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At least 631 records · Page 35Linked to original sources
PubMed2006

Smoking and structural brain deficits: a volumetric MR investigation.

Growing evidence from animal studies indicates brain-damaging properties of nicotine exposure. Investigations in humans found a wide range of functional cerebral effects of nicotine and cigarette smoking, but studies focusing on brain damage are sparse. In 22 smokers and 23 never-smokers possible differences of the cerebral structures were investigated using magnetic resonance imaging and voxel-based morphometry. Significantly smaller grey matter volume and lower grey matter density (P = 0.05, corrected) were observed in the frontal regions (anterior cingulate, prefrontal and orbitofrontal cortex), the occipital lobe and the temporal lobe including parahippocampal gyrus, in smokers than in never-smokers. Group differences of either grey matter volume or grey matter density were also found in the thalamus, cerebellum and substantia nigra, among other regions. Smokers did not show greater volumes than never-smokers in any cerebral region. Magnitude of lifetime exposure to tobacco smoke (pack-years) was inversely correlated with volume of frontal and temporal lobes and cerebellum (P = 0.001, uncorrected). The data indicate structural deficits of several cortical and subcortical regions in smokers relative to never-smokers. The topographic profile of the group differences show some similarities to brain networks known to mediate drug reinforcement, attention and working memory processing. The present findings may explain in part the frequently reported cognitive dysfunctions in chronic cigarette consumers.

Adult↗
PubMed2006

Relationships between plasma leptin concentrations and human brain structure: a voxel-based morphometric study.

We have previously demonstrated that obese people have reduced grey matter (GM) in several brain areas, including regions implicated in the regulation of taste (i.e., inferior frontal operculum and postcentral gyrus), reward (i.e., putamen), and behavioural processing (i.e., middle frontal gyrus), compared with their lean counterparts. It is well established that the brain may serve as a direct target for adiposity signals, one of the most important being leptin. We investigated the relationships between fasting plasma leptin concentrations and brain tissue composition in a group of 32 young adult Caucasians (12M/20F, age 32+/-1 years, body fat 29+/-1%, mean+/-S.E.) with normal glucose tolerance by using voxel-based morphometry of magnetic resonance imaging scans. Fasting plasma leptin concentrations were positively correlated with GM volumes of the left cerebellum and left inferior temporal gyrus and negatively associated with GM volumes of the left inferior frontal operculum, left postcentral gyrus, and right putamen (P<0.001, uncorrected for multiple comparisons) after adjustment for sex, percent body fat, age, fasting plasma insulin concentrations (i.e., the major determinants of plasma leptin), and global GM volume (thus allowing for an assessment of regional effects only). This study showed an independent, negative correlation between fasting plasma leptin concentrations, which are increased in obesity, and the volumes of GM in brain areas where obese people have reduced GM compared to their lean counterparts. These relationships may explain some of the abnormalities in brain morphology recently found to be associated with excess body fatness.

Adolescent↗
PubMed2002

MR image-based measurement of rates of change in volumes of brain structures. Part II: application to a study of Alzheimer's disease and normal aging.

We present global and regional rates of brain atrophy measured on serially acquired T1-weighted brain MR images for a group of Alzheimer's disease (AD) patients and age-matched normal control (NC) subjects using the analysis procedure described in Part I. Three rates of brain atrophy: the rate of atrophy in the cerebrum, the rate of lateral ventricular enlargement and the rate of atrophy in the region of temporal lobes, were evaluated for 14 AD patients and 14 age-matched NC subjects. All three rates showed significant differences between the two groups. However, the greatest separation of the two groups was obtained when the regional rates were combined. This application has demonstrated that rates of brain atrophy, especially in specific regions of the brain, based on MR images can provide sensitive measures for evaluating the progression of AD. These measures will be useful for the evaluation of therapeutic effects of novel therapies for AD.

Aged↗
PubMed2004

Reelin receptors in developing laminated brain structures of mouse and human.

Reelin is an extracellular matrix protein secreted by a variety of cell types throughout the developing brain. The target cells for reelin express the cytoplasmic adapter protein Dab1, which binds to the reelin receptors VLDLR and ApoER2. In the present work, we have studied the localization of both receptors in developing mouse and human cortex, olfactory bulb and cerebellum. In mouse, some Cajal-Retzius cells express reelin and VLDLR; in humans, all the components of the signalling pathway (Reelin, Dab1, VLDLR and ApoER2) are present in subsets of Cajal-Retzius cells. In the mouse cortical plate, VLDLR and ApoER2 are present from E15 to postnatal stages; in human cortical plate they are most prominent at approximately 20 gestational weeks. In mice, cerebellar Purkinje cells only express VLDLR whereas in humans they express both VLDLR and ApoER2. Mitral cells of the mouse olfactory bulb are ApoER2-positive and VLDLR-negative. In sum, the receptor expression patterns are similar in the human and mouse cortical plate but differ in Cajal-Retzius and Purkinje cells, which in humans express additional components of the reelin-Dab1 pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Electronic structure of brain: structure-activity relationships between electronic structure and neurotransmitters based on molecular hardness concept.

In order to understand the relation between the electronic structure of neurotransmitters and the brain, a model of the brain based on absolute hardness (eta) and absolute electronegativity (chi) is described. It was found that the coordinate r(chi, eta) of electronic structures of neurotransmitters obtained using the parameters eta and chi can be graphically classified into three groups: catecholamine type (group I), gamma-aminobutanoic acid (GABA) type (group II), and acetylcholine (ACh) type (group III) in the eta-chi diagram. The results suggest that the brainstem and neocortex in the brain are chemically soft and hard, respectively, because they show that the myelinated nerve is chemically soft and the unmyelinated nerve is chemically hard. If one calculates the r(chi, eta) to understand which group a drug belongs to, one can predict the target receptors of the drug from the eta-chi diagram. Using eta-chi maps, one is then able to design medications like antidepressants, tranquilizers, and ACh agonists.

Brain↗
PubMedDate not supplied

[Synaptic reactions of sensomotor cortex neurons to stimulation of emotionally significant brain structures].

The study deals with synaptic and spike responses of neurones in the rat sensorimotor cortex to stimulation of the lateral and medial hypothalamus, locus coeruleus and raphe nuclei. The activity of 57 neurones was recorded, 41 of them intracellularly and quasi-intracellularly, in response to the stimulation of sites in these structures, which were previously identified as "emotionally/ significant. No considerable differences in the effects of the stimulation of different "emotiogenic" zones were found. The stimulation parameters, differing from the "behavioural" ones by a greater strength, elicited in the majority of neurones clear post-synaptic responses, often in the form of EPSP-IPSP. Latencies of the responses varied from 3 to 80 msec. The most stable and pronounced responses were obtained to the stimulation of the lateral hypothalamus. No significant correlations of the latencies of the responses to the stimulation of different "emotiogenic" structures were found.

Animals↗
PubMed2005

Three-dimensional visualization of protein expression in mouse brain structures using imaging mass spectrometry.

We have developed a method to visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions. Details of the methodology are exemplified using the 3-D reconstruction of myelin basic protein (MBP) in the corpus callosum of a mouse brain. In this procedure, optical images obtained from serial coronal sections are first aligned to each other to reconstruct a surface of the corpus callosum from segmented contours of the aligned images. The MALDI IMS data are then coregistered to the optical images and superimposed into the surface to create the final 3-D visualization. Correlating proteomic data with anatomical structures provides a more comprehensive understanding of healthy and pathological brain functions, and holds promise to be utilized in more complex anatomical arrangements.

Animals↗
PubMed2002

Effect of the disruption of body fluid balance on pyroglutamyl aminopeptidase (Type-1) in rat brain structures.

The activity of soluble and membrane-bound pyroglutamyl aminopeptidase Type-1 (PAP I) was evaluated in the hypothalamus, hippocampus, thalamus, brain cortex, and pituitary gland of rats after applying certain hydromineral challenges. Compared to euhydrated rats, decreased enzyme activity was found in the hypophysis of rats deprived of water for 48 h, or rats drinking ad libitum hypertonic sodium chloride solution (2%) for 6 days or distilled water for 6 days and then submitted to acute water overload. PAP I cleaves the pGlu-amino acid bond of neuropeptides such as thyroliberin, luliberin, neurotensin, and bombesin. The decay of particulate PAP I activity may cause an increase of these pyroglutamate peptides in the whole pituitary. Although the deleterious or pro-homeostatic influence of this decay remains to be elucidated, the present data provide evidence for the involvement of this enzyme activity at this anatomical location in the water-electrolyte imbalance.

Animals↗
PubMed2000

Brain structures and mechanisms involved in the control of cortical activation and wakefulness, with emphasis on the posterior hypothalamus and histaminergic neurons.

Wakefulness is a functional brain state that allows the performance of several "high brain functions", such as diverse behavioural, cognitive and emotional activities. Present knowledge at the whole animal or cellular level suggests that the maintenance of the cerebral cortex in this highly complex state necessitates the convergent and divergent activity of an ascending network within a large reticular zone, extending from the medulla to the forebrain and involving four major subcortical structures (the thalamus, basal forebrain, posterior hypothalamus and brainstem monoaminergic nuclei), their integral interconnections and several neurotransmitters, such as glutamate, acetylcholine, histamine and noradrenaline. In this mini-review, the importance of the thalamus, basal forebrain and brainstem monoaminergic neurons in wake control is briefly summarized, before turning our attention to the posterior hypothalamus and histaminergic neurons, which have been far less studied. Classical and recent experimental data are summarized, supporting the hypothesis that (1) the posterior hypothalamus constitutes one of the brain ascending activating systems and plays an important role in waking; (2) this function is mediated, in part, by histaminergic neurons, which constitute one of the excitatory sources for cortical activation during waking; (3) the mechanisms of histaminergic arousal involve both the ascending and descending projections of histaminergic neurons and their interactions with diverse neuronal populations, such as neurons in the pre-optic area and cholinergic neurons; and (4) other widespread-projecting neurons in the posterior hypothalamus also contribute to the tonic cortical activation during wakefulness and/or paradoxical sleep.

Journal Article↗
PubMed2002

Physiological implications of mechanical effects of +Gz accelerations on brain structures.

BACKGROUND: In certain flight configurations, fighter pilots are exposed to high Gz acceleration (G) which may induce inflight loss of consciousness (G-LOC). When acceleration is of high amplitude, and the onset rate very rapid, G-LOC can occur extremely suddenly. HYPOTHESIS: Mechanisms other than brain hypoxia could be involved, enhancing its effects. In order to study the mechanical effects induced by such accelerations on cerebral structures, we estimated the stresses imposed on cerebral tissue when the brain is exposed to +Gz acceleration forces. METHODS: An "in vitro" experiment was performed to measure brain deformations during centrifugation. A finite element model of the brain was formulated. RESULTS: Computations indicate that traction and shear stresses are enhanced around the tentorial notch, and that compression stresses increase at the base of the cerebral hemispheres. CONCLUSION: The amplitude of these stresses is not sufficient to directly disturb proper nerve cell functioning. However, they could interfere with brain vessels as external surface forces, thus enhancing vessel collapse and brain ischemia.

Aerospace Medicine↗
PubMed1985

[Effect of antihypoxic agents on the cyclic nucleotide content in different brain structures in normo-oxia and hypoxia].

A study was made of the effects of isothiobarbamine and guthimine (10 and 50 mg/kg, respectively) on the content of cAMP and cGMP in the brain cortex (BC) and hippocamp under normal conditions and hypoxia. Isothiobarbamine did not change the content of both cyclic nucleotides under normoxia, whereas under hypoxia it reduced the level of the cyclic nucleotides in the BC and raised it in the hippocamp. Guthimine increased their content in the BC and did not change it in the hippocamp under normoxia, whereas under hypoxia it increased the cAMP content in the hippocamp and did not change it in the BC. The cGMP content descended in both the structures under study.

Animals↗