Effect of alloxan administration upon Channa punctatus (Bloch)

Channa punctatus, a fresh water teleost, was administered intramuscularly with alloxan in doses varying between 200 and 600 mg/kg body weight. The course of cytological events occurring in the islets of alloxanized fish was followed over a period of 120 hours post injection. Alloxan caused mild degranulation of some of the beta cells in the beginning but later nuclear pycnosis, vacuolization and necrosis of the beta cells was observed. Like other vertebrates, Channa punctatus is alloxan-sensitive and its islet beta cells are susceptible to the cytotoxic effects of alloxan.     

Nature of the air-breathing organs of the Indian fishes Channa, Amphipnous, Clarias and Saccobranchus as shown by electron microscopy

The structure of the air-breathing organs of the Indian fishes Channa punctatus, Channa Striatus, Amphipnous cuchia, Clarias batrachus and Saccobranchus fossilis has been investigated using electron microscopy. In all species the barrier separating the air from the blood consists of three main layers (epithelium, basal lamina and endothelium). The total thickness ranging from 0.78 μm in C. punctatus 1.6 μm in S. fossilis.
In Clarias and Saccobranchus the presence of pillar cells characteristic of gill secondary lamellae confirms evidence for the origin of these organs by modification of a typical gill structure.
In Amphipnous and two species of Channa , however, the evidence suggests that the accessory organs represent modified gills. The presence of valve-like structures between the afferent and efferent blood spaces of the vascular papillae gave the appearance of pillar cells under the light microscope.
The structure of these organs is correlated with physiological studies on the degree of their importance in the life of the animal and the degree of gill development     

Cytotoxic effects of streptozotocin and N-nitrosomethylurea on the pancreatic B cells with special regard to the role of nicotinamide–adenine dinucleotide

The effects on the pancreatic B cell of streptozotocin and its aglucone derivative N-nitrosomethylurea were investigated in obese-hyperglycaemic mice and their lean littermates. Both streptozotocin and N-nitrosomethylurea were found to be B-cytotoxic although N-nitrosomethylurea produced less islet damage. Both substances decreased the concentrations of NAD(+) in the islet cells to about 10% of the control values within 2h after injection. This NAD(+) depletion was prevented by injection of nicotinamide 10min after the administration of streptozotocin or N-nitrosomethylurea. In islets taken from animals 10min after injection of streptozotocin or N-nitrosomethylurea there was no stimulatory effect of glucose on the respiration or insulin release and the oxidation of glucose was markedly decreased. Addition of nicotinamide (10mm) to the incubated islets restored glucose stimulation of both the oxygen consumption and insulin release. It is concluded that islet NAD(+) depletion is probably important for the B-cytotoxin action of N-nitrosomethylurea and streptozotocin. The glucose residue in the streptozotocin molecule may potentiate the B-cytotoxic action of this drug in mice.     

Cell types in the peripheral blood of an air-breathing fish Channa punctatus

Different cell types found in the peripheral blood of Channa punctatus , an air-breathing freshwater fish have been characterized and identified using morphological, morphometric, cytochemical and autoradiographic techniques. Some of the cytochemical methods used, particularly that of differential staining of haemoglobin have been developed and used for the first time in fishes.     

Glucose intolerance and reduced islet blood flow in transgenic mice expressing the FRK tyrosine kinase under the control of the rat insulin promoter

The FRK tyrosine kinase has previously been shown to transduce beta-cell cytotoxic signals in response to cytokines and streptozotocin and to promote beta-cell proliferation and an increased beta-cell mass. We therefore aimed to further evaluate the effects of overexpression of FRK tyrosine kinase in beta-cells. A transgenic mouse expressing kinase-active FRK under control of the insulin promoter (RIP-FRK) was studied with regard to islet endocrine function and vascular morphology. Mild glucose intolerance develops in RIP-FRK male mice of at least 4 mo of age. This effect is accompanied by reduced glucose-stimulated insulin secretion in vivo and reduced second-phase insulin secretion in response to glucose and arginine upon pancreas perfusion. Islets isolated from the FRK transgenic mice display a glucose-induced insulin secretory response in vitro similar to that of control islets. However, islet blood flow per islet volume is decreased in the FRK transgenic mice. These mice also exhibit a reduced islet capillary lumen diameter as shown by electron microscopy. Total body weight and pancreas weight are not significantly affected, but the beta-cell mass is increased. The data suggest that long-term expression of active FRK in beta-cells causes an in vivo insulin-secretory defect, which may be the consequence of islet vascular abnormalities that yield a decreased islet blood flow.     

Characterization of Streptozotocin-induced Diabetic Rats and Pharmacodynamics of Insulin Formulations

Morphological and functional changes of rat pancreatic islets caused by administration of streptozotocin (STZ) and the bioavailability of insulin formulations administered to STZ-induced diabetic rats with fasting (12 h) or non-fasting were investigated. Islets isolated from normal rats maintained a good three-dimensional structure and the islet yield was 962.5±86.5 islet equivalent number (IEQ, islets converted to an average diameter of 150 μm). In the diabetic group (>500 mg/ml blood glucose), the islet yield was only 44.4±8.3 IEQ and the islet was severely damaged. The minimum reduction of blood glucose of each formulation, such as insulin solution, microcrystal, and insulin microcrystal capsule, was shown to be 11.3, 11.0, and 16.3 mg/dl, respectively, at 6 h in fasting with diabetic rats. These results indicated that the administration of insulin formulations to the fasting groups increased the severe hypoglycemic effect of insulin action more than in non-fasting diabetic rats. The diabetic rat with fasting has a regulatory disorder in maintaining the blood glucose level. Accordingly, the validity of pharmacological availability as an optimal modeling of insulin formulations is best in non-fasting STZ-induced diabetic rats.     

Characterization of streptozotocin-induced diabetic rats and pharmacodynamics of insulin formulations

Morphological and functional changes of rat pancreatic islets caused by administration of streptozotocin (STZ) and the bioavailability of insulin formulations administered to STZ-induced diabetic rats with fasting (12 h) or non-fasting were investigated. Islets isolated from normal rats maintained a good three-dimensional structure and the islet yield was 962.5+/-86.5 islet equivalent number (IEQ, islets converted to an average diameter of 150 microm). In the diabetic group (>500 mg/ml blood glucose), the islet yield was only 44.4+/-8.3 IEQ and the islet was severely damaged. The minimum reduction of blood glucose of each formulation, such as insulin solution, microcrystal, and insulin microcrystal capsule, was shown to be 11.3, 11.0, and 16.3 mg/dl, respectively, at 6 h in fasting with diabetic rats. These results indicated that the administration of insulin formulations to the fasting groups increased the severe hypoglycemic effect of insulin action more than in non-fasting diabetic rats. The diabetic rat with fasting has a regulatory disorder in maintaining the blood glucose level. Accordingly, the validity of pharmacological availability as an optimal modeling of insulin formulations is best in non-fasting STZ-induced diabetic rats.     

DJ-1 Protects Pancreatic Beta Cells from Cytokine- and Streptozotocin-Mediated Cell Death

A hallmark feature of type 1 and type 2 diabetes mellitus is the progressive dysfunction and loss of insulin-producing pancreatic beta cells, and inflammatory cytokines are known to trigger beta cell death. Here we asked whether the anti-oxidant protein DJ-1 encoded by the Parkinson’s disease gene PARK7 protects islet cells from cytokine- and streptozotocin-mediated cell death. Wild type and DJ-1 knockout mice (KO) were treated with multiple low doses of streptozotocin (MLDS) to induce inflammatory beta cell stress and cell death. Subsequently, glucose tolerance tests were performed, and plasma insulin as well as fasting and random blood glucose concentrations were monitored. Mitochondrial morphology and number of insulin granules were quantified in beta cells. Moreover, islet cell damage was determined in vitro after streptozotocin and cytokine treatment of isolated wild type and DJ-1 KO islets using calcein AM/ethidium homodimer-1 staining and TUNEL staining. Compared to wild type mice, DJ-1 KO mice became diabetic following MLDS treatment. Insulin concentrations were substantially reduced, and fasting blood glucose concentrations were significantly higher in MLDS-treated DJ-1 KO mice compared to equally treated wild type mice. Rates of beta cell apoptosis upon MLDS treatment were twofold higher in DJ-1 KO mice compared to wild type mice, and in vitro inflammatory cytokines led to twice as much beta cell death in pancreatic islets from DJ-1 KO mice versus those of wild type mice. In conclusion, this study identified the anti-oxidant protein DJ-1 as being capable of protecting pancreatic islet cells from cell death induced by an inflammatory and cytotoxic setting.     

Effect of ascorbic acid deficiency on the uptake of iodine by thyroid and non-thyroid tissues of an air-breathing freshwater fish Channa punctatus Bloch

Using ¹³¹I as tracer, iodine uptake by various thyroid and non-thyroid tissues has been reported in Channa punctatus in which vitamin C deficiency was experimentally induced by feeding vitamin C deficient diet to a level when morphological deficiency syndromes appeared. This was compared with a parallel control, fed a complete diet. The study showed a highly significant decrease in iodine uptake by thyroid tissues in vitamin C deficient fish as compared to the controls. However, the blood and other non-thyroid tissues recorded a significant increase in absorption and distribution of iodine. These findings suggested hypofunctioning of thyroid gland due to a prolonged deficiency of vitamin C.     

Effect of propranolol on glucose-induced insulin response in rats with insulinomas

This paper describes an inhibitory effect of propranolol on insulin secretion in rats with pancreatic islet cell tumors which have been induced by streptozotocin (65 mg/kg body weight) and nicotinamide (500 mg/kg). Following glucose ingestion (3 g/kg), propranolol (4 mg/kg) was injected into the tumor-bearing rats. Plasma insulin decreased paradoxically despite an increase in blood glucoses. In contrast, propranolol did not suppress insulin secretion in normal rats. The drug was found to have no effect on glucagon secretion in either experimental or control animals during glucose load. This may suggest that the experimentally induced insulinoma in hypersensitive to propranolol for inhibiting insulin secretion.     

沉默长链非编码RNA Meg3损伤小鼠胰岛细胞的胰岛素分泌功能

MEG3是一种长链非编码RNA。已有研究证明,鼠源Meg3参与小鼠诱导多能干细胞、神经元和视网膜的分化过程。最新报道,MEG3在人胰岛β细胞中高表达,但其对维持成年胰岛β细胞的功能尚不清楚。本研究旨在探讨Meg3在小鼠胰岛细胞胰岛素分泌功能中的作用。实时定量PCR揭示,与Balb/c小鼠心、肝、脾、肺、肌、肾等组织/器官比较,Meg3在胰腺组织中高表达。在非糖尿病小鼠发生自发性糖尿病的第8、12周,Meg3在胰岛中的表达水平分别下调24%±8%和29%±9% (P<0.01);而当血糖升高20 mmol/L,小鼠胰岛中Meg3表达下调72%±16%(P<0.01)。在MIN6细胞中采用RNA干扰敲减Meg3的表达,在高糖浓度（20 mmol/L）刺激条件下,胰岛素分泌显著减少。小鼠静脉注射siRNA,结合血糖测定或葡萄糖耐受试验（IPGTT）显示,si-Meg3小鼠血清胰岛素水平显著下降。注射葡萄糖前血糖升高,注射葡萄糖后耐受能力降低;免疫组化分析显示,si-Meg3小鼠胰岛素阳性细胞的面积减少。实验结果提示,Meg3通过参与胰岛素的合成和分泌维持成年小鼠胰岛功能。Meg3表达失调可能参与I型糖尿病（T1DM）发病过程。     

Adenovirus-mediated hepatocyte growth factor expression in mouse islets improves pancreatic islet transplant performance and reduces beta cell death

Hepatocyte growth factor (HGF) increases beta cell proliferation and function in rat insulin promoter (RIP)-targeted transgenic mice. RIP-HGF mouse islets also function superiorly to normal islets in a transplant setting. Here, we aimed to determine whether viral gene transfer of the HGF gene into mouse islets ex vivo could enhance the performance of normal islets in a streptozotocin-diabetic severe combined immunodeficient mouse marginal islet mass model in which 300 uninfected or adenovirus (Adv) LacZ-transduced islet equivalents were insufficient to correct hyperglycemia. In dramatic contrast, 300 AdvHGF-transduced islet equivalents promptly (day 1) and significantly (p < 0.01) decreased random non-fasting blood glucose levels, from 351 +/- 20 mg/dl to an average of 191 +/- 7 mg/dl over 8 weeks. At day 1 post-transplant, beta cell death was significantly (p < 0.05) decreased, and the total insulin content was significantly (p < 0.05) increased in AdvHGF-transduced islets containing grafts. This anti-beta cell death action of HGF was independently confirmed in RIP-HGF mice and in INS-1 cells, both treated with streptozotocin. Activation of the phosphatidylinositol 3-kinase/Akt intracellular-signaling pathway appeared to be involved in this beta cell protective effect of HGF in vitro. In summary, adenoviral delivery of HGF to murine islets ex vivo improves islet transplant survival and blood glucose control in a subcapsular renal graft model in immuno-incompetent diabetic mice.     

Nerve growth factor increases in pancreatic beta cells after streptozotocin-induced damage in rats

We investigated short-term in vivo and in vitro effects of streptozotocin (STZ) on pancreatic beta cells. Male Wistar rats were treated with 75 mg/kg STZ, and, after 4 hrs blood glucose and insulin were measured and islet cells were isolated, cultured for 16 hrs, and challenged with 5.6 and 15.6 mM glucose. Treated rats showed hyperglycemia (approximately 14 mM) and a 70% decrease in serum insulin levels as compared with controls. Although insulin secretion by isolated beta cells from STZ-treated rats was reduced by more than 80%, in both glucose concentrations, nerve growth factor (NGF) secretion by the same cells increased 10-fold. Moreover, NGF messenger RNA (mRNA) expression increased by 30% as compared with controls. Similar results were obtained in an in vitro model of islet cells, in which cells were exposed directly to STZ for 1, 2, and 4 hrs and then challenged for 3 hrs with the same glucose concentrations. Our data strongly suggest that an early increase in NGF production and secretion by beta cells could be an endogenous protective response to maintain cell survival and that diabetes mellitus may occur when this mechanism is surpassed.     

Isolation and characterization of a new lectin from plasma of fish Channa punctatus

A soluble lectin is purified to apparent homogeneity from plasma of Channa punctatus by affinity chromatography on N-acetyl-D-galactosamine coupled to epoxy-activated cellulose. The lectin has 140 kDa native molecular mass and 68 kDa subunit molecular mass, as determined by native and sodium dodecyl sulphate denaturing polyacrylamide gel electrophoresis, respectively. The lectin agglutinates human A and AB blood groups and rat, mice and guinea pig erythrocytes in the presence of Ca2+ and Mg2+ or Mn2+ ions. These divalent cations, but not thiol group, are obligatory requirements for the lectin activity. Gal(beta 1----3)GalNAc (0.09 mM) is the most potent inhibitor of the lectin.     

Dietary restriction prevents diabetogenic effect of streptozotocin in mice

The beneficial role of dietary restriction (DR) was studied in streptozotocin (STZ)-induced diabetes in mice. The DR mice exhibited the lower blood glucose (mg/dl) level as compared to ad libitum (AL) fed ones. After 3 months' DR, STZ treatment to both AL and DR mice showed significant (p < 0.001) elevation of the blood glucose level in AL-fed mice, while a lower level of glucose was maintained in DR-fed mice. The ability of maintaining a low blood glucose level in STZ-treated DR mice indicated that STZ might have been ineffective from its action on beta cells of pancreas by long-term DR. Thus, these findings suggested that DR may be an important tool for preventing the diabetic conditions. However, further studies are required to know the mechanism(s) of DR protection against diabetogenic action of STZ in experimental animals.     

An autoradioraphic and cytochemical study of erythropoiesis in a fresh water fish, Channa punctatus Bloch

Using spleen and head kidney imprints, studies on erythropoiesis in Channa punctalus have been made describing each developmental stage with regard to its morphology, morpho-metry and cytochemistry. This has been undertaken using the new techniques available for haematopoietic studies of fishes. These include autoradiography for information on DNA synthesis and Graham-Knoll's benzidine method with Giemsa used as a counterstain for the differential staining of haemoglobin. Thus, a more definitive picture of the haematopoietic phenomenon in Channa punctatus has been evolved.     

Vanadium induced changes in glycogen content of Clarias batrachus (Linn) and Channa punctatus (Bloch)

Clarias batrachus (Linn) and Channa punctatus (Bloch) were exposed to 5, 10 and 15 ppm of vanadium and investigated the effects on tissue glycogen at 3, 6 and 9 hrs. Results indicated the variations in the level of glycogen were highest at 15 ppm after 9 hr exposure in liver than muscle, brain, kidney and heart of Clarias batrachus as compared to Channa punctatus. The variation recorded in tissue glycogen content was discussed in relation to respiratory distress, formation of mucus on the whole fish and disturbed behaviour of the fish.     

Glucagon secretion by dispersed alpha cell enriched islets from streptozotocin treated hamsters in perifusion

Streptozotocin (70 mg/kg) was administered intravenously to female Syrian hamsters. The hamsters received insulin (5U/animal/day). Insulin treatment was withdrawn 3 days before sacrifice in one group, while another group was maintained on insulin until sacrifice. Ten to 14 days following streptozotocin administration the animals were killed, and the pancreatic islets isolated and subsequently dispersed. Islet DNA content was decreased while the glucagon content was elevated by streptozotocin treatment. The glucagon secretory responsiveness of the dispersed alpha cells of control animals was stimulated by glucopenia and decreased by glucose. Alpha cells of streptozotocin hamsters were not only suppressed but were actually stimulated by high glucose concentrations. Treatment with insulin in vivo but not in vitro, resulted in a restoration of the alpha cells responsiveness to glucose suppression. Dispersed alpha cells from control and streptozotocin treated animals were stimulated by arginine. Basal and total glucagon secretion was greatest in dispersed alpha cells from streptozotocin treated animals. We concluded: that the paradoxical response of alpha cells to glucose noted in diabetes is not due to short term insulin deprivation or the lack of morphologic contact with beta cells; that the alpha cells require and insulin stimulated islet metabolite and extra islet materials to respond appropriately to glucose; and that the alpha cells response to arginine is mediated independently of glucose regulation.     

Intraportal autotransplantation of cryopreserved porcine islets of Langerhans

Mechanically prepared isolated islets of Langerhans were cryopreserved in liquid nitrogen for a period of 4 days. Intraportal autotransplantation studies were performed on two groups of six pigs rendered diabetic by total pancreatectomy (group 2) or by partial pancreatectomy combined with streptozotocin (group 4) and compared with two control groups (groups 1 and 3, respectively). The pigs were assessed for survival, weight gain, glycosuria, polyuria, systemic blood sugar and insulin, and, in selected pigs, intravenous glucose tolerance tests. Results showed that partial pancreatectomy with streptozotocin was the better tolerated experimental diabetes. Variable control of hyperglycemia was obtained over an experimental period of 3 months. Random blood glucose returned to normal in one of six pigs in the totally pancreatectomized group and three of six pigs in the partial pancreatectomy and streptozotocin group. Despite these normal circulating glucose levels, imperfect glucose homeostasis was achieved as shown by the response to glucose tolerance testing. These results report blood glucose control after cryopreserved islet autotransplants in diabetic pigs but further study is still necessary to achieve consistency.     

The effect of porcine calcitonin on plasma calcium in Channa punctatm Bloch

The effect of porcine calcitonin on the plasma calcium of the freshwater Indian murrel, Channa punctatus Bloch has been studied. An injection of 200 MRC mU of porcine calcitonin was given intraperitoneally, while control fish received the gelatin carrier. A significant hypocalcaemia was noted I h after calcitonin treatment (P < 0.001). The plasma calcium had returned to the normal level by the 6th h.