bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ontogeny of corticotropin releasing hormone gene expression in rat hypothalamus — comparison with somatostatin
Authors: Baram Tallie Z. , Lerner Stephen P. 
Published: April 2003

AbstractUsing in situ hybridization histochemistry, corticotropin‐releasing hormone gene expression is first detectable in the parvocellular portion of the rat paraventricular nucleus on the 17th fetal day. The prevalence of messenger RNA for corticotropin releasing hormone decreases perinatally, specifically between the 19th and 21st fetal days. By the 4th postnatal day, CRH gene expression is similar to that of the adult rat. Somatostatin messenger‐RNA is detectable on the 14th fetal day in the periventricular nucleus. No perinatal hiatus in somatostatin gene expression is evident.
Effects of selective inhibition of protein kinase C, cyclic AMP‐dependent protein kinase, and Ca2+‐calmodulin‐dependent protein kinase on neurite development in cultured rat hippocampal neurons
Authors: Cabell Leigh , Audesirk Gerald 
Published: April 2003

AbstractA variety of experimental evidence suggests that calmodulin and protein kinases, especially protein kinase C, may participate in regulating neurite development in cultured neurons, particularly neurite initiation. However, the results are somewhat contradictory. Further, the roles of calmodulin and protein kinases on many aspects of neurite development, such as branching or elongation of axons vs dendrites, have not been extensively studied. Cultured embryonic rat hippocampal pyramidal neurons develop readily identifiable axons and dendrites. We used this culture system and the new generation of highly specific protein kinase inhibitors to investigate the roles of protein kinases and calmodulin in neurite development. Neurons were cultured for 2 days in the continuous presence of calphostin C (a specific inhibitor of protein kinase C), KT5720 (inhibitor of cyclic AMP‐dependent protein kinase), KN62 (inhibitor of Ca2+‐calmodulin‐dependent protein kinase II), or calmidazolium (inhibitor of calmodulin), each at concentrations from approximately 1 to 10 times the concentration reported in the literature to inhibit each kinase by 50%. The effects of phorbol 12‐myristate 13‐acetate (an activator of protein kinase C) and 4α‐phorbol 12,13‐didecanoate (an inactive phorbol ester) were also tested.At concentrations that had no effect on neuronal viability, calphostin C reduced neurite initiation and axon branching without significantly affecting the number of dendrites per neuron, dendrite branching, dendrite length, or axon length. Phorbol 12‐myristate 13‐acetate increased axon branching and the number of dendrites per cell, compared to the inactive 4α‐phorbol 12,13‐didecanoate. KT5720 inhibited only axon branching. KN62 reduced axon length, the number of dendrites per neuron and both axon and dendrite branching. At low concentrations, calmidazolium had no effect on any aspect of neurite development, but at high concentrations, calmidazolium inhibited every parameter that was measured (including viability).These results suggest that these three protein kinases selectively modulate different aspects of neurite development. The universality of effects caused by calmodulin inhibition make it impossible to determine if there are specific targets of calmodulin action involved in neurite development. Finally, our data indicate that some superficially similar characteristics of neuronal differentiation, such as neurite initiation and branching, may be controlled by quite different molecular mechanisms.
Influence of culture substrata on the differentiation of advanced passage glial cells in cultures from aged mouse cerebral hemispheres
Authors: Kozlova Marina , Kentroti Susan , Vernadakis Antonia 
Published: April 2003

AbstractWe have previously reported that glial cells derived from aged mouse cerebral hemispheres (MACH) in primary cultures and after several passages consist of protoplasmic astrocytes (Type 1), differentiated stellate astrocytes (Type 2), a few oligodendrocytes and also glial precursors.4,33,34 In this study, we examined the influence of culture substrata: plastic, poly‐l‐lysine, laminin or collagen on the differentiation of MACH glial cells of advanced passages (P18–19) using glutamine synthetase (GS) and cyclic nucleotide phosphohydrolase (CNP) activity as biochemical markers for astrocytes and oligodendrocytes, respectively. Cultures were also examined morphologically using light microscopy. In general, GS activity was increased in cultures grown on the three chemical substrata versus plastic alone with the most striking effect being the 2‐fold increase observed in those cells grown in laminin. No differences were noted in CNP activity. Morphologically, proliferation of protoplasmic (Type 1) astrocytes was enhanced by culture day 2 on polylysine substratum and stellate differentiated (Type 2) astrocytes were noted on collagen. The striking feature in cultures grown on laminin was the presence of astrocytes with markedly long processes. Thus, morphological astrocyte differentiation appears to correspond to the increased GS activity. We propose that the extracellular matrix components such as collagen and laminin may play an important role in promoting glial precursors to differentiate into astrocytes.
A developmental study of lactate dehydrogenase isozyme and aspartate aminotransferase activity in organotypic rat hippocampal slice cultures and primary cultures of mouse neocortical and cerebellar neurons
Authors: Schousboe Inger , Tønder Niels , Zimmer Jens , Schousboe Arne 
Published: April 2003

AbstractThe development of enzyme activity and isozyme distribution of lactate dehydrogenase (LDH) was studied in murine organotypic hippocampal slice cultures and dissociated cultures of neocortical neurons and cerebellar granule cells and compared with that of the respective brain regions invivo. In the hippocampal slice cultures and the hippocampus invivo, the activity of aspartate aminotransferase (AAT) was also measured. During development in culture the specific activity of LDH increased in all types of cultures reaching values similar to that found in the corresponding brain areas invivo. However, significant differences in the isozyme distribution were observed between the preparations in vitro and invivo. During development invivo, the LDH isozyme pattern changed from a preferential M‐subunit composition to a preferential H‐subunit composition regardless of the brain area. This shift was not observed in the respective cultures where the M4‐isozyme prevailed at all culture periods examined accounting for 30–45% of the total LDH activity. The cultured cerebellar granule cells did not express the H4‐isozyme at all, while in the hippocampal slice cultures and the cultured neo‐cortical neurons this isozyme accounted for about 5% of the total LDH activity. The activity of AAT in the hippocampal organotypic slice cultures increased considerably during the culture period in parallel with the increase in AAT activity during postnatal development of hippocampus invivo. The activity of AAT in the slice cultures was, however, consistently lower than the corresponding activity invivo. The results show that perinatal hippocampal tissue and neurons from neocortex or cerebellum retain their immature LDH‐isoenzyme distribution when grown as organotypic slice cultures or dissociated cell cultures, respectively. This lack of shift from the M4 to the H4 LDH isozyme which is typical of tissues relying on aerobic glycolysis has several implications but does not apparently interfere with the otherwise normal differentiation of morphological, biochemical and electrophysiological characteristics of these preparations.
Combined pre‐ and postnatal ethanol exposure alters the development of bergmann glia in rat cerebellum
Authors: Shetty Ashok K. , Burrows Robert C. , Wall Kenneth A. , Phillips Dwight E. 
Published: April 2003

AbstractThe development and maturation of Bergmann glial cells in the rat cerebellum was evaluated on postnatal day 15 by glial fibrillary acidic protein (GFAP) immunocytochemistry, following combined gestational and 10‐day postnatal ethanol exposure (a full three trimester human equivalency). GFAP‐positive Bergmann glial fibers of lobules I, III, VIb, VII and X of the cerebellar vermis were examined and counted in the molecular layer (ML), the external granular layer (EGL) and the external limiting membrane (ELM). Ethanol exposure reduced: (1) the number of GFAP‐positive fibers (per unit length of folia surface) at all three levels; (2) the percentage of mature fibers; and (3) the cross‐sectional area in all lobules examined. When data from the five lobules were pooled, there were 7% fewer GFAP‐positive fibers in the ML, 15% fewer in the EGL and 20% fewer in the ELM; the percentage of mature fibers was reduced by 16%; and the cross‐sectional areas of lobules were reduced by 16%. The altered development of Bergmann glia could be one of the factors causing delayed migration of granular neurons and reductions in the number of granule cells reported in other studies following developmental ethanol exposures and could help to explain some of the motor dysfunctions reported in FAS victims.
Spatial control of neuronal cell attachment and differentiation on covalently patterned laminin oligopeptide substrates
Authors: Ranieri John P. , Bellamkonda Ravi , Bekos Evan J. , Gardella Joseph A. , Mathieu Hans J. , Ruiz Laurence , Aebischer Patrick 
Published: April 2003

AbstractThe spatial control of neuronal cell attachment and differentiation via specific receptor mediated interactions, may provide an effective means for the in vitro reconstruction of neuronal cell architecture. In this study, receptor‐specific oligopeptide sequences derived from the extracellular matrix (ECM) molecule laminin, a potent neural cell attachment and differentiation promoter were covalently bound on fluorinated ethylene propylene (FEP) films. The degree of receptor‐specific cell attachment and the ability to spatially control neurite outgrowth by covalently patterning the oligopeptide sequences on the FEP film surface were assessed.FEP films were first chemically activated with a Radio Frequency Glow Discharge (RFGD) process that covalently replaces the surface fluorine atoms with reactive hydroxyl groups. Oligopeptides containing the YIGSR sequence from the B1 chain of laminin and the water soluble oligopeptide containing the IKVAV sequence (CSRARKQAASIKVAVSADR) from the A chain were covalently bound to the hydroxylated FEP films. Electron Spectroscopy for Chemical Analysis (ESCA) verified the covalent attachment of the oligopeptides to the material surface.The degree of receptor mediated NG108‐15 cell attachment on immobilized CDPGYIGSR films was determined using competitive binding media. A 78% reduction in cell attachment was observed on films containing CDPGYIGSR in the cell plating medium. Only a 23% reduction in cell attachment was noted on films plated in medium containing a mock CDPGYIGSK sequence. FEP films immobilized with the IKVAV oligopeptide sequence were shown to mediate PC12 cell attachment and a competitive binding medium also significantly attenuated cell attachment on the immobilized films.The spatial patterning of these oligopeptide sequences to the FEP surface was shown to localize cell attachment and neurite extension on the patterned pathways. The surrounding unmodified FEP surface was inhibitory in serum containing medium and prevented cellular interactions outside the oligopeptide modifications. The spatial immobilization of laminin oligopeptides on FEP films provides a means to organize the attachment and differentiation of neuronal cells in a receptor‐specific manner.
Leptomeningeal and skin fibroblasts: Two different cell types?
Authors: Colombo J.A. , Napp M.I. , Puissant V. 
Published: April 2003

AbstractLeptomeningeal and skin fetal (E16‐17) fibroblasts were subcultured in vitro either in DMEM/F12 basal medium (with or without 10% FCS) or in astroglial conditioned medium (ACM). Both populations were characteristically composed of flat, undifferentiated, fibronectin(+), GFAP(‐)cells where cultured in fetal serum supplemented basal media. When exposed to ACM leptomeningeal cells developed a population of thin, elongated, fibronectin(+) cells with radial type long processes while skin fibroblasts did not show significant changes in their characteristic morphotype. Exposure to db cAMP in basal medium resulted within 3 hr in their transformation to an astrocytic‐like morphotype characterized by a condensed soma and multiple, short processes. Twenty‐four hours later skin fibroblasts had returned to their flat appearance while leptomeningeal ones showed elongated, radial‐like forms. Results indicate the possible existence of different receptors (to ACM factors) and/or cytoskeletal properties, and suggest that ACM‐reactive fibroblasts of leptomeningeal origin represent a different cell type from those of skin origin. The hypothetical role of leptomeningeal cells during brain development is considered.
Kinetic studies on the inhibition of creatine kinase activity by branched‐chain α‐amino acids in the brain cortex of rats
Authors: Pilla Carmen , de Oliveira Cardozo Rui Felipe , Dornelles Paula Karine Barcelos , Dutra‐Filho Carlos Severo , de Souza Wyse Angela Terezinha , Wajner Moacir , Wannmacher Clóvis Milton Duval 
Published: April 2003

AbstractMaple syrup urine disease (MSUD) is a metabolic disorder biochemically characterized by the accumulation of branched‐chain α‐amino acids (BCAA) and their branched‐chain α‐keto acids (BCKA) in blood and tissues. Neurological dysfunction is usually present in the patients, but the mechanisms of brain damage in this disease are far from be understood. The main objective of this study was to investigate the mechanisms by which BCAA inhibit creatine kinase activity, a key enzyme of energy homeostasis, in the brain cortex of 21‐day‐old Wistar rats. For the kinetic studies, Lineweaver–Burk and a modification of the Chevillard et al. plots were used to characterize the mechanisms of enzyme inhibition. The results indicated that BCAA inhibit creatine kinase by competition with the substrates phosphocreatine and ADP at the active site. Considering the crucial role creatine kinase plays in energy homeostasis in brain, if these effects also occur in the brain of MSUD patients, it is possible that inhibition of this enzyme activity may contribute to the brain damage found in this disease. In this case, it is possible that creatine supplementation to the diet might benefit MSUD patients.
The impact of firm size on bank debt use
Authors: Hooks Linda M. 
Published: April 2003

AbstractI use a sample of US firms to examine the determinants of the concentration of bank debt in total debt. The results indicate that the factors vary by size of the firm. A small‐ to medium‐sized firm has a high concentration of bank debt when it has a low level of discretionary spending. In contrast, a large firm has a high concentration of bank debt when it is difficult for outsiders to observe. The results support the Diamond [J Polit Econ 99 (1991) 689] reputation view that a firm faces different debt choices as it grows. When evaluating bank regulations, policymakers should consider the importance of the reputation‐building services, which a bank provides to businesses.
pH Dependence of structural stability of interleukin‐2 and granulocyte colony‐stimulating factor
Authors: Ricci Margaret Speed , Sarkar Casim A. , Fallon Eric M. , Lauffenburger Douglas A. , Brems David N. 
Published: April 2003

AbstractAfter a cytokine binds to its receptor on the cell surface (pH ∼7), the complex is internalized into acidic endosomal compartments (pH ∼5–6), where partially unfolded intermediates can form. The nature of these structural transitions was studied for wild‐type interleukin‐2 (IL‐2) and wild‐type granulocyte colony‐stimulating factor (G‐CSF). A noncoincidence of denaturation transitions in the secondary and tertiary structure of IL‐2 and tertiary structural perturbations in G‐CSF suggest the presence of an intermediate state for each, a common feature of this structural family of four‐helical bundle proteins. Unexpectedly, both IL‐2 and G‐CSF display monotonic increases in stability as the pH is decreased from 7 to 4. We hypothesize that such cytokines with cell‐based clearance mechanisms in vivo may have evolved to help stabilize endosomal complexes for sorting to lysosomal degradation. We show that mutants of both IL‐2 and G‐CSF have differential stabilities to their wild‐type counterparts as a function of pH, and that these differences may explain the differences in ligand trafficking and depletion. Further understanding of the structural changes accompanying unfolding may help guide cytokine design with respect to ligand binding, endocytic trafficking, and, consequently, therapeutic efficacy.
Compensation Increase in Organic Anion Excretion in Rats with Acute Biliary Obstruction: Role of the Renal Organic Anion Transporter 1
Authors: Brandoni Anabel , Quaglia Nora B. , Torres Adriana M. 
Published: April 2003

The purpose of the present study was to examine in rats the effects of acute bile duct ligation on the expression of the organic anion transporter 1 in the kidney and the consequences of these effects on the systemic clearance of organic anions, particularly on <i>p</i>-aminohippurate (PAH) clearance, since it has been viewed as the prototypic organic anion. Male Wistar rats underwent bile duct ligation (BDL rats). Pair-fed sham-operated rats served as controls. All studies were carried out 21 h after surgery. Our data revealed that BDL rats had a higher expression of organic transporter 1 protein in kidney cortex homogenates. Accordingly, systemic clearance of PAH and urinary excretion of PAH were both higher in BDL rats. These findings suggest that impairment of the liver function after BDL is followed by a distinct and statistically significant increase in renal excretion of PAH, indicating a possible compensation mechanism.
Levofloxacin Kills <i>Chlamydia pneumoniae</i> and Modulates Interleukin 6 Production by HEp-2 Cells
Authors: Baltch Aldona L. , Smith Raymond P. , Ritz William J. , Carpenter-Knaggs Andrea , Michelsen Phyllis B. , Carlyn Cynthia J. , Bopp Lawrence H. , Hibbs Jonathan R. 
Published: April 2003

<i>Background:</i><i>Chlamydia pneumoniae</i> is known to cause acute respiratory infection and more recently it has been studied as a pathogen causing inflammatory changes in chronic diseases such as atherosclerosis. This study addresses the antichlamydial effect of levofloxacin and its role in modulation of a proinflammatory cytokine IL-6 production by uninfected and infected HEp-2 cells. <i>Methods:</i> HEp-2 cell monolayers were infected with previously prepared and frozen aliquots of <i>C. pneumoniae</i> [1 × 10<sup>3</sup> inclusion-forming units (IFU)/ml] by centrifugation for 30 min and incubation at 37°C for 1 h. Infected monolayers were treated with levofloxacin (3 or 8 µg/ml) immediately after infection (0 h) or 24 h after infection. Monolayers were examined daily for 96 h after infection by counting inclusions with fluorescently labeled antichlamydial monoclonal antibody. Aliquots of disrupted monolayers were titrated to determine the numbers of viable <i>C. pneumoniae</i> IFU/ml. IL-6 concentrations in cell supernatants were determined by ELISA assays. <i>Results:</i> Infected HEp-2 cells produced IL–6. Noninfected HEp-2 cells demonstrated modulation of IL-6 production by levofloxacin. No viable <i>C. pneumoniae</i> were detected in infected HEp-2 cells when the monolayer was treated with levofloxacin immediately after infection (0 h). In contrast, when cells were treated 24 h after infection, a gradual decline in the number of viable <i>C. pneumoniae</i> occurred; by 96 h into the assay ≧98% of <i>C. pneumoniae</i> were killed. IL-6 concentrations were similar in the supernatants of levofloxacin-treated and nontreated HEp-2 cells. <i>Conclusions:</i> (1) Levofloxacin is effective in eliminating <i>C. pneumoniae</i> from infected HEp-2 cells; (2) although levofloxacin modulates the production of IL-6 in untreated HEp-2 cells, no evidence for such modulation was observed in HEp-2 cells infected with <i>C. pneumoniae</i>. (3) Presence of viable <i>C. pneumoniae</i> may not be necessary for IL-6 production by infected and treated HEp-2 cells.
Success and Failure Suppressing Reflexive Behavior
Authors: Curtis Clayton E. , D'Esposito Mark 
Published: April 2003

Abstract
The dynamic interplay between reflexive and controlled determinants of behavior is one of the most general organizing principles of brain function. A powerful analogue of this interplay is seen in the antisaccade task, which pits reflexive and willed saccadic mechanisms against one another. Event-related functional magnetic resonance imaging of the human brain showed greater prestimulus preparatory activity in the pre-supplementary motor area before voluntary antisaccades (saccades away from a target) compared with reflexive prosaccades (saccades to a target). Moreover, this preparatory activity was critically associated with reflex suppression; it predicted whether the reflex was later successfully inhibited in the trial. These data illustrate a mechanism for top-down control over reflexive behavior.
Lexical and Sublexical Components of Age-related Changes in Neural Activation during Visual Word Identification
Authors: Whiting Wythe L. , Madden David J. , Langley Linda K. , Denny Laura L. , Turkington Timothy G. , Provenzale James M. , Hawk Thomas C. , Coleman R. Edward 
Published: April 2003

Abstract
Positron emission tomography data (Madden, Langley, et al., 2002) were analyzed to investigate adult age differences in the relation between neural activation and the lexical (word frequency) and sublexical (word length) components of visual word identification. The differential influence of these components on reaction time (RT) for word/nonword discrimination (lexical decision) was generally similar for the two age groups, with word frequency accounting for a greater proportion of lexical decision RT variance relative to word length. The influence of word length on RT, however, was relatively greater for older adults. Activation in regions of the ventral occipito-temporal cortex was related to the RT changes associated with word frequency and length for older adults, but not for younger adults. Specifically, older adults' frequency effects were related to activation in both anterior (Brodmann's area [BA] 37) and posterior (BAs 17 and 18) regions of the occipito-temporal pathway, whereas word length effects were only associated with posterior activation (BA 17). We conclude that aging affects the neural mechanisms supporting word identification performance although behavioral measures of this ability are generally constant as a function of age.