Features of the morphofunctional state of the endocrine part of the pancreas during the development of experimental diabetes in the presence of regulatory peptides

The multiple 7-day intranasal introduction of PGArg and GPArg peptides at a dose of 1 mg per kg body weight before the injection of the diabetogenic dose of alloxan provided the maintenance of normoglycemia in rats. The similar introduction of PGPArg peptide did not provide any protection against the development of diabetes mellitus. The quantity of pancreatic islets in the animals from this group remained quite comparable to the norm, but the total number of cells per islet was below the norm, as well as in the control group. The GPArg peptide showed the best results as a preventive anti-diabetic agent.     

Antidiabetogenic action of Pro-Gly-Arg and Pro-Gly-Pro-Arg peptides after their intranasal chronic administration to animals

It was shown that chronic (over 7 days) intranasal injection of the Pro-Gly-Arg tripeptide to rats in the dose 1 mg/kg before the injection of a diabetogenic dose of alloxan, promotes effective defense against development of insulin dependent diabetes mellitus. At the same time, the tetra-peptide Pro-Gly-Pro-Arg did not show a hypoglycemic affect during diabetes mellitus provocation. Administration of Pro-Gly-Arg and Pro-Gly-Pro-Arg peptides also activates anticoagulation potential.     

Changes in somatotropic and lactotropic functions of the adenohypophysis of rats with acute alloxan diabetes

Increased growth hormone and prolactin contents of the rat adenohypophysis during the development of experimental diabetes were found by colorimetric studies of stained electrophoregrams. 4 to 5 days after alloxan administration the levels of somatotropic hormone (STH) and prolactin were higher in comparison to those in intact animals by 58% and 43%, respectively. Experiments on the primary cell culture using the precursor 14C-L-leucine revealed an enhanced secretion of somatotropic hormone and prolactin by cells of the rats with alloxan diabetes. A possible role of the adenohypophyseal changes in the development of experimental diabetes is discussed.     

The protective effect of the arginine-heparin complex under simulation of insulin-dependent diabetes

Daily intramuscular injections of the arginine-heparin complex for 5 days before injection of diabetogenic metabolite alloxan did not cause insulin-dependent diabetes in animals for 3 weeks. As a result of these injections, the anticoagulant fibrinolytic pattern of the anticoagulant system was activated and the platelet aggregation decreased. This effect held for 7 days after injection.     

The modern concept of the regulatory role of peptides of the glyproline family in the correction of hemostasis system function during development of diabetes mellitus

The experimental data on the therapeutic and prophylactic antidiabetogenic effect of di-, tri-, and tetrapeptides of the glyproline family with the additional inclusion of arginine or leucine at different positions are presented. The results are obtained using two animal models: with insulin-dependent diabetes mellitus (type 1), and persistent hyperglycemia similar to development of non-insulin-dependent diabetes mellitus (type 2) in humans. It is shown that repeated intranasal administration of Pro-Gly, Pro-Gly-Pro, Pro-Gly-Pro-Arg, Pro-Gly-Arg, Arg-Pro-Gly, Arg-Pro-Gly-Pro, Gly-Pro-Arg, Pro-Arg-Gly, Pro-Gly-Pro-Leu, Leu-Pro-Gly-Pro peptides to rats with hyperglycemia of different etiology led to the combined normoglycemic and anticoagulant effects in the blood plasma. The concept of the regulatory role of short proline-containing peptides, involving the universality of their action in the organism and directed towards the regulation of both hemostasis and insular systems in a variety of their physiological and clinical manifestations, was formulated.     

Effects of Iscador and Vincristine and 5-Fluorouracil on Brain, Liver, and Kidney Element Levels in Alloxan-Induced Diabetic Mice

Exposure to substance toxicity is especially dangerous for diabetics because it accelerates and intensifies diabetic complication. Homeostasis of trace elements can be disrupted by diabetes mellitus. On the other hand, disturbance in trace element status in diabetes mellitus may contribute to insulin resistance and development of diabetic complications. The aim of the present study was to compare the concentration of elements in the brain, liver, and kidneys of animals with induced diabetes after the administration of plant preparations (iscador and vincristine) and 5-fluorouracil. The experiments were carried out on male mice. The animals were divided into five groups of ten mice each: one control and four experimental groups. The first experimental group was administered alloxan at 75 mg/kg b.w. for 4 days, the second group was administered both alloxan at 75 mg/kg b.w. and vincristine 1 mg/kg b.w. for 4 days, and the third group was administered both alloxan at 75 mg/kg b.w. and 5-fluorouracil 75 mg/kg b.w. for 4 days. The animals of the fourth group were administered both alloxan at 75 mg/kg b.w. and iscador Qu at 5 mg/kg b.w. for 4 days. Calcium, magnesium, iron, copper, zinc, sodium, and potassium levels in the tissues were analyzed by flame atomic absorption spectrophotometer. We observed that zinc, copper, magnesium, sodium, and potassium were lower in the brain as compared to the control animals. The copper levels in the liver were also lower in diabetic groups than in control groups. However, the iscador and vincristine and 5-fluorouracil did not induce significant differences in the five groups. In conclusion, results of the current study indicated that changes of the investigated essential elements may contribute to explaining the role of impaired element metabolism of some elements in the progression of diabetic complications.     

Concentration of sialic acid in alloxan diabetic rat islets of Langerhans.

A microanalytical procedure for the determination of total and surface sialic acid concentrations was employed to establish their changes in relation to the length of alloxan diabetes in rat islets of Langerhans. 14 and 60 days after alloxan administration (65 mg/kg), the number of Langerhans islets was significantly decreased (p < 0.001) compared to the control. According to their size, the distribution of islets displayed no significant difference in diabetic and control animals 14 days after alloxan administration, while after 60 days no large islets (dia > or = 128 microns) were found in diabetic animals. The surface sialic acid was significantly increased in the small islets (p < 0.001), whereas no change was found in the large islets 14 days after alloxan administration. After 60 days, the surface sialic acid of both small and large islets was significantly decreased (p < 0.001). These results demonstrate that chronic beta-cell destruction induces a decrease in the sialic acid content in the pancreatic islet cells, suggesting that sialic acid might play a role in insulin secretory regulation regarding chronic effects of alloxan beta-cytotoxicity.     

Comparative studies of anticoagulant and fibrinolytic effects of glyprolines Gly-Pro and Gly-Pro-Arg in conditions of immobilization stress

It has been shown that proline-containing peptides Gly-Pro and Gly-Pro-Arg in vitro had anticoagulant and nonenzymatic fibrinolytic activity. It was established that after intranasal introduction of these peptides to a rat, anticoagulant and fibrinolytic activity of enzymatic and nonenzymatic nature increased in the rat blood. The peptide protective effect against hypercoagulation induced by immobilization stress was found after repeated intranasal introduction of each peptide into the animal.     

Diabetogenic action of alloxan in short-term termination of the blood supply to the pancreas and spleen

It has been shown that the development of alloxan diabetes in rats and the appearance of diabetogenic factor in blood is caused by the direct alloxan action on pancreas and spleen--the organs supplying by blood through the spleen artery. The stopping of blood circulation in that artery preserves rat's organism from the development of general toxic effect of alloxan. The inactivation of alloxan as a diabetogenic agent has been shown after its 5-minute at 37 degrees C incubation with blood. It has been established that the half activity of intravenous injected alloxan disappears in rat's organism during 50 s. and does not depend on alloxan sensitivity of animals.     

Synthesis of N-acyl derivatives of Pro-Gly-Pro-Leu peptide: Proteolytic stability in vitro and effects on mouse macrophage cells RAW264.7

Acetyl, oleoyl, arachidonoyl, and docosahexaenoyl derivatives of the Pro-Gly-Pro-Leu peptide with a chemical purity of 99.8% were synthesized. The degradation kinetics of the Pro-Gly-Pro-Leu derivatives under the action of leucine aminopeptidase, nasal mucus, and microsomal fraction of the brain and blood of rats was studied. It was shown that the N-acyl derivatives of Pro-Gly-Pro-Leu proved to be more resistant to the action of leucine aminopeptidase and other enzyme systems. The study of the cytotoxic and anti-inflammatory activity of preparations on the mouse macrophage cell line RAW264.7 showed that acylation with oleic and arachidonic acid makes the peptide cytotoxic with LC50 in the range of 70–15 μM and gives it anti-inflammatory properties with EC50 of 32 and 36 μM, respectively.     

Decreased expression of liver epidermal growth factor receptors in rats with alloxan and streptozotocin diabetes

Male rats (200 g) were rendered diabetic with one intraperitoneal injection of alloxan (150 mg/kg) or streptozotocin (60 mg/kg). In hyperglycemic animals within 3 hours after the injection, the binding of EGF to liver membranes decreased by 43-52%; the maximal drop was by 70% and persisted for the 20 days of the experiment. EGF receptors decreased in number with almost no changes in their affinity. Autophosphorylation of the receptors decreased parallel to the ligand binding. In animals that received lower doses and did not develop diabetes and in animals in whom diabetes was prevented by the injections of glucose (before alloxan) or nicotinamide (before streptozotocin) the binding of EGF to liver receptors remained normal. We conclude that the decreased expression of EGF receptors was caused by diabetes and not by the toxic effects of the diabetogenic compounds on the liver.     

四氧嘧啶诱发糖尿病模型效果的性别差异

目的了解性别因素对四氧嘧啶诱发糖尿病动物模型的影响,为提高动物模型的复制效率提供实验依据。方法分别给雌、雄比格犬和昆明小鼠注射不同剂量的四氧嘧啶,药后3、7、14、21 d测定血糖值,同时统计实验期间动物的死亡情况。结果给予同等剂量的四氧嘧啶,雌性比雄性动物的血糖升高更快,浓度更高。雌性犬四氧嘧啶的最适造模剂量为40 mg/kg,而雄性犬在此剂量下的模型成功率只有40%,二者差异极显著（70%VS40%,P〈0.01）;雄性犬的最适使用剂量为50 mg/kg,但在此剂量下有高达30%的雌性犬因高血糖而死亡。四氧嘧啶对小鼠的影响与犬基本一致,雌雄鼠的最佳剂量分别为200 mg/kg和250 mg/kg。结论雌性动物对四氧嘧啶的敏感性较雄性动物高,雄性动物在使用四氧嘧啶复制糖尿病模型时,其剂量通常需要较雌性动物高20%左右。     

Effects of chemical sympathectomy by means of 6-hydroxydopamine on insulin secretion and islet morphology in alloxan-diabetic mice

Activation of sympathetic nerves increases circulating glucose and inhibits insulin release from the islet beta-cells, which might contribute to stress-related diabetes. Accordingly, we have shown previously that blockade of parasympathetic activity aggravates diabetes in alloxan-treated mice, suggesting that unopposed sympathetic activity impairs diabetes. In this study, we tested whether elimination of sympathetic nerve activity by chemical sympathectomy with 6-hydroxydopamine (6-OHDA; 60 mg/kg) ameliorates the diabetogenic effects of alloxan (50 mg/kg) in NMRI mice. Mice given alloxan alone developed manifest diabetes after 2 days, as indicated by hyperglycemia. The diabetes persisted throughout the 35-day study period. Pretreatment with 6-OHDA did not, however, affect the glucose levels or the low, 2-min in vivo insulin response to glucose (1 g/kg) after alloxan. In situ hybridization at day 35 revealed a significantly reduced grain area of insulin-mRNA in the alloxan-treated animals, which was not affected by 6-OHDA, and an altered islet architecture, with accumulation of glucagon cells in the central portion. Also 6-OHDA alone reduced the insulin mRNA area, but this was accompanied by an increase in the total islet area. We conclude that, in contrast to cholinergic inhibition, sympathectomy does not perturb the development of chemically induced diabetes in mice. Alone, however, sympathectomy reduces insulin gene expression and induces increased islet size, suggesting that sympathetic nerves are of importance for long-term islet function.     

Implantation of embryonic pancreas into the anterior chamber of healthy and diabetic rats

The possibility of pancreatic-islet embryonic implantation into the frontal chamber of the eye in Wistar rats has been demonstrated. The implantation was followed by the induction of alloxan diabetes. Clinical diabetic compensation has been shown in a number of experimental animals (maximum time of experiments--45 days). The formation of islet-like structures in the frontal chamber of the eye was confirmed microscopically. The structures contained B cells in their cytoplasm. Cellular differentiation leading to the appearance of functionally active endocrine cells has been noted in the implants.     

Alloxan-induced diabetes in the rat - protective action of (-) epicatechin?

Administration of alloxan (150 mg/kg body weight, i.p.) to male Wistar rats induced a reproducible and persistent diabetes mellitus as evidenced by elevated serum glucose and low serum insulin concentrations. Administration of either (-)epicatechin or (+)catechin (250 mg/kg, i.p. on each occasion) at 36, 24, 12 and 1 hour before and at 12 and 24 hours after alloxan administration did not prevent the induction of the diabetes. Similarly, treatment of animals with (-)epicatechin or (+)catechin (125 mg/kg i.p. twice daily) for 21 days commencing 24 hours after alloxan administration did not reverse the peristing elevated serum glucose and low serum insulin concentrations. Moreover, administration of these compounds did not relieve any of the symptoms of the alloxan-induced diabetes such as poor weight gain, polyuria or polydipsia.     

Comparative study of alloxan effects in copper-loaded and iron-loaded rats: lipid peroxidation, protein oxidation, proteasome and antioxidant enzyme activities

The in-vivo effects of alloxan on protein oxidation and lipid peroxidation, as well as on proteasome and antioxidant enzyme activities in liver and kidney of copper-loaded and iron-loaded rats, were studied. In control animals, a single alloxan dose (120 mg/kg, i.p.) increased blood-glucose concentration at the 24^th hr and 48^th hr and, especially, on the 5^th day. For these periods of alloxan action, no changes in lipid peroxidation and antioxidant enzyme activities were found; only a slight increase of carbonyl content and strong increase of trypsin-like proteasome activity in rat liver on the 5^th day was observed. Five days after alloxan injection, the blood-glucose concentration in iron-pretreated rats was similar to that of the controls. However, it was significantly lower in copper-pretreated animals; hence, insulin-mimetic action of copper might be suggested. The lower proteasome activity, measured in liver of copper-pretreated diabetic rats is probably due to a potential copper-chelating ability of alloxan. The present results showed that the action of alloxan was different in copper-and iron-pretreated rats. Analogous studies, using pretreatment with other metals, would contribute to a further elucidation of the role of different metals in diabetes development, especially in regions with environmental metal contamination.     

Experimental diabetes in cats induced by partial pancreatectomy alone or combined with local injection of alloxan

Experimental diabetes was produced in cats by partial pancreatectomy using a short and technically simple surgical procedure. Electrocautery was used to cauterize pancreatic blood vessels and seal free edges of remaining pancreatic tissue to prevent secretion of pancreatic enzymes into the peritoneal cavity. In a second group of animals, partial pancreatectomy was followed by local injection of alloxan into an arterial branch of the cranio-mesenteric artery. The combined procedure resulted in diabetes mellitus in 100% (8 of 8) animals as compared to only 70% (14 of 20) in those subjected to partial pancreatectomy alone. In addition, the alloxan-pancreatectomized cats had a reduced latency period prior to onset of chronic hyperglycemia (4.8 days compared to 19.3 days postoperatively in pancreatectomized cats). The diabetic cats were maintained in poor metabolic control (blood glucose approximately 300 mg/dl) by daily injections of low doses of long-acting insulin. Pancreatic enzyme supplementation was given by mouth. Weight changes and blood glucose levels were monitored carefully to maintain the health of the animals while keeping them in poor metabolic control.     

Role of ubiquitin-proteasome-dependent proteolytic process in degradation of muscle protein from diabetic rabbits.

The activity of ATP, ubiquitin (Ub)-dependent proteases partially purified from skeletal muscle (psoas) from alloxan diabetic rabbits was determined at different periods of insulin deficiency. Two days after alloxan injection, no change was observed in the activity of ATP, Ub-dependent proteases, but this activity increased 3 and 5 days after diabetes induction, attaining 181% of control values on the 5th day. However, after this early rise, the activity of muscle ATP, Ub-dependent proteases decreased, returning to values that did not differ significantly from controls 7 and 10 days after alloxan injection. After 15 days, the activity of these proteases was 57% lower than in muscle from control rabbits. Both the initial increase and the subsequent fall in the activity of the enzymes were prevented by insulin treatment of alloxan diabetic rabbits. The data suggest that Ub-proteasome-dependent proteolysis have an important role in the control of muscle protein degradation and may be regulated by insulin.     

Dynamic changes in the indices of lipid metabolism in erythrocyte membranes at different times of the development of alloxan diabetes

The changes in the content of phospholipids (PL), cholesterol (cr) and its fractions were studied in the processes of lipid peroxidation. At the different periods of alloxan diabetes development the CS/LP ratio coefficient was determined (7, 14, 21 days). The results of our investigations we explain by erythrocyte membranes destruction in the molecular mechanism of which the significant role has played the activation of free radical lipid oxidation processes.     

Atomic-force microscopy of erythrocytes and metabolic disorders in experimental diabetes mellitus and during the correction of diabetes with lipoic acid

Lipid peroxidation in blood plasma and red blood cells was shown to have minor effects on the state of the erythrocyte membranes in rats with alloxan diabetes. Administration of α-lipoic acid to rats with alloxan diabetes affected the metabolism of the animals and induced significant changes in erythrocyte morphology, as demonstrated by atomic-force microscopy.