The intravenous glucose tolerance test in cannulated Wistar rats: a robust method for the in vivo assessment of glucose-stimulated insulin secretion

INTRODUCTION: Glucose-stimulated insulin secretion (GSIS) is critical in mammalian fuel homeostasis and is diminished early in the evolution of beta-cell dysfunction, ultimately contributing to the development of Type 2 diabetes. We sought to standardise and validate the intravenous glucose tolerance test (IVGTT), a commonly used technique to assess GSIS, in anaesthetised and conscious cannulated male Han Wistar rats. METHODS: Male Han Wistar rats were cannulated via the right jugular vein and left carotid artery. Anaesthetised and chronically cannulated conscious models underwent IVGTT using increasing doses of glucose (0.2, 0.5 and 1.0 g glucose/kg LBM) or following pre-treatment with Exendin-4 (EX-4) before receiving a 0.5 g glucose/kg LBM bolus dose. Blood glucose, plasma insulin and plasma C-peptide were measured at time-points throughout the experiments. RESULTS: Dose-dependent increases in blood glucose, insulin and C-peptide (where measured) were observed following administration of increasing doses of an intravenous glucose bolus in both the anaesthetised and conscious cannulated rats. The 0.5 g glucose/kg LBM bolus resulted in an intermediate response and was used in the second part of the study. EX-4 pre-treatment in combination with glucose resulted in GSIS potentiation, as assessed by plasma insulin measurement alone (anaesthetised model) or insulin and C-peptide measurements (conscious model). DISCUSSION: The IVGTT was standardised in anaesthetised and conscious cannulated male Han Wistar rats by performing a glucose dose response study and validated by examining GSIS potentiation using EX-4. Based on these results, the 0.5 g glucose/kg LBM bolus dose is recommended as the dose to use to assess GSIS in any standardised screening phase of new compounds with the potential to enhance glucose-sensitive pancreatic function. The experimental conditions described in these studies could be transferred to disease models for more detailed assessment of novel compound efficacy.     

Characterization of cationic amino acid transport systems in rat erythrocytes: lack of effect of uraemia on L-arginine influx

1. Chronic renal failure (CRF) is associated with the abnormal regulation of nitric oxide (NO) synthesis at the systemic level. The transport of L-arginine, upregulated in blood cells from uraemic patients, modulates NO synthesis in this pathological condition. The model of partial nephrectomy in rats is widely accepted as a valid model of uraemia. Because there are no reports of L-arginine transport in blood cells from uraemic rats, the aim of the present study was to investigate L-arginine transport in red blood cells (RBCs) from these rats. 2. The kinetics of L-arginine transport in RBC and plasma and the amino acid profiles of RBC were investigated in control, sham-operated and subtotally nephrectomized rats. 3. L-Arginine transport was mediated via the cationic amino acid transport system y+ and a transport system with kinetics resembling the human system y+L. In control RBC, the apparent Ki for L-leucine inhibition of L-arginine transport via system y+L was 0.16 +/- 0.02 and 4.8 +/- 2 mmol/L in the presence of Li+ and Na+, respectively. 4. The Vmax values for L-arginine transport via system y+L and system y+ were similar in RBC from control sham-operated and uraemic rats. Moreover, L-arginine concentrations in plasma and RBC were not affected by uraemia. 5. The findings of the present study provide the first evidence that L-arginine transport in rat erythrocytes is mediated by two distinct cationic transport systems with characteristics of systems y+ and y+L, which accept neutral amino acids only in the presence of Li+. In contrast with previous studies in uraemic patients, plasma levels and maximal transport rates of L-arginine were not altered in this rat model of CRF.     

Transient inhibitory effect of methoxychlor on testicular steroidogenesis in rat: an in vivo study

Methoxychlor, an organochlorine pesticide, has been reported to induce reproductive abnormalities in male reproductive tract. To get more insight into the mechanism(s) of gonadal toxicity provoked by methoxychlor, we investigated whether treatment with methoxychlor at low observed adverse effect level (LOAEL) would alter the activities of steroidogenic enzymes such as Δ⁵3β-hydroxysteroid dehydrogenase (3β-HSD) and Δ⁵17β-hydroxysteroid dehydrogenase (17β-HSD), the expression levels of steroidogenic acute regulatory (StAR) protein and androgen binding protein (ABP) in the testis of adult male rats. The experimental rats were exposed to a single dose of methoxychlor (50 mg/kg body weight) orally. The rats were killed at 0, 3, 6, 12, 24 and 72 h following treatment using anesthetic ether and testes were collected, processed and used to measure the activities of 3β-HSD, 17β-HSD, levels of hydrogen peroxide produced and the expression levels of StAR protein, and ABP. Methoxychlor administration resulted in a sequential reduction in the expression of StAR protein and activities of 3β-HSD, 17β-HSD with concomitant increase in the levels of hydrogen peroxide in the testis. These changes were significant between 6–12 h following treatment. The levels of ABP declined at 6–12 h following exposure to methoxychlor. The present study demonstrates transient effect of methoxychlor at LOAEL on testicular steroidogenesis and the possible role of hydrogen peroxide in mediating these effects.     

Important role of 3-methoxytyramine in the inhibition of cocaine sensitization by 1-methyl-1,2,3,4-tetrahydroisoquinoline: an in vivo microdialysis study

1-Methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ) is an endogenous compound with neuroprotective and antidopaminergic activities. Our previous research has shown that 1MeTIQ prevents morphine addiction and abates the expression of the reinstatement of cocaine self-administration. The current study investigated the mechanism of action of 1MeTIQ that is responsible for its considerable anticraving potential. Accordingly, we performed behavioral tests that measured the influence of 1MeTIQ on the locomotor activity of rats (Wistar) after a single cocaine (15 mg/kg, i.p.) dose and during cocaine sensitization (15 mg/kg, i.p.). In a neurochemical study, we examined the influence of 1MeTIQ on dopamine release in the rat striatum after a single cocaine administration and during cocaine sensitization using an in vivo microdialysis methodology. The data showed that 1MeTIQ (50 mg/kg, i.p.) only slightly inhibited cocaine-induced hyperactivity but completely antagonized the expression of locomotor cocaine sensitization. The in vivo microdialysis study demonstrated that the administration of 1MeTIQ before the acute cocaine injection intensified the cocaine-induced increase in dopamine release and produced a huge and long-lasting elevation of the extraneuronal concentration of dopamine (by approximately 1400%, p < 0.01) in the rat striatum. A significant increase in 3-methoxytyramine (3-MT) (by approximately 400%, p < 0.01) was also observed. During the expression of cocaine sensitization, the administration of 1MeTIQ before the reminder dose of cocaine produced an additional elevation of dopamine release but considerably more strongly increased the concentration of 3-MT in the synaptic cleft (by about 800%, p < 0.01). In light of these data and of our earlier in vitro and in vivo experiments showing a physiological role of 3-MT in the inhibitory regulation of excessive stimulation, we suggest that locomotor hyperactivity is dependent not only on dopamine concentration in the extracellular space, but also on the ratio of [DA/3-MT]. 1MeTIQ administered before the reminder dose of cocaine to cocaine-experienced rats plainly normalized the [DA/3-MT] ratio, which was increased by cocaine, and this effect may be responsible for its anti-addictive action. The results strongly support the view that 1MeTIQ may have a more general anti-abuse potential, and the extraneuronal metabolite of dopamine, 3-MT, may play a crucial role in its anti-craving effects.     

Vascular effects of loop diuretics: an in vivo and in vitro study in the rat

The vascular effects of loop diuretics were studied in two models designed to eliminate hemodynamic repercussions linked to sodium and water depletion: in vivo, in unilaterally nephrectomized rats with a contralateral uretero-venous shunt, and in vitro, in the isolated perfused rat kidney.In anesthetized rats, local vascular resistance was calculated from the simultaneous recording of blood pressure and renal, iliac and carotid blood flows (electromagnetic flowmeter, Skalar). Furosemide and piretanide (10 to 80 mg/kg i. v.) induced a comparable dose-dependent decrease in renal vascular resistance, which was not modified by reserpine and indomethacin pre-treatment. The iliac relaxing response was blunted by vasoconstriction, which disappeared after combined treatment with reserpine and indomethacin. The relaxation induced in the iliac and carotid vasculature persisted after bilateral nephrectomy.In vitro, the vasorelaxing effect of diuretics in isolated rat kidneys perfused in an open circuit was studied after vascular tone had been re-established by a continuous perfusion of PGF₂. Furosemide, piretanide and ozolinone induced a concentration-dependent decrease in renal tone (EC₅₀ = 0.47 × 10-4 mol/l, 1.03 × 10^–4 mol/l and 2.07 × 10^–4 mol/l respectively) in Wistar rats. A similar response to piretanide was found in spontaneously hypertensive stroke-prone rats (EC₅₀ = 0.32 × 10^–4 mol/l) and in their normotensive controls (EC_SO = 0.74 × 10^–4 mol/l).Our results show that loop diuretics induce a direct relaxation in the renal, iliac and carotid vasculature. This vascular effect, which appears at relatively high concentrations of the drugs, is prostaglandin independent and persists after bilateral nephrectomy. Correspondence to: M. Barthelmebs at the above address     

褐藻多糖GS201对脑神经细胞生存的影响

采用体外神经细胞培养的方法 ,检测 GS2 0 1对神经细胞的营养作用。结果表明 ,GS2 0 10 .0 1、0 .1、1、10 mg· L-1能显著提高神经细胞的存活率 ,其中 10 mg· L-1效果最好 ,并呈一定的量效关系     

泛昔洛韦体内抗鸭乙型肝炎病毒的药效研究

目的：观察核苷酸类似物泛昔洛韦体内抗鸭乙型肝炎病毒（ＤＨＢＶ）的作用。方法：采用重庆麻鸭乙型肝炎动物模型,用泛昔洛韦灌胃治疗１月,检测用药前后血清中的ＤＨＢＶＤＮＡ及血清转氨酶（ＡＬＴ、ＡＳＴ）、肝组织ＨＥ染色病理检查。结果：泛昔洛韦各剂量组用药２周、１月均能使血清中ＤＨＢＶＤＮＡ滴度总体水平显著降低（Ｐ〈０．０５（）或极显著降低（Ｐ〈０．０１）,停药１周后小剂量组有ＤＮＡ滴度回升现象,而中、大剂     

In vivo antifungal effect of Combretum and Terminalia species extracts on cutaneous wound healing in immunosuppressed rats

Acetone leaf extracts of Combretaceae species Combretum imberbe Wawra, Combretum nelsonii Duemmer, Combretum albopunctatum Suesseng, and Terminalia sericea Burch ex DC and a mixture of asiatic acid and arjunolic acid isolated from C. nelsonii were tested for antifungal activity against Candida albicans, Cryptococcus neoformans, Microsporum canis, and Sporothrix schenckii on wounds of immunocompromised Wistar rats. The therapeutic agents were selected based on low MIC values ranging 0.02–2.5?mg/mL and low toxicity (LC₅₀) ranging 75.7–168.6 μg/mL. Seven circular, full-thickness wounds were made on the back skin of 24 Wistar rats, under general anesthetic and using an aseptic technique. Rats were infected with different fungal pathogens in groups of six. The treatments were administered topically using 20% concentrations of each extract in aqueous cream. Amphotericin B was used as positive control. Erythema, exudate, crust formation, swelling, and ulceration were used to determine the wound healing process. Throughout the experiment, body temperature, measured using a subcutaneous probe, and weight of the rats were found to be within normal ranges. Epithelial closure in all rats occurred by 17 days. There was no significant difference in contraction of the lesion areas treated with different extracts. The variability in erythema at each lesion in rats infected with different fungal pathogens differed with treatments; the lesion without treatment took a longer time to heal in all cases. Exudate formation was observed until day 12 in rats infected with C. albicans and day 8 in rats infected with C. neoformans. In lesions infected with M. canis and S. schenckii, exudate formation was observed until day 10. The treated group presented a rigid, dark, and thick crust formation after day 3 until day 15. During histopathological evaluations, scant fungi were noted in all the wounds, indicating that infection had occurred but had generally cleared. The antifungal potential of crude extracts of selected plants and a mixture of asiatic acid and arjunolic acid on the wounds of immunocompromised rats was confirmed. The extracts of these plants may possibly be further developed into drugs for topical treatment of fungally infected wounds.     

Preventive effect of naringin on isoproterenol-induced cardiotoxicity in Wistar rats: an in vivo and in vitro study

This study was aimed to evaluate the preventive role of naringin on heart weight, blood glucose, total proteins, albumin/globulin (A/G) ratio, serum uric acid, serum iron, plasma iron binding capacity and membrane bound enzymes such as sodium potassium-dependent adenosine triphosphatase (Na(+)/K(+) ATPase), calcium-dependent adenosine triphosphatase (Ca(2+) ATPase) and magnesium-dependent adenosine triphosphatase (Mg(2+) ATPase) and glycoproteins such as hexose, hexosamine, fucose and sialic acid in isoproterenol (ISO)-induced myocardial infarction (MI) in rats and in vitro free radical scavenging assay. Male albino Wistar rats were pretreated with naringin (10, 20 and 40 mg/kg, respectively) for a period of 56 days. After the treatment period, ISO (85 mg/kg) was subcutaneously injected to rats at an interval of 24 h for 2 days. ISO-induced rats showed a significant (P<0.05) increase in the heart weight, blood glucose, serum uric acid, serum iron and a significant (P<0.05) decrease in the levels of total proteins, A/G ratio and iron binding capacity. A significant (P<0.05) decrease in the activity of Na(+)/K(+) ATPase and increase in the activities of Ca(2+) and Mg(2+) ATPase in the heart and a significant (P<0.05) increase in the levels of glycoproteins in serum and the heart were also observed in ISO-induced rats. Pretreatment with naringin for a period of 56 days exhibited a significant (P<0.05) effect and altered these biochemical parameters positively in ISO-induced rats. Naringin also scavenges 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and nitric oxide (NO) radicals in vitro. Thus, our study shows that naringin has cardioprotective role in ISO-induced MI in rats.     

Evidence of a flip-flop phenomenon in acamprosate pharmacokinetics: an in vivo study in rats

The pharmacokinetics of acamprosate were examined in the rat after oral and intravenous administration in order to detect the possible presence of a flip-flop phenomenon. Rats received 9.3 or 73.3 mg/kg of the drug as an intravenous bolus. The same doses were orally administered via gastric intubation. Plasma samples were taken from the jugular vein for determination of acamprosate concentration by liquid scintillation counting. The drug content was also quantified in urine and faeces. The acamprosate bioavailability was close to 20%, the amount recovered in the faeces being around 80% of the administered dose. The terminal slope of the oral plasma curve was significantly lower than that obtained after intravenous administration of the drug at both doses tested (p<2 x 10(-6) in both cases). Moreover, the downward slope after oral administration (lambda2=0.006 +/- 0.001 min(-1)) practically coincided with the first-order absorption rate constant, previously reported by us, obtained using an in situ rat gut technique. It is concluded that the acamprosate absorption rate is considerably slower than its elimination rate so that the drug exhibits flip-flop pharmacokinetics after oral administration. The lower intrinsic first-order absorption rate constant, ka, is responsible for this phenomenon.     

The effect of silybin on passive avoidance learning and pathological changes in hippocampal CA1 and DG regions in male Wistar rats offspring

Silybin, an extract from seeds of milk thistle (Silybum marianum), is known to have hepato-protective, anticarcinogenic, and estrogenic effects. Given that estrogen effects on memory have been reported, silybin may cause structural changes in the hippocampal CA1 and dentate gyrus (DG) neurons and as a result it may enhance learning and memory. Wistar rats were provided with silybin (from day 7 of gestational age up to 4 weeks after birth) with 2 dosages of 18 mg/kg in the experimental group 1 (Exp1) and 9 mg/kg in the experimental group 2 (Exp2). Offspring memory retention was compared by duration of step-through latency in passive avoidance apparatus. Furthermore, histological changes were investigated in experimental groups and control group (CG). Both the experimental groups showed significantly longer step-through latency than CG (p < 0.001 for Exp1 and p < 0.01 for Exp2). The average number of pyramidal cells in hippocampal CA1 and granular cells in hippocampal DG was remarkably higher in Exp1 and Exp2 compared with CG. The difference was significant between Exp1 and Exp2 for pyramidal cells (p < 0.05) but not for granular cells. Silybin administration during pregnancy resulted in histological changes in hippocampus and better memory function. These data may lay the ground work using silybin in memory impairment diseases.     

Quercus suber cork extract displays a tensor and smoothing effect on human skin: an in vivo study

Recently, it has become indispensable for anti-aging active ingredients to provide a visible and immediate smoothing antiwrinkle effect. In Quercus suber, suberin is the most important structural component of cork cell walls. Studies have shown that suberin is made up mostly of hydroxycarboxylic acids and that it is endowed with many special mechanical and chemical properties that evoke a possible smoothing effect on the surface of the skin. Therefore, we were interested in investigating the effect of this cork extract on the skin's surface in a double-blind clinical study. The study was conducted in 15 healthy volunteers, aged 22 to 52 years. The volunteers applied a gel formula with 3% of cork extract, or placebo gel, on each forearm. Skin surface roughness was evaluated visually by pictures and by silicone replicas 1 and 2 h after application, followed by statistical analysis using the matched-pairs McNemar statistical test. McNemar analysis of the pictures revealed that application of cork extract on the skin resulted in a highly significant reduction of roughness 1 h after application. This effect was observed in 73.3% of volunteers. Two hours after cork extract application, a highly significant improvement of skin roughness was found in 78.6% of volunteers. Moreover, silicone replica treatment confirmed significant improvement in average of roughness at 2 h. These results demonstrate that cork extract provides a remarkable and highly significant tensor and smoothing effect on the skin, which could be of great use in anti-aging skin care products.     

线栓法制备Wistar大鼠局灶性脑缺血模型的实验研究

目的:建立一种简便可靠,创伤较小的Wistar大鼠局灶性脑缺血模型。方法:参照Zealonga及Koizum的线栓法,加以改进,制作Wistar大鼠局灶性脑缺血模型,随后行神经病学检查,测定脑组织含水量、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性,并进行病理组织学检查,以观察模型的可靠性。结果:大鼠大脑中动脉阻断2小时(MCAO2h)后,出现神经功能障碍,缺血脑组织含水量及MDA含量增加,SOD活性下降,HE染色显示明显脑水肿。结论:该改良法制备的模型简便易行,结果可靠,创伤小,稳定性好,是用于研究局灶性脑缺血较为理想的实验动物模型。     

Rapid and widespread distribution of doxycycline in rat brain: a mass spectrometric imaging study

1. The penetration of tetracyclines into the brain has been widely documented. The aim of this work was to develop a matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI MSI) method for the molecular histology of doxycycline (DOX) in the healthy rat brain.

2. The time-dependent distribution was investigated after an i.p. dose of 25?mg/kg at 0, 5, 30, 120, 240, 360 and 480?min postdose. LCMS/MS was used to quantify the drug in plasma and brain homogenates and MALDI MSI was used to determine the distribution of the analyte.

3. Within the first-hour postdose, the drug showed slow accumulation into the plasma and brain tissues. DOX brain concentration gradually increased and reached a peak (C_max) of 1034.9?ng/mL at 240?min postdose, resulting in a brain plasma ratio of 31%. The images acquired by MSI matched the quantification results and clearly showed drug distribution over the entire rat brain coronal section from 5?min and its slow elimination after 360-min postdose.

4. Our findings confirm that MALDI MSI provides an advanced, label-free and faster alternative technique for xenobiotic distribution such as DOX in tissues, making it an essential drug discovery tool for other possible neuroprotective agents.     

金银花在体内抗氧化作用的实验研究

目的探讨金银花在体内的抗氧化作用。方法将20只Wistar大鼠随机分为两组。其中,实验 1组(大剂量组10只)予金银花水煎液(10g／kg)灌胃;实验2组(小剂量组10只)予金银花水煎液(5g／kg) 灌胃;另设对照组(10只)予蒸馏水灌胃。分别在灌胃前、灌胃后1、2h由眼眶取血,分离血浆,检测不同时间血浆内T-AOC、GSH-Px、GSH、MDA、NOS、NO、SOD的变化。结果实验1组和实验2组与对照组相比,灌胃1、2h后T-AOC、GSH-Px、GSH、SOD都有明显增加,而NOS和NO无明显变化,MDA明显下降; 1h时增加或减少幅度大于2h。结论金银花可提高体内抗氧化作用,且有剂量依赖性。     

铁包金总黄酮体内对S180实体瘤的抑制作用

目的研究铁包金总黄酮对小鼠移植性肿瘤S180的生长抑制作用,并探讨其可能的作用机制。方法用动物移植性肿瘤在体实验法,观察抑瘤率、胸腺脾脏及肝脏指数;检测血清中SOD、MDA变化;病理切片观察瘤细胞生长及病理形态变化情况;免疫组化检验肿瘤组织中p53、TNF-α、Caspase-3蛋白的表达。结果①铁包金总黄酮高、中、低剂量组的抑瘤率分别50.35%、35.66%、23.08%,阳性对照组的抑瘤率为83.22%,各组小鼠的胸腺、脾脏、肝脏指数与空白组比较差异无显著性(P>0.05),阳性对照组与空白组比较明显降低(P<0.01);②铁包金总黄酮各组升高小鼠血清的SOD值,且降低其MDA值,具有一定的量效关系。阳性组降低小鼠的SOD值,且升高MDA值。与空白组相比差异有显著性(P<0.01);③病理切片显示给药各组和阳性组坏死面积比空白组大;④免疫组化显示高、中、低各组p53蛋白表达依次升高,TNF-α和Caspase-3蛋白表达依次降低。结论铁包金总黄酮通过清除氧自由基和调节p53,TNF-α和Caspase-3蛋白的表达来抑制肿瘤生长。     

Anticonvulsive effects of carbenoxolone on penicillin-induced epileptiform activity: an in vivo study

Epilepsy is an important problem in neurological disorders. Recent studies claimed that gap junctions have a critical role in epileptic neuronal events. The aim of present study is to investigate the effects of gap junction blocker carbenoxolone on penicillin-induced experimental epilepsy. For this purpose, 4-month-old male Wistar rats were used in the present study. Permanent screw electrodes allowing EEG monitoring from conscious animals and permanent cannula providing the administration of the substances to the brain ventricle were placed into the cranium of rats under general anesthesia. At the end of the postoperative recovery period, epileptiform activity was generated by injecting 300 IU crystallized penicillin through the ventricular cannula. Epileptiform activity monitored from a digital recording system, when it reached its maximum intensity, carbenoxolone (100, 200, 500 nmol) was applied in the same way with penicillin. Effects of carbenoxolone on epileptiform activity were assessed by both electrophysiological and behavioral analysis. Carbenoxolone suppressed epileptiform activity by decreasing the amplitude and frequency of epileptiform spikes and by attenuating the epileptiform behavior. The results of this study suggest that the blockade of electrical synapses may contribute to the prevention and amelioration of epileptic activity.