bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growing tips of embryonic cerebellar axons in vivo
Authors: Mason C.A. 
Published: January 2005

AbstractFew studies have focused on the transformation of growth cones to mature synaptic arbors. To study these events in developing axons in vivo, we have labeled growing cerebellar axons with horseradish peroxidase (HRP) in postnatal stages [Mason and Gregory, 1984]. This report will provide the first data on embryonic cerebellar axons, and will ask whether growth cones differ in tracts and in target tissue and what features characterize axons that enter the cerebellum in fetal periods.During the earliest embryonic (E) periods examined (E16–19), axons in tracts have enlarged growth cones with lamellopodia and short filopodia that contain small and large vesicles. In contrast, axons within the cerebellar anlage from E16‐postnatal day (P) 5 have fine calibers with a minimum of branching, and have small tapered growing tips. If synaptic contacts are made by such growing tips, there is little concomitant change in their shape. As target cells form layers and as their dendrites extend (P5–P7), growing tips and synaptic boutons differentiate according to the type of synaptic arrangement in which they engage. Enlarged, irregular expansions of growing tips correspond to synaptic contacts with multiple dendritic partners and are filled with large and small clear vesicles. Filopodia arising from such swellings, like the small undifferentiated growing tips of the type seen on embryonic axons, contain a mixture of vesicle types but make simple synapses with single profiles. Many axons make both kinds of synaptic structures, especially during the period when maturing axons give rise to long filopodia.Thus, growing tips have immature forms long after synaptogenesis begins, and use filopodial structures to elaborate synaptic arrangements. This analysis should elucidate the changes in growth cone form and cytology that reflect cell‐cell interactions during synaptogenesis.
Regulation of growth cone morphology by nerve growth factor: A comparative study by scanning electron microscopy
Authors: Connolly J.L. , Seeley P.J. , Greene L.A. 
Published: January 2005

AbstractThe object of this study was to document and analyze local regulation by nerve growth factor (NGF) of neuronal growth cone properties and to explore the possible diversity of this effect in various NGF‐responsive preparations. In particular, scanning electron microscopy was used to characterize the morphology of neuronal growth cones in cultures of dissociated chick embryo dorsal root ganglia (DRG) under conditions of continuous NGF exposure, withdrawal of NGF for 5–6 hr, and restoration of NGF for various times. Comparison was made with similarly manipulated cultures of dissociated newborn rat sympathetic ganglia and neurite‐bearing PC12 pheochromocytoma cells. The growth cones of most of the continuously NGF‐treated DRG neurons (cultured on poly‐L‐lysine or collagencoated glass coverslips) had relatively compact central flattened areas and numerous prominent filopodia. Withdrawal of NGF resulted in a marked spreading of the central growth cone area so that the average maximum width of this structure increased by about threefold as compared to nondeprived cultures. The mean number and lengths of filopodia were unaffected. Restoration of NGF brought about, over a time course of tens of minutes, a return of the original type of growth cone morphology. Rather different responses were observed for the sympathetic neuron and PC12 cultures. Here, surface ruffles, only rarely seen in the chick cultures, were a major feature of the growth cones, whereas filopodia, though present, were less prominent. Removal of NGF led to loss of ruffles and to rounding up of the growth cones; NGF readdition elicited a rapid (< 30 sec) reinitiation of ruffling and a more gradual (over tens of minutes) respreading of growth cones. These findings illustrate not only that NGF can regulate growth cone properties, but also that there is a diversity as to how this is manifested. Possible mechanisms and biological roles for this regulation are discussed.
Single channel activity differs in growing and nongrowing growth cones of isolated identified neurons of Helisoma
Authors: Cohan C.S. , Haydon P.G. , Kater S.B. 
Published: January 2005

AbstractWhen plated in cell culture, Helisoma neurons extend new neurites with large growth cones. These growth cones progress from actively growing organelles to stable structures over a period of several days. The ability to distinguish morphologically between these growth states has provided the opportunity to test whether changes in growth status are correlated with changes in the ionic properties of the growth cone membrane. This investigation has begun to study these changes by examining single channel ionic currents using patch clamp recording techniques and has demonstrated the presence of at least one ion channel having a conductance of 70 pS in the membrane of Helisoma growth cones. Recordings from cell‐attached patches show that this channel is normally active in growing growth cones, whereas channel activity is absent in recordings from stable growth cones. The absence of channel activity in growth cones that have reached the stable state is not due to the loss of channels from these growth cones. Rather, the channel is present in an inactivated state. The activity of this channel is not dependent on the presence of Ca, as channel activity persists when Ca is removed from the solution that bathes the internal surface of the membrane. These data demonstrate a correlation between channel activity and the growth state of neuronal growth cones.
An analysis of peripheral neuronal survival factors present in muscle
Authors: Bonyhady R.E. , Hendry I.A. , Hill C.E. , Watters D.J. 
Published: January 2005

AbstractExtracts of bovine heart, rat heart, and rat skeletal muscle were chromatographically separated and the fractions tested for their ability to maintain the survival of dissociated sympathetic, parasympathetic, and sensory neurones. Bovine heart contained at least five, rat heart at least six, and rat skeletal muscle at least four active components differing in their physicochemical properties and their target selectivity. Bovine and rat heart appeared to contain at least two components in common. The differences in active components found in the three tissues are consistent with a complex and perhaps tissue‐specific system regulating neuronal survival.
Synthesis of arachidonoyl coenzyme a and docosahexaenoyl coenzyme a in synaptic plasma membranes of cerebrum and microsomes of cerebrum, cerebellum, and brain stem of rat brain
Authors: Reddy T.S. , Bazan N.G. 
Published: January 2005

AbstractSynthesis of arachidonoyl CoA and docosahexaenoyl CoA in homogenates and microsomes from cerebrum, cerebellum, and brain stem and in synaptic plasma membranes from cerebrum of control rats and rats undergoing bicuculline‐induced status epilepticus were studied. Arachidonoyl CoA synthesis was 3–5 times higher than docosahexaenoyl CoA in homogenates and microsomes. The synaptic plasma membranes showed only 1.5‐ to 2.5‐fold higher activity. The presence of Triton X‐100 (0.1%) in the incubation medium did not alter the activity of arachidonoyl CoA synthesis but did increase the synthesis of docosahexaenoyl CoA in homogenates, microsomes, and especially in synaptic plasma membranes. The synthesis of these polyenoic fatty acyl CoAs were 4–6 times higher in microsomes than in homogenates. Synaptic plasma membranes exhibited about the same amount of activity as homogenates in the synthesis of docosahexaenoyl CoA, but only half the activity of the latter in arachidonoyl CoA synthesis. The synthesis of arachidonoyl CoA and docosahexaenoyl CoA in cerebral homogenates and microsomes was higher than that of cerebellum and brain stem.The apparent Km values for labeled arachidonic acid (17 μM) and docosahexaenoic acid (12 μM) in synaptic plasma membranes were lower than the values for microsomes isolated from different brain regions. The Vmax values were also 4–10 times lower. Microsomes from different regions did not differ in their apparent Km values, but did show variations in apparent Vmax values. Cerebellar microsomes showed lower Vmax values than the other two regions. The presence of Triton X‐100 caused a significant decrease in the apparent Km values with little change in the Vmax values. Bicuculline‐induced seizures did not alter the kinetic properties of arachidonoyl CoA and docosahexaenoyl CoA synthesis, except there was a significant decrease in the apparent Km and Vmax values for cerebellar microsomal docosahexaenoyl CoA synthesis. In conclusion, there were marked differences in the activation of polyenoic fatty acids in different parts of the brain and in subcellular fractions. Although bicuculline‐induced convulsions accumulate free polyenoic fatty acids in the brain, no changes were detected when the fatty activation was assayed with exogenous cofactors, except in cerebellum.
Functional role of the potassium‐induced stimulation of oxygen uptake in brain slices studied with cesium as a probe
Authors: Hertz L. , Kjeldsen C. S. 
Published: January 2005

AbstractThe potassium‐induced stimulation of oxygen consumption in brain slices has a threshold value of 15–20 mM potassium, and it reaches its maximum at 35–50 mM. Although this phenomenon now has been known for almost 50 years, its physiological role remains undetermined. One reason for this may be that the high concentration of potassium that are required for this response also have many other consequences, e.g., a depolarization of the cells, and that the different effects to some extent may mask each other. For this reason this investigation studied the effects of cesium, which evokes a maximal stimulation of oxygen consumption already at 15 mM. Like potassium, concentrations of cesium that stimulate oxygen consumption also lead to an enhanced swelling. Unlike potassium, the sodium content is affected very little by these concentrations of cesium, whereas cesium and chloride contents are increased. On this basis it is concluded that the cesium‐induced stimulation of oxygen uptake is a metabolic manifestation of an active uptake of cesium and chloride, which secondarily leads to an uptake of water, i.e., the cesium‐induced swelling. Analogously, it is suggested that the potassium‐induced stimulation of oxygen uptake represents an active accumulation of potassium and chloride.
Deacylation of myelin proteolipid protein in organic solvents
Authors: Bizzozero O. A. , Dominguez F. , Pasquini J. M. , Soto E. F. 
Published: January 2005

AbstractA procedure has been developed for the deacylation of the hydrophobic, myelin proteolipid apoprotein using hydroxylamine in an alkaline organic solvent medium. Complete removal of covalently bound fatty acids was obtained after 4 hr of treatment. After deacylation, no changes could be detected in the electrophoretic pattern or in the number of free sulfhydryl groups. The deacylated apoprotein remains soluble in chloroform‐methanol mixtures and is suitable for further physicochemical characterization.
Tuning the power spectrum of physiological finger tremor frequency with flickering light
Authors: Isokawa‐Akesson M. , Komisaruk B. R. 
Published: January 2005

AbstractFast Fourier Transform analyses were performed on finger tremor movements at 0.2‐Hz intervals from 0.4 to 40 Hz in 10 human subjects, under a flickering light condition of 4–15 Hz and an unstimulated control condition. Under the control condition, the power spectrum showed an essentially normal curve distribution, except for an early frequency component in the histogram. In contrast, when the flickering light stimulus was presented, the power of specific frequency components at 8–1 Hz was strongly enhanced. This effect was induced exclusively at a frequency of 8, 9, or 11 Hz of flickering light, and this flickering frequency producing the enhancement effect differed from subject to subject. There existed a significant correlation between the frequencies of flicker and tremor at the tuned frequency. These findings demonstrate that a specific frequency of flickering light can intensify a specific frequency of physiological finger tremor, and that different individuals exhibit different optimal “tuning” frequencies.
Development and elimination of presynaptic elements on polylysine‐coated beads implanted in neonatal rat cerebellum
Authors: Burry R. W. , Hayes D. M. 
Published: January 2005

AbstractPolylysine‐coated sepharose beads were implanted in the cerebellum of neonatal rats and examined at 3 hr, 3 days, 14 days, and 21 days after surgery. Previous studies at 5 or 8 days after implantation showed that axons formed neuronal swellings that appeared to be presynaptic elements, with the bead surface in the position of a postsynaptic element. Results reported here show that no beads at 3 hr had presynaptic elements, whereas the number of beads with presynaptic elements increased to high levels at 3 and 7 days but dropped to low values at 14 and 21 days after implantation. Presynaptic elements were seen on beads regard less of their distance from cerebellar tissue except at 3 hr, when no axons were seen in the implant, indicating that axons first grew into the implant and then formed presynaptic elements. The morphological measurements of presynaptic elements on beads at 3 to 7 days after implantation showed increases in area and number of synaptic vesicles, which then decreased at 14 and 21 days after implantation.These results show that axons can grow into implants of polylysine‐coated beads and form presynaptic elements that do not survive with increased time after implantation. The survival of presynaptic elements on beads can be used as a model for investigations into regeneration of axons and presynaptic elements in the injured brain.
Growth patterns of glial cells dissociated from newbron and aged mouse brain with cell passage
Authors: Vernadakis A. , Davies D. , Sakellaridis N. , Mangoura D. 
Published: January 2005

AbstractGlial cell cultures derived from newbron and aged (18‐month‐old) mouse cerebral hemispheres and maintained up to cell passage 11 were characterized immunocytochemically by using glial fibrillary acidic protein (GFA), and biochemically by using glutamine synthetase (GS), for astrocytes, and 2′,3′ cyclic nucleotide 3′ phosphohydrolase (CNP) for oligodendrocytes. We report here the changes occurring during passages 5–1. GS and CNP activities did not significantly changes with cell passage in cultures from newbron mouse. In cultures derived from aged mouse, CNP activity did not change signigicantly whereas GS activity increased severalfod. A characteristic finging in higher cell passages (passage #7) was the loss of GFA‐positive stained cells and the appearance of multinucleated cells. We interpret these changes in culture to represent possible signs of cellular senescence.
μ‐type calcium‐activated neutral protease in the rat peripheral nerve
Authors: Kamakura K. , Ishiura S. , Sugita H. 
Published: January 2005

AbstractPreviously we reported results of an incubation experiment with neurofilaments that supported the existence of a μ‐type of Ca2+‐activated neutral protease in the rat peripheral nerve; it was active with μM order Ca2+ (μ‐CANP). This time, we partially purified the μ‐CANP from a crude CANP fraction of rat peripheral nerve by using a DE52 column and a Phenyl‐Sepharose column followed again by DE52 column chromatography. The presence of μ‐CANP was verified by an immunoblotting technique. The μ‐CANP degraded the neurofilament triplet as previously reported; i.e., among the neurofilament triplet, the 160K component was most sensitive, and in the order of the 160K, 68K, and 200K components, respectively.
Metabolism of choline in brain of the aged CBF‐1 mouse
Authors: Saito M. , Kindel G. , Karczmar A. G. , Rosenberg A. 
Published: January 2005

AbstractIn order to quantify the changes that occur in the cholinergic central nervous system with aging, we have compared acetylcholine (Ach) formation in brain cortex slice preparations from 2‐year‐old aged CBF‐1 mouse brains and compared the findings with those in 2–4‐month‐old young adult mouse brain slices. Incorporation of exogenous radioactively labelled choline (31 nM [3H] choline) into acetyl choline in incubated brain slices was linear with time for 90 min. Percentage of total choline label distributed into Ach remained constant from 5 min after starting the incubation to 90 min. In contrast, distribution of label into intracellular free choline (Ch) and phosphorylcholine (Pch) changed continuously over this period suggesting that the Ch pool for Ach synthesis in brain cortex is different from that for Pch synthesis. Incorporation of radioactivity into Ach was not influenced by administration of 10 μM eserine, showing that the increment of radioactivity in Ach reflects rate of Ach formation, independently from degradation by acetylcholine esterases. Under our experimental conditions, slices from cortices of aged 24‐month‐old mouse brain showed a significantly greater (27%) incorporation of radioactivity into intracellular Ach than those from young, 2–4‐month‐old, brain cortices. Inhibitors of Arch release, 1 mM ATP or GABA, had no effect. Since concentration of radioactive precursor in the incubation medium was very low (31 nM), the Ch pool for Ach synthesis in slices was labelled without measurably changing the size of the endogenous pool. These data suggest a compensatory acceleration of Ach synthesis or else a smaller precursor pool specific for Ach synthesis into which labelled Ch migrated in aged brain. We also measured in detail the incorporation of [3H]CH into choline phospholipids: phosphatidyl choline, lysophosphatidyl choline, and sphingomyelin of young and old mouse brain. We could not detect any difference between young and old mouse brain cortical slices, suggesting that the difference in Ach synthesis that we have observed may reflect a specific alteration with aging in the metabolic mechanism for Ach synthesis.
Effect of selective kainate lesions on the release of glutamate and aspartate from chick retina
Authors: López‐Colomé A. M. , Somohano F. 
Published: January 2005

AbstractIn order to contribute evidence leading to establishing the excitatory pathways in the vertebrate retina, we selectively lesioned chick retinas by intraocular injection of 6, 60, 120, and 200 nmol of kainate, which selectively damages OFF‐bipolars, amacrines, horizontals, and ON‐bipolars, and measured the K+‐stimulated, Ca++‐dependent release of L‐(3H)‐glutamate and L‐(3H)‐aspartate. We also measured (3H)‐GABA release as a marker for horizontal cells and a population of amacrines, as well as (14C)‐glycine release as a tracer of a different subpopulation of amacrines. All four amino acids were released from control retinas by a depolarizing K+ concentration in a Ca++‐dependent fashion. GABA and glycine, however, showed an additional Ca++‐independent component of release. Lesion induced by 6 nmol of kainate decreased by 50% the release of glutamate and by 20% that of aspartate; glycine release was reduced 40% while GABA release was unaffected. Injection of 60 nmol of kainate reduced glutamate release a further 20% and significantly decreased GABA (50%) and glycine (75%) release; aspartate release remained unmodified; 120 nmol of kainate caused a further 30% reduction in aspartate and GABA release. Neither compound was significantly released after treatment with 200 nmol of kainate. These results seem to suggest that while OFF‐bipolars could release glutamate as transmitter, aspartate is released from a different cell population which is less sensitive to kainate, probably ON‐bipolars.
Differential effects of kainic‐acid‐induced hippocampal lesions on the acquisition of the jump‐box avoidance task in mice
Authors: Ozaki H. S. , Murakami T. H. , Toyoshima T. , Shimada M. 
Published: January 2005

AbstractThis research examined the effects of kainic‐acid (KA)‐induced hippocampal lesions on the acquisition of a jump‐box avoidance task in mice. When the hippocampal lesion was unilateral, mice with lesions in the lateral portion of the CAI region showed deficits in acquisition while those with lesions in the CA3 region and/or the medial portion of the CA1 region did not. When the hippocampal lesion was bilateral, on the other hand, mice with lesions in the CA3 region and/or the lateral portion of the CA1 region were deficient in acquisition while those with lesions in the medial portion of th CA1 region were not. Among the mice with various KA‐induced hippocampal lesions avoidance responses were not correlated with the level of open field activity, indicating that acquisition differences observed are not dependent upon, nor secondary to, levels of spontaneous activity. These results strongly suggest that there exist regional differences in the involvement of hippocampal pyramidal cell layers in acquisition of the jump‐box avoidance task: both the CA3 region and the lateral portion of the CA1 region are involved in acquisition, while the medial portion of the CA1 region is not.
Developmental features of rat cerebellar neural cells cultured in a chemically defined medium
Authors: Gallo V. , Ciotti M. T. , Aloisi F. , Levi G. 
Published: January 2005

AbstractWe studied some aspects of the differentiation of rat cerebellar neural cells obtained from 8‐day postnatal animals and cultured in a serum‐free, chemically defined medium (CDM). The ability of the cells to take up radioactive transmitter amino acids was analyzed autoradiographically. The L‐glutamate analogue 3H‐D‐aspartate was taken up by astroglial cells, but not by granule neurons, even in late cultures (20 days in vitro). This is in agreement with the lack of depolarization‐induced release of 3H‐D‐aspartate previously observed in this type of culture. In contrast, 3H‐(GABA) was scarcely accumulated by glial‐fibrillary‐acidic‐protein (GFAP)‐positive astrocytes, but taken up by glutamate‐decarboxylase‐positive inhibitory interneurons and was released in a Ca2+‐dependent way upon depolarization: 3H‐GABA evoked release progressively increased with time in culture. Interestingly, the expression of the vesicle‐associated protein synapsin I was much reduced in granule cells cultured in CDM as compared to those maintained in the presence of serum. These data would indicate that in CDM the differentiation of granule neurons is not complete, while that of GABAergic neurons is not greatly affected. Whether the diminished differentiation of granule cells must be attributed only to serum deprivation or also to other differences in the composition of the culture medium remains to be established. 3H‐GABA was avidly taken up also by a population of cells which were not recognized by antibodies raised against GFAP, glutamate decarboxylase, and microtubule‐associated protein 2. These cells exhibited a stellate morphology, were stained by the monoclonal antibody A2B5, and have been characterized elsewhere [Levi et al, 1986] as bipotential precursors of oligodendrocytes and of a subpopulation of astrocytes bearing a stellate shape and capable of high‐affinity 3H‐GABA uptake.