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Biomedical subjects

H Bartel

Publications and source records attributed to H Bartel.

At least 19 recordsLinked to original sources
PubMed2004

Contribution of the colmation layer to the elimination of coliphages by slow sand filtration.

River bank or slow sand filtration is a major procedure for processing surface water to drinking water in central europe. In order to model the performance of river bank and slow sand filtration plants, we are studying the different mechanisms by which the elimination of pathogens is realized. An important question concerning the mode of action of slow sand filters and river bank filtration units is the role of the colmation layer or "schmutzdecke" on the elimination of human pathogens. The schmutzdecke is an organic layer which develops at the surface of the sand filter short after the onset of operation. We have inoculated a pilot plant for slow sand filtration with coliphages and determined their rate of breakthrough and their final elimination. In the first experiment, with a colmation layer still missing, the breakthrough of the coliphages in the 80 cm mighty sandy bed amounted to ca. 40 %. In contrast, less than 1 % of coliphages escaped from the filter as the same experiment was repeated two months later, when a substantial colmation layer had developed. Our preliminary conclusions are that the colmation layer is extremely efficient in eliminating of viruses.

Coliphages↗
PubMed2002

As(III) removal from groundwaters using fixed-bed upflow bioreactors.

The application of biological oxidation of iron and manganese, as a potential treatment method for the removal of arsenic from contaminated groundwaters, was examined in this paper. This method was based on the growth of certain species of indigenous bacteria, which are capable of oxidizing the soluble iron and manganese ions; the oxidized forms can be subsequently removed from the aqueous stream by over 97%, through their transformation to insoluble oxides and separation by a suitable filter medium. Arsenic was removed by around 80%, under certain conditions, which were found to be sufficient for Fe(II) removal (dissolved oxygen 2.7 mg/l, redox 280-290 mV, pH 7.2, U 8.25 m/h). The specific treatment technique presents several advantages towards conventional physicochemical treatment methods, such as enhanced coagulation or direct adsorption since: (a) it does not require the addition of other chemicals for oxidizing and removing As(III), (b) it does not require close monitoring of a breakthrough point, as in conventional column adsorption processes and (c) it could find application for the removal of, at least, three groundwater contaminants (Fe, Mn, As).

Adsorption↗
PubMed2001

Quantitative microvascular corrosion casting by 2D- and 3D-morphometry.

As a system of tubes (blood vessels) the cardiovascular system changes actively and passively diameters to adapt its transport capacities for respiratory gases, nutrients, heat, metabolites and waste products to and off the body's organs, tissues and cells. In most healthy organs blood vessels form a hierarchically arranged three-dimensional network with the geometry defined by vessel diameters, interbranching distances (defining branching frequencies and number of branching sites, i.e. nodes), intervascular distances, and branching angles. In the present study 2D- and 3D-morphometry is applied to quantify these parameters and their changes as they occur in resin casts during metamorphosis of the tadpole lung (2D-morphometry) and filter apparatus vasculature (3D-morphometry). It is shown that 2D-morphometry should be limited to the analysis of high powered images of flat two-dimensional vascular networks (example: tadpole lung alveolar vascular bed) to prevent underestimation of parameters. In contrast, 3D-morphometry can be applied over a wide range of magnifications whereby accuracy of measurements increases with the portion the structure to be measured occupies within the field of view. Together with a careful control of precasting conditions (application of vasoactive drugs, anaesthetics), casting conditions (pressure during rinsing and casting, amount of final shrinkage of casting media), and postcasting conditions (thermal burdening during maceration, sputtering, evaporation, and SEM inspection; thickness of conductive metal layers) 3D-morphometry enables to gain reliable data from resin casts of highly complex real vascular networks in healthy and diseased organs in the developing, juvenile, adult and aged state, as well as in different physiological states.

Aging↗
PubMed2000

Intussusceptive microvascular growth in the lung of larval Xenopus laevis Daudin: a light microscope, transmission electron microscope and SEM study of microvascular corrosion casts.

The remodeling of the uniform wide, plexus-like capillary bed of the lung of metamorphosing tadpoles of the South African clawed toad Xenopus laevis (Daudin) is studied from developmental stages 54 to 65 by scanning electron microscopy (SEM) of microvascular corrosion casts (VCCs), light microscopy (LM) and transmission electron microscopy (TEM). VCCs reveal that the remodeling of the existing uniform, plexus-like lung capillary bed into well-defined alveolar capillary meshworks starts in the caudal lung and then gradually proceeds cranially. Vascular remodeling is entirely by intussusceptive microvascular growth through insertion and enlargement of new and fusion of pre-existing capillary meshes. Analyses of lung tissue serial sections at the LM and TEM level confirm the presence of intracapillary cushions and tissue posts and correlate these structures in respect of size and location to the round to slit-like imprints and tiny "holes" found in VCCs. Additionally, SEM of VCCs give clear evidence that intussusceptive microvascular growth is also involved in the remodeling and maturation of alveolar arterioles and venules.

Animals↗
PubMed2000

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study.

Structural changes of the ventral velum of Xenopus laevis tadpoles from late prometamorphosis (stage 58) to the height of metamorphic climax (stage 62) were examined by light and transmission electron microscopy. Special emphasis was given to the blood vessel regression. Early changes of velar capillaries were formation of luminal and abluminal endothelial cell processes, vacuolation, and cytoplasmic and nuclear chromatin condensation. At the height of metamorphic climax, transmission electron microscopy revealed apoptotic endothelial cells with nuclear condensation and fragmentation, intraluminal bulging of rounded endothelial cells which narrowed or even plugged the capillary, and different stages of endothelial cell detachment ('shedding') into the vessel lumen. These changes explain the 'miniaturisation' of the velar microvascular bed as well as the typical features found in resin-casts of regressing velar vessels which have been observed in a previous scanning electron microscopy study of the ventral velum.

Animals↗
PubMed2000

Proliferative activity of gastric epithelial cells in Helicobacter pylori infected children.

Helicobacter pylori infection has been associated with gastric carcinogenesis. Gastric epithelial cells proliferative rate is accelerated in H. pylori infected adult patients. Our study was performed to evaluate proliferative cell activity in gastric epithelium in the course of H. pylori infection in the early stage of its natural history. Gastric antral biopsy specimens were obtained from thirteen H. pylori positive and seven negative children. To assess replication rates we used nucleolar organiser regions staining with colloidal silver nitrate technique (AgNOR). The number of AgNORs per nucleus, area of single AgNOR, and the quotient of these two parameters (AgNOR content) were analysed. The mean area of AgNOR was lower in H. pylori positive than in negative children. Conversely, both the mean number of AgNOR per nucleus and AgNOR content were higher in infected than non infected subjects. These results show accelerated proliferation of gastric antral epithelial cells in the course of H. pylori infection in children. Such alteration of cell replication occurring in an initial phase of natural history of long lasting infection provides an explanation for the association between acquisition of H. pylori infection in the first years of life and the development of gastric cancer.

Adolescent↗
PubMed1998

Ultrastructural changes of the filtration barrier during mouse nephron development.

The development of mouse renal corpuscles localized in the juxtamedullary zone of renal cortex was assessed with the aid of light and electron microscopy. The observations have confirmed the existence of four developmental phases of the nephron. The analysis of filtration barrier components has shown that during the development of the kidney the height of maturing podocytes becomes markedly reduced, and that adherence and occluding junctions formed between them shift from their apices towards their bases. Ladder-like junctions have also been observed between podocytes. The number of their foot processes steadily grows, they become narrower and filtration slit diaphragms begin appear between them. Fusion of podocytes basement membranes and endotheliocytes leads to formation of a doubly thick filtration membrane. As the tuft of the capillary glomerulus grows, newly formed fragments of the basement membrane in the form of loops and pouches start to be evident in its close neighborhood. Large endotheliocytes become greatly flattened and numerous fenestrae appear in their cytoplasm.

Animals↗
PubMed1995

Electron microscopic study of association between coccoid forms of Helicobacter pylori and gastric epithelial cells.

OBJECTIVE: To investigate the relationship between helical and coccoid forms of Helicobacter pylori and gastric epithelial cells. METHODS: Gastric antral and body biopsies were obtained from eight children, aged 10-17 yr, who underwent diagnostic gastroscopy. Specimens were processed for electron microscopy. The location of organisms and ultrastructural features were assessed with a transmission electron microscope. RESULTS: We observed two morphological forms of bacteria in three of eight H. pylori-positive patients. Helical forms were localized only in the proximity to unchanged or variously damaged mucous cells, but coccoid forms were present only above strongly damaged epithelial cells. CONCLUSION: Coccoid forms of H. pylori are closely associated with damaged gastric mucous cells. Possible explanations for this phenomenon are discussed.

Adolescent↗
PubMed1995

Colloidal gold-RNase labeling of RNA in regenerating rat liver hepatocytes.

During the early liver regeneration following partial hepatectomy, distinct changes of the transcriptional activity of hepatocyte nuclei are observed. Changes in the proportion of dense fibrillar component (DFC) and granular component (GC) of nucleoli are related to pre-rRNA synthesis. The RNase-gold ultracytochemical method was applied to localize RNA molecules in thin sections of regenerating rat liver hepatocyte nuclei. The method allowed for the detection of pre-rRNA molecules at the periphery of fibrillar centers (FC). The distribution of colloidal gold-RNase complexes in combination with quantification of labeling density demonstrated the highest transcriptional activity of nucleoli 18 hours following partial hepatectomy.

Animals↗
PubMed1994

Effects of polycations on ion channels formed by neutral and negatively charged alamethicins.

The effects of the peptide polycations salmon protamine (M(r) = 4332, z = +21) and poly-L-lysine (M(r) approximately equal to 100,000, z approximately equal to +775) on ion channels formed by synthetic alamethicin Alm-F30 (one negative charge), natural Alm-F50 (neutral) and phosphorylated Alm-F50 (two negative charges) reconstituted in planar lipid bilayers have been studied at the single channel level. It was observed that both polycations in micromolar concentrations transiently block ion permeation through the channels formed by each alamethicin analogue, although in case of the neutral Alm-F50 to a significantly lesser extent. Poly-L-lysine showed to be more effective than protamine in blocking these channels. If either polycation is present in the cis-compartment, blockade occurs only at cis positive membrane voltages. At constant polycation concentration, dwell times in the blocked state increase when salt concentration is lowered, and decrease at acidic pH with an apparent pK of 4.8. Mean lifetime of blockade events shortens when membrane voltage is increased, which suggests that both polycations may permeate through the oligomeric alamethicin channels if conductance levels are > 2. We suggest that blockade is caused by electrostatic binding of a single polycation molecule to the C-terminal channel mouth; in case of Alm-F30, Glu18 has to be considered as the putative binding site. Our results provide further evidence for the barrel-stave model and a parallel orientation of dipole monomers in the channel aggregate, the C-termini facing the membrane side with the more positive membrane potential.

Action Potentials↗
PubMed1992

Some ultrastructural aspects of Helicobacter pylori gastritis.

Ultrastructural examinations of biopsy specimens of the gastric mucosa were performed in 20 patients with chronic gastritis proven by endoscopy and microscopy. The presence of the Helicobacter pylori bacteria was found in close contact with epithelial cells of the antrum and corpus of the stomach. The bacteria were not present in the areas of frequently observed intestinal metaplasia. There were ultrastructural changes on the surface and within the cytoplasm of the epithelial mucous cells, which indicated their disturbed metabolism.

Chronic Disease↗
PubMed1991

Distribution of argyrophilic proteins in the nuclei of hepatocytes.

The ultrastructural study on the distribution of argyrophilic proteins of hepatocytes was carried out. Because it has been suggested that the numbers of silver grains were connected with transcriptional activity of nucleoli, we used in our studies as a model the regenerating liver. Among extranucleolar structures affinity to silver interchromatin granules and weakly perichromatin granules was demonstrated. Deposits of silver grains were always located within dense fibrillar components and fibrillar centers. Our study does not enable to indicate a direct relationship between numbers of silver grains deposits and transcriptional activity of nucleoli.

Animals↗