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Biomedical subjects

M Gehrke

Publications and source records attributed to M Gehrke.

12 recordsLinked to original sources
PubMed2005

Influence of balance of protein and energy metabolism in rumen on hypomagnesaemia in cows.

This study was carried out in order to determine the influence of nitrogen excess in rumen and deficit of digestible organic matter in a feed ration for dairy cows on hypomagnesaemia at the beginning of green forage feeding. The balance of nitrogen and energy metabolism in rumen was determined using the rules of evaluation of the nutritional value of fodder (PDI system) according to the Institut National de la Recherche Agronomique (INRA), taking into consideration a potential protein synthesis from nitrogen by microorganisms in rumen (MPRN) and microbial protein synthesized from digestible organic matter (MP(RE)). It was found that an increase in the amount of rumen degradable protein (RDP) and MPRN-MPRE balance leads to a significant increase of urea nitrogen in serum (p < 0.05). An increase of total MPRN-MPRE balance in rumen results in a decrease of Mg concentration in serum. It has been demonstrated that in cows fed green forage at the end of spring (2nd half of May to 1st half of June) when the MPRN-MPRE balance is not higher than 187 g, adding 7 g or 25 g of MgO/cow/day to the same extent successfully prevents hypomagnesaemia.

Animal Feed↗
PubMed2002

High-throughput peptide synthesis and peptide purification strategy at the low micromol-scale using the 96-well format.

The increasing demand for short- and medium-sized peptides in many fields of biological, medical and pharmaceutical research requires optimized and universally applicable high-throughput synthesis and purification techniques at the low-micromol scale. Here, we describe a continuous peptide synthesis/purification approach using the 96-well format. First, a micromol scale peptide synthesis on resin beads was optimized on a novel miniaturized 96-reaction vessel block employing standard Fmoc/tBu-chemistry. Almost 90% of the synthesized peptides contained the target sequence as the main component, as judged from matrix-assisted laser desorption/ionization (MALDI) mass spectra. Impurities were mostly related to partially protected peptides. Second, we tested the applicability of ion pair reversed-phase solid-phase extraction (IP-RP-SPE) to purify individual peptides. Depending on the length and predicted hydrophobicity of the peptides, elution was performed with 25 or 35% aqueous acetonitrile in the presence of 0.1% trifluoroacetic acid (TFA). Thus, scavengers used during TFA cleavage and partially protected peptides carrying very hydrophobic protecting groups were effectively removed. Using a narrow step gradient, the target peptides were even separated from deleted sequences and protected peptides with similar hydrophobicities. Third, we combined the micromol-scale synthesis in the 96-well format with purification by IP-RP-SPE on a 96-well micro-extraction plate format. This simple, fast and parallel approach was tested on 12-mer and 15-mer peptides to map epitopes of T- and B-cell clones, respectively. Approximately 80% of all peptides were obtained at purities > 90% without purification by RP-HPLC. In summary, this novel approach has several advantages: (i) the micromol-scale reduced the cost of peptide synthesis, (ii) large numbers of peptides were purified faster, (iii) the volumes of eluents and waste were significantly reduced, and (iv) the RP-HPLC column was not contaminated with hydrophobic impurities.

Acetonitriles↗
PubMed2000

Application of electron-attachment reactions to enhance selectivity of electron-capture detector for nitroaromatic explosives.

The differences in the extent of electron-attachment reactions between thermal electrons and selected classes of organic molecules with high electron affinities were investigated. The investigations showed that interactions of thermal electrons with nitroaromatic compounds lead to the formation of neutral products with very low electron affinities. By contrast, a number of other analytes with high electron affinities such as polyhalogenated organic compounds, lead to products with high electron affinities. This difference was exploited to differentiate between nitroaromatic and polychlorinated organic compounds with a tandem arrangement consisting of two electron-capture detectors connected in series with an electron-attachment reactor.

Electrons↗
PubMed1997

Coping with hallucinations: exploring stress and coping framework.

This study explored application of the theoretical framework of Lazarus & Folkman (1984) to coping with hallucinations in schizophrenia. Eighty-one patients were interviewed with a structured schedule. Unprompted reports of coping indicated wide use of both 'hallucination-specific' and 'general' strategies. Factor analysis of a coping checklist produced three factors which were utilized in regression analyses. The active acceptance factor may relate to control of hallucinations, the passive coping factor predicted distress reduction but, surprisingly, the resistance coping factor, which contained hallucination-specific coping strategies, predicted poor distress reduction. Clinical and research implications are noted.

Adaptation, Psychological↗
PubMed1991

Effect of recombinant beet necrotic yellow vein virus with different RNA compositions on mechanically inoculated sugarbeets.

Beet necrotic yellow vein virus (BNYVV) inocula with different RNA compositions were prepared from infectious transcripts of RNAs 3 and 4 and the Rg 1 isolate, which has a genome consisting only of RNAs 1 and 2. The recombinant viruses were inoculated on 6- to 8-day-old sugarbeet seedlings by 'vortexing'. Inocula containing RNAs 1 and 2 or 1, 2 and 4 produced some growth reduction, but the most dramatic effects, with yield reductions of about 95% in a highly susceptible variety, were seen when RNA 3 was also present in the inoculum. Under these conditions the side roots were brown and brittle and often deteriorated, but 'root beardedness' was not observed. This might be due to the fact that our experiments were done in the absence of Polymyxa betae. Alternatively, the heavy inoculation at a very young age may either have weakened the plants to such an extent that extensive root proliferation was impaired or it may have led to rapid deterioration of the proliferating rootlets, which would therefore be lost prior to or during removal of the tap roots from the soil. In the presence of RNA 3 the virus concentrations in tap roots were markedly increased suggesting that this RNA facilitates the multiplication and/or spread of the virus in root tissues.

Plant Diseases↗
PubMedDate not supplied

A high efficiency all glass sampling and concentration device for adsorptive semivolatile organics.

A low-volume, inert sampling and enrichment device for semivolatile organic vapors is described. The device consists of two concentric fused silica capillaries. A small portion of the inter-capillary volume, cooled with a burst of compressed carbon dioxide, serves as a trap for the semivolatile organics. The low mass of the trap permits rapid sampling and desorption cycles suitable for applications requiring fast monitoring of semivolatile chemicals. The device is devoid of switching valves in the sampling train and consequently does not suffer from analyte loss due to irreversible adsorption or interference resulting from cross contamination. The device was successfully used for sampling low concentrations of highly adsorptive nitroaromatic compounds and is applicable for polychlorinated dibenzo-p-dioxins (PCDDs) and polyaromatic hydrocarbons (PAHs).

Carbon Dioxide↗