Effects of chelating reagents on the hippocampal EEG and histochemical Timm staining pattern in a mouse brain

A series of experiments we examined in detail the effects of four chelating reagents, dithizone, DEDTC, oxine and EDTA, upon (1) Timm's staining in the hippocampal formation, (2) brain electrical activity recorded from hippocampal and cortical electrodes, (3) recovery effect with zinc acetate or zinc sulfate on abolished brain electrical activity, (4) open field activity, (5) toxicity, (6) and heart rate. Dithizone, DEDTC and oxine influenced all measures, and the degree of effect varied directory with dose. But EDTA has not any significant effect on biological system. Resulting data were summarized in Table 4.     

Copper complexing decreases the ability of amyloid beta peptide to cross the BBB and enter brain parenchyma

The amyloid hypothesis states that amyloid beta protein (Abeta) plays a major causal role in the onset of Alzheimer's disease. Toxicity of Abeta can be modified by metal ions. Two mechanisms by which such Abeta and metal ions could interact are by enhanced oxidative stress or by altered fibrillation. Specifically, Abeta fibrillation is increased by aluminum (Al) and copper (Cu) and Al also increases Abeta uptake into brain. Here, we determined whether chelation with Cu would alter uptake of the human or rat 1-42 form of Abeta (Abeta42) by brain or alter Abeta-induced oxidative stress in an immortalized line of rat brain endothelial cells (RBE4). We found that Cu enhanced cytotoxicity of rat, but not of human Abeta, had no effect on glutathione (GSH) or cysteine (CYS) levels. Cu significantly decreased homocysteine (HCYS) levels when complexed with Abeta. Cu chelation did not alter Abeta uptake into brain or other tissues (except for kidney) or alter clearance from blood or brain in vivo, but did increase efflux in an in vitro model of the blood-brain barrier (BBB). Chelation to Cu also impaired the capillary to brain transport of Abeta, an effect opposite to that previously found for chelation of Abeta to Al. These results show that metal ions have varied effects on Abeta uptake by brain and that Cu could be protective against the neurotoxic effects of circulating Abeta.     

Effects of etretinate on the distribution of elements in rats

We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations.     

A static magnetic field attenuates lipopolysaccharide-induced neuro-inflammatory response via IL-6-mediated pathway

An effective method for controlling brain damage and neurodegeneration caused by inflammation remains elusive. Down-expression of the lipopolysaccharide (LPS)-induced inflammatory cytokines resulting in endotoxin tolerance is reported as an alternative anti-infection treatment. Nonetheless, because the dosage and action site are hard to control, endotoxin tolerance caused by low-dose LPS injection in brain tissue may induce side effects. The aim of this study was to test the hypothesis that static magnetic fields (SMF) stimulate endotoxin tolerance in brain tissue. In this study, survival rate and pathological changes in brain tissues of LPS-challenged mice were examined with and without SMF treatment. In addition, the effects of SMF exposure on growth rate and cytokine expression of LPS-challenged BV-2 microglia cells were monitored. Our results showed that SMF pre-exposure had positive effects on the survival rate and histological outcomes of LPS-treated mice. Furthermore, SMF exposure significantly decreased IL-6 expression in BV-2 cells (p?相似文献   

Increased acetylcholinesterase activities in specimens of Sparus auratus exposed to sublethal copper concentrations

The present study looks at possible changes in the activity of acetylcholinesterase (AChE) in tissues (brain and white muscle) of the Mediterranean bony fish Sparus auratus after a 20 days exposure to sublethal concentrations (0.1 or 0.5 ppm) of copper in the marine water and on control untreated animals. The trials also included measurements of Cu concentration in the tissues to evaluate possible metal accumulation. Moreover, sedimentation analysis as well as V(max) and K(m) determination were carried out in tissue extracts of Cu-exposed or control animals. V(max) and K(m) were also determined with or without addition of Cu(2+) in the assay. No Cu accumulation occurred in brain and muscle after Cu exposure. AChE showed in both tissues a molecular polymorphism with putative globular (G) and asymmetric (A) forms. Cu exposition led to an increased specific activity and improved catalytic efficiency of AChE in brain and muscle, seemingly regarding G forms. The increase in catalytic efficiency also resulted from the in vitro assay with tissue extracts and Cu(2+) addition. The higher AChE activity and catalytic efficiency in both tissues after Cu exposition and without metal accumulation, suggests an increase of free Cu aliquot into the cells, likely due to mechanisms of metal homeostasis.     

Chemical Blocking of Zinc Ions in CNS Increases Neuronal Damage Following Traumatic Brain Injury (TBI) in Mice

Background

Traumatic brain injury (TBI) is one of the leading causes of disability and death among young people. Although much is already known about secondary brain damage the full range of brain tissue responses to TBI remains to be elucidated. A population of neurons located in cerebral areas associated with higher cognitive functions harbours a vesicular zinc pool co-localized with glutamate. This zinc enriched pool of synaptic vesicles has been hypothesized to take part in the injurious signalling cascade that follows pathological conditions such as seizures, ischemia and traumatic brain injury. Pathological release of excess zinc ions from pre-synaptic vesicles has been suggested to mediate cell damage/death to postsynaptic neurons.

Methodology/Principal Findings

In order to substantiate the influence of vesicular zinc ions on TBI, we designed a study in which damage and zinc movements were analysed in several different ways. Twenty-four hours after TBI ZnT3-KO mice (mice without vesicular zinc) were compared to littermate Wild Type (WT) mice (mice with vesicular zinc) with regard to histopathology. Furthermore, in order to evaluate a possible neuro-protective dimension of chemical blocking of vesicular zinc, we treated lesioned mice with either DEDTC or selenite. Our study revealed that chemical blocking of vesicular zinc ions, either by chelation with DEDTC or accumulation in zinc-selenium nanocrystals, worsened the effects on the aftermath of TBI in the WT mice by increasing the number of necrotic and apoptotic cells within the first 24 hours after TBI, when compared to those of chemically untreated WT mice.

Conclusion/Significance

ZnT3-KO mice revealed more damage after TBI compared to WT controls. Following treatment with DEDTC or selenium an increase in the number of both dead and apoptotic cells were seen in the controls within the first 24 hours after TBI while the degree of damage in the ZnT3-KO mice remained largely unchanged. Further analyses revealed that the damage development in the two mouse strains was almost identical after either zinc chelation or zinc complexion therapy.     

Prostaglandins E2 and F alpha levels in white and brown adipose tissues of cold acclimated rats as measured by a new micromethod.

A new micro-method was used to determine the effects of cold acclimation of rats on the levels of prostaglandin E2 and F alpha in both white and brown adipose tissues. Whereas PGF alpha levels were significantly higher than PGE2 levels in white fat, no difference between the amounts of the two prostaglandins was observed in brown fat. In both tissues, cold acclimation did not induce any change in prostaglandin levels.     

Glucose transporter protein responses to selective hyperglycemia or hyperinsulinemia in fetal sheep

The acute effect of selective hyperglycemia or hyperinsulinemia on late gestation fetal ovine glucose transporter protein (GLUT-1, GLUT-3, and GLUT-4) concentrations was examined in insulin-insensitive (brain and liver) and insulin-sensitive (myocardium and fat) tissues at 1, 2.5, and 24 h. Hyperglycemia with euinsulinemia caused a two- to threefold increase in brain GLUT-3, liver GLUT-1, and myocardial GLUT-1 concentrations only at 1 h. There was no change in GLUT-4 protein amounts at any time during the selective hyperglycemia. In contrast, selective hyperinsulinemia with euglycemia led to an immediate and persistent twofold increase in liver GLUT-1, which lasted from 1 until 24 h with a concomitant decline in myocardial tissue GLUT-4 amounts, reaching statistical significance at 24 h. No other significant change in response to hyperinsulinemia was noted in any of the other isoforms in any of the other tissues. Simultaneous assessment of total fetal glucose utilization rate (GURf) during selective hyperglycemia demonstrated a transient 40% increase at 1 and 2.5 h, corresponding temporally with a transient increase in brain GLUT-3 and liver and myocardial GLUT-1 protein amounts. In contrast, selective hyperinsulinemia led to a sustained increase in GURf, corresponding temporally with the persistent increase in hepatic GLUT-1 concentrations. We conclude that excess substrate acutely increases GURf associated with an increase in various tissues of the transporter isoforms GLUT-1 and GLUT-3 that mediate fetal basal glucose transport without an effect on the GLUT-4 isoform that mediates insulin action. This contrasts with the tissue-specific effects of selective hyperinsulinemia with a sustained increase in GURf associated with a sustained increase in hepatic basal glucose transporter (GLUT-1) amounts and a myocardial-specific emergence of mild insulin resistance associated with a downregulation of GLUT-4.     

Ytterbium and trace element distribution in brain and organic tissues of offspring rats after prenatal and postnatal exposure to ytterbium

Lanthanides, because of their diversified physical and chemical effects, have been widely used in a number of fields. As a result, more and more lanthanides are entering the environment and eventually accumulating in the human body. Previous studies indicate that the impact of lanthanides on brain function cannot be neglected. Although neurological studies of trace elements are of paramount importance, up to now, little data are provided regarding the status of micronutritional elements in rats after prenatal and long-term exposure to lanthanide. The aim of this study is to determine the ytterbium (Yb) and trace elements distribution in brain and organic tissues of offspring rats after prenatal and long-term exposure to Yb. Wistar rats were exposed to Yb through oral administration at 0,0.1, 2, and 40 mg Yb/kg concentrations from gestation day 0 through 5 mo of age. Concentrations of Yb and other elements (Mg, Ca, Fe, Cu, Mn, and Zn) in the serum, liver, femur, and brain regions (cerebral cortex, hippocampus, cerebellum, and the rest) of offspring rats at the age of 0 d, 25 d, and 5 mo were analyzed by inductively coupled plasma-mass spectrometry. The accumulation of Yb in the brain, liver, and femur is observed; moreover, the levels of Fe, Cu, Mn, Zn, Ca, and Mg in the brain and organic tissues of offspring rats are also altered after Yb exposure. This disturbance of the homeostasis of trace elements might induce adverse effects on normal physiological functions of the brain and other organs.     

Intra- and extracellular dehydration has no effect on plasma levels of angiotensin II in an amphibian

Previous studies have demonstrated that both dehydration (intra and extracellular) and treatment with angiotensin II (A-II) induce changes in thirst-related behavior in the spadefoot toad, Scaphiopus couchii. One of the steps in determining a causal relationship between a hormone and a behavior is to determine that there is association between an animal's performance of the behavior and changes in endogenous hormonal concentrations. The hypothesis tested that plasma levels of the peptide hormone A-II would change as a result of dehydration known to induce water absorption response (WR) behavior in the spadefoot toad. Plasma samples were taken from toads dehydrated intracellularly by injection of hypertonic solutions of NaCl or sucrose at levels known to induce WR behavior. As an osmotic control, a group of animals was injected with urea, which has been demonstrated to not induce WR behavior. In order to determine the effects of extracellular dehydration on plasma, A-II levels in toads dehydrated by plasma volume depletion via cardiac puncture were compared to sham-punctured controls. None of the treatments in any experiment resulted in significant differences in plasma levels of angiotensin II among groups sampled at the time when WR behavior occurs. These results do not support the hypothesis that dehydration-induced thirst is stimulated by changes in plasma A-II concentrations at the onset of WR behavior. J. Exp. Zool. 286:343-349, 2000.     

Metal ions differentially influence the aggregation and deposition of Alzheimer's beta-amyloid on a solid template

The abnormal deposition and aggregation of beta-amyloid (Abeta) on brain tissues are considered to be one of the characteristic neuropathological features of Alzheimer's disease (AD). Environmental conditions such as metal ions, pH, and cell membranes are associated with Abeta deposition and plaque formation. According to the amyloid cascade hypothesis of AD, the deposition of Abeta42 oligomers as diffuse plaques in vivo is an important earliest event, leading to the formation of fibrillar amyloid plaques by the further accumulation of soluble Abeta under certain environmental conditions. In order to characterize the effect of metal ions on amyloid deposition and plaque growth on a solid surface, we prepared a synthetic template by immobilizing Abeta oligomers onto a N-hydroxysuccinimide ester-activated solid surface. According to our study using ex situ atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), and thioflavin T (ThT) fluorescence spectroscopy, Cu2+ and Zn2+ ions accelerated both Abeta40 and Abeta42 deposition but resulted only in the formation of "amorphous" aggregates. In contrast, Fe3+ induced the deposition of "fibrillar" amyloid plaques at neutral pH. Under mildly acidic environments, the formation of fibrillar amyloid plaques was not induced by any metal ion tested in this work. Using secondary ion mass spectroscopy (SIMS) analysis, we found that binding Cu ions to Abeta deposits on a solid template occurred by the possible reduction of Cu ions during the interaction of Abeta with Cu2+. Our results may provide insights into the role of metal ions on the formation of fibrillar or amorphous amyloid plaques in AD.     

Benzodiazepine agonists reverse the effects of noise exposure on central benzodiazepine receptors and cardiac responsiveness

Rats were submitted to 110 dB white noise exposure for 1, and 6 hours and brain α₁, β₁ and benzodiazepine receptor binding was evaluated with selective ligands. An increase in cerebral benzodiazepine receptor (CBR) concentration, without any significant change in affinity constant, occurred after the 6 h treatment; no change was observed in adrenergic receptor binding at any period of exposure. Both diazepam and clonazepara pre-treatment reversed the effects of noise on CBR binding, confirming a role of these receptors in the response to noise stress. Furthermore, these benzodiazepine agonists influenced the response of cardiac and aortic tissues, which are known to be changed by stress exposure. Diazepam and clonazepam pre-treatment protected cardiac tissue from the effects of 6h noise stress, and a potentiation of aortic responses was detected, although at different tunes of exposure. The differences between the responses of these peripheral tissues to benzodiazepine treatment suggest that the expression depends on the tissue examined and the period of exposure.     

No evidence for the 'expensive-tissue hypothesis' from an intraspecific study in a highly variable species

The 'expensive-tissue hypothesis' states that investment in one metabolically costly tissue necessitates decreased investment in other tissues and has been one of the keystone concepts used in studying the evolution of metabolically expensive tissues. The trade-offs expected under this hypothesis have been investigated in comparative studies in a number of clades, yet support for the hypothesis is mixed. Nevertheless, the expensive-tissue hypothesis has been used to explain everything from the evolution of the human brain to patterns of reproductive investment in bats. The ambiguous support for the hypothesis may be due to interspecific differences in selection, which could lead to spurious results both positive and negative. To control for this, we conduct a study of trade-offs within a single species, Thalassoma bifasciatum, a coral reef fish that exhibits more intraspecific variation in a single tissue (testes) than is seen across many of the clades previously analysed in studies of tissue investment. This constitutes a robust test of the constraints posited under the expensive-tissue hypothesis that is not affected by many of the factors that may confound interspecific studies. However, we find no evidence of trade-offs between investment in testes and investment in liver or brain, which are typically considered to be metabolically expensive. Our results demonstrate that the frequent rejection of the expensive-tissue hypothesis may not be an artefact of interspecific differences in selection and suggests that organisms may be capable of compensating for substantial changes in tissue investment without sacrificing mass in other expensive tissues.     

Silencing the activity and proliferative properties of the human EagI Potassium Channel by RNA Interference

EagI potassium channels are natively expressed in the mammalian brain as well as in many cancer cell lines and tumor tissues. The role of EagI in malignant transformation has been suggested by several experiments, but the lack of specific EagI inhibitors has made it difficult to examine the influence of the channel on oncogenesis and its potential as a therapeutic target. We have used short interfering RNA to test the effects of EagI reduction on the behavior of tumor cells in vitro. By generating and optimizing an EagI-specific short interfering RNA system, we were able to study the effects of EagI depletion on several cancer cell lines that endogenously express this protein. We show here that our short interfering RNA sequences act specifically on EagI, reproducibly induce a significant decrease in the proliferation of tumor cell lines, and do not trigger any observable nonspecific responses.     

Distribution of 14 elements in various rat tissues following hypophysectomy,thyroparathyroidectomy, adrenalectomy,and castration

The tissue distribution of 14 elements was simulatneously determined in rats 28 d after hypophysectomy (HPY), thyroparathyroidectomy (TPTY), adrenalectomy (ADY), and castration (CTN). The elements Na, K, Ca, Mg, Fe, S, P, Rb, Sr, Mn, Cu, and Zn were investigated in whole blood, plasma, brain, liver, kidney, heart, skeletal muscle, and bone. Additionally Mo was determined in kidney and liver. The following results were obtained: 1) With regard to hormone deficiency: HPY induced the most noticeable, variations on all the elements tested owing probably to the direct and indirect effects of adenohypophyseal hormones. ADY led to the expected modification of Na and K but also to a Sr accumulation and a Rb depletion. TPTY induced a sharp decrease in plasma and tissues Ca, an increase in plasma P, but did not disturb the two elements in bone. An increase of Rb in many tissues and of Fe in heart, kidney, and liver were also observed. CTN had little consequences except in bone whose Cu and Fe contents were increased: 2) With regard to element variations: K, Mg, and S underwent little change. Discriminations were revealed between elements such as K and Rb, Ca and Sr, Ca and Mg, and Cu and Zn. The changes of Rb and Sr were consistent with regulatory mechanisms. The accumulation of Fe and Cu in tissues such as liver after HPY, TPTY, and ADY, suggest that the hormonal deficiencies could worsen the hemochromatosis with Wilson's disease; 3), With regard to plasma and tissues: No correlation appeared in element levels between plasma and other tissues. Brain was the least affected and liver, kidney and bone the most.     

Cyclic AMP stimulation of Cl- secretion by the opercular epithelium: the apical membrane chloride conductance

Chloride secretion (Isc) by the opercular epithelium of the teleost, Fundulus heteroclitus, is stimulated by elevations in intracellular cyclic AMP (cAMP) elicited by beta-adrenergic agonists, such as isoproterenol, and is accompanied by a small but significant increase in the transepithelial conductance (Gt). Cupric ions (Cu2+) have been shown to block the apical membrane Cl- channels in this epithelium, leading to a reduction in both the Isc and Gt (Degnan, '85). In the present studies, the effects of Cu2+ on cAMP-elevated and cAMP-depleted epithelia were observed to define the actions of cAMP in this stimulatory process. At a concentration of 5 X 10(-4) M in the mucosal solution, Cu2+ inhibited the Isc 79.8% and reduced the Gt 39.2%. Isoproterenol produced an attenuated stimulation of the Isc in these tissues compared to untreated controls, but had no effect on the Gt. In tissues bathed bilaterally with Cl- -free Ringer, the Isc was virtually abolished and the Gt was reduced 37.0%; neither Cu2+ nor isoproterenol had any effects on the Isc or Gt under this condition. Simultaneous 2 2Na and 3 6 Cl unidirectional flux determinations indicated that the only effects of both isoproterenol and Cu2+ were on the active Cl- secretory flux. An inhibitor of adenylate cyclase, 2',5' dideoxyadenosine (DDA), reduced the Isc and Gt 39.8% and 20.8% respectively. This inhibitor had no additional effects in Cu2+ -treated tissues and the action of Cu2+ on the Gt was reduced in DDA-treated tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lovastatin exacerbates atypical absence seizures with only minimal effects on brain sterols

AY-9944 (AY) exacerbates chronic recurrent seizures in rats that are analogous to atypical absence epilepsy in humans. The mechanism by which AY affects the slow spike-and-wave discharges associated with these seizures is not known, but is thought to involve inhibition of cholesterol synthesis. We tested the hypothesis that seizures seen with AY are due to significant reduction in brain cholesterol and/or elevated brain 7-dehydrocholesterol by assessing whether three other cholesterol synthesis inhibitors mimic AY seizures in rats. Effects of AY on brain sterols and spike-and-wave discharge duration were compared with those of two other late-stage cholesterol inhibitors [BM 15.766 (BM) and U18666A (UA)] and to an HMG-CoA reductase (early-stage cholesterol) inhibitor, lovastatin. With BM or UA, prolongation of seizure duration and brain sterol changes was similar to that caused by AY. AY effects on both brain sterols and seizure duration were dose-related. Lovastatin, with or without concurrent AY, mimicked AY seizures but reduced brain cholesterol by <10% and did not significantly change brain 7-dehydrocholesterol. Either lovastatin has a different mechanism of action than these late-stage cholesterol inhibitors or the brain sterol changes are not directly responsible for seizures in this model.     

Oxidative stress impairs glutamate uptake in fibroblasts from patients with Alzheimer's disease

Oxidative stress has been demonstrated in Alzheimer's disease (AD) brain and may affect glutamate transport (GT), thereby leading to excitotoxic neuronal death. Since oxidative stress markers have been shown also in peripheral tissues, we investigated possible GT alterations in fibroblast cultures obtained from 18 patients with AD and 15 control patients and analyzed the effects of the lipoperoxidation product 4-hydroxynonenal (4-HNE) and antioxidants. Basal GT was decreased by 60% in fibroblasts from patients with AD versus control patients. Exposure to HNE did not affect GT in control patients, but it reduced GT by 50% in patients with AD, without any concomitant change in cell viability; conversely, HNE exposure induced a larger increase in ROS intracellular levels in AD than in control fibroblasts. Glutathione and N-acetylcysteine completely blocked 4-HNE effects and also increased basal uptake in AD cells. Moreover, inhibition of glutathione synthesis in control fibroblasts by pretreatment with buthionine sulfoximine resulted in GT reduction (40%) and an increase in ROS levels after exposure to 4-HNE. Nevertheless, since there are no differences between GSH basal level in controls and patients with AD, the alteration of other antioxidant systems cannot be excluded. Our study supports the hypothesis of a systemic impairment of GT in AD, possibly linked to oxidative stress and to reduced antioxidant defenses, which may be partially reversed by antioxidant treatment. Therefore, we suggest fibroblast cultures as a tool for exploring pathogenetic mechanisms and possible therapeutic strategies in patients with AD.