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Biomedical subjects

H Hummel

Publications and source records attributed to H Hummel.

At least 19 recordsLinked to original sources
PubMed2001

Distribution of dissolved and labile particulate trace metals in the overlying bottom water in the Vistula River plume (southern Baltic Sea).

Overlying bottom water samples were collected in the Vistula River plume, southern Baltic Sea, (Poland) and analysed for dissolved and labile particulate (1 M HCl extractable) Cu, Pb, Zn, Mn, Fe and Ni, hydrological parameters being measured simultaneously. Particulate organic matter (POM), chlorophyll a and dissolved oxygen are key factors governing the chemical behaviour of the measured metal fractions. For the dissolved Cu, Pb, Zn, Fe and Ni two maxima, in the shallow and in the deeper part of the river plume, were found. In the shallow zone desorption from seaward fluxing metal-rich riverine particles account for markedly increased metal concentrations, as confirmed also by high particulate metal contents. For Pb, atmospheric inputs were also considered to have contributed to the elevated concentrations of dissolved Pb adjacent to the river mouth. In the deep zone desorption from detrital and/or resuspended particles by aerobic decomposition of organic material may be the main mechanism responsible for enrichment of particle-reactive metals (Cu, Pb, Zn) in the overyling bottom waters. The increased concentrations of dissolved Fe may have been due to reductive dissolution of Fe oxyhydroxides within the deep sediments by which dissolved Ni was released to the water. The distribution of Mn was related to dissolved oxygen concentrations, indicating that Mn is released to the water column under oxygen reduced conditions. However, Mn transfer to the dissolved phase from anoxic sediments in deeper part of the Vistula plume was hardly evidenced suggesting that benthic flux of Mn occurs under more severe reductive regime than is consistent with mobilization of Fe. Behaviour of Mn in a shallower part has been presumably affected by release from porewaters and by oxidization into less soluble species resulting in seasonal removal of this metal (e.g. in April) from the dissolved phase. The particulate fractions represented from about 6% (Ni) and 33% (Mn, Zn, Cu) to 80% (Fe) and 89% (Pb) of the total (labile particulate plus dissolved) concentrations. The affinity of the metals for particulate matter decreased in the following order: Pb > Fe > Zn > or = > Cu > Mn > Ni. Significant relationships between particulate Pb-Zn-Cu reflected the affinity of these metals for organic matter, and the significant relationship between Ni-Fe reflected the adsorption of Ni onto Fe-Mn oxyhydroxides. A comparison of metal concentrations with data from other similar areas revealed that the river plume is somewhat contaminated with Cu, Pb and Zn which is in agreement with previous findings on anthropogenic origin of these metals in the Polish zone of southern Baltic Sea.

Adsorption↗
PubMed2000

The respiratory performance and survival of the bivalve Macoma balthica (L.) at the southern limit of its distribution area: a translocation experiment.

The hypothesis was tested that animals near their extreme Southern limits, due to high temperatures, have a high respiration rate, whereby they reach an extreme low weight-index and ultimately disappear. At estuarine stations the respiration rate of Macoma balthica (L.) (Baltic clam) did not show interseasonal changes, indicating seasonal acclimation, but within the season the respiration increased with increasing temperature, indicating the absence of short-term acclimation. In clams translocated from the Netherlands towards the Bidasoa estuary, 200 km South of their Southern distribution limit, their respiration rate was higher and weight-index lower than in specimens living in Dutch estuaries. Irrespective of an effect of the temperature, clams exposed in experiments to water from Bidasoa showed a higher respiration than clams exposed to water from the other stations. Moreover, at non-estuarine stations with a low food content, the clams showed reversed acclimation, i.e., the respiration rates in winter were much lower than summer rates, most probably a strategy to conserve energy by means of a depressed metabolism. A weight index of 5 mg DW/cm(3) and glycogen content of 2% DW are suggested as the minimal values below which the metabolic energy balance of Baltic clams becomes more negative and the clam population disappears. It was concluded that factors other than temperature influenced the respiration and weight-index of clams, and hence their presence or absence, e.g., food concentration, innate seasonal cycles, and possible pollutants in the water.

Journal Article↗
PubMed1998

Metallothioneins in Arctic bivalves.

In the framework of an International Association for the Promotion of Cooperation with Scientists from the Independent States of the Former Soviet Union (INTAS) Project on biodiversity and adaptation strategies of Arctic coastal marine benthos, research was focused on the role of metallothioneins as a possible indicator of the effect on animals and availability of trace metals in the Arctic. Metallothioneins are low-molecular-weight, cysteine-rich proteins known to be induced by high environmental levels of trace metals. Specimens of Macoma balthica and Mytilus edulis were collected along several Arctic estuaries in the White and Pechora seas; whole tissues for M. balthica and the digestive gland and gills for M. edulis were dissected, frozen in liquid nitrogen, and lyophilized onboard. Metallothionein concentrations were determined by a polarographic assay. From the same stations organisms and sediments were also collected for metal analysis. The results revealed significant differences in metallothionein concentrations among the stations for M. balthica. Similar, although less marked, differences were also obtained in the organs of M. edulis. Data on metallothionein were compared with trace metal concentrations in both the organisms and sediments. Also, the relationship with abiotic factors (salinity) and biological variables (size of sampled organisms) was determined. In particular, biological variables seemed to influence metallothionein concentration in the organisms and their effect should be carefully considered for a correct assessment of differences between stations.

Animals↗
PubMed1998

Trace metals and variations of antioxidant enzymes in Arctic bivalve populations.

In the framework of an INTAS project, arctic populations of the clam Macoma balthica were collected from seven stations (Mezen, Khaypudyr, Pechora 3, Pechora 5, Dvina, Keret 1, and Keret 2) in the White Sea and Pechora Sea. The main objectives of this research were to define baseline concentrations of trace metals (As, Cd, Cr, Cu, Fe, Mn, Pb, Zn) in M. balthica and to evaluate antioxidant responses as biomarkers of anthropogenic stress in these organisms. The antioxidant parameters examined included the levels of glutathione and the activities of several glutathione-dependent and antioxidant enzymes: glyoxalase I and glyoxalase II (EC 4.4.1.5 and EC 3.1.2.6), glutathione S-transferases (EC 2.5.1.18), glutathione reductase (EC 1.6.4.2), glutathione peroxidases (EC1.11.1.9 and EC 2.5.1.18, respectively, for Se-dependent and Se-independent forms), superoxide dismutase (SOD, EC 1.15.1.1), and catalase (EC 1.11.1.6). Organisms revealed enhanced concentrations of lead in both Keret stations, Khaypudyr, and Mezen, and high levels of copper in Keret and cadmium in Khaypudyr. At the biochemical level, organisms from Pechora 3, Pechora 5, and Dvina were not statistically different, whereas those from Mezen and Khaypudyr exhibited higher activities of superoxide dismutase, glutathione peroxidase, and glyoxalase II. Catalase levels were lower in Mezen and Khaypudyr. More heterogeneous were the responses of glyoxalase I and glutathione S-transferases, while no significant differences among the stations were observed for glutathione reductase. Multiple regression analyses revealed significant positive relationships between the main antioxidant enzymes (glutathione peroxidases, superoxide dismutase, glyoxalase I, and glyoxalase II), and confirmed the exception of catalase, which, when significant, was negatively correlated with the other parameters. The results support the suitability of antioxidant responses as biomarkers of pollutant exposure and/or toxicity for arctic biomonitoring programs even though only moderately polluted sites were sampled.

Alkyl and Aryl Transferases↗
PubMed1996

[Osteomyelitis from Cryptococcus neoformans].

A forty-three-year old patient suspected of having a bone tumor in his left femur, was submitted to the hospital. However, osteomyelitis caused by Cryptococcus neoformans has been demonstrated by culture. The history of the patient revealed a long-term therapy with corticosteroids due to sarcoidosis. The osteomyelitis was treated with fluconazole (200 mg daily p.o.) for three months. Under this therapy the infection resolved.

Adrenal Cortex Hormones↗
PubMed1987

23S ribosomal RNA mutations in halobacteria conferring resistance to the anti-80S ribosome targeted antibiotic anisomycin.

Halobacterium (H.) halobium and H. cutirubrum mutants resistant to the anti-80S ribosome targeted inhibitor anisomycin were isolated. Three classes of mutants were obtained: Class I displayed a minimal inhibitory concentration (MIC) to anisomycin of 10 micrograms/ml, class II of 25 micrograms/ml and class III of at least 400 micrograms/ml. In vitro polyphenylalanine synthesis assays demonstrated that in those cases tested resistance was a property of the large ribosomal subunit. By primer extension analysis, each mutation class could be correlated with a distinct base change within the peptidyltransferase loop of 235 rRNA. In class I A2472 was changed to C, in class II G2466 was changed to C and in the high-level resistant class III C2471 was replaced by U. A. double mutant - obtained by selection of a class I mutant for high-level anisomycin resistance - acquired the C2471 to U replacement of class III in addition to the class I mutation. The results provide information on the action of a eukaryotic protein synthesis inhibitor on archaebacterial ribosomes and demonstrate the suitability of organisms with a single rRNA transcriptional unit on the chromosome for direct selection of mutations in ribosomal RNA.

Anisomycin↗
PubMed1987

Thiostrepton resistance mutations in the gene for 23S ribosomal RNA of halobacteria.

Mutants of Halobacterium (H.) halobium and H. cutirubrum were isolated which are resistant to the 70S ribosome inhibitor thiostrepton. Using primer extension analysis, resistance was shown to correlate with base changes at position 1159, which corresponds to position 1067 of the E. coli 23S rRNA. In four mutants, A1159 was replaced by U, in one mutant by G. The results show that not only methylation (Cundliffe & Thompson (1979) Nature 278, 859-861) of A1067 (E. coli nomenclature), but also base changes at this position cause high-level resistance to thiostrepton.

Anti-Bacterial Agents↗
PubMed1986

Transcription signals for stable RNA genes in Methanococcus.

A previous survey of upstream sequences of tRNA genes from the archaebacterium Methanococcus vannielii has revealed that there are two boxes of sequence homology: A box "A" of about 20 conserved nucleotides at a distance of 30 to 49 basepairs upstream from the gene and a box "B" 18 to 19 nucleotides downstream from box "A" (Wich, G., Sibold, L., and Böck, A. (1985) System. Appl. Microbiol. (in press). Nuclease S1 mapping experiments were carried out with two of these tRNA transcriptional units and with a ribosomal RNA operon, to determine whether these consensus sequences have a function in the initiation of transcription. Use was made of the fact that cells from Methanococcus accumulate primary transcript and processing intermediates of ribosomal RNA under conditions of protein synthesis inhibition. The following results were obtained: (i) Transcription in all three systems starts at the G within the conserved trinucleotide TGC of box "B". Since the box "B" motif, 5'TGCaagT3', also occurs at the site of transcription initiation of protein encoding genes, both in methanogenic and halophilic organisms, it appears to constitute a frequently used transcription start signal within these archaebacterial groups. (ii) The box "A" motif occurs with constant spacing, relative to box "B", in all 10 tRNA and ribosomal RNA transcriptional units investigated from Methanococcus. Since it is not present in the leader region of genes coding for proteins, it seems to function as a specific element which is required for the expression of genes for stable RNA. (iii) Termination of transcription of the ribosomal RNA operon from Methanococcus occurs at a distinct T within an oligo-T stretch immediately downstream from the 3'-terminal 5S RNA gene. This signal occurs in all 3'-flanking regions of transcriptional units for stable RNA from the Methanococcus strains studied. Termination signals for stable RNA genes in Methanococcus appear to be similar with those of stable RNA genes in eukaryotes. (iv) By nuclease S1 mapping a recognition site was identified for a processing enzyme involved in the maturation of preribosomal RNA.

Chromosome Mapping↗
PubMed1986

Unique antibiotic sensitivity of archaebacterial polypeptide elongation factors.

The antibiotic sensitivity of the archaebacterial factors catalyzing the binding of aminoacyl-tRNA to ribosomes (elongation factor Tu [EF-Tu] for eubacteria and elongation factor 1 [EF1] for eucaryotes) and the translocation of peptidyl-tRNA (elongation factor G [EF-G] for eubacteria and elongation factor 2 [EF2] for eucaryotes) was investigated by using two EF-Tu and EF1 [EF-Tu(EF1)]-targeted drugs, kirromycin and pulvomycin, and the EF-G and EF2 [EF-G(EF2)]-targeted drug fusidic acid. The interaction of the inhibitors with the target factors was monitored by using polyphenylalanine-synthesizing cell-free systems. A survey of methanogenic, halophilic, and sulfur-dependent archaebacteria showed that elongation factors of organisms belonging to the methanogenic-halophilic and sulfur-dependent branches of the "third kingdom" exhibit different antibiotic sensitivity spectra. Namely, the methanobacterial-halobacterial EF-Tu(EF1)-equivalent protein was found to be sensitive to pulvomycin but insensitive to kirromycin, whereas the methanobacterial-halobacterial EF-G(EF2)-equivalent protein was found to be sensitive to fusidic acid. By contrast, sulfur-dependent thermophiles were unaffected by all three antibiotics, with two exceptions; Thermococcus celer, whose EF-Tu(EF1)-equivalent factor was blocked by pulvomycin, and Thermoproteus tenax, whose EF-G(EF2)-equivalent factor was sensitive to fusidic acid. On the whole, the results revealed a remarkable intralineage heterogeneity of elongation factors not encountered within each of the two reference (eubacterial and eucaryotic) kingdoms.

Aminoglycosides↗
PubMed1985

Studies of the GTPase domain of archaebacterial ribosomes.

Ribosomes from the methanogens Methanococcus vannielii and Methanobacterium formicicum catalyse uncoupled hydrolysis of GTP in the presence of factor EF-2 from rat liver (but not factor EF-G from Escherichia coli). In this assay, and in poly(U)-dependent protein synthesis, they were sensitive to thiostrepton. In contrast, ribosomes from Sulfolobus solfataricus did not respond to factor EF-2 (or factor EF-G) but possessed endogenous GTPase activity, which was also sensitive to thiostrepton. Ribosomes from the methanogens did not support (p)ppGpp production, but did appear to possess the equivalent of protein L11, which in E. coli is normally required for guanosine polyphosphate synthesis. Protein L11 from E. coli bound well to 23S rRNA from all three archaebacteria (as did thiostrepton) and oligonucleotides protected by the protein were sequenced and compared with rRNA sequences from other sources.

Anti-Bacterial Agents↗
PubMed1980

30S subunit mutations relieving restriction of ribosomal misreading caused by L6 mutations.

Mutants were analyzed biochemically and genetically in which restriction of translational misreading by ribosomes containing an altered L6 protein is relieved. Amongst 100 such strains eight possessed an altered S4 and two a mutant S5 protein. The protein-chemical type of L6 mutation seems to influence the kind of S4 mutant form selected. Also, only a few types of S4 ram mutations are obtained and they are different from those usually found amongst suppressors of streptomycin-dependent (SmD) strains. The S4 mutations selected are able to reduce the level of streptomycin-resistance of strA1 or strA40 strains and they confer extreme hypersensitivity to aminoglycosides when present alone. On the other hand, S4 mutations from SmD suppressor strains only weakly reverse L6 restriction. The results imply that control of translational fidelity is an intersubunit function and that protein L6 (an interface protein) cooperates with 30S proteins by directly or indirectly determining parameters involved in aminoacyl-tRNA recognition.

Aminoglycosides↗
PubMed1979

Analysis of lincomycin resistance mutations in Escherichia coli.

High level lincomycin resistant strains of Escherichia coli were isolated and screened for altered ribosomal proteins and functions. Amongst 58 strains investigated by electrophoresis one had an altered ribosomal protein S7, another one a mutated L14 and two showed altered L15 proteins. A correlation between these alterations and lincomycin resistant growth could not be demonstrated by genetic analysis for any of the mutants. In vitro, however, extracts from the two L15 mutants were less sensitive to inhibition by the drug. A gene locus (linR) responsible for the lincomycin resistance phenotype was mapped at min 30 of the Escherichia coli chromosome near tyrR; it seems to be identical to the previously described linB locus (Apirion, 1967); however, in contrast to these reports it does not seem to alter any ribosomal function.

Bacterial Proteins↗