bluuebunny/crossref_metadata_2025_split huggingface dataset:
Barium action potentials in regenerating axons of the lamprey spinal cord
Authors: Macvicar's B.A. , Llinás R.R. 
Published: January 2005

AbstractIntracellular recordings were obtained from growing tips of regenerating giant axons in the lamprey spinal cord, the recording sites verified by Lucifer yellow injection. In the presence of extracellular Ba++ (3–6 mM), tetraethylammonium (10–15 mM), and 4‐aminopyridine (4–6 mM), action potentials showed prolonged plateaus. The fast initial phase of the action potential, but not the plateau (Ba++‐spike), was blocked by tetrodotoxin (10−6 gm/ml). The Ba++ spike was associated with increased membrane conductance and could be terminated with hyperpolarizing current pulses. Normal axons did not generate similar Ba++ spikes. However, TTX‐resistant, voltage‐dependant conductance changes could be elicited in normal axons if much higher concentrations of Ba++ (18–30 mM) were used. Their rate of rise was slower than in regenerating axons (0.6 V/sec vs 3.2 V/sec; n = 5), and the response did not outlast the current pulse. The Ba++ responses in normal and regenerating axons were blocked by ions known to block voltage‐gated Ca++ conductances (Co++, Ni++, or Cd++). Therefore, these spikes probably represent Ba++ entry through voltage‐dependent Ca++ channels, suggesting the presence of a higher‐than‐average voltage‐dependent Ca++ conductance in the growing axon. However, Ca++‐dependent spikes could not be obtained under any conditions in either normal or regenerating axons. Simultaneous intracellular recordings from growth cones and axons indicated that the Ba++ spike was initiated, in most cases, at the growth cone. The Ba++ spikes were recorded in regenerating axons for as long as 50 days following cord transection and were not correlatable with the “dying‐back” phenomenon in cut axons, which usually is over before day 6.The concept of a higher‐than‐average voltage‐dependent Ca++ conductance in growing tips of regenerating axons is in agreement with the hypothesis that Ca++ is important in regeneration and that regeneration may be related to the process of chemical synaptic transmission.
Disruption of the blood‐brain barrier in hyperammonemic coma and the pharmacologic effects of dexamethasone and difluoromethyl ornithine
Authors: Sears E. S. , McCandless D. W. , Chandler M. D. 
Published: January 2005

AbstractBoth hyperammonemia and blood‐brain barrier (BBB) breakdown have been implicated in the evolution of hepatic encephalopathy. To define a possible relationship, Swiss Albino mice were subjected to sublethal encephalopathic doses of ammonium acetate; the integrity of the BBB was determined grossly with Evans blue and quantitatively with [14C]‐α‐aminoisobutyrate (AIB). Some animals were injecte with a dose of ammonium acetate sufficient to maintain coma for 1 hr (AC group). One group, termed stuporous (AS), received only enough ammonium acetate to interfere with grooming and exploratory activity; this dosage was insufficient to completely block the righting response, which was absent in the AC group. When compared to that of controls (CON) receiving normal saline instead of ammonium acetate, cerebral tisue from the AC group was stained blue and contained nearly double the amount of AIB; AS group brain tissue was unstained and the AIB content did not differ significantly from normal. Some of the AC group were pretreated with drugs known to retard BBB breakdown; one set received dexamethasone (AC‐DXMN), another the ornithine decarboxylase inhibitor difluoromethyl ornithine (AC‐DFMO), and a third L‐ornithine (AC‐ORN). Brain tissue from the AC‐ORN group stained blue and AIB content did not differ significantly from that of the untreated AC group. Cerebral tissue of the AC‐DXMN pretreatment group stained light blue; AIB content was significantly lower than in the AC group and greater than the CON group. The AC‐DFMO brains were unstained and AIB content was significantly lower than in the AC group but did not differ significantly from CON. These results indicate that hyperammonemia may induce BBB breakdown but that the disruption of barrier integrity is not antecedent to the development of coma, although it seems to coincide with coma in time. DFMO is more effective than DXMN in preventing ammonium acetate‐induced BBB breakdown, but in this study neither drug prevented the development of coma.
Effect of pyridoxine deficiency in young rats on high‐affinity serotonin and dopamine receptors
Authors: Paulose C. S. , Dakshinamurti K. 
Published: January 2005

AbstractThe high‐affinity bindings of [3H]‐5‐hydroxytryptamine to serotonin S‐l receptors, [ H]‐ketanserin to serotonin S‐2 receptors in the cerebral cortex, [3H]‐fluphenazine to dopamine D‐l receptors, and [3H]‐spiroperidol to dopamine D‐2 receptors in the corpus striatum were studied in pyridoxine‐deficient rats and compared to pyridoxine‐supplemented controls. There was a significant increase in the maximal binding (Bmax) of serotonin S‐l and S‐2 receptors with a significant decrease in their binding affinities (Kd). However, there were no significant changes either in the maximal binding or binding affinity of striatal dopamine D‐1 and D‐2 receptors. Receptor sensitivity seems to correlate negatively with the corresponding neurotransmitter concentrations in the pyridoxine‐deficient rats.
Cultured peripheral nervous system cells support peripheral nerve regeneration through tubes in the absence of distal nerve stump
Authors: Shine H. D. , Harcourt P. G. , Sidman R. L. 
Published: January 2005

AbstractAxons of a cut peripheral nerve will grow across a gap ( ≤ 10 mm in adult rodents) formed when the proximal and distal stumps are placed at opposite ends of an impermeable, inert tube, but will not grow to the end of a blind‐ended tube in the absence of the distal stump [Williams et al, 1984]. Work reported here demonstrates that cultured peripheral nervous system (PNS) cells suspended in a collagen matrix will provide an effective milieu that directs and supports axonal regeneration from a severed nerve into a blind‐ended tube in the absence of a distal stump. Adult mouse sciatic nerves were cut and the proximal stumps were inserted into close‐ended tubes that contained either a collagen matrix containing dissociated cells from embryonic mouse dorsal root ganglia (DRG), a collagen matrix saturated with medium conditioned by cultured DRG cells, or a collagen matrix saturated with fresh medium. In all three cases cellular cables formed that ran the full length of the tubes, but myelinated and unmyelinated axons regenerated the length of the tubes only when cultured cells had been added. The critical factor in influencing axonal regerneration through the length of the tubes was the presence of cultured cells, since collagen alone or collagen saturated with conditioned medium did not support axonal regrowth even though cells had migrated into the chambers from the proximal stumps in all cases. Ordered structure was not a requisite for axonal growth, since the cultures consisted of random arrays of dissociated cells.
Theiler's virus replication in isolated schwann cell cultures
Authors: Frankel G. , Friedmann A. , Amir A. , David Y. , Shahar A. 
Published: January 2005

AbstractTheiler's murine encephalomyelitis viruses causing both fatal encephalitis (GDVII virus) and chronic demyelinating disease (WW virus) are capable of replicating in isolated Schwann cell cultures. Light microscopy combined with immunohistochemical staining of viral antigens revealed that large numbers of Schwann cells infected with the two viruses show cytopathic effect (rounding) and contain viral antigens. Electron microscopy of virus‐infected Schwann cells shows that the morphological alterations that the cells undergo following infection by the two virus isolates are different. In the early stages of GDVII and WW virus infection, different inclusion bodies are formed in the cells cytoplasm. At late stages of the infection GDVII virions are found in all infected cells and are arranged in crystalline arrays around inclusion bodies. In contrast, in WW virus‐infected Schwann cells only in few cells virions were observed and they appeared aligned between two membrane units.
Association of endogenous substrate with solubilized bovine brain sialidase
Authors: Schengrund C.‐L. , Repman M. A. 
Published: January 2005

AbstractNonidet P4O solubilized up to 90% of the sialidase, active towards added ganglioside substrate, that was associated with the total membrane fraction prepared from gray matter of bovine brains. Solubilized sialidase acted upon endogenous substrate (sialic acid containing compounds solubilized with the enzyme), hydrolyzing approximately 50% of the readily available sialosyl residues within 20 min. During a 2‐hr reaction time 80% of the polysialylated gangliosides solubilized with the enzyme were acted upon. A 20‐min lag was observed before sialidase acted upon added ganglioside substrate. The lag could be reduced to less than 2 min when the enzyme was allowed to act on endogenous substrate prior to exposure to exogenous substrate, suggesting that the solubilized enzyme acted preferentially on endogenous substrate. A protease inhibitor prevented much of the 86% loss of activity towards added substrate that was seen when the enzyme was stored at 4°C for 6 days; activity towards endogenous substrate decreased only 34%.
Blood‐CSF barrier to CCK and effect of centrally administered bombesin on release of brain CCK
Authors: Zhu X.‐G. , Greeley G. H. , Lewis B. G. , Lilja P. , Thompson J. C. 
Published: January 2005

AbstractThe purpose of this study, in part, was to determine the ability of cholecystokinin (CCK‐33/39 and CCK‐8) to penetrate the blood cerebrospinal fluid (CSF) barrier in dogs by measuring these forms of CCK in plasma and in CSF. In addition, the effectiveness of centrally administered bombesin in releasing brain CCK‐33/39 and CCK‐8 was evaluated. Six groups of five dogs each were studied. Each group received one of the following: (1) intravenous infusion of CCK‐33/39 (1.3 μg/kg/hr); (2) intravenous infusion of CCK‐8 (0.4 μg/kg/hr); (3) intrathecal infusion of CCK‐33/39 (1.3 μg/kg/hr); (4) intrathecal infusion of CCK‐8 (0.5 μg/kg/hr); (5) intravenous infusion of bombesin (1 μg/kg/hr); and (6) intrathecal infusion of bombesin (1 μg/kg/hr). Plasma concentrations of CCK‐33/39 significantly increased during intravenous infusion of CCK‐33/39 (from basal of 84 ± 8 to 142 ± 2 pg/ml) or bombesin (from basal of 78 ± 13 to 325 ± 87 pg/ml); however, CSF perfusate concentration of CCK‐33/39 did not increase. CCK‐33/39 levels of the CSF perfusate increased significantly (P <.05) from 211 ± 84 to 9,873 ± 3,368 pg/ml during intrathecal infusion of CCK‐33/39, but failed to rise simultaneously in the systemic circulation. Similarly, intravenous infusion of CCK‐8 caused a fivefold elevation in plasma CCK‐8 levels and no change in CSF perfusate levels of CCK‐8; moreover, intrathecal infusion of CCK‐8 failed to elevate peripheral CCK‐8 level, despite CSF perfusate CCK‐8 levels of 92, 300 ± 18,598 pg/ml. Intrathecal concentrations of neither CCK‐33 nor CCK‐8 were affected by intravenous or intrathecal administration of bombesin. We conclude that (1) CCK‐33/39 and CCK‐8 do not penetrate the blood‐cerebrospinal fluid barrier in dogs, and (2) centrally administred bombesin is ineffective in causing releas of cholecystokinin from brain tissue into the CSF.
Ultrastructural localization of phenylethanolamine N‐methyltransferase in sensory and motor nuclei of the vagus nerve
Authors: Pickel V. M. , Chan J. , Park D. H. , Joh T. H. , Milner T. A. 
Published: January 2005

AbstractThe ultrastructural localization of phenylethanolamine N‐methyltransferase (PNMT), the enzyme used in the final step in the synthesis of adrenaline, was examined in the medial nuclei of the solitary tracts (m‐NTS) and in the dorsal motor nuclei of the vagus. Adult rats were anesthetized with Nembutal (50 mg/kg intraperitoneally), and the brains were fixed by vascular perfusion with a solution containing 3.75% acrolein and 2% paraformaldehyde in 0.1 M phosphate buffer. Coronal Vibratome sections were collected through the intermediate portions of the m‐NTS at the level of the area postrema. These sections were immunocyto‐chemically labeled employing a rabbit polyclonal antiserum against PNMT and the peroxidase‐antiperoxidase method. Immunoreactivity was detected in perikarya, dendrites, and axon terminals in the intermediate portion of the m‐NTS. The labeled perikarya were either small (10–15 μm diameter) and oval or large 20–30 μm) with two or more proximal processes. The PNMT‐containing dendrites received synaptic input from unlabeled, small (0.5–1.0 μm) and large (2–3 μm) vagal‐like afferents as well as from a few terminals, which also showed PNMT immunoreactivity.Axons and axon terminals containing immunoreactive PNMT were more frequently observed than the perikarya or dendrites in the m‐NTS and were the only labeled profiles in the dorsal motor nuclei. In both regions the PNMT‐labeled terminals formed principally symmetric synapses with unlabeled dendrites. However, a few asymmetric axodendritic and symmetric axosomatic synapses also were detected. These findings indicate that the adrenergic neurons may have multiple, but principally inhibitory, actions on other neurons within cardiovagal portions of baroreflex pathways.
Ependyma formation in adult rat spinal cord after transplantation of fetal cerebral cortex homografts
Authors: Bernstein J. J. 
Published: January 2005

AbstractThe ependymal cells in rat host spinal cord were studied after transplantation of fetal cerebral cortex homografts. Adult Sprague‐Dawley male rats had pieces of E14 fetal rat cortex pressure‐injected into the spinal cord at T6. The tissue was prepared for light and electron microscopy and studied for over 2 months postimplantation. At 7 and 14 days postimplantation (DPI), there were dividing ventricular‐ependymal cells lining cysts in the host spinal cord. After 21 days, cell division was no longer observed in these cells, and only mature ependymal cells lined these cysts. Mature ependymal cells were either: columnar, pseudocolumnar, cuboidal, squamous, or pseudomorphic; had cilia and villi on only one surface of the cell and shared tight junctions when contiguous. These data show that ependymal cells were mature cellular components of adult spinal cord after transplantation of fetal CNS grafts. In addition, ventricular‐ependymal cells continued to divide within the parenchyma of the graft, indicating continued growth of transplanted fetal cerebral cortex in host spinal cord.
Isolation and sequence of cDNA clones coding for the precursor to the γ subunit of mouse muscle nicotinic acetylcholine receptor
Authors: Boulter J. , Evans K. , Martin G. , Mason P. , Stengelin S. , Goldman D. , Heinemann S. , Patrick J. 
Published: January 2005

AbstractcDNA libraries have been constructed in plasmid (pBR322) and bacteriophage (λgt10) vectors with poly (A +) RNA isolated from the nonfusing mouse muscle cell line BC3H‐1. The libraries were screened with a restriction fragment derived from a genomic clone coding for a human acetylcholine receptor γ subunit. Several clones were obtained whose cDNA inserts possessed nucleotide and deduced amino acid sequence homology with acetylcholine receptor γ subunits from Torpedo californica, chick, calf, and human. One isolate, λBMG419, has 88 nucleotides of 5′‐untranslated sequence, an open reading frame of 1,557 nucleotides coding for the precursor to the mouse acetylcholine receptor γ subunit, and 144 nucleotides of 3′‐untranslated sequence. Alignment of the λBMG419‐deduced amino acid sequence with homologs from other species predicts a precursor peptide of 519 amino acids and a mature protein of 497 amino acids, with nonglycosylated molecular weights of 58,744 and 56,424 daltons, respectively. Comparison of the deduced amino acid sequence of the mouse γ subunit with Torpedo, chick, calf, and human sequences showed overall homologies of 54%, 67%, 90%, and 90%, respectively; however, significantly higher homologies were found in several putative functional domains. Radiolabeled λBMG419 has been used to identify homologous RNA species, one of approximately 2 kb and one of about 3.5 kb, in poly (A +) RNA prepared from BC3H‐1 cells and denervated mouse limb muscle. γ Subunit‐coding RNA species are considerably more abundant in denervated than in innervated muscle, suggesting that neural regulation of the abundance of theγ subunit is exerted through regulation of the amount of its mRNA.
Extensive postmortem stability of RNA from rat and human brain
Authors: Johnson S.A. , Morgan D.G. , Finch C.E. 
Published: January 2005

AbstractThe postmortem stability of brain RNA was measured in rat and human samples for up to 48hr. Whole rat brains, cooled at a rate approximating that of human brains awaiting autopsy, were collected at intervals from 0 to 48 hr after death and frozen. These samples were compared with freshly obtained, unfrozen rat brains. Two potentially independent characteristics of these RNA populations were measured: (1) the recovery or yield of RNA/gram tissue (quantity) and (2) the integrity or extent of degradation (quality). Total RNA yields were similar after all postmortem delays. Hybridization of [32P]‐labeled cDNA probes to nitrocellulose filter blots of electrophoretically separated rat brain RNA failed to reveal degradation of the specific rat brain mRNAs during the postmortem period. Similarly, in vitro translation of these same rat total RNA samples produced high molecular weight translation products with no differences between long and short postmortem times.Human cerebral cortex RNA was prepared by the same methods as those used for rat brain from a neurosurgical sample and four other donors with postmortem intervals from 7 to 36 hr. Typically, the yield of total RNA from human brain was 40–50% of the yield from rat brain. When analyzed by RNA gel blot hybridization studies, as for rat brain RNA, human cortical RNA appeared slightly degraded. However, the degree of apparent RNA degradation was not related to the postmortem interval. In vitro translation products of human cortical RNA revealed high molecular weight peptides at all postmortem intervals, but slightly less [35S]incorporation into these bands was found at the longer postmortem intervals relative to the shorter times. Together, these results demonstrate an extensive stability of brain RNA that invites aggressive use of molecular genetic techniques for the study of human neurodegenerative diseases.
Lipophilin (PLP) Gene in X‐linked myelin disorders
Authors: Fahim S. , Riordan J.R. 
Published: January 2005

AbstractThere are several X‐linked diseases in animals and at least one in man in which there is a failure of CNS myelination. We have recently cloned cDNAs for lipophilin (PLP) with which PLP sequences were localized to a region of the long arm of the X chromosome (Xq13–q22 in man) close to the jimpy (jp) locus in that mouse mutant. The present communication pursues the postulate that some of this class of diseases may involve mutations at the PLP locus. Blot hybridization analysis of PLP mRNA levels revealed a five‐to tenfold reduction in the brains of hemizygous jp/Y mice. The major PLP mRNA species of those mice was also reduced in size. However, Southern blots of jp DNA digested with many different restriction enzymes failed to detect major deletions or other rearrangements in the PLP gene. A human PLP cDNA was isolated and employed to similarly analyze DNA from four patients diagnosed as having Pelizaeus‐Merzbacher disease. In one of these four a significant rearrangement of the PLP gene was found. These findings suggest that there may be alterations in the PLP gene in both jp mouse and Pelizaeus‐Merzbacher disease.
In vitro cytotoxicity and demyelination induced by theiler viruses in cultures of spinal cord slices
Authors: Shahar A. , Frankel G. , David Y. , Friedmann A. 
Published: January 2005

AbstractThe cytopathic effects caused by Theiler viruses to myelinated organotypic spinal cord cultures was studied by light and electron microscopy. Heavily myelinated cultures, 2–3 weeks in vitro were infected with WW and GD VII viruses. Mock infection served as control. On light microscopy cytopathic effects and demyelination become evident about 16–17 hr after infection. Demyelination observed in WW virus‐infected cultures was much more pronounced than in cultures infected with GD VII viruses. The myelin in mock‐infected cultures remained undamaged.Electron microscopy revealed that in control cultures cells were intact, exhibiting numerous synapses and a network of axons enwrapped by multilayered myelin sheaths. Virus‐infected spinal cord slices showed that a more severe cytotoxicity was caused by GD VII virus than by WW virus. The cytopathology included accumulation of cytoplasmatic vacuoles, margination of chromatin, synapse and cell disintegration, and various degrees of demyelination. Several GD VII virions were observed, arranged in crystalline arrays, mainly in electron‐opaqe cells, but not within axons. WW virions on the other hand were only occasionally encountered.
Nerve growth factor (NGF) in serum: Evaluation of serum NGF level with a sensitive bioassay employing embryonic sensory neurons
Authors: Stephani U. , Sutter A. , Zimmermann A. 
Published: January 2005

AbstractConsiderable controversy surrounds the question of whether or not nerve growth factor (NGF) or a related nerve growth‐promoting factor is present in serum. Recently, supporting its role as a local neuronotrophic factor, the presence of NGF in glial cells and its production in target tissues of NGF‐responsive neurons were demonstrated [Rush: Nature 312:364–367, 1984; Heumann, Korsching, Scott, Thoenen: EMBOJ 3:3183–3189, 1984; Shelton and Reichardt: Proc Natl Acad Sci USA 81:7952–7955, 1984]. At the same time, the concept that NGF may play a role as a humoral factor has been questioned, since careful analyses of serum with specific and sensitive radioimmunoassays [Suda, Barde, Thoenen: Proc Natl Acad Sci USA 75:4042–4046, 1978; Korsching and Thoenen; Proc Natl Acad Sci USA 80:3513–3516, 1983; Furukawa, Kamo, Furukawa, Akazawa, Satoyoshi, Itoh, Hayashi: J Neurochem 40:734–744, 1983] as well as bioassays [Skaper and Varon: Exp Neurol 76:655–665, 1982] have not confirmed earlier reports [Levi‐Montacini and Booker; Proc Natl Acad Sci USA 46:373–391, 1960; Banks, Banthorpe, Charlwood, Pearce, Vernon: Nature 246:503–504, 1973; Hendry: Biochem J 128:1265–1272, 1972] on NGF's representation in serum.In this study serum from mouse, rat, and man was analyzed with an in vitro bioassay system which employs sensory neurons from chicken embyro dorsal root ganglia and which allows the measurement of NGF concentrations as low as 0.8 pM. It was found that sera from all these species contained neuronotrophic activity (S‐NGF). The target cell spectrum as well as characteristic parameters of the neuronal growth response of S‐NGF and of NGF were identical. S‐NGF of mouse serum was completely inhibitable by polyclonal and monoclonal antibodies to mouse submandibular gland β NGF. On polyacrylamide isoelectric focussing gels mouse and human S‐NGF could be recovered from the same position as NGF as well as from the region where α2‐macroglobulin and serum albumin focused.In newborn and adult male and female mice basal S‐NGF levels were equivalent to 10–50 pM NGF. A. fraction of the serum samples of male mice showed elevated S‐NGF levels. The incidence of high S‐NGF levels was more frequent in NMRI and C57BL/6 males than in BALB/c males. Following sialectomy of male mice only basal S‐NGF levels were observed up to 5 weeks after the operation. This indicates that although the submandibular gland may contribute to S‐NGF levels in serum under certain conditions that appeared to be stress related, it cannot be the only source of S‐NGF.