Maturational Patterns of Iodothyronine Phenolic and Tyrosyl Ring Deiodinase Activities in Rat Cerebrum, Cerebellum, and Hypothalamus

To explore the control of thyroid hormone metabolism in brain during maturation, we have measured iodothyronine deiodination in homogenates of rat cerebrum, cerebellum, and hypothalamus from 1 d postnatally through adulthood. Homogenates were incubated with ¹²⁵I-l-thyroxine (T₄) + [¹³¹I]3,5,3′-l-triiodothyronine (T₃) + 100 mM dithiothreitol. Nonradioactive T₄, T₃, and 3,3′,5′-triiodothyronine (rT₃) were included, as appropriate. The net production rate of [¹²⁵I]T₃ from T₄ in 1-d cerebral homogenates was similar to the rate in adult cerebral homogenates (9.9±2.5[SEM]% vs. 8.9±1.2% T₄ to T₃ conversion in 2 h). Production of T₃ was not detectable in 1-d cerebellar and hypothalamic homogenates. The net T₃ production rate in adult cerebellar homogenates was twice as great as, and that in adult hypothalamic homogenates similar to, the rate in cerebral homogenates.     

Reactive oxygen intermediates contribute to necrotic and apoptotic neuronal injury in an infant rat model of bacterial meningitis due to group B streptococci.

Reactive oxygen intermediates (ROI) contribute to neuronal injury in cerebral ischemia and trauma. In this study we explored the role of ROI in bacterial meningitis. Meningitis caused by group B streptococci in infant rats led to two distinct forms of neuronal injury, areas of necrosis in the cortex and neuronal loss in the dentate gyrus of the hippocampus, the latter showing evidence for apoptosis. Staining of brain sections with diaminobenzidine after perfusion with manganese buffer and measurement of lipid peroxidation products in brain homogenates both provided evidence that meningitis led to the generation of ROI. Treatment with the radical scavenger alpha-phenyl-tert-butyl nitrone (PBN) (100 mg/kg q8h i.p.) beginning at the time of infection completely abolished ROI detection and the increase in lipidperoxidation. Cerebral cortical perfusion was reduced in animals with meningitis to 37.5+/-21.0% of uninfected controls (P < 0.05), and PBN restored cortical perfusion to 72.0+/-8.1% of controls (P < 0.05 vs meningitis). PBN also completely prevented neuronal injury in the cortex and hippocampus, when started at the time of infection (P < 0.02), and significantly reduced both forms of injury, when started 18 h after infection together with antibiotics (P < 0.004 for cortex and P < 0.001 for hippocampus). These data indicate that the generation of ROI is a major contributor to cerebral ischemia and necrotic and apoptotic neuronal injury in this model of neonatal meningitis.     

Effects of hypertonic (3%) saline in rats with circulatory shock and cerebral ischemia after heatstroke

Objective To evaluate the effects of hypertonic (3%) saline in heatstroke rats with circulatory shock, intracranial hypertension, and cerebral ischemia.Design and setting Urethane-anesthetized rats were exposed to a high ambient temperature of 42°C until mean arterial pressure and local cerebral blood flow (CBF) in the corpus striatum began to decrease from their peak levels, which was arbitrarily defined as the onset of heatstroke. Control rats were exposed to 24°C.Measurements and results Extracellular concentrations of glutamate and lactate/pyruvate ratio (cellular ischemia markers), and glycerol (a cellular injury marker) in the corpus striatum of rat brain were assessed by intracerebral microdialysis methods. Striatal PO₂, temperature, and local CBF were measured with a combined OxyLite PO₂, thermocouple, and OxyFlo LDF, respectively. The values of mean arterial pressure, cerebral perfusion pressure, and striatal CBF and PO₂ in rats treated with 0.9% NaCl solution after the onset of heatstroke were all significantly lower than those in normothermic controls. In contrast, the values of intracranial pressure, brain temperature, and extracellular concentrations of glutamate, glycerol, and lactate/pyruvate in the corpus striatum were greater. Intravenous infusion of hypertonic (3%) saline solution either "0" time before the start of heat exposure or right after the onset of heatstroke significantly attenuated the heatstroke-induced arterial hypotension, intracranial hypertension, decreased cerebral perfusion, and cerebral ischemia and damage and resulted in prolongation of survival time.Conclusions Our results strongly suggest that the experimental heatstroke syndromes can be effectively prevented and treated by hypertonic saline.An editorial regarding this article can be found in the same issue ()     

Lipopolysaccharide infusion enhances dynamic cerebral autoregulation without affecting cerebral oxygen vasoreactivity in healthy volunteers

Introduction

Sepsis may be associated with disturbances in cerebral oxygen transport and cerebral haemodynamic function, thus rendering the brain particularly susceptible to hypoxia. The purpose of this study was to assess the impact of isocapnic hypoxia and hyperoxia on dynamic cerebral autoregulation in a human-experimental model of the systemic inflammatory response during the early stages of sepsis.

Methods

A total of ten healthy volunteers were exposed to acute isocapnic inspiratory hyperoxia (F_IO₂ = 40%) and hypoxia (F_IO₂ = 12%) before and after a 4-hour lipopolysaccharide (LPS) infusion (2 ng kg^-1). Middle cerebral artery blood follow velocity was assessed using transcranial Doppler ultrasound, and dynamic autoregulation was evaluated by transfer function analysis.

Results

Transfer function analysis revealed an increase in the phase difference between mean arterial blood pressure and middle cerebral artery blood flow velocity in the low frequency range (0.07–0.20 Hz) after LPS (P<0.01). In contrast, there were no effects of either isocapnic hyperoxia or hypoxia on dynamic autoregulation, and the cerebral oxygen vasoreactivity to both hyperoxia and hypoxia was unaffected by LPS.

Conclusions

The observed increase in phase suggests that dynamic cerebral autoregulation is enhanced after LPS infusion and resistant to any effects of acute hypoxia; this may protect the brain from ischaemia and/or blood–brain barrier damage during the early stages of sepsis.     

Antiviral Activity of Cytarabine in Herpesvirus–Infected Rats

Intranasal inoculation of herpesvirus (approximately 1.8 mean lethal doses [LD₅₀] in 0.1 ml) into 105- to 115-g rats produces paralytic disease in 4 to 5 days and 80 to 100% mortality in 8 to 12 days. Cytarabine (ara-C) (40 to 320 mg/kg), administered subcutaneously to inoculated rats, delays the onset of paralysis and protects the animals from death. Drug treatments were given twice daily for 5 days. Beneficial drug effects were observed even when initiation of therapy was delayed for 3 days after virus inoculation. A dose-response relationship existed when therapy was initiated at 4 h after virus inoculation. However, when therapy was delayed for 3 days, it appeared that the highest drug level (320 mg/kg twice daily) was somewhat less effective than the lower doses (160 and 80 mg/kg twice daily). Virus could be detected in homogenates of brain beginning 3 days after inoculation, and the titer increased through 7 days. Ara-C treatment, initiated 4 h after inoculation, caused a delay in the appearance of virus, and a reduction in the titer in the brain homogenates. No virus was detected in blood serum, or in homogenates prepared from lung, kidney, thymus, or spleen of infected rats. The virus titration studies are in agreement with the illness and mortality produced by herpesvirus infection.     

脑缺血-再灌注诱导大鼠皮层和纹状体组织信号转导与转录激活子-3的激活变化

目的研究局灶脑缺血诱导大鼠皮层和纹状体信号转导与转录激活子-3(STAT3)的激活变化。方法采用SD雄性大鼠线栓法制作右大脑中动脉缺血(MCAO)局灶脑缺血模型。运用抗STAT3和抗磷酸化STAT3抗体做免疫印迹(IB)检测皮层和纹状体STAT3的表达及激活变化。结果缺血-再灌注不同时间并不能引起皮层及纹状体STAT3蛋白表达变化,但可诱导其磷酸化水平显著增加。缺血-再灌注24h达到峰值,与假手术组相比分别增加约5.5倍和8.4倍。结论局灶脑缺血-再灌注能引起缺血同侧皮层和纹状体STAT3磷酸化水平的显著增加,提示缺血性脑损伤诱导STAT3的激活可能参与缺血皮层区和纹状体神经元细胞的病理生理过程。     

全脑缺血再灌注损伤早期脑皮质超微结构的变化

目的探讨全脑缺血再灌注损伤大鼠早期脑皮质神经元、胶质细胞和血脑屏障的变化。方法将6只Wistar大鼠随机分为缺血再灌注组（n=3）和假手术对照组（n=3）。制备大鼠全脑缺血再灌注模型。缺血再灌注组于缺血再灌注1h、假手术组于手术后1h取脑，电镜观察皮质超微结构的变化。结果缺血再灌注早期（1h）皮质神经细胞发生不同程度的固缩，胶质细胞肿胀，核内染色质溶解，核膜不清；血管周围足突轻度肿胀，与基膜分离；微管有部分溶解。结论再灌注损伤早期皮质神经元、胶质细胞、细胞骨架和血脑屏障即发生变化。     

Phenolic and Tyrosyl Ring Deiodination of Iodothyronines in Rat Brain Homogenates

Conversion of thyroxine (T₄) to 3,5,3′-triiodothyronine (T₃) in rat brain has recently been shown in in vivo studies. This process contributes a substantial fraction of endogenous nuclear T₃ in the rat cerebral cortex and cerebellum. Production of T₄ metabolites besides T₃ in the brain has also been suggested. To determine the nature of these reactions, we studied metabolism of 0.2-1.0 nM [¹²⁵I]T₄ and 0.1-0.3 nM [¹³¹I]T₃ in whole homogenates and subcellular fractions of rat cerebral cortex and cerebellum. Dithiothreitol (DTT) was required for detectable metabolic reactions: 100 mM DTT was routinely used. Ethanol extracts of incubation mixtures were analyzed by paper chromatography in t-amyl alcohol:hexane:ammonia and in 1-butanol:acetic acid. Rates of production of iodothyronines from T₄ and T₃ were greater at pH 7.5 than at 6.4 or 8.6 and greater at 37°C than at 22° or 4°C. Lowering the pH, reducing the protein or DTT concentrations, and preheating homogenates to 100°C all increased excess I⁻ production but reduced iodothyronine production.     

Repeated short-term daily exercise ameliorates oxidative cerebral damage and the resultant motor dysfunction after transient ischemia in rats

Long-term exercise prior to brain ischemia enhances the activities of antioxidant enzymes and leads to a significant reduction in brain damage and neurological deficits in rats subjected to transient middle cerebral artery occlusion. However, it has not been established whether relatively short-term exercise generates similar results following middle cerebral artery occlusion. We aimed to determine whether short-term exercise could reduce oxidative damage and prevent sensori-motor dysfunction. Male Wistar rats were subjected to perform daily exercise on a treadmill for 30 min at a speed of 15 m/min for 3 weeks, followed by a 90-min middle cerebral artery occlusion. Animals were assessed after middle cerebral artery occlusion for neurological deficits and sensori-motor function. Brain tissues were processed to evaluate infarct volume and oxidative damage. Oxidative stress was assessed using immunohistochemistry for 4-hydroxy-2-nonenal-modified proteins and 8-hydroxy-2''-deoxyguanosine. Antioxidant enzymes were evaluated using immunohistochemistry for thioredoxin and activity assay for superoxide dismutase. Exercise for 3 weeks decreased the severity of paralysis and impairment in forelimb motor coordination. Furthermore, exercise had effect on superoxide dismutase and reduced the infarct volume and the number of cells immunopositive for 4-hydroxy-2-nonenal-modified proteins and 8-hydroxy-2''-deoxyguanosine. Our results suggest that pre-conditioning treadmill exercise for 3 weeks is useful for ameliorating ischemia-induced brain injury.     

Reduction of the infarct size by simultaneous administration of L-histidine and diphenhydramine in ischaemic rat brains

Aims

While diphenhydramine is a histamine H₁ receptor antagonist, the agent has been shown to inhibit histamine-N-methyltransferase, a histamine inactivating enzyme in the brain. Since an increase in the brain concentration of histamine ameliorates reperfusion injury after cerebral ischaemia, effects of postischaemic administration of diphenhydramine were evaluated in rats treated with l-histidine, a precursor of histamine.

Methods

The right middle cerebral artery was occluded for 2 h, and the infarct size was determined 24 h after reperfusion of cerebral blood flow. Brain oedema was evaluated by comparing the area of the right hemisphere to that of the left hemisphere.

Results

Focal cerebral ischaemia provoked marked damage in saline-treated control rats, and infarct volumes in the striatum and cerebral cortex were 56 (49-63) mm³ and 110 (72-148) mm³, respectively (means and 95% confidence intervals, n = 6). Administration of l-histidine (1000 mg/kg, intraperitoneal) immediately after reperfusion did not affect the infarct size. Simultaneous administration of diphenhydramine (20 mg/kg, intraperitoneal) with l-histidine reduced the infarct size to 25% and 21% of that in the control group, respectively. The combination therapy completely reduced ischaemia-induced brain oedema.

Conclusion

Because histamine H₁ action does not influence ischaemic brain damage, elevation of the central histamine concentration by blockade of histamine-N-methyltransferase may be a likely mechanism responsible for the alleviation.     

脑缺血合并高脂血症模型大鼠脑组织的病理改变

背景：大多数脑缺血是在高血压、高脂血症、糖尿病等基础病变条件下发生的。因此,构建高脂血症复合脑缺血大鼠模型,研究基础性病变对脑缺血的影响具有重要意义。目的：观察高脂血症复合脑缺血大鼠模型脑组织病理学改变,及其高脂血症病理因素对脑缺血的影响。方法：实验以高脂饲料喂养大鼠制备高脂血症大鼠模型,然后线栓法制备局灶性脑缺血大鼠模型,建模成功后 3,7 d,采用 TTC 染色的方法,观察各组大鼠脑组织缺血部位体积,苏木精-伊红染色观察各组大鼠脑组织缺血边缘区组织病理学改变,透射电镜观察各组大鼠脑组织缺血边缘区细胞超微结构改变。结果与结论：TTC 染色结果显示高脂＋脑缺血 7 d 组大鼠的脑缺血部位体积明显减小。苏木精-伊红染色结果显示所有脑缺血模型都呈典型的缺血性改变,脑缺血 7 d 的小胶质细胞数量比 3 d 的明显减少,高脂＋脑缺血7d 相对于 3 d 的变化更明显。超微结构显示所有脑缺血模型的神经元和胶质细胞核膜皱缩,线粒体嵴基本完全消失,内皮细胞线粒体减少,神经突触的突触小泡大部分溶解,缺血 7 d,尤其是高脂＋脑缺血 7 d 的上述损伤减轻,神经元变性、坏死减少,线粒体损伤恢复,线粒体嵴也明显增多,神经突触的突触小泡明显恢复。说明高脂血症促进了脑缺血损伤的恢复,其原因可能是高脂血症因素激活了体内某种保护机制。     

白藜芦醇甙对大鼠局灶性脑缺血的保护作用

背景脑缺血时大量的自由基生成,使脑内脂质过氧化作用加强,导致细胞及细胞屏障损害,神经元坏死或凋亡,引起和加重缺血脑组织水肿.目的通过观察白藜芦醇甙对大鼠局灶性脑缺血后脑组织自由基、脂质过氧化物含量、脑含水量及病理形态学的影响,探讨其对脑缺血的保护作用.设计随机对照实验.单位重庆医科大学附属第二医院ICU和重庆医科大学附属儿童医院儿科医学研究所.材料实验于2001-10/2002-07在重庆医科大学儿科医学研究所完成.将48只健康成年雄性Wistar大鼠随机分为3组,每组16只.缺血前白藜芦醇甙处理组缺血前30 min,经颈外静脉注射6 g/L白藜芦醇甙(12 mg/kg)溶液.假手术组大鼠仅在麻醉状态下分离右侧颈总动脉,不予阻断血流.缺血模型组建立大鼠右侧大脑中动脉梗死模型.假手术组、缺血模型组与缺血前白藜芦醇甙处理组以同样方式、剂量静脉给予生理盐水.大鼠大脑中动脉阻塞后2 h在麻醉状态下快速断头取脑.每组随机选取8只大鼠测定脑组织含水量,其余8只大鼠测定脑组织自由基及脂质过氧化物含量.方法应用干-湿重法测脑组织含水量,以硫代巴比妥酸法检测丙二醛水平、黄嘌呤氧化酶法检测超氧化物歧化酶活性、化学比色法测定谷胱甘肽过氧化物酶活性、化学比色法检测一氧化氮合酶活性,以比色法测定过氧化氢酶活性,并按Folin-酚试剂法标定蛋白含量,所有操作均严格按说明书进行.主要观察指标①各组大鼠脑组织含水量.②各组大鼠脑组织中丙二醛含量,超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶及一氧化氮合酶活性.③各组大鼠脑组织病理学观察.结果48只大鼠均进入结果分析.①缺血前白藜芦醇甙处理组脑组织中超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶活性明显高于缺血模型组[(226.43±8.69),(193.37 ±11.14)NU/mg;(244.38±12.34),(211.71±16.50)μkat/g;(59.85±9.67),(35.51±7.67)μkat/g,(q=4.38～10.45,P＜0.01)].②缺血前白藜芦醇甙处理组脑组织中丙二醛含量、脑含水量明显低于缺血模型组[(6.38±0.54),(8.63±0.78)μmol/g;(78.72±0.43),(80.41±0.64),%,P＜0.01].③白藜芦醇甙有降低缺血脑组织中一氧化氮合酶活性的趋势,但与缺血模型组非常接近[(12.00±1.00),(12.84±1.17)μkat/g,P＞0.05].④病理学组织检查显示,白藜芦醇甙能减轻缺血所导致的脑水肿.结论白藜芦醇甙能减轻脂质过氧化反应,降低缺血脑组织中丙二醛含量,提高体内超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶活性,抑制或减轻脑水肿形成,保护细胞膜功能,减轻缺血神经元功能损害,对局灶脑缺血性脑损伤具有明显的保护作用.     

Interleukin 3 Prevents Delayed Neuronal Death in the Hippocampal CA1 Field

In the central nervous system, interleukin (IL)-3 has been shown to exert a trophic action only on septal cholinergic neurons in vitro and in vivo, but a widespread distribution of IL-3 receptor (IL-3R) in the brain does not conform to such a selective central action of the ligand. Moreover, the mechanism(s) underlying the neurotrophic action of IL-3 has not been elucidated, although an erythroleukemic cell line is known to enter apoptosis after IL-3 starvation possibly due to a rapid decrease in Bcl-2 expression. This in vivo study focused on whether IL-3 rescued noncholinergic hippocampal neurons from lethal ischemic damage by modulating the expression of Bcl-x_L, a Bcl-2 family protein produced in the mature brain. 7-d IL-3 infusion into the lateral ventricle of gerbils with transient forebrain ischemia prevented significantly hippocampal CA1 neuron death and ischemia-induced learning disability. TUNEL (terminal deoxynucleotidyltransferase–mediated 2′-deoxyuridine 5′-triphosphate-biotin nick end labeling) staining revealed that IL-3 infusion caused a significant reduction in the number of CA1 neurons exhibiting DNA fragmentation 7 d after ischemia. The neuroprotective action of IL-3 appeared to be mediated by a postischemic transient upregulation of the IL-3R α subunit in the hippocampal CA1 field where IL-3Rα was barely detectable under normal conditions. In situ hybridization histochemistry and immunoblot analysis demonstrated that Bcl-x_L mRNA expression, even though upregulated transiently in CA1 pyramidal neurons after ischemia, did not lead to the production of Bcl-x_L protein in ischemic gerbils infused with vehicle. However, IL-3 infusion prevented the decrease in Bcl-x_L protein expression in the CA1 field of ischemic gerbils. Subsequent in vitro experiments showed that IL-3 induced the expression of Bcl-x_L mRNA and protein in cultured neurons with IL-3Rα and attenuated neuronal damage caused by a free radical–producing agent FeSO₄. These findings suggest that IL-3 prevents delayed neuronal death in the hippocampal CA1 field through a receptor-mediated expression of Bcl-x_L protein, which is known to facilitate neuron survival. Since IL-3Rα in the hippocampal CA1 region, even though upregulated in response to ischemic insult, is much less intensely expressed than that in the CA3 region tolerant to ischemia, the paucity of IL-3R interacting with the ligand may account for the vulnerability of CA1 neurons to ischemia.     

山莨菪碱对全脑缺血-再灌流后脑线粒体损伤的保护作用

目的：探讨山莨菪碱对急性全脑缺血－再灌流后脑线粒体损伤的保护作用。方法：采用家兔全脑缺血－再灌流损伤模型。缺血20min，再灌流2h,观察脑线粒体呼吸功能、呼吸缺氧化酶活性、线粒体内Ca^2 和丙二醛含量的变化。结果：脑缺血－再灌流后，脑线粒体呼吸控制率、磷氧化、氧化磷酸化效率及烟酰胺腺嘌呤二核苷酸氧化酶、琥珀酸氧化酶、细胞色素C氧化酶活性明显降低（P＜0．01），而线粒体Ca^2 、丙二醛含量明显升高（P＜0．01）；再灌流早期给予山莨菪碱治疗后，上述线粒体损伤性改变明显减轻。结论：山莨菪碱对脑缺血－再灌流后线粒体损伤具有一定的保护作用，其机制可能与Ca^2 拮抗、抑制脂质过氧化及保护呼吸链酶活性有关。     

Identification of aldehyde oxidase 3 as a binding protein for squid ink polysaccharides using magnetic nanoparticles

To explore the interactive molecules of squid ink polysaccharides (SIP) for further understanding the action mechanisms of SIP bio-function, this study prepared SIP binding proteins from mouse liver using superparamagnetic nanometer beads. Michaelis–Menten constant (K_m) was detected from a Lineweaver–Burk double reciprocal plot to assess effect of SIP on activity of aldehyde oxidase (AOX). Results showed that three proteins, AOX-3, regucalcin (RGN) and α1-antitrypsin (A1AT3) were separated from mouse liver by magnetic nanoparticles conjugated with SIP. Contents of AOX-3 were much more than RGN and A1AT3. SIP (0.5 mg mL⁻¹) reduced K_m value of aldehyde oxidase of mouse liver from 91.79 μmol L⁻¹ to 43.70 μmol L⁻¹.

Superparamagnetic nanometer beads bonding SIP was employed to pull down the binding protein from the liver of mouse, which was identified as aldehyde oxidase 3. By means of enzyme kinetics analysis, SIP was found to activate AOX3 enzyme activity.     

Postischemic alteration of muscarinic acetylcholine and adenosine A1 binding sites in gerbil brain

We studied the alterations in the binding of muscarinic cholinergic and adenosine A₁ receptors following transient cerebral ischemia in Mongolian gerbils and examined the effects of the novel vinca alkaloid derivative vinconate and pentobarbital against the alterations in the binding of these receptors. Animals were allowed to survive for 5 h and 7 days after 10 min of cerebral ischemia induced by bilateral occlusion of common carotid arteries. [³H]Quinuclidinyl benzilate (QNB) and [³H]cyclohexyladenosine (CHA) were used to label muscarinic cholinergic and adenosine A₁ receptors, respectively. The [³H]QNB and [³H]CHA bindings showed no significant alteration in the gerbil brain 5 h after ischemia. However, these bindings in the striatium, the hippocampal CA1 sector, and the hippocampal CA3 sector revealed a significant reduction 7 days after ischemia. The [³H]CHA binding also showed a significant decline in the dentate molecular layer 7 days after ischemia. Intraperitoneal application of vinconate (100 and 300 mg/kg) 10 min and pentobarbital (40 mg/kg) 30 min before ischemia showed a mild reduction in the [³H]CHA binding in the brain 5 h after ischemia. Especially, the reduction was found in the hippocampal CA1 sector and the dentate molecular layer. However, the [³H]QNB binding revealed no significant alteration in the brain 5 h after ischemia. Seven days after ischemia, both drugs prevented a marked reduction in the [³H]CHA binding in the striatium, but not in the hippocampal CA1 sector, the hippocampal CA3 sector, and the dentate molecular layer. By contrast, vinconate and pentobarbital failed to prevent the reduction in the [³H]QNB binding in the striatum. Morphological study indicated that vinconate and pentobarbital ameliorated the neuronal damage to the striatum, but not the hippocampal damage 7 days after ischemia. This histological finding was relatively consistent with the alteration in the [³H]CHA binding. these receptor autoradiographic and histological data suggest that vinconate and pentobarbital can protect the brain from both cellular and functional consequences of ischemia. These findings are of interest in relation to the mechanisms of ischemic brain damage.     

Pharmacokinetics and Distribution over the Blood-Brain Barrier of Zalcitabine (2′,3′-Dideoxycytidine) and BEA005 (2′,3′-Dideoxy-3′-Hydroxymethylcytidine) in Rats, Studied by Microdialysis

Microdialysis was applied to sample the unbound drug concentration in the extracellular fluid in brain and muscle of rats given zalcitabine (2′,3′-dideoxycytidine; n = 4) or BEA005 (2′,3′-dideoxy-3′-hydroxymethylcytidine; n = 4) (50 mg/kg of body weight given subcutaneously). Zalcitabine and BEA005 were analyzed by high-pressure liquid chromatography with UV detection. The maximum concentration of zalcitabine in the dialysate (C_max) was 31.4 ± 5.1 μM (mean ± standard error of the mean) for the brain and 238.3 ± 48.1 μM for muscle. The time to C_max was found to be from 30 to 45 min for the brain and from 15 to 30 min for muscle. Zalcitabine was eliminated from the brain and muscle with half-lives 1.28 ± 0.64 and 0.85 ± 0.13 h, respectively. The ratio of the area under the concentration-time curve (AUC) (from 0 to 180 min) for the brain and the AUC for muscle (AUC ratio) was 0.191 ± 0.037. The concentrations of BEA005 attained in the brain and muscle were lower than those of zalcitabine, with C_maxs of 5.7 ± 1.4 μM in the brain and 61.3 ± 12.0 μM in the muscle. The peak concentration in the brain was attained 50 to 70 min after injection, and that in muscle was achieved 30 to 50 min after injection. The half-lives of BEA005 in the brain and muscle were 5.51 ± 1.45 and 0.64 ± 0.06 h, respectively. The AUC ratio (from 0 to 180 min) between brain and muscle was 0.162 ± 0.026. The log octanol/water partition coefficients were found to be −1.19 ± 0.04 and −1.47 ± 0.01 for zalcitabine and BEA005, respectively. The degrees of plasma protein binding of zalcitabine (11% ± 4%) and BEA005 (18% ± 2%) were measured by microdialysis in vitro. The differences between zalcitabine and BEA005 with respect to the AUC ratio (P = 0.481), half-life in muscle (P = 0.279), and level of protein binding (P = 0.174) were not statistically significant. The differences were statistically significant in the case of the half-life in the brain (P = 0.032), clearance (P = 0.046), volume of distribution (P = 0.027) in muscle, and octanol/water partition coefficient (P = 0.019).     

Phytochemical composition and the cholinesterase and xanthine oxidase inhibitory properties of seed extracts from the Washingtonia filifera palm fruit

The chemical composition and biological properties of palm Washingtonia filifera (Lindl.) H. Wendl. seeds are seldom studied. Bearing this in mind, the seeds of W. filifera fruits were analysed for their fatty acid and phenolic composition and their antioxidant activity in addition to their cholinesterase and xanthine oxidase inhibitory activities. Seed extracts were revealed as a good source of phenolics with significant antioxidant activity. The phenolic profile mainly consisted of proanthocyanidins or procyanidin dimers B1–B4 among the major compounds. The highest butyrylcholinesterase inhibitory activity was found in the ethanolic extracts of seeds, with IC₅₀ values of 13.73 ± 1.31 μg mL⁻¹. Seed alcoholic extracts also displayed interesting xanthine oxidase inhibitory activity, with IC₅₀ values ranging between 75.2 ± 17.0 μg mL⁻¹ and 95.8 ± 5.9 μg mL⁻¹. Procyanidin B1, a major component in the extracts, could be an important contributor to that activity, as it was found to possess good xanthine oxidase inhibition capacity (IC₅₀ value of 53.51 ± 6.03 μg mL⁻¹). Docking studies were also performed to predict the binding sites of procyanidins B1 and B2 within the xanthine oxidase structure. In all, W. filifera seeds appear as a promising natural source for the extraction of bioactive compounds with antioxidant and butyrylcholinesterase as well as xanthine oxidase inhibitory potential.

The chemical composition and biological properties of palm Washingtonia filifera (Lindl.) H. Wendl. seeds are seldom studied.     

全脑缺血再灌注后脑线粒体功能变化及山莨菪碱的保护作用

目的：探讨全脑缺血再灌注后脑线粒体功能变化及山莨菪碱的保护作用。方法：采用家兔全脑缺血再灌注损伤模型，缺血20min、再灌注2h观察脑线粒体呼吸功能、呼吸链氧化酶活性、线粒体内Ca^2 和MDA含量的变化。结果:脑缺血再灌注后，脑线粒体呼吸控制率、磷氧比、氧化磷酸化效率及烟酰胺腺喋呤二核苷酸氧化酶、琥珀酸氧化酶、细胞色素C氧化酶活性明显降低(P＜0、01)，而线粒体Ca^2 、MDA含量明显升高(P＜0．01)；再灌注早期给予山莨菪碱治疗后，上述线粒体损伤性改变明显减轻。结论：山莨菪碱对脑缺血再灌注后线粒体损伤具有一定的保护作用，其机制可能与Ca^2 拮抗、抑制脂质过氧化及保护呼吸链酶活性有关。