A型肉毒毒素降低大鼠胃平滑肌收缩及P物质含量

目的：在胃窦前壁注射A型肉毒毒素( BTX-A)后观察局部P物质（substance P）含量和分布的变化及其胃平滑肌收缩的变化，揭示两者之间的关系。 方法： 健康Wistar大鼠30只（普通级），体重260-300 g，雌雄不限。随机分为BTX-A组（B group）及对照组(A group)，在胃体前壁与幽门部交界线中点平滑肌内分别注射0.3 mL BTX-A (20 U/kg)，或0.9 % 氯化钠溶液0.3 mL； 记录胃肌电24 min后，切取局部胃前壁组织行放射免疫测定和免疫组化。结果： ① 放射免疫检测结果提示胃前壁组织中BTX-A组SP平均含量较对照组低28%（P＜0.01），免疫组化结果显示BTX-A组SP免疫反应阳性产物含量较对照组低11%（P＜0.05）；②注射BTX-A 12 min，24 min后， BTX-A组胃肌电的各项指标除24 min后峰电位发生率无显著差异(P＞0.05)外，其它均低于对照组（P＜0.05）。结论： BTX-A可以减少局部SP的含量，这种减少导致了胃肠平滑肌收缩功能的抑制。     

Glomerular renin angiotensin system in streptozotocin diabetic and Zucker diabetic fatty rats

Substantial evidence suggests that the intrarenal renin-angiotensin system (RAS) plays a role in the pathogenesis of diabetic nephropathy. Although the glomerular RAS is activated in the streptozotocin (STZ)-diabetic rat, the status of the glomerular RAS in the Zucker diabetic fatty (ZDF) rat, which is a commonly used genetic model of diabetes, is not known. Angiotensinogen (AGT), angiotensin II (Ang II), angiotensin converting enzyme (ACE), and angiotensin converting enzyme 2 (ACE2) were measured in glomeruli isolated from 4-week-old STZ-diabetic rats and 32-week-old ZDF rats. Glomerular injury was evaluated by histopathologic methods. Both STZ-diabetic and ZDF rats exhibited marked hyperglycemia and renal hypertrophy, but only ZDF rats demonstrated proteinuria and glomerulosclerosis. Glomerular AGT and Ang II levels were increased significantly in STZ-diabetic compared with nondiabetic control rats, accompanied by a reduction in ACE2 activity. In contrast, glomerular AGT, Ang II, and ACE2 were similar in ZDF rats and lean controls. ACE levels were not affected by diabetes in either diabetic model. In conclusion, the glomerular RAS is activated in the STZ diabetic rat but not in the ZDF rat despite a similar degree of hyperglycemia. The mechanism of nephropathy in the ZDF rat may involve factors other than hyperglycemia and RAS activation, such as hypertension and hyperlipidemia.     

Ultrastructure of the macula densa in streptozotocin diabetic rats

Morphometric analyses of the macula densa in streptozotocin diabetic rats have revealed, that the volume density of the large lateral intercellular spaces, which are present in normal animals between the macula densa cells, decreases significantly in magnitude from 8.7 to 1.5% in diabetic animals. The volume density of cytoplasmic glycogen in the macula densa cells increases significantly from 5.4% in the controls to 14.8% in the diabetic animals, but the total volume density of mitochondria is the same in the two groups. The contact area between macula densa cells and the Goorgmaghtigh cells is increased by 38% in the diabetic animals compared with controls. The structural abnormalities in the macula densa in response to diabetes might be considered a structural counterpart to the alterations in the tubuloglomerular feedback mechanism and the increase in glomerular filtration rate in diabetes.     

链脲佐菌素诱导MSG大鼠糖尿病心脏病模型的研究

目的:探讨腹腔注射链脲佐菌素(Streptozotocin,STZ)诱导L-谷氨酸钠(Monosodium glutamate,MSG)肥胖大鼠建立糖尿病心脏病模型。方法:选用新生SD大鼠随机分为两组:MSG组和正常对照组(NS组)。MSG组新生大鼠自出生第2d起颈部皮下注射L-谷氨酸钠5g·kg-1,隔天一次,共三次;正常对照组于皮下注射等体积无菌注射用水。MSG组于6周龄时再随机分为4个小组,腹腔注射链脲佐菌素0mg·kg-1,20mg·kg-1,30mg·kg-1,40mg·kg-1。于注射STZ 4w后测定各心脏血流动力学相关指标,同时取血测定其胰岛素水平及血液脂质等指标。结果:注射STZ 4w后,MSG组大鼠Lee’s指数显著增加,心脏指数明显降低,血浆高密度胆固醇(HDL)、低密度胆固醇(LDL)升高,收缩压(SBP)、舒张压(DBP)、平均动脉压(MAP)、心率(HR)、左心室收缩压(LVSP)、左心室内压最大上升速率(+dp/dt)、下降速率(-dp/dt)均显著升高,心电图显示其Q-T间期缩短,与对照组比较有统计学差异。MSG+STZ 30mg·kg-1组大鼠SBP、DBP、MAP、HR、+dp/dt、-dp/dt均显著降低,与MSG组比较有统计学差异。MSG+STZ 40mg·kg-1组大鼠SBP、DBP、MAP、HR、LVSP、+dp/dt、-dp/dt均显著降低,Lee’s指数降低,胰岛素浓度降低,血糖水平及心脏指数升高,血浆LDL水平降低,Q-T间期延长,与MSG组比较有统计学差异。结论:研究表明MSG大鼠在6周龄时腹腔注射STZ 40mg·kg-1,有利于糖尿病心脏病模型的建立,为研究、开发防治2型糖尿病心脏病的新药提供了一种良好的动物模型。     

Lack of cardiotoxic effect of isoproterenol in streptozotocin diabetic rats

Summary The well known cardiotoxic effect of isoproterenol (ISO) was investigated in normal and streptozotocin diabetic rats. Seven days after the subcutaneous injection of ISO (15 mg/kg) the hearts were perfusion fixed and 12 sections from each heart were stained (Masson's trichrome). ISO induced myocardial fibrosis was quantified at the light microscopic level according to established morphometric principles. Pulse rate and ST elevation were recorded by EEC (3 standard leads) before and after the ISO injection. Non-diabetic control animals showed marked fibrosis after ISO, but surprisingly the diabetic animals showed no fibrosis after ISO treatment. These findings were in accordance with an ISO induced ST elevation seen only among control animals although both groups showed the same degree of tachycardia. Insulin treatment prevented the protection against ISO and when streptozotocin was injected 24 h after the ISO a normal quantitative and qualitative appearance of the scar tissue was seen. It thus seems that streptozotocin diabetic rats are protected against the toxic effect of ISO, leaving the haemodynamic response unaffected. Which factor in the diabetic metabolism is reponsible for the present phenomenon is not known, but a defect in the signal transmission from the -receptor to the adenylcyclase is suggested as a possible explanation.     

Physiological responses to acute stress in alloxan and streptozotocin diabetic rats

Physiological responses to acute stress were assessed in alloxan diabetic, streptozotocin diabetic and control laboratory rats. Rats were prepared with indwelling tail artery catheters to allow for direct measurement of mean arterial pressure (MAP, mmHg) and heart rate (HR, beats per minute) and remote sampling of blood. Within 24 hours after surgery, basal values of MAP and HR were determined. Two days after surgery, rats were subjected to 5 minutes of intermittent footshock. Blood samples were collected before footshock stress and immediately and 15 minutes after termination of footshock. Plasma levels of norepinephrine (NE) and epinephrine (EPI) increased significantly above basal values in all animals exposed to acute footshock stress. However, in approximately one-half of alloxan and streptozotocin diabetic rats, plasma levels of EPI under basal conditions and following footshock stress were elevated significantly compared to controls and the remaining diabetic animals. We have denoted these subgroups of diabetic animals as reactive responders (plasma EPI greater than controls) and nonreactive responders (plasma EPI similar to controls), respectively. Plasma levels of NE under basal conditions and following footshock stress were similar in reactive responders and nonreactive responders compared to matched controls. Baseline blood glucose levels were elevated in alloxan and streptozotocin diabetic rats compared to controls. Blood glucose levels increased reliably in all animals following footshock stress. Basal MAPs were reduced significantly in both subgroups of alloxan and streptozotocin diabetic rats compared to matched controls. In contrast, resting HRs were similar between diabetic rats and their corresponding controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic effects of gamma-linolenic acid-alpha-lipoic acid conjugate in streptozotocin diabetic rats

Data suggesting the involvement of increased oxidative stress in the pathophysiology of diabetes has raised interest in the potential therapeutic benefit of antioxidants. Although beneficial metabolic effects of antioxidant supplementation have been suggested, an antioxidant mode of action, particularly in skeletal muscle, has not been documented. In the present study, we evaluate the metabolic effects of a gamma-linolenic acid-alpha-lipoic acid conjugate (GLA-LA) in streptozotocin-induced diabetic rats, and assess its potential mode of action by comparing its effects with equimolar administration of LA and GLA alone. Ten days of oral supplementation of 20 mg/kg body weight GLA-LA, but not LA or GLA alone, caused a mild reduction in fasting blood glucose concentration as compared with vehicle-treated diabetic rats (375 +/- 11 vs. 416 +/- 16 mg/dl, p = 0.03), with no change in fasting plasma insulin levels. A peripheral insulin-sensitizing effect could be observed with GLA-LA, LA, and GLA treatments, as demonstrated by a significant (p < 0.04) 23%, 13%, and 10% reduction, respectively, in the area under the glucose curve following an intravenous insulin tolerance test. This effect was associated with a 67% and 50% increase in GLUT4 protein content in the membranes of gastrocnemius muscle of GLA-LA and LA-treated animals, respectively; however, no change was observed with GLA treatment alone. Interestingly, both GLA-LA and LA treatments corrected a diabetes-related decrease in the gastrocnemius muscle low-molecular-weight reduced thiols content. These data demonstrate insulin-sensitizing properties of the GLA-LA conjugate by distinct mechanisms attributable to each of its components, which are associated with antioxidant effects.     

Radiotherapy-induced bone deterioration is exacerbated in diabetic rats treated with streptozotocin

Following radiotherapy, patients have decreased bone mass and increased risk of fragility fractures. Diabetes mellitus (DM) is also reported to have detrimental effects on bone architecture and quality. However, no clinical or experimental study has systematically characterized the bone phenotype of the diabetic patients following radiotherapy. After one month of streptozotocin injection, three-month-old male rats were subjected to focal radiotherapy (8 Gy, twice, at days 1 and 3), and then bone mass, microarchitecture, and turnover as well as bone cell activities were evaluated at 2 months post-irradiation. Micro-computed tomography results demonstrated that DM rats exhibited greater deterioration in trabecular bone mass and microarchitecture following irradiation compared with the damage to bone structure induced by DM or radiotherapy. The serum biochemical, bone histomorphometric, and gene expression assays revealed that DM combined with radiotherapy showed lower bone formation rate, osteoblast number on bone surface, and expression of osteoblast-related markers (ALP, Runx2, Osx, and Col-1) compared with DM or irradiation alone. DM plus irradiation also caused higher bone resorption rate, osteoclast number on bone surface, and expression of osteoclast-specific markers (TRAP, cathepsin K, and calcitonin receptor) than DM or irradiation treatment alone. Moreover, lower osteocyte survival and higher expression of Sost and DKK1 genes (two negative modulators of Wnt signaling) were observed in rats with combined DM and radiotherapy. Together, these findings revealed a higher deterioration of the diabetic skeleton following radiotherapy, and emphasized the clinical importance of health maintenance.     

In vitro motor activity and compliance of the caecum in streptozotocin diabetic rats

In order to characterize the diabetic gastrointestinal disorders such as constipation, the motor activity and the compliance of the caecum of streptozotocin diabetic rats were studied in vitro. The time course of enlargement of the caecum was also examined. Significant enlargement of the caecum was noticed in diabetic rats, 10 days after streptozotocin injection (65 mg/kg). It reached two times heavier in 30 days and three times in 90 days when compared with age-matched controls. The motor activity as studied by in vitro recording of the intraluminal pressure changes associated with spontaneous activity revealed the depression both in amplitude and frequency. The compliance was noticed to be significantly increased in the diabetic caecum as compared to age-matched controls when studied by passive Krebs solution injection. Threshold intraluminal pressure for inducing the reflex motor activity of the diabetic caecum was larger than that of the normal. These factors may contribute to the retention of content inside of the diabetic caecum.     

Minute rhythms of spike activity in intestinal smooth muscles during transition processes

A more informative method of transforming electromyograms to assess the spike activity of intestinal smooth muscles is proposed. The presence of minute rhythms of spike activity during the transition from the resting phase to regular activity is confirmed. These rhythms are recorded in the proximal part of the small intestine during the irregular phase of fasting periodic activity. It is found that the appearance of minute rhythms of spike activity on days 3–4 of modeled peritonitis may mark the beginning of the transition from pathology to health and indirectly indicate the regression of the pathological process. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 1, pp. 36–38, January, 1996 Presented by N. A. Agadzhanyan, Member of the Russian Academy of Medical Sciences     

Insulin reduces serum glycosylphosphatidylinositol phospholipase D levels in human type I diabetic patients and streptozotocin diabetic rats

The enzyme glycosylphosphatidylinositol phospholipase D has a postulated role in the insulin-mimetic signaling pathway of glycosylphosphatidylinositol compounds. We have investigated enzyme activity in the serum of human type I diabetic patients and plasma and tissues of streptozotocin-induced diabetic rats following insulin administration. In the human diabetic patients serum enzyme activity fell by an average of 10.6% (SEM = 2.7; P = 0.008; n = 20) following administration of insulin. In addition serum enzyme activity appeared to be depleted by 27% (SEM = 8.8; P = 0.011; n = 10) compared to nondiabetic controls. In untreated diabetic rats plasma enzyme activity gradually increased 0.3-fold over a 6-week period (P < 0.001; n = 8), this increase was reversed and activity normalized when these animals were treated with insulin. Cloning of the rat glycosylphosphatidylinositol phospholipase D cDNA enabled confirmation of the liver as the principal organ of synthesis. Analysis of mRNA levels in the livers of the diabetic rats showed that gene expression was reduced in the insulin-treated animals compared to the noninsulin-treated controls by 0.7-fold (P = 0.004; n = 4). Tissue enzyme activity was also reduced in the insulin-treated rats; in skeletal muscle enzyme activity was 0.3-fold lower (P = 0.001; n = 4). Insulin therefore decreases glycosylphosphatidylinositol phospholipase D synthesis in diabetic animals resulting in decreased serum enzyme levels, suggesting a relationship between this enzyme and the function of insulin.     

Stress and behavior in streptozotocin diabetic rats: biochemical correlates of passive avoidance learning

Retention of one-trial passive avoidance training was compared in diabetic and nondiabetic rats. Also compared were corticosterone concentrations associated with both training and retention testing, catecholamine excretion related to training, and regional brain catecholamine concentrations accompanying retention testing. Diabetic rats showed significantly better retention for the task than did nondiabetic rats. Associated with retention differences, diabetic rats had higher epinephrine excretion and nondiabetic rats had lower excretion after footshock training relative to baseline measures. Norepinephrine excretion was elevated in diabetics both in baseline measurement and during the 24 hr following footshock training. No differences were found in baseline or stimulated corticosterone concentration between diabetic and nondiabetic rats. Diabetic rats had higher concentrations of norepinephrine (NE) and dopamine (DA) and lower 3,4-dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratios in hypothalamus and higher NE in brain stem and amygdala than did nondiabetics, although both diabetic and nondiabetic rats had reduced DA and NE following retention testing. The results indicate that there are biochemical alterations in diabetes that may have important behavioral impact.     

Developmental studies on vasoactive intestinal peptide,substance P and calcitonin gene-related peptide in salivary glands of postnatal rats

The development of vasoactive intestinal peptide, substance P and calcitonin gene-related peptide in parotid, submandibular and sublingual glands of the male rat was followed by immunochemistry and immunocytochemistry. The total amounts of these peptides increased in surges during the first 8 weeks of the animal's life; one within 2–4 weeks and the other beginning 1–2 weeks later. Nerve fibres containing these peptides were present at birth showing a pattern of distribution similar to that in adults. During the first 4 weeks the nerve fibres increased in number.     

Conduction velocity of motor nerve and cervical sympathetic and vagus nerve in streptozotocin diabetic rats

We investigated the conduction velocity of motor and autonomic nerves, motor nerve to foot interosseous muscle and cervical vagus and sympathetic nerve, in streptozotocin diabetic rats (1-3 months duration of diabetes) and compared it with that of age-matched controls. In diabetic rats, the motor nerve conduction velocity was significantly reduced but the conduction velocity of cervical vagus and sympathetic nerves was not reduced.     

Long-term changes in the diabetic state induced by different doses of streptozotocin in rats

The long-term effects of different doses (0, 25, 35, 45, 55, 65 and 100 mg/kg) of streptozotocin (STZ) in male Wistar rats had been followed over a 16 week period. The weight-gain curve and the epididymal fat pad weight were significantly different (P less than 0.05) from control after 1 week with the 65 and 100 mg/kg doses and after 4 weeks with the 45 and 55 mg/kg doses; there were no significant changes with the 25 and 35 mg/kg doses even after 16 weeks. An i.v. glucose tolerance test (0.5 g/kg) was performed at 1, 4 or 16 weeks after the injection of STZ. The basal levels of glucose were significantly elevated (P less than 0.05) after 1 week with the greater than or equal to 55 mg/kg doses, and after 16 weeks with the greater than or equal to 45 mg/kg doses; there was also an overall increase in the basal glucose levels between 1 and 16 weeks in rats treated with the greater than or equal to 45 mg/kg doses. The basal insulin levels were significantly decreased (P less than 0.05) after 1 week with the greater than or equal to 65 mg/kg doses, after 4 weeks with the greater than or equal to 55 mg/kg doses and after 16 weeks with the greater than or equal to 35 mg/kg doses. The insulin peak 2 min after the glucose load was significantly less (P less than 0.05) after 1 week with the greater than or equal to 35 mg/kg doses and after 16 weeks with the greater than or equal to 25 mg/kg doses. The use of an insulinogenic index to assess the insulin secretory capacity showed a significant decrease (P less than 0.05) for the greater than or equal to 35 mg/kg doses at each tested time; with the 45 mg/kg dose, there was a further significant decrease (P less than 0.01) between the first and sixteenth week. The present long-term studies showed that there is a progressive deterioration in the glucose tolerance and insulin secretion after the injection of different doses of STZ. Furthermore, changes in glucose-insulin interrelationships over time suggest that the insulin insensitivity previously described in STZ diabetic rats might be only an early transient phenomenon.     

Anti-diabetic effect of orally administered Otostegia persica extract on streptozotocin diabetic rats

Anti-diabetic effect of the alcoholic extract of Otostegia persica was investigated on 40 streptozotocin diabetic rats in four equal groups. Animals in the first group did not receive any extract and acted as a control for the other groups. Rats in group II, III, and IV received a daily oral dose of O. persica extract at 200, 350, and 500 mg/kg, respectively, for 3 weeks. Blood glucose level was estimated three times a day (8:00 and 11:00 am and 5:30 pm) in all groups. Statistical analysis of the results by t test showed that the extract produced a dose-dependent decrease in the blood glucose level especially in the fourth group (p < 0.0001) in comparison the control group. Thus, study indicates that O. persica has a strong anti-diabetic action and can decrease blood glucose levels.     

糖尿病大鼠创面愈合过程中成纤维细胞增殖及Ⅰ型胶原合成减少

目的：观察链脲佐菌素诱导的大鼠糖尿病复合创伤修复过程中成纤维细胞增殖与胶原合成的变化。 方法： 实验采用Wistar大鼠112只，随机分对照组和模型组。模型组大鼠腹腔注射链脲佐菌素（STZ）55 mg/kg，3周后各组动物复合背部2.04 cm²全厚皮切除形成伤口。观察创面愈合时间和愈合率；采用HE染色和免疫组化法观察成纤维细胞和增殖细胞核抗原(PCNA)表达水平；采用苦味酸-天狼星红染色和图像分析技术观察创面Ⅰ、Ⅲ型胶原含量及Ⅰ/Ⅲ型比值。 结果： STZ诱发的糖尿病大鼠复合创伤后创面的愈合时间为(27.13±1.81)d，明显长于对照组（15.25±1.67）d，P<0.01；模型组在创伤第3、7和15 d创面愈合率明显低于对照组，分别P<0.01；在3、5、7和9 d模型组创面成纤维细胞数量和PCNA表达也明显少于对照组，分别P<0.05和P<0.01。两组创面在不同时点上Ⅰ型胶原分布均呈递增趋势，但对照组明显多于模型组，分别P＜0.05；尽管对照组在创伤3、7 d Ⅲ型胶原含量高于模型组，但在创伤3、7和11 d模型组Ⅰ/Ⅲ胶原比值都明显低于对照组，分别P＜0.01。 结论： STZ可能通过影响创面细胞增殖和创面胶原合成，从而导致创面愈合迟缓。