Cardiovascular responses to intrathecal administration of endomorphins in anesthetized rats

Endomorphins (EMs), the endogenous, potent and selective mu-opioid receptor agonists, have been shown to decrease systemic arterial pressure (SAP) in rats after intravenous (i.v.) administration. In the present study, cardiovascular responses to intrathecal (i.t.) injection of EMs were investigated in urethane-anesthetized rats. It is noteworthy that EMs elicited decreases in SAP and heart rate (HR) in a dose-dependent manner; 10-300nmol/kg were injected intrathecally. Furthermore, these vasodepressor and bradycardic effects were significantly antagonized by naloxone (0.5mg/kg, i.t.). Interestingly, i.t. (5mg/kg) or i.v. (50mg/kg) administrations of N(omega)-nitro-l-arginine methylester (l-NAME) attenuated the vasodepressor and bradycardic effects. Moreover, pretreatment of the rats with muscarinic receptor antagonist atropine (2mg/kg, i.v.) and alpha-adrenoceptor antagonist phentolamine (1mg/kg, i.v.) significantly reduced the vasodepressor effects of EMs. Nevertheless, pretreatment with beta-adrenoceptor antagonist propranolol (2mg/kg, i.v.) could only block the bradycardia effects induced by EMs, but had no significant effects on the hypotension. In summary, all the results suggested that i.t. administration of EMs decreased SAP and HR which were possibly mediated by the activation of opioid receptors in the rat spinal cord. In addition, nitric oxide (NO) release in both the spinal cord and in peripheral tissues might regulate the cardiovascular activities of EMs, and the muscarinic receptor and adrenoceptor played an important role in the regulation of the cardiovascular responses to i.t. administration of EMs.     

The adrenocortical function of alloxan-induced diabetic rats

The purpose of this study is to investigate the adrenocortical function of alloxan-induced diabetic rats. Male rats of Wistar strain, weighing 200-250 gm were used. The results indicated that the adrenocortical response to stress and exogenous corticotropin (ACTH1-24) is decreased during the early diabetic stages (up to 6 days). Evidence from in vivo and in vitro studies shows that the depression is caused by the toxicity of alloxan on the adrenal cortex cells and not by the sudden rise of blood glucose levels. Streptozotocin (another diabetogen) has the same effect as alloxan on adrenal cortex cells.     

Antidiabetic activity of levan polysaccharide in alloxan-induced diabetic rats

This study aims to examine the effects of polysaccharide levan on oxidative stress and hyperglycemia in alloxan-induced diabetic rats. Levan, used in this study, was a microbial levan synthetisized by a non pathogenic bacteria recently isolated and identified as Bacillus licheniformis. Animals were allocated into four groups of six rats each: a control group (Control), diabetic group (Diab.), normal rats received levan (L) and diabetic rats fed with levan (DL). Treated diabetic rats were administrated with levan in drinking water through oral gavage for 60 days. The administration of polysaccharide levan in diabetic rats caused a significant increase in glycogen level by 52% and a decrease in glucose level in plasma by 52%. Similarly, the administration of polysaccharide levan in diabetic rats caused a decrease in the thiobarbituric acid-reactive substances (TBARS) by 31%, 41%, 39% and 25%, an increase in superoxide dismutase (SOD) by 40%, 50%, 44% and 34%, and in catalase (CAT) by 18%, 20%, 12% and 18% in liver, kidney, pancreas and heart, respectively. Furthermore, a significant decrease in hepatic and renal indices toxicity was observed, i.e. alkalines phosphatases (ALP), aspartate and lactate transaminases (AST and ALT) activities, total bilirubin, creatinine and urea levels by 19%, 31%, 32%, 36%, 37% and 23%, respectively. The results show that administration of polysaccharide levan can restore abnormal oxidative indice near normal levels. This study demonstrates, for the first time, that polysaccharide levan is efficient in inhibiting hyperglycemia and oxidative stress induced by diabetes and suggests that levan supplemented to diet may be helpful in preventing diabetic complications in adult rats.     

Supraspinal anti-allodynic and rewarding effects of endomorphins in rats

Two potent endogenous opioid peptides, endomorphin-1 (EM-1) and -2 (EM-2), which are selective micro-opioid agonists, have been identified from bovine and human brain. These endomorphins were demonstrated to produce a potent anti-allodynic effect at spinal level. In the present study, we further investigated their supraspinal anti-allodynic effects and rewarding effects. In a neuropathic pain model (sciatic nerve crush in rats), EM-1 and -2 (15 microg, i.c.v.) both showed significant suppressive effects in the cold-water allodynia test, but EM-1 showed a longer duration than EM-2. Naltrexone (NTX; 15 microg) and naloxonazine (NLZ; 15 microg) were both able to completely block the anti-allodynic effects of EM-1 and -2. In the tests of conditioned place preference (CPP), only EM-2 at the dose of 30 microg showed significant positive rewarding effect, whereas both endomorphins did not induce any reward at the dose of 15 microg. Due to the low solubility and the undesired effect (barrel rotation of the body trunk), EM-1 was not tested for the dose of 30 microg in the CPP tests. It was also found that acute EM-2 (30 microg) administration increased dopamine turnover in the shell of nucleus accumbens in the microdialysis experiments. From these results, it may suggest that EM-1 and -2 could be better supraspinal anti-allodynic agents compared with the other opioid drugs, although they may also induce rewarding.     

Anti-diabetic and anti-oxidant effects of Zingiber Officinale on alloxan-induced and insulin-resistant diabetic male rats

This study was designed to investigate the hypoglycaemic and anti-oxidant effects of Zingiber officinale on experimentally induced diabetes mellitus using alloxan and insulin resistance. Aqueous extracts of raw ginger was administered orally at a chosen dose of 500mg/ml for a period of 4 weeks to alloxan-induced diabetic and insulin resistant diabetic rats. The experimental rats exhibited hyperglycaemia accompanied with weight loss to confirm their diabetic state. Ginger effectively reduced fasting blood glucose and malonydealdehyde levels in alloxan-induced diabetic and insulin resistant diabetic rats compared to control and ginger only treated rats. Furthermore, ginger increased serum insulin level and also enhanced insulin sensitivity in alloxan-induced diabetic and insulin resistant diabetic rats compared to control and ginger only treated rats. The results of the study clearly show that dietary ginger has hypoglycaemic effect, enhances insulin synthesis in male rats and has high antioxidant activity. One of the likely mechanisms is the action of malonydealdehyde, which acts as a scavenger of oxygen radicals. Keywords: Diabetes mellitus, Insulin resistance, Zingiber officinale, Malonydealdehyde.     

Ultrastructural determination of gingival Langerhans cells in alloxan-induced diabetic rats

The ultrastructure of Langerhans cells has not been fully investigated in diabetes-associated gingival tissues. The present study was carried out to investigate the ultrastructure of gingival Langerhans cells in alloxan-induced diabetic rats. Gingival biopsies were obtained from 22 diabetic and 18 control rats. Langerhans cells were observed by transmission electron microscopy (TEM) in the basal layers of healthy oral epithelium. On rare occasions, Langerhans cells were found in the suprabasal layers of the oral epithelium. Langerhans cells in the oral epithelium of diabetic rats were seen in the basal and suprabasal layers. Usually, Langerhans cells had clear cytoplasm and convoluted or indented nuclei and few or no specific granules. The clear cytoplasm contained mitochondria, lysosomes and a small number of rough-surfaced endoplasmic reticulum regions, but it lacked tonofilament. Occasionally, centrioles were also observed in the cytoplasm. The membrane of Langerhans cells had no junctional complexes such as desmosomes. In diabetic rats, Langerhans cell precursors were developed into specific granule-bearing cells. Both Langerhans cells and their granules were more frequent in the gingiva of diabetic rats than in the control group. These data suggest that Langerhans cells play an important role in explaining the pathogenesis and development of diabetic gingivitis.     

Anti-diabetic properties of chromium citrate complex in alloxan-induced diabetic rats

The chromium citrate complex [CrCIT] was synthesized and its structure was determined by infrared, UV-visible and atomic absorption spectroscopy, elemental and thermodynamic analysis. Anti-diabetic activity, oxidative DNA damage capacity and acute oral toxicity of [CrCIT] were investigated and compared with that of chromium trichloride hexahydrate. [CrCIT] was synthesized in a single step reaction by chelating chromium(III) with citric acid in aqueous solution. The molecular formula of [CrCIT] was inferred as CrC(6)H(5)O(7)·4H(2)O. The anti-diabetic activity of the complex [CrCIT] was assessed in alloxan-diabetic rats by daily oral gavage for 3 weeks. The biological activity results showed that the complex at the dose of 0.25-0.75 mg Cr/kg body weight could decrease the blood glucose level and increase liver glycogen level in alloxan-diabetic rats. [CrCIT] had more beneficial influences on the improvement of controlling blood glucose, serum lipid and liver glycogen levels compared with CrCl(3)·6H(2)O. Furthermore, [CrCIT] did not cause oxidative DNA damage under physiologically relevant conditions, and [CrCIT] did not produce any hazardous symptoms or deaths in acute oral toxicity test, showing the LD(50) value for female and male rats were higher than 15.1 g/kg body weight. The results suggested that [CrCIT] might represent a novel and proper chromium supplement with potential therapeutic value to control blood glucose in diabetes.     

Ultrastructural changes in the gracile nucleus of alloxan-induced diabetic rats

The present study reports ultrastructural changes in the gracile nucleus of male Wistar rats after alloxan-induced diabetes. During the acute phase (3-7 days) degenerating electron-dense dendrites and axon terminals were dispersed in the neuropil. Degenerating dendrites were characterized by an electron-dense cytoplasm, swollen mitochondria, dilated endoplasmic reticulum and randomized ribosomes. Degenerating axon terminals were characterized by an electron-dense cytoplasm and clustering of small spherical agranular vesicles. Degenerating axon terminals may form the central element or part of a synaptic glomerulus. Macrophages were present in the neuropil and in the process of engulfing neuronal elements. During the medium phase (1-6 months), most of the degenerating dendrites and axon terminals had been engulfed or removed by macrophages. During the late phase (9-12 months), a second wave of degeneration occurred in the gracile nucleus, similar to the acute phase.     

Hypoglycemic activity of curcumin synthetic analogues in alloxan-induced diabetic rats

The currently available therapies for type 2 diabetes have been unable to achieve normoglycemic status in the majority of patients. The reason may be attributed to the limitations of the drug itself or its side effects. In an effort to develop potent and safe oral antidiabetic agents, we evaluated the in vitro and in vivo hypoglycemic effects of 10 synthetic polyphenolic curcumin analogues on alloxan-induced male diabetic albino rats. In vitro studies showed 7-bis(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione (4) to be the most potential hypoglycemic agent followed by 1,5-bis(4-hydroxy-3-methoxyphenyl)penta-1,4-dien-3-one (10). Structure activity relationship (SAR) of the tested compounds was elucidated and the results were interpreted in terms of in vitro hypoglycemic activities. Furthermore, oral glucose tolerance test (OGTT) with compounds 4, 10 and reference hypoglycemic drug glipizide showed that compound 4 and glipizide had relatively similar effects on the reduction of blood glucose levels within 2?h. Thus, compound 4 might be regarded as a potential hypoglycemic agent being able to reduce glucose concentration both in vitro and in vivo.     

Sodium molybdate improves the phagocytic function in alloxan-induced diabetic rats

Diabetes mellitus is a disease, which virtually affects all the systems in the body including the immune system. Bacterial infections are important causes of increased morbidity and mortality in diabetic patients. In the present study, we assessed the effect of molybdate on immune responses of diabetic rats. The phagocytic potency and nitroblue tetrazolium dye reduction capacity were found to be considerably lowered whereas soluble immune complex formation enhanced significantly in diabetic rats when compared with control rats. From our findings, it is suggested that dietary intake of molybdate may have a vital role in enhancing immune functions during diabetic mellitus.     

Antihyperglycemic activity of Eclipta alba leaf on alloxan-induced diabetic rats

Eclipta alba, an indigenous medicinal plant, has a folk (Siddha and Ayurvedha) reputation in rural southern India as a hypoglycemic agent. In order to confirm this claim, the present study was carried out to evaluate the antihyperglycemic effect of E. alba and to study the activities of liver hexokinase and gluconeogenic enzymes such as glucose-6-phosphatase and fructose 1,6-bisphosphatase in the liver of control and alloxan-diabetic rats. Oral administration of leaf suspension of E. alba (2 and 4 g/kg body weight) for 60 days resulted in significant reduction in blood glucose (from 372.0 +/- 33.2 to 117.0 +/- 22.8), glycosylated hemoglobin HbA(1)c, a decrease in the activities of glucose-6 phosphatase and fructose 1,6-bisphosphatase, and an increase in the activity of liver hexokinase. E. alba at dose of 2 g/kg body weight exhibited better sugar reduction than 4 g/kg body weight. Thus, the present study clearly shows that the oral administration of E. alba possess potent antihyperglycemic activity.     

Hypoglycemic and hypolipidemic effects of aqueous extract of Arachis hypogaea in normal and alloxan-induced diabetic rats.

The hypoglycemic and hypolipidemic effect of aqueous extract of Arachis hypogaea was investigated in normal and alloxan-induced diabetic rats. The extract caused a significant (P < 0.05) decrease of fasting blood glucose of both normal and alloxan-induced diabetic rats from 102.60 +/- 1.65 mg/dl to 88.79 +/- 0.94 mg/dl for normal and 189.0 +/- 30.79 mg/dl to 107.55 +/- 1.54 mg/dl for alloxan-induced diabetic rats. The extract also caused a significant (P < 0.05) decrease in serum triglyceride, total cholesterol, HDL-cholesterol and LDL-cholesterol in both normal and alloxan-induced diabetic rats.     

The ultrastructure of the capillaries in the gingiva of alloxan-induced diabetic rats

The diabetic effects of alloxan (type I diabetes mellitus) were investigated in 40 Wistar albino rats (18 controls and 22 diabetics). Alloxan in sterile physiological saline was injected into animals intravenously. After the induction of diabetes with alloxan, the ultrastructure of the capillaries in the gingiva was examined by transmission electron microscopy. The thickness of the basement membranes was observed closely adherent to the endothelial cells of the capillary alloxan-diabetic rats. It was greatly thickened owing to the increase in its amorphous, granular and filamentous material with occasional scattered collagen fibres. In some sections, the capillary lumens of the diabetics were closed by epithelial cells. Loss of cytoplasmic material and hyalinization were seen in some smooth muscle cells. In addition, the mitochondrial cristae of smooth muscle cell and epithelial cells disappeared. There was endothelial integrity throughout the smooth muscle cells.     

Characterization of the ultrastructure of gingival mast cells in alloxan-induced diabetic rats

The morphological changes of gingival mast cells of alloxan-induced diabetic rats were studied by electron microscopy. The following observations were made. The cell nucleus and cytoplasm degenerated. The electron density of the granules in the cell cytoplasm clearly decreased. Some granules had dense irregular threads and the granules were surrounded by a thin vacuole. A ghost vacuole formed in some mast cells and disorganized materials accumulated in the cytoplasm. The mast cell nuclei were generally irregular and degenerating mast cells had pyknotic nuclei. General destruction of the cell membrane and granule shedding in some samples was noted and mitochondria with atypical cristae in the cytoplasm of the mast cells were seen. We conclude that the characteristics of the ultrastructure of gingival mast cells in diabetics are distinctive and should be used as criteria for pathogenesis of gingival inflammation.     

Hypoglycemic,antiperoxidative and antihyperlipidemic effects of saponins from Solanum anguivi Lam. fruits in alloxan-induced diabetic rats

The present study evaluates the hypoglycemic, antiperoxidative and antihyperlipidemic activities of saponins from Solanum anguivi fruits in alloxan induced diabetes rats. Diabetic rats were treated with saponin (20–100 mg/kg) for 21 days. Results indicated that administration of saponins significantly reduced the elevated levels of glucose, decreased total cholesterol (TC), total triglycerides (TG), low density lipoprotein (LDL) and increased high density lipoprotein (HDL) in the serum towards normalcy when compared to the diabetic control (p < 0.05). In addition, saponins exhibited strong inhibition of lipid peroxidation and increased the levels of antioxidant enzymes (superoxide dismutase and catalase) in the serum, liver and pancreas when compared to the diabetic control (p < 0.05). Our results suggest that saponins from S. anguivi fruit can enhance the hypoglycemic, hypolipidemic and antioxidant properties in alloxan-induced diabetic rats, and may have the potential to be used in the prevention or in the management of diabetes.     

Effect of sodium molybdate on carbohydrate metabolizing enzymes in alloxan-induced diabetic rats

We evaluated the effect of sodium molybdate on carbohydrate metabolizing enzymes and mitochondrial enzymes in diabetic rats. Diabetic rats showed a significant reduction in the activities of glucose metabolising enzymes like hexokinase, glucose-6-phosphate dehydrogenase, glycogen synthase and in the level of glycogen. An elevation in the activities of aldolase, glucose-6-phosphatase, fructose 1,6- bisphosphatase, glycogen phosphorylase and in the level of blood glucose were also observed in diabetic rats when compared to control rats. The activities of mitochondrial enzymes isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, NADH-dehydrogenase and cytochrome-C-oxidase were also significantly lowered in diabetic rats. Molybdate administration to diabetic rats reversed the above changes in a significant manner. From our observations, we conclude that administration of sodium molybdate regulated the blood sugar levels in alloxan-induced diabetic rats. Sodium molybdate therapy not only maintained the blood glucose homeostasis but also altered the activities of carbohydrate metabolising enzymes. Molybdate therapy also considerably improved the activities of mitochondrial enzymes, thereby suggesting its role in mitochondrial energy production.     

Alterations in beta-islets of Langerhans in alloxan-induced diabetic rats by marine Spirulina platensis

Marine Spirulina platensis may potentially influence the metabolic process in animal cells, and the effect of marine Spirulina platensis in normal and alloxan-induced diabetic rats was therefore investigated. Normal and diabetic rats (albino Wistar strain) were orally administered marine Spirulina platensis for 30 days and their blood levels of glucose and insulin and body weight changes were determined. Pancreatic histopathology was also noted. Treatment with marine Spirulina platensis caused significant alterations in the content of these indicators and therefore in the antidiabetic capacity of the treated animals compared to control rats.     

C-terminal amide to alcohol conversion changes the cardiovascular effects of endomorphins in anesthetized rats

Endomorphin1-ol (Tyr-Pro-Trp-Phe-ol, EM1-ol) and endomorphin2-ol (Tyr-Pro-Phe-Phe-ol, EM2-ol), with C-terminal alcohol (-ol) containing, have been shown to exhibit higher affinity and lower intrinsic efficacy in vitro than endomorphins. In the present study, in order to investigate the alterations of systemic hemodynamic effects induced by C-terminal amide to alcohol conversion, responses to intravenous (i.v.) or intracerebroventricular (i.c.v.) injection of EM1-ol, EM2-ol and their parents were compared in the system arterial pressure (SAP) and heart rate (HR) of anesthetized rats. Both EM1-ol and EM2-ol induced dose-related decrease in SAP and HR when injected in doses of 3-100 nmol/kg, i.v. In terms of relative vasodepressor activity, it is interesting to note that EM2-ol was more potent than endomorphin2 [the dose of 25% decrease in SAP (DD25) = 6.01+/-3.19 and 13.99+/-1.56 nmol/kg, i.v., respectively] at a time when responses to EM1-ol were less potent than endomorphin1. Moreover, decreases in SAP in response to EM1-ol and EM2-ol were reduced by naloxone, atropine sulfate, L-NAME and bilateral vagotomy. It indicated that the vasodepressor responses were possibly mediated by a naloxone-sensitive, nitric oxide release, vagus-activated mechanism. It is noteworthy that i.c.v. injections of -ol derivatives produced dose-related decreases in SAP and HR, which were significantly less potent than endomorphins and were attenuated by naloxone and atropine sulfate. In summary, the results of the present study indicated that the C-terminal amide to alcohol conversion produced different effects on the vasodepressor activity of endomorphin1 and endomorphin2 and endowed EM2-ol distinctive hypotension characters in peripheral (i.v.) and central (i.c.v.) tissues. Moreover, these results provided indirect evidence that amidated C-terminus might play an important role in the regulation of the cardiovascular system.     

Hepatic and pancreatic effects of polyenoylphosphatidylcholine in rats with alloxan-induced diabetes

Polyenoylphosphatidylcholine (PPC: 100 or 300 mg kg^?1 b.w., by gastric intubation for 30 days) produced a clearcut protection of the liver of rats treated with alloxan (150 mg kg^?1 b.w., i.p.). The liver of rats treated with alloxan was characterized by hydropic dystrophy and lymphocytic infiltrations. Treatment with alloxan increased serum γ-GT and ALAT activities. The liver structure of rats treated with PPC did not differ from the liver of control animals. PPC normalized the biochemical abnormalities caused by the diabetes. The number of pancreatic islets and β/α; cell ratio decreased in the diabetic rats. A number of β-cells in this group did not contain granules. PPC prevented the decrease in the number of islets and the β/α; cell ratio in the pancreas of the diabetic rats. The intensity of staining of β-cell granules in the pancreas of PPC-treated rats had a position intermediate between the control and diabetic groups. Alloxan increased the blood glucose content where treatment with PPC decreased this. The results suggest that PPC acts as a cytoprotector in the liver and pancreas of rats with experimental diabetes induced by alloxan.