Evidence from action and fluorescence spectra that UV-induced violet-blue-green fluorescence enhances leaf photosynthesis.

We assessed the contribution of UV-induced violet-blue-green leaf fluorescence to photosynthesis in Poa annua, Sorghum halepense and Nerium oleander by measuring UV-induced fluorescence spectra (280-380 nm excitation, 400-550 nm emission) from leaf surfaces and determining the monochromatic UV action spectra for leaf photosynthetic O2-evolution. Peak fluorescence emission wavelengths from leaf surfaces ranged from violet (408 nm) to blue (448 nm), while excitation peaks for these maxima ranged from 333 to 344 nm. Action spectra were developed by supplementing monochromatic radiation from 280 to 440 nm, in 20 nm increments, to a visible nonsaturating background of 500 mumol m-2 s-1 photosynthetically active radiation and measuring photosynthetic O2-evolution rates. Photosynthetic rates tended to be higher with the 340 nm supplement than with higher or lower wavelength UV supplements. Comparing photosynthetic rates with the 340 nm supplement to those with the 400 nm supplement, the percentage enhancement in photosynthetic rates at 340 nm ranged from 7.8 to 9.8%. We suspect that 340 nm UV improves photosynthetic rates via fluorescence that provides violet-blue-green photons for photosynthetic energy conversion because (1) the peak excitation wavelength (340 nm) for violet-blue-green fluorescence from leaves was also the most effective UV wavelength at enhancing photosynthetic rates, and (2) the magnitude of photosynthetic enhancements attributable to supplemental 340 nm UV was well correlated (R2 = 0.90) with the apparent intensity of 340 nm UV-induced violet-blue-green fluorescence emission from leaves.

Protective effect of secoisolariciresinol diglucoside against streptozotocin-induced diabetes and its mechanism.

OBJECTIVES: Reactive oxygen species (ROS) have been implicated in the development of streptozotocin (STZ)-induced diabetes mellitus. Secoisolariciresinol diglucoside (SDG) isolated from flaxseed is an antioxidant. An investigation was made of the effects of SDG on the development of STZ-induced diabetes in rat, to determine if SDG can prevent/reduce the development of diabetes and if this prevention/reduction is associated with reduction in oxidative stress. DESIGN AND METHODS: The rats were divided into 4 groups: Group I, Control; Group II, SDG (22 mg/kg body wt, orally) for 24 days; Group III, STZ (80 mg/kg intraperitoneally); Group IV, SDG in the dose similar to Group II three days prior to STZ and 21 days thereafter. Oxidative stress was assessed by measuring serum and pancreatic lipid peroxidation product malondialdehyde (MDA), pancreatic antioxidant reserve (pancreatic-CL) and oxygen free radical producing activity of white blood cells (WBC-CL). A diagnosis of diabetes was made on the basis of glucosuria and was confirmed at the time of sacrifice (21 days after STZ treatment) by the presence of hyperglycemia. At the end of the protocol blood samples were collected for estimation of glucose, MDA and WBC-CL, and pancreas were removed for estimation of MDA and antioxidant reserve. RESULTS: Incidence of diabetes was 100% in Group III and 25% in Group IV. SDG prevented the development of diabetes by 75%. Development of diabetes was associated with an increase in serum and pancreatic MDA, and in WBC-CL, and a decrease in pancreatic antioxidant reserve. Prevention of diabetes by SDG was associated with a decrease in serum and pancreatic MDA and WBC-CL and an increase in pancreatic antioxidant reserve. CONCLUSIONS: These results suggest that STZ-induced diabetes is mediated through oxidative stress and that SDG is effective in reducing the STZ-induced diabetes mellitus.

Protection of coronary angioplasty-induced oxidative stress by Isovue used during angioplasty.

BACKGROUND: Oxygen free radicals (OFRs) have been implicated in ischemic-reperfusion cardiac injury. Use of percutaneous transluminal coronary angioplasty (PTCA) has created renewed interest in salvation of ischemic myocardium. The PTCA procedure is similar to the ischemia-reperfusion model. It is possible that OFRs are increased following PTCA. However, OFR-related cardiac complications are uncommon and the evidence for lipid peroxidation is conflicting. PATIENTS AND METHODS: In this study the levels of plasma malondialdehyde, OFR-producing activity of polymorphonuclear leukocytes (PMNL-CL) and blood antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) were measured in peripheral venous blood of 50 consecutive patients with stable angina undergoing elective PTCA. The ability of Isovue (used during PTCA) and of streptokinase (used during thrombolysis) to scavenge OH in the high performance liquid chromatography method and to reduce OH-induced lipid peroxidation were also assessed. Patients were divided into three groups: group 1, single vessel PTCA; group 2, two or more vessel PTCA; and group 3, combined single and multivessel PTCA. RESULTS: The results indicated that there was an increase in PMNL-CL (22% to 44%) and a decrease in plasma malondialdehyde (33% to 40%) at 60 mins following PTCA. The activity of antioxidant enzymes remained unaltered. Isovue scavenged OH in a concentration-dependent manner and was complete at a concentration below that used in patients. Streptokinase, on the other hand, was ineffective in scavenging OH. CONCLUSIONS: These results suggest that, in spite of increased production of OFR by polymorphonuclear leukocytes and unaltered activity of antioxidant enzymes, lipid peroxidation decreased. Lack of lipid peroxidation may have been due to the OH-scavenging property of Isovue. The observed differences in OFR-related complications between PTCA and thrombolytic therapy may have been due to the antioxidant activity of Isovue.

Increased oxidative stress in rat liver and pancreas during progression of streptozotocin-induced diabetes.

1. Oxygen free radicals have been suggested to be a contributory factor in complications of diabetes mellitus. There are many reports indicating the changes in parameters of oxidative stress in diabetes mellitus. In this study we aimed to identify whether oxidative stress occurs in the liver and pancreas in the initial stages of development of diabetes. 2. We therefore investigated the lipid peroxide level (thiobarbituric acid-reactive substances, TBARS) and activities of antioxidant enzymes [superoxide dismutase (SOD), catalase and glutathione peroxidase] in liver and pancreas of control and streptozotocin-induced diabetic rats at various stages of development of diabetes. 3. Male Sprague-Dawley rats were divided into two groups: group I, control (n = 42) and group II, diabetic (n = 42). Each group was further subdivided into seven groups consisting of six rats each. Rats in these subgroups were studied at weekly intervals (0 to 6 weeks). Plasma glucose levels, TBARS levels and activities of antioxidant enzymes were measured in liver and pancreas at various time intervals. 4. There was a significant (P < 0.05) and progressive increase in TBARS levels of liver and pancreas in the diabetic group. Total SOD and Cu-Zn-SOD activity increased (P < 0.05) with progression of diabetes while Mn-SOD activity showed no significant change in either tissue. Catalase and glutathione peroxidase activities increased significantly (P < 0.05) in liver and pancreas. 5. Immunohistochemical study of pancreatic islet revealed a decrease in the expression of insulin with progression of diabetes. However, glucagon and somatostatin showed an increase in immunoreactivity and a difference in their distribution pattern. 6. The findings of the present study suggest that oxidative stress starts at early onset of diabetes mellitus and increases progressively. In conclusion, the structural damage to these tissues or complications of diabetes mellitus may be due to oxidative stress.

Reduction of hypercholesterolemic atherosclerosis by CDC-flaxseed with very low alpha-linolenic acid.

Flaxseed (Type I flaxseed) with 51-55% alpha-linolenic acid in its oil and richest source of plant lignans, has been shown to reduce hypercholesterolemic atherosclerosis by 46% without lowering serum lipids. Antiatherogenic activity was claimed to be due to its alpha-linolenic acid and/or lignan content. If alpha-linolenic acid component of flaxseed is responsible for antiatherogenic activity, then, CDC-flaxseed (Type II flaxseed) which has similar oil and lignan content but has very little (2-3% of the total oil) alpha-linolenic acid would have no antiatherogenic effect. An investigation, therefore, was made of Type II flaxseed on high cholesterol diet-induced atherosclerosis and serum lipids [total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C)] in rabbits. Rabbits were assigned to four groups: Group I, Control; Group II, Type II flaxseed diet (7.5 g/kg orally daily); Group III, 1% cholesterol diet; Group IV, 1% cholesterol diet supplemented with Type II flaxseed (7.5 g/kg orally daily). Blood samples were collected before (0 time) and after 4 and 8 weeks of experimental diets for measurement of serum lipids. Aorta was removed at the end of 8 weeks for assessment of atherosclerotic plaques. Serum TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were lower in Group IV as compared to Group III by 14 and 31%, 17 and 32%, 28 and 34% and 24 and 32%, respectively, at 4 and 8 weeks. HDL-C was not affected by Type II flaxseed in hypercholesterolemic rabbit. TG and VLDL-C were markedly increased in Group IV as compared to Group III. Type II flaxseed reduced the development of atherosclerosis by 69%. Histological changes in the atherosclerotic regions were qualitatively similar in Groups III and IV. Results indicate that reduction in hypercholesterolemic atherosclerosis by Type II flaxseed is due to a decrease in serum TC and LDL-C. In conclusion, antiatherogenic activity of Type II flaxseed is not due to alpha-linolenic acid.

Antioxidant defense system in diabetic kidney: a time course study.

Oxygen free radicals (OFRs) have been suggested to be a contributory factor in complications of diabetes mellitus. In the present study, we investigated the lipid peroxide level measured as thiobarbituric acid reactive substances (TBARS) and activities of antioxidant enzymes viz., [superoxide dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GSH-Px)] in the kidney of streptozotocin induced diabetic rats at various stages of development of diabetes. Sprague Dawley rats were divided into two groups: group I, control (n = 42) and group II, diabetic (n = 42). Each group was further subdivided into seven groups each consisting of six rats. Rats in subgroups were studied at weekly intervals (0 to 6 weeks). Blood glucose levels were estimated at the time of sacrifice. TBARS levels and activity of antioxidant enzymes were measured in kidney. The levels of TBARS in the diabetic group increased initially, dropped to baseline level after 2 weeks and then progressively increased at 5th and 6th week (p < 0.05). There was an increase in catalase activity at first week after that it decreased as compared to control group. However, GSH-Px activity in the diabetic group increased after 1 week and then remained at the same level except a small drop in the 2nd week. Total SOD and CuZn-SOD activity increased significantly in diabetic kidney as compared to controls at all time intervals, while Mn-SOD activity showed no change. The present findings suggest that oxidative stress accompanies at early onset of diabetes mellitus and the susceptibility of the kidney to oxidative stress during the early stages may be an important factor in the development of diabetic nephropathy.

Time course study of oxidative stress in aorta and heart of diabetic rat.

1. Oxygen free radicals have been suggested to be a contributory factor in complications of diabetes mellitus. In the present study, we investigated the lipid peroxide level [thiobarbituric acid-reactive substances (TBARS)] and activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in aorta, heart and blood of control and streptozotocin-induced diabetic rats at various stages of development of diabetes (0 to 6 weeks). 2. There was no change in the TBARS levels of aorta, heart and blood in the control group. A significant (P < 0.05) increase in TBARS levels of aorta, heart and blood was observed in the diabetic group. 3. There were no significant changes in the activities of superoxide dismutase, catalase and glutathione peroxidase in the aorta, heart and blood of control rats at all time intervals. In the diabetic group, there was a significant (P < 0.05) increase in the activity of superoxide dismutase and glutathione peroxidase in aorta from the fourth week onwards while the activity of catalase increased at all time intervals. In the heart of diabetic rats, the activity of total superoxide dismutase and Cu-Zn-superoxide dismutase increased significantly (P < 0.05) from the second week onwards while activity of Mn-superoxide dismutase decreased at the fourth week and increased at the sixth week. The activity of catalase and glutathione peroxidase increased significantly (P < 0.05) at all time intervals. In the blood, the activity of superoxide dismutase and glutathione peroxidase increased from the third week while catalase activity increased from the fourth week. 4. The present findings suggest that oxidative stress starts at early onset of diabetes mellitus and increases progressively.

Oxidative stress as a mechanism of cardiac failure in chronic volume overload in canine model.

We investigated the effects of chronic volume overload in the absence or presence of vitamin E supplements on the cardiac function and contractility, cardiac malondialdehyde (MDA)--a lipid peroxidation product--cardiac antioxidant enzyme activity and antioxidant reserve in canine model. The dogs were divided into three groups of seven dogs each: group I, control; group II, mitral regurgitation (MR) of 4 months duration; and group III, MR of 4 months duration receiving vitamin E (40 U/kg/daily) orally. MR was created by detaching two or more chordae tendinae to raise left atrial pressure to 2.5 to three times normal. MR produced a decrease in the index of myocardial contractility with little change in myocardial function. Decrease in myocardial (left and right ventricles) contractility was associated with an increase in cardiac MDA, and a decrease in cardiac antioxidant reserve and antioxidant enzyme activity. Prevention of volume overload-induced decrease in myocardial contractility by vitamin E was associated with a decrease in cardiac MDA and an increase in cardiac antioxidant reserve and glutathione peroxidase activity towards control levels. Superoxide dismutase and catalase activity remained depressed in vitamin E-treated group. The results indicate that chronic volume overload decreases the contractility of both right and left ventricles and is associated with oxidative stress in both ventricles. These results support the hypothesis that oxygen free radicals are involved in the chronic volume overload-induced cardiac depression.

Effects of probucol on hypercholesterolemia-induced changes in antioxidant enzymes.

Effects of high cholesterol diet (0.5% and 1%) on the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px)] in the aortic tissue of rabbits were investigated in the absence or presence of probucol (0.5 gm/kg daily, orally). Five groups of ten rabbits each were studied. Group I, regular rabbit chow diet; Group II, chow + 0.5% cholesterol; Group III, chow + 0.5% cholesterol+probucol; Group IV, chow + 1% cholesterol and Group V, chow + 1% cholesterol+probucol. The aorta was removed at the end of 4 months for measurement of the antioxidant enzymes. An increase in activity of aortic antioxidant enzymes was noted in cholesterol-fed rabbits (Groups II and IV), being similar for SOD and catalase but higher for GSH-Px in Group IV as compared to Group II. Probucol was ineffective in altering this cholesterol-induced increase in enzyme activity except in Group III where it increased the activity of GSH-Px. These results suggest that aortic antioxidant enzymes are affected in hypercholesterolemia and that probucol is ineffective in altering the aortic antioxidant enzyme activity except GSH-Px activity which increased in 0.5% cholesterol-fed rabbits. The protective effects of probucol against hypercholesterolemic atherosclerosis may be partly due to an increase in the GSH-Px activity at low levels of hypercholesterolemia. At higher levels of hypercholesterolemia, the protective effects of probucol could be due to its antioxidant activity.

Lipid peroxidation and activity of antioxidant enzymes in diabetic rats.

We hypothesized that oxygen free radicals (OFRs) may be involved in pathogenesis of diabetic complications. We therefore investigated the levels of lipid peroxidation by measuring thiobarbituric acid reactive substances (TBARS) and activity of antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT)] in tissues and blood of streptozotocin (STZ)-induced diabetic rats. The animals were divided into two groups: control and diabetic. After 10 weeks (wks) of diabetes the animals were sacrificed and liver, heart, pancreas, kidney and blood were collected for measurement of various biochemical parameters. Diabetes was associated with a significant increase in TBARS in pancreas, heart and blood. The activity of CAT increased in liver, heart and blood but decreased in kidney. GSH-Px activity increased in pancreas and kidney while SOD activity increased in liver, heart and pancreas. Our findings suggest that oxidative stress occurs in diabetic state and that oxidative damage to tissues may be a contributory factor in complications associated with diabetes.

Protective effects of lazaroids against oxygen-free radicals induced lysosomal damage.

Lipid peroxidation of membranes by oxygen free radicals has been implicated in various disease states. Different antioxidants and iron chelators have been used to reduce lipid peroxidation. Lazaroids have been used for the acute treatment of central nervous system disorders such as trauma and ischemia wherein lipid peroxidative processes take place. In this study we evaluated the effect of lazaroids (U-78518F and U-74389F) on the release of acid phosphatase activity and formation of malondialdehyde (MDA) in rat liver lyosomes subjected to exogenously generated oxygen free radicals. There was a significant increase in the acid phosphatase release and MDA formation in the presence of oxygen free radicals. This was prevented by both the lazaroids. In a separate study the effect of lazaroid U-74389F was seen on the zymosan-stimulated polymorphonuclear (PMN) leukocyte-derived chemiluminescence. The PMN leukocyte chemiluminescent activity was attenuated by the lazaroid in a dose-dependent manner. These studies suggest that lazaroids may inhibit lipid peroxidation and stabilize the membrane.

Antioxidant enzymes in hypercholesterolemia and effects of vitamin E in rabbits.

We investigated the effects of high cholesterol diet in the absence and presence of vitamin E on the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)] in rabbits. The animals were divided into 4 groups each comprising of 10 rabbits. Group I, regular rabbit chow diet; Group II, regular rabbit chow diet with added vitamin E; Group III, high cholesterol diet; and Group IV, high cholesterol diet+vitamin E. Antioxidant enzymes of blood were measured in each group before and after 1, 2, 3, and 4 months on the experimental diets. The aorta was removed at the end of the protocol for measurement of antioxidant enzymes. There was a decrease in activity of SOD and GSH-Px and an increase in activity of catalase in blood of Group III. Vitamin E produced a decrease in blood SOD, catalase and GSH-Px activity in Group II and prevented the decrease in SOD and GSH-Px activity in Group IV but did not affect the changes in the catalase activity. SOD, catalase and GSH-Px activity of aortae from Group III increased significantly, while catalase activity increased and GSH-Px activity decreased in those from Group II. Vitamin E prevented the cholesterol-induced rise in catalase and GSH-Px activity in aorta but did not prevent the rise in SOD activity. These results suggest that the activity of antioxidant enzymes in blood is affected differently from that in aortic tissue. There appears to be a mutually supportive interaction among the antioxidant enzymes which provide defense against oxidant injury. The protective effects of vitamin E against hypercholesterolemic atherosclerosis may not be due to changes in the antioxidant enzymes but may be mainly mediated through its chain-breaking antioxidant activity.

Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence.

Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)]. The control values for left and right ventricular CL and malondialdehyde were 81.1 +/- 15.4 (S.E.) and 182.4 +/- 50.3 (S.E.), mv.min.mg protein-1; and 0.024 +/- 0.006 (S.E.) and 0.324 +/- 0.005 (S.E.) nmoles.mg protein-1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 +/- 1.73 (S.E.) U.mg protein-1, 5.35 +/- 0.51 (S.E.) K.10(-3).sec-1.mg protein-1, and 77.50 +/- 7.70 (S.E.) nmoles NADPH.min-1.mg protein-1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion. These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury.

Oxygen free radical producing activity of polymorphonuclear leukocytes in patients with Parkinson's disease.

Oxygen free radicals (OFRs) have been suggested in the pathogenesis of Parkinson's disease (PD). These free radicals exert their cytotoxic effect by peroxidation of lipid membrane resulting in the formation of malondialdehyde (MDA). Polymorphonuclear (PMN) leukocyte is one of the major sources of OFR. However, the oxygen free radical producing activity of PMN leukocytes in patients with PD is not known. We therefore studied the oxygen free radical producing activity of polymorphonuclear leukocytes and MDA levels in the serum of healthy subjects and in patients with Parkinson's disease. The oxygen free radical producing activity of PMN leukocytes in blood and the MDA content in serum were significantly higher in patients with Parkinson's disease than in healthy subjects. These results indicate a possible role of oxygen free radicals in the pathogenesis of Parkinson's disease.

Serum antioxidant enzyme activity in Parkinson's disease.

The activities of superoxide dismutase (SOD; EC 1.15.1.1) and glutathione peroxidase (GSHPx; EC 1.11.1.9), the enzymes that metabolize the superoxide anion and hydrogen peroxide, respectively, were measured in serum from healthy subjects and patients with Parkinson's disease (PD). The activities of SOD and GSHPx in patients with PD were higher than those in normal healthy individuals. These results suggest that the increased activities of these enzymes could be due to oxidative stress in the initial stages of this disease.

Decrease of liver protein kinase C in streptozotocin-induced diabetic rats and restoration by vanadate treatment.

Effects of streptozotocin-induced diabetes and administration of the insulinmimetic agent, vanadate in rats on the liver protein kinase C-induced phosphorylation of exogenous C (Histone III-S) and endogenous substrates were investigated. Diabetes caused a significant fall (40-60%) in liver cytosolic protein C activity measured using both types of substrates. Vanadate treatment for a period of 5 weeks restored them to normal levels. Phosphorylation of cytosolic target proteins for protein kinase C followed a similar pattern in response to diabetes and vanadate. These treatments had no effect on particulate protein kinase C activity. Vanadate also had no effect in normal livers with respect to the protein kinase C system.

Inhibitory effect of H-7, H-8 and polymyxin B on liver protein kinase C-induced phosphorylation of endogenous substrates.

Inhibitory actions of 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7), N-[2-(methylamine)ethyl]-5-isoquinolinesulfonamide [H-8] and polymyxin B on the calcium-activated, phospholipid-dependent protein kinase (protein kinase C) of rat liver were compared. Using a partially purified liver protein kinase C and an exogenous substrate histone-III S, polymyxin B showed maximum inhibition (IC50, 9.5 microM) followed by H-7 (IC50, 25 microM) and H-8 (IC50, 36 microM). These inhibitors also inhibited protein kinase C-induced phosphorylation of endogenous cytosolic and particulate proteins in a dose-dependent manner though polymyxin B was relatively less effective with the particulate fraction. With the aid of protein kinase-C activators and these inhibitors, seven proteins in cytosolic (Mr 170K, 150K, 43K, 34K, 30K, 25K and 19K daltons) and six proteins in particulate (Mr 150K, 43K, 34K, 25K, 19K and 16K daltons) fractions were identified as probable substrates for protein kinase C in liver. The identity of these proteins remains to be determined.