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R Conrad

Publications and source records attributed to R Conrad.

At least 19 recordsLinked to original sources
PubMed2005

Pathways for methanogenesis and diversity of methanogenic archaea in three boreal peatland ecosystems.

The main objectives of this study were to uncover the pathways used for methanogenesis in three different boreal peatland ecosystems and to describe the methanogenic populations involved. The mesotrophic fen had the lowest proportion of CH4 produced from H2-CO2. The oligotrophic fen was the most hydrogenotrophic, followed by the ombrotrophic bog. Each site was characterized by a specific group of methanogenic sequences belonging to Methanosaeta spp. (mesotrophic fen), rice cluster-I (oligotrophic fen), and fen cluster (ombrotrophic bog).

DNA, Archaeal↗
PubMed2004

Methanogenic pathway and archaeal community structure in the sediment of eutrophic Lake Dagow: effect of temperature.

Methanogenic degradation of organic matter is an important microbial process in lake sediments. Temperature may affect not only the rate but also the pathway of CH4 production by changing the activity and the abundance of individual microorganisms. Therefore, we studied the function and structure of a methanogenic community in anoxic sediment of Lake Dagow, a eutrophic lake in north-eastern Germany. Incubation of sediment samples (in situ 7.5 degrees C) at increasing temperatures (4, 10, 15, 25, 30 degrees C) resulted in increasing production rates of CH4 and CO2 and in increasing steady-state concentrations of H2. Thermodynamic conditions for H2/CO2 -dependent methanogenesis were only exergonic at 25 and 30 degrees C. Inhibition of methanogenesis with chloroform resulted in the accumulation of methanogenic precursors, i.e., acetate, propionate, and isobutyrate. Mass balance calculations indicated that less CH4 was formed via H2 at 4 degrees C than at 30 degrees C. Conversion of 14CO2 to 14CH4 also showed that H2/CO2 -dependent methanogenesis contributed less to total CH4 production at 4 degrees C than at 30 degrees C. [2-14 C]Acetate turnover rates at 4 degrees C accounted for a higher percentage of total CH4 production than at 30 degrees C. Collectively, these results showed a higher contribution of H2-dependent methanogenesis and a lower contribution of acetate-dependent methanogenesis at high versus low temperature. The archaeal community was characterized by cloning, sequencing, and phylogenetic analysis of the 16S rRNA genes retrieved from the sediment. Sequences were affiliated with Methanosaetaceae, Methanomicrobiaceae, and three deeply branching euryarchaeotal clusters, i.e., group III, Rice cluster V, and a novel euryarchaeotal cluster, the LDS cluster. Terminal restriction fragment length polymorphism (T-RFLP) analysis showed that 16S rRNA genes affiliated to Methanosaetaceae (20-30%), Methanomicrobiaceae (35-55%), and group III (10-25%) contributed most to the archaeal community. Incubation of the sediment at different temperatures (4-30 degrees C) did not result in a systematic change of the archaeal community composition, indicating that change of temperature primarily affected the activity rather than the structure of the methanogenic community.

Archaea↗
PubMed2004

Archaeal community structure and pathway of methane formation on rice roots.

The community structure of methanogenic Archaea on anoxically incubated rice roots was investigated by amplification, sequencing, and phylogenetic analysis of 16S rRNA and methyl-coenzyme M reductase (mcrA) genes. Both genes demonstrated the presence of Methanomicrobiaceae, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Rice cluster I, an uncultured methanogenic lineage. The pathway of CH4 formation was determined from the 13C-isotopic signatures of the produced CH4, CO2 and acetate. Conditions and duration of incubation clearly affected the methanogenic community structure and the pathway of CH4 formation. Methane was initially produced from reduction of CO2 exclusively, resulting in accumulation of millimolar concentrations of acetate. Simultaneously, the relative abundance of the acetoclastic methanogens (Methanosarcinaceae, Methanosaetaceae), as determined by T-RFLP analysis of 16S rRNA genes, was low during the initial phase of CH4 production. Later on, however, acetate was converted to CH4 so that about 40% of the produced CH4 originated from acetate. Most striking was the observed relative increase of a population of Methanosarcina spp. (but not of Methanosaeta spp.) briefly before acetate concentrations started to decrease. Both acetoclastic methanogenesis and Methanosarcina populations were suppressed by high phosphate concentrations, as observed under application of different buffer systems. Our results demonstrate the parallel change of microbial community structure and function in a complex environment, i.e., the increase of acetoclastic Methanosarcina spp. when high acetate concentrations become available.

Acetates↗
PubMed2003

[Somatization and alexithymia in male infertility. A replication study].

BACKGROUND AND OBJECTIVE: In a previous study, we found a higher degree of alexithymia and somatization in infertile men (Hum Reprod 2001 Vol.16(3),587-592). This study was designed to confirm the findings of the former study PATIENTS/METHODS: 88 infertile men (48 idiopathic infertility, 40 somatic infertility) were consecutively enrolled in the study. The control group consisted of 44 healthy men. Alexithymia was measured by the 20-item-Toronto-Alexithymia-Scale;somatization was measured by the Symptom Checklist-90-R. RESULTS: There were no differences between the subgroups of infertile men. The study group showed a significantly higher sum score in the TAS-20 (p<0.01) and a higher score on the scale somatization in the Symptom Checklist-90-R (p<0.05) compared to the control group. CONCLUSIONS: Our study replicated the findings of the previous investigation. Alexithymia and somatization are discussed as consequences of coping with male infertility.

Adult↗
PubMed2003

[Effect of iron oxide addition on hydrogen, carbon dioxide and methane geneses in paddy soil].

Paddy soil is an important contributor for atmospheric methane. The methanogenesis is related to the production of acetate, hydrogen and carbon dioxide during the decomposition of organic matter under anaerobic conditions. As electron acceptors, iron (III) oxides can effectively compete with electrons in the transformation of organic matter into methane. Its mechanism maybe relates to the consumption of H2 and CO2. After added ferrihydrite and lepidocrocite, the H2, CO2 and CH4 were determined during the anaerobic incubation of slurries at 25 degrees C for 105 days. The results indicated that the addition of ferrihydrite and lepidocrocite could greatly decrease the concentration of H2, CO2 and CH4, and ferrihydrite had a stronger effect than lepidocrocite. In this system, the balance of organic-C was disturbed, CH4-C and CO2-C were reduced, but the CO3(2-)-C fixed by slurry was greatly increased.

Carbon Dioxide↗
PubMed2002

Relationships between personality traits, seminal parameters and hormones in male infertility.

In this study we investigated the relationship between personality attitudes, psychopathological symptoms and biological parameters in male infertility. Eighty-four infertile men underwent a psychological and medical examination at our clinic. The psychological tests comprised the Symptom Checklist 90-R, the Toronto Alexithymia Scale and the NEO-Five Factor Inventory. Seminal parameters, gonadotrophins, sex steroids, cortisol and prolactin were analyzed to obtain biological data. Compared with questionnaires completed by normal populations those in the study group scored higher on the scales for 'conscientiousness', 'agreeableness', 'alexithymia' and 'somatization' and lower on the scale for 'neuroticism'. Regarding psychobiological correlations we found a negative correlation between seminal parameters and 'extraversion', 'anxiety' and 'psychoticism'. 'Alexithymia' was negatively correlated with stress hormones and 'conscientiousness' was correlated with sex steroids. The findings suggest above average social competence in the study group. The psychobiological correlations indicate a link between social-competence-related personality traits such as 'extraversion' and 'conscientiousness' and biological fertility characteristics. Implications of a higher alexithymia in infertile men, which is negatively correlated with stress hormones, are discussed.

Adult↗
PubMed2001

Improving the detectability of focal liver lesions on T2-weighted MR images: ultrafast breath-hold or respiratory-triggered thin-section MRI?

The purpose of this study was to determine whether a respiratory-triggered (RT) T2-weighted turbo spin-echo (TSE) sequence with thin section can improve the detectability of focal liver lesions compared to a breath-hold (BH) T2-weighted TSE sequence. In 25 patients an RT TSE with 8-mm sections (8-TSE RT) and 5-mm sections (5-TSE RT) and a BH TSE sequence with 8-mm sections (8-TSE BH) were performed. Forty-one focal liver lesions (mean: 1.8 +/- 1.2 cm; 14 lesions < or =1 cm; 27 lesions >1 cm) were evaluated. The 5-TSE RT was significantly better in lesion detection compared to the 8-TSE BH sequence for all sizes of lesions (40/41 vs. 33/41; P = 0.014). For lesions >1 cm no relevant differences in the detection rate of the sequences were found (8-TSE RT, 26/27; 5-TSE RT, 26/27; 8-TSE BH, 25/27), for lesions < or =1 cm the 5-TSE RT provided significantly better sensitivity than the 8-TSE BH (14/14 vs. 8/14, P = 0.015). The results of this study suggest that lesion detection could be significantly improved by using an RT TSE sequence with thin sections compared with a BH TSE sequence.

Female↗
PubMed2001

Functional patterns and temperature response of cellulose-fermenting microbial cultures containing different methanogenic communities.

The effect of microbial composition on the methanogenic degradation of cellulose was studied using two lines of anaerobic cellulose-fermenting methanogenic microbial cultures at two different temperatures: that at 15 degrees C being dominated by Methanosaeta and that at 30 degrees C by Methanosarcina. In both cultures, CH4 production and acetate consumption were completely inhibited by either 2-bromoethanesulfonate or chloroform, whereas H2 consumption was only inhibited by chloroform, suggesting that homoacetogens utilized H2 concomitantly with methanogens. Hydrogen was the intermediate that was consumed first, while acetate continued to accumulate. At 15 degrees C, acetoclastic methanogenesis smoothly followed H2-dependent CH4 production. Fluorescence in situ hybridization showed that populations of Methanosaeta steadily increased with time from 5 to 25% of total cell counts. At 30 degrees C, two phases of CH4 production were obtained, with acetate consumed after the abrupt increase of Methanosarcina from 0 to 45% of total cell counts. Whereas populations of Methanosaeta were able to adapt after transfer from 15 to 30 degrees C, those of Methanosarcina were not, irrespective of during which phase the cultures were transferred from 30 degrees C to 15 degrees C. Our results thus show that the community structure of methanogens indeed affects the function of a cellulose-fermenting community with respect to temperature response.

Archaea↗
PubMed2001

[Calcium pyrophosphate arthropathy (pseudogout) of the temporomandibular joint].

The temporomandibular joint is rarely affected by crystal deposition disease (gout and pseudogout). Only the temporomandibular joint was affected in a 69-year-old patient with calcium pyrophosphate dihydrate deposition disease (pseudogout). This case is described here. Clinically presenting as painless swelling, computed tomography and magnetic resonance imaging showed signs of a chronic destructive arthritis. The evidence for calcium pyrophosphate dihydrate crystals was provided by histological examination. Diagnostic criteria, differential diagnosis and possibilities for treatment are discussed on the basis of our own experience and the literature.

Aged↗
PubMed2001

Molecular analyses of methyl-coenzyme M reductase alpha-subunit (mcrA) genes in rice field soil and enrichment cultures reveal the methanogenic phenotype of a novel archaeal lineage.

The diversity of methanogen-specific methyl-coenzyme M reductase alpha-subunit (mcrA/mrtA) genes in Italian rice field soil was analysed using a combination of molecular techniques and enrichment cultures. From 75 mcrA/mrtA clones retrieved from rice field soil, 52 were related to members of the Methanosarcinaceae, Methanosaetaceae and Methanobacteriaceae. However, 19 and four clones formed two novel clusters of deeply branching mcrA sequences, respectively, which could not be affiliated to known methanogens. A new methanogen-specific fingerprinting assay based on terminal restriction fragment length polymorphism (T-RFLP) analysis of fluorescently labelled polymerase chain reaction (PCR) products allowed us to distinguish all environmental mcrA/mrtA sequences via group-specific Sau96I restriction sites. Even genes for the isoenzyme methyl-coenzyme M reductase two (mrtA) of Methanobacteriaceae present in rice field soil were represented by a unique 470 bp terminal restriction fragment (T-RF). Both cloning and T-RFLP analysis indicated a significant representation of novel environmental mcrA sequences in rice field soil (238 bp T-RF). To identify these mcrA sequences, methanogenic enrichment cultures with rice field soil as inoculum were established with H2/CO2 as substrates at a temperature of 50 degrees C, and these were monitored using molecular tools. In subsequent transfers of these enrichment cultures, cloning and T-RFLP analysis detected predominantly SSU rRNA genes of rice cluster I (RC-I), an uncultivated euryarchaeotal lineage discovered previously in anoxic rice field soil. In parallel, both mcrA cloning and T-RFLP analyses of the enrichment culture identified the more frequent cluster of novel environmental mcrA sequences as belonging to members of RC-I. Thus, we could demonstrate the genotype and phenotype of RC-I Archaea by the presence of a catabolic gene in a methanogenic enrichment culture before the isolation of pure cultures.

Archaea↗
PubMed2001

Thermophilic methanogens in rice field soil.

The soil temperature in flooded Italian rice fields is generally lower than 30 degrees C. However, two temperature optima at approximately 41 degrees C and 50 degrees C were found when soil slurries were anoxically incubated at a temperature range of 10-80 degrees C. The second temperature optimum indicates the presence of thermophilic methanogens in the rice field soil. Experiments with 14C-labelled bicarbonate showed that the thermophilic CH4 was exclusively produced from H2/CO2. Terminal restriction fragment length polymorphism (T-RFLP) of archaeal SSU rRNA gene fragments revealed a dramatic change in the archaeal community structure at temperatures > 37 degrees C, with the euryarchaeotal rice cluster I becoming the dominant group (about 80%). A clone library of archaeal SSU rRNA gene fragments generated at 49 degrees C was also dominated (10 out of 11 clones) by rice cluster I. Our results demonstrate that Italian rice field soil contains thermophilic methanogenic activity that was most probably a result of members of the as yet uncultivated euryarchaeotal rice cluster I.

Anaerobiosis↗
PubMed2001

Functional and structural response of a cellulose-degrading methanogenic microbial community to multiple aeration stress at two different temperatures.

Two cellulose-fermenting methanogenic enrichment cultures originating from rice soil, one at 15 degrees C with Methanosaeta and the other at 30 degrees C with Methanosarcina as the dominant acetoclastic methanogen, both degraded cellulose anaerobically via propionate, acetate and H2 to CH4. The degradation was a two-stage process, with CH4 production mainly from H2/CO2 and accumulation of acetate and propionate during the first, and methanogenic consumption of acetate during the second stage. Aeration stress of 12, 24, 36 and 76 h duration was applied to these microbial communities during both stages of cellulose degradation. The longer the aeration stress, the stronger the inhibition of CH4 production at both 30 degrees C and 15 degrees C. The 72 h stressed culture at 30 degrees C did not fully recover. Aeration stress at 30 degrees C exerted a more pronounced effect, but lasted for a shorter time than that at 15 degrees C. The aeration stress was especially effective during the second stage of fermentation, when consumption of acetate (and to a lesser extent propionate) was also increasingly inhibited as the duration of the stress increased. The patterns of CH4 production and metabolite accumulation were consistent with changes observed in the methanogenic archaeal community structure. Fluorescence in situ hybridization showed that the total microbial community at the beginning consisted of about 4% and 10% archaea, which increased to about 50% and 30% during the second stage of cellulose degradation at 30 degrees C and 15 degrees C respectively. Methanosarcina and Methanosaeta species became the dominant archaea at 30 degrees C and 15 degrees C respectively. The first round of aeration stress mainly reduced the non-Methanosarcina archaea (30 degrees C) and the non-Methanosaeta archaea (15 degrees C). Aeration stress also retarded the growth of Methanosarcina and Methanosaeta at 30 degrees C and 15 degrees C respectively. The longer the stress, the lower was the percentage of Methanosarcina cells to total microbial cells after the first stress at 30 degrees C. A later aeration stress decreased the population of Methanosarcina (at 30 degrees C) in relation to the duration of stress, so that non-Methanosarcina archaea became dominant. Hence, aeration stress affected the acetotrophic methanogens more than the hydrogenotrophic ones, thus explaining the metabolism of the intermediates of cellulose degradation under the different incubation conditions.

Air↗
PubMed2001

Localization of processes involved in methanogenic degradation of rice straw in anoxic paddy soil.

In anoxic paddy soil, rice straw is decomposed to CH(4) and CO(2) by a complex microbial community consisting of hydrolytic, fermenting, syntrophic and methanogenic microorganisms. Here, we investigated which of these microbial groups colonized the rice straw and which were localized in the soil. After incubation of rice straw in anoxic soil slurries for different periods, the straw pieces were removed from the soil, and both slurry and straw were studied separately. Although the potential activities of polysaccharolytic enzymes were higher in the soil slurry than in the straw incubations, the actual release of reducing sugars was higher in the straw incubations. The concentrations of fermentation products, mainly acetate and propionate, increased steadily in the straw incubations, whereas only a little CH(4) was formed. In the soil slurries, on the other hand, fermentation products were low, whereas CH(4) production was more pronounced. The production of CH(4) or of fermentation products in the separated straw and soil incubations accounted in sum for 54-82% of the CH(4) formed when straw was not removed from the soil. Syntrophic propionate degradation to acetate, CO(2) and H(2) was thermodynamically more favourable in the soil than in the straw fraction. These results show that hydrolysis and primary fermentation reactions were mainly localized on the straw pieces, whereas the syntrophic and methanogenic reactions were mainly localized in the soil. The percentage of bacterial relative to total microbial 16S rRNA content was higher on the straw than in the soil, whereas it was the opposite for the archaeal 16S rRNA content. It appears that rice straw is mainly colonized by hydrolytic and fermenting bacteria that release their fermentation products into the soil pore water where they are further degraded to CH(4). Hence, complete methanogenic degradation of straw in rice soil seems to involve compartmentalization.

Anaerobiosis↗
PubMed2001

Evidence for anaerobic syntrophic acetate oxidation during methane production in the profundal sediment of subtropical Lake Kinneret (Israel).

Methane production was measured in samples of the profundal sediment from Lake Kinneret. Production rates of CH(4) were higher at 30 degrees C than at the in situ temperature of 15 degrees C and were higher in the top 5 cm layer than below. Turnover of [2-(14)C]-acetate resulted in the production of (14)CH(4) and (14)CO(2) with turnover times of < 42 min. However, < 30% of the added radioactivity was converted to gaseous products, indicating that only part of the acetate pool was microbially available. The calculated acetate turnover rates were sufficient to account for total CH(4) production, indicating that CH(4) was produced exclusively from acetate. This conclusion was confirmed by inhibition of methanogens with chloroform, which resulted in an almost stoichiometric accumulation of acetate. However, a large percentage (30-60%) of [2-(14)C]-acetate was converted to (14)CO(2), despite lack of reducible sulphate or other oxidants in the sediment. Anoxic preincubation of the sediment did not result in reduced production of (14)CO(2). Therefore, part of the acetate must have been oxidized rather than methanogenically cleaved. Conversion of [(14)C]-bicarbonate to (14)CH(4) indicated that 30-50% of total CH(4) production originated from reduction of CO(2). To reconcile the relatively high contribution of H(2)/CO(2)-dependent methanogenesis with the relatively high oxidative conversion of acetate, we assume that part of the acetate was used syntrophically by consortia of acetate-oxidizing bacteria and H(2)/CO(2)-using methanogens. This conclusion is supported by favourable thermodynamic conditions for syntrophic acetate oxidation under in situ conditions and complete inhibition of [2-(14)C]-acetate turnover at high H(2) partial pressures. Further evidence to support this conclusion comes from the analysis of the structure of the archaeal community. Terminal restriction fragment length polymorphism (T-RFLP) and partial sequence analysis of the SSU rRNA genes amplified from DNA extracts of the sediment showed Methanomicrobiaceae as the dominant methanogenic group, whereas acetoclastic methanogens could not be detected.

Acetates↗
PubMed2001

[Incidence and significance of small focal liver lesions in MRI].

PURPOSE: Analysis of the frequency and significance of small focal liver lesions (< or = 2 cm) detected on MRI in the presence or absence of a history of malignancy. METHODS: 628 MRI examinations of the liver performed during 1994-1996 were evaluated. The inclusion criterion into the study was the detection of a focal liver lesion with a size < or = 2 cm. The frequency, the size, the diagnostic proof, and the differential diagnosis of the focal liver lesions were analysed with regard to the patients history of a known malignant tumor. RESULTS: Overall, 179 of the 628 patients (28.5%) had focal liver lesions < or = 2 cm (n = 338). 58.9% of the lesions could be classified based upon follow-up studies by ultrasound, CT or MRI, or by biopsy. The remaining 41.1% of the lesions could not be classified due to the absence of follow-up examinations. 57.3% of all proven lesions were benign and 42.7% were malignant. A history of a malignant tumor was present in 76.7% of all patients with small liver lesions; however, lesions were benign in these patients in 50.6% of the cases. In patients with no known history of a malignancy, 75% of the lesions were benign and 25% were malignant. However, these malignant lesions were in 10/11 cases hepatocellular carcinomas in patients with liver cirrhosis. CONCLUSION: Even in the presence of a history of a malignant tumor, about 50% of the detected small liver lesions on MRI are benign. In the absence of a tumor history the probability of a small malignant liver lesion is very low, if the patients does not have liver cirrhosis where small hepatocellular carcinomas can be present.

Biopsy↗
PubMed2001

Alexithymia in male infertility.

The continuing confrontation with the thoughts and feelings surrounding an unfulfilled wish for a child makes coping very difficult. There is empirical evidence that, in medical illnesses associated with stress and loss of quality of life, patients react with alexithymia, which means a difficulty to communicate emotions. In this study we compared 84 infertile men with a group of 96 healthy men and 43 male psychosomatic outpatients concerning their ability to communicate feelings, measured by the Twenty-Item Toronto Alexithymia Scale and the amount of psychopathologically relevant symptoms, especially somatization, measured by the Symptom Checklist 90-R and a List of Complaints (Beschwerden-Liste). The results showed a significantly higher alexithymia in infertile men compared with healthy men (P < 0.05), but a significantly lower alexithymia compared with psychosomatic outpatients (P < 0.05). Furthermore the study group showed significantly more somatic complaints in the List of Complaints compared with healthy men (P < 0.05). The importance of alexithymia in male infertility is discussed on the basis of empirical results that it might play a defensive role as far as depression is concerned but on the other hand increases the possibility of somatic complaints. The need for prospective studies in further research is emphasized.

Adult↗