Biomedical subjects
Publications and source records attributed to Doina Gazdaru.
The purpose of this paper is to study the effects of some alkyl-phenyl-pyridinium compounds (which are in fact cytostatics) on the pseudotumoral tissues after their exposure to optical UV- vis beams.
The effects produced by fast neutrons (0-100 Gy) on chromatin structure were analyzed by (i) [1H]-NMR spectroscopy, (ii) time resolved spectroscopy, and (iii) fluorescence resonance energy transfer (FRET). Two types of chromatin were tested: (i) a chromatin from a normal tissue (liver of Wistar rats) and (ii) a chromatin from a tumoral tissue (Guerin limphotrope epithelioma, a rat solid tumor). The fast-neutron action on chromatin determines greater values of the [1H]-NMR transverse relaxation time, indicating a more injured structure. Time-resolved fluorescence measurements show that the relative contribution of the excited state lifetime of bound ethidium bromide to chromatin DNA diminishes with increasing irradiation doses. This reflects the damage that occurs in DNA structure: production of single- and double-strand breaks due to sugar and base modifications. By the FRET method, the distance between dansyl chloride and acridine orange coupled at chromatin was determined. This distance increases upon fast-neutron action. The radiosensitivity of the tumor tissue chromatin seems higher than that of the normal tissue chromatin, probably because of its higher (loose) euchromatin/(compact) heterochromatin ratio. As the values of the physical parameters analyzed are specific for a determined dose, the establishment of these parameters may constitute a criterion for the microdosimetry of chromatin radiolesions produced by fast neutrons.
The effects of fast neutrons (10-100 Gy) on chromatin extracted from normal (liver of Wistar rats) and tumor (Walker carcinosarcoma maintained on Wistar rats) tissues were compared. The spectroscopic assays used were (i) chromatin intrinsic fluorescence, (ii) time-resolved fluorescence of chromatin - proflavine complexes, and (iii) fluorescence resonance energy transfer (FRET) between dansyl chloride and acridine orange coupled to chromatin. For both normal and tumor chromatin, the intensity of intrinsic fluorescence specific for acidic and basic proteins decreased with increasing dose. The relative contributions of the excited-state lifetime of proflavine bound to chromatin were reduced upon fast-neutron irradiation, indicating a decrease in the proportion of chromatin DNA available for ligand binding. The Forster energy transfer efficiencies were also modified by irradiation. These effects were larger for chromatin from tumor tissue. In the range 0-100 Gy, fast neutrons induced alterations in DNA and acidic and basic proteins, as well as in global chromatin structure. The radiosensitivity of chromatin extracted from tumor tissue seems to be higher than that of chromatin extracted from normal tissue, probably because of its higher euchromatin (loose)--heterochromatin (compact) ratio.
The absorption, excitation and emission spectra of methotrexate (MTX) solutions in natural saline water and sodium hydroxide at 10(-4)-10(-5) MpH=8.4 were measured, while they were exposed to coherent and uncoherent visible and near ultraviolet (UV) light. Xe and Hg lamp and also a nitrogen pulsed laser radiation were used. The absorption spectra exhibited spectral bands between 225 nm and 450 nm. The 200 nm - 500 nm excitation spectra were measured with emission centred on 470 nm; fluorescence excitation was observed at 340 nm and 370 nm; emission fluorescence was detected between 400 nm and 600 nm, showing a maximum at 470 nm. Spectra modifications, non-linearly depending on exposure time (varying from 3 min to 180 min), indicated the photodissociation of MTX to the fluorescent compound 2,4 diamino-formylpteridine. In a preliminary in vivo experiment, rapid destruction of neovascularisation was observed in the MTX-impregnated conjunctive of the rabbit eye exposed to uncoherent UV and visible light.