RESUMEN
Periodontal mesenchymal stem cells (MSCs) play a crucial role in maintaining periodontium homeostasis and in tissue repair. However, little is known about how periodontal MSCs in vivo respond under periodontal disease conditions, posing a challenge for periodontium tissue regeneration. In this study, Gli1 was used as a periodontal MSC marker and combined with a Gli1-cre ERT2 mouse model for lineage tracing to investigate periodontal MSC fate in an induced periodontitis model. Our findings show significant changes in the number and contribution of Gli1+ MSCs within the inflamed periodontium. The number of Gli1+ MSCs that contributed to periodontal ligament homeostasis decreased in the periodontitis-induced teeth. While the proliferation of Gli1+ MSCs had no significant difference between the periodontitis and the control groups, more Gli1+ MSCs underwent apoptosis in diseased teeth. In addition, the number of Gli1+ MSCs for osteogenic differentiation decreased during the progression of periodontitis. Following tooth extraction, the contribution of Gli1+ MSCs to the tooth socket repair was significantly reduced in the periodontitis-induced teeth. Collectively, these findings indicate that the function of Gli1+ MSCs in periodontitis was compromised, including reduced contribution to periodontium homeostasis and impaired injury response.
Asunto(s)
Células Madre Mesenquimatosas , Periodontitis , Ratones , Animales , Proteína con Dedos de Zinc GLI1 , Osteogénesis , Periodoncio/fisiología , Células Madre Mesenquimatosas/fisiología , Ligamento PeriodontalRESUMEN
Dental pulp stem cells (DPSCs) have the potential to polarize, differentiate, and form tubular dentin under certain conditions. However, the factors that initiate and regulate DPSC polarization and its underlying mechanism remain unclear. Identification of the factors that control DPSC polarization is a prerequisite for tubular dentin regeneration. We recently developed a unique bioinspired 3-dimensional platform that is capable of deciphering the factors that initiate and modulate cell polarization. The bioinspired platform has a simple background and confines a single cell on each microisland of the platform; therefore, it is an effective tool to study DPSC polarization at the single-cell level. In this work, we explored the effects of biophysical factors (surface topography, microisland area, geometry, tubular size, and gravity) on single DPSC polarization. Our results demonstrated that nanofibrous architecture, microisland area, tubular size, and gravity participated in regulating DPSC polarization by influencing the formation of the DPSC process and relocation of the Golgi apparatus. Among these factors, nanofibrous architecture, tubular size, and appropriate microisland area were indispensable for initiating DPSC polarization, whereas gravity served as an auxiliary factor to the process of DPSC polarization. Meanwhile, microisland geometry had a limited effect on DPSC polarization. Collectively, this work provides information on DPSC polarization and paves the way for the development of new biomaterials for tubular dentin regeneration.
Asunto(s)
Pulpa Dental , Células Madre , Diferenciación CelularRESUMEN
For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no national database to track those trainees and no evidence to indicate that they entered academia upon graduation. The objective of this study was to assess outcomes of dental school-affiliated oral sciences PhD program enrollment, graduates, and placement between 1994 and 2016. Using the American Dental Association annual survey of advanced dental education programs not accredited by the Commission on Dental Accreditation and data obtained from 22 oral sciences PhD programs, we assessed student demographics, enrollment, graduation, and placement. Based on the data provided by program directors, the average new enrollment was 33, and graduation was 26 per year. A total of 605 graduated; 39 did not complete; and 168 were still in training. Among those 605 graduates, 211 were faculty in U.S. academic institutions, and 77 were faculty in foreign institutions. Given that vacant budgeted full-time faculty positions averaged 257 per year during this period, graduates from those oral sciences PhD programs who entered academia in the United States would have filled 9 (3.6%) vacant faculty positions per year. Therefore, PhD programs have consistently generated only a small pipeline of dental school faculty. Better mentoring to retain talent in academia is necessary. Stronger support and creative funding plans are essential to sustain the PhD program. Furthermore, the oral sciences PhD program database should be established and maintained by dental professional organizations to allow assessments of training models, trends of enrollment, graduation, and placement outcomes.
Asunto(s)
Educación de Posgrado en Odontología/estadística & datos numéricos , Humanos , Facultades de Odontología/estadística & datos numéricos , Encuestas y Cuestionarios , Estados UnidosRESUMEN
Three samples of commercially available mineral-based sorbents (zeolite, bentonite and diatomaceous earth) were selected and evaluated for Hg capture under conditions of simulated dry flue gas atmosphere typical in Municipal Solid Waste Incineration (MSWI). The experiments were carried out in a lab-scale fixed-bed device at temperatures between 120 and 200⯰C. Two samples of activated carbons (AC) (raw-AC and sulphur impregnated AC) were tested under the same conditions. The mineral-based sorbents were chemically promoted by sulphur, FeCl3 and CaBr2, achieving an improvement in the overall reduction percentage of Hg0out (g) up to 85%, which was comparable to that obtained using a commercial activated carbon for Hg capture (sulphur impregnated AC). The study demonstrates that sorbents with a matrix relatively richer in TiO2, Fe2O3 and Al2O3, as bentonite, favour Hg heterogeneous oxidation. The best Hg capture capacity was achieved with a zeolite sorbent sample characterized by high specific surface (132â¯m2/g) and impregnated with elemental sulphur. The final form of mercury retained in this sorbent was HgS with proved long-term stability in disposal and landfilling. The higher the temperature, the lower the efficiency of Hg capture being the optimum temperature for Hg-capture in the range of 120-150⯰C. This study provides a basis for the development of new efficient non-carbon sorbents for mercury removal in the air pollution control lines of MSWI facilities considering the non-hazardous final form of mercury and its long-term landfilling/sequestration.
Asunto(s)
Contaminantes Atmosféricos/química , Incineración , Mercurio/química , Adsorción , Contaminantes Atmosféricos/análisis , Contaminación del Aire , Compuestos Férricos , Gases , Mercurio/análisis , Eliminación de ResiduosRESUMEN
This study describes the main mechanisms that take part in the mercury homogeneous oxidation pathway in presence of some of the main reactive compounds formed during waste incineration processes (O2, HCl, SO2 and NO). Series of model, synthetic dry flue gases were used to elucidate the effects of HCl, SO2, NO and their proportions in the gas on mercury behaviour. Three samples of fly ash collected from a MSWI facility were characterized and evaluated both for Hg heterogeneous oxidation and Hg removal in a laboratory scale device. The results obtained in this study showed that homogeneous mercury oxidation in the models MSWI and coal combustion flue gas atmospheres was 52 ± 5% and 25%, respectively. SO2, NO and HCl have a synergetic effect in Hg oxidation in presence of oxygen, but the main differences found are mainly caused by the strong influence of HCl and the likely inhibitory oxidation effects of SO2. Surface area together with carbon and chloride content of the fly ashes were correlated with their capacity for Hg-heterogeneous oxidation and adsorption. The sample of fly ash with relatively high content of unburnt carbon and chlorine, and with BET surface (2.42 m2/g) was able to remove up to 100% of Hg0 (g) during 300 min. The results obtained in this study provide a complete overview of the behaviour of mercury during MSWI processes and may help to clarify the fate/behaviour of mercury in a filter (e.g. electrostatic precipitator) providing a deeper knowledge about the impacts of fly ash properties on mercury fate in waste incineration.
Asunto(s)
Contaminantes Atmosféricos , Ceniza del Carbón , Mercurio/química , Carbón Mineral , Gases , Incineración , Oxidación-ReducciónRESUMEN
Previous studies demonstrated that chondroitin sulfate proteoglycans (CSPGs) on apical surfaces of palatal medial edge epithelial (MEE) cells were necessary for palatal adhesion. In this study, we identified 2 proteoglycans, biglycan and decorin, that were expressed in the palatal shelves prior to adhesion. In addition, we established that these proteoglycans were dependent on transforming growth factor ß (TGFß) signaling. Laser capture microdissection was used to collect selected palatal epithelial cells from embryonic mouse embryos at various palate development stages. The expression of specific messenger RNA (mRNA) for biglycan and decorin was determined with quantitative real-time polymerase chain reaction. The TGFßrI kinase inhibitor (SB431542) was used in palatal organ cultures to determine if blocking TFGß signaling changed biglycan and decorin distribution. Immunohistochemistry of both biglycan and decorin revealed expression on the apical and lateral surfaces of MEE cells. Biglycan protein and mRNA levels peaked as the palatal shelves adhered. Decorin was less abundant on the apical epithelial surface and also had reduced mRNA levels compared to biglycan. Their proteins were not expressed on MEE cells of palates treated with SB431542, an inhibitor of TGFß signaling. The temporal expression of biglycan and decorin on the apical surface of MEE, combined with the evidence that these proteins were regulated through the TGFß pathway, indicated that they may be important for adhesion.
Asunto(s)
Biglicano/metabolismo , Adhesión Celular/fisiología , Decorina/metabolismo , Hueso Paladar/citología , Animales , Benzamidas/farmacología , Dioxoles/farmacología , Inmunohistoquímica , Captura por Microdisección con Láser , Ratones , Hueso Paladar/embriología , ARN Mensajero/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Transducción de Señal , Factor de Crecimiento Transformador beta/farmacologíaRESUMEN
The mechanisms linking sensation and action during learning are poorly understood. Layer 2/3 neurons in the motor cortex might participate in sensorimotor integration and learning; they receive input from sensory cortex and excite deep layer neurons, which control movement. Here we imaged activity in the same set of layer 2/3 neurons in the motor cortex over weeks, while mice learned to detect objects with their whiskers and report detection with licking. Spatially intermingled neurons represented sensory (touch) and motor behaviours (whisker movements and licking). With learning, the population-level representation of task-related licking strengthened. In trained mice, population-level representations were redundant and stable, despite dynamism of single-neuron representations. The activity of a subpopulation of neurons was consistent with touch driving licking behaviour. Our results suggest that ensembles of motor cortex neurons couple sensory input to multiple, related motor programs during learning.
Asunto(s)
Retroalimentación Sensorial/fisiología , Aprendizaje/fisiología , Modelos Neurológicos , Corteza Motora/fisiología , Animales , Conducta Animal/fisiología , Hipocampo/fisiología , Potenciación a Largo Plazo/fisiología , Ratones , Microscopía , Corteza Motora/citología , Plasticidad Neuronal/fisiología , Desempeño Psicomotor/fisiología , Ratas , Lengua/fisiología , Tacto/fisiología , Vibrisas/fisiologíaRESUMEN
The authors present a case of a 40-year-old man who intentionally stabbed himself several times in the trachea and larynx during a suicide attempt, and also inflicted other penetrating injuries of the stomach and liver upon himself. The preoperative examination using fiber-optic tracheoscopy and CT revealed only transection of the ligamentum cricothyroideum; the remaining two defects were discovered later, during the surgical revision. All three injuries were successfully treated with sutures, in one case using the transtracheal approach.
Asunto(s)
Laringe/lesiones , Laringe/cirugía , Intento de Suicidio , Tráquea/lesiones , Tráquea/cirugía , Heridas Penetrantes/diagnóstico por imagen , Heridas Penetrantes/cirugía , Adulto , Humanos , Laringectomía/métodos , Laringe/diagnóstico por imagen , Masculino , Radiografía , Tráquea/diagnóstico por imagen , Traqueotomía/métodos , Resultado del TratamientoRESUMEN
Accuracy of MRI reports is taken for granted. In this paper the inter-observer reliability in the interpretation of meniscal lesions, degree of chondropathy, and integrity of the ACL was analyzed while taking the radiologist's experience and field strength into account. Fifty-two MRI studies of knees were interpreted by 11 radiologists independently. Twenty-two were acquired on 1.0-T, 20 on 1.5-T, and 10 on 3.0-T systems. Four of the radiologists had more than 5 years and seven had 3 to 5 years of experience in interpreting MRI studies. The findings were compared with the intra-operative findings. Inter-observer variance, specificity, and sensitivity were evaluated for each field strength. Inter-observer correlation ranged between 0.370 for cartilage lesions and 0.597 for meniscal tears. Correlation values did not increase with experience or field strength. The number of false reports was dependent on the observer, but not on field strength. The rate of false interpretations was significantly higher for most criteria in the less experienced group. In conclusion, inter-observer correlation was low, although the diagnostic criteria were defined. The use of the classification scheme should be standardized by uniform training. Radiologist experience seems to be more important than field strength.
Asunto(s)
Lesiones del Ligamento Cruzado Anterior , Ligamento Cruzado Anterior/patología , Aumento de la Imagen/métodos , Traumatismos de la Rodilla/diagnóstico , Imagen por Resonancia Magnética/métodos , Meniscos Tibiales/patología , Lesiones de Menisco Tibial , Adolescente , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Variaciones Dependientes del Observador , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Adulto JovenRESUMEN
BACKGROUND: Central neurocytoma (CN) represents a rare, relatively recently described primary central nervous system tumor. It ranks among intraventricular tumors due to its predominant location within the lateral brain ventricles. CN occurs mostly in young adults around the 3rd decade of life; almost a fifth of the cases are children under 18 years of age. OBJECTIVES: The authors present three cases of patients with histopathologically confirmed CN, emphasizing diagnostic imaging issues. A review of the literature concerning differential diagnosis and clinical and therapeutic aspects is also presented. CONCLUSION: Literature reports of CN comprise most likely case reports, small cohorts of patients, and meta-analytic studies due to the generally low incidence of this tumor. In the current paper, the authors summarize up-to-date knowledge of this rare disease on the background of their own observations. CN should be included in the list for differential diagnostics of intraventricular brain tumors, especially those located in lateral ventricles.
Asunto(s)
Neoplasias del Ventrículo Cerebral/diagnóstico por imagen , Neurocitoma/diagnóstico por imagen , Adolescente , Adulto , Neoplasias del Ventrículo Cerebral/patología , Neoplasias del Ventrículo Cerebral/terapia , Terapia Combinada , Diagnóstico Diferencial , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Neurocitoma/patología , Neurocitoma/terapia , Procedimientos Neuroquirúrgicos , Radioterapia , Tomografía Computarizada por Rayos XRESUMEN
Epithelial to mesenchymal phenotype transition is a common phenomenon during embryonic development, wound healing, and tumor metastasis. This transition involves cellular changes in cytoskeleton architecture and protein expression. Specifically, this highly regulated biological event plays several important roles during craniofacial development. This review focuses on the regulation of epithelial-mesenchymal transformation (EMT) during neural crest cell migration, and fusion of the secondary palate and the upper lip.
Asunto(s)
Epitelio/embriología , Desarrollo Maxilofacial/genética , Mesodermo/citología , Paladar Duro/embriología , Animales , Labio Leporino/embriología , Fisura del Paladar/embriología , Regulación del Desarrollo de la Expresión Génica , Humanos , Labio/embriología , Cresta Neural/citología , Transducción de SeñalRESUMEN
Current thinking about long-term memory in the cortex is focused on changes in the strengths of connections between neurons. But ongoing structural plasticity in the adult brain, including synapse formation/elimination and remodelling of axons and dendrites, suggests that memory could also depend on learning-induced changes in the cortical 'wiring diagram'. Given that the cortex is sparsely connected, wiring plasticity could provide a substantial boost in storage capacity, although at a cost of more elaborate biological machinery and slower learning.
Asunto(s)
Corteza Cerebral/citología , Corteza Cerebral/fisiología , Memoria/fisiología , Animales , Corteza Cerebral/anatomía & histología , Humanos , Modelos Neurológicos , Plasticidad Neuronal/fisiología , Neuronas/citología , Neuronas/fisiologíaRESUMEN
OBJECTIVES: To analyze the effects of nicotine on palatal fusion inhibition in vitro and determine if nicotine modulated transforming growth factor beta3 or phosphatidylinositol-3 kinase signaling. A second objective was to determine the localization and regulation of nicotinic receptors in the medial edge epithelia (MEE) during palatal fusion. DESIGN: Palatal shelves from embryonic day (E) 13.5 mice were cultured in serum free media and treated with 0, 0.06, 0.6, or 6 mM nicotine, nicotinic receptor antagonist alpha-bungarotoxin, or the combination of nicotine and alpha-bungarotoxin. Tissues harvested at 72 h were analyzed for epithelial-mesenchymal transformation (EMT) and fusion. MEE samples collected at 20 h were analyzed for phosphorylated Akt-Ser473, phosphorylated Smad2, and nicotinic receptors. RESULTS: Nicotine inhibited palatal fusion in vitro in a dose dependent manner. Activated Akt-Ser473 was greater in control MEE than in nicotine treated tissues; while there was no difference in activated Smad2 between groups. The alpha7 subunit of nicotinic receptor was expressed in MEE during palate fusion and increased in nicotine treated tissues. Alpha-bungarotoxin did not rescue the nicotine treated palates. CONCLUSION: Nicotine treatment had no effect on Smad2, but caused a down regulation of the PI-3 kinase pathway that may have contributed to inhibiting palatal fusion in vitro.
Asunto(s)
Fisura del Paladar/inducido químicamente , Fisura del Paladar/embriología , Nicotina/toxicidad , Agonistas Nicotínicos/toxicidad , Paladar Duro/efectos de los fármacos , Paladar Duro/embriología , Proteínas Serina-Treonina Quinasas , Transducción de Señal/efectos de los fármacos , Animales , Bungarotoxinas/farmacología , Proteínas de Unión al ADN/metabolismo , Epitelio/efectos de los fármacos , Epitelio/embriología , Inmunohistoquímica , Mesodermo/efectos de los fármacos , Ratones , Ratones Endogámicos , Microscopía Confocal , Técnicas de Cultivo de Órganos , Fosfatidilinositol 3-Quinasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Receptores Nicotínicos/metabolismo , Proteína Smad2 , Transactivadores/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Factor de Crecimiento Transformador beta3RESUMEN
The purpose of this study was to classify selective oestrogen receptor modulators based on gene expression profiles produced in breast cancer cells expressing either wtERalpha or mutant(351)ERalpha. In total, 54 microarray experiments were carried out by using a commercially available Atlas cDNA Expression Arrays (Clontech), containing 588 cancer-related genes. Nine sets of data were generated for each cell line following 24 h of treatment: expression data were obtained for cells treated with vehicle EtOH (Control); with 10(-9) or 10(-8) M oestradiol; with 10(-6) M 4-hydroxytamoxifen; with 10(-6) M raloxifene; with 10(-6) M idoxifene, with 10(-6) M EM 652, with 10(-6) M GW 7604; with 5 x 10(-5) M resveratrol and with 10(-6) M ICI 182,780. We developed a new algorithm 'Expression Signatures' to classify compounds on the basis of differential gene expression profiles. We created dendrograms for each cell line, in which branches represent relationships between compounds. Additionally, clustering analysis was performed using different subsets of genes to assess the robustness of the analysis. In general, only small differences between gene expression profiles treated with compounds were observed with correlation coefficients ranged from 0.83 to 0.98. This observation may be explained by the use of the same cell context for treatments with compounds that essentially belong to the same class of drugs with oestrogen receptors related mechanisms. The most surprising observation was that ICI 182,780 clustered together with oestrodiol and raloxifene for cells expressing wtERalpha and clustered together with EM 652 for cells expressing mutant(351)ERalpha. These data provide a rationale for a more precise and elaborate study in which custom made oligonucleotide arrays can be used with comprehensive sets of genes known to have consensus and putative oestrogen response elements in their promoter regions.
Asunto(s)
Neoplasias de la Mama/genética , Receptores de Estrógenos/genética , Neoplasias de la Mama/metabolismo , Receptor alfa de Estrógeno , Perfilación de la Expresión Génica , Humanos , Análisis de Secuencia por Matrices de Oligonucleótidos , Receptores de Estrógenos/metabolismo , Células Tumorales CultivadasRESUMEN
Apoptosis is involved in many biological processes, especially during chemotherapy in cancer patients. Chemotherapy is also associated with an increased risk of thrombosis. The relationship between thrombogenicity and apoptosis was studied in various human tumour cell lines and non-tumour cell lines. Apoptosis was induced by the chemotherapeutic agent camptothecin and by Fas ligand, then quantified by staining with fluorescein isothiocyanate-conjugated annexin V and propidium iodide. A significant correlation between thrombin generation and degree of apoptosis was observed (P < 0.0005). Addition of anti-tissue factor antibody in excess or of tissue factor pathway inhibitor partially inhibited thrombin generation, suggesting that tissue factor activation was responsible for this process. A statistical correlation between tissue factor activity and degree of apoptosis was also found (P < 0.005). Both thrombin generation and tissue factor activity were blocked by the addition of annexin V, which binds and inhibits phosphatidylserine. This indicates that the exteriorization and exposure of phosphatidylserine on the cell surface membrane during apoptosis were essential for both thrombin generation and tissue factor activation.
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Apoptosis/fisiología , Neoplasias/metabolismo , Trombina/biosíntesis , Anexina A5/farmacología , Antineoplásicos Fitogénicos/farmacología , Apoptosis/efectos de los fármacos , Camptotecina/farmacología , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Humanos , Neoplasias/patología , Fosfatidilserinas/antagonistas & inhibidores , Fosfatidilserinas/fisiología , Tromboplastina/metabolismo , Células Tumorales CultivadasRESUMEN
Programmed cell death is a normal aspect of neuronal development. Typically, twice as many neurons are generated than survive. In extreme cases, all neurons within a population disappear during embryogenesis or by early stages of postnatal development. Examples of transient neuronal populations include Cajal-Retzius cells of the cerebral cortex and Rohon-Beard cells of the spinal cord. The novel mechanisms that lead to such massive cell death have not yet been identified. We provide evidence that electrical activity regulates the cell death program of zebrafish Rohon-Beard cells. Activity was inhibited by reducing Na+ current in Rohon-Beard cells either genetically (the macho mutation) or pharmacologically (tricaine). We examined the effects of activity block on three different reporters of cell death: DNA fragmentation, cytoskeletal rearrangements and cell body loss. Both the mao mutation and pharmacological blockade of Na+ current reduced these signatures of the cell death program. Moreover, the mao mutation and pharmacological blockade of Na+ current produced similar reductions in Rohon-Beard cell death. The results indicate that electrical activity provides signals that are required for the normal elimination of Rohon-Beard cells.
Asunto(s)
Apoptosis , Canales de Sodio/metabolismo , Médula Espinal/embriología , Pez Cebra/embriología , Acetilación , Aminobenzoatos/farmacología , Anestésicos/farmacología , Animales , Cationes Monovalentes/metabolismo , Conductividad Eléctrica , Mutación , Estimulación Física , Sodio/metabolismo , Canales de Sodio/genética , Médula Espinal/citología , Tacto , Tubulina (Proteína)/análogos & derivados , Tubulina (Proteína)/metabolismoRESUMEN
Cortical synaptic circuitry develops rapidly in the second postnatal week, simultaneous with experience-dependent turnover of dendritic spines. To relate the emergence of sensory maps to synaptogenesis, we recorded synaptic potentials evoked by whisker deflection in layer 2/3 neurons from postnatal day (P) 12 to 20. At P12, synaptic responses were undetectable. Only 2 days later in life (P14), receptive fields had mature organization. Sensory deprivation, if initiated before P14, disrupted receptive field structure. In layer 4, responses and maps were already mature by P12 and insensitive to deprivation, implying that barrel cortex develops from layer 4 to layer 2/3. Thus, P12-14 is a critical period shared by layer 2/3 synapses and their spines, suggesting that spine plasticity is involved in the refinement of maps.
Asunto(s)
Plasticidad Neuronal , Corteza Somatosensorial/crecimiento & desarrollo , Envejecimiento , Animales , Dendritas/fisiología , Dendritas/ultraestructura , Electroencefalografía , Potenciales Evocados , Potenciales de la Membrana , Neuronas/fisiología , Neuronas/ultraestructura , Ratas , Ratas Sprague-Dawley , Corteza Somatosensorial/fisiología , Corteza Somatosensorial/ultraestructura , Sinapsis/fisiología , Vibrisas/inervaciónRESUMEN
Fragile X syndrome is caused by a mutation in the FMR1 gene leading to absence of the fragile X mental retardation protein (FMRP). Reports that patients and adult FMR1 knock-out mice have abnormally long dendritic spines of increased density suggested that the disorder might involve abnormal spine development. Because spine length, density, and motility change dramatically in the first postnatal weeks, we analyzed these properties in mutant mice and littermate controls at 1, 2, and 4 weeks of age. To label neurons, a viral vector carrying the enhanced green fluorescent protein gene was injected into the barrel cortex. Layer V neurons were imaged on a two-photon laser scanning microscope in fixed tissue sections. Analysis of >16,000 spines showed clear developmental patterns. Between 1 and 4 weeks of age, spine density increased 2.5-fold, and mean spine length decreased by 17% in normal animals. Early during cortical synaptogenesis, pyramidal cells in mutant mice had longer spines than controls. At 1 week, spine length was 28% greater in mutants than in controls. At 2 weeks, this difference was 10%, and at 4 weeks only 3%. Similarly, spine density was 33% greater in mutants than in controls at 1 week of age. At 2 or 4 weeks of age, differences were not detectable. The spine abnormality was not detected in neocortical organotypic cultures. The transient nature of the spine abnormality in the intact animal suggests that FMRP might play a role in the normal process of dendritic spine growth in coordination with the experience-dependent development of cortical circuits.
Asunto(s)
Extensiones de la Superficie Celular/metabolismo , Extensiones de la Superficie Celular/patología , Síndrome del Cromosoma X Frágil , Proteínas del Tejido Nervioso/deficiencia , Proteínas de Unión al ARN , Envejecimiento/patología , Análisis de Varianza , Animales , Extensiones de la Superficie Celular/ultraestructura , Dendritas/metabolismo , Dendritas/patología , Dendritas/ultraestructura , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil , Síndrome del Cromosoma X Frágil/genética , Genes Reporteros , Técnicas In Vitro , Masculino , Ratones , Ratones Noqueados , Proteínas del Tejido Nervioso/genéticaRESUMEN
Dendritic spines are cellular microcompartments that are isolated from their parent dendrites and neighboring spines. Recently, imaging studies of spine Ca(2+) dynamics have revealed that Ca(2+) can enter spines through voltage-sensitive and ligand-activated channels, as well as through Ca(2+) release from intracellular stores. Relationships between spine Ca(2+) signals and induction of various forms of synaptic plasticity are beginning to be elucidated. Measurements of spine Ca(2+) concentration are also being used to probe the properties of single synapses and even individual calcium channels in their native environment.