Agyi hypoperfúzió korai stádiumának jellemzése patkányban = Early characteristics of cerebral hypoperfusion in the rat

A krónikus agyi hipoperfúzió szoros összefüggésben áll az kognitív funkciók időskori romlásával, valamint az Alzheimer kórral. Patkányban a kétoldali carotis com. elzárásával olyan állatmodellt sikerült kialakítani, amely segítségével eredményesen tanulmányozható a krónikus agyi hipoperfúzió számos aspektusa (neuronális károsodás, mikroglia aktiváció stb.). A jelzett kórfolyamatban számos tényező, köztük az oxidatív stressz is szerepet játszik. Kísérleteinkben a prooxidáns és antioxidáns enzimek változásait jellemeztük a hipoperfúzió korai szakaszában. Western blot analízissel vizsgáltuk a COX-2, and endotheliális, a neuronális és az indukálható NOS izoformák, valamint az MnSOD változásait különböző agyi régiókban(hippocampus, cortex). Eredményeink szerint a COX-2 és eNOS enzimek jelentősen megemelkednek a hipoperfúzió korai szakaszában (< 1 hét), míg az nNOS, az iNOS és az MnSOD szintek nem változnak számottevően. Továbbá primer neuron sejtkultúrán vizsgáltuk a korai prekondicionálás mechanizmusát és kerestük a kialakuló védelemben szerepet játszó intracelluláris komponenseket. Eredményeink szerint a reaktív oxigén specieszektől függő és –független prekoncicionálás alakítható ki különböző sejtalkotókra (plazma membrán, mitochondrium stb.) ható vegyületekkel. Ezek alapján a hipoperfúzió által okozott sejtkárosodások és az endogén citoprotekció új mechanizmusait sikerült jellemeznünk | Chronic cerebral hypoperfusion is associated with a cognitive decline which is prevalent during senescence or Alzheimer's disease. Its animal model compromises permanent occlusion of the common carotid arteries (2VO) in rats, which results in neuronal damage and microglia activation. Various mechanisms, including oxidative stress, have been proposed to be involved in this process. We characterized changes induced in the expressions of several pro-oxidant and antioxidant enzymes in cerebral hypoperfusion. Western blot analysis was applied to determine the expressions of cyclooxygenase-2 (COX-2), endothelial, neuronal and inducible nitric oxide synthase (eNOS, nNOS and iNOS, respectively) and manganese superoxide dismutase (MnSOD). During the early phase of hypoperfusion, the COX-2 and eNOS enzyme levels increased in both the hippocampus and the frontal cortex, indicating the presence of excitotoxicity and vascular reactions caused by ischemia, while the expressions of nNOS, iNOS and MnSOD were less affected. We also investigated the mechanism of immediate preconditioning in cultured rat cortical neurons and elucidated subsequent intracellular events. We characterized how ROS dependent and –independent preconditioning can be induced by various pharmacological compounds aiming at the ion channels of the plasma membrane and the mitochondria. Our finings help in understanding the mechanisms of hypoperfusion-induced cellular damage and endogenous citoprotection

Peri-infarktus depolarizáció (PID) akut fokális agyi ischemiában = Peri-infarct depolarization (PID) in acute focal cerebral ischemia

Az itt elvégzett kutatás célja az volt, hogy megértsük a stroke során kialakuló peri-infarktus depolarizációk (PID) természetét, és azok szerepét az agyi infarktus kiterjedésének növekedésében. Az előirányzott kísérletek újonnan kifejlesztett képalkotó eljárásokra támaszkodtak, melyeket a stroke különböző patkány modelljeiben alkalmaztunk. A kutatás során három fő célkitűzés teljesült: kifejlesztettünk egy többkomponensű képalkotó eljárást az agyi membránpotenciál-változások és a velük járó hemodinamikai jelenségek direkt megfigyelésére. A laboratóriumunkban kidolgozott módszert egy kísérletes, globális agyi ischemia modellben alkalmaztuk; eredményeink arra engedtek következtetni, hogy az így regisztrált PID-k az agyszövetre káros hatást fejtettek ki, és súlyosbították a stroke kimenetelét. Végül módszerünk segítségével a PID-k tulajdonságait egy kísérletes, fokális agyi ischemia modellben is jellemeztük, amelyben a korai fázisra jellemző PID-k valószínűleg nem növelték az ischemiás károsodás mértékét. Megfigyeléseink árnyalják az eddig érvényben levő hipotézist, mely szerint a PID-k minden esetben károsítják az ischemiás szövetet: azok a PID-k, amelyekkel nem jár repolarizáció és inverz neurovaszkuláris csatolás jellemzi, károsak a sérült agyszövetre, míg azok a PID-k amelyek a mebránpotenciál gyors helyreállásával és tranziens hiperémiával járnak, nem mélyítik at ischemiás károsodást. | Our overall aim was to improve our understanding of the genesis and propagation of stroke-related peri-infarct depolarization (PID), and of their contribution to infarct expansion and maturation. The proposed research relied on novel imaging techniques applied to relevant rat models. The research has obtained 3 goals: First, a multi-modal, live imaging strategy was established to monitor membrane potential variations and associated hemodynamic changes in the brain cortex directly. Second, the technology designed and developed in our lab was applied in a global ischemia model, in which PID proved to be deleterious to the tissue and are proposed to contribute to infarct evolution. Third, our method was used to detect PID in a focal ischemia model, in which early PID appeared to be harmless to the brain, and are suggested not to worsen ischemia outcome. Our observations modify the view held so far, that PID are invariably damaging to the brain tissue. Instead, PID that are not followed by the recovery of membrane potential and involve inverse neurovascular coupling (i.e. decreased CBF) are suggested to be destructive, while PID with repolarization and associated transient functional hyperemia appear not to be harmful to the nervous tissue

Cerebral Microcirculatory Responses of Insulin-Resistant Rats are Preserved to Physiological and Pharmacological Stimuli

AbstractWe study a programming language with a built-in ground type for real numbers. In order for the language to be sufficiently expressive but still sequential, we consider a construction proposed by Boehm and Cartwright. The non-deterministic nature of the construction suggests the use of powerdomains in order to obtain a denotational semantics for the language. We show that the construction cannot be modelled by the Plotkin or Smyth powerdomains, but that the Hoare powerdomain gives a computationally adequate semantics. As is well known, Hoare semantics can be used in order to establish partial correctness only. Since computations on the reals are infinite, one cannot decompose total correctness into the conjunction of partial correctness and termination as is traditionally done. We instead introduce a suitable operational notion of strong convergence and show that total correctness can be proved by establishing partial correctness (using denotational methods) and strong convergence (using operational methods). We illustrate the technique with a representative example

Diazoxide and dimethyl sulphoxide alleviate experimental cerebral hypoperfusion-induced white matter injury in the rat brain

Aging and dementia are accompanied by cerebral white matter (WM) injury, which is considered to be of ischemic origin. A causal link between cerebral ischemia and WM damage has been demonstrated in rats; however, few attempts appear to have been made to test potential drugs for the alleviation of ischemia-related WM injury. We induced cerebral hypoperfusion via permanent, bilateral occlusion of the common carotid arteries of rats. A mitochondrial ATP-sensitive potassium channel opener diazoxide (5 mg/kg) or its solvent dimethyl sulphoxide (DMSO) was administered i.p. (0.25 ml) on 5 consecutive days after surgery. Sham-operated animals served as control for surgery, and non-treated rats as controls for treatments. Thirteen weeks after surgery, the animals were sacrificed and astrocytes and microglia were labeled immunocytochemically in the internal capsule, the corpus callosum and the optic tract. The astrocytic proliferation was enhanced by cerebral hypoperfusion in the optic tract, and reduced by diazoxide in DMSO, but not by DMSO alone in the corpus callosum. After carotid artery occlusion, microglial activation was enhanced two-fold in the corpus callosum and four-fold in the optic tract. DMSO decreased microglial activation in the optic tract, while diazoxide in DMSO, but not DMSO alone, restored microglial activation to the control level in the corpus callosum. In summary, the rat optic tract appeared to be particularly vulnerable to ischemia, while the effect of diazoxide was restricted to the corpus callosum. We conclude that diazoxide dissolved in DMSO can moderate ischemia-related neuroinflammation by suppressing glial reaction in selective cerebral WM areas.

Diazoxide and dimethyl sulphoxide prevent cerebral hypoperfusion-related learning dysfunction and brain damage after carotid artery occlusion

Chronic cerebral hypoperfusion, a mild ischemic condition is associated with advancing age and severity of dementia; however, no unanimous therapy has been established to alleviate related neurological symptoms. We imposed a permanent, bilateral occlusion of the common carotid arteries of rats (n = 18) to create cerebral hypoperfusion. A mitochondrial ATP-sensitive K+ channel opener diazoxide (DZ, 5 mg/kg) or its solvent dimethyl sulphoxide (DMSO) were administered i.p. (0.25 ml) on five consecutive days after surgery. Sham-operated animals (n = 18) served as control for the surgery, while nontreated rats were used as control for the treatments. Three months after the onset of cerebral hypoperfusion, the rats were tested in a hippocampus-related learning paradigm, the Morris water maze. Subsequently, the animals were sacrificed and neurons, astrocytes and microglia were labeled with immunocytochemistry in the dorsal hippocampus. DMSO and diazoxide dissolved in DMSO restored cerebral hypoperfusion-related learning dysfunction and prevented cyclooxygenase-2-positive neuron loss in the dentate gyrus. Cerebral hypoperfusion led to reduced astrocyte proliferation, which was not clearly affected by the treatment. Microglia activation was considerably enhanced by cerebral hypoperfusion, which was completely prevented by diazoxide dissolved in DMSO, but not by DMSO alone. We conclude that diazoxide can moderate ischemia-related neuroinflammation by suppressing microglial activation. Furthermore, we suggest that DMSO is a neuroprotective chemical in ischemic conditions, and it must be considerately used as a solvent for water-insoluble compounds in experimental animal models.

Protection against Recurrent Stroke with Resveratrol: Endothelial Protection

Despite increased risk of a recurrent stroke following a minor stroke, information is minimal regarding the interaction between injurious mild cerebral ischemic episodes and the possible treatments which might be effective. The aim of the current study was to investigate recurrent ischemic stroke and whether resveratrol, a nutritive polyphenol with promising cardio- and neuro- protective properties, could ameliorate the associated brain damage. Experiments in adult rats demonstrated that a mild ischemic stroke followed by a second mild cerebral ischemia exacerbated brain damage, and, daily oral resveratrol treatment after the first ischemic insult reduced ischemic cell death with the recurrent insult (P<0.002). Further investigation demonstrated reduction of both inflammatory changes and markers of oxidative stress in resveratrol treated animals. The protection observed with resveratrol treatment could not be explained by systemic effects of resveratrol treatment including effects either on blood pressure or body temperature measured telemetrically. Investigation of resveratrol effects on the blood-brain barrier in vivo demonstrated that resveratrol treatment reduced blood-brain barrier disruption and edema following recurrent stroke without affecting regional cerebral blood flow. Investigation of the mechanism in primary cell culture studies demonstrated that resveratrol treatment significantly protected endothelial cells against an in vitro 'ischemia' resulting in improved viability against oxygen and glucose deprivation (39.6+/-6.6% and 81.3+/-9.5% in vehicle and resveratrol treated cells, respectively). An inhibition of nitric oxide synthesis did not prevent the improved cell viability following oxygen glucose deprivation but SIRT-1 inhibition with sirtinol partially blocked the protection (P<0.001) suggesting endothelial protection is to some extent SIRT-1 dependent. Collectively, the results support that oral resveratrol treatment provides a low risk strategy to protect the brain from enhanced damage produced by recurrent stroke which is mediated in part by a protective effect of resveratrol on the endothelium of the cerebrovasculature