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Functional MRI in neonates using neonatal head coil and MR compatible incubator.

Structural and functional magnetic resonance imaging of the newborn brain is a complex and challenging task. Term and preterm neonates require a controlled microenvironment and close monitoring during the MRI study to maintain respiratory and cardiovascular functions, body temperature, and fluid and electrolyte homeostasis. In addition, to minimize motion artifacts, most neonates also need to be sedated, which carries the risk of respiratory depression compromising the neonate's ability to maintain appropriate ventilation and oxygenation during the procedure. Finally, because of their small head size, the use of the standard MR head coils results in suboptimal picture quality in the neonate. Thus, these limitations affect our ability to obtain both high quality structural and functional MRI studies. To overcome these difficulties, we have utilized an MR compatible incubator with a built-in radiofrequency head coil optimized for the neonatal brain volume. In this study we demonstrate that functional MRI and high-resolution structural MRI of the newborn brain can be achieved with this novel design. The use of this equipment offers potential for studying the development of the preterm and term neonatal brain and obtaining state-of-the-art, high-resolution structural and functional imaging in this most vulnerable patient population.

Chloral Hydrate↗

What is immune privilege (not)?

The 'immune privilege' of the central nervous system (CNS) is indispensable for damage limitation during inflammation in a sensitive organ with poor regenerative capacity. It is a longstanding notion which, over time, has acquired several misconceptions and a lack of precision in its definition. In this article, we address these issues and re-define CNS immune privilege in the light of recent data. We show how it is far from absolute, and how it varies with age and brain region. Immune privilege in the CNS is often mis-attributed wholly to the blood-brain barrier. We discuss the pivotal role of the specialization of the afferent arm of adaptive immunity in the brain, which results in a lack of cell-mediated antigen drainage to the cervical lymph nodes although soluble drainage to these nodes is well described. It is now increasingly recognized how immune privilege is maintained actively as a result of the immunoregulatory characteristics of the CNS-resident cells and their microenvironment.

Animals↗

Ontogenetic development of the brain of the platyhelminth Fasciola hepatica.

During ontogenetic development in the definitive host, the cerebral ganglia of the parasitic flatworm Fasciola hepatica lose their cell rind integrity and develop specialized nerve processes. The organization and cytological features of the central nervous system were examined during three developmental stages in the parasitic life cycle of F. hepatica to determine when the changes occur. The cerebral ganglion cell bodies of migrating juvenile worms (5 days post-infection) are organized into a one-cell-thick rind that surrounds a central neuropile composed of small unmyelinated nerve processes (less than 3 microns in diameter). In young, sexually-immature adult worms (30 days post-infection), the cell bodies of the ganglia are no longer organized into a complete or tight cell rind around the ganglia. In addition, large diameter ('giant') unmyelinated nerve processes (greater than 12 microns) are found in the neuropile area. These giant nerve processes are also found in the transverse commissure and the longitudinal nerve cords. In mature adult worms (4-6 months post-infection), the rind of nerve cell bodies has completely disappeared and cell bodies are scattered around and within the neuropile. More than half of the volume of the mature adult neuropile is composed of giant nerve processes. The three developmental stages of the parasite that were used in this study differ significantly in their sizes, behaviours and microhabitat locations in the host. The results suggest that the organizational and morphological changes in the ganglia reflect selective adaptations to changes in the parasitic microenvironment.

Animals↗

Differences in multidrug resistance phenotype and matrix metalloproteinases activity between endothelial cells from normal brain and glioma.

Endothelial cells (ECs) are new targets for tumor therapy. In this work, we purified endothelial cells from intracerebral and subcutaneous experimental gliomas as well as from normal brain in order to define some of the phenotypical differences between angiogenic and quiescent brain vasculature. We show that the multidrug resistance genes encoding drug efflux pumps at the brain endothelium are expressed differently in normal and tumoral vasculature. We also show that ECs from gliomas present increased activity of gelatinase B (MMP9), key enzyme in the angiogenic process. Importantly, we observe a different phenotype between ECs in the intracerebral and subcutaneous models. Our results provide molecular evidence of phenotypic distinction between tumoral and normal brain vasculature and indicate that the EC phenotype depends on interactions both with tumor cells and also with the microenvironment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Molecular basis for the bidirectional modulation of the neuroendocrine and the immune systems.

Experimental evidence in many fields point towards the existence of a bidirectional communication between the neuroendocrine and immune systems. The immune response unifies the endocrine, nervous and immune systems. This integrated microenvironment includes lymphoid cell, nonlymphoid cells, cholinergic and adrenergic neurons and their neurohumoral products, biologically active substances including the cytokines and lymphokines produced by lymphoid and nonlymphoid cells, hormones and neuropeptides released by endocrine glands and regulatory cells of the brain, membrane and intracellular receptors which make possible the immune connections, and ions which are involved in the transmission of information and the higher nervous system activity which influences the immune microenvironment. Neuroendocrine circuits constitute only one type of efferent link between the brain and the immune compartment. The autonomic nervous system, via its innervation of many peripheral target tissues throughout the body, might also prove to be an important link to the immune system. While the precise mechanism(s) of neuroendocrine-immune relationships may not as yet completely defined, it is apparent that such interrelationships exist.

Adjuvants, Immunologic↗

Distribution of endogenous tumour necrosis factor alpha in gliomas.

AIMS: To determine the distribution and cellular origin of endogenous tumour necrosis factor alpha (TNF alpha) in the cellular components of human gliomas. METHODS: Frozen sections of 26 gliomas (four astrocytomas (As); two oligoastrocytomas (OA); one ansplastic astrocytoma (AA); one anaplastic oligoastrocytoma (AOA); 18 glioblastomas (GB)) were examined immunohistochemically using antihuman TNF alpha and anti-Leu-M5 (CD11c) antibodies. Additional studies with double immunohistocchemical procedures were performed with anti-glial fibrillary acidic protein and anti-neurofilament antibodies. RESULTS: Eighty per cent of the AA, AOA, and GB (16 of 20) had a positive reaction for TNF alpha, but only 17% of As and OA (one of six) were positive. Positive cells were seen in both the tumour tissue and adjacent brain tissues. TNF alpha protein was detected not only in the tumour cells but also in the endothelium of tumour vessels as well as reactive astrocytes and neurons. CONCLUSIONS: Endogenous TNF alpha is present in cells of various origins in glial tumours including tumour vessels; however, the role of TNF alpha may be different in different types of cells or altered microenvironment.

Brain Chemistry↗

Altered antigen expression of microglia in the aged rodent CNS.

Microglia, the resident macrophages of the central nervous system, are characterised by a highly specialized morphology and unusual antigenic phenotype. Microglia appear to be downregulated by their microenvironment when compared to other tissue macrophages. We have studied the microglia in brains of healthy, aged rats with a panel of monoclonal antibodies. We have found that microglia in the brains of these aged rats express antigens that are downregulated or absent from microglia of juvenile rats. The stimuli which give rise to this upregulated phenotype are not known. Age related changes in the phenotype of microglia should be taken into account when considering the possible role of microglia in neuropathological conditions.

Aging↗

Matrix metalloproteinase 2 (MMP2) and MMP9 secreted by erythropoietin-activated endothelial cells promote neural progenitor cell migration.

We investigated the hypothesis that endothelial cells activated by erythropoietin (EPO) promote the migration of neuroblasts. This hypothesis is based on observations in vivo that treatment of focal cerebral ischemia with EPO enhances the migration of neuroblasts to the ischemic boundary, a site containing activated endothelial cells and angiogenic microvasculature. To model the microenvironment within the ischemic boundary zone, we used a coculture system of mouse brain endothelial cells (MBECs) and neural progenitor cells derived from the subventricular zone of the adult mouse. Treatment of MBECs with recombinant human EPO (rhEPO) significantly increased secretion of matrix metalloproteinase 2 (MMP2) and MMP9. rhEPO-treated MBEC supernatant as conditioned medium significantly increased the migration of neural progenitor cells. Application of an MMP inhibitor abolished the supernatant-enhanced migration. Incubation of neurospheres alone with rhEPO failed to increase progenitor cell migration. rhEPO activated phosphatidylinositol 3-kinase/Akt (PI3K/Akt) and extracellular signal-regulated kinase (ERK1/2) in MBECs. Selective inhibition of the PI3K/Akt and ERK1/2 pathways significantly attenuated the rhEPO-induced MMP2 and MMP9, which suppressed neural progenitor cell migration promoted by the rhEPO-activated MBECs. Collectively, our data show that rhEPO-activated endothelial cells enhance neural progenitor cell migration by secreting MMP2 and MMP9 via the PI3K/Akt and ERK1/2 signaling pathways. These data demonstrate that activated endothelial cells can promote neural progenitor cell migration, and provide insight into the molecular mechanisms underlying the attraction of newly generated neurons to injured areas in brain.

Animals↗

Ligand-induced growth cone collapse: amplification and blockade by variant GAP-43 peptides.

Growth cones are powerful amplifiers for signals from the microenvironment. Their collapse can be triggered by cell surface components of myelin and brain membranes, as well as by soluble ligands, including neurotransmitters. GAP-43 is a protein concentrated on the inner surface of the growth cone membrane. Assayed in isolation, it interacts with the heterotrimeric protein, G(o), and in oocytes it amplifies the effects of ligand-triggered G protein activation. We wished to examine whether GAP-43 serves to amplify signals at the growth cone. The G(o) stimulating region of GAP-43 is encoded in the 10 amino acids (MLCCMRRT-KQ) of the first exon. We examined the effect of this peptide upon chick dorsal root ganglion growth cone collapse and neurite retraction triggered by brain membranes or myelin, as well as by serotonin. We find that application of the GAP-43 1-10 peptide amplifies the effects of all three ligands. The amplification is greater when GAP-43 1-10 is injected intracellularly. Peptides with amino acid substitutions for the two cysteine residues manifest parallel changes in growth cone collapse and G(o) stimulation. In particular, tyrosine or methionine substitutions cause the peptide to inhibit G(o) and to block induced growth cone collapse. The GAP-43 peptides therefore regulate the sensitivity of growth cones to extrinsic signals. The modified peptides serve as a starting point for the design of reagents to enhance CNS regeneration.

Amino Acid Sequence↗

Extracellular (36Cl) space, electrolyte, protein, and DNA content in brain of DBA and C57 mice: effects of age.

DBA/2J (DBA) mice are susceptible to audiogenic seizures (AGSs) in an age-dependent manner, susceptibility being maximal at 21 days and absent at 110 days of age. Previous studies have demonstrated that there is a decrease in anion transport and an increase in carbonic anhydrase (CA) activity in brain from DBA mice as compared with C57BL/6J (C57, non-AGS) mice at 21 days. Since these results suggest that there are alterations in cellular and electrolyte composition of brain from DBA mice, the present work was directed toward determining electrolyte content, extracellular space, and DNA content of brain from DBA and C57 mice at 21 and 110 days of age. There was a decrease in intracellular chloride and sodium content, and an increase in intracellular potassium content in cerebral cortex, cerebellum, and brainstem from DBA mice at both 21 and 110 days. Also, extracellular space was larger in these three brain tissues from DBA mice at both ages. DNA content, not different between the strains at 21 days, was significantly lower in cerebellum from DBA mice at 110 days. These findings give further evidence of alterations in the transport of ions in brain from DBA mice. In addition, they demonstrate that there are alterations in the intracellular and extracellular space values, an indication of changes in cellular composition of brain in these mice. Such changes may contribute to AGS susceptibility by disrupting the balance that normally exists in the neuronal microenvironment of the central nervous system.

Acoustic Stimulation↗

Tumoral micro-blood vessels and vascular microenvironment in human astrocytic tumors. A transmission electron microscopy study.

The development of peritumoral edema is thought to be due to extravasation of plasma water and macromolecules through a defective blood-brain barrier (BBB), but the exact mechanism by which occurs is poorly understood. The aim of this study was analyze at submicroscopic level the morphological changes in both micro-blood vessels and vascular microenvironment of astrocytic tumors in an attempt of understanding the pathological aspects that may help in the future researches for the design of future therapeutic strategies. Biopsies of 25 patients with pathological diagnosis of astrocytic tumors were examined with the transmission electron microscope. Both open and close tight junctions were observed in the micro-blood vessels, inclusive in a same tumor. Cytoskeletal disorganization associated with disintegrated perijunctional actin filaments were seen. The paracellular space showed enlargement and commonly occupied by fluid proteinaceous, endothelial cells display oncotic and ischemic changes, basal lamina reveals enlargement, edema, vacuolization and collagen fibers disposed in irregular array. Pericytes exhibited edema and phagocytoced material, astrocytic perivascular-feet showed signs of oncosis and necrosis, co-option vessels totally surrounding by neoplastic cells also were seen. The ultrastructural abnormalities observed in both junctional complexes and vascular microenvironment suggest a multi-factorial pathobiology process, probably hypoxia intratumoral, calcium overload in endothelial cells, and degradative effects of metalloproteinases over the basal membrane appear as determinant factors that leading to structural modifications of junctional complexes, therefore, treatment with both HIF-1alpha and metalloproteinases inhibitors possibly can contribute with the pharmacological handling of the peritumoral edema associated with astrocytic tumors.

Astrocytoma↗

GBMdeconvoluteR accurately infers proportions of neoplastic and immune cell populations from bulk glioblastoma transcriptomics data.

BACKGROUND: Characterizing and quantifying cell types within glioblastoma (GBM) tumors at scale will facilitate a better understanding of the association between the cellular landscape and tumor phenotypes or clinical correlates. We aimed to develop a tool that deconvolutes immune and neoplastic cells within the GBM tumor microenvironment from bulk RNA sequencing data. METHODS: We developed an IDH wild-type (IDHwt) GBM-specific single immune cell reference consisting of B cells, T-cells, NK-cells, microglia, tumor associated macrophages, monocytes, mast and DC cells. We used this alongside an existing neoplastic single cell-type reference for astrocyte-like, oligodendrocyte- and neuronal progenitor-like and mesenchymal GBM cancer cells to create both marker and gene signature matrix-based deconvolution tools. We applied single-cell resolution imaging mass cytometry (IMC) to ten IDHwt GBM samples, five paired primary and recurrent tumors, to determine which deconvolution approach performed best. RESULTS: Marker-based deconvolution using GBM-tissue specific markers was most accurate for both immune cells and cancer cells, so we packaged this approach as GBMdeconvoluteR. We applied GBMdeconvoluteR to bulk GBM RNAseq data from The Cancer Genome Atlas and recapitulated recent findings from multi-omics single cell studies with regards associations between mesenchymal GBM cancer cells and both lymphoid and myeloid cells. Furthermore, we expanded upon this to show that these associations are stronger in patients with worse prognosis. CONCLUSIONS: GBMdeconvoluteR accurately quantifies immune and neoplastic cell proportions in IDHwt GBM bulk RNA sequencing data and is accessible here: https://gbmdeconvoluter.leeds.ac.uk.

Humans↗

Regional growth of different human melanomas as metastases in the brain of nude mice.

Cells from eight different human melanomas and two murine melanomas were injected into the internal carotid artery of anesthetized nude mice. Although all were injected by the same route, particular melanomas produced lesions in different regions of the brain. Two melanoma cell lines isolated originally from brain metastases in patients produced metastases predominantly in the brain parenchyma. In contrast, melanoma cells from subcutaneous or lymph node metastases produced more lesions in the meninges, choroid plexus, and ventricles than in the brain parenchyma. All of the melanomas grew in the brain after a direct intracerebral injection. The pattern of brain metastasis did not correlate with tumorigenicity per se or with the ability of the melanomas to grow in the lungs of nude mice. Two mouse melanomas showed different patterns of experimental metastasis after internal carotid artery injection, with one growing predominantly in the parenchyma and the other more frequently in the meninges and choroid plexus. The growth pattern of human melanoma metastasis in the brain of T cell-deficient nude mice suggests that it is determined by properties unique to each tumor interacting with the host's organ microenvironment.

Animals↗

Experimental and theoretical analysis of oxygen transport in fetal brain.

Based on the results obtained in this study and the results of others it seems safe to conclude the following: 1) Fetal brain PO2 values are considerably lower than those found in adult brain. 2) Administration of 100% oxygen to the mother can (but not always) significantly raise the PO2 at a specific point in the fetal cortex. 3) The response of fetal brain PO2 to changes in maternal arterial PO2 is delayed by a finite quantity of time of the order of magnitude of 38 seconds. 4) The time required for the fetal brain PO2 to reach a minimum following a decrease in the PO2 of maternal arterial blood coincides closely with the time required for the maternal arterial PO2 to reach its minimum plus the pure transport delay time (38 seconds). 5) The fetus has available a control mechanism which acts to compensate for periods of reduced PO2 in the microenvironment of the fetal cortex.

Animals↗

Distribution of pluripotent neural crest cells in the embryo and the role of brain-derived neurotrophic factor in the commitment to the primary sensory neuron lineage.

Many early migratory neural crest cells are pluripotent in the sense that their progeny are able to generate more than one differentiated phenotype (Sieber-Blum and Cohen, 1980, Dev. Biol. 80:95-106; Baroffio, Dupin, and Le Douarin, 1988, Proc. Natl. Acad. Sci. USA 85:5325-5329; Bronner-Fraser and Fraser, 1988, Nature 335:161-164; Sieber-Blum, 1989a, Science 243:1608-1611; Ito and Sieber-Blum, 1991, Dev. Biol. 148:95-106). At trunk levels, the neural crest contains two classes (Sieber-Blum and Cohen, 1980) and at posterior rhombencephalic levels, three different classes of pluripotent cells (Ito and Sieber-Blum, 1991). We investigated cell differentiation by in vitro clonal analysis to determine when in development the pool of pluripotent neural crest cells becomes exhausted. The data suggest that different classes of pluripotent cells, precursor cells with more restricted developmental potentials, and apparently committed cells, exist at sites of advanced migration (posterior branchial arches) and even at target sites of neural crest cell differentiation [posterior branchial arches, dorsal root ganglia (DRG), sympathetic ganglia (SG), and epidermal ectoderm]. Some putative classes of pluripotent cells persist well into the second half of embryonic development. These observations have implications for our understanding of the mechanisms that control neural crest cell migration and differentiation. They support the idea that cues originating from the microenvironment affect differentiation of pluripotent neural crest cells. One such signal appears to be brain-derived neurotrophic factor (BDNF). In the presence of BDNF, but not nerve growth factor (NGF), there is a significant increase in the number of neural crest cells per colony that express a sensory neuron-specific marker. Because this increase is not accompanied by a corresponding increase in the total number of cells per colony, this suggests that BDNF plays a role in cell type specification.

Animals↗

MOP3, a component of the molecular clock, regulates the development of B cells.

Differentiation and proliferation of haematopoietic progenitor cells occur in intimate contact with the bone marrow microenvironment which is composed of stromal cells and extracellular matrix proteins. MOP3 (also known as brain and muscle Arnt-like protein-1, BMAL1), a master regulator of circadian rhythm, plays important roles in the regulation of cell differentiation and general physical functions. In the present studies, MOP3-deficient mice had significantly reduced levels of B cells in the peripheral blood, spleen and bone marrow compared MOP3(+/-) or MOP3(+/+) littermates. Flow cytometry analysis showed the levels of pre-B cells in bone marrow of MOP3(-/-) mice were similar as that in control mice. Adoptive transfer of MOP3(-/-) bone marrow cells (BMC) to lethally irradiated BALB/c Rag2(-/-) recipients, normal T and B cell development was observed, whereas Adoptive transfer of BALB/c BMC to lethally irradiated MOP3(-/-) recipients, B-cell development was significantly impaired. These results presented herein with MOP3-deficient mice reveal the involvement of MOP3 in the development of B cells, but not other immune cells. The effect of MOP3 on the differentiation of pre-B cells to mature B cells might be mediated by the bone marrow microenvironment. This study also showed a connection between a master regular of circadian rhythm with B-cell development in mice.

ARNTL Transcription Factors↗

Brain mapping activity and mental performance after chronic treatment with CDP-choline in Alzheimer's disease.

CDP-choline participates in brain phospholipid metabolism and acts as an endogenous intermediate in a biosynthetic pathway incorporating free choline into phosphatidylcholine and choline plasmalogens in several tissues, including the central nervous system (CNS). In patients with chronic cerebrovascular disorders, CDP-choline reduces the slow delta frequencies and increases alpha activity in spectral electroencephalogram analysis. We have studied the effect of CDP-choline (cytidine-S-diphosphate-choline; 1000 mg/day x 30 days, p.o.) on brain electrical activity mapping and mental performance in 19 Alzheimer's disease (AD) patients (10 males/9 females; age: 66.21 +/- 1.48 years; Mini-Mental State Examination (MMSE): 26.55 +/- 1.22, Spanish version max. score 35). EEG was registered from 19 electrodes placed according to the 10-20 system and digitalized online. Artefact-free 2-s periods were visually selected, submitted to a frequency analysis and averaged across periods. CDP-choline significantly decreased spectral amplitude in the theta band in F4, F8, and T4 electrodes, and did not modify relative power parameters in any of the frequency bands (delta, theta, alpha, beta) as compared to basal recordings. In patients with late-onset AD (LOAD; N = 6; age: 73.5 +/- 1.34 years; MMSE: 28.75 +/- 2.33), CDP-choline tended to increase relative alpha power in O1 and O2 electrodes. No changes were found in early-onset AD patients (EOAD; N = 13; age: 62.85 +/- 1.21 years; MMSE: 25.54 +/- 1.4). We detected a significant improvement in mental performance after 1 month of treatment with CDP-choline in patients with early-onset AD in whom brain electrical activity data correlated with cognitive parameters. It is likely that the bioelectrical changes induced by CDP-choline in AD are the result of its immunogenic and/or neurotrophic activity in the vicinity of the vascular microenvironment.

Aged↗

Comparison of the inhibitory effects of mercuric chloride on cytosolic and mitochondrial hexokinase activities in rat brain, kidney and spleen.

Hg2+ (10-20 microM), at concentrations comparable to mercury levels reportedly occurring in mercury neurotoxicity (Minamata disease), effectively inhibited both cytosolic (IC50 for Hg2+ = 4.1 microM) and mitochondrial (IC50 for Hg2+ = 1.4 microM) rat brain hexokinases. Kidney (IC50 for Hg2+ approximately equal to 3 microM) and spleen hexokinases were less susceptible to inhibition by Hg2+. IC50 values for Hg2+ in inhibiting cytosolic and mitochondrial spleen hexokinases were 8.9 and 3.1 microM, respectively. In both brain and spleen, mitochondrial hexokinases were more susceptible to inhibition by Hg2+ than cytosolic forms, suggesting that the microenvironment of the mitochondrial membranes may exert some modulatory effects on the properties of hexokinases. These results also suggest that inhibition of glucose utilization may be an important mechanism of tissue damage in mercury poisoning.

Animals↗