0000000000017735
AUTHOR
J. Peters
showing 18 related works from this author
Effect of Torasemide — A New Cl--Transport Inhibitor on Glial Swelling by Lactacidosis and Glutamate
1993
Cytotoxic brain edema, i.e. swelling of glial- and nerve cells is a common result of cerebral ischemia, brain trauma, metabolic disorders, and develops secondarily in vasogenic edema. During ischemia and severe head injury, brain tissue homeostasis is severely changed, and many parameters are simultaneously affected. To dissect and isolate the causal mechanisms leading to swelling of nerve- and glial cells, our laboratory has established an in vitro model [4, 5]. Thereby pathomechanisms can be studied in isolation without interference of epiphenomena taking place in damaged brain tissue under circumstances of cerebral ischemia or trauma. In previous studies the role of acidosis in cell swel…
Aufnahme und Phototoxizität von Hämatoporphyrinderivat in normalen und malignen Zellen
1992
Die Photodynamische Therapie (PDT) stellt neben der Chemo-, Radio- und chirurgischen Therapie ein neues alternatives Therapiekonzept in der Behandlung von malignen Tumoren dar. Das Prinzip beruht auf der systemischen Applikation (i.v. Injektion) einer photosensibilisierenden Substanz, z.B. Hamatoporphyrinderivat (HPD), und der nachfolgenden Bestrahlung mit Licht geeigneter Wellenlange, z.B. Laserlicht (630 nm). Fur die tumorselektive Wirkung dieser Therapie werden die selektive Aufnahme bzw. vermehrte Speicherung der photoaktiven Substanzen im Tumorgewebe [1] sowie auch eine im Vergleich zum Normalgewebe erhohte Sensibuitat von Tumorgewebe gegenuber der PDT postuliert. Ungeklart ist, ob die…
Cytotoxic Glial Swelling by Arachidonic Acid
1994
Arachidonic acid (AA, 20:4) is a major constituent of membrane phospholipids in brain tissue. Normally, the free fatty acid is present only in a small amount, but it accumulates under adverse conditions, such as ischemia or brain injury [1,9]. The release of free fatty acid involves activation of phospholipases and breakdown of membrane phospholipids. AA in particular is considered to mediate pathological processes. The polyunsaturated compound is a precursor of prostaglandins, leukotrienes, and oxygen-derived free radicals [11]. In cerebral ischemia concentrations of free AA of up to 0.5 mM/kg have been found in brain tissue [9].
Earth system data cubes unravel global multivariate dynamics
2020
Understanding Earth system dynamics in light of ongoing human intervention and dependency remains a major scientific challenge. The unprecedented availability of data streams describing different facets of the Earth now offers fundamentally new avenues to address this quest. However, several practical hurdles, especially the lack of data interoperability, limit the joint potential of these data streams. Today, many initiatives within and beyond the Earth system sciences are exploring new approaches to overcome these hurdles and meet the growing interdisciplinary need for data-intensive research; using data cubes is one promising avenue. Here, we introduce the concept of Earth system data cu…
An in vitro model to study cellular photosensitizer uptake and photodynamic dose-response relationships of tumor cells
1993
Cellular fluorescence intensity (CFI) after incubation with varying concentrations of the photosensitizer Photofrin and the photodynamically induced dose-response relationships of hamster melanoma cells (A-MEL-3) were studied in a recently developed in vitro model. After administration of Photofrin to the extracellular serum-free medium, CFI was evaluated by flow cytometry together with constantly fluorescing latex particles used as a reference. After 5 min, 50% of maximal CFI was found, and after 60 min CFI was maximal. No further increase was obtained during the exposure to Photofrin over the incubation period of 4 h. During this plateau phase, CFI was significantly related to the concent…
Glial Swelling and Damage by Arachidonic Acid
1994
Arachidonic acid (AA) is a major constituent of membrane phospholipids in brain tissue. Normally, the free fatty acid is present only in small amounts, but it accumulates under adverse conditions such as ischemia (Kinouchi et al. 1990). The release of free fatty acids involves activation of phospholipases and breakdown of membrane phospholipids. A A in particular is considered to mediate pathological processes. It is a polyunsaturated compound and precursor of prostaglandins, leukotrienes, and oxygen-derived free radicals (Wolfe 1982). In cerebral ischemia concentrations of free AA of up to 0.5mM/kg were found (Kinouchi et al. 1990). But also brain injury and seizures cause increased levels…
Anoxia in vitro does not induce neuronal swelling or death
1996
To improve the understanding of neuronal cell swelling in cerebral ischemia, cell volume regulation, viability, intracellular electrolytes, and lactate production of Neuro-2A neuroblastoma cells were studied using an in vitro model. The volume regulatory capacity of Neuro-2A cells was assessed after incubation in hypo- and hypertonic media. Anoxia was studied alone and together with inhibition of glycolysis by iodoacetate. Reducing the tonicity of the incubation medium to 250, 200, or 150 mosm/l caused immediate swelling followed by a regulatory volume decrease within 20 min, which, however, was not complete. The final cell volume after regulation depended on the tonicity of the medium and …
Swelling, Intracellular Acidosis, and Damage of Glial Cells
1996
Cerebral ischemia and severe head injury among others are associated with a limited availability of oxygen, leading to cell catabolism as well as anaerobic glycolysis. Resulting metabolites, such as arachidonic- and lactic acid, can be expected to leak into perifocal brain areas, contributing there to cytotoxic swelling and damage of neurons and glia. Since elucidation of mechanisms underlying cell swelling and damage in the brain is difficult in vivo, respective investigations were carried out in vitro using suspended glial cells. Thereby, effects of arachidonic acid (AA) and of lactacidosis on glial cell volume, intracellular pH (pHi), and cell damage were analyzed utilizing flow cytometr…
Swelling, Acidosis, and Irreversible Damage of Glial Cells from Exposure to Arachidonic Acid in vitro
1994
Swelling and damage of C6 glioma cells and of primary cultured astrocytes were analyzed in vitro during incubation with arachidonic acid (AA; 20:4). The cells were suspended in a physiological medium supplemented with AA at concentrations of 0.001–1.0 m M. Cell swelling was quantified by flow cytometry with hydrodynamic focusing. Flow cytometry was also utilized for assessment of cell viability by exclusion of the fluorescent dye propidium iodide and for measurement of the intracellular pH (pHi) by 2′,7′-bis-(2-carboxyethyl)−5(and −6)carboxyfluorescein. Administration of AA caused an immediate dose-dependent swelling of C6 glioma cells, even at a concentration of 0.01 m M. At this level cel…
Swelling of glial cells in lactacidosis and by glutamate: significance of Cl(-)-transport.
1993
Swelling of glial and nerve cells is characteristic of brain damage in cerebral ischemia or trauma. The therapeutical efficiency of inhibition of Cl(-)-transport by a novel antagonist, the diuretic torasemide, on cytotoxic swelling of glial cells from lactacidosis, or glutamate was analyzed. Lactacidosis and the interstitial accumulation of glutamate are hallmarks of the pathophysiological alterations in ischemic or traumatic brain tissue. C6 glioma cells harvested from culture and suspended in a physiological medium were either exposed to pH 6.2, or 5.0 by lactic acid, or exposed to 1 mM glutamate at normal pH. Cell swelling and viability were quantified by flow cytometry. Lactacidosis of …
Clearance and metabolism of arachidonic acid by C6 glioma cells and astrocytes.
1995
Effects of increased levels of arachidonic acid (AA) were analyzed in vitro by employment of C6 glioma cells and astrocytes from primary culture. The cells were suspended in a physiological medium added with arachidonic acid (AA) in a concentration range from 0.01 to 0.5 mM. The concentration profiles of the fatty acid and AA-metabolites were subsequently followed for 90 min. AA was measured by gas chromatography, whereas the AA-metabolites PGF2 alpha and LTB4 by radioimmunoassay (RIA). Following administration of AA at 0.05 or 0.1 mM the medium was completely cleared from the fatty acid within 10 to 15 min. However, when 0.5 mM were added, AA concentrations of 0.36 +/- 0.055 mM were found …
Relation of early Photofrin uptake to photodynamically induced phototoxicity and changes of cell volume in different cell lines.
1994
For efficacy of photodynamic therapy, selective uptake and retention of photoactive substances has been postulated. Therefore, measurements were performed to find out whether the photosensitiser Photofrin® is taken up differently in malignant and non-malignant cells in vitro . In addition, the sensitivity of malignant cells and nonmalignant cells to photodynamic exposure was investigated, by quantifying viability and volume alterations of the cells. Bovine aortic endothelial cells, mouse fibroblasts and amelanotic hamster melanoma cells were suspended in a specially designed incubation chamber under controlled conditions (e.g. pH, p O 2 , p CO 2 and temperature). After establishing constant…
Significant correlations between certain spectra of atmospherics and daily periodic activities of Mongolian gerbils (Meriones unguiculatus L.).
1995
We describe significant correlations between 10 and 28 kHz atmospherics (according to Baumer) and the running activities of ten Mongolian gerbils (Meriones unguiculatus L.) depending on their circadian rhythm over a 42-day period (August/September 1988).
Mechanisms of Glial Swelling by Arachidonic Acid
1994
The effect of arachidonic acid (AA, 20:4) was analyzed in vitro by employment of C6 glioma cells and astrocytes from primary culture. The cells were suspended in an incubation chamber under continuous control of pH, pO2, and temperature. Cell swelling was quantified by flow cytometry. After a control period, the suspension was added with AA at concentrations of 0.01 to 1.0 mM. Administration of AA induced an immediate, dose dependent swelling in C6 glioma cells or astrocytes. AA-concentrations of 0.01 mM led to an increase of the glial cell volume to 103.0 ± 1.0% of control, 0.1 mM to 110.0 ± 1.5%, and l.0 mM to 118.8 ± 1.5% within 10 min. The swelling response to linoleic acid (18 : 2) was…
Mechanisms of arachidonic acid induced glial swelling
2000
Accumulation of arachidonic acid (AA) in the brain during ischaemia may contribute to development of brain oedema. In this study we investigated the effect of selected drugs on AA-induced cytotoxic brain oedema in C6 glioma cells. Suspended C6 glioma cells were preincubated with drugs and AA (0.1 mM) was added. When no drug was administered cell volume increased immediately after the addition of AA with a maximum cell swelling of 13.1+/-1.9% at 15 min (mean +/- S.E. M.). Preincubation of cells with BW 755C, a dual inhibitor of cyclo- and lipoxygenases, showed no reduction in cell swelling from AA, whereas superoxide dismutase, amiloride and the protein kinase inhibitor H-9370 led to a signi…
In-vitro Untersuchungen zu photodynamisch induzierten Dosis-Wirkungs-Beziehungen
1992
Im Gegensatz zu fruheren Annahmen wurde von Rodgers 1990 in Frage gestellt, das aus der Quantifizierung der Fluoreszenz im Gewebe Aussagen uber die Konzentration des Photosensibilisators noch uber die zu erwartenden photodynami-schen Effekte moglich sind (1).
Glial ion transport and volume control.
1991
K(+)-induced glial swelling results from an intricate interaction of transport and diffusion processes and metabolic stimulation, with many open questions remaining. Our concept of the major mechanisms involved can be summarized as follows: high extracellular K+ causes a burst-like stimulation of Na+/K+ ATPase and, hence, increases the metabolic demands. Lactate is produced; the cell is slightly acidified. To maintain a normal intracellular pH, the Na+/K+ antiporter extrudes protons and supplies Na+ for further Na+/K+ exchange. In addition, K+ ions enter the cell via membrane channels or furosemide-inhibitable transport. K+, Cl-, and lactate- ions accumulate as the osmotic basis for cell sw…
Brain lateralization probed by water diffusion at the atomic to micrometric scale
2019
International audience; Combined neutron scattering and diffusion nuclear magnetic resonance experiments have been used to reveal significant interregional asymmetries (lateralization) in bovine brain hemispheres in terms of myelin arrangement and water dynamics at micron to atomic scales. Thicker myelin sheaths were found in the left hemisphere using neutron diffraction. 4.7 T dMRI and quasi-elastic neutron experiments highlighted significant differences in the properties of water dynamics in the two hemispheres. The results were interpreted in terms of hemisphere-dependent cellular composition (number of neurons, cell distribution, etc.) as well as specificity of neurological functions (s…