bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of nitrendipine on the voltage‐sensitive calcium channel in mammalian sensory neurons
Authors: Litzinger M. J. , Nelson P. G. , Pun R. Y. K. 
Published: January 2005

AbstractWe examined the ability of nitrendipine, a calcium antagonist believed to block the voltage‐sensitiv calcium channels in a number of excitable membranes, to affect the calcium spike duration and rate of rise (Dv/Dt) in 4‐week‐old cultured mouse dorsal root ganglion neurous. Concentrations of 10 nM‐1:0 μM intrendipine reduced but did not eliminate calcium spike as measured by the rate of rise. These results were obtained at either 22° rate of rise (Dv/Dt) in 4‐week‐old cultured mouse dorsal root ganglion neurous. Concentrations of 10 nM‐1:0 μM intrendipine reduced but did not eliminate calcium spike as measured by the rate of rise. These results were obtained at either 22° or 37°C in solutions containing 5 mM calcium. A similar lack of total block was seen with prolonged incubation in sodium‐free recording media containing 1 μM tetrodotoxin (TTX), 1.8 mM calcium, and 1 μM nitrendipine. Calcium spike duration was affected in an inconsistent manner by nitrendipine and other 1,4 dihydropyridines. Cobalt (10 mM) totally blocked the voltage‐dependent calcium mechanism as measured by either the spike duration or the rate of rise. We conclude that calcium influx through the voltage‐sensitive calcium channel in mouse dorsal root ganglion neurons is not blocked by even high concentrations of nitrendipine.
Rat brain α2‐pre‐ and postsynaptic receptors are different or differently modulated?
Authors: Cerrito F. , Preziosi P. 
Published: January 2005

AbstractIn order to get better characterization of α2‐pre‐ and postsynaptic noradrenergic receptors in the rat brain, we investigated the α2‐receptor changes which take place during a 12‐day treatment with the α2‐antagonists yohimbine (4 mg/kg) and mianserin (10 mg/kg). These treatments caused a significant increase in the sensitivity of hypothalamic synaptosomes to the inhibitory action of the noradrenergic agonist clonidine on the 3H‐noradrenaline release elicited by K depolarization. Frontal cortex α2‐autoreceptors were not affected by drug treatments. However, the 3H‐p‐aminoclonidine (3H‐PAC) bindig to membranes from hypothalamus or frontal cortex from treated animals was the same as in controls.Changes in neural firing, elicited by the α2‐antagonists on noradrenergic neurons, could explain our results.The presynaptic autoreceptors may thus become hypersensitive to counteract the enhanced neurotransmitter release in the hypothalamus, where the noradrenaline is accumulated at the synaptic cleft. In the frontal cortex, where it seems that only 5% of the noradrenergic terminals make synaptic contacts with postsynaptic elements, the α2‐autoreceptors are less sensitive to an enhanced neurotransmitter release. Alternatively, they have scarce functional importance because the noradrenaline release is effectively modulated by the inhibitory recurrent locus coeruleus collaterals.At the postsynaptic level, the receptor down‐regulation might be prevented by chronic presence of the antagonist drug.Thus the different behavior between pre‐ and postsynaptic α2‐receptors and between α2‐receptors of different brain areas may be ascribed to a different modulation rather than to different molecular arrangements.
Purification and characterization of cultures of oligodendroglia from rat brain
Authors: Poduslo S. E. , Curbeam R. , Miller K. , Reier P. 
Published: January 2005

AbstractIt is possible to purify dary cells from rat brain which by ultrastructural criteria are oligodendroglia. The modified technique involves the use of an isolation medium less damaging to the initial cell suspension and then differential plating of a stratified primary cell culture obtained from 1–3‐day‐old rat brain which has been described. Five percent serum encourages the growth of oligodendroglia. In this system, the oligodendroglia can be harested several times from the primary cultures. To retain the homogeneous populations of oligodendroglia, it is necessary to constantly manipulate the cultures by hitting the flasks and replating the suspended cells. Electron microscopy reveals that the small dark cells are differentiated oligodendroglia with prominent microtubules. Immunofluorescence staining of the cells shows that the majority of the cells are negative for known surface markers which include cerebrosides and 04 antigen (markers for oligodendroglia), glial fibrillary acidic protein, and fibronectin. Interestingly, it is possible to increase the number of 04‐positive cells by the addition of dibutyryl cyclic AMP to the medium. Rat oligodendroglia are able to incorporate about 20% of the radioactivity into cerebrosides, using the substrate, [3H]galactose; this is a biochemical feature unique to oligodendroglia. The expression of all the oligodendroglial antigens should be remarkably enhanced when the cells are induced to produce myelin.
Lipid and glycolipid metabolism of cultured astrocytes: A time course study
Authors: Yim S. H. , Monsma S. , Hertz L. , Szuchet S. 
Published: January 2005

AbstractPrimary cultures of astrocytes free of neurons and containing less than 1% of oligodendrocytes were examined for their ability to incorporate labeled precursors into lipids and glycolipids. At selected developmental stages cultures were doublelabeled with either [3H]glycerol and [14C]acetate or with [3H]galactose and Na2[35SO4] for a total of 72 hr. Lipids were extracted with CHCl3/CH3OH, fractionated on a silicic acid column, and further resolved by two‐dimensional thin‐layer chromatography. It was found that (1) cultured astrocytes actively incorporate acetate and glycerol into various phospholipids; (2) they have very limited ability to utilize galactose and virtually lack the synthetic machinery to use Na2SO4 for the synthesis of sulfated sphingogalactolipids; and (3) their overall lipid metabolism is very distinct from that of oligodendrocytes. It was also found that cultured astrocytes have low levels of 2′,3′ cyclic phosphodiesterase and glycerol phosphate dehydrogenase activities; the latter is less than one fifth of that in oligodendrocytes.
Glial differentiation in dissociated cell cultures of neonatal rat brain: Noncoordinate and density‐dependent regulation of oligodendroglial enzymes
Authors: Wernicke J. F. , Volpe J. J. 
Published: January 2005

AbstractThe mixed glial system of primary cultures of cells dissociated from neonatal rat brain was utilized to study glial differentiation. The investigation was addressed specifically to the possibility of noncoordinate regulation of two manifestations of oligodendroglial differentiation, i.e., activities of glycerol‐3‐phosphate dehydrogenase (GPDH) and of 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNP), as well as the effects of initial cell density on the time of onset and the intensity of expression of these aspects of oligodendroglial differentiation. Simultaneously, glutamine synthetase activity was studied to determine effects on astrocytic differentiation. GPDH exhibited a major developmental increase in specific activity between 20 and 32 days in culture. However, CNP activity exhibited a major developmental increase that commenced approximately 2 weeks earlier. The onset of these expressions of oligodendroglial differentiation was not affected by such environmental factors as initial cell density. However, the intensity of expression of the temporally separate increases in GPDH and CNP activities was markedly density‐dependent. The highest activities were attained in cultures plated at the lowest cell densities. The astrocytic enzyme, glutamine synthetase, also exhibited a striking developmental increase (approximately tenfold between 13 and 30 days in culture), but initial cell density affected neither the time of onset nor the intensity of expression of this aspect of astrocytic differentiation. The data demonstrate a striking developmental increase in GPDH activity that is not coordinate with that in CNP. The noncoordinate manifestations of oligodendroglial differentiation commence as a function of time in culture, whereas the intensity of expression of this differentiation can be influenced by such environmental factors as initial cell density. Neither the onset of nor the extent of the sharp increase in glutamine synthetase activity, an expression of astrocytic differentiation, is affected by initial cell density.
The role of charge microheterogeneity of basic protein in the formation and maintenance of the multilayered structure of myelin: A possible role in multiple sclerosis
Authors: Moscarello M. A. , Brady G. W. , Fein D. B. , Wood D. D. , Cruz T. F. 
Published: January 2005

AbstractIsolation of several of the charge isomers from both normal and multiple sclerosis (MS) myelin basic protein (MBP) was achieved on CM‐52 columns at pH 10.6. In liquid x‐ray diffraction and agregation experiments, corresponding charge isomers were equally effective in the formation of multilayers, demonstrating the dominant role of overall net positive charge. These studies demonstrated that the change in overall charge of MBP of one net positive charge was sufficient produce large changes in aggregation and in multilayer formation. The x‐ray diffraction experiments showed that component 1 was twice as effective as component 2 although they differed in charge by a single positive charge. Component 3 was less effective than component 2 and component “8” was not effective at all. Vesicle aggregation also showed a dependence on net positive charge. In order of decreasing effectiveness, component 1 > component 2 > component 3 > component “8”.Since overall charge on MBP is determined by contributions from the various charge isomers, the relative proportions of these charge isomers favoring the less cationic components could explain the observation that MBP from MS victims was less effective than MBP form normal brain in vesicle aggregation and multilayer formation. The isolation of myelin‐containing white matter fractions from both normal and MS tissue in which the loss of some of the most cationic charge isomers was correlated with presence of less compact myelin supports this hypothesis.
Acidic lipids enhance cathepsin D cleavage of the myelin basic protein
Authors: Williams K. R. , Williams N. D. , Konigsberg W. , Yu R. K. 
Published: January 2005

AbstractSome acidic lipids including sulfatide and phosphatidylinositol were found to increase greatly the rate of cathepsin D cleavage of the myelin basic protein. Since a similar effect was seen when the substrate was changed to cytochrome C, but not when the enzyme was changed to pepsin, these acidic lipids seem to be acting on cathepsin D rather than on myelin basic protein itself. Even so, chemical modification studies suggest that this phenomenon is only seen when the myelin basic protein is in its native conformation. Succinylation of MBP increases its rate of cleavage by cathepsin D by at least tenfold and, in addition, with this modified and presumably denatured MBP as substrate, activation of cathepsin D is no longer seen with acidic lipids. These findings suggest that the native conformation of MBP is both an important determinant of its rate of cleavage by cathepsin D and is also essential for observing activation of this reaction by acidic lipids. The acidic lipids seem to alter the “extended active site” of cathepsin D in such a way as to enable this enzyme better to utilize the native myelin basic protein as a substrate. Cathepsin D has previously been implicated as the protease responsible for the release into cerebrospinal fluid in multiple sclerosis patients of an encephalitogenic fragment derived from myelin basic protein. It is possible that the elevated levels of cathepsin D and sulfatide that have previously been found associated with multiple sclerosis plaques in vivo act in concert to bring about the rapid cleavage and subsequent loss of the myelin basic protein from these localized regions in the myelin sheath.
Reversal by estrogen of the effect of dorsal raphe stimulation on release of LH but not prolactin
Authors: Kitts C. S. , Johnson J. H. 
Published: January 2005

AbstractElectrical stimulation of the dorsal raphe nucleus (DRN) was administered to rats 2–4 weeks after ovariectomy and at last 7 days following implantation of a bipolar electrode. During stimulation the concentration of luteinizing hormone (LH) decreased whereas that of prolactin (Prl) increased in serial plasma samples obtained from the unanesthetized animals via a cannula chronically implanted in the right external jugular vein. Administration of estradiol benzoate (5 μ/100 g BW) for 2 days prior to the experiment reversed the effect of stimulation of LH but augmented the Prl response, suggesting modulation by estrogen of the relative effectiveness of opposing pathways ascending from DRN to influence LH release. It is also apparent that LH and Prl release are controlled by distinct mechanisms since estrogen exerted opposite influences on the responses of these two hormones to stimulation of DRN.
High molecular weight microtubule‐associated proteins: Purification by electro‐elution and amino acid compositions
Authors: Kosik K. S. , Bakalis S. F. , Selkoe D. J. , Pierce M. W. , Duffy L. K. 
Published: January 2005

AbstractThe high molecular weight microtubule‐associated proteins (MAPs) consist of MAPs 1A, 1B, 1C, 2A, and 2B. The proteins have been prepared from rat brain by using taxol and resolved by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. The individual proteins were purified by electro‐elution from stained fixed gels and shown to migrate at their original mobility without proteolysis. Amino acid compositions of purified MAP 1 and 2 component proteins are reported and compared.
Purification and characterization of plasma membranes obtained from rat neurons prepared by bulk‐isolation
Authors: Poduslo S. E. , Chechik T. , Filbin M. T. , Rosenfeld J. 
Published: January 2005

AbstractThe properties of neuronla plasma membranes are highly specialized, since they include the receptors by which many hormones, neurotransmitters, drugs, and toxins initiate their actions, as well as the components necessary for receiving synaptic input from a variety of sources and for generating the appropriate pattern of action potentials. To be able to study plasma membranes of neurons, it is necessary to separate sufficient quantities of neurons from the other cell types, processes, and myelin found in brain. The methodology for obtaining neurons by bulk‐isolation from 10‐day‐old rat brain has been established, and techniques for purifying the plasma membranes are presented here. The procedure involves swelling the cells in a buffered solution, homogenizing the cells vigorously, and separating the membrane fragments on discontinuous sucrose gradients. The plasma membrane fraction is enriched in plasma membrane marker enzymes and has low activity for contaminating enzymes for subcellular organelles. Electron micrographs show that the fraction consists of membrane vesicles and profiles of various sizes. The protein composition reveals over 60 proteins with molecular weights as high as 100,000 to a low of 14,000. This plasma membrane fraction now can be the focus for studying receptors, glycoproteins, and cell‐specific markers of neurons in health and disease.
Effect of nicotine aerosol on slowly adapting receptors in the airways of the dog
Authors: Taylor R. F. , Lee L.‐Y. , Jewell L. A. , Frazier D. T. 
Published: January 2005

AbstractThe response of slowly adapting airway stretch receptors to nicotine aerosol was studied in the paralyzed, artificially ventilated, anesthetized dog. Single‐unit stretch receptor recordings were made from individual vagus nerve filaments placed on a pair of platinum hook electrodes. Administration of 2% nicotine aerosol for five consecutive breaths caused an increase in both the peak transpulmonary pressure (Ptp) and in the activity of the slowly adapting stretch receptors (SARs). The results suggest that tracheal SARs were more affected than those receptors located distal to the carina. Adminsitration of nicotine aerosols following pretreatment with isoproterenol, a bronchodilator, failed to significantly increase Ptp and, concomitantly, the activity of SARs. Therefore, the stimulatory effect of nicotine on SARs appeared to involve primarily an indirect activation of SARs vianicotine‐induced bronchoconstriction. It is suggested that the activation of SARs may be involved in the reported nicotine‐dependent cigarette smoke‐induced apnea.
Sequence homology between tyrosine hydroxylase mRNA and a rat adrenal medullary cDNA
Authors: O'Malley K.L. 
Published: January 2005

AbstractA rat adrenal medullary recombinant clone has been isolated by cross‐hybridization with a tyrosine hydroxylase (TH) cDNA. The new clone has a mRNA size of 5.6 kb and also hybridizes to the 1.9‐kb tyrosine hydroxylase message. Southern blot analysis reveals several hybridizing bands in common between the TH cDNA and the adrenal medullary clone. These results demonstrate that the adrenal clone shares sequences in common with the TH gene and/or is closely linked to it in the genome. Hybrid‐selected mRNA translation products of the adrenal clone can be immunoprecipitated with dopamine beta hydroxylase antisera. This suggests that the adrenal medullary cDNA may code for another catecholamine pathway enzyme.
Gene expression in hypothalamic neurons: Luteinizing hormone releasing hormone
Authors: Pfaff D.W. 
Published: January 2005

AbstractIn situ hybridization allows the detection and measurement of specific messenger RNAs in individual hypothalamic neurons, and has shown, among magnocellular neurons, not only which cells express the genes for oxytocin and vasopressin but also how they change with physiological stimulation. With this technique, neurons expressing a gene for luteinizing hormone releasing hormone‐like messenger RNA have been discovered in the preoptic area and diagonal bands of the rat forebrain. Seven days of estrogen treatment of ovariectomized female rats increases the LHRH‐like messenger RNA in this neuronal system.
Regional distribution of messenger RNAs in postmortem human brain
Authors: Wood T.L. , Frantz G.D. , Menkes J.H. , Tobin A.J. 
Published: January 2005

AbstractThe ability to isolate intact RNAs from postmortem human brain permits analysis of gene expression and may help uncover the nature of the molecular lesions in neurological diseases. Starting with poly(A) RNA from postmortem brain of neurologically normal patients, we have constructed two complementary DNA libraries in the plasmid vector pBR322. Each of these libraries contains 2–3 × 104 recombinants. One library represents RNA species from the cerebellar cortex, the other from the neostriatum.Using differential colony hybridization, we identified more than 100 relatively abundant RNA species that appeared to be expressed in brain but not in liver. We then used 16 of these clones to analyze brain and liver RNAs by RNA blot hybridization. Thirteen of the 16 clones hybridized to RNAs of both liver and brain. One clone hybridized only to brain RNA, while seven hybridized to RNA species that were present at higher concentrations in brain than in liver. Eleven of the 16 clones hybridized to more than one species of RNA.None of the RNA species examined by RNA blot hybridization was limited to a single brain region, though seven of the cDNA clones hybridized to RNAs that were present at different concentrations in different regions. We have also examined the regional distribution of the RNA encoding glutamic acid decarboxylase, which catalyzes the production of gamma‐aminobutyric acid (GABA). GAD RNA showed differential expression among brain regions and was not detectable in liver or kidney. Our data support a model of gene regulation that is based on cell identity, rather than regional specificity.
Growth patterns of primary cultures dissociated from 3‐day‐old chick embryos: Morphological and biochemical comparisons
Authors: Vernadakis A. , Sakellaridis N. , Mangoura D. 
Published: January 2005

AbstractCultures were prepared by dissociating 3‐day‐old whole chick embryos and plating the dispersed cells on poly‐L‐Iysine‐coated dishes in Dulbecco's Modified Eagle's Medium with 10% fetal calf serum. By 48 hr in culture, aggregates and neuritic sprouting were observed. Long neuritic bundles connecting cell aggregates were evident by 4 days in culture. Consistent patterns throughout the lifespan of the cultures were contacts bwtween neurites, and flat isolated cells, presumptively glial, emerged. Throughout the lifespan of the cultures, the cholinergic cell poopulation was characterized histochemically by the method of Karnovsky and Roots and biochemical by assaying choline acetyltransferase. By 4 days in culture, all aggregates showed light cholinesterase‐positive staining; however, with days in culture, several aggregates had no staining, and some positive‐stained aggregates were interconnected with other aggregates showing only spotted positive staining. Choline acetyltransferase activity showed a developmental profile in agreement with the histological findings. The early presence of choline acetyltransferase activity is taken as indication of the early commitment of cholinergic neurons.
Chloride‐dependent binding sites for L‐[3H]glutamate on dendrodendritic synaptosomal membranes of rat olfactory bulb
Authors: Quinn M.R. , Spraguer P.A. 
Published: January 2005

AbstractDendrodendritic synapses occur between granule cell dendrites and secondary dendrites of mitral cells within the olfactory bulb and are attainable in a subcellular fraction (DDS). Since the mitral cells are thought to utilize an excitatory amino acid as a neurotransmitter, we determined the pharmacologic specificity of Na+‐independent L‐[3H]glutamate binding to fresh membrances of DDS in 50 mM Tris‐HCI, pH 7.1. Binding of L‐glutamate to membrances of DDS was specific, CI− dependent, and saturable. Scatchard plots were analyzed by nonlinear regression analysee using the computer program LIGAND, and the data was best‐fitted to a one‐site model with KD of 0.56 ± 0.04 μM and an apparent Bmax of 48 ± 5 pmol/mg protein. Hill plots also indicated the presence of one site and no cooperativity (nH = 0.99 ± 0.03). However, the relative effictiveness of several compounds in inhibiting L‐glutamate binding to membranes of DDS clearly demonstrated the presence of more than one site. Electrophysiological studies suggest that 2‐amino‐4‐phosphonobutyrate (APB) is a potent antagonist of evoked responses elicited by simulation of mitral cell axons and that quisqualate is a potent agonist; both of these compounds were highly effective inhibitors of L‐glutamate binding to DDS membrances. APB displaced about 70% of tke sites labeled with 200 nM L‐glutamate with a K1 of 1.6 μM, whereas quisqualate inhibition of L‐glutamate binding yielded a line that was curvilinear in the Scatchard plot and was resolved into two sites of relatively high affinity (K1 values of 0.02 and 0.65 μM). Several other compounds, including N‐methyl‐D‐aspartate and kainate, were relatively ineffective inhibitors. Although a small amount of CI−‐independent L‐glutamate binding was demonstrable in the preparation, CI−‐dependent sites predominated and were stimulated by clacium. These results suggest an important role of L‐glutamate, or a closely related compound, at dendrodendritic synapses of the olfactory bulb.