Structural modification of human erythrocyte membranes following gamma-irradiation

Changes in plasma amino acids during conditioning therapy prior to bone marrow transplantation: Their relevance to antioxidant status

Bone marrow transplant (BMT) recipients undergo a bimodal regimen of conditioning therapy, the precise prescription being dependent upon the primary disease of the individual patient. Generally, this treatment consists of chemotherapy and total body irradiation prior to transplantation, although the latter may or may not be included in the regimen. We have investigated amino acid metabolism and oxidant status in in a small series of BMT recipients before and after conditioning therapy.Plasma amino acids were measured by HPLC on 10 BMT recipients prior to commencing conditioning therapy, and again one week later before transplantation. In addition some general nutritional parameters and antioxidant components were measured. A marked decrease in the plasma concentration of a number of amino acids, especially those concerned with antioxidants, was observed over the 7 days of conditioning therapy.There is also a significant reduction in antioxidant capability, as reflected by measurements of glutathione and erythrocyte glutathione peroxidase (GSHPx), which may have an influence upon post-transplant recovery and graft function. Such a reduction in antioxidant concentrations may also have an influence upon the erythrocyte and platelet support required post-grafting.The data presented in this paper adds to the evidence for the conditional essentiality of some amino acids such as taurine and glutamine, and may support the case for specific antioxidant intervention treatment prior to, and/or after conditioning therapy together with monitoring antioxidant status during the post-grafting period.

Management of Radiation Injuries by Panax ginseng Extract

Chemical radiation protection is an important strategy to protect living beings against the deleterious effects of radiation. In the present study, the radioprotective effect of hydro-alcoholic extract of Panax ginseng extract (PGR-HAE) was studied on radiation-induced deleterious alterations in Swiss albino mice. Oral administration of such extract (25 mg/kg b wt/day/animal) for 5 consecutive days, half an h. before whole-body exposure to 6 Gy gamma radiation, enhanced the 30 days survival and also inhibited the radiogenic sickness, weight loss and life shortening. PGR-HAE ameliorated radiation induced depletion in blood constituents at different necropsy intervals between 12 h to 30 d, and significantly increased the number of femoral spleen colony forming units that survived after irradiation. Furthermore, it checked depletion of glutathione and antioxidant enzymes (superoxide dismutase, catalase, and glutathione S-transferase) as well as elevation of lipid peroxidation (LPO) level in blood and liver. The significant reduction in the yield of LPO demonstrates that PGR-HAE protects the membranes against radiation-induced oxidative damage. These findings conclude that such plant extract provides significant radioprotection, and it may be potentially valuable in the prevention of injuries caused during planned and unplanned radiation exposure.

Cinnamon extract ameliorates ionizing radiation-induced cellular injury in rats

The present study aimed to investigate the protective role of cinnamon extract against inflammatory and oxidative injuries in gamma irradiated rats. Rats were subjected to fractionated doses of gamma radiation. Cinnamon extract were daily administrated before starting irradiation and continued after radiation exposure. The results obtained revealed that the administration of cinnamon extract to irradiated rats significantly ameliorated the changes induced in liver antioxidant system; catalase, superoxide dismutase and glutathione peroxidase activities as well as reduced glutathione concentration. The liver's lipid peroxidation and protein oxidation indices were significantly decreased when compared with their equivalent values in irradiated rats. Furthermore, the changes induces in xanthine oxidoreductase system were significantly diminished. In addition, the changes in liver nitric oxide contents, serum tumor necrosis factor alpha and C-reactive protein levels were markedly improved. In conclusion, the administration of cinnamon extract might provide substantial protection against radiation-induced oxidative and inflammatory damages.

Gamma-irradiation and UV-C light-induced lipid peroxidation: a Fourier transform-infrared absorption spectroscopic study

Fourier transform-infrared spectroscopy of dry, multibilayer films has been used to study gamma-radiation and UV-C light induced lipid peroxidation in 1,2-dilinoleoyl-sn-glycero-3-phosphocholine liposomes. The observed spectral changes were compared with the results obtained from measurement of hydroperoxides, conjugated dienes and to the formation of thiobarbituric acid reactive substances, such as malondialdehyde (MDA) or MDA-like substances. Upon irradiation a decrease in intensity of the asymmetric C - H stretching vibration (va(CH2)) of the isolated cis C = C - H groups (3010 cm-1) was observed. Directly correlated with the decrease of the va(CH2) absorption was a shift of the asymmetric phosphate ester stretching vibration (va(P = O)) towards smaller wavenumbers (1260-->1244 cm-1), indicating that the lipid peroxidation induced molecular alterations in the fatty acid chains influence the packing of the phospholipids in dry multibilayer films. In addition, the formation of a new absorption band at 1693 cm-1 could be detected, the intensity of which was comparable with the formation of thiobarbituric acid reactive substances and, therefore, attributed to the (C = O) stretching of alpha, beta unsaturated aldehydes. Dose-dependent studies using ionizing radiation showed that the decrease of va(CH2) was directly correlated with an increase in absorption of the conjugated dienes at 234 nm and with the formation of hydroperoxides suggesting that the absorption at 3010 cm-1 is solely due to isolated cis C = C - H groups and hence subject to the early stages of the radical chain reaction. UV-C light induced lipid peroxidation revealed a non-linear decrease of I3010, which was directly correlated with the formation of hydroperoxides. The observed early saturation of the conjugated dienes was attributed to an early photodecomposition of the conjugated double bonds.

Lipoperoxides as an index of free radical activity in bone marrow transplant recipients. Preliminary observations

It has been previously demonstrated that the conditioning therapy given to bone marrow transplant (BMT) recipients creates a high oxidant stress, resulting in a measured reduction in antioxidants, such as glutathione peroxidase (GSH-Px), vitamin E, and cell peroxide fragilities. As part of a current intervention trial of antioxidant therapy in BMT recipients, plasma thiobarbituric acid reactive substances (TBARS) were measured to assess peroxidation and free radical activity. Measurements were performed before and after conditioning therapy, and then at weekly intervals for a period of 6 wk after transplantation in 20 patients (10 controls and 10 antioxidant therapy [AOT] recipients). The TBARS results were compared with concurrent measurements of more specific elements of the antioxidant pathways, such as red blood cell glutathione peroxidase (RBC-GSH-Px), plasma vitamin C, and serum vitamin E. In all cases, TBARS concentration was significantly increased after conditioning compared with baseline levels (p < 0.001), an increase that correlated inversely with RBC-GSH-Px (r = -0.81; p < 0.01). The TBARS concentration fell gradually after conditioning in all patients. The fall in the AOT group was more rapid than in the control group, and it paralleled the gradual return toward normal levels of the other antioxidants. The change in TBARS concentration occurred faster than changes in other indices, suggesting that TBARS might be a better index of overall free radical activity. Although the patient numbers are small, there is some evidence to suggest that MDA may act as a prognostic marker.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiation-induced structural alterations in fish red blood cells

The structural properties of gamma-irradiated fish red blood cells were studied using a spin labelling method. The gradient increase of lipid fluidity with the increasing gamma radiation doses was indicated by methyl 5-doxylpalmitate and methyl 12-doxylstearate spin labels spectra. In turns, the spectra of maleimide spin label (4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) indicated a modification of the internal proteins and the increased internal viscosity of red blood cells. The results encourage the conclusion that the increase in membrane fluidity may result from the alternations in lipid-protein interactions rather than lipid peroxidation.

Decreased essential antioxidants and increased lipid hydroperoxides following high-dose radiochemotherapy

The blood from 19 patients having bone marrow transplantation was examined for the essential antioxidants alpha-tocopherol and beta-carotene as well as lipid hydroperoxides before, at and after bone marrow transplantation (BMT). Conditioning therapy, preceding BMT in order to achieve marrow ablation and immunosuppression, consists of high-dose chemotherapy which is mostly combined with total body irradiation (TBI). In order to see a possible difference between patients with and without additional TBI, we divided the patients up into two groups; patients receiving TBI (RT+) and patients without TBI (RT-). All patients required total parenteral nutrition beginning one week prior to BMT. After conditioning therapy plasma levels of absolute and lipid-standardized alpha-tocopherol and beta-carotene decreased in both groups, presumably as a result of an enhanced breakdown of these antioxidants. The loss of these lipid-soluble antioxidants has to be considered as a possible cause for early post-transplant toxicity. Lipid hydroperoxides increase significantly in the group of patients with additional TBI, whereas the other group, receiving no additional TBI, showed no significant change. We suggest high-dose supplementation of essential antioxidants for patients undergoing BMT.

Qinghaosu does not affect the major thermotropic phase transition in model membranes of dipalmitoylphosphatidylcholine

The effect of the antimalarial agent qinghaosu (artemisinin) on the major thermotropic phase transition in bilayer membranes of dipalmitoylphosphatidylcholine has been studied by differential scanning calorimetry and by the use of fluorescent probes (pyrene excimer formation and depolarization of diphenylhexatriene fluorescence). Addition of up to 40 mol% qinghaosu to dipalmitoylphosphatidylcholine bilayer caused no observable effect on the temperature or enthalpy of the phase transition. The results suggest that the antimalarial action of qinghaosu is not due to a direct effect on the lipid structure of the parasite membrane.

Radioprotective effect of 2-mercaptopropionyl glycine on radiation-induced lipid peroxidation and enzyme release in erythrocytes

gamma-Irradiation of erythrocyte suspensions resulted in lipid peroxidation and enzyme (acetylcholinesterase, AChE) release. The presence of 2-mercaptopropionyl glycine (MPG) during irradiation decreased lipid peroxidation and enzyme (acetylcholinesterase, AChE) release. The presence of 2-mercaptopropionyl glycine (MPG) during irradiation decreased lipid peroxidation and from erythrocytes of high and low concentrations was observed at 480 and 320 Gy, respectively. This implied that the extent of enzyme release is likely to be masked when only a single dose of radiation is used, unless it happens to be an optimum dose. MPG mediated inhibition of lipid peroxidation and enzyme release indicated that lipid peroxidation may induce the breakdown of the phosphatidylinositol/enzyme interaction. Further, the enzyme damage was assigned to the direct and indirect effects of radiation on the enzyme in situ.

Radiation-induced lipid peroxidation and the fluidity of erythrocyte membrane lipids

The effect of radiation-induced peroxidation on the fluidity of the phospholipids of the erythrocyte membrane was studied using both erythrocyte ghosts and liposomes formed from the polar lipids of erythrocytes. In liposomes, the oxidation of the phospholipids increased with radiation dose, but there was no change in the fluidity of the lipids as measured by spin-label motion. Under the same conditions of irradiation, no oxidation of phospholipid was detected in erythrocyte ghosts, although changes occurred in the motion of spin labels intercalated with the membrane. These changes were attributed to radiation-induced alterations in the membrane proteins. It is concluded that alterations in motion of spin labels, observed with intact membranes after irradiation, are most likely the result of changes in the structure of membrane proteins rather than the lipids.

Nuclear medicine and the environment: radiation interactions

The effect of radiation interactions on the environment may be considered from the perspective of the purely physical phenomena occurring or from the effects the interactions produce in organized biological systems. The physical processes by which radiation interacts with the environment are quite well defined. Although these processes differ depending upon the nature (either electromagnetic or particulate) of the primary radiation, the ultimate result is the production in the medium of high-speed, secondary charged particles. Some of the energy of these particles is absorbed by the medium, while a portion may be lost as bremsstrahlung. The energy that is absorbed produces excitation and ionization, which can be disruptive to biological systems. The effects produced by ionizing radiations at the biochemical, cellular, and organ level are less well defined. Nevertheless, available data indicate that certain generalizations are possible. For example, given the ubiquitous nature of water in tissues, macromolecules, regardless of their structural types, tend to serve as acceptors of the energy and products of water radiolysis. However, a deeper insight into the consequences of irradiation requires an understanding of the interplay of such parameters as the type and energy of the radiation, and the dose and rate of its application. Furthermore, at the cellular level, the type and age of the irradiated cells, the concentration of oxygen in their environment, and their cell-cycle phase are all important factors in determining the consequences of irradiation.

The use of a phospholipid analogue of diphenyl-1,3,5-hexatriene to study melittin-induced fusion of small unilamellar phospholipid vesicles

A phospholipid analogue incorporating the diphenyl-1,3,5-hexatriene (DPH) chromophore has been synthesized. The compound has been shown to have similar fluorescence properties to DPH itself but, unlike DPH, is unable to exchange freely through solution when incorporated as probe in a subset of phospholipid vesicles of given composition. The non-exchangeability of this probe has been exploited to study the fusion of phospholipid vesicles to form larger structures. The peptide melittin was used to initiate fusion, and it was shown that vesicles which had been induced to fuse by heating in the presence of melittin would not fuse with subsequently added vesicles.