Acute restraint-mediated increases in glutamate levels in the rat brain: an in vivo ¹H-MRS study at 4.7 T.

It is well known that a variety of stressors induces a significant alteration in various putative neurotransmitters in the mammalian CNS. However, relatively little attention has been paid on the alteration of central glutamate neurotransmission, which is a major excitatory neurotransmitter in the brain. The present study aimed to determine whether acute restraint stress induces the changes in neurotransmitter level, especially glutamate, in rat brain and to examine whether 1-h recovery time after the termination of stress can revert to its pre-stress state. In vivo ¹H-NMR spectra were acquired from the cerebral cortex and hippocampus (control: N = 10, stress: N = 10, stress + 1 h rest: N = 10) immediately or after 1 h rest from restraint stress. All in vivo proton spectra were automatically analyzed using LCModel. We found that acute restraint stress induced significant increase in glutamate concentrations in the cerebral cortex and the hippocampus of rat. However, the level could not revert to its pre-stress state by the end of 1-h recovery period in cerebral cortex of rats. In addition, glutamine/glutamate ratio, which may function as an index of the glutamatergic neurotransmission, was significantly lower in the cerebral cortex of both stress and 1 h stress + 1 h recovery groups, as compared to control. Our finding may provide important evidence for altered glutamatergic activity after the stress and suggest a potential biochemical marker for eventual diagnosis and/or therapy monitoring in mood disorder.

Tracheal replacement with fresh and cryopreserved aortic allograft in adult dog.

BACKGROUND: Many reports have described tracheal replacement using aortic allografts, with varying results and minimal understanding of the mechanism of tracheal regeneration. The present study attempted tracheal regeneration in adult dogs using fresh aortic allografts (FAA) and cryopreserved aortic allografts (CAA). MATERIALS AND METHODS: Twelve adult beagles underwent tracheal resection and were transplanted with FAA (n = 5) or CAA (n = 7). Animals were followed-up with serial radiography and magnetic resonance imaging, and were euthanized at predetermined times up to 16 mo post-surgery. RESULTS: There were no procedural deaths, but two animals died due to stent migration. Stent migration occurred in seven of the 12 animals. Evidence of regeneration of tracheal epithelium was observed in the surviving animals, with the transformation of squamous metaplasia to mucociliary epithelium being time-dependent. Islet of cartilage were observed in animals after 6 mo, but ring-like cartilage structures were absent, even after 16 mo. During autopsy, axial graft contractions up to 68% were observed. Serial radiographs show that most of the contraction occurred within 1 mo. The results of the MRI showed that the graft area was strongly enhanced for up to 2 mo, but was clearly reduced after 3 mo. CONCLUSIONS: Tracheal replacement in adult dogs using FAA or CAA is feasible. However, immaturity of the neotracheal cartilage did not allow the tissue to function as native tracheal tissue. Prolonged stenting should be considered in adult if the procedure is to be clinically contemplated.

In vivo and ex vivo evidence for ketamine-induced hyperglutamatergic activity in the cerebral cortex of the rat: Potential relevance to schizophrenia.

Subanesthetic doses of ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, impair prefrontal cortex (PFC) function in the rat and produce symptoms in humans similar to those observed in patients with schizophrenia. In the present study, in vivo (1) H-MRS and ex vivo (1) H high-resolution magic angle spinning (HR-MAS) spectroscopy was used to examine the brain metabolism of rats treated with subanesthetic doses of ketamine (30 mg/kg) for 6 days. A single voxel localization sequence (PRESS, TR/TE = 4000/20 ms and NEX=512) was used to acquire the spectra in a 30-µl voxel positioned in the cerebral cortex (including mainly PFC) of the rats (ketamine group: n=12; saline group: n=12) anesthetized with isoflurane. After the in vivo (1) H-MRS acquisition, the animals were sacrificed and the cerebral cortex tissues were extracted (ketamine group: n=7; saline group: n=7) for ex vivo (1) H HR-MAS spectroscopy (CPMG sequence, 2.0-s presaturation delay, 2.0-s acquisition time, 128 transients and 4-ms inter-pulse delay) using a 500-MHz NMR spectrometer. All proton metabolites were quantified using the LCModel. For the in vivo spectra, there was a significant increase in glutamate concentration in the cerebral cortex of the ketamine group compared with the controls (p<0.05). For the ex vivo HR-MAS spectra, there was a significant increase in the glutamate/total creatine ratio, and a decrease in the glutamine/total creatine and glutamine/glutamate ratios in the cerebral cortex tissue of the ketamine group compared with the controls. The results of the present study demonstrated that administration of subanesthetic doses of ketamine in the rat may exert at least part of their effect in the cerebral cortex by activation of glutamatergic neurotransmission.

Differential neurochemical responses of the canine striatum with pentobarbital or ketamine anesthesia: a 3T proton MRS study.

Although anesthetic agents are known to affect cerebral metabolism, pentobarbital and ketamine have been widely used for animal imaging studies. The purpose of this study is to evaluate alterations in striatum metabolites in dogs between anesthetized with pentobarbital and with ketamine in proton magnetic resonance spectroscopy ((1)H-MRS). (1)H-MRS was performed to ten healthy adult beagle dogs (9-11 kg) at a field strength of 3 T in order to identify metabolic changes after pentobarbital or ketamine administration in the striatum in vivo. Ten dogs were divided into 2 groups as follows: 5 as the pentobarbital-administered group (P group) and 5 as the ketamine-administered group (K group). We found that levels of Glx of the P group was significantly lower than that of the K group (6.90 +/- 0.99 (SD) vs 9.77 +/- 1.14 in 5 dogs, p= 0.003). In addition, the P group also has lower levels of Cr (6.29 +/- 0.44 vs 7.89 +/- 0.91 in 5 dogs, p=0.009) and NAA (5.02 +/- 0.65 vs 6.45 +/- 1.13 in 5 dogs, p=0.041) compared to the K group. However, there were no significant difference between the P group and the K group in striatal levels of Cho and Ins (p>0.1). We demonstrated that MRS-measured metabolites in the specific regions of the brain can be influenced by anesthetic agents.

Intraarterially delivered human umbilical cord blood-derived mesenchymal stem cells in canine cerebral ischemia.

The present study examined the effects of human umbilical cord blood-derived mesenchymal stem cells (HUCB-derived MSCs) delivered through the basilar artery in a canine thromboembolic brain ischemia model. Cerebral ischemia was induced through occlusion of the middle cerebral artery by injecting thrombus emboli into 10 beagles. In the HUCBC group (n = 5), 1 x 10(6) HUCB-derived MSCs were transplanted through the basilar artery 1 day after ischemic induction using an endovascular interventional approach. In the control group (n = 5), phosphate-buffered saline (PBS) was injected in the same manner in as the HUCBC group. Upon neurobehavioral examination, earlier recovery was observed in the HUCBC group. The HUCBC group showed a decrease in the infarction volume at 1 week after cerebral ischemic induction, whereas the control group showed an increase in the infarction volume at 1 week, by magnetic resonance image analysis. Transplanted cells had differentiated into neurons and astrocytes and were observed in and around endothelial cells that were positive for von Willebrand factor (vWF). HUCB-derived MSCs expressed neuroprotective factors, such as brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), at 4 weeks after the transplantation. The transplanted cells demonstrated their efficacy by reducing the infarction lesion volume and through earlier recovery from the neurological deficit. These results suggest that intraarterial transplantation of HUCB-derived MSCs could be useful in clinical treatment of cerebral ischemia.

Development of an improved canine model of percutaneous spinal cord compression injury by balloon catheter.

We developed a minimally invasive canine model of spinal cord injury (SCI). A balloon catheter was inserted into the epidural space via the lumbosacral space, and inflated between L2 and L3 for 30 or 60 min under fluoroscopic guidance. Motor function after SCI was assessed using modified Tarlov scale. All seven dogs showed complete paraplegia after the procedure, neurological problems were evident and the modified Tarlov scores remained at zero after the SCI procedure; no improvement in clinical signs was observed. The dogs underwent 3T MR imaging at 3 days and 1 year after SCI. Histopathologic examinations were conducted at 2 weeks, 12 weeks and 1 year after SCI. In the present study, we described an animal model of minimally invasive spinal cord injury using a balloon catheter without laminectomy under fluoroscopic guidance. And, this percutaneous spinal cord compression injury model has many potential applications. The described percutaneous spinal cord compression injury model offers a new means of administering SCI and has many potential applications.

A proposed transpositional acupoint system in a mouse and rat model.

In acupuncture, the specificity of the point and the reproducibility of the location of the point are prerequisite to the specificity and reproducibility of research involving acupuncture stimulation. The transpositional method, which locates animal acupoints (AAs) on the surface of animal skin corresponding to the anatomic site of a human acupoint, has been generally adopted for research modeling. However, there remains a lack of consensus on the specific location of AA among researchers. The potential problems that the discrepancy in acupoint locating methods causes include the attempt to compare research results. This report is a conceptual study that calls attention to the problems of inconsistency in AA location, and proposes a transpositional 121 AA system in a mouse and rat model. Further discussion, and the establishment of reproducible transpositional AA systems, will prompt further quantitative research and exchange of scientific ideas.

Variation of the choline signal intensity in the dorsolateral prefrontal cortex of rats exposed to the forced swimming test as detected by in vivo 1H MR spectroscopy.

BACKGROUND: (1)H magnetic resonance spectroscopy (MRS) has documented an increased Cho/Cr ratio in the dorsolateral prefrontal cortex (DLPFC) in major depressive disorder (MDD). The aim of this study was to investigate neurochemical alterations in the left DLPFC, considered a main area of pathogenesis in depression, using rats exposed to the forced swimming test (FST). MATERIALS AND METHODS: Twenty-four male rats were used for the MRI and in vivo(1)H MRS studies. Rats exposed to the FST to induce a depressed mental status. Using in vivo(1)H MRS, the metabolite ratios of the rats with a depressed mental status and the controls, were measured and the values of the two groups were compared. RESULTS: The Cho/Cr and Cho/NAA ratios in the DLPFC of the rats with a depressed mental status were significantly higher than that in the controls. CONCLUSIONS: The present study demonstrates a significantly increased Cho/Cr ratio in the DLPFC of rats with depression compared with controls. This result may suggest an accelerated turnover of membrane without neuronal loss is occurring in the DLPFC of the rats with depression.

Expression of neurotrophic factors in injured spinal cord after transplantation of human-umbilical cord blood stem cells in rats.

We induced percutaneous spinal cord injuries (SCI) using a balloon catheter in 45 rats and transplanted human umbilical cord blood derived mesenchymal stem cells (hUCB-MSCs) at the injury site. Locomotor function was significantly improved in hUCB-MSCs transplanted groups. Quantitative ELISA of extract from entire injured spinal cord showed increased expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3). Our results show that treatment of SCI with hUCB-MSCs can improve locomotor functions, and suggest that increased levels of BDNF, NGF and NT-3 in the injured spinal cord were the main therapeutic effect.

In vivo 1H MR spectroscopic findings in traumatic contusion of ICR mouse brain induced by fluid percussion injury.

PURPOSE: The purpose of this study was to investigate the proton metabolic differences of the right parietal cortex with experimental brain contusions of ICR mouse induced by fluid percussion injury (FPI) compared to normal controls and to test the possibility that 1H magnetic resonance spectroscopy (MRS) findings could provide neuropathologic criteria in the diagnosis and monitoring of traumatic brain contusions. MATERIALS AND METHODS: A homogeneous group of 20 ICR male mice was used for MRI and in vivo 1H MRS. Using image-guided, water-suppressed in vivo 1H MRS with a 4.7 T MRI/MRS system, we evaluated the MRS measurement of the relative proton metabolite ratio between experimental brain contusion of ICR mouse and healthy control subjects. RESULTS: After trauma, NAA/Cr ratio, as a neuronal marker decreased significantly versus controls, indicating neuronal loss. The ratio of NAA/Cr in traumatic brain contusions was 0.90+/-0.11, while that in normal control subjects was 1.13+/-0.12 (P=0.001). The Cho/Cr ratio had a tendency to rise in experimental brain contusions (P=0.02). The Cho/Cr ratio was 0.91+/-0.17, while that of the normal control subjects was 0.76+/-0.15. However, no significant difference of Glx/Cr was established between the experimental traumatic brain injury models and the normal controls. DISCUSSION AND CONCLUSIONS: The present 1H MRS study shows significant proton metabolic changes of parietal cortex with experimental brain contusions of ICR mouse induced by FPI compared to normal controls. In vivo 1H MRS may be a useful modality for the clinical evaluation of traumatic contusions and could aid in better understanding the neuropathologic process of traumatic contusions induced by FPI.

Infiltrative lipoma in cervical bones in a dog.

A 4-year-old, neutered male Maltese presented with a 2-month history of right hemiparesis. The radiographic findings revealed bone lysis, and sclerotic changes in the right section of the fifth and sixth cervical bones with a mild radiolucent mass around the lesion. The magnetic resonance imaging revealed a hyperintense mass located in the region extending from the muscles to the bones and compressing the spinal cord. The mass was removed via a hemilaminectomy in the cervical area using the ventral and dorsal approach, and a histological examination confirmed that it was adipose tissue. An infiltrative lipoma was diagnosed based on these findings. The dog has ambulated normally for 24 months since undergoing surgery.

Neural pathway interference by retained acupuncture: a functional MRI study of a dog model of Parkinson's disease.

OBJECTIVE: The aims of this study were to investigate the interference of the brain activation during a passive movement task (PMT) by retained acupuncture at the ST 36 acupoint and to compare these effects between normal brain and Parkinson's disease (PD) brain. METHODS: Functional magnetic resonance imaging (fMRI) techniques have been used to study neurophysiology in animals. Eight healthy beagle dogs were divided into two groups of four dogs each, a normal control group and a PD model group. PD was induced by intravenous injection of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-HCl. During fMRI, the PMT was performed in the right tarsal joint during three different sessions, which consisted of PMT only, PMT while an acupuncture needle was inserted at the ST 36 acupoint, and PMT while needle was inserted at a sham point. RESULTS AND DISCUSSION: Standard veterinary neurological examination was performed on dogs with MPTP-induced PD. A homogeneous grade similar to human PD patients was evident in all dogs. The fMRI study showed that insertion of the acupuncture needle at acupoint ST 36 significantly affected the proprioceptive brain activation by decreasing blood oxygenation level-dependent signal intensity in basal ganglia, limbic system, and cerebellum. Compared with normal and PD brain, we suggest that acupuncture at ST 36 has different modulation effects depending on the pathologic condition of the brain. The study provides evidence of the potential clinical applications of retained acupuncture at ST 36 for rehabilitation therapy of PD patients.

Improved rat spinal cord injury model using spinal cord compression by percutaneous method.

Here, percutaneous spinal cord injury (SCI) methods using a balloon catheter in adult rats are described. A balloon catheter was inserted into the epidural space through the lumbosacral junction and then inflated between T9-T10 for 10 min under fluoroscopic guidance. Animals were divided into three groups with respect to inflation volume: 20 µL (n = 18), 50 µL (n = 18) and control (Fogarty catheter inserted but not inflated; n = 10). Neurological assessments were then made based on BBB score, magnetic resonance imaging and histopathology. Both inflation volumes produced complete paralysis. Gradual recovery of motor function occurred when 20 µL was used, but not after 50 µL was applied. In the 50 µL group, all gray and white matter was lost from the center of the lesion. In addition, supramaximal damage was noted, which likely prevented spontaneous recovery. This percutaneous spinal cord compression injury model is simple, rapid with high reproducibility and the potential to serve as a useful tool for investigation of pathophysiology and possible protective treatments of SCI in vivo.

Percutaneous transplantation of human umbilical cord-derived mesenchymal stem cells in a dog suspected to have fibrocartilaginous embolic myelopathy.

The use of human umbilical cord blood-derived mesenchymal stem cells for cell transplantation therapy holds great promise for repairing spinal cord injury. Here we report the first clinical trial transplantation of human umbilical cord (hUCB)-derived mesenchymal stem cells (MSCs) into the spinal cord of a dog suspected to have fibrocartilaginous embolic myelopathy (FCEM) and that experienced a loss of deep pain sensation. Locomotor functions improved following transplantation in a dog. Based on our findings, we suggest that transplantation of hUCB-derived MSCs will have beneficial therapeutic effects on FCEM patients lacking deep pain sensation.

Differential localization of pain-related neural responses during acupuncture stimulation using Blood Oxygen Level Dependent (BOLD) fMRI in a canine model.

The objective of this study was to differentiate the neuronal responses, which was related or unrelated, to pain associated with acupuncture stimulation, and to localize the brain regions with response to stimulation that is unrelated to pain by using Blood Oxygen Level Dependent (BOLD) functional MRI (fMRI). BOLD fMRI was performed in six normal healthy beagle dogs, during placebo and verum acupuncture stimulations, at the right side of BL60 (KunLun) acupoint before and after local anesthesia of the acupoint. The order of the four sessions was placebo; verum acupuncture stimulation; before local anesthesia; and followed by the same stimulation after local anesthesia. One-sample t-test analysis was performed to localize the activated or deactivated areas, during both pre-anesthesia and post-anesthesia. In order to compare the pre-anesthesia to post-anesthetic responses, and placebo to verum acupuncture stimulation, within-subject analysis was performed. The post-anesthetic verum acupuncture stimulation resulted in increased activations in the left somatic afferent area I and II, right visual and auditory association area, and the descending reticular activating system of the brainstem. In addition, differential areas during post-anesthesia compared to that of the pre-anesthesia were in the left olfactory peduncle and descending reticular activating system of the brainstem. These results indicate that the areas of specific neural pathway are considered to be unrelated to the pain response during acupuncture stimulation.

Preliminary study for a newly designed silicone stent and delivery system for canine obstructive tracheal disease.

The goal of this study was to prove the possibility of using silicone stents broadly used for human medicine in canine obstructive tracheal disease. A silicone stent anatomically designed for canine trachea was tested on 5 beagle dogs for 8 weeks. The stent was carefully inserted using a newly developed delivery device under fluoroscopic guidance. There were no technical difficulties in placing the stent during the procedure. Previously reported complications of airway stenting such as stent migration or granulation tissue formation did not occur in any of the cases. In addition, removal of the stent was as simple as inserting it, and complications were absent. The stent introduced in this study could possibly be applied to various canine obstructive tracheal diseases.

Ex vivo detection for chronic ethanol consumption-induced neurochemical changes in rats.

The aim of this study was to quantitatively investigate the chronic ethanol-induced cerebral metabolic changes in various regions of the rat brain, using the proton high resolution magic angle spinning spectroscopy technique. The rats were divided into two groups (control group: N=11, ethanol-treated group: N=11) and fed with the liquid diets for 10 weeks. In each week, the mean intake volumes of liquid diet were measured. The brain tissues, including cerebellum (Cere), frontal cortex (FC), hippocampus (Hip), occipital cortex (OC) and thalamus (Thal), were harvested immediately after the end of experiments. The ex vivo proton spectra for the five brain regions were acquired with the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence at 500-MHz NMR spectrometer. All of the spectra were processed using the LCModel software, with simulated basis-set file, and the metabolite levels were referenced to total creatine. In the ethanol liquid diet group, there were significant increases in the metabolites ratio levels, as compared to control (Cere: alanine, glutathione, and N-acetlyaspartate; FC: phosphocholine and taurine; Hip: alanine, glutamine, and N-acetylaspartate; OC: glutamine; Thal: alanine, γ-aminobutyric acid, glutamate, glycerophosphocholine, phosphocholine, taurine, and free choline). However, in the ethanol liquid diet group, the myo-inositol levels of the OC were significantly lower. The present study demonstrates how chronic ethanol consumption affects cerebral metabolites in the chronic ethanol-treated rat. Therefore, this result could be useful to pursue clinical applications for quantitative diagnosis in human alcoholism.

Schwann cell-like remyelination following transplantation of human umbilical cord blood (hUCB)-derived mesenchymal stem cells in dogs with acute spinal cord injury.

Human umbilical cord blood derived mesenchymal stem cells (hUCB-MSCs) have significant therapeutic potential in cell-based therapies following spinal cord injury (SCI). To evaluate this potential, we conducted our preliminary investigations on the remyelination of injured spinal cords with hUCB-MSC transplantations and we observed its long term effects on dogs with SCI. Of the ten injured dogs, seven were transplanted with hUCB-MSCs 1 week after SCI, whereas the remaining three dogs were not transplanted. Two transplanted dogs died over the first month after transplantation because of urinary tract infection, bedsores and sepsis. The SCI dogs showed no improvement in motor and sensory functions and their urinary dysfunction persisted until they were euthanized (from 3 months to 1 year) while hind-limb recovery in 4 dogs among the five transplanted dogs was significantly improved. In the recovered dogs, functional recovery was sustained for three years following transplantation. Histological results from five transplanted dogs showed that many axons were remyelinated by P0-positive myelin sheaths after transplantation. Our results suggest that transplantation of hUCB-derived MSCs may have beneficial therapeutic effects. Furthermore, histological results provided the first in vivo evidence that hUCB-MSCs are able to enhance the remyelination of peripheral-type myelin sheaths following SCI.

Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.

Desipramine attenuates forced swim test-induced behavioral and neurochemical alterations in mice: an in vivo(1)H-MRS study at 9.4T.

The forced swim test (FST) is a behavioral paradigm that is predicative of antidepressant activity in rodents. The objective of this study was to examine the effects of desipramine (DMI) pretreatment on behavioral and regional neurochemical responses in the left dorsolateral prefrontal cortex (DLPFC) and hippocampus of mice exposed to the FST using proton magnetic resonance spectroscopy ((1)H-MRS). An ultra short echo stimulated echo acquisition (STEAM) localization sequence (TR/TM/TE=5000/20/2.2ms) was used to measure in vivo proton spectra from the left DLPFC (voxel volume: 7microl) and hippocampus (6microl) of C57BL/6 mice at 9.4T and acquired proton spectra post-processed offline with LCModel. The FST induced significant increase of glutamate (Glu) and myo-inositol (mIns) concentrations in the left DLPFC and hippocampus, respectively. In addition, creatine+phosphocreatine (Cr+PCr) concentrations in the left DLPFC were significantly decreased as compared to control. The metabolic alterations induced by the FST were reverted to level similar to control by acute DMI administration. Our results suggest that glutamatergic activity and glial cell dysfunction may contribute to the pathophysiological mechanisms underlying depression and that modulation of synaptic neurotransmitter concentrations represents a potential target for antidepressant drug development.