Effects of hypothermia on blood flow and neural activity in rabbit spinal cord during postischemic reperfusion

The effects of hypothermia on blood flow and neural activity were investigated in rabbit spinal cord during the acute phase of ischemia/reperfusion. Rabbits were exposed to ischemia for 10 or 40 min by occluding the abdominal aorta, using a balloon catheter. The body temperature was maintained either at 38 degrees C (normothermia) or 34 degrees C (hypothermia). Hyperperfusion was observed within 10 min after the cessation of ischemia in all rabbits exposed to ischemia. The magnitude of hyperperfusion in spinal cord blood flow (SCBF) was not significantly different between the 10 and 40 min ischemia rabbits, but the time for 50% recovery from the hyperperfusion was longer in the 40 min ischemia group (26.1 +/- 2.5 min) than in the 10 min group (15.1 +/- 2.1 min). The amplitude of evoked spinal cord potential decreased during ischemia and recovered to the baseline level during 8 h of reperfusion in the 10 min ischemia group. However, in the 40 min ischemia group, the amplitude was 40 +/- 8% of the baseline value after 8 h of reperfusion. Hypothermia prevented the delay of recovery from hyperperfusion and the reduction of evoked spinal cord potential. These results suggest that hypothermia plays a beneficial role in protecting tissue injury in the acute phase of ischemia/reperfusion in the spinal cord by shortening the time for recovery from postischemic hyperperfusion.     

己酮可可碱对兔缺血再灌注损伤脊髓的保护作用及机制

目的： 对己酮可可碱(PTX)在脊髓缺血再灌注损伤中神经元的保护作用及其机制进行初步探讨。方法: 采用日本大耳白兔腹主动脉夹闭法建立脊髓缺血再灌注损伤动物模型，随机分为A组（假手术组，8只）、B组（对照组，20只）、C组（夹闭血管前用药组，20只）、D组（再灌注即刻用药组，20只）。于再灌注后12 h、24 h、48 h、72 h检测血TNF-α活性、组织MPO活性、免疫组化法观察并检测PECAM-1及caspase-3表达、HE染色观察神经元并计数坏死神经元、TUNEL染色观察并计数凋亡神经元、电镜观察坏死及凋亡神经元形态改变，并于再灌注后48 h进行运动功能评分（改良Tarlov评分）。结果: 用药组（C组及D组）改良Tarlov评分明显高于对照组（P<0.05），血TNF-α、组织MPO含量、免疫组化PECAM-1及caspase-3表达强度均明显下降，HE及TUNEL染色切片中坏死细胞及凋亡细胞均明显减少，与对照组有显著差异（P<0.05）。假手术组未见坏死及凋亡细胞。结论: 己酮可可碱在脊髓缺血再灌注损伤中能够发挥抑制神经元坏死及凋亡的双重脊髓保护作用。     

Bradykinin preconditioning induces protective effects on the spinal cord ischemic injury of rats

The study was performed to investigate the effects of bradykinin preconditioning on spinal cord ischemic injury using an in vivo transient spinal cord ischemia model in rats. Prior to ischemia, bradykinin was infused continuously via the left femoral artery starting 15min before ischemia. Neurological functions were evaluated for 7 days postoperatively using modified Tarlov's scores. Tarlov's score outcomes showed a marked improvement in the bradykinin group compared to the ischemia group. The blood-spinal cord barrier (BSCB) permeability was also decreased by bradykinin preconditioning after 72 h reperfusion focal spinal cord in rats, which was greatly reversed by B9430 (bradykinin B2 receptor antagonist). Immunohistochemical and Western blot analysis of spinal cords revealed a significant increase in basic fibroblast growth factor protein (bFGF) levels. The study demonstrated that bradykinin preconditioning induces protection against spinal cord ischemic injury, and this protection is likely due to the protection of the vasculature of the spinal cord and the promotion of neuronal survival.     

Hypothermia enhances the colocalization of calmodulin kinase IIα with neuronal nitric oxide synthase in the hippocampus following cerebral ischemia

Hypothermia has been shown to have neuroprotective effects against neurotrauma and cerebrovascular disease. Cerebral ischemia induces the activation of calcium/calmodulin kinase II (CaM-KII), which modulates many enzymes. We have previously demonstrated that CaM-KIIα downregulates neuronal nitric oxide synthase (nNOS) activity. However, precise details regarding the neuroprotective mechanism of hypothermia largely remain to be elucidated. Therefore, in this study, we investigated the neuroprotective mechanism of hypothermia, focusing on the association between CaM-KIIα and nNOS in CA1 hippocampus after focal cerebral ischemia in mice. The temperature was maintained at normothermia (36.5-37.5°C) or mild hypothermia (31.5-32.5°C) during these procedures. Focal cerebral ischemia induced significant dissociation of CaM-KIIα from nNOS in the CA1 hippocampus but not in the cerebral cortex under normothermia. Hypothermia did not change the expression of nNOS, but it significantly induced the colocalization of CaM-KIIα with nNOS in CA1 hippocampus immediately after cerebral ischemia. These results presumably result in the attenuation of nNOS activity and could contribute to the tolerance to post-ischemic damage. This effect could be one of the neuroprotective mechanisms of hypothermia.     

Motor impairment and neuronal damage following hypothermia in tropical amphibians

Although the induction of mild to moderate cerebral hypothermia in mammals can have neuroprotective activity, some deleterious effects have been described when inducing deep hypothermia during cooling of the brain. In the spinal cord, rapid deep cooling can induce seizure activity accompanied by release of the excitatory neurotransmitters, glutamate and aspartate. We used cold-sensitive tropical amphibians as a model to determine (a) the critical temperature inside the central nervous system necessary to induce seizures during rapid cooling; (b) the survival rate during slow deep cooling of the whole animal; and (c) whether deep cooling can cause neuronal cell damage. Seizures induced by deep rapid (or=30 min) deep cooling of the whole animal (12 h at 2-3 degrees C), around 70% of animals died. Spinal reflexes were enhanced when temperatures within the spinal cord reached between 9.0 degrees C and 11.6 degrees C. A fivefold increase in blood glucose level was observed during slow deep cooling. Recovery after slow deep cooling was accompanied by motor impairment and the main histological findings were condensation of the cytoplasm and nuclear pyknosis. Severe neuronal cell damage was characterized by swelling, vacuolated cytoplasm with distended neuronal bodies. These results indicate that deep cooling can easily induce neuronal cell damage in the central nervous system of cold-sensitive animals. They also warn us to the potential sequels associated with the use of deep brain cooling as a neuroprotective strategy.     

缺血预处理快速效应对兔急性缺血脊髓的保护作用

目的:探讨缺血预处理快速相对兔腹主动脉短暂阻断致缺血脊髓的保护作用。方法:36只雄性新西兰兔随机分成3组(n=12):即缺血再灌注损伤组(IR组)、缺血预处理组(IPC+IR组)及假手术组(Sham组)。IR组阻闭兔腹主动脉肾下段20min,复制兔脊髓缺血损伤模型;IPC+IR组预先阻闭腹主动脉肾下段6min,再灌注30min后再次阻闭腹主动脉肾下段20min;Sham组除不夹闭腹主动脉外,其余处理同IR组。再灌注后8h、12h、24h和48h分别对动物神经功能评分,然后,处死动物取脊髓(L_5-7),分别行组织病理学观察及测定脊髓组织中Na⁺,K⁺-ATP酶的活性。结果:Sham组及IPC+IR组神经功能评分各时点均明显高于IR组(P＜0.01);Sham组及IPC+IR组脊髓前角正常神经细胞数明显多于IR组(P＜0.01);Sham组及IPC+IR组脊髓组织中Na⁺,K⁺-ATP酶的活性明显高于IR组(P＜0.01)。结论:缺血预处理快速相对兔急性缺血脊髓有显著的保护作用,这种保护作用可能与稳定Na⁺,K⁺-ATP酶的活性有关。     

缺血后处理对兔缺血/再灌注损伤脊髓的保护作用可能与PI3K/Akt信号有关

目的 探讨缺血后处理对兔缺血/再灌注损伤脊髓的保护作用及PI3K/Akt传导通路在其中的作用.方法 42只日本大耳白兔(2-2.5kg),随机分为7组,分别为缺血组(Ⅰ组);缺血后处理组(PB组);PB+DMSO组(D组);PB+Ly294002 5μg组(PY5组);PB+LY294002 10μg组(PY10组);...     

脊髓缺血性再灌注损伤和预处理保护作用的实验研究

目的：探讨缺血预处理对家兔须缺血性损伤的保护作用。方法：家兔18只，随机分为Ⅰ组（假手术组）、Ⅱ组（缺血预处理组）和Ⅲ组（缺血再灌组），每组6只，Ⅰ组开腹后，在左肾动脉起点以下0．5cm处暴露并分离腹主动脉即关腹；Ⅲ组一次性阻断腹主动脉血流30min，松夹后关腹；Ⅱ组阻断腹主动脉血流5min，松夹后再灌注10min（如此反复2次），最后再持续夹闭腹主动脉30min，松夹后关腹。结果：Ⅰ组术后后肢运动功能全部正常，光镜和电镜检查显示组织结构变化甚微。Ⅲ组术后后肢运动功能发生严重障碍，脊髓组织严重损伤，与Ⅲ组比较，Ⅱ组术后后肢运动功能障碍较轻微，须组织损伤明显减轻，神经功能评价各组差异具有显著性（P12h=0.006和P36h=0.001)。结论：缺血预处理能够促进神经功能的恢复，减轻脊髓组织损伤，提示预处理对脊因再灌注损伤具有保护作用。     

Ischemic preconditioning suppresses apoptosis of rabbit spinal neurocytes by inhibiting ASK1-14-3-3 dissociation

The mechanism by which a brief episode of sublethal ischemia followed by reperfusion (ischemic preconditioning, IPC) prevents the lethal effects of subsequent periods of prolonged ischemia, are poorly understood. A completely randomized, controlled study was designed to study the effect of IPC using a rabbit model of ischemic spinal cord injury. Twenty-four white adult New England rabbits were randomly assigned to one of 3 groups (n=8 per group); the groups were assigned as follows: Group I: sham-operation group, Group II: ischemic reperfusion (I/R) group, and Group III: ischemic preconditioning group. Spinal cord ischemia was induced by introducing an infra renal aortic cross-clamp for 30min. Following injury, rabbits were subjected to 30min, 2h, or 8h of reperfusion in Group II. In Group III, subjects underwent three cycles, 5min each, of ischemia followed by 5min of reperfusion, before receiving 30min of ischemia. We previously reported that the association between ASK1 (apoptosis signal-regulating kinase 1) and 14-3-3 played an important role in regulating ischemia/reperfusion spinal cord injuries. To evaluate the effect of ischemic preconditioning in injured spinal cords, we examined alterations in spinal tissue morphology, activation of key members of the ASK1-mediated signaling pathway, and the association between ASK1 and 14-3-3. Changes in spinal cord morphology were observed with hematoxylin and eosin (H&E) staining and electron microscopy. The phosphorylation levels of ASK1, JNK, and p38 were assessed by immunoblot analysis. The association between ASK1 and 14-3-3 was analyzed by co-immunoprecipitation experiments. We observed that swelling of the neurocyte bodies and hemorrhage of the spinal cord were dramatically decreased in Group III compared to Group II. In addition, the degree of apoptosis among neurocytes was reduced in Group III compared to Group II. Finally, the phosphorylation of ASK1, JNK, p38 and the dissociation of ASK1 from 14-3-3 were dramatically decreased in Group III compared with Group II. These results indicate that ischemic preconditioning may have a protective affect against ASK1/14-3-3 dissociation-induced spinal cord injuries.     

Delayed preconditioning effect of isoflurane on spinal cord ischemia in rats

Paraplegia is one of the most common complications following aortic aneurysmal surgery. This study was designed to determine if isoflurane-induced delayed preconditioning is mediated by nuclear factor kappaB (NF-kappaB) in the rat spinal cord. The animals were divided into four groups: the control group, the pyrrolidinedithio carbamate (PDTC, an NF-kappaB inhibitor)-treated group, the isoflurane-treated group, and the PDTC/isoflurane-treated group. In the PDTC-treated groups, 2% 100mg/kg PDTC was administered intraperitoneally at 1h before operation and at 24h and 48 h after reperfusion. The rats in the isoflurane-treated groups received 30 min inhalation of 2.8% isoflurane at 24h before spinal cord ischemia. Pretreatment with NF-kappaB inhibitor significantly reduced NF-kappaB expression and the number of intact motor neurons when compared to the control group. Preconditioning with isoflurane increased the number of normal motor neurons, whereas pretreatment with both PDTC and isoflurane significantly decreased them, compared to the isoflurane-treated group. Isoflurane-induced delayed preconditioning on spinal cord ischemia improved histopathological outcomes. This neuroprotective effect of isoflurane preconditioning on spinal cord ischemia is associated with NF-kappaB expression.     

Intrathecally injected granulocyte colony-stimulating factor produced neuroprotective effects in spinal cord ischemia via the mitogen-activated protein kinase and Akt pathways

Granulocyte colony-stimulating factor (G-CSF) is a potent hematopoietic factor. Recently, this factor has been shown to exhibit neuroprotective effects on many CNS injuries. Spinal cord ischemic injury that frequently results in paraplegia is a major cause of morbidity after thoracic aorta operations. In the present study, we examined the neuroprotective role of G-CSF on spinal cord ischemia-induced neurological dysfunctions and changes in the mitogen-activated protein kinase (MAPK) and Akt signaling pathways in the spinal cord. Spinal cord ischemia was induced in male Wistar rats by occluding the descending aorta with a 2F Fogarty catheter for 12 min 30 s. Immediately after ischemia surgery, the rats were administered G-CSF (10 mug) or saline by intrathecal (i.t.) injection. The rats were divided into four groups: control, ischemia plus saline, ischemia plus G-CSF and G-CSF alone. The neurological dysfunctions were assessed by calculating the motor deficit index after ischemia surgery. The expressions of MAPK and Akt were studied using Western blotting and double immunohistochemistry. First, we observed that ischemia plus i.t. G-CSF can significantly reduce the motor function defects and downregulate phospho-p38 and phospho-c-Jun N-terminal kinase protein expressions-this can be compared with the ischemia plus saline group. In addition, G-CSF inhibited the ischemia-induced activation of p38 in the astrocytes. Furthermore, we concluded that i.t. G-CSF produced a significant increase in phospho-Akt and phospho-ERK in the motor neurons and exhibited beneficial effects on the spinal cord ischemia-induced neurological defects.     

Accelerated functional recovery and neuroprotection by agmatine after spinal cord ischemia in rats

Treatment with agmatine, decarboxylated arginine, proved to be non-toxic and to exert neuroprotective effects in several models of neurotoxic and ischemic brain and spinal cord injuries. Here we sought to find out whether agmatine treatment would also prove beneficial in a rat spinal cord ischemia model (balloon occlusion of the abdominal aorta bellow the branching point of the left subclavian artery for 5 min). Agmatine was injected (100 mg/kg, i.p. ) 5 min after beginning of re-perfusion and again once daily for the next 3 post-operative days. Motor performance ('combined motor score') was recorded for up to 17 days post-operative and motoneuron cell counts (in representative spinal cord sections) performed on the 17th post-operative day. Agmatine treatment was found to accelerate recovery of motor deficits and to prevent the loss of motoneurons in the spinal cord after transient ischemia. Together, the present and previous findings demonstrate that agmatine is an efficacious neuroprotective agent and that this naturally occurring non-toxic compound should be tried for therapeutic use after neurotrauma and in neurodegenerative diseases.     

Electron Microscopy of Cat Spinal Cord Subject to Circulatory Arrest and Deep Local Hypothermia (15 C)

Circulatory arrest to the lumbar spinal cord of adult cat was produced by occlusion of the descending aorta and concurrent arterial hypotension. Local hypothermia of the cord was induced by paraffin oil at 5 C, which was circulated over the exposed surface of the cord, using the laminectomy wound as a trough. Intramedullary temperature was 15 C at a depth of 5 mm. In 10 control animals oil at 37 or 5 C was circulated over the exposed cords (normal-normothermic and normal-hypothermic controls with 1 and 2 hours hypothermia). Three animals had circulatory arrest and recirculation in normothermia (ischemic-normothermic) and 3 in hypothermia (ischemic-simultaneous hypothermia). Three had circulatory arrest and 15 minutes of recirculation in normothermia followed by 1 hour of hypothermia (ischemic-delayed hypothermia). The medial and lateral portions of the anterior gray horns of the last lumbar spinal segment were studied in the light and electron microscopes. Ischemic-normothermic tissue showed 20% shrinkage in mean areas of neuronal perikarya and massive “watery” swelling of astrocytic cell bodies and processes. Within neuronal perikarya and dendrites, cytoplasm increased in electron density, ribosomes dispersed, Golgi apparatus swelled and mitochondria swelled with loss of matrix density and disruption of cristae. Axons and axon terminals did not increase in size, but mitochondria within these structures doubled in size without loss of matrix density or change in pattern of cristae. Synaptic vesicles were no longer uniform in size, and they were clumped away from the synaptic cleft and diminished in number. Lysosomes were unchanged in appearance and size. Mitochondria of astrocytes underwent approximately fourfold enlargement without loss of matrix density or pattern of cristae. Bundles of astrocytic microfilaments were fragmented, spread apart and diminished in quantity. Oligodendroglia and endothelial cells were unchanged. Normal-hypothermic animals were similar to normal-normothermic except for clefts in rough endoplasmic reticulum of neurons and dendrites. These clefts were formed by a separation of the cisternal membrane from the adjacent row of ribosomal rosettes. Ischemic-simultaneous hypothermia animals had findings identical to normal-hypothermic animals. Ischemic-delayed hypothermia animals were similar to ischemic-normothermic animals except for less swelling of astrocytic processes, greater swelling of astrocytic mitochondria and less alteration of microfilaments. The findings show that ischemia in normothermia brings about alterations in virtually every organelle of the neurronal perikaryon except the lysosome. Simultaneous hypothermia in ischemia prevents the protean alterations of ischemia, whereas hypothermia delayed until after the ischemic episode only slightly modifies the cellular lesions found in ischemic-normothermic animals.     

Dynamic changes in cortical NADH fluorescence in rat focal ischemia: evaluation of the effects of hypothermia on propagation of peri-infarct depolarization by temporal and spatial analysis

Suppression of peri-infarct depolarizations (PIDs) is one of the major mechanisms of hypothermic protection against transient focal cerebral ischemia. Previous studies have shown the lack of hypothermic protection against permanent focal ischemia. We hypothesized the lack of hypothermic protection was due to the poor efficacy in suppression of PIDs. To examine the hypothesis, we elucidated the effects of hypothermia on the manner of propagation of PIDs with temporal and spatial resolutions using NADH (reduced nicotinamide adenine dinucleotide) fluorescence images by illuminating the parietal-temporal cortex with ultraviolet light. Spontaneously hypertensive rats (n=14) were subjected to permanent focal ischemia by occlusion of the middle cerebral and left common carotid arteries. 2-h hypothermia (30 degrees C) was initiated before ischemia. Although hypothermia delayed the appearance of PIDs, it did not suppress their appearance. Furthermore, 54% of the PIDs enlarged the high-intensity area of NADH fluorescence in the hypothermia group, similar to the normothermia group (53%). The high-intensity area of NADH fluorescence widened by each PID was larger in the hypothermia group than in the normothermia group. These findings suggest that PIDs even in hypothermia are one of the major factors causing growth of infarction, emphasizing the importance of therapy that targets suppression of PIDs even during hypothermia.     

Isoflurane preconditioning protects motor neurons from spinal cord ischemia: its dose-response effects and activation of mitochondrial adenosine triphosphate-dependent potassium channel

We examined in a rabbit model of transient spinal cord ischemia (SCI) whether isoflurane (Iso) preconditioning induces ischemic tolerance to SCI in a dose-response manner, and whether this effect is dependent on mitochondrial adenosine triphosphate-dependent potassium (K(ATP)) channel. Eighty-six rabbits were randomly assigned to 10 groups: Control group (n=8) received no pretreatment. Ischemic preconditioning (IPC) group (n=8) received 5 min of IPC 30 min before SCI. The Iso 1, Iso 2 and Iso 3 groups (n=10, 9, 8) underwent 30 min of 1.05, 2.1 and 3.15% Iso inhalation commencing 45 min before SCI. The Iso 1HD, Iso 2HD and Iso 3HD groups (n=9, 9, 8) each received a specific mitochondrial K(ATP) channel blocker, 5-hydroxydecanoic acid (5HD, 20mg/kg), 5 min before each respective Iso inhalation. The 5HD group (n=8) received 5HD without Iso inhalation. The sham group (n=9) had no SCI. SCI was produced by infra-renal aortic occlusion via the inflated balloon of a Swan-Ganz catheter for 20 min. The Iso 1, Iso 2 and Iso 3 groups showed a better neurologic outcome and more viable motor nerve cells (VMNCs) in the anterior spinal cord 72 h after reperfusion than the control group (p<0.05). Iso 3 group showed a better neurologic outcome and more VMNCs than Iso 1 group (p<0.05). And, the Iso 1, Iso 2 and Iso 3 groups showed a better neurologic outcome and higher VMNC numbers than the corresponding Iso 1HD, Iso 2HD and Iso 3HD groups (p<0.05). This study demonstrates that Iso preconditioning protects the spinal cord against neuronal damage due to SCI in a dose-response manner via the activation of mitochondrial K(ATP) channels.     

选择性深低温血流阻断猴海马超微结构和波形蛋白表达的变化**

背景：前期研究显示,选择性深低温顺行脑灌注能提高猴脑对缺血缺氧的耐受性。 目的：观察选择性深低温血流阻断对猴海马超微结构和波形蛋白表达的影响。 方法：将8只健康成年恒河猴随机分为两组：深低温组(n=5)在常温下阻断猴双侧颈总动脉及颈内静脉10 min,然后通过一侧颈内动脉灌注4 ℃林格氏液,同侧颈内静脉回流,使脑温维持在18 ℃以下,60 min后恢复脑血流;常温组(n=3)除灌注液改为37 ℃林格氏液外,其余与深低温组相同。 结果与结论：深低温组猴全部成功复苏,海马组织形态及超微结构未见明显异常。常温组猴全部死亡,未能成功复苏,海马组织形态及超微结构有不同程度异常。与常温组比较,深低温组海马波形蛋白表达显著降低(P < 0.01)。说明阻断双侧颈总动脉10 min后行选择性深低温顺行脑灌注可下调海马波形蛋白表达,保护海马组织,减轻脑缺血损害。     

Neuroprotective effect of atorvastatin in spinal cord ischemia-reperfusion injury

OBJECTIVES:

Prevention of the development of paraplegia during the repair of the damage caused by descending thoracic and thoracoabdominal aneurysms remains an important issue. Therefore, we investigated the protective effect of atorvastatin on ischemia-induced spinal cord injury in a rabbit model.

METHOD:

Thirty-two rabbits were divided into the following four equally sized groups: group I (control), group II (ischemia-reperfusion), group III (atorvastatin treatment) and group IV (atorvastatin withdrawal). Spinal cord ischemia was induced by clamping the aorta both below the left renal artery and above the iliac bifurcation. Seventy-two hours postoperatively, the motor function of the lower limbs of each animal was evaluated according to the Tarlov score. Spinal cord and blood samples were obtained for histopathological and biochemical analyses.

RESULTS:

All of the rabbits in group II exhibited severe neurological deficits. Atorvastatin treatment (groups III and IV) significantly reduced the level of motor dysfunction. No significant differences were observed between the motor function scores of groups III and IV at the evaluated time points. Light microscopic examination of spinal cord tissue samples obtained at the 72^nd hour of reperfusion indicated greater tissue preservation in groups III and IV than in group II.

CONCLUSION:

This study demonstrates the considerable neuroprotective effect of atorvastatin on the neurological, biochemical and histopathological status of rabbits with ischemia-induced spinal cord injury. Moreover, the acute withdrawal of atorvastatin therapy following the induction of spinal cord ischemia did not increase the neuronal damage in this rabbit model.     

Magnetic resonance spectroscopy of the brain under mild hypothermia indicates changes in neuroprotection-related metabolites

Brain hypothermia has demonstrated pronounced neuroprotective effect in patients with cardiac arrest, ischemia and acute liver failure. However, its underlying neuroprotective mechanisms remain to be elucidated in order to improve therapeutic outcomes. Single voxel proton magnetic resonance spectroscopy (¹H-MRS) was performed using a 7 Tesla MRI scanner on normal Sprague–Dawley rats (N = 8) in the same voxel under normothermia (36.5 °C) and 30 min mild hypothermia (33.5 °C). Levels of various brain proton metabolites were compared. The level of lactate (Lac) and myo-inositol (mI) increased in the cortex during hypothermia. In the thalamus, taurine (Tau), a cryogen in brain, increased and choline (Cho) decreased. These metabolic alterations indicated the onset of a number of neuroprotective processes that include attenuation of energy metabolism, excitotoxic pathways, brain osmolytes and thermoregulation, thus protecting neuronal cells from damage. These experimental findings demonstrated that ¹H-MRS can be applied to investigate the changes of specific metabolites and corresponding neuroprotection mechanisms in vivo noninvasively, and ultimately improve our basic understanding of hypothermia and ability to optimize its therapeutic efficacy.     

Ubiquitin and endogenous antioxidant enzymes participate in neuroprotection of the rabbit spinal cord after ischemia and bradykinin postconditioning

The aim of this study was to investigate neuroprotective effect of bradykinin postconditioning on the rabbit spinal cord after 20 min of ischemia and 3 days of reperfusion. Bradykinin was administered by single i.p. application at 1, 6, 12 or 24 h after ischemia. Assessment of neurological function of hind limbs (Tarlov score) was estimated. Quantitative analysis was evaluated by Fluoro Jade B method, NeuN and ubiquitin immunohistochemistry in anterior horn neurons of the spinal cord. Histomorphologically distribution of ubiquitin and endogenous antioxidant enzymes (SOD1, SOD2, catalase) immunoreaction was described. Bradykinin postconditioning showed decreased number of degenerated neurons, increased number of surviving neurons and increase in number of ubiquitin positive neurons in all bradykinin postconditioned groups versus ischemia/reperfusion group. According to our results bradykinin postconditioning applied 24 h after ischemia significantly decreased (p < 0.001) number of degenerated neurons versus ischemia/reperfusion group. The least effective time window for bradykinin postconditioning was at 12 h after ischemia. Tarlov score was significantly improved (p < 0.05) in groups with bradykinin postconditioning applied 1, 6 or 24 h after ischemia versus ischemia/reperfusion group. Tarlov score in group with bradykinin application 12 h after ischemia was significantly decreased (p < 0.05) versus sham control group. Neuronal immunoreaction of ubiquitin, SOD1, SOD2 and catalase influenced by bradykinin postconditioning was dependent on neuronal survival or degeneration. In conclusion, bradykinin postconditioning showed protective effect on neurons in anterior horns of the rabbit spinal cord and improved motor function of hind limbs.     

局部亚低温对大鼠局灶脑缺血再灌注后神经营养因子-3表达的影响

目的：观察病变侧缺血至再灌期亚低温(32～33 ℃)对局灶脑缺血再灌注后梗死体积和神经营养因子-3(neurotrophin-3,NT-3)表达的影响。方法：采用改良线栓法建立大鼠大脑中动脉缺血再灌注模型,随机分为假手术组、常温缺血组和亚低温缺血组,缺血30 min后应用负反馈控温半导体制冷块对大鼠病变侧给予亚低温治疗并持续至再灌期。处死大鼠前进行神经功能缺陷评分,氯化三苯四氮唑染色及计算机图像分析技术观察脑梗死体积,采用免疫组织化学方法检测NT-3表达,末端脱核苷酸转移酶介导的dUTP缺口标记技术观察神经细胞凋亡情况。结果：同常温缺血组相比,亚低温缺血组梗死体积明显减少,NT-3阳性细胞数量增加,凋亡的神经细胞明显减少(均P<0.05)。神经功能缺陷评分亚低温缺血组明显低于相应时间点常温缺血组(P<0.05或P<0.01)。结论：病变侧亚低温可通过增加脑缺血后NT-3的表达水平,抑制细胞凋亡而发挥脑保护作用。