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At least 307 records · Page 17Linked to original sources

PubMed2004

Quantum models of the mind: are they compatible with environment decoherence?

Quantum models of the mind associate consciousness with coherent superposition of states in the brain. Some authors consider consciousness to be the result of a kind of internal quantum measurement process in the brain. In this paper we discuss the ideas of Hameroff-Penrose and Tegmark and their calculation for an estimate of decoherence time. We criticize the Hameroff-Penrose model in the context of a quantum brain model by gravitational collapse orchestrated objective reduction (OOR), assumed by Penrose, and we propose instead that the decoherence process is caused by interaction with the environment. We consider it useful to exploit this possibility because of the growing importance of the decoherence theory in quantum measurement, and also because quantum mechanics can be applied to brain study independently of the Hameroff-Penrose model for mind and consciousness. Our conclusion is that the Hameroff-Penrose model is not compatible with decoherence, but nevertheless the quantum brain can still be considered if we replace gravitational collapse OOR with decoherence. However, our result does not agree with Tegmark's conclusion of refuting not only the Hameroff-Penrose gravitational collapse but also the quantum brain, based on decoherence time calculations in specific cases in the brain. In spite of this fact we also disagree with some points of the response to Tegmark's article given by Hagan, Hameroff, and Tuszynski.

Adaptation, Physiological↗

PubMed1991

Fatty acid acylated Fab-fragments of antibodies to neurospecific proteins as carriers for neuroleptic targeted delivery in brain.

A method for targeted delivery of neuroleptics from blood in brain based on using Fab-fragments of antibodies to antigens of brain glia cells (acid gliofibrillar antigen and alpha 2-glycoprotein) is suggested. The essence of the technique is that the molecule of neuroleptic (trifluoperazine) is conjugated with Fab-fragments of these antibodies. The conjugate thus obtained is modified by stearoylchloride in the system of Aerosol OT reversed micelles in octane. The study of the distribution of 125I-labelled conjugates in the rat organism after intracordial introduction is performed. On the contrary to the nonmodified conjugates and conjugate, containing fatty acylated Fab-fragments of antibodies, nonspecific to the rat brain, the conjugate of trifluoperazine with stearoylated Fab-fragments of antibodies to neurospecific antigens accumulate in brain tissues. The drastic increase of the neuroleptic activity of trifluoperazine resulting from its coupling with stearoylated Fab-fragments of antiglial antibodies is observed.

Acylation↗

PubMed2004

Complexity quantification of dense array EEG using sample entropy analysis.

In this paper, a time series complexity analysis of dense array electroencephalogram signals is carried out using the recently introduced Sample Entropy (SampEn) measure. This statistic quantifies the regularity in signals recorded from systems that can vary from the purely deterministic to purely stochastic realm. The present analysis is conducted with an objective of gaining insight into complexity variations related to changing brain dynamics for EEG recorded from the three cases of passive, eyes closed condition, a mental arithmetic task and the same mental task carried out after a physical exertion task. It is observed that the statistic is a robust quantifier of complexity suited for short physiological signals such as the EEG and it points to the specific brain regions that exhibit lowered complexity during the mental task state as compared to a passive, relaxed state. In the case of mental tasks carried out before and after the performance of a physical exercise, the statistic can detect the variations brought in by the intermediate fatigue inducing exercise period. This enhances its utility in detecting subtle changes in the brain state that can find wider scope for applications in EEG based brain studies.

Adult↗

PubMedDate not supplied

[A broad subfrontal access to the tumors in the base of the skull].

A total of 30 patients, aged 16 to 67, with neoplasms in the brain base and in paranasal sinuses were operated on, during 1997-2002, at Burdenko's Research Institute for Neurosurgery of the Russian Academy of Medical Sciences (RAMS). A majority of patients (21) had meningiomas. Other observations included: fibrous dysplasia of the anterior cranial fossa in 3 patients, chondroma in 2 patients, angiofibroma in 2 patients, pituitary adenoma in 1 patient and adamantinoma in 1 patient. The application of diluted subfrontal approach and of its modifications is indicated for extradural tumors located in the anterior cranial fossa and extending into the latticed main sinus of the nasopharynx. No increasing neurological symptomatology was noticed in any patients. Nasal liquor was not noted either. A seizure of an essential reduction of exophthalmos was registered in cases with crania-orbital neoplasm. It restored postoperatively in all patients with malfunctions of nasal breathing. Two patients died. The death reasons are not directly related with the approach technique. The diluted subfrontal approach is effective in extensive tumors of the anterior cranial fossa involving the latticed and main sinuses. Our experience of using the diluted subfrontal approach showed its efficiency not only in extensive extradural neoplasms but also in large meningiomas of the anterior cranial fossa extending into the latticed sinus, main bone platform, tubercle of sella turcica and into both optic canals. The discussed approach ensures essentially reduced brain traction as compared with the traditional subfrontal approach. The hermetic closure of defects formed in the brain basis is an important surgery stage involving the diluted subfrontal approach. This approach is, under modern conditions, a valuable addition to the methods, which are generally accepted in neurosurgery, and it has undoubtedly an indisputable perspective.

Adenoma↗

PubMed2005

Proteomic-based prognosis of brain tumor patients using direct-tissue matrix-assisted laser desorption ionization mass spectrometry.

Clinical diagnosis and treatment decisions for a subset of primary human brain tumors, gliomas, are based almost exclusively on tissue histology. Approaches for glioma diagnosis can be highly subjective due to the heterogeneity and infiltrative nature of these tumors and depend on the skill of the neuropathologist. There is therefore a critical need to develop more precise, non-subjective, and systematic methods to classify human gliomas. To this end, mass spectrometric analysis has been applied to these tumors to determine glioma-specific protein patterns. Protein profiles have been obtained from human gliomas of various grades through direct analysis of tissue samples using matrix-assisted laser desorption ionization mass spectrometry (MS). Statistical algorithms applied to the MS profiles from tissue sections identified protein patterns that correlated with tumor histology and patient survival. Using a data set of 108 glioma patients, two patient populations, a short-term and a long-term survival group, were identified based on the tissue protein profiles. In addition, a subset of 57 patients diagnosed with high-grade, grade IV, malignant gliomas were analyzed and a novel classification scheme that segregated short-term and long-term survival patients based on the proteomic profiles was developed. The protein patterns described served as an independent indicator of patient survival. These results show that this new molecular approach to monitoring gliomas can provide clinically relevant information on tumor malignancy and is suitable for high-throughput clinical screening.

Biomarkers, Tumor↗

PubMed1991

Molecular cloning of a GTPase activating protein specific for the Krev-1 protein p21rap1.

The rap1/Krev-1 gene encodes a ras-related protein that suppresses transformation by ras oncogenes. We have purified an 88 kd GTPase activating protein (GAP), specific for the rap1/Krev-1 gene product, from bovine brain. Based on partial amino acid sequences obtained from this protein, a 3.3 kb cDNA was isolated from a human brain library. Expression of the cDNA in insect Sf9 cells resulted in high level production of an 85-95 kd rap1GAP that specifically stimulated the GTPase activity of p21rap1. The complete deduced amino acid sequence is not homologous to any known protein sequences, including GAPs specific for p21ras. Northern and Western blotting analysis indicate that rap1GAP is not ubiquitously expressed and appears most abundant in fetal tissues and certain tumor cell lines, particularly the Wilms' kidney tumor, SK-NEP-1, and the melanoma, SK-MEL-3, cell lines.

Amino Acid Sequence↗

PubMed2000

Brain dysmaturity index for automatic detection of high-risk infants.

The definition of an electroencephalographic (EEG)-based brain dysmaturity index that could allow automatic detection of neonates who deviate from expected ontogenetic patterns is proposed. The investigation was performed in a group of 94 term and preterm infants (28-112 weeks postconceptional age). For each neonate, one continuous two-channel EEG of 1-6 hours was recorded. The cluster analysis of different age groups was performed with a self-referential neural network. The network performed a nonlinear discriminant analysis; the synaptic strength of input nodes indicates the relevance of an individual EEG feature. The most relevant EEG features are given by the average amplitude in the delta and theta bands and by the relative amplitudes of beta-1/theta and beta-1/delta, respectively. The correlation between the frequency shifts and the postconceptional age agreed with measures of brain dysmaturity in healthy preterm neonates. Thus the presented trend in early EEG development demonstrates that it is possible to establish clinically relevant age dysmaturity scores.

Brain↗

PubMed2001

Estrogen and the aging brain.

Evidence is presented indicating a role for estrogen in the function and maintenance of the aging brain. Based on complementary data that estrogen regulates the function of the immune--brain barrier, the hypothesis is presented that estrogen contributes to brain homeostasis via regulation of microglial activation, enabling immune-privileged status in the brain. Diminished estrogen levels during the menopause compromise the immune--brain barrier fostering inflammatory processes in the brain. This has potentially lethal consequences for brain cells, and may contribute to brain pathologies such as Alzheimer's disease.

Aged↗

PubMedDate not supplied

[Disorders of energy metabolism in the rat brain under extreme exposures: a new method for assessing the energy state of the brain].

We propose a new method to evaluate energy state of the brain based on vital assay for phosphate metabolites and intracellular pH in the brain. A proposed Z-index describes a set of correlations between phosphates involved in brain energy metabolism assayed in vivo by magnetic resonance spectroscopy on 31P nuclei. We tried to use Z-index as a quantitative test for disturbed energy metabolism. Potentialities of Z-index for evaluating rat brain energy state after extreme influences (gamma [correction of X-] irradiation and postoperative shock of the brain cortex) have been demonstrated.

Animals↗

PubMed2005

Brain dynamics during natural viewing conditions--a new guide for mapping connectivity in vivo.

We describe here a new way of obtaining maps of connectivity in the human brain based on interregional correlations of blood oxygen level-dependent (BOLD) signal during natural viewing conditions. We propose that anatomical connections are reflected in BOLD signal correlations during natural brain dynamics. This may provide a powerful approach to chart connectivity, more so than that based on the 'resting state' of the human brain, and it may complement diffusion tensor imaging. Our approach relies on natural brain dynamics and is therefore experimentally unbiased and independent of hypothesis-driven, specialized stimuli. It has the advantage that natural viewing leads to considerably stronger cortical activity than rest, thus facilitating detection of weaker connections. To validate our technique, we used functional magnetic resonance imaging (fMRI) to record BOLD signal while volunteers freely viewed a movie that was interrupted by resting periods. We used independent component analysis (ICA) to segregate cortical areas before characterizing the dynamics of their BOLD signal during free viewing and rest. Natural viewing and rest each revealed highly specific correlation maps, which reflected known anatomical connections. Examples are homologous regions in visual and auditory cortices in the two hemispheres and the language network consisting of Wernicke's area, Broca's area, and a premotor region. Correlations between regions known to be directly connected were always substantially higher than between nonconnected regions. Furthermore, compared to rest, natural viewing specifically increased correlations between anatomically connected regions while it decreased correlations between nonconnected regions. Our findings therefore demonstrate that natural viewing conditions lead to particularly specific interregional correlations and thus provide a powerful environment to reveal anatomical connectivity in vivo.

Acoustic Stimulation↗

PubMed1997

Simultaneous measurement of DeltaR2 and DeltaR2* in cat brain during hypoxia and hypercapnia.

One of the most important issues in blood-oxygen-level-dependent (BOLD)-based brain functional magnetic resonance imaging is the understanding of the vascular structures that are responsible for the signal changes observed. The T2*-related signal changes observed during variations in susceptibility-induced magnetic field gradients are a function both of non-refocusable mechanisms, such as diffusion, and of refocusable effects such as field inhomogeneities. Conversely, T2-related signal changes are only a function of non-refocusable effects. It has been suggested that T2-weighted images could be less sensitive to blood susceptibility changes in a macrovascular environment than T2*-weighted images and could thus be more accurate in identifying the "activation" of the parenchyma rather than "draining vein" effects. In this study we use hypoxia and hypercapnia challenges in cats to provide a change in blood deoxyhemoglobin concentration (as a model for classic BOLD changes and not as a model for neuronal activation). A combined gradient echo and spin echo echo-planar-imaging (EPI) pulse sequence was used to map DeltaR2 (i.e., Delta(1/T2)) and DeltaR2* (i.e., Delta(1/T2*)) changes during the challenges. Our experiments demonstrate that: (i) the acquisition of T2-weighted EPI data does not in itself differentiate signal changes in the parenchyma from those occurring in regions around larger vessels, but that (ii) the simultaneous acquisition of T2- and T2*-weighted images could be useful in identifying microvascular regions in gray matter by analyzing the ratio DeltaR2/DeltaR2*. This value seems independent of the degree of deoxyhemoglobin concentration change, but is related to properties of the vascular environment. We suggest a possible application of the results to the study of brain function in humans.

Animals↗

PubMed2003

Expression pattern of the stem cell leukaemia gene in the CNS of the embryonic and adult mouse.

The basic helix-loop-helix (bHLH) transcription factor stem cell leukaemia (SCL) is a 'master regulator' of haematopoiesis, where SCL is pivotal in cell fate determination and differentiation. SCL has also been detected in CNS, where other members of the bHLH-family have been shown to be indispensable for neuronal development; however, no detailed expression pattern of SCL has so far been described. We have generated a map of SCL expression in the embryonic and adult mouse brain based on histochemical analysis of LacZ reporter gene expression in sequential sections of brain tissue derived from SCL-LacZ knockin mice. The expression of LacZ was confirmed to reflect SCL expression by in situ hybridisation. LacZ expression was found in a range of different diencephalic, mesencephalic and metencephalic brain nuclei in adult CNS. Co-localisation of LacZ with the neuronal marker NeuN indicated expression in post-mitotic neurons in adulthood. LacZ expression by neurons was confirmed in tissue culture analysis. The nature of the pretectal, midbrain and hindbrain regions expressing LacZ suggest that SCL in adult CNS is potentially involved in processing of visual, auditory and pain related information. During embryogenesis, LacZ expression was similarly confined to thalamus, midbrain and hindbrain. LacZ staining was also evident in parts of the intermediate and marginal zone of the aqueduct and ventricular zone of the fourth ventricle at E12.5 and E14. These cells may represent progenitor stages of differentiating neural cells. Given the presence of SCL in both the developing brain and in post-mitotic neurons, it seems likely that the function of SCL in neuronal differentiation may differ from its function in maintaining the differentiated state of the mature neuron.

Animals↗

PubMed1978

An integrated model for haemorrhagic and ischaemic lesions in the newborn brain.

The vascular anatomy of the developing brain changes from a predominantly basal ganglia orientated pattern at 24 wk to a cortically orientated pattern by 34 wk. This information, combined with other known data on cerebral vascular anatomy and physiology, allows us to develop a model for haemorrhagic and ischaemic lesions in the newborn brain based on two main series of reactions. One series involves the effects of hypoxia and hypercapnia in leading to breakdown of the blood--brain barrier with resultant oedema or haemorrhage. The other links a fall in perfusion pressure and factors causing vasoconstriction with the development of ischaemic lesions. Application of the model involves additional consideration of the state of development of the cerebral vessels at the gestational age concerned. The model helps to explain the observed findings in germinal layer haemorrhage/intraventricular haemorrhage, periventricular leukomalacia and venous infarction, in the preterm brain. Its use also suggests that there are three patterns of vulnerability in the term infant brain. The model carries several implications for the neonatal management of preterm infants. Routine continuous monitoring of blood pressure is of critical importance as cerebral blood flow may vary with blood pressure in the ill newborn. It is important to avoid head compression which may lead to impaired cerebral perfusion. Finally, control of the acid--base status is essential for maintenance of the blood--brain barrier. Correction of abnormal values must be carried out without provoking rapid swings in either the serum osmolarity or the blood pressure.

Blood Pressure↗

PubMed1993

Neural expression of a novel alternatively spliced and polyadenylated Gs alpha transcript.

We have isolated an alternative transcript of the rat Gs alpha signal transduction protein gene, referred to as Gs alpha N1. Gs alpha N1 was isolated by differential hybridization screening of genes induced upon dexamethasone treatment of the neuronal-like CA77 rat thyroid C-cell line. The 1-kilobase Gs alpha N1 transcript is generated by alternative splicing and polyadenylation of a novel terminal exon. This exon lies 800 base pairs downstream of exon 3 in the Gs alpha gene. Dexamethasone differentially induced Gs alpha N1 severalfold relative to Gs alpha mRNA in the CA77 cells, similar to the bias seen with alternative processing of the calcitonin/calcitonin gene-related peptide transcript. In addition to the differential regulation by dexamethasone, the expression pattern of Gs alpha N1 in rat tissues differed markedly from Gs alpha. Gs alpha N1 mRNA was much more abundant in the brain, with intermediate levels in skeletal muscle and very low levels in other tissues. This was in contrast to the more ubiquitously expressed Gs alpha mRNA. Within the brain, Gs alpha N1 was particularly abundant in discrete regions of the brainstem and hypothalamus that modulate autonomic functions. Examination of rat embryos demonstrated that Gs alpha is expressed in both brain and nonneural tissue at least 1 day before Gs alpha N1 mRNA could be detected in the embryonic brain. Based on the regulated expression of the Gs alpha N1 transcript and previous studies on G alpha proteins, the predicted Gs alpha N1 protein may potentially modulate several heterotrimeric G protein functions in the nervous system.

Alternative Splicing↗

PubMed2007

The representation of object concepts in the brain.

Evidence from functional neuroimaging of the human brain indicates that information about salient properties of an object-such as what it looks like, how it moves, and how it is used-is stored in sensory and motor systems active when that information was acquired. As a result, object concepts belonging to different categories like animals and tools are represented in partially distinct, sensory- and motor property-based neural networks. This suggests that object concepts are not explicitly represented, but rather emerge from weighted activity within property-based brain regions. However, some property-based regions seem to show a categorical organization, thus providing evidence consistent with category-based, domain-specific formulations as well.

Anomia↗

PubMed1992

Molecular cloning, sequence analysis and translation of proenkephalin mRNA from rat heart.

Proenkephalin mRNA is abundant in rat cardiac ventricles but surprisingly low levels of opioid peptides or precursor forms derived from proenkephalin are present in tissue extracts. Proenkephalin mRNA in rat heart was characterized at the molecular level with the use of cDNA sequencing, in vitro translation, and primer extension. Two positive proenkephalin cDNA clones were obtained by screening approx. 20,000 recombinant phages from a heart cDNA library. Sequence analysis of the cDNA clones indicated that the heart transcript was the same form as in rat brain, but differed from the germ cell-specific testis transcript that utilizes a different transcriptional start site. Heart proenkephalin cRNA translated efficiently, resulting in the synthesis of a 35 kDa protein that was immunoprecipitated by an antibody specific to the protein. The transcriptional initiation sites utilized in the heart were the same as in the brain, based on primer extension studies. These data suggest that the proenkephalin transcript found in abundance in rat heart is the same form as found in the brain, and differs from the testis-type transcript. We conclude that the scant level of proenkephalin-derived peptides in the heart is not due to an intrinsic inability of the proenkephalin transcript to translate.

Amino Acid Sequence↗

PubMed1993

Biochemical comparison of brain glycosaminoglycans between normal and reeler mutant mice.

Glycosaminoglycans (GAGs) were isolated from the brains of reeler and normal mice on postnatal days 13 and 20. The GAG content of the reeler mouse brain, based upon the amount of DNA, was about 150% that of the normal mouse brain on both days. The GAGs consisted of chondroitin sulfate (CS), heparan sulfate (HS), hyaluronic acid (HA) and polysialosyl glycopeptides. There was no significant difference in the composition of GAGs isolated from either reeler or normal brain. Repeating disaccharide compositions of CS and HS were also similar in reeler and normal brains. Core proteins of brain chondroitin sulfate proteoglycans (CSPGs), solubilized with phosphate buffered saline, were prepared by digesting purified CSPGs with chondroitinase ABC, and were analyzed by SDS-polyacrylamide slab gel electrophoresis. There was no difference in the composition of core proteins from either reeler or normal brain. These results indicate that, although the GAG content of the reeler mouse brain is higher than the normal, all structural parameters of GAGs/CSPGs so far examined were normal. The rate of synthesis and/or degradation of brain GAGs may be affected in the mutant mouse brain.

Animals↗

PubMed1974

Distribution of monoamine-containing terminals and fibers in the central nervous system of the chicken.

In the mesencephalon of the chicken, the two large groups of CA terminals and fibers appeared to correspond to the dorsal and ventral bundles of the CA containing fibers in the rat. These ran rostrally in the medial forebrain bundle and appeared to terminate within the thalamus, hypothalamus, preoptic region and corpus striatum. 5-HT containing terminals and fibers also were observed in the mesencephalon and appeared to run rostrally in the medial part of the medial forebrain bundle. In comparison with the CA terminals, however, 5-HT terminals were for the greater part, difficult to observe in many areas of the brain. Based on the observation concerning postnatal ontogeny of monoamine-containing neurons, the chicken brain appears to acquire behavioral and functional maturity at an earlier stage after birth than does that of the rat. Effect of reserpine, nialnmide, L-Dopa and 5-HTP on the monoamine-containing terminals and fibers are briefly discussed.

Amines↗