Quantitative in Vivo Detection of Brain Cell Death after Hypoxia Ischemia Using the Lipid Peak at 1.3 ppm of Proton Magnetic Resonance Spectroscopy in Neonatal Rats

This study was performed to determine the accuracy of proton magnetic spectroscopy (1H-MRS) lipid peak as a noninvasive tool for quantitative in vivo detection of brain cell death. Seven day-old Sprague Dawley rats were subjected to 8% oxygen following a unilateral carotid artery ligation. For treatment, cycloheximide was given immediately after hypoxic ischemia (HI). Lipid peak was measured using 1H-MRS at 24 hr after HI, and then brains were harvested for fluorocytometric analyses with annexin V/propidium iodide (PI) and fluorescent probe JC-1, and for adenosine-5'-triphosphate (ATP) and lactate. Increased lipid peak at 1.3 ppm measured with 1H-MRS, apoptotic and necrotic cells, and loss of mitochondrial membrane potential (DeltaPsi) at 24 hr after HI were significantly improved with cycloheximide treatment. Significantly reduced brain ATP and increased lactate levels observed at 24 hr after HI showed a tendency to improve without statistical significance with cycloheximide treatment. Lipid peak at 1.3 ppm showed significant positive correlation with both apoptotic and necrotic cells and loss of DeltaPsi, and negative correlation with normal live cells. Lipid peak at 1.3 ppm measured by 1H-MRS might be a sensitive and reliable diagnostic tool for quantitative in vivo detection of brain cell death after HI.

Neuroprotective Effects of Growth Hormone Against Hypoxic-Ischemic Brain Injury in Neonatal Rats: 1H Magnetic Resonance Spectroscopic Study

Using 1H-MRS, we evaluated the effects of growth hormone (GH) as a caspase inhibitor on hypoxic-ischemic injury in neonatal rat brains. The right common carotid arteries of rats were ligated, allowed to recover for 3 hr, and exposed to 8% oxygen for 2 hr. GH was given just prior to HI insult and animals were divided into four groups: control, intracerebroventricular (ICV), intracerebroventricular/intraperitoneal (ICV/IP), and intraperitoneal (IP). Localized in vivo 1H-MRS and TUNEL staining were performed 24 hr after HI injury. Lipid/N-acetyl aspartate (NAA) and lipid/creatine (Cr) ratios were used as apoptotic markers. Gross morphologic changes at 2 weeks were used to evaluate the effects of GH. The lipid/NAA ratio was lower in the ICV and ICV/IP groups than in the control, and the lipid/Cr ratio was lower in the ICV group than in the control. The number of TUNEL positive cells was decreased in the ICV and ICV/IP groups, and the degree of morphologic change indicative of brain injury was lower in the ICV group and somewhat lower in the ICV/IP group. The degree of morphologic change correlated with the lipid/NAA and lipid/Cr ratios. These findings suggest that GH exerts neuroprotective effects in cerebral hypoxicischemic injury.

The Protective Effect of Ischemic and Hypoxic Preconditioning on Hypoxic-ischemic Brain Injury in the Neonatal Rat: 1H Magnetic Resonance Spectroscopic Study / 대한마취과학회지

BACKGROUND: A brief episode of cerebral ischemia confers transient ischemic tolerance to a subsequent ischemic challenge. We examined the effect of ischemic and hypoxic preconditioning in the neonatal rat. METHODS: Seven-day old Sprague-Dawley rat pups were divided into three groups:control (n = 53), ischemic preconditioning (n = 51), and hypoxic preconditioning (n = 48). For ischemic preconditioning, the right common carotid artery was occluded for 10 min. Rats in the hypoxic preconditioning group were kept under hypoxic (8% oxygen/92% nitrogen) conditions for 4h. Twenty-four hours after the preconditioning, rats from all groups were exposed to the right common carotid artery ligature, followed by 2.5 h of hypoxia. Lipid/N-acetyl aspartate (Lip/NAA) and lipid/creatine (Lip/Cr) ratios from 1H MR spectroscopy and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) were evaluated as measures of apoptosis 1 and 7 days after hypoxic-ischemic injury. RESULTS: In the ischemic and hypoxic preconditioning groups, the Lip/NAA and Lip/Cr ratios and the numbers of TUNEL-positive cells were significantly lower than those in the control group (P < 0.05), but there were no significant differences between the two preconditioning groups. CONCLUSIONS: These results suggest that ischemic and hypoxic preconditioning in the neonatal rat attenuate the apoptosis that is caused by hypoxic-ischemic brain injury.

Localized 1H-MR Spectroscopy in Moyamoya Disease before and after Revascularization Surgery

OBJECTIVE: To evaluate, using localized proton magnetic resonance spectroscopy (1H-MRS), the cerebral metabolic change apparent after revascularization surgery in patients with moyamoya disease. MATERIALS AND METHODS: Sixteen children with moyamoya disease and eight age-matched normal controls underwent MR imaging, MR angiography, conventional angiography, and 99mTc- ECD SPECT. Frontal white matter and the basal ganglia of both hemispheres were subjected to localized 1H-MRS, and after revascularization surgery, four patients underwent follow-up 1H-MRS. RESULTS: Decreased NAA/Cr ratios (1.35+/-0.14 in patients vs. 1.55+/-0.24 in controls) and Cho/Cr ratios (0.96+/-0.13 in patients vs. 1.10+/-0.11 in controls) were observed in frontal white matter. After revascularization surgery, NAA/Cr and Cho/Cr ratios in this region increased. In the basal ganglia, there is no abnormal metabolic ratios. CONCLUSION: Localized 1H-MRS revealed abnormal metabolic change in both hemispheres of children with moyamoya disease. Because of its non-invasive nature, 1H-MRS is potentially useful for the preoperative evaluation of metabolic abnormalities and their postoperative monitoring.

Early Prediction of Hypoxic-Ischemic Brain Damage in Newbon Rats Using Proton Magnetic Resonance Spectroscopy and Neuroprotective Effect of EGb 761

PURPOSE: This study was designed to evaluated the relationship between the morphological changes of hypoxic-ischemic injured brain and the magnetic resonance spectroscopic (MRS) findings, and the efficacy of Egb 761, a free radical scavenger, as a neuroprotective agent for hypoxic-ischemic brain injury. METHODS: Seven-day old Sprague-Dawley rat pups were used. Right common carotid artery was ligated under halothene anesthesia. After a recovery period of 3 hours, they were divided into two groups : for group 1, EGb 761 100 mg/kg (treatment group) and for group 2, normal saline (control group) were given intraperitoneally. Both groups were exposed to 8% oxygen at 37degrees C for 90 minutes. Sixty-four rat pups (30 control, 34 treatment group) were examined with localized 1H MRS on days 1 and 7 after the hypoxic insult. One day 14, the degree of brain injury was scored by morphological changes. RESULTS: The 1H MRS obtained on day 1 after the hypoxic insult showed increased Lip/NAA and Lip/Cr ratios in the right cerebral hemisphere in comparison with those in the left hemisphere (P<0.01). The degree of morphological changes of the brain injury on day 14 correlated with both Lip/NAA and Lip/Cr ratios obtained on days! and 7 after the hypoxic insult [r=0.410, 0.457 on day 1, and r=0.749, 0.720 on day 7, respectively (P< 0.01)]. The therapeutic potential of EGb 761 for the hypoxic-ischemic brain seemed insignificant, as was evident from no differences between the control group and the EGb 761 treatment group in the Lip/NAA and Lip/Cr ratios as well as in morphological changes. CONCLUSION: Early changes of Lip/NAA and Lip/Cr ratios in the 1H MRS seems to be related to the degree of morphological changes in the rat brain of hypoxic-ischemic injury. Therefore, the increased lipid content of brain observed by 1H MRS can be used as a marker to predict the degree of the hypoxic-ischemic injury. The neuroprotectiveeffect of EGb 761 in hypoxic-ischemic brain injury is insignificant.

Gadomer-17 in Contrast Enhanced MR Imaging of Reperfused Myocardial Infarction in a Cat Model

PURPOSE: To evaluate in reperfused myocardial infarction in a cat model, the time-course of signal enhancement as seen on Gadomer-17 enhanced MRI, and to correlate the size of the enhanced area with that of the infarct area as revealed by on histochemical examination. MATERIALS AND METHODS: Five cats which had undergone occlusion of the LAD followed by reperfusion underwent MR imaging. After T2-weighted imaging, Gadomer-17 enhanced T1-weighted images were obtained in four cats during a six-hour period, and in one during a three-hour period. Signal intensities were measured in the enhanced and non-enhanced areas of enhanced T1-weighted images. and using 2,3,5-triphenyl tetrazolium chloride (TTC) histochemical staining, the size of the abnormal signal area on each image was compared with that of the infarct area. RESULT: The enhanced area seen on enhanced T1-weighted images showed rapidly increased signal intensity following the administration of Gadomer-17. Maximum enhancement was detected during a 40 -60 minutes period, with an average enhancement of 168 +/-9.9% of normal myocardium. TTC staining revealed that the size of the high signal area on T2-weighted images and of the enhanced area on enhanced T1-weighted images was greater than that of the infarct area (p<0.05). CONCLUSION: In reperfused myocardial infarction in a cat model, Gadomer-17 enhanced MR imaging delineates both reversibly and irreversibly damaged myocardium, with strong enhancement and a broad temporal window. We may therefore expect that Gadomer-17 is useful for demonstrating myocardial injury.

Myocardial Assessment during Subacute Stage after Ischemia-Reperfusion: Gd-DTPA-polylysine Enhanced MR Imagingin Cats

PURPOSE: To investigate changes in the size and degree of signal enhancement of reperfused myocardium during the subacute stage of an ischemic episode, using Gd-DTPA-polylysine enhanced magnetic resonance imaging. MATERIALS AND METHODS: In six cats, the left anterior descending artery was occluded for 150 minutes, and this was followed by reperfusion. Contrast enhanced T1-weighted spin echo magnetic resonance imaging using gadolinium diethylene triamine penta acetic acid-polylysine (Gd-DTPA-polylysine) was performed on the 1st , 2nd, and 6th days of the reperfusion period. The size of ischemic myocardium was estimated each day on MR images by measuring the size of signal enhanced area and the degree of signal enhancement according to time was measured. After sacrificing the animals on day 6, the myocardial specimen was histochemically stained with 2,3,5-triphenyltetrazoliumchloride(TTC). RESULTS: Signal enhancement and the size of the ischemic myocardium, as seen on MR images,decreased linearly during the six days of the subacute stage. On the 6th day, however, signal intensity was still higher than that of normal myocardium, and the size of signal enhanced area measured on MR images was significantly larger than on TTC-stained specimens (p<0.001). CONCLUSION: We conclude that the size of enhanced area and degree of signal enhancement decreased linearly during the subacute stage of reperfused myocardialinfarction and that the area of MR signal enhancement during the acute stage includes both irreversibly andreversibly damaged myocardium.