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Biomedical subjects

Harry Friedmann

Publications and source records attributed to Harry Friedmann.

6 recordsLinked to original sources
PubMed2006

Photochemistry and photobiology of light absorption by living cells.

In this review, we summarize a part of our research concerning photobiostimulative effects on cardiomyocytes, sperm cells, and nerve cells. We concentrate on results demonstrating that photobiostimulation can be described by the Arndt-Schultz (A.S.) curve. Results monitoring an increase in reactive oxygen species (ROS) concentration following visible light irradiation describe the ascending part of the A.S. curve, whereas those that describe the antioxidant role of photobiostimulation represent the descending part of the curve.

Animals↗
PubMed2005

Er:YAG laser promotes gingival wound repair by photo-dissociating water molecules.

OBJECTIVE: The aim of the present study was to show that rapid wound repair following Er:YAG treatment and its bactericidal effect can also be related to reactive oxygen species (ROS) generation in irradiated tissue. BACKGROUND DATA: The Er:YAG laser with a wavelength of 2,940 nm (corresponding to the vibrational OH stretch frequency of water) is of great value in dental medicine, owing to its dual ability to ablate soft and hard tissues with minimal damage to surrounding structures. The relatively rapid postoperative healing time seen after ablation of the gingiva is attributed to the very narrow zone of thermal disruption. METHODS: Water was irradiated with an Er:YAG laser at an energy of 100-130 mJ/cm(2) and 10-30-Hz pulse repetition rate The concentration of OH radicals produced following irradiation was assessed by spin trapping coupled with electron paramagnetic resonance (EPR) spectroscopy. RESULTS: We found that the Er-YAG laser dissociates water and generates OH radicals. The concentration of radicals produced was strongly dependent on the pulse repetition rate and energy density per laser pulse. CONCLUSIONS: The dissociation of water needed to generate OH radicals is possibly due to intermolecular vibrational (V-V) energy transfer in water, competing with vibrational relaxation, thus leading to water dissociation. High amounts of oxygen radicals (e.g., hydroxyl groups) have a sterilization effect, whereas low concentrations of ROS stimulate fibroblasts, causing collagen and extracellular matrix formation. ROS formation may explain the wound healing effect of the Er-YAG laser in dentistry.

Laser Therapy↗
PubMed2005

Final results of the Austrian Radon Project.

The Austrian Radon Project started in 1992 and ended in 2001. The Austrian Radon Project had two aims: firstly, finding areas of enhanced indoor radon concentration for future radon mitigations, and, secondly, defining areas with elevated radon risk where radon safe construction is necessary for new houses. The project was based on systematic indoor measurements in randomly selected houses using different types of detectors. Successful intercomparison tests were made in a radon chamber, but simultaneous measurements by different detectors normally used in homes deviated sometimes up to a factor of two. We have to assume that this results from manipulations of the detectors by the inhabitants. The mean radon concentration in Austrian homes was found to be 99 Bq m(-3). A radon potential was derived from the results of the measurements and the information received from questionnaires. This radon potential was defined as an expected radon concentration in a standard situation and characterizes the radon risk from ground sources with all the influences of different living situations eliminated. A mean radon potential was computed for every municipality and the information is displayed as a map. The uncertainty and the reliability of the classification of municipalities according to the radon potential are discussed in more detail and compared with results from Switzerland.

Air Pollutants, Radioactive↗
PubMed2004

ESR detection of 1O2 reveals enhanced redox activity in illuminated cell cultures.

Low-energy visible light (LEVL) has previously been found to modulate various processes in different biological systems. One explanation for the stimulatory effect of LEVL is light-induced reactive oxygen species formation. In the present study, both sperm and skin cells were illuminated with LEVL and were found to generate singlet oxygen (1O2). The detection of 1O2 was performed using a trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron paramagnetic resonance spectroscopy. In addition, we have shown that, together with O2 generation, LEVL illumination increases the reductive capacity of the cells, which explains the difficulties encountered in 1O2 detection. The potential of visible light to change the cellular redox state may explain the recently observed biostimulative effects exerted by LEVL.

Animals↗
PubMed2003

Low energy visible light induces reactive oxygen species generation and stimulates an increase of intracellular calcium concentration in cardiac cells.

Low energy visible light (LEVL) irradiation has been shown to exert some beneficial effects on various cell cultures. For example, it increases the fertilizing capability of sperm cells, promotes cell proliferation, induces sprouting of neurons, and more. To learn about the mechanism of photobiostimulation, we studied the relationship between increased intracellular calcium ([Ca2+]i) and reactive oxygen species production following LEVL illumination of cardiomyocytes. We found that visible light causes the production of O2. and H2O2 and that exogenously added H2O2 (12 microm) can mimic the effect of LEVL (3.6 J/cm2) to induce a slow and transient increase in [Ca2+]i. This [Ca2+]i elevation can be reduced by verapamil, a voltage-dependent calcium channel inhibitor. The kinetics of [Ca2+]i elevation and morphologic damage following light or addition of H2O2 were found to be dose-dependent. For example, LEVL, 3.6 J/cm2, which induced a transient increase in [Ca2+]i, did not cause any cell damage, whereas visible light at 12 J/cm2 induced a linear increase in [Ca2+]i and damaged the cells. The linear increase in [Ca2+]i resulting from high energy doses of light could be attenuated into a non-linear small rise in [Ca2+]i by the presence of extracellular catalase during illumination. We suggest that the different kinetics of [Ca2+]i elevation following various light irradiation or H2O2 treatment represents correspondingly different adaptation levels to oxidative stress. The adaptive response of the cells to LEVL represented by the transient increase in [Ca2+]i can explain LEVL beneficial effects.

Animals↗