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R Ramponi

Publications and source records attributed to R Ramponi.

28 records · Page 2Linked to original sources
PubMed1986

Effects of hematoporphyrin-derivative on mouse erythroleukemia cells in the absence of light irradiation.

This paper concerns a general study on the effects of hematoporphyrin-derivative (HpD) on mouse erythroleukemia (MEL) cells, in the absence of light irradiation. In particular, HpD intrinsic cytotoxicity was evaluated at different doses and the results correlated with those referring to membrane functional and morphological changes. HpD uptake and release processes were also studied and compared with the above-mentioned results. In order to have an overall picture of HpD-cell interactions, time-resolved fluorescence measurements were performed on both undifferentiated and differentiated MEL cells. The results obtained indicate that, even at HpD doses exhibiting neither any cytotoxicity nor any morphological damage (1-10 micrograms/ml), membrane permeability alterations are observed. Thirty minutes of treatment are sufficient for HpD to develop its toxic effect: indeed, no differences in HpD influence on cell viability can be observed after 30 min, 60 min or 5 days of treatment. HpD cytotoxicity is reduced by high protein content in the incubation culture medium. The presence of both monomeric species and 580 nm emitting species was observed at cellular level. The latter is likelier in undifferentiated MEL cells, which also exhibit higher overall HpD uptake, as compared with differentiated MEL cells.

Animals↗
PubMed1984

The time-dependent behaviour of hematoporphyrin-derivative in saline: a study of spectral modifications.

Hematoporphyrin-Derivative (HpD), a widely-used tumor-specific photosensitizer, is a complex mixture of porphyrins whose composition has yet to be clarified. This paper reports on the behaviour of HpD in saline. From a spectroscopic point of view, the fresh solution is characterized by two main absorption peaks, attributable to monomeric and dimeric forms. With aging, a new porphyrin species (NPS) appears. To define the NPS, absorption, excitation and emission spectra were measured in different conditions and time-resolved fluorescence measurements were also performed. This species exhibits an absorption/excitation peak at 405 nm, an emission peak at 575 nm and a fluorescence decay time of approximately 3.5 ns. Its formation is strongly influenced by many environmental factors: in particular, gases diluted in the solution, temperature, pH and concentration. The presence of Oxygen and a pH value outside the 6-8 range may be considered inhibiting factors. The NPS seems to be quite important in the understanding of HpD tumor-specificity, since the presence of an emission band similar to the NPS one seems to be favoured in tumor cells as compared with normal cells.

Hematoporphyrin Derivative↗
PubMed1984

Time-resolved fluorescence spectroscopy of hematoporphyrin-derivative in human lymphocytes.

This paper reports on time-resolved microfluorimetric measurements on hematoporphyrin-derivative (HpD)-treated lymphocytes. HpD is at present widely used as a tumor-locating and photosensitizing drug. It is therefore of great importance to study the extent to which the HpD uptake process depends on cell functional and structural properties. Time-resolved fluorescence measurements in single cells are very useful in this respect, since they give information on the content of fluorescent molecules through fluorescence peak-intensity, and, indirectly, on the binding properties through the fluorescence decay times. In particular, we studied the dependence of HpD fluorescence on the cellular functional state. To this end, we performed in-cell fluorescence measurements on human lymphocytes, both in quiescent conditions and in the pre-replicative phase, after stimulation with phytohemagglutinin (PHA). We found a higher HpD content in stimulated lymphocytes. Moreover, we found a spectral band around 575 nm, corresponding to a particular porphyrin species, in which the differences between normal and stimulated lymphocytes are more striking. The porphyrin species emitting in this band seems to play a role in the specific interaction of HpD with tumors, since a similar emission band has also been found in tumor cells containing HpD.

Hematoporphyrin Derivative↗
PubMed1984

Spectroscopic studies of hematoporphyrin-derivative in culture medium.

This work reports on studies of hematoporphyrin-derivative (HpD) behaviour in culture medium. Absorption, excitation and emission spectra, together with time-resolved fluorescence measurements, were performed. In previous works, similar studies had been carried out on HpD in saline and in lymphocytes: a new porphyrin species (NPS) and the environmental conditions for its formation in saline were studied. A fluorescent emission similar to that presented by the NPS is reported to be more likely in tumor rather than in normal HpD-treated cells, it was also found in greater amounts in lymphocytes in the pre-replicative phase, as compared with quiescent ones. The higher NPS content in stimulated rather than in quiescent lymphocytes may be due either to a differential uptake, as compared with other HpD components, or to a differential formation rate in cells, because of different microenvironmental conditions. To distinguish between these two main assumptions, the formation of NPS in culture medium was studied. The process was very slow: no NPS appeared within the first 40 h. The incubation time of lymphocytes in culture medium added with HpD in the experiments performed was only 1 h and therefore a differential formation rate of NPS may explain the higher content found in stimulated lymphocytes.

Culture Media↗
PubMed1984

An automatic pulsed laser microfluorometer with high spatial and temporal resolution.

The paper describes an automatic pulsed laser microfluorometer with high spatial and temporal resolution, developed in our laboratories. The instrument consists of: (i) a nitrogen-laser-pumped dye-laser for the excitation of the fluorescence, (ii) a microscope with additional optics to focus the excitation beam on the sample and to collect the fluorescence, (iii) filters or monochromators to select the output wavelength, (iv) a fast photomultiplier tube to detect the signal, and (v) a dual time-scale microprocessor-controlled signal averager for the acquisition and processing of the signal. Examples are given that show the potential of the time-resolved fluorescence microscopy in studying, quantitatively and qualitatively, the properties of fluorescent molecules.

Animals↗
PubMed1982

Time-resolved fluorescence microscopy of hematoporphyrin-derivative in cells.

This work presents measurements of time-resolved fluorescence microscopy of hematoporphyrin-derivative (HpD) in single cells of mice tissue (both tumor and normal cells), in HeLa Cells, and in solution. The measurements were performed using a pulsed-laser microfluorometer with high spatial and temporal resolution. In agreement with the results obtained with other techniques, it has been found that the tumor cells examined present an HpD uptake about five times higher than that of the normal cells of the corresponding tissue and that, within a cell, HpD become localized mainly in the cytoplasm. It has also been found that the fluorescence decay time is different in cells as compared with solution, and that the presence of HpD stabilizes cell auto-fluorescence. These results are discussed.

Animals↗