Short-term melatonin treatment improved diabetic nephropathy but did not affect hemorheological changes in diabetic rats.

Increased oxidative stress and hemorheological disturbances may play very important roles in the development of microangiopathies in diabetes mellitus. This study was designed to determine the healing effect of melatonin on hemorheological parameters and diabetic nephropathy in streptozotocin (STZ)-induced diabetic rats. Wistar male rats were divided into four groups as control, untreated-diabetic, melatonin-treated control and melatonin-treated diabetic rats. Diabetes was induced by injecting streptozotocin (45 mg/kg, i.p.). Fourteen weeks after inducement of diabetes, melatonin (10 mg/kg) was administered intraperitoneally for 5 days to the rats. Erythrocyte deformability and aggregation were measured by laser differaction analysis (LORCA). Diabetic nephropathy was assessed by histopathologic evaluation and TUNEL stain in the diabetic kidney. Decreased erythrocyte deformability and increased erythrocyte aggregation indices were determined in the diabetic group. Melatonin treatment did not improve these hemorheological abnormalities. However, renal injuries were diminished in the melatonin-treated diabetic group compared to the untreated diabetic group. Also, melatonin had an antiapoptotic effect on the diabetic kidney. It was concluded that i.p. administration of melatonin for 5 days improved renal injury in diabetic rats, probably by decreasing oxidative stress, but did not affect hemorheological changes.

Comparison of leptin levels in serum and follicular fluid during the oestrous cycle in cows.

Leptin is mainly synthesised in white adipose tissue. Besides its effects on body weight and metabolic homeostasis, leptin also has effects on puberty, sexual maturation and reproduction. In this study the relationship between leptin, IGF-1, oestradiol (E2) and progesterone levels were investigated in serum and follicular fluid from cows. This study included 72 healthy, Brown Swiss cows aged 4-5 years. Samples from the jugular vein and follicular fluids were collected. Phases of the oestrus cycle of cows were classified according to their serum progesterone levels (< 3.18 nmol/l, follicular phase and the others as luteal phase). Follicles were grouped as large (> or = 8 mm) or small (< 8 mm). Leptin, IGF-1, oestradiol and progesterone levels were measured from serum and follicular fluid. Leptin concentrations were found to be significantly higher in luteal-phase follicular fluid of small follicles (P < 0.05). These were classified as atretic follicles. There was a positive correlation between serum and follicular fluid leptin levels in the luteal phase. Serum leptin was found to have a positive correlation with follicular fluid progesterone level (P = 0.01) in the preovulatory follicles. The present study shows that there is a relationship between the concentration of leptin in follicular fluid and atresia in small follicles.

Blood lactate disappearance dynamics in boys and men following exercise of similar and dissimilar peak-lactate concentrations.

Characteristically, children recover faster than adults from various types of exercise. The purpose of the present study was to explain the children's faster recovery, in part, by addressing lactate (La) removal and comparing La disappearance dynamics in the two age groups following exercise of both similar and dissimilar peak blood-lactate concentration values ([La]pk). The subjects were 14 prepubertal boys and 12 men of similar peak oxygen consumption, normalized for body mass. All subjects performed 30 s supra-maximal cycling (Wingate anaerobic test [WAnT]). [La]pk was 10.7 +/- 1.9 and 14.7 +/- 1.7 mmol x l(-1) for the boys and men, respectively (p < 0.001). The men were later retested in shortened versions of the WAnT so as to attain [La]pk values (10.5 +/- 0.7 mmol x l(-1)) comparable to those achieved by the boys. [La]pk lag time following the boys' standard WAnT was similar to that found in the men following the shortened WAnT (5.0 +/- 2.6 vs 5.7 +/- 1.3 min, respectively), but considerably shorter than that following the men's 30s-WAnT (7.6 +/- 2.1 min; p < 0.05). The La disappearance dynamics were closely matched between groups following the matched [La]pk WAnTs. [La] half-life was similar under all conditions (ca. 20 min). It is concluded that prepubertal boys are characterized by a lower [La]pk and a shorter time lag before reaching it, following 30-s supra-maximal cycling exercise. However, boys' La disappearance dynamics are not different from that of men.

Both zinc deficiency and supplementation affect plasma melatonin levels in rats.

At physiological levels, zinc and various hormones affect each other reciprocally. Reduction in zinc levels in pinealectomized rats suggests the relation between zinc and melatonin. The effect of both zinc deficiency and supplementation on plasma melatonin levels in rats were investigated in this study. The study was done in Selçuk University, Experimental Medicine Research and Application Center. Twenty-four adult male Sprague Dawley rats were divided into 3 groups. Eight rats were fed with zinc-deficient diet. Zinc supplementation was administered intaperitoneally to 8 rats. The remaining 8 rats were used as controls. All rats sacrificed 3 weeks later. Plasma melatonin and zinc levels were determined. The plasma zinc levels of the zinc-supplemented group were higher than those of the other groups as expected (P<0.01). Similarly, the melatonin levels in the zinc-supplemented group were higher than those in the other groups. A significant decrease was observed in melatonin levels of the zinc-deficient group compared to the control and zinc-supplemented group (P<0.01). The results of this study suggest that zinc deficiency decreases the melatonin levels and zinc supplementation may increase the plasma melatonin levels in rats.

Basal metabolic rates of Turkish women during pregnancy.

The purpose of the present study was to investigate the basal metabolic rates (BMRs) of pregnant Turkish women and to compare them with values from other countries. Twenty-four pregnant women (aged 24.8+/-5.7 years) were studied longitudinally from early pregnancy through to the end of pregnancy. BMR values were measured in the 1st, 2nd and 3rd trimesters by indirect calorimetry. While the measured BMR significantly increased (279+/-212 kcal/day between the 1st and 3rd trimesters), no change was found when BMR was expressed per unit of body weight. BMR in the 2nd and 3rd trimesters showed a significant correlation with body weight. The BMR increase in pregnant Turkish women was close to that reported in developed countries, and higher than that reported in developing countries. Knowing the metabolic changes of the pregnant women may contribute to dietary recommendations for them.

A combined method for estimating ventilatory threshold.

BACKGROUND: The aims of this study were to compare two new methods (Dmax and CUSUM) for determination of the ventilatory threshold and to examine the consequences of estimation by application of these methods in combination. EXPERIMENTAL DESIGN: a comparative design was used. SETTING: the study was performed in the Exercise Physiology Laboratory in the Faculty of Medicine, Selçuk University. PARTICIPANTS: thirty-two untrained males (20.6 +/- 1.2 yrs) performed an incremental exercise test on a cycle ergometer. INTERVENTIONS: there is no intervention. MEASURES: ventilatory and gas exchange variables were measured breath-by-breath. The ventilatory thresholds were detected by conventional linear regression, CUSUM, Dmax and combined CUSUM-Dmax methods. RESULTS: The ventilatory thresholds determined by Dmax method gave the highest r-values compared to the criterion method. There was no statistical difference between thresholds determined by all methods or by the same method using different variables. Ventilatory thresholds could not be determined by the conventional linear regression method in three subjects but were determined in all subjects by the other three methods. CONCLUSIONS: Although all methods presented in this study can be used in the determination of ventilatory threshold, the Dmax method was found to be the most valid one. When using the CUSUM method, combining it with the Dmax method increases the validity of the measurement.

Reliability of peak-lactate, heart rate, and plasma volume following the Wingate test.

PURPOSE: The 30-s Wingate Anaerobic Test (WAnT) has been used to assess anaerobic performance capacity and to evaluate physiological responses to supramaximal exercise. Blood lactate concentration ([La]) following supramaximal exercise is often used in the field and in the laboratory to assess the glycolytic contribution to exercise. Although the reliability of the performance in the WAnT has been established, this has not been the case with the WAnT's [La] response. Thus, the main purpose of this research was to study the test-retest reliability of peak [La] following the WAnT. Additionally, the test-retest reliability of the heart rate (HR) and plasma volume changes (deltaPV) response was also evaluated. METHODS: Twenty-nine subjects (15 male, 14 female) of diverse training levels as well as physical characteristics (mean +/- SD: 23.3+/-7.0 yr, 62.5+/-12.0 kg, 170.8+/-9.7 cm, and 16.3+/-6.2% fat) performed two WAnTs within 1 wk. Capillary blood was sampled from a prewarmed fingertip at rest, just before the WAnT and at 3, 5, 7, and 9 min following it. HR was also measured during these times. RESULTS: Mean-power (MP) (+/-SE) in test 1 and test 2 was 8.4+/-0.2 and 8.3+/-0.2 W X kg(-1) body mass, respectively. Peak [La] was attained 5-7 min following the WAnTs and was not significantly different between test 1 and test 2 (9.7+/-0.3 vs 9.8+/-0.3 mM, respectively). Peak HR occurred within 5 s post-WAnT and was not different between tests (170.8+/-2.2 and 171.3+/-2.2 beats X min(-1), in test 1 and test 2, respectively). Peak deltaPV was not different between tests (-12.0+/-3.4 and -11.1+/-3.2%, in test 1 and test 2, respectively). The intraclass reliability coefficients for peak [La]. peak HR and deltaPV were 0.926, 0.941, and 0.878, respectively, whereas the corresponding value for MP was 0.982. CONCLUSIONS: We conclude that peak [La], peak HR, and deltaPV following the WAnT are reliable measures.

Comparison of the aerobic contributions to Wingate anaerobic tests performed with two different loads.

BACKGROUND: The purpose of the present study was to compare the aerobic contribution of the Wingate anaerobic test by increasing the test load and power output. SETTING: The study was performed in the Physiology Department of the Faculty of Medicine, Selçuk University. PARTICIPANTS: Thirty sedentary male university students volunteered to this study. EXPERIMENTS: The subjects performed two Wingate tests against resistance of 75 g.kg-1 and 95 g.kg-1 body weight on Monark 818E bicycle ergometer. Breath-by-breath oxygen consumption rates were measured using an automated metabolic measurement chart (Sensormedics 2900). Aerobic contribution was determined by dividing energy equivalence of net oxygen consumption to the total work. RESULTS: The mean total work values obtained from tests performed at 75 g.kg-1 and 95 g.kg-1 loads were 13.9 +/- 1.5 kjoules and 14.5 +/- 1.8 kjoules (t = 2.32, p = 0.03). Mean total oxygen consumptions were 765 +/- 105 ml and 770 +/- 110 ml, respectively (t = 0.24, p = 0.81). Assuming 20% mechanical efficiency for both tests, aerobic contributions were calculated as 19.5 +/- 3.7% and 18.9 +/- 3.7%, respectively (t = 1.01, p = 0.30). CONCLUSIONS: Although the power outputs of the two tests were different, the difference between aerobic contributions was not statistically significant. So, it was failed to say that the increase in the power outputs might be related to higher contribution of anaerobic processes. However, if different mechanical efficiencies could be used, relationship between aerobic contributions of two tests might have been different.

Pulmonary function of workers in the aluminum industry.

The effects of aluminum on the pulmonary function of aluminum workers were investigated in this study. Serum aluminum levels and spirometry were measured in 55 male workers and 30 male controls. The mean serum aluminum level of workers (72.7 +/- 9.9 ng/ml) was significantly high compared to that of controls, indicating aluminum toxicity. Spirometric parameters were significantly lower in workers than in controls and correlated negatively with both exposure time and serum aluminum levels. The impairment in pulmonary function may be due to exposure time and insufficient protection.

The effects of rHuEPO administration on pulmonary functions in haemodialysis patients.

The aim of this study was to investigate the effects of erythropoietin therapy on pulmonary functions in haemodialysis patients. Thirteen patients with chronic renal failure on regular haemodialysis and in need of treatment for anaemia were treated with 45-60 U/kg erythropoietin three times a week. Thirteen haemodialysis patients constituted the control group. Patients receiving erythropoietin were given pulmonary function tests prior to the treatment and after Hb levels had reached 10 g/dl. The interval between first and second pulmonary function tests was similar for both the control group and the erythropoietin group. There was no significant difference between the results of the first and the second pulmonary function tests of the control group. However, in the erythropoietin group, the diffusing capacity, maximal voluntary ventilation, forced vital capacity and peak expiratory flow rate values increased significantly. The existence of a relationship between the diffusing capacity and anaemia is well known. Rises in other parameters following erythropoietin administration might be the result of a gain in respiratory muscle strength consequent to anaemia correction.

Determination of the heart rate deflection point by the Dmax method.

OBJECTIVE: Conconi et al. proposed that the point where heart rate departed from linearity in an incremental exercise test was a good indicator of the anaerobic threshold. However, the heart rate deflection points (HRDPs) can not be determined in many subjects. The aim of this study was to determine the heart rate deflection point by the Dmax method and to compare it with the conventional linear method. SETTING: The study was performed in the Exercise Physiology Laboratory in the Faculty of Medicine, Selçuk University. PARTICIPANTS: Thirty-two untrained males (aged 18-22) performed a maximal exercise test on a cycle ergometer. RESULTS: The deflection from linearity of HR could not be detected in nine subjects (28%) by the linear method. The HRDPs could be detected in all subjects by the Dmax method. It was observed that the HR values in the HRDPs determined by both methods were close to the maximal HR values (approximately 90% of maximum). There were high correlations and no differences (p more than 0.05) between the deflection points expressed as oxygen uptake, HR and work rate determined by two methods (correlation coefficients 0.93, 0.93, 0.97, respectively, p less than 0.001). CONCLUSIONS: The Dmax method is more useful than linear method. The HRDPs of all the people can easily and objectively be found by this method.