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M Kirchner

Publications and source records attributed to M Kirchner.

At least 19 recordsLinked to original sources
PubMed2026

Genomic characterisation of Enterococcus cecorum isolated from broiler chickens in the United Kingdom.

Enterococcus cecorum is an important poultry pathogen associated with lameness and increased mortality, leading to major welfare and economic impacts. Treatment is often challenging because disease is frequently detected late and the organism can localise in bone and joints, limiting antimicrobial efficacy. Presence of antimicrobial resistance (AMR) genes may further complicate treatment. Despite increasing global genomic research, only one recent study has investigated the phylogeny of E. cecorum from conventional UK broiler farms, using limited samples and a restricted time frame. In this study, 283 E. cecorum isolates were analysed, including 158 from the United Kingdom and 125 global non‑UK isolates. UK isolates comprised 123 archived by the Animal and Plant Health Agency (APHA) between 2003 and 2022, predominantly from clinical outbreaks with increased welfare culling and mortality, and 35 isolates from a UK study including clinical and environmental samples. Genome sequencing was used to assess phylogeny, AMR determinants and virulence factors (VFs). Single nucleotide polymorphism phylogenetic analysis identified eight major UK lineages with limited intra‑lineage diversity, indicating that UK isolates were genetically distinct from non‑UK populations. Using a 60‑SNP threshold, APHA isolates formed 18 subclusters, consistent with long‑term persistence and recurrent farm transmission, while multiple subclusters detected on some farms suggested repeated introductions. UK isolates carried fewer AMR genes than non‑UK isolates, with erm(B), lnu(C), tet(M) and tet(L) most prevalent. Screening of VF genes identified nine genes present in all isolates, with the remainder variably distributed. A subset of 60 UK isolates was examined for 13 previously described virulence‑associated genes, with phylogenetic clustering indicating associations between gene presence or absence and clinical status or mortality classification. The capsular polysaccharide gene cpsO was assessed in this subset and most non‑clinical or environmental isolates were cpsO‑negative, although several isolates from high‑mortality outbreaks also lacked this gene. Overall, this study provides insight into the phylogeny, AMR profiles and virulence gene diversity of E. cecorum within the UK broiler sector, supporting targeted surveillance and investigation of pathogenic mechanisms.

Antimicrobial resistance↗
PubMed2006

Changed vegetation composition in coniferous forests near to motorways in Southern Germany: the effects of traffic-born pollution.

To estimate the effect of traffic emissions on the vegetation composition of coniferous forests near to motorways, three transects of 520 m length were studied by analysing vegetation composition, soil parameters and deposition data in the Munich-area, Southern Germany. The detected patterns suggest that motorways have an impact on the vegetation composition in the neighbourhood of roads. Depending on the wind direction, the influences of the motorways reaches up to 230 m on downwind side and up to 80 m on upwind side. The vegetation is mainly affected by the deposition of nitrogen deriving from fuel combustion and by basic substances added to road salt. By monitoring vegetation changes near to motorways, it is possible to estimate the areas where harmful alterations of the ecosystem can be expected.

Air Pollutants↗
PubMed2005

A double-blind randomized controlled trial comparing alternate forms of high molecular weight hyaluronan for the treatment of osteoarthritis of the knee.

OBJECTIVE: To compare the safety and effectiveness of a high molecular weight hyaluronan produced by biological fermentation (Bio-HA) with those of avian-derived hyaluronan that uses cross-linking to achieve high molecular weight (CL-HA). DESIGN: This was a prospective, multicenter, randomized, double-blind trial evaluating patients with confirmed osteoarthritis of the knee. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC Index) pain subscale was the primary effectiveness measure (visual analog scale). Both products were administered via three weekly injections, with follow-up evaluations at weeks 3, 6 and 12. Acetaminophen was permitted as rescue medication and quantitated by pill counts. RESULTS: Analyses were performed on the intent-to-treat population, defined as all patients receiving at least one injection. Of the 321 patients randomized to treatment, 314 patients (98%) completed the final study assessment. Improvement in the average WOMAC Index pain score was 29.8mm (-61.6%) for Bio-HA and 28.8mm (-54.9%) for CL-HA, meeting the prospective criteria for non-inferiority. For the secondary outcome measures, statistically significant differences favored Bio-HA for the number of patients requiring acetaminophen (P=0.013) and patient global satisfaction evaluations (P=0.03). Local reactions differed between the products in that 15 effusions were reported in 13 CL-HA patients (8.1%) after injection, compared to one effusion (0.6%) after Bio-HA injection (P=0.0015). CONCLUSION: The effectiveness of Bio-HA was not inferior to that of CL-HA. The significantly higher incidence of post-injection effusion in the CL-HA group provides a safety advantage for Bio-HA. These data suggest that Bio-HA has an improved benefit-risk profile compared with CL-HA.

Adjuvants, Immunologic↗
PubMed2005

Fast gas chromatography with solid phase extraction clean-up for ultratrace analysis of pesticide residues in baby food.

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level < or = 10 microg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 microg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 microg/kg for the majority of compounds. The repeatability of gas chromatography-mass spectrometry (GC-MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.

Chromatography, Gas↗
PubMed2001

Effects of Oxyrrhis marina (Dinoflagellata), bacteria and vitamin D(2) on population dynamics of Tisbe holothuriae (Copepoda).

Laboratory experiments were performed to determine which food combinations had the most favorable effect on population dynamics of the harpacticoid copepod Tisbe holothuriae. In addition to basic diets of TetraMin (T), rice (R) or a mixture of both (T+R), supplements consisting of the following were given: the heterotrophic dinoflagellate Oxyrrhis marina, a bacterial suspension and vitamin D(2). Results show a beneficial effect of bacteria at a given concentration on T. holothuriae, which is enhanced in combination with vitamin D(2). A higher concentration of bacteria together with vitamin D(2), however, has a reverse effect leading to greater mortality, lower sex ratio and number of ovigerous females, and a dramatic decrease in production of eggs, regardless of the basic diet. We conclude that different concentrations of a given bacterial community may have variable effects on the reproduction of harpacticoid copepods and that, in addition to the bacteria, vitamin D(2) may also play a role in invertebrate nutrition.

Journal Article↗
PubMed2001

Principal component analysis and cluster analysis for measuring the local organisation of human atrial fibrillation.

The distribution of atrial electrogram types has been proposed to characterise human atrial fibrillation. The aim of this study was to provide computer procedures for evaluating the local organisation of intracardiac recordings during AF as an alternative to off-line manual classification. Principal component analysis (PCA) reduced the data set to a few representative activations, and cluster analysis (CA) measured the average dissimilarity between consecutive activations of an intracardiac signal. The data set consisted of 106 bipolar signals recorded on 11 patients during electrophysiological studies for catheter ablation. Performances of PCA and CA in distinguishing between organised (type I) and disorganised (type II/III, Wells criteria) were assessed, in comparison with manual reading, by evaluating the predictive parameters of the classification analysis. Both methods gave high accuracy (92% for PCA and 89% for CA), confirming the feasibility of on-line characterisation of AF. Sensitivity was lower than specificity (81% against 98% for PCA, and 77% against 97% for CA), with seven out of eight misclassifications of PCA in common with CA. Differences between manual and computer analysis may be related to the higher resolution of PCA and CA in the measurement of the organisation of atrial activations. These procedures are suitable for providing automatic (by CA) or semi-automatic (by PCA) measures of the extent of local organisation of AF in the pre-ablation treatment phase.

Atrial Fibrillation↗
PubMed1999

Field intercomparison of diffusive samplers for measuring ammonia.

Agricultural production systems are recognised as a major source of atmospheric ammonia. Deposition of ammonia and ammonium may contribute to undesired changes in oligotrophic ecosystems. The continuous measurement of atmospheric ammonia requires expensive and sophisticated techniques and is performed only in a very restrict number of ambient air stations in Europe. Therefore, the application of passive samplers, which have the advantage of being easy to handle and cost-efficient, is useful. In the past the comparability of different passive samplers must be considered as rather scarce. In a joint European project under the leadership of the GSF-Forschungszentrum für Umwelt und Gesundheit, Neuherberg, in 1997 a comparison of different passive ammonia monitoring methods was carried out in a prealpine rural site near Garmisch-Partenkirchen. It was considered valuable to include not only well established systems but also methods still being developed. For the comparative test ten working groups with different methods took part. A wet annular denuder system, which has been developed by the Netherlands Energy Research Foundation for on-line measurement of atmospheric ammonia, served as reference of passive methods. The experiment, which started in June and finished in December, showed that most of the passive samplers fulfil the requirements and can be recommended for further measurements. Additional measurements of meteorological parameters were performed to check the influences of different weather conditions on passive sampling.

Agriculture↗
PubMed1998

Atrial mapping and radiofrequency catheter ablation in patients with idiopathic atrial fibrillation. Electrophysiological findings and ablation results.

BACKGROUND: Knowledge of the electrophysiological substrates and the cure of atrial fibrillation (AF) is still unsatisfactory. The goal of this study was to evaluate the electrophysiological features of idiopathic AF and their relationship to the results of radiofrequency (RF) catheter ablation of AF and the safety and effectiveness of this procedure. METHODS AND RESULTS: Sixteen patients with idiopathic AF underwent atrial mapping during AF and then RF ablation in the right atrium. The atrial activation was simultaneously recorded in four regions in the right atrium: high lateral wall (HL), low lateral wall (LL), high septum (HS), and low septum (LS) and in the left atrium through the coronary sinus (CS). In these regions, we evaluated the atrial fibrillation intervals (FF) and the morphological features of AF recordings by Wells' classification. No complications occurred during RF ablation. Of the 16 patients, 9 (56%) without AF recurrences during the follow-up (11 +/- 4 months) were considered successfully ablated. These patients showed a significantly shorter mean FF interval in the HS and the LS (122 +/- 32 and 126 +/- 28 ms, respectively), than in the HL and LL (159 +/- 24 and 156 +/- 28 ms, respectively). Moreover, the septum had more irregular electrical activity with greater beat-to-beat changes in FF and a higher prevalence of type III AF than the lateral region. The CS had similar behavior to the septum. Conversely, patients with unsuccessful ablation had an irregular atrial activity in the lateral wall, septum, and CS with no significant differences between the different sites. CONCLUSIONS: Right atrial endocardial catheter ablation of AF is a safe procedure and may be effective in some patients with idiopathic AF. The atrial mapping during AF showed a more disorganized right atrial activation in the septum than in the lateral wall in patients with successful ablation.

Adult↗
PubMed1996

Peptide-mass profiles of polyvinylidene difluoride-bound proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in the presence of nonionic detergents.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), in conjunction with enzymatic digestion of proteins and molecular weight search of peptide-mass database is a powerful technique for peptide/protein identification. Ideally, peptide mixtures should be compatible with both MALDI-TOF and microsequencing. In our laboratory, enzymatic digestion and extraction of peptides from polyvinylidene difluoride (PVDF)-bound proteins is performed in the presence of nonionic detergents. However, nonionic detergents have been shown to cause signal suppression in MALDI-TOF analysis. This study demonstrates that by using a modified matrix solution, peptide-mass fingerprinting of PVDF-bound proteins by MALDI-TOF can be obtained in the presence of nonionic detergents such as hydrogenated Triton X-100 (RTX-100), octylglucopyranoside, and Tween 20.

Amino Acid Sequence↗
PubMed1996

Amino acid polymorphism and rare electrophoretic variants of G6PD from natural populations of Drosophila melanogaster.

Identifying the amino acid changes responsible for electrophoretic variants is essential to understanding the significance of allozyme polymorphism in adaptation. The amino acid mutations responsible for the common G6PD allozyme polymorphisms in Drosophila melanogaster have been recently described. This study characterizes the amino acid changes associated with 11 rare electrophoretic G6PD variants. The 11 rare electrophoretic variants result from six independent amino acid mutations. The in vivo function of the rare variants was determined in an earlier study and most variants fell into one of two function classes. It is shown here that the function of the rare variants reflects the state of the Pro/Leu mutation responsible for the A/B allozyme polymorphism in each variant. Two mutations destabilize quaternary structure resulting in shifts from tetrameric dimeric alleles, and one of these also results in a variant with in vivo function intermediate to A and B. That mutation is an aspartic-acid-to-asparagine change that is two residues away from the Pro/Leu polymorphism responsible for the A/B dimertetramer quaternary shift. Structure-function relationships based on studies of human G6PD deficiency-associated mutations predict that these last two amino acid changes fall within the protein domain responsible for NADP binding.

Amino Acid Sequence↗
PubMed1996

Historical selection, amino acid polymorphism and lineage-specific divergence at the G6pd locus in Drosophila melanogaster and D. simulans.

The nucleotide diversity across 1705 bp of the G6pd gene is studied in 50 Drosophila melanogaster and 12 D. simulans lines. Our earlier report contrasted intraspecific polymorphism and interspecific differences at silent and replacement sites in these species. This report expands the number of European and African lines and examines the pattern of polymorphism with respect to the common A/B allozymes. In D. melanogaster the silent nucleotide diversity varies 2.8-fold across localities. The B allele sequences are two-to fourfold more variable than the derived A allele, and differences between allozymes are twice as among B alleles. There is strong linkage disequilibrium across the G6pd region. In both species the level of silent polymorphism increases from the 5' to 3' ends, while there is no comparable pattern in level of silent site divergence or fixation. The neutral model is not rejected in either species. Using D. yakuba as an outgroup, the D. melanogaster lineage shows a twofold greater rate of silent fixation, but less than half the rate of amino acid replacement. Lineage-specific differences in mutation fixation are inconsistent with neutral expectations and suggest the interaction of species-specific population size differences with both weakly advantageous and deleterious selection.

Animals↗
PubMed1995

Differential accumulation of the transcripts of 22 novel protein kinase genes in Arabidopsis thaliana.

22 novel members of the Arabidopsis thaliana protein kinase family (AKs) were identified by using degenerate oligonucleotide primers directed to highly conserved amino acid sequences of the protein kinase (PK) catalytic domain. Of these 22 genes, 16 turned out to carry intron sequences. Homologies of AK sequences were detected to S-locus receptor protein kinases (SRKs) from Brassica spp., to SRK-like PKs from maize and A. thaliana and to several other receptor PKs from A. thaliana. Sequence similarity was also detected to Ca(2+)-dependent PKs (CDPKs) from rape and soybean, to SNF1 and to CDC2 homologues. The genomic organization and the accumulation of the mRNAs from these 22 AK genes were investigated.

Amino Acid Sequence↗
PubMed1994

Synthesis and SAR studies of novel triazolopyrimidine derivatives as potent, orally active angiotensin II receptor antagonists.

The synthesis and pharmacological activity of new nonpeptide angiotensin II (AII) receptor antagonists are presented. These [1,2,4]-triazolo[1,5-c]pyrimidine and 1,2,4-triazolo[4,3-c]pyrimidine derivatives represent a new class of bicyclic antagonists that produced a potent, oral antihypertensive activity in the renal artery-ligated rat model. In vitro, they displayed a high affinity for rat adrenal AII receptors and were found to be specific for the AT1 receptor subtype. A SAR study has shown the importance of the 8-[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl for oral activity and the critical role of alkyl substituents at 5- and 7-positions. No significant differences were found between the [1,5-c] and [4,3-c]series. UP 269-6 (5-methyl-7-n-propyl-8-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl ]- [1,2,4]-triazolo[1,5-c]pyrimidin-2(3H)-one, derivative 29) was selected as the lead compound. It was shown to be a highly potent antihypertensive derivative (decrease in mean arterial pressure of 39.6 +/- 7.2 mmHg at 1 mg/kg po in renal artery-ligated rat) with a long duration of action which displayed a high affinity for adrenal AII receptors with a marked selectivity for the AT1 receptor subtype (Ki AT1 = 24 nM; Ki AT2 = 79,200 nM). This compound is currently undergoing extensive pharmacological and clinical development.

Administration, Oral↗
PubMed1994

Synthesis and angiotensin II receptor antagonist activity of C-linked pyrazole derivatives.

The synthesis and pharmacological activity of new nonpeptide angiotensin II (AII) receptor antagonists are presented. These 5-O-substituted and 5-C-substituted 3-alkylpyrazole derivatives represent a new series of antagonists and have led to the discovery of compounds with potent oral antihypertensive activity in a renal artery-ligated rat model. In vitro, they displayed a high affinity for rat adrenal AII receptors. In vivo structure-activity relationship study has shown the importance of the 4-[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl moiety for oral activity and the critical role of alkyl substituents at the 1- or 2-position. In the case of oral administration, 5-C derivatives were found to be, on the whole, more potent than 5-O derivatives. UP 221-78, 5-hydroxymethyl-3-n-propyl-1-(2,2,2-trifluoroethyl)-4- [[2'-(1H-tetrazol-5-yl)biphenyl-4-]methyl]-1H-pyrazole (79), displayed equivalent antihypertensive activity to the well known antagonist Losartan at 3 mg/kg p.o. in renal artery-ligated rats, with maximal decreases in mean arterial pressure of 60 and 63 mmHg for Losartan and UP 221-78, respectively.

Angiotensin Receptor Antagonists↗
PubMed1993

Evidence for adaptive evolution of the G6pd gene in the Drosophila melanogaster and Drosophila simulans lineages.

Proponents of the neutral theory argue that evolution at the molecular level largely reflects a process of random genetic drift of neutral mutations. Under this theory, levels of interspecific divergence and intraspecific polymorphism are expected to be correlated across classes of nucleotide or amino acid sequences with different degrees of functional constraint, such as synonymous and replacement sites. Nucleotide sites with reduced polymorphism should show comparably reduced levels of interspecific divergence. To examine this hypothesis, we have sequenced 32 and 12 copies of the glucose-6-phosphate dehydrogenase (G6pd) gene in Drosophila melanogaster and Drosophila simulans, respectively. Both species exhibit similar levels of nucleotide polymorphism at synonymous sites. D. melanogaster shows two amino acid polymorphisms, one associated with the cosmopolitan allozyme polymorphism and a second with an allozyme polymorphism endemic to European and North African populations. In contrast, D. simulans shows no replacement polymorphism. While synonymous divergence between species is 10%, which is typical of other genes, there are 21 replacement differences. This level of amino acid sequence divergence, when contrasted with levels of amino acid polymorphism, silent polymorphism, and divergence, is in 10-fold excess over that expected under the neutral model of molecular evolution. We propose that this excess divergence reflects episodes of natural selection on G6pd resulting in fixation of advantageous amino acid mutations in these two recently separated lineages.

Adaptation, Physiological↗