Regional cerebral blood flow after a localized cerebral contusion in pigs

Summary Regional cerebral blood flow (rCBF) in anaesthetized pigs is investigated before and after an induced focal cerebral contusion. Mean intracranial pressure increased for a short period following the contusion and reduced perfusion pressure to 60% of control pressure. Forty five minutes later the mean intracranial pressure was still high and different from the control values. Global flow and cerebral production of CO² increased concomitantly. In the cortical region where the contusion was visible macroscopically the rCBF diminished from 36.5 to 29.1 ml/min/100g. In the rest of the grey matter the rCBF raised after the contusion with an increase away from the centre of the lesion. CBF of cortical grey matter in the region symmetrically to the contusion increased significantly more than in the traumatized hemisphere. White matter rCBF changed least in the region underlying the contusion, while an increase was observed away from the contusion and on the opposite side of the brain. The correlation between tension of CO₂ in arterial blood and regional cerebral blood flow disappeared in the region of the contusion. The correlation between global metabolism and regional cerebral blood flow disappeared after the contusion in all regions. Local flow modulating factors influencing flow in the region of macroscopically visible injury has influence abating with distance from the centre of the injury together with a possible neuronally transmitted drive on flow in the opposite hemisphere.     

Regional cerebral blood flow in the pig after a localized cerebral contusion treated with barbiturates

Summary Regional cerebral blood flow determined with microsphere technique in anaesthetized pigs was measured before and after a localized cerebral contusion as well as after treatment with pentobarbital.No overall reduction in intracranial pressure or perfusion pressure was observed. Flow reduction due to pentobarbital was different in different regions with a high percentage change in the highly perfused basal structures and cortical grey matter except in the centre of the contusion where the reduction was half compared to the rest of cortical grey matter. Changes in white matter were less than in cortical grey matter but more pronounced than in the very high flow areas (choroid plexus and pineal gland). The accumulated change was greatest in the damaged region. Contralateral to the contusion, where a significant increase in flow was noticed after the contusion, there was a very low accumulated change in flow. In white subcortical matter underlying the contusion a similar low flow change was observed but this was not accompanied by as large an accumulated change as in grey cortical matter. At each fraction of injected pentobarbital a short-lasting increase in intracranial pressure and a reduction in mean arterial blood pressure was observed. The amplitude and the height of the intracranial pressure change was reduced during the pentobarbital injections.     

Quantifying the contributions of structure to annulus fibrosus mechanical function using a nonlinear, anisotropic, hyperelastic model.

The annulus fibrosus of the intervertebral disc is comprised of concentric lamella of oriented collagen fibers embedded in a hydrated proteoglycan matrix with smaller amounts of minor collagens, elastin, and small proteoglycans. Its structure and composition enable the disc to withstand complex loads and result in inhomogeneous, anisotropic, and nonlinear mechanical behaviors. The specific contributions of the annulus fibrosus constituent structures to mechanical function remain unclear. Therefore, the objective of this study was to use a structurally motivated, anisotropic, nonlinear strain energy model of annulus fibrosus to determine the relative contributions of its structural components to tissue mechanical behavior. A nonlinear, orthotropic hyperelastic model was developed for the annulus fibrosus. Terms to describe fibers, matrix, and interactions between annulus fibrosus structures (shear and normal to the fiber directions) were explicitly included. The contributions of these structures were analyzed by including or removing terms and determining the effect on the fit to multidimensional experimental data. Correlation between experimental and model-predicted stress, a Bland-Altman analysis of bias and standard deviation of residuals, and the contribution of structural terms to overall tissue stress were calculated. Both shear and normal interaction terms were necessary to accurately model multidimensional behavior. Inclusion of shear interactions more accurately described annulus fibrosus nonlinearity. Fiber stretch and shear interactions dominated contributions to circumferential direction stress, while normal and shear interactions dominated axial stress. The results suggest that interactions between fibers and matrix, perhaps facilitated by crosslinks, elastin, or minor collagens, augment traditional (i.e., fiber-uncrimping) models of nonlinearity.     

Selective lenticulostriate arterial occlusion. A reproducible model of primate focal cerebral ischemia

The anatomic variations of the lateral lenticulostriate arteries of 13 baboons have been detailed from surgical exposures and postmortem silicone rubber-injected specimens. Although the lateral lenticulostriate arteries most frequently arise directly from the orbital frontal artery, they may also arise directly from the middle cerebral artery. Extraparenchymal anastomoses between the medial and lateral lenticulostriates were not found in our operations. Through a microsurgical procedure, selective occlusion of the origins of the lateral lenticulostriate arteries has been accomplished consistently, immediately creating an area of absent flow and subsequent infarction within the normal distribution of these vessels. We believe that selective lateral lenticulostriate occlusion in the baboon produces a lesion that should be useful in the study of cerebral infarction and its treatment.     

Ultrastructural changes induced by experimental subarachnoid haemorrhage and 6-hydroxydopamine in cat cerebral arteries

Summary Transmission electron microscopy of the middle cerebral artery from cats exposed to subarachnoid injection of blood 3 and 7 days before, showed several damage of the vascular ultrastructure. The intima was thickened with swelling and vacuolization of endothelial cells, with a plump appearance and disruption of tight junctions. The cellular surface was corrugated and the subendothelial space contained proliferating and vacuolated smooth muscle cells capped by elastin and collagen fibres. The internal elastic lamina was also corrugated and disrupted. The adventitial changes were axonic cytoplasmic and mitochondrial swelling, virtual absence of synaptic vesicles, and disruption of the outer axonal membrane, suggesting denervation of cerebral vessels. With administration of 6-hydroxydopamine (6-OHDA), similar ultrastructural changes were observed in the adventitia. These observations indicate that denervation induced by subarachnoid bleeding could be involved in the pathophysiology of cerebrovascular spasm. Subarachnoid haemorrhage, but not 6-OHDA, affects also intima and tunica media, suggesting other mechanisms, in addition to denervation, can participate in the vasospasm.     

Ascorbic acid and focal cerebral ischaemia in a primate model

Summary Neuronal cell damage following ischaemia is postulated to be due to free radical induced lipid peroxidation, and ascorbic acid is supposedly an important non-enzymatic scavenger of such free radicals. This study was undertaken to evaluate the protective effect of ascorbic acid on the brain in a primate model after focal cerebral ischaemia. Consumption of ascorbic acid in the monkey brain following ischaemia and its effect on macroscopic infarct size as demonstrated by 2, 3, 5, Triphenyl tetrazolium chloride (TTC) staining were used as parameters.The monkeys in the treated group were given 1 gram ascorbic acid parenterally every day for six days. The mean level of total ascorbic acid in right basal ganglia was 35.1±4.2 g/mg of protein in the treated group as opposed to 22.9±2.1 g/mg of protein in the nontreated group both before ischaemia. After right middle cerebral artery occlusion to produce focal cerebral ischaemia, the total ascorbic acid in the right basal ganglia 2 hours post ischaemia was 13.3±3.1 g/mg of protein in the treated group as opposed to 9±1.6 g/mg of protein in the untreated group. The average consumption of total ascorbic acid was 21.8 g/mg of protein in the treated group and 13.9 g/mg of protein in the nontreated group.Macroscopic infarct size as determined by TTC staining in the right cerebral hemisphere was 11.7±6.9 in treated group whereas it was 24.4±4.4 (expressed as percentage of right hemisphere) in the non-treated group. There was significant reduction in the size of the infarct in the treated group.A short course of mega-dose Ascorbic acid therapy was found to significantly decrease the macroscopic infarct size. Pretreatment with ascorbic acid enhanced its storage and utilization during ischaemia resulting in its protective effect.     

No influence of the endothelin receptor antagonist bosentan on basal and indomethacin-induced reduction of cerebral blood flow in pigs

BACKGROUND: The mechanism behind indomethacin-induced cerebral vasoconstriction is incompletely understood. We tested the hypothesis that the mixed endothelin-1 receptor antagonist bosentan would modify or prevent indomethacin-induced reduction of CBF in the anaesthetized pig. Furthermore, we investigated the effect of bosentan on resting CBF and CMRO2. METHODS: Twelve pigs were randomized in two groups of six, and received either bosentan and indomethacin (group 1), or placebo and indomethacin (group 2). Anaesthesia was induced with ketamine and midazolam and maintained with fentanyl, nitrous oxide and pancuronium. Baseline measurements of CBF and CMRO2 were performed before intravenous bolus injection of bosentan (10 mg/kg) or placebo (0.9% NaCl). The second CBF and CMRO2 measurement was performed 30 min after administration of bosentan/placebo. A 40-min infusion of indomethacin (0.05 mg/kg/min) was administered and the third CBF and CMRO2 measurement was performed 80 min after administration of bosentan/placebo. Independently, pharmacokinetic data of bosentan were generated in four pigs. RESULTS: In group 1, baseline CBF was 55 +/- 7 ml/100 cm3/min. Administration of bosentan i.v. did not change CBF significantly. Indomethacin decreased CBF to 41 +/- 5 ml/100 cm3/min (P < 0.002). In group 2, baseline CBF was 54 +/- 10 ml/100 cm3/min. Placebo did not change CBF while indomethacin decreased CBF significantly to 41 +/- 5 ml/100 cm3/min (P < 0.002). No significant changes in CMRO2 were observed. In group 2, a significant increase in MABP was observed after administration of indomethacin. No change in MABP was observed in the bosentan-treated animals. Total plasma concentrations of bosentan at the time of the first and the second PET measurement were 3.9 and 1.4 microg/ml, respectively. The corresponding values for the pharmacologically active metabolite Ro 48-5033 were 1.2 and 0.4 microg/ml. CONCLUSION: These findings indicate that endothelin receptor stimulation is not involved in indomethacin-induced cerebral vasoconstriction or maintenance of cerebrovascular tone in the anaesthetized pig. However, our results suggest that the increase in MABP is mediated through endothelin receptors.     

机械灌注与单纯冷保存对猪DCD供胰影响的对比研究

目的  对比研究机械灌注与单纯冷保存对猪心脏死亡器官捐献(DCD)供胰的影响。方法  健康猪10只, 随机分为单纯冷保存组和机械灌注组两组(每组各5只)。制备DCD猪模型, 胰腺切取后采用威斯康星大学保存液(UW液)保存。单纯冷保存组给予单纯UW液冷保存, 机械灌注组给予机械灌注保存。分别于保存1、2、3、4、6、24 h时点在胰尾部取材, 制作组织切片, 予苏木素-伊红(HE)染色。两组进行胰腺组织病理学检查, 并对病理学评分进行比较。结果  猪DCD供胰在机械灌注180 min时胰腺微血栓已被清除, 又避免了过度灌注对胰岛的损害。机械灌注组病理学评分为(4.2±0.8)分, 单纯冷保存组病理学评分为(8.4±1.1)分, 比较差异有统计学意义(P < 0.05)。结论  机械灌注可以有效清除胰腺血管内血栓。与单纯冷保存比较, 保存相同时间后, 机械灌注组更能维持胰岛的完整性。     

Effects of 1 to 3 years' treatment with alendronate on mechanical properties of the femoral shaft in a canine model: Implications for subtrochanteric femoral fracture risk

Bisphosphonate (BP) treatment used to prevent bone loss in postmenopausal osteoporosis has recently been implicated in an apparent increase in subtrochanteric femoral fractures. Previous work showed that BPs can reduce the energy to fracture of cancellous bone, but limited data exist on material‐level mechanical properties of compact bone from the long bones. This study examined intrinsic mechanical properties of the femoral diaphysis of a canine model treated for 1 or 3 years with alendronate at two different doses. Seventy‐two dogs were treated orally with 0.2 mg/kg/day alendronate or 1.0 mg/kg/day alendronate; a control group was administered saline. Prismatic beam specimens were tested in four‐point bending under displacement control, and the intrinsic mechanical properties were calculated. No significant differences were found among groups in any mechanical property at either 1 or 3 years of treatment. We conclude that the material properties of the femoral diaphysis are not degraded following 1 to 3 years treatment with alendronate, even at high doses. Longer periods of treatment have not been studied using clinical doses of alendronate, but such studies need to be carried out to confirm a lack of effect of alendronate on mechanical properties of cortical bone in the subtrochanteric region of the femur. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1288–1292, 2009     

The quantification of ADAMTS expression in an animal model of cerebral ischemia using real-time PCR

BACKGROUND: ADAMTS1 and ADAMTS8 are proteases involved in extracellular matrix proteolysis and antiangiogenesis, but little is known about their expression and function in cerebral ischemia. We investigated the changes in ADAMTS1 and ADAMTS8 in a rat model of permanent middle cerebral artery occlusion (pMCAO). The expressions of glyseraldehyde-3-phosphate dehydrogenase (GAPDH), beta-actin, cyclophilin, and RPL13A were examined in order to validate the appropriate housekeeping genes for a long duration after inducing cerebral ischemia. METHODS: Male Sprague-Dawley rats were subjected to pMCAO, and ischemic penumbra was collected at 2, 24 h, 3, 7, and 21 days after inducing ischemia, ADAMTS1, ADAMTS8, and the four housekeeping genes were quantified using real-time polymerase chain reaction (PCR). RESULTS: The expression of beta-actin increased up to 21 days, and that of GAPDH decreased at 24 h after pMCAO, with no statistically significant changes in RPL13A and cyclophilin being detected. ADAMTS1 mRNA increased at 2 h after pMCAO, peaked at 24 h, and remained at a high level until 21 days. The expression of ADAMTS8 mRNA decreased at 2 and 24 h after pMCAO, followed by a slight increase at 3 days, and then decreased again at 7 days. CONCLUSION: The results suggest that RPL13A and cyclophilin are two appropriate housekeeping genes for the rat pMCAO model up to 21 days. ADAMTS1 mRNA levels increased, but ADAMTS8 decreased after pMCAO. Our data provide new insight into the mechanism of brain ischemia and self-repair after injury.     

硝普钠对大鼠局脑缺血/再灌注后神经型一氧化氮合酶的影响

目的 观察硝普钠(sodium nitroprusside,SNP)对大鼠局灶性脑缺血再灌注后海马区神经型一氧化氮合酶(neuronal nitricoxide synthase,nNOs)表达的影响及在脑保护作用中的机制. 方法108只健康雄性SD大鼠,体重250 g～300 g,采用线栓法建立大鼠左侧大脑中动脉(middle cerebral artery,MCA)梗塞局灶性脑缺血模型,随机分为3组,每组36只.正常对照组(C组):左侧脑室内注射生理盐水5μl后,暴露颈内动脉但不栓塞MCA;局灶性脑缺血组(I组):左侧脑室内注射生理盐水5μl后,栓塞MCA 2 h;硝普钠组(s组):左侧脑室内注射硝普钠0.055 mg,kg(溶于5μl生理盐水中)后,栓塞MCA 2 h.各实验组按不同再灌注时间随机分为3个亚组(n=12):分别为冉灌注2 h组、6 h组和12 h组.各实验组于动物清醒后进行神经学功能评分;苏木素咿红(HE)染色,观察脑组织病理学改变;免疫组织化学(IH)法测定海马区nNOS蛋白表达;半定量逆转录-聚合酶链反应(RT-PCR)法测定海马区nNOS mRNA表达. 结果 I组和S组各亚组神经细胞死亡率均高于C组(P<0.05);与I组2 h(43.8±2.1)、6 h(73.9±4.7)亚组比较,S组2 h(36.5±1.2)、6 h(42.6±1.9)亚组神经细胞死亡率降低(P<0.05).I组和S组各亚组nNOS mRNA的表达均高于C组(P<0.05);与I组2 h(0.472 1±0.011 5)、6 h(0.744 2±0.011 6)亚组比较,S组2 h(0.428 3±0.000 4)、6 h(0.482 7±0.005 2)亚组nNOS mRNA的表达降低(P<0.05).I组和S组各亚组nNOS蛋白表达,除S组6 h亚组外,均高于C组(9<0.05);与I组2 h(0.265 8±0.000 5)、6 h(0.284.0±0.0134)亚组比较,S组2 h(0.251 4±0.001 1)、6 h(0.25 9±0.0040)亚组nNOS蛋白的表达降低(P<0.05).结论 硝普钠对大鼠局灶性脑缺血/再灌注损伤有保护作用,其机制可能与抑制nNOS的表达有关.     

The effect of intracranial hypotension on cerebral blood flow in a feline model

Summary Intracranial hypotension is a known clinical entity but its pathophysiology has been meagerly studied. Any setting with cerebrospinal fluid leakage or drainage can cause intracranial hypotension. A feline model of kaolin induced chronic hydrocephalus with controlled cerebrospinal fluid drainage from a lateral ventricle yields reproducible intracranial hypotension of up to –15 torr for several hours to –80 torr of about 10 minutes. The magnitude of this hypotension is significantly greater than can be attained by cisterna magna drainage. This new model allows multiple cerebral parameters to be studied during intracranial hypotension.In 11 cats with stable blood pressure and intracranial hypotension of at least –15 torr, regional blood flow utilizing the hydrogen clearance method in the cerebral cortex and subcortical nuclei was unchanged relative to the baseline. These results imply that: 1) cerebral vascular autoregulation is maintained during significantly increased perfusion pressure due to negative intracranial pressure, 2) the symptomatology of clinical intracranial hypotension is not due to decreased cerebral perfusion.     

Effects of sevoflurane on intracranial pressure, cerebral blood flow and cerebral metabolism: A dose-response study in patients subjected to craniotomy for cerebral tumours

Background: Studies concerning the cerebrovascular effects of sevoflurane in patients with space-occupying lesions are few. This study was carried out as a dose-response study comparing the effects of increasing sevoflurane concentration (1.5% (0.7 MAC) to 2.5% (1.3 MAC)) on cerebral blood flow (CBF), intracranial pressure (ICP), cerebrovascular resistance (CVR), metabolic rate of oxygen (CMRO₂) and CO₂-reactivity in patients subjected to craniotomy for supratentorial brain tumours.
Methods: Anaesthesia was induced with propofol/fentanyl/atracurium and maintained with 1.5% sevoflurane in air/oxygen at normocapnia. Blood pressure was maintained constant by ephedrine. In group 1 (n=10), the patients received continuously 1.5% sevoflurane. Subdural ICP, CBF and CMRO₂ were measured twice at 30-min intervals. In group 2 (n=10), sevoflurane concentration was increased from 1.5% to 2.5% after CBF₁. CBF₂ was measured after 20 min during 2.5% sevoflurane. Finally, CO₂-reactivity was studied in both groups.
Results: In group 1, no time-dependent alterations in CBF, CVR, ICP and CMRO₂ were found. In group 2, an increase in sevoflurane from 1.5% to 2.5% resulted in an increase in CBF from 29 ± 10 to 34±12 ml 100g⁻¹ min⁻¹ and a decrease in CVR from 2.7±0.9 to 2.3±1.2 mmHg ml⁻¹ min 100g ( P <0.05), while ICP and CMRO₂ were unchanged. CO₂-reactivity was maintained at 1.5% and 2.5% sevoflurane.
Conclusion: Sevoflurane is a cerebral vasodilator in patients with cerebral tumours. Sevoflurane increases CBF and decreases CVR in a dose-dependent manner. CO₂-reactivity is preserved during 1.5% and 2.5% sevoflurane.     

EPO在犬蛛网膜下腔出血模型中对脑血管痉挛的影响

目的观察促红细胞生成素（erythropoietin,EPO）在蛛网膜下腔出血模型中的血管影象学改变及NO含量的改变,从而推测EPO对血管痉挛的治疗作用。方法27只健康成年犬随机分为阴性对照组、单纯注血组和EPO治疗组,于动物模型制作成功后1h、3rdday、7thday和14thday行全脑血管造影术了解血管痉挛情况,并采集脑脊液及血浆标本,测定其一氧化氮（Nitric oxide,NO）含量变化。结果在单纯注血组中,脑血管造影结果提示基底动脉在第3天发生明显的血管痉挛,在第7天达到高峰,第14天有较大改善,血浆及脑脊液中的一氧化氮（NO）浓度也有同样变化（P〈0.01）。在EPO治疗组和阴性对照组中,脑血管造影的结果和血清及脑脊液中NO的变化没有显著差异（P〉0.05）,但与单纯注血组比有显著性差异（P〈0.01）。结论NO是脑组织内最重要的血管舒张因子,对维持正常脑血管功能具有重要作用。本实验从影象学和NO变化两个角度提示EPO在脑血管痉挛发生中具有重要的保护作用。     

Regional cerebral blood flow after omental transposition to the ischaemic brain in man. A five year follow-up study

Summary Regional cerebral blood flow, recorded by the¹³³Xenon inhalation method, was measured preoperatively and over a five years postoperative period in six patients with completed stroke and stabilized neurological deficits, who had undergone omental transposition for revascularization of the ischaemic brain. Comparisons of the preoperative blood flow values with those recorded following surgery demonstrate a postoperative increase of blood flow in five patients, with a high statistical degree of significance in four of them at the final examination. The flow increase was noted over the infarcted areas of the brain, upon which the omentum had been placed, as well as areas of the ischaemic hemisphere without omental placement and the contralateral hemisphere. Out of the five patients who demonstrated preoperative flow values below the expected norm for age, four showed final postoperative cerebral blood flow within the normal limits for their age. The results are consistent with the assumption that the transposed omentum played a role in postoperative blood flow increase, by adding collateral circulation to the ischaemic brain.     

A simple method of using a foley catheter to drain pleural effusion

Pleural effusion is a common problem, and various techniques of pleural fluid drainage have been described. We report our experience of using a Foley-type catheter to drain pleural effusion. After the injection of local anesthesia, the catheter is inserted, usually through the 7th intercostal space, with the patient sitting upright. The size of the catheter is selected according to the predicted fluid characteristics, and ranges from 18 to 24 F. Once the catheter is positioned in the pleural space, the balloon is inflated with diluted soluble contrast material and connected to a urine collection bag. During the last 10 years, we have used 3500 catheters for this purpose. The catheter site can be used as a port for various procedures, including needle biopsy of the parietal pleura, talc-slurry pleurodesis, and intra-pleural fibrinolysis. This method of pleural drainage is simple, reliable, and inexpensive.     

Collagen V haploinsufficiency in a murine model of classic Ehlers–Danlos syndrome is associated with deficient structural and mechanical healing in tendons

Classic Ehlers–Danlos syndrome (EDS) patients suffer from connective tissue hyperelasticity, joint instability, skin hyperextensibility, tissue fragility, and poor wound healing due to heterozygous mutations in COL5a1 or COL5a2 genes. This study investigated the roles of collagen V in establishing structure and function in uninjured patellar tendons as well as in the injury response using a Col5a1^+/− mouse, a model for classic EDS. These analyses were done comparing tendons from a classic EDS model (Col5a1^+/− ) with wild‐type controls. Tendons were subjected to mechanical testing, histological, and fibril analysis before injury as well as 3 and 6 weeks after injury. We found that Col5a1^+/− tendons demonstrated diminished recovery of mechanical competency after injury as compared to normal wild‐type tendons, which recovered their pre‐injury values by 6 weeks post injury. Additionally, the Col5a1^+/− tendons demonstrated altered fibril morphology and diameter distributions compared to the wild‐type tendons. This study indicates that collagen V plays an important role in regulating collagen fibrillogenesis and the associated recovery of mechanical integrity in tendons after injury. In addition, the dysregulation with decreased collagen V expression in EDS is associated with a diminished injury response. The results presented herein have the potential to direct future targeted therapeutics for classic EDS patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2707–2715, 2017.

     

Proximal superficial temporal artery to proximal middle cerebral artery bypass using a radial artery graft: an anatomic approach

We present the use of radial artery graft for bypass of the proximal superficial temporal artery to the proximal middle cerebral artery. Six adult cadaver sites were used bilaterally. After apterional incision, 2×2-cm minicraniectomy was performed which began 2 cm behind the zygomatic process of the frontal bone. The superficial temporal artery was transsected before exposing the zygomatico-orbital artery branch. The proximal side of the radial artery graft was anastomosed end-to-end to the proximal superficial temporal artery and the distal side end-to-side to the proximal middle cerebral artery. The mean calibers of the proximal superficial temporal artery and largest trunk of the middle cerebral artery were 2.25±0.35 mm and 2.3±0.3 mm, respectively. The average graft length was 85±5.5 mm. We conclude that such bypasses are simpler than proximal middle cerebral artery revascularization using long vein grafts. This method proves that the caliber of the proximal superficial temporal artery is more suited to providing sufficient flow than the distal superficial temporal artery, and the graft is short. Such bypasses to the middle cerebral artery may be an alternative to those from the distal superficial temporal artery or extracranial carotid artery.