bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retinal degeneration in 3‐month‐old rhesus monkey infants fed a taurine‐free human infant formula
Authors: Imaki H. , Moretz R. , Wisniewski H. , Neuringer M. , Sturman J. 
Published: January 2005

AbstractRhesus monkey infants were raised from birth on a taurine‐free soy protein‐based human infant formula or on the same formula supplemented with taurine. The monkeys were killed 3 months after birth and the retinas examined by light and electron microscopy. All of the monkeys raised on formula alone showed degenerative ultrastructural changes in photoreceptor outer segments that ranged froom swelling and disorientation to fragmentation and disorganiozation. Cones were more severely affected than rods, and changes were most pronounced in the foveal region. Changes were also noted ion the fine structure of the retinal pigment epithelium. These changes were prevented in all but one monkey fed the same formula supplemented with taurine. These results provide further support for the addition of taurine to commercial human infant formulas.
Damaged rat peripheral nerves do not contain detectable amounts of α‐MSH
Authors: Verhaagen J. , Edwards P. M. , Gispen W. H. 
Published: January 2005

AbstractPeptides related to α‐MSH (collectively termed melanocortins) stimulate nerve growth following injury and may play a physiological role in the repair process. Melannocortins are not normally present in mature peripheral nerves but MSH‐like bioactivity has been observed in extracts of injured nerves. α‐MSH could derive from reexpression of the POMC prohormone in injured nerves or from proteolysis of the intermediate‐size neurofilament protein that bears antigenic similarities to melanocortins. Using a radioimmunoassay that will distinguish between α‐MSH and neurofilament‐derived fragments, we have shown that α‐MSH is not present (detection limit 74 pg α‐MSH/mg protein) in damaged rat sciatic nerves.
Purification and partial amino acid sequence of bvino adernal phenylethanolamine N‐methyltransfersase: A comparision of nucleic acid and protein sequence data
Authors: Weisberg E. P. , Batter D. K. , Brown W. E. , Kaplan B. B. 
Published: January 2005

AbstractRecently, We have reported the isolation and characterization of a putative genomic DNA clone encoding bovine adernal phenylethanolamine N‐methyltrasferase (PNMT) (Batter et al., 1988). However, the lack of primary amino‐acid sequence data for this enzyme precluded a definitive proof of the authenticity of this clone. To establish identity, the amino acid sequence of several peptides generated by chemical and enzymatic hydrolysis of purifide PNMT was compared to that predicted from the nucleotid sequence of the exons of the putative PNMT gene. Bovine adrenomedullary PNMT was purified by ammonium sulfate precipitation, gel filtration, and ion exchange chromatography. Treatment with 70% formic acid cleaved the protein at a single Asp‐Pro bond near the N‐terminus. The purified protein was also cleaved at a single methionine residue near the C‐terminus by treatment with cyanogen bromide. N‐terminal amino acid sequence analysis identified 8 and 10 amino acid residues, respectively, following each of the scissile peptide bonds. Four tryptic peptides, generated by complete enzymatic digestion, were isolated by reverse‐phase HPLC and subjected to sequence analysis. Combined, the amino acid sequence of these six peptides represent 20% of the PNMT protein. These amino acid sequence matched exactly the sequences predicted from the exons of the putative PNMT genomic clone.
The induction of the major heat‐stress protein in purified rat glial cells
Authors: Nishimura R. N. , Dwyer B. E. , Welch W. , Cole R. , de Vellis J. , Liotta K. 
Published: January 2005

AbstractCultured purified oligodendroglia and astroglia exposed to heat stress (45 °C, 10 or 20 min) synthesized a 68‐kDa heat‐stress protein, which migrates on twodimensional gel electrophoresis and reacts with a specific monoclonal antibody suggesting it is similar to a major 72‐kDa heat‐shock protein previously reported in other cell types. This protein was not detected in control glial cultures. Actinomycin D prevented synthesis of this protein demonstrating an absolute requirement for newly synthesized mRNA. The response was prolonged by increasing the period of heat stress from 10 to 20 min. In addition to the 68‐kDa HSP protein, the incorporation of radioactivity into 70‐, 89‐, and 97‐kDa proteins was also increased after heating, but in contrast to the 68 kDa protein these proteins appeared to be made in control glial cultures.
Influence of monensin on ganglioside anabolism and neurite stability in cultured chick neurons
Authors: Hogan M. V. , Saito M. , Rosenberg A. 
Published: January 2005

AbstractWe have examined the effects of monensin, a monovalent cationophore that disrupts exo‐ and endocytosis of membrane vesicles and diminishes Golgi anabolic function, on the incorporation of [3H]‐galactose into glycosphingolipids in neurited primary cultures of chick embryo central nervous system neurons. A linear rate of incorporation into all ganglioside species from extracellular‐‐labeled galactose was observed. Specific activity of anabolic labeling was markedly lower in GT1b and GQ1b than in the other major gangliosides of the embryonic neuron (GM3, GD3; GM2, GD2; GM1, GD1a, GD1b). With 100 nM monensin in the extracellular medium, the rate of labeling of GT1b diminished markedly to 20% of control; GD1a, GD1b, and GD2, to 35%; GQ1B to 48%; GD3 to 60%. Vigorous incorporation of label into GM3 was entirely undiminished by monesin. From these findings, it is suggested that ganglioside biosynthesis is compartmentalized in the cytodifferentiating embryonic neuron, with GM3 entirely, and GD3 and GQ1b partially, an extra‐Golgi product. Extensive loss of neurites that occurred after several hours of exposure of the neurons to monensin could not be correleated directly with decreased ganglioside anabolism.
Phosphofructokinase in the rat nervous system: Regional differences in activity and characteristics of axonal transport
Authors: Oblinger M. M. , Foe L. G. , Kwiatkowska D. , Kemp R. G. 
Published: January 2005

AbstractThe distribution of phosphofructokinase (PFK) in gray and white matter regions of the rat nervous system was evaluated. Determinations of PFK activity revealed that cell body enriched regions (sensorimotor cortex) had a significantly higher level of activity than axonal regions (sciatic nerve, dorsal roots, and optic nerve). The level of PFK activity was also significantly higher in central axons (optic nerve) than in peripheral axons (sciatic nerve). Differences in PFK activity could be largely attributed to differences in tissue content of the enzyme rather than to differences in the types of PFK isozymes present. Cortex contained significantly larger amounts of PFK relative to total protein than did peripheral nerve. However, purification of PFK revealed that all three of the PFK isozymes, C (86 kd), A (84 kd), and B (80 kd), were present in both cortex and sciatic nerve. Both SDS/PAGE and immunoblotting studies using PFK isozyme‐specific antibodies demonstrated that the relative proportions of the three PFK isozymes were similar in cell body and axonal regions of the nervous system. The PFK‐C and PFK‐A isozymes each comprised about half the total and only small amounts of the PFK‐B isozyme were present in both regions. However, immunoprecipitation experiments suggested that quantitatively different proportions of the possible PFK hybrids (tetramers) may be distributed between axonal and cell body regions. The transport of PFK was examined in this study and PFK was identified in slow component b (SCb) of axonal transport. SCb moves at a rate of 2–4 mm/day in rat axons and is known to contain several other enzymes of intermediary metabolism as well as actin. The finding that PFK, the rate limiting enzyme in glycolysis, is present in SCb lends support to the hypothesis that glycolytic enzymes are not freely diffusing proteins in axons but, instead, are present as organized assemblies that have long‐term, yet flexible, associations with structural elements of the cytoplasm.
Insulin/insulin‐like growth factor I and other epigenetic modulators of myelin basic protein expression in isolated oligodendrocyte progenitor cells
Authors: Saneto R. P. , Low K. G. , Melner M. H. , de Vellis J. 
Published: January 2005

AbstractThe expression of myelin basic protein by the oligodendrocyte is an integral event in the maturation of central nervous sytem function. Although much is known concerning the various myelin basic protein species, their temporal expression, and processing of RNA transcripts, little is known about the epigenetic factors responsible for the regulation of myelin basic protein (MBP) expression. In this study, we present evidence that insulin/insulin‐like growth factor‐I can increase the levels of MBP protein in isolated oligodendrocyte progenitor cells cultured in a serumless, chemically defined medium (ODM). Insulin was found to increase MBP protein in a dose‐responsive manner, reaching a maximal level at 72 hr of exposure. Both insulin‐like growth factor‐I (IGF‐I) and insulin were demonstrated to have no effect on MBP RNA levels. These data indicate that insulin/IGF‐I increased MBP protein levels at a level distal to transcription The dose response of insulin action suggests that it may have a MBP regulatory function, distinct from IGF‐I. When added individually, the other supplements of ODM, transferrin (500 ng/ml), and basic fibroblast growth factor (5 ng/ml) had no effect on MBP expression. However, when all three components were combined, a synergistic effect resulting in increased MBP protein and total RNA levels was found. The phorbol ester 12‐O‐tetradecanoyl phorbol acetate was found to reduce intracellular MBP RNA levels. The cAMP analogue/dibutyryl cAMP had contrasting effects on MBP RNA levels; no effect occurred in cultures grown in fetal calf serum, but a reduction in RNA levels was found in cultures grown in ODM. These data suggest that only a select range of extrinsic factors may be involved in MBP regulation, and depending on the environmental milieu, epigenetic agents may modulate gene activity differently.
Differential expression of galactocerebroside, myelin basic protein, and 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase during development of oligodendrocytes in vitro
Authors: Knapp P. E. , Skoff R. P. , Sprinkle T. J. 
Published: January 2005

AbstractThis paper describes the differential expression and localization of myelin components within membrane sheets produced by oligodendrocytes in vitro. In double‐labeling experiments using antibodies to the myelin antigens 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNP) and galactocerebroside (GC), the two antigens were coexpressed in at least 95% of oligodendrocytes at all ages examined. A small population of relatively undifferentiated cells expressed one antigen before the other. Within the membrane sheets produced by the cultured cells, CNP and GC are distributed differently. CNP is highly concentrated in cell bodies, in a network of processes extending from the cell body into the sheets, and around the perimeter of the sheets. CNP staining cannot be detected in some areas within the body of the sheet. When present, it is of low intensity. Under our labeling conditions, GC staining is found throughout the membrane sheets, except in the network of veins which are CNP+. GC and myelin basic protein (MBP) staining are seen in similar membrane domains even though GC is a surface component while MBP resides on the cytoplasmic face.Both the timing and localization of CNP immunostaining show that CNP is as early a marker for oligodendrocytes as GC, and support the idea that CNP may play a structural role in the myelin membrane. Double‐labeling studies with GC and CNP antibodies also show that the true shape of a cell and the extent of its development are not always revealed by a single antigen. The differential distribution of antigens within membrane sheets illustrates that they contain areas of structural specialization that may reflect the situation in intact myelin.
Peripheral motoneuron interactions with laminin and schwann cell‐derived neurite‐promoting molecules: Developmental regulation of laminin receptor function
Authors: Tomaselli K. J. , Reichardt L. F. 
Published: January 2005

AbstractSchwann cells synthesize several neurite outgrowthpromoting molecules and localize them in either the extracellular matrix (ECM; e.g., laminin) or on the plasma membrane (e.g., L1/NgCAM and N‐cadherin). Neurite outgrowth by embryonic chick ciliary ganglion (CG) neurons in response to these Schwann cell molecules largely depends on several specific neuronal cell surface receptors: integrin β1‐class ECM receptors, L1/NgCAM, and N‐cadherin (Bixby et al.: Journal of Cell Biology 107:353–361 1988). To address whether neuronal ECM receptors are regulated independently of cell surface adhesion molecules, we studied the ability of dissociated CG neurons from different developmental ages to extend neurites rapidly on (1) substrates coated with the ECM glycoprotein laminin (either from Schwann cell‐conditioned medium or purified from the Engelbreth‐Holm Swarm sarcoma) or (2) the surfaces of Schwann cells or Schwannoma (RN22) cells. CG neurons gradually lost the ability between embryonic day 8 (E8) and E14 to attach to and extend neurites in an integrin‐dependent fashion on purified laminin or Schwann cellderived laminin. The inability of E14 CG neurons to respond to laminin was partially reversed after explantation for 2.5 days in vitro, which increased the percentage of responsive neurons approximately tenfold. E14 neurons remained capable of extending neurites rapidly on the surfaces of Schwann and Schwannoma cells. Thus, the inability of E14 neurons to respond to laminin reflects a specific loss of laminin receptor function, while other receptors, most likely N‐cadherin and L1/NgCAM, remain capable of promoting neurite outgrowth on Schwann cell surfaces. Since integrin β1‐class heterodimers have been shown to function directly as receptors mediating neuronal attachment and process outgrowth on laminin, our results imply that the expression or function of laminin‐binding integrin heterodimers is regulated during the development of CG neurons. The apparent loss of integrin receptor function occurs during the period when the axons of CG neurons innervate their targets. Substantial integrin receptor function is recovered when target contact is disrupted by explantation. Thus, the functions of integrin‐class receptors in CG neurons may be regulated by target contact.
A gradient molecule in developing rat retina: Expression of 9‐O‐acetyl GD3 in relation to cell type, developmental age, and GD3 ganglioside
Authors: Sparrow J. R. , Barnstable C. J. 
Published: January 2005

AbstractIn the embryonic and postnatal rat retina a cell surface antigen that is detected by monoclonal antibody JONES is distributed in a dorsoventral gradient. Biochemical analysis has determined that the antigen is a modified ganglioside, 9‐O‐acetyl GD3. In the present study, the distributions of 9‐O‐acetyl GD3 and its possible precursor GD3 in developing rat retina were compared immunocytochemically using specific monoclonal antibodies JONES and R24. On embryonic day 13 (E13) immunoreactivity to JONES was localized to central retina; however, R24 stained throughout the retinal epithelium. By E20, when JONES binding was distributed in a gradient along the dorsoventral axis, R24 again stained dorsal and ventral regions with uniform intensity. Analysis of freshly dissociated retinal cells further revealed that GD3 and 9–O‐acetyl GD3 expressions do not necessarily coincide. At E15 and postnatal day 2 (PN2), the majority of cells (78 and 92%, respectively) were immunolabeled by antibody to GD3, while between E15 and PN2 the percentage of cells immunolabeled by antibody to 9–O‐acetyl GD3 rose from 19 to 68%. By PN4, labeling decreased for both molecules; however, the rate of decline in 9–O‐acetyl GD3 labeling was more pronounced. Regulation of the numbers of JONES‐positive cells does not appear to depend on interaction with the extraretinal environment, for in neural retina explanted at E15 the proportions of 9–O‐acetyl GD3–bearing cells was found to be similar to the percentage observed in neural retina developing to an equivalent age in vivo. Experiments to identify the retinal cell types bearing 9‐O‐acetyl GD3 revealed that it is expressed by both neurons and glia growing in monolayer cultures of rat perinatal neural retina. Examination of freshly dissociated retinal cells following simultaneous labeling for some specific cell types and 9–O‐acetyl GD3 demonstrated that the latter determinant is present on photoreceptor, amacrine, and ganglion cells. For each neuronal cell type, however, not all of the cells were immunoreactive with JONES.We conclude that the differences in the percentages of JONES‐ and R24‐positive cells, and in particular the different rates at which JONES and R24 staining declined with age, indicate that the expression of the JONES epitope is regulated with some independence from parent ganglioside GD3. In addition, since JONES is expressed on a variety of retinal cells, both neurons and glia, and since the rate of decline in proportions of JONES‐labeled cells was found to be the same for at least two neuronal cell types, regulation of the expression of the JONES epitope, in keeping with its dorsoventral gradient of distribution, is probably not based on cell type.
Regulation of Schwann cell nerve growth factor receptor by cyclic adenosine 3′,5′‐monophosphate
Authors: Mokuno K. , Sobue G. , Reddy U. R. , Wurzer J. , Kreider B. , Hotta H. , Baron P. , Ross A. H. , Pleasure D. 
Published: January 2005

AbstractPrevious studies indicated that Schwann cells in immature nerves express nerve growth factor (NGF) receptors, and that this expression is down regulated during development but re‐induced by Wallerian degeneration. It was also shown that immature Schwann cells are induced to express galactocerebroside and other molecules characteristic of mature Schwann cells by either contact with an axon or treatment with the cyclic adenosine 3′,5′‐monophosphate (cAMP) analogues dibutyryl cAMP (dbcAMP) and 8‐bromo cAMP or the adenylate cyclase activator forskolin. In the present study, NGF receptors on the surface of cultured Schwann cells were demonstrated by binding of an anti‐rat NGF receptor monoclonal antibody or of radioiodinated NGF. Treatment of cultured Schwann cells with cAMP analogues or forskolin resulted in a progressive decrease in both immunoreactive NGF receptors and radioiodinated NGF binding. The cultured Schwann cells contained a polyadenylated RNA species homologous with human melanoma NGF receptor mRNA in sequence and size. The amount of this NGF mRNA was lower in cAMP analogue‐treated than in untreated Schwann cells.
Role of protein kinase C in glial cell proliferation
Authors: Bhat N. R. 
Published: January 2005

AbstractPhorbol 12‐myristate 13‐acetate (PMA) has been shown to stimulate DNA synthesis and cell proliferation in a population of glial cells isolated from newborn rat brain. The non‐tumor promoter 4α‐phorbol 12,13‐didecanoate (4α‐PDD), on the other hand, was without an effect. The cultures treated with PMA displayed an extensive process formation and an increase in cell content. The tumor promoter‐induced [3H]thymidine incorporation into acid‐precipitable material was completely blocked by 1‐(5‐isoquinolinylsulfonyl)‐2‐methylpiperazine (H‐7), a potent inhibitor of protein kinase C (PKC), thereby suggesting a role for PKC in the control of DNA synthesis in glial cells. Subcellular fractionation and in vitro assay of PKC activity revealed a translocation of the enzyme from cytosol to particulate fraction in PMA‐treated cultures.
Neurotoxic effect induced by quinolinic acid in dissociated cell culture of mouse hippocampus
Authors: Khaspekov L. , Kida E. , Victorov I. , Mossakowski M. J. 
Published: January 2005

AbstractQuinolinic acid (QUIN), an endogenous convulsant that is a product of tryptophan metabolism, is suggested to belong to the pathogenic factors in some neurodegenerative disorders of the central nervous system (CNS). The aim of the present study was to evaluate the effect of QUIN on hippocampal nerve cells in dissociated cell culture at different periods of its development in vitro. The neurodegenerative effect of QUIN in vitro was found 1.5 to 2 hr after exposure to QUIN (500 μM) in differentiated hippocampal culture 20–21 days in vitro (DIV). The cytotoxic action depended on the nature of the interneuronal relations established in culture and on the period of neuronal development in vitro. Neurons in 11‐DIV cultures were undamaged even 10 days after exposure to QUIN; nor were the individual, isolated neurons probably not connected synaptically with the other ones in 20–21 DIV cultures. Ultrastructural analysis of 20–21 DIV cultures exposed to QUIN showed acute swelling and destruction of postsynaptic elements and severe degeneration of individual nerve cells located in cellular aggregates, whereas presynaptic axon terminals remained intact. The results emphasize the utility of QUIN as a tool to model degenerative changes of CNS and confirm the participation of mature synaptic junctions in QUIN neurotoxicity.
Compartmentalization of acetylcholinesterase in the chick retina
Authors: Ramírez G. , Barat A. , Donoso J. A. , Fernández H. L. 
Published: January 2005

AbstractUsing selective inhibitor treatments, we have studied the distribution of asymmetric (A) and globular (G) forms of acetylcholinesterase (AChE) in the extra‐ and intracellular compartments of chick retina, a specialized region of chick central nervous system (CNS). Our results show that the chick retinal collagen‐tailed AChE (an example of class II asymmetric molecular forms) is essentially an extracellular form of the enzyme; this is the first demonstration of the extracellular localization of asymmetric AChE in the vertebrate CNS. The active site of most of the hydrophobic, membrane‐bound G4‐form is also exposed to the external environment. In turn, the smaller molecular weight G‐forms (G2 and G1) are localized within the cells, where they may represent intermediate components in the assembly or degradation of the more complex enzymatic molecular species.Histoenzymatic ultrastructural techniques show internal AChE in amacrine as well as in ganglion cell bodies, and external enzyme, specifically associated with synapses and axons, in the inner plexiform layer. The probable cooperation of the extracellular A12‐forms and the membrane‐bound G species (mainly G4) of the enzyme to the hydrolysis of acetylcholine (ACh) released into the external compartment is suggested and discussed.
A volume‐dependent, chloride—sensitive component of taurine release stimulated by potassium from retina
Authors: Domínguez L. , Montenegro J. , Pasantes‐Morales H. 
Published: January 2005

AbstractChick retinas exposed to 56 mM KCl showed marked swelling of cells and synaptic structures, detected by morphological examination as well as by measurements of cell water content. Retinal cell swelling is prevented by omission of chloride. Potassium chloride, 56 mM, elicited the efflux of [3H]taurine by a process that is partly calcium‐dependent, highly chloride‐dependent (80%), and sensitive to furosemide. The release of [3H]dopamine under the same conditions is completely calcium‐dependent and increases in the absence of chloride. The chloride‐dependent component of [3H]taurine efflux seems related to increases in volume changes since it is markedly reduced when cell swelling is prevented either by maintaining constant the K × Cl product (Donnan equilibrium) or by making the solution hypertonic with mannitol. Omission of calcium and of chloride showed additive effects, practically suppressing the potassium‐stimulated release of taurine. These results suggest that the potassium‐stimulated efflux of [3H]taurine consists of a large component associated to changes in cell volume and a small component probably related to the depolarizing effects of potassium.