Sorbitol as a Sweetener in the Diet of Insulin-dependent Diabetes

ABSTRACT. We compared sorbitol given alone and as part of a mixed meal to nine insulin-dependent diabetics (IDD's) during continuous subcutaneous insulin infusion (CSII). Blood glucose, sorbitol and breath hydrogen+methane were measured following six test meals: Pure glucose, sorbitol and lactulose, a mixed meal alone, and sweetened with sorbitol and sucrose. Blood glucose increase was very small after lactulose and sorbitol, significantly larger after glucose. A considerable increase in breath hydrogen+methane appeared after sorbitol and lactulose, but not after glucose. No differences in blood glucose responses were found after the mixed meal alone or sweetened with sorbitol and sucrose. A sustained low level increase in breath hydrogen+methane occurred after all solid meals. Sorbitol was not detected in serum after any meal. Conclusion: Sorbitol ingested by IDD's during CSII in watery solution is not absorbed in the small intestine and causes osmotic diarrhoea. Ingested in a composite meal it does not affect blood glucose and does not cause osmotic diarrhoea.     

The immunochemical effects of metal substitution in the prosthetic group of hemoglobin

We have used immunodiffusion, quantitative precipitin analyses and radioimmunoassay measurements to investigate the immunochemistry of various metallo- and non-metallohemoglobin A₀ derivatives. Hemoglobin A₀ reconstituted with iron(III), manganese(III), cobalt(II), copper(II), nickel(II), zinc(II) and protoporphyrin IX along with apohemoglobin were studied to determine the effects of these substitutions on the antigenic properties of the protein. Immunodiffusion studies showed that reconstituted iron(III), manganese(III), cobalt(II), copper(II) and apohemoglobin reacted with complete identity to hemoglobin A₀ with antibodies raised against hemoglobin A₀, while nickel(II), zinc(II) and protoporphyrin IX reacted with partial identity. Quantitative precipitin analyses showed that reconstituted iron(III), cobalt(II) and copper(II) hemoglobins are identical to the native protein, whereas manganese(III) and protoporphyrin IX differed only slightly. However, large differences were seen with the nickel(II), zinc(II) and apohemoglobin derivatives. Radioimmunoassay of the various hemoglobin derivatives showed that the reconstituted iron(III), manganese(III) and cobalt(II) derivatives completely displaced all of the labelled hemoglobin A₀ from its antibody. Protoporphyrin IX and apohemoglobin were found to have displacement curves similar to each other but different from hemoglobin A₀. Copper(II), nickel(II) and zinc(II) hemoglobins showed significant differences in their displacement curves, indicating some structural reorganization which affects antigenic binding sites. These results indicate that electronic changes in the center of the porphyrin ring can be detected by quantitative immunochemical procedures as structural changes on the surface of the hemoglobin molecule.     

Methane plasma as a protective coating on intraocular lenses: An in vitro study

A new methane plasma polymer was used to treat eight polymethylmetacrylate intraocular lenses (IOL). Another group of four lenses which had no treatment was used as control. The groups were compared in terms of the amount of endothelial cell damage caused after each of the twelve IOLs touched the central endothelium of 12 separate New Zealand rabbit corneas for 30 secondsin vitro. The amount of damage was estimated by means of vital staining with nitroblue tetrazolium and scanning electron microscopy. We found that the untreated (control) group of IOL produced significantly more endothelial cell damage in comparison with the treated groups. Further studies are needed to evaluate the clinical significance of our findings.     

Effect of Ruthenium and Cerium Oxide (IV) Promotors on the Removal of Carbon Deposit Formed during the Mixed Methane Reforming Process

This work investigates the effect of the addition of Ru and CeO₂ on the process of gasification of carbon deposits formed on the surface of a nickel catalyst during the mixed methane reforming process. Activity studies of the mixed methane reforming process were carried out on (Ru)-Ni/CeO₂-Al₂O₃ catalysts at the temperature of 650–750 °C. The ruthenium-promoted catalyst exhibited the highest activity. Carbonized post-reaction catalyst samples were tested with the TOC technique to investigate the carbonization state of the samples. The bimetallic catalyst had the lowest amount of carbon deposit (1.5%) after reaction at 750 °C. The reactivity of the carbon species was assessed in mixtures of oxygen, hydrogen, carbon dioxide, and water. Regardless of the gasifying agent used, the carbon deposit was removed from the surface of the catalytic system. The overall mechanism of mixed methane reforming over Ru and CeO₂ was shown.     

三格式厕所和沼气池杀灭血吸虫卵效果

目的了解在不同季节或温度下三格式厕所和斜置椭球B型沼气池现场杀灭血吸虫卵的时间和效果,以评估这2种类型厕所在血吸虫病疫区推广应用的价值。方法在不同的季节里,将感染家兔后获得的血吸虫卵置于三格式厕所和沼气池中,在第5、10、15、20、25、30、40、50天和第60天分别取出虫卵进行孵化试验,观察并计算毛蚴数。结果三格式厕所在冬、春（秋）季和夏季完全杀灭“虫卵粪渣”中血吸虫卵的时间分别为50、30d和15d;完全杀灭100个血吸虫卵的时间分别为40、20d和10d。沼气池在冬、春（秋）季和夏季完全杀灭“虫卵粪渣”中血吸虫卵的时间分别为30、15d和10d;完全杀灭100个血吸虫卵的时间分别为20、15d和5d。结论三格式厕所和斜置椭球B型沼气池是血吸虫病疫区杀灭人、畜粪便中血吸虫卵的有效途径之一。在江西省血吸虫病疫区,不同季节按照完全杀灭血吸虫卵的时间,均可以达到国家粪便无害化的卫生标准。     

Hydrogen and Methane Breath Test in the Diagnosis of Lactose Intolerance

The hydrogen (H₂) breath test is a non-invasive investigation used to diagnose lactose intolerance (LI). Patients with LI may also expire increased amounts of methane (CH₄) during a lactose test. The aim of this study is to evaluate the contribution of CH₄ measurements. We tested 209 children (1–17 years old) with symptoms suggesting LI with lactose H₂ and CH₄ breath tests. The result was positive when the H₂ excretion exceeded 20 parts per million (ppm) and the CH₄ was 10 ppm above the baseline. A clinician, blinded for the results of the breath test, registered the symptoms. Of the patient population, 101/209 (48%) were negative for both H₂ and CH₄; 96/209 (46%) had a positive H₂ breath test result; 31/96 (32%) were also positive for CH₄; 12/209 (6%) patients were only positive for CH₄. The majority of hydrogen producers showed symptoms, whereas this was only the case in half of the H₂-negative CH₄ producers. Almost all patients treated with a lactose-poor diet reported significant symptom improvement. These results indicate that CH₄ measurements may possibly be of additional value for the diagnosis of LI, since 5.7% of patients were negative for H₂ and positive for CH₄, and half of them experienced symptoms during the test.     

Diverse methylotrophic methanogenic archaea cause high methane emissions from seagrass meadows

Marine coastlines colonized by seagrasses are a net source of methane to the atmosphere. However, methane emissions from these environments are still poorly constrained, and the underlying processes and responsible microorganisms remain largely unknown. Here, we investigated methane turnover in seagrass meadows of Posidonia oceanica in the Mediterranean Sea. The underlying sediments exhibited median net fluxes of methane into the water column of ca. 106 µmol CH₄ ⋅ m⁻² ⋅ d⁻¹. Our data show that this methane production was sustained by methylated compounds produced by the plant, rather than by fermentation of buried organic carbon. Interestingly, methane production was maintained long after the living plant died off, likely due to the persistence of methylated compounds, such as choline, betaines, and dimethylsulfoniopropionate, in detached plant leaves and rhizomes. We recovered multiple mcrA gene sequences, encoding for methyl-coenzyme M reductase (Mcr), the key methanogenic enzyme, from the seagrass sediments. Most retrieved mcrA gene sequences were affiliated with a clade of divergent Mcr and belonged to the uncultured Candidatus Helarchaeota of the Asgard superphylum, suggesting a possible involvement of these divergent Mcr in methane metabolism. Taken together, our findings identify the mechanisms controlling methane emissions from these important blue carbon ecosystems.

About one-half of global methane emissions [ca. 270 Tg CH₄ ⋅ yr⁻¹ (1)] stem from aquatic environments, mainly the inland waters. In the marine environment, coastal areas represent methane hotspots, releasing around 8 to 13 Tg CH₄ ⋅ yr⁻¹ (1, 2) thus highly exceeding emissions from the open ocean [0.6 to 1.2 Tg CH₄ ⋅ yr⁻¹ (3)]. High methane emissions from coastal regions are caused by high fluxes of methane from the sediment, of which more than two-thirds is biogenic in origin [i.e., produced by a microbial process called methanogenesis (4, 5)]. Methanogenesis is a form of anaerobic respiration during which oxidized carbon is used as the terminal electron acceptor. The biochemical pathway of methanogenesis contains a conserved set of enzymes (6) of which methyl-coenzyme M reductase (Mcr) is the key one. Therefore, the gene encoding for Mcr (mcrA) is generally used as a universal phylogenetic marker to identify methanogenic microorganisms.The capacity for methanogenesis is constrained to a group of strictly anaerobic methanogenic archaea (7, 8). Until recently, methanogens were believed to belong exclusively to the phylum Euryarchaeota, and to date, most described methanogens still affiliate with this phylum. However, several recent studies have described novel putatively methanogenic archaeal phyla based on the presence of the mcrA gene in their genomes. These novel putative methanogens belong to Candidatus Bathyarchaeota (9), Candidatus Methanomethyliaceae [formerly Verstraetarchaeota (10)], and Thermoplasmata (11). These observations suggest that the metabolic trait of methanogenesis is phylogenetically more widespread than previously thought. Additionally, genes encoding putative methyl-CoM reductase–like enzymes have also been found in the genomes of Candidatus Syntrophoarchaeum (12) and Candidatus Helarchaeota (13), albeit here this enzyme is presumed to be involved in the anaerobic oxidation of butane.Due to their obligately anaerobic nature, methanogens are typically constrained to permanently anoxic habitats where other, thermodynamically more favorable electron acceptors are absent. Methanogens have a very limited substrate range and can only use a handful of simple organic compounds. Depending on the utilized substrate, the pathways of methanogenesis classify as hydrogenotrophic (use H₂ to reduce CO₂ to CH₄), acetoclastic (use acetate disproportionation to form CH₄), and methylotrophic (use methyl groups of methylated compounds, such as methylamine, to form CH₄).Hydrogenotrophic methanogenesis is the predominant pathway of methane production in anoxic marine sediments, followed by acetate disproportionation (14). Both hydrogen and acetate are formed in situ mainly through the activity of fermentative bacteria. Additionally, plant-associated fungi can facilitate plant tissue breakdown (15), thereby providing methanogenic substrates to the microbial community. However, hydrogen and acetate can also be used by sulfate-reducing bacteria (SRB) and, in fact, SRB routinely outcompete methanogens for these compounds (16, 17). Therefore, hydrogenotrophic and acetoclastic methanogenesis usually do not co-occur with sulfate reduction in marine sediments (7, 16, 18), and H₂ and acetate are thus also referred to as so-called competitive substrates (19).In contrast, methylated compounds such as methylated amines (mono-, di-, and trimethylamine) or methylated sulfides (dimethylsulfide; DMS) can exclusively be used by methanogens and represent so-called noncompetitive substrates (20). Methylotrophic methanogenesis can therefore readily proceed under high ambient sulfate concentrations and has been reported to dominate in, for example, organic-rich muddy sediments (21, 22) and hypersaline environments (23). Methylated compounds, such as betaines and methylamines, are ubiquitous in coastal marine environments (24, 25) as different marine organisms (including marine plants) produce them to cope with osmotic stress (26). The degradation of these compounds can lead to the release of methane, and methylotrophic methanogenesis is thus expected to play an important role in coastal sediments with high salinity and under the influence of algae or plants (18, 20).Many shallow coastlines are vegetated by macroalgae and seagrasses (27). Seagrasses are marine flowering plants that form some of the most productive ecosystems on Earth (28). At the same time, seagrass ecosystems, such as sediments colonized by eelgrass (Zoster sp.) and turtlegrass (Thalassia sp.) are recognized as important sources of methane to the atmosphere (29–31) with estimated emissions ranging from about 0.1 to 2.7 Tg CH₄ ⋅ yr⁻¹ (1, 31, 32). Methane emissions from seagrass ecosystems are somewhat lower than from mangroves and salt marshes, but seagrasses cover more coastal areas than mangroves and marshes combined (32). Posidonia seagrasses can be found throughout the Mediterranean Sea (Posidonia oceanica) and around the southern coast of Australia (Posidonia australis). Due to their large size and their capacity to form massive underground peat deposits (33), Posidonia meadows represent an important marine blue carbon ecosystem (34, 35). To date, there are no reported methane production rates for Posidonia seagrasses, and the metabolic processes and microorganisms involved in methane metabolism in seagrass ecosystems are still largely unknown.In this study, we describe the mechanism by which methane emissions are sustained from sediments underlying living and dead seagrass meadows of P. oceanica in the Mediterranean Sea, and we quantify the efficiency of the biological methane filter in these sediments. We also present a comprehensive analysis of the microbial community associated with these important coastal habitats, with a particular focus on the diversity of methanogenic microorganisms.     

肠道产甲烷菌与肠道疾病的关系研究进展

肠道产甲烷菌是一类将氢气和二氧化碳生成甲烷的厌氧菌,研究证实其与人体肠道疾病密切相关,因此深入探索肠道产甲烷菌在肠道疾病中的作用机制具有重要意义。本文就肠道产甲烷菌的特点、种类、定植特征,及其与肥胖、肠易激综合征、炎症性肠病、结直肠癌、憩室病等疾病之间的关系进行综述,着重梳理肠道产甲烷菌在这些疾病中可能发生的机制,为人体肠道疾病的预防、诊断和治疗提供一定的新思路。     

Modeling Analysis of a Polygeneration Plant Using a CeO2/Ce2O3 Chemical Looping

In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO₂ emissions. A plant for the multiple productions of electrical energy, thermal heat, DME, syngas, and methanol is discussed and analyzed, integrating a chemical cycle for CO₂/H₂O splitting driven using concentrated solar energy and biomethane. Two-stage chemical looping is the central part of the plant, operating with the CeO₂/Ce₂O₃ redox couple and operating at 1.2 bar and 900 °C. The system is coupled to biomethane reforming. The chemical loop generates fuel for the plant’s secondary units: a DME synthesis and distillation unit and a solid oxide fuel cell (SOFC). The DME synthesis and distillation unit are integrated with a biomethane reforming reactor powered by concentrated solar energy to produce syngas at 800 °C. The technical feasibility in terms of performance is presented in this paper, both with and without solar irradiation, with the following results, respectively: overall efficiencies of 62.56% and 59.08%, electricity production of 6.17 MWe and 28.96 MWe, and heat production of 111.97 MWt and 35.82 MWt. The fuel production, which occurs only at high irradiance, is 0.71 kg/s methanol, 6.18 kg/s DME, and 19.68 kg/s for the syngas. The increase in plant productivity is studied by decoupling the operation of the chemical looping with a biomethane reformer from intermittent solar energy using the heat from the SOFC unit.     

Practical application of breath tests in disorders of gut–brain interaction

Frequently occurring diseases of disordered gut–brain interactions are the irritable bowel syndrome and functional dyspepsia. Breath tests are noninvasive and are used to monitor a variety of gastrointestinal functions or conditions. Their general principle is the oral application of a test substance, the metabolism of which results in a substrate that can be measured in expiratory air. Clinically used breath tests use carbohydrates or stable ¹³C-enriched substrates. This review will focus on two questions, which breath tests are relevant for initiating treatments and which breath tests are useful for assessing treatment response? Recently published guidelines have described breath tests in detail and the recommendations for their use will be based on recommendations of these guidelines.