25297993
Glioma-induced remodeling of the neurovascular unit
The normal BBB (blood-brain barrier) consists of a series of structures collectively known as neurovascular units, or NVU, that are composed of endothelial cells and astrocyte endfeet separated by a basal lamina at their interface. The integrity of the BBB and specifically endothelial tight junctions is maintained by interactions between these different components and the local microenvironment of the NVU. Central nervous system cancers such as gliomas disrupt the integrity of the BBB and this compromise is associated with increased tumor growth and invasion of the surrounding brain parenchyma. Because the relationship between glioma-induced BBB breakdown and glioma invasion remains poorly understood, and the host microenvironment can influence tumor cell migration, we used immunohistochemical techniques to characterize tumor associated BBB remodeling. Using an orthotopic xenograft model of glioma, we demonstrate that tumor cells induce specific changes in the composition of the basal lamina and in astrocytic components of the NVU. We suggest that these changes may be essential to understand the capacity of gliomas to regulate BBB integrity and as such, glioma invasion into brain parenchyma.
207620666
Conditional deletion of the focal adhesion kinase FAK alters remodeling of the blood-brain barrier in glioma.
Gliomas generally infiltrate the surrounding normal brain parenchyma, a process associated with increased vascular permeability (VP) and dysregulation of the blood-brain barrier (BBB). However, the molecular mechanisms underlying glioma-induced VP in the brain remain poorly understood. Using a conditional, endothelium-specific deletion of the focal adhesion kinase (FAK) in the mouse (FAK CKO), we show that FAK is critical for destabilization of the tumor endothelium in tumor-bearing mice, with mutant mice exhibiting a relatively normalized vasculature compared with wild-type mice (FAK WT). Tumor vessels in the FAK CKO mice displayed reduced VP compared with FAK WT mice, resulting in reduced tumor growth. Additionally, FAK CKO mice displayed partial restoration of cell-cell junction proteins in the tumor vessels and astrocyte-endothelium interactions in tumors, revealing an additional role of astrocytes in mediating tumor-induced VP. Together, these results provide genetic evidence that FAK is a mediator of tumor-induced VP in the brain. Our findings may help understand how therapeutics might be used to regulate specific cell-type interactions to restore BBB structure/function in cancer and perhaps other pathologic conditions.
32880620
In vivo measurement of glioma-induced vascular permeability.
The normal blood-brain barrier (BBB) consists of tight interendothelial cell junctions and adjacent astrocyte end feet separated by a basal lamina surrounding the endothelium. The interactions between the different cell types of BBB are disrupted in distinct patterns in the microenvironment of glioma. Malignant gliomas infiltrate the surrounding normal brain parenchyma; a process associated with vascular permeability (VP) and breakdown of the BBB. Herein, we describe methods to quantitatively measure glioma-induced vascular permeability, utilizing an orthotopic xenograft model of glioma.
5519498
Non-invasive quantification of brain tumor-induced astrogliosis
BackgroundCNS injury including stroke, infection, and tumor growth lead to astrogliosis, a process that involves upregulation of glial fibrillary acidic protein (GFAP) in astrocytes. However, the kinetics of astrogliosis that is related to these insults (i.e. tumor) is largely unknown.ResultsUsing transgenic mice expressing firefly luciferase under the regulation of the GFAP promoter (GFAP-luc), we developed a model system to monitor astrogliosis upon tumor growth in a rapid, non-invasive manner. A biphasic induction of astrogliosis was observed in our xenograft model in which an early phase of activation of GFAP was associated with inflammatory response followed by a secondary, long-term upregulation of GFAP. These animals reveal GFAP activation with kinetics that is in parallel with tumor growth. Furthermore, a strong correlation between astrogliosis and tumor size was observed.ConclusionsOur results suggest that non-invasive, quantitative bioluminescent imaging using GFAP-luc reporter animal is a useful tool to monitor temporal-spatial kinetics of host-mediated astrogliosis that is associated with glioma and metastatic brain tumor growth.
14664327
Protein loop modeling by using fragment assembly and analytical loop closure.
Protein loops are often involved in important biological functions such as molecular recognition, signal transduction, or enzymatic action. The three dimensional structures of loops can provide essential information for understanding molecular mechanisms behind protein functions. In this article, we develop a novel method for protein loop modeling, where the loop conformations are generated by fragment assembly and analytical loop closure. The fragment assembly method reduces the conformational space drastically, and the analytical loop closure method finds the geometrically consistent loop conformations efficiently. We also derive an analytic formula for the gradient of any analytical function of dihedral angles in the space of closed loops. The gradient can be used to optimize various restraints derived from experiments or databases, for example restraints for preferential interactions between specific residues or for preferred backbone angles. We demonstrate that the current loop modeling method outperforms previous methods that employ residue-based torsion angle maps or different loop closure strategies when tested on two sets of loop targets of lengths ranging from 4 to 12.
9605549
Spectrum measurement of fast optical signal of neural activity in brain tissue and its theoretical origin
Functional brain imaging technologies have enabled recent advances in understanding human brain function. In particular, a noninvasive and fast optical technique will become one of the most promising tools for future studies. As a fundamental ex vivo study for the development of such a technique, this paper demonstrates the spectral measurement of fast optical changes associated with neural activity in bulk brain tissue. For this purpose, a high-speed confocal near-infrared spectrometer was built and used. The results verified that observed transient optical responses (tORs) are associated with neural activity by showing that the following: tORs were concurrent and correlated with local field potentials (LFPs); tORs disappeared following tetrodotoxin application; and tORs were reproducibly observed across preparations. In addition, the amplitude of tORs was statistically significantly larger in longer wavelengths (approximately 1200 nm). The time course of tORs, however, is quite different from that of LFPs. Since this difference implies that tORs may originate not directly from the electric potential variation but from other neurophysiological events accompanying excitation, this paper tested the hypothesis that tORs are attributed to transient cellular volume changes (tCVCs). With no previous dynamic equation to elucidate such different temporal dynamics of the optical responses, a novel mathematical neuron model to describe tCVCs was developed. This neuron model, along with finite-difference time-domain simulations, showed that tCVCs and tORs were similar in the temporal dynamics, order of magnitude, response direction, and detectability in the bulk tissue; thus supporting the hypothesis.
11070685
Establishing a case for improved food phenolic analysis
Future phenolic research findings using a multidisciplinary approach will ensure profitability and sustainability of specialty crop industries, while also improving the nutritional and economic choices available to increasingly health- and environmentally conscious consumers. Recent examples of phenolics used in commercial and research scenarios, and new phenolic research discoveries are discussed. Despite being a heavily researched topic, there remains a need to identify, develop, and define analyses targeted for specific quality-related plant metabolites.
16672801
Complex data analysis in high-resolution SSFP fMRI.
In transition-band steady-state free precession (SSFP) functional MRI (fMRI), functional contrast originates from a bulk frequency shift induced by a deoxygenated hemoglobin concentration change in the activated brain regions. This frequency shift causes a magnitude and/or phase-signal change depending on the off-resonance distribution of a voxel in the balanced-SSFP (bSSFP) profile. However, in early low-resolution studies, only the magnitude signal activations were shown. In this paper the task-correlated phase-signal change is presented in a high-resolution (1 x 1 x 1 mm3) study. To include this phase activation in a functional analysis, a new complex domain data analysis method is proposed. The results show statistically significant phase-signal changes in a large number of voxels comparable to that of the magnitude-activated voxels. The complex-data analysis method successfully includes these phase activations in the activation map and thus provides wider coverage compared to magnitude-data analysis results.
31281743
Respiration-induced B0 field fluctuation compensation in balanced SSFP: real-time approach for transition-band SSFP fMRI.
In functional MRI (fMRI) the resonance frequency shift induced from respiration is a major source of physiological noise. In transition-band SSFP fMRI the respiration-induced resonance offset not only increases noise interference, it also shifts the activation band. This leads to a reduction in the contrast-to-noise ratio (CNR) and the potential for varying contrast levels during the experiment. A novel real-time method that compensates for the respiration-induced resonance offset frequency is presented. This method utilizes free induction decay (FID) phase information to measure the resonance offset. For compensation, one can update the resonant frequency in real time by changing the transmit RF pulse and receiver phases to track the measured offset. The results show decreased signal power in the respiration frequency band and increased numbers of activated voxels with higher Z-scores compared to uncompensated experiments.