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Hypothalamic Adult Neurogenesis (hAN) has been implicated in regulating energy homeostasis. Adult-generated neurons and adult Neural Stem Cells (aNSCs) in the hypothalamus control food intake and body weight. Conversely, diet-induced obesity (DIO) by high fat diets (HFD) exerts adverse influence on hAN. However, the effects of anti-obesity compounds on hAN are not known. To address this, we administered a lipidized analogue of an anti-obesity neuropeptide, Prolactin Releasing Peptide (PrRP), so-called LiPR, to mice. In the HFD context, LiPR rescued the survival of adult-born hypothalamic neurons and increased the number of aNSCs by reducing their activation. LiPR also rescued the reduction of immature hippocampal neurons and modulated calcium dynamics in iPSC-derived human neurons. In addition, some of these neurogenic effects were exerted by another anti-obesity compound, Liraglutide. These results show for the first time that anti-obesity neuropeptides influence adult neurogenesis and suggest that the neurogenic process can serve as a target of anti-obesity pharmacotherapy.
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Neuropeptídeos , Obesidade , Camundongos , Humanos , Animais , Hormônio Liberador de Prolactina/farmacologia , Hormônio Liberador de Prolactina/uso terapêutico , Obesidade/tratamento farmacológico , Peso Corporal , Neurogênese , HipotálamoRESUMO
Insights from embryonic development suggest chromatin remodeling is important in adult neural stem cells (aNSCs) maintenance and self-renewal, but this concept has not been fully explored in the adult brain. To assess the role of chromatin remodeling in adult neurogenesis, we inducibly deleted Brg1--the core subunit of SWI/SNF-like Brg1/Brm-associated factor chromatin remodeling complexes--in nestin-expressing aNSCs and their progeny in vivo and in culture. This resulted in abnormal adult neurogenesis in the hippocampus, which initially reduced hippocampal aNSCs and progenitor maintenance, and later reduced its responsiveness to physiological stimulation. Mechanistically, deletion of Brg1 appeared to impair cell cycle progression, which is partially due to elevated p53 pathway and p21 expression. Knockdown of p53 rescued the neurosphere growth defects caused by Brg1 deletion. Our results show that epigenetic chromatin remodeling (via a Brg1 and p53/p21-dependent process) determines the aNSCs and progenitor maintenance and responsiveness of neurogenesis.
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Células-Tronco Adultas/metabolismo , DNA Helicases/metabolismo , Hipocampo/metabolismo , Nestina/metabolismo , Células-Tronco Neurais/metabolismo , Neurogênese , Proteínas Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Células-Tronco Adultas/citologia , Animais , DNA Helicases/genética , Regulação da Expressão Gênica , Hipocampo/citologia , Camundongos , Camundongos Transgênicos , Nestina/genética , Células-Tronco Neurais/citologia , Proteínas Nucleares/genética , Fatores de Transcrição/genética , Proteína Supressora de Tumor p53/biossíntese , Proteína Supressora de Tumor p53/genéticaRESUMO
Myocyte enhancer factor (Mef)-2 transcription factors are implicated in activity-dependent neuronal processes during development, but the role of MEF2 in neural stem/progenitor cells (NSPCs) in the adult brain is unknown. We used a transgenic mouse in which Mef2a, -c, and -d were inducibly deleted in adult nestin-expressing NSPCs and their progeny. Recombined cells in the hippocampal granule cell layer were visualized and quantified by yellow fluorescent protein (YFP) expression. In control mice, postmitotic neurons expressed Mef2a, -c, and -d, whereas type 1 stem cells and proliferating progenitors did not. Based on this expression, we hypothesized that Mef2a, -c, and -d deletion in adult nestin-expressing NSPCs and their progeny would result in fewer mature neurons. Control mice revealed an increase in YFP(+) neurons and dendrite formation over time. Contrary to our hypothesis, inducible Mef2 KO mice also displayed an increase in YFP(+) neurons over time-but with significantly stunted dendrites-suggesting an uncoupling of neuron survival and dendritogenesis. We also found non-cell-autonomous effects after Mef2a, -c, and -d deletion. These in vivo findings indicate a surprising functional role for Mef2a, -c, and -d in cell- and non-cell-autonomous control of adult hippocampal neurogenesis that is distinct from its role during development.
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Dendritos , Nestina/metabolismo , Neurogênese , Células-Tronco/metabolismo , Animais , Hipocampo/metabolismo , Camundongos , Camundongos KnockoutRESUMO
PURPOSE: To compare health-related quality of life (QoL) in urinary, bowel, and sexual domains after combined external beam radiation therapy (EBRT) and either low-dose rate (LDR) or high-dose rate (HDR) prostate brachytherapy (BT). METHODS AND MATERIALS: Eligible men with intermediate or high-risk prostate cancer treated with combined pelvic EBRT and BT were randomly assigned to either HDR (15 Gy) or LDR (110 Gy) boost. International Prostate Symptom Score, Index of Erectile Function, and Expanded Prostate Cancer Composite were collected at baseline, 1, 3, 6, and 12 months, every 6 months to 3 years and then annually along with prostate-specific antigen/testosterone. Fisher's exact test compared categorical variables and the Mann-Whitney U test Expanded Prostate Cancer Index Composite (EPIC) domain scores. RESULTS: From January 2014 to December 2019, a random number generator assigned 195 men: 108 to HDR and 87 to LDR. Median age was 71 years. Risk group was high in 57% and unfavorable intermediate in 43%. Androgen deprivation (used in 74%) began with 3 months neoadjuvant and continued for median 12 months. Baseline EPIC scores were similar for the LDR/HDR cohorts: 89 and 88 respectively for Genito-urinary; 92 and 93 for Gastro-intestinal. EPIC urinary scores decreased at 1 month for HDR but recovered promptly to a steady state by 6 months. LDR scores reached a nadir at 3 months with slow recovery to 18 months, after which urinary QoL was similar for HDR and LDR. Bowel QOL scores fell in both cohorts reaching respective nadirs at 12 months. HDR patients recovered close to baseline and maintained higher scores than LDR patients to 5 years. The decline for LDR patients remained more than the minimum clinically important difference out to 5 years. CONCLUSIONS: The patient experience for combined EBRT and prostate BT is improved with HDR BT. Urinary QoL improves over time to be equivalent between the 2 modalities after 18 months, but LDR patients report lasting bowel symptoms.
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Braquiterapia , Neoplasias da Próstata , Qualidade de Vida , Dosagem Radioterapêutica , Masculino , Humanos , Braquiterapia/métodos , Braquiterapia/efeitos adversos , Neoplasias da Próstata/radioterapia , Idoso , Pessoa de Meia-Idade , Antagonistas de Androgênios/uso terapêutico , Pelve , Disfunção Erétil/etiologia , Idoso de 80 Anos ou mais , Antígeno Prostático Específico/sangueRESUMO
PURPOSE: This trial examined if patients with ≤5 sites of oligoprogression benefit from the addition of stereotactic ablative radiotherapy (SABR) to standard of care (SOC) systemic therapy. METHODS: We enrolled patients with 1-5 metastases progressing on systemic therapy, and after stratifying by type of systemic therapy (cytotoxic vs. non-cytotoxic), randomized 1:2 between continued SOC treatment vs. SABR to all progressing lesions plus SOC. The trial was initially limited to non-small cell lung cancer but was expanded to include all non-hematologic malignancies to meet accrual goals. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), lesional control, quality of life, adverse events (AEs), and duration of systemic therapy post-randomization. RESULTS: Ninety patients with 127 oligoprogressive metastases were enrolled across 8 Canadian institutions, with 59 randomized to SABR and 31 to SOC. Median age was 67 years and 39 (43%) were female. The most common primary sites were lung (44%), genitourinary (23%) and breast (13%). Protocol adherence in the SOC arm was suboptimal, with 11 patients (35%) either receiving high-dose/ablative therapies (conflicting with trial protocol) or withdrawing from the study. Median follow-up was 31 months. There was no difference in PFS between arms (median PFS 8.4 months in the SABR arm vs. 4.3 months in the SOC arm but curves cross and 2-year PFS was 9% vs. 24% respectively, p=0.91). Median OS was 31.2 months vs. 27.4 months, respectively (p=0.22). Lesional control was superior with SABR (70% vs. 38% respectively, p=0.0015). There were 2 (3.4%) grade 3 and no grade 4/5 AEs attributable to SABR. CONCLUSION: SABR was well-tolerated with superior lesional control but did not improve PFS or OS. Accrual to this study was difficult, and the results may have been impacted by an unwillingness to forgo ablative treatments on the SOC arm. (NCT02756793).
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Radial glia-like cells (RGCs) are the hypothesized source of adult hippocampal neurogenesis. However, the current model of hippocampal neurogenesis does not fully incorporate the in vivo heterogeneity of RGCs. In order to better understand the contribution of different RGC subtypes to adult hippocampal neurogenesis, we employed widely used transgenic lines (Nestin-CreER(T2) and GLAST::CreER(T2) mice) to explore how RGCs contribute to neurogenesis under basal conditions and after stimulation and depletion of neural progenitor cells. We first used these inducible fate-tracking transgenic lines to define the similarities and differences in the contribution of nestin- and GLAST-lineage cells to basal long-term hippocampal neurogenesis. We then explored the ability of nestin- and GLAST-lineage RGCs to contribute to neurogenesis after experimental manipulations that either ablate neurogenesis (i.c.v. application of the anti-mitotic AraC, cytosine-ß-D-arabinofuranoside) or stimulate neurogenesis (wheel running). Interestingly, in both ablation and stimulation experiments, labeled RGCs in GLAST::CreER(T2) mice appear to contribute to neurogenesis, whereas RGCs in Nestin-CreER(T2) mice do not. Finally, using NestinGFP reporter mice, we expanded on previous research by showing that not all RGCs in the adult dentate gyrus subgranular zone express nestin, and therefore RGCs are antigenically heterogeneous. These findings are important for the field, as they allow appropriately conservative interpretation of existing and future data that emerge from these inducible transgenic lines. These findings also raise important questions about the differences between transgenic driver lines, the heterogeneity of RGCs, and the potential differences in progenitor cell behavior between transgenic lines. As these findings highlight the possible differences in the contribution of cells to long-term neurogenesis in vivo, they indicate that the current models of hippocampal neurogenesis should be modified to include RGC lineage heterogeneity.
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Linhagem da Célula/fisiologia , Transportador 1 de Aminoácido Excitatório/metabolismo , Hipocampo/citologia , Nestina/metabolismo , Neurogênese/fisiologia , Animais , Proteínas do Domínio Duplacortina , Transportador 1 de Aminoácido Excitatório/genética , Proteína 7 de Ligação a Ácidos Graxos , Proteínas de Ligação a Ácido Graxo/metabolismo , Proteína Glial Fibrilar Ácida/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas Associadas aos Microtúbulos/metabolismo , Atividade Motora/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Nestina/genética , Neuroglia/fisiologia , Neurônios/fisiologia , Neuropeptídeos/metabolismo , Técnicas de Cultura de Órgãos , Fatores de Transcrição SOXB1/metabolismo , Células-Tronco/fisiologiaRESUMO
Adult neurogenesis occurs throughout life in the mammalian hippocampus and is essential for memory and mood control. There is significant interest in identifying ways to promote neurogenesis and ensure maintenance of these hippocampal functions. Previous work with a synthetic small molecule, isoxazole 9 (Isx-9), highlighted its neuronal-differentiating properties in vitro. However, the ability of Isx-9 to drive neurogenesis in vivo or improve hippocampal function was unknown. Here we show that Isx-9 promotes neurogenesis in vivo, enhancing the proliferation and differentiation of hippocampal subgranular zone (SGZ) neuroblasts, and the dendritic arborization of adult-generated dentate gyrus neurons. Isx-9 also improves hippocampal function, enhancing memory in the Morris water maze. Notably, Isx-9 enhances neurogenesis and memory without detectable increases in cellular or animal activity or vascularization. Molecular exploration of Isx-9-induced regulation of neurogenesis (via FACS and microarray of SGZ stem and progenitor cells) suggested the involvement of the myocyte-enhancer family of proteins (Mef2). Indeed, transgenic-mediated inducible knockout of all brain-enriched Mef2 isoforms (Mef2a/c/d) specifically from neural stem cells and their progeny confirmed Mef2's requirement for Isx-9-induced increase in hippocampal neurogenesis. Thus, Isx-9 enhances hippocampal neurogenesis and memory in vivo, and its effects are reliant on Mef2, revealing a novel cell-intrinsic molecular pathway regulating adult neurogenesis.
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Hipocampo/fisiologia , Isoxazóis/farmacologia , Neurogênese/efeitos dos fármacos , Tiofenos/farmacologia , Animais , Barreira Hematoencefálica/metabolismo , Proliferação de Células/efeitos dos fármacos , Células Dendríticas/efeitos dos fármacos , Giro Denteado/fisiologia , Hipocampo/efeitos dos fármacos , Isoxazóis/metabolismo , Fatores de Transcrição MEF2 , Aprendizagem em Labirinto/efeitos dos fármacos , Memória/efeitos dos fármacos , Camundongos , Camundongos Transgênicos , Fatores de Regulação Miogênica/fisiologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/fisiologia , Tiofenos/metabolismoRESUMO
Adult neural stem cells (aNSCs) are the source for the continuous production of new neurons throughout life. This so-called adult neurogenesis has been extensively studied; the intermediate cellular stages are well documented. Recent discoveries have raised new controversies in the field, such as the notion that progenitor cells hold similar self-renewal potential as stem cells, or whether different types of aNSCs exist. Here, we discuss evidence for heterogeneity of aNSCs, including short-term and long-term self-renewing aNSCs, regional and temporal differences in aNSC function, and single cell transcriptomics. Reviewing various genetic mouse models used for targeting aNSCs and lineage tracing, we consider potential lineage relationships between Ascl1-, Gli1-, and Nestin-targeted aNSCs. We present a multidimensional model of adult neurogenesis that incorporates recent findings and conclude that stemness is a phenotype, a state of properties that can change with time, rather than a cell property, which is static and immutable. We argue that singular aNSCs do not exist.
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Células-Tronco Adultas , Células-Tronco Neurais , Animais , Camundongos , Neurogênese/genética , NeurôniosRESUMO
Large-conductance voltage- and calcium-activated potassium (BK) channels are large-conductance calcium- and voltage-activated potassium channels critical for neuronal excitability. Some neurons express so called fast-gated, type I BK channels. Other neurons express BK channels assembled with the accessory ß4 subunit conferring slow gating of type II BK channels. However, it is not clear how protein phosphorylation modulates these two distinct BK channel types. Using ß4-knockout mice, we compared fast- or slow-gated BK channels in response to changes in phosphorylation status of hippocampus dentate gyrus granule neurons. We utilized the selective PP2A/PP4 phosphatase inhibitor Fostriecin to study changes in action potential shape and firing properties of the neurons. In ß4-knockout neurons, Fostriecin increases BK current, speeds up BK channel activation and reduces action potential amplitudes. Fostriecin increases spiking during early components of an action potential train. In contrast, inhibition of BK channels through ß4 in wild-type neurons or by the BK channel inhibitor Paxilline opposes Fostriecin effects. Voltage clamp recordings of neurons reveal that Fostriecin increases both calcium and BK currents. However, Fostriecin does not activate BK α channels in transfected HEK293 cells lacking calcium channels. In summary, these results suggest that fast-gating, type I BK channels lacking ß4 can increase neuronal excitability in response to reduced phosphatase activity and activation of calcium channels. By opposing BK channel activation, the ß4 subunit plays an important role in moderating firing frequency regardless of changes in phosphorylation status.
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Giro Denteado/citologia , Subunidades beta do Canal de Potássio Ativado por Cálcio de Condutância Alta/metabolismo , Neurônios/fisiologia , Potenciais de Ação/fisiologia , Animais , AMP Cíclico/metabolismo , Inibidores Enzimáticos/farmacologia , Células HEK293 , Humanos , Subunidades beta do Canal de Potássio Ativado por Cálcio de Condutância Alta/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/efeitos dos fármacos , Técnicas de Patch-Clamp , Fosfoproteínas Fosfatases/antagonistas & inibidores , Fosfoproteínas Fosfatases/metabolismo , Fosforilação , Polienos/farmacologia , Proteína Fosfatase 2/antagonistas & inibidores , Proteína Fosfatase 2/metabolismo , Pironas/farmacologiaRESUMO
PURPOSE/OBJECTIVE Permanent seed Low-Dose-Rate brachytherapy is planned and delivered using transrectal ultrasound (TRUS). Post-implant evaluation for quality assurance is usually performed using Computed Tomography (CT). Registration of the CT images with MRI reduces subjectivity in contouring by improving prostate edge detection. We hypothesized that a set of TRUS images post procedure may provide the same benefit. MATERIAL/METHODS Consecutive patients undergoing Low-Dose-Rate prostate brachytherapy were recruited. TRUS images were recorded under anesthesia at completion of their implant. In addition, all patients underwent standard post-implant quality assurance including prostate CT and MRI at day 30. These were co-registered, contoured and seeds were identified. Three independent observers contoured and registered the post implant TRUS images to the Day 30 CT using seed matching. Prostate volumes and dosimetric parameters were compared through Intraclass Correlation Coefficient (ICC) to evaluate the concordance between MRI and ultrasound (US). RESULTS 26 patients were recruited from 10/17 to 01/18. Mean prostate volume was 34.5 (SD 10.8) cm3 at baseline on planning TRUS images, 37.4 (SD 11.3) cm3 on Day 0 post implant TRUS and 36.7 (SD 11.7) cm3 on Day 30 MRI. D90 was 112.6% (SD 9.3) on CT-MRI and 112.9% (SD 11.1) on CT-US. V100 was 94.6% (SD 3.8) for CT-MRI, 95.1% (SD 4.3) for CT-US. Student t-tests were used to compare groups. No significant differences were noted. CONCLUSION Post implant TRUS may be useful for quality assurance for post-implant dosimetry particularly if access to an MRI is limited.
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Braquiterapia , Neoplasias da Próstata , Braquiterapia/métodos , Humanos , Imageamento por Ressonância Magnética , Masculino , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Dosagem Radioterapêutica , Tomografia Computadorizada por Raios XRESUMO
Radial glia-like (RGL) stem cells persist in the adult mammalian hippocampus, where they generate new neurons and astrocytes throughout life. The process of adult neurogenesis is well documented, but cell-autonomous factors regulating neuronal and astroglial differentiation are incompletely understood. Here, we evaluate the functions of the transcription factor zinc-finger E-box binding homeobox 1 (ZEB1) in adult hippocampal RGL cells using a conditional-inducible mouse model. We find that ZEB1 is necessary for self-renewal of active RGL cells. Genetic deletion of Zeb1 causes a shift toward symmetric cell division that consumes the RGL cell and generates pro-neuronal progenies, resulting in an increase of newborn neurons and a decrease of newly generated astrocytes. We identify ZEB1 as positive regulator of the ets-domain transcription factor ETV5 that is critical for asymmetric division.
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Autorrenovação Celular/fisiologia , Hipocampo/metabolismo , Homeobox 1 de Ligação a E-box em Dedo de Zinco/metabolismo , Animais , Diferenciação Celular/genética , Células Ependimogliais/metabolismo , Transição Epitelial-Mesenquimal/fisiologia , Hipocampo/efeitos dos fármacos , Humanos , Camundongos , Neurogênese/fisiologia , Neurônios/metabolismoRESUMO
These are exciting times for research on adult hippocampal neurogenesis (AHN). Debate and controversy regarding the existence of generation of new neurons in the adult, and even diseased human brain flourishes as articles against and in favor accumulate. Adult neurogenesis in the human brain is a phenomenon that does not share the qualities of quantum mechanics. The scientific community should agree that human AHN exists or does not, but not both at the same time. In this commentary, we discuss the latest research articles about hAHN and what their findings imply for the neurogenesis field.
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One hallmark of adult neurogenesis is its adaptability to environmental influences. Here, we uncovered the epithelial sodium channel (ENaC) as a key regulator of adult neurogenesis as its deletion in neural stem cells (NSCs) and their progeny in the murine subependymal zone (SEZ) strongly impairs their proliferation and neurogenic output in the olfactory bulb. Importantly, alteration of fluid flow promotes proliferation of SEZ cells in an ENaC-dependent manner, eliciting sodium and calcium signals that regulate proliferation via calcium-release-activated channels and phosphorylation of ERK. Flow-induced calcium signals are restricted to NSCs in contact with the ventricular fluid, thereby providing a highly specific mechanism to regulate NSC behavior at this special interface with the cerebrospinal fluid. Thus, ENaC plays a central role in regulating adult neurogenesis, and among multiple modes of ENaC function, flow-induced changes in sodium signals are critical for NSC biology.
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Canais Epiteliais de Sódio/metabolismo , Líquido Extracelular/metabolismo , Células-Tronco Neurais/metabolismo , Animais , Proliferação de Células , Células Cultivadas , Líquido Extracelular/citologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neurais/citologiaRESUMO
Adult neurogenesis in the mammalian brain is often viewed as a continuation of neurogenesis at earlier, developmental stages. Here, we will critically review the extent to which this is the case highlighting similarities as well as key differences. Although many transcriptional regulators are shared in neurogenesis at embryonic and adult stages, recent findings on the molecular mechanisms by which these neuronal fate determinants control fate acquisition and maintenance have revealed profound differences between development and adulthood. Importantly, adult neurogenesis occurs in a gliogenic environment, hence requiring adult-specific additional and unique mechanisms of neuronal fate specification and maintenance. Thus, a better understanding of the molecular logic for continuous adult neurogenesis provides important clues to develop strategies to manipulate endogenous stem cells for the purpose of repair.
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Neurogênese , Adulto , Animais , Ciclo Celular , Linhagem da Célula , HumanosRESUMO
Despite the widespread interest in direct neuronal reprogramming, the mechanisms underpinning fate conversion remain largely unknown. Our study revealed a critical time point after which cells either successfully convert into neurons or succumb to cell death. Co-transduction with Bcl-2 greatly improved negotiation of this critical point by faster neuronal differentiation. Surprisingly, mutants with reduced or no affinity for Bax demonstrated that Bcl-2 exerts this effect by an apoptosis-independent mechanism. Consistent with a caspase-independent role, ferroptosis inhibitors potently increased neuronal reprogramming by inhibiting lipid peroxidation occurring during fate conversion. Genome-wide expression analysis confirmed that treatments promoting neuronal reprogramming elicit an anti-oxidative stress response. Importantly, co-expression of Bcl-2 and anti-oxidative treatments leads to an unprecedented improvement in glial-to-neuron conversion after traumatic brain injury in vivo, underscoring the relevance of these pathways in cellular reprograming irrespective of cell type in vitro and in vivo.
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Técnicas de Reprogramação Celular , Reprogramação Celular , Neuroglia/metabolismo , Neurônios/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/biossíntese , Transdução Genética , Animais , Camundongos , Neuroglia/citologia , Neurônios/citologia , Estresse Oxidativo , Proteínas Proto-Oncogênicas c-bcl-2/genéticaRESUMO
For patients who have stages I and II non-small cell lung cancer (NSCLC) and who are unable or unwilling to undergo surgical resection, nonsurgical treatment modalities have been used with curative intent. Conventionally fractionated radiotherapy has been the mainstay of nonsurgical therapy; however, advances in technology and the clinical application of radiobiologic principles have allowed more accurately targeted treatment that delivers higher effective doses to the tumor, while respecting the tolerance of surrounding normal tissues. This article discusses nonsurgical approaches to the treatment of early-stage NSCLC, including several promising techniques, such as radiation dose escalation, altered radiation fractionation, stereotactic radiotherapy, and radiofrequency ablation.
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Carcinoma Pulmonar de Células não Pequenas/radioterapia , Neoplasias Pulmonares/radioterapia , Carcinoma Pulmonar de Células não Pequenas/patologia , Humanos , Neoplasias Pulmonares/patologia , Estadiamento de Neoplasias , Radioterapia AdjuvanteRESUMO
The high-LET HZE particles from galactic cosmic radiation pose tremendous health risks to astronauts, as they may incur sub-threshold brain injury or maladaptations that may lead to cognitive impairment. The health effects of HZE particles are difficult to predict and unfeasible to prevent. This underscores the importance of estimating radiation risks to the central nervous system as a whole as well as to specific brain regions like the hippocampus, which is central to learning and memory. Given that neurogenesis in the hippocampus has been linked to learning and memory, we investigated the response and recovery of neurogenesis and neural stem cells in the adult mouse hippocampal dentate gyrus after HZE particle exposure using two nestin transgenic reporter mouse lines to label and track radial glia stem cells (Nestin-GFP and Nestin-CreERT2/R26R:YFP mice, respectively). Mice were subjected to 56Fe particle exposure (0 or 1 Gy, at either 300 or 1000 MeV/n) and brains were harvested at early (24h), intermediate (7d), and/or long time points (2-3mo) post-irradiation. 56Fe particle exposure resulted in a robust increase in 53BP1+ foci at both the intermediate and long time points post-irradiation, suggesting long-term genomic instability in the brain. However, 56Fe particle exposure only produced a transient decrease in immature neuron number at the intermediate time point, with no significant decrease at the long time point post-irradiation. 56Fe particle exposure similarly produced a transient decrease in dividing progenitors, with fewer progenitors labeled at the early time point but equal number labeled at the intermediate time point, suggesting a recovery of neurogenesis. Notably, 56Fe particle exposure did not change the total number of nestin-expressing neural stem cells. These results highlight that despite the persistence of an index of genomic instability, 56Fe particle-induced deficits in adult hippocampal neurogenesis may be transient. These data support the regenerative capacity of the adult SGZ after HZE particle exposure and encourage additional inquiry into the relationship between radial glia stem cells and cognitive function after HZE particle exposure.
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PURPOSE: High-dose-rate brachytherapy of the prostate is commonly performed using transrectal ultrasound (US) guidance, with CT imaging used for needle reconstruction and treatment planning. Transrectal ultrasound images can, however, be used for the entire process, allowing treatment without changes in the patient position. This study assesses needle reconstruction accuracy using US images. METHODS AND MATERIALS: Prostate phantoms were implanted with 10-18 needles. Three-dimensional US images were acquired, and needles were reconstructed using specialized software. A CT scan was also obtained. The image sets were registered and needle reconstruction errors were assessed. A dose plan was obtained using the US images and the dwell times were transferred to the CT reconstruction to obtain the true "delivered dose," which was evaluated using standard dosimetric parameters. RESULTS: Two sources of error were identified. First, reconstruction based on the bright echoes in the US images introduces a systematic error because these echoes correspond to the proximal wall of the needle, and not the center of the needle channel. If left uncorrected, this shift can lead to an underestimate of urethral doses. Second, incorrect needle tip identification can occur in the cranial-caudal direction. Errors up to 5.8mm were observed. A measurement of needle lengths protruding beyond the template can be used to compensate for this. CONCLUSIONS: Factors limiting the accuracy of US-based needle reconstruction have been identified. Once recognized, these errors can be corrected for, resulting in accurate implant geometry. This facilitates a treatment technique combining excellent anatomic definition, minimal prostate motion, and accurate dose planning and delivery.
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Braquiterapia/instrumentação , Braquiterapia/métodos , Agulhas , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Ultrassonografia de Intervenção/métodos , Sistemas Computacionais , Humanos , Masculino , Imagens de Fantasmas , Implantação de Prótese/instrumentação , Implantação de Prótese/métodos , Dosagem Radioterapêutica , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Ultrassonografia de Intervenção/instrumentaçãoRESUMO
The early postnatal period is a unique time of brain development, as diminishing amounts of neurogenesis coexist with waves of gliogenesis. Understanding the molecular regulation of early postnatal gliogenesis may provide clues to normal and pathological embryonic brain ontogeny, particularly in regards to the development of astrocytes and oligodendrocytes. Cyclin dependent kinase 5 (Cdk5) contributes to neuronal migration and cell cycle control during embryogenesis, and to the differentiation of neurons and oligodendrocytes during adulthood. However, Cdk5's function in the postnatal period and within discrete progenitor lineages is unknown. Therefore, we selectively removed Cdk5 from nestin-expressing cells and their progeny by giving transgenic mice (nestin-CreERT2/R26R-YFP/CDK5(flox/flox) [iCdk5] and nestin-CreERT2/R26R-YFP/CDK5(wt/wt) [WT]) tamoxifen during postnatal (P) days P2-P 4 or P7-P 9, and quantified and phenotyped recombined (YFP+) cells at P14 and P21. When Cdk5 gene deletion was induced in nestin-expressing cells and their progeny during the wave of cortical and hippocampal gliogenesis (P2-P4), significantly fewer YFP+ cells were evident in the cortex, corpus callosum, and hippocampus. Phenotypic analysis revealed the cortical decrease was due to fewer YFP+ astrocytes and oligodendrocytes, with a slightly earlier influence seen in oligodendrocytes vs. astrocytes. This effect on cortical gliogenesis was accompanied by a decrease in YFP+ proliferative cells, but not increased cell death. The role of Cdk5 in gliogenesis appeared specific to the early postnatal period, as induction of recombination at a later postnatal period (P7-P9) resulted in no change YFP+ cell number in the cortex or hippocampus. Thus, glial cells that originate from nestin-expressing cells and their progeny require Cdk5 for proper development during the early postnatal period.
Assuntos
Animais Recém-Nascidos , Quinase 5 Dependente de Ciclina/metabolismo , Nestina/metabolismo , Neurogênese , Neuroglia/citologia , Células-Tronco/metabolismo , Animais , Encéfalo/citologia , Encéfalo/metabolismo , Camundongos , Camundongos Transgênicos , Neuroglia/enzimologia , Células-Tronco/citologia , Tamoxifeno/administração & dosagemRESUMO
PURPOSE: To compare 30-day seed displacement and seed loss of standard loose seeds to specially engineered coated seeds. METHODS AND MATERIALS: Forty patients with prostate cancer were randomized and treated with either loose seeds or loose "coated" seeds. Implants were preplanned using transrectal ultrasound and performed using preloaded needles containing either standard or coated iodine-125 seeds according to randomization. Pelvic X-rays and CT were performed on Days 0 and 30 and a pelvic magnetic resonance scan on Day 30. Cranial-caudal displacement relative to the center of mass (COM) of the seed cloud of the six most peripheral basal and apical seeds was determined from Day 0 and 30 CT scans using custom software. Day 30 magnetic resonance-CT fusion was performed using a seed-to-seed match for soft tissue contouring on MRI. RESULTS: The mean displacement for the six basal seeds was 0.32 cm (standard deviation [SD], 0.25 cm) and 0.33 cm (SD, 0.27 cm) toward the COM for the regular and coated seeds, respectively (p = 0.35). For the apical seeds, mean displacement was 0.31 cm (SD, 0.35 cm) and 0.43 cm (SD, 0.26 cm) (p = 0.003) toward the COM. More regular seeds (n = 8) were lost from the apical region as compared with one coated seed (p = 0.015). There was a trend to reduction in total seeds lost: 1% for regular seeds as compared with 0.3% for coated seeds. CONCLUSIONS: Coated seeds were found to have a significant anchoring effect that was effective in reducing the number of apical seeds lost because of venous migration.