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Biomedical subjects

A Yasar

Publications and source records attributed to A Yasar.

13 recordsLinked to original sources
PubMed2006

Effects of vitamin E against aluminum neurotoxicity in rats.

The present study examined the protective effects of vitamin E against aluminum-induced neurotoxicity in rats. Wistar rats were given daily aluminum via their drinking water containing 1600 mg/liter aluminum chloride for six weeks. Aluminum induced a significant increase in lipid peroxidation (LPO) in hippocampus and frontal cortex. Furthermore, aluminum caused marked elevation in the levels of the glial markers (glial fibrillary acidic protein (GFAP) and S100B) and proinflammatory cytokines (TNF-alpha and IL-1beta) in both brain areas. Vitamin E treatment reduced the contents of glial markers and cytokines and the levels of LPO. In conclusion, this study demonstrates that vitamin E ameliorates glial activation and reduces release of proinflammatory cytokines induced by aluminum.

Aluminum↗
PubMed2006

Melatonin prevents oxidative stress and inhibits reactive gliosis induced by hyperhomocysteinemia in rats.

Homocysteine (Hcy), an independent risk factor for atherosclerosis, undergoes auto-oxidation and generates reactive oxygen species, which are thought to be main cause of Hcy neurotoxicity. However, the mechanisms leading to neurodegenerative disorders are poorly understood because studies that have investigated the potential neurotoxicity of hyperhomocysteinemia in vivo are scarce. The purpose of this study was to test whether daily administration of methionine, which induces hyperhomocysteinemia, causes glial hyperactivity, and also to investigate the protective effects of melatonin on the brain tissue against oxidative stress of Hcy in rats. There was a significant development of oxidative stress as indicated by an increase in malondialdehyde + 4-hydroxyalkenals in hippocampus and cortex of hyperhomocysteinemic rats, whereas significant reduction was found in the activity of glutathione peroxidase (GSH-Px). Co-treatment with melatonin inhibited the elevation of lipid peroxidation and significantly increased GSH-Px activity in the brain regions studied. Western blot analysis revealed an increase in glial fibrillary acidic protein (GFAP) contents both in hippocampus and frontal cortex (p < 0.001) of hyperhomocysteinemic rats compared to the controls. Administration of melatonin significantly decreased GFAP contents in hippocampus and cortex (p < 0.05). S100B contents increased only in frontal cortex in hyperhomocysteinemic rats compared to the control (p < 0.01) and was inhibited by melatonin treatment (p < 0.01). The present findings show that Hcy can sensitize glial cells, a mechanism which might contribute to the pathogenesis of neurodegenerative disorders, and further suggest that melatonin can be involved in protecting against the toxicity of Hcy by inhibiting free radical generation and stabilizing glial cell activity.

Administration, Oral↗
PubMed2004

Early changes in glial reactivity and lipid peroxidation in diabetic rat retina: effects of melatonin.

Diabetes mellitus, the most common serious metabolic disorder, is characterized by functional and structural changes in the peripheral and central nervous systems. Glial cells provide structural and metabolic support for retinal neurons. During diabetes, one of the early pathogenic events is retinal glial reactivity. We studied the effects of melatonin, which is known to reduce oxidation-based neurotoxicity, on glial reactivity and lipid peroxidation in the retina of diabetic rats. Diabetes was induced by a single injection of streptozotocin (STZ), and these diabetic rats were treated daily either with melatonin (10 mg/kg) or saline vehicle. After 6 weeks of diabetes, we determined the extents of lipid peroxidation and glial reactivity in retina. Lipid peroxidation, measured on the basis of malondialdehyde and 4-hydroxyalkenals concentrations, was increased in diabetic rats (p<0.01) and this increase was prevented by melatonin treatment (p<0.05). Furthermore, gial reactivity, determined immunohistochemically from the levels of glial fibrillary acid protein (GFAP), was also increased significantly (p<0.01). Melatonin administration partially prevented this increase in GFAP content (p<0.05). In conclusion, glial reactivity is an early pathogenic event in diabetic retina and both reactive gliosis and accumulation of malondialdehyde and 4-hydroxyalkenals are prevented by melatonin supplementation.

Animals↗
PubMed2004

Neuroprotection by alpha-lipoic acid in streptozotocin-induced diabetes.

Glial cells provide structural and metabolic support for neurons, and these cells become reactive to any insult to the central nervous system. The streptozotocin (STZ) rat model was used to study glial reactivity and the prevention of gliosis by alpha-lipoic acid (alpha-LA) administration. The expression of glial fibrillary acidic protein (GFAP), S100B protein, and neuron specific enolase (NSE) was determined as well as lipid peroxidation (LPO) and glutathione (GSH) levels in some brain tissues. Western blot analyses showed GFAP, S100B, and NSE levels significantly increased under STZ-induced diabetes in brain, and LPO level increased as well. Administration of alpha-LA reduced the expression both of glial and neuronal markers. In addition, alpha-LA significantly prevented the increase in LPO levels found in diabetic rats. GSH levels were increased by the administration of alpha-LA. This study suggests that alpha-LA prevents neural injury by inhibiting oxidative stress and suppressing reactive gliosis.

Animals↗
PubMed2001

Effects of pinealectomy and exogenous melatonin on serum leptin levels in male rat.

The effects of pinealectomy and exogenous melatonin (N-acetyl-5-methoxytryptamine) on serum leptin levels were investigated in rats. Exogenous administration of melatonin to intact rats resulted in significant decreases in serum leptin levels (P < 0.05) compared to those of the intact control group. Serum leptin levels were significantly elevated in the pinealectomised rats in comparison to the sham-pinealectomised animals (P < 0.001) and were significantly suppressed by exogenous administration of melatonin compared to those of non-treated pinealectomised rats (P < 0.001). Hormone concentrations in the melatonin-treated pinealectomised group were found to be similar to those seen in the sham-pinealectomised group. These results suggest that pineal gland has an effect on leptin release.

Animals↗
PubMed2001

Effects of pinealectomy on the circadian release pattern of leptin in male rat.

OBJECTIVES: Exogenous and endogenous melatonin decrease leptin release. It is not known whether melatonin also has an effect on circadian release pattern of leptin. So, this study was planned to investigate the possible changes in the circadian release of leptin following pinealectomy. METHODS: A group of rats were surgically pinealectomized while some others were exposed to sham operation. The animals were decapitated at 13.30 p.m. and 01.30 a.m. Serum leptin levels were measured by radioimmunoassay. RESULTS: Serum leptin levels at 13.30 p.m. were lower than the values at 01.30 a.m. in both pinealectomized (P<0.002) and sham rats P<0.001). Serum leptin levels measured at 13.30 p.m. and 01.30 a.m. were significantly elevated (P<0.05 and P<0.01, respectively) in the pinealectomized rats in comparison to sham animals. CONCLUSION: The circadian release of leptin does not seem to be regulated by melatonin release from the pineal gland whereas melatonin, physiologically released, may have a decreasing effect on leptin release.

Animals↗
PubMed1997

Pseudomyxoma peritonei in association with primary malignant tumor of the ovary and colon.

Pseudomyxoma peritonei (PMP) is a rare entity that is characterised by abundant intraperitoneal mucinous and gelatinous material associated with an intraperitoneal adenocarcinoma. We report the case of a patient who presented with PMP associated with a ruptured well-differentiated mucinous adenocarcinoma of the ovary and an infiltrating moderately-differentiated mucinous adenocarcinoma of the sigmoid. Diagnosis was made by ultrasonography and CT. Due to the presence of 2 mucinous tumors with different histological grade the most likely pathogenesis was that of multifocal metaplasia. The ovarian and colonic mucinous tumors were independent primary neoplasms and PMP probably was the result of rupture of one of these tumors with peritoneal seeding of viable mucus secreting tumor cells. Aggressive surgical debulking in addition to left hemicolectomy and radical hysterectomy were performed.

Adenocarcinoma, Mucinous↗
PubMed1995

Association of relative nocturnal hypertension and autonomic neuropathy in insulin-dependent diabetic children.

Twenty-four hour BP and heart rate measurements were carried out in fourteen newly diagnosed-, and in twenty-eight diabetics with 5-13 years of duration; and in eight healthy control children. Mean arterial BP rose at night in five-, fell slightly (less than 10%) in five- and fall markedly (more than 10%) in eighteen diabetics with longer duration of the disease. The diurnal-nocturnal difference of mean arterial pressure was significantly lower in the groups with nocturnal BP rise and slight nocturnal BP fall, compared to the control group (< 0.001; p < 0.01, respectively). The diurnal-nocturnal differences of heart rates were significantly lower in diabetics with relative "nocturnal hypertension" compared to the control group (p < 0.05). The presence of subclinical signs of diabetic autonomic neuropathy was significantly higher in patients with nocturnal BP rise and slight nocturnal BP fall compared to patients with marked nocturnal BP fall and newly diagnosed diabetics (chi squared p = 0.02 and p = 0.01, respectively). In conclusion, the prevalence of autonomic symptoms in diabetic children could be related to change in diurnal/nocturnal arterial BP, however longitudinal studies of ABPM are needed to define, whether patients with abnormal BP profiles are candidates for the development of diabetic vascular disease.

Adolescent↗
PubMed1994

Relative nocturnal hypertension in children with insulin-dependent diabetes mellitus.

Twenty-four-hour blood pressure and heart rate measurements were carried out in 14 newly diagnosed diabetics and in 28 diabetics with 5-13 years' duration of the disease; 8 healthy children were used as controls. Mean arterial blood pressure increased at night in 5, decreased slightly (less than 10%) in 5 and decreased markedly (more than 10%) in 18 diabetics with longer duration of the disease. The diurnal-nocturnal differences in heart rates were significantly lower in diabetics with relative "nocturnal hypertension" compared to the control group (p < 0.05). A significant negative correlation was found between maximal arterial blood pressure during physical exercise and the diurnal-nocturnal differences in mean arterial blood pressure in diabetics (r = -0.58; p < 0.02). In conclusion, we found elevated nocturnal blood pressure in a subgroup of children with longer duration of diabetes and without increased albumin excretion. However, longitudinal studies of blood pressure profiles are needed to identify the candidates for diabetic vasculopathy among diabetic children.

Adolescent↗
PubMed1992

The role of sympathetic-adrenergic activity in the regulation of acid-base homeostasis and renal sodium excretion under acute physical stress in type-I diabetic children (IDDM).

To evaluate the ability of stress response, plasma and urinary catecholamine concentrations, urinary electrolytes and acid-base status were measured in IDDM children (Group I: newly diagnoses 2-4 weeks, n = 7; Group II: duration 5-7 yr, n = 9; Group III: duration 10-13 yr, n = 12). The data were compared to healthy controls, n = 7, (mean +/- SD). Physical stress was induced by 2 W/kg/10 min bicycle ergometer. IDDM children exhibited metabolic acidosis under stress (pH: Group I = 7.24 +/- 0.08; Group II = 7.25 +/- 0.05; Group III = 7.19 +/- 0.03 vs C = 7.36 +/- 0.02). Stress induced an increase in the concentration of plasma norepinephrine (PNE in each group, the most pronounced elevation was seen in Group I (19.36 +/- 8.8 nmol/I vs C = 8.3 +/- 3.2, p < 0.2). Baseline PNE level showed a significant decrease with the duration of IDDM. Excretion of urinary NE (UNE) also increased under stress, however, the highest levels were measured in Group III (580 +/- 209 pmol/min/l. 73m2 vs 290 +/- 124 in Group I, p < .01). Baseline urinary dopamine (UDA) excretions were similar in each group. Stress caused an elevation in UDA only in C (2.05 +/- 1.8 vs 4.59 +/- 2.9 pmol/min.l. 73m2). The ratio of baseline UNE/UDA was similar in Groups I, II and C, but higher in Group III. Stress induced a shift towards NE excretion only in diabetic children which was most pronounced in children having IDDM more than 10 years. Stress did not affect urine output in Groups I. and II., but a decrease was observed in Group III (1.1 +/- 0.3 vs 0.7 +/- 0.3 ml/min.1.73 m2, p < .007). Urinary sodium excretion also decreased in Group III after physical loading (130 +/- 47 vs 66 +/- 33 umol/min/1.73 m2). The data show, that physical stress induces a severe lactic acidosis in IDDM. In spite of the decreased systemic sympathetic activity, the renal catecholamine response showed a shift towards vasoconstriction, sodium and fluid retention under physical stress in IDDM. These changes correlate with the duration of the underlying disease.

Acid-Base Equilibrium↗
PubMed1988

Analysis of magnesium and trace elements in urinary calculi by atomic absorption spectrophotometry.

Magnesium and trace element determinations in 29 urinary tract calculi were carried out using an atomic absorption spectrophotometric method. Of the calculi examined, 9 were pure calcium oxalate, 5 were mixed calcium oxalate/uric acid, 5 were mixed calcium oxalate/phosphate, 5 were magnesium ammonium phosphate and 5 were pure cystine. The measurement of magnesium and trace element levels has been considered useful in the elucidation of the mechanism of stone formation and the evaluation of factors leading to pathological consequences. In this study, the Mg, Zn, Cu, Fe, Cd and Pb content in all of the samples was determined and an attempt was made to compare the levels of these elements in calculi with the levels in normal hair.

Humans↗