The effect of nephropathy on plasma sphingosine 1-phosphate concentrations in patients with type 2 diabetes.

OBJECTIVES: Sphingosine 1-phosphate (S1P) is carried in plasma by the HDL particles and albumin. It mediates several protective functions of HDL. Because of its barrier-enhancing effect, it has attracted attention in diseases associated with endothelial dysfunction. We examined the impact of circulating levels of S1P in diabetic nephropathy together with apoprotein M, a S1P-binding protein in HDL. Plasma levels of dimethylarginines were evaluated in this context. DESIGN AND METHODS: Patients with type 2 diabetes mellitus were divided into three groups according to daily albumin excretion: normoalbuminuria, microalbuminuria and macroalbuminuria (n=30 in each). In addition to routine analysis, S1P and apo M in plasma were measured using the enzyme-linked immunosorbent assays. Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and l-arginine were determined by HPLC. Tukey's or Mann-Whitney U-test was used for the statistics. RESULTS: Plasma S1P levels showed a significant decline in parallel to kidney dysfunction. The highest significance was detected in the macroalbuminuric group. Although a significant increase in plasma SDMA in albuminuric groups was observed, apo M, l-arginine and ADMA levels were similar between the groups. CONCLUSION: Low plasma levels of S1P seemed to be associated with diabetic nephropathy. The main reason for the decreased S1P levels in our patients seems to be severe urinary albumin loss due to nephropathy. Low levels of S1P in patients with nephropathy may adversely affect the endothelial integrity and barrier function, thus causing a vicious circle.

Collagen synthesis, nitric oxide and asymmetric dimethylarginine in diabetic subjects undergoing hyperbaric oxygen therapy.

The main pathological condition in patients with impaired wound healing is diabetes mellitus. These patients have significantly low circulating nitric oxide (NO) levels because the stimulatory action of insulin on NO synthesis is absent. Additionally, asymmetric dimethylarginine (ADMA), an inhibitor of NO synthase, is increased owing to the generation of oxidative stress. NO was thought to contribute to wound healing. Hyperbaric oxygen (HBO) treatment is generally used in order to accelerate the healing of wounds. The aim of this study was to determine the changes in plasma procollagen type I and III N-terminal peptides (PINP and PIIINP), total nitrite/nitrate (NO(x)) and ADMA levels; and to evaluate their relation to healing during the HBO treatment of foot ulcers. Data obtained from 18 diabetic patients before and after the HBO therapy were compared statistically by the Wilcoxon test. NO(x) was increased in 11 and ADMA was decreased in 12 patients following HBO treatment. Both PINP (32.6 +/- 29.4 microg/l vs 44.3 +/- 33.4 microg/l) and PIIINP (6.97 +/- 3.01 microg/l vs 7.92 +/- 2.49 microg/l) were significantly increased (p < 0.05). Progressive reductions were observed in wound areas, as assessed by the digital wound imaging. In 12 patients, wounds healed by 50% or higher; whereas only two subjects had minimal improvements (15% or less healing). The duration of diabetes correlated negatively with wound healing (r = -498, p < 0.05). This study suggests that increased collagen synthesis is associated with wound healing during hyperbaric oxygen therapy. Nitric oxide generation may also contribute to the healing process.

Association of paraoxonase 55 and 192 gene polymorphisms on serum homocysteine concentrations in preeclampsia.

Paraoxonase 1 (PON1) is thought to influence serum homocysteine concentrations, at least in part, due to its homocysteine thiolactonase activity and to play a role in preeclampsia and atherosclerosis. We investigated the effects of PON 55 and PON 192 polymorphisms on plasma total homocysteine (tHcy) concentrations in preeclamptic and healthy pregnants among Turkish population (N = 106). PON 55 and 192 genotypes were determined by PCR RFLP techniques. Plasma tHcy concentrations were measured by high-performance liquid chromatography. No differences were observed in the distribution of PON 1 55/192 genotypes and allele frequencies between the preeclamptic and healthy pregnants. tHcy level in the plasma of preeclamptic women was found to be increased in comparison with healthy pregnants (P < 0.01). Preeclamptic women bearing the mutated PON 192 RR and wild-type PON1 55 LL genotypes had higher tHcy levels than those of the healthy pregnants with the corresponding genotypes, supporting the possibility that the hyperhomocysteinaemia seen in preeclamptic women is associated with the PON genotypes. However, no influence of the allelic distribution on plasma tHcy concentrations was detected in either group. Our results suggest that PON1 55 and 192 genotypes might have an important role in developing hyperhomocysteinaemia and may also have a role in the pathogenesis of preeclampsia in a Turkish population.

Early and late effects of hyperbaric oxygen treatment on oxidative stress parameters in diabetic patients.

Exposure to hyperbaric oxygen leads to increased amount of reactive oxygen species (ROS) that are derived from various sources. After the discovery that ROS can function as signaling molecules, the idea of ROS being hazardous to biological tissues has been challenged. The aim of this study was to examine the changes in oxidative stress parameters in diabetics undergoing hyperbaric oxygen therapy (HBOT) due to foot ulcers. Twenty patients, who received HBOT for diabetic foot ulcers, were included in the study. Blood samples were taken before HBOT and 30 min after exit from the chamber, on the day of the first and the fifteenth HBOT sessions. They were used for the determinations of malondialdehyde (MDA), 8-isoprostane and advanced oxidation protein products (AOPPs). 8-Isoprostane and AOPP levels were not altered significantly after the first HBOT session, while both were increased on the fifteenth day (p<0.05). MDA was significantly increased only after the first HBOT session, and remained unchanged on the fifteenth day (within-day variations). Plasma AOPP levels were lowered significantly after fifteen consecutive HBOT sessions (between-day variations). Decreased AOPP levels suggest that increased oxygenation of tissues due to HBO therapy may activate some endogenous factors that prevent hazardous effects of the disease itself.

Circulating ghrelin levels in obese women: a possible association with hypertension.

OBJECTIVE: The orexigenic hormone ghrelin induces weight gain by stimulating food intake. Ghrelin has been shown to modulate sympathetic activity, to exert vasodilative effects and to counterreact with leptin on both food intake and blood pressure. Of these two hormones, ghrelin levels are decreased in obesity, whereas leptin levels are increased. In this cross-sectional study, differences in serum ghrelin and leptin levels were examined in normotensive and hypertensive obese women. MATERIAL AND METHODS: Sixty-one normotensive and hypertensive women were classified according to the body mass indices as follows: (a) 18 healthy subjects with BMI 21.5-27.5 kg/m(2); (b) 22 normotensive subjects with BMI 30-47 kg/m(2); (c) 21 hypertensive obese subjects (BMI 30-48 kg/m(2)) with systolic blood pressure > or =140 mmHg or diastolic blood pressure > or =90 mmHg. Anthropometric measurements including height, weight, BMI, waist and hip circumferences and blood pressure were recorded. The levels of ghrelin and leptin were determined in sera using the commercial ELISA kits. RESULTS: In normotensive obese subjects, ghrelin levels were significantly lower than in controls (0.21+/-0.13 vs 0.60+/-0.3 ng/mL), whereas hypertensive obese women had elevated ghrelin levels (0.64+/-0.36 ng/mL). Ghrelin concentration was decreased despite the presence of hypertension in the patients who had BMIs above 35 kg/m(2). Leptin levels were significantly higher in both normotensive and hypertensive obese groups (19.54+/-11.19 and 21.61+/-12.7 ng/mL, respectively) than in controls (7.61+/-3.3 ng/mL), and were not affected by the presence of hypertension in obese subjects. CONCLUSION: Ghrelin was positively associated with hypertension in obese women and this association was inversely influenced by the increase of BMI.

The effect of COX-2 inhibitor, nimesulide, on angiogenetic factors in primary endometrial carcinoma cell culture.

Angiogenesis, the development of new blood vessels from preexisting capillaries, is essential for the development, growth and advancement of solid tumours. Angiogenesis is enhanced by prostaglandins (PGs) that are synthesised by the catalysis of cyclooxygenases (COX-1 and COX-2) from arachidonic acid. COX-2 is upregulated in a variety of malignancies and favours the growth of malignant cells by stimulating proliferation and angiogenesis. The aim of this study is to investigate the angiogenetic process by determining the levels of vascular endothelial growth factor (VEGF), monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8 in endometrial cancer cells and to study the effect of nimesulide, a selective COX-2 inhibitor, on these mediators using cell culture. Endometrial tissue specimens were obtained from subjects with endometrial cancer and intramural leiomyoma. Cells were incubated with either 10 or 50 microM nimesulide for 24 h. VEGF, MCP-1 and IL-8 concentrations were determined by sandwich quantitative enzyme immunoassay (ELISA). VEGF concentration was significantly higher in cancer cells than normal endometrial cells. VEGF was decreased with 10 microM nimesulide in cancer cells whereas it remained unaltered in normal cells. Both MCP-1 and IL-8 concentrations were lower in cancer cells than normal cells. MCP-1 levels were decreased with both doses of nimesulide in normal cells, whereas IL-8 levels were significantly affected only by 50 microM of nimesulide. These results suggest that COX-2 inhibitors may be effective in the treatment of endometrial cancer via suppression of angiogenesis.

Advanced oxidation protein products in obese women: its relation to insulin resistance and resistin.

Obesity is a major risk factor for insulin resistance and type 2 diabetes mellitus (T2DM). Resistin, an adipocyte-secreted hormone, is thought to take a part in the development of insulin resistance and T2DM. The aim of this study was to characterise the changes in circulating levels of resistin and proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 in diabetic and prediabetic obese patients and to explore their relationship to insulin resistance. Attempts were also made to see whether resistin levels are related to the degree of oxidative stress, as determined by the measurement of advanced oxidation protein products (AOPPs). The study groups consisted of obese diabetic (BMI: 30-42 kg/m(2), n=28) and prediabetic (BMI: 29-41 kg/m(2), n=23) women. Fourteen healthy women, with BMI in the range 21.5-25.5 kg/m(2), were taken as controls. Serum levels of TNF-a, IL-6, resistin, glucose, insulin and AOPPs were measured. Insulin resistance was calculated by the homeostasis model assessment (HOMA-IR). Diabetic and prediabetic obese patients had increases in serum resistin and TNF-alpha levels (P<0.01 and P<0.001, respectively). IL-6 levels in diabetic patients were significantly higher than in prediabetics (P<0.05). AOPP levels were also significantly higher in diabetics than prediabetics and controls (P<0.05 and P<0.001, respectively); and positively correlated with blood glucose. Insulin was significantly associated with circulating resistin and TNF-alpha. The development of insulin resistance may contribute to the elevation of circulating resistin or vice versa. Determination of AOPPs may be helpful for monitoring the impaired glucose metabolism in obesity.

Cystatin-C and creatinine as indices of glomerular filtration rate in the immediate follow-up of renal transplant patients.

Serum cystatin-C (cys-C), creatinine (Cr), C-reactive protein (CRP) and amyloid A have been shown to provide useful information for renal function following transplantation. In this study, we wanted to evaluate the impact of these parameters as markers of the glomerular filtration rate (GFR) on the third and seventh days of the post-transplantation period. Cys-C was determined by the particle-enhanced immunoturbidimetric assay, and serum amyloid A (SAA) by the sandwich-enzyme immunoassay kit. Cr and CRP concentrations were measured by the Cobas Integra 400 autoanalyser. The patients (n=35) were followed with daily repetitive measurements of serum Cr and urine output per hour, and with Doppler ultrasonography against the risk of rejection. Statistical evaluations were made using the ANOVA and Pearson's test. Serum cys-C and Cr levels on both the 3rd and 7th days after transplantation were lower than those of pretransplantation values (P<0.001). The Cr/cys-C ratio was decreased on the 3rd day of the post-transplantation period, and kept declining on the 7th day. This ratio was high only in the patient with an acute rejection episode. None of the patients with high pretransplant CRP levels had a rejection episode during a six-month follow-up. SAA concentrations were found to be higher than the pretransplant values in the early post-transplant period. Cys-C had good sensitivity to estimate the renal function in the very early period of transplantation, but its value as a marker of GFR was decreased at the end of first week. As none of the 34 patients had a rejection episode, the observed rise in SAA and CRP levels is not specific to rejection.

Effect of exogenous melatonin on ethanol-induced changes in Na(+),K(+)- and Ca(2+)-ATPase activities in rat synaptosomes.

In the present study, the effects of acute ethanol (EtOH) toxicity and of exogenous melatonin (MLT) on this toxicity were examined by measuring membrane-bound ATPases and acetylcholinesterase activities in rat synaptosomal membranes. The concentrations of plasma alpha-tocopherol and adrenal ascorbic acid (AA) were also measured. Synaptosomal Na(+),K(+)-ATPase and Ca(2+)-ATPase activities were significantly depressed in acute EtOH-intoxicated rats compared with controls, while acetylcholinesterase activity remained unaltered. Pretreatment with MLT (10 mg/kg) prior to acute EtOH administration prevented EtOH-induced inhibition of ATPases. Adrenal AA and plasma alpha-tocopherol levels were also depressed regardless of MLT pretreatment. MLT treatment alone affected neither membrane-bound enzyme activities nor tissue and blood levels of vitamins C and E. It is concluded that acute EtOH intoxication disturbs neural transport functions through the membrane-bound ATPase activity depression. Reduced AA and alpha-tocopherol levels may contribute to the neurodegenerative effects of EtOH. However, pretreatment with a high dose of MLT before EtOH administration may be beneficial to prevent EtOH-induced toxicity on ATPase-mediated neural transport functions.

Coadministration of melatonin and estradiol in rats: effects on oxidant status.

This study was designed to investigate the effects of melatonin and estradiol (E2) on lipid peroxidation and antioxidant defense enzymes in blood and liver tissue when administered in vivo. Wistar albino rats were divided into three experimental groups and treated with either estradiol (25 mg/kg bw, s.c.), melatonin (i. p.), or melatonin plus E2, whereas control animals had diluent injections only. Melatonin was given 10 mg/kg bw x 2 intraperitoneally 30 min before and 60 min after E2 treatment to the melatonin plus E2 group. Animals were sacrificed three hours after the estradiol injection, and their blood and liver tissues were prepared for biochemical analyses. Tissue malondialdehyde (MDA) levels and antioxidant enzyme activities--superoxide dismutase (SOD) and glutathione peroxidase (GPx)--were determined in the postmitochondrial fraction, and the results were compared. Estradiol injection caused significant increases in both MDA levels and GPx activity in liver. When melatonin was administered in combination with E2, the effect of estradiol on MDA levels was abolished. A significant decrement in SOD activity occurred in melatonin-treated animals. GPx activity in the blood of E2 plus melatonin-injected animals was significantly higher than those in control animals. Melatonin-treated animals exhibited relatively lower levels of SOD activity than those from the control and E2 plus melatonin groups. This indicates that estradiol could exert oxidant action resulting in an increment in tissue malondialdehyde levels. Enhanced activity of GPx in both liver and blood following melatonin injection may indicate the contribution of this neurohormone on the antioxidant defense.

The effects of acute melatonin and ethanol treatment on antioxidant enzyme activities in rat testes.

The pineal hormone melatonin (N -acetyl, 5-methoxytryptamine) was recently accepted to act as an antioxidant under both in vivo and in vitro conditions. In this study, we examined the possible preventive effect of melatonin on ethanol-induced lipid peroxidation in rat testes. Thirty-seven male Wistar albino rats, 5.5--6 months old, were randomly divided into four groups (9--10 animals in each). The first group (control animals) received 4% ethanol at similar intervals to the experimental groups to equalize the stress effect. The second group received only melatonin i.p. 7 mg kg(-1)bw three times over 1.5 h intervals. The third group received only 30% alcohol 3 g kg(-1)bw twice daily. The fourth group were treated with melatonin and ethanol according to the above protocol, melatonin injections preceding ethanol treatments. The product of lipid peroxidation, malondialdehyde (MDA) and antioxidant enzymes, superoxide dismutase (Cu--Zn SOD), glutathione peroxidase (GPx) and catalase (CAT) were measured in the post-mitochondrial fraction of the testes. MDA levels were significantly increased due to acute ethanol intoxication. GPx activity was higher in the three experimental groups than the control levels. The activity of CAT was increased significantly in the melatonin plus ethanol-treated group but the other groups appeared not to be influenced by acute ethanol treatment. Cu--Zn SOD activity remained unaltered. These results suggest that antioxidants may be a protective agent for the testicular injury caused by ethanol consumption.

Response in DNA ploidy of hepatocytes to tamoxifen and/or melatonin in vivo.

Tamoxifen is known to induce hepatocarcinogenesis in experimental animals and reversible chronic liver diseases in humans. Melatonin has been recently introduced as an oncostatic agent, especially for hormone-dependent tumors. This study was designed in order to investigate whether melatonin has an effect onthe tamoxifen-induced hepatotoxicity. Wistar albino rats were injected tamoxifen citrate intraperitoneally in three different doses (10 mg/kg and 20 mg/kg bw for 26 days; and 45 mg/kg bw for three days). Another group of animals were treated with melatonin once a week in addition to daily tamoxifen injections, whereas the third group received melatonin only. The control animals were injected an equal volume of diluent at corresponding intervals. At the end of the experimental period, the animals were sacrificed and the livers were prepared for the flow cytometric DNA analysis. DNA histograms were analyzed using the multicycle program. In experimental groups, all animals had aneuploid cell population. The difference in the diploid/ aneuploid ratio of each experimental group as compared to the control group according to Fischer's exact test was found to be highly significant (p < 0.002 MEL vs control; and p < 0.0001 for both TAM vs control and MEL+TAM vs control). Among the tamoxifen-injected animals, the proportion of multiploidy to aneuploid cell population was 17, similar to those treated solely with melatonin. Although the melatonin plus tamoxifen group had higher multiploidy percentage (38%), the difference was not statistically significant as compared to the tamoxifen (or melatonin) groups. No significant difference was noted between the animals which were treated with three different doses of tamoxifen. S-phase fraction percentage was significantly different in melatonin- and melatonin plus tamoxifen-injected animals with regard to controls, the degree of significancy being < 0.05 for both. According to our data, tamoxifen injections induced DNA aneuploidy, but did not stimulate proliferation in the liver as estimated by S-phase fraction. Melatonin, whether alone or in combination with tamoxifen, stimulated cell proliferation and produced aneuploidy.

Evaluation of the effect of low-dose oral theophylline therapy on some bone turnover markers and serum prolidase I activity in mild asthmatics.

Hypercalcemia and hypercalciuria observed both in humans and in animals who were on long-term theophylline therapy, prompted us to investigate whether oral theophylline treatment at optimal doses causes any adverse side effects on bone metabolism in mild asthmatics. Therefore, serum osteocalcin (BGP) and total alkaline phosphatase (TALP, EC 3.1.3.1) as bone formation markers, serum prolidase I (EC 3.4.13.9) activity as a marker for collagen metabolism, urinary deoxypyridinoline (Dpd), hydroxyproline (Hyp) and fasting urinary calcium as bone resorption markers, were measured in 18 mild asthmatics who had been treated with theophylline over 1-10 years. Among measured bone turnover markers, BGP, TALP, and Hyp levels were found to be increased in mild asthmatics; and BGP showed the greatest percent mean increase (98%) over the healthy subjects. However, these increments did not exceed the upper reference limits. Serum prolidase I activity was also increased in mild asthmatics receiving theophylline. Our results indicate that theophylline therapy at optimal doses may not exert adverse side effects on bone homeostasis, but patients receiving supratherapeutic doses of theophylline should be under close examination in order to predict future bone mass status.

Acute effects of estradiol and of diethylstilbestrol: pro- or antioxidant potential?

This study was aimed to examine the effects of a single high dose of natural and synthetic estrogens on the antioxidant defense enzymes in liver and blood. Female Wistar albino rats, four to six months old, were divided into three groups, and received either i.p. injections of diethylstilbestrol (DES ; 150 mg kg(-1) b.w.) or s.c. injections of estradiol (E2; 25 mg kg(-1) b.w.), and the third group (control) was injected the solvent. Animals were killed under light ether anesthesia three hours after injection. Cu-Zn superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (Cat) enzyme activities and fluorometric malondialdehyde (MDA) determination were performed in liver tissue homogenates and in blood. Acute estradiol injection caused a significant increase in both MDA levels and GPx activity in liver tissue when compared to the controls, (p <0.05 and p <0.02; respectively). Changes in both enzyme activities and MDA concentration were unremarkable following acute DES injection. In blood, only Cu-Zn SOD activity was significantly altered in blood following E2 injection. Although the significance of alteration in GPx activity remains unclear, it is most likely related to enhanced generation of lipoperoxides. A significant increase in MDA concentrations in liver tissue is indicative of pro-oxidative damage rather than an antioxidant action by E2.

The effect of melatonin administration on ethanol-induced lipid peroxidation in rats.

This study was carried out in order to determine the role of melatonin in preventing lipid peroxidation due to acute ethanol intoxication. Male Wistar Albino rats, 2.5-3 months old, were divided into two groups. Melatonin (in 1% ethanol, 2 mg kg-1 body weight) was given intraperitoneally (i.p.) for 21 days to experimental rats whereas controls received 1% ethanol only. On day 21, 6 g kg-1 body weight ethanol was injected to half of the animals in each group and the remainder were kept as corresponding controls. Animals were killed 5 h after ethanol injection. Malondialdehyde (MDA), reduced glutathione (GSH) and the antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase and catalase) were determined in liver tissue homogenates. MDA levels were increased whereas GSH levels tend to decrease following alcohol injection. Melatonin administration prior to ethanol did not alter MDA and GSH levels of tissue and among antioxidant defence enzymes studied, only CuZn-SOD was found to be increased in animals that received melatonin + ethanol. According to the findings of this study, melatonin did not appear to have any direct effect on alcohol-induced lipid peroxidation.

Changes in enzymatic antioxidant defense system in blood and endometrial tissues of women after menopause.

The effects of menopause on antioxidant enzyme activities were investigated in blood and endometrial tissues of women. Endometrial pieces were obtained from pre- or postmenopausal patients who had hysterectomy due to descendus or prolapsus uteri. In endometrium homogenates, both cytosolic superoxide dismutase (CuZn-SOD) and catalase (CAT) activities were similar in pre- or postmenopausal women (median ages 41 and 64, respectively); whereas GPx (glutathione peroxidase) activity was significantly decreased (p < 0.001). Activity of these enzymes were also compared in the blood of premenopausal and late menopausal women, and only GPx activity was found significantly low (p < 0.01). Subsequent measurements were carried out in blood of healthy menopausal women who were in the same age intervals with the premenopausal subjects studied, and GPx activity was found indifferent in two groups, indicating that the decrement is due to aging rather than the change in hormonal status. CuZn-SOD activity was highest in blood of late menopausal group compared with those in both premenopausal and early menopausal group, giving a significant difference with the latter (p < 0.001). In other words, SOD activity was increased in menopausal women at an older age, showing a diverse change with GPx activity.

Variations in serum cholinesterase activity in different age and sex groups.

Measurements of serum cholinesterase activity has been used to assess liver function, predict susceptibility to prolonged apnoea after administration of the muscle relaxant succinylcholine and monitor excessive exposure to the anti-cholinesterase organophosphorus insecticides (1, 2). Serum cholinesterase activity can be affected by many physiological and pathological conditions such as age, pregnancy, puerperium, obesity, some drug therapy, and liver diseases. Additionally, congenital cholinesterase deficiency, which is due to several genetic variants of the enzyme, has also been reported (3, 4). Since the enzyme activity is altered by many factors, we aimed to show the distribution of serum cholinesterase activity levels in different age and sex groups, in order to establish the reference limits in our population.

Fluoride concentration and profile in different cementum surfaces.

This study was performed to determine the fluoride concentration of the various cementum surfaces in different tooth groups to find out the most proper teeth and tooth surfaces for different cementum studies. For this purpose, direct measurements of phosphorus and fluoride were carried out in an acid etch biopsy solution. The findings indicate that incisors with exposed cementum are the most inappropriate teeth in comparison with the other groups. According to the results obtained it may be recommended that the studies related to fluoride uptake for cementum should be performed on teeth with no gingival recession or on the unerupted teeth.

The effects of fluorides and/or trace elements on the solubilities of enamel and cementum.

The purpose of this study is to determine the effects of fluorides and trace elements applied alone or in combination at different concentrations on the solubilities of enamel and cementum surfaces of the same teeth. The study has been performed on enamel and cementum surfaces of the impacted third molars extracted by surgical operation. Aqueous solutions of sodium fluoride, aluminum potassium phosphate, strontium chloride and titanium tetrachloride at different concentrations were applied to the surfaces. The solubilities of enamel and cementum and the depth of etchings have been calculated by means of the inorganic phosphorus in these etching solutions. According to the results, higher concentrations of fluoride and lower concentrations of strontium and titanium led to a significant reduction into solubilities of enamel and cementum. As certain combined applications of fluorides and trace elements decreased both of the enamel and cementum solubilities, it may be assumed that if such a treatment is beneficial during the adolescence of an individual, it may also be used when he is older.

Selenium-induced activation of brain Na(+)-K(+)-ATPase in rats.

The influence of selenium supplementation on the activity of Na(+)-K(+)-ATPase and on the degree of free radical generation was studied in brain tissue of rats. Selenium was administered for 5 months in drinking water, and was measured in plasma by the fluorometric method at the end of the experimental period. Animals were sacrificed and brain tissue homogenates were used for enzyme assay and for assessment of lipid peroxide formation. Brain tissue from rats who received selenium showed significantly increased Na(+)-K(+)- ATPase activity but also significantly decreased lipid peroxide farmation. Since this enzyme is known to be inhibited by oxygen free radicals, selenium supplementation appears to exert a beneficial effect on the Na(+)-K(+)-ATPase activity by preventing free radical-induced damage.