Influence of occupational exposure to low-dose ionizing radiation on the plasma activity of superoxide dismutase and glutathione level.

BACKGROUND/AIM: During exposure to low-level doses (LD) of ionizing radiation (IR), the most of harmful effects are produced indirectly, through radiolysis of water and formation of reactive oxygen species (ROS). The antioxidant enzymes--superoxide dismutase (SOD): manganese SOD (MnSOD) and copper-zinc SOD (CuZnSOD), as well as glutathione (GSH), are the most important intracellular antioxidants in the metabolism of ROS. Overproduction of ROS challenges antioxidant enzymes. The aim of this study was to examine if previous exposure to low doses of IR induces adaptive response by means of stimulation of intracellular antioxidant defense system. METHODS: We investigated a group of medical workers occupationally exposed to IR (n = 44), 29 male and 15 female. The controls (n = 33) consisted of medical workers not exposed to IR, 23 male and 10 female. The examinees from both groups worked in the same environment and matched in crucial characteristics. All measurements were performed by a calibrated thermoluminiscent dosimeter type CaF2:Mn. SOD activity and GSH content were measured spectrophotometrically in the plasma of both groups of medical workers. Half of each blood sample was irradiated by 2Gy of gamma radiation, dose-rate 0.45 Gy/min, and the distance from the source of 74 cm. RESULTS: The dosimetry results indicate that occupational doses were very low. Our results confirmed significantly higher SOD activity in the exposed vs. unexposed workers (p < 0.00006). SOD activity after irradiation of blood samples failed to show a significant difference between the exposed workers and the controls (p = 0.905), even the difference in each group before and after the irradiation was significant. In blood samples of the exposed workers expression of enzymes after the irradiation, was not as high as in the controls, or even in the case of the exposed in nuclear medicine personnel, SOD activity was decreased. There were no significant differences in the content of GSH between the groups. CONCLUSION: Our results pointed out that occupational exposure to low doses of IR compromised mitochondrial function. During occupational exposure, the activity of antioxidant enzymes was increased as a protection against the increased production of ROS. After high-dose irradiation dysfunction of mitochondrial system was noticed, suggesting the break-down of antioxidant defense and failure of an adaptive response. Therefore, the "chronic oxidative stress" might reduce antioxidant defense in the case of accidental exposure to high doses of IR. It could indirectly increase the incidence of some other "free radicals' diseases" in occupationally exposed personnel.

[Occupational exposure to ionizing radiation and the occurrence of cataract]. / Profesionalna ekspozicija jonizujucem zracenju i katarakta.

Radiation cataract is one of ensuing effects of ionizing radiation, since its threshold dose under which it does not occur, and above which it shows dose dependency, has been observed. Clinical course of radiation cataract is identical for all the types of ionizing radiation and is very typical. Minimal dose for progressive cataract formation is determined by the type of radiation, i.e., its relative biological efficacy, dose, and the duration of the exposure period. Theoretically, threshold dose existence does not exclude the incidence of cataract formation under significantly smaller doses, as well. The aim of this study was to analyze the incidence of cataract formation among the medical staff professionally exposed to ionizing radiation. Neither of the diagnosed cataracts had typical morphology, nor was the correlation established between the dose, exposure time, and the cataract formation. All the diagnosed cataracts were described as premature, and therefore ionizing radiation was considered as a co-factor in premature cataract formation in the examined groups.

[Endothelial trauma in the surgery of cataract]. / Trauma endotela kod hirurskog lecenja katarakte.

Cataract surgery is most common in human surgery and comprises 80% of eye surgery programs. Owing to sophisticated technologies, it has become a routine surgery with lowered complications rate; hence, the functional outcome is more conditioned by operative trauma. The aim of this study was to demonstrate the significance of specular microscopy in the evaluation of operative trauma during extracapsular cataract extraction (ECCE) and phacoemulsification (P), in a controlled environment. The study included 100 consecutive patients who met the established criteria, and groups were formed according to the type of surgery by the assignment of successive numbers from a random number table. Examination and photographs of the corneal endothelium, as well as pachymetry were performed on Keeler-Konan Poclington Specular Microscope (KSP). The obtained results revealed significant dissimilarity in endothelial cell reduction (9.17% in group E, and 4.72% in group P), which generated statistically significant correlation of preoperative and post-operative pachymetry in the group E (p=0.0004). On the basis of the results obtained by specular microscopy, it was concluded that under the same conditions phacoemulsification caused reduced operative trauma of the corneal endothelium.