Ultrastructure and membrane permeability of cultured pancreaticβ-cells exposed to alloxan or 6-hydroxydopamine

Summary Stereological techniques on electron microscopy micrographs were used to evaluate the morphological changes of cultured islet cells that had been exposed to alloxan or 6-hydroxydopamine.Trypan Blue exclusion by cells cultured for 3 days indicated that the cells were 100% viable. Electron microscopy revealed that nearly all of the surviving cultured cells were cells.Exposure to 5 mmol/l alloxan or 1–5 mmol/l 6-hydroxydopamine for 10 or 30 min caused a general swelling of the cultured cells with a concomitant swelling of mitochondria and nuclei. The size of the secretory granules was not affected by the drugs. Only 3–10% of the cells excluded Trypan Blue after exposure to 5 mmol/l alloxan or 6-hydroxydopamine.The data conform with the hypothesis that a primary action of alloxan and 6-hydroxydopamine is at the plasma membrane level of cells.Abbreviations and definitions A _cell Cell profile area (µm²), surface area of one cell section surface - V _n Nuclear volume density (%), number of points over the nucleus divided by the number of points over the total cell area × 100 - V _m Mitochondrial volume density (%), number of points over mitochondria divided by hits over the cytoplasm (points over the cell minus points over the nucleus) × 100 - V _g Granular volume density (%), number of points over granules divided by hits over the cytoplasm × 100     

Anti-Diabetic Activities of the Methanol Leaf Extracts of Hymenocardia Acida (Tul.) in Alloxan-Induced Diabetic Rats

The effect of methanolic extract of Hymenocardia acida leaves on diabetes and associated lipidemia were investigated on experimentally-induced diabetic rats. The extract did not demonstrate any acutely toxic effect in rats within the dose range (250 mg/kg – 2000 mg/kg) employed in the study; hence it was well tolerated by the rats. In all experiments, the anti-diabetic effects were dose-dependent and comparable to that of glibenclamide (2 mg/kg) standard. At a dose of 500 mg/kg, lipid profile markers such as the serum total cholesterol (TC) levels, LDL-C, triglycerides and HDL-C were significantly lower (p <0.05) than those of both the treated and untreated controls.     

A method for enzymatic dissociation of cells from isolated pancreatic islets

Summary An enzymatic method for isolation of single cells from the islets of Langerhans is described. The isolated cells appeared well preserved and survived for at least 7 days when maintained in culture. The dry mass of the isolated islet cells was found to be decreased 30 min after administration of alloxan to obese-hyperglycemic mice. Isolated individual islet cells from obese-hyperglycemic mice had a higher dry mass than those from their lean litter mates. Traduzione a cura di G. U.     

The effect of acute alloxan diabetes on the sensitivity of the rat skeletal neuromuscular junction to drugs

Summary Preparations from alloxan diabetic rats showed a reduced sensitivity to the neuromuscular blocking action of (+)-tubocurarine but no alteration in sensitivity to the deplolarizing neuromuscular blocking drug decamethonium. Physostigmine was less effective in augmenting twitch height in preparations from alloxan diabetic rats and such preparations had a significantly lowered total cholinesterase activity compared with control preparations. An additional observation was a reduction in the effectiveness of the pre-junctionally active agent β-bungarotoxin in producing neuromuscular blockade in physostigmine-treated preparations from alloxan diabetic rats. All the changes produced by alloxan administration were prevented by treatment with insulin.     

Myocardial injury following endogenous catecholamine release in rabbits

Catecholamines (CAT) given in large doses produce cardiomyopathic changes in several animal species. This study was designed to determine if endogenous release can also induce cardiac injury. Rabbits were infused with doses of tyramine (TYR), ranging from 200 to 500 micrograms/min/kg, i.v. for 90 min. Arterial pressure and heart rate were measured, as were total CAT concentrations, blood gases, pH and glucose. Two days later the animals were killed and cardiac injury assessed using a histological scoring system. All data were compared with controls given saline. Initial CAT averaged 452 pg/ml, rose to 2890 pg/ml after starting TYR, 500 micrograms/min/kg, and remained elevated for the duration of infusion. Circulating CAT levels were a function of TYR dose, and bore a linear relationship to the histological score (P less than 0.001). Development of lesions was unaltered by beta 1 blockade with practolol, but sharply reduced by alpha blockade with phentolamine (P less than 0.01). Pretreatment with insulin also reduced lesion formation, but diabetic (alloxan) rabbits showed no greater CAT injury. It is concluded that endogenous release of CAT induces myocardial injury in the rabbit in a dose-dependent manner. This is unrelated to myocardial O2 demand, and microvascular pathology was absent. Activation of alpha adrenergic pathways is likely the dominant or exclusive mechanism.     

Increased intestinal absorption of insulin in a micellar solution: Water-in-oil-in-water insulin micelles

Summary Water-in-oil-in-water (W/O/W) insulin micelles were prepared, and the possibility of insulin absorption in a micellar form was examined. In this preparation, insulin was trapped in oil droplets of oleic acid in glyceryl-α-monooleate. (1) W/O/W insulin micelles were absorbed from the ligated jejunal loop of rabbits to the order of 12.3 to 58.5% of the dose given (10 U/kg body weight) during the 3-h experimental period. (2) Alloxan diabetic rats were treated with intrajejunal administration of W/O/W insulin micelles at a dosage of either 25 or 50 U/100 g body weight, three times daily for as longs as 14 days. During treatment, a significant reduction in the daily excretion of urinary glucose was observed, concomitant with a decrease in fasting blood glucose. Quantitative estimates suggested that the effectiveness of 25 U/100 g of intrajejunal W/O/W insulin micelles was comparable to that of regular insulin at a dosage of 1 U/100 g i.m. These results would indicate that W/O/W insulin micelles, when given enterally, are more effective in lowering blood and urinary glucose levels than W/O/W insulin emulsions in which insulin was trapped in oil droplets of triglyceride.     

Antidiabetic and antihyperlipidaemic activity of ethanol extract of Melastoma malabathricum Linn. leaf in alloxan induced diabetic rats

ObjectiveTo evaluate the antidiabetic and antihyperlipidaemic effect of ethanol extract of Melastoma malabathricum (M. malabathricum) Linn. leaf in alloxan induced diabetic rats.MethodsDiabetes was induced in albino rats by administration of alloxan monohydrate (150 mg/kg i.p). the ethanol extracts of M. malabathricum at a dose of 150 and 300 mg/kg of body weight were administrated at a single dose per day to diabetes induced rats for a period of 14 d. The effect of ethanol extract of M. malabathricum leaf extract on blood glucose, plasma insulin, creatinine, glycosylated haemoglobin, urea serum lipid profile [total cholesterol, triglycerides, low density lipoprotein-cholesterol, very low density lipoprotein-cholesterol, high density lipoprotein-cholesterol and phospholipid, serum protein, albumin, globulin, serum enzymes (serum glutamate pyruvate transaminases), serum glutamate oxaloacetate transaminases, and alkaline phosphatase] were measured in the diabetic rats.ResultsIn the acute toxicity study, ethanol extract of M. malabathricum leaf was non-toxic at 2 000 mg/kg in rats. The increased body weight, decreased blood glucose, glycosylated haemoglobin and other biochemical parameters level were observed in diabetic rats treated with both doses of ethanol extract of M. malabathricum leaf compared to diabetic control rats. In diabetic rats, ethanol extract of M. malabathricum leaf administration, altered lipid profiles were reversed to near normal than diabetic control rats.ConclusionsEthanol extract of M. malabathricum leaf possesses significant antidiabetic and antihyperlipidaemic activity in diabetic rats.     

Changes of ground substance in the inner ear in Alloxan diabetic mice

Summary One of the important substances in the ground substance is acidic glycosaminoglycans (AGAGs). Changes of AGAGs in the inner ear and in other organs were investigated using alloxan diabetic mice in order to contribute to the understanding of diabetic hearing impairment. In the diabetic group, gradual increases of AGAGs were observed in each tissue. On the 60th day after alloxan injection, AGAG values were increased 3.5-fold in the cochlea, 2.5-fold in the brain, 13-fold in the liver, twofold in the kidney, and fivefold in the pancreas compared with the control values. It is interesting to note that both the cochlea and pancreas showed continuous increases of AGAGs.This research was supported by grant no. 757202 from the Ministry of Education. A part of this paper was read at the 16th workshop on Inner Ear Biology, Bern, Switzerland     

四氧嘧啶致糖尿病大鼠模型血糖稳定性考察

目的探讨四氧嘧啶致糖尿病大鼠的血糖波动情况，考察模型的稳定性，为药效观察时机的选择提供依据和指导。方法四氧嘧啶40ms／ks给禁食大鼠尾静脉注射致糖尿病，长期连续观察造型大鼠空腹血糖、非空腹血糖与尿糖。结果造模大鼠10d后非空腹血糖趋于稳定，直到120d其非空腹血糖仍维持在较高水平；但其空腹血糖却一直在波动之中。结论①用四氧嘧啶可以造成长期稳定的大鼠高血糖模型；②用该模型观察药物的降糖作用宜在造模10d之后开始，此时模型基本趋于稳定。③应舍弃人们习惯采用的空腹血糖，改用非空腹血糖为宜。