Some aspects of radiation effects on cell membranes

Association of Therapeutic Radiation with Golgi Complex Hypertrophy in Human Urinary Bladder Carcinomas: Quantitative Electron Microscopy Studies

The volume (Vv) and surface area (surface density; Sv) of the Golgi complex were measured by electron microscopy stereologic techniques in 17 patients with urinary bladder transitional cell carcinomas. Seven patients were irradiated prior to surgical removal, 4 had recurrent carcinomas that arose from previously irradiated bladder urothelium, and the remaining 6 patients had bladder carcinoma but no prior history of therapeutic irradiation. There were significant differences in the Vv and Sv of Golgi complexes per unit of cytoplasmic volume in carcinomas from irradiated and nonirradiated patients (p < 0.01). In carcinomas obtained from irradiated urinary bladders, the Vv was 3.45 +/- 0.24% (mean +/- SE). In contrast, the Vv was 0.98 +/- 0.15% for tumors in the nonirradiated group. Sv values were 1.51 +/- 0.09 microm2/microm3 in carcinomas from irradiated bladders, and in the nonirradiated group, the mean Sv was 0.76 +/- 0.07 microm2/microm3. These results support the hypothesis that therapeutic irradiation to the urinary bladder induces hyperplasia of Golgi complexes.

Influence of glutathione on the induction of chromosome aberrations, delay in cell cycle kinetics and cell cycle regulator proteins in irradiated mouse bone marrow cells

PURPOSE

Reduced glutathione (GSH) is an endogenous thiol and has long been thought to affect the sensitivity of cells to radiation. The aim was to see the influence of GSH on: (i) the production of all types of radiation-induced chromosome aberrations (CA), and (ii) the radiation-induced delay in cell cycle and the levels of cell cycle regulator proteins.

MATERIALS AND METHODS

Cell cycle kinetics were determined by scoring the mitotic index (MI). CA and MI were scored in gamma-irradiated buthionine sulfoximine (BSO) (10 h) or GSH (1 h) pretreated and untreated mouse bone marrow cells (BMC). The expression of p53 and p21 proteins after 2 and 6 h of irradiation and for the B-cell lymphoma 2 (Bcl-2) associated X-protein (Bax) after 24 h of irradiation with or without BSO or GSH treatment was analyzed by immunoblotting.

RESULTS

Radiation delays mouse BMC in their passage through the cell cycle and induces CA. Exogenous addition of GSH protected CA uniformly at lower doses of radiation but differentially at higher doses, whereas GSH-depletion by BSO increased the frequency of radiation-induced CA. Both GSH and BSO-pretreated cells reduced the delay in cell kinetics after irradiation. Levels of both p53 and p21 were enhanced after irradiation to BSO-pretreated cells. However, in GSH-pretreated cells the level of these proteins was reduced.

CONCLUSION

Data indicate that the induction of CA and delay in cell kinetics by radiation may not always be interlinked and that the level of endogenous GSH exerts its influence on these parameters. Both GSH and BSO pretreatment reduce delays in cell kinetics of irradiated cells which may die apoptotically, since they have either a higher frequency of exchange aberrations or CA, respectively.

Influence of endogenous glutathione level on X-ray induced cell cycle delay in human lymphocytes

Here, induction of chromosomal aberration after X-irradiation and the pattern of cell cycle kinetics have been investigated in human lymphocytes, after exogenous addition of reduced glutathione or by depleting levels of reduced glutathione endogenously. Involvement of cell cycle regulator proteins such as p53 and p21 has been investigated to elucidate their role in induction of delay in cell cycle progression after irradiation.

The influence of radiation quality on radiation-induced hemolysis and hemoglobin oxidation of human erythrocytes

Human erythrocytes were exposed to gamma-rays and alpha-particles to assess radiation-induced membrane damage and hemoglobin oxidation and denaturation. With all parameters measured, the alpha-particles proved to be less efficient than the gamma-rays. The time-dependence of hemolysis showed also clear differences: with the gamma-rays the process was faster, reaching saturation after 40-90 min (depending on dose), but with the alpha-particles the final level was attained only after about 3-7 h. Hemoglobin oxidation and denaturation could be measured only after gamma-exposure, but they were negligible with the alpha-particles when comparable doses were applied. These results are interpreted by proposing that OH-radicals, whose yields are smaller with densely ionizing radiation, play a crucial role in the induction of the processes for radiation-induced erythrocyte damage.

Dose-dependency of radiation on enzyme production in Trichoderma reesei

Effect of irradiation dose on the production of cellulase and amylase related enzymes in Trichoderma reesei was studied, in which post-irradiation time response pattern was measured. The damage of the cells irradiated with certain irradiation doses (1.40 +/- 0.20 x 10(5), 2.20 +/- 0.10 x 10(5), 3.00 +/- 0.50 x 10(5) and 3.50 +/- 0.20 x 10(5) rad) was rapidly recovered. The increased enzyme production in the culture of the irradiated cells resulted from the recovery of radiation damage after irradiation. The function of cell growth was not affected by irradiation below dose of 5 x 10(5) rad, though the function of enzyme synthesis was drastically affected.

Irradiation of Langmuir-Blodgett multilayer preparations of phospholipids and a fatty acid. 1: Effect of UV radiation

Langmuir-Blodgett (LB) preparations containing stacked monolayers of phospholipids or stearic acid were irradiated with UV light and the electric conductance perpendicular to the planes of the monolayers was measured. There was no observable change of conductance when LB preparations of stearic acid were irradiated. For LB preparations of phospholipids, a rise of conductance, dependent on dose rate, was observed, reaching an equilibrium level after a few hours. After irradiation the conductance fell with a temperature-dependent time constant, and eventually reached a final level a little above the initial value. A three-state model is proposed for the LB phospholipid preparations. This suggests that the absorption of one photon raises a molecule from the ground to an excited state; and the absorption of a second photon carries it into a damaged but repairable or metastable state.

Rubidium transport in X-irradiated human erythrocytes

Outflow of 86Rb, a radioactive analogue of potassium, from human erythrocytes X-irradiated in vitro was studied with the following results. (1) The 86Rb level in the supernatants of irradiated and control cell suspensions reflected mainly 86Rb outflow and much less its active re-uptake. (2) The effect of irradiation on 86Rb outflow was more pronounced at a low temperature (4 degrees C) than at 37 degrees C; the lowest dose of X-radiation exhibiting a significant effect on 86Rb outflow at 4 degrees C was 2.5 Gy. (3) K/Rb exchange did not seem to play an appreciable role in radiation-induced 86Rb outflow. (4) Calcium and its accumulation in irradiated cells was not found to be the cause of the effect of radiation on 86Rb outflow. (5) The effect of radiation on 86Rb outflow was higher in low Na medium but it was not inhibited by bumetanide. Rb/Na counter- or co-transport do not therefore seem to be involved in radiation-induced Rb+ outflow.

Vestibular hair cell pathology following low-dose irradiation during embryonic development

Pregnant CBA/CBA mice (total gestational age 20-21 days) were whole-body irradiated on the 12th, 13th and 16th gestational days with single doses of 1 and 2 Gy using a 60Co source. Litters were taken for morphological analysis 14-21 days after birth. Irradiation on the 12th and 13th gestational days was thus performed prior to morphologic inner ear organogenesis and cytodifferentiation. In approximately 20% of the total postnatal vestibular hair cell population cytological alterations were evident: giant cytoplasmic protrusions, sensory hair fusion and disintegration of the cuticular plate. The other parts of the hair cells remained intact, including nerve endings. Morphometry was not performed. Hair cells type I are more vulnerable to ionizing irradiation during cytodifferentiation than hair cells of type II. All investigated animals showed clinically a normal balance and a normal righting reflex.

Effect of gamma radiation on enzymatic activity and sulphydryl groups of human erythrocyte membrane

The effect of ionizing radiation on human erythrocyte ghost membranes was studied by following changes in membrane -SH groups and activities of four membrane bound enzymes: Na+K+Mg2+ ATP-ase, Mg2+Ca2+ ATP-ase, Na+K+ATP-ase, and AChE. Irradiation up to 100 Gy gamma X-rays produced a significant decrease in the activity of ATP-ase and an increase in AChE activity. At higher radiation doses a marked decrease in the activities of all the enzymes was observed. A correlation between radiation-induced perturbations in enzyme activities and changes in membrane -SH groups was found.

The effect of ionizing radiation on tryptophan fluorescence of thymocyte and erythrocyte plasma membranes

The effect of ionizing radiation on tryptophan fluorescence of thymocyte and erythrocyte plasma membrane preparations was studied. The intensity of tryptophan fluorescence decreased after applying radiation doses up to 15 Gy. The radiosensitivity of thymocyte membranes appeared to be higher than that of the erythrocyte ghosts. Tryptophan radiolysis did not significantly contribute to the effects of radiation. The fraction of tryptophan residues accessible for quenching by I- decreased from 0.87 in the untreated membranes to 0.63 and 0.49 in membranes after doses of 10 and 250 Gy, respectively. The effective quenching constant and the tryptophan fluorescence polarization increased after irradiation. The mechanisms producing these radiation-induced changes are discussed.

Chemical damage in gamma-irradiated human erythrocyte membranes

In air saturated suspensions of erythrocyte ghost membranes gamma-irradiation causes formation of lipid peroxides, measured as malonaldehyde, and a loss of membrane protein sulphydryl groups. Addition of N-(p-amino-benzoyl)-1-glutamate prevented peroxidation up to doses of 2 x 10(3) Gy, due to scavenging of hydroxyl radicals. Another hydroxyl scavenger sodium formate, also prevented peroxidation at low doses, but lost its protective effect at higher doses probably because of secondary reactions of the resulting superoxide radical anion. Two sulphur containing radioprotectants also were able to reduce the extent of lipid peroxidation. The enzymes catalase and superoxide dismutase were added to the irradiated suspensions in order to determine the contribution from hydrogen peroxide and superoxide to peroxidation. The extents of peroxidation are compared with structural modification of the membrane under the same conditions of irradiation.

Structural modification of human erythrocyte membranes following gamma-irradiation

Structural damage to isolated erythrocyte membranes ('ghosts') has been studied following gamma-irradiation under a variety of conditions. For this two fluorescent probes were used; one 1-anilino-8-naphthalene sulphonate probes the lipid-aqueous interface, the other, diphenylhexatriene, was used to probe the membrane fluidity. Irradiation of the membranes caused a decrease in fluorescent intensity of the added probes, and changes in polarization of fluorescence. Oxygen was found to enhance the radiation damage, and scavenger experiments showed the hydroxyl radical was the major radical species involved. The structural modifications are therefore interpreted in terms of preliminary chemical damage involving peroxidation of unsaturated lipids. In addition sensitization and protection was observed in the presence of known dose-modifying chemicals.

Radiation killing of E. coli K1060: role of membrane fluidity, hypothermia and local anaesthetics

The enhancement of killing by gamma-irradiation, which is seen when E. coli K1060 are cooled below the transition temperature of their membrane lipids, is blocked by procaine-HCl. These data are consistent with the hypothesis that increased killing associated with irradiation at 0 degree C is the result of membrane microviscosity increases, since procaine is known to fluidize membranes. A cooling enhancement ratio (c.e.r.) is defined as the ratio of radiation D0 at 22 degrees C to its value at 0 degree C. The c.e.r. for oxygen-bubbled cells is 1.5 and for nitrogen-bubbled cells is 2.1. In the presence of 25 mM procaine the respective c.e.r. values are 1.08 and 1.29. The oxygen enhancement ratio (o.e.r.) at 22 degree C is 3.43 and at 0 degree C is 2.45. The addition of procaine does not change the o.e.r. Thus, the temperature effect on o.e.r. does not appear to be related to membrane fluidity.

Cytoplasmic effects of x-irradiation on cultured cells in a nondividing stage. 1. Establishment of an experimental model

The investigation was initiated with the aim of establishing a suitable experimental model with respect to mode of radiation and radiation dose for elucidating morphologically the sequential development of radiation induced damage of interphase cells (human glia cells in vitro). Adequately defined and reproducible cellular changes were obtained using X-radiation generated by an 8 MeV linear accelerator at a dose of 20,000 rad. The cellular alterations were studied in the light microscope and by scanning and transmission electron microscopy. The most conspicuous changes--first appreciable about 5 hours after irradiation--occurred in the lysosomal vacuome, and the plasma membrane and associated structures.

A pulse radiolysis study of some free radical reactions with erythrocyte membranes

The reactions of the free radicals eaq- minus, OH and Br2- minus with haemoglobin-free erythrocyte ghost membranes have been studied by producing the radicals by pulse radiolysis and monitoring their reactions by optical spectroscopy. Hydrated electrons react rapidly with the membrane, but no attack at disulphide links was observed. Hydroxyl radical attack produced transient species absorbing weakly in the ultraviolet, which may arise from carbohydrate residues, such as N-acetyl neuraminic acid and N-acetyl glucosamine, on the membrane surface. No evidence was obtained for OH attack at ring-containing amino acid residues of the protein component. The Br2- minus radical, a more selective electrophile than OH, reacted only slowly with erythrocyte ghosts. Solubilization of the membranes with dodecylsulphate or digestion with alkali exposed protein containing tyrosine and tryptophan residues which reacted with Br2- minus. These results support other evidence for the absence of reactive protein at the membrane surface.