SURGICAL MANAGEMENT OF DISSECTING ANEURYSM—The Use of a Simplified Bypass

The alarming mortality in cases of dissecting aneurysm of the aorta has stimulated the development of a surgical technique which results in re-entry of the dissecting channel. During the operative procedure prolonged cross-clamping of the aorta is necessary. While hypothermia will provide protection to the spinal cord and kidneys during reasonable periods of aortic occlusion it will not relieve back pressure on the left ventricle.By the use of a simple bypass blood is drained from the left atrium into a reservoir and then pumped into the lower aorta via the femoral artery. Thus an adequate supply of oxygenated blood is delivered to the spinal cord and kidneys distal to the occlusion while the left ventricular pressure is decompressed to normal levels. The volume of the shunted blood is simply controlled by monitoring the brachial artery pressure with a cuff sphygmomanometer. This simplified bypass has permitted successful repair of a dissecting aneurysm with complete occlusion of the thoracic aorta for a period of two hours.     

Neuronal Nitric Oxide Synthase Immunopositivity in Motoneurons of the Rabbit's Spinal Cord After Transient Ischemia/Reperfusion Injury

Summary 1. Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. To evaluate the role of nitric oxide (NO) in the pathophysiology of the spinal cord ischemia, the expression of neuronal nitric oxide synthase (nNOS) in the motoneurons of the lumbosacral spinal cord was examined in the rabbit model of transient abdominal aorta occlusion.2. The aim of the present study was to find if there is any consensus between the duration of transient abdominal aorta occlusion, nNOS positivity of the motoneurons and neurological hind limb impairment.3. According to the degree of neurological damage (i.e., from the group with almost no sign of damage to a group with fully developed paraplegia), the experimental animals were divided into three groups. The respective spinal cord segments of each experimental group were compared to the control group.4. Spinal cord ischemia (15 min) was induced by Fogarty arterial embolectomy catheter occlusion of abdominal aorta with a reperfusion period of 7 days. On seventh day, the sections of lumbosacral segments were immunohistochemically treated and L1–L7, and S1–S2 segment sections were monitored using light microscopy.     

缺血预处理对兔脊髓缺血再灌注损伤水通道蛋白-4表达的影响

目的探讨缺血预处理（IPC）对兔脊髓缺血再灌注损伤后水通道蛋白-4（AQP-4）表达的影响。方法日本大耳白兔72只,随机分为3组：假手术组（S组）、脊髓缺血再灌注损伤组（I／R组）和缺血预处理组（IPC组）。I／R组和IPC组阻断腹主动脉30min造成脊髓缺血再灌注损伤,IPC组在损伤前短暂阻断腹主动脉5min二次实施预处理,S组暴露肾动脉下腹主动脉但不阻断。分别于再灌注损伤后4h和24h进行神经功能评分,并取L4—6脊髓缺血节段,计算脊髓组织含水量,免疫组化法测定脊髓组织中AQP-4表达水平。结果与S组比较,I／R组神经运动功能评分降低,脊髓组织含水量增加,AQP-4表达增加（P〈0．05）。与I／R组比较,IPC组神经运动功能评分增高,脊髓组织含水量降低,AQP-4表达减少（P〈0．05）。结论IPC可抑制脊髓损伤后AQP-4的表达,进而减轻脊髓水肿,保护缺血再灌注损伤的脊髓。     

Neuroprotective Effects of PEP-1-Cu,Zn-SOD against Ischemic Neuronal Damage in the Rabbit Spinal Cord

A rabbit model of spinal cord ischemia has been introduced as a good model to investigate the pathophysiology of ischemia-reperfusion (I-R)-induced paraplegia. In the present study, we observed the effects of Cu,Zn-superoxide dismutase (SOD1) against ischemic damage in the ventral horn of L(5-6) levels in the rabbit spinal cord. For this study, the expression vector PEP-1 was constructed, and this vector was fused with SOD1 to create a PEP-1-SOD1 fusion protein that easily penetrated the blood-brain barrier. Spinal cord ischemia was induced by transient occlusion of the abdominal aorta for 15 min. PEP-1-SOD1 (0.5 mg/kg) was intraperitoneally administered to rabbits 30 min before ischemic surgery. The administration of PEP-1-SOD1 significantly improved neurological scores compared to those in the PEP-1 (vehicle)-treated ischemia group. Also, in this group, the number of cresyl violet-positive cells at 72 h after I-R was much higher than that in the vehicle-treated ischemia group. Malondialdehyde levels were significantly decreased in the ischemic spinal cord of the PEP-1-SOD1-treated ischemia group compared to those in the vehicle-treated ischemia group. In contrast, the administration of PEP-1-SOD1 significantly ameliorated the ischemia-induced reduction of SOD and catalase levels in the ischemic spinal cord. These results suggest that PEP-1-SOD1 protects neurons from spinal ischemic damage by decreasing lipid peroxidation and maintaining SOD and catalase levels in the ischemic rabbit spinal cord.     

Protective Effect of Mild Hypothermia on Spinal Cord Ischemia-Induced Delayed Paralysis and Spinal Cord Injury

Neurochemical Research - To explore the mechanism regarding the regulation of spinal cord ischemia (SCI) in rats by mild hypothermia. A SCI rat model was established through aorta occlusion, and in...     

Degradation of Spectrin via Calpains in the Ventral Horn after Transient Spinal Cord Ischemia in Rabbits

In the present study, we investigated chronological changes of μ-calpain, m-calpain and cleaved spectrin αII immunoreactivity in the ventral horn after transient spinal cord ischemia to investigate relationship between calpains and vulnerability to ischemia using abdominal aorta occlusion model in rabbits. Spinal cord sections at the level of L₇ were immunostained with calpains and cleaved spectrin αII monoclonal antibodies. μ-Calpain and m-calpain immunoreactivity was significantly increased in the ischemic ventral horn at 30 min and 1 h after ischemia/reperfusion, respectively. Thereafter, they were decreased with time after ischemia/reperfusion: at 48 h after ischemia, their immunoreactivities nearly disappeared in the ischemic ventral horn. Cleaved spectrin αII immunoreactivity was significantly increased in the ventral horn of spinal cord at 12 h after ischemia/reperfusion, and thereafter, its immunoreactivity was decreased with time after ischemia/reperfusion. In addition, spectrin αII protein level (280 kDa) was decreased from 12 h after ischemia/reperfusion; in contrast, cleaved spectrin αII protein level (150 kDa) was significantly increased at 12 h after ischemia/reperfusion. In conclusion, our observations in this study indicate that calpain is associated with neuronal degeneration in the ventral horn at early time after transient spinal cord ischemia via the proteolysis of spectrin αII.Jae-Chul Lee and In Koo Hwang equally contribute to this article.     

缺血预处理对缺血再灌注后兔脊髓磷酸腺苷代谢的影响

目的：研究缺血参处理对缺血再灌注后兔脊髓磷酸腺苷代谢的影响。方法：往置入腹主动脉的Swan-Ganz导管气囊内注气造成兔腰髓缺血模型。将实验兔分为假手术组、缺血组和预处理组。应用反相高效液相色谱方法（reverse phase HPLC),对缺血再灌注后不同时间点腰髓组织中磷酸腺苷（ATP、ADP、AMP）的含量进行检测。结果：和假手术组相比,缺血组兔再灌后各时间点腰髓组织ATP含量有明显下降（P＜0．01）。与缺血组相应时间点相比,预处理组兔再灌注后腰髓组织ATP含量明显提高（P＜0．01）。结论：缺血预处理显著提高缺血再灌注后兔脊髓组织ATP含量,这可能是缺血预处理对脊髓缺血再灌注损伤产生保护作用的机制之一。     

Fluoro-Jade B evidence of induced ischemic tolerance in the rat spinal cord ischemia: physiological, neurological and histopathological consequences

Fluoro-Jade B, a marker of degenerating neurons, was used to label histopathological changes in the rat spinal cord after transient ischemia and ischemic preconditioning (IPC). To characterize postischemic neurodegenerations and consequent neurological changes, a particular attention was paid to the standardization of ischemic conditions in animals of both groups. 1. The control ischemic rats were submitted to a reversible occlusion of descending aorta by insertion and subsequent inflation of a 2F Fogarty catheter for 12 min. 2. In the IPC rats, an episode of short 3 min occlusion and 30 min reperfusion preceded the 12 min ischemia. Postischemic motor function testing (ambulation and stepping) was provided repeatedly for evaluation of neurological status 2 h and 24 h after surgery and at the end of postischemic survival, i.e. after 48 h. Fluoro-Jade B staining was used to demonstrate degenerated neurons. In the control rats, neurological consequences of histopathological changes in lumbosacral spinal cord, manifested as paraplegia, were present after 12 min ischemia. Thus, numbers of degenerated Fluoro-Jade B positive cells were visible in gray matter of the most injured L(4)-S(2) spinal cord segments. Slight motor function impairment, consequential from significant decreasing in Fluoro-Jade B-positivity in the L(4)-S(2) spinal cord segments of the IPC rats, was considered the pathomorpfological evidence that IPC induces spinal cord tolerance to ischemia. Our results are consistent with the previously published silver impregnation method for histopathological demonstration of ischemic degeneration.     

Effects of incomplete ischemia and subsequent recirculation on free palmitate, stearate, oleate and arachidonate levels in lumbar and cervical spinal cord of rabbit

The effect of severe incomplete ischemia, induced by abdominal aorta ligation for 40 minutes, and subsequent recirculation for one and four days on accumulation of free fatty acids was studies in the lumbar and cervical part of rabbit spinal cord. Changes in free fatty acid levels were determined separately in gracile fascicle (Fg), dorsal part (Dp, without Fg) and ventral part (Vp) of both spinal cord regions. In lumbar spinal cord increases in free fatty acid levels, especially that of arachidonate, were observed in Fg, Dp and Vp a the end of the ischemic period. During recirculation all values were similar to nonischemic controls. In cervical spinal cord a slight increase in free fatty acid levels was found in Fg after four days of recirculation, and in Dp arachidonate and stearate levels were most markedly elevated after one day of recirculation. No changes at any interval were found in Vp of cervical spinal cord. The present results indicate that the experimental insult induced typical ischemic injury to spinal cord tissue demonstrated by fatty acid liberation from membrane lipids. This injury may affect neurotransmission and other processes and free fatty acids themselves impair tissue metabolism (inhibition of oxidative phosphorylation, edema precipitation, synthesis of eicosanoids) and thus restrict the possibilities to enhance recovery in the recirculation period.     

Effect of ischaemia on protein synthesis in vitro

Changes in the incorporation of 14C-amino acids into proteins in vitro were followed under conditions of ischemia induced by abdominal aorta ligature and subsequent recirculation in dogs. Cell saps isolated from L-S spinal cord, spinal ganglia, the sciatic nerve and medulla oblongata were added to the incorporation mixture composed of ribosomes and an enzymatic system from intact brains. Cytosols isolated from ischemic animals affected the rate of in vitro protein synthesis moderately, while repeated ischemia caused a profound decrease in the incorporation of amino acids into proteins. Cytosols from L-S spinal cord and especially from spinal ganglia after three days of recirculation substantially enhanced incorporation thus indicating a massive response of these tissues to ischemic injury. Cell saps from the medulla oblongata increased amino acid incorporation into proteins in vitro in all experimental groups.     

Arylamidase activity in the rabbit spinal cord after ligation of the abdominal aorta

Effect of ischaemia, induced by abdominal aorta occlusion, and subsequent survival on the activity of arylamidases was studied in the lumbar and cervical spinal cord of the rabbit. No effect of 40 min ischaemia on the activity of arylamidases was found either in homogenates or in subcellular fractions of the spinal cord. In the lumbar spinal cord a moderate decrease in arylamidase activity was observed after 1 day of survival and a marked decrease was found after 4 days. The decrease were localized in the microsomal and, particularly, in the cytosole fraction. No changes were found in the cervical spinal cord at the corresponding intervals.     

Effect of ischemia in vivo and oxygen-glucose deprivation in vitro on NOS pools in the spinal cord: comparative study

1. This study was performed to compare both the Ca(2+)-dependent nitric oxide synthase (NOS) activity and the neuronal nitric oxide synthase immunoreactivity (nNOS-IR) in the rabbit lumbosacral spinal cord after 15 min abdominal aorta occlusion (ischemia in vivo) and oxygen-glucose deprivation of the spinal cord slices for 45 and 60 min (ischemia in vitro). All ischemic periods were followed by 15, 30 and 60 min reoxygenation in vitro. 2. Catalytic nitric oxide synthase activity was determined by the conversion of (L)-[(14)C]arginine to (L)-[(14)C]citrulline. Neuronal nitric oxide synthase immunoreactivity in the spinal cord was detected by incubation of sections with polyclonal sheep-nNOS-primary antibody and biotinylated anti-sheep secondary antibody. 3. Our results show that ischemia in vivo and the oxygen-glucose deprivation of spinal cord slices in vitro result in a time-dependent loss of constitutive NOS activity with a partial restoration of enzyme activity during 15 and 45 min ischemia followed by 30 min of reoxygenation. A significant decrease of enzyme activity was found during 60 min ischemia alone, which persisted up to 1 h of oxygen-glucose restoration. The upregulation of neuronal nitric oxide synthase was observed in the ventral horn motoneurons after all ischemic periods. The remarkable changes in optical density of neuronal nitric oxide synthase immunoreactive motoneurons were observed after 45 and 60 min ischemia in vitro followed by 30 and 60 min reoxygenation. 4. Our results suggest that the oxygen-glucose deprivation followed by reoxygenation in the spinal cord is adequately sensitive to monitor ischemia/reperfusion changes. It seems that 15 min ischemia in vivo and 45 min ischemia in vitro cause reversible changes, while the decline of Ca(2+)-dependent nitric oxide synthase activity after 60 min ischemic insult suggests irreversible alterations.     

低温在脊髓损伤治疗中应用的研究进展

脊髓损伤多由高空坠落、车祸、运动冲击等原因引起,是脊柱外科的一种常见疾病,至今仍是一个治疗难题。低温疗法是一种重要的物理治疗手段,以多种机制减少脊髓损伤后有害因素的产生,是一种有效的脊髓保护途径。其在脊髓损伤的研究中表现出很好的效果,为脊髓损伤的治疗提供了新的思路,然而也发现一些低温治疗导致的全身性或某些系统为主的不良影响,需要我们进一步研究和解决,以期达到更好的治疗效果。本文就低温治疗用于脊髓损伤应用中的研究进展进行综述。     

Effect of partial ischemia on phospholipids and postischemic lipid peroxidation in rabbit spinal cord

Rabbit spinal cord, subjected to severe partial ischemia induced by abdominal aorta ligation tightly below the renal arteries, was analyzed for phospholipid composition and levels of lipid peroxidation products after 10, 20, and 40 min of the insult. Under conditions when spinal cord blood flow was decreased below 5% of control, concentrations of inositol and ethanolamine phospholipids were decreased by 30% and 10%, respectively. Phosphatidic acid concentration was also altered during ischemia. No accumulation of thiobarbituric acid reactive substances (TBA-RS), conjugated dienes and fluorescent lipid soluble material was found throughout the ischemic period. Pattern of TBA-RS, conjugated diene, and fluorophore formation during postischemic in vitro incubation without and with a peroxidation couple (Fe²⁺, ascorbic acid) showed increased susceptibility to postischemic lipid peroxidation in tissues after 20 and 40 min of ischemia.     

Influence of blood sera from dogs subjected to ischemia and recirculation on incorporation of14C-amino acids in vitro

Incomplete ischemia of the spinal cord was produced in dogs by 40 min occlusion of the abdominal aorta that was followed by 5–40 min of recirculation. Amino acid incorporation into ribosomes in vitro in the presence of venous blood sera was estimated. The most significant reduction in incorporation was produced by sera of the dogs following a short recirculation period (5–10 min). No significant changes were observed at the end of the ischemic period nor at longer periods of recirculation. The decrease in incorporation might be the consequence of inactivation or absence of a substance stimulating polypeptide synthesis in vitro, normally present in blood sera of intact dogs, that temporarily loses its activity during recirculation.     

Regulation and localization of neuronal nitric oxide synthase in the ischemic rabbit spinal cord

The expression and cellular localization of neuronal nitric oxide (NO) synthase (nNOS) were studied in the rabbit spinal cord following ischemic injury induced by clamping the descending aorta. In the normal spinal cord, nNOS immunoreactivity was localized to certain motor neurons located in the margin of the ventral horn. Following transient ischemia, immunoreactive spinal neurons increased in number, peaking five days after reperfusion. Quantitative evaluation by western blotting showed that nNOS peaked at 180% of control levels five days after reperfusion and decreased to 120% of controls by 14 days. These findings suggest that overproduced NO may act as a neurotoxic agent in the ischemic spinal cord.     

The Effect of Long-Term Reduction of Aortic Blood Flow on Spinal Cord Gray Matter in the Rabbit. Histochemical Study of NADPH-Diaphorase

1. The aim of this work was to study the influence of reduced aortic blood flow on NADPH-diaphorase (NADPH-d) staining in the gray matter of L4–S3 spinal cord segments.2. Surgery was performed on the abdominal aorta of the rabbit. Spinal cord ischemia was introduced by infrarenal aortic constriction to 30% from the normal blood flow. Animals were allowed to survive 1 week, 1 month and 3 months after surgery. Neurological outcome was studied in relation to the duration of aortic occlusion. The NADPH-d histochemistry was used for the visualisation of spinal cord sections.3. The most affected area of the spinal cord was pericentral region, and slight changes were seen in the NADPH-d activities of both dorsal and ventral horns. One week after surgery, NADPH-d positive pericentral neurons were almost unchanged in their shape and intensity of staining, the only difference was seen in slightly increased staining of the background around the central canal. One month following surgery neurons exhibited shrinkage or were swollen, NADPH-d staining was less intensive in the pericentral zone and positively stained vessels were present.4. Three months of ischemia influenced the NADPH-d activity: (a) In the pericentral region were seen intensively NADPH-d stained neurons almost normal in shape of their bodies but with shortened processes or without them; (b) NADPH-d staining of neuropil was greatly enhanced mostly around the central canal and in the dorsal commissure; (c) Numerous vessels were present in the pericentral zone and in the location of the ventral horn.5. It can be concluded that the reduction of blood flow in the abdominal aorta makes most changes in the pericentral region of the rabbit spinal cord. Increased NADPH-d staining of neuropil and the presence of positively stained vessels reflect increased NADPH-d/NOS production in the spinal cord gray matter after long-term incomplete aortic occlusion.     

脊髓缺血损伤合并脓毒症后脊髓ZnT1表达的研究

目的：研究脊髓缺血损伤合并脓毒血症后大鼠脊髓的病理改变及脊髓组织中锌转运体1（zinc transporter1,ZnT1）的表达规律。方法：将32只wistar大鼠随机分为假手术组（s组,n=8）、腹主动脉阻断组（I／R组,n=8）、内毒素组（LPS组,n=8）和腹主动脉阻断＋内毒素组（I／R＋LPS组,n=8）。用HE染色的方法检测脊髓组织病理损害,用免疫组织化学的方法检测脊髓组织中ZnTl的表达规律。结果：1．病理结果改变：除S组外,I／R组、LPS组、UR＋LPS组三组大鼠HE染色切片中均可见脊髓组织损伤,各组脊髓损伤的严重程度有以下规律：S组〈I/R组〈LPS组〈I／R＋LPS组。2．免疫组化结果：脊髓损伤组ZnT1的表达较假手术组均增加（P〈0．05）。结论：1．脊髓缺血损伤合并内毒素攻击可导致严重的脊髓损伤。2．腹主动脉阻断合并内毒素攻击所致脊髓损伤早期脊髓组织中ZnT1表达上调,可能通过调节脊髓损伤早期脊髓组织中锌稳态平衡进而在脊髓损伤后脊髓神经元的病理生理活动中发挥重要作用,这一实验结果可为寻找早期脊髓损伤预防措施提供新的思路。     

Tat-DJ-1 Protects Neurons from Ischemic Damage in the Ventral Horn of Rabbit Spinal Cord Via Increasing Antioxidant Levels

The DJ-1 gene is highly conserved in diverse species and DJ-1 is known as an anti-oxidative stress factor. In this study, we investigated the neuroprotective effects of DJ-1 against ischemic damage in the rabbit spinal cord. Tat-DJ-1 fusion proteins were constructed to facilitate the penetration of DJ-1 protein into the neurons. Tat-1-DJ-1 fusion protein was administered to the rabbit 30 min after ischemia/reperfusion, and transient spinal cord ischemia was induced by occlusion of the aorta at the subrenal region for 15 min. The administration of Tat-DJ-1 significantly improved the Tarlov score compared to that in the Tat (vehicle)-treated group at 24, 48 and 72 h after ischemia/reperfusion. At 72 h after ischemia/reperfusion, the number of cresyl violet-positive neurons was significantly increased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. Lipid peroxidation as judged from the malondialdehyde levels was significantly decreased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. In contrast, superoxide dismutase and catalase levels were significantly increased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. This result suggests that DJ-1 protects neurons from ischemic damage in the ventral horn of the spinal cord via its antioxidant effects.     

The arrangement of endoplasmic reticulum and proteosynthesis in spinal ganglia neurons of dog after ischemia

The authors studied ultrastructural and biochemical changes in spinal ganglia neurons of dogs after ischemia. Partial spinal cord ischemia was induced by occlusion of the abdominal aorta just below the renal arteries and the arterial blood pressure was registered above and below the occlusion. - In the course of 2-4 hours' ischemia the amount of free ribosomes increased. In some cases the formation of filamentous material or tubular structures inside the cisterns of endoplasmic reticulum was apparent. The proteosynthesis declined. Incorporation of 14C - leucine into the spinal ganglion was 50% as compared to the control animals. The morphological and biochemical changes were more pronounced after 4 h ischemia.