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Biomedical subjects

B Markert

Publications and source records attributed to B Markert.

15 recordsLinked to original sources
PubMed2002

Heavy metals in emergent trees and pioneers from tropical forest with special reference to forest fires and local pollution sources in Sarawak, Malaysia.

Leaf samples of tropical trees, i.e. Dryobalanops lanceolata (Kapur paji), Dipterocarpaceae and Macaranga spp. (Mahang), Euphorbiaceae were analyzed for 21 chemical elements. The pioneer Macaranga spp. exhibited higher concentrations for the majority of elements compared to the emergent species of Dryobalanops lanceolata, which was attributed to the higher physiological activity of the fast growing pioneer species compared to emergent trees. Lead showed rather high concentrations in several samples from the Bakam re-forestation site. This is suggested to be caused by emissions through brick manufacturing and related activities in the vicinity. A comparison of Dryobalanops lanceolata samples collected in 1993, 1995 and 1997 in the Lambir Hills National Park revealed that certain heavy metals, i.e. Co, Cu, Mn, Ni, Pb and Ti showed higher values in 1997 compared to the previous years, which could indicate an atmospheric input from the haze caused by the extensive forest fires raging in Borneo and other parts of Southeast Asia.

Ecosystem↗
PubMed2001

Distribution of lanthanoids, Be, Bi, Ga, Te, Tl, Th and U on the territory of Bulgaria using Populus nigra 'Italica' as an indicator.

The concentrations of lanthanoids, Be, Bi,Ga, Te, Tl, Th and U have been determined using ICP-MS for 100 standardized samples of poplar leaves collected from the territory of Bulgaria. The investigated elements are log-normally distributed on the territory. Using cluster analysis of the analytical data the samples were grouped according soil type on which the plants are growing.

Bulgaria↗
PubMed2001

Effects of endocrine disruptors on prosobranch snails (Mollusca: Gastropoda) in the laboratory. Part III: Cyproterone acetate and vinclozolin as antiandrogens.

The effects of suspected endocrine disrupting chemicals on freshwater and marine prosobranch species were analysed in laboratory experiments. In this last of three publications, the responses of the fresh water snail Marisa cornuarietis and of two marine prosobranchs (Nucella lapillus, Nassarius (Hinia) reticulatus) to the antiandrogenic model compounds cyproterone acetate (CPA) and vinclozolin (VZ) are presented. The snails were exposed to nominal CPA concentrations of 1.25 mg/L alone and simultaneously to a potent synthetic estrogen (ethinylestradiol), androgen (methyltestosterone) or an indirectly acting xeno-androgen (tributyltin) in experiments with adult specimens and in a life cycle test for 12 months. Marisa and Nucella were furthermore exposed to nominal concentrations of 0.03-1.0 microgram VZ/L for up to 5 months. The antiandrogens induced a number of biological responses in all three species. The length of the penis and of accessory male sex organs (e.g., penis sheath, prostate) were significantly reduced. For Marisa, this effect occurred only in sexually immature specimens and was reversible as the males attained puberty. Typical androgen-mediated responses (imposex development, delayed spermatogenesis, tubulus necrosis of the testis with orchitis and Leydig cell hyperplasia) were partially or totally suppressed by a simultaneous administration of CPA. In the two marine species even adult, sexually mature males responded to antiandrogens with a reduction of the male sex organs and an advancement of the sexual repose phase. The results for CPA and VZ are compared with the effects of an exposure to xeno-estrogens (bisphenol A, octylphenol) and xeno-androgens (triphenyltin, tributyltin) in the same species. Each group of endocrine disruptors induces a characteristic set of toxicological effects in prosobranch snails which can be used as endpoints in an organismic invertebrate test for the identification of endocrine mimetic test compounds. Estrogens cause primarily an induction of superfemales resulting in an increased female mortality by the enhancement of spawning mass and egg production. The main effects of androgens are a virilization of females by imposex development and a marked decrease of the fecundity. Compared with estrogens and androgens, the antiandrogen responses seem to be less drastic and might have--in contrast to the two other disruptor classes--no biologically significant effects at the population level.

Androgen Antagonists↗
PubMed2001

A linear viscoelastic biphasic model for soft tissues based on the Theory of Porous Media.

Based on the Theory of Porous Media (mixture theories extended by the concept of volume fractions), a model describing the mechanical behavior of hydrated soft tissues such as articular cartilage is presented. As usual, the tissue will be modeled as a materially incompressible binary medium of one linear viscoelastic porous solid skeleton saturated by a single viscous pore-fluid. The contribution of this paper is to combine a descriptive representation of the linear viscoelasticity law for the organic solid matrix with an efficient numerical treatment of the strongly coupled solid-fluid problem. Furthermore, deformation-dependent permeability effects are considered. Within the finite element method (FEM), the weak forms of the governing model equations are set up in a system of differential algebraic equations (DAE) in time. Thus, appropriate embedded error-controlled time integration methods can be applied that allow for a reliable and efficient numerical treatment of complex initial boundary-value problems. The applicability and the efficiency of the presented model are demonstrated within canonical, numerical examples, which reveal the influence of the intrinsic dissipation on the general behavior of hydrated soft tissues, exemplarily on articular cartilage.

Animals↗
PubMed2000

The Biological System of the Elements (BSE). Part II: a theoretical model for establishing the essentiality of chemical elements. The application of stoichiometric network analysis to the biological system of the elements

Stoichiometric Network Analysis (SNA), originally developed by the Canadian chemist Bruce L. Clarke during the 1970s, provides a most efficient means of reducing the background topology of complex interaction networks to some skeleton topology around which systems dynamics can be understood without jeopardising insight into complex dynamics by over- or miss-simplification. Since it focuses on the corresponding autocatalytic (AC) features of a feedback system as those which control overall behaviour to some extent, SNA deals with reaction kinetics in and beyond chemistry, e.g. with nuclear reactions. It is therefore quite straightforward to apply this manner of simplification, which in turn is supported by a number of mathematical theorems on systems behaviour and properties of AC cycles, to biological systems although their 'full' complexity may not even be assessed in the yet rare cases of complete genetic sequencing. Assuming there is a relationship between the kinds of metal or metalloid species and key biological/biochemical transformations to be promoted with their aid--this relationship being the subject of bio-inorganic chemistry--and that biochemistry is, in effect, about systems which can reproduce and thus behave autocatalytically, one can expect SNA to yield formally sound statements on basic features of biology and biochemistry too. If we sum up the facts and considerations concerning essentiality or possible essentiality in a biological system of elements (Markert, 1994), this means joining the triangular representation of BSE, including statements on (the degree of biological) evolution and aggregation levels, to SNA treatment of autocatalysis within hierarchical systems from metalloenzymes to entire biocoenoses. Arguments using preferred cluster sizes and aggregation tendencies from coordination chemistry are then employed to circumscribe possible functions within the BSE. They are also extended to metals hitherto not known to be essential, such as tellurium or scandium.

Journal Article↗
PubMed2000

Deposition and disease: a moss monitoring project as an approach to ascertaining potential connections.

In the years 1995 and 1996 the atmospheric deposition of elements in the EuroRegion Neisse (ERN) was determined in a biomonitoring project using mosses. The mosses Pleurozium schreberi and Polytrichum formosum were chosen as biomonitors because of their wide distribution in the area studied. The moss samples were analysed by ICP-MS and ICP-OES for their concentrations of 37 chemical elements. The results were shown in the form of maps. The data from the moss monitoring project served as a basis for determining those elements in the deposited material that promote the occurrence of disease. This was done by correlating the figures for the various diseases with the appropriate element concentrations in the mosses. Indications were found that a connection exists between the thallium content of mosses and the occurrence of cardiovascular disease and between Ce, Fe, Ga and Ge levels in the mosses and the incidence of diseases of the respiratory system.

Adolescent↗
PubMed2000

Analysis of phytochelatins in plant matrices by pre-column derivatization, high-performance liquid chromatography and fluorescence-detection.

A sensitive method for the determination of phytochelatins in plant matrices by pre-column derivatization with monobromobimane (mBrB) and high-performance liquid chromatography (HPLC) on reversed phases and fluorescence-detection has been developed and applied to cucumber sprouts (Cucumis sativus) treated with cadmium and to the water moss Fontinalis antipyretica (Cd in environmentally-relevant concentrations). Whereas phytochelatins were found in the Cd-treated sprouts, no phytochelatins were detected in Fontinalis anitipyretica.

Bryopsida↗
PubMed2000

Effects of endocrine disruptors on prosobranch snails (Mollusca: Gastropoda) in the laboratory. Part II: Triphenyltin as a xeno-androgen.

In laboratory experiments the effects of suspected endocrine disrupting chemicals on freshwater and marine prosobranch species were analysed. In this second of three publications the responses of the freshwater ramshorn snail Marisa cornuarietis and of two marine prosobranchs (the dogwhelk Nucella lapillus and the netted whelk Hinia reticulata) to the xeno-androgenic model compound triphenyltin (TPT) are presented. Marisa and Nucella were exposed via water (nominal concentrations 5-500 ng TPT-Sn/L) and Hinia via sediments (nominal concentrations 50-500 micrograms TPT-Sn/kg dry wt.) for up to 4 months. Female ramshorn snails but not the two marine species developed imposex in a time and concentration dependent manner (EC10 4 months: 12.3 ng TPT-Sn/L) with a comparable intensity as described for tributyltin. TPT reduced furthermore the fecundity of Marisa at lower concentrations (EC10 4 months: 5.59 ng TPT-Sn/L) with a complete inhibition of spawning at nominal concentrations > or = 250 ng TPT-Sn/L (mean measured +/- SD: > or = 163 +/- 97.0 ng TPT-Sn/L). The extension of the pallial sex organs (penis with accessory structures and prostate gland) of male ramshorn snails and dogwhelks were reduced by up to 25% compared to the control but not in netted whelks. Histopathological analyses for M. cornuarietis and H. reticulata provide evidence for a marked impairment of spermatogenesis (both species) and oogenesis (only netted whelks). The test compound induced a highly significant and concentration independent increase in the incidence of hyperplasia on gills, osphradia and other organs in the mantle cavity of N. lapillus indicating a carcinogenic potential of TPT. The results show that prosobranchs are sensitive to endocrine disruption at environmentally relevant concentrations of TPT. Also, M. cornuarietis is a promising candidate for a future organismic invertebrate system to identify endocrine-mimetic test compounds.

Androgens↗
PubMed2000

Effects of endocrine disruptors on prosobranch snails (Mollusca: Gastropoda) in the laboratory. Part I: Bisphenol A and octylphenol as xeno-estrogens.

The effects of suspected endocrine disrupting chemicals on freshwater and marine prosobranch species were analysed in laboratory experiments. In this first publication, the responses of the freshwater snail Marisa cornuarietis and of the marine prosobranch Nucella lapillus to the xeno-estrogenic model compounds bisphenol A (BPA) and octylphenol (OP) are presented at nominal concentration ranges between 1 and 100 micrograms/L. Marisa was exposed during 5 months using adult specimens and in a complete life-cycle test for 12 months. In both experiments, the xeno-estrogens induced a complex syndrome of alterations in female Marisa referred to as "superfemales" at the lowest concentrations. Affected specimens were characterised by the formation of additional female organs, an enlargement of the accessory pallial sex glands, gross malformations of the pallial oviduct section resulting in an increased female mortality, and a massive stimulation of oocyte and spawning mass production. The effects of BPA and OP were comparable at the same nominal concentrations. An exposure to OP resulted in inverted U-type concentration response relationships for egg and spawning mass production. Adult Nucella from the field were tested for three months in the laboratory. As in Marisa, superfemales with enlarged accessory pallial sex glands and an enhancement of oocyte production were observed. No oviduct malformations were found probably due to species differences in the gross anatomical structure of the pallial oviduct. A lower percentage of exposed specimens had ripe sperm stored in their vesicula seminalis and additionally male Nucella exhibited a reduced length of penis and prostate gland when compared to the control. Because statistically significant effects were observed at the lowest nominal test concentrations (1 microgram BPA or OP/L), it can be assumed that even lower concentrations may have a negative impact on the snails. The results show that prosobranchs are sensitive to endocrine disruption at environmentally relevant concentrations and that especially M. cornuarietis is a promising candidate for a future organismic invertebrate model to identify endocrine-mimetic test compounds.

Animals↗
PubMed1996

The German heavy metal survey by means of mosses.

This is the first attempt to determine pollution with metals throughout the Federal Republic of Germany by analysing moss samples. Samples of Pleurozium schreberi, Scleropodium purum, Hypnum cupessiforme and Hylocomium splendens were collected at 593 sites and analysed by ICP-AES and AAS for the elements As, Cd, Cr, Cu, Fe, Ni, Pb, V and Zn. Citrus leaves and pine needles were used as reference materials to ensure the quality of the results. In many cases it was possible to trace the areas affected by known sources of heavy-metal emissions in addition to isolated local increases in the values. The moss monitoring programme showed up the highly industrialized and urban locations such as the Ruhr, parts of the Saarland and Baden-Wurttemberg and large areas of eastern Germany. Lower levels of many elements were found in wide stretches of Lower Saxony and Bavaria. The results largely reflect the pollution patterns found in these areas. On the other hand, expected correlations between the effects of traffic (e.g. Pb) and concentrations in moss could not be demonstrated with certainty. The element data yielded by this project are Germany's contribution to the European project 'Atmospheric Heavy Metal Deposition in Europe -- Estimations based on Moss Analysis'.

Air Pollutants↗
PubMed1996

Tributyltin biomonitoring using prosobranchs as sentinel organisms.

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produce a variety of pathological reactions in animals. A reliable biomonitoring method to assess the degree of environmental TBT pollution has been described based on investigations of virilization phenomena in prosobranch snails (Mollusca: Gastropoda). Examples are the imposex phenomenon in marine and freshwater species, the intersex reaction in littorinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. The degree of imposex or intersex in populations is determined by different biomonitoring indices which allow to assess the TBT pollution of the environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Ireland indicating that there is still a continuing threat to sensitive marine organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena seem due to an inhibition of the cytochrome P-450 dependent aromatase by this organotin compound.

Journal Article↗
PubMed1989

Use of Polytrichum formosum (moss) as a passive biomonitor for heavy metal pollution (cadmium, copper, lead and zinc).

After sampling over regular intervals from 1985 to 1987 the heavy metals Cd, Cu, Pb and Zn were quantitatively determined by atomic emission spectrometry/inductively coupled plasma in above-ground parts of the moss Polytrichum formosum (Hedw.). All metals present a typical summer-winter oscillation (seasonal variation), which is much greater than the "inter-stand" variation of Polytrichum formosum within the forest ecosystem under investigation. To obtain comparable results on a regional or global scale it is suggested to collect all samples of Polytrichum formosum for biomonitoring purposes in the last week of September.

Cadmium↗
PubMed1989

Normalization and calculation of lanthanide element concentrations in environmental samples.

A mathematical model for the prediction of lanthanide element concentrations in soil and plant samples is presented. A comparison between predicted and measured lanthanide values in soil and plant samples show, that the model produces good results for the elements in the soil samples and for most elements in plant material. The accuracy of prediction worsens with decreasing concentration of the heavier lanthanide elements. The mathematical model presented is not valid on other environmental samples like aerosols, because no data for these matrices are available yet to calibrate our normalized curves.

Mathematics↗
PubMed1980

Health effects of traffic noise.

In 57 test persons having worked 1 day under traffic noise (Leq = 85 dB(A) and 1 day without noise (Leq < 50 dB(A), blood pressure and pulse frequency were measured at 1 h intervals and total urine was collected during working hours. Additionally, blood was sampled at the end of each working day. Psychological parameters were assessed by means of questionnaires. Statistically significant reactions to noise were found in the following fields: 1. Ergnomics--decrease of working quality; 2. Psychology--increase of psychical tension; 3. Blood circulation--increase of blood pressure and pulse frequency; 4. Biochemistry--increase of epinephrine, cAMP, urine and serum Mg, protein, cholesterol plus decrease of erythrocyte Na, and renin. Hypothetical mechanisms of the action of traffic noise are discussed.

Adolescent↗