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BACKGROUND AND PURPOSE: The underlying mechanisms leading to altered cognitive, behavioral, and vision outcomes in children with prenatal opioid exposure are yet to be fully understood. Some studies suggest WM alterations in infants and children with prenatal opioid exposure; however, the time course of WM changes is unknown. We aimed to evaluate differences in diffusion tensor imaging MRI parameters in the brain between opioid exposed fetuses and normal controls. MATERIALS AND METHODS: This is a pilot, prospective cohort study in which subjects in the third trimester of pregnancy underwent fetal DTI of the brain with 20 noncolinear diffusion directions and a b-value of 500 s/mm2 at 2.5-mm isotropic resolution. RESULTS: The study included a total of 26 fetuses, 11 opioid-exposed (mean gestational age, 32.61 [SD, 2.35] weeks) and 15 unexposed controls (mean gestational age, 31.77 [SD, 1.68] weeks). After we adjusted for gestational age, fractional anisotropy values were significantly higher in opioid-exposed fetuses relative to controls in 8 WM tracts: the bilateral lemniscus (left: P = .017; right: P = .020), middle cerebellar peduncle (P = .027), left inferior cerebellar peduncle (P = .026), right sagittal stratum (P = .040), right fornix stria terminalis (P = .022), right inferior fronto-occipital fasciculus (P = .011), and the right uncinate fasciculus (P = .033). Significant alteration was also identified in other DTI indices involving a series of brain regions. CONCLUSIONS: Our data demonstrate initial evidence of cerebral WM microstructural differences between opioid-exposed fetuses and unexposed controls. Further studies in larger patient populations will be needed to fully understand these findings.
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Imagen de Difusión Tensora , Sustancia Blanca , Lactante , Niño , Humanos , Adulto , Imagen de Difusión Tensora/métodos , Analgésicos Opioides , Estudios Prospectivos , Encéfalo , FetoRESUMEN
BACKGROUND AND PURPOSE: There is a wide range of clinical and radiographic factors affecting individual surgeons' ultimate decision for CSF diversion for pediatric patients following prenatal myelomeningocele repair. Our aim was to construct a composite index (CSF diversion surgery index) that integrates conventional clinical measures and neuroimaging biomarkers to predict CSF diversion surgery in these pediatric patients. MATERIALS AND METHODS: This was a secondary retrospective analysis of data from 33 patients with prenatal myelomeningocele repair (including 14 who ultimately required CSF diversion surgery). Potential independent variables, including the Management of Myelomeningocele Study Index (a dichotomized variable based on the shunt-placement criteria from the Management of Myelomeningocele Study), postnatal DTI measures (fractional anisotropy and mean diffusivity in the genu of the corpus callosum and the posterior limb of internal capsule), fronto-occipital horn ratio at the time of DTI, gestational ages, and sex, were evaluated using stepwise logistic regression analysis to identify the most important predictors. RESULTS: The CSF diversion surgery index model showed that the Management of Myelomeningocele Study Index and fractional anisotropy in the genu of the corpus callosum were significant predictors (P < .05) of CSF diversion surgery. The predictive value of the CSF diversion surgery index was also affected by fractional anisotropy in the posterior limb of the internal capsule and sex with marginal effect (.05
.10). The overall CSF diversion surgery index model fit the data well with statistical significance (eg, likelihood ratio: P < .001), with the performance (sensitivity = 78.6%; specificity = 86.5%, overall accuracy = 84.8%) superior to all individual indices in sensitivity and overall accuracy, and most of the individual indices in specificity. CONCLUSIONS: The CSF diversion surgery index model outperformed all single predictor models and, with additional validation, may potentially be developed and incorporated into a sensitive and robust clinical tool to assist clinicians in hydrocephalus management.
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Hidrocefalia , Meningomielocele , Embarazo , Femenino , Humanos , Niño , Meningomielocele/diagnóstico por imagen , Meningomielocele/cirugía , Meningomielocele/complicaciones , Estudios Retrospectivos , Hidrocefalia/cirugía , Derivación Ventriculoperitoneal , Ventriculostomía/métodosRESUMEN
Cavernous malformations (CM) are vascular malformations of the central nervous system that may occur in the brain and spinal cord. They are one of the four major types of vascular malformations that also includes developmental venous anomalies (DVA)s, arteriovenous malformations (AVMs), and capillary telangiectasias. CMs are a common vascular malformation, and 25% of them occur in the pediatric age group. They can present with acute or chronic symptoms including headache, neurologic deficits secondary to hemorrhage, mass effect, or epilepsy. This review will focus on the neurosurgical management of intracranial cavernous malformations in children. Pediatric CMs have special considerations different from CM that occur in the adult population which are highlighted throughout this review. Characteristics specific to pediatric CM epidemiology, genetics, presentation, pathology, location, size, epilepsy, and management will be discussed. Specific considerations must be entertained with the diagnosis of pediatric CM in that management needs to include consideration of the lifetime risk of hemorrhage, as well as the possibility of development of epilepsy. If in an accessible location, most cavernomas should be surgically removed in a timely fashion to provide lifelong cure for pediatric patients. The review closes with the discussion of two interesting cavernous malformation cases occurring in a 12-year old male and a 12-year old female that exhibit many of the important aspects specific to the management of a pediatric patient with CM, highlighting the importance of a multidisciplinary approach to treatment.
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Neoplasias del Sistema Nervioso Central/cirugía , Hemangioma Cavernoso del Sistema Nervioso Central/cirugía , Niño , Femenino , Humanos , MasculinoRESUMEN
BACKGROUND AND PURPOSE: Hydrocephalus is a severe pathologic condition in which WM damage is a major factor associated with poor outcomes. The goal of the study was to investigate tract-based WM connectivity and DTI measurements in children with hydrocephalus by using the probabilistic diffusion tractography method. MATERIALS AND METHODS: Twelve children with hydrocephalus and 16 age-matched controls were included in the study. Probabilistic diffusion tractography was conducted to generate tract-based connectivity distribution and DTI measures for the genu of the corpus callosum and the connectivity index. Tract-based summary measurements, including the connectivity index and DTI measures (fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity), were calculated and compared between the 2 study groups. RESULTS: Tract-based summary measurement showed a higher percentage of voxels with lower normalized connectivity index values in the WM tracts in children with hydrocephalus. In the genu of the corpus callosum, the left midsegment of the corticospinal tract, and the right midsegment of the corticospinal tract, the normalized connectivity index value in children with hydrocephalus was found to be significantly lower (P < .05, corrected). The tract-based DTI measures showed that the children with hydrocephalus had significantly higher mean diffusivity, axial diffusivity, and radial diffusivity in the genu of the corpus callosum, left midsegment of the corticospinal tract, and right midsegment of corticospinal tract and lower fractional anisotropy in the genu of the corpus callosum (P < .05, corrected). CONCLUSIONS: The analysis of WM connectivity showed that the probabilistic diffusion tractography method is a sensitive tool to detect the decreased continuity in WM tracts that are under the direct influence of mechanical distortion and increased intracranial pressure in hydrocephalus. This voxel-based connectivity method can provide quantitative information complementary to the standard DTI summary measures.
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Algoritmos , Encéfalo/patología , Imagen de Difusión Tensora/métodos , Hidrocefalia/complicaciones , Hidrocefalia/patología , Interpretación de Imagen Asistida por Computador/métodos , Fibras Nerviosas Mielínicas/patología , Preescolar , Interpretación Estadística de Datos , Femenino , Humanos , Aumento de la Imagen/métodos , Lactante , Recién Nacido , Masculino , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
BACKGROUND AND PURPOSE: DTI is an advanced neuroimaging technique that allows in vivo quantification of water diffusion properties as surrogate markers of the integrity of WM microstructure. In our study, we investigated normative data from a large number of pediatric and adolescent participants to examine the developmental trends in DTI during this conspicuous WM maturation period. MATERIALS AND METHODS: DTI data in 202 healthy pediatric and adolescent participants were analyzed retrospectively. Fractional anisotropy and mean diffusivity values in the corpus callosum and internal capsule were fitted to an exponential regression model to delineate age-dependent maturational changes across the WM structures. RESULTS: The DTI metrics demonstrated characteristic exponential patterns of progression during development and conspicuous age-dependent changes in the first 36 months, with rostral WM tracts experiencing the highest slope of the exponential function. In contrast, the highest final FA and lowest MD values were detected in the splenium of the corpus callosum and the posterior limb of the internal capsule. CONCLUSIONS: Our analysis shows that the more caudal portions of the corpus callosum and internal capsule begin the maturation process earlier than the rostral regions, but the rostral regions develop at a more accelerated pace, which may suggest that rostral regions rely on development of more caudal brain regions to instigate their development. Our normative DTI can be used as a reference to study normal spatiotemporal developmental profiles in the WM and help identify abnormal WM structures in patient populations.
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Cuerpo Calloso/anatomía & histología , Imagen de Difusión Tensora/métodos , Cápsula Interna/anatomía & histología , Neuroimagen/métodos , Adolescente , Factores de Edad , Anisotropía , Niño , Preescolar , Cuerpo Calloso/crecimiento & desarrollo , Estudios de Seguimiento , Humanos , Aumento de la Imagen/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Lactante , Cápsula Interna/crecimiento & desarrollo , Estudios RetrospectivosRESUMEN
BACKGROUND AND PURPOSE: White matter structural alterations and the correlation with neuropsychological deficits in children with hydrocephalus have not been well investigated. In this prospective study, the objectives were the following: 1) to apply DTI to detect in vivo white matter alterations based on diffusion properties in children with acute hydrocephalus, 2) to quantify early neuropsychological deficits, and 3) to explore the correlation between potential neuropsychological deficits and abnormalities in functionally related white matter. MATERIALS AND METHODS: A total of 44 children, 24 with hydrocephalus and 20 controls, were enrolled in the study. DTI indices, FA, MD, AD, and RD, were evaluated in the gCC, sCC, PLIC, and ALIC. The ABAS-II was used as a broad screener of development, including conceptual, social, practical, and motor skills. The correlation between the Motor Scale and DTI indices in the PLIC was analyzed. RESULTS: DTI analyses showed that the gCC and sCC in children with hydrocephalus had lower FA and higher MD, driven by the increased RD with statistical significance (P < .05) or trend-level significance (P = .06). The PLIC and ALIC had significantly higher AD in children with hydrocephalus (P < .05). On the ABAS-II, parent ratings of general adaptive skills, conceptual skills, and motor skills were significantly lower in children with hydrocephalus (all at P < .05). The MD and RD values in the PLIC were found to have trend-level or significant correlation with the Motor Scale (P = .057, .041, respectively). CONCLUSIONS: DTI reveals alterations in the white matter structure in children with hydrocephalus with preliminary findings suggesting correlation with clinical motor deficits.
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Trastornos del Conocimiento/patología , Cuerpo Calloso/patología , Imagen de Difusión Tensora , Hidrocefalia/patología , Cápsula Interna/patología , Enfermedad Aguda , Preescolar , Femenino , Humanos , Lactante , Recién Nacido , Leucoencefalopatías/patología , Estudios Longitudinales , Masculino , Destreza Motora , Pruebas Neuropsicológicas , Estudios Prospectivos , Conducta SocialRESUMEN
PURPOSE: To compare a pediatric population diagnosed with benign external hydrocephalus (BEH) to normal age-matched controls using diffusion tensor imaging (DTI) techniques. METHODS: We retrospectively identified 17 BEH patients by specific clinical and neuroimaging criteria. Fractional anisotropy (FA) and mean diffusivity (MD) values obtained from DTI scans were compared to a population of age-matched controls and group differences were examined by mixed model analysis. A longitudinal comparison was completed on a subset that underwent multiple scans (n = 8). RESULTS: In the genu of the corpus callosum (gCC), six of 15 BEH children had an FA value above the upper limit of 95% prediction interval, nine of 15 BEH children had MD values below the lower limit of 95% prediction interval. A similar trend applied to the other regions of interest (ROIs): splenium of the corpus callosum (sCC), ALIC, and PLIC. Statistical analysis demonstrated significant differences in FA within the gCC, sCC, and PLIC and in MD within the sCC between BEH patients and controls given (P = 0.05). No statistical differences were identified at any ROIs at the later scans. CONCLUSIONS: We found a significant increase in FA and decrease in MD in children with BEH compared with normal children in specific white matter (WM) ROIs, notably in the gCC and sCC; furthermore, in longitudinal comparison, DTI parameters normalized over time. The current study further demonstrates the ability of DTI to distinguish between subtle diffusion changes in periventricular white matter and establishes preliminary objective radiographic parameters for watchful observation of patients with BEH.
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Imagen de Difusión Tensora , Hidrocefalia/patología , Anisotropía , Niño , Preescolar , Femenino , Humanos , Interpretación de Imagen Asistida por Computador , Lactante , Masculino , Estudios RetrospectivosRESUMEN
OBJECTIVES: To evaluate the diagnostic value of individual noninvasive presurgical modalities and to study their role in surgical management of nonlesional pediatric epilepsy patients. METHODS: We retrospectively studied 14 children (3-18 years) with nonlesional intractable focal epilepsy. Clinical characteristics, surgical outcome, localizing features on 3 presurgical diagnostic tests (subtraction peri-ictal SPECT coregistered to MRI [SISCOM], statistical parametric mapping [SPM] analysis of [18F] FDG-PET, magnetoencephalography [MEG]), and intracranial EEG (iEEG) were reviewed. The localization of each individual test was determined for lobar location by visual inspection. Concordance of localization between each test and iEEG was scored as follows: 2=lobar concordance; 1=hemispheric concordance; 0=discordance or nonlocalization. Total concordance score in each patient was measured by the summation of concordance scores for all 3 tests. RESULTS: Seven (50%) of 14 patients were seizure-free for at least 12 months after surgery. One (7%) had only rare seizures and 6 (43%) had persistent seizures. MEG (79%, 11/14) and SISCOM (79%, 11/14) showed greater lobar concordance with iEEG than SPM-PET (13%, 3/14) (p<0.05). SPM-PET provided hemispheric lateralization (71%, 10/14) more often than lobar localization. Total concordance score tended to be greater for seizure-free patients (4.7) than for non-seizure-free patients (3.9). CONCLUSIONS: Our data suggest that MEG and SISCOM are better tools for lobar localization than SPM analysis of FDG-PET in children with nonlesional epilepsy. A multimodality approach may improve surgical outcome as well as selection of surgical candidates in patients without MRI abnormalities.
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Mapeo Encefálico , Encéfalo/patología , Diagnóstico por Imagen/métodos , Epilepsia/diagnóstico , Epilepsia/cirugía , Adolescente , Encéfalo/cirugía , Niño , Electroencefalografía/métodos , Epilepsia/fisiopatología , Femenino , Fluorodesoxiglucosa F18 , Humanos , Procesamiento de Imagen Asistido por Computador , Magnetoencefalografía/métodos , Masculino , Pruebas Neuropsicológicas , Estudios Retrospectivos , Grabación en VideoRESUMEN
BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) can noninvasively detect in vivo white matter (WM) abnormalities on the basis of anisotropic diffusion properties. We analyzed DTI data retrospectively to quantify the abnormalities in different WM regions in children with hydrocephalus during early infancy. MATERIALS AND METHODS: Seventeen infants diagnosed with hydrocephalus (age range, 0.13-16.14 months) were evaluated with DTI and compared with 17 closely age-matched healthy children (age range, 0.20-16.11 months). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity values in 5 regions of interest (ROIs) in the corpus callosum and internal capsule were measured and compared. The correlation between FA and age was also studied and compared by ROI between the 2 study groups. RESULTS: Infants with hydrocephalus had significantly lower FA, higher MD, and higher radial diffusivity values for all 3 ROIs in the corpus callosum, but not for the 2 ROIs in the internal capsule. In infants with hydrocephalus, the increase of FA with age during normal development was absent in the corpus callosum but was still preserved in the internal capsule. There was also a significant difference in the frequency of occurrence of abnormal FA values in the corpus callosum and internal capsule. CONCLUSIONS: This retrospective DTI study demonstrated significant WM abnormalities in infants with hydrocephalus in both the corpus callosum and internal capsule. The results also showed evidence that the impact of hydrocephalus on WM was different in the corpus callosum and internal capsule.
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Algoritmos , Imagen de Difusión por Resonancia Magnética/métodos , Hidrocefalia/patología , Interpretación de Imagen Asistida por Computador/métodos , Anisotropía , Femenino , Humanos , Aumento de la Imagen/métodos , Lactante , Recién Nacido , Masculino , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Astroblastoma, a unique glial tumor, has been described in the literature in case reports and small series. Its rarity has prevented evidenced-based treatment stratification. An 8-year-old boy presented with signs and symptoms of raised intracranial pressure. Imaging studies of the brain demonstrated a large heterogeneously enhancing solid mass in the left frontal lobe with punctate calcifications and cystic components that created subfalcine and uncal herniation. After tumor resection, histological diagnosis revealed a high-grade cerebral astroblastoma. The child's postoperative recovery was complicated by hydrocephalus that necessitated placement of a ventriculoperitoneal shunt. Fifty-four months after undergoing gross total resection and adjuvant radiation therapy, the patient, now 12-years-old, remains tumor free and neurologically stable. Chemotherapy was reserved in the event of tumor recurrence. Since the first description of astroblastoma, its histopathological and clinical features have been debated. We review the histology, immunohistochemistry, and cytogenetics of astroblastoma as well as examine the current literature and treatment strategies for the management of both low and high-grade tumors. Continued clinical studies and longer patient follow-up with a tumor based registry would further clarify optimal treatment for this rare tumor.
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Neoplasias Encefálicas/patología , Neoplasias Encefálicas/fisiopatología , Lóbulo Frontal/patología , Lóbulo Frontal/fisiopatología , Neoplasias Neuroepiteliales/patología , Neoplasias Neuroepiteliales/fisiopatología , Factores de Edad , Biomarcadores de Tumor/análisis , Biomarcadores de Tumor/metabolismo , Edema Encefálico/etiología , Edema Encefálico/fisiopatología , Neoplasias Encefálicas/terapia , Niño , Aberraciones Cromosómicas , Análisis Mutacional de ADN , Lóbulo Frontal/diagnóstico por imagen , Humanos , Hidrocefalia/etiología , Hidrocefalia/fisiopatología , Hidrocefalia/terapia , Hipertensión Intracraneal/etiología , Hipertensión Intracraneal/patología , Hipertensión Intracraneal/fisiopatología , Imagen por Resonancia Magnética , Masculino , Neoplasias Neuroepiteliales/terapia , Procedimientos Neuroquirúrgicos , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/fisiopatología , Complicaciones Posoperatorias/terapia , Radioterapia , Tomografía Computarizada por Rayos X , Resultado del Tratamiento , Derivación VentriculoperitonealRESUMEN
CASE REPORT: An 11-month-old boy presented with a 3-month history of lower extremity weakness. CT and MRI of the spine revealed an enhancing epidural mass, extending from T1 through T5 and exiting through multiple foramina. The largest extraspinal extent was located at the T3 vertebral level and was accompanied by complete T3 vertebral collapse. A second lytic lesion at the L2 vertebral body without an obvious enhancing mass was also noted. Open biopsy and decompression of the spinal cord were performed, and histopathological analysis revealed a mixed inflammatory lesion with abundant S-100 and CD1a immunoreactive Langerhans cells consistent with the diagnosis of Langerhans cell histiocytosis (LCH). DISCUSSION: The authors present a very rare pediatric case of spinal LCH causing spinal cord compression. Possible clues to early detection, consideration of differential diagnoses, and a brief literature review are presented.
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Histiocitosis de Células de Langerhans/patología , Enfermedades de la Columna Vertebral/patología , Descompresión Quirúrgica , Histiocitosis de Células de Langerhans/fisiopatología , Histiocitosis de Células de Langerhans/cirugía , Humanos , Lactante , Vértebras Lumbares , Masculino , Compresión de la Médula Espinal/etiología , Compresión de la Médula Espinal/cirugía , Enfermedades de la Columna Vertebral/fisiopatología , Enfermedades de la Columna Vertebral/cirugía , Vértebras TorácicasRESUMEN
A multicystic meningioma in an octogenerian whose tissue diagnosis was ill-defined and misleading on preoperative neuroradiologic imaging is presented. Nauta has described four cyst types that can develop in cystic meningiomas. We report the first case in which three cyst types are demonstrated concurrently, describe the histopathology and surgical management. This case represents a rare variant of a common tumour in an unusual age group, and underscores the need for definitive biopsy and resection as indicated. Furthermore, the diagnosis of multicystic meningioma does not favour an aggressive histopathology in this case.
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Neoplasias Meníngeas/diagnóstico , Meningioma/diagnóstico , Anciano , Anciano de 80 o más Años , Humanos , Imagen por Resonancia Magnética , Masculino , Neoplasias Meníngeas/cirugía , Meningioma/cirugíaRESUMEN
Although gliosis has been reported to be a common and persistent feature in the white matter of hydrocephalic brains, no studies have identified the cell types that characterize this response. Therefore, the present study has employed histochemical methods to evaluate microglial cells in the brains of infant rats with inherited hydrocephalus. This strain of rats acquires hydrocephalus during late fetal stages due to aqueductal stenosis. Tissue from the sensorimotor and auditory cortices of 12- and 21-day-old hydrocephalic and normal H-Tx rats was processed and stained for the lectin microglial marker Griffonia simplicifolia (GSA-IB4). During the progression of hydrocephalus, GSA-positive cells exhibited three changes: (1) Cytologically, the cell bodies were enlarged, and their processes were thicker, longer and more numerous. These changes were most notable in the gray matter. (2) The packing density of GSA-positive cells was either increased or decreased, depending on the age of the animal and the severity of hydrocephalus. (3) Localized clusters of GSA-positive cells were conspicuous in the white matter of 12-day animals with mild hydrocephalus, and in the gray matter of 21-day animals with severe hydrocephalus. These results indicate that the microglial response is initiated during intermediate stages of hydrocephalus, and is not restricted to the periventricular white matter. These changes may signal other pathophysiologic events in the hydrocephalic brain, and demonstrate that microglia constitute one important element in the gliosis that accompanies hydrocephalus.
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Acueducto del Mesencéfalo/patología , Gliosis/patología , Hidrocefalia/patología , Microglía/fisiología , Animales , Acueducto del Mesencéfalo/fisiopatología , Ventrículos Cerebrales/fisiopatología , Constricción Patológica/genética , Constricción Patológica/patología , Constricción Patológica/fisiopatología , Modelos Animales de Enfermedad , Femenino , Gliosis/fisiopatología , Hidrocefalia/genética , Hidrocefalia/fisiopatología , Masculino , Microglía/citología , Corteza Motora/citología , Corteza Motora/fisiopatología , Ratas , Ratas Endogámicas , Corteza Somatosensorial/citología , Corteza Somatosensorial/fisiopatologíaRESUMEN
A ventrally localized melanization-inhibiting factor (MIF) may play an important role in the expression of dorsal-ventral pigment patterns of amphibians. In efforts to purify this putative MIF, ventral skin conditioned medium (VCM) from Rana forreri was partially fractionated and used to immunize mice. A monoclonal antibody that has the ability to block the activity of MIF was isolated, and an immunoaffinity matrix was prepared by cross-linking the antibody to protein G-Sepharose. The fraction of VCM that bound to the affinity matrix decreased the number of melanized cells in the Xenopus laevis neural tube explant assay, but did not reduce significantly the number of cells that emigrated. The monoclonal antibody was used for immunohistochemical studies on R. pipiens skin. Strong staining with the antibody was observed beneath the basement membrane, in mucous glands, and in the subcutaneous tissue of the ventral skin. A weak staining was also observed in the ground substances of both ventral and dorsal skin. These results confirm that a monoclonal antibody has been secured against at least one of the MIF constituents and that it is useful as a probe in detecting the distribution of MIF in tissues. The results of its use in this study support the hypothesis that MIF plays a role in the expression, development, and maintenance of the dorsal-ventral pigmentation patterns of frogs.
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Hormona Inhibidora de la Liberación de MSH/fisiología , Melanocitos/química , Pigmentación , Piel/química , Animales , Anticuerpos Monoclonales/inmunología , Cromatografía de Afinidad , Hormona Inhibidora de la Liberación de MSH/aislamiento & purificación , Melanocitos/fisiología , RanidaeRESUMEN
Consistent with the concept that specific pigment patterns of amphibians might result from the highly localized distribution of stimulators and inhibitors of pigment cell expression in the skin, the spot pattern of the leopard frog, Rana pipiens, was examined through the use of the Xenopus neural tube explant assay system (Fukuzawa and Ide, 1988). Media conditioned with pieces of skin from dorsal black spotted areas promoted melanization of neural crest cells at a significantly higher level than did media conditioned with dorsal interspot skin in the absence of extra tyrosine. All conditioned media contained exceedingly low concentrations of tyrosine. With the addition of supplemental tyrosine, the melanization capacity of conditioned media from the interspot areas was elevated to that of the spotted skin. Control media conditioned with ventral frog skin inhibited melanization, as usual, because of the presumed presence of melanization inhibiting factor (MIF). It is considered that dorsal skin contains a melanization stimulating factor (MSF) which is present in significantly higher levels in spotted skin than in interspot areas and that expression of the particular pigmentary pattern of this leopard frog is regulated by the relative distribution of MIF, MSF, and possibly other intrinsic substances present in the skin.