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Biomedical subjects

M Köck

Publications and source records attributed to M Köck.

At least 19 recordsLinked to original sources
PubMed2006

Tissue-specific expression of tomato Ribonuclease LX during phosphate starvation-induced root growth.

Ribonuclease LX (RNaseLX) from tomato (Solanum lycopersicum L.) belongs to the RNase T2/S-RNase superfamily of plant endoribonucleases and this is a report on the characterization of the RNaseLX gene and its encoded protein as a member of the phosphate starvation response in tomato. RNaseLX gene sequences were cloned by a PCR-assisted approach. RNaseLX promoter sequences contained the conserved binding motif of the transcription factor PHR1 known to mediate phosphate starvation-dependent gene expression. The increase of RNaseLX transcript levels in roots during phosphate starvation correlated with high promoter activity in transgenic plants carrying a PromLX::uidA gene construct and pointed to transcriptional control of RNaseLX expression. Histochemical staining for beta-glucuronidase activity and immunodetection of RNaseLX protein revealed striking RNaseLX expression in main and lateral root tips of phosphate-starved transgenic plants, specifically in epidermal cells, as well as in lateral and adventitious root primordia. Induced RNaseLX expression in roots correlated with stimulated growth and elongation of primary and lateral roots during phosphate deprivation. Phosphate-starvation-induced RNaseLX transcript levels in roots were not modulated by auxin or ethylene. These data indicate that the role of intracellular RNaseLX in the phosphate starvation response is connected with specific RNA turnover processes at the root tip.

Binding Sites↗
PubMed2004

Effects of weak 16 3/2 Hz magnetic fields on growth parameters of young sunflower and wheat seedlings.

Previous studies on effects of magnetic fields on plants focussed on the power frequencies (50-60 Hz), but in Austria and Germany electric railways are powered by a frequency of 16 2/3) Hz. In the present study, sunflower and wheat seedlings were exposed to 16 2/3 Hz sinusoidal 20 muT (rms) vertical magnetic fields. Seeds were germinated in a germination roll and grown for 12 days under continued exposure. Seven series with sunflower and six series with wheat were done over 2 years. Sunflower seedlings exposed to experimental magnetic field showed small, but significant increases in total fresh weights, shoot fresh weights, and root fresh weights, whereas dry weights and germination rates remained unaffected. Experimentally treated wheat exhibited marginally (but significantly) higher root fresh and dry weights, total fresh weights, and higher germination rates.

Electromagnetic Fields↗
PubMed2001

New antifeedant bromopyrrole alkaloid from the Caribbean sponge Stylissa caribica.

In this first report on the chemistry of the sponge Stylissa caribica, two known bromopyrrole metabolites and a new compound, N-methyldibromoisophakellin (1), were isolated and identified. The structure of 1 was determined using spectroscopic methods and the computer program COCON. N-Methyldibromoisophakellin (1) was shown to be the only secondary metabolite in Stylissa caribica that, at its natural concentration, is active as a feeding deterrent against a common omnivorous reef fish.

Alkaloids↗
PubMed2001

Sventrin, a new bromopyrrole alkaloid from the Caribbean sponge Agelas sventres.

A detailed analysis of the secondary metabolites of a specimen of Agelas sventres was carried out here for the first time. The chemistry of Agelas sponges is dominated by bromopyrrole derivatives. Besides three known bromopyrrole metabolites, a new compound, sventrin (1), was isolated and its structure identified using spectroscopic methods. Sventrin (1) was shown to be a feeding deterrent compound against a common omnivorous reef fish.

Alkaloids↗
PubMed2001

The chemical composition of African haze.

The LAMMA technique (Laser Microprobe Mass Analyzer) is a valuable and powerful technique for the analysis and characterization of particulate air pollutants. At seven sites in Zimbabwe, Africa, dust particles were collected and 200 single particles were analyzed for each sampling point. The main chemical species present in the particles are Na+, K+, Cl, NO3+ and SO4(2-). Beside these, soot particles, containing carcinogenic polynuclear aromatic hydrocarbons were found. Biomass burning was identified as the major source of the dust particles what is in accordance with the assumed air quality for our sampling period.

Air Pollutants↗
PubMed2001

Tomato ribonuclease LX with the functional endoplasmic reticulum retention motif HDEF is expressed during programmed cell death processes, including xylem differentiation, germination, and senescence.

We have studied the subcellular localization of the acid S-like ribonuclease (RNase) LX in tomato (Lycopersicon esculentum Mill.) cells using a combination of biochemical and immunological methods. It was found that the enzyme, unexpectedly excluded from highly purified vacuoles, accumulates in the endoplasmic reticulum. The evidence that RNase LX is a resident of the endoplasmic reticulum (ER) is supported by an independent approach showing that the C-terminal peptide HDEF of RNase LX acts as an alternative ER retention signal in plants. For functional testing, the cellular distribution of chimeric protein constructs based on a marker protein, Brazil nut (Bertholletia excelsa) 2S albumin, was analyzed immunochemically in transgenic tobacco (Nicotiana tabacum) plants. Here, we report that the peptide motif is necessary and sufficient to accumulate 2S albumin constructs of both vacuolar and extracellular final destinations in the ER. We have shown immunochemically that RNase LX is specifically expressed during endosperm mobilization and leaf and flower senescence. Using immunofluorescence, RNase LX protein was detected in immature tracheary elements, suggesting a function in xylem differentiation. These results support a physiological function of RNase LX in selective cell death processes that are also thought to involve programmed cell death. It is assumed that RNase LX accumulates in an ER-derived compartment and is released by membrane disruption into the cytoplasma of those cells that are intended to undergo autolysis. These processes are accompanied by degradation of cellular components supporting a metabolic recycling function of the intracellular RNase LX.

Amino Acid Motifs↗
PubMed2000

Oxepinamides A-C and fumiquinazolines H--I: bioactive metabolites from a marine isolate of a fungus of the genus Acremonium.

Three new oxepin-containing natural products (1-3) and two new fumiquinazoline metabolites (4-5) have been isolated from organic extracts of the culture broth and mycelia of an Acremonium sp., a fungus obtained from the surface of the Caribbean tunicate Ecteinascidia turbinata. The structures of the five compounds were determined through extensive analysis of 1D- and 2D-NMR data, and mass spectrometry. Compound 1 exhibited good anti-inflammatory activity in a topical RTX-induced mouse ear edema assay. Compounds 4 and 5 exhibited weak antifungal activity toward Candida albicans in a broth microdilution assay.

Acremonium↗
PubMed2000

Synthesis of the marine natural product nalpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine, a putative biogenetic precursor of the pyrrole-imidazole alkaloids.

Lysine is proposed as an alternative biosynthetic precursor of the pyrrole-imidazole alkaloids frequently found in marine sponges. As a putative key intermediate, the natural product Nalpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine (1) from the sponge Agelas wiedenmayeri was synthesized in the solid phase starting from Fmoc/Pmc-protected L-homoarginine and in solution starting from readily available L-lysine methyl ester.

Alkaloids↗
PubMed1999

Computer-assisted constitutional assignment of large molecules: COCON analysis of ascomycin.

[structure: see text] The computer-assisted constitutional assignment of ascomycin (1) is discussed. This example demonstrates that the NMR-based structure generator COCON is able to analyze data sets of organic molecules covering the full known range in size and complexity. The structural proposals of ascomycin were validated by calculating the 13C NMR chemical shifts using the computer program SpecEdit. The enhanced calculation time of COCON achieved by preorganizing the input data is also demonstrated for the data sets of aflatoxin B1 (2), 11-hydroxyrotenone (3), and haemoventosin (4).

Aflatoxin B1↗
PubMed1999

Arsenic speciation in human urine reference materials using high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection.

Six arsenic compounds including arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid were separated by high-performance liquid chromatography (HPLC) on a Hamilton PRP-X100 anion-exchange column using isocratic elution and detected by inductively coupled plasma mass spectrometry (ICP-MS). This analytical procedure was applied to the speciation of arsenic compounds in human urine. The influence of urine matrix on the separation of arsenic compounds was evaluated and the determination of arsenic compounds was not hampered by the ArCl interference which has often been encountered in ICP-MS. Three human urine reference materials, SRM 2670 normal level, SRM 2670 elevated level and Lyphocheck urine metal control 1, were analyzed with respect to arsenic compounds by HPLC-ICP-MS. The results were found to be in good agreement with the certified total arsenic concentration in the reference materials. Six arsenic compounds were detected. Arsenobetaine was found to be present in all of the investigated human urine reference materials.

Arsenic↗
PubMed1999

Comparative investigations of airborne culturable microorganisms in selected waste treatment facilities and in neighbouring residential areas.

The evaluation of airborne microorganisms in waste treatment facilities is complicated by different measuring systems, a lack of measuring standards and large variations between individual counts. In the present study, different sectors of the waste management industry were compared by determining median values of airborne culturable microorganisms from numerous parallel counts over a prolonged time period. The samples were taken during the warm season using the six-stage Andersen volumetric sampler in a large composting plant and its immediate vicinity, in an agricultural composting plant, a waste disposal site, and a sorting facility for recyclable materials. Control samples were taken at a site not influenced by the waste management industry in an open and largely uninhabited area. The highest median values for culturable bacteria (37 degrees C) found were 1.1 x 10(5) CFU/m3, for moulds (25 degrees C) 1.4 x 10(5) CFU/m3, and for A. fumigatus (37 degrees C) 1.7 x 10(4) CFU/m3 in the sorting cabins of the sorting facility (p < 0.001). The highest median values for thermophilic bacteria (actinomycetes and bacillaceae, 50 degrees C) were 7.3 x 10(3) CFU/m3 in the large composting facility. In all other facilities as well as in the neighbouring residential areas of all facilities investigated, all median values were significantly lower and corresponded to the naturally occurring levels: approx. 10(2) CFU/m3 for bacteria, approx. 10(3) CFU/m3 for moulds and approx. 10(1) CFU/m3 for A. fumigatus and thermophilic bacteria. Only in the neighbouring residential area of the large composting plant, the median values for thermophilic bacteria were approx. 10(2) CFU/m3, but an additional impact from farms cannot be excluded in this case. These results show permanent increased loads of the investigated microorganisms inside large composting facilities and especially in the sorting cabins for recyclable materials. The increasing number of reports on potential health hazards in these areas require adequate measures on the part of occupational medicine in order to limit the health risk to a minimum. The most important task is the automatization of the sorting process for recyclable materials.

Air Microbiology↗
PubMed1998

The peptide HDEF as a new retention signal is necessary and sufficient to direct proteins to the endoplasmic reticulum.

The key feature of tomato RNase LX localised solely outside the vacuole is the C-terminal peptide HDEF which is very similar to known endoplasmic reticulum (ER) retention signals. For functional testing of the ER-targeting ability of HDEF, different constructs including the complete RNase LX, two truncated forms without HDEF and the truncated chitinase FB7-1deltaVTP C-terminally flanked by HDEF, were expressed in Saccharomyces cerevisiae. The majority of RNase and chitinase, both containing HDEF, accumulates within the ER. However, the truncated constructs without the peptide are released into the medium. We provide compelling evidence that peptide HDEF at the C-terminus of secretory plant proteins is a new ER retention signal in yeast and most likely in plants.

Amino Acid Sequence↗
PubMed1998

Air-borne microorganisms in the metropolitan area of Graz, Austria.

Urban and rural regions are affected by different microorganism loads depending on their structure and utilization. At 7 sampling sites in the metropolitan area of Graz, counts of airborne bacteria as well as yeasts and molds were conducted over a one-year period at two-week intervals. Bacteria and yeasts/molds counts in a village area to the South of Graz dominated by agriculture exceeded the corresponding counts in a suburban residential area fourfold (327 CFU/m3 air-bacteria) and twofold (185 CFU/m3 air-yeasts/molds) respectively. In the vicinity of a composting facility located in the same residential area, microorganism counts exceeded those of the neighboring "unaffected" area by 29% in the case of bacteria and by 54% in the case of yeasts/molds. At an industrial and business site with heavy traffic, the counts are twice that of the area affected by the composting facility (146 CFU/m3 for bacteria and 168 CFU/m3 for yeasts/molds). The proportion of Aspergillus fumigatus is highest in the village area with 23%, compared to 10% in the open land. 49% of the bacteria and 54% of the yeasts and molds can be shown on stages 4-6 of the Andersen-Volumetric-Sampler registering the respirable particle sizes.

Air Microbiology↗
PubMed1998

The interaction of particulate matter and gaseous automobile exhaust in the city of Graz, Austria.

Aerosol particles collected at urban locations contain a significant portion of automobile exhaust emissions, especially lead and zinc. The most important emitted gases, carbon monoxide (CO), hydrocarbons (HC), and the nitrogen oxides (NOx) play an important role in the formation of photochemical smog in urban areas. Nitrate formation through heterogeneous reactions on dust particles may provide a removal mechanism for the nitrogen oxides in the atmosphere. As a consequence dust can reduce ozone formation rates by up to 25%. At 47 sites within the city of Graz, Austria dust particles were collected. Two hundred particles with a diameter of about 1 microns were analyzed with a Laser Microprobe Mass Analyzer (LAMMA) for each sampling point: one half for laser generated cations and the other half for anions. The frequencies of occurrence of elements in 100 particles were used as a measure for the air quality. Isolines (lines of equal element frequencies) were employed to outline polluted regions and identify the sources of dust particles. A summation method was used to monitor nitrogen oxides. Particulate nitrate correlates well with lead frequencies in aerosols as well as with NOx levels. This indicates that the NOx emitted by traffic exhaust is at least partially deposited on particulate matter.

Aerosols↗
PubMed1998

Air pollution by particulate matter in the industrialized city of Leoben, Austria.

At seven sites in Leoben, Austria, aerosol particles were sampled in two size fractions by a dichotomous sampler using virtual impaction: the fine fraction (alveolar aerosol) with an aerodynamic diameter dac < 2.5 microns (PM2.5), and the coarse fraction (tracheobronchial aerosol) with an dac between 2.5 and 10 microns. It is believed that these particles are able to reach the lower regions of the human respiratory tract, and thus be responsible for most of the adverse health effects associated with suspended particulate pollution. A second sampling procedure was made collecting the PM2.5 fraction and after leaching with nitric acid, lead, zinc, cadmium, copper, chromium and vanadium were determined with an inductively coupled plasma mass spectrometer (ICP-MS). For one sample point a third sampling was carried out and both fractions were subsequently leached with water and dilute hydrochloric acid. Pb, Zn, Mn, Fe, Cd, Ni, Cu, Rb, Sr, Mo, Cs, Ba and Tl were determined by ICP-MS.

Air Pollution↗
PubMed1997

The base specificities of tomato ribonuclease (RNase LE) and its Asp44 mutant enzyme expressed from yeast cells.

RNase LE from cultured tomato cells is a member of the RNase T2 family. It is, however, distinguishable from RNase Rh from Rhizopus niveus, a typical RNase of the RNase T2 family, by its CD spectrum in the 200-250 nm region. In order to reinvestigate the base specificity of RNase LE and to study the role of Asn44 in RNase LE, which is considered to correspond to the base recognition site Asp51 of RNase Rh, RNase LE, and its Asp mutant at the 44th position were expressed from yeast cells with the same expression system as RNase Rh [K. Ohgi, et al., J. Biochem., 109, 776-785 (1991)]. RNase LE with four extra amino acid residues at the 2nd amino acid residue of mature RNase LE and its Asp44 mutant were secreted from yeast cells to give a yield of 10 mg/liter and 0.5 mg/liter culture broth, respectively. The expressed RNase LE (RNase RNAP LE) had the same characteristics as native RNase LE in the CD spectrum and specific activity. This is the first example of the expression of plant RNase from microbes and in sufficient amount to perform further enzymological research. The base specificity of RNase LE was guanylic acid preferential and that of N44D was changed to a more adenylic acid preference as compared to that of RNase LE. These experiments showed that Asn44 of RNase LE is crucial for base recognition as the case of Asp51 in RNASE Rh, and also suggested that the base recognition mechanism of RNase LE is very similar to that of RNase Rh.

Amino Acid Sequence↗