Effect of ovariectomization on Alzheimer-like phosphorylation of Tau in hippocampus of rats

AIM: To explore the effect of ovariectomization on Alzheimer-like phosphorylation of Tau in hippocampus of Sorague-Dawlery rats. METHODS: An animal model was developed using ovariectimized (OVX) rats, and the phosphorylation of Tau protein was measured by Western blot. RESULTS: The levels of phosphorylated Tau at PHF-1epitope were elevated in ovariectimized rat brain hippocampus 4 weeks and 8 weeks after ovariectomization, when compared with sham-OVX rats (P<0.05). On the other hand, the levels of non-phosphorylated Tau at Tau-1site were decreased in same brain regions at the same time point examined (P<0.05). No significant difference of phosphorylated Tau at those epitops was seen 1 week, 2 weeks, 3 weeks after ovariectomization between sham-OVX group and OVX group (P>0.05). CONCLUSION: Ovariectomization may induce Alzheimer-like hyperphosphorylation of Tau protein in brain hippocampus of rats.     

Pre-treatment with melatonin inhibits oleic acid-induced acute lung injury in rats

AIM: To assess the protective role of melatonin (MEL) in a rat model of oleic-induced acute lung injury.METHODS: Twenty-four rats were randomly allocated to three groups as follows: saline(NS) injection group, oleic acid(OA) injection group and MEL plus OA injection group, the lavage protein, lung wet-to-dry weight ratio, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity and lung histopathology were examined. RESULTS: (1) Injection 0.15 mL/kg of OA led to a severe acute lung injury(ALI), characterized by significantly increasing in lavage protein, lung coefficient (P<0.01), and by histopathological alterations which presented hemorrhage, edema, thickened alveolar septum and the existence of inflammatory cells in alveolar spaces; (2) Infusion of MEL (20 mg/kg, intraperitoneally for 60 min before the oleic acid) markedly alleviated above-mentioned symptom induced by OA, consistent with decrease of MDA level (P<0.01) and the increase of SOD activty (P<0.01). CONCLUSION: Pre-treatment with MEL can attenuate the OA-induced ALI in rats via cleaning and preventing the formation of free radicals and further lessening the increase of alveolocapillary membrane permeability, these data suggest that MEL may be effective in the prevention of ALI.     

Adiponectin attenuates H2O2-induced SH-SY5Y cell injury and tau hyperphosphorylation via activating PP2A

AIM: To study the effects of adiponectin on H₂O₂-induced cell injury and tau hyperphosphorylation in human neuroblastoma SH-SY5Y cells. METHODS: Cell viability was determined by MTT assay. H₂O₂-induced cell injury and morphological changes in the SH-SY5Y cells with or without adiponectin treatment were observed. The level of tau phosphorylation as well as the activities of protein phosphatase 2A(PP2A) and of glycogen synthase kinase-3β(GSK-3β) were examined by Western blotting. RESULTS: Adiponectin significantly attenuated H₂O₂-induced cell injury(P<0.01). Adiponectin upregulated the activity of PP2A and decreased phosphorylation levels of tau under the stimulation with H₂O₂ (P<0.01). Okadaic acid, a specific inhibitor of PP2A, blocked the protective effects of adiponectin(P<0.01). Adiponectin increased the phosphorylation level of GSK-3β at Ser9 site under H₂O₂ stimulation(P<0.01). CONCLUSION: Adiponectin protects SH-SY5Y cells against H₂O₂-induced cell injury and decreases tau hyperphosphorylation by activating PP2A and inactivating GSK-3β.     

Effects of low-glucose on long-term potentiation in the hippocampal slices of immature and adult rats

AIM: The effects of low-glucose on long-term potentiation (LTP) in the CA1 region of hippocapal slices of immature (15-16 days old) and adult (56-63 days old) rats were examined. METHODS: The technique of electrophysiology was used, and the slopes of the field excitatory postsynaptic potentials (S-EPSP) were measured. RESULTS: When slices were exposed to glucose medium at concentrations of 3 or 1.5 mmol/L, S-EPSP decreased significantly. In the slices from adult rats, only short-term potentiation was elicited by high frequency stimulation in the medium of 3 or 1.5 mmol/L glucose. However, in the slices from immature rats, LTP was still induced in the medium of 3 mmol/L glucose. CONCLUSION: Low-glucose medium depressed the synaptic transmission. In terms of the synaptic plasticity, the low-glucose endurance in immature rats was stronger than that in adult rats.     

Effect of tenuigenin on tau protein phosphorylation at Ser396 site in neurons of AD rats induced by Aβ1-40

AIM:To investigate the effect of tenuigenin(TEN) on hyperphosphorylation of tau protein in neurons of amyloid β-peptide_1-40(Aβ_1-40) -induced Alzheimer disease(AD) rats. METHODS:Aβ_1-40 was injected into hippocampus CA1 region of the rats to establish AD model. TEN at different doses(18.5 mg/kg, 37.0 mg/kg and 74.0 mg/kg) was intragastrically administered. The protein expression of protein kinase A(PKA),protein phosphatase 2A(PP2A), total tau and p-tau(Ser³⁹⁶) in the neurons was observed by the method of immunohistochemistry. The protein content of total tau and p-tau(Ser³⁹⁶), and the expression level of PKA and PP-2A were detected by Western blotting analysis. RESULTS:In Aβ_1-40 group, the level of total tau, the phosphorylation of tau protein and the expression of PKA were significantly increased compared with those in sham operation group. Meanwhile, the expression of PP2A in Aβ_1-40 group was lower than that in sham operation group. In TEN treatment group, the level of total tau, the phosphorylation of tau protein and the expression of PKA were markedly decreased, and the expression of PP2A was increased as compared with Aβ_1-40 group. CONCLUSION:TEN may protect the neurons from the toxic effect of Aβ_1-40 and reduce the hyperphosphorylation of tau(Ser³⁹⁶) in the neurons of AD rats by activating the expression of PP2A and inhibiting the expression of PKA.     

Effects of prenatal stress on neurons and neuronal ultrastructure of developing hippocampus in rats

AIM:To investigate the effects of prenatal stress (PS) on neurons and neuronal ultrastructure of hippocampus in offspring rats, and to explore the role of the overproduction of oxidants. METHODS:One month male offspring rats were obtained to observe the neuronal number, neuronal ultrastructure and the number of nNOS -positive cell in hippocampus. RESULTS:The neuronal number of CA1 and CA4 subregions in late gestation stress (LS) offspring decreases significantly. The neuronal ultrastructure of CA1 subregion in MS (stress in 7-13 days of gestation) and LS offspring appeared bulgy mitochondria, unclear membrane and irregular electron density. Lipofuscin pigments increased; The number of nNOS-positive cell in CA1, CA2, CA3 subregions and DG of MS group and the whole hippocampus of LS group increased significantly. CONCLUSION:PS damaged the neurons and neuronal ultrastructure of hippocampus of offspring rats. The damages were associated with the overproduction of oxidants.     

Relationship between meso-hippocampal dopaminergic projections and hippocampal P300-like potentials in rats

AIM: To evaluate the role of the meso-hippocampal dopaminergic systems in the generation of hippocampal P300-like potentials. METHODS: Changes of ventral hippocampal P300-like potentials were examined after lesions of the meso-hippocampal dopaminergic systems.The extracellular DA and DOPAC were collected by the push-pull method in the ventral and dorsal hippocampus and their contents were measured by high-performance liquid chromatography with electrochemical detection(HPLC-EC). RESULTS: The contents of DA and DOPAC in the ventral hippocampus were higher than those in the dorsal hippocampus in the normal animals. The peak latencies of P300-like potentials were prolonged and the contents of DA and DOPAC decreased in the ventral hippocampi after lesions of the meso-hippocampal dopaminergic systems. CONCLUSIONS: There exist meso-hippocampal dopaminergic systems in rats;The meso-hippocampal dopaminergic terminals is mainly located in the ventral hippocampal area in rats; The meso-hippocampal dopaminergic projections take part in the generation of the hippocampal P300-like potentials in rats.     

Effect of 5-HT1A receptor in hippocampal CA1 region on spatial memory of PTSD rats

AIM: To investigate the change of long-term potentiation (LTP), and the expression of 5-hydroxytryptamine 1A receptor (5-HT_1A receptor) and postsynaptic density protein 95 (PSD-95) in the hippocampus of the rats with posttraumatic stress disorder (PTSD), and to explore the mechanism of 5-HT_1A receptor in the regulation of spatial memory in the PTSD rats.METHODS: Healthy adult SD rats (n=36) were randomly divided into control group and model group, with 18 rats in each group. The rats in model group were treated with single prolonged stress to construct the model of PTSD. Morris water maze (MWM) was used to test the learning and memory ability. The LTP induced by high-frequency stimulation (HFS) was detected by electrophysiological method. The protein expression of 5-HT_1A receptor and PSD-95 in the hippocampus was determined by Western blot and immunofluorescence. RESULTS: The MWM analysis showed that the latency of the rats searching for the underwater platform in model group was significantly longer than that in control group (P<0.01). The results of electrophysiological analysis showed that the amplitude of the evoked potential in both groups were significantly increased after HFS in the hippocampus, but that in model group was significantly lower than that in control group (P<0.01). The results of Western blot and immunofluorescence analysis showed that compared with control group, the protein expression of 5-HT_1A receptor was obviously increased (P<0.05), while the expression of PSD-95 was obviously decreased in model group (P<0.05).CONCLUSION: The spatial memory impairment in the PTSD rats may be associated with the increase in the expression of 5-HT_1A receptor and the decrease in the expression of PSD-95 in the CA1 region of hippocampus.     

Effect of heat shock precondition on reperfusion arrhythmia in rats

AIM:To investigate the effect of the heat shock response on the reperfusion arrhythmias(RAs) and the possible mechanism involved. METHODS:Fifty-five Sprague Dawley rats were randomly divided into 2 groups: the heat shock group (group H,n=29) and the control group (group C,n=26). The rats in group H were preconditioned with heat shock 24 hours before, and that in group C were not. The hearts of 16 rats in group H and 16 in group C were exercised and mounted on a non-circulating Langendorff perfusion apparatus and perfused retrogradely with modified K-H buffer and mimic ischemia/reperfusion was applied. Additionally, conventional intracellular microelectrode techniques were used for recording such electrophysiological parameters as resting potential(RP), action potential amplitude(APA), over shot(OS), maximum depolarization velocity(Vmax) of the hearts of other 13 rats in group H and 10 in group C. RESULTS:①Prior heat stress significantly decreased reperfusion arrhythmia. ②The amount of CK release in the effluent in group H was much less than that in group C. ③Myocardial HSP70 content was elevated significantly in group H. ④Heat stress significantly increased myocardial anti-oxydases activity and decreased lipid peroxydative products. Additionally, heat stress significantly reduced the Vmax of action potential. It indicated that rapid Na⁺ channel of papillary muscles may be inhibited by heat shock. The degree of change of Vmax after ischemia in H group was significantly less than that in group C. And the time of reperfusoin with Tyrode's solution till the action potential appeared as large as that before perfusion with mimic ischemic solution is shorter in group H than in group C. CONCLUSION:Heat shock pretreatment markedly reduces ischemia/reperfusion-induced injury of heart and ventricular arrhythmias in rats and this effect may be associated with the inhibition of rapid Na⁺ channel of papillary muscles by heat shock and the increase in myocardial HSP70 and anti-oxydase activity.     

Protective effect of bactericidal/permeability-increasing protein on sepsis induced by intra-abdominal infection in rats

AIM:To investigate the protective effect of bactericidal/permeability-increasing protein (BPI) on sepsis induced by intra-abdominal infection in rats and its mechanism.METHODS:Intra-abdominal infection induced sepsis was reproduced by cecal ligation and puncture (CLP). BPI or equal volume of physiological saline was intra-abdominally given immediately after CLP and 12 hours after CLP respectively (2.5 mg/kg of BPI each time). Plasma endotoxin levels were determined with limulus amebocyte chromogenic assay.RESULTS:(1)The survival time in BPI group was significantly higher than in physiological saline (PS) group. (2)The values of MAP, LVSP, IP, d p /d t max and-d p /d t max in BPI group, although decreasing,were markedly higher than those in PS group. (3) Plasma glutamate-pyruvate transaminase and urea nitrogen levels in BPI group, though increasing, were significantly lower than those in PS group.(4) There was no significant change of plasma endotoxin levels in BPI group, while plasma endotoxin levels were markedly increased in PS group. There was significantly different between two groups. CONCLUSIONS:BPI has an obvious protective effect on intra-abdominal infection induced sepsis, which might be related to its antagonism against endotoxin.     

Changes in phosphorylation of tau protein and COX-2 expression in colon submucosal neurons of IBD model rats induced by TNBS

AIM: To investigate the change of phosphorylation of tau protein and expression of cyclooxygenase 2 (COX-2) in colon submucosal neurons of enteric nerve system in inflammatory bowel disease (IBD) rats induced by trinitrobenzene sulfonic acid (TNBS). METHODS: Male rats (n=30) were randomly assigned to 3 groups (n=10 each): control group, IBD group and TNBS group. The IBD rats were induced by TNBS+ethanol enema for 14 d. The control and TNBS rats were given an equal volume of saline and TNBS, respectively. The general situation and the histopathologic change of the rat colon were observed. Immunofluorescence was used to check the change of phosphalated tau protein and COX-2 expression in the submucosal neurons of the colon. The expression of COX-2 and phosphorylated tau231 and tau262 in the rat colon submucosal neurons was observed by double immunofluorescence staining. RESULTS: Compared with control group, the number of neurons in the colon of IBD rats decreased obviously and the expression of phospholated tau231 and tau262 was significantly increased. The number of neurons in the colon of TNBS rats showed no significant difference compared with control rats. The rat neurons in control group and TNBS group did not express COX-2. COX-2 expression was observed in the nucleus and cytoplasm of colonic neurons in IBD rats, which showed significantly different from control and TNBS rats. CONCLUSION: The decreased neurons in the enteric nerve system of IBD rats might be associated with the phosphorylation of tau protein and the expression of inducible COX-2.     

Effect of ACTH on pain behavior and the level of brain-derived neurotrophic factor and corticotropin-releasing hormone in the hippocampus of rats with chronic pain

AIM: To observe the effect of adrenocorticotropic hormone(ACTH) on the levels of brain-derived neurotrophic factor(BDNF), trkB and corticotropin-releasing hormone(CRH) in the hippocampus of arthritic rats.METHODS: The BDNF immunoreactivity(IR) and CRH-positive neurons were stained with immunohistochemistry and in situ hybridization methods, respectively.RESULTS: The BDNF-IR, CRH mRNA-positive neurons in the contralateral hippocampus of the arthritic rats were increased significantly, which was decreased markedly by intraperitoneal injection of ACTH. However, the effect of ACTH was attenuated after adrenalectomy(ADX).CONCLUSION: These results suggest that BDNF and CRH in the hippocampus of arthritic rats were involved in the modulation of chronic pain, ACTH produced its analgesic effect by inhibiting the increase in BDNF and CRF level. Adrenal is critical to the analgesic action of ACTH.     

Dynamic changes and significance of axon damages in experimental allergic encephalomyelitis in Wistar rats

AIM: To study the dynamic changes and significance of axon damages in different stages of experimental allergic encephalomyelitis (EAE). METHODS: Tissue sections were processed with HE staining to observe inflammatory damages. The expression and distribution of β-amyloid precursor protein (β-APP) and tau protein were detected by the method of immunohistochemistry in acute and relapsing-remitting stages of EAE. RESULTS: Many inflammatory cells were infiltrated in the tissues of spinal cord and strong β-APP expression was observed in the area full of inflammatory cells in acute EAE rats. Meanwhile, a small amount of tau protein, the marker of neurodegeneration, was found. There were many perivascular cuffings in the tissues enclosed by the inflammatory cells, and there was also strong β-APP expression in the tissues where there was no inflammatory cell infiltration in paralyzed rats. Tau protein also largely precipitated in the spinal tissues of paralyzed rats with the repeated episodes, indicating that persistence of axon damages and evident axon degeneration existed. Positive cells of β-APP and tau protein in acute group and relapsing-remitting group were larger than those in normal group with statistical differences. A statistical difference between acute group and relapsing-remitting group was also observed. CONCLUSION: Axon damages are concerned with inflammation in the spinal cord. Axon damages accompany with neural degeneration during the process of chronic EAE. The permanent damages of axon are in the course of EAE. The degeneration of axon happens in the late time of relapsing-remitting EAE and results in irreversible neurological deficits.     

Change of synapsins in hippocampal formation during spacial learning and memory in rats

AIM and METHODS: The immunohistochemical method was used to study the on synapsin express in hippocampal formation during spatial learning and memory in rats.RESULTS: (1) In control group there are diffuse brown granules without any obvious granular product in hippocampal formation and in model group there are synapsin products in the hippocampal formation ,especially in the subregion CA3 , CA4 and the dentate gyrus after water maze trained for one week. After two weeks water maze trained the hippocampal formation appear the same distribution of the product granules with darker staining. (2) The light dendity of synapsin products between the model and the control groups showed significant differences, that in the model group was highter than that in the control group (P＜0.05). The light dendity of synapsin products increased with the training time from the first week to the second week in the model group. And there is no increase with the training time from the second week to the third week . The light dendity is higher in the CA3, CA4 subregion and the dentate gyrus than the CA1 and CA2 subregion (P＜0.05).CONCLUSIONS: (1) As mentioned above, it is believed that the new synapes are formed in the hippocampal formation of the rat by spacial learning and memory training. (2) The CA3, CA4 subregion and the dentate gyrus are correlated with the spacial learning and memory.     

Influence of mitochondrial deficiency on expression of microtubule-associated proteins in primary cultured hippocampal neurons of neonatal rats

AIM: In order to study the relationship between mitochondrial deficiency and Alzheimer's disease(AD), we used sodium azide, a specific inhibitor of cytochrome C oxidase (COX), to develop a cell model of mitochondrial complex IV deficiency and investigated the impairment of microtubules and microtubule-associated proteins. METHODS: Primary cultured hippocampal neurons of hewborn rats were exposed to sodium azidethen cell viability was measured by MTT method; cell morphology, immunofluorecence-stained cellular microtubules and microtubule-associated proteins were observed by confocal microscopy. RESULTS: Primary cultured hippocampal neurons were exposed to 8-128 mmol/L sodium azide for 3-24 h, MTT absorbance decreased dose-and time-dependently. Exposed to 64 mmol/L sodium azide for 6 h, the processes of cells retracted, synapses disappeared, axons were shortened under contrast microscope. Meanwhile, microtubles were disassembled and became disorderly, the expression of microtubule-associated proteins were also reduced especially in the processes observed by confocal microscopy. CONCLUSION: Sodium azide inhibits the assembly and polymerization of tubulin in microtubules which may be reduced by low expression of microtubule-associated proteins in nerve cells. The damage of axons induced by microtubule collapse further blocks the intercellular signal transduction and intracellular material transportation which are important causes in cell death.     

Effect of Zhongfeng Nao De Ping on delayed neuronal death in hippocampus following cerebral ischemia/reperfusion in rats

AIM: To investigate the effect of Zhongfeng Nao De Ping, a traditional chinese medicine, on the cerebral ischemia/reperfusion injury in rats. METHODS: Delayed neuronal death(DND) model was established by bilateral carotid arteries occlusion for l0 min followed by 1 day and 7 days reperfusion. Effects of sodium glutamate, ketamine and Zhongfeng Nao De Ping on DND in the hippocampus was examined by counting neuronal density in CAl Sector, and the contents of Ca²⁺ and amino acids in the hippocampus were also measured. RESULTS: The contents of the glutamate and aspartate in the hippocampus were increased significantly at l0 min after transient cerebral ischemia. Sodium glutamate markedly decreased the neuronal density in hippocampal CAl sector, while ketamine and Zhongfeng Nao De Ping increased it significantly in the same sector. The level of Ca²⁺ increased on day 1, day 7 after the reperfusion, while Zhongfeng Nao De Ping inhibited the increase in Ca²⁺ concentration in hippocampus. CONCLUSION: These results suggested that Zhongfeng Nao De Ping has an effective protection against DND in hippocampus following cerebral ischemia/reperfusion in rats.     

外源褪黑素对桃生长及果实品质的影响

[目的]探讨外源褪黑素对桃生长和果实品质的影响.[方法]以早熟桃'早蜜'为试材,于果实膨大期对其叶片喷施不同浓度的褪黑素,测定了桃果实成熟期的新梢生长量、生理状况和果实品质指标.[结果]50?150 pmol?L-1的褪黑素处理能促进桃新梢的生长,增加其茎长和茎粗.150μmol L1褪黑素提高了桃叶片超氧化物歧化酶活...     

Intervention of hydrogen on memory damage induced by chronic hypoxia-hypercapnia in rats

AIM: To investigate the effects of hydrogen on the memory damage caused by chronic hypoxia-hypercapnia in rats. METHODS: Twenty-four SD rats trained by eight-arm radial maze test were randomly divided into 3 groups:normal control group (NC), hypoxia-hypercapnia+saline group (MS) and hypoxia-hypercapnia+ hydrogen group (MH). The rats in the latter 2 groups were placed in a closed cabin for 8 h/day,6 days/week and lasted for 4 weeks, in which O₂ was 9％-11％ and CO₂ was 5％-6％. In every time after the animals were out of the cabin, the MS rats were intraperitoneally injected with saline (5 mL/kg) and the MH rats were intraperitoneally injected with hydrogen solution at the same dose. The learning and memory function, the activity of superoxide dismutase (SOD), the content of malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were examined after the cabin training. The ultramicrostructures of hippocampus were also observed. RESULTS: (1) Compared with NC group, the number of working memory errors, the total errors, the content of hippocampus 8-OHdG and serum MDA in MS and MH groups were higher and the activity of serum SOD was lower (P<0.05). The hippocampus structure was destroyed and some degree of edema and more apoptosis in the neurons were obserued in MS group and MH group. (2) Compared with MS group, the number of working memory errors(WME), the total errors, the content of hippocampus 8-OHdG and serum MDA were lower and the activity of serum SOD was higher in MH group (P<0.05). In MH group, the morphology of hippocampus structures kept nearly normal arrangement and the only mild edema and fewer apoptosis in the neurons were found. CONCLUSION: Hydrogen may attenuate chronic hypoxia-hypercapnia-induced memory damage in rats by inhibiting apoptosis of the neurons and decreasing detrimental free radicals reaction.     

Effects of melatonin on apoptosis of lymphocytes induced by ionizing radiation in mice

AIM: To explore the effect of melatonin (MLT) on the apoptosis of thymocytes and splenocytes in mice induced by ionizing radiation and its mechanism. METHODS: The percentages of apoptotic bodies and the DNA lytic rates of thymocytes and splenocytes in mice in vitro and in vivo were detected with flow cytometry and fluorospectrophotometry, respectively. RESULTS: The apoptosis of mouse thymocytes and splenocytes in vitro increased with significant dose-dependence in 0.5-6.0 Gy X-irradiation. When MLT of 2 mmol·L^-1 was added into thymocytes or splenocytes in vitro before irradiation with 0.5-6.0 Gy X-rays, the percentages of apoptotic bodies and the DNA lytic rates all decreased significantly as compared with those in the irradiation group. The percentages of apoptotic bodies in these two kinds of cells were 86.25% and 89.22% of those in the irradiation group, respectively, and the DNA lytic rates were 87.23% and 89.16%, respectively. When MLT was injected into intraperitonium in mice 60 min before whole-body irradiation with 2 Gy X-rays, the percentages of apoptotic bodies and the DNA lytic rates were significantly lower than those in the irradiation group, and near or lower than those in the sham-irradiation group. MLT of 0.1-2.5 mg/kg decreased the lymphocyte apoptosis, but without significant dose-dependence. CONCLUSION: The protective effects of MLT on mouse lymphocytes damaged by irradiation in vivo were obvious than those in vitro.