Brain Metabolism and Intracellular pH During Ischaemia and Hypoxia: An In Vivo 31P and 1H Nuclear Magnetic Resonance Study in the Lamb

Brain metabolism and intracellular pH were studied during and after episodes of ischaemia and hypoxia-ischaemia in lambs anaesthetised with sodium pentobarbitone. 31P and 1H magnetic resonance spectroscopy methods were used to monitor brain pHi and brain concentrations of Pi, phosphocreatine (PCr), beta--nucleoside triphosphate (beta NTP), and lactate. Simultaneous measurements were made of cerebral blood flow and cerebral oxygen and glucose consumption. Cerebral ischaemia sufficient to reduce oxygen delivery to 75% of control values was associated with a fall in brain pHi and increase in brain Pi. Progressively severe hypoxia-ischaemia was associated with a progressive fall in brain pHi, PCr, and beta NTP and increase in brain Pi. In two animals the increase in brain lactate during hypoxia-ischaemia measured by 1H nuclear magnetic resonance (NMR) could be quantitatively accounted for by the increased net uptake of glucose by the brain in relation to oxygen, but was insufficient to account for the concomitant acidosis according to previous estimates of brain buffering capacity. In four animals brain pHi, PCr, Pi, and beta NTP had returned to normal 1 h after the hypoxic-ischaemic episode. In one animal brain pHi had reverted to normal at a time when 1H NMR indicated persistent elevation of brain lactate.     

Diagnosis and management of brain death.

Finland was the first country in which brain death was legally accepted. Since 1975, 37 cases of brain death had been recorded in a university hospital in Finland, and these were reviewed. The cause for brain death was intracranial bleeding in 32 cases, other cerebrovascular disorder in two, and intracranial neoplasm in three. In 21 brain death was diagnosed clinically. In 16 cases confirmatory investigations (electroencephalography, cerebral angiography) were needed. After brain death had been established artificial support was withdrawn in 15 patients and organ transplantation was carried out in 10. In 12 patients, however, diagnosis of brain death did not influence management, though the heart stopped beating on average 25 hours after diagnosis. The Finnish criteria for brain death seem to be reliable and suitable for routine use.     

Glutathione pathways in the brain

The antioxidant glutathione (GSH) is essential for the cellular detoxification of reactive oxygen species in brain cells. A compromised GSH system in the brain has been connected with the oxidative stress occuring in neurological diseases. Recent data demonstrate that besides intracellular functions GSH has also important extracellular functions in brain. In this respect astrocytes appear to play a key role in the GSH metabolism of the brain, since astroglial GSH export is essential for providing GSH precursors to neurons. Of the different brain cell types studied in vitro only astrocytes release substantial amounts of GSH. In addition, during oxidative stress astrocytes efficiently export glutathione disulfide (GSSG). The multidrug resistance protein 1 participates in both the export of GSH and GSSG from astrocytes. This review focuses on recent results on the export of GSH and GSSG from brain cells as well as on the functions of extracellular GSH in the brain. In addition, implications of disturbed GSH pathways in brain for neurodegenerative diseases will be discussed.     

Energetic trade-offs between brain size and offspring production: Marsupials confirm a general mammalian pattern

Recently, Weisbecker and Goswami presented the first comprehensive comparative analysis of brain size, metabolic rate, and development periods in marsupial mammals. In this paper, a strictly energetic perspective is applied to identify general mammalian correlates of brain size evolution. In both marsupials and placentals, the duration or intensity of maternal investment is a key correlate of relative brain size, but here I show that allomaternal energy subsidies may also play a role. In marsupials, an energetic constraint on brain size in adults is only revealed if we consider both metabolic and reproductive rates simultaneously, because a strong trade-off between encephalization and offspring production masks the positive correlation between basal metabolic rate and brain size in a bivariate comparison. In conclusion, starting from an energetic perspective is warranted to elucidate relations between ecology, social systems, life history, and brain size in all mammals.     

水通道蛋白4与脑水肿研究进展

水通道蛋白4(AQP4)是膜水通道蛋白家族的一员,在脑组织中高表达,是控制水进出脑组织的通道。近年来发现,AQP4的功能和表达与脑水肿密切相关。同时脑水肿又是和脑疾病治疗密切相关的病理过程,对两者的研究或许可以为我们带来更多的临床治疗新思路。本文综述了AQP4的结构、表达、调控与功能以及AQP4与脑水肿关系的研究进展。     

Adult human brain cell culture for neuroscience research

Studies of the brain have progressed enormously through the use of in vivo and in vitro non-human models. However, it is unlikely such studies alone will unravel the complexities of the human brain and so far no neuroprotective treatment developed in animals has worked in humans. In this review we discuss the use of adult human brain cell culture methods in brain research to unravel the biology of the normal and diseased human brain. The advantages of using adult human brain cells as tools to study human brain function from both historical and future perspectives are discussed. In particular, studies using dissociated cultures of adult human microglia, astrocytes, oligodendrocytes and neurons are described and the applications of these types of study are evaluated. Alternative sources of human brain cells such as adult neural stem cells, induced pluripotent stem cells and slice cultures of adult human brain tissue are also reviewed. These adult human brain cell culture methods could benefit basic research and more importantly, facilitate the translation of basic neuroscience research to the clinic for the treatment of brain disorders.     

Effect of stobadine on lipid peroxidation in brain and heart after ischemia and reperfusion of the brain

Stobadine (ST), a novel drug with pyridoindol structure, was recently found to prevent reperfusion injury in rat brain. The aim of the present study was to reveal whether ST may prevent peroxidative changes in the heart and brain that were triggered by postischemic reperfusion of the brain. In the brain, reperfusion significantly increased the contents of malondialdehyde (MDA) by 43.8% and conjugated diens (CD) by 24.5% when compared with the end of ischemia. In the heart, contents of MDA and CD in reperfusion became elevated three fold and by 41.7%, respectively, when comparing to the values at the end of ischemia. In the heart, no significant changes in activities of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) induced by ischemia or reperfusion were detected. In contrast, reperfusion induced a slight decrease in GPx activity in the brain. In accordance with our previous results, an application of ST (2 mg/kg) to the femoral artery shortly prior to reperfusion of the ischemic brain, prevented significantly MDA and CD accumulation in brain. Nevertheless, ST was not able to prevent the brain-ischemia/reperfusion-induced elevation of MDA and CD contents in the heart.     

EVALUATION OF IN SITU FREEZING OF CAT BRAIN BY NADH FLUORESCENCE

Abstract— Cat brain was frozen in situ with liquid nitrogen. In order to locate areas with ischemic artifact, frozen brain slices were surveyed for regions of increased NADH fluorescence. In addition, levels of ATP, phosphocreatine, lactate, and NADH were determined in various brain regions. High levels of ATP and phosphocreatine, and low levels of lactate and NADH were present in all brain regions except the depths of some cortical sulci. These regions of ischemic change were easily detected by virtue of increased NADH fluorescence in frozen brain slices. Deep brain structures such as basal ganglia and hippocampus showed neither high tissue fluorescence nor ischemic changes of the metabolites measured. Therefore, in situ freezing of cat brain adequately preserves metabolite levels in most regions.     

Immunohistochemical Staining and Enzyme Activity Measurements Show myo-Inositol-1-Phosphate Synthase to Be Localized in the Vasculature of Brain

Rabbit anti-bovine myo-inositol-1-phosphate synthase was used to examine the distribution of that enzyme in perfused and immersion-fixed bovine brain and testis. In brain, intense and specific staining was found in the walls of all the vascular elements including cerebral capillaries. The remainder of brain parenchyma exhibited only low levels of background staining. In testis, an organ rich in the enzyme, blood vessels showed no specific staining. Instead, the enzyme was found in the seminiferous epithelium of the seminiferous tubules, perhaps localized in spermatozoa. To confirm the brain finding, the activity of myo-inositol-1-phosphate synthase was measured in bovine brain microvessel preparations and brain pial vessels. In these preparations the activity of the enzyme was found on average to be 7 and 22 times enriched over that in whole brain, respectively. The activities of two other enzymes of inositol metabolism, myo-inosose reductase and myo-inositol-1-phosphatase, were also examined for their distribution in brain. Those enzymes were found to be generally distributed. The surprising finding of a vascular localization of myo-inositol-1-phosphate synthase in brain raises new questions about the mechanism by which myo-inositol is concentrated to such high cellular levels in the principal substance of that organ.     

Different Subcellular Localization of Muscarinic and Serotonin (S2) Receptors in Human, Dog, and Rat Brain

Cortex from rat, dog, and human brain was submitted to subcellular fractionation using an analytical approach consisting of a two-step procedure. First, fractions were obtained by differential centrifugation and were analyzed for their content of serotonin S2 and muscarinic receptors, serotonin uptake, and marker enzymes. Second, the cytoplasmic extracts were subfractionated by equilibration in sucrose density gradient. In human brain, serotonin and muscarinic receptors were found associated mostly with mitochondrial fractions which contain synaptosomes, whereas in rat brain they were concentrated mainly in the microsomal fractions. Density gradient centrifugation confirmed a more marked synaptosomal localization of receptors in human than in rat brain, the dog displaying an intermediate profile. In human brain, indeed, more receptor sites were found to be associated with the second peak characterized in electron microscopy by the largest number of nerve terminals. In addition, synaptosomes from human brain are denser than those from rat brain and some marker enzymes reveal different subcellular distribution in the three species. These data indicate that more receptors are of synaptosomal nature in human brain than in other species and this finding is compatible with a larger amount of synaptic contacts in human brain.     

Brain Pericytes: Emerging Concepts and Functional Roles in Brain Homeostasis

Brain pericytes are an important constituent of neurovascular unit. They encircle endothelial cells and contribute to the maturation and stabilization of the capillaries in the brain. Recent studies have revealed that brain pericytes play pivotal roles in a variety of brain functions, such as regulation of capillary flow, angiogenesis, blood brain barrier, immune responses, and hemostasis. In addition, brain pericytes are pluripotent and can differentiate into different lineages similar to mesenchymal stem cells. The brain pericytes are revisited as a key player to maintain brain function and repair brain damage.     

Ontogenetic Shape Change in the Chicken Brain: Implications for Paleontology

Paleontologists have investigated brain morphology of extinct birds with little information on post-hatching changes in avian brain morphology. Without the knowledge of ontogenesis, assessing brain morphology in fossil taxa could lead to misinterpretation of the phylogeny or neurosensory development of extinct species. Hence, it is imperative to determine how avian brain morphology changes during post-hatching growth. In this study, chicken brain shape was compared at various developmental stages using three-dimensional (3D) geometric morphometric analysis and the growth rate of brain regions was evaluated to explore post-hatching morphological changes. Microscopic MRI (μMRI) was used to acquire in vivo data from living and post-mortem chicken brains. The telencephalon rotates caudoventrally during growth. This change in shape leads to a relative caudodorsal rotation of the cerebellum and myelencephalon. In addition, all brain regions elongate rostrocaudally and this leads to a more slender brain shape. The growth rates of each brain region were constant and the slopes from the growth formula were parallel. The dominant pattern of ontogenetic shape change corresponded with interspecific shape changes due to increasing brain size. That is, the interspecific and ontogenetic changes in brain shape due to increased size have similar patterns. Although the shape of the brain and each brain region changed considerably, the volume ratio of each brain region did not change. This suggests that the brain can change its shape after completing functional differentiation of the brain regions. Moreover, these results show that consideration of ontogenetic changes in brain shape is necessary for an accurate assessment of brain morphology in paleontological studies.     

Failure of Glucose and Branched-Chain Amino Acids to Normalize Brain Glucose Use in Portacaval Shunted Rats

Several abnormalities in brain and plasma amino acid concentrations caused by portacaval shunting in rats return toward normal after 4 days of intravenous infusion with either glucose or glucose with branched-chain amino acids. To assess the effect of such treatment on brain energy metabolism, regional brain glucose use was measured using [14C]glucose and autoradiography, 5 weeks after portacaval shunting. In one experiment intravenous glucose or glucose with branched-chain amino acids was given for 4 days. In a separate experiment the treatment was given orally for 2 weeks, and in addition to glucose use, brain monoamines and amino acids were measured. No other food was provided; the rats had free access to water. Normally fed shunted rats and sham-operated rats served as controls. Both types of oral treatment lowered the high concentrations of tyrosine, phenylalanine, and glutamine in plasma and brain. Glucose without amino acids normalized brain tryptophan. Levels of brain norepinephrine, 5-hydroxytryptamine (serotonin), and 5-hydroxyindoleacetic acid were significantly raised after shunting. Treatment had no effect on norepinephrine but the glucose diet brought the indoles into the normal range. In contrast, neither intravenous nor oral treatment affected brain glucose use, which remained depressed by 25-30% in all brain areas examined.     

Emerging Bioelectronics for Brain Organoid Electrophysiology

Human brain organoids are generated from three-dimensional (3D) cultures of human induced pluripotent stem cells and embryonic stem cells, which partially replicate the development and complexity of the human brain. Many methods have been used to characterize the structural and molecular phenotypes of human brain organoids. Further understanding the electrophysiological phenotypes of brain organoids requires advanced electrophysiological measurement technologies to achieve long-term stable 3D recording over the time course of the organoid development with single-cell, millisecond spatiotemporal resolution. In this review, first, we briefly introduce the development, generation, and applications of human brain organoids. We then discuss the conventional methods used for characterizing the morphological, genetic, and electrical properties of brain organoids. Next, we highlight the need for characterizing electrophysiological properties of brain organoids in a minimally invasive manner. In particular, we discuss recent advances in the multi-electrode array (MEA), 3D bioelectronics, and flexible bioelectronics and their applications in brain organoid electrophysiological measurement. In addition, we introduce the recently developed cyborg organoids platform as an emerging tool for the long-term stable 3D characterization of the brain organoids electrophysiology at high spatiotemporal resolution. Finally, we discuss the perspectives of new technologies that could achieve the high-throughput, multimodal characterizations from the same brain organoids.     

Development and Regional Distribution of Methionine Synthetase in Rabbit Brain

The development and regional distribution of methionine synthetase (EC 2.1.1.13) in rabbit brain was determined. In adult rabbits, the specific activity (units per milligram protein) of methionine synthetase in cortex, cerebellum, brain stem, and corpus striatum was comparable to the specific activity in whole brain (0.5 units/mg). In the first few weeks of life, the specific activity of methionine synthetase in whole rabbit brain declined from a value of 1.1 units/mg at 1 day of age to 0.5 units/mg at 6–10 weeks. Two-year-old rabbits had 0.6 units/mg in whole brain. These results show that: (a) methionine synthetase is distributed widely in mammalian brain and (b) methionine synthetase activity in brain declines relatively little with development.     

Towards the virtual brain: network modeling of the intact and the damaged brain

Neurocomputational models of large-scale brain dynamics utilizing realistic connectivity matrices have advanced our understanding of the operational network principles in the brain. In particular, spontaneous or resting state activity has been studied on various scales of spatial and temporal organization including those that relate to physiological, encephalographic and hemodynamic data. In this article we focus on the brain from the perspective of a dynamic network and discuss the role of its network constituents in shaping brain dynamics. These constituents include the brain's structural connectivity, the population dynamics of its network nodes and the time delays involved in signal transmission. In addition, no discussion of brain dynamics would be complete without considering noise and stochastic effects. In fact, there is mounting evidence that the interaction between noise and dynamics plays an important functional role in shaping key brain processes. In particular, we discuss a unifying theoretical framework that explains how structured spatio-temporal resting state patterns emerge from noise driven explorations of unstable or stable oscillatory states. Embracing this perspective, we explore the consequences of network manipulations to understand some of the brain's dysfunctions, as well as network effects that offer new insights into routes towards therapy, recovery and brain repair. These collective insights will be at the core of a new computational environment, the Virtual Brain, which will allow flexible incorporation of empirical data constraining the brain models to integrate, unify and predict network responses to incipient pathological processes.     

The brain structure of selected trypanorhynch tapeworms

The brain architecture in four species of tapeworms from the order Trypanorhyncha has been studied. In all species, the brain consists of paired anterior and lateral lobes, and an unpaired central lobe. The anterior lobes connect by dorsal and ventral semicircular commissures; the central and lateral lobes connect by a median and an X-shaped crisscross commissure. In the center of the brain, five well-developed compact neuropils are present. The brain occupies a medial position in the scolex pars bothrialis. The ventral excretory vessels are situated outside the lateral lobes of the brain; the dorsal excretory vessels are located inside the brain and dorsal to the median commissure. The brain gives rize four anterior proboscis nerves and four posterior bulbar nerves with myelinated giant axons (GAs). The cell bodies of the GAs are located within the X-commissure and in the bulbar nerves. Highly developed serotonergic neuropils are present in the anterior and lateral lobes; numerous 5-HT neurons are found in the brain lobes including the central unpaired lobe. The X-cross commissure consists of the α-tub-immunoreactive and 5-HT-IR neurites. Eight ultrastructural types of neurons were found in the brain of the three species investigated. In addition, different types of synapses were present in the neuropils. Glial cells ensheath the brain lobes, the neuropils, the GAs, and the bulbar nerves. Glia cell processes form complex branching patterns of thin cytoplasmic sheets sandwiched between adjacent neural processes and filling the space between neurons. Multilayer myelin-like envelopes and a mesaxon-like structure have been found in Trypanorhyncha nervous system. We compared the brain architecture of Trypanorhyncha with that of an early basal cestode taxon, that is, Diphyllobothriidea, and present a hypothesis about the homology of the anterior brain lobes in order Trypanorhyncha; and the lateral lobes and median commissure are homologous brain structures within Eucestoda.     

Recent advances in nanotechnology based drug delivery to the brain

Drug delivery into the brain was difficult due to the existence of blood brain barrier, which only permits some molecules to pass through freely. In past decades, nanotechnology has enabled many technical advances including drug delivery into the brain with high efficiency and accuracy. In the present paper, we summarize recent important advances in employing nanotechnology for drug delivery to the brain as well as controlled drug release.     

Brain microvascular P-glycoprotein and a revised model of multidrug resistance in brain

1. P-Glycoprotein is a 170-kDa transmembrane glycoprotein active efflux system that confers multidrug resistance in tumors, as well as normal tissues including brain.2. The classical model of multidrug resistance in brain places the expression of P-glycoprotein at the luminal membrane of the brain microvascular endothelial cell. However, recent studies have been performed with human brain microvessels and double-labeling confocal microscopy using (a) the MRK16 antibody to human P-glycoprotein, (b) an antiserum to glial fibrillary acidic protein (GFAP), an astrocyte foot process marker, or (c) an antiserum to the GLUT1 glucose transporter, a brain endothelial plasma membrane marker. These results provide evidence for a revised model of P-glycoprotein function at the brain microvasculature. In human brain capillaries, there is colocalization of immunoreactive P-glycoprotein with astrocytic GFAP but not with endothelial GLUT1 glucose transporter.3. In the revised model of multidrug resistance in brain, P-glycoprotein is hypothesized to function at the plasma membrane of astrocyte foot processes. These astrocyte foot processes invest the brain microvascular endothelium but are located behind the blood–brain barrier in vivo, which is formed by the brain capillary endothelial plasma membrane.4. In the classical model, an inhibition of endothelial P-glycoprotein would result in both an increase in the blood–brain barrier permeability to a given drug substrate of P-glycoprotein and an increase in the brain volume of distribution (V _D) of the drug. However, in the revised model of P-glycoprotein function in brain, which positions this protein transporter at the astrocyte foot process, an inhibition of P-glycoprotein would result in no increase in blood–brain barrier permeability, per se, but only an increase in the V _D in brain of P-glycoprotein substrates.     

Brain Ion and Amino Acid Contents During Edema Development in Hepatic Encephalopathy

Abstract: Brain edema in hepatic encephalopathy has been associated with circulating ammonia that is metabolized to glutamine. We measured alterations in blood chemistry and brain regional specific gravity and ion and amino acid contents in models of simple hyperammonemia and liver failure induced by daily administrations of ammonium acetate (AAc) or thioacetamide (TAA), respectively. Serum and brain ammonia increased to similar levels (200 and 170% of control, respectively) in both experimental groups. Serum transaminase activities increased 10-fold in animals injected with TAA but were unchanged in animals given AAc injections. In both experimental groups glutamine was elevated in cerebral white matter, cerebral gray matter, and basal ganglia, whereas brain tissue specific gravity decreased in all brain regions, indicating edema formation. In the AAc group, we observed a decrease in glutamate and taurine contents concomitant with the development of brain edema. In these animals, cerebral gray matter specific gravity and taurine contents returned to control levels 24 h after the third AAc injection. TAA-injected animals demonstrated similar decreases in brain tissue specific gravity, whereas glutamine, glutamate, and taurine contents were all elevated. During hepatic encephalopathy, ammonia-induced changes in brain amino acid content may contribute to brain edema development.