Biomedical subjects

K Michel

Publications and source records attributed to K Michel.

At least 19 recordsLinked to original sources

PubMed2006

Region-specific effects of STW 5 (Iberogast) and its components in gastric fundus, corpus and antrum.

Functional dyspepsia (FD) is a disorder that involves impaired gastric accommodation, antral hypomotility, and upper abdominal pain. The herbal drug STW 5 (Iberogast) is used to successfully treat FD patients. Here, we report in vitro data revealing the mode of action of STW 5 and its individual herbal extracts on gastric motility. STW 5 evoked a relaxation of the proximal stomach but increased antral motility. Both effects are myogenic. The extracts of Angelica root, chamomile flower and liquorice root mimicked the inhibitory effects in the proximal stomach whereas the extracts of greater celandine herb, Melissa leaf, caraway fruit and bitter candy tuft increased motility of the proximal stomach. All extracts increased motility in the antrum comparable to the effects of STW 5. We conclude that the differential effects of STW 5 on proximal and distal stomach motor activity are not caused by solely spasmolytic or anti-spasmolytic effects of the individual components. It is suggested that the individual extracts target transduction mechanisms that are specifically expressed in the proximal vs. distal stomach. We present a rationale for the differential effect of STW 5 which is a result of the combined actions of its individual components and reason that the inhibitory effects in the proximal and the excitatory effects in the distal stomach may contribute to symptom relief in FD patients treated with STW 5 (Iberogast).

Animals↗

PubMed2006

Diabetes mellitus increases adverse neurocognitive outcome after coronary artery bypass grafting surgery.

BACKGROUND: Cognitive dysfunction is a well known problem in the postoperative period in cardiac surgery. We hypothesised that the incidence of postoperative cognitive dysfunction in patients with diabetes mellitus is higher than in the nondiabetic patient. METHODS: Thirty-four patients (11 females, 23 males) with a mean age of 62.44 +/- 7.52 undergoing on-pump CABG surgery were studied in a prospective manner. Fourteen patients had treated diabetes mellitus (Group I) and 20 were nondiabetic (Group II). All patients were operated upon by the same surgeon under standardised intra- and perioperative conditions. Patients with preoperative dementia (MMSE < 24) or advanced cerebrovascular disease were excluded. An extensive set of tests examining emotional and cognitive state, stress-coping and quality of life were performed preoperatively. Emotional and cognitive variables were assessed daily from day two to five postoperatively. RESULTS: All tests showed comparable results between the groups preoperatively. The perfusion lasted considerably longer in Group I (102.5 +/- 16.61 vs. 83.9 +/- 14.1 min) as did the cross clamping (64.21 +/- 18.31 vs. 51.75 +/- 10.88 min). Postoperative cognitive outcome was significantly worse in Group I with regard to the Stroop Test (29.46 +/- 8.6 vs. 24.01 +/- 6.23, P = 0.02), the Abbreviated Mental Test (8.04 +/- 0.71 vs. 8.68 +/- 0.78, P = 0.02) and the Trial Making Test (35.72 +/- 11.38 vs. 29.3 +/- 7.77 P = 0.04). These differences persisted even after adjustment for perfusion- and cross-clamping time. CONCLUSION: The cognitive outcome in the early postoperative period is worse in diabetic patients compared to nondiabetics. Speed-related cognitive functions are mainly affected. Probably, this reflects a different physiology of cerebral perfusion during extracorporeal circulation. Optimising perfusion strategies to improve the outcome of diabetic patients should be the next topic of study.

Aged↗

PubMed2006

Syringolin A, a new plant elicitor from the phytopathogenic bacterium Pseudomonas syringae pv. syringae, inhibits the proliferation of neuroblastoma and ovarian cancer cells and induces apoptosis.

Syringolin A is a new plant elicitor produced by the plant pathogen Pseudomonas syringae pv. syringae. The goal of this study was to investigate whether syringolin A exhibits anti-proliferative properties in cancer cells. The treatment of human neuroblastoma (NB) cells (SK-N-SH and LAN-1) and human ovarian cancer cells (SKOV3) with syringolin A (0-100 microm) inhibited cell proliferation in a dose-dependent manner. The IC(50) (50% inhibition) for each cell line ranged between 20 microm and 25 microm. In SK-N-SH cells, the treatment with 20 microm syringolin A led to a rapid (24 h) increase of the apoptosis-associated tumour suppressor protein p53. In addition, we found that the treatment of SK-N-SH cells caused severe morphological changes after 48 h such as rounding of cells and loss of adherence, both conditions observed during apoptosis. The induction of apoptosis by syringolin A was confirmed by both poly (ADP-ribose) polymerase (PARP) cleavage and annexin V assay. Taken together, we show for the first time that the natural product syringolin A exhibits anti-proliferative activity and induces apoptosis. Syringolin A and structurally modified syringolin A derivatives may serve as new lead compounds for the development of novel anticancer drugs.

Animals↗

PubMed2005

Early age-related cognitive impairment in mice lacking cannabinoid CB1 receptors.

The molecular mechanisms contributing to the normal age-related decline of cognitive functions or to pathological learning and memory impairment are largely unknown. We demonstrate here that young mice (6-7 weeks) with a genetic deletion of the cannabinoid CB1 receptor performed as well as WT mice, or often better, in a number of learning and memory paradigms, including animal models of skill-learning, partner recognition, and operant conditioning. In contrast, the performance of mature mice (3-5 months) lacking CB1 receptors was much worse than that of age-matched WT animals. In most tests, these mice performed at the same level as old animals (14-17 months), suggesting that the decline in cognitive functions is accelerated in the absence of CB1 receptors. This rapid decline in CB1-deficient animals is accompanied by a loss of neurons in the CA1 and CA3 regions of the hippocampus.

Aging↗

PubMed2005

Mosquito immunity against Plasmodium.

Understanding the molecular mechanisms of the innate immune responses of Anopheles gambiae against Plasmodium parasites is of great importance for current efforts to develop novel strategies for malaria disease control. The parasite undergoes substantial stage-specific losses during its development in the mosquito, which in some cases lead to complete refractoriness of the mosquito against the parasite. The underlying genetics of refractoriness are complex and multifactorial. Completion of the genome sequence of An. gambiae 2 years ago, together with the development of DNA microarrays in this species and the extension of the RNAi technique to adult mosquitoes, has allowed comparative and functional genomic approaches of the mosquito innate immune system. A variety of factors were shown to negatively affect the development of Plasmodium parasites in the mosquito, in some cases leading to complete transmission blockage. In addition, mosquito factors have been identified that play positive roles and are required for successful transmission of the parasite. These findings indicate a highly complex interplay between parasite and vector. Research is continuing to identify new factors involved in this interaction and to decipher the interplay of these molecules and their regulation.

Animals↗

PubMed2005

Human mast cell mediator cocktail excites neurons in human and guinea-pig enteric nervous system.

Neuroimmune interactions are an integral part of gut physiology and involved in the pathogenesis of inflammatory and functional bowel disorders. Mast cells and their mediators are important conveyors in the communication from the innate enteric immune system to the enteric nervous system (ENS). However, it is not known whether a mediator cocktail released from activated human mast cells affects neural activity in the ENS. We used the Multi-Site Optical Recording Technique to image single cell activity in guinea-pig and human ENS after application of a mast cell mediator cocktail (MCMC) that was released from isolated human intestinal mucosa mast cells stimulated by IgE-receptor cross-linking. Local application of MCMC onto individual ganglia evoked an excitatory response consisting of action potential discharge. This excitatory response occurred in 31%, 38% or 11% neurons of guinea-pig submucous plexus, human submucous plexus, or guinea-pig myenteric plexus, respectively. Compound action potentials from nerve fibres or fast excitatory synaptic inputs were not affected by MCMC. This study demonstrates immunoneural signalling in the human gut and revealed for the first time that an MCMC released from stimulated human intestinal mast cells induces excitatory actions in the human and guinea-pig ENS.

Animals↗

PubMed2004

Acute toxicity investigations of ester-based lubricants by using biotests with algae and bacteria.

Although ester-based lubricants are ecologically acceptable due to their good biodegradability, there are still some environmental ecotoxicological impacts that have to be considered. Information on the acute ecotoxicological behavior of lubricants is obtained in this work using several single species bioassays. In previous studies it was observed that lubricating fluids containing additives for the enhancement of their technical performance were more problematic than base fluids especially with respect to algae growth inhibition. In order to clarify the influence of additives, the anti-wear additive tri-n-butyl phosphate was tested. It was very toxic to algae though not to bacteria. Additionally, a mixture of this additive with a base fluid is characterized. Despite the high toxicity of the single additive, the water extract of the mixture of tri-n-butyl phosphate with hydraulic base fluid caused almost no toxicity. Therefore, tri-n-butyl phosphate cannot explain the effect observed for the toxicity of water extracts of the commercially available lubricants.

Biological Assay↗

PubMed2004

Development of automated high-throughput ecotoxicity and genotoxicity test systems and fields of application.

Bioassays like growth inhibition and genotoxicity assays are frequently used for the characterization of chemicals and contaminated environmental samples. In this work two standardized bioassays are automated completely using newly developed liquid handling stations and robotics. A high-throughput algal growth inhibition assay prototype is set up and optimized in cooperation with Hoelle & Huettner AG (Tuebingen, Germany) and Polygen GmbH (Langen, Germany). A software package for both the control of the test system and for data evaluation has been developed (Biolane Supervisor, BioLane Manager HTT). The applicability of the prototype is demonstrated by testing reference compounds with the automated assay in parallel with the Erlenmeyer flask assay. It is shown that EC50-values of chemicals do not differ significantly when incubation parameters like homogeneity of light intensity, temperature and evaporation during 72 hours of incubation are optimized. The umu-genotoxicity test is automated completely using a "RoboSeq 4204 SE" pipetting station (MWG AG, Ebersberg, Germany) equipped with two shakers, microplate photometer, four pipettes, stacker for ten microplates and incubation cabin with temperature regulation. As a result of miniaturization and automation large numbers of toxicants and far more treatments and parallels can be tested and, additionally, only low sample volumes are needed.

Automation↗

PubMed2003

Nuclear localization of the Hermes transposase depends on basic amino acid residues at the N-terminus of the protein.

For the Hermes transposable element to be mobilized in its eukaryotic host, the transposase, encoded by the element, must make contact with its DNA. After synthesis in the cytoplasm, the transposase has to be actively imported into the nucleus because its size of 70.1 kDa prevents passive diffusion through the nuclear pore. Studies in vitro using transient expression of a Hermes-EGFP fusion protein in Drosophila melanogaster Schneider 2 cells showed the transposase was located predominantly in the nucleus. In silico sequence analysis, however, did not reveal any nuclear localization signal (NLS). To identify the sequence(s) responsible for localization of Hermes transposase in the nucleus, truncated or mutated forms of the transposase were examined for their influence on sub-cellular localization of marker proteins fused to the transposase. Using the same expression system and a GFP-GUS fusion double marker, residues 1-110 were recognized as sufficient, and residues 1-32 as necessary, for nuclear localization. Amino acid K25 greatly facilitated nuclear localization, indicating that at least this basic amino acid plays a significant role in this process. This sequence overlaps the proposed DNA binding region of the Hermes transposase and is not necessarily conserved in all members of the hAT transposable element family.

Amino Acid Sequence↗

PubMed2003

Toxin B of Clostridium difficile activates human VIP submucosal neurons, in part via an IL-1beta-dependent pathway.

This study investigated whether toxin B of Clostridium difficile can activate human submucosal neurons and the involved pathways. Isolated segments of human colon were placed in organ culture for 3 h in the presence of toxin B or IL-1beta. Whole mounts of internal submucosal plexus were stained with antibodies against c-Fos, neuron-specific enolase (NSE), vasoactive intestinal polypeptide (VIP), and substance P (SP). The membrane potential (Vm) response of submucosal neurons to local application of toxin B and IL-1beta was determined by a multisite optical recording technique. Toxin B (0.1 to 10 ng/ml) increased the proportion of c-Fos-positive neurons dose dependently compared with the control. In the presence of toxin B (10 ng/ml), most c-Fos-positive neurons were immunoreactive for VIP (79.8 +/- 22.5%) but only 19.4 +/- 14.0% for SP. Toxin B induced a rapid rise in IL-1beta mRNA level and a sixfold increase in IL-1beta protein in supernatant after 3 h of incubation. c-Fos expression induced by toxin B was reduced dose dependently by IL-1 receptor antagonist (0.1-10 ng/ml). IL-1beta significantly increased c-Fos expression in submucosal neurons compared with the control (34.2 +/- 10.1 vs. 5.1 +/- 1.3% of NSE neurons). Microejection of toxin B had no effect on the Vm of enteric neurons. Evidence of a direct excitatory effect of IL-1beta on Vm was detected in a minority of enteric neurons. Therefore, toxin B of C. difficile activates VIP-positive submucosal neurons, at least in part, via an indirect IL-1beta-dependent pathway.

Aged↗

PubMed2003

The C-terminus of the Hermes transposase contains a protein multimerization domain.

Transposase activity that mediates the mobility of class II transposable elements, is most commonly initiated by the assembly of higher order synaptic complexes, called transpososomes. The formation of these complexes, that contain the transposable element's DNA as well as two or more molecules of the transposase, is dependent on interactions between transposase molecules. Using the yeast Two-Hybrid system, we were able to identify three regions mediating multimerization of the Hermes transposase, an element used for germline transformation of insects belonging to the hAT family of transposable elements. One region facilitating protein binding of Hermes transposase molecules was found within the first 252 amino acids of the transposase. The second region was located at the C-terminus of the transposase, and was found to be specific for Hermes transposase multimerization. Amino acids 551-569 were not only required for multimerization but were also necessary for transposition of the element. The third region was located between amino acids 253 and 380 and was found to eliminate the non-specific protein binding ability of the N-terminal protein interaction region but was required for the specific protein binding ability of the C-terminal region of the transposase. Five point mutations affecting the structural integrity of the C-terminal multimerization region abolished or significantly reduced transpositional activity. The same region had been previously identified to mediate dimerization in Activator (Ac), another hAT element, indicating that hAT transposase multimerization is likely to be a prerequisite for mobility of their elements.

Amino Acid Sequence↗

PubMed2003

In situ sensing of volatile organic compounds in groundwater: first field tests of a mid-infrared fiber-optic sensing system.

A prototype mid-infrared sensor system for the determination of volatile organic pollutants in groundwater was developed and tested under real-world conditions. The sensor comprises a portable Fourier transform infrared spectrometer, coupled to the sensor head via mid-infrared transparent silver halide fiber-optic cables. A 10 cm unclad middle section of the 6-m-long fiber is coated with ethylene propylene copolymer in order to enrich the analytes within the penetration depth of the evanescent field protruding from the fiber sensor head. A mixture of tetrachloroethylene, dichlorobenzene, diethyl phthalate, and xylene isomers at concentrations in the low ppm region was investigated qualitatively and quantitatively in an artificial aquifer system filled with Munich gravel. This simulated real-world site at a pilot scale enables in situ studies of the sensor response and spreading of the pollutants injected into the system with controlled groundwater flow. The sensor head was immersed into a monitoring well of the aquifer system at a distance of 1 m downstream of the sample inlet and at a depth of 30 cm. Within one hour, the analytes were clearly identified in the fingerprint region of the IR spectrum (1300 to 700 cm(-1)). The results have been validated by head-space gas chromatography, using samples collected during the field measurement. Five out of six analytes could be discriminated simultaneously; for two of the analytes the quantitative results are in agreement with the reference analysis.

Equipment Design↗

PubMed2002

Does the proposed DSE motif form the active center in the Hermes transposase?

Donor cleavage and strand transfer are two functions performed by transposases during transposition of class II transposable elements. Within transposable elements, the only active center described, to date, facilitating both functions, is the so-called DDE motif. A second motif, R-K-H/K-R-H/W-Y, is found in the site-specific recombinases of the tyrosine recombinase family. While present in many bacterial insertion sequences as well as in the eukaryotic family of mariner/Tc1 elements, the DDE motif was considered absent in other classes of eukaryotic class II elements such as P, and hAT and piggyBac. Based on sequence alignments of a hobo-like element from the nematode Caenorhabditis elegans, to a variety of other hAT transposases and several members of the mariner/Tc1 group, Bigot et al. [Gene 174 (1996) 265] proposed the presence of a DSE motif in hAT transposases. In the present study we tested if each of these three residues is required for transposition of the Hermes element, a member of the hAT family commonly used for insect transformation. While D402N and E572Q mutations lead to knock-out of Hermes function, mutations S535A and S535D did not affect transposition frequency or the choice of integration sites. These data give the first experimental support that D402 and E572 are indeed required for transposition of Hermes. Furthermore, this study indicates that the active center of the Hermes transposase differs from the proposed DSE motif. It remains to be shown if other residues also form the active site of this transposase.

Amino Acid Motifs↗

PubMed2002

Repetition of suicidal behaviour in elderly Europeans: a prospective longitudinal study.

The aim of this study was to assess any predictive factors for repeated attempted suicide and completed suicide in a 1-year follow-up on a sample of elderly European suicide attempters (60 years and over). From 1990 to 1993, 63 subjects completed the first interview and were recontacted after 1 year. At follow-up, eight subjects (12.7%) had taken their lives and seven (11.1%) had repeated at least one suicide attempt. On comparison of repeaters and non-repeaters, differences emerged in terms of death of the father in childhood and for mean Suicidal Intent Score. At the end of follow-up period, repeaters reported a more frequent desire to repeat suicidal behaviour and judged their mental health and social assistance received to be worse. Suicides and non-repeaters differed especially in relation to death of father during childhood and number of contacts with General Practitioner. Interpretation of the results must take into account the smallness of the test sample, the difficulties in obtaining complete data for the follow-up interview, the lack of a control group and a diagnosis formulated in a hospital consultation setting. The study confirms, however, the high risk of repetition of suicidal behaviour in the elderly. In old age suicidal ideation is often sustained over long periods of time and requests for help are addressed to relatives and GPs. An interesting finding is the more frequent death of the father during childhood among repeaters.

Aged↗

PubMed2001

Glycine activates myenteric neurones in adult guinea-pigs.

1. We studied the effects of glycine on myenteric neurones and muscle activity in the colon and stomach of adult guinea-pigs. 2. Intracellular recordings revealed that myenteric neurones responded to local microejection of glycine (1 mM) with a fast, transient membrane potential depolarisation (57 % of 191 colonic neurones and 26 % of 50 gastric neurones). Most glycine-sensitive neurones had ascending projections and were choline acetyltransferase immunoreactive. Glycine preferentially activated neurones with a late afterhyperpolarisation (AH-neurones) and tonic spiking neurones with fast synaptic inputs (tonic S-neurones) but less frequently phasic S-neurones and inexcitable (non-spiking) neurones. The depolarisation had a reversal potential at -19 +/- 13 mV, which was increased by 18 +/- 10 % upon lowering extracellular chloride concentration and decreased by 38 +/- 14 % in furosemide (frusemide, 2 mM). 3. Strychnine (300 nM) reversibly abolished the glycine-induced depolarisation and the Cl(-) channel blocker picrotoxin (100 microM) reduced the amplitude of the depolarisation by 55 +/- 5 %. The glycine effect was a postsynaptic response because it was not changed after nerve blockade with tetrodotoxin (1 microM) or blockade of synaptic transmission in reduced extracellular [Ca(2+)]. The effect was specific since the response was not changed by the nicotinic antagonists hexamethonium (200 microM) and mecamylamine (100 microM), the GABA(A) receptor antagonist bicuculline (10 microM), the NMDA antagonist MK-801 (20 microM) or the 5-HT(3) antagonist ICS 205930 (1 microM). 4. Glycine (1 mM) induced a tetrodotoxin- and strychnine-sensitive contractile response in the colon; the contractile response in the stomach was tetrodotoxin insensitive. 5. Glycine activated myenteric neurones in the adult enteric nervous system through strychnine-sensitive mechanisms. The glycine-evoked depolarisation was caused by Cl(-) efflux and the maintenance of relatively high intracellular chloride concentrations involved furosemide-sensitive cation-chloride co-transporters.

Animals↗

PubMed2001

Enteric pathways in the stomach.

This report summarises the characteristics of target specific projection and neurochemical coding patterns of motor and interneuronal pathways in the gastric enteric nervous system (ENS) which are involved in the innervation of the mucosa, the circular and the longitudinal muscle. The pathways were identified by retrograde tracing and further characterised by optical and intracellular recordings of the synaptic activation of muscle motor neurones, and by recordings of pathway-specific muscle responses. All motor pathways had polarised projections consisting of ascending cholinergic and descending nitrergic populations. Thus, both muscle layers were innervated by excitatory and inhibitory motor neurones. Their projections indicated the presence of intrinsic circuits that mediate excitatory and inhibitory components of a peristaltic reflex and/or are involved in reflex mediated changes in gastric tone. Although polarised projections were also identified for interneuronal pathways, a substantial proportion of descending interneurones was cholinergic. Interneurones and longitudinal muscle motor pathways had longitudinal projection preferences whereas circular muscle motor pathways had circumferential projection preferences. Target-specific coding was primarily revealed for cholinergic populations; ChAT/ENK/+/-SP neurones projected to the muscle layers, ChAT/NPY/+/-VIP projected to the mucosa and ChAT/+/-SP/+/-5-HT/+/-Calret/+/-Calb were interneurones. Muscle strip recordings revealed the functional significance of ascending excitatory and descending inhibitory pathways to the circular muscle and the prominent influence of ascending and descending cholinergic interneurones which activated excitatory and inhibitory circular muscle motor neurones through nicotinic synapses. It is concluded that enteric pathways in the stomach have region specific features which reflect structural and functional adaptation of the gastric ENS.

Animals↗

PubMed2001

Attempted and completed suicide in older subjects: results from the WHO/EURO Multicentre Study of Suicidal Behaviour.

OBJECTIVE: The authors present an analysis of findings for the 65 years and over age group from the WHO/EURO Multicentre Study of Suicidal Behaviour (1989-93). METHODS: Multinational data on non-fatal suicidal behaviour is derived from 1518 subjects in 16 European centres. Local district data on suicide were available from 10 of the collaborating centres. RESULTS: Stockholm (Sweden), Pontoise (France) and Oxford (UK) had the highest suicide attempts rates. In most centres, the majority of elderly who attempted suicide were widow(er)s, often living alone, who used predominantly voluntary drug ingestion. Non-fatal suicidal behaviour decreased with increasing age, whereas suicide rates rose. The ratio between fatal and non-fatal behaviours was 1:2, that for males/females almost 1:1. In the years considered, substantial stability in suicide and attempted suicide rates was observed. As their age increased, suicidal subjects displayed only a limited tendency to repeat self-destructive acts. Moreover, there was little correlation between attempted suicide and suicide rates, which carries different clinical implications for non-fatal suicidal behaviour in the elderly compared with younger subjects in the same WHO/EURO study.

Age Distribution↗

PubMed2001

Projections of excitatory and inhibitory motor neurones to the circular and longitudinal muscle of the guinea pig colon.

The aim of this study was to identify myenteric pathways to the circular and longitudinal muscle of the guinea pig proximal colon. To identify excitatory and inhibitory muscle motoneurones, we applied the neuronal retrograde tracer DiI onto the circular or longitudinal muscle layer and performed additional immunohistochemistry for nitric oxide synthase (NOS) and choline acetyltransferase (ChAT). On average 166 +/- 81 circular muscle motoneurones (CMMN) and 100 +/- 74 longitudinal muscle motoneurones (LMMN) were labelled by DiI tracing. Myenteric pathways innervating the muscle were either ascending (DiI-labelled neurones with oral projections) or descending (DiI-labelled neurones with anal projections). The circular muscle was preferentially innervated by ascending pathways (66.0 +/- 9.1%). Most ascending CMMN were ChAT-positive (87.2 +/- 8.5%), whereas descending CMMN were mainly NOS-positive (82.3 +/- 14.6%). Most ascending (62.2 +/- 11.1%) and descending (82.0 +/- 12.5%) CMMN had circumferential projection preferences (circumferential projections were longer than projections along the longitudinal gut axis). In contrast to the polarised projections to the circular muscle, the longitudinal muscle was equally innervated by ascending (46.2 +/- 15.1%) and descending (53.9 +/- 15.1%) neurones. Ascending and descending pathways to the longitudinal muscle consisted predominantly of ChAT-positive neurones (98.1 +/- 1.9% and 68.0 +/- 8.5%, respectively), and both pathways had prominent longitudinal projection preferences. Only 25.5% of the descending LMMN were NOS-positive. In conclusion, the circular muscle in the proximal colon is innervated by descending inhibitory (NOS-positive neurones) and ascending excitatory (ChAT-positive neurones) pathways. In contrast, the longitudinal muscle is primarily innervated by ascending and descending excitatory motoneurones, and only a small proportion of the descending pathway consisted of inhibitory motoneurones.

Animals↗