Retrograde axonal transport

Summary The accumulation of ³H-fucose labelled glycoprotein and ³⁵S-methionine labelled protein carried by the retrograde axonal transport in the sensory fibres of the sciatic nerve was examined on the day after injection of streptozotocin in rats. The accumulation of fucose-label was reduced (2.8 ± 0.4 (SD) versus 2.1 ± 0.5 (arbitrary units), 2p = 0.0044) indicating a decreased retrograde flux of glycoproteins. This early transport abnormality could have a key role in the development of peripheral neuropathy in diabetes.     

Axonal transport in rats after galactose feeding

Summary Axonal transport was studied in galactosefed rats. Precursors for proteins and glycoproteins were injected into the fifth lumbar spinal ganglion and retrograde axonal transport as well as slow axonal transport were estimated at different time intervals during the following 4 weeks. Galactose-feeding was found to produce a progressive reduction of the retrograde axonal transport of glycoproteins in intact nerve (2.9±0.2 (arbitrary units) after five days of galactose-feeding as compared to 1.9±0.7 after 28 days, 2p=0.025). The slow axonal transport velocity of structural proteins was reduced from 0.97 ±0.09 mm/day to 0.84±0.04 mm/day, 2p=0.0030. The present findings as well as structural and electrophysiological abnormalities of the nerves of galactose-fed rats are similar to the changes found in diabetic rats. The similarities point to a decisive role for glucose or its metabolites in the development of diabetic neuropathy.     

Sodium-potassium-ATPase activity in the dorsal root ganglia of rats with streptozotocin-induced diabetes

Summary Sodium-potassium-ATPase activity was measured in excised dorsal root ganglia of streptozotocin-diabetic rats, 2 months after induction of diabetes. In comparison with agematched controls, there was a decrease in both the total and ouabain-insensitive activity, indicating an overall reduction in ouabain-sensitive activity of 46%. This decrease may explain the reduced amino-acid uptake exhibited by diabetic sensory ganglia and could be relevant to the development of diabetic neuropathy.     

Reduced noradrenaline turnover in streptozotocin-induced diabetic rats

Summary To clarify whether activity of the sympathetic nervous system is decreased in streptozotocin-induced diabetic rats, noradrenaline turnover, which is a reliable indicator of sympathetic nervous system activity, was measured in the interscapular brown adipose tissue, heart and pancreas of streptozotocin diabetic rats. Results from studies using inhibition of noradrenaline biosynthesis with -methyl-p-tyrosine demonstrated significant reductions (p<0.05-0.001) in sympathetic nervous system activity in the interscapular brown adipose tissue, heart and pancreas of streptozotocin (65 mg/kg) diabetic rats, compared with measurements in streptozotocin (35 mg/kg) diabetic and saline-control rats. The daily injections of neutral protamine Hagedorn insulin to streptoz/otocin (65 mg/kg) diabetic rats prevented the decrease of noradrenaline turnover in the interscapular brown adipose tissue and heart significantly (p<0.02), but this was less marked in pancreas, compared with non-treated streptozotocin (65 mg/kg) diabetic rats. Furthermore reduced noradrenaline turnover was also observed in the control rats which showed comparable changes in body weight to the rats injected with streptozotocin (65 mg/kg). These results suggest that poorly controlled streptozotocin diabetic rats may have reduced sympathetic nervous function, and that insulin therapy might prevent this.     

Adenosine triphosphatase in nerves and ganglia of rats with streptozotocin-induced diabetes or galactosaemia; effects of aldose reductase inhibition

Summary This study measured the ouabain-sensitive and ouabain-resistant adenosine triphosphatase activity in homogenates of the sciatic nerves and of pooled fourth and fifth lumbar dorsal root ganglia from rats fed 20% galactose or made diabetic with streptozotocin for either 4 or 8 weeks. Diabetes caused reductions in both fractions of sciatic nerve adenosine triphosphatase activity. After 8 weeks the ouabainsensitive fraction was 54% of control (p<0.05) and the ouabain-resistant fraction was 57% of control (p<0.05). Galactose feeding more than doubled the ouabain-sensitive adenosine triphosphatase activity in the sciatic nerve (225% of control after 4 weeks, 215% of control after 8 weeks of galactose feeding, bothp<0.01) and produced a progressive increase in the ouabain-resistant fraction (119% of control at 4 weeks (p<0.05) and 176% of control at 8 weeks (p<0.01)). In a group of rats fed galactose for 5 days, sciatic nerve ouabain-sensitive adenosine triphosphatase activity was 165% of control. Treatment with the aldose-reductase inhibitors tolrestat, ponalrestat or sorbinil prevented accumulation of polyol and depletion of myo-inositol in the sciatic nerves, indicating effective inhibition of aldose reductase. These drugs prevented completely the effect of galactose on the sciatic nerve adenosine triphosphatase activity, but had no significant effect on the reduction in adenosine triphosphatase activity in the sciatic nerves of diabetic rats. In the dorsal root ganglia galactose feeding had no measurable effect on the adenosine triphosphatase activity. Diabetes caused a modest numerical reduction in the ouabain-sensitive activity only. The findings indicate markedly different effects of diabetes and galactosaemia on the adenosine triphosphatase activity in rat sciatic nerve and show that the reduction in activity seen in the nerves of diabetic rats was not related to exaggerated polyol pathway flux.     

Effects of nerve compression on fast axonal transport in streptozotocin-induced diabetes mellitus

Summary The hypothesis that nerves in diabetes mellitus exhibit an increased susceptibility to compression was experimentally tested. Inhibition of fast axonal transport was induced by local compression in sciatic nerves of rats with streptozotocin-induced diabetes mellitus. Fast anterograde axonal transport was measured after application of³H-leucine to the motor neurone cell bodies in the spinal cord. The sciatic nerve as subjected to local, graded compression in vivo by a small compression chamber. The amount of accumulation of proteins was quantified by calculation of a transport block ratio. Compression at 30 mm Hg for 3 h induced a significantly greater (p<0.05) accumulation of axonally transported proteins at the site of compression in nerves of diabetic animals (transport block ratio: 1.01±0.35; n=7) than in nerves of controls (0.67±0.16;n=7). Accumulation was significantly higher in ligature experiments of both control (1.34±0.44;n=8;p< 0.01) and diabetic animals (1.45±0.30;n=8 ;p< 0.05), indicating that the block of transport in compressed nerves was incomplete. Neither sham compressed diabetic (0.50±0.09;n=6) nor control (0.49±0.11;n=6) nerves showed any block of axonal transport. The possible causes of the increased inhibition of fast axonal transport in diabetic rats are discussed. The results indicate that diabetes may lead to an increased susceptibility of peripheral nerves to compression.     

Effects of streptozotocin-induced diabetes and noradrenaline infusion on cardiac output and its regional distribution in pithed rats

Summary ⁴⁶Sc-and ^99mTc-labelled microspheres were used to measure the effects of noradrenaline infusion on cardiac output and its regional distribution in 10 control and 10 streptozotocin-diabetic pithed rats. Plasma noradrenaline concentrations during the infusion were similar in both groups. Pressor responses were significantly smaller in the diabetic animals (controls: + 79, diabetic: +44mmHg; p<0.001). Cardiac output remained similar in both groups before and during the noradrenaline infusion. Total peripheral resistance was similar in both groups before noradrenaline but the noradrenaline-mediated increase was significantly smaller in the diabetic animals (controls: +150%, diabetic: + 76%; p<0.05). Noradrenaline-mediated resistance increases were significantly reduced in several tissues of the diabetic rats including the small intestine (controls: + 132%, diabetic: –4%; p<0.005), the large intestine (controls: +150%, diabetic: +39%; p<0.05) and the kidneys (controls: +180%, diabetic: + 27%;p<0.05), but were very similar in other areas, e.g. in the hindlimbs and tails.     

Fast orthograde axonal transport in sciatic motoneurones and nerve temperature in streptozotocin-diabetic rats

Summary This study measured the velocity of fast orthograde axonal transport of incorporated ³H-proline in motoneurones of the sciatic nerve in control rats and in rats with streptozotocin-induced diabetes of 3 weeks duration. Sciatic nerve and abdominal cavity temperatures were monitored throughout the period of measurement of transport velocity, and the rats were warmed to minimise hypothermia at both sites. There was marked abdominal and sciatic nerve hypothermia immediately after operation, and this effect was more intense in diabetic rats than in control rats. In steady state, abdominal cavity temperature (mean±SEM) was 38.1±0.1 °C in both control and diabetic rats, and the sciatic nerve temperatures were 37.8±0.1 °C in controls and 37.1±0.3 °C in diabetic rats. The difference was not statistically significant. The velocities of orthograde axonal transport for the fastest molecules containing ³H-proline were 14.0±0.9 (SEM)mm/h for controls and 13.9±1.1 (SEM)mm/h for diabetic rats. Thus, no velocity difference was observed. The findings are discussed in relation to measurements of fast orthograde transport velocity in experimental diabetes in other studies. It is suggested that, where velocity deficits have been seen in diabetic rats, nerve hypothermia should be considered as a contributory factor.     

Increased O-GlcNAc transferase in pancreas of rats with streptozotocin-induced diabetes

Aims/hypothesis. Streptozotocin (STZ), a chemically reactive analogue of N-acetylglucosamine, induces necrosis of the beta cells, resulting in diabetes mellitus. Glucose-induced insulin resistance is mediated by increased activity of the hexosamine pathway. We aimed to examine the regulation of O-GlcNAc transferase expression and activity in the normal and streptozotocin diabetic pancreas.¶Methods. Rats were made diabetic by an injection of streptozotocin (65 mg/kg). The expression of O-GlcNAc transferase protein was examined by immunoblot analysis. Activity of O-GlcNAc transferase was assayed by the incorporation of [³H]GlcNAc into the synthetic peptide. Localization of O-GlcNAc transferase was done by immunohistochemistry. The change of O-GlcNAc modification of proteins was examined by immunoblot analysis.¶Results. In the STZ-induced diabetic pancreas, a severe loss of beta cells was observed, whereas alpha cells had increased in number. The diabetic pancreas showed an increase in the expression of O-GlcNAc transferase at the protein level and the O-GlcNAc transferase activity in it was increased significantly (p < 0.05). An increase in the immunostaining intensity in the cytoplasm of islet beta cells was also observed in the diabetic pancreas, whereas exocrine cells and islet cells other than beta cells showed little change in immunostaining intensity. The pancreas of STZ-diabetic rats showed a 3.1-fold increase in total cellular O-GlcNAc-modified proteins.¶Conclusion/interpretation. These findings indicate that O-GlcNAc transferase plays an important part in the modulation of O-GlcNAc concentrations in the pancreas and suggest that the increase in O-GlcNAc modification of the proteins correlates closely with diabetes. [Diabetologia (2000) 43: 1239–1247]     

Modification of streptozotocin-induced diabetes in rats by pretreatment with cortisone

Summary Cortisone pretreatment considerably enhances the mortality of young, male, streptozotocin-injected Holtzman rats. In those that survive, cortisone pretreatment decreases the ensuing hyperglycaemia, extends the period during which streptozotocin-induced B cell damage can be observed from less than two to as much as four to seven days and permits the persistence of poorly granulated B cells in such animals. These effects are at least partially attributable to a cortisone-induced augmentation of the total B cell mass. Compared with the high degree of protection against alloxan-induced damage afforded the pancreatic B cells of cortisone-pretreated rabbits, the protective effect of cortisone against B cell destruction in streptozotocin-injected rats is thus much more limited in scope. Species differences as well as differing pathogenetic mechanisms may account for these results.Presented at the Ninth International Diabetes Federation Congress, New Delhi, India, October 31–November 5, 1976     

Antidiabetic activity of gossypin, a pentahydroxyflavone glucoside, in streptozotocin-induced experimental diabetes in rats

Background: Most of the currently available oral hypoglycemic drugs for the treatment of diabetes mellitus elicit detrimental side effects. Hence, the search for plant‐derived products for the treatment of diabetes continues. Gossypin, a pentahydroxy flavone glucoside found in the flowers of Hibiscus vitifolius, has many biological properties, including as an antioxidant, anti‐inflammatory and anticancer agent. The aim of the present study was to evaluate the effect of gossypin in streptozotocin (STZ)‐induced experimental diabetes in rats. Methods: Diabetic rats were administered 20 mg/kg per day gossypin orally for 30 days. On the 28th day, rats were subjected to an oral glucose tolerance test. In addition, blood glucose, plasma insulin, hemoglobin, and HbA1c levels were determined, as was the glycogen content of the liver and muscles. Plasma protein and blood urea were also estimated. Results: Oral administration of gossypin to diabetic rats resulted in improved glucose tolerance. Increased blood glucose and HbA1c levels and the reduced plasma insulin and hemoglobin levels in diabetic rats were significantly reversed to near normal after oral administration of gossypin. Furthermore, the glycogen content of the liver and muscles was significantly improved after gossypin treatment of diabetic rats, and plasma protein and blood urea levels were almost normalized. The data obtained in gossypin‐treated rats were comparable with those obtained following gliclazide treatment of rats, a standard reference drug for diabetes. Conclusions: The results of the present study indicate that gossypin has potent antidiabetic activity in STZ‐induced experimental diabetes in rats.     

Insulin mimetic effects of macrocyclic binuclear oxovanadium complexes on streptozotocin-induced experimental diabetes in rats

Aim:  The vanadium complexes so far tested for their insulin mimetic effects are either mono- or binuclear and contain only acyclic ligands. The leaching or hydrolysis of vanadyl ions from these complexes is much easier, and hence they elicit side effects. In the present study, a new binuclear macrocyclic oxovanadium complex was synthesized, and its efficacy was studied on streptozotocin (STZ)-induced diabetic rats over a period of 30 days.
Methods:  The insulin mimetic effect of the complex was tested on the blood sugar level in the STZ-diabetic rats and on the activities of the carbohydrate-metabolizing enzymes present in the liver.
Results:  Administration of vanadium complex to STZ-induced diabetic rats decreased blood glucose levels from hyperglycaemic to normoglycaemic when compared to diabetic rats. The activity of carbohydrate-metabolizing enzymes such as hexokinase, glucose-6-phosphate dehydrogenase, glycogen synthase and glycogen content were increased to near normal in vanadium complex-administered diabetic rats. The biochemical studies such as assay of blood urea and glutamate oxaloacetate transaminases revealed that the complex is not toxic to the system.
Conclusion:  The nontoxic nature of this complex may be due to the presence of the vanadyl ions in an intact macrocyclic form. Further, the vanadyl ions present in the macrocyclic binuclear oxovanadium complex are very close to each other, and this may enhance the insulin mimetic activity by synergic effect.     

Axonal dwindling in early experimental diabetes. II. A study of isolated nerve fibres

Summary In a morphometric study of isolated fibres of the common peroneal nerve in short-term diabetic rats reduced fibre calibre was observed. No segmental demyelination or remyelination was found, but the nodes of Ranvier were slightly widened and paranodal bulbi were swollen relative to fibre calibre. It is suggested that axonal dwindling is the primary event in experimental diabetes. The reduction of the myelin sheath may be a consequence of the abnormal nerve cell offshoot. The results obtained suggest that streptozotocin diabetes in the rat is a useful model for the elucidation of diabetic neuropathy.     

Novel biphenyl compound, VMNS2e, ameliorates streptozotocin-induced diabetic nephropathy in rats

Aim: To study the effect of a new biphenyl synthetic compound showing interactions with the active site of protein tyrosine phosphatase 1B by docking and molecular dynamics, VMNS2e in streptozotocin‐induced diabetic nephropathy in rats with various renal function parameters and renal ultrastructure. Methods: Streptozotocin (55 mg/kg)‐induced diabetic rats were orally treated once daily with VMNS2e (30, 60, and 120 mg/kg) for 8 weeks. The body weight and blood glucose levels of the rats were recorded during the study period. After 8 weeks of treatment creatinine clearance, urinary protein, blood urea nitrogen, urinary albumin excretion rate, and insulin levels were measured. An ultrastructure study of the kidney tissue was performed and the glomerular basement membrane thickness was measured. Results: Eight weeks of VMNS2e treatment significantly reduced the fasting blood glucose level, attenuated elevating blood urea nitrogen levels, and reduced glomerular basement membrane thickness. Conclusion: It is concluded that VMNS2e treatment at 30 and 60 mg/kg, when given for 8 weeks, partly ameliorated early diabetic nephropathy in diabetic rats.     

Essential fatty acid treatment prevents nerve ischaemia and associated conduction anomalies in rats with experimental diabetes mellitus

Summary In rats with 6 weeks streptozotocin-diabetes there was a 53% reduction in sciatic nerve laser Doppler flux compared to controls (p<0.01). Treatment of a parallel group of diabetic rats with evening primrose oil, by dietary admixture throughout the protocol, prevented this ischaemia (Doppler flux was 91% of evening primrose oil-treated controls and was not significantly different). There were no differences in systemic arterial pressure. In another experiment evening primrose oil markedly antagonised the development of exaggerated resistance to anoxic conduction failure in sciatic nerves from diabetic rats. The resistance to anoxia of nerves from non-diabetic rats was also reduced by evening primrose oil. These observations suggest that the sciatic nerves of diabetic rats with short-term streptozotocin-diabetes are markedly ischaemic and that this ischaemia is involved in the development of increased resistance to anoxic/ischaemic conduction failure in diabetic nerve. The findings also promote evening primrose oil as a potential treatment to prevent nerve ischaemia.     

Impaired axonal transport of acetylcholinesterase in the sciatic nerve of alloxan-diabetic rats: effect of ganglioside treatment

Summary The anterograde and retrograde axonal flow of acetylcholinesterase were studied in the sciatic nerve of alloxandiabetic rats after five weeks of experimental diabetes. A slight reduction of the anterograde axonal flow of the enzyme was found in alloxan-diabetic compared to control rats. Sedimentation analysis revealed a major reduction of anterograde axonal flow of the light globular forms of the enzyme (G₁ +G₂), which are probably conveyed by slow transport. There was also a minor reduction of the anterograde flow of the globular form G₄, while no modification of the axonal flow of the heavy asymmetric form A₁₂ was found. Both G₄ and A₁₂ molecular forms are conveyed by fast axonal transport. In contrast, no abnormality of the retrograde axonal flow of acetylcholinesterase was observed. Ganglioside treatment antagonized the decline of the anterograde axonal flow of the enzyme in alloxan-diabetic rats. These results are consistent with the view that experimental diabetic neuropathy is associated with axonal transport defects, and suggest a protective effect of ganglioside treatment against neuronal damage(s) related to the diabetic syndrome.     

Glucagon,insulin and somatostatin secretion in response to sympathetic neural activation in streptozotocin-induced diabetic rats. A study with the isolated perfused rat pancreas in vitro

Summary Changes in glucagon, insulin and somatostatin secretion induced by electrical splanchnic nerve stimulation were examined in rats treated with streptozotocin as neonates and as adults. In order to study the direct neural effects we used the isolated perfused rat pancreas with intact left splanchnic nerve in vitro. In normal rats splanchnic nerve stimulation causes significant decreases in insulin (30–40%) and somatostatin (30–50%) secretion at both 16.7 mmol/l and 1 mmol/l glucose concentrations. In the neonatal streptozotocin-diabetic rats splanchnic nerve stimulation at 16.7 mmol/l glucose decreased insulin secretion (14%) further than in the control rats (30%), however, somatostatin secretion did not decrease to the same extent. Similar results were also observed at the low (1 mmol/l) glucose concentration. On the other hand, percent decreases of insulin and somatostatin secretion induced by splanchnic nerve stimulation in the streptozotocin-diabetic rats were similar to the values observed in the normal control rats. The glucagon secretion in response to splanchnic nerve stimulation at 16.7 mmol/l glucose from pancreatic Alpha cells in both types of induced diabetes is exaggerated, and the degree of exaggeration seems to parallel the severity of the hyperglycaemia. However, the splanchnic nerve stimulation-induced glucagon secretion at 1 mmol/l glucose was impaired in the streptozotocin-diabetic rats, but not in the neonatal streptozotocin-diabetic rats. These data suggest that the sensitivity of diabetic Alpha and Delta cells to sympathetic neural activation are blunted, whereas the sensitivity of Beta cells is enhanced in the diabetic animal model.     

Arterial lipid metabolism in relation,to blood glucose and plasma insulin in rats with streptozotocin-induced diabetes

Summary D-glucose-U-¹⁴C incorporation into arterial lipidsin vitro was greater (p<0.025) in control than in streptozotocin-treated (65 mg/kg) rats. A significant positive correlation between this effect and the plasma immunoreactive insulin levels was achieved, although there was no correlation with the blood glucose levels. It is suggested that the state of circulating insulin in the animal is important in modifying arterial lipid metabolism independent of changes in serum lipids.

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Lipidmetabolismus der Arterien in Beziehung zu Blutzucker und Plasmainsulin bei der Ratte mit Streptozotozin-Diabetes

Zusammenfassung Die Inkorporation von D-U-¹⁴C-Glucose in die Lipide der Arterien warin vitro bei den Kontrolltieren höher (p < 0,025) als bei den mit Streptozotozin (65 mg/kg) behandelten Ratten. Eine signifikant positive Korrelation konnte zwischen diesem Effekt und dem immunologisch reaktiven Plasmainsulin gefunden werden, obgleich keine Korrelation mit den Blutzuckerwerten bestand. Es wird angenommen, daß die Menge des im Tier zirkulierenden Insulins wesentlich ist, um den arteriellen Lipidmetabolismus unabhängig von den Veränderungen der Serumlipide zu beeinflussen.

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Métabolisme des lipides des artères en relation avec le glucose sanguin et l'insuline du plasma chez le rat rendu diabétique par la streptozotocine

Résumé L'incorporation du D-glucose-U-¹⁴C dans les lipides des artèresin vitro était plus grande (p<0.025) chez les témoins que chez les rats traités à la streptozotocine (65 mg/kg). Une corrélation positive et significative entre cet effet et les taux de l'insuline immunoréactive du plasma a été réalisée, bien qu'il n'y ait aucune corrélation avec les taux du glucose sanguin. On suggère que le taux de l'insuline circulant dans l'animal est important par le fait qu'il modifie le métabolisme des lipides des artères indépendamment des changements dans les lipides du sérum.

     

Essential fatty acid treatment — effects on nerve conduction,polyol pathway and axonal transport in streptozotocin diabetic rats

Summary This study was designed to examine the effect of dietary supplementation with essential fatty acids (evening primrose oil — 5% weight:weight added to the diet) on acute neurophysiological and neurochemical defects in streptozotocin-diabetic rats. Diabetic rats, which were not given evening primrose oil, showed highly significant elevations of nerve sorbitol and fructose combined with a depletion of nerve myo-inositol. In those animals there was also a 40% reduction (p<0.02) in the accumulation of axonally transported substance P-like immunoreactivity proximal to a 12 h sciatic nerve ligature together with reduced motor nerve conduction velocity (13% [p<0.001] and 20% [p<0.001] in two separate experiments). Treatment of other diabetic rats with evening primrose oil prevented completely the development of the motor nerve conduction velocity deficit without affecting sorbitol, fructose or myo-inositol levels or the deficit in axonal transport of substance P. In a second experiment, treatment of diabetic rats with evening primrose oil was associated with significant attenuation of the conduction velocity deficit, but not complete prevention.     

STZ诱导的2型糖尿病大鼠心肌组织TRPC7的表达上调

目的:观察2型糖尿病(T2DM)大鼠心肌组织损伤过程中,TRPC7的表达变化。方法:以高脂饲料喂养并辅以腹腔注射小剂量链脲佐菌素(Streptozotocin,STZ)来建立T2DM大鼠模型,采用蛋白印迹及免疫组化染色方法检测TRPC7在T2DM大鼠心肌组织的表达变化。结果:1T2DM大鼠造模成功且T2DM大鼠心肌组织发生损伤性变化:与正常组大鼠相比,T2DM组大鼠血糖明显升高且体重显著降低(P0.05);T2DM组大鼠心脏体积与质量显著减小(P0.05);T2DM组大鼠心脏质量指数(heart weight index,HWI)明显高于正常组(P0.05);2在T2DM大鼠心肌损伤过程中TRPC7表达上调:TRPC7在正常及T2DM大鼠心肌组织中均有表达,但与正常大鼠相比,T2DM大鼠心肌组织TRPC7蛋白的表达显著增高(P0.05)。结论:首次证实在损伤的T2DM大鼠心肌组织中,TRPC7的表达显著上调。