Ulku Comelekoglu

Biomechanical evaluation in osteoporosis : ovariectomized rat model

The aim of our study was to investigate the effects of ovariectomy on rat femur biomechanical parameters. Bone mineral density (BMD) and histological investigation were also evaluated. Fourteen female Sprague–Dawley rats (seven ovariectomized, seven control) were used. BMD was measured by dual-energy X-ray absorbsiometry. Bone biomechanical parameters were measured in femoral midshaft with tensile test using a biomaterial testing machine and maximum load, stiffness, energy absorption capacity (structural properties), ultimate stress, ultimate strain, and elastic modulus (material properties) were calculated. Diaphyseal cortical bone thickness was measured by using histological method. The ovariectomized (OVX) rat femur’s BMD was 14% lower than control rats (p=0.006). Mean maximum load was 55% less than the control group’s (p=0.0001). Stiffness was 72% less in OVX rats (p=0.05). Femurs of rats with OVX had 32% less absorbed energy than controls (p=0.09). From the stress–strain curve ultimate stress, ultimate strain and elastic modulus was calculated. Elastic modulus was 53% less than controls (p=0.05). Ultimate stress decreased 21% in OVX rats (p=0.097). Ultimate strain was 25% less than controls in OVX rats. Cortical thickness was significantly decreased in OVX rats than in controls (p<0.05). In conclusion, femur biomechanical parameters are decreased in osteoporosis.

A study on the investigation of cadmium chloride genotoxicity in rat bone marrow using micronucleus test and chromosome aberration analysis

In this study, we investigated the genotoxic and cytotoxic potential of cadmium chloride (CdCl2)in Wistar rat tibia bone marrow cells, using the structural chromosomal aberration (SCA) and micronucleus (MN) test systems. CdCl2 was administered to adult female rats as repeated i.p. doses of 0.5 mg/kg b.w. for 18 week (four months) at 48 h intervals. Mitomycin C (MMC) was used as a positive control (2 mg/kg b.w.). This study shows that cadmium chloride treatment significantly induced the frequency of micronucleus in polychromatic erythrocytes in tibia bone marrow. This increase in micronucleus frequency shows that cadmium has a genotoxic effect on bone marrow at this level. Also, in order to determine cytotoxicity in bone marrow, the ratio of polychromatic erythrocytes to normochromatic erythrocytes was calculated in bone marrow. The results of this study indicate that CdCl2 decreased this ratio. The decrease of this ratio in bone marrow shows CdCl2 may lead to cytotoxicity. We have reported that 0.5 mg/kg-level chronic exposure to cadmium (Cd) has an injurious effect on bone marrow. Our findings indicate that CdCl2 has a cytotoxic and genotoxic effect on rat bone marrow at chronic exposure.

No effect of GA-AS (904 nm) laser irradiation on the intact skin of the injured rat sciatic nerve

AbstractWe evaluated the electrophysiological and histopathological effects of low-energy gallium arsenide (904 nm) laser irradiation on the intact skin injured rat sciatic nerve. Twenty-four male Wistar rats were divided into three groups (n=8 each). At the level of proximal third of the femur the sciatic nerve was crushed bilaterally with an aneursym clip (Aesculap FE 751, Tuttingen, Germany) for half a second. A gallium arsenide laser (wavelength 904 nm, pulse duration 220 ns, peak power per pulse 27 W, spot size 0.28 cm2, pulse repetition rate 16, 128 and 1000 Hz; total applied energy density 0.31, 2.48 and 19 J/cm2) was applied to the right sciatic nerve for 15 min daily at the same time on 7 consecutive days. The same procedure was performed on the left sciatic nerve of same animal, but without radiation emission, and this was accepted as control. Compound muscle action potentials were recorded from right and left sides in all three groups before surgery, just at the end of injury, at the 24th hour and on the 14th and 21st days of injury in all rats using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara, USA). BIOPAC Acknowledge Analysis Software (ACK 100 W) was used to measure CMAP amplitude, area, proximal and distal latency, total duration and conduction velocity. Twenty-one days after injury, the rats were sacrificed. The sciatic nerves of the operated parts were harvested from the right and left sides. Histopathological evaluation was performed by light microscopy. Statistical evaluation was done using analysis of variance for two factors (right and left sides) repeated-measures (CMAP variables within groups) and the Tukey–Kramer Honestly Significant Difference test (CMAP variables between laser groups). The significance was set at p ≤ 0.05. No statistically significant difference (p ≥ 0.05) was found regarding the amplitude, area, duration and conduction velocity of CMAP for each applied dose (0.31, 2.48 and 19 J/cm2) on the irradiated (right) side and the control (left) side, or between irradiated groups. Twenty-one days after injury there were no qualitative differences in the morphological pattern of the regenerated nerve fibres in either irradiated (0.31, 2.48 and 19 J/cm2) or control nerves when evaluated by light microscopy. This study showed that low-energy GaAs irradiation did not have any effect on the injured rat sciatic nerve.

THE EFFECTS OF DEXAMETHASONE ON LIPID PEROXIDATION AND NITRIC OXIDE LEVELS ON THE HEALING OF TRACHEAL ANASTOMOSES: AN EXPERIMENTAL STUDY IN RATS

Corticosteroids are shown to have deleterious effects on wound healing for various tissues. Arginine metabolism and nitric oxide (NO) synthesis play an important role in many aspects of inflammation and wound healing. The study was designed to evaluate the relationship of dexamethasone impaired healing of tracheal anastomoses to NO metabolism and lipid peroxidation. Forty-two adult Wistar rats were randomly divided into five groups. The animals underwent tracheal transection and primary anastomoses. The groups were assigned as follows: Group I (GI) (sham, N = 6); Group II (GII) (control, N = 6); Group III (GIII), dexamethasone, 0.1 mg kg(-1) per day, intramuscularly for a week (N = 10); Group IV (GIV), dexamethasone, 1 mg kg(-1) per day, intramuscularly for a week (N = 10); Group V (GV), dexamethasone, 6 mg kg(-1) intramuscularly as a single dose (N = 10). After 7 days, bursting pressure was used to evaluate anastomotic healing. Serum nitrite/nitrate and malondialdehyde (MDA) levels were measured as an index of NO synthesis and lipid peroxidation, respectively. The bursting pressure significantly decreased in GIII and GIV when compared to the control group. The difference between GIII and GIV was also statistically significant. Nitrite/nitrate and MDA levels of GIII were found to be significantly higher than the control group. Also, the difference was found to be statistically significant between GIII and GIV in regard to nitrite/nitrate levels. The present study demonstrates that daily administration of dexamethasone for a week inhibits NO synthesis in a dose-dependent manner on tracheal anastomotic healing. Besides the generally accepted evaluation parameters including bursting pressure and hydoxyproline content; NO and MDA levels may be helpful in the assessment of wound healing especially for the investigation of impairment mechanism.

The effects of corticosteroids and vitamin A on the healing of tracheal anastomoses

OBJECTIVE This study investigates the deleterious effects of corticosteroids on tracheal anastomotic healing and the ability of vitamin A to reverse these effects in a rat model. METHODS Forty-two adult Wistar rats were randomly divided into five groups. The animals underwent tracheal transection and primary anastomoses. The groups were assigned as follows: Group I, sham (N=6); Group II, control (N=6); Group III, dexamethasone, 0.1 mg/kg/day intramuscularly (N=10); Group IV, dexamethasone 0.1 mg/kg/day intramuscularly+vitamin A 10000 IU/kg/day by gavages (N=10); and Group V, vitamin A 10000 IU/kg/day by gavages for a week (N=10). After 7 days, anastomotic healing was assessed by measurement of bursting pressure, hydroxyproline content and subsequent histological grading using the modified Ehrlich/Hunt scale. RESULTS Bursting pressures and hydroxyproline contents were as follows: Group I: 977+/-8 mmHg and 11.80+/-0.3 microg/mg (mean+/-standard error of the mean); Group II: 890+/-55 mmHg and 9.93+/-0.6 microg/mg; Group III: 555+/-26 mmHg and 11.90+/-1.3 microg/mg; Group IV: 873+/-73 mmHg and 10.24+/-2.2 microg/mg; Group V: 905+/-45 mmHg and 7.51+/-0.8 microg/mg, respectively. Bursting pressure of Group III was found to be significantly lower when compared to other groups (P<0.0001). However, statistical significance was not found among the study groups for the hydroxyproline content. Except for inflammatory cell infiltration, histological parameters including epithelial regeneration, fibroblast proliferation, collagen content, and angiogenesis demonstrated significant differences among the groups. CONCLUSION The present study demonstrates that dexamethasone significantly impairs the healing of tracheal anastomoses in rats and postoperative administration of vitamin A appreciably reverses this inhibitory effect. Patients receiving corticosteroids may benefit from vitamin A when undergoing prolonged intubation and laryngotracheal reconstruction.

Evaluation of Cerebral Maturation by Visual and Quantitative Analysis of Resting Electroencephalography in Children With Primary Nocturnal Enuresis

This study was undertaken to evaluate resting electroencephalographic (EEG) changes and their relations to cerebral maturation in children with primary nocturnal enuresis. Cerebral maturation is known to be important in the pathogenesis of this disorder. Twenty-five right-handed patients with primary nocturnal enuresis, aged 6 to 14 years, and 23 age- and sex-matched healthy children were included in this cross-sectional case-control study. The abnormalities detected using such techniques as hemispheral asymmetry, regional differences, and hyperventilation response in addition to visual and quantitative EEG analysis were examined statistically by multivariate analysis. A decrease in alpha activity in the left (dominant hemisphere) temporal lobe and in the frontal lobes bilaterally and an increase in delta activity in the right temporal region were observed. We concluded that insufficient cerebral maturation is an important factor in the pathogenesis of primary nocturnal enuresis, and EEG, as a noninvasive and inexpensive method, could be used in evaluating cerebral maturation. (J Child Neurol 2001;16:714-718).

Strontium ranelate treatment improves oxidative damage in osteoporotic rat model.

BACKGROUND Osteoporosis is the most common skeletal disorder and is considered a risk of fracture. Most medication used for the treatment of osteoporosis is antiresorptive; however, strontium ranelate (Sr) therapy in postmenopausal women has shown a double effect on resorption and bone formation. In this study, the effect of Sr on status of the oxidative stress and antioxidant defence system was investigated. METHODS Twenty-one adult albino female Wistar rats were used. The animals were randomly assigned into three groups, control (sham operated rats, received saline), OVX (ovariectomized rats), OVX + Sr (4 months later ovariectomy, strontium ranelate treatment was begun and continued for 120 days) each containing 7 animals. Strontium ranelate (500 mg/kg/day) and placebo (saline) were administered via oral gavage. At the end of the treatment, liver and kidney of rats were removed and malondialdehyde (MDA) level, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities were determined by biochemical analysis methods. RESULTS In liver, MDA levels were significantly higher in the OVX and OVX + Sr groups than the control group. GSH-Px activity decreased in OVX group and increased in OVX + Sr group compared with values of control group. CAT activity was increased in the OVX + Sr group when compared to control group. In kidney, MDA level was increased in OVX group. SOD activity was decreased in the OVX + Sr group. GSH-Px activity decreased in OVX group and increased in OVX + Sr group compared with control group. CAT activity increased in the OVX + Sr group when compared to control. CONCLUSION According to our results, Sr has preventive effect on oxidative damage in ovariectomized rats.

Effects of trapidil on the healing of colonic anastomoses in an experimental rat model.

Background:  Trapidil has various properties including vasodilatation, inhibition of lipid peroxidation and platelet aggregation as well as, and reduction of, the inflammatory response to injury. The aim of the present study was to investigate the effects of trapidil on dexamethasone‐impaired colonic anastomotic healing in an experimental rat model.

ELECTROPHYSIOLOGICAL AND HISTOPATHOLOGICAL EVALUATION OF RESPIRATORY TRACT, DIAPHRAGM, AND PHRENIC NERVE AFTER DICHLORVOS INHALATION IN RATS

The aim of this study was to investigate the dose-related effects of dichlorvos inhalation on electrophysiological alterations of diaphragm and phrenic nerve and the changes in the histologic structure of respiratory system. This study was performed on 33 rats divided into 5 groups, inhaling 1, 2, 5, 10, and 15 µg/L of dichlorvos, respectively. Electrodiagnostic investigations of diaphragm and phrenic nerve were made before and after inhalations. Aspiration samples were taken from lungs to evaluate the presence of infection agents. The airways, lungs, and diaphragms were dissected out for histologic investigation. Rats exposed to a low concentration of dichlorvos (1-5 µg/L) showed no symptoms of intoxication, but exposure to higher doses (10-15 µg/L) induced dyspnea in several animals. Lower doses of dichlorvos revealed no electromyographic changes on diaphragm, whereas higher doses revealed a clear neuropathic involvement. Delayed phrenic nerve motor conduction velocity was noted for each group (p < .05). Morphologic changes on the tracheal epithelium, hyperplasia, thickening of the blood-air barrier, degeneration in alveoli, and ductus alveolaris were seen in histopathologic investigation. In conclusion, the acute inhalation of dichlorvos caused clear evidence of neuropathic involvement of the diaphragm and the phrenic nerve. Also, toxic pneumonitis and injury to the tracheal epithelial were noticed.

Acute Electrophysiological Effect of Pulsed Gallium–Arsenide Low-Energy Laser Irradiation on Isolated Frog Sciatic Nerve

We evaluated the acute electrophysiological effects of low-energy pulsed laser irradiation on isolated frog sciatic nerve measured by extracellular recording technique. A pulsed gallium–arsenide (GaAs) laser (wavelength: 904 nm, pulse duration 220 ns, peak power per pulse: 27 W, spot size: 0.28 cm2, total applied energy density: 0.005–2.5 J/cm2) was used for the experiment. Sixty isolated nerves were divided into six groups (n=10), each of which received a different laser dose. In each group, action potentials were recorded before laser irradiation which served as the control data. The extracellular action potentials were recorded for each combination of 1, 3, 5, 7, 10, 13 and 15 minutes of irradiation time and 4, 8, 16, 32, 64 and 128 repetition frequency by using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara, USA). Action potential amplitude, area, duration and conduction velocity were measured. Statistical evaluation was performed using repeated measures variance analysis by SPSS 9.0. There were no statistically significant differences for action potential amplitude, area and conduction velocity among the laser groups and control data (p>0.05). The study showed that low-energy GaAs irradiation at 4–128 Hz repetition frequencies administered for irradiation times of 1–15 min generates no effect on action potential amplitude, area, duration and conduction velocity in isolated frog sciatic nerve.