Recommendations for the management of irritable bowel syndrome in family practice

To help family physicians manage patients with irritable bowel syndrome (IBS), a consensus conference was convened in June 1997 at which 5 internationally recognized experts in IBS presented position papers on selected topics previously circulated to the conference participants. Five working groups comprising family physicians, gastroenterologists and allied health care professionals from across Canada were then charged with developing recommendations for the diagnosis, patient education, psychosocial management, dietary advice and pharmacotherapy, respectively. An evidence-based approach was used where possible; otherwise, recommendations were made by consensus. The participants concluded that family physicians can make a positive diagnosis of IBS using symptom criteria. The pathophysiology is poorly understood, but motility and sensory disturbances appear to play a role. Neither psychological nor specific dietary factors cause IBS, but both can trigger symptoms. Drug therapy is not recommended for the routine treatment of IBS, but short-term trials of drug therapy may be targeted to predominant symptoms in selected patients. A step-wise, patient-centred approach to management is outlined.     

肠道菌群与肠易激综合征相关研究进展

肠易激综合征(irritable bowel syndrome,IBS)是一种功能性肠病,目前已有研究表明IBS的致病机制、症状的产生和持续时间可能与肠道菌群失调有关,且不同IBS亚型患者体内的肠道菌群种类有差异。IBS的发病机制尚不完全清楚,临床表现存在较大的个体差异。IBS的诊断和治疗尚未形成统一的标准。但已经有较多研究提示IBS可能与胃肠道动力、内脏高敏感性、肠道免疫反应和模式识别受体等密切相关,并且可以通过益生菌、益生元、抗生素、粪菌移植和饮食习惯等调节肠道菌群的失调,从而改善IBS的症状。这也为未来治疗IBS提供了新的思路。本文就肠道菌群的概况、IBS患者肠道菌群的特点、肠道菌群失衡导致IBS发病的可能机制以及IBS肠道菌群的相关治疗方法的研究进展作一综述。     

Blastocystis sp. in Irritable Bowel Syndrome (IBS) - Detection in Stool Aspirates during Colonoscopy

Blastocystis is one of the most common gut parasites found in the intestinal tract of humans and animals. Its'' association with IBS is controversial, possibly as a result of irregular shedding of parasites in stool and variation in stool detection. We aimed to screen for Blastocystis in colonic stool aspirate samples in adult patients with and without IBS undergoing colonoscopy for various indications and measure the interleukin levels (IL-8, IL-3 and IL-5). In addition to standard stool culture techniques, polymerase chain reaction (PCR) techniques were employed to detect and subtype Blastocystis. All the serum samples collected were subjected for ELISA studies to measure the interleukin levels (IL-8, IL-3 and IL-5). Among 109 (IBS n = 35 and non-IBS n = 74) adults, direct stool examination and culture of colonic aspirates were initially negative for Blastocystis. However, PCR analysis detected Blastocystis in 6 (17%) IBS and 4 (5.5%) non-IBS patients. In the six positive IBS patients by PCR method, subtype 3 was shown to be the most predominant (3/6: 50%) followed by subtype 4 (2/6; 33.3%) and subtype 5 (1/6; 16.6%). IL-8 levels were significantly elevated in the IBS Blasto group and IBS group (p<0.05) compared to non-IBS and non-IBS Blasto group. The level of IL-3 in were seen to be significantly higher in than IBS Blasto group and IBS group (p<0.05) compared to non-IBS. Meanwhile, the IL-5 levels were significantly higher in IBS Blasto group (p<0.05) compared to non-IBS and non-IBS Blasto group. This study implicates that detecting Blastosystis by PCR method using colonic aspirate samples during colonoscopy, suggests that this may be a better method for sample collection due to the parasite’s irregular shedding in Blastocystis-infected stools. Patients with IBS infected with parasite showed an increase in the interleukin levels demonstrate that Blastocystis does have an effect in the immune system.     

HRV Biofeedback for Pediatric Irritable Bowel Syndrome and Functional Abdominal Pain: A Clinical Replication Series

Irritable bowel syndrome (IBS) and Functional Abdominal Pain (FAP) are among the most commonly reported Functional Gastrointestinal Disorders. Both have been associated with varying autonomic dysregulation. Heart Rate Variability Biofeedback (HRVB) has recently begun to show efficacy in the treatment of both IBS and FAP. The purpose of this multiple clinical replication series was to analyze the clinical outcomes of utilizing HRVB in a clinical setting. Archival data of twenty-seven consecutive pediatric outpatients diagnosed with IBS or FAP who received HRVB were analyzed. Clinical outcomes were self-report and categorized as full or remission with patient satisfaction, or no improvement. Qualitative reports of patient experiences were also noted. Full remission was achieved by 69.2 % and partial remission was achieved by 30.8 % of IBS patients. Full remission was achieved by 63.6 % and partial remission was achieved by 36.4 % of FAP patients. No patients in either group did not improve to a level of patient satisfaction or >50 %. Patient’s commonly reported feeling validated in their discomfort as a result of psychophysiological education. Results suggest that HRVB is a promising intervention for pediatric outpatients with IBS or FAP. Randomized controlled trials are necessary to accurately determine clinical efficacy of HRVB in the treatment of IBS and FAP.     

A public health approach to cholesterol. Confronting the 'TV-auto-supermarket society'.

Coronary heart disease has been proved to be associated with a "high-risk" diet and with elevated blood cholesterol levels. The National Cholesterol Education Program has embarked on a campaign based on intensive medical treatment of 60 million Americans with high blood cholesterol levels, but the degree of benefit of dietary change or pharmaceutical intervention or both to reduce blood cholesterol values remains a subject of disagreement within the scientific community. Evidence from comparative international studies suggests that to lower coronary heart disease mortality substantially, dietary alterations and general societal changes must be greater than those possible under the National Cholesterol Education Program''s approach of physician-centered patient counseling. The nation''s priority to prevent coronary heart disease should be a public policy approach, the goal of which is to reduce for the entire population all coronary disease risk factors. In the dietary area, three proposals to reduce the availability of atherogenic foods are the use of warning labels on atherogenic foods, the prohibition of advertising for such high-risk foods, and the imposition of an excise tax on the same foods. We must confront the "TV-auto-supermarket society" that underlies our nation''s high rate of coronary heart disease.     

美常安干预肠易激综合征伴小肠细菌过度生长的研究

目的通过美常安干预肠易激综合征(IBS)伴小肠细菌过度生长(SIBO)患者,探讨IBS与SIBO之间的关系。方法选取40例IBS患者为IBS组,40例健康志愿者为对照组,两组患者治疗前均进行乳果糖氢呼气试验(LHBT)明确SIBO情况。IBS组中SIBO阳性者予美常安干预,观察其治疗前后的症状变化,疗程结束后复查LHBT。结果 IBS组患者SIBO发病率为55.0%,对照组为10.0%,两组患者SIBO发病率比较差异有统计学意义(P0.05);IBS组中SIBO阳性患者治疗后显效1例,有效12例,无效6例,脱落3例,有效率为68.0%,SIBO转阴率为57.9%。IBS组中SIBO阳性患者治疗前后腹胀程度、排便频率异常时间、排便时腹痛率及总积分比较差异有统计学意义(P0.05)。结论 IBS患者SIBO发病率远高于健康者,美常安能改善IBS伴SIBO患者部分症状及SIBO发病率,IBS的发生与SIBO之间存在一定关系,但对于IBS患者单纯补充益生菌制剂疗效并不理想,仍需结合其他手段进行干预。     

The Incidence of Other Gastroenterological Disease following Diagnosis of Irritable Bowel Syndrome in the UK: A Cohort Study

Background

Guidelines recommend Irritable Bowel Syndrome (IBS) diagnosis and management in primary care with minimal investigations; however little evidence exists regarding risk of organic gastrointestinal conditions following diagnosis of IBS and how such risks vary over the long term. This study assesses excess incidence of coeliac disease, inflammatory bowel disease (IBD) and colorectal cancer (CRC) and variation with age and time after IBS diagnosis.

Methods

IBS patients and controls were identified within the UK Clinical Practice Research Dataset. Incidence rates were calculated and stratified by age and time since IBS diagnosis with incident rate ratios generated.

Results

Fifteen years after IBS diagnosis there is a significant cumulative excess incidence of coeliac disease, IBD and CRC in IBS of 3.7% compared to 1.7% in controls. For every 10000 patient years, IBS patients experienced an additional 4 diagnoses of coeliac disease, 13 of IBD and 4 CRCs. In each condition peak excess incidence was in the 6 months following diagnosis. After one year, increased incidence of coeliac disease remained consistent without variation by age. IBD incidence fell slowly, with higher rates in those under 30. CRC incidence was increased only in patients aged 30 to 74 during the first 5 years.

Conclusion

Some IBS patients later receive organic gastrointestinal diagnoses, with the early excess incidence likely detected during diagnostic investigation at the time of IBS diagnosis. More than 5 years after IBS diagnosis there is no increased risk of CRC compared to the general population, but a small excess risk of coeliac disease and IBD persists. Overall, though our findings provide reassurance that non-specialists, especially those in primary care, are unlikely to be missing an organic condition in the majority of their patients. This suggests that current guidelines suggesting avoidance of universal referral for these patients are appropriate.     

Comparison of methods for detection of Blastocystis infection in routinely submitted stool samples, and also in IBS/IBD Patients in Ankara, Turkey

Background

This study compared diagnostic methods for identifying Blastocystis in stool samples, and evaluated the frequency of detection of Blastocystis in patients with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Results and Discussion

From a set of 105 stool specimens submitted for routine parasitological analysis, 30 were identified as positive for Blastocystis by the culture method. From that group of 30 positives, Lugol''s stain, trichrome staining, and an immunofluorescence assay identified 11, 15, and 26 samples as positive respectively. Using culture as a standard, the sensitivity of Lugol''s stain was 36.7%, trichrome staining was 50%, and the IFA stain was 86.7%. The specificity of Lugol''s stain was 91%, trichrome staining was 100%, and the IFA stain was 97.3%. In the group of 27 IBS and IBD patients, using all methods combined, we detected Blastocystis in 67% (18/27) of the patients. Blastocystis was detected in 33% (2/6) of IBD patients and 76% (16/21) of IBS patients. For comparison, trichrome staining alone, the method most frequently used in many countries, would have only identified Blastocystis infection in 29% (6/21) of the IBS patients. No parasitic co-infections were identified in the IBS/IBD patients. Most Blastocystis-positive IBS/IBD patients were over 36 with an average length of illness of 4.9 years.

Conclusions

Most IBS patients in this study were infected with Blastocystis. IFA staining may be a useful alternative to stool culture, especially if stool specimens have been chemically preserved.     

The influence of the two different light intensities duringthe daytime on the colon motility in patients with irritable bowel syndrome (IBS): a preliminary report

Irritable bowel syndrome (IBS) is the most frequent functional disorder of the gastrointestinal tract, with great economical impact. The etiology and pathogenesis of the disease are unclear. Among patients seeking medical attention for IBS, 70 - 90% have psychiatric co-morbidity, most commonly major depression. In this study we test the influence of bright light on colon motility and subjectively felt symptoms. Eight IBS patients participated in the experiment. The passage rate was evaluated twice for every person: (1) after three days of exposure to bright light -3000 lux (from 8:00 to 18:00), (2) after three days exposure to dim light -100 lux (from 8:00 to 18:00). The comparison of colonic time in IBS patients point to differences in the elimination of markers, depending on experimental light conditions. After bright light conditions a tendency is observed to slower elimination of markers in the IBS-diarrhoea patients, and to a quicker elimination in the IBS-constipated patients. According to subjective feeling, all IBS patients reported an improvement in bowel function and relief of pain after bright but not after dim light application. Results of this preliminary study suggest that phototherapy might be a valuable addition to the conventional treatment of IBS.     

Towards positive diagnosis of the irritable bowel.

A questionnaire to establish the presence of 15 symptoms thought to be typical of the irritable bowel syndrome (IBS) was given to 109 unselected patients referred to gastroenterology or surgery clinics with abdominal pain or a change in bowel habit or both. Review of case records 17--26 months later established a definite diagnosis of IBS in 32 patients and of organic disease in 33. Four symptoms were significantly more common among patients with IBS--namely, distension, relief of pain with bowel movement, and looser and more frequent bowel movements with the onset of pain. Mucus and a sensation of incomplete evacuation were also common in these patients. The more of these symptoms that were present the more likely was it that the patient''s pain or altered bowel habit, or both, was due to IBS. We conclude that a careful history can increase diagnostic confidence and reduce the amount of investigation in many patients with chronic abdominal pain.     

Allowing for missing data at highly polymorphic genes when testing for maternal, offspring and maternal-fetal genotype incompatibility effects

Genes can be associated with disease through an individual's inherited genotype, the maternal genotype or the interaction between these two. When the gene is highly polymorphic, it is more difficult to identify the gene's functional role than for less polymorphic loci, because different alleles at the locus may be associated with the disease through separate and joint effects from maternal and offspring genotypes. Family-based studies are used to test genetic associations because of their robustness to population stratification. However, parental genotype data are often missing, and omitting incompletely genotyped families is inefficient. Methods have been proposed to accommodate incomplete families in family-based association studies. They are not easily generalized to allow simultaneous examination of offspring allelic, maternal allelic and maternal-fetal genotype (MFG) incompatibility effects. Since many MFG incompatibility effects occur through matching between maternal and offspring's genotypes, we present an identity-by-state (IBS) framework to incorporate incomplete families in the MFG test when modeling genetic effects produced by a polymorphic gene. Using simulations, we examine the MFG test's performance with incomplete parental genotype data and an IBS framework. The MFG test using the IBS framework is immune to population stratification and efficiently uses information from incomplete families.     

Application of O-(4-diazo-3-[125I]iodobenzoyl)sucrose for the detection of the catabolic sites of low density lipoprotein

The sites of degradation of human low density lipoprotein (LDL), are analyzed using the novel labelling compound O-(4-diazo-3-[125I]iodobenzoyl)sucrose (D125IBS). The decay from rat serum of D125IBS-labelled LDL is identical to the serum decay of conventionally iodinated (ICI method) LDL. The radioactivity derived from D125IBS-labelled LDL accumulates predominantly in the liver after intravenous injection and the hepatic radioactivity remains associated with the lysosomal compartment for an extended period of time, when compared to the radioactivity derived from conventionally iodinated LDL. It is concluded that the D125IBS labelling procedure is an interesting new tool to study the sites of catabolism of serum lipoproteins.     

Candidate genes and sensory functions in health and irritable bowel syndrome

Adrenergic and serotonergic (ADR-SER) mechanisms alter gut (GI) function; these effects are mediated through G protein transduction. Candidate genetic variations in ADR-SER were significantly associated with somatic scores in irritable bowel syndrome (IBS) and gastric emptying but not small bowel or colonic transit. Our aim was to assess whether candidate ADR-SER genes are associated with motor and sensory GI functions in IBS and subgroups on the basis of bowel dysfunction. In 122 patients with IBS and 39 healthy controls, we assessed gastrointestinal somatic symptoms and affect by validated questionnaires. We measured: gastric volume (GV), maximum tolerated volume, rectal compliance, sensation thresholds and ratings, and genetic variations including alpha2A (C-1291G), alpha2C (Del 332-325), GNbeta3 (C825T), and 5-HTTLPR. Demographics and genotype distributions were similar in the patients with IBS subgrouped on bowel function. There were significant associations between 5-HTTLPR SS genotype and absence of IBS symptoms and between 5-HTTLPR LS/SS genotype and increased rectal compliance and increased pain ratings, particularly at 12 and 24 mmHg distensions. GNbeta3 was associated only with fasting GV; we did not detect associations between alpha2A genotype and the gastrointestinal sensory or motor functions tested. We concluded that 5-HTTLPR LS/SS genotype is associated with both increased pain sensation and increased rectal compliance though the latter effect is unlikely to contribute to increased pain sensation ratings with LS/SS genotype. The data suggest the hypotheses that the endophenotype of visceral hypersensitivity in IBS may be partly related to genetic factors, and the association of GNbeta3 with fasting GV may explain, in part, the reported association of GNbeta3 with dyspepsia.     

Exon sequence requirements for excision in vivo of the bacterial group II intron RmInt1

Background

Group II intron splicing proceeds through two sequential transesterification reactions in which the 5' and 3'-exons are joined together and the lariat intron is released. The intron-encoded protein (IEP) assists the splicing of the intron in vivo and remains bound to the excised intron lariat RNA in a ribonucleoprotein particle (RNP) that promotes intron mobility. Exon recognition occurs through base-pairing interactions between two guide sequences on the ribozyme domain dI known as EBS1 and EBS2 and two stretches of sequence known as IBS1 and IBS2 on the 5' exon, whereas the 3' exon is recognized through interaction with the sequence immediately upstream from EBS1 [(δ-δ' interaction (subgroup IIA)] or with a nucleotide [(EBS3-IBS3 interaction (subgroup IIB and IIC))] located in the coordination-loop of dI. The δ nucleotide is involved in base pairing with another intron residue (δ') in subgroup IIB introns and this interaction facilitates base pairing between the 5' exon and the intron.

Results

In this study, we investigated nucleotide requirements in the distal 5'- and 3' exon regions, EBS-IBS interactions and δ-δ' pairing for excision of the group IIB intron RmInt1 in vivo. We found that the EBS1-IBS1 interaction was required and sufficient for RmInt1 excision. In addition, we provide evidence for the occurrence of canonical δ-δ' pairing and its importance for the intron excision in vivo.

Conclusions

The excision in vivo of the RmInt1 intron is a favored process, with very few constraints for sequence recognition in both the 5' and 3'-exons. Our results contribute to understand how group II introns spread in nature, and might facilitate the use of RmInt1 in gene targeting.     

Change in Quality of Life for Patients with Irritable Bowel Syndrome following Referral to a Gastroenterologist: A Cohort Study

BackgroundIrritable bowel syndrome (IBS), a chronic functional condition, considerably reduces quality of life (QoL) and referral to gastroenterology is common. Until now, however, the impact of seeing a gastroenterologist for IBS on patients’ QoL and utility has not been assessed.MethodsPatients referred with “probable IBS” to the Nottingham Treatment Centre between October 2012 and March 2014 were invited to complete a QoL questionnaire (EuroQol–5 Dimension) before their first appointment. Patients with confirmed IBS who completed this baseline assessment were sent follow-up questionnaires three and twelve months later. Global QoL and utility were measured at each time point and change from baseline calculated. Paired t-tests analysed the significance of any change.ResultsOf 205 invited patients, 69 were eligible and recruited. Response at three and twelve months was 45% and 17% respectively. Median global QoL at baseline was 67.5 (Interquartile range [IQR] 50.0 to 80.0), with a mean increase of 3.25 (95% confidence interval [CI] -5.38 to 11.88) three months later and a mean decrease of -1.82 (95% CI -16.01 to 12.38) after one year. The median utility at baseline was 0.76 (IQR 0.69 to 0.80), with a mean increase of 0.06 (95%CI -0.01 to 0.14) at three months and no change, 0.00 (-0.16 to 0.16), after one year.ConclusionPatients experienced a small but not statistically significant increase in QoL and utility three months after seeing a gastroenterologist for IBS, which was not maintained. Gastroenterology referral does not appear to appreciably improve Qol for most people with IBS.     

Biases in Studying the Diet of the Bearded Vulture

Abstract: We compared methods of assessing the diet of the bearded vulture (Gypaetus barbatus) during the nestling period in the Pyrenees, northeast Spain. We determined diet from direct observations of food items delivered to the nest, recent prey remains present in the nest, remains collected in the nests after fledging, and remains collected in the ossuaries (bone-breaking sites). Data suggest that direct observation (food items delivered and recent prey remains present in the nest) is the only valid method of assessing the bearded vulture's diet accurately. Remains overestimated the presence of large mammals, such as cows (Bos taurus) and horses (Equus caballus), Suidae, and birds; delivered samples contained a higher proportion of small mammals, medium-sized mammals, micromammals, and reptiles. Ossuaries also differed from delivered samples because remains collected there overestimated large and medium-sized mammals. Concerning the skeletal parts, ossuaries, compared to all other methods, underestimated extremities and overestimated long bones, such as femur, humeri and tibiae, scapulae, vertebrae, and skulls. Remains samples, which overestimated scapulae, also differed from delivered and present samples. Our results suggest that bearded vultures favor extremities of prey (78% of the mammal remains, which make up 95% of the diet). The prevalence of small carcasses (almost 17%) suggests that vultures select small animals for food for the young. Because food quality may influence breeding success, future conservation projects based on the selective provision of food to breeding pairs should add to food stations meat remains and small carcasses consistent with our assessment of the birds’ dietary needs.     

Selenium Was a Time Bomb

At high dietary levels, selenium causes adverse effects in animals. Aquatic birds are among the more sensitive wildlife species, because their reproduction can be impaired when dietary selenium levels exceed about 4?µg/g (dry weight basis). Fish can also be adversely affected at similar dietary exposures. Conversely, low dietary levels of selenium (below about 0.1 to 0.5?µg/g) cause nutritional deficiencies in domestic animals, fish, and wildlife. Selenium became recognized as a significant environmental contaminant for wildlife in 1983, with the discovery of developmental abnormalities and excessive embryonic mortality in aquatic birds at Kesterson Reservoir, California. There are a number of environmental settings in which selenium warrants concern and must be considered carefully in relation to potential effects to fish and wildlife, and there may still be surprises in which it unexpectedly becomes a significant ecological issue. However, if selenium is included among the chemicals of potential ecological concern when ecological risk assessments are planned and conducted, there is enough information to thoroughly evaluate its environmental significance in much the same way as other contaminants. The main difference is that it is essential to have a good understanding of selenium's occurrence, complex biogeochemistry, and ecotoxicology to avoid serious errors.     

基于脑-肠-微生物轴的肠易激综合征机制与治疗研究进展

肠易激综合征(irritablebowelsyndrome,IBS)是常见的功能性肠病之一,目前尚缺乏可用器质性疾病解释的临床特征,最新研究将其机制描述为脑-肠-微生物轴紊乱,强调了肠道微生物群在调节脑肠互动中的中介作用,而中医药对于脑肠稳态调节有着悠久广泛的治疗经验并取得了良好疗效,但两者关联性缺乏论述。因此,本文以脑肠轴为切入点,以肠道微生物作为介质,基于脑肠轴-中医药的良性互动,结合我们相关工作,综述了目前与脑-肠-微生物轴相关的IBS的中西医研究,为同行提供参考。     

Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which abdominal pain is associated with a defect or a change in bowel habits. Gut inflammation is one of the proposed mechanisms of pathogenesis. Recent studies have described a possible role for protozoan parasites, such as Blastocystis hominis and Dientamoeba fragilis, in the etiology of IBS. Dientamoeba fragilis is known to cause IBS-like symptoms and has a propensity to cause chronic infections but its diagnosis relies on microscopy of stained smears, which many laboratories do not perform, thereby leading to the misdiagnosis of dientamoebiasis as IBS. The role of B. hominis as an etiological agent of IBS is inconclusive, due to contradictory reports and the controversial nature of B. hominis as a human pathogen. Although Entamoeba histolytica infections occur predominately in developing regions of the world, clinical diagnosis of amebiasis is often difficult because symptoms of patients with IBS may closely mimic those patients with non-dysenteric amoebic colitis. Clinical manifestations of Giardia intestinalis infection also vary from asymptomatic carriage to acute and chronic diarrhoea with abdominal pain. These IBS-like symptoms can be continuous, intermittent, sporadic or recurrent, sometimes lasting years without correct diagnosis. It is essential that all patients with IBS undergo routine parasitological investigations in order to rule out the presence of protozoan parasites as the causative agents of the clinical signs.     

The Role of Mg(II) in DNA Cleavage Site Recognition in Group II Intron Ribozymes: SOLUTION STRUCTURE AND METAL ION BINDING SITES OF THE RNA·DNA COMPLEX*

Group II intron ribozymes catalyze the cleavage of (and their reinsertion into) DNA and RNA targets using a Mg²⁺-dependent reaction. The target is cleaved 3′ to the last nucleotide of intron binding site 1 (IBS1), one of three regions that form base pairs with the intron''s exon binding sites (EBS1 to -3). We solved the NMR solution structure of the d3′ hairpin of the Sc.ai5γ intron containing EBS1 in its 11-nucleotide loop in complex with the dIBS1 DNA 7-mer and compare it with the analogous RNA·RNA contact. The EBS1·dIBS1 helix is slightly flexible and non-symmetric. NMR data reveal two major groove binding sites for divalent metal ions at the EBS1·dIBS1 helix, and surface plasmon resonance experiments show that low concentrations of Mg²⁺ considerably enhance the affinity of dIBS1 for EBS1. Our results indicate that identification of both RNA and DNA IBS1 targets, presentation of the scissile bond, and stabilization of the structure by metal ions are governed by the overall structure of EBS1·dIBS1 and the surrounding loop nucleotides but are irrespective of different EBS1·(d)IBS1 geometries and interstrand affinities.