فهرست مطالب bijan farzami

Sulfonylurea agents such as Glibenclamide (Glyburide) have been widely prescribe in treatment of type 2 diabetic patients for decades, but controversy remains about their precise mechanism of action. On the other hand, glucokinase serves as a glucose sensor in pancreatic β-cells and plays a key role in the regulation of insulin secretion and glucose homeostasis. The aim of the present study was to evaluate the effect of Glibenclamide on insulin secretion and glucokinase activity in the rat isolated pancreatic islets of Langerhans. The islets from normal and type 2 diabetic rats were isolated by collagenase digestion method. Glucokinase activity was measured via determination the rate of glucose-6-phosphate formation in the fluorometric assay. Insulin secretion from hand-picked islets was evaluated by static incubation technique. Insulin concentration was measured by rat insulin ELISA kit. Our findings obtained from incubation of Glybenclamide with pancreatic islets revealed that this agent increases basal insulin secretion (at 2.8 mM glucose) in both normal and diabetic rats as compared it with control islet (without drug). However, the increase of insulin secretion in response to 16.7 mM glucose was not significant. On the other hand, Glybenclamide had no activating and/or inhibiting effect on pancreatic glucokinase activity in both diabetic and normal Rats. But reduced activity of this enzyme in diabetic rats was significant in comparison with normal. These data show that increasing effect of Glybenclamide on insulin secretion is through a mechanism other than affecting Glucose Mediated Insulin Release. Moreover, the regulation of pancreatic glucokinase does not depend on glybenclamid.

Glucokinase serves as a glucose sensor in pancreatic β-cells and plays a key role in glucose homeostasis and glucose-stimulated insulin secretion (GSIS). In the present study we examined the effect of glucosamine, a glucokinase inhibitor, on the pancreatic glucokinase and hexokinase activities and on insulin secretion from freshly rat pancreatic islets of Langerhans. Insulin concentration was measured by rat insulin ELISA kit. The pancreatic islets from normal and type 2 diabetic (nSTZ) rats were isolated by collagenase digestion method. Glucose phosphorylation was quantitated by measuring the rate of glucose-6-phosphate formation in the fluorometric assay. Insulin secretion from hand-picked islets was evaluated in static incubation system. Insulin concentration was measured by rat insulin ELISA kit. Our findings demonstrate that glucosamine in a dose dependent manner, reduced glucokinase activity in islet extract, but had no effect on hexokinase activity. The glucose-stimulated insulin secretion, was inhibited by glucosamine but it had no effect on the basal insulin secretion. In diabetic rats glucokinase was decreased while the basal insulin secretion and the activity of hexokinase were higher than normals. Based on results obtained from the present study, the assumption could be made that the decrease in the activity of glucokinase of pancreatic islets could be related to the impaired glucose stimulated insulin secretion. The increase in basal insulin secretion of diabetic rats may be due to an increase in pancreatic hexokinase activity.

Sulfonylurea agents such as Glibenclamide (Glyburide) have been widely prescribe in treatment of type 2 diabetic patients for decades, but controversy remains about their precise mechanism of action. On the other hand, glucokinase serves as a glucose sensor in pancreatic β-cells and plays a key role in the regulation of insulin secretion and glucose homeostasis. The aim of the present study was to evaluate the effect of Glibenclamide on insulin secretion and glucokinase activity in the rat isolated pancreatic islets of Langerhans.
The islets from normal and type 2 diabetic rats were isolated by collagenase digestion method. Glucokinase activity was measured via determination the rate of glucose-6-phosphate formation in the fluorometric assay. Insulin secretion from hand-picked islets was evaluated by static incubation technique. Insulin concentration was measured by rat insulin ELISA kit.
Our findings obtained from incubation of Glybenclamide with pancreatic islets revealed that this agent increases basal insulin secretion (at 2.8 mM glucose) in both normal and diabetic rats as compared it with control islet (without drug). However, the increase of insulin secretion in response to 16.7 mM glucose was not significant. On the other hand, Glybenclamide had no activating and/or inhibiting effect on pancreatic glucokinase activity in both diabetic and normal Rats. But reduced activity of this enzyme in diabetic rats was significant in comparison with normal.
These data show that increasing effect of Glybenclamide on insulin secretion is through a mechanism other than affecting Glucose Mediated Insulin Release. Moreover, the regulation of pancreatic glucokinase does not depend on glybenclamid.

Zn (II) is an important regulator of caspase-3, as well as an antioxidant, microtubule stabilizer, growth cofactor, and anti-inflammatory agent. Over the past 30 years, many researchers have demonstrated the important role of Zn (II) in a variety of physiological processes, including growth and development, maintenance and priming of the immune system, and in tissue repair and regeneration. In this study, we present evidence that chelation of extracellular zinc by diethylenetriaminepentacetic acid (DTPA) in different concentrations causes cell death in carcinoma cell lines, HT29/219 and SW742. Hoechst 33258 staining revealed that cell death was mainly by apoptosis. Additionally, significant increases in the activity of caspase-3 and -9 were observed in both cell lines. Caspase-8 activation was negligible in both cell lines. The cytotoxicity/apoptotic effect of DTPA was inhibited significantly by Zn (II), Cu (II) and N-Acetyl-L-Cysteine (NAC) (P<0.05). Therefore, DTPA, the membrane-impermeable metal ion chelator, induces apoptosis through the depletion of extracellular zinc ion.

The determination of insulin receptors on RBC membrane is a suitable tool for the study of these receptors in diabetes and its related complications. The common methods for the study is the biopsy of fat or muscular tissues, cell culture or a preparation of certain amount of monocytes which is associated with some difficulties. Present study utilizes RBC's for this purpose. Certain amount of RBCs were exposed to a known amount of labeled Insulin and varying concentration of unlabelled Insulin. The competitive effect of Insulin replacement was determined by the measurement of residual receptor radioactivity. This study was carried out in three groups of healthy, poor controlled and good controlled diabetics. There were significant differences between the normal and poor controlled diabetics (P=0.017). In addition differences in receptor binding was obtained between good controlled diabetics and normal which were not significant (P=0.09). All changes were inversely proportional to the HbA1C of specimen. Using Scat chard plots the number of receptors in each group, normal, poor controlled and good controlled were determined to be 1820 (± 72.8), 1026 (±40.4) and 1230 (± 49.2) respectively. Considering the above results, it could be seen that the evaluation of the number of receptors in RBC could be a suitable tool for studying the state of insulin receptor in both physiological and pathological conditions.

Glucokinase serves as a glucose sensor in pancreatic β-cells and plays a key role in glucose homeostasis and glucose-stimulated insulin secretion (GSIS). In the present study we examined the effect of glucosamine, a glucokinase inhibitor, on the pancreatic glucokinase and hexokinase activities and on insulin secretion from freshly rat pancreatic islets of Langerhans. Insulin concentration was measured by rat insulin ELISA kit.
The pancreatic islets from normal and type 2 diabetic (nSTZ) rats were isolated by collagenase digestion method. Glucose phosphorylation was quantitated by measuring the rate of glucose-6-phosphate formation in the fluorometric assay. Insulin secretion from hand-picked islets was evaluated in static incubation system. Insulin concentration was measured by rat insulin ELISA kit.
Our findings demonstrate that glucosamine in a dose dependent manner, reduced glucokinase activity in islet extract, but had no effect on hexokinase activity. The glucose-stimulated insulin secretion, was inhibited by glucosamine but it had no effect on the basal insulin secretion. In diabetic rats glucokinase was decreased while the basal insulin secretion and the activity of hexokinase were higher than normals.
Based on results obtained from the present study, the assumption could be made that the decrease in the activity of glucokinase of pancreatic islets could be related to the impaired glucose stimulated insulin secretion. The increase in basal insulin secretion of diabetic rats may be due to an increase in pancreatic hexokinase activity.

The determination of insulin receptors on RBC membrane is a suitable tool for the study of these receptors in diabetes and its related complications. The common methods for the study is the biopsy of fat or muscular tissues, cell culture or a preparation of certain amount of monocytes which is associated with some difficulties. Present study utilizes RBC's for this purpose.
Certain amount of RBCs were exposed to a known amount of labeled Insulin and varying concentration of unlabelled Insulin. The competitive effect of Insulin replacement was determined by the measurement of residual receptor radioactivity. This study was carried out in three groups of healthy, poor controlled and good controlled diabetics.
There were significant differences between the normal and poor controlled diabetics (P=0.017). In addition differences in receptor binding was obtained between good controlled diabetics and normal which were not significant (P=0.09). All changes were inversely proportional to the HbA1C of specimen. Using Scat chard plots the number of receptors in each group, normal, poor controlled and good controlled were determined to be 1820 (± 72.8), 1026 (±40.4) and 1230 (± 49.2) respectively.
Considering the above results, it could be seen that the evaluation of the number of receptors in RBC could be a suitable tool for studying the state of insulin receptor in both physiological and pathological conditions.

Insulin dependant Diabetes Mellitus (IDDM) is associated with a reduction in production or secretion of insulin from pancreatic Islets. On the other hand increase in insulin secretion will result in destruction of islets that will lead to Diabetes. Therefore the factors that could regulate secretion will prevent the onset of diabetes. Glucose metabolism that commences with the glucokinase action is closely related to insulin secretion. The aim of this study is to survey the effect of eat ions Zn2+, V5+ and W5+ on insulin secretion and on the key enzyme, glucokinase, which is known to play an important role in insulin secretion. 20 single islets were seprated from pancreatic tissues of each normal and diabetic rats and placed in tubes containing perfusion medium. Method ions with different concentrations/ and controls were provided with each set of experiment. Insulin secretion were determined using IDMA method. Glucokinaes activity in homogenate supernatant of normal and diabetic rats was assayed by spectropho to metric methods. the level of insulin concernlyation was shown to increase with vandate and tungsten treatment in normal and diabetic rats / and decreased by zinc. The effect of zinc on glucokinase activity was similarly reducing. Tungsten caused an increase in glucokinase activity (p<.001) while vandate showed no effect on the activity of enzyme. The inhibitory effect of zinc on insulin secretion and the enhancing effect of tungsten correlate closely with their effect on glucokinase activity. There for the effect in insulin secretion could be assumed to be via glucokinase activation or inhibition. The effect of vandate on insulin secretion my be through other mechanisms which is not yet clarified.

Insulin dependant Diabetes Mellitus (IDDM) is associated with a reduction in production or secretion of insulin from pancreatic Islets. On the other hand increase in insulin secretion will result in destruction of islets that will lead to Diabetes .Therefore the factors that could regulate secretion will prevent the onset of diabetes . Glucose metabolism that commences with the glucokinase action is closely related to insulin secretion.
The aim of this study is to survey the effect of eat ions Zn2, V5 and W5 on insulin secretion and on the key enzyme, glucokinase, which is known to play an important role in insulin secretion.
20 single islets were seprated from pancreatic tissues of each normal and diabetic rats and placed in tubes containing perfusion medium . Method ions with different concentrations/ and controls were provided with each set of experiment . Insulin secretion were determined using IDMA method. Glucokinaes activity in homogenate supernatant of normal and diabetic rats was assayed by spectropho to metric methods.
the level of insulin concernlyation was shown to increase with vandate and tungsten treatment in normal and diabetic rats / and decreased by zinc .The effect of zinc on glucokinase activity was similarly reducing . Tungsten caused an increase in glucokinase activity (p The inhibitory effect of zinc on insulin secretion and the enhancing effect of tungsten correlate closely with their effect on glucokinase activity. There for the effect in insulin secretion could be assumed to be via glucokinase activation or inhibition . The effect of vandate on insulin secretion my be through other mechanisms which is not yet clarified.

The non-enzymatic glycosylation (NEG) of proteins in diabetes damages both the structure and function of these proteins. In vivo and in vitro studies have shown that NEG of proteins and advanced glycosylation end-products (AGE) contribute to the pathogenesis of both macrovascular, such as atherosclerosis, and microvascular complications, such as retinopathy and nephropathy, in diabetes.
We studied the electrophoretic mobility, fluorescence at isoelectric pH, and time-dependent AGE formation of glycosylated albumin. For the first time, we have used isoelectric focusing to study serum glycosylated albumin in diabetic patients and healthy controls.
After 10 weeks incubation with glucose, the electrophoretic mobility of glycosylated albumin increased 21.3% compared with normal albumin. The isoelectric pH of albumin decreased from 4.6 on day 1 to 4.1 on day 7. The increase in electrophoretic mobility was accompanied by the drop in pH during the first week of incubation. These changes correlated well with those observed by fluorescence. The glucose content of the albumin samples decreased during the first week of incubation, but gradually increased thereafter. Fluorescence readings agreed with these observations. Using isoelectric focusing, there was a significant difference between the serum albumin of diabetic and normal individuals (p Increased electrophoretic mobility during the first week with a simultaneous decline in isoelectric pH shows that AGE formation begins after the first week. The reduction in glucose concentration during the first week and its subsequent increase during the second week may be attributed to the formation and hydrolysis of AGE. This method may be used to determine the stability or progress of diabetes.

The non-enzymatic glycosylation (NEG) of proteins in diabetes damages both the structure and function of these proteins. In vivo and in vitro studies have shown that NEG of proteins and advanced glycosylation end-products (AGE) contribute to the pathogenesis of both macrovascular, such as atherosclerosis, and microvascular complications, such as retinopathy and nephropathy, in diabetes. We studied the electrophoretic mobility, fluorescence at isoelectric pH, and time-dependent AGE formation of glycosylated albumin. For the first time, we have used isoelectric focusing to study serum glycosylated albumin in diabetic patients and healthy controls. After 10 weeks incubation with glucose, the electrophoretic mobility of glycosylated albumin increased 21.3% compared with normal albumin. The isoelectric pH of albumin decreased from 4.6 on day 1 to 4.1 on day 7. The increase in electrophoretic mobility was accompanied by the drop in pH during the first week of incubation. These changes correlated well with those observed by fluorescence. The glucose content of the albumin samples decreased during the first week of incubation, but gradually increased thereafter. Fluorescence readings agreed with these observations. Using isoelectric focusing, there was a significant difference between the serum albumin of diabetic and normal individuals (p<0.001). Increased electrophoretic mobility during the first week with a simultaneous decline in isoelectric pH shows that AGE formation begins after the first week. The reduction in glucose concentration during the first week and its subsequent increase during the second week may be attributed to the formation and hydrolysis of AGE. This method may be used to determine the stability or progress of diabetes.

Urtica dioica, or the stinging nettle, is recommended by ancient medical texts for the treatment of high blood sugar.
We set up a perifusion system, in which an exact number of islets of Langerhans were exposed to an active component of the leaf extract of Urtica dioica, obtained by TLC. The active component was then injected into the peritoneum of both normal and diabetic rats to evaluate response in vivo.
There was a marked increase in insulin secretion in vitro, as determined by ELISA. In vivo, there was an increase in blood insulin content following intraperitoneal injection. The increase in serum insulin observed at 60 minutes was associated with a decrease in blood glucose, checked several times during the observation period. Maximum insulin release over 120 minutes was equal to five times the baseline value. The decrease in blood sugar correlated with both the timing and magnitude of insulin release.
Notwithstanding the magnitude of the changes observed, the results obtained in normal and diabetic rats were similar.

Urtica dioica, or the stinging nettle, is recommended by ancient medical texts for the treatment of high blood sugar. We set up a perifusion system, in which an exact number of islets of Langerhans were exposed to an active component of the leaf extract of Urtica dioica, obtained by TLC. The active component was then injected into the peritoneum of both normal and diabetic rats to evaluate response in vivo. There was a marked increase in insulin secretion in vitro, as determined by ELISA. In vivo, there was an increase in blood insulin content following intraperitoneal injection. The increase in serum insulin observed at 60 minutes was associated with a decrease in blood glucose, checked several times during the observation period. Maximum insulin release over 120 minutes was equal to five times the baseline value. The decrease in blood sugar correlated with both the timing and magnitude of insulin release. Notwithstanding the magnitude of the changes observed, the results obtained in normal and diabetic rats were similar.

Ribonuclease inhibitor is an acidic protein, soluble in cytoplasm. It is abundantly present in human placenta. It could be extracted from this organ to the extent of 1mg/placenta using chemical ion exchange and affinity techniques. Molecular weight of this protein is estimated by electophoresis or SDS-PAG electrophoresis using standards of known proteins.
Molecular weight has been found to be 48000D. The inhibitor could from a 1 :1 complex with bovine pancreatic ribpnuclease in a noncompetitive fashion (Ki= 2.9. 10-10). Optimal PH for such inhibition is found to be 7.6±0.1
This compound is currently for nucleic acid separations due to its protective abilities and also in genetic engineering, to identify genetic defects in a wide variety of diseases. Thus, due to the importance of the subject, we undertook the kinetic - inhibitory studies of this inhibitor to obtain more insight about the regulatory mechanism of the protein.

Derivatives of phenyl-keto butenoic acids have been reported to be inhibitors of pyruvate decarboxylase, (PDC). The inhibition of transketolase, a thiamine requiring enzyme such as PDF, by meta nitrophenyl derivative of 2-oxo-3-butenoic acid (MNPB) is reported here. These studies indicate that the inhibitor binds to the enzyme at the active site. A two-step inhibition was observed, first the inhibitor reacts with the enzyme on one site- non-cooperative with Mg2+, and TPP, inhibiting the enzyme, second in higher concentration of the inhibitor an abrupt enhancement of the inhibition takes place. In the absence of cofactors, the lower concentration of the inhibitor caused an enhancement of activation to 150% of original enzyme activity followed by a drop to a low 50%  in 60 minutes. Higher concentration of the inhibitor produced an inhibition with a half-life that was pronouncedly larger than when cofactors were present (). We conclude therefore that the enzyme contains a regulatory and a catalytic site with the regulatory site functional, without the aid of cofactors and that the cofactors are auxiliary for the action of the enzyme. The lowering effect of the reaction half-life by the cofactors is due to the rate enhancement caused by cofactors in the catalytic site of the enzyme.