Cross hippocampal influence in mesial temporal lobe epilepsy measured with high temporal resolution functional magnetic resonance imaging

Purpose Mesial temporal lobe epilepsy (mTLE) is a chronic disorder with spontaneous seizures recurring for years, or even decades. Many structural and functional changes have been detected in both the seizure focus and distal regions throughout the brain over this duration that may reflect the development of epileptogenic networks. Resting state functional magnetic resonance imaging (fMRI) connectivity mapping has the potential to elucidate and quantify these networks. The network between the left and right hippocampus may very likely be one of the most susceptible to changes due to long‐term seizure propagation effects. Therefore, the objective of this study was to quantify cross hippocampal influence in mTLE using high temporal resolution fMRI, and to determine its relationship with disease duration. Methods fMRI images were acquired in the resting (interictal) state with 500 ms temporal resolution across the temporal lobes of 19 mTLE patients (13 left, 6 right). The left and right hippocampi were identified on each subject’s images using both structurally defined and functionally defined boundaries. The cross hippocampal influence was quantified in two ways for each pair of regions: (1) the nondirectional hippocampal functional connectivity calculated as the Pearson’s correlation between the average time series in the left and the right hippocampus regions, and (2) the Granger causality (GC) laterality measure, which implies directional influence by determining temporal precedence. Each of these measures was correlated with age, age of onset, and disease duration across subjects to investigate relationship to disease progression. Key Findings The hippocampal connectivity was not significantly different between patients with left and right mTLE using either the structurally or the functionally defined regions. Across all patients, hippocampal connectivity was not correlated significantly with age of onset or duration of disease. However, as duration of disease increased after 10 years (nine patients), the hippocampal connectivity increased linearly. Using the functionally defined regions, the GC laterality was increased in the right mTLE over the left mTLE, indicating that the left hippocampus was influencing the right hippocampus more than the right influencing left. This was also positively correlated with age of onset. Furthermore, like hippocampal connectivity, the relationship between GC laterality and duration of disease changes after 10 years duration of disease. After this duration, the GC laterality was positive in the three of three patients with right mTLE (left influencing right), whereas the GC laterality was negative in five of six patients with left mTLE (right influencing left). Significance This study reveals a relationship between fMRI functional connectivity and causal influence of the left and right hippocampi and duration of disease in mTLE. During the interictal state, the interhemispheric hippocampal connectivity initially is disrupted and then linearly increases as the epilepsy progresses longer than 10 years. This increase in connectivity appears to be due to the hippocampus contralateral to the epileptogenic focus exerting more influence over the ipsilateral hippocampus. These findings may have implications in understanding the functional development of epileptic networks and possibly prediction of surgical outcome of mTLE.     

Pharmacologic Modification of Tumor Blood Flow and Interstitial Fluid Pressure in a Human Tumor Xenograft: Network Analysis and Mechanistic Interpretation

Various vasoactive agents have been used to modify tumor blood flow with the ultimate goal of improving cancer detection and treatment, with widely disparate results. Furthermore, the lack of mechanistic interpretations has hindered understanding of how these agents affect the different physiological parameters involved in perfusion. Thus, there is a need to develop a unified framework for understanding the interrelated physiological effects of pharmacological and physical agents, The goals of this study were (1) to develop a mathematical model which helps determine the location and magnitude of changes in the vascular resistance of tumor and normal tissues and (2) to test the model with our own experimental studies and by comparison with results from the literature. The systemic and interstitial pressures and relative tumor blood flow were measured before and after administration of angiotensin II, epinephrine, norepinephrine, nitroglycerin, and hydralazine in SCID mice bearing LS174T human colon adenocarcinoma xenografts. A mathematical model was developed in analogy to electrical circuits which examined the pressure, flow, and resistance relationships for arterial and venous segments of the vasculature of a tumor and surrounding normal tissue. Vasoconstrictor-induced increases in the mean arterial blood pressure led to increases in tumor blood flow and interstitial pressure with the magnitude of change dependent on the agent (percentage change in blood flow: angiotensin > epinephrine > norepinephrine). The vasodilating agents induced decreases in tumor blood flow in parallel to the induced decreases in the systemic pressure, but only the long-acting arterial vasodilator hydralazine was capable of effecting a decrease in tumor interstitial pressure. The model was also found to be consistent with other data available in the literature on norepinephrine, pentoxifylline, nicotinamide, and hemodilution, and was useful in providing input as to the location and degree of the physiological effects of these agents. The results of the data and model show that the steal phenomenon is the dominant mechanism for redistribution of host blood flow to the tumor. However, some degree of arterial control was found to be present in the tumors. Moreover, the parallel increases in tumor interstitial pressure and blood flow contradict any hypothesis suggesting that elevated interstitial fluid pressure precipitates chronic vascular collapse, thus decreasing blood flow.     

Apparent alpha-inhibin subunit immunoactivity in porcine and ovine luteal extracts is due to interference by cytosolic proteases in the assay.

Immunoreactive alpha-inhibin (ir-inhibin) was measured in luteal homogenates and subcellular fractions of ovine and porcine corpora lutea (CL) and in pig granulosa cells (GCs), using a sensitive radioimmunoassay specific for the 1-26 amino acid sequence of the N-terminus of the alpha chain of porcine inhibin (p1-26 alpha-inhibin). Inclusion of N-ethylmaleimide (N-EM) and/or EDTA in the immunoassay had no effect on the measurement of p1-26 alpha-inhibin peptide standards, on ir-inhibin levels in ovine follicular fluid and serum, or on ir-inhibin in subcellular fractions of pig GC. Fractionation of porcine GC homogenates on sucrose gradients demonstrated a major particular peak of ir-inhibin (buoyant density, 1.15-1.21 g/cm3) with variable activity in the cytosol. The particulate ir-inhibin peak was released into the cytosol by pretreatment of GC homogenates with the saponin, digitonin, prior to fractionation. Porcine GC extracts contained a protein (M(r) 45,000) which immunoblotted against p1-26 alpha-inhibin antibody. In the absence of inhibitors of proteolysis, apparent ir-inhibin activity was very high in extracts of sheep and pig CL. However, inclusion of N-EM or EDTA in the radioimmunoassay significantly reduced ir-inhibin levels in porcine and ovine CL extracts in a dose-dependent manner. Measurements of peptide tracer integrity indicated that porcine luteal cytosol degraded 125I-labelled p1-26 alpha-inhibin peptide. Subcellular fractionation studies demonstrated high levels of apparent ir-inhibin in luteal cytosol fractions, with only minor activity peaks associated with particulate fractions; however, this material was not releasable by digitonin. Immunoblotting of detergent extracts of porcine luteal particulate fractions failed to demonstrate alpha-inhibin material, and immunocytochemical localization studies of alpha-inhibin in porcine and ovine luteal sections were negative. Our results are consistent with the intracellular packaging/storage of a form of alpha-inhibin (M(r) similar to that of alpha-inhibin subunit precursor) in the porcine granulosa cell. However, luteinization of the porcine follicle was associated with a dramatic fall in ir-inhibin content, and the loss of immunostaining for alpha-inhibin peptides. We conclude that porcine and ovine CL contain little, if any, authentic inhibin. These studies emphasize the importance of excluding proteolytic artefacts when measuring biological peptides in luteal tissue extracts by radioimmunoassay.     

Understanding the role of human variation in vaccine adverse events: the Clinical Immunization Safety Assessment Network

The Clinical Immunization Safety Assessment (CISA) Network is a collaboration between the Centers for Disease Control and Prevention (CDC) and 6 academic medical centers to provide support for immunization safety assessment and research. The CISA Network was established by the CDC in 2001 with 4 primary goals: (1) develop research protocols for clinical evaluation, diagnosis, and management of adverse events following immunization (AEFI); (2) improve the understanding of AEFI at the individual level, including determining possible genetic and other risk factors for predisposed people and subpopulations at high risk; (3) develop evidence-based algorithms for vaccination of people at risk of serious AEFI; and (4) serve as subject-matter experts for clinical vaccine-safety inquiries. CISA Network investigators bring in-depth clinical, pathophysiologic, and epidemiologic expertise to assessing causal relationships between vaccines and adverse events and to understanding the pathogenesis of AEFI. CISA Network researchers conduct expert reviews of clinically significant adverse events and determine the validity of the recorded diagnoses on the basis of clinical and laboratory criteria. They also conduct special studies to investigate the possible pathogenesis of adverse events, assess relationships between vaccines and adverse events, and maintain a centralized repository for clinical specimens. The CISA Network provides specific clinical guidance to both health care providers who administer vaccines and those who evaluate and treat patients with possible AEFI. The CISA Network plays an important role in providing critical immunization-safety data and expertise to inform vaccine policy-makers. The CISA Network serves as a unique resource for vaccine-safety monitoring efforts conducted at the CDC.     

X-ray CT dose in normoxic polyacrylamide gel dosimetry

This study reports on the effects of x-ray CT dose in CT imaged normoxic polyacrylamide (nPAG) gel dosimeters. The investigation is partitioned into three sections. First, the CT dose absorbed in nPAG is quantified under a range of typical gel CT imaging protocols. It is found that the maximum absorbed CT dose occurs for volumetric imaging and is in the range of 4.6 +/- 0.2 cGy/image. This does scales linearly with image averaging. Second, using Raman spectroscopy, the response of nPAG to CT imaging photon energies (i.e., 120-140 kVp) is established and compared to the well known dose response of nPAG exposed to 6 MV photons. It is found that nPAG exhibits a weaker response (per unit dose) to 140-kVp incident photons as compared to 6 MV incident photons (slopes m6 mv = -0.0374 +/- 0.0006 Gy(-1) and m140 kVp = -0.016 +/- 0.001 Gy(-1)). Finally, using the above data, an induced change in CT number (deltaN(CT)) is calculated for nPAG imaged using a range of gel imaging protocols. It is found that under typical imaging protocols (120-140 kVp, 200 mAs, approximately 16-32 image averages) a deltaN(CT) < 0.2 H is induced in active nPAG dosimeters. This deltaN(CT) is below the current limit of detectability of CT nPAG polymer gel dosimetry. Under expanded imaging protocols (e.g., very high number of image averages) an induced deltaN(CT) of approximately 0.5 H is possible. In these situations the additional polymerization occurring in nPAG due to the imaging process may need to be accounted for.     

Contribution of VANGL2 mutations to isolated neural tube defects

Kibar Z, Salem S, Bosoi CM, Pauwels E, De Marco P, Merello E, Bassuk AG, Capra V, Gros P. Contribution of VANGL2 mutations to isolated neural tube defects. Vangl2 was identified as the gene defective in the Looptail (Lp) mouse model for neural tube defects (NTDs). This gene forms part of the planar cell polarity (PCP) pathway, also called the non‐canonical Frizzled/Dishevelled pathway, which mediates the morphogenetic process of convergent extension essential for proper gastrulation and neural tube formation in vertebrates. Genetic defects in PCP signaling have strongly been associated with NTDs in mouse models. To assess the role of VANGL2 in the complex etiology of NTDs in humans, we resequenced this gene in a large multi‐ethnic cohort of 673 familial and sporadic NTD patients, including 453 open spina bifida and 202 closed spinal NTD cases. Six novel rare missense mutations were identified in seven patients, five of which were affected with closed spinal NTDs. This suggests that VANGL2 mutations may predispose to NTDs in approximately 2.5% of closed spinal NTDs (5 in 202), at a frequency that is significantly different from that of 0.4% (2 in 453) detected in open spina bifida patients (p = 0.027). Our findings strongly implicate VANGL2 in the genetic causation of spinal NTDs in a subset of patients and provide additional evidence for a pathogenic role of PCP signaling in these malformations.     

Discovery and genetic localization of Down syndrome cerebellar phenotypes using the Ts65Dn mouse

Down syndrome (DS) is the most common genetic cause of mental retardation and affects many aspects of brain development. DS individuals exhibit an overall reduction in brain size with a disproportionately greater reduction in cerebellar volume. The Ts65Dn mouse is segmentally trisomic for the distal 12-15 Mb of mouse chromosome 16, a region that shows perfect conserved linkage with human chromosome 21, and therefore provides a genetic model for DS. In this study, high resolution magnetic resonance imaging and histological analysis demonstrate precise neuro- anatomical parallels between the DS and the Ts65Dn cerebellum. Cerebellar volume is significantly reduced in Ts65Dn mice due to reduction of both the internal granule layer and the molecular layer of the cerebellum. Granule cell number is further reduced by a decrease in cell density in the internal granule layer. Despite these changes in Ts65Dn cerebellar structure, motor deficits have not been detected in several tests. Reduction in granule cell density in Ts65Dn mice correctly predicts an analogous pathology in humans; a significant reduction in granule cell density in the DS cerebellum is reported here for the first time. The candidate region of genes on chromosome 21 affecting cerebellar development in DS is therefore delimited to the subset of genes whose orthologs are at dosage imbalance in Ts65Dn mice, providing the first localization of genes affecting a neuroanatomical phenotype in DS. The application of this model for analysis of developmental perturbations is extended by the accurate prediction of DS cerebellar phenotypes.     

Immunopathogenesis,loss of T cell tolerance and genetics of autoimmune gastritis

Over the past 10 years experimental autoimmune gastritis has been established as a highly defined model of organ-specific autoimmunity. Autoimmune gastritis represents one of the few autoimmune diseases in which the causative autoantigens, namely the gastric H/K ATPase alpha- and beta-subunits, are defined. Furthermore, it has been clearly established that a CD4+ T cell response to the H/K ATPase beta-subunit, in particular, is essential for the initiation of autoimmune gastritis. The immunopathology of autoimmune gastritis is due to a disruption of the normal developmental pathways of the mucosa, rather than a direct depletion of the end-stage parietal and zymogenic cells. CD4+CD25+ regulatory T cells were first described in experimental autoimmune gastritis and there has been a recent explosion of interest in the potential role of these immunoregulatory T cells in protection against a variety of autoimmune diseases. The availability of H/K ATPase deficient mice has begun to provide considerable insight into the basis for tolerance to the gastric autoantigens. Experimental autoimmune gastritis has also provided valuable insight into our understanding of the genetics of disease susceptibility and four distinct genetic regions have been identified which confer susceptibility to this organ-specific disease. The highlights of these recent advances are the subject of this review.