Small intestinal bacterial overgrowth in irritable bowel syndrome: association with colon motility, bowel symptoms, and psychological distress

Abstract  Small intestinal bacterial overgrowth (SIBO) has been implicated in the pathogenesis of irritable bowel syndrome (IBS), although the issue is still under debate. The aim of this study was to determine the prevalence of SIBO in those with IBS and its association with colonic motility, bowel symptoms and psychological distress. Sucrose hydrogen and methane breath tests were performed in 158 IBS patients and 34 healthy controls (HC). Thresholds for pain and urgency were tested by barostat in the descending colon. The motility index (MI) was calculated as the average area under the curve for all phasic contractions. Questionnaires assessed psychological distress, IBS symptom severity (IBS-SS), IBS quality of life (IBS-QOL) and self-reported bowel symptoms. Fifty-two of 158 (32.9%) IBS patients had abnormal breath tests compared with six of 34 (17.9%) HC (χ² = 0.079). SIBO (SIBO+) and non-SIBO (SIBO−) patients did not differ in the prevalence of IBS subtypes, IBS-SS, IBS-QOL and psychological distress variables. IBS patients had a greater post-distension increase in MI than HC, but there was no difference between SIBO+ and SIBO− patients. Predominant methane producers had higher urge thresholds (28.4 vs 18.3, P  < 0.05) and higher baseline MI (461 vs 301.45, P  < 0.05) than SIBO− IBS patients, and they reported more 'hard or lumpy stools' when compared with predominant hydrogen producers ( P  < 0.05) and SIBO− IBS patients ( P  < 0.05). SIBO is unlikely to contribute significantly to the pathogenesis of IBS. Methane production is associated with constipation.     

A possible role for bile acid in the control of methanogenesis and the accumulation of hydrogen gas in the human colon

Abstract This study investigated a possible role for primary bile acid in the control of methanogenesis in the human colon. Production of hydrogen and methane was measured in anaerobic faecal cultures derived from faeces of six 'non-methanogenic' and three methanogenic healthy humans. Using a sensitive technique for gas measurement, methane was detected in all faecal cultures, including those from 'non-methanogenic' humans. Bile acid inhibited methanogenesis in a dose-response fashion in the in vitro 'non-methanogenic' and methanogenic faecal cultures. Inhibition was significant at bile acid concentrations > 0.05%. Methanogenesis correlated with methanogen (methanogenic bacteria) numbers. If this inhibition occurs in vivo , then it would explain much of the epidemiology of non-methanogenesis in humans. From an analysis of net hydrogen production by the faecal cultures, it is inferred that bile acid inhibits other hydrogen-consuming bacteria in addition to methanogens. These in vitro data suggest a major role for bile acid in the accumulation of hydrogen gas in the colon. Possible links between bile acid induced accumulation of gas and irritable bowel syndrome are discussed.     

新型金属一体化催化剂在甲烷催化燃烧中的性能

以Clad芯材铝板(Al/Alloy/Al)为原材料,利用铝的阳极氧化技术制备出新型金属一体化阳极氧化-γAl2O3载体。并利用这种载体采用浸渍法制备了Pt/Al2O3/Alloy、Pd/Al2O3/Alloy及Pd-Pt/Al2O3/Alloy催化剂,考察了各催化剂在甲烷燃烧中的性能。结果表明:低温下(<500℃)Pt/Al2O3/Alloy催化剂活性较差,而在高温下(>700℃)Pd/Al2O3/Alloy催化剂容易失活。向Pd/Al2O3/Alloy催化剂中加入一定量的Pt后(Pd-Pt/Al2O3/Alloy),明显提高了PdO的分解温度,从而提高了催化剂的活性及稳定性。     

Do Interventions Which Reduce Colonic Bacterial Fermentation Improve Symptoms of Irritable Bowel Syndrome?

Abnormal fermentation may be an important factor in irritable bowel syndrome (IBS). Gastroenteritis or antibiotic therapy may damage the colonic microflora, leading to increased fermentation and the accumulation of gas. Gas excretion may be measured by whole-body calorimetry but there has only been one such study on IBS to date. We aimed to assess the relationship between IBS symptoms and fermentation rates in IBS. A purpose-built, 1.4-m³, whole-body calorimeter was used to assess excretion of H₂ and CH₄ in IBS subjects while consuming a standard diet and, again, after open randomization on either the standard diet together with the antibiotic metronidazole or a fiber-free diet to reduce fermentation. Metronidazole significantly reduced the 24-hr excretion of hydrogen (median value compared to the control group, 397 vs 230 ml/24 hr) and total gas (H₂ + CH₄; 671 vs 422 ml/min) and the maximum rate of gas excretion (1.6 vs 0.8 ml/min), as did a no-fiber polymeric diet (hydrogen, 418 vs 176 ml/min; total gas, 564 vs 205 ml/min; maximum rate of gas excretion, 1.35 vs 0.45 ml/min), with a significant improvement in abdominal symptoms. IBS may be associated with rapid excretion of gaseous products of fermentation, whose reduction may improve symptoms.     

DNA repair processes in germ cells demonstrated in ejaculated sperms of rabbits treated with methyl methane sulfonate

Male rabbits were treated with a single i.v. injection of 22.5 mg/kg methyl methane sulfonate (MMS). 0–24 h later [³H]-thymidine was injected in both testicles. Incorporation of the isotope in germ cell DNA was demonstrated in ejaculated sperms. In controls labeled sperms were demonstrated first on day 40–43. These cells were in the preleptotene spermatocyte phase at the time of [³H]-thymidine injection. In rabbits treated with MMS significant radioactivity occurred in sperms collected from day 19 onwards. These cells were in late spermatocyte and early spermatid phase of maturation when [³H]-thymidine was injected. Incorporation of thymidine in these cell populations is interpreted as an expression of unscheduled DNA synthesis, a repair process initiated after chemical damage of germ cell DNA by MMS. The usefulness of the rabbit test system within the framework of conventional mutagenicity screening tests is discussed.     

二苯甲撑二异氰酸酯对男工性激素水平的影响

目的 探讨二苯甲撑二异氰酸酯（MDI）对作业男工体内性激素水平的影响。方法 对某化工厂84名接触MDI的男工和96名对照男工血清睾酮（T）、卵泡刺激素（FSH）和黄体生成素（LH）水平进行检测和比较。结果 MDI作业男工血清T水平显著低于对照组（P＜0．01）;FSH及LH水平显著高于对照组（P＜0．01）;高浓度接触组男工血清T显著低于中浓度组和低浓度组（P＜0．01）;而LH及FSH却显著高于中浓度组和低浓度组（P＜0．01）;MDI作业男工性功能与对照组比显著减退（P＜0．01）;吸烟饮酒可导致血清T水平显著低于未吸烟饮酒组（P＜0．01）,而LH及FS未吸烟饮酒组无明显差异（P＞0．05）,且MDI与吸烟饮酒三者存在协同作用的关系。结论 MDI具有一定的生殖毒性。     

Breath Methane Excretion and Intestinal Methanogenesis in Children and Adults in Rural Nigeria

Breath methane excretion was measured in 274 healthy subjects from 2 rural communities in northern Nigeria. Studies in 24 adults showed a normal faecal flora with no enteric pathogens. Breath methane was detected in 122 (77%) of 159 adults, 19 (40%) of 47 older children (2-6 years), and 4 (8%) of 68 young children (<2 years). Women were slightly more commonly breath methane-positive than men (82% versus 75%, respectively). Hyperventilation did not influence the specificity of the breath methane assay, although levels were circa 30% lower after deliberate hyperventilation. Methanogens were estimated by enrichment culture of faeces from 49 subjects. Of the subjects 76% had faecal methanogens estimated at ≥10²/g, 45% at ≥10⁴/g, and 16% at ≥10⁶/g. There was no significant difference in distribution of methanogenic cultures between different age or tribal groups, and there were no obvious correlations between breath methane excretion and either the faecal carriage of methanogens per se or numbers present.     

Carbohydrate Malabsorption: Quantification by Methane and Hydrogen Breath Tests

Rumessen JJ, Nordgaard-Andersen I, Gudmand-Høyer E. Carbohydrate malabsorption: quantification by methane and hydrogen breath tests. Scand J Gastroenterol 1994;29:826-832.

Background: Previous studies in small series of healthy adults have suggested that parallel measurement of hydrogen and methane resulting from gut fermentation may improve the precision of quantitative estimates of carbohydrate malabsorption. Systematic, controlled studies of the role of simultaneous hydrogen and methane measurements using end-expiratory breath test techniques are not available. Methods: We studied seven healthy, adult methane and hydrogen producers and seven methane non-producers by means of end-expiratory breath test techniques. Breath gas concentrations and gastrointestinal symptoms were recorded at intervals for 12 h after ingestion of 10,20, and 30 g lactulose. Results: In the seven methane producers the excretion pattern was highly variable; the integrated methane responses were disproportional and not reliably reproducible. However, quantitative estimates of carbohydrate malabsorption on the basis of individual areas under the methane and hydrogen excretion curves (AUCs) tended to improve in methane producers after ingestion of 20 g lactulose by simple addition of AUCs of methane to the AUCs of the hydrogen curves. Estimates were no more precise in methane producers than similar estimates in non-producers. Gastrointestinal symptoms increased significantly with increasing lactulose dose; correlation with total hydrogen and methane excretion was weak. Conclusions: Our study suggests that in methane producers, simple addition of methane and hydrogen excretion improves the precision of semiquantitative measurements of carbohydrate malabsorption. The status of methane production should, therefore, be known to interpret breath tests semiquantitatively. The weak correlation between hydrogen and methane excretion and gas-related abdominal complaints suggests that other factors than net production of these gases may be responsible for the symptoms.     

Polymorphism and polyamorphism in bilayer water confined to slit nanopore under high pressure

A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I–ice XIV) and at least 3 glassy forms of water, namely, low-density amorphous, high-density amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7–9 Å apart, numerous bilayer (BL) ices (or polymorphs) can arise [e.g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on graphene/Pt(111) substrate has been achieved experimentally. Herein, we report computer simulation evidence of pressure-induced amorphization from BL-ice I to BL-amorphous and then to BL-VHDA₂ at 250 K and 3 GPa. In particular, BL-VHDA₂ can transform into BL-VHDA₁ via decompression from 3 to 1.5 GPa at 250 K. This phenomenon of 2D polyamorphic transition is akin to the pressure-induced amorphization in 3D ice (e.g., from hexagonal ice to HDA and then to VHDA via isobaric annealing). Moreover, when the BL-ice I is compressed instantly to 6 GPa, a new very-high-density BL ice is formed. This new phase of BL ice can be viewed as an array of square ice nanotubes. Insights obtained from pressure-induced amorphization and crystallization of confined water offer a guide with which to seek a thermodynamic path to grow a new form of methane clathrate whose BL ice framework exhibits the Archimedean 4⋅8² (square-octagon) pattern.     

Direct measurements of methane emissions from abandoned oil and gas wells in Pennsylvania

Abandoned oil and gas wells provide a potential pathway for subsurface migration and emissions of methane and other fluids to the atmosphere. Little is known about methane fluxes from the millions of abandoned wells that exist in the United States. Here, we report direct measurements of methane fluxes from abandoned oil and gas wells in Pennsylvania, using static flux chambers. A total of 42 and 52 direct measurements were made at wells and at locations near the wells (“controls”) in forested, wetland, grassland, and river areas in July, August, October 2013 and January 2014, respectively. The mean methane flow rates at these well locations were 0.27 kg/d/well, and the mean methane flow rate at the control locations was 4.5 × 10⁻⁶ kg/d/location. Three out of the 19 measured wells were high emitters that had methane flow rates that were three orders of magnitude larger than the median flow rate of 1.3 × 10⁻³ kg/d/well. Assuming the mean flow rate found here is representative of all abandoned wells in Pennsylvania, we scaled the methane emissions to be 4–7% of estimated total anthropogenic methane emissions in Pennsylvania. The presence of ethane, propane, and n-butane, along with the methane isotopic composition, indicate that the emitted methane is predominantly of thermogenic origin. These measurements show that methane emissions from abandoned oil and gas wells can be significant. The research required to quantify these emissions nationally should be undertaken so they can be accurately described and included in greenhouse gas emissions inventories.Abandoned oil and gas wells provide a potential pathway for subsurface migration and emissions to the atmosphere of methane and other fluids (1). According to one recent study, there are an estimated 3 million abandoned oil and gas wells throughout the United States (2). Methane emissions from these wells are assumed to be the second largest potential contribution to total US methane emissions above US Environmental Protection Agency estimates and are not included in any emissions inventory (2). There is a lack of empirical studies that can be used to estimate the methane emission potential of these wells (2).Methane is a greenhouse gas (GHG) and its oxidation produces ozone (O₃) that degrades air quality and adversely impacts human health, agricultural yields, and ecosystem productivity (3). Therefore, it is important to understand methane emission sources so that appropriate mitigation strategies can be developed and implemented.Efforts to improve estimates of methane emissions to the atmosphere from oil and gas production in the United States are being driven, in part, by growth in unconventional production. Estimates of methane emissions from activities on producing oil and gas sites, including well completion, routine maintenance, and equipment leaks, are used to develop bottom–up estimates (4, 5). Overall, a comparison of bottom–up and top–down estimates indicate that there may be missing sources in bottom–up estimates (2, 6–8, 9). Here, we focus on one missing source: abandoned oil and gas wells.There is no regulatory requirement to monitor or account for methane emissions from abandoned wells in the United States. Methane leakage through abandoned wells linked to recent growth in unconventional oil and gas production is being studied as a groundwater contamination issue (10–14), but no direct evidence for leakage through abandoned wells to groundwater aquifers currently exists. Abandoned wells have been connected to subsurface methane accumulations that have caused explosions, which are major concerns in urban areas with oil and gas development or natural gas storage reservoirs, as well as in coal mines (15, 16). Therefore, existing monitoring is focused on detecting large concentrations. The result is a lack of information to quantify methane emissions from abandoned oil and gas wells.To characterize abandoned oil and gas wells’ potential as a significant methane source, we made first-of-a-kind direct measurements of methane flow rates from 19 wells in various locations across McKean and Potter counties in Pennsylvania (PA) (Fig. 1). The measured wells were selected mainly based on logistical and legal access (Supporting Information). As of January 17, 2014, only 1 of the 19 wells was on the PA Department of Environmental Protection’s (DEP’s) list of abandoned and orphaned wells. (Orphaned wells can be defined as abandoned wells with no responsible party available, other than the state.) The DEP database provides information on the well status (abandoned, plugged, or orphan) and well type (gas, oil, combined oil and gas, or undetermined) but does not provide other information such as well age and depth. No additional information on the measured wells is available. This is indicative of the general scarcity of available information on this class of old wells in PA. Given the lack of records on the wells we measured, no distinction was made between oil and gas wells; the wells were simply categorized as plugged or unplugged, based on surface evidence of cementing and/or presence of a marker. With this criterion, 5 of the 19 measured wells (26%) were classified as plugged.Open in a separate windowFig. 1.The 19 measured wells are located in McKean County and Potter County in Pennsylvania. There are 12,127 abandoned, orphaned, and plugged wells on the Pennsylvania DEP’s website (as of January 17, 2014), with 4,273 in McKean County and 188 in Potter County. The map shows the DEP wells that are in the region of our field study. Note that only the western portion of Potter County is shown in the detailed map.In addition to methane, we also analyzed the collected samples for ethane, propane, n-butane, and carbon isotopes of methane, to provide insight on the potential sources of the emitted methane. This work provides previously unavailable data on methane leakage rates and other emissions from abandoned oil and gas wells.