Hypertension after bilateral kidney irradiation in young and adult rats

The mechanism of a rise in blood pressure after kidney irradiation is unclear but most likely of renal origin. We have investigated the role of the renin-angiotensin system and dietary salt restriction in the development of systolic hypertension after bilateral kidney irradiation in young and adult rats. Three to 12 months after a single X-ray dose of 7.5 or 12.5 Gy to both kidneys of young and adult rats, the systolic blood pressure (SBP) and plasma renin concentration (PRC) were measured regularly. A single X-ray dose of 12.5 Gy caused a moderate rise in SBP and a slight reduction in PRC in both young and adult rats. A dose of 7.5 Gy did not significantly alter the SBP or PRC during the follow-up period of 1 year. In a second experiment, the kidneys of young rats received an X-ray dose of 20 Gy. Subsequently, rats were kept on a standard diet (110 mmol sodium/kg) or a sodium-poor diet (10 mmol sodium/kg). On both diets, SBP started to rise rapidly 3 months after kidney irradiation. Sodium balance studies carried out at that time revealed an increased sodium retention in the irradiated rats compared to controls on the same diet. In rats on a low sodium intake, there was neither a delay nor an alleviation in the development of hypertension. Compared to controls, the PRC tended to be lower in irradiated rats up to 4 months after irradiation. Subsequently, malignant hypertension developed in all 20 Gy rats, resulting in pressure natriuresis, stimulating the renin-angiotensin system. Our findings indicated that hypertension after bilateral kidney irradiation was not primarily the result of an activation of the renin-angiotensin system. Although there were some indications that sodium retention played a role, dietary sodium restriction did not influence the development of hypertension.     

Identification of differentially expressed genes in mouse kidney after irradiation using microarray analysis

Irradiation of the kidney induces dose-dependent, progressive renal functional impairment, which is partly mediated by vascular damage. The molecular mechanisms underlying the development of radiation-induced nephropathy are unclear. Given the complexity of radiation-induced responses, microarrays may offer new opportunities to identify a wider range of genes involved in the development of radiation injury. The aim of the present study was to determine whether microarrays are a useful tool for identifying time-related changes in gene expression and potential mechanisms of radiation-induced nephropathy. Microarray experiments were performed using amplified RNA from irradiated mouse kidneys (1 x 16 Gy) and from sham-irradiated control tissue at different intervals (1-30 weeks) after irradiation. After normalization procedures (using information from straight-color, color-reverse and self-self experiments), the differentially expressed genes were identified. Control and repeat experiments were done to confirm that the observations were not artifacts of the array procedure (RNA amplification, probe synthesis, hybridizations and data analysis). To provide independent confirmation of microarray data, semi-quantitative PCR was performed on a selection of genes. At 1 week after irradiation (before the onset of vascular and functional damage), 16 genes were significantly up-regulated and 9 genes were down-regulated. During the period of developing nephropathy (10 to 20 weeks), 31 and 42 genes were up-regulated and 9 and 4 genes were down-regulated. At the later time of 30 weeks, the vast majority of differentially expressed genes (191 out of 203) were down-regulated. Potential genes of interest included TSA-1 (also known as Ly6e) and Jagged 1 (Jag1). Increased expression of TSA-1, a member of the Ly-6 family, has previously been reported in response to proteinuria. Jagged 1, a ligand for the Notch receptor, is known to play a role in angiogenesis, and is particularly interesting in the context of radiation-induced vascular injury. The present study demonstrates the potential of microarrays to identify changing patterns of gene expression in irradiated kidney. Further studies will be required to evaluate functional involvement of these genes in vascular-mediated normal tissue injury.     

Studies on the termination of immunological tolerance in the mouse thymus cell population after irradiation

Immunological tolerance in the mouse thymus cell population induced by the intravenous injection of deaggregated bovine gamma globulin was terminated by whole body irradiation. After irradiation, the weight of the thymus recovered biphasically, and the termination of tolerance occurred as early as in the first phase. Both Thy-1 antigen expression and helper activity of the thymus cell population in irradiated mice recovered in parallel with the recovery of the thymus weight. Sensitivity of the regenerating thymus cell to the tolerogen was not different from that of the normal thymus cell. The first phase of thymus regeneration may be caused by the proliferation and differentiation of relatively radioresistant and tolerogen insensitive precursors residing in the thymus. Tolerogen and/or immunogen reactive thymus cells may originate from the precursor.     

Antioxidant potential of cancerous human kidney tissues

Antioxidant potentials (AOP) of cancerous and noncancerous adjacent human kidney tissues from 12 patients were measured. AOP of the cancerous tissues was found to be significantly lower than that of noncancerous ones. However, tissue malondialdehyde (MDA) levels were significantly higher in the cancerous tissues compared with noncancerous ones. In the intra-correlation analysis, carried out between AOP and MDA levels, significant correlation was found in the cancerous tissues (r = 0.9) but no correlation observed in the noncancerous ones. In the inter-correlation analysis, negative correlation was found between AOP's of cancerous and noncancerous tissues (r = -0.49) and positive correlation between MDA levels (r = 0.51). Results suggest that antioxidant potential of cancerous kidney tissues is significantly reduced compared with noncancerous ones. Therefore, they expose to high oxidant stress and free radical-induced peroxidative attacks, the results of which are cellular deformations.     

Intestinal tolerance in mice after low dose rate 60CO irradiation. Implications for radiotherapy]

Influence of absorbed dose rate has been studied in BALB/c mice for early intestinal tolerance. After selective abdominal irradiation, LD50 at 5.5 days increases from 12.36 to 20.22 and 21.79 Gy when dose rate decreases from 0.61 to 0.054 and 0.026 Gy/mn. LD50 at 6.5 days increases from 12.05 to 19.22 and 21.58 Gy respectively. The LD50 ratios are then 1.6 and 1.8 for both endpoints. After total body irradiation. LD50 at 5.5 days increases from 9.92 to 15.20and 16.83 Gy when dose rate decreases from 0.56 to 0.049 and 0.024 Gy/mn. The corresponding LD50 ratios, i.e. 1.5 and 1.7, are then similar to the former ones. Increase of LD50 when decreasing dose rate is in agreement with that expected taking into account only repair of sublethal lesions, for the generally accepted cellular models.     

Antioxidant system is essential to increase drought tolerance of sugarcane

Drought is one of the main factors affecting the productivity of agricultural crops, and plants respond to such stress by activating various physiological and biochemical mechanisms against dehydration. The present study investigated two varieties of sugarcane (Saccharum spp.) with contrasting responses to drought (RB867515, more tolerant; and RB855536, less tolerant) and subjected them to progressive drought conditions (2, 4, 6 and 8 days) followed by rehydration. Drought caused a decrease in water potential (ψ_w) and osmotic potential (ψ_os) in the leaves, which recovered to normal levels after rehydration only up to the fourth day of drought. Water stress changed the carbon metabolism of leaves by reducing starch and sucrose contents and increasing glucose and fructose contents in both varieties. Water deficit caused a significant reduction in the maximum quantum efficiency of photosystem II (F_v/F_m) and effective quantum yield (Φ_PSII) in both varieties; however, RB867515 recovered faster after rehydration. Under water stress, the more tolerant variety RB867515 exhibited increased activity of the antioxidant enzymes catalase, ascorbate peroxidase and superoxide dismutase compared with the RB855536 variety. The results suggest that RB867515 is more tolerant to drought conditions because of a more efficient antioxidant system, which results in reduced photosynthesis photoinhibition during water stress, thus revealing itself as a potential physiological marker for drought tolerance studies.     

Antioxidant role of N-acetyl cysteine isomers following high dose irradiation

High dose, acute radiation exposure, as in radiation accidents, induces three clinical syndromes that reflect consequences of oxidative protein, lipid, and DNA damage to tissues such as intestine, lung, and liver. In the present study, we irradiated C57BL/6 mice with 18 Gy whole-body radiation (XRT) and evaluated N-acetyl cysteine (NAC) isomers LNAC and DNAC as potential radioprotectors under conditions that would model the gastrointestinal syndrome. We focused on tissues thought not immediately involved in the gastrointestinal syndrome. Both LNAC and DNAC protected the lung and red blood cells (RBC) from glutathione (GSH) depletion following radiation exposure. However, only LNAC also supplemented the spleen GSH levels following XRT. Protection from increased malondialdehyde (MDA) levels (lung) and increased 8-hydroxy-deoxyguanosine (8-oxo-dG) presence (liver) following XRT was observed with treatment by either isomer of NAC. These results imply that either NAC isomer can act as a radioprotectant against many aspects of oxidative damage; chirality is only important for certain aspects. This pattern would be consistent with direct action of NAC in many radioprotection and repair processes, with a delimited role for NAC in GSH synthesis in some aspects of the problem.     

Antioxidant enzymes and steroid-induced proliferation of kidney tubular cells

Diethylstilbestrol induces proliferation of Syrian hamster renal proximal tubular cells. By counting the number of cells in culture, we showed that liposomes containing superoxide dismutase or catalase suppressed diethylstilbestrol-induced proliferation, whereas empty liposomes or liposomes containing inactivated superoxide dismutase did not. Liposomes containing antioxidant enzymes did not suppress proliferation of cells in control media or of cells treated with ethinyl estradiol. In the absence of liposomes, exogenous superoxide dismutase did not suppress diethylstilbestrol-induced proliferation. The decrease in cell number when diethylstilbestrol-treated cells were treated with antioxidant enzyme-containing liposomes was not due to decreased cell viability. Results were confirmed by measuring a correlate of cell proliferation immunohistochemically, using an antibody to proliferating cell nuclear antigen. A larger proportion of diethylstilbestrol-treated cells than of control cells showed nuclear immunostaining with this antibody. The number of cells immunostained in diethylstilbestrol-treated cultures was sharply decreased by the addition of superoxide dismutase- or catalase-containing liposomes. Our studies suggest a role for active oxygen species in diethylstilbestrol-induced proliferation of cultured proximal tubular cells.     

Antioxidant and detoxifying enzymes in the liver and kidney of pheasants after intoxication by herbicides MCPA and ANITEN

The activity of antioxidant and detoxifying enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glutathione reductase, glutathione-S-transferase (GST), the contents of thiobarbituric acid reactive substances, and the superoxide dismutase and glutathione-S-transferase isoenzyme patterns, were determined in the liver and kidney of pheasants after acute intoxication by herbicides MCPA and ANITEN I. In the liver, the activity of antioxidant enzymes was significantly decreased in the group given ANITEN I. New superoxide dismutase isoforms (pI 6.30, 6.85, 7.00) and higher intensity of isoform with pI 6.60 were observed after isoelectrofocusing in all experimental groups. In the kidney, the activity of superoxide dismutase was significantly decreased, and a higher intensity of superoxide dismutase isoforms (pI 6.00 and 6.60) was observed in all experimental groups. The contents of thiobarbituric acid reactive substances were significantly increased in the group with ANITEN I. The glutathione-S-transferase isoenzyme pattern was studied by using subunit-specific substrates and by Western blotting. The activity of glutathione-S-transferase with ethacrynic acid and cross-reactivity with rat subunit 7 was lower in all experimental groups in the kidney and liver, except in the liver of the group given a higher dose of ANITEN I. In this group, we have found a 2.10-fold higher activity to ethacrynic acid and a strong induction of subunit 7. © 1998 John Wiley & Sons, Inc. J Biochem Toxicol 12: 235–244, 1998     

Dynamic changes in kidney function after the whole-body gamma irradiation of rats at a dose of 7.4 Gy

In experiments on female Wistar rats it was shown that whole-body gamma-irradiation (7.4 Gy) impairs the hemodynamics and function of kidneys, particularly their filtering capacity, the dynamics of which was of an undulatory character. The most pronounced changes occurred during the first 30 days following irradiation, later on the functional status normalized.     

Increased glomerular Vwf after kidney irradiation is not due to increased biosynthesis or endothelial cell proliferation.

Kuin, A., Citarella, F., Oussoren, Y. G., Van der Wal, A. F., Dewit, L. G. H. and Stewart, F. A. Increased Glomerular Vwf after Kidney Irradiation is not due to Increased Biosynthesis or Endothelial Cell Proliferation. Radiat. Res. 156, 20-27 (2001).Irradiation of the kidney induces dose-dependent, progressive renal functional impairment, which is partly mediated by vascular damage. It has previously been demonstrated that reduced renal function is preceded by an increased amount of von Willebrand factor (Vwf) in the glomerulus. The underlying mechanism and significance of this observation are unknown but, since it is an important mediator of platelet adhesion, Vwf in increased amounts could be implicated in glomerular thrombosis, resulting in impairment of renal function. Increased Vwf could be the result of increased biosynthesis by endothelial cells, or from increased numbers of endothelial cells after compensatory proliferation induced by irradiation, or it could be secondary to other events. In the present study, expression levels of mRNA for glomerular Vwf and glomerular cell proliferation rates were measured in control mouse kidneys and after irradiation with a single dose of 16 Gy. There were no significant changes in mRNA ratios for Vwf/beta-actin at 10 to 30 weeks after irradiation compared with unirradiated samples, whereas increased amounts of Vwf protein were seen in the glomeruli at these times. Labeling studies with IdU or staining for Ki67 demonstrated that glomerular proliferation was increased from 10 to 30 weeks after irradiation. Despite the increased proliferation rates, there was an absence of glomerular hyperplasia and no increase in the endothelial cell surface coverage in the glomeruli. Staining with antibodies against smooth muscle actin (SMAalpha) revealed that the observed proliferation mainly involved mesangial cells. These results indicate that the increased presence of glomerular Vwf after irradiation is not due to an increased number of endothelial cells per glomerulus, or to an increased production of Vwf. It is presumably secondary to other events, such as increased release of Vwf by damaged endothelial cells or entrapment of Vwf in the irradiated mesangial matrix.     

Antioxidant properties of proteins after freezing-thawing

Experimental data are presented which were obtained under comparative evaluation of influence of different freezing-thawing conditions on antioxidant properties of isolated proteins: human serum albumin, cytochrome c from the horse heart and glucose oxidase from Aspergillus niger. The observed protein antioxidant activity alterations are assumed to be a result of protein conformational changes. The character of freezing-thawing influence on the protein antioxidant activity depends on the molecular structure and cooling conditions.     

Improving Glycyrrhiza uralensis salt tolerance with N+ ion irradiation

Low energy (25 keV) N⁺ ions were implanted into liquorice (Glycyrrhiza uralensis) seeds at a fluency of either zero (control) or 900 × (2.6 × 10¹³) ions/cm². After irradiation, all the seeds were planted in the plastic pots for a growth period of one month. Thereafter, the seedlings in the pot were subjected to saline stress at 600 mM for about 3 days. The morphological and physiological characteristics such as total chlorophyll content, proline level, activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ATPase, and triphenyl tetrazolium chloride (TTC) reduction in seedling roots were investigated. Our results indicated that ion irradiation significantly increased the shoot height, leaflet number, taproot lenght, lateral root number, and shoot and root weights of liquorice seedlings with or without saline stress. Furthermore, the total chlorophyll content, proline level, SOD, POD, CAT, ATPase activities, and root TTC reduction vigor of seedlings were all found to be significantly increased under saline stress by ion irradiation compared with their corresponding controls. These results indicated that ion irradiation can strengthen the resistance of liquorice seedlings to saline stress and may have a potential application for the improvement of plants in sand areas.     

Antioxidant enzymatic activity is linked to waterlogging stress tolerance in citrus

Soil flooding constitutes a seasonal factor that negatively affects plant performance and crop yields. In this work, the relationship between oxidative damage and flooding sensitivity was addressed in three citrus genotypes with different abilities to tolerate waterlogging. We examined leaf visible damage, oxidative damage in terms of malondialdehyde (MDA) concentration, leaf proline concentration, leaf and root ascorbate and glutathione contents and the antioxidant enzyme activities superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6) and glutathione reductase (EC 1.8.1.7). No differences in the extent of oxidative damage relative to controls were found among genotypes. However, a different ability to delay the apparition of oxidative damage was associated to a higher tolerance to waterlogging. This ability was linked to an enhanced activated oxygen species' scavenging capacity in terms of an increased antioxidant enzyme activity and higher content in polar antioxidant compounds. Therefore, the existence of a direct relationship between stress sensitivity and the early accumulation of MDA is proposed. In addition, data indicate that the protective role of proline has to be considered minimal as its accumulation was inversely correlated with tolerance to the stress. The positive antioxidant response in Carrizo citrange ( Poncirus trifoliata L. Raf. ×  Citrus sinensis L. Osb.) and Citrumelo CPB 4475 ( Poncirus trifoliata L. Raf. ×  Citrus paradisi L. Macf.) might be responsible for a higher tolerance to flooding stress, whereas in Cleopatra mandarin ( Citrus reshni Hort. Ex Tan.), the early accumulation of MDA seems to be associated to an impaired ability for H₂O₂ scavenging.     

Simulation of CFU-s kinetics after irradiation

A simulation model of the CFU-s population is used to interpret data from experimental studies of bone marrow recovery after irradiation. The model includes an original hypothesis that the proliferation rate in the CFU-s population depends on the number of DNA-synthesizing CFU-s. It is assumed that the DNA-synthesizing CFU-s produce a factor in the presence of which CFU-s enter the resting state G0 after mitosis and remain there for prolonged periods of time. The model can adequately reproduce complex CFU-s kinetics observed after severe damage caused by irradiation with a unique set of parameters.