bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the visual cortex on responses of retinal ganglion cells in the rat
Authors: Molotchnikoff S. , Tremblay F. 
Published: January 2005

AbstractThe objective of the present investigation was to answer the following question: Does the visual cortex affect the neuronal firing of retinal ganglion cells in the rat? To test this hypothesis, the visual cortex was inactivated by a reversible cryoblockade. Action potentials of a ganglion cell were recorded from its axon at the optic tract level prior to, during, and following cortical blockade. The results indicated that indeed the visual cortex influenced the retinal output since its inactivation led to a modification of the firing pattern evoked in response to a flash of light. In most cases the modification was an increase of the bursting pattern of the evoked discharges. By contrast cooling nonvisual areas failed to modify ganglion cells' discharge. A comparison between cortico‐geniculate and cortico‐retinal feedback loops seems to suggest that the first path is involved mostly with the spatial organization of center‐surround receptive fields, whereas the second path is associated with temporal aspects of the retinal responses in the rat.
Intracellular ion changes of astrocytes in response to extracellular potassium
Authors: Walz W. , Hertz L. 
Published: January 2005

AbstractIntracellular changes of K+, Na+, and Cl− were investigated by the aid of radiotracers in primary cultures of astrocytes when extracellular K+ was (1) increased from 3 to 12 mM and subsequently again decreased to 3 mM; and (2) increased from 5.4 to 54 mM with subsequent decrease to 5.4 mM. In both situations the K+ content increased by 50% within seconds, and it doubled within 1‐2 min. The increase must be carrier mediated, because keeping the K x Cl product (Donnan equilibrium) constant did not lower the K+ accumulation rates. The Na+ content decreased when K+ was increased to 12 mM, but the decrease corresponded only to 10% of the accumulated K+. When K+ was increased to 54 mM, the Na+ content increased transiently. Cl− increased by about 15‐25% of the accumulated K+. Return of extracellular K+ to original levels evoked a very fast K+ release, reversing all ion changes. The Na+ content increased transiently during the release process. For an interpretation of these observations, it is necessary to postulate endogenous production of an anion and of H+, which in turn is partly exchanged with Na+.
Neurons cultured from developing rat brain attach and spread preferentially to laminin
Authors: Liesi Päivi , Dahl D. , Vaheri A. 
Published: January 2005

AbstractNeurons, mechanically dissociated from newborn rat brain and identified by immunostaining for neurofilaments, attached preferentially to laminin‐coated coverslips without need of an underlying glial monolayer. The most extensive neurite outgrowth was seen when 20–30 μg/ml of laminin was used to coat the coverslips. Higher concentrations of laminin (> 30 μg/ml) supported single neurons to spread on the coverslips. Fibronectin coating of the coverslips allowed glial cells to attach more rapidly than on uncoated surfaces, but it did not support neuronal spreading or neurite outgrowth. Spreading of neurons and neurite outgrowth were completely inhibited by preincubation of laminin‐coated coverslips with laminin antibodies but were unaffected by fibronectin antibodies. These results indicate that laminin is an attachment and spreading factor for central neurons in culture and suggest the presence of a laminin receptor on the neuronal cell surfaces.
Reversal potential of the end‐plate currents and potassium feedback at the neuromuscular synapse
Authors: Matyushkin D. P. , Krivoj I. I. , Shabunova I. A. 
Published: January 2005

AbstractThe experiments were carried out at the neuromuscular junction of the frog. Erev of epc was estimated by two methods—extrapolation and interpolation. In K+‐ enriched solution Erev obtained by linear extrapolation from high‐mp region changed according to the Takeuchi equation. The behavior of Erev obtained by interpolation was better described by the Goldman‐Hodgkin‐Katz equation. Under the change of the nerve stimulation frequency from 0.5 to 50/sec, the positive shift of Erev estimated by both methods was observed. This indicates K+ accumulation in active synaptic segments during activity. The elimination of the potassium current of epc by clamping of mp at the − 130 mV level resulted in the lowering of facilitation under paired nerve stimulation (20 msec interval) and in the decrease of the rate of facilitation under 50/sec frequency stimulation. The data support the presence of antidromic K+ action in the neuromuscular synapse.
Formation of desTyr dynorphins 5–17 by a purified cytosolic aminopeptidase of rat brain
Authors: Berg M. J. , Marks N. 
Published: January 2005

AbstractAn aminopeptidase purified to homogeneity from cytosol of rat brain cleaved dynorphins having 5–17 residues and selected proenkephalins at the Tyr–Gly bond only to release Tyr and the desTyr fragments. The enzyme protein consisted of a single polypeptide chain of Mr 103,000 and was inhibited by puromycin, bestatin, and chelating reagents to yield Ki in the micromolar range. Hydrolysis of Leu‐2‐naphthylamide was inhibited by Dyn 1–5 competitively (Ki, 18 μM); the Km for Dyn 1–5, the best substrate of the series, was 63.8 μM (Kcat/Km ratio 580 mM−1 min−1). Rates of N‐tyrosyl release decreased with peptide size; the presence of Arg in position 6 led to 50% loss for Dyn 1–6, and the C‐terminal extensions of Dyn 1‐13 or 1–17 to a 98% loss in activity as compared to the pentapeptide. Rapid degradation of small peptides is consistent with a paracrine (neurotransmitter) role as compared to the postulated precursor or exocrine roles for the dynorphins with 13 residues or more.
Effects of dopamine on photopic L‐type s‐potentials in the catfish retina
Authors: Hida E. , Negishi K. , Naka K.‐I. 
Published: January 2005

AbstractPhotopic L‐type responses were recorded from the soma and the axon terminal of horizontal cells of the catfish (Ictalurus punctatus) retina in eye‐cup preparations. The responses were produced by a spot of light with 100‐μm diameter (intensity, 10 μ/ cm2), which was flashed or steadily illuminated and swept along a 6‐mm length over the retinal surface at a speed of 0.95 mm/sec. In some experiments, a traveling random bar stimulus was used instead of the sweeping spot. While recording the responses, dopamine (DA) was applied in a jet form via a nebulizer over the retinal preparation or as superfusate to the eye‐cup preparation. DA increased the response amplitude by about 50% and markedly narrowed the spatial profile of the responses from the soma but not from the axon terminal. These DA effects were observed in both normal retinas and those from which DA cells had been deprived by prior intraocular injection of 6‐hydroxydopamine. Deprival of DA cells from the retina resulted in a slightly wider spatial profile of the soma and axon terminal responses than that in normal retinas. The results indicate that the spatial properties of photopic L‐type responses are modulated by DA at the soma level of horizontal cells.
The influence of systemic factors on acrylamide‐induced changes in brain, nerve, and other tissues
Authors: Lapin E. P. , Maker H. S. , Weissbarth S. , Weiss C. , Lehrer G. M. 
Published: January 2005

AbstractIn order to define the locus of acrylamide neurotoxicity, the effects of chronic intoxication (total dose 500 mg/kg) on cholinergic synthesis and transport, the Schwann cell‐myelin complex, lysosomal activity, and several metabolic pathways were determined in rat sciatic nerve, spinal cord, and brain. No changes were found in hematological measures or in the levels of clinically important blood enzymes, indicating no major damage to other organs. The activities of choline acetyltransferase (ChAT), 2′,3′‐cyclic nucleotide phosphohydrolase, beta‐glucuronidase, and lactate dehydrogenase were unaffected in acrylamide paralyzed animals, but creatine kinase (CK) decreased in sciatic nerve, muscle, and brain, particularly in animals dying of the intoxication. CK blood and the CK isoenzyme patterns in blood were unchanged. The synthesis of protein in brain and spinal cord (measured in vivo) were decreased in rats exposed to high‐dose acrylamide. However, in brain and cord, CK decreased only after animals became systemically ill and suffered weight loss, with the lowest activities in those animals sick enough to die. The degree of stress to which the animals had been subjected was indicated by enlargement of the adrenal glands and decreased sulfolipid synthesis in the adrenals. Rats exposed to 25 mg/kg/day acrylamide to a total dose of 250 mg/kg developed leg weakness but not paralysis or weight loss and had a 25% decrease in CK only in the distal sciatic nerve. Because of the apparently stress‐related or agonal loss of CK, no specific effect of acrylamide on the enzyme could be definitely demonstrated. Neither could the changes in protein synthesis be attributed solely to a direct effect of the toxin. These results illustrate the difficulties encountered in interpreting intoxication studies that produce systemic illness and support the suggestion that CK activity may be a useful marker of the severity and duration of the agonal state in studies of postmortem human brain.
Detection of a cell surface antigen found on rat peripheral nervous system neurons and multiple glia: Astrocytes, oligodendrocytes, and Schwann cells
Authors: Akeson R. , Warren S. L. 
Published: January 2005

AbstractA cell surface component has been identified that is found on cultured rat dorsal root ganglion neurons and Schwann cells and also cultured brain astrocytes and oligodendrocytes. This component was detected with a monoclonal antibody originally generated to the NG108 (N18 mouse neuroblastoma × C6 rat astrocytoma) hybrid cell line. The antibody, designated B2C11, binds to cultured peripheral nervous system cells: intact dorsal root ganglion and trigeminal neurons and cultured dorsal root ganglion and sciatic nerve Schwann cells. The binding of B2C11 to dorsal root ganglion neurons in vivo was confirmed by immunofluorescence analysis of cryostat sections. However, cultured embryonic rat central neurons showed no detectable binding of B2C11. Cultured brain cells containing glial fibrillary acidic protein (astrocytes) and also oligodendrocytes cultured from corpus collosum did bind B2C11 on their surfaces. B2C11 immunoprecipitation of detergent‐solubilized membrane proteins from both lactoperoxidase iodinated C6 and PC12 rat pheochromocytoma cells indicated a single band with an apparent molecular weight of 21,000–23,000. Analysis of B2C11 binding to particulate protein preparations from adult rat organs showed highest specific activity in dorsal root ganglia. Other neural tissues had substantial binding. Some nonneural tissues (lung, kidney, and small intestine) expressed significant antigen levels, whereas others (heart, liver, and skeletal muscle) had a B2C11 antigen‐specific activity less than 5% of that of dorsal root ganglia. Thus the B2C11 antigen is enriched in neural tissues, where it is found on the surfaces of a unique set of neuronal and glial cells.
Acquisition of submandibular gland nerve growth factor (SMG‐NGF) responsiveness to thyroxine administration in neonatal mice
Authors: Lakshmanan J. , Beri U. , Perheentupa J. , Grueters A. , Kim H. , Macaso T. , Fisher D. A. 
Published: January 2005

AbstractThe growth of the submandibular gland (SMG) was studied in newborn mice from birth to 15 days of age. Progressive changes in wet weight were observed to accompany changes in biochemical constituents such as RNA, protein, and lipid. Thyroxine (T4) administration from days 0–6 produced changes in SMG growth and SMG accumulation of RNA, protein, and lipid components relative to control pups treated with a similar volume of vehicle. This hormone regimen produced no measurable changes in SMG nerve growth factor (SMG‐NGF) concentration. T4 responsiveness also was studied from days 0–15. Three patterns of T4 injection (from days 0–6, 7–14, and 0–14) were found to elicit a differential response in the three biochemical constituents measured, but treatment from days 7–14 and 0–14 elicited precocious increments in SMG‐NGF concentrations on day 15. The effect of T4 injection from birth was more effective in augmenting SMG‐NGF concentration than hormone treatment initiated from days 7–14. A persistent T4 effect on SMG‐NGF also was observed on day 21 following hormone treatment from days 7–14 or 0–14. In summary, the acquisition of SMG‐NGF responsiveness to T4 appears to develop during the neonatal period. The administration of T4 during this period also precociously stimulates the mechanisms that govern the normal ontogeny of SMG‐NGF at the time of weaning.
Inhibition of the chicken retinal UDP‐GalNAc:GM3, N‐acetylgalactosaminyltransferase by blood serum and by pineal gland extracts
Authors: Quiroga S. , Caputto B. L. , Caputto R. 
Published: January 2005

AbstractThe effects of the pineal gland extract and blood serum on the activity of the UDP‐GalNAc:GM3, N‐acetylgalactosaminyltransferase (GM3:GalNAc‐T) from chicken retina were studied. Both preparations have inhibitory capability on the enzyme activity. Two types of inhibitory capabilities were found: one is heat labile and decomposes UDP‐GalNAc and another is heat stable.When the pineal gland extracts were prepared from light‐exposed chickens, the inhibitory capability increased with respect to the extracts from dark‐maintained animals; vice versa, blood serum from dark‐maintained animals had higher heat‐labile and heat‐stable capabilities than that from light‐exposed chickens.In in vitro experiments, no difference was found in the inhibitory capability of blood serum extracts from pinealectomized animals compared to control animals. In vivo labeling experiments with pinealectomized animals in either light or dark showed similar differences in the labeling of the optic tectum gangliosides as the normal animals.
Biological activity of preformed cholera toxin‐ganglioside GM1 complex
Authors: Fiani M. L. , Macioce P. , Gallina A. , Tomasi M. 
Published: January 2005

AbstractSynthetic and natural amphiphiles, octyl glucoside, Nonidet P40, sodium dodecyl sulfate (SDS), gangliosides GM1 and GD1a, interact with cholera toxin (CLT) and with its active region (protomer A). The formation of CLT‐amphiphile complex leads to inhibition of ADP‐ribosyltransferase activity, a characteristic of protomer A elicited after thiol‐reagents treatment. In all cases the interaction produces the maximum inhibitory effect above the critical micellar concentration of amphiphiles, although monomers of SDS show inhibition activity as well. The gangliosides appear to be capable of altering bilayer organization of membrane, similar to synthetic detergents.When CLT‐ganglioside complexes were incubated with cell culture medium containing 10% fetal calf serum (FCS) the ADP‐ribosyltransferase activity was completely restored both in cholera toxin and in protomer A. Some protein of FCS, which is avid of gangliosides, seems to be responsible for reversibility of inhibition. The results indicate that the active site of protomer A may be located in a hydrophobic pocket of the toxin structure.Furthermore, CLT was bound to reconstituted Sendai virus envelopes (RSVEs), containing a small amount of GM1. The RSVEs are made of membranous vesicles, capable of binding and fusing with host cell membrane. The incubation for 1 lhr of RSVE bearing CLT with Friend's erythroleukemic cells produced the stimulation of adenylate cyclase. This stimulation appears to be due to the translocation of the active subunit of CLT in the inner half of plasma membrane.
GM1 micelles modify the transport properties of the lonophore gramicidin D in artificial planar bilayers
Authors: Gambale F. , Marchetti C. , Usai C. , Robello M. , Gorio A. 
Published: January 2005

AbstractWe have analyzed the effects induced in different phospholipid planar bilayers by monosialoganglioside micelles containing the inonophore gramicidin D. The membrane conductance increases after the addition of GM1 micelles at various ionophore/ganglioside ratios. We believe this fact may be ascribed to gramicidin molecules that incorporate into the bilayer together with gangliosides.In the presence of micelles the mean lifetime and the amplitude of the gramicidin single channel did not present relevant modifications when dioleoylphosphatidylcholine or phosphatidylserine were used to form the bilayer. Calcium proved to trigger the interaction between phosphatidylethanolamine membranes and GM1 micelles containing gramicidin. In this case the ionic pore presents a longer lifetime and a lower amplitude with respect to pure gramicidin.We suggest that different properties developed by gramicidin may depend on structural organization of gangliosides when incorporated into the phospholipid bilayer.
Interaction of ganglioside GM1 and myelin basic protein studied by carbon‐13 and proton nuclear magnetic resonance spectroscopy
Authors: Ong R. L. , Yu R. K. 
Published: January 2005

AbstractThe interaction of the myelin basic protein (MBP) and the major endogenous ganglioside GM1 in myelin of the central nervous system has been investigated using both 500‐MHz 1H and 67.89 MHz 13C NMR. Titration of MBP by GM1 resulted in 13C NMR signal shifts for the Ile and His residues of MBP at a GM1/MBP mole ratio of one or less. The carbohydrate head group of GM1 was also found to be perturbed. 1H NMR results obtained in a similar manner demonstrated the perturbation of His and Phe residues. At a GM1/MBP mole ratio of 0.5, small perturbation of Trp #116 was observed, and at mole ratios of two and beyond significant involvement of Phe residues and methylated Arg #107 was found. Met #167 was more perturbed than Met #20; hence, more extensive interaction of the lipid is occurring with the C‐terminus of the protein than with the N‐terminus. No resonances from GM1 bound to MBP at mole ratios of up to one appeared in the spectra. However, as the GM1/MBP mole ratio was increased to eight or greater a major conformational change of MBP was detected. An upfield shift of the GM1 midchain methylene resonance was observed for the GM1/MBP complex. This observation provides strong evidence that the state of GM1 interacting with MBP is different from that of GM1 micelles. The number of saturable GM1 binding sites on MBP is estimated to be four. The data also favor a rapid exchange between bound GM1 and GM1 micelles. Interaction of MBP with the oligosaccharide derived from GM1 was found to be weaker than with GM1. Based on our data, a model for the interaction can be proposed: the first GM1 molecule is bound to the protein molecule through its head group and hydrocarbon chains, followed by the formation of a GM1/MBP complex with a concomitant conformational change of MBP as more GM1 is added.
Endogenous material in brain inhibiting [3H]nicotine and [3H]acetylcholine binding
Authors: Sershen H. , Reith M. E. A. , Hashim A. , Lajtha A. 
Published: January 2005

AbstractThe supernatant obtained from mouse brain homogenates contains material that inhibits the saturable binding of [3H]nicotine in mouse cerebral cortex. This inhibitory material was further purified by heat denaturation, ultrafiltration through an Amicon PM‐10 membrane filter, and gel chromatography on Sephadex G‐10. The material inhibited the binding of [3H]acetylcholine with the same potency as it did that of [3H]nicotine. It also had some affinity for the sites that specifically bind [3H]D‐Ala, D‐Leu enkephalin, but had much lower affinity for the binding sites for [3H]quinuclidinyl benzilate (QNB), [3H]spiroperidol, [3H]naloxone, or [3H]imipramine. Acid hydrolysis destroyed the activity. These preliminiary results suggest the presence in brain of “nicotinelike” substances, one of which may be the endogenous ligand for the sites that specifically bind [3H]nicotine.
Estimation of the apparent affinity of the striatal dopamine receptors for the radioligand [3H]spiperone([3H]spiroperidol)
Authors: Hruska R. E. 
Published: January 2005

AbstractThe characteristics of the receptor population labeled by the ligand [3H]spiperone were determined by several experimental procedures. Varying the assay volumes, and hence both the receptor and ligand concentrations, did not alter the specificity for the dopamine (DA) receptor. The density of binding sites estimated from saturation analyses varied little (6%) over a greater than 50‐fold tissue concentration range. In contrast, variation in tissue concentration did alter the apparent affinity of [3H]spiperone for the DA receptors more than 16‐fold, as determined from saturation analyses. This was most marked at large receptor or tissue concentrations. The standard correction for depletion of the free ligand by that bound to the receptors reduced the range to threefold or 200%. Two separate measurements of the DA receptor affinity, using the rates of association and dissociation and the shift in Ki for DA, gave affinity measurements in the same range as that obtained using low concentrations of receptors in saturation analyses. Therefore, three separate estimates for the affinity of [3H]spiperone binding to the striatal DA receptors agreed that it is probably in the range of 10–15 pM, and single saturation experiments reach this level when the tissue concentration is very low, ie, less than 15 μg protein per 1 ml assay volume.
Membrane specializations of neuritic growth cones in vivo: A quantitative IMP analysis
Authors: Small R.K. 
Published: January 2005

AbstractThe internal structure of the membranes of axonal and Schwann cell growth processes was examined by freeze‐fracture in the growing olfactory nerve, a simple in vivo system consisting of a homogeneous neuronal population. Excision of the mature nerve of adult bullfrogs provides well‐synchronized primary neuritic outgrowth that is highly enriched in growth cones at its distalmost segment. The extreme uniformity of olfactory axons in terms of their diameter and their intramembrane particle (IMP) composition permits clear identification of the cellular origin of the growth cone structures observed in replicas. In vivo, growth cones of the olfactory nerve appear as irregularly shaped enlargements of the distal tip; filopodia are only infrequently exposed by the fracture plane. Axonal and Schwann cell growth cones are distinguished by (1) the larger size of the Schwann cell growth cone and the smaller diameter of its attached processes, and (2) the distinct differences in IMP composition of Schwann cell and axonal growth cones and cell processes. Schwann cell growth cones display a uniformly high IMP density on their P‐face leaflet, with the exception of circumscribed moundlike protrusions that are relatively free of IMPs. In contrast, axonal growth cones display sharp regional variation in IMP density on their P‐face: broad regions almost devoid of IMPs are interspersed with zones of high IMP density. Cytotic profiles occur within high IMP density zones located, most often, at the base of the axonal growth cone. A comparison of IMP size histograms of both high and low‐density regions of axonal growth cones and that of the neighboring distal shaft of the axon indicates a strict partitioning of membrane components between these two regions. The IMP profile of the axonal growth cone, notable for its relative enrichment in large‐diameter particles, suggests that IMP components of the growth cone are delivered to the distal tip by a mechanism that is distinct from the lateral diffusion process described for particles of the growing axon's shaft [cf. Small and Pfenninger, 1984]. The IMP profile of the concave P‐face leaflet of the internal vesicles found clustered at the base of the growth cone is more similar in composition to the profile of the neuronal shaft than that of the growth cone.