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The Delayed Luminescence of temperature sensitive Saccharomyces Cerevisiae CDC 28-1 was measured under two different conditions: firstly yeast maintained at the restrictive temperature of 38.5 °C for some hours (and for this should be at the same step of the division cycle ) and secondly samples that remained always at 23 °C.
In both cases DL shows a typical hyperbolic trend but the DL parameters appears to be different according to the previous history of the culture.
The connection between the DL parameters and some parameters of the culture (thermal treatment, glucose contents of extracellular liquid, density and age of the culture) has been evinced.

Ionizing Radiation

In the framework of the interaction between the ionizing radiation and the biological systems, the analysis of ultraweak luminescence could give information towards the answer of living systems to radiation. In particular the analysis of ultraweak luminescence, giving very sensitive indication of the functional state of the biological system, could be particularly useful to study the effect of the ionizing radiation low doses.
Preliminary results were obtained on the measurement of photoinduced luminescence on biological samples that were irradiated by gamma rays, X rays and UV at doses where it has been possible to measure a change of the biological behaviour of the samples.
The lettuce seeds were irradiated by 6 MeV gamma rays at different doses (0.1, 1, 10 and 100 Gy). The measured biological effect was the production of mass. It is possible to observe a good discrimination of the biological effect due to the different doses. The parameters connected to growth and delayed luminescence were respectively the production of mass and the total radiation after the illumination of the sample; from the analysis of the above parameters it is possible to observe the total counts showing the same trend as the growth, inside the experimental errors.
In collaboration with other researchers from Modena University (I) delayed luminescence from yeast cell was measured irradiated by soft X-rays. The total remitted radiation for this experiment also shows a monotonic decrease vs the X-rays dose.
The above preliminary results were obtained for relatively high doses and showed that equally in the case of damage induced by ionizing radiation it is possible to discriminate the effects by means of an ultraweak luminescence analysis. Besides, once this correlation at high doses will have been experimentally consolidated, one should try to make the experiments at low doses where the peculiarity of the proposed analysis is more suitable. At low doses, in fact, the interesting biological mechanisms from ionizing radiation seem to be attributed to a different cellular answer and for this reason the ultraweak luminescence should be sensitive enough, since it reflects the behaviour of the whole system, that is strictly connected to the behaviour of the cellular mechanism.

Publications in this field:

1) D. Batani, A. Conti, A. Masini, M. Milani, M. Costato, A. Pozzi, E. Turcu, R. Allot, N. Lisi, F. Musumeci, A. Triglia "Biosystem Response to Soft X-Rays Irradiation: Nonmonotonic Effects in the Relevant Biological Parameters of Yeast Cell" Il Nuovo Cimento D - 18 (1996) 657-662
2) A. Triglia, F. Musumeci, A. Scordino, G. Blandino, I. Milazzo, A. Zgierun "Ionizing Radiations and Ultraweak Luminescence" 2° Convegno Nazionale Congiunto SIRR-GIRR, Palermo, 11-14 Settembre 1996

Acetabularia

To study the connection between stress condition and DL behaviour, several experiments are performed on Acetabularia Acetabulum. In particular we are studying:

1. the dependence of the emission spectrum on temperature.

These spectra show a very weak dependence on temperature; it appears that, on decreasing the temperature the spectrum moves towards higher frequencies while a measurable change of form is not noticed.
2. the dependence of dynamics on the wavelength and on the intensity of the source.

There is a small but clear change in the slope of the curves dependent on the excitation wavelength. On the other hand there is a strong dependence of the slope on the intensity of illumination. In fact, on increasing the intensity of the illumination source the slope of the curves increases up to a saturation value. The slope Then begins to decrease while characteristic oscillations appears.
Another aspect of the problems connected to the interpretation of the dependence of the dynamics on the intensity of the source is the fact that the same A.A. sample illuminated with light of the same frequency and with the same times of illumination but with different intensities present decay curves that often cross each other.
This fact is incompatible with a simple description of the phenomenon involving the population and the following depletion of electronic levels.
3. the dependence of dynamics on temperature.

As it concerns the dependence of dynamics on temperature the existence of two regimes is evident: in the first regime, which is the range of temperature within which the Acetabularia could survive, it is possible to bring the Acetabularia to the initial conditions again , even if not immediately but following a kind of cycle; instead in the second regime, characterised by excessively high temperatures, the D.L. emission from the Acetabularia decreases in a irreversible way and after some time the sample dies.
This decreasing of the DL emission probably is connected to the damages the extreme temperatures causes on the functional structure of the Acetabularia. In fact even if, after a rapid freezing in liquid air, an Acetabularia sample is brought again to its normal temperature, the DL emission practically disappears as in the samples submitted to high temperatures.
4. the dependence of dynamics on some specific ions

It seems that the presence of Ca++ seems to produce a strong decrement both of the total number of excited levels and of the decay probability.
In fact if it is present only Na+ and Ca++ the total number of excited levels go down very speedily (reaching 10% of the initial value in about 1 hour) and the Acetabularia appear strongly damaged.
The presence of others cations K+ and Mg++ seems to reduce the effect of Ca++. In fact if they are presents together the Acetabularia lives a long time and its DL is quite constant. Moreover if only they are present there is no big effect on the behaviour of DL at least in the first hours.
This fact is confirmed also if only K+ is present for the first 4 hours. On the contrary the presence of Mg++ produce strong changes of DL.
Moreover it is shown clearly that the decreasing of the absolute value of the membrane potential causes a quenching of the D.L. with a diminution of the total number of excited centres and an increase of the decay probability.

1) F. Musumeci, M. Godlewski, F. A. Popp and M.W. Ho "Time Behaviour of Delayed Luminescence in Acetabularia Acetabulum" Recent Advances in Biophoton Research, F.A. Popp, K.H. Li and Q. Gu Eds, World Scientific, Singapore (1992) 307-326
2) A. Scordino, F. Grasso, F. Musumeci, A. Triglia "Physical Aspects of Delayed Luminescence in Acetabularia Acetabulum" Experientia, 49 (1993) 702-705
3) F. Musumeci, A. Scordino, A. Triglia "Interaction between the Visible Electromagnetic Field and the Living Matter: Experimental Basis for a Biophysical Approach" Current Development of Biophysics, C. Zhang, F. A. Popp and M. Bischof Eds, Hangzhou University Press, 1996
4)Musumeci F., Scordino A., Triglia A. "Delayed Luminescence from Simple Biological Systems" Rivista di Biologia Biology Forum (1997) in press.

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