bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of corticosterone and 5α‐dihydrocorticosterone on brain excitability in the rat
Authors: Dubrovsky B. , Williams D. , Kraulis I. 
Published: January 2005

AbstractThe effects of corticosterone (B) and its reduced metabolite 5 ç‐dihydrocorticosterone (DHB) on CNS activity in the rat were examined. Two indices of brain excitability were evaluated: (1) amplitude of population responses (evoked potentials [EP] to sciatic nerve stimulation and 2) changes in the rate of firing of tonically discharging neuron‐both at pontine brainstem regions of the reticular formation. Experiments were carried out in adrenalectomized rats, and recordings were under urethane anesthesia. Steroids wer dissolved in a 4:1 saline:Cremophor‐El (Sigma) solution and does of 750 μg/0.5 ml were injected (IV). The effects of B on EPs were bidirectional. Increases (8 animals) and decreases (6 animals) of the amplitude responses in different animals were observed. In 4 animals, no changes were detected. In contrast, injection of DHB produced a consistent and significant reduction of brainstem sciatic evoked potentials in 10 of 12 animals tested; 2 animals did not respond to the steroid. At the neuronal level, the effects of the steroids were evaluated by the change they induced in the mean firing frequency (P < 0.01) measured during 5‐min intervals as determined by a one‐way analysis of variance and analysis with a test of multiple comparisons. Only cells that fired in stationary mode for 15 min before the steriod injection were stuided. A more consistent pattern of responses to B was observed at the single‐cell level. From 31 neurons that responded to the hormone, of 76 examined, 27 showed an increase in their firing rate and only 4 neurons showed a decrease. The increase in firing rate has an onset latency of 2–5 min (x = 3.5, SE 0.43) with a duration of 16–25 min (x = 17.5, SE 2.7). Of 69 neurons that were tested with DHB, 51 showed a significant decrease in their mean firing frequency. Onset latency of the effect was 2–8 min (x = 40.0, SE 1.21) and the duration of the induced changes was 16–40 min (x = 30.0, SE 3.47). Central interactions of DHB and B when sequentially administered were examined in 28 neurons. Of these, 21 responded to DHB administration with a significant decrease in their firing rates. In 11 of these neurons, injection of B, 5 min after DHB, was followed by a rapid (1–2 min) return of the neurons to baseline firing rates. In the other 10 neurons, injection of corticoterone altered neither the median return time (30 min) nor the slope of recovery to baseline firing levels. The results presented support the notion that nuclear saturated 3.20 oxygenated steroids are endowed with CNS depressant potency and support the contention that ring A‐reduced metabolites of ovarian and adrenal steroids may fulfill an important biologic role in modulating brain excitability. Further, the data support the concept that steroid interaction at nonnuclear site (S) may complement actions at the neclear level as well as the notion that a hormones may act at multiple loci in target cells.
Hormones and growth factors induce the synthesis of glial fibrillary acidic protein in rat brain astrocytes
Authors: Morrison R. S. , De Vellis J. , Lee Y. L. , Bradshaw R. A. , Eng L. F. 
Published: January 2005

AbstractGlial fibrillary acidic protein (GFAP) is the major constituent of glial filaments and is restricted within the CNS to astrocytes. As with other classes of intermediate filament proteins, the regulation of GFAP expression is poorly understood. Utilizing highly purified cultures of astrocytes and a chemically defined (CD) medium, we have demonstrated that the expression of GFAP is subject to regulation by hormones and growth factors. The concentration of GFAP/mg protein was induced 2–4‐fold in the presence of hydrocortisone, putrescine, prostaglandin F‐2α (PGF2α), and pituitary fibroblast growth factor (FGF). Augmentation of the levels of GFAP continued for up to 3 weeks after conversion to CD medium and paralleled the morphological maturation of astrocytes. The accumulation of GFAP resulted from an increase in its specific rate of synthesis. Conversion of astrocytes from serum‐supplemented (SS) to CD medium did not alter its rate of degradation. GFAP appeared quite stable under both sets of conditions, exhibition a half‐life of approximately 7.5 days. The data demonstrate that GFAP expression in astrocytes is subject to hormonal regulation, which may have implications for gliosis.
Stimulation of oligodendrocytes by extracts from astrocyte‐enriched cultures
Authors: Bhat S. , Pfeiffer S. E. 
Published: January 2005

AbstractA soluble, heat‐labile, trypson‐sensitive factor present in extracts of astrocyteenriched cultures enhances the expression of myelination‐associated events in rat brain cultures enriched in oligodendrocytes. Both the number of oligodendrocytes detected by immunofluorescence microscopy and the levels of biochemical activities associated with oligodendrocyte differentiation increased in the cultures in respose to the extract in a time‐ and concentration‐dependent fashion. The possible significance of these studies of normal oligodendrocytes function, and thus myelination, is discussed.
Synthesis of a myelin‐like membrane by oligodendrocytes in culture
Authors: Rome L. H. , Bullock P. N. , Chiappelli F. , Cardwell M. , Adinolfi A. M. , Swanson D. 
Published: January 2005

AbstractWe have prepared highly purified cultures of rat oligodendrocytes by a modification of the procedure of McCarthy and de Vellis [1980]. By utilizing a substratum derived from lysed glia and a calf serum‐containing medium with a high concentration of transferrin, the oligodendrocyte cultures display a high degree of purity, the ability to survive several months of culture, and a striking ability to produce a myelin‐like membrane. We have examined the production of this myelin‐like membrane using immunocytochemical and biochemical probes as well as an extensive morphological examination at the electron microscopic level. The membrane appears to be produced in a similar developmental pattern to that observed in vivo and it has the structural characteristics of loosely packed central nervous system myelin.
Tissue culture analysis of neurite outgrowth in the presence and absence of serum: Possible relevance for central nervous system regeneration
Authors: Oorschot D. E. , Jones D. G. 
Published: January 2005

AbstractA tissue culture model has been developed to examine the hypothesis that axons can only regenerate when their growing tips are surrounded by extracellular fluid containing proteins derived from the blood. Fetal rat cerebral explants were cultured in serum medium for 10 days, followed by serum‐free (SF) medium (from which serum had been removed) until 18 days in vitro (DIV). All explants cultured in serum medium for 0–10 DIV exhibited greater than 77% neurite viability (neurite viability ratio, NVR, 3.10). This degree of neurite viability was maintained for those explants exposed to serum until 18 DIV (NVR 2.82 at 18 DIV). By contrast, explants maintained in SF medium from 10–18 DIV had a much lower NVR, which, by 18 DIV, had declined to 0.30 (7.5% viability). Transmission electron microscopic analysis of explants fixed at 18 DIV confirmed these phase‐contrast results and also showed a predominance of axonal profiles within the neurite population. In the center of explants, tissue viability was in excess of 75% in both the serum and SF media, suggesting that serum is of primary importance for axonal extension rather than neuronal survival. These data strengthen the hypothesis that blood‐derived proteins may be needed for prolonged axonal regeneration.
Ultrastructural evaluation of the damage of postsynaptic elements after kainic acid injection into the rat neostriatum
Authors: Matyja E. 
Published: January 2005

AbstractInjury to the nervous tissue was studied in the electron microscope after unilateral stereotaxic injection of kainic acid into the rat striatum. Progressive degeneration of neurons and selective injury of dendritic processes was noted. On the third day of the experiment three types of degeneration of the postsynaptic elements could be distinguished: shrinkage of the dendritic spines and swelling or increase of electron density of the postsynaptic dendrites. Most axonal boutons did not show morphological changes.
A model for the acetylcholine binding site of the nicotinic acetylcholine receptor
Authors: Luyten W.H.M.L. 
Published: January 2005

AbstractA detailed model for the acetylcholine binding site on the nicotinic acetylcholine receptor is proposed. It is derived from assumptions based on existing biochemical, structural, and pharmacological data, combined with molecular modeling and principles of protein evolution and architecture. Acetylcholine is proposed to fit into a pocket on one face of an antiparallel β‐pleated sheet formed by residues 128–142 on the α‐subunit. This sheet is flexible yet stable, in part because of a double cystine bridge at its end. Asp 138, Thr 133, and Gln 140 provide a ring of negative charges around the quaternary ammonium group of acetylcholine, Ile 131 and alkane segments of the other residues in the binding site provide hydrophobic interactions, and Gln 140 provides a hydrogen bond for acetylcholine's carbonyl group; Glu 129 would form part of the second anionic subsite for the bis‐quaternary ammonium compounds and curares. The model is compatible with the available evidence pertaining to the binding site and with structure‐activity relationship studies. It is precise and detailed, thereby making clear predictions, which are directly testable by affinity labeling and site‐directed mutagenesis. It should prove useful in the design of such experiments.
Changes in the dynamic state of brain proenkephalin‐derived peptides during amygdaloid kindling
Authors: Naranjo J.R. , Ladarola M.J. , Costa E. 
Published: January 2005

AbstractThe dynamic state of the proenkephalin (PE) gene products during and after development of amygdaloid kindling was assayed by monitoring changes of the accumulation of PE mRNA and changes in proenkephalin‐related peptides. A parallel determination of PE mRNA and peptides from the same sample was conducted in this study.Electrical stimulation of the amygdala causes early increases in the PE mRNA content in that structure and in the hippocampus. Other areas related with the amygdaloid complex do not exhibit such an early increase, but this alteration occurs when the kindling process is fully established. Enkephalin content increases early in amygdala and hippocampus presumably owing to an increase in synthesis rate. Also, the enkephalin content of areas connected with amygdala and hippocampus such as the entorhinal cortex, the nucleus accumbens, and the frontal and occipital cortex exhibits an increase.A clear tendency towards normalization is observed after a recovery period of 2–3 months. Rekindling of the animals after this recovery period does not elicit a similar pattern of changes in the dynamic state of enkephalin system, even though the animals rekindle with just one single stimulation.The present data suggest that the enkephalinergic neurons participate in the development and spreading of kindling phenomena after amygdaloid stimulation, but they do not seem to play any role in mediating maintenance of the kindling state.
Localization of proopiomelanocortin mRNA in functional subsets of neurons defined by their axonal projections
Authors: Wilcox J.N. , Roberts J.L. , Chronwall B.M. , Bishop J.F. , O'Donohue T. 
Published: January 2005

AbstractIn situ cDNA:mRNA hybridization is a technique that has been developed for the visualization of cDNA:mRNA hybrids in individual cells. To use this technique to answer questions of regulation in heterogeneous populations of cells in the brain, it must be combined with other procedures allowing for the identification of functional subgroups of neurons. We report here a procedure by which in situ cDNA:mRNA hybridization may be combined with retrograde axonal tracing using the fluorescent tracer fast blue. Using this technique, it now becomes possible to measure mRNA regulation in functional subsets of cells defined by their axonal projections.
pp60c‐src encoded by the proto‐oncogene c‐src is a product of sensory neurons
Authors: Maness P.F. 
Published: January 2005

AbstractThe advent of recombinant DNA technology has led to the identification in the DNA of normal animal cells of over 30 proto‐oncogenes that are homologous to retroviral transforming genes. One of these encodes a protein kinase (pp60c‐src) of unknown function, that is preferentially synthesized in brain and neural retina. Here the expression of pp60c‐src in the peripheral nervous system was examined in sensory neurons from chick dorsal root ganglia with antisera raised against the transforming protein of Rous sarcoma virus (pp60c‐src) expressed in Escherichia coli carrying the cloned v‐src gene. This antiserum recognizes pp60c‐src specifically in normal chicken cells. Western immunoblotting showed that dorsal root ganglia of stage 30 (day 6.5) chick embryos contained elevated levels of pp60c‐src. Immunoperoxidase staining of neuron‐enriched cultures prepared from chick dorsal root ganglia showed pp60c‐src immunoreactivity in cells with neuronal morphology; flat, fibroblastic cells contained no detectable immunoreactivity. Indirect double immunofluorescence with pp60c‐src antibodies and monoclonal antibodies against the 200‐kD subunit of neurofilament protein confirmed that the cells expressing pp60c‐src were neurons. Ninety‐six percent of the neurofilament‐positive cells were immunoreactive with pp60c‐src antibodies, and conversely, all pp60c‐src‐positive cells were immunoreactive with neurofilament antibodies. pp60c‐src immunofluorescence appeared to be distributed over the cell body, processes, and growth cones. These results clearly demonstrate that pp60c‐src is a product of neurons and is expressed in sensory neurons in culture.
Isolation and characterization of a cDNA coding for a novel human 17.3k myelin basic protein (MBP) variant
Authors: Roth H.J. , Kronquist K. , Pretorius P.J. , Crandall B.F. , Campagnoni A.T. 
Published: January 2005

AbstractHuman fetal spinal cord poly A (+) mRNA was found to direct the synthesis of three major myelin basic protein (MBP) variants with molecular weights of 17K, 18.5K, and 21.5K when translated in reticulocyte lysates. In order to investigate the structural relationships between these MBP variants and their corresponding mouse variants, human fetal spinal cord and mouse brain cDNA libraries were constructed and screened for MBP cDNAs. A number of MBP cDNA clones were isolated and characterized. One of these, PP535 contained the entire coding region of the mouse 14K MBP; and another mouse cDNA clone, PP1.85, was almost full‐length and coded for either the 21.5K MBP or the 18.5K MBP. A human clone (KK36), 1,173 nucleotides in length, contained the entire coding region of an MBP variant with a molecular weight of 17,342. The structure of this clone within its coding region is significantly different from the corresponding mouse 17K MBP cDNA. It is missing two sequences found in the mouse 17K MBP cDNA (exons 2 and 5); and it contains a sequence (exon 6) that is missing from the mouse 17K MBP cDNA. Thus, this human 17.3K cDNA codes for a “17K” human MBP variant that is quite different from the corresponding mouse variant and is identical to the human 18.5K MBP except for a deletion of a peptide consisting of 11 amino acids that includes the single tryptophan residue of the 18.5K MBP. An analysis of the structure of this 17.3K human MBP cDNA suggests that the major pathway for splicing the primary human MBP gene product may be different from that in the mouse.
Search for virus nucleic acid sequences in postmortem human brain tissue using in situ hybridization technology with cloned probes: Some solutions and results on progressive multifocal leukoencephalopathy and subacute sclerosing panencephalitis tissue
Authors: Shapshak P. , Tourtellotte W.W. , Wolman M. , Verity N. , Verity M.A. , Schmid P. , Syndulko K. , Bedows E. , Boostanfar R. , Darvish M. , Nakamura S. , Tomiyasu U. , Steiner R.C. , Hawkins S. , Hoffman D. , Adhami F. , Martinez S. 
Published: January 2005

AbstractIn order to obtain a useful and readily applicable in situ hybridization (ISH) protocol for progressive central nervous system (CNS) diseases of unknown etiology that are possibly due to persistent viral infection, known and well described diseases were studied, namely, progressive multifocal leukoencephalopathy (PML) and subacute sclerosing panencephalitis (SSPE). The procedures described were validated by confirming results obtained by other investigators using histology, immunocytochemistry, electron microscopy, and ISH. A number of frequently encountered problems of tissue preparation are addressed as well as techniques to reduce autoradiography exposure times. A multi‐staged specific, sensitive, reliable, and valid procedure for detection of viral genomes, mRNA and proteins is approached.Formalin‐fixed and paraffin‐embedded (FFPE) brain material from six patients who died with PML and one patient who died from SSPE were studied using ISH with a tritium‐labeled cloned JC virus DNA probe and a measles‐cloned nucleocapsid (NC) gene cDNA probe, respectively. This report constitutes a methodological framework as well as a detailed neuropathological analysis of identified brain cell populations within which in situ hybridization was detected. In early PML lesions, swollen nuclei or oligodendrocytes were the predominant cells labeled, whereas older lesions revealed increased numbers of reactive and bizarre hypertrophic astrocytes hybridized at the outer periphery of the demyelinated lesions. The hybridization varied greatly in intensity in different cells. Intense hybridization was noted very rarely in microglial cells, including rod cells and rarely in venular pericytes, intravascular mononuclear cells, or in vascular endothelial cells. These results, considered together with previous findings, indicate that in PML the viral infection runs different courses in the various cells: in astrocytes the viral genome persists for a long time inducing pathological changes in some cells. In oligodendrocytes the infection rapidly lyses the cells. There was a good correlation between chromatic changes observable in routinely stained sections and virus presence.In addition, in situ hybridization using a measles‐NP‐cloned probe in white matter from FFPE SSPE brain is presented confirming earlier results in SSPE cryopreserved brain.
Defining the lower limits of blood‐brain barrier permeability: Factors affecting the magnitude and interpretation of permeability‐area products
Authors: Preston E. , Haas N. 
Published: January 2005

AbstractExperimental alteration in the restricted permeability of the blood‐brain barrier to polar, blood‐borne molecules is often quantitated in the rat with use of 14C‐sucrose or 3H‐mannitol delivered as a test substance into the circulation. The underlying principle is to relate the quantity of saccharide that has permeated into brain parenchyma, after an arbitary time period, to some index of the circulating tracer level. This study indicates that to correct the radioactivity level in the brain tissue for intravascular tracer, it is an erroneous practive to estimae the latter as the poduct of tissue blood volume and the tracer concentration measured in a systematic blood sample. Dissected brain tissue was found to have a lower hematocrit and thereby larger plasma/tracer compartment per unit blood volume than femoral arterial blood. It is further shown that, although commercially supplied stocks of 14C‐sucrose or 3H‐mannitol may contain only small quantities of radioactive impurities, their inclusion in injectates and preferential uptake into brain may cause significant overestimation of permeability to the parent tracer. It is also confirmed that magnitude of permeability‐area (PA) products for permeation of purified sucrose or mannitol into brain varies inversely with the length of time allotted for tracer circulation in the bloodstream. This finding is at variance with the assumptions of a two‐compartment (plasma/brain) diffusion model underlying such measurements and supports a recently published model for blood‐to‐brain transfer based on multiple uptake compartments in brain parenchyma. The factors compromising PA values published from several laboratories that had been attributed to genetic differences in laboratory rats.
Neuritic growth from a new subline of PC12 pheochromocytoma cells: Cyclic AMP mimics the action of nerve growth factor
Authors: Katoh‐Semba R. , Kitajima S. , Yamazaki Y. , Sano M. 
Published: January 2005

AbstractWe have identified a new subline of PC12 pheochromocytoma cells (PC12D cells) in which neurites are extended within 24 hr in response to cAMP‐enhancing reagents as well as in response to nerve growth factor (NGF), but not in response to epidermal growth factor or phorbol diester. Anti‐NGF antiserum did not affect forskolin (FRK)‐induced neuritic recruitment. FRK‐induced neurites exhibited growth cones and contained secretion granules and many parallel arrays of microtubules as was the case with NGF‐induced neurites. FRK, but not NGF, increased the levels of intracellular cAMP and activated adenylate cyclase in the membrane fraction. Both NGF and FRK enhanced the activities of tyrosine hydroxylase (TH), acetylcholinesterase (AchE), and ornithine decarboxylase (ODC), but not the levels of neuron‐specific enolase. Enhanced levels of intracellular cAMP mimicked the effects of NGF on neuritic growth, TH, AchE, and ODC activities in PC12D cells, even though NGF does not act through elevation of levels of cAMP.
Evidence for the expression of four myelin basic protein variants in the developing human spinal cord through cDNA cloning
Authors: Roth H. J. , Kronquist K. E. , de Rosbo N. Kerlero , Crandall B. F. , Campagnoni A. T. 
Published: January 2005

AbstractFour human myelin basic protein (MBP) variants with molecular masses of 21.5, 20.2, 18.5, and 17.3 kilodaltons (kDa) have been identified in the developing human spinal cord and their structures determined through an analysis of cDNA clones of their mRNAs. The 20.2‐kDa MBP mRNA encoded a novel MBP variant, the structure of which has not been reported in any species. Its amino acid sequence was identical with that of the 21.5‐kDa MBP except for a deletion of 11 amino acid residues encoded by exon 5 of the MBP gene. All four human MBP variants were identical except for the insertion or deletion of two peptide fragments corresponding to those encoded by exons 2 and 5 of the MBP gene. In this study, no mature human MBP cDNAs missing exon 6 sequences were identified. This suggests that, unlike the mouse, the four human MBP mRNAs encoding these MBP variants arise by the alternative splicing of only exons 2 and 5 from the primary MBP gene transcript. This indicates that the predominant MBP splicing pathways in human and mouse are different.Immunoblots of human fetal spinal cords (11–21 weeks) indicated that MBP expression turned on abruptly between 14 and 16 weeks. Expression of the 20.2‐kDa MBP variant was most evident at 16 weeks and its relative proportion declined thereafter, suggesting that its expression was developmentally regulated.
Psychoneuroimmunology: Interactions between central nervous system and immune system
Authors: Solomon G. F. 
Published: January 2005

AbstractPsychoneuroimmunology, a rapidly developing field, has to do with the complex bidirectional interactions between the central nervous system and the immune system. Neuroendocrine influences modulate immune function, and there is feedback from the immune system to the brain. CNS‐immune interaction appears to play a role in psychosocial influences on immunologically resisted and mediated diseases. With the growing evidence now at hand, over 30 “postulates” can be proposed for specific implication of CNS‐immune interaction.