bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic mechanism of inhibition of long duration in aplysia synapse
Authors: Sawada M. , Enomoto K. , Maeno T. , Blankenship J. E.
Published: January 2005

In the abdominal ganglion of Aplysia kurodai, three neurons were identified that responded with inhibition of long duration (ILD) to a single stimulation of the siphon nerve and to bath and iontophoretic application of dopamine. The ILD is a long‐lasting (15–60 sec) hyperpolarizing potential, typically associated with a conductance increase but with a reversal potential more negative than the potassium equilibrium potential. Exchange of half the external chloride with acetate induced no change in the ILD. The ILD was reduced in amplitude in the presence of 0.1 normal K+ in the external medium and enhanced in two times normal K+ solution. The ILD amplitude, but not conductance, was progressively impaired by cooling and by the metabolic inhibitors ouabain and strophanthidin. These results suggest that the ILD is composed of an increase in K+ conductance and activity of the electrogenic Na‐pump. Theophylline potentiated the ILD, especially its duration. Furthermore, bath application of dibutyryl cAMP augmented the amplitude of the synaptically elicited ILD and the dopamine responses by 30% over controls without any effect on the change in membrane conductance. Intracellularly injected cAMP also increased the ILD, but 5′‐AMP showed no such effect. These data suggest that dopamine acts on the ILD neurons by increasing K+ conductance and the activity of the electrogenic Na‐pump and that cAMP might selectively stimulate the pump component of the ILD.
Cysteinesulfinate decarboxylase activity as an index of taurine‐containing structures
Authors: Staines Wm. A. , Benjamin A. M. , McGeer E. G.
Published: January 2005

The distribution of cysteinesulfinic acid decarboxylase (CSAD) activity has been studied for some time on the assumption that this activity was a marker for taurine‐containing structures in the CNS. We have found that various in vivo and in vitro treatments of CNS tissues result in parallel changes in the activities of CSAD and glutamic acid decarboxylase (GAD). This suggests that the assay for CSAD is in fact measuring predominantly GAD activity. This hypothesis is tested by lesion, regional distribution, kinetic, inhibitor, and stability studies.
The effect of the repetitive propagation of action potentials on the structure of toad sciatic nerve myelin membranes: An X‐ray diffraction study at 11 Å resolution
Authors: Padrón Raúl , Mateu L.
Published: January 2005

Equatorial sections of the x‐ray diffraction patterns of myelin from toad sciatic nerves recorded at 11 Å resolution during long supramaximal repetitive stimulation (240 Hz for two hours) were used to calculate the relative electron density profile of the myelin membranes in this physiological state. The profile was compared to the one determined for the same nerve at rest. The difference between the stimulated profile and the control profile was found to be statistically non‐significant. Therefore, when the sciatic nerve fibers are excited the structure of the internodal myelin membranes does not significantly change at 11 Å resolution.
The K+ liquid ion exchange electrode system: Responses to drugs and neurotransmitters
Authors: Kuramoto T. , Haber B.
Published: January 2005

K+ ‐sensitive liquid ion exchange electrode systems respond with a slow potential change to acetylcholine, choline, anticholinergic drugs, biogenic amines, and glutamic acid. The response threshold has been defined, and in most cases it is at extremely low concentrations (10−7–10−;5 M). The direction of the potential change varies, but in most instances it is additive to that produced by external K+. The K+ electrode system is further sensitive to decreasing pH, within a narrow and possibly physiological range of pH. These findings suggest that small measured changes in extracellular K+ are biased by the chemosensitivity of the liquid ion exchange electrode system to some compounds of physiological importance.
Sodium dependence of high affinity glutamic acid transport in cortical synaptosomes—a comparison of Long‐Evans and Sprague‐Dawley rats
Authors: Wheeler D. D.
Published: January 2005

The sodium dependence of high affinity glutamic acid transport has been studied in cortical synaptosomes from Sprague‐Dawley rats and compared to previous studies with Long‐Evans rats. Initial velocity of uptake was measured as a function of both glutamate and sodium concentration, and the data fitted to the rate equations for the same set of models that was utilized in the Long‐Evans studies. The minimal best‐fit model was found to be identical to that found previously for Long‐Evans animals. Thus there are no fundamental differences in the basis of the sodium dependence of high affinity glutamate transport between the two groups.

However, since the constants describing the best fit model are different for the two groups of animals, there are quantitative differences in the transport mechanism between the two groups. The rate equation for the minimal best‐fit model permits certain functions to be defined in terms of dissociation and translocation constants, substrate, sodium, and total carrier concentrations. These functions were calculated and then utilized to demonstrate the quantitative differences in the transport mechanism in the two groups.
Effect of essential fatty acid deficiency on the synthesis and turnover of myelin lipid
Authors: Miller Sheldon L. , Klurfeld David M. , Weinsweig David , Kritchevsky David
Published: January 2005

The metabolism of myelin glycerophospholipids as a function of essential fatty acid (EFA) deficiency was studied in rats. Mothers were fed a lipid‐free diet from the eighth day of pregnancy throughout the suckling period. Pups were continued on the diet after weaning. Control mothers and pups were fed the same diet as experimental rats plus 3% corn oil for the same periods. Pups fed the lipid‐free diet had lower total body weight, brain weight, and total myelin phospholipid levels than controls.

At 17 days of age, each rat pup was injected with a mixture of [3H]‐glycerol and [1‐14C]‐acetate and were killed up to 80 days after injection. Lipids were extracted from isolated myelin. The 3H/14C ratio for choline, serine, and ethanolamine glycerophospholipids decreased more slowly in experimental rats than in controls, suggesting an alteration in either the turnover of myelin phospholipids or the recycling of phospholipids into myelin. Radiolabelled acyl moieties were isolated from myelin lipids and separated according to the degree of unsaturation. Acyl groups with three double bonds, presumably 20:3 (ω−9), isolated from EFA‐deficient rats appeared to be synthesized from a long‐lived pool of precursor. The relative synthesis of other unsaturated acyl moieties appeared to be the same in both groups of rats. These results indicate that EFA deficiency affects myelin metabolism.
Pool size of CDP‐choline in the brain, heart, and lung of normal and hypoxic guinea pigs
Authors: Alberghina M. , Viola M. , Giuffrida A. M.
Published: January 2005

The pool size of CDP‐choline in the brain, heart, and lung of normal and hypoxic animals was measured by radioactive isotopic dilution. The effect of exogenous CDP‐choline administration on the pool size in these experimental groups was also examined. The hypoxic treatment caused a significant decrease of endogenous CDP‐choline in the brain and lung only; no significant effect was observed in the examined organs after CDP‐choline treatment.
Ultrastructural changes accompanying the growth of isolated oligodendrocytes
Authors: Wollmann R. L. , Szuchet S. , Barlow J. , Jerkovic M.
Published: January 2005

The changes in the ultrastructure of oligodendrocytes with time in culture were examined by transmission electron microscopy. Oligodendrocytes were isolated from ovine white matter and maintained in Dulbecco's modified Eagle's medium supplemented with 20% horse serum. One day after being placed in plastic culture dishes, most cells aggregate into clusters that do not attach to the surface for several days. Cells within these clusters form junctional complexes resembling gap junctions, their nuclear chromatin becomes uniformly dispersed, they are rich in polyribosomes, and their cytoplasm is less osmiophilic than oligodendrocytes in ovine white matter or cells fixed immediately after isolation. At this time, the cells in culture fit the description of light oligodendrocytes. After several days in culture, the cells become attached to the plastic surface, chromatin once again becomes clumped beneath the nuclear membrane, rough endoplasmic reticulum accumulates within the cytoplasm and the cells extend long processes containing cytoplasmic organelles. From these observations, it appears that oligodendrocytes undergo a transient dedifferentiation during their recovery from the trauma of isolation, not unlike the central chromatolysis seen in neurons following axonal injury. After acclimatization to tissue culture conditions, isolated oligodendrocytes show many of the morphologic features seen in vivo and therefore offer a good model to study myelination.
Studies in neuronal ceroid‐lipofuscinosis: Heterogeneous nature of neuronal autofluorescent lipopigments
Authors: Garg Hari S. , Awasthi Yogesh C. , Srivastava Satish K.
Published: January 2005

A method has been developed for the complete extraction and fractionation of the autofluorescent lipopigments present in the neuronal tissue of Batten‐Spielmeyer‐Vogt (BSV) patient and normal subject, respectively. The fluorescent lipopigments that were about three‐fold higher in BSV patient's brain as compared with normal subjects were separated into at least 7 fluorometrically and chromatographically distinct fractions by thin layer chromatography (TLC). Although the fluorescent lipopigments of the brain tissue of BSV patient and normal subject showed identical pattern of separation on TLC, the fluorescence spectra of the individual lipopigment fractions from BSV patient was different from those of the corresponding fractions from the normal subject. The ultraviolet spectral studies with individual fluorescent lipopigment fractions indicated the presence of highly unsaturated conjugated chromophore.
Proliferation of glial‐derived cells in defined media
Authors: Michler‐Stuke Angelika , Bottenstein Jane E.
Published: January 2005

A serum‐free defined medium has been formulated that supports proliferation and morphologic differentiation of U‐251 MGsp human and C6‐2BD rat glioma cells. This defined medium consists of a basal medium supplemented with transferrin, fibroblast growth factor, hydrocortisone, selenium, biotin, and fibronectin (G2 medium). When U‐251 cells were plated in G2 medium on poly‐D‐lysine precoated dishes, their growth rate was 77% and final cell density was 82% of serum‐grown counterparts. The growth rate of C6 cells in G2 medium was 67% compared to cells cultured in serum supplemented medium. Although G2 medium supported the growth of human and rat glioma cells, LA‐N‐1 human neuroblastoma and WI‐38 human fibroblast cells showed no increase in cell number when grown in G2 medium compared to basal medium. A similar formulation (G3 medium), lacking fibroblast growth factor and hydrocortisone, supported the proliferation of RN‐22 rat schwannoma cells. Morphologic differences were observed between cells grown in the presence of serum and in defined media. All three glial cell lines changed from a flattened shape in serum supplemented medium to a more spherical appearance in defined medium. In addition, both U‐251 and C6 cells developed numerous processes, some reaching several cell diameters in length. These defined media will facilitate studies of the growth and differentiation of glial‐derived cells.
Sonication‐enhanced histochemistry of wheat germ agglutinin binding to intracellular sites of rat layer V cortical neurons and spinal motoneurons
Authors: Wells Michael R. , Bernstein Jerald J.
Published: January 2005

Cellular surface carbohydrates have been studied extensively in relation to cell interactions. However, the presence of intracellular carbohydrates not associated with cell surface membranes has not been well‐defined histochemically. We describe a technique for the ultrastructural localization of intracytoplasmic carbohydrates using a wheat germ agglutinin peroxidase conjugate.

The ultrastructural aspects of wheat germ agglutinin (WGA) binding to intracellular structures of rat somatomotor cortex layer V neurons and spinal cord motoneurons were examined using sonication to enhance penetration of the lectin–peroxidase conjugate. In addition to the membrane‐associated structures previously described by others, WGA binding was observed on neuronal nuclear chromatin, nuclear pores, ribosomes, microtubules, vesicular organelles, and to synaptic complexes, primarily in the presynaptic bouton. The results support data indicating that complex carbohydrates may be important in neuronal molecular processing.
Prenatal development of the human spinal cord. I. Ventral motor neurons
Authors: Rath G. , Gopinath G. , Bijlani V.
Published: January 2005

Differentiation of the ventral motor neurons were followed in the developing human spinal cord from week 8 to week 26 of intrauterine life by thionin staining and the rapid Golgi method. Ventral roots were seen as translucent rootlets by week 8 and the ventral motor neurons were clearly identifiable by week 10, indicating that the ventral grey was earlier to differentiate than the dorsal grey, which showed a small, darkly stained, undifferentiated cell population. Lateral groupings of the motor neurons in the cervical and lumbar enlargements were obvious by week 10. Nissl substance and dendrites had reached an adult pattern by about week 18 of intrauterine life.
Kinetic evidence for decreased methionine adenosyltransferase activity in erythrocytes from schizophrenics
Authors: Kelsoe John R. , Tolbert Lelland C. , Crews Eugene L. , Smythies John R.
Published: January 2005

We have observed significantly lower kinetic parameters (KM and Vmax) for methionine adenosyltransferase activity in erythrocytes obtained from early onset schizophrenics when compared to samples from normal subjects. These differences are apparently not due to differences in S‐adenosylmethionine (SAM) utilization. These results offer an explanation for the conflicting reports of previous investigators and support the concept that undermethylation may characterize some forms of schizophrenia. Methylation is involved in multiple aspects of metabolism and although similar differences in the MAT enzyme in the brain have not been reported, such a deficit could have profound effects on the nervous system. Decreased availability of SAM could decrease catecholamine metabolism or rates of phospholipid methylation.
Serum‐free culture of chicken embryonic sensory ganglia in a balanced salt solution with nerve growth factor for periods up to two weeks
Authors: Rusenko Kirt W. , Stach Robert W.
Published: January 2005

Culture of embryonic chicken dorsal root ganglia for periods exceeding a week generally require serum supplementation and a trophic factor such as nerve growth factor. In this communication we describe the culture of chicken E‐9 dorsal root ganglia for period up to 2 weeks in a system that is composed only of a simple basic salts solution and 10 ng/ml (3.8 × 10−10 M) β nerve growth factor. Commercially available tissue culture dishes are used which have a hydrophilic, gas‐diffusable membrane on the bottom to which the ganglia directly attach, eliminating the need for added substratum. Sparse fiber outgrowth appears after 24 hours and growth of the fibers continues for 120 hours of incubation. At this time, the fibers are extremely dense and reach approximately 3.5–4.0 diameters from the body of the ganglion. Continued survival of these fibers appears to depend on the concentration of nonneuronal cells present in the dish. No fiber outgrowth occurs at any time in the absence of β nerve growth factor. The simplicity and purity of this culture system makes it an attractive tool in the study of primary cell‐cell interactions, the production of trophic factors by non‐neuronal cells, and biochemical and physiological analyses of growing neurons.
Target control of neuronal development during formation of the spinal reflex arc: An operant model
Authors: Pollack Emanuel D. , Muhlach William L.
Published: January 2005

The effects of target tissues on the neural centers of the developing spinal reflex arc of frog tadpoles have been integrated to form a model explaining the spatial and temporal interactions of neuron and target. Spinal cord responds to appropriate targets earlier than does sensory ganglion in tissue culture. Neuronal growth and survival responses to target tissues in vitro may explain the regulation of development in situ.
Labeling of poly(A) associated RNA in synaptosomes and the other subcellular fractions of rat cerebral cortex in basal conditions and during training
Authors: Cupello Aroldo , Hyden Holger
Published: January 2005

The labeling of total and poly(A) associated RNA from the subcellular fractions of cerebral cortex was studied after a 1‐hour 3H‐uridine pulse in control and trained rats. In the control animals, the fraction of newly synthesized brain cortex RNA which is found in synaptosomes is the minimal one. However, in synaptosomes the proportion of poly(A)+ RNA within newly synthesized RNA is maximal. Training of the rats does not influence total incorporation of label into RNA in the brain cortex and the distribution of newly synthesized RNA within the subcellular fractions. The proportions of poly(A)+ RNA within total labeled RNA in the various fractions are also unaffected.
Development of bilateral somesthetic inputs into the pericruciate cortex of kittens: Postsynaptic and evoked potentials
Authors: Lenkov Dmitrij N. , Vasilieva Liudmila A.
Published: January 2005

The early postnatal development of somesthetic inputs into the pericruciate cortex of kittens was studied by intra‐ and extracellular recording and cortical surface evoked potential monitoring. Equipotent bilateral influences from the forepaw and hindpaw skin to cortical neurons during the initial postnatal weeks in kittens were revealed. During the fourth week, the functional dominance of contralateral inputs into the motor area becomes evident. Considerable reduction of the latency of postsynaptic and evoked responses only to the contralateral stimulation and the enhancement of their stability and intensity occur.
Loss of Purkinje cell‐associated benzodiazepine receptors spares a high affinity subpopulation: A study with pcd mutant mice
Authors: Vaccarino F. M. , Ghetti B. , Wade S. E. , Rea M. A. , Aprison M. H.
Published: January 2005

In order to identify the relative number of benzodiazepine (BZ) receptors in Purkinje and granule cells, the Purkinje cell degeneration (pcd) mutant mouse was used at, different ages. In these mice, Purkinje cells have degenerated almost completely by 45‐50 days of age. Granule cell loss occurs only later, and is most severe between 180 and 300 days. [3H]Flunitrazepam (FNZ) and [3H]ethyl‐carboline‐3‐carboxylate (β‐CC) were used as ligands. In the 45‐50‐day‐old pcd mice, it was found that there is approximately a 50% decrease in the number of receptors as labeled by [3H]/β‐CC or [3H]FNZ, when the binding is expressed as fmol/cerebellum. The binding decreased by approximately 80%in 300‐day‐old pcd mice (frnol/cerebellum). [3H]FNZ was not displaced by 1 μM R05‐4864, ruling out binding to glial cells. Nonlinear regression analysis of FNZ saturation data provided evidence for two populations of receptors (high and low affinity sites). Only the low‐affinity sites were reduced in number at 45 days. [3H]β‐CC saturation data showed, however, only one population of receptors. The total number of receptors (Bmax) was significantly lower for β‐CC than for FNZ in the control mice. It appears that 50% of the total BZ receptors is associated with Purkinje cells. In addition, our data on 300‐day‐old pcd mutants strongly suggest the existence of granule cell‐associated BZ receptors.
Mouse sciatic nerve regeneration through semipermeable tubes: A quantitative model
Authors: Uzman B. G. , Villegas G. M.
Published: January 2005

The regeneration of transected mouse sciatic nerves using semipermeable acrylic copolymer tubes to enclose both stumps has been qualitatively assessed from 1 to 30 weeks post‐operative. Quantitative morphometric analysis of electron micrograph montages of complete transverse sections of the segment regenerated between stumps has permitted determinations of the percents of total area occupied by the various tissue constituents—blood vessels, epineurium, perineurium, endoneurium, myelinate d axon/Schwann cell units, and unmyelinated axon/Schwann cell units. Significant differences were found in the total cross‐sectional area of segments regenerated through tubes of 1.0 mm versus 0.5 mm internal diameters. Segments regenerated with the distal stump inserted in the tube contained significantly greater percentages of neural units and were significantly larger at 8 weeks post‐operative compared to segments regenerated for 9‐10 weeks with the distal stump avulsed. The morphometric method permits rapid quantitation of sizeable electron micrograph montages which at 1300 × permit all types of tissue components, including the unmyelinated axons, to be visualized.
Distribution of radioactivity among total myelin protein amino acids following administration of labeled glycine, leucine, or methionine
Authors: Wiggins R. C. , Morell P.
Published: January 2005

This paper analyzes the distribution of radioactivity in the different amino acids of brain myelin protein for up to 6‐7 weeks after an intracranial pulse administration of radioactive leucine, glycine, or methionine. Results show that there is no significant accumulation or reutilization of protein radiactivity in any form other than the one administered.
Postnatal development of aminergic projections to frontal cortex: Effects of cortical lesions
Authors: Beaulieu M. , Coyle J. T.
Published: January 2005

The effects of lesions induced by fetal treatment with methylazoxymethanol acetate (MAM) on the developmental synaptic chemistry of the frontal cortex of rats were examined. Treatment at 14 days' gestation (DG) resulted in a 50% decrease in frontal cortical mass whereas treatment at 15 DG caused a 40% decrement. No difference in concentration between MAM and control rats was observed in the postnatal development of the GABA‐ergic markers, glutamate decarboxylase, and GABA. In contrast, the concentrations of the presynaptic markers for the dopaminergic, noradrenergic, and serotonergic terminals were generally elevated in the MAM lesioned frontal cortex throughout postnatal development. The effects of MAM lesion on cholinergic markers were mixed, with minimal alterations in concentration during the first 2 postnatal weeks followed by an increasing disparity thereafter. The results of this study provide additional evidence in support of the differential impact of the cortical hypoplasia on intrinsic neurons as contrasted to aminergic afferents.
Characterization of a subset of oligodendrocytes separated on the basis of selective adherence properties
Authors: Szuchet S. , Yim S. H.
Published: January 2005

A subset of oligodendrocytes (B3,f) was isolated by taking advantage of selective cell–substratum interaction. B3,f cells were characterized morphologically, biochemically, and immunocytochemically. Oligodendrocytes were isolated from 4‐to‐6‐month‐old lamb brains by a modified version of our published procedure [Szuchet et al, J Neurosci Methods 3:7–19, 1980]. Freshly isolated cells from band III were plated on plastic culture plates at a concentration of 2 × 106 cells/ml. Approximately 40% of the cells attached to the plate under these conditions. The remaining cells formed small floating clusters. We refer to the latter as B3,f oligodendrocytes. After 4 to 5 days, the supernatant containing B3,f cells was removed and centrifuged, and the pellet was resuspended in culture medium and replated on polylysine‐coated petri dishes. B3,f oligodendrocytes attached to this surface and extended an intricate network of processes. The purity of the cultures, judged by the number of cells staining with a monoclonal antibody against galactocerebroside was 98–99%. This high degree of cell homogeneity was maintained throughout the life of the cultures. B3,f cells appeared to be highly differentiated and remained so in vitro. This is surmised by the expression of oligodendrocytic characteristic functions such as high levels of CNPase activity typically, 5 μM/min/mgP; high incorporation of H2 35SO4 into sulfatides, an overall lipid metabolism that mimics events associated with myelinogenesis [Szuchet et al, PNAS 80:7019–7023, 1983]; the presence, detected immunocytochemically, of myelin‐associated glycoprotein and myelin basic proteins. It is concluded that this culture system offers an opportunity for studying the biology of interfascicular oligodendrocytes and their interaction with neurons and/or astrocytes. It also should open up a way of examining the relevance of oligodendrocyte polymorphism.
Evidence for an organized lattice in the intercellular space of vestibular sensory cat epithelia
Authors: Favre Daniel , Sans A.
Published: January 2005

The intracellular space between sensory hair cells and nerve endings and between supporting cells of the vestibular epithelia in the cat contains a fine network of microstructures arranged obliquely between the cell membranes of adjacent cells. In situ immersion‐perfusion fixation, electron microscopy complemented by lanthanum negative‐contrast and freeze‐fracture methods suggest that these intercellular structures are tubular with an external diameter between 3 and 6 nm and an internal diameter of 1.5 nm. They could serve as intercytoplasmic tunnels. We discuss the evidence concerning the analogy between the present microchannels and the passageways regularly arranged in the intercellular space of gap‐junctions which would permit the transport of low molecular weight substances from one cell to other.
Cerebral endogenous substrate utilization during the recovery period after profound hypoglycemia
Authors: Benzi G. , Villa R. F. , Dossena M. , Vercesi L. , Gorini A. , Pastoris O.
Published: January 2005

Markedly decreased levels of energy‐rich phosphates were seen in cerebral cortex after severe hypoglycemia, followed by their partial restitution during the recovery period. During hypoglycemia the nonglucose endogenous substrates were provided by glycolytic intermediates, by Krebs cycle intermediates, and by related amino acids. Other potential substrates for brain oxidation were provided by the breakdown of phospholipids and fatty acids.

After a 20‐min period of posthypoglycemic recovery, partial restoration of carbohydrates and amino acids occurred, although the amino acid pool size was still reduced. The alterations in phospholipids and fatty acids persisted, while there was a tendency toward normalization of the free fatty acid content. During the posthypoglycemic recovery, treatment with some specific metabolic modulators (6‐aminonicotinamide, hopantenate, uridine, L‐acetylcarnitine) suggested the possibility of an alternative cerebral substrate utilization owing to modulation of the cerebral biochemical machinery. Thus, increased carbohydrate utilization by hopantenate was consistent with decreased lipid breakdown, while increased carbohydrate utilization by uridine was concomitant with decreased amino acid degradation. In this way, decreased cerebral carbohydrate utilization by 6‐aminonicotinamide was associated with increased lipid and amino acid breakdown. Furthermore, the increased loss of cerebral phospholipids and phospholipid‐bound fatty acids by L‐acetylcarnitine occurred in the presence of a large glucose availability and was associated with an extensive reduction of cerebral glycolytic flux.
Astrocyte cell lineage. V. Similarity of astrocytes that form in the presence of dBcAMP in cultures to reactive astrocytes in vivo
Authors: Fedoroff S. , McAuley W. A. J. , Houkle J. D. , Devon R. M.
Published: January 2005

The relationship between astrocytes forming in the presence of dibutyryl cyclic AMP (dBcAMP) in culture and reactive astrocytes responding to a cerebral cortex stab wound was investigated using computerized image analysis (Zeiss IBAS 1) and immunocytochemical staining. The diameters of the nuclei of astrocytes in primary cultures of newborn mouse neopallial cells were compared to those of the nuclei of normal and reactive astrocytes in histological sections of mouse cerebral cortex. We found that the nuclei of astrocytes that formed in the presence of dBcAMP in cultures are significantly larger than those of spontaneously occurring small stellate astrocytes in culture and of normal astrocytes of the cerebral cortex in vivo but corresponded more closely to the nuclei of reactive astrocytes in the area surrounding a stab wound in the cerebral cortex. Large stellate cells formed in the presence of dBcAMP had vimentin and an increase in GFP‐containing intermediate filaments. Formation of reactive astrocytes in vivo is also associated with an increase in both vimentin and GFP‐containing intermediate filaments. These observations indicate a closer relationship of astrocytes formed in the presence of dBcAMP in cultures to the reactive astrocytes in the cerebral cortex than to normal astrocytes. We propose, therefore, that the large stellate astrocytes that form in the presence of dBcAMP be referred to as reactive astrocytes in culture.
Ganglioside biosynthesis in Golgi apparatus: New perspectives on its mechanism
Authors: Yusuf H. K. M. , Pohlentz G. , Sandhoff K.
Published: January 2005

The synthesis of gangliosides GM1 and GM2 in intact rat liver Golgi vesicles is stimulated by phosphatidylglycerol as much as or even more than by detergents (Triton X‐100 and octyglucoside, respectively). The antibiotic tunicamycin, known as an inhibitor of the N‐glycosylation of proteins, strongly inhibits the synthesis of the above gangliosides, in the presence as well as in the absence of the phospholipid. Both phosphatidylglycerol dependence and tunicamycin inhibition disappear when the Golgi vesicles are solubilized by addition of detergents or disrupted by ultrasonication or pretreated with pronase.

Transport studies with UDP‐[3H]Gal show that tunicamycin blocks the penetration of the sugar nucleotide into the Golgi vesicles in a concentration‐dependent manner up to 80%. The results show that tunicamycin inhibits ganglioside biosynthesis by blocking the transport of the nucleotide sugar and not by inhibiting the transferase directly.

Studies on glycoprotein‐galactosyltransferase with ovalbumin as exogenous acceptor showed that phosphatidylglycerol does not destroy the integrity of the Golgi vesicles. So this phospolipid is an excellent tool for studying ganglioside biosynthesis at optimal transferase activities without solubilizing the Golgi membranes.
Lateral distribution of gangliosides in bilayer membranes: Lipid and ionic effects
Authors: Peters M. W. , Barber K. R. , Grant C. W. M.
Published: January 2005

Native Ricinus communis agglutinin (RCA 60) has been used as a visual marker to localize the ganglioside GM1 under a variety of conditions in model membranes. By employing the technique of freeze‐etch electron microscopy, it was possible to resolve membrane structural details down to some 3 nm. The most striking feature was frequent existence of the marker lectin in clusters—presumably reflecting the underlying presence of clustered receptor. This feature persisted at glycolipid concentrations from 0.5 to 7 mol%. It was visible in membranes of single pure phospholipids above and below their phase transition temperatures, in membranes of mixed phospholipids, and in membranes containing cholesterol. The presence of cations, including Ca2+, was not seen to alter the pattern of lectin binding at a resolution of 3 nm. In pure dipalmitoyl phosphatidylcholine, a lining‐up of glycolipid in the “troughs” between ripples in rigid lipid was apparent, in agreement with a similar phenomenon reported by Tillack et al for a neutral glycosphingolipid in pure dimyristoyl phosphatidylcholine [1982: Biochim Biophys Acta 691:261–273]; but this feature was not evident in host matrices composed of several different lipids.
Release of polyunsaturated fatty acids from phospholipids and alteration of brain membrane integrity by oxygen‐derived free radicals
Authors: Hoo Chan P. , Fishman R. A. , Schmidley J. W. , Chen S. F.
Published: January 2005

We studied the effects of oxygen‐derived free radicals on the ultrastructure of brain cortical slices and the release of fatty acids from phospholipids of crude synaptosomes. Xanthine oxidase, hypoxanthine, and ADP‐Fe3+, a free‐radical‐generating system, caused swelling of cellular processes and mitochondria. The oxygen‐derived free radicals also caused the rapid release and accumulation of endogenous polyunsaturated fatty acids (PUFA) from membrane phospholipids as determined by high‐performance liquid chromatography (HPLC). Furthermore, [3H]‐arachidonic acid was also rapidly released from prelabeled phospholipids concomitant with a decrease in radioactivity in various phospholipid fractions. The radioactivities of neutral lipids including diacylglycerols were unchanged by free radicals. These data indicate that the activation of phospholipase A2 and the release of PUFA may have overt effect on membrane integrity and the subsequent development of cellular injury and brain edema.
Growth cones of developing retinal cells in vivo, on culture surfaces, and in collagen matrices
Authors: Harris W.A. , Holt C.E. , Smith T.A. , Gallenson N.
Published: January 2005

The outgrowth of axons from the early retina in vivo is compared with that from retinal explants in two types of culture systems. The normal time course of axonal growth along the primordial optic pathway to the optic tectum is characterized, using tritiated proline and horseradish peroxidase (HRP) as anterograde tracers. The rate of axonal elongation in vivo is estimated to be about 32 μm/hr at 22°C. The HRP technique allows visualization of retinal growth cones in vivo. Observations can thus be made on their microanatomy and on the environment through which they navigate. The growth cones of retinal ganglion cells in the embryo have lamellipodia and fairly short filopodia ( ∼ 10 μm) which are directed forward. The growth cones are found near the pial surface of the brain but do not seem to maintain contact with it.

Two culture systems were developed to investigate axonal pathways in vitro. In the first, different substrates and culture media were explored. Results indicate that growth cones prefer a polyornithine substrate over a collagen one. The media that promotes the best neurite outgrowth consists of L15 (60%), fetal calf serum (10%) and Xenopus embryo extract (1 mg/ml). Time‐lapse video monitoring of substrate cultures reveals an average rate of outgrowth of about 18 μm/hr with great variability. The growth cones in these cultures are large, flattened, and complex compared to those in vivo, and their filopodia extend in many different directions.

The second culture system is a collagen gel infiltrated with growth medium. In these conditions neurite outgrowth more closely mimics that in vivo. The rate is faster than on substrates, and the growth cones appear morphologically similar to those in the embryo. Preliminary experiments using the gel culture system to test for chemotaxis of retinal axons toward their targets failed to demonstrate such an effect.
Barium action potentials in regenerating axons of the lamprey spinal cord
Authors: Macvicar's B.A. , Llinás R.R.
Published: January 2005

Intracellular 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

Both 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

The 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

Axons 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

Theiler'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

Nonidet 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

The 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.