RESUMO
BACKGROUND: Spinal cord injury (SCI) produces acute hemodynamic alterations through disruption of sympathetic output of the autonomic nervous system and places individuals with SCI at high risk of secondary ischemic insult to the spinal cord as well as to other organs. The purpose of this study was to examine hemodynamics and serum vasopressin concentration in the acute period following complete cervical SCI in piglets. METHODS: We developed a new model of traumatic complete cervical SCI in piglets and measured acute hemodynamic variables and serum arginine vasopressin (AVP) concentrations at baseline and for 4 h after SCI under fentanyl anesthesia. RESULTS: Complete cervical SCI caused an immediate tachycardia which lasted for approximately 1 h, immediate hypotension which was sustained for the 4-h duration of the study, decreases in both systemic and pulmonary vascular resistance, and a compensatory increase in cardiac output, which resulted initially from an increase in heart rate (HR) but was later sustained after resolution of tachycardia by an increase in cardiac stroke volume. Serum AVP concentration increased significantly after SCI and did not change in the control group. Neurogenic shock did not occur due to the robust increase in cardiac output and cardiac stroke volume. CONCLUSIONS: Complete cervical SCI produces hemodynamic alterations consistent with the withdrawal of sympathetic tone. Although mean arterial pressure (MAP) decreased significantly after SCI, the increase in serum vasopressin may have played a role in maintaining blood pressure and preventing circulatory collapse, a complication which is encountered frequently in patients with cervical and upper thoracic SCI.
Assuntos
Arginina Vasopressina/sangue , Hemodinâmica , Traumatismos da Medula Espinal/fisiopatologia , Animais , Animais Recém-Nascidos , Pressão Sanguínea , Débito Cardíaco , Vértebras Cervicais , Frequência Cardíaca , Imageamento por Ressonância Magnética , Circulação Pulmonar , Medula Espinal/patologia , Traumatismos da Medula Espinal/sangue , Traumatismos da Medula Espinal/diagnóstico , Volume Sistólico , Suínos , Fatores de Tempo , Resistência VascularRESUMO
We have developed a piglet model to assess chemotherapy administration directly into the fourth ventricle as a potential treatment for medulloblastoma and other malignant posterior fossa tumors. The objective of this study was to assess safety and pharmacokinetics after methotrexate infusions into the fourth ventricle. Catheters were inserted into the fourth ventricle and lumbar cistern in five piglets. Two milligrams of Methotrexate (MTX) was infused into the fourth ventricle on five consecutive days. Safety was assessed by neurological examination, 4.7 T MRI, and post-mortem pathological analysis. MTX levels in serum and cerebrospinal fluid (CSF) were measured, and area under the concentration-time curve (AUC) was calculated for CSF samples. No neurological deficits were caused by MTX infusions. One piglet died from complications of anesthesia induction for MRI scanning. MRI scans showed accurate catheter placement without signal changes in the brainstem or cerebellum. One piglet had asymptomatic ventriculomegaly. Pathological analysis demonstrated meningitis and choroid plexitis consisting predominantly of CD-3 positive T-lymphocytes in all piglets and a small focal area of subependymal necrosis in one. In all piglets, mean peak MTX level in fourth ventricular CSF exceeded that in lumbar CSF by greater than five-fold. Serum MTX levels were undetectable or negligible. Statistically significant differences between fourth ventricle and lumbar AUC were detected at peaks (P = 0.01) and at all collection time points (P = 0.01) but not at troughs (P = 0.36). MTX can be infused into the fourth ventricle without clinical or radiographic evidence of damage. An inflammatory response without clinical correlate is observed. Significantly higher peak MTX levels are observed in the fourth ventricle than in the lumbar cistern.
Assuntos
Inibidores Enzimáticos/administração & dosagem , Inibidores Enzimáticos/farmacocinética , Quarto Ventrículo/efeitos dos fármacos , Metotrexato/administração & dosagem , Metotrexato/farmacocinética , Animais , Área Sob a Curva , Contagem de Células/métodos , Inibidores Enzimáticos/sangue , Inibidores Enzimáticos/líquido cefalorraquidiano , Imageamento por Ressonância Magnética/métodos , Metotrexato/sangue , Metotrexato/líquido cefalorraquidiano , Modelos Animais , Suínos , Fatores de TempoRESUMO
OBJECTIVE: To develop a new, clinically relevant large animal model of pediatric spinal cord injury (SCI) and compare the clinical and experimental features of pediatric SCI. METHODS: Infant piglets (3-5 weeks old) underwent contusive SCI by controlled cortical impactor at T7. Severe complete SCI was induced in 6 piglets, defined as SCI with no spontaneous return of sensorimotor function. Eight piglets received incomplete SCI, which was followed by partial recovery. Somatosensory evoked potentials, magnetic resonance imaging, neurobehavioral function, and histopathology were measured during a 28-day survival period. RESULTS: Mean SCI volume (defined as volume of necrotic tissue) was larger after complete compared with incomplete SCI (387 +/- 29 vs 77 +/- 38 mm3, respectively, P < 0.001). No functional recovery occurred after complete SCI. After incomplete SCI, piglets initially had an absence of lower extremity sensorimotor function, urinary and stool retention, and little to no rectal tone. Sensory responses recovered first (1-2 days after injury), followed by spontaneous voiding, lower extremity motor responses, regular bowel movements, and repetitive flexion-extension of the lower extremities when crawling. No piglet recovered spontaneous walking, although 4 of 8 animals with incomplete injuries were able to bear weight by 28 days. In vivo magnetic resonance imaging was performed safely, yielded high-resolution images of tissue injury, and correlated closely with injury volume seen on histopathology, which included intramedullary hemorrhage, cellular inflammation, necrosis, and apoptosis. CONCLUSION: Piglets performed well as a reproducible model of traumatic pediatric SCI in a large animal with chronic survival and utilizing multiple outcome measures, including evoked potentials, magnetic resonance imaging, functional outcome scores, and histopathology.
Assuntos
Modelos Animais de Doenças , Pediatria , Traumatismos da Medula Espinal , Vias Aferentes/fisiopatologia , Animais , Animais Recém-Nascidos , Tornozelo/inervação , Eletroencefalografia/métodos , Potenciais Somatossensoriais Evocados/fisiologia , Humanos , Laminectomia/métodos , Imageamento por Ressonância Magnética/métodos , Exame Neurológico , Recuperação de Função Fisiológica , Medula Espinal/patologia , Traumatismos da Medula Espinal/patologia , Traumatismos da Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/terapia , Suínos , Fatores de Tempo , Caminhada/fisiologiaRESUMO
We hypothesize that infusion of chemotherapeutic agents directly into the fourth ventricle potentially may play a role in treating malignant posterior fossa brain tumors. Accordingly, we used a piglet model developed in our laboratory to test the safety of etoposide infusions into the fourth ventricle and to study the pharmacokinetics associated with these infusions. In 5 piglets, closed-tip silicone catheters were inserted into the fourth ventricle and lumbar cistern. Five consecutive daily infusions of etoposide (0.5 mg) were administered via the fourth ventricle catheter. Serum and CSF from both catheters were sampled for measurement of etoposide level by reversed-phase high performance liquid chromatography (HPLC). For CSF samples, area under the concentration-time curve (AUC) was calculated. Piglets underwent daily neurological examinations, a 4.7 Tesla MRI scan, and then were sacrificed for post-mortem brain examination. No neurological deficits or signs of meningitis were caused by intraventricular chemotherapy infusions. MRI scans showed catheter placement within the fourth ventricle but no signal changes in the brain stem or cerebellum. In all piglets, the mean fourth ventricular CSF peak etoposide level exceeded the mean peak lumbar etoposide levels by greater than 10-fold. Statistically significant differences between fourth ventricle and lumbar AUC were noted at peaks (DeltaAUC = 3384196 ng h/ml with 95%CI: 1758625, 5009767, P = 0.0044) and at all collection time points (DeltaAUC = 1422977 ng h/ml with 95%CI: 732188, 2113766, P = 0.0046) but not at troughs (DeltaAUC = -29546 ng h/ml (95%CI: -147526, 88434.2, P = 0.5251). Serum etoposide was absent at two and four hours after intraventricular infusions in all animals. Pathological analysis demonstrated meningitis, choroid plexitis, and ependymitis in the fourth and occasionally lateral ventricles. Etoposide can be infused directly into the fourth ventricle without clinical or radiographic evidence of damage. Autopsy examination revealed ventriculitis and meningitis which did not have a clinical correlate. Etoposide does not distribute evenly throughout CSF spaces after administration into the fourth ventricle, and higher peak CSF levels are observed in the fourth ventricle than in the lumbar cistern.
Assuntos
Antineoplásicos Fitogênicos/administração & dosagem , Antineoplásicos Fitogênicos/farmacocinética , Etoposídeo/administração & dosagem , Etoposídeo/farmacocinética , Quarto Ventrículo/efeitos dos fármacos , Neoplasias Infratentoriais/patologia , Animais , Antineoplásicos Fitogênicos/sangue , Antineoplásicos Fitogênicos/líquido cefalorraquidiano , Antineoplásicos Fitogênicos/farmacologia , Área Sob a Curva , Contagem de Células , Cromatografia Líquida de Alta Pressão/métodos , Intervalos de Confiança , Modelos Animais de Doenças , Etoposídeo/sangue , Etoposídeo/líquido cefalorraquidiano , Etoposídeo/farmacologia , Neoplasias Infratentoriais/tratamento farmacológico , Imageamento por Ressonância Magnética/métodos , Exame Neurológico/métodos , Suínos , Fatores de TempoRESUMO
The roles of protein tyrosine phosphatases (PTPs) in differentiation and axon targeting by dorsal root ganglion (DRG) neurons are essentially unknown. The type III transmembrane PTP, PTPRO, is expressed in DRG neurons, and is implicated in the guidance of motor and retinal axons. We examined the role of PTPRO in DRG development and function using PTPRO(-/-) mice. The number of peptidergic nociceptive neurons in the DRG of PTPRO(-/-) mice was significantly decreased, while the total number of sensory neurons appeared unchanged. In addition, spinal pathfinding by both peptidergic and proprioceptive neurons was abnormal in PTPRO(-/-) mice. Lastly, PTPRO(-/-) mice performed abnormally on tests of thermal pain and sensorimotor coordination, suggesting that both nociception and proprioception were perturbed. Our data indicate that PTPRO is required for peptidergic differentiation and process outgrowth of sensory neurons, as well as mature sensory function, and provide the first evidence that RPTPs regulate DRG development.
Assuntos
Gânglios Espinais , Proteínas Tirosina Fosfatases Classe 3 Semelhantes a Receptores/metabolismo , Células Receptoras Sensoriais/fisiologia , Animais , Comportamento Animal/fisiologia , Gânglios Espinais/citologia , Gânglios Espinais/crescimento & desenvolvimento , Gânglios Espinais/fisiologia , Camundongos , Camundongos Knockout , Vias Neurais/anormalidades , Vias Neurais/anatomia & histologia , Vias Neurais/fisiologia , Dor/metabolismo , Medição da Dor , Proteínas Tirosina Fosfatases Classe 3 Semelhantes a Receptores/genética , Células Receptoras Sensoriais/citologia , Medula Espinal/citologia , Medula Espinal/metabolismoRESUMO
OBJECT: The authors hypothesized that chemotherapy infusions directly into the fourth ventricle may potentially play a role in treating malignant posterior fossa tumors. In this study the safety and pharmacokinetics of etoposide administration into the fourth ventricle was tested using an indwelling catheter in piglets. METHODS: A closed-tip silicone lumbar drain catheter was inserted into the fourth ventricle via a posterior fossa craniectomy and 5 daily infusions of etoposide (0.5 mg in 5 animals) or normal saline (in 2 animals) were instilled. Piglets (10-18 kg, 2-3 months of age) underwent daily neurological examinations and 4.7-T magnetic resonance (MR) imaging after the final infusion and were then killed for postmortem examination. Pharmacokinetics were studied using reversed-phase high-performance liquid chromatography on cerebrospinal fluid (CSF) samples at 0.25, 1, 2, 4, 8, 12, and 24 hours after etoposide infusion. Peak and trough CSF etoposide levels were measured for each subsequent infusion. Serum etoposide levels were obtained at 2 and 4 hours after infusion. RESULTS: All piglets remained neurologically intact, and MR images demonstrated catheter placement within the fourth ventricle without signal changes in the brainstem or cerebellum. Serum etoposide was absent at 2 and 4 hours after intraventricular infusions. When adequate samples could be obtained for analysis, CSF etoposide levels peaked 15 minutes after infusion and progressively decreased. Cytotoxic levels (> 0.1 microg/ml) were maintained for 5 consecutive peak and trough measurements with 1 exception. Etoposide-related neuropathology included moderate-to-severe T-lymphocytic meningitis and fourth and lateral ventricular choroid plexitis with associated subependymal inflammation. CONCLUSIONS: Etoposide can be infused directly into the fourth ventricle without clinical or imaging evidence of damage. Cytotoxic CSF etoposide levels can be maintained for 24 hours with a single daily infusion into the fourth ventricle using an indwelling catheter. Intraventricular etoposide elicits an inflammatory response, the long-term effects of which are as yet undetermined.
Assuntos
Antineoplásicos Fitogênicos/administração & dosagem , Antineoplásicos Fitogênicos/farmacocinética , Cateterismo , Etoposídeo/administração & dosagem , Etoposídeo/farmacocinética , Quarto Ventrículo/cirurgia , Animais , Área Sob a Curva , Cateteres de Demora , Quarto Ventrículo/metabolismo , Quarto Ventrículo/patologia , Infusões Parenterais , Modelos Animais , SuínosRESUMO
BACKGROUND: Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets. METHODS: The focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM). RESULTS: A significant area of hypoperfusion (P < 0.01) was found as a response to the TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM. CONCLUSION: The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques.
Assuntos
Lesões Encefálicas/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Cisteína/análogos & derivados , Interpretação de Imagem Assistida por Computador/métodos , Microesferas , Compostos de Organotecnécio , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Animais , Circulação Cerebrovascular , Cisteína/química , Interpretação Estatística de Dados , Aumento da Imagem/métodos , Masculino , Compostos de Organotecnécio/química , Compostos Radiofarmacêuticos/química , SuínosRESUMO
The full-length extracellular domain (ECD) of protein tyrosine phosphatase delta (PTP-delta) functions as a ligand to promote cell adhesion and neurite outgrowth; this ECD contains three immunoglobulin (Ig) repeats and eight fibronectin type III (FN III) repeats. However, it is not known which regions of the ECD regulate its ligand functions. Therefore, we constructed and expressed a fusion protein of the PTP-delta ECD lacking FN III repeats 4-8, and tested this protein for neuronal adhesion and neurite-promoting ability. Compared to the full-length isoform, the truncated ECD was poorer at promoting adhesion, but a more potent promoter of neurite growth. The results suggest that distal FN III repeats of PTP-delta are important in adhesive functions, but dispensable for neurite outgrowth promotion. As the predominant isoform of PTP-delta during neural development (type D) also lacks distal FN III repeats, the functional properties we observe may be relevant to periods of axon extension, suggesting that splice variants of receptor PTPs play distinct roles in neural development.