Deletion-type Mutations Research Articles

Effect of PI3-kinase inhibitors on DNA double strand break repair pathways: observations using a site specific DSB induction system.

We established two types of site-specific DNA double strand breaks (DSB) induction systems to elucidate factors which affect the efficiency or quality of DSB repair. For mutation assays, a site specific DSB was generated by the transient expression of a zinc finger nuclease which targets the human HPRT1 gene. A cell line in which time and site specific DSBs can be generated in a HR reporter construct was used for homology-directed repair (HR) analysis. By using these two systems, we investigated the effects of PI3-kinase inhibitors on the efficiency and quality of DSB repair. Ataxia telangiectasia mutated (ATM) kinase inhibition resulted a decrease in mutant frequency and a slight increase in deletion-type mutations accompanied by microhomology. Furthermore, the HR frequency increased significantly when ATM kinase activity was inhibited. Thus, ATM kinase activity might be involved in the suppression of DSB end resection, and this may promote DSB repair through canonical non-homologous end joining.

Clinical and genetic characterization of Duchenne Muscular Dystrophy

Introduction: people with disabilities represent around 10% of the population. The most common of the muscular dystrophies is Duchenne, a recessive X-linked disorder that affects 1 in 3,500 males. Objectives: characterize the clinical and genetic findings of Duchenne muscular dystrophy. Methods: an observational and descriptive study was carried out in a series of 9 patients evaluated at the Department of Medical Genetics of Pinar del Río, Cuba in the period from January 2014 to December 2023. Results: 78% of the total cases were diagnosed between 5 and 8 years of age, in 66.6% of the patients a family history of the disease was reported. Delayed psychomotor development and gastrocnemius pseudohypertrophy were highlighted in 100% of cases followed by gait disturbance, Gowers sign and hyporeflexia in 88.8% of patients. In 77.7% of the patients, deletion-type mutations were identified in some of the exons analyzed. Conclusions: The clinical and molecular characterization of the disease allows the diagnosis to be made and subsequently provides tools to primary care professionals to provide assistance, coordinate care with appropriate specialists, provide genetic counseling not only to the index case but also to the families to screen for female carriers..

Clinical and molecular findings in 6 Turkish cases with Krabbe disease.

Krabbe disease is a rare lysosomal storage disorder with a neurodegenerative course that occurs because of the deficiency of the beta-galactocerebrosidase (GALC) enzyme activity. The genetic basis of Krabbe disease consists of biallelic mutations in the GALC gene, but the genetic spectrum in the Turkish population is poorly defined. We aimed to present a Turkish case-series with infantile-onset Krabbe disease, define the clinical and molecular findings and compare the genetic spectrum with the mutations previously reported in the literature. Six cases, who were referred to our clinic between 2015-2019, with a definite diagnosis of infantileonset Krabbe disease were included in the study. The family history, clinical information, biochemical and radiological examinations of the patients were screened and evaluated. All encoded exons and exon-intron regions of the GALC gene were sequenced using next generation sequencing technology. Multiplex ligationdependent probe amplification analysis was used for deletion type mutations that could not be detected by sequence analysis. GALC gene sequence analysis revealed four known mutations including c.1394C > T (p.Thr465Ile), c.411_413delTAA (p.Lys139del), c.820G > C (p.Glu274Gln), and 30 kilobase deletion mutation among the exons 11-17 (IVS10del30kbp). Moreover, the c.1623G > A (p.Trp541Ter) variant, which was not previously reported in the literature, was detected in two cases. We believe that the demonstration of the genetic spectrum of infantile-onset Krabbe disease in Turkish patients will be an important contribution to the GALC mutation data in our country. More importantly, two novel variants were defined. This knowledge may enable early detection and treatment with the advent of a carrier or newborn screening tests.

Neurodevelopment and Genetic Evaluation of Sotos Syndrome Cases with a Novel Mutation: a Single-Center Experience.

Sotos syndrome is a non-progressive neurological disease with overgrowing, increased bone age, and developmental retardation. The aim of this study is to evaluate the prenatal, natal, and postnatal clinical findings of patients with Sotos syndrome. Sixteen patients suspected to have Sotos syndrome with clinical findings were examined retrospectively, ranging in ages between 3 and 23. In our file screening, we screened the FISH results of all 16 patients, but not all patients had NSD1 gene analysis results. We collected NSD1 gene analysis results, if there were any. The parameters that we investigated for these patients are birth weight, birth length, Apgar score at the 5th minute, dysmorphological face appearance, bone age, seizure, learning disability, feeding difficulties, surgical operation, and other accompanying abnormalities (brain MRI, abnormal echocardiographic findings, chronic otitis media, etc.). The anamnesis, clinical examination findings, and genetic reports of the patients were examined. For this, the hospital registration system was used. Breech presentation, Apgar score in the 5th minute of between 4 and 7, atrial septal defect at echocardiography, and consanguineous marriage rate were detected to be increased in individuals with Sotos syndrome compared to the normal population. When compared to the general population, delayed psychomotor development was determined. Macrocephaly, increased bone age, chronic otitis media frequency, and hernia operation frequency were determined to see if all patients were consistent with the literature. As a result of NSD1 gene sequencing analyses (NSD1 gene analysis was performed in 6 patients and a mutation was detected in 3 of them), three were found to have NSD1 gene mutation (one of them was novel). A novel deletion-type mutation that was not previously reported in the literature in the 19th exon of the NSD1 gene was determined. Xiphoidal protrusion was detected on this patient that had the novel mutation, and this situation has not been reported in the literature previously. If a patient has rapid growth, difficulty in learning, macrocephaly, speech delay, and timid personality, Sotos syndrome can be considered at the pre-diagnosis stage.

Electronic characteristics of BRCA1 mutations in DNA.

The efficient and low-cost way for gene mutation detection and identification are conducive for the detection of disease. Here, we report the electronic characteristics of the gene of breast cancer 1 in four common mutation types: duplication, single nucleotide variant, deletion, and indel. The electronic characteristics are investigated by the combination of density functional theory and non-equilibrium Green's function formulation with decoherence. The magnitude of conductance of these DNA molecules and mutational changes are found to be detectable experimentally. In this study, we also find the significant mutation type dependent on the change of conductance. Hence these mutations are expected to be identifiable. We find deletion type mutation shows the largest change in relative conductance (~97%), whereas the indel mutation shows the smallest change in relative conductance (~27%). Therefore, this work presents a possibility of electronic detection and identification of mutations in DNA, which could be an efficient method as compared to the conventional methods.

Genetic analysis results of patients with a retinoblastoma refractory to systemic chemotherapy

ObjectiveTo analyse the genetic alterations identified in the RB1 gene in retinoblastoma patients who do not respond to systemic chemotherapy. MethodsA genetic analysis was performed on 115 patients with retinoblastoma, 40 of whom had received systemic chemotherapy, and 29 of them had bilateral disease. Descriptive and retrospective study. Non-responders were considered as patients who are finally enucleated. ResultsPatients with deletion type mutations are those with less preservation of the eyeball (Pearson chi-square, P=.055). Patients with an impaired nonsense-frameshift type are more likely to preserve the eyeball. Of the 3 patients who had undergone bilateral enucleation, 2 of them had deletions and one missense alteration. Survival analysis (Kaplan–Meier curve) shows that patients with deletion type mutations are more resistance to chemotherapy, are suffering higher rates of enucleation, and for a shorter period of time (log rank [Mantel–Cox] with a significance level of P=.053), which are also associated with increased rate of being bilateral. ConclusionsPatients with a genotype show increased resistance to chemotherapy should be evaluated more closely and treated with various therapeutic weapons early. Patients that have deletions in the RB1 gene are at increased risk of chemoresistance. It is likely that other genetic alterations other than RB1 gene may be related to tumour aggressiveness and treatment resistance.

Resultados del analisis genético de los pacientes con retinoblastoma resistente a quimioterapia sistémica

ObjectiveTo analyze the genetic alterations identified in the RB1 gene in retinoblastoma patients who do not respond to systemic chemotherapy. MethodsA genetic analysis was performed on 115 patients with retinoblastoma, 40 of whom had received systemic chemotherapy, and 29 of them had bilateral disease. Descriptive and retrospective study. Non-responders were considered as patients who are finally enucleated. ResultsPatients with deletion type mutations are those with less preservation of the eyeball (Pearson Chi-square, P=.055). Patients with an impaired nonsense-frameshift type are more likely to preserve the eyeball. Of the 3 patients who had undergone bilateral enucleation, 2 of them had deletions and one missense alteration. Survival analysis (Kaplan-Meier curve) shows that patients with deletion type mutations are more resistance to chemotherapy, are suffering higher rates of enucleation, and for a shorter period of time (log rank [Mantel-Cox] with a significance level of P=.053), which are also associated with increased rate of being bilateral. ConclusionsPatients with a genotype show increased resistance to chemotherapy should be evaluated more closely and treated with various therapeutic weapons early. Patients that have deletions in the RB1 gene are at increased risk of chemoresistance. It is likely that other genetic alterations other than RB1 gene may be related to tumor aggressiveness and treatment resistance.

Integrating Genotype in Risk Classification for Gist Recurrence. a Spanish Group for Sarcoma Research (Geis) Study

ABSTRACT Aim: Relevant prognostic factors for relapse free survival (RFS) in GIST relies on clinical and pathologic variables as size, mitoses, location or tumor rupture. However, being GIST a solid tumor model for molecular research and targeted therapies, it seems legitimate to explore the integration of relevant molecular prognostic factors into the risk classification. Several authors have pointed out the detrimental prognostic role of deletion type mutations involving 557/558 (DEL-5758) codons of exon 11 in KIT gene. On the other hand, mutations of PDGFR (MUT-PDGFR) gene have been associated with lower risk of recurrence. We will analyze the influence of these genotype factors for each Miettinen risk category (MRC). Methods: Clinical data, therapeutic and follow-up procedures stemmed from the GIST Registry of GEIS. Main inclusion criteria were: localized GIST, adequate surgery, size>2 cm, complete genotype for KIT and PDGFR genes, no adjuvant imatinib and minimum follow-up of 3 years. RFS was measured by Kaplan-Meier method. For each MRC, RFS was estimated for those harboring DEL-5758 or MUT-PDGFR. Univariate and multivariate analysis were performed using log-rank test and Cox regression. Results: 429 patients were identified according to the inclusion criteria, 35 of them had insufficient data, thus 394 patients entered into the analysis. Median size was 7 cm and with a median follow-up of 84 months there were 137 recurrences (37%). DEL-5758 and MUT-PDGFR were present in 65 and 25 cases respectively. The 7-year RFS for low MRC were 93% in MUT-PDGFR, 76% in DEL-5758 and 90% in the remainder (p=0.35), for Intermediate MRC were 80%, 26% and 64% (p=0-009) respectively and for high MRC were 40%, 21% and 28% (p=0.79) respectively. On univariate analysis: mitoses, size, location (gastric vs non gastric) and genotype were found to be significantly correlated with RFS. Multivariate analyses revealed that size (HR 1.75; CI 1.04-2.90), location (HR 1.79; CI 1.24-2.60), mitoses (RR 3.4; CI 2.31-5.05) and DEL-5758 (RR 1.5; CI 1.02-2.32) were independent prognostic factors for RFS. Conclusions: Genotype significantly affects prognosis in localized GIST and therefore should be integrated into the risk classification especially in intermediate MCR. Disclosure: All authors have declared no conflicts of interest.

EGFR and KRAS mutations in Turkish non-small cell lung cancer patients: a pilot study

EGFR and KRAS mutation profile in non-small cell lung cancers (NSCLCs) shows wide variations due to geographic and ethnic background. We aimed to determine the frequency and types of EGFR and KRAS mutations in a sample group of Turkish NSCLC cases. The study included 14 adenocarcinomas (ACs), 11 squamous cell carcinoma (SCC) patients selected from archival material including small biopsy or surgical specimens. Their formalin fixed paraffin-embedded tumor tissues were used for genomic DNA extraction for EGFR exon 19 and 21, and KRAS exon 2 mutations. Eleven NSCLCs (44 %) had EGFR mutations. Exon 19 and 21 mutations were found in 8 (32 %) and 5 (20 %) cases. Two cases showed double EGFR mutations. In ACs, 5 (35.7 %) patients had EGFR gene mutation, 3 in exon 19 and 3 in exon 21. In SCCs, 6 (54.5 %) cases had EGFR mutation, 5 in exon 19 and 2 in exon 21. All exon 19 mutations were deletion-type mutations. For exon 21, 3 cases had L858R point mutation (CTG>CGG) and two cases showed deletion-type mutations. Six (24 %) NSCLCs showed KRAS mutations (three ACC, three SCC), 5 codon 12 mutations (G>T, T>C, G>A) and one codon 13 mutation (G>T). Three NSCLC cases showed both EGFR and KRAS mutations together. The profile of KRAS mutation in our AC cases was quite similar to those seen in the Western countries; however, frequency and clustering of EGFR mutations were similar to those seen in the Eastern countries.

Global Developmental Delay, Progressive Relapsing-Remitting Parkinsonism, and Spinal Syrinx in a Child With SOX6 Mutation

SOX6, a member of the SOX gene family, plays a key role in the development of several mammalian tissues and organs, including the central nervous system. Specifically, this gene modulates the differentiation and proliferation of interneurons in the medial ganglionic eminence, as well as oligodendrocytes in the spinal cord. We describe the case of a 4-year-old girl with global developmental delay and a spinal cord syrinx who presented with recurrent episodes of parkinsonian symptoms subsequent to febrile illnesses. The symptoms included gait instability, tremor, and dysarthria, with a progressive relapsing-remitting course over the span of 2 years. The patient was later found to have a large deletion-type mutation in the SOX6 gene. This case is the first report in humans implying a role for SOX6 in basal ganglia function, as well as spinal cord development.

DELETIONS IN MITOCHONDRIAL DNA FROM LASER MICRODISSECTED BLOOD VESSELS OF ALZHEIMER BRAINS

The role of neurovascular dysfunction has long been suggested to be of relevance in the disease pathology of Alzheimer's. However, a mitochondrial genetic cause for vascular dysfunction has yet to be investigated in depth. We examined the mtDNA of individual cerebral endothelial cells obtained by laser micro‐dissection from 9 Alzheimer disease brains in late Braak & Braak topographical stages of pathology. The objective of our study was to detect deletion‐type mutations in the mtDNA by scanning a region of the genome in which deletions have been most commonly detected. We detected 4 separate mtDNA mutations from a total of 18 endothelial cells isolated from 9 Alzheimer brains (2 cells from each). These mutations were characterized by sequence analysis. We suggest that the presence of mtDNA mutations in the small number of endothelial cells from Alzheimer brains indicates that the microvascular cell population may harbor a high aggregate level of such mutations, potentially underlying increasing vascular dysfunction in Alzheimer disease and, possibly, in aging.

Severe brain atrophy after long-term survival seen in siblings with familial amyotrophic lateral sclerosis and a mutation in the optineurin gene: a case series

IntroductionPrevious studies have shown widespread multisystem degeneration in patients with sporadic amyotrophic lateral sclerosis who develop a total locked-in state and survive under mechanical ventilation for a prolonged period of time. However, the disease progressions reported in these studies were several years after disease onset. There have been no reports of long-term follow-up with brain imaging of patients with familial amyotrophic lateral sclerosis at an advanced stage of the disease. We report the cases of siblings with amyotrophic lateral sclerosis with homozygous deletions of the exon 5 mutation of the gene encoding optineurin, in whom brain computed tomography scans were followed up for more than 20 years.Case presentationThe patients were a Japanese brother and sister. The elder sister was 33 years of age at the onset of disease, which began with muscle weakness of her left lower limb. Two years later she required mechanical ventilation. She became bedridden at the age of 34, and died at the age of 57. A computed tomography scan of her brain at the age of 36 revealed no abnormality. Atrophy of her brain gradually progressed. Ten years after the onset of mechanical ventilation, atrophy of her whole brain, including the cerebral cortex, brain stem and cerebellum, markedly progressed. Her younger brother was 36 years of age at the onset of disease, which presented as muscle weakness of his left upper limb. One year later, he showed dysphagia and dysarthria, and tracheostomy ventilation was performed. He became bedridden at the age of 37 and died at the age of 55. There were no abnormal intracranial findings on brain computed tomography scans obtained at the age of 37 years. At the age of 48 years, computed tomography scans showed marked brain atrophy with ventricular dilatation. Subsequently, atrophy of the whole brain rapidly progressed as in his elder sister.ConclusionWe conclude that a homozygous deletion-type mutation in the optineurin gene may be associated with widespread multisystem degeneration in amyotrophic lateral sclerosis.

Mutations Induced by Tritiated Water in Mouse Spleen

We first examined two lines of transgenic mouse, gpt delta and Muta, for sensitivity of radiation-induced mutations in spleen. The gpt delta mouse could detect mutations induced by 2 to 8 Gy of gamma-rays with 2-times higher sensitivity than Muta mouse. The reason seemed to be that radiation induces predominantly deletion type mutation which is rather rare in natural background and gpt delta mouse can detect exclusively this deletion type mutation, whereas Muta mouse detects all types of mutation including the deletion. Next, we applied the gpt delta mouse to study mutation induction by tritiated water. A half ml of saline containing 0, 266 or 532 MBq of tritiated water was administered to the mice intraperitoneally and mutations in spleen were examined 7 days later. The estimated absorbed doses were 0, 3 and 6 Gy, respectively. With 3 Gy, the mutant frequency was elevated approximately 2-fold above control level, and it remained at a similar level with 6 Gy. These indicate that gpt delta mouse could be a good model animal to study genotoxicity of tritium.

* Cetuximab combined with multi-targeted sirna against HSP90, UBCH5, and SRC circumvented oncogene addiction, transactivation, and acquired resistance as a result of EGFR ubiquitination, and mutations/deletions in the kinase domain of EGFR in colorectal CA

IntroductionColorectal carcinoma (CRC) cells develop resistance to cetuximab through insertion mutations at exon 20, ubiquitination and c-Src which activates EGFR in the absence of ligand despite treatment with cetuximab. We...

Radiation Dose-Rate Effect on Mutation Induction in Spleen and Liver of gpt delta Mice

The effect of dose rate on radiation-induced mutations in two somatic tissues, the spleen and liver, was examined in transgenic gpt delta mice. These mice can be used for the detection of deletion-type mutations, and these are the major type of mutation induced by radiation. The dose rates examined were 920 mGy/min, 1 mGy/min and 12.5 microGy/min. In both tissues, the number of mutations increased with increasing dose at each of the three dose rates examined. The mutation induction rate was dependent on the dose rate. The mutation induction rate was higher in the spleen than in the liver at the medium dose rate but was similar in the two tissues at the high and low dose rates. The mutation induction rate in the liver did not show much change between the medium and low dose rates. Analysis of the molecular nature of the mutations indicated that 2- to 1,000-bp deletion mutations were specifically induced by radiation in both tissues after high- and low-dose-rate irradiation. The occurrence of deletion mutation without any sequence homology at the break point was elevated in spleen after high-dose-rate irradiation. The results indicate that the mutagenic effects of radiation in somatic tissues are dependent on dose rate and that there is some variability between tissues.

EGFR exon 20 insertion mutation in Japanese lung cancer

Mutations of the epidermal growth factor receptor (EGFR) gene have been reported in non-small cell lung cancer (NSCLC), especially in female, never smoker patients with adenocarcinoma. Some common somatic mutations in EGFR, including deletion mutations in exon 19 and leucine to arginine substitution at amino acid position 858 (L858R) in exon 21, have been examined for their ability to predict sensitivity to gefitinib or erlotinib. On the other hand, previous report has shown that the insertion mutation at exon 20 is related to gefitinib resistance. We investigated the exon 20 EGFR mutation statuses in 322 surgically treated non-small cell lung cancer cases. Two hundred and five adenocarcinoma cases were included. The presence or absence of EGFR mutations of kinase domains was analyzed by direct sequences. EGFR insertion mutations at exon 20 were found from 7 of 322 (2.17%) lung cancer patients. We also detected the 18 deletion type mutations in exon 19, and 25 L858R type mutations in exon 21. There was a tendency towards higher exon 20 insertion ratio in never smoker (never smoker 4.4% versus smoker 1.3%, p=0.0996) and female (female 4.5% versus male 1.3%, p=0.0917). Two exon 20 insertion cases were treated with gefitinib and failed to response. EGFR insertion mutation in exon 20 could not be ignored from Japanese lung cancers.

Characteristics of mutations generated through digestion with restriction enzyme and ligation in plasmid DNA.

Recently, the use of restriction enzymes has been extended to studies in which rare events such as mutation and mistakes in DNA repair are examined. In these studies, the specificity of restriction enzymes becomes critical. To clarify the nature of the rare unexpected events occurring in the process of cutting of DNA with restriction enzymes then ligating it, we studied the molecular characteristics of unexpected plasmid DNAs that were retrieved as mutants of the plasmid after transfection to E. coli. The plasmid used was pUR288, containing lacZ as a marker of mutation. It was digested with restriction enzymes under the conditions recommended by the supplier of the enzymes and under the presence of DMSO, which is known to induce star activity of the enzymes. Comparisons of mutant frequencies and of nucleotide sequences of the mutants found in the different conditions indicated that nonspecific endonucleolytic activity similar to that found under star activity was present under the recommended conditions and, further, was responsible for the creation of deletion-type mutations. The frequency of these events ranged from 10(-5) to 10(-3), depending on the kind of restriction enzymes analyzed. Although the levels of the nonspecificity were not high, they should be considered in assays such as mutation and mistakes in DNA repair, where rare events are examined.

Analysis of deletion mutations of the rpsL gene in the yeast Saccharomyces cerevisiae detected after long-term flight on the Russian space station Mir

Using the yeast Saccharomyces cerevisiae on board the Russian space station Mir, we studied the effects of long-term space flight on mutation of the bacterial ribosomal protein L gene ( rpsL) cloned in a yeast- Escherichia coli shuttle vector. The mutation frequencies of the cloned rpsL gene on the Mir and the ground (control) yeast samples were estimated by transformation of E. coli with the plasmid DNAs recovered from yeast and by assessment of the conversion of the rpsL wild-type phenotype (Sm S) to its mutant phenotype (Sm R). After a 40-day space flight, some part of space samples gave mutation frequencies two to three times higher than those of the ground samples. Nucleotide sequence analysis showed no apparent difference in point mutation rates between the space and the ground mutant samples. However, the greater part of the Mir mutant samples were found to have a total or large deletion in the rpsL sequence, suggesting that space radiation containing high-linear energy transfer (LET) might have caused deletion-type mutations.

CYP2A6 Gene Deletion Reduces Susceptibility to Lung Cancer

CYP2A6 is an enzyme with a high ability to activate a nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), to its potent and ultimate carcinogen. In the present study, we investigated the relationship between genetic polymorphism of CYP2A6 and lung cancer risk in a case-control study of Japanese subjects. Genotyping of the CYP2A6 gene in both healthy volunteers and lung cancer patients was conducted. The frequency with which the subjects carried homozygotes of the CYP2A6 gene deletion-type mutation (deletion), which causes lack of the enzyme activity, was lower in the lung cancer patients than in the healthy control subjects. The odds ratio (OR) of the group homozygous for the deletion was significantly lower and calculated to be 0.25 (95% CI; 0.08–0.83) when the OR for the population with homozygotes of the CYP2A6 wild-type gene was defined as 1.00. In the allelic-base analysis, there was also a significant decrease in the OR for the deletion allele. These data suggest that deficient CYP2A6 activity due to genetic polymorphism reduces lung cancer risk.

A novel gain-of-function mutation of c- kit gene in gastrointestinal stromal tumors

Background & Aims: The c- kit gene encodes a receptor tyrosine kinase (KIT). Recently, we found gain-of-function mutations of the c- kit gene in gastrointestinal stromal tumors (GISTs). All mutations were confined within the 11 amino acids (Lys-550 to Val-560) in the juxtamembrane domain, but one GIST showed a novel deletion-type mutation at codon 579 (Asp) in the juxtamembrane domain. The aim of this study was to clarify whether the mutation is activating. Methods: Mutant c- kit cDNA was transfected into an interleukin 3 (IL-3)-dependent Ba/F3 murine lymphoid cell line, and the magnitude of autophosphorylation of the mutant KIT was examined with or without stem cell factor (SCF), a ligand of KIT. An in vitro kinase assay was also performed. The biological behavior of the transfectant was estimated by both an in vitro proliferation assay and in vivo transplantation to nude mice. Results: The mutant KIT exhibited constitutive phosphorylation and strong kinase activity without SCF. The transfectant grew autonomously without IL-3 and SCF, and it formed tumors in nude mice. Conclusions: Deletion at codon 579 (Asp) in the juxtamembrane domain of the c- kit gene is a novel gain-of-function mutation other than the region between Lys-550 and Val-560. GASTROENTEROLOGY 1998;115:1090-1095