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1.
Sci Rep ; 10(1): 8063, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32415137

RESUMO

Saturation transfer MRI can be useful in the characterization of different tumour types. It is sensitive to tumour metabolism, microstructure, and microenvironment. This study aimed to use saturation transfer to differentiate between intratumoural regions, demarcate tumour boundaries, and reduce data acquisition times by identifying the imaging scheme with the most impact on segmentation accuracy. Saturation transfer-weighted images were acquired over a wide range of saturation amplitudes and frequency offsets along with T1 and T2 maps for 34 tumour xenografts in mice. Independent component analysis and Gaussian mixture modelling were used to segment the images and identify intratumoural regions. Comparison between the segmented regions and histopathology indicated five distinct clusters: three corresponding to intratumoural regions (active tumour, necrosis/apoptosis, and blood/edema) and two extratumoural (muscle and a mix of muscle and connective tissue). The fraction of tumour voxels segmented as necrosis/apoptosis quantitatively matched those calculated from TUNEL histopathological assays. An optimal protocol was identified providing reasonable qualitative agreement between MRI and histopathology and consisting of T1 and T2 maps and 22 magnetization transfer (MT)-weighted images. A three-image subset was identified that resulted in a greater than 90% match in positive and negative predictive value of tumour voxels compared to those found using the entire 24-image dataset. The proposed algorithm can potentially be used to develop a robust intratumoural segmentation method.

2.
Brain ; 143(1): 359-373, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31782760

RESUMO

Failure of Alzheimer's disease clinical trials to improve or stabilize cognition has led to the need for a better understanding of the driving forces behind cognitive decline in the presence of active disease processes. To dissect contributions of individual pathologies to cognitive function, we used the TgF344-AD rat model, which recapitulates the salient hallmarks of Alzheimer's disease pathology observed in patient populations (amyloid, tau inclusions, frank neuronal loss, and cognitive deficits). scyllo-Inositol treatment attenuated amyloid-ß peptide in disease-bearing TgF344-AD rats, which rescued pattern separation in the novel object recognition task and executive function in the reversal learning phase of the Barnes maze. Interestingly, neither activities of daily living in the burrowing task nor spatial memory in the Barnes maze were rescued by attenuating amyloid-ß peptide. To understand the pathological correlates leading to behavioural rescue, we examined the neuropathology and in vivo electrophysiological signature of the hippocampus. Amyloid-ß peptide attenuation reduced hippocampal tau pathology and rescued adult hippocampal neurogenesis and neuronal function, via improvements in cross-frequency coupling between theta and gamma bands. To investigate mechanisms underlying the persistence of spatial memory deficits, we next examined neuropathology in the entorhinal cortex, a region whose input to the hippocampus is required for spatial memory. Reduction of amyloid-ß peptide in the entorhinal cortex had no effect on entorhinal tau pathology or entorhinal-hippocampal neuronal network dysfunction, as measured by an impairment in hippocampal response to entorhinal stimulation. Thus, rescue or not of cognitive function is dependent on regional differences of amyloid-ß, tau and neuronal network dysfunction, demonstrating the importance of staging disease in patients prior to enrolment in clinical trials. These results further emphasize the need for combination therapeutic approaches across disease progression.

3.
Hypertension ; 74(4): 1041-1051, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31476904

RESUMO

Transient hypertension is a risk factor for Alzheimer disease (AD), but the effects of this interaction on brain vasculature are understudied. Addressing vascular pathology is a promising avenue to potentiate the efficacy of treatments for AD. We used arterial spin labeling magnetic resonance imaging to longitudinally assess brain vascular function and immunohistopathology to examine cerebrovascular remodeling and amyloid load. Hypertension was induced for 1 month by administration of l-NG-nitroarginine-methyl-ester in TgF344-AD rats at the prodromal stage. Following hypertension, nontransgenic rats showed transient cerebrovascular changes, whereas TgF344-AD animals exhibited sustained alterations in cerebrovascular function. Human umbilical cord perivascular cells in combination with scyllo-inositol, an inhibitor of Aß oligomerization, resulted in normalization of hippocampal vascular function and remodeling, in contrast to either treatment alone. Prodromal stage hypertension exacerbates latter AD pathology, and the combination of human umbilical cord perivascular cells with amyloid clearance promotes cerebrovascular functional recovery.


Assuntos
Doença de Alzheimer/fisiopatologia , Hipertensão/fisiopatologia , Doença de Alzheimer/etiologia , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Hemodinâmica/fisiologia , Hipertensão/complicações , Hipertensão/terapia , Imagem por Ressonância Magnética , Ratos , Marcadores de Spin
4.
Neuroimage ; 202: 116101, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31425794

RESUMO

The 3D organization of cerebral blood vessels determines the overall capacity of the cerebral circulation to meet the metabolic requirements of the brain. Imaging methodologies which combine 3D microvascular structural imaging with blood flow quantification can shed light on the relationship between vascular structure and function, in health and disease. This study applies Arterial Spin Labeling (ASL) MRI with a hypercapnic challenge and ex vivo Serial Two-Photon Tomography (STPT) to examine the relationship between blood flow and vascular architecture following traumatic brain injury (TBI) in a mouse. Mice were exposed to a controlled cortical impact TBI and allowed to recover for either 1 day or 4 weeks. At each time point, ASL MRI was performed to quantify cerebral perfusion and the brain vasculature was imaged in 3D with STPT. Registration of ASL to STPT enabled flow changes to be related to the underlying microvascular structure in each ASL voxel. Hypoperfusion under rest and hypercapnia was observed both 1 day and 4 weeks post-TBI. Vessel density and vascular volume were reduced 1 day post-TBI, recovering by 4 weeks; however, the reorganized vasculature at the latter time point possessed an abnormal radial pattern. Our findings demonstrate functionally significant long-term changes in the vascular architecture following injury and illustrate why metrics beyond traditional measures of vessel density are required to understand the impact of vascular structure on function.

5.
Sci Rep ; 9(1): 5499, 2019 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-30940849

RESUMO

Longitudinal studies using two-photon fluorescence microscopy (TPFM) are critical for facilitating cellular scale imaging of brain morphology and function. Studies have been conducted in the mouse due to their relatively higher transparency and long term patency of a chronic cranial window. Increasing availability of transgenic rat models, and the range of established behavioural paradigms, necessitates development of a chronic preparation for the rat. However, surgical craniotomies in the rat present challenges due to craniotomy closure by wound healing and diminished image quality due to inflammation, restricting most rat TPFM experiments to acute preparations. Long-term patency is enabled by employing sterile surgical technique, minimization of trauma with precise tissue handling during surgery, judicious selection of the size and placement of the craniotomy, diligent monitoring of animal physiology and support throughout the surgery, and modification of the home cage for long-term preservation of cranial implants. Immunohistochemical analysis employing the glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) showed activation and recruitment of astrocytes and microglia/macrophages directly inferior to the cranial window at one week after surgery, with more diffuse response in deeper cortical layers at two weeks, and amelioration around four weeks post craniotomy. TPFM was conducted up to 14 weeks post craniotomy, reaching cortical depths of 400 µm to 600 µm at most time-points. The rate of signal decay with increasing depth and maximum cortical depth attained had greater variation between individual rats at a single time-point than within a rat across time.

6.
Neuroimage ; 192: 135-144, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-30669007

RESUMO

The rapid growth in the use of optogenetics for neuroscience applications is largely driven by two important advantages: highly specific cellular targeting through genetic manipulations; and precise temporal control of neuronal activation via temporal modulation of the optical stimulation. The difference between the most commonly used stimulation modalities, namely diffused (i.e. synchronous) and focused (i.e. asynchronous) stimulation has not been described. Furthermore, full realization of optogenetics' potential is hindered by our incomplete understanding of the cellular and network level response to photoactivation. Here we address these gaps by examining the neuronal and cerebrovascular responses to focused and diffuse photostimulation of channelrhodopsin in the Thy1-ChR2 mouse. We presented the responses of photoactivation via 470-nm fiber optic illumination (diffuse) alongside 458-nm raster-scan (focused) stimulation of the barrel field. Local field potentials (LFP) assessment of intracerebral electrophysiology and two-photon fluorescence microscopy measurements of red blood cell (RBC) speed (vRBC) in cortical penetrating vessels revealed ∼40% larger LFP responses (p = 0.05) and twice as large cerebrovascular responses (p = 0.002) under focused vs. diffuse photostimulation (focused: 1.64 ±â€¯0.84 mV LFP amplitude and 75 ±â€¯48% increase in vRBC; diffuse: 1.14 ±â€¯0.75 mV LFP amplitude and 35 ±â€¯23% increase in vRBC). Compared to diffuse photostimulation, focused photostimulation resulted in a ∼65% increase in the yield of cerebrovascular responses (73 ±â€¯10% for focused and 42 ±â€¯29% for diffuse photostimulation) and a doubling of the signal-to-noise ratio of the cerebrovascular response (20.9 ±â€¯14.7 for focused and 10.4 ±â€¯1.4 for diffuse photostimulation). These data reveal important advantages of focused optogenetic photoactivation, which can be easily integrated into single- or two-photon fluorescence microscopy platforms, as a means of assessing neuronal excitability and cerebrovascular reactivity, thus paving the way for broader application of optogenetics in preclinical models of CNS diseases.


Assuntos
Encéfalo/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Channelrhodopsins/metabolismo , Optogenética/métodos , Animais , Encéfalo/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos
7.
Front Mol Neurosci ; 11: 338, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30271324

RESUMO

Although epidemiological evidence suggests significant sex and gender-based differences in stroke risk and recovery, females have been widely under-represented in preclinical stroke research. The neurovascular sequelae of brain ischemia in females, in particular, are largely uncertain. We set out to address this gap by a multimodal in vivo study of neurovascular recovery from endothelin-1 model of cortical focal-stroke in sham vs. ovariectomized female rats. Three weeks post ischemic insult, sham operated females recapitulated the phenotype previously reported in male rats in this model, of normalized resting perfusion but sustained peri-lesional cerebrovascular hyperreactivity. In contrast, ovariectomized (Ovx) females showed reduced peri-lesional resting blood flow, and elevated cerebrovascular responsivity to hypercapnia in the peri-lesional and contra-lateral cortices. Electrophysiological recordings showed an attenuation of theta to low-gamma phase-amplitude coupling in the peri-lesional tissue of Ovx animals, despite relative preservation of neuronal power. Further, this chronic stage neuronal network dysfunction was inversely correlated with serum estradiol concentration. Our pioneering data demonstrate dramatic differences in spontaneous recovery in the neurovascular unit between Ovx and Sham females in the chronic stage of stroke, underscoring the importance of considering hormonal-dependent aspects of the ischemic sequelae in the development of novel therapeutic approaches and patient recruitment in clinical trials.

8.
Stroke ; 49(9): 2173-2181, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30354983

RESUMO

Background and Purpose- Recent evidence suggests great potential of metabolically targeted interventions for treating neurological disorders. We investigated the use of the endogenous ketone body ß-hydroxybutyrate (BHB) as an alternate metabolic substrate for the brain in the acute phase of ischemia because postischemic hyperglycemia and brain glucose metabolism elevation compromise functional recovery. Methods- We delivered BHB (or vehicle) 1 hour after ischemic insult induced by cortical microinjection of endothelin-1 in sensorimotor cortex of rats. Two days after ischemic insult, the rats underwent multimodal characterization of the BHB effects. We examined glucose uptake on 2-Deoxy-d-glucose chemical exchange saturation transfer magnetic resonance imaging, cerebral hemodynamics on continuous arterial spin labeling magnetic resonance imaging, resting-state field potentials by intracerebral multielectrode arrays, Neurological Deficit Score, reactive oxygen species production, and astrogliosis and neuronal death. Results- When compared with vehicle-administered animals, BHB-treated cohort showed decreased peri-infarct neuronal glucose uptake which was associated with reduced oxidative stress, diminished astrogliosis and neuronal death. Functional examination revealed ameliorated neuronal functioning, normalized perilesional resting perfusion, and ameliorated cerebrovascular reactivity to hypercapnia, suggesting improved functioning. Cellular and functional recovery of the neurogliovascular unit in the BHB-treated animals was associated with improved performance on the withdrawal test. Conclusions- We characterize the effects of the ketone body BHB administration at cellular and system levels after focal cortical stroke. The results demonstrate that BHB curbs the peri-infarct glucose-metabolism driven production of reactive oxygen species and astrogliosis, culminating in improved neurogliovascular and functional recovery.


Assuntos
Ácido 3-Hidroxibutírico/farmacologia , Astrócitos/efeitos dos fármacos , Isquemia Encefálica/metabolismo , Encéfalo/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Ácido 3-Hidroxibutírico/metabolismo , Acetoacetatos/metabolismo , Animais , Astrócitos/patologia , Glicemia/metabolismo , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Encéfalo/patologia , Isquemia Encefálica/diagnóstico por imagem , Isquemia Encefálica/patologia , Morte Celular/efeitos dos fármacos , Circulação Cerebrovascular , Modelos Animais de Doenças , Fenômenos Eletrofisiológicos , Endotelina-1 , Hemodinâmica , Imagem por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Microinjeções , Neurônios/patologia , Ratos , Espécies Reativas de Oxigênio/metabolismo , Córtex Sensório-Motor
9.
Sci Rep ; 8(1): 10447, 2018 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-29992999

RESUMO

The ability of MRI to differentiate between normal and radioresistant cancer was investigated in prostate tumour xenografts in mice. Specifically, the process of magnetization exchange between water and other molecules was studied. It was found that magnetization transfer from semisolid macromolecules (MT) and chemical exchange saturation transfer (CEST) combined were significantly different between groups (p < 0.01). Further, the T2 relaxation of the semisolid macromolecular pool (T2,B), a parameter specific to MT, was found to be significantly different (p < 0.01). Also significantly different were the rNOE contributions associated with methine groups at -0.9 ppm with a saturation B1 of 0.5 µT (p < 0.01) and with other aliphatic groups at -3.3 ppm with 0.5 and 2 µT (both p < 0.05). Independently, using a live-cell metabolic assay, normal cells were found to have a greater metabolic rate than radioresistant ones. Thus, MRI provides a novel, in vivo method to quantify the metabolic rate of tumours and predict their radiosensitivity.


Assuntos
Imagem por Ressonância Magnética/métodos , Neoplasias da Próstata/diagnóstico , Tolerância a Radiação , Animais , Metabolismo Basal , Linhagem Celular , Diagnóstico Diferencial , Xenoenxertos , Humanos , Magnetismo , Masculino , Camundongos , Consumo de Oxigênio , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/fisiopatologia
10.
J Neurochem ; 144(5): 669-679, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-28777881

RESUMO

Alzheimer's disease (AD) is pathologically characterized by amyloid-ß peptide (Aß) accumulation, neurofibrillary tangle formation, and neurodegeneration. Preclinical studies on neuronal impairments associated with progressive amyloidosis have demonstrated some Aß-dependent neuronal dysfunction including modulation of gamma-aminobutyric acid-ergic signaling. The present work focuses on the early stage of disease progression and uses TgF344-AD rats that recapitulate a broad repertoire of AD-like pathologies to investigate the neuronal network functioning using simultaneous intracranial recordings from the hippocampus (HPC) and the medial prefrontal cortex (mPFC), followed by pathological analyses of gamma-aminobutyric acid (GABAA ) receptor subunits α1, α5, and δ, and glutamic acid decarboxylases (GAD65 and GAD67). Concomitant to amyloid deposition and tau hyperphosphorylation, low-gamma band power was strongly attenuated in the HPC and mPFC of TgF344-AD rats in comparison to those in non-transgenic littermates. In addition, the phase-amplitude coupling of the neuronal networks in both areas was impaired, evidenced by decreased modulation of theta band phase on gamma band amplitude in TgF344-AD animals. Finally, the gamma coherence between HPC and mPFC was attenuated as well. These results demonstrate significant neuronal network dysfunction at an early stage of AD-like pathology. This network dysfunction precedes the onset of cognitive deficits and is likely driven by Aß and tau pathologies. This article is part of the Special Issue "Vascular Dementia".


Assuntos
Doença de Alzheimer/fisiopatologia , Hipocampo/fisiopatologia , Neurônios/fisiologia , Córtex Pré-Frontal/fisiopatologia , Doença de Alzheimer/patologia , Animais , Ondas Encefálicas , Modelos Animais de Doenças , Feminino , Glutamato Descarboxilase/metabolismo , Hipocampo/metabolismo , Hipocampo/patologia , Masculino , Vias Neurais/fisiopatologia , Placa Amiloide/metabolismo , Córtex Pré-Frontal/patologia , Ratos Endogâmicos F344 , Ratos Transgênicos , Receptores de GABA-A/metabolismo
11.
PLoS One ; 12(10): e0186676, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29053753

RESUMO

Ex vivo 2-photon fluorescence microscopy (2PFM) with optical clearing enables vascular imaging deep into tissue. However, optical clearing may also produce spherical aberrations if the objective lens is not index-matched to the clearing material, while the perfusion, clearing, and fixation procedure may alter vascular morphology. We compared in vivo and ex vivo 2PFM in mice, focusing on apparent differences in microvascular signal and morphology. Following in vivo imaging, the mice (four total) were perfused with a fluorescent gel and their brains fructose-cleared. The brain regions imaged in vivo were imaged ex vivo. Vessels were segmented in both images using an automated tracing algorithm that accounts for the spatially varying PSF in the ex vivo images. This spatial variance is induced by spherical aberrations caused by imaging fructose-cleared tissue with a water-immersion objective. Alignment of the ex vivo image to the in vivo image through a non-linear warping algorithm enabled comparison of apparent vessel diameter, as well as differences in signal. Shrinkage varied as a function of diameter, with capillaries rendered smaller ex vivo by 13%, while penetrating vessels shrunk by 34%. The pial vasculature attenuated in vivo microvascular signal by 40% 300 µm below the tissue surface, but this effect was absent ex vivo. On the whole, ex vivo imaging was found to be valuable for studying deep cortical vasculature.


Assuntos
Encéfalo/irrigação sanguínea , Algoritmos , Animais , Imageamento Tridimensional , Camundongos
12.
J Magn Reson Imaging ; 46(2): 505-517, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28703413

RESUMO

PURPOSE: Stroke is the leading cause of adult disability worldwide. The absence of more effective interventions in the chronic stage-that most patients stand to benefit from-reflects uncertainty surrounding mechanisms that govern recovery. The present work investigated the effects of a novel treatment (selective cyclooxygenase-1, COX-1, inhibition) in a model of focal ischemia. MATERIALS AND METHODS: FR122047 (COX-1 inhibitor) was given beginning 7 days following stroke (cortical microinjection of endothelin-1) in 23 adult male rats. Longitudinal continuous-arterial-spin-labeling was performed prior to treatment (7 days), and repeated following treatment (21 days) on a 7T magnetic resonance imaging (MRI) system to estimate resting perfusion and reactivity to hypercapnia. These in vivo measurements were buttressed by immunohistochemistry. RESULTS: Stroke caused an increase in perilesional resting perfusion (peri-/contralesional perfusion ratio of 170 ± 10%) and perfusion responses to hypercapnia (180 ± 10%) at 7 days. At 21 days, placebo-administered rats showed normalized perilesional perfusion (100 ± 20%) but persistent hyperreactivity (190 ± 20%). Treated animals exhibited sustained perilesional hyperperfusion (180 ± 10%). Further, reactivity lateralization did not persist following treatment (peri- vs. contralesional reactivity: P = 0.002 at 7 vs. P = 0.2 at 21 days). Hemodynamic changes were accompanied by neuronal loss, increased endothelial density, and widespread microglial and astrocytic activation. Moreover, relative to controls, treated rats showed increased perilesional neuronal survival (22 ± 1% vs. 14.9 ± 0.8%, P = 0.02) and decreased microglia/macrophage recruitment (17 ± 1% vs. 20 ± 1%, P = 0.05). Finally, perilesional perfusion was correlated with neuronal survival (slope = 0.14 ± 0.05; R2 = 0.7, P = 0.03). CONCLUSION: These findings shed light on the role of COX-1 in chronic ischemic injury and suggest that delayed selective COX-1 inhibition exerts multiple beneficial effects on the neurogliovascular unit. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 4 J. MAGN. RESON. IMAGING 2017;46:505-517.


Assuntos
Inibidores de Ciclo-Oxigenase/farmacologia , Isquemia/diagnóstico por imagem , Imagem por Ressonância Magnética , Proteínas de Membrana/antagonistas & inibidores , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/fisiopatologia , Animais , Ciclo-Oxigenase 1 , Modelos Animais de Doenças , Endotelina-1/química , Macrófagos/patologia , Masculino , Microglia/patologia , Neuroglia/patologia , Neurônios/patologia , Perfusão , Piperazinas/química , Ratos , Ratos Sprague-Dawley , Marcadores de Spin , Tiazóis/química
13.
Sci Rep ; 7: 46427, 2017 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-28401931

RESUMO

Alzheimer's disease (AD), pathologically characterized by amyloid-ß peptide (Aß) accumulation, neurofibrillary tangle formation, and neurodegeneration, is thought to involve early-onset neurovascular abnormalities. Hitherto studies on AD-associated neurovascular injury have used animal models that exhibit only a subset of AD-like pathologies and demonstrated some Aß-dependent vascular dysfunction and destabilization of neuronal network. The present work focuses on the early stage of disease progression and uses TgF344-AD rats that recapitulate a broader repertoire of AD-like pathologies to investigate the cerebrovascular and neuronal network functioning using in situ two-photon fluorescence microscopy and laminar array recordings of local field potentials, followed by pathological analyses of vascular wall morphology, tau hyperphosphorylation, and amyloid plaques. Concomitant to widespread amyloid deposition and tau hyperphosphorylation, cerebrovascular reactivity was strongly attenuated in cortical penetrating arterioles and venules of TgF344-AD rats in comparison to those in non-transgenic littermates. Blood flow elevation to hypercapnia was abolished in TgF344-AD rats. Concomitantly, the phase-amplitude coupling of the neuronal network was impaired, evidenced by decreased modulation of theta band phase on gamma band amplitude. These results demonstrate significant neurovascular network dysfunction at an early stage of AD-like pathology. Our study identifies early markers of pathology progression and call for development of combinatorial treatment plans.


Assuntos
Doença de Alzheimer/fisiopatologia , Encéfalo/fisiopatologia , Circulação Cerebrovascular/fisiologia , Rede Nervosa/fisiopatologia , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/metabolismo , Modelos Animais de Doenças , Feminino , Masculino , Rede Nervosa/metabolismo , Neurônios/metabolismo , Neurônios/fisiologia , Fosforilação , Ratos , Ratos Transgênicos , Proteínas tau/metabolismo
14.
J Cereb Blood Flow Metab ; 37(3): 1046-1059, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27683451

RESUMO

Aerobic activity has been shown highly beneficial to brain health, yet much uncertainty still surrounds the effects of exercise on the functioning of cerebral microvasculature. This study used two-photon fluorescence microscopy to examine cerebral hemodynamic alterations as well as accompanying geometric changes in the cortical microvascular network following five weeks of voluntary exercise in transgenic mice endogenously expressing tdTomato in vascular endothelial cells to allow visualization of microvessels irrespective of their perfusion levels. We found a diminished microvascular response to a hypercapnic challenge (10% FiCO2) in running mice when compared to that in nonrunning controls despite commensurate increases in transcutaneous CO2 tension. The flow increase to hypercapnia in runners was 70% lower than that in nonrunners (p = 0.0070) and the runners' arteriolar red blood cell speed changed by only half the amount seen in nonrunners (p = 0.0085). No changes were seen in resting hemodynamics or in the systemic physiological parameters measured. Although a few unperfused new vessels were observed on visual inspection, running did not produce significant morphological differences in the microvascular morphometric parameters, quantified following semiautomated tracking of the microvascular networks. We propose that voluntary running led to increased cortical microvascular efficiency and desensitization to CO2 elevation.


Assuntos
Córtex Cerebral/irrigação sanguínea , Condicionamento Físico Animal/fisiologia , Animais , Circulação Cerebrovascular , Hemodinâmica , Hipercapnia/fisiopatologia , Camundongos , Camundongos Transgênicos , Microscopia de Fluorescência/métodos , Corrida/fisiologia
15.
Biomed Opt Express ; 7(9): 3596-3609, 2016 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-27699123

RESUMO

We report on a miniature label-free imaging system for monitoring brain blood flow and blood oxygenation changes in awake, freely behaving rats. The device, weighing 15 grams, enables imaging in a ∼ 2 × 2 mm field of view with 4.4 µm lateral resolution and 1 - 8 Hz temporal sampling rate. The imaging is performed through a chronically-implanted cranial window that remains optically clear between 2 to > 6 weeks after the craniotomy. This imaging method is well suited for longitudinal studies of chronic models of brain diseases and disorders. In this work, it is applied to monitoring neurovascular coupling during drug-induced absence-like seizures 6 weeks following the craniotomy.

16.
Brain ; 138(Pt 4): 1046-58, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25688079

RESUMO

Most patients with Alzheimer's disease exhibit accumulation of amyloid-ß peptide on leptomeningeal and cortical arterioles, or cerebral amyloid angiopathy, which is associated with impaired vascular reactivity and accelerated cognitive decline. Despite widespread recognition of the significance of vascular dysfunction in Alzheimer's disease aetiology and progression, much uncertainty still surrounds the mechanism underlying Alzheimer's disease vascular injury. Studies to date have focused on amyloid-ß-induced damage to capillaries and plaque-associated arterioles, without examining effects across the entire vascular bed. In the present study, we investigated the structural and functional impairment of the feeding arteriolar versus draining venular vessels in a transgenic murine Alzheimer's disease model, with a particular focus on the mural cell populations that dictate these vessels' contractility. Although amyloid-ß deposition was restricted to arterioles, we found that vascular impairment extended to the venules, which showed significant depletion of their mural cell coverage by the mid-stage of Alzheimer's disease pathophysiology. These structural abnormalities were accompanied by an abolishment of the normal vascular network flow response to hypercapnia: this functional impairment was so severe as to result in hypercapnia-induced flow decreases in the arterioles. Further pharmacological depletion of mural cells using SU6668, a platelet-derived growth factor receptor-ß antagonist, resulted in profound structural abnormalities of the cortical microvasculature, including vessel coiling and short-range looping, increased tortuosity of the venules but not of the arterioles, increased amyloid-ß deposition on the arterioles, and further alterations of the microvascular network cerebral blood flow response to hypercapnia. Together, this work shows hitherto unrecognized structural alterations in penetrating venules, demonstrates their functional significance and sheds light on the complexity of the relationship between vascular network structure and function in Alzheimer's disease.


Assuntos
Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Circulação Cerebrovascular , Modelos Animais de Doenças , Vênulas/patologia , Vênulas/fisiopatologia , Animais , Cricetinae , Humanos , Camundongos , Camundongos da Linhagem 129 , Camundongos Transgênicos , Microscopia de Fluorescência por Excitação Multifotônica/métodos
17.
Eur J Neurosci ; 41(1): 79-88, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24893679

RESUMO

A role for arginine vasopressin in the circadian regulation of voluntary locomotor behavior (wheel running activity) was investigated in the golden hamster, Mesocricetus auratus. Spontaneous nocturnal running was suppressed in a dose-dependent manner by systemic injections of vasopressin, and also in a concentration-dependent manner by microinjections directly into the hypothalamic suprachiasmatic nucleus. Pre-injections of a vasopressin V1 receptor antagonist into the nucleus reduced the suppression of behavior by vasopressin. Ethogram analyses revealed that peripheral drug injections predominantly increased grooming, flank marking, and sleep-related behaviors. Central injections did not induce sleep, but increased grooming and periods of 'quiet vigilance' (awake but not moving). Nocturnal behavioral profiles following either peripheral or central injections were similar to those shown by untreated animals in the hour prior to the onset of nocturnal wheel running. Site control vasopressin injections into the medial preoptic area or periaqueductal gray increased flank marking and grooming, but had no significant effect on locomotion, suggesting behavioral specificity of a vasopressin target near the suprachiasmatic nucleus. Both peripheral and central administration increased FOS-like immunoreactivity in the retinorecipient core of the suprachiasmatic nucleus. The distribution of FOS-positive cells overlapped the calbindin subregion, but was more extensive, and most calbindin-positive cells did not co-express FOS. We propose a model of temporal behavioral regulation wherein voluntary behavior, such as nocturnal locomotor activity, is inhibited by the activity of neurons in the suprachiasmatic ventrolateral core that project to the posterior hypothalamus and are driven by rhythmic vasopressin input from the dorsomedial shell.


Assuntos
Fármacos do Sistema Nervoso Central/administração & dosagem , Ritmo Circadiano/fisiologia , Atividade Motora/efeitos dos fármacos , Núcleo Supraquiasmático/efeitos dos fármacos , Vasopressinas/administração & dosagem , Animais , Antagonistas dos Receptores de Hormônios Antidiuréticos/farmacologia , Relação Dose-Resposta a Droga , Masculino , Mesocricetus , Modelos Neurológicos , Atividade Motora/fisiologia , Proteínas Oncogênicas v-fos/metabolismo , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Substância Cinzenta Periaquedutal/fisiologia , Fotoperíodo , Área Pré-Óptica/efeitos dos fármacos , Área Pré-Óptica/fisiologia , Receptores de Vasopressinas/metabolismo , Núcleo Supraquiasmático/fisiologia
18.
PLoS One ; 6(11): e27799, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22132145

RESUMO

The pituitary is a complex endocrine tissue composed of a number of unique cell types distinguished by the expression and secretion of specific hormones, which in turn control critical components of overall physiology. The basic function of these cells is understood; however, the molecular events involved in their hormonal regulation are not yet fully defined. While previously established cell lines have provided much insight into these regulatory mechanisms, the availability of representative cell lines from each cell lineage is limited, and currently none are derived from adult pituitary. We have therefore used retroviral transfer of SV40 T-antigen to mass immortalize primary pituitary cell culture from an adult mouse. We have generated 19 mixed cell cultures that contain cells from pituitary cell lineages, as determined by RT-PCR analysis and immunocytochemistry for specific hormones. Some lines expressed markers associated with multipotent adult progenitor cells or transit-amplifying cells, including SOX2, nestin, S100, and SOX9. The progenitor lines were exposed to an adenylate cyclase activator, forskolin, over 7 days and were induced to differentiate to a more mature gonadotrope cell, expressing significant levels of α-subunit, LHß, and FSHß mRNAs. Additionally, clonal populations of differentiated gonadotropes were exposed to 30 nM gonadotropin-releasing hormone and responded appropriately with a significant increase in α-subunit and LHß transcription. Further, exposure of the lines to a pulse paradigm of GnRH, in combination with 17ß-estradiol and dexamethasone, significantly increased GnRH receptor mRNA levels. This array of adult-derived pituitary cell models will be valuable for both studies of progenitor cell characteristics and modulation, and the molecular analysis of individual pituitary cell lineages.


Assuntos
Técnicas de Cultura de Células/métodos , Diferenciação Celular/efeitos dos fármacos , AMP Cíclico/farmacologia , Gonadotrofos/citologia , Hipófise/citologia , Fatores de Transcrição SOXB1/metabolismo , Células-Tronco/citologia , Envelhecimento/efeitos dos fármacos , Envelhecimento/metabolismo , Animais , Biomarcadores/metabolismo , Linhagem Celular Transformada , Colforsina/farmacologia , Meios de Cultura Livres de Soro , Subunidade beta do Hormônio Folículoestimulante/genética , Subunidade beta do Hormônio Folículoestimulante/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Subunidade alfa de Hormônios Glicoproteicos/genética , Subunidade alfa de Hormônios Glicoproteicos/metabolismo , Gonadotrofos/efeitos dos fármacos , Gonadotrofos/metabolismo , Hormônio Luteinizante/genética , Hormônio Luteinizante/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fatores de Transcrição SOXB1/genética , Células-Tronco/efeitos dos fármacos , Células-Tronco/metabolismo
19.
Chronobiol Int ; 28(7): 553-62, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21834641

RESUMO

Loss of Dexras1 in gene-targeted mice impairs circadian entrainment to light cycles and produces complex changes to phase-dependent resetting responses (phase shifts) to light. The authors now describe greatly enhanced and phase-specific nonphotic responses induced by arousal in dexras1(-/-) mice. In constant conditions, mutant mice exhibited significant arousal-induced phase shifts throughout the subjective day. Unusual phase advances in the late subjective night were also produced when arousal has little effect in mice. Bilateral lesions of the intergeniculate leaflet (IGL) completely eliminated both the nonphotic as well as the light-induced phase shifts of circadian locomotor rhythms during the subjective day, but had no effect on nighttime phase shifts. The expression of FOS-like protein in the suprachiasmatic nucleus (SCN) was not affected by either photic or nonphotic stimulation in the subjective day in either genotype. Therefore, the loss of Dexras1 (1) enhances nonphotic phase shifts in a phase-dependent manner, and (2) demonstrates that the IGL in mice is a primary mediator of circadian phase-resetting responses to both photic and nonphotic events during the subjective day, but plays a different functional role in the subjective night. Furthermore, (3) the change in FOS level does not appear to be a critical step in the entrainment pathways for either light or arousal during the subjective day. The cumulative evidence suggests that Dexras1 regulates multiple photic and nonphotic signal-transduction pathways, thereby playing an essential role modulating species-specific characteristics of circadian entrainment.


Assuntos
Relógios Biológicos/fisiologia , Ritmo Circadiano/fisiologia , Corpos Geniculados/anatomia & histologia , Corpos Geniculados/fisiologia , Proteínas ras/genética , Proteínas ras/metabolismo , Animais , Nível de Alerta , Comportamento Animal/fisiologia , Marcação de Genes , Corpos Geniculados/patologia , Luz , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/fisiologia , Neuropeptídeo Y/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Núcleo Supraquiasmático/citologia , Núcleo Supraquiasmático/fisiologia
20.
FASEB J ; 23(12): 4256-65, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19703933

RESUMO

The distinct lack of cell lines derived from the adult brain is evident. Ciliary neurotrophic factor (CNTF) triggers neurogenesis in primary culture from adult mouse hypothalamus, as detected by bromodeoxyuridine and Ki67 immunostaining. Using SV-40 T-antigen, we immortalized dividing neurons and generated clonal cell lines expressing neuropeptides and receptors involved in neuroendocrine function. We hypothesized that proglucagon-derived peptides may be the mechanistic downstream effectors of CNTF due to documented neuroprotective and proliferative effects. Indeed, proglucagon gene expression was induced by CNTF, and exposure of primary cells to glucagon-like peptide-1 receptor (GLP-1) agonist, exendin-4, induced cell proliferation. Intracerebroventricular injection of CNTF into adult mice caused increased expression of proglucagon peptide in the hypothalamus. Using a specific GLP-1-receptor antagonist, we found that neurogenesis was significantly attenuated and primary culture from GLP-1-receptor-knockout mice lacked CNTF-mediated neuronal proliferation, thus linking the induction of neurogenesis in the hypothalamus to GLP-1-receptor signaling.


Assuntos
Fator Neurotrófico Ciliar/farmacologia , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Hipotálamo/citologia , Neurogênese/fisiologia , Neurônios/citologia , Animais , Linhagem Celular , Proliferação de Células , Fator Neurotrófico Ciliar/metabolismo , Regulação da Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proglucagon/genética , Proglucagon/metabolismo , Transdução de Sinais
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