Changes in the magnitude and pattern of translocation of photoassimilated ¹CO in soybean plants following an acute exposure to gamma radiation /

Young soybean plants (Glycine ~. L. cultivar Harosoy '63), grown under controlled conditions, were exposed to gamma radiation on a single occasion. One hour following exposure to 3,750 rads, the mature trifoliate leaf of the soybean plant was isolated in a closed system and permitted to photoassimilate approximately 1-5 pCi of 14C02 for 15 minutes. After an additional 45 minute-period, the plant was sacrificed and the magnitude of translocation and distribution pattern of 14C determined. In the non-irradiated plants 18~ of the total 14C recovered was outside the fed leaf blades and of this translocated 14c, 28~ was above the node of the fed leaf, 38~ in the stem below the node, 28~ in the roots and 7~ in the petiole. As well, in the irradiated plants, a smaller per cent (6~) of the total 14 C recovered was exported out of the source leaf blades. Of this translocated 14c , a smaller per cent (20~) was found in the apical region above the node of the source leaf and a higher per cent (45~) was recovered from the stem below the node and in the petiole (11~). The per cent of exported 14 C recovered from the root was unaffected by the radiation. Replacement of the shoot apex with 20 ppm IAA immediately following irradiation, only J partially increased the magnitude of translocation but did completely restore the pattern of distribution to that observed in the non-irradiated plants. From supplementary studies showing a radiationinduced reduction of photosynthetic rates in the source leaf and a reduction of the cumulative stem and leaf lengths in the apical sink region, the observed effects of radiation on the translocation process have been correlated to damage incurred by the source and sink regions. These data suggest that the reduction in the magnitude of translocation is the result of damage to both the source and sink regions rather than the phloem conducting tissue itself, whereas the change in the pattern of translocation is probably the result of a reduced rate of 14C-assimilate movement caused by a radiation-induced decrease of sink metabolism, especially the decrease in the metabolism of the apical sink.

A relationship between photosynthesis and translocation in plants stressed by ionizing radiation

Since previous investigations have shown that low levels of ionizing radiation can induce a reduction in the rates of apparent photosynthesis and in the magnitude of photoassimilated l4C exported out of a leaf, the present studies were designed and conducted to determine the relationship, if any, between the radiation effects on these two physiological processes. The experiments were particularly designed to determine if the radiation-induced reduction in export is the result of the reduction in photosynthesis and hence availability of materials for translocation or the result of a reduction in the amount of energy available for the vein loading process. This study has shown that the radiation-induced reduction in l4C export out of a leaf is likely related to a loss of energy available for the vein loading process rather than a reduction in the supply of materials available for export due to reduced C02 uptake. The process of photophosphorylation was shown to be reduced by exposure to radiation to an extent similar to the reduction in the export of l4C which was also observed. Both of these processes returned to their pre-irradiation rates 120 minutes following radiatruon exposure. The rate of photosynthetic C02 uptake was also reduced by radiation exposur~ howeve~ this process did not return to the control level nor was the extent of reduction as large as observed for photophosphorylation and photoassimilate export. The observed relationship between the reductions of export and photoph~sphorylation pointed to the utilization of photosynthetically produced ATP in the vein loading process. The radiation-induced reduction in the export of l4C was observed at the highest light intensity used in this study which would also imply the involvement of the photophosphorylation process as an energy seurce for vein loading. The lack of radiation-induced reduction in export at low light intensities was interpreted as being due to the utilization of respiratory derived ATP, a process known to be insensitive to radiation at the levels used in this study, as the energy source for the vein loading process. Studies using plants not stressed by radiation showed that there was an increase in export of 14C with higher light intensities. In summary, the data has been interpreted as showing that at high light intensities the ATP, produced by photophosphorylation, is available for use in the vein loading process. The site of ATP utilization could not be determined from the data obtained in this study but possible sites have been indicated from the work done by other physiologists and are discussed in the thesis.

Identifying the psychosexual implications of radical radiation treatment in prostate cancer

The purpose of this study was to determine whether there was any evidence of psychosexual morbidity among men who experienced radical radiation treatment for prostate cancer. With relatively little known or available retrospective data on the psychosexual implications of radical radiation treatment in men with prostate cancer, this study posited eight research questions which provided the basis for the research. Fifty men from Southern Ontario, between the ages of 52 to 78 years, were included in the study. They had been previously randomized to a clinical trial comparing radical radiation therapy by external beam radiation, or radical radiation using a combination of a temporary iridium implant plus external beam radiation, for localized or locally advanced prostate cancer. Assessment of sexual functioning, drive, attitudes, body image, and sexual satisfaction was drawn from a multidimensional approach, since psychosexuality was viewed as having an impact on biological, psychological, and sociological domains of functioning. Medical chart reviews, semi-structured interviews, demographical profiles of each participant, and the Derogatis Sexual Functioning Inventory (DSFI) were the methods used to collect data over a four-month period. Both quantitative and qualitative research methods were incorporated in the design and evaluation of the study. Frequencies, contingency analysis, Pearson's coefficient of correlation, t-tests, and ANOVA comprised the quantitative analysis. Data obtained from audio-taped interviews were analyzed qualitatively, and used for offering further insight and for facilitating the quantitative aspect of the analysis. Overall, there was sufficient evidence to suggest psychosexual morbidity among men who were treated with radiation therapy for prostate cancer. As well,there were a number of significant findings available to answer all of the posited research questions. The most significant findings were noted in post-treatment erectile ability and sexual activity. A post-treatment change in erectile ability was reported by eighty percent of men. Sixty percent of men noted a decrease in their ability to achieve an erection by reporting some morning stiffness only, penile rigidity insufficient for penetration, decreased control of erection, and loss of spontaneous erection. Other contributing factors associated with change in erectile status were: pain or altering sensation of orgasm, blood in ejaculate, pain and decreased amount of ejaculate, and penile numbness or pain. Eighty-two percent of men experienced a post-treatment change in sexual function, primarily due to the impact of decreasing erectile status. Only seven men reported that they experienced a decrease in desire mentally, whereas the vast majority did not experience any change in desire. Changes in foreplay, stress with optimal sexual positioning, and reduced spontaneity of sex, were other factors reported with the changes in sexual activity. The findings in this study broaden our understanding of what middle- to later-aged men feel and experience as they venture onward following treatment. This was the first study that evaluated available prospective data on pre-treatment erectile status and sexual activity. As well, this study was the first (with participant compliance rates of 100 percent) to have included an interview format to capture the views of such a large number of men. This study concluded with recommendations and implications for future research and practice as we move in the direction of understanding what is necessary for preserving psychosexual well being and enhancing quality of life in men treated with radiation therapy for prostate cancer.

Radiation-induced changes in the export of photoassimilated carbon /|nBarry Jess Shelp. -- 260 0 St. Catharines, [Ont. : s. n.],

Low levels of ionizing radiation induce two translocation responses in soybean: a reduction in photoassimilate export from leaves and a change in the distribution pattern of exported photoassimilate within the plant. In this investigation these responses have been further studied specifically to ascertain the site of radiation damage and to better understand the physiological responses observed. Experimentally the primary data was obtained from studies in which a mature trifoliate leaf of a young soybean plant (Glycine ~ L. cultivar Harosoy '63) is isolated in a closed transparent chamber and allowed to photoassimilate 14C02 for 15 minutes. This is followed by an additional 45 ~_il'1;ute period before the plant is sectl.o ne d an d 14 C-ra dl' oactl.v.l ty d eterml. ne d'l n a 11 parts. Such 14c data provides one with the magnitude and distribution pattern of translocation. Further analyses were conducted to determine the relative levels of the major photosynthetic products using the techniques of paper chromatography and autoradiography. Since differences between control and irradiated P 1 ants were not 0 b serve d l' n t h e par tl't"lo nlng 0 f 14 C between the 80% ethanol-soluble and -insoluble fractions 14 or in the relative amounts of C-products of photosynthesis, the reduction in export in irradiated plants is not likely due to reduced availability of translocatable materials. Data presented in this thesis shows that photoassimilate export was not affected by gamma radiation until a threshold dose between 2.0 and 3.0 krads was reached. It was also observed that radiation-induced damage to the export process was capable of recovery in a period of 1 to 2 hours provided high light intensity was supplied. In contrast, the distribution pattern was shown to be extremely radiosensitive with a low threshold dose between .25 and .49 krads. Although this process was also capable of recovery,lt" occurred much earlier and was followed by a secondary effect which lasted at least for the duration of the experiments. The data presented in this thesis is interpreted to suggest that the sites of radiation action for the two translocation responses are different. In regards to photoassimilate export, the site of action of ionizing radiation is the leaf, quite possibly the process of photophosphorylation which may provide energy directly for phloem loading and for membrane integrity of the phloem tissue* In regards to the pattern of distribution of exported photoassimilate, the site is likely the apical sink, possibly the result of changes of levels of endogenous hormones. By the selection of radiation exposure dose and time post-irradiation, it is possible to affect independently these two processes suggesting that each may be regulated independent of the other and involves a distinct site.