bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of dihydropteridine reductase by catechol estrogens
Authors: Shen R.‐S. , Abell C. W. 
Published: January 2005

AbstractCatechol 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

AbstractUptake 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

AbstractLipid 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

AbstractIn 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

AbstractSubcutaneous 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

AbstractThe 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

AbstractKindling 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

AbstractAxonally 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

AbstractThe 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

AbstractA 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.
Cytoplasmic morphology weaver (wv) mouse cerebellar neurons at the culture substratum
Authors: Willinger M. , Haaksma C. 
Published: January 2005

AbstractThe 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

AbstractMonopolar 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

AbstractIn 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

AbstractThere 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

AbstractBovine 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

AbstractAnimals 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

AbstractImpulse 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.