bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissociation of rapid eye movement (REM) sleep features: Possible implications for REM triggering mechanisms
Authors: Drucker‐Colín René , Dreyfus‐Cortés G. , Chávez L. , Aguilar R. , McGinty D. , Bowersox S.
Published: January 2005

Neurophysiological and biochemical mechanisms regulating REM sleep episodes were studied in behaving cats with chronic electrodes. Push‐pull perfusion of the midbrain or pontine reticular formation (RF) by a protein synthesis inhibitor, chloramphenicol (CAP), reduced neuronal unit discharge, particularly discharge bursts, within the perfused area, and reduced the incidence of sustained REM periods. During transitions to “aborted” as compared to sustained REM episodes. RF unit discharge was reduced, under all conditions. In 72‐hour sleep deprived cats, systemic injections of both atropine (ATR) and CAP attenuated REM rebound, but with different patterns. CAP reduced REM episode frequency. ATR reduced REM duration. ATR also reduced PGO wave frequency. Combined CAP and ATR treatment produced additive REM depressant effects. These data suggest that cholinergic mechanisms regulate PGO activity and maintenance of REM episodes and that protein synthesis‐dependent mechanisms regulate RF unit discharge bursts, and REM triggering.
Evidence for a cyclic GMP mechanism in the mediation of hippocampal post‐tetanic potentiation
Authors: DeFrance J. F. , Stanley J. C. , Marchand J. E. , Divakaran P. , Clement‐Cormier Y.
Published: January 2005

Correlative electrophysiological and biochemical techniques were used to study hippocampal post‐tetanic potentiation in acutely prepared rabbits following stimulation of the medial septal region and contralateral hippocampal field CA3. The results indicate that calcium ions, guanosine‐3′:5′‐monophosphate, and phospho‐diesterase inhibitors selectively enhanced the duration of post‐tetanic potentiation. Potassium ions selectively enhanced tetanic potentiation. Adenosine‐3′:5′‐cyclic monophosphate suppressed both tetanic and post‐tetanic potentiation. The electrophysiological findings were supported by biochemical observations that guanosine‐3′:5′‐monophosphate levels show marked increases following tetanic stimulation of either the medial septal region or contralateral hippocampal field CA3 pathways.

The data suggest that a calcium‐dependent process in the presence of a guanosine‐3′:5′‐monophosphate mechanism promotes periods of hippocampal pyramidal cell hyperexcitability. The mechanism by which the cyclic nucleotide alters potentiation does not appear to be coupled to a single receptor variety.
Influence of Venezuelan equine encephalomyelitis virus on catecholamine metabolism in mouse CNS: Early changes in turnover rates and content
Authors: Lima L. , Borges J. M. Díaz , Walder R.
Published: January 2005

The influence of two strains of Venezuelan equine encephalomyelitis virus on catecholamine metabolism in the central nervous system (CNS) of the mouse was studied by the intracranial inoculation of NMRT‐IVTC mice, 24 days old. Doses of 300 LD50 of the moderately virulent Pixuna strain and 104 LD50 of the non‐virulent TC‐83 strain were used. The animals were sacrificed 4, 7, 12, and 18 days after the inoculation, and the CNS contents of dopamine, norepinephrine, and adrenaline were determined by a radioenzymatic method. The turnover of these compounds was studied with the aid of the enzymatic inhibitors pargyline and alpha‐methyl tyrosine. With the Pixuna strain a decrease in the level and turnover of catecholamines was observed in all eight brain areas studied: cerebellum, pons‐medulla, hypothalamus, mesencephalon, striatum, olfactory bulb‐tuberculum, hippocampus, and cerebral cortex. In some regions the levels returned to normal in 12–18 days, but in the striaturn, mesencephalon, hypothalamus, and olfactory bulb‐tuberculum, recovery was slower and required at least 18 days after inoculation. The levels of catecholamines in the brain of mice inoculated with the nonvirulent TC‐83 strain were not modified, but there was a decrease in the turnover.
Commentary: Na+‐dependent and Na+‐independent binding of GABA in CNS subcellular particles – a search for GABA receptors
Authors: DeFeudis F. V.
Published: January 2005

Studies of the Na+‐dependent and Na+‐independent binding of [3H] γ‐aminobutyric acid ([3H]GABA) and [3H]muscimol to central nervous system (CNS) subcellular preparations have been briefly reviewed and analyzed. Although some of the binding processes that have been detected in vitro, in the presence or absence of Na+, appear to represent GABA‐receptor interactions, further studies conducted with physiologic media and with highly purified membrane preparations are necessary in order to define the properties of those neuronal membrane receptors that mediate the in vivo actions of GABA.
The biosynthesis of p‐tyramine, m‐tyramine, and β‐phenylethylamine by rat striatal slices
Authors: Dyck L. E. , Yang C. R. , Boulton A. A.
Published: January 2005

Slices of striatal tissue obtained from saline‐injected rats were incubated with 3H‐phenylalanine in the presence of pargyline. This resulted in the formation of 3H−m‐tyramine, 3H−p‐tyramine, and 3H‐phenylethylamine. Pretreatment of the rats with α‐methyl‐p‐tyrosine reduced the formation of 3H−m‐tyramine and 3H‐p‐tyramine, but enhanced the formation of 3H‐phenylethylamine.

After incubation of striatal tissue obtained from saline‐injected rats with 3H‐ptyrosine, only 3H‐p‐tyramine was produced. In this case, α‐methyl‐p‐tyrosine pretreatment enhanced 3H‐p‐tyramine formation.

Striatal slices incubated with 3H‐m‐tyramine or 3H‐p‐tyramine did not yield any significant quantity of 3H‐phenylethylamine; nor was 14C‐phenylethylamine converted to 14C‐m‐tyramine or 14C‐p‐tyramine. Pretreatment of the rats with the monoamine oxidase inhibitor pargyline did not appreciably affect these findings.

After incubation with 3H‐dopamine very small quantities of 3H‐m‐tyramine and 3H‐p‐tyramine were formed, the ratio between them being 7:1.

It is concluded that the major biosynthetic route for m‐tyramine formation in the rat straitum is by hydroxylation of phenylalanine, probably by tyrosine hydroxylase to m‐tyrosine, followed by decarboxylation, probably by L‐aromatic amino acid decarboxylase, to m‐tyramine. para‐Tyramine is formed by decarboxylation of p‐tyrosine, and phenylethylamine similarly by decarboxylation of phenylalanine.
Inhibition of dihydropteridine reductase by catechol estrogens
Authors: Shen R.‐S. , Abell C. W.
Published: January 2005

Catechol estrogens, such as 2‐hydroxyestriol, 2‐hydroxyestradiol, and 2‐hydroxyestrone, inhibit human liver dihydropteridine reductase noncompetitively with Ki values ranging from 1.5 to 4.6 × 10−6M. Catechol estrogens lose approximately half of their inhibitory potency if the C‐2 hydroxyl groups are methylated. Thus, 2‐methoxyestrogens have inhibitory potencies equivalent to those of their parent estrogens—estriol, estradiol, and estrone. Aromatization of ring B or stereoisomerism at C‐17 does not affect the inhibitory potency of estrogens, although stereoisomerism at C‐16 enhances the inhibitory potency of estriol. These results support the hypothesis that catechol estrogens may interfere with catecholamine metabolism by acting as inhibitors of enzymes involved in catecholamine metabolism, such as dihydropteridine reductase.
Incorporation of 3H‐valine into soluble protein of cultivated astroglial cells after morphine treatment
Authors: Hansson E. , Rönnbäck L.
Published: January 2005

Uptake and incorporation of 3H‐valine into soluble protein of cultivated astroglial cells from newborn rat cerebral hemispheres increased after incubating the cells for 4 hr in 10−6 or 10−5 M morphine. The effects, inhibited by high naloxone concentrations, were not mediated by cyclic adenosine monophosphate (cAMP) activated binding sites for morphine or D‐alanine2‐methionine‐enkephalin‐amide (D‐ala2met‐enk‐amide). The cultures consisted of 60‐70% astrogliallike cells. By changing the kinetics of labeling it was shown that morphine affects protein synthesis of the cells in a concentration‐ and time‐dependent way. Even in the incubation medium increased amounts of labeled proteins were found in a time‐dependent way after morphine administration in different doses.

Gel electrophoresis in sodium‐dodecyl sulphate (SDS) revealed that proteins with subunits in molecular weight (m.w.) regions of 40,000‐50,000 were increased in the cells and in the medium after morphine (10−6 or 10−5 M) treatment. Labeled proteins with subunits of ∼ 40,000 and ∼ 70,000 in the cells and medium, respectively, were decreased after morphine treatment.

By exploring the field of glial protein metabolism after morphine treatment, information could be obtained on the interactions between astroglia and neurons in opiate action and during tolerance development.
The effect of cytidine‐diphosphate choline (CDP‐choline) on brain lipid changes during aging
Authors: de Medio G. E. , Trovarelli G. , Piccinin G. L. , Porcellati G.
Published: January 2005

Lipid synthesis has been tested in vivo in different brain areas of 12‐month‐old male rats. Cortex, striatum, brainstem, and subcortex of brain have been examined. The cerebellum was discarded. Mixtures of (2‐3H)glycerol and (Me‐14C)choline were injected into the lateral ventricle of the brain as lipid precursors, and their incorporation into total lipid, water‐soluble intermediates and choline‐containing phospholipids was examined 1 hr after isotope injection. In another series of experiments cytidine‐5′‐diphosphate choline (CDP‐choline) was injected intraventricularly to the aged rats 10 min before sacrifice with a simultaneous injection, and radioactivity assays were performed as above.

Distribution of radioactivity content of CDP‐choline among brain areas 10 min after its administration showed a noticeable enrichment of the nucleotide and water‐soluble‐related compounds in the examined areas, but to a lesser degree in the cerebral cortex. The incorporation of labelled glycerol, which is severely depressed in aged rats in all four areas [Gaiti et al, 1982, 1983], was increased in all areas, although by different degrees. Incorporation of radioactive choline, which is also depressed by aging in all areas [Gaiti et al, 1982, 1983], was increased only in the cortex, and apparently decreased in the other areas. This last result is probably due to a dilution effect brought about by the administered cold CDP‐choline upon the (14C)‐containing water‐soluble metabolites. As a consequence, the (3H)/(14C) ratio in total lipid and in isolated phosphatidylcholine and choline plasmalogen increased after CDP‐choline treatment.
Formation of 10‐nanometer filaments from the 150k‐dalton neurofilament protein in vitro
Authors: Gardner E. E. , Dahl D. , Bignami A.
Published: January 2005

In the present study we report self‐assembly of individual neurofilament (NF) triplet proteins (70K, 150K, and 200K daltons) isolated by anion exchange chromatography from bovine spinal cord. Formation of smooth 10‐nm filaments by both NF 150K and NF 70K is shown. Optimal conditions for NK 150K filament formation were incubation in 100 mM MES, 0.2 M NaCl, 1 mM DTT, 0.5 mM EGTA, pH 6.5, at 37°C for 24 hr. Under the same assembly conditions, NF 200K formed 7‐nm coiled structures. These thin filaments were similar to those formed by NF 70K and 150K under less than optimal conditions. Our results indicate that NF 150K is an integral part of the filament (self‐assembly of NF 70K was previously demonstrated by others). We suggest that the optimal conditions resulting in the formation of a 10‐nm 200K homopolymer remain to be determined and that the thin coiled structures formed by all three NF proteins are protofilaments that coalesce to form a double helical 10‐nm filament.
The role of the adrenal gland in cytoprotection against stress‐induced gastric ulcers in rats
Authors: Hernandez Daniel E. , Adcock J. W. , Nemeroff C. B. , Prange A. J.
Published: January 2005

Subcutaneous treatment with either prednisone or isoproterenol significantly prevented the development of cold plus restraint stress (CRS)‐induced gastric ulcers in rats. The effect of each agent was dose‐dependent. Bilateral adrenalectomy prevented isoproterenol, but not prednisone‐induced gastric cytoprotection. However, prednisone (1 mg/kg × 5 days) restored the ability of isoproterenol to afford cytoprotection in adrenalectomized rats. Finally, inhibition of prostaglandin synthesis with indomethacin (5 mg/kg) totally abolished the cytoprotective response to both prednisone and isoproterenol in this CRS model. These results indicate that glucocorticoids modulate the cytoprotective effect of adrenal catecholamines, and that both adrenal glucocorticoids and catecholamines require an intact prostaglandin synthetic pathway for expression of their cytoprotective properties.
Age‐related alteration in catecholamine activity within microdissected brain regions of ovariectomized fischer 344 rats
Authors: Estes K. S. , Simpkins J. W.
Published: January 2005

The effects of increasing age on catecholamine (CA) metabolism in microdissected brain regions and on serum and pituitary hormone levels were examined in ovariectomized Fischer 344 rats. Young (4 to 5 months old) and middle‐aged (9 to 10 months old) normally cycling and old repeated pseudopregnant rats (21–22 months old, PP) were ovariectomized to eliminate the complicating effects of cyclic gonadal steroid fluctuations. CA metabolism was examined 2 weeks later. To determine CA turnover rates, each agegroup was subdivided into three groups, which were killed by decapitation 0, 45, or 90 min after administration of α‐methyl‐para‐tyrosine (α‐mpt). Dopamine (DA) and norepinephrine (NE) concentrations were determined in microdissected brain regions by radioenzymatic assay, and turnover rates were estimated.

Steady‐state concentrations of NE were not altered in middle‐aged rats, but NE turnover rates increased in middle‐aged rats in five of the six areas examined. While NE concentrations did not change with age in the median eminence (ME), NE turnover rates increased significantly in the two older age groups. These data indicate that the age‐related decline in NE concentrations in several ventral diencephalic nuclei is preceded by a period of hyperactivity in noradrenergic neurons.

DA concentrations were generally decreased in most areas examined in old versus young rats, with dramatic DA depletions (42–78%) observed in five regions. However, no consistent relationship between DA concentrations and turnover rates was seen either in regions with stable DA levels or in those which showed an age‐associated decrease in DA concentrations. In the ME, a 42% decline in DA concentration was associated with an increase in the DA turnover rate in the oldest group of rats. Serum luteinizing hormone (LH) levels were similar in all three age groups of ovariectomized rats, while serum prolactin was elevated four‐fold in old compared to younger animals. These data indicate that a complex pattern of regional alterations in CA metabolism accompanies the aging process and these may be related to the pseudopregnant state and hormone secretory capacity of aging Fischer 344 rats.
Hippocampal kindling in the rat: Intrastructural differences
Authors: Lerner‐Natoli M. , Rondouin G. , Baldy‐Moulinier M.
Published: January 2005

Kindling patterns were compared in different regions of the hippocampus of the rat. The duration, morphology, and frequency of the electrical responses were different after stimulation of the dorsal and the ventral hippocampus, but these parameters showed the same evolution as kindling progressed. Comparison of the threshold intensity and of the kindling rate revealed some differences not only between dorsal and ventral hippocampus, but also within the dorsal hippocampus: The central layers had higher thresholds and longer kindling periods than the outer layers and the fimbria hippocampi. We suggest that stimulation of hippocampal efferents is responsible for the greater ease of kindling in the outer layers than in the central regions of this structure. The degree of connection of the different parts of the hippocampus with the amygdala and the influence of the intrinsic inhibitory GABAergic circuitry are discussed.
Ganglioside changes in the regenerating goldfish optic system: Comparison with glycoproteins and phospholipids
Authors: Sbaschnig‐Agler M. , Ledeen R. W. , Grafstein B. , Alpert R. M.
Published: January 2005

Axonally transported radioactivity in sialoglycoconjugates, labeled by intraocular injection of [3H]N‐acetylmannosamine, increased significantly during regeneration of goldfish optic axons at 30°C. Ganglioside radioactivity showed the largest increase—approximately eightfold—in the optic nerve tract at 8 days after optic nerve crush while sialoglycoprotein radioactivity increased fourfold under the same conditions. As regeneration proceeded the magnitude of the increase in the nerve tract diminished for both glycoconjugates. In the optic tectum, however, transported radioactivities remained approximately twofold higher than controls between 15 and 25 days postcrush. The zwitterionic fraction of glycerophospholipids, labeled by intraocular injection of [14C]glycerol, also showed large increases during regeneration, but the acidic glycerophospholipids showed only modest increases. Thus while membrane components in general were elevated during the early stages of regeneration, the most pronounced increases occurred in gangliosides and certain glycerophospholipids. The significance of these changes in the regeneration process remain to be determined.
Effect of GM1 ganglioside treatment on postlesion responses of cholinergic enzymes in rat hippocampus after various partial deafferentations
Authors: Oderfeld‐Nowak B. , Skup M. , Ułas J. , Jezierska M. , Gra̧dkowska M. , Zaremba M.
Published: January 2005

The effect of intramuscular administration of monosialoganglioside (GM1) on postlesion responses of choline acetyltransferase and acetylcholinesterase activity in partially deafferented rat hippocampus was studied at various survival times. Lesions partially destroying the medioventral, septal area, or lesions performed in supracallosal stria including corpus callosum and cingulum evoked cholinergic denervation of the hippocampus, while those made in entorhinal cortex resulted in partial glutamatergic deafferentation. GM1 treatment potentiates the responses of both cholinergic enzymes, independently of whether the partial deafferentation was homo‐ or heterotypical. These data indicate that GM1 may facilitate the regrowth of new cholinergic nerve terminals. However, an effect on other compensatory processes, especially in the first postoperative period, is also possible.
Growth requirements of immature astrocytes in serum‐free hormonally defined media
Authors: Fischer G.
Published: January 2005

A chemically defined serum‐free medium is described that has been optimized for the selective growth of immature astrocytes starting from early postnatal mouse cerebellar cultures. The medium is a modification of one described recently [Fischer et al, 1982] and consists of epidermal growth factor (EGF, 10 nM), transferrin (10 μg/ml), insulin (10 μg/ml), and bovine serum albumin (BSA, 1 mg/ml) in BME with Earle's salts. None of these constituents of the medium alone nor combinations of two of them can stimulate the proliferation and survival of immature astrocytes. Only with a combination of EGF and transferrin together with either insulin or BSA can proliferation of the cells be obtained. For optimal growth all four constituents are needed. However, the immature astrocytes can only grow for a limited time period of about 2–3 wk in this medium. Therefore they can be selected for and characterized but not continously cultivated in this medium.
Further thoughts on directional cell movement during morphogenesis
Authors: Trinkaus J. P.
Published: January 2005

This essay discusses the directional movements of metazoan tissue cells generally, with special emphasis on neurons, in an attempt to show that the directional movements of all share fundamental similarities.
Cytoplasmic morphology weaver (wv) mouse cerebellar neurons at the culture substratum
Authors: Willinger M. , Haaksma C.
Published: January 2005

The purpose of this study was to determine the structural basis for the hypermotility and impaired growth cone elongation of the homozygous weaver (wv/wv) mouse cerebellar granule cell neurons in culture. Two‐day cultures of dissociated week‐old normal (+/+) and wv/wv cerebellum were processed for electron microscopy of intact cells and cytoskeleton. Serial sections parallel to and starting from the substrate were examined. Fine‐caliber neurites of normal granule cells are packed with parallel arrays of microtubules at all levels. Microfilament‐packed microspikes are present at substrate level emanating from a cortical microfilament lattice at the terminus of neurites of varying length. Homozygous weaver granule cells at substrate level have lateral cytoplasmic extensions along the neurite. Microtubules that curve throughout the neurite are separated by cytoplasm. The lateral extensions and growth cone cytoplasmic projections contain microfilaments and occasionally microtubules. Microfilament‐packed microspikes are not observed. Immunofluorescent detection of actin confirms the ultrastructural picture. A hallmark of the wv/wv cytopathology is the presence of large numbers of coated vesicles throughout the neurite shaft at the cell‐substratum interface. These are rare at similar locations in +/+ neurites. We hypothesize that reduced tension in the growth cone and neurite owing to the presence of lateral extensions and absence of stable microspikes are responsible for the impaired elongation and hypermotility of mutant neurons.
Response of nerve growth cone to focal electric currents
Authors: Patel N.B. , Xie Z‐P. , Young S.H. , Poo M‐m.
Published: January 2005

Monopolar electric current pulses were focally applied through a micropipette to the growth cone of Xenopus embryonic neurons in culture. Application of the current directly in front of the growth cone modulated the rate of growth cone extension: Negative (sink) currents increased the growth rate, while positive (source) currents reduced the growth rate. When the currents were applied in a direction perpendicular to the direction of the neurite growth, both negative and positive currents produced inhibitory effects. Application of a negative focal current at a 45° angle with respect to the direction of neurite growth resulted in an oriented growth of the neurite toward the current sink. However, after the growth cone had been attracted to the vicinity of a current sink, further extension of the neurite was inhibited. These current effects occur rapidly after the onset of the current application, and are at least partially reversible within 1 hr after the termination of the current. The magnitude of current density required to induce a growth cone response was found to be in the order of a few pA per μm2. Such current density is close to that which may be generated at the muscle cell surface by the acetylcholine molecules released from the growth cone during the early phase of nerve‐muscle contact.
Assessment of membrane permeability in primary cultures of neurons and glia in response to osmotic perturbation
Authors: Fischel's S.V. , Medzihradsky F.
Published: January 2005

In primary cultures of neurons and astrocytes from rat brain, the cellular contents of K+ and Na+ were used to assess plasma membrane permeability in response to osmotic shock. In contrast to trypan blue exclusion, the measure of ionic content reflected both transient and permanent membrane damage, and was also applicable to aggregates of cells. In steady state, the neurons and glia exhibited a K+ to Na+ ratio of 3–5, and the mean cellular contents (μEq/mg protein) of K+ and Na+ were 0.72 and 0.17 for astrocytes and 0.78 and 0.23 for neurons. Both hypo‐ and hypertonicity resulted in marked efflux of cell K+, but elevation of cellular Na+ occurred only under severe hypertonic conditions. Relative to neurons, astrocytes displayed considerably higher resistence to osmotic shock. During subsequent isotonic incubation, these cells were able to completely recover from transient membrane damage caused by a 10‐min exposure to fourfold hypertonicity. Permanent changes in glial permeability were obtained only after a 20‐min hypertonic shock. In contrast, 5 min hypertonic treatment of neurons decreased the ratio of cellular K+ to Na+ from 4.5 to 1. This ratio was restored twofold by isotonic incubation, but decreased permanently to below 1 after 10 min of hypertonic shock. The results describe marked differences in the osmotic fragility of neurons and glia and demonstrate that the determination of cellular K+ and Na+ provides a sensitive and accurate indicator of membrane permeability in neural cells propagated as surface‐growing cultures. The approach has wide‐ranging applicability.
Calcium‐Activated neutral protease in the peripheral nerve, which requires μM order Ca2+, and its effect on the neurofilament triplet
Authors: Kamakura K. , Ishiura S. , Suzuki K. , Sugita H. , Toyokura Y.
Published: January 2005

There are two types of calcium‐activated neutral protease (CANP), m‐CANP and μ‐CANP, following the nomenclature of Suzuki et al to show that each requires mM and μM Ca2+, respectively, for its activation. We found μ‐CANP activity in a crude CANP fraction extracted from the peripheral nerve, which degraded the neurofilament (Nf) triplet (200 K, 160 K, 68 K), especially the 160 K component, at Ca2+ concentrations of 50 μM and 0.1 mM. The triplet was degraded in the order of the 160 K, 68 K, and 200 K components, respectively. In addition, the effects of partially purified μ‐CANP of rabbit skeletal muscle, purified natural μ‐CANP of bovine liver, derived μ‐CANP prepared by autodigestion of chicken muscle m‐CANP, m‐CANP of chicken skeletal muscle, and cathepsin B of rat liver on the Nf were examined. Among the triplet components, the 160 K component was most rapidly degraded by all proteases so far tested. The difference in the effect of μ‐CANP and m‐CANP or cathepsin B on susceptibility of the 200 K component to degradation might be due to the difference of the relative amounts of enzymes to Nf.
An immunochemical investigation of 2′:3′‐cyclic nucleotide 3′ ‐phosphodiesterase (CNP) in bovine cerebrum and human oligodendroglioma
Authors: Sheedlo H.J. , Yaghmai F. , Wolfe L. , Sprinkle T.J.
Published: January 2005

Bovine cerebrum, including the corpus callosum, and a human oligodendroglioma were investigated by an immunohistochemical technique to determine the distribution of 2′:3′‐cyclic nucleotide 3′‐phosphodiesterase (CNP). Also, three human oligodendrogliomas (ODG) were characterized by an immunoblot procedure to identify a protein(s) with cross‐reacting determinants to CNP and assayed for CNP activity. CNP was localized to oligodendrocytes in the corpus callosum and subcortical white matter and gray matter. Also, nerve fibers appeared to be stained. Further, cells of the human oligodendroglioma were immunostained which were similar in morphology to those cells stained in the bovine cerebrum; however, fewer than 5% of the oligodendroglioma cells were immunostained. Immunoblotting revealed two separate and distinct bands for the three oligodendrogliomas, showing cross‐reactivity to bovine CNP antisera at about 53,000 and 46,000 daltons. Specific CNP activity of the three human oligodendrogliomas ranged from 0.4 to 1.6 μmole of 2′:3′‐cAMP hydrolyzed/min/mg protein.
Alterations in muscarinic cholinergic receptor densities induced by thiamine deficiency: Autoradiographic detection of changes in high‐ and low‐affinity agonist binding
Authors: Gehlert D.R. , Morey W.A. , Wamsley J.K.
Published: January 2005

Animals fed a diet deficient in thiamine or treated with a drug preventing the utilization of thiamine (thiamine antagonis) exhibited alterations in ligand binding to muscarinic receptors in several brain regions. Using quantitative techniques of receptor autoradiography, an increase in muscarinic receptor binding was demonstrated in such regions as the corpus callosum, lamina VI of the parietal cortex, caudate‐putamen, ventral nucleus of the thalamus, stratum lacunosum moleculare and stratum oriens of the hippocampus, and the hilus of the area dentata. As a result of thiamine deficiency, this increase in muscarinic receptor populations was primarily due to an increase in the binding of the low‐affinity agonist site. In the same experiment, a decrease in muscarinic receptor binding was found in the ventromedial region of the hypothalamus. Thiamine deficiency thus causes an up‐regulation of muscarinic receptor binding in several regions of rat brain while causing a down‐regulation of these same receptors in other brain areas.
Effects of perfusion pressure on the bursting neurones in the intact or segmented cardiac ganglion of the lobster, Panulirus japonicus
Authors: Kuramoto T. , Ebara A.
Published: January 2005

Impulse activity of the bursting neurones in the intact or segmented cardiac ganglion could be recorded in the isolated and freely beating hearts of lobsters. In the segmented ganglion, the four large cells (LCs), the medium cell (MC), and the four small cells (SCs) generated phasic, short tonic, and long tonic bursts of impulses with different rhythms, respectively. The periodic bursts of the LCs, the MC, and the SCs in the intact and the segmented ganglia were perturbed by a change of heart tonus which reflected a change of perfusion pressure in the heart. When correlation between period and duration of the perturbed bursts was plotted, the LCs, the MC, and the SCs in the segments were different from one another in distribution of the plots. Further, the correlation plots for the bursts of the MC in the intact ganglia were compared to those of the LCs, the MC, and the SCs in the segmented ganglia. The burst period and duration of the MC in the intact ganglion were altered markedly by a change of the burst period of the LCs and the burst duration of the SCs, as well as by change of heart tonus.
Effects of corticosterone and 5α‐dihydrocorticosterone on brain excitability in the rat
Authors: Dubrovsky B. , Williams D. , Kraulis I.
Published: January 2005

The 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

Glial 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

A 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

We 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

A 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

Injury 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

A 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

The 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

In 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

The 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

Human 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.