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G M Artmann

Publications and source records attributed to G M Artmann.

18 recordsLinked to original sources
PubMed2007

Decrease in extracellular collagen crosslinking after NMR magnetic field application in skin fibroblasts.

Although biological effects of electromagnetic fields were investigated intensively, there is still no agreement on the significance of their effects. The underlying mechanisms and therapeutic importance are still mostly unknown too. In this study, primary cultures of human dermal fibroblasts were exposed to magnetic field at nuclear magnetic resonance (NMR) conditions for in total 5 days and 4 h/day. Among the investigated parameters were: cell proliferation rate, cell morphology, total protein concentration as well as content of skin-specific collagen types I, III, IV. NMR exposure induced distinct changes both in cellular and extracellular components. The extracellular matrix (ECM) of NMR-exposed cells had less cross-linked collagen. In particular, the increase of collagen of the soluble fraction was at 17.2 +/- 2.9% for type I, 27.0 +/- 1.86% for type III, 17.3 +/- 1.46% for type IV (N = 6). In the absence of resonance frequency, the effects of magnetic field on ECM were less profound.

Body Water↗
PubMed2006

Body temperature-related structural transitions of monotremal and human hemoglobin.

In this study, temperature-related structural changes were investigated in human, duck-billed platypus (Ornithorhynchus anatinus, body temperature T(b) = 31-33 degrees C), and echidna (Tachyglossus aculeatus, body temperature T(b) = 32-33 degrees C) hemoglobin using circular dichroism spectroscopy and dynamic light scattering. The average hydrodynamic radius (R(h)) and fractional (normalized) change in the ellipticity (F(obs)) at 222 +/- 2 nm of hemoglobin were measured. The temperature was varied stepwise from 25 degrees C to 45 degrees C. The existence of a structural transition of human hemoglobin at the critical temperature T(c) between 36-37 degrees C was previously shown by micropipette aspiration experiments, viscosimetry, and circular dichroism spectroscopy. Based on light-scattering measurements, this study proves the onset of molecular aggregation at T(c). In two different monotremal hemoglobins (echidna and platypus), the critical transition temperatures were found between 32-33 degrees C, which are close to the species' body temperature T(b). The data suggest that the correlation of the structural transition's critical temperature T(c) and the species' body temperature T(b) is not mere coincidence but, instead, is a more widespread structural phenomenon possibly including many other proteins.

Adult↗
PubMed2005

Bactericidal effects of plasma-generated cluster ions.

Air purification by plasma-generated cluster ions (PCIs) relies on a novel technology producing hydrated positive and negative ions. Phenomenological tests have shown strong evidence of lethal effects of the PCIs on various micro-organisms. However, the mechanisms of PCI action are still widely unknown. The aim was thus to test the bactericidal efficacy of PCI technology on common indoor micro-organisms and to explore possible PCI mechanisms of action. According to time/dose-dependent experiments with Staphylococcus, Enterococcus, Micrococcus and Bacillus, the inhibiting effects became apparent within the first few minutes of PCI exposure and led to an irreversible 99.9% destruction within the following 2-8 h of exposure. The destructive effect of the PCIs corresponded to membrane damage of the bacteria. Use of the techniques of both SDS PAGE and 2D PAGE revealed changes in the bacterial surface protein composition induced by the PCIs. In contrast, neither DNA nor cytoplasm protein damage was detected electrophoretically. The antimicrobial action of the PCIs seems to occur because of chemical modification of the surface proteins of bacteria. In situ hydroxyl radical formation on the surface of bacteria was proposed as the leading mechanism of the protein damage caused by the PCIs. At the same time, DNA damage seems not to be involved in the antibacterial action of the PCIs. The data obtained would broaden the knowledge concerning the antibacterial effects of air-born plasma-generated cluster ions and help to produce more efficient air-cleaning devices.

Air Ionization↗
PubMed2004

Evaluation of lateral mechanical tension in thin-film tissue constructs.

Fibroblast-populated collagen matrices provide a simplified tissue model for wound healing and development processes. A technology (CELLDRUM Technology) evaluating lateral mechanical tension in fibroblast-populated collagen matrices (tissue constructs) with a thickness of 1 mm was introduced. Defined mechanical boundary conditions together with the known number and orientation of the cells revealed precise data on the average tension exerted by a single cell. Circular cell-populated collagen gels were manufactured inside the CELLDRUM on top of a flexible membrane. The collagen matrix was then excited by a sound pulse. The resulting resonance oscillation was monitored by a laser-based deflection sensor and frequency and damping were analyzed giving information on mechanical properties of the tissue construct. Several evaluation experiments were performed. Calf serum enhanced contractile forces of fibroblasts dose dependently. After the gels were treated with cytochalasin D for 24 h, the cell forces were reduced by 42% of control. The remaining tension was attributed to the extracellular matrix remodeling occurring during cell growth and to other cytoskeletal structures like microtubules and intermediate filaments. We also found that only after a few hours of culture fibroblast-seeded collagen gels began developing significant mechanical tension. A mechanical tension profile of proliferating fibroblasts in collagen gels over culture time was obtained.

3T3 Cells↗
PubMed2003

Biological and mechanical quality of red blood cells cultured from human umbilical cord blood stem cells.

Human umbilical cord blood (CB) has moved from the status of biological waste to that of a valuable source of haematopoietic stem (HS) cells. There are potentially three major clinical applications for HS cells and ex vivo-expanded HS cells: reconstitution of haematopoiesis in patients undergoing chemotherapy; gene therapy (e.g. in thalassaemia, sickle cell anaemia); and large-scale production of mature blood cells. Erythropoiesis is accomplished by highly complex interactions of haematopoietic progenitor cells, stromal cells and cytokines in the bone marrow. Among them, erythropoietin is the principal regulator. Ex vivo cell culture experiments to obtain mature red blood cells were the focus of this study. Attempts to elucidate appropriate medium components and amounts of haematopoietic growth factors were successful: enucleated and haemoglobin-filled erythroid cells were obtained from primitive HS cells. Dimethylsulphoxide (DMSO) was found to be of particular importance as an efficient differentiation inducer. The differentiation process was followed microscopically and by fluorescence-activated cell sorting (FACS). Using the micropipette aspiration technique, the elastic properties of erythroid cells were evaluated as erythropoiesis progressed. Discocyte-like cells, comprising reticulocytes and finally differentiated red blood cells, showed an about ten-fold higher membrane shear modulus compared with control cells.

Cell Culture Techniques↗
PubMed2002

Determination of the elastic shear modulus of cultured human red blood cells.

In this study we investigated the mechanical properties of in vitro cultured red blood cells (RBCs) in a liquid system. We used human umbilical cord blood as a highly efficient source of hematopoietic stem cells (HS). Our first goal was to establish an optimal medium composition in order to yield finally differentiated RBCs, i.e. enucleated and hemoglobin-filled cells. Different stages of cell differentiation were distinguished based on morphological observations and flow cytometry measurements. By means of the micropipette aspiration technique we estimated the deformability characteristics of the cultured cells. Up to the stage of oxiphilic normoblasts they readily deformed. Reticulocytes and mature RBCs showed an enhanced stiffness as compared to RBCs obtained from donors.

Adult↗
PubMed2002

A novel method to quantify mechanical tension in cell monolayers.

A new technology to analyze mechanical properties of adherent cell monolayers grown on elastic silicon membranes is introduced. Measurements were performed using 3T3 (NIH) fibroblasts under the influence of Cytochalasin D and Thrombin. The stress-strain relation of the cell monolayer-silicon-composite was monitored. The drum-like construct of the culture chamber opens new roads for studying the mechanics of cell monolayers and of ultra flat tissue constructs. Steady state as well dynamic mechanical studies can be performed. Defined mechanical boundary conditions together with the known number and orientation of the cells allow precise information on the average tension exerted by a single cell within the monolayer.

3T3 Cells↗
PubMed2001

Temperature transition of human hemoglobin at body temperature: effects of calcium.

We studied the effects of calcium ion concentration on the temperature dependence of rheological behavior of human red blood cells (RBCs) and concentrated hemoglobin solutions. Our previous study (G. M. Artmann, C. Kelemen, D. Porst, G. Büldt, and S. Chien, 1998, Biophys. J., 75:3179-3183) showed a critical temperature (Tc) of 36.4 +/- 0.3 degrees C at which the RBCs underwent a transition from non-passage to passage through 1.3 microm micropipettes in response to an aspiration pressure of -2.3 kPa. An increase in intracellular Ca2+ concentration by using the ionophore A23187 reduced the passability of intact RBCs through small micropipettes above T(c); the micropipette diameter needed for >90% passage increased to 1.7 microm. Viscometry of concentrated hemoglobin solutions (45 and 50 g/dl) showed a sudden viscosity transition at 36 +/- 1 degrees C (Tc(eta)) at all calcium concentrations investigated. Below Tc(eta), the viscosity value of the concentrated hemoglobin solution at 1.8 mM Ca(2+) was higher than that at other concentrations (0.2 microM, 9 mM, and 18 mM). Above Tc(eta), the viscosity was almost Ca2+ independent. At 1.8 mM Ca2+ and 36 +/- 1 degrees C, the activation energy calculated from the viscometry data showed a strong dependence on the hemoglobin concentration. We propose that the transition of rheological behavior is attributable to a high-to-low viscosity transition mediated by a partial release of the hemoglobin-bound water.

Blood Viscosity↗
PubMed2001

Evidence for a second valve system in lymphatics: endothelial microvalves.

The mechanism for interstitial fluid uptake into the lymphatics remains speculative and unresolved. A system of intralymphatic valves exists that prevents reflow along the length of the lymphatic channels. However, these valves are not sufficient to provide unidirectional flow at the level of the initial lymphatics. We investigate here the hypothesis that initial lymphatics have a second, separate valve system that permits fluid to enter from the interstitium into the initial lymph channels but prevents escape back out into the tissue. The transport of fluorescent microspheres (0.31 microm) across endothelium of initial lymphatics in rat cremaster muscle was investigated with micropipette manipulation techniques. The results indicate that microspheres can readily pass from the interstitium across the endothelium into the lumen of the initial lymphatics. Once inside the lymphatic lumen, the microspheres cannot be forced out of the lumen even after elevation of the lymphatic pressure by outflow obstruction. Reaspiration of the microspheres inside the lymphatic lumen with a micropipette is blocked by the lymphatic endothelium. This blockade exists whether the aspiration is carried out at the microsphere entry site or anywhere along the initial lymphatics. Nevertheless, puncture of the initial lymphatic endothelium with the micropipette leads to rapid aspiration of intralymphatic microspheres. Investigation of lymphatic endothelial sections fixed during lymph pumping shows open interendothelial junctions not found in resting initial lymphatics. These results suggest that initial lymphatics have a (primary) valve system at the level of the endothelium. In conjunction with the classical (secondary) intralymphatic valves, the primary valves provide the mechanism that facilitates the unidirectional flow during periodic compression and expansion of initial lymphatics.

Abdominal Muscles↗
PubMed2000

Chlorpromazine modulates the morphological macro- and microstructure of endothelial cells.

Chlorpromazine (CP), an amphipathic, antipsychotic agent, causes concave membrane bending in red blood cells with formation of stomatocytic shapes by modulation of the phospholipid bilayer. This study was designed to investigate the effects of CP on the shape of bovine aortic endothelial cells (BAEC) and their membranes in confluent monolayers with phase-contrast and transmission electron microscopy. Exposure of BAECs to nanomolar levels of CP leads to membrane curvature changes. With increasing CP concentrations, the membrane assumed a shape with enhanced numbers of intracellular caveolae and projection of pseudopodia at all junctions. At higher CP concentrations (up to 150 microM), the endothelial cells assumed almost spherical shapes. The evidence suggests that CP may affect lipid bilayer bending of BAECs in analogy with previous observations on erythrocytes, supporting the formation of caveolae and pseudopodia in BAECs due to the induction of concave membrane bending, as well as an effect on endothelial cell membrane adhesion at higher CP concentrations with loss of cellular attachment at junctions.

Animals↗
PubMed2000

Hypochlorous acid and human blood low density lipoproteins modified by hypochlorous acid increase erythrocyte adhesion to endothelial cells.

The ability of hypochlorous acid (HOCl) (anion form - hypochlorite, OCl-) and HOCl/OCl- -modified human blood low density lipoproteins (HOCl-LDLs) to stimulate erythrocyte adhesion to endothelial cell monolayers was studied. LDLs were modified by incubating at different HOCl/OC- concentrations. This led to a damage of proteins and lipids. We found (1) a more than 20-fold decrease of LDL fluorescence intensity (extinction at 285 nm, emission at 340 nm), (2) accumulation of secondary (TBA-reactive substances) and final (Schiff bases) products of lipid peroxidation, and (3) increase in the electrophoretic mobility of LDLs. Preincubation of endothelial cells (ECs) with HOCI/OCl- (up to 50 microM) enhanced erythrocyte adhesion to the EC monolayer. Preincubation of ECs with HOCl-LDLs (up to 250 microM of HOCI//OCl- during LDL modification) (1) caused an increase in the cholesterol/phospholipid molar ratio in EC and (2) enhanced adhesion of erythrocytes to endothelium. Application of HOCl/OCl- at concentrations above 50 microM or treatment of LDLs with 500 microM HOCl resulted in the cytotoxic effect on ECs and led to a decrease in the molar cholesterol/phospholipid ratio in ECs and adhesion of erythrocytes to endothelium. The results suggest that HOCl/OCl- at physiological concentrations stimulates the adhesion of blood cells to the endothelium and cholesterol accumulation in the vessel wall ECs either directly or due to LDL modification. Both effects could be important in the development of many vascular diseases.

Arteriosclerosis↗
PubMed1998

Temperature transitions of protein properties in human red blood cells.

Human red blood cells (RBC) undergo a sudden change from blocking to passing through 1.3 +/- 0.2-micrometer micropipettes at a transition temperature (Tc) of 36.4 degrees C. For resealed RBC ghosts this transition occurs at 28.3 degrees C (Tg). These findings are attributed to an elastomeric transition of hemoglobin from being gel-like to a fluid and to an elastomeric transition of membrane proteins such as spectrin. Spectrin shows a uniform distribution along the aspirated RBC tongue above Tg in contrast to the linear gradient below Tg.

Biophysical Phenomena↗
PubMed1998

Hemorheology and walking of peripheral arterial occlusive diseases patients during treatment with Ginkgo biloba extract.

AIM: To study the effects of Ginkgo biloba extract 761 (GbE) from the points of view of hemorheology for patients of peripheral arterial occlusive diseases (PAOD). METHODS: The treatment with GbE (240 mg.d-1, po) and the pain-free walking distance (PFWD) were carried out for 24 PAOD patients (12 nondiabetic, ND and 12 diabetic, D) over 48 wk. The parameters erythrocyte stiffness (ES) and relaxation time (RT), the blood plasma viscosity (eta), the plasma fibrinogen concentration (Cf) and the blood sedimentation rate (BSR), the PFWD, and maximal walking distance (MWD) were determined at 6 wk before treatment (-6), at the beginning of the treatment (0), and after 6, 11, 16, and 48 wk of treatment. RESULTS: At wk -6, ES and RT of both the ND- and D-group were not significantly different from a healthy control group. At wk 0, stiffness and RT were significantly higher than healthy control, and the mean PFWD was only 111 m. The eta value was significantly elevated and Cf and BSR were enhanced. Throughout 11 wk of treatment ES, RT, eta, and Cf decreased gradually and PFWD improved. Between 16 and 48 wk, ES, and RT were no longer significantly different from the controls, whereas eta and Cf decreased gradually but remained higher than normal, BSR decreased, and the PFWD improved by a factor of 3.8 times (D) and 3.3 times (ND). CONCLUSION: GbE gives therapeutic effects in PAOD patients.

Aged↗
PubMed1997

Micropipette aspiration of human erythrocytes induces echinocytes via membrane phospholipid translocation.

When a discocytic erythrocyte (RBC) was partially aspirated into a 1.5-microns glass pipette with a high negative aspiration pressure (delta P = -3.9 kPa), held in the pipette for 30 s (holding time, th), and then released, it underwent a discocyte-echinocyte shape transformation. The degree of shape transformation increased with an increase in th. The echinocytes recovered spontaneously to discocytes in approximately 10 min, and there was no significant difference in recovery time at 20.9 degrees C, 29.5 degrees C, and 37.4 degrees C, respectively. At 11 degrees C the recovery time was significantly elevated to 40.1 +/- 6.7 min. At 20.9 degrees C the shape recovery time varied directly with the isotropic RBC tension induced by the pipetting. Sodium orthovanadate (vanadate, 200 microM), which inhibits the phospholipid translocase, blocks the shape recovery. Chlorpromazine (CP, 25 microM) reversed the pipette-induced echinocytic shape to discocytic in < 2 min, and the RBC became a spherostomatocyte-II after another 30 min. It was hypothesized that the increase in cytosolic pressure during the pipette aspiration induced an isotropic tension in the RBC membrane followed by a net inside-to-outside membrane lipid translocation. After a sudden release of the aspiration pressure the cytosolic pressure and the membrane tension normalized immediately, but the translocated phospholipids remained temporarily "trapped" in the outer layer, causing an area excess and hence the echinocytic shape. The phospholipid translocase activity, when not inhibited by vanadate, caused a gradual return of the translocated phospholipids to the inner layer, and the RBC shape recovered with time.

Blood Specimen Collection↗
PubMedDate not supplied

Microscopic photometric quantification of stiffness and relaxation time of red blood cells in a flow chamber.

The Microscopic Photometric Monolayer Technique provides a tool to measure red blood cell (RBC) stiffness (resistance to elongation) and relaxation time. It combines many of the advantages of flow channel studies of point-attached RBCs with the simplicity, sensitivity and accuracy of photometric light transmission measurement. This technique allows the study of the effects of physicochemical factors on the elongation and relaxation time of the same cells within an average of four to five thousand cells adhered as a monolayer to glass. Further, the time course of physicochemical effects on cell membrane and wash-in/wash-out kinetics of interactions can be followed. An automated version of this technique was developed. A dense monolayer of point-attached RBCs was prepared at the bottom of a flow-chamber. A steady-state flow, with stepwise increases of flow rate, induced the RBC elongation. The light transmission perpendicular through the monolayer plane was measured photometrically. Photomicrographs compared with photometric results showed that the flow-induced bending and curvature change of RBC membrane was associated with the increase of light transmission. There was a linear correlation between the photometric index of elongation and the elongation taken from photomicrographs for shear stresses up to 0.75 Pa. A stiffness parameter, S (in Pa), was defined as the ratio of shear stress and elongation at a shear stress of 0.25 Pa. Following a sudden flow stoppage, the RBCs returned to their resting shape and the RBC relaxation time was measured. The stiffness-relaxation time product, V (in mPas), was calculated to provide an estimate of viscosity. Diamide treatment, known to stiffen RBCs, did result in dose-dependent decreases of elongation and relaxation time. With increasing temperature, the relaxation time decreased at a rate of -2.96 ms/K; the stiffness increased significantly at a rate of 0.0038 Pa/K, and the stiffness-relaxation time product decreased with -2.95 mPas/K, reflecting an inverse relationship between RBC viscosity and temperature. Using the automated version of this technique (Elias-c-) to test RBCs of 36 healthy subjects, we found the inter-individual coefficients of variation to be 8.6% for stiffness, 7.9% for relaxation time and 12.4% for stiffness-relaxation time product.

Adult↗
PubMedDate not supplied

A photometric method to analyze induced erythrocyte shape changes.

In this paper, a photometric method was introduced to quantify biochemically-induced red blood cell (RBC) shape changes when no shear force was acting on the cells. To obtain the photometric RBC shape parameter (RF1), a monolayer of point-attached RBCs was prepared on the floor of a flat flow chamber and the transmission of light perpendicular to the monolayer plane was measured: 1) in phosphate buffered saline with 0.1% bovine serum albumin (PBS+) and 2) in PBS+, containing a shape changing compound (in both, the RBCs were not deformed due to shear flow). To normalize the data, a third transmission value at a shear stress of 3 Pa was measured in PBS+ from the same RBC monolayer. To validate the photometric data, RF1 of RBCs exposed to shape changing agents was correlated by linear regression analysis with 1) data obtained with the tangent-counting technique (TC) and 2) the morphological index (MI). The coefficient of correlation was calculated at 0.95 for the TC data and 0.94 for the MI data, respectively. The sensitivity of the photometric method was tested with stomatocytogenic chlorpromazine (CP) and echinocytogenic sodium salicylate (SA). CP (2.5 microM) induced a significant decrease of RF1 to -0.045 (N = 6 donors, p < 0.01), whereas SA (2.5 mM) increased RF1 to +0.027 significantly (N = 6, donors, p < 0.01). Both the CP-induced and the SA-induced shape changes appeared less than 2 min after application of the shape changing agents, and changed gradually within another 30 min when the agent was present in PBS+, partly disappearing within about 2 min after reincubation of the shape transformed RBCs in PBS+ not containing the agent.

Adult↗
PubMedDate not supplied

NMR in vitro effects on proliferation, apoptosis, and viability of human chondrocytes and osteoblasts.

This study presents findings on the proliferation rate, cellular apoptosis, and viability of human chondrocyte and osteoblast cultures before and after treatment with NMR pulse sequences. A commercially available nuclear magnetic resonance machine (MBST(R)-Nuclear Magnetic Resonance Therapy) was used for treatment. The study was carried out for 19 days, including 9 days of NMR exposure in a controlled, double-blind, randomized manner, using commercially available human cell lines. The study revealed that NMR treatment did not induce apoptosis or inhibit cell viability, but revealed a tendency of an elevated cell proliferation rate as observed by cell count.

Apoptosis↗