

Changes in reactivity of vascular smooth muscles of male alloxan-induced diabetes-susceptible (ALS) and resistant (ALR) mice aorta were investigated at 2 weeks, 1, 2 and 4 month(s) after the injection of alloxan (45 mg/kg, i.v.). The glucose levels in blood and urine of all the alloxan-treated ALS mice were markedly elevated while those in alloxan-treated ALR and non-treated ALS and ALR mice were not altered. The magnitude of high K+ (65.4 mM)-induced contractions were not affected by the treatment of alloxan. Norepinephrine-induced contractions in vascular smooth muscles of ALS mice in a diabetic state for 2 or 4 months were significantly potentiated. The contractile sensitivity to prostaglandin F2 alpha (PGF2 alpha) was increased in the 4-month-diabetic state. Responsiveness to 5-HT did not vary in the diabetic mouse. Vasorelaxation induced by nitroprusside was attenuated in 2 weeks, 2 or 4 month-diabetic ALS mice. Similarly the inhibitory effects of levcromakalim were attenuated at 2 and 4 months. The influences of diabetes on the inhibitory effects of forskolin or verapamil were very small or not detected. The effects of the vasomodulators used in this study on the vascular smooth muscles of alloxan-treated ALR mice did not differ from those of untreated ALR mice. The results from using ALS and ALR mice suggest that the vasoreactivities to some vasomodulators are changed especially in the long-term diabetic state and that when diabetes was not induced the dose of alloxan does not have any effect on vascular smooth muscle.

In vitro cell-free conversion of noninfectious Moloney retrovirus particles to an infectious form by the addition of the vesicular stomatitis virus surrogate envelope G protein

In the absence of envelope gene expression, retrovirus packaging cell lines expressing Moloney murine leukemia virus (MLV) gag and pol genes produce large amounts of noninfectious virus-like particles that contain reverse transcriptase, processed Gag protein, and viral RNA (gag-pol RNA particles). We demonstrate that these particles can be made infectious in an in vitro, cell-free system by the addition of a surrogate envelope protein, the G spike glycoprotein of vesicular stomatitis virus (VSV-G). The appearance of infectivity is accompanied by physical association of the G protein with the immature, noninfectious virus particles. Similarly, exposure in vitro of wild-type VSV-G to a fusion-defective pseudotyped virus containing a mutant VSV-G markedly increases the infectivity of the virus to titers similar to those of conventional VSV-G pseudotyped viruses. Furthermore, similar treatment of an amphotropic murine leukemia virus significantly allows infection of BHK cells not otherwise susceptible to infection with native amphotropic virus. The partially cell-free virus maturation system reported here should be useful for studies aimed at the preparation of tissue-targeted retrovirus vectors and will also aid in studies of nucleocapsid-envelope interactions during budding and of virus assembly and virus-receptor interactions during virus uptake into infected cells. It may also represent a potentially useful step toward the eventual development of a completely cell-free retrovirus assembly system.

Enhanced gene transfer with fusogenic liposomes containing vesicular stomatitis virus G glycoprotein

Exposure of Lipofectin-DNA complexes to the partially purified G glycoprotein of the vesicular stomatitis virus envelope (VSV-G) results in loss of serum-mediated inhibition and in enhanced efficiency of gene transfer. Sucrose density gradient sedimentation analysis indicated that the VSV-G associates physically with the DNA-lipid complex to produce a VSV-G liposome. The ability to incorporate surrogate viral or cellular envelope components such as VSV-G into liposomes may allow more-efficient and possibly targeted gene delivery by lipofection, both in vitro and in vivo.

A combination therapy with simvastatin and ursodeoxycholic acid is more effective for cholesterol gallstone dissolution than is ursodeoxycholic acid monotherapy

Inhibitors of 3-hydroxy,3-methylglutaryl coenzyme A (HMG-CoA) reductase have been reported to decrease the cholesterol saturation index (CSI) in duodenal bile in humans and to prevent formation of cholesterol gallstones in animal studies. We performed a prospective study to evaluate the role of HMG-CoA reductase inhibitors as gallstone-dissolving agents. Fifty patients with radiolucent gallstones in a gallbladder opacifying at drip infusion cholecystography were treated with either 10 mg/day simvastatin plus 600 mg/day ursodeoxycholic acid (group 1, n=26) or 600 mg/day ursodeoxycholic acid alone (group 2, n=24) for 12 months. The ratio of solitary to multiple gallstone cases was 21:29. Plasma lipid levels were assessed and ultrasonographic examination of the gallbladder was performed at baseline and at 3-month intervals during treatment. Duodenal bile sampling was performed in five patients in each group at baseline and after 12 months of treatment. Plasma cholesterol decreased significantly in group 1 but not in group 2. In solitary gallstone cases, no significant difference in dissolution rates was observed between groups 1 (3 of 9, 33%) and 2 (4 of 12, 33%). In contrast, the dissolution rate in multiple gallstone cases was significantly higher in group 1 (12 of 17, 71%) than in group 2 (3 of 12, 25%) (p < 0.01). Bile cholesterol saturation index was significantly decreased (p < 0.01) but did not significantly differ between the two groups. These results suggest that combination therapy with simvastatin and ursodeoxycholic acid is more effective for cholesterol gallstone dissolution than ursodeoxycholic acid monotherapy in patients with multiple gallstones.