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At least 829 records · Page 46Linked to original sources
PubMed1982

[Some features of electrical and mechanical stunning in ruminants].

The present studies are concerned with methods of mechanical and electrical stunning as used in ruminants. The object is to acquire a scientific basis for the correct use of these procedures in slaughter-houses. In all experiments studies on living animals, cerebral activity (electro-encephalogram) was measured using electrodes which had been surgically implanted the previous day. When animals are stunned by concussion, unconsciousness is not induced in every case. When a slaughtering mask was frontally or occipitally applied to the head, unconsciousness was produced. To effectively induce unconsciousness, the bolt of the captive bolt pistol should carry sufficient energy to damage the cerebral cortex and the deeper portions of the brain directly or by shock waves following penetration of the cranium. The forces which may be developed by the variously coloured cartridges of the brands of captive bolt pistol differ markedly. Regulations regarding the relationship between the colour of the cartridge and the potential forces would appear to be essential.

Abattoirs↗
PubMed1999

Electrical stimulation of the amygdala increases the amplitude of elicited ponto-geniculo-occipital waves.

The amygdala projects massively via its central nucleus (CNA) into brain stem regions involved in alerting and ponto-geniculo-occipital (PGO) wave generation. Electrical stimulation of CNA is known to enhance the acoustic startle response (ASR) and influence spontaneous PGO waves. The role of the amygdala in the modulation of ASR and elicited PGO waves (PGOE) was investigated in albino rats. Electrically stimulating CNA within 25 ms prior to an auditory stimulus enhanced ASR and PGOE amplitude in a similar way, with the largest response occurring when the electrical and auditory stimuli were given simultaneously. The data suggest that CNA modulates alerting mechanisms.

Acoustic Stimulation↗
PubMedDate not supplied

Effect of hyperthermia on somatosensory evoked potentials in the anaesthetized rat.

In the rat heat stroke model, established by heating to a climatic chamber temperature of 42 degrees C, the brain temperature was found to be consistently lower than the rectal temperature, suggesting efficient brain cooling mechanisms in the rat. In response to heating, with increasing brain temperature, the latencies of the somatosensory evoked potentials (SEPs) showed an initial decrease followed by an increase (inflection point). Studies were done on rats heated up to, before, or after the inflection point and then cooled. Reversibility with cooling of functional and structural changes induced by heat was evaluated by analysis of SEPs, survival time, brain blood perfusion and histopathology. The evidence from these studies demonstrated that the brain temperature at which the inflection in wave P2 latency occurred was critical, beyond which hyperthermia produced irreversible changes in the SEP, shorter survival time, relative reduction in brain blood perfusion and evidence of brain histopathological damage. The suggestion that endorphins may mediate brain dysfunction in hyperthermia was investigated. In rats heated and then cooled after wave P2 latency inflection naloxone, the endorphin antagonist, was injected (10 mg/kg, intravenously) just prior to the inflection. It produced reversibility of SEP changes as well as longer survival time (P less than 0.001) compared to saline-treated rats.

Animals↗
PubMed1996

Brain-stem auditory evoked potentials (BAEPs) from basal surface of temporal lobe recorded from chronic subdural electrodes.

BAEPs were recorded from the basal surface of the temporal lobe by subdural electrodes chronically implanted in 6 patients who were evaluated for surgical management of intractable partial seizures. Near-field recordings were obtained by recording between the subdural electrode closest and most distant to the brain-stem. Far-field recordings were obtained by recording between the subdural electrodes and an indifferent electrode over the spinal process of the seventh cervical vertebrae. The recordings were compared with standard ear-vertex recordings. After ipsilateral ear stimulation, the subdural electrode closest to the brain-stem recorded large amplitude waves I and II followed by less well-defined waves of longer latencies. Recordings to contralateral stimulation showed no clearly defined waves I and II and a large amplitude wave Vn. Waves III, IV, V, Vn and VI were of opposite polarity after ipsi- and contralateral stimulation. These findings indicate that waves I and II are generated ipsilaterally to the stimulation side, whereas wave Vn has a contralateral origin. Wave Vn may be generated in the brachium of the inferior colliculus, as suggested from dipole configuration studies. This conclusion is consistent with the classical anatomical observations that the supracollicular auditory pathways are predominantly crossed.

Acoustic Stimulation↗
PubMed1990

Mapping of spontaneous spike and wave discharges in Wistar rats with genetic generalized non-convulsive epilepsy.

Electrical activity was recorded in different parts of the brain in Wistar rats from a strain with genetic generalized non-convulsive epilepsy (GNCE or absence epilepsy). Movable bipolar electrodes were lowered stereotaxically by 1 mm steps into the brain in immobilized animals. Spontaneous spike and wave discharges (SWD) of the largest amplitude were recorded in the cortex and in lateral nuclei of the thalamus where they appeared occasionally to precede. Smaller amplitude SWD were recorded in the striatum, hypothalamus, tegmentum and substantia nigra. No SWD were recorded in limbic structures. Partial limbic seizures induced by the introduction of the electrode did not interfere with occurrence of cortical SWD. These results confirm the primacy of thalamocortical involvement in SWD of GNCE. The absence of spread to limbic structures and the implication of a precisely limited substrate in GNCE accounts for the clinical and pharmacological specificity of this particular kind of epilepsy.

Animals↗
PubMed2003

Measurement of brain electrical impedance: animal studies in rheoencephalography.

INTRODUCTION: In spite of the known importance of cerebral blood flow (CBF) monitoring for aviation, spaceflight, military and emergency medicine, and neurosurgical intra- and postoperative monitoring, there is no standard noninvasive technique for continuous CBF monitoring. One potential method for this purpose is the electrical impedance technique, called rheoencephalography (REG). The development of improved electronics and computation tools has done much to overcome the difficulties of REG measurement. REG technology now has possibilities for application to the fields mentioned above. HYPOTHESIS: Our hypothesis was that REG would reflect CBF changes. METHODS: Three experimental studies were undertaken to further define in vivo (rat, pig) CBF measurements by analysis of REG pulse waves. CO2 inhalation (4-20%), brain electrical stimulation, and aorta compression (5 min) were the applied CBF manipulations. In the case of aorta compression, global CBF was measured by REG, and local CBF by the laser Doppler method. Data were digitized and processed off-line. RESULTS: During CO2 inhalation and electrical stimulation of the brain, REG amplitude increased, indicating increased cerebral fluid volume. A linear relationship was established between CO2 concentration and REG peak amplitude (correlation coefficient: 0.88, p = 0.05), and the ascending portion of the curve (0.88, p = 0.05). During aorta compression, systemic arterial pressure increased (p = 0.008), and REG amplitude decreased (-23.75%, p = 0.01). CONCLUSION: These studies have confirmed the REG amplitude changes during known CBF manipulations. The difference between local and global CBF response demonstrated CBF autoregulation and heterogeneity. Together, these studies indicate the usefulness and potential benefit of computerized REG monitoring for the above-mentioned fields.

Animals↗
PubMed2003

Signaling at the gliovascular interface.

Advances in fluorescent calcium indicating dyes over the past decade have identified calcium signaling as the tool by which astrocytes communicate among themselves and with neighboring neurons. Studies of astrocyte-neuron interactions have shown that calcium signaling is a potent modulator of the strength of both excitatory and inhibitory synapses. The concept that astrocytes possess a mechanism for rapid cell communication has not been incorporated, however, into the supportive functions of astrocytes. Because many of the classical tasks of astrocytes are linked to the blood-brain barrier, we have here examined the expression of proteins required for calcium signaling in their vascular end-foot processes. The gap junction protein, Cx43, was expressed intensively around the vessels interconnecting astrocytic end-foot processes. These gap junctions permitted diffusion of Lucifer yellow, specifically along the path of glial end feet apposed to the vessel wall. The purinergic receptors, P2Y(2) and P2Y(4), were also strongly expressed at the gliovascular interface and colocalized with GFAP around larger vessels in cortex. Multiphoton imaging of freshly prepared brain slices loaded with Fluo-4/AM revealed that ATP mobilized cytosolic calcium in astrocytic end feet, whereas electrical stimulation triggered calcium waves propagating along the vessel wall. Brain endothelial cells and pericytes were physically separated from astrocytes by the basal lamina and responded only weakly to ATP. These observations identify astrocytic end-foot processes plastered at the vessel wall as a center for purinergic signaling. It is speculated that calcium signaling may play a role in astrocytic functions related to the blood-brain barrier, including blood flow regulation, metabolic trafficking, and water homeostasis.

Adenosine Triphosphate↗
PubMed2006

Rapid discrimination of visual scene content in the human brain.

The rapid evaluation of complex visual environments is critical for an organism's adaptation and survival. Previous studies have shown that emotionally significant visual scenes, both pleasant and unpleasant, elicit a larger late positive wave in the event-related brain potential (ERP) than emotionally neutral pictures. The purpose of the present study was to examine whether neuroelectric responses elicited by complex pictures discriminate between specific, biologically relevant contents of the visual scene and to determine how early in the picture processing this discrimination occurs. Subjects (n = 264) viewed 55 color slides differing in both scene content and emotional significance. No categorical judgments or responses were required. Consistent with previous studies, we found that emotionally arousing pictures, regardless of their content, produce a larger late positive wave than neutral pictures. However, when pictures were further categorized by content, anterior ERP components in a time window between 200 and 600 ms following stimulus onset showed a high selectivity for pictures with erotic content compared to other pictures regardless of their emotional valence (pleasant, neutral, and unpleasant) or emotional arousal. The divergence of ERPs elicited by erotic and non-erotic contents started at 185 ms post-stimulus in the fronto-central midline region, with a later onset in parietal regions. This rapid, selective, and content-specific processing of erotic materials and its dissociation from other pictures (including emotionally positive pictures) suggests the existence of a specialized neural network for prioritized processing of a distinct category of biologically relevant stimuli with high adaptive and evolutionary significance.

Adolescent↗
PubMed1980

Neurohumoral control of gastrointestinal motility.

The progress of gastrointestinal physiology is presently dominated by the concept of neuroendocrine regulation and the control of motility is in keeping with this concept. Progress in biochemistry, immunocytochemistry and radioimmunoassay in the past few years has produced a whole new collection of peptide molecules extracted from the digestive tract. Two facts are evident from these new data: (i) many peptides in the gastrointestinal tract are present in both endocrine cells and nerve fibers, and (ii) many peptides are found in both the brain and the gastrointestinal tract. There is thus a large wave of interest in the so-called brain-gut axis and in the relations between brain and gut and between nerves and hormones. The motile system of the gastrointestinal tract is a complex whole having several organizational levels. The morphological, fixed structure is a "cable" network comprising smooth muscle and intrinsic and extrinsic nerves. Control feedback loops may be evidenced at all levels-muscular, intrinsic, ganglionic and central. Local concentrations of circulating (endocrine) or paracrine peptides may act as modulators of this basic pattern by contributing to the depolarization or the hyperpolarization of smooth muscle cell membranes. The mode of action of these peptides reveals at least two different kinds of receptor sites: one on the smooth muscle cells and the other on the axons or cell bodies of intramural excitatory or inhibitory neurons. In addition, central nervous system effects may centrally modulate the long pathway reflexes travelling in the main vagosympathetic trunks. It is no longer possible to separate completely the neural from the hormonal in studying motility control. The whole neuroendocrine control complex must be investigated.

Animals↗
PubMed2000

Spatiotemporal induction patterns of cytokine and related immune signal molecule mRNAs in response to intrastriatal injection of lipopolysaccharide.

The brain's response to a direct immune challenge was examined by in situ hybridization histochemistry. Lipopolysaccharide (bacterial endotoxin) injected acutely into rat striatum induced mRNA expression for inhibitory factor kappaBalpha, interleukin (IL)-1beta, tumor necrosis factor-alpha, IL-6, IL-12 p35, inducible nitric oxide synthase, IL-1 receptor antagonist, and the type 1 IL-1 receptor. Expression patterns were evaluated at select time points ranging from 15 min to 3 days post-injection. Rats injected with vehicle alone were used to control for mechanical effects. Following lipopolysaccharide administration, a wave of mRNA induction within brain parenchyma radiated outward from the injection site, generally peaking in intensity at the 16-h time point. The individual profiles of cytokine mRNA induction patterns reveal that the brain's immune response to local inflammatory stimulation is quite elaborate and in many ways resembles the progression of cytokine induction customary of localized inflammation in peripheral tissues.

Animals↗
PubMed2000

Spatiotemporal induction patterns of cytokine and related immune signal molecule mRNAs in response to intrastriatal injection of lipopolysaccharide.

The brain's response to a direct immune challenge was examined by in situ hybridization histochemistry. Lipopolysaccharide (bacterial endotoxin) injected acutely into rat striatum induced mRNA expression for inhibitory factor kappaBalpha, interleukin (IL)-1beta, tumor necrosis factor-alpha, IL-6, IL-12 p35, inducible nitric oxide synthase, IL-1 receptor antagonist, and the type 1 IL-1 receptor. Expression patterns were evaluated at select time points ranging from 15 min to 3 days post-injection. Rats injected with vehicle alone were used to control for mechanical effects. Following lipopolysaccharide administration, a wave of mRNA induction within brain parenchyma radiated outward from the injection site, generally peaking in intensity at the 16-h time point. The individual profiles of cytokine mRNA induction patterns reveal that the brain's immune response to local inflammatory stimulation is quite elaborate and in many ways resembles the progression of cytokine induction customary of localized inflammation in peripheral tissues.

Animals↗
PubMed1985

A new interpretation of the generators of BAEP waves I-V: results of a spatio-temporal dipole model.

Brain-stem auditory evoked potential (BAEP) scalp distribution, recorded in 10 normal subjects, was analysed using a spatio-temporal dipole model. This model can simulate surface wave forms due to overlapping activity from multiple dipolar sources within a 3-shell head model. The conventional 5-peak (I-V) hypothesis could not fully account for the experimental BAEP distribution, particularly around waves I- and III-. When the temporal course of dipole strength was modelled according to a triphasic compound action potential, 6 dipolar sources were sufficient to fit all BAEP wave forms. Location, orientation and latency of the dipoles indicated generation of dipole 1 at the distal end of the auditory nerve (AN), of dipole III in, or near to, the cochlear nucleus (CN), of dipole III- in the trapezoid body and of dipoles IV and V in the superior olivary complexes and in the lateral lemnisci. Dipole I-, peaking only 0.65 msec after wave I, is suggested to result from the electric inhomogeneity at the porus acusticus internus. Wave II required no extra model dipole, but was attributable, in part, to the second peak of dipole I. Estimation of latencies based on AN conduction velocity, synaptic delay and differences in AN length amongst species confirmed that second order neuronal activity cannot arise before wave III. Second order axons, spreading widely through the brain-stem, apparently cause major contributions also to waves III-, IV and V. The new source hypothesis must leave open questions concerning the amount of contribution from third order neurones or from ipsi- versus contralateral structures to the IV/V wave complex.

Adult↗
PubMed2001

Temporal binding at gamma frequencies in the brain: paving the way to epilepsy?

Fast (beta-gamma band 20-100 Hz) rhythms of electrical activity of the brain have been suggested to play an important role in perception, cognition and consciousness providing temporal binding of neural activities and allowing the formation of mental representations. The recent advances in the concept of temporal binding and their relation to the theory of neural networks (connectionism) are reviewed here as well as some experimental results concerning the intensified gamma rhythms and epilepsy. The hippocampal-neocortical gamma rhythms are extremely intense and hypersynchronous at onset of the epileptiform discharges induced by systemic kainic acid in the rat. Those gamma rhythms are followed by a slow rhythm of epileptiform spikes/sharp waves or spike-wave complexes ('spike-wave' activity). During spike-wave activity, gamma synchronisation is significantly decreased. A novel unifying concept is proposed which relates the associative principle of neural networks to the mechanism of temporal binding at high frequencies. It suggests that for each memory stored in an associative network there is a corresponding quasi-stable state of synchronous oscillation at some frequency within the gamma band. It also suggests that excessive temporal binding ("over-binding") occurs at seizure onset when abnormally intensified and globally synchronous fast activity is often observed. "Over-binding" may cause the undesirable formation of false associations due to inadequate synaptic modifications. To prevent this process, spike-wave discharge develops as an extreme activation of the mechanism capable to desynchronise and eventually suppress fast activity and erase the spurious modes of activity associated with hypersynchronous gamma rhythms. Thus, spike-wave activity is suggested to be the "anti-binding" mechanism. This mechanism is also related to the spikes/sharp waves normally occurring in the brain mostly in sleep. It is qualitatively similar to the "unlearning" mechanism of Crick and Mitchison presumably associated with the PGO spikes of the REM sleep.

Action Potentials↗
PubMed2001

Wave onset in central gray matter - its intrinsic optical signal and phase transitions in extracellular polymers.

The brain is an excitable media in which excitation waves propagate at several scales of time and space. "One-dimensional" action potentials (millisecond scale) along the axon membrane, and spreading depression waves (seconds to minutes) at the three dimensions of the gray matter neuropil (complex of interacting membranes) are examples of excitation waves. In the retina, excitation waves have a prominent intrinsic optical signal (IOS). This optical signal is created by light scatter and has different components at the red and blue end of the spectrum. We could observe the wave onset in the retina, and measure the optical changes at the critical transition from quiescence to propagating wave. The results demonstrated the presence of fluctuations preceding propagation and suggested a phase transition. We have interpreted these results based on an extrapolation from Tasaki's experiments with action potentials and volume phase transitions of polymers. Thus, the scatter of red light appeared to be a volume phase transition in the extracellular matrix that was caused by the interactions between the cellular membrane cell coat and the extracellular sugar and protein complexes. If this hypothesis were correct, then forcing extracellular current flow should create a similar signal in another tissue, provided that this tissue was also transparent to light and with a similarly narrow extracellular space. This control tissue exists and it is the crystalline lens. We performed the experiments and confirmed the optical changes. Phase transitions in the extracellular polymers could be an important part of the long-range correlations found during wave propagation in central nervous tissue.

Animals↗
PubMed2006

Task-related temporal and topographical changes of cortical activity during ultra-rapid visual categorization.

The aim of our study was to provide electrophysiological evidence about the modulation of the categorization process by task requirements in the human brain. Event-related potentials (ERP) were recorded during three different categorization tasks using matched stimulus sets. In all cases, the subjects were required to differentiate between "animal" and "non-animal" stimuli. In the first task (two-choice task), they were asked to press corresponding buttons to each stimulus types. The second task was a go/no-go paradigm, only animal stimuli required motor response. The third task was a counting task; participants had to count the animal stimuli without any motor response. The reaction times in the go/no-go paradigm were significantly shorter. ERP differences between animal and non-animal pictures in the go/no-go task also appeared earlier and were localized at more posterior scalp positions compared to the two-choice task. Comparing animal responses in the two-choice task and in the go/no-go paradigm, we found a significant difference in the 130- to 170-ms time window over the fronto-central, centro-parietal regions. Similar differences were found between the responses to animal pictures in the two-choice task and in the counting paradigm. We used brain electric source analysis (BESA) algorithm on difference waves to localize the best fitting dipoles and determine the localization of brain areas contributing to scalp potential differences. The results show that different task requirements evoke different activity in the medial part of the temporal pole. The data we provided here draw attention to the careful handling of results obtained from categorization experiments, because different task requirements can affect the early categorization process itself.

Adult↗
PubMed1985

Radiotracers for functional brain imaging.

The rapid growth of nuclear medicine 25 years ago was in large part related to the success of brain tumor imaging using radiopharmaceuticals designed to detect changes in the blood-brain barrier (BBB). The success of computed tomography, and more recently nuclear magnetic resonance, in imaging these lesions has all but eliminated the use of radioactive agents for brain tumor detection. But, in recent years there has been a new wave of interest in isotope studies of the brain. The recent emphasis has been on agents which enter the brain across the BBB and are designed to provide functional data ranging from regional perfusion and metabolism to the distribution of binding sites for neuroactive compounds. While none of these new radiopharmaceuticals has yet come into widespread clinical application, the research results already achieved clearly indicate that brain imaging will again be an important aspect of nuclear medicine practice.

Amphetamines↗