Morphologic disturbance of lung maturation in fetuses of alloxan diabetic rabbits

Maturation of lungs was studied morphologically in fetuses of does made diabetic with alloxan. The lungs of fetuses of does treated with alloxan 24 h after mating appeared to be less mature than control lungs, as shown by significant decrease in areal density of air space (p < 0.01) and by increases in areal density of alveolar epithelium and capillaries (p < 0.02). In alloxan fetuses, ultrastructural techniques revealed that type II cells had 10 times the control value for areal density of glycogen (p < 0.01) and 2.5 times that of rough endoplasmic reticulum (p < 0.05), but the proportion of type II cells and the number of lamellar bodies per type II cell profile were similar in both groups. Ultrastructural examination of capillaries demonstrated that their migration and the fusion of their basement membrane with that of alveolar epithelium did not occur as frequently in alloxan fetuses as in control fetuses. Biochemically, the lungs of alloxan fetuses contained significantly more glycogen and protein (p < 0.01) than control lungs, but the deoxyribonucleic acid was similar. The alloxan fetuses had a disturbance of lung structural maturation that was consistent with our previous findings of delayed functional maturation without accompanying change in disaturated phosphatidylcholine levels and ratio of lecithin to sphingomyelin.     

A new diabetes model induced by neonatal alloxan treatment in rats

Anti-leishmanial activity of chloroform and methanol extracts of Vernonia amygdalina, a plant widely used in Ethiopia for the treatment of parasitic infections, has been assessed in vitro on Leishmania aethiopica. Amastigotes were more sensitive to V. amygdalina than promastigotes. The chloroform extract had a stronger parasiticidal activity, with median effective doses (ED50) of 18.5 micrograms/ml and 13.3 micrograms/ml for promastigotes and amastigotes, than the methanol extract with ED50 of 74.4 micrograms/ml and 45.8 micrograms/ml respectively. Cytotoxicity caused by V. amygdalina to host cells, the human leukaemia monocyte THP-1 cell line, as determined by the methyl tetrazolium assay, resulted in a median lethal dose (LD50) of 19.6 micrograms/ml for the chloroform extract and 243.4 micrograms/ml for the methanol extract. In comparison, the ED50 and LD50 of pentamidine, a standard anti-leishmanial drug, were 0.5 micrograms/ml and 1.4 micrograms/ml respectively. These results indicate that V. amygdalina displays potent anti-leishmanial activities and warrants further investigation.     

Plasma leptin in diabetic and insulin-treated diabetic and normal rats

Adipose tissue leptin mRNA levels are decreased by food deprivation or induction of insulin-deficient diabetes. To determine whether plasma leptin concentrations are similarly affected, whether treatment of diabetes with insulin restores plasma leptin, and whether this requires restoration of body weight (lost as a result of diabetes) and/or normalization of glycemia, we measured plasma leptin concentrations in control, untreated streptozotocin (STZ)-diabetic, and insulin-treated STZ-diabetic rats. Plasma leptin was markedly reduced in untreated STZ-diabetic rats. Insulin treatment for 4 to 17 days increased plasma leptin approximately twofold above control levels. However, despite the hyperleptinemia, insulin-treated diabetic rats gained weight at a rate equal to that of sham-treated controls. Epididymal adipose tissue leptin mRNA levels in 17-day insulin-treated diabetic rats were equal to but did not exceed sham-control levels, unlike plasma leptin. Plasma glucose concentrations in insulin-treated STZ-diabetic rats were lower than in sham controls. Therefore, to determine whether hypoglycemia may be important in increasing plasma leptin, we measured plasma leptin levels in diabetic rats infused with insulin for 3 hours along with a variable-rate glucose infusion targeting glycemia to 200 or 40 mg/100 mL. Plasma leptin rapidly increased in these rats irrespective of target glycemia. Plasma leptin also increased rapidly in normal rats infused with insulin and glucose (target glycemia, 200 mg/100 mL). We conclude that plasma leptin concentrations are markedly reduced under conditions of insulin deficiency and rapidly increased by insulin treatment. The increase in plasma leptin does not require restoration of body weight and, under glucose clamp conditions, does not depend on target glycemia. Hyperleptinemia in insulin-treated diabetic rats is not explained on the basis of steady-state leptin mRNA levels, at least as reflected in epididymal fat.     

Proliferation of corneal epithelial cells in diabetic rats

In order to elucidate the mechanisms of diabetic corneal epitheliopathy, we investigated the proliferation of corneal epithelial cells of streptozotocin-induced diabetic rats in the 1st, 2nd, 3rd and 6th months after the onset of diabetes using 3H-thymidine autoradiography. After the 1st month in diabetic rats, histological examination revealed that corneal epithelial layer was thin, and proliferation of corneal epithelial cells was decreased compared with that of normal untreated rats. After the 2nd month, proliferation of corneal epithelial cells showed no difference from normal rats. After the 3rd month in diabetic rats, the attachment of the epithelial layer to the stroma was loose and proliferation of corneal epithelial cells was increased compared with that of normal untreated rats. After the 6th month, proliferation of corneal epithelial cells showed no difference between diabetic rats and normal rats. We suggest that increased turnover rate of corneal epithelial cells may account for increased proliferation of corneal epithelial cells in diabetic rats during the 3rd month.     

Activity of glutathione-dependent enzymes in long term diabetes. II. Glutathione contents and activity of glutathione-dependent enzymes: S-transferase and peroxidase in the kidney cytosol of alloxan induced diabetic rats

To better understand the uptake of oligonucleotides into cells, we have studied the labeling of cell surface proteins by an oligonucleotide conjugated to a radiolabeled photoactivatable crosslinker (Denny-Jaffe reagent). When HL60 cells are treated with the conjugate for 2 hours in a medium containing bovine serum albumin (BSA), almost all of the cell-associated label is found in one protein, which we identify as BSA. Cells grown and treated in a serum-free medium do not show this protein, whereas it is plainly seen in cells that are grown in serum-containing medium but then treated in serum-free medium. Overall association of the oligonucleotide with cells is much higher in serum-free medium than in BSA-containing medium, but the oligonucleotide is mostly not protein-associated in the absence of BSA. We conclude that (1) BSA from the medium serves to block overall association of oligonucleotide with cells, and (2) BSA is the main cell surface protein binding oligonucleotides. We discuss the possible role of albumin in endocytic uptake of oligonucleotides in the cell and in the biodistribution of oligonucleotides in vivo.     

Changes in the fractional collagen composition of the kidneys in rats under immobilization stress and alloxan diabetes

There were examined 106 patients with purulent-necrotic complications (PNC) of erysipelas and 102 patients without PNC. Significant disorders of the immune status were revealed: the reduction of T-lymphocytes quantity, their subpopulational content dysbalance, the rise of level of a middle- and small-molecular immune complexes. In patients with PNC the immunocorrection conduction is expedient.     

3-hydroxy-3-methylglutaric acid and experimental atherosclerosis in rats

In rats 3-hydroxy-3-methylglutaric acid effectively counteracts the lipemic and atherosclerotic response of massive doses of vitamin D2. It regressed the formation of atheromatous arterial lesions. Furthermore the significant decrease in serum beta-lipoprotein levels on HMG treatment could be due to decrease in VLDL triglyceride and cholesterol levels.     

Complement activation accelerates glomerular injury in diabetic rats

A case of hemispheric infarction involving the territory of the right middle cerebral artery and the thalamus showed conspicuous asymmetric degeneration in the substantia nigra, red nuclei, inferior olivary nuclei and dentate nuclei with concomitant changes of progressive supranuclear palsy (PSP). The right substantia nigra and red nucleus showed loss of neurons and proliferation of astrocytes. The right olivary nucleus was hypertrophic, while the neuronal loss and astrocytosis in the dentate nucleus were predominant on the contralateral side. Modified Gallyas-Braak staining revealed the extensive distribution of neurofibrillary tangles (NFTs), threads and intraglial argyrophilic structures in the globus pallidus, subthalamic nuclei, cerebral cortex and dentate nuclei, as well as in the affected brain stem nuclei, with a distinct predominance on the affected side. In this case, the one-sided predominance of the extended degeneration in these brain stem and cerebellar areas is considered, in addition to the PSP changes, to be due to secondary retrograde degeneration via the nigrostriatal and dentato-rubro-thalamic pathways following the hemispheric infarction, and to also be the result of disruption of the dentato-olivary fiber connections. In addition, because of the predominant distribution of NFTs on the more degenerated side, it is surmised that the formation of NFTs may be accelerated by secondary degeneration.     

Contrast media-induced renal morphologic lesions in diabetic rats

Diabetes mellitus was induced in rats with streptozotocin and after 3 months the animals (n = 48) received an i.v. injection of 1 or 3 g I/kg in the form of high-osmolar diatrizoate, low-osmolar iopromide or iohexol, or of 0.6 g I/kg of high-osmolar Gd-DTPA. The controls were given an i.v. injection of physiologic saline. After 2 hours the kidneys were fixed by perfusion and the renal morphologic changes were semiquantitatively analyzed by two independent observers unaware of the agent administered. The contrast media (CM) induced pronounced cytoplasmic vacuolization in the proximal convoluted tubular cells. Such a lysosomal alteration may indicate CM uptake into the cell, and the ultrastructural evaluation revealed intracellular injuries related to the process. The alterations were most marked following administration of iohexol, but diatrizoate also induced a statistically highly significant vacuolization (p < 0.001). The lysosomal alterations following iopromide administration were not as striking, and Gd-DTPA induced only minor changes.     

Kidney drug metabolizing activities in streptozotocin diabetic rats

1. Streptozotocin-induced diabetes produced significant changes on the drug metabolizing enzyme machinery of rat kidney microsomes. 2. It reduced the cytochrome P-450 content by 30%, this effect being reversed by insulin therapy. 3. Total androstenedione oxidative metabolism was increased 2.5-fold and insulin treatment partially antagonized this activation. 4. Total testosterone hydroxylase activities were not modified by diabetes nor by insulin but the formation of 2 alpha OH testosterone and 6 beta OH testosterone were distinct in diabetes or insulin treated diabetic rats. 5. Only UDP-glucuronyltransferase activity for PNP was found in kidney microsomes. Diabetes determined a lower UDPGT substrate efficiency not reversed by insulin therapy.     

Decrease of vascular response to iloprost in diabetic rats

The current advances in molecular genetics and gene transfer are introduced together with the existing international research programs on these technologies. The opportunities for exploitation are discussed and how they could be incorporated into current breeding programs. Finally, issues of public concern and acceptability are raised and put into the context of existing breeding schemes and regulations.     

Thickening of glomerular basement membrane in spontaneously diabetic rats

The glomerular basement membrane of spontaneously diabetic rats was investigated by quantitative analysis using electron microscopy, with special reference to the effect of ageing. Constant age-related increase in the width of basement membrane was ascertained both in diabetic and control rats, and the mean values of basement membrane thickness were always higher in the spontaneously diabetic rats than in normal control rats. Significant thickening of glomerular basement membrane was found in the diabetic rats at 12 weeks of age, while younger diabetic rats had no definite increase. The difference in basement membrane thickness between diabetic and normal control rats became larger with increasing age.     

Effects of bifemelane hydrochloride on atherosclerosis in aged rats fed low-calcium diets

The preventative effects of bifemelane (4-(o-benzylphenoxy)-N-methylbutylamine hydrochloride) on atherosclerosis in aged rats fed low-calcium diets were investigated. Male 18-month-old Wistar rats were maintained for 90 days on the following: (A) standard diet (n = 7), (B) low calcium, low magnesium, high aluminium diet (n = 8), (C) standard diet plus oral intubation with 10 mg bifemelane/kg daily (n = 6), (D) low calcium and magnesium, high aluminium diet plus oral intubation with 10 mg bifemelane/kg daily (n = 6). All groups were give these diets and water ad lib for 90 days, after which blood samples were taken from the abdominal aorta and samples of aorta were examined for atherosclerotic changes. The serum concentrations of the following were determined: calcium, magnesium, zinc, aluminium, inorganic phosphorus, cholesterol, glutamate-oxaloacetate transaminase, glutamate-pyruvate transaminase, lactate dehydrogenase, cholinesterase, creatine phosphokinase, blood urea nitrogen and N-terminal parathyroid hormone. The only significant differences between the groups in serum chemistry were reduced concentrations of cholinesterase and magnesium in groups B and D, increased aluminium in group B, and increased N-terminal parathyroid hormone in groups B and D. In groups C and D the atherosclerosis was much improved compared with that in groups A and B. It appears that bifemelane largely prevents atherosclerosis caused by calcium deposition in the arteries of rats fed low-calcium diets, due to its effect in maintaining magnesium and calcium in bones.     

Hydroxyl radical formation in diabetic rats induced by streptozotocin

Production of hydroxyl radicals was examined in the diabetic rats induced by streptozotocin to prove its involvement to the pathogenesis of diabetes. Hydroxyl radicals generated in plasma, heart muscle, liver and brain of the hyperglycemic rats were quantitatively assayed by trapping hydroxyl radicals with salicylic acid as 2,3- and 2,5-dihydroxybenzoic acid. The concentrations of 2,3- and 2,5-dihydroxybenzoic acid were significantly increased in all the tissues of the diabetic rats. In the brain and heart muscle of the diabetic rats, the increase of 2,3-dihydroxybenzoic acid was more manifest than that of 2,5-dihydroxybenzoic acid, while in liver 2,5-dihydroxybenzoic acid increased markedly. All the values of 2,3-dihydroxybenzoic acid detected in the tissues of the diabetic rats were quite higher than those in control. Hydroxyl radical production and blood glucose concentration were depended almost linearly on the amount of streptozotocin injected to rats up to 60 mg/kg body weight. It was suggested that 2,3-dihydroxybenzoic acid was produced from hydroxyl radicals themselves, while 2,5-dihydroxybenzoic acid was produced by hydroxylation of salicylic acid not only with hydroxyl radicals, but also by enzymatic reaction of microsomal cytochrome-P450. Hydroxyl radical formation may account for some pathological process especially in the heart muscle and brain.     

Bimoclomol improves early electrophysiological signs of retinopathy in diabetic rats

A silent process involving both neural and vascular structures in diabetic retina persists for several years before clinically detectable retinopathy. Recordings of the electroretinogram (ERG) and visual evoked potential (VEP) provide early warning of abnormalities in the visual pathway of diabetic patients and animal models. Treatment of streptozotocin-diabetic rats for 1 or 2 months with the heat-shock protein coinducer bimoclomol, a drug ameliorating experimental neuropathy, prevented and corrected the abnormal increase in latency and reduction of amplitude of ERG and VEP waves both in acute and chronic experiments. Improvements may be explained by cytoprotective effect of bimoclomol on retinal glia and/or neurons against diabetes-related ischemic cell damages. These findings suggest that bimoclomol may have future therapeutic use in diabetic retinopathy.     

Pharmacokinetics of recombinant human insulin-like growth factor-I in diabetic rats

Pharmacokinetics of recombinant human insulin-like growth factor-I (rhIGF-I) was investigated after iv administration (0.32, 1.0, and 3. 2 mg/kg) to normal and streptozotocin-induced diabetic rats. rhIGF-I was eliminated from plasma biexponentially in both normal and diabetic rats. Plasma concentrations of rhIGF-I were lower at almost all the time points examined in diabetic rats than in normal rats. The pharmacokinetic parameters of total body clearance (CLtotal), mean residence time (MRT), and elimination rate constant (kel) indicated that rhIGF-I disappeared more rapidly in diabetic rats than in normal rats at any dosage. The amounts of IGF binding proteins (IGFBPs) in plasma were assessed by determining the endogenous IGF-I and. Levels of the 150 kDa complex, a ternary complex of IGF-I with IGFPB-3 and an acid-labile subunit, the 50 kDa complex, a complex of IGF-I with IGFBP-2, were found to be lower in diabetic rats than in normal rats. Fractions of rhIGF-I free and bound to the binding proteins were estimated by gel chromatographic separation of rhIGF-I in plasma after iv administration, and the pharmacokinetics of free and bound rhIGF-I was analyzed independently. Plasma concentrations of free and bound rhIGF-I were lower in diabetic rats than in normal rats, especially the concentrations of the 150 kDa complex were much lower. The reduced IGFBP-3 would be responsible for the faster elimination of rhIGF-I in diabetic rats.     

Endothelial dysfunction and metabolic control in streptozotocin-induced diabetic rats

1. The aim of this work was to study the influence of the metabolic control, estimated by the levels of glycosylated haemoglobin in total blood samples (HbA1c), in developing vascular endothelial dysfunction in streptozotocin-induced diabetic rats. Four groups of animals with different levels of insulin treatment were established, by determining HbA1c values in 5.5 to 7.4%, 7.5 to 9.4%, 9.5 to 12% and > 12%, respectively. 2. The parameters analysed were: (1) the endothelium-dependent relaxations to acetylcholine (ACh) in isolated aorta and mesenteric microvessels; (2) the vasodilator responses to exogenous nitric oxide (NO) in aorta: and (3) the existence of oxidative stress by studying the influence of the free radical scavenger superoxide dismutase (SOD) on the vasodilator responses to both ACh and NO. 3. In both isolated aortic segments and mesenteric microvessels, the endothelium-mediated concentration-dependent relaxant responses elicited by ACh were significantly decreased when the vessels were obtained from diabetic animals but only with HbA1c values higher than 7.5%. There was a high correlation between HbA1c levels and the impairment of ACh-induced relaxations, measured by pD2 values. 4. The concentration-dependent vasorelaxant responses to NO in endothelium-denuded aortic segments were significantly reduced only in vessels from diabetic animals with HbA1c values higher than 7.5%. Again, a very high correlation was found between the HbA1c values and pD2 for NO-evoked responses. 5. In the presence of SOD, the responses to ACh or NO were only increased in the segments from diabetic rats with HbA1c levels higher than 7.5%, but not in those from non-diabetic or diabetic rats with a good metabolic control (HbA1c levels <7.5%). 6. These results suggest the existence of: (1) a close relation between the degree of endothelial dysfunction and the metabolic control of diabetes, estimated by the levels of HbA1c; and (2) an increased production of superoxide anions in the vascular wall of the diabetic rats, which is also related to the metabolic control of the disease.