Mustafa Emre

Oxidative Stress and Apoptosis in Relation to Exposure to Magnetic Field

We investigated the effect of extremely low-frequency electromagnetic field (ELF-EMF) with pulse trains exposure on lipid peroxidation, and, hence, oxidative stress in the rat liver tissue. The parameters that we measured were the levels of plasma alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase as well as plasma albumin, bilirubin, and total protein levels in 30 adult male Wistar rats exposed to ELF. We also determined the percentage of apoptotic and necrotic cells of the kidney extracts from the animals by flow cytometry method. Apoptotic cell death was further characterized by monitoring DNA degradation using gel electrophoresis. The results showed an increase in the levels of oxidative stress indicators, and the flow cytometric data suggested a possible relationship between the exposure to magnetic field and the cell death. We showed significantly lower necrotic cell percentages in experimental animals compared to either unexposed or sham control groups. However, DNA ladder analyses did not differentiate between the groups. Our results were discussed in relation to the response of biological systems to EMF.

The effects of rosiglitazone on oxidative stress and lipid profile in left ventricular muscles of diabetic rats.

We investigated the effect of rosiglitazone (RSG), a high‐affinity ligand for the peroxisome proliferator‐activated receptor gamma which mediates insulin‐sensitizing actions, on the lipid profile and oxidative status in streptozotocin (STZ)‐induced Type 2 diabetes mellitus (DM) rats. Wistar albino male rats were randomly divided into an untreated control group (C), a C + RSG group which was treated with RSG (4 mg kg−1) two times a day by gavage, a diabetic group (D) that was treated with a single intraperitoneal injection of STZ (45 mgkg−1), D + RSG group which were treated with RSG two times a day by gavage, respectively. Lipid profiles, HbA1c and blood glucose levels in the circulation and malondialdehyde (MDA) and 3‐nitrotyrosine (3‐NT) levels in left ventricular muscle were measured. Treatment of D rats with RSG resulted in a time‐dependent decrease in blood glucose. We found that the lipid profile and HbA1c levels in D + RSG group reached the C rat values at the end of the treatment period. There was a statistically significant difference between the C + RSG and C groups in 3‐NT levels. In group D, 3‐NT and MDA levels were found to be increased when compared with C, C + RSG and D + RSG groups. In the D + RSG group, MDA levels were found to be decreased when compared with C and C + RSG. Our study suggests that the treatment of D rats with RSG for 8 weeks may decrease the oxidative/nitrosative stress in left ventricular tissue of rats. Thus in diabetes‐related vascular diseases, RSG treatment may be cardioprotective. Copyright

Effects of rosiglitazone on altered electrical left ventricular papillary muscle activities of diabetic rat

The action potential configuration of the left ventricular papillary muscle as well as the rosiglitazone-dependent changes in ventricular papillary muscle action potential amplitude were studied, and the duration was studied and compared in both healthy and diabetic rats. In this study, we used four groups: (1) nondiabetic control animals (C), (2) rosiglitazone-treated nondiabetic control animals (C+RSG), (3) diabetic animals (D), and (4) rosiglitazone-treated diabetic animals (D+RSG). Diabetes was induced by a single intravenous (i.v.) injection of streptozotocin (STZ). Conventional microelectrode techniques were applied to record action potentials after the establishment of diabetes (8 weeks after STZ treatment). Resting membrane potential (RMP) was decreased significantly in both RSG-treated C and D rats (from −70.2 ± 0.7 to −63.2 ± 0.7 and from −69.2 ± 0.4 to −61.2 ± 0.4). C+RSG and D+RSG groups showed increase in action potential amplitude compared with C and D groups (from 67.1 ± 0.8 to 68.2 ± 0.5 and from 67.1 ± 0.8 to 80.1 ± 0.8 and from 68.2 ± 0.5 to 79.3 ± 0.3) Depolarization time was significantly prolonged in diabetic rats (12.1 ± 0.4 to 27.5 ± 0.9). However, this prolongation in D+RSG group was significantly lower according to D group (from 27.5 ± 0.9 to 19.2 ± 0.7). There was no difference between C and C+RSG rats (12.1 ± 0.4 to 11.6 ± 0.2). Half repolarization time was also prolonged in diabetic rats (17.5 ± 0.6 to 59.9 ± 1.0). Moreover, D+RSG rats showed a slight and statistically insignificant difference according D rats (59.9 ± 1.0 to 55.9 ± 1.7). C+RSG rats showed a slight significant increase in half repolarization time compared with C group (17.5 ± 0.6 to 29.4 ± 0.7). Treatment of rats with RSG markedly decreased insulin resistance and also increased insulin sensitivity of the heart. Our data suggest that the beneficial effects of RSG treatment on the electrical activities of the diabetic rat papillary appear to be due to the diminished K+ currents, partially related to the decrease of hyperglycemia.

Repetitive 50 Hz pulsed electromagnetic field ameliorates the diabetes-induced impairments in the relaxation response of rat thoracic aorta rings

Purpose: To evaluate the characteristic features of mechanical responses and the membrane potential changes induced by repetitive pulsed electromagnetic field (PEMF, 50 Hz, 5 mT) in thoracic aorta rings obtained from streptozotocin-induced diabetic and healthy control rats to determine if PEMF could ameliorate problems associated with diabetes. Methods: Sixty male Wistar rats weighing 250–290 g were randomly divided into two experimental groups, each containing 30 animals. Streptozotocin was given via tail vein to produce diabetes mellitus (DM) in the first group rats. The second group rats were treated only with % 0.9 saline and considered as non-DM group. Both groups were also divided into two subgroups as DM + PEMF, DM + sham, PEMF and sham, each containing 15 animals. Although the DM + PEMF and PEMF groups were treated, the DM + sham and sham groups were not treated with PEMF. The PEMF treatment occurred four times daily for 30 min at 15-min intervals repeated daily for 30 days. Thoracic aorta rings from both DM and non-DM rats exposed to PEMF were evaluated for contraction and relaxation responses and membrane potential changes in the presence or absence of chemical agents that were selected to test various modes of action. Results: Relaxation response of thoracic aorta rings was significantly reduced in DM than non-DM group. PEMF treatment significantly increased the relaxation response of the diabetic rings to acetylcholine, and reduced the concentration response to phenylephrine. Resting membrane potential was significantly higher in DM than in non-DM group. Inhibitors of nitric oxide (NO), both nitro-L-arginine (L-NO-ARG) and L-NO-ARG + indometacin combination, produced a significant transient hyperpolarisation in all groups. Inhibitors of potassium channel activity, charybdotoxin or apamine, produced a membrane depolarisation. However, PEMF did not induce any significant effect on the membrane potential in DM group. Conclusions: Diabetes reduced the relaxation response of thoracic aorta rings. It also affected the membrane potentials of the rings. Treatment with PEMF ameliorated the diabetes-induced impairments in the relaxation response of these rings.

The acute effect of trimetazidine on the high frequency fatigue in the isolated rat diaphragm muscle.

The objective of this study was to determine the acute effect of trimetazidine (TMZ) on the pre-fatigue, fatigue and post-fatigue contractile characteristics and tension-frequency relationships of isolated rat diaphragm muscle. Muscle strips were taken from the ventral-costal aspects of the diaphragm muscle of rats killed by decapitation. The muscle strips were suspended in organ baths containing Krebs solution, with a gas mixture of 95% O2 and 5% CO2 at 37°C and pH 7.35-7.45. After determining the thermoregulation and optimum muscle length the muscles were subjected to direct supramaximal stimulation with 0.05 Hz frequency square pulses for periods of 0.5 msec to obtain control values. After adding 5x10p-6 and 5x10p-5 M trimetazidine solution to the respective bath media, the contractile parameters of the muscles were recorded. The contractile parameters were also recorded for both the trimetazidine and tri-metazidine-free media after application of the high frequency fatigue protocols. Later, the tension-frequency relationship was determined by applying stimulating pulses of 10, 20, 50 and 100 Hz to the muscle strips. Whilst the twitch tension obtained from the 5x10p-6 and 5x10p-5 M trimetazidine media showed numerical increases compared to that of the controls, these were not statistically significant (p>0.05). The contraction time exhibited a dose dependent increase (p<0.001), whilst the contraction and relaxation rates did not differ significantly. The isometric contraction forces obtained with the different stimulating frequencies showed a significant increase in the tetanic contraction only at 100 Hz (p<0.05). A comparison of the pre-and post-fatigue twitch tensions in the trimetazidine media showed the postfatigue twitch tensions to be significantly higher than those of the pre-fatigue contraction forces (p<0.05). In the 5x10p-6 and 5x10p5 M trimetazidine media the increases in the post-fatigue contraction force were 22 and 30%, respectively. These results demonstrated that in isolated rat diaphragm muscle, TMZ significantly limited the mechanical performance decrease during fatigue. It is our opinion that trimetazidine contributed to the observed fatigue tolerance by eliminating the factors of fatigue, due to preservation of intracellular calcium homeostasis, provision of the ATP energy levels needed by ATPase dependent pumps and especially by keeping the intracellular pH within certain limits.

The Effects of Magnetic Field on the Biomechanics Parameters of Soleus and Extensor Digitorum Longus Muscles in Rats with Streptozotocin-Induced Diabetes

BACKGROUND The aim of this study was to determine the effects of the magnetic field (MF) on the isometric contractile characteristics of the soleus and extensor digitorum longus (EDL) muscles in rats both with and without diabetes. METHODS Biomechanical parameters were recorded in vitro from Wistar rats without diabetes (Group I, n=20), rats without diabetes exposed to MF (Group II, n=20), rats with streptozotocin-induced diabetes (Group III, n=20), and rats with diabetes exposed to MF (Group IV, n=20). Muscle strips were taken from the distal tendon soleus and EDL muscles of rats killed by decapitation. The muscles were hung in organ baths containing Krebs solution (pH 7.4) with a gas mixture of 95% O2 and 5% CO2. Then the muscles were triggered to direct supramaximal stimulation with 0.05 Hz frequency square pulses for periods of 0.5 ms to obtain control values. The contractile parameters were also determined for two muscles of the four groups. Later, the tension-frequency relationship was determined by applying stimulating pulses of 10, 20, 50, and 100 Hz to the muscles. RESULTS Diabetes caused a certain amount of decrease in the contractile force of the two muscles compared with that of control values. However, MF increased the contractile force of the two muscles in rats both with and without diabetes. The isometric contraction forces obtained by different stimulating frequencies showed a significant linear increase in the tetanic contraction (P<0.05). Diabetes increased the contraction time of the isometric twitch tension compared with that of the control group with a statistically significant difference (P<0.05). MF decreased the contraction time of the two muscles of rats without diabetes (P<0.05) but increased that of rats with diabetes (P>0.05). CONCLUSION In our study, these results suggest that MF exposure regulates the isometric contractile characteristics of the soleus and EDL muscles of rats with diabetes, positively.

The effect of 900 and 1800 MHz GSM-like radiofrequency irradiation and nicotine sulfate administration on the embryonic development of Xenopus laevis

The aim of this study was to investigate the effects of GSM-like radiofrequency electromagnetic radiation (RF EMR) and nicotine sulfate (NS) exposure on Xenopus embryonic development.The developmental effects of GSM-like RF-EMR (900-1800 MHz, at a SAR value of 1W/kg and NS on Xenopus laevis embryos were investigated). Following the application of radiofrequency radiation and/or NS administration, the embryos were closely examined in order to determine their possible teratogenic effects. Xenopus frogs obtained from the Department of Physiology of the Cukurova University, in accordance described by the Standard Guide of the American Society for Testing and Materials (ASTM). Following the exposure of Xenopus embryos to RF-EMR at 900 and 1800 MHz (1.0W/kg) for 4, 6 and 8h; the whole body specific energy absorption rate (SAR) of the embryos was calculated. With the exception of irradiation at 1800 MHz no dramatic developmental anomalies were observed in the Xenopus embryos in association with RF-EMR applications. Combined RF-EMR and NS applications resulted in dramatic abnormalities and death among the Xenopus embryos. The study results indicated that GSM-like RF-EMR (e.g. radiation from cell phones) was not as harmful to Xenopus embryos as might have been expected. However, the combined effects of GSM-like RF-EMR and NS on Xenopus embryos were more severe than the effect of RF-EMR or NS alone. In conclusion, the study results appear to suggest that the combined use of nicotine and cell phones might result in more pronounced detrimental effects on the health of smokers.

Effects of Rosiglitazone with Insulin Combination Therapy on Oxidative Stress and Lipid Profile in Left Ventricular Muscles of Diabetic Rats

Purpose. In this study, we tested the hypothesis that rosiglitazone (RSG) with insulin is able to quench oxidative stress initiated by high glucose through prevention of NAD(P)H oxidase activation. Methods and Materials. Male albino Wistar rats were randomly divided into an untreated control group (C), a diabetic group (D) that was treated with a single intraperitoneal injection of streptozotocin (45 mgkg−1), and rosiglitazone group that was treated with RSG twice daily by gavage and insulin once daily by subcutaneous injection (group B). HbA1c and blood glucose levels in the circulation and malondialdehyde and 3-nitrotyrosine levels in left ventricular muscle were measured. Result. Treatment of D rats with group B resulted in a time-dependent decrease in blood glucose. We found that the lipid profile and HbA1c levels in group B reached the control group D rat values at the end of the treatment period. There was an increase in 3-nitrotyrosine levels in group D compared to group C. Malondialdehyde and 3-nitrotyrosine levels were found to be decreased in group B compared to group D (P < 0.05). Conclusion. Our data suggests that the treatment of diabetic rats with group B for 8 weeks may decrease the oxidative/nitrosative stress in left ventricular tissue of rats. Thus, in diabetes-related vascular diseases, group B treatment may be cardioprotective.

Nonsynergistic effects of trimetazidine and selenium combination therapy on renal ischemic-reperfusion injury in rats.

Reactive oxygen species (ROS) have been postulated to play a major role in postischemic acute renal injury. Moreover, lipid peroxidation has been described as an important pathway of ROS-induced postischemic acute renal failure. To evaluate effects of selenium (Se) and trimetazidine (TMZ) on postischemic renal failure, renal tissue malondialdehyde (MDA) and superoxide dismutase (SOD) concentrations were measured in Wistar rats with ischemic renal failure. Treatment groups consisted of rats treated with TMZ (5 mg/kg orally) or Se (30 μg/kg orally) or TMZ+Se for 15 days. Ischemic groups consisted of rats with clamped left renal arteries for 1 hour. Before left renal arterial clamping, right nephrectomy was performed; after 24 hours, left nephrectomy was done. The animals were divided into 5 groups. Group 1 (n=7) was the nonischemic control group without treatment; Group 2 (n=6) was the ischemic control group treated with physiologic solution; Group 3 (n=5) received TMZ; Group 4 (n=5) received Se; and Group 5 (n=6) received TMZ+Se for 15 days. After TMZ and Se treatment, right renal tissue MDA significantly decreased in Groups 3–5 when compared with those in Group 1. There was no significant difference between non-ischemic and ischemic renal tissue MDA in Groups 3, 4, and 5. Postischemic renal tissue SOD levels were higher than nonischemic levels in Group 3. In Groups 4 and 5, no significant differences were observed between nonischemic and ischemic renal tissue SOD levels. Moreover, total scores obtained from histopathologic evaluation of ischemic and nonischemic kidney samples in Groups 3, 4, and 5 were similar, but these scores in Group 2 were significantly different from those of Groups 3, 4, and 5. These results indicate that, under these study conditions, TMZ, Se, and TMZ+Se treatments prevent lipid peroxidation in ischemic and nonischemic renal tissue. Moreover, these treatments prevent histologic findings of postischemic-perfusion renal injury.

Effects of trimetazidine and selenium on high-frequency fatigue in isolated rat diaphragm muscle.

Trimetazidine (TMZ), which has been used in numerous experimental studies, is applied nowadays with the aim of reducing myocardial ischemia. The aim of this study was to determine the prefatigue and postfatigue contractile characteristics associated with the relationship between the force and frequency of contraction in muscle. The study was conducted using diaphragm muscle isolated from 40 male Wistar rats weighing 230 to 270 g. The rats were divided into 4 groups of 10 animals each: controls and TMZ-, selenium (Se)-, and TMZ+Se-treated groups. The rats in the control group were treated with 2 mL of physiologic serum (SF), those in the second group with Se 30 μg/kg in 2mL of SF, those in the third group with TMZ 5 mg/kg in 2 mL of SF, and those in the fourth group with a combination of TMZ 5 mg/kg + Se 30 μg/kg in 2 mL of SF. All rats were treated twice daily for 15 days by means of gastric lavage. The rats were then killed by cervical dislocation. The diaphragm muscle bands were removed and placed in an organ bath. After a 2-hour thermoregulatory period, muscles were fatigued with 5-ms pulses at a frequency of 40 Hz. Force-frequency relationships were studied after the application of 10, 50, and 100 Hz and the development of contraction curves. Contraction forces for the groups treated with TMZ, Se, and TMZ+Se (1 6.1 ±1.2, 13.2±1.3, and 14.9±1.0 g, respectively) were significantly lower than for the control group (17.0±1.4 g) during the prefatigue period (P<.001). Similarly, postfatigue contraction forces for the treated groups (15.7±1.3, 8.8±1.0, and 12.0±1.4g, respectively) were significantly lower than for the control group (12.4±1.2 g, P<.001, P<.001, and P<.05, respectively). A significant decrease was noted in postfatigue contraction forces and contraction and relaxation rates in the Se-and TMZ+Se-treated groups compared with prefatigue values (P<.001), but the difference was not significant. Force-frequency relationships were evaluated at 10, 50, and 100 Hz. The tetanic contraction forces for the control, Se-, TMZ-, and TMZ+Se-treated groups at 100 Hz were 81 3±5.7, 91.6±6.8, 65.3±5.0, and 84.9±7.5 g, respectively. In the TMZ-treated group, a significant increase was observed in tetanic contraction forces at 100 Hz compared with controls (P<.001); no significant changes were seen in the force-frequency relationships at 10 and 50 Hz. The decrease in the contraction force in the postfatigue period was prevented to a larger extent in the TMZ-treated group than in the TMZ+Se-and Se-treated groups.