bluuebunny/crossref_metadata_2025_split huggingface dataset:
The orienting response to brief auditory stimuli in preweanling and adult rats
Authors: Richardson Rick , Hess Maureen , Campbell Byron A. 
Published: January 2005

AbstractThe cardiac orienting response to brief auditory stimuli was measured in preweanling and adult rats. The eliciting stimulus varied in duration (2 or 10 s) and complexity (continuous or pulsing). Stimulus complexity affected response magnitude with the pulsing stimulus eliciting a larger response than the continuous stimulus. Stimulus duration affected response persistence but only when a pulsing stimulus was used. In contrast to recent research with stimuli of much longer duration, age did not significantly affect any aspect of the cardiac response to the novel auditory stimuli in the present study. These results are discussed in terms of (1) the effects of stimulus duration on the heart‐rate component of the orienting response and (2) two‐stage models of attention.© 1994 John Wiley & Sons, Inc.
Specific postnatal auditory stimulation interferes with species‐typical visual responsiveness in bobwhite quail chicks
Authors: McBride Thomas , Lickliter Robert 
Published: January 2005

AbstractThe effects that a manipulation of sensory experience may have on perceptual development are likely to depend on a number of factors, including the amount and the type of stimulation provided. To examine the relative influence of these stimulation factors on early perceptual organization, this study exposed bobwhite quail hatchlings to augmented amounts of bobwhite chick distress calls, bobwhite chick contentment calls, domestic chicken distress calls, or no additional auditory stimulation during the first 72 hr following hatching. Results showed that bobwhite hatchlings exposed to bobwhite chick distress calls do not exhibit species‐typical visual responsiveness to maternal cues. In contrast, bobwhite hatchlings exposed to bobwhite chick contentment calls, domestic chicken hatchling distress calls, or no agumented auditory stimulation exhibited species‐typical auditory and visual responsiveness to maternal cues. These results demonstrate intermodal effects of postnatal sensory stimulation and suggest that specific types of postnatal auditory stimulation, rather than simply increased amount of stimulation, are necessary to interfere with species‐typical intersensory functioning.© 1994 John Wiley & Sons, Inc.
No‐difference research
Authors: Yeaton William H. , Sechrest Lee 
Published: January 2005

AbstractBecause no‐difference research has been relatively unexplored by evaluators, a series of empirical studies was conducted. In this chapter distinguishing characteristics of no‐difference research are examined, its acceptance by the research community is probed, and possible strategies for conducting no‐difference studies are discussed. The centrality of no‐difference findings within the experimental and non‐experimental paradigms is also discussed.
State evaluation in an executive environment: Policy research meets political reality
Authors: Mahone John A. , Corbin‐Howerton Lin 
Published: January 2005

AbstractThe Virginia Department of Planning and Budget's evaluation section was created in 1983 to conduct program evaluations and special studies for the governor, the governor's secretaries, and the legislature. Consisting of nine evaluation analysts, an assistant, and a manager, the section functioned on a budget of approximately $450,000 in fiscal year 1986–87. By the close of that year, the section had completed more than thirty reports that influenced major decisions about program funding, staffing, and policy direction within each of the state government's functional areas.
Business perspectives on internal/external evaluation
Authors: Cummings Oliver W. , Nowakowski Jeri R. , Schwandt Thomas A. , Eichelberger R. Tony , Kleist Kimball C. , Larson Colleen L. , Knott Tara D. 
Published: January 2005

AbstractThe role of internal evaluators in large organizations continues to expand. Several difficult and complex issues related to evaluator functions are emerging. In this chapter these issues are reflected on by evaluators who represent multiple perspectives along the continuum of external to internal evaluation.
Transmittal letter: Program evaluation issues
Authors: Bowsher Charles A. 
Published: January 2005

AbstractIn November 1988, the comptroller general of the United States, Charles A. Bowsher, issued the report Program Evaluation Issues, which documented a serious decline in program evaluation capacity in the federal government. Reproduced below is his letter transmitting the report to the executive and legislative branches of government. The letter is significant because it is an unusually clear and forceful—and rare—statement of the essential role of program evaluation in government.
Strengthening causal interpretations of nonexperimental data: The role of meta‐analysis
Authors: Cordray David S. 
Published: January 2005

AbstractThe validity of results generated within any individual study are likely to be equivocal because of many threats to validity that cannot be tested directly. Using meta‐analysis, this chapter shows how it is possible to examine, empirically, the influence of between‐study differences in research designs, measures, intervention strategies, and contextual factors on various forms of validity of study results.
Issues in implementing a randomized experiment in a field setting
Authors: Devine Joel A. , Wright James D. , Joyner Laurie M. 
Published: January 2005

AbstractBecause of the differential perspectives, needs, and interests that undergird clinical and research objectives, program staff may wittingly or unwittingly sabotage randomization. A case study of the New Orleans Homeless Substance Abusers Program amply documents this process.
Astrocytes in the guinea pig, horse, and monkey retina: Their occurrence coincides with the presence of blood vessels
Authors: Schnitzer Jutta 
Published: January 2005

AbstractIn the present study the distribution of astrocytes in the nerve fiber layer (NFL) has been studied in the sparsely vascularized retinae of the guinea pig and horse and in the richly vascularized retina of the Old World monkey (Cercopithecus aethiops) using immunocytochemical methods. In the guinea pig retina glial fibrillary acidic protein (GFAP)‐positive astrocytes could not be detected. They were found, however, in the myelinated region of the optic nerve. The optic nerve head and a small retinal region immediately adjacent to it contained few vimentin‐positive astrocytes. Histological sections confirmed the restriction of astrocytes to a small retinal region and showed that this is also the only retinal area that is vascularized. Astrocytes showing GFAP and vimentin immunoreactivity were absent from most of the horse retina. They were found only in a narrow zone close to the optic disc, which is also the only region of the horse retina that is vascularized. Thus, as in the rabbit retina (Schnitzer: J. Comp. Neurol. 240:128–142, 1985), in the guinea pig and horse retina astrocytes are not present ubiquitously in the NFL but coexist with blood vessels. In the monkey retina, GFAP‐positive astrocytes were found ubiquitously in the NFL. Astrocytes were absent from the avascular foveal region only. It is suggested that the concurrence of retinal astrocytes and intraretinal vascularization may be a feature common to many, if not all, mammalian species.
Growth factors for human glial cells in culture
Authors: Yong Voon Wee , Kim Seung U. , Kim Myong W. , Shin Doo H. 
Published: January 2005

AbstractUsing a new double‐labeling immunofluorescence technique, we assessed various growth factors on their ability to promote proliferation of cultured human glial cells. Cells studied were fetal astrocytes, fetal Schwann cells, adult astrocytes, and adult oligodendrocytes. Effective agents for fetal astrocytes were glial growth factor from the bovine pituitary, platelet‐derived growth factor, fibroblast growth factor, and 4β‐phorbol 12, 13‐dibutyrate. For fetal Schwann cells, mitogens were glial growth factor from the bovine pituitary, platelet‐derived growth factor, nerve growth factor, and 4β‐phorbol 12, 13‐dibutyrate. Adult astrocytes and oligodendrocytes did not normally divide in culture, and none of the agents tested were effective in inducing their proliferation. The report that interleukin‐2 was a mitogen for oligodendrocytes could not be replicated in the present study on any of the glial cell types.
Tetanus toxin binding to isolated and cultured rat retinal glial cells
Authors: Huba Reiner , Hofmann Hans‐Dieter 
Published: January 2005

AbstractThe presence of immunocytochemically detectable membrane receptors for tetanus toxin, supposedly composed of higher gangliosides, is widely accepted as a marker of neuronal cells. We now demonstrate that Müller cells, a unique glial cell type of the vertebrate retina, possess specific tetanus toxin (TT)‐binding sites. Single cell suspensions were prepared from adult rat retina by a gentle dissociation method, and the Müller cells, unequivocally identified by their morphology, could be immunocytochemically double‐labeled by antisera to vimentin and to TT. The expression of complex gangliosides by identified Müller cells was also demonstrated by immunofluorescence labeling with the monoclonal antibody A2B5. Using the double‐immunolabeling method for the identification of Müller cells we show that specific tetanus toxin binding is acquired by these cells during postnatal maturation both in vivo and in vitro. In vivo the percentage of tetanus toxin‐positive Müller cells increases from 0% in 4‐day‐old animals to 10% on postnatal day 8, reaching the adult level of about 95–100% around day 30. In retinal monolayer cultures prepared from newborn rats, the majority (65%) of vimentin‐positive non‐neuronal cells became TT‐positive during a 2‐week culture period, indicating that this population of non‐neuronal cells represents differentiating Müller cells. Again, comparable results were obtained with A2B5, supporting the conclusion that Müllerian glia expresses surface molecules, which are normally regarded as neuronal markers.
Optical recording of electrical activity from axons and glia of frog optic nerve: Potentiometric dye responses and morphometrics
Authors: Konnerth A. , Orkand P. M. , Orkand R. K. 
Published: January 2005

AbstractVoltage‐sensitive dyes were used to study the changes in membrane potential in axons and glial cells of the frog optic nerve following electrical stimulation. The lack of a signal in the unstained nerve and the multiphasic action spectra after staining indicated that the optical responses were from the extrinsic dyes. Changes in dye absorption and fluorescence had rapid and slow phases. The rapid phases resulted from action potentials in myelinated and unmyelinated axons. The kinetics of the slow phase of the optical response were similar to the depolarization recorded from the glial cells with intracellular electrodes. The ratio of the amplitudes of the fast and slow phases was characteristic for each type of dye. Pharmacological analysis of the action potential of the unmyelinated axons revealed tetrodotoxin‐sensitive sodium channels and 4‐aminopyridine‐sensitive potassium channels. Repeated exposure of the stained preparation to light led to photodynamic damage as shown by a block of recovery of the glial depolarization. An electron microscopic morphometric study of the nerve was carried out in an effort to understand the contribution of the various anatomical elements to the compound optical response. The ratio of unmyelinated axon membrane to glial membrane was much greater than was the ratio of the fast and slow components of the signal, suggesting that the dyes either had a higher affinity for glial membrane or did not penetrate the nerve uniformly.
Lactate release from cultured astrocytes and neurons: A comparison
Authors: Walz Wolfgang , Mukerji Srimathie 
Published: January 2005

AbstractLactate released into the surrounding salt solution as well as the cellular lactate content were measured in cerebral primary cultures of mouse astrocytes and of mouse neurons. Any newly produced lactate was immediately released as lactic acid into the extracellular compartment via a lactate/proton cotransport. The astrocytic release was about 2,000 nmol × mg−1 × hr−1; the neuronal release was about 300 nmol × mg−1 × hr−1. However, if election transport was blocked with dinitrophenol, the neuronal lactate release was as high as the astrocytic one under normal conditions. High glucose (30 mM) and K+ (60 mM) increased lactate release of astrocytes but not of neurons. In contrast it was found that insulin (1 μM) exposure mainly stimulated neuronal lactate release rather than glial release. Adenosine stimulated both neuronal and glial release. Neither intracellular lactate content nor concentration changed significantly in either cell type under any conditions tested. The pathophysiological implications of these measurements are discussed.
Lactic acid inhibition of gap junctional intercellular communication in in vitro astrocytes as measured by fluorescence recovery after laser photobleaching
Authors: Anders Juanita J. 
Published: January 2005

AbstractLactic acid can permeate plasma membranes, causing intracellular acidosis. Gap junctions are sensitive to pHi and can be reversibly uncoupled by weak acids. In this study, dye coupling between in vitro astrocytes, presumably mediated by gap junctions, was measured in the absence and presence of lactic acid. Fluorescence recovery after laser photobleaching (gap‐FRAP analysis) was used to measure dye coupling. Astrocytes bathed in Eagle's minimum essential medium (EMEM) with lactic acid, pHo 5.5–6, showed no difference in their dye coupling (mean recovery of fluorescence 30%) when compared to control astrocytes (mean recovery of fluorescence 26%). However, 24 mM lactic acid in EMEM, pHo 4.5, decreased dye coupling (mean recovery of fluorescence 2.0%). This effect occurred within 5 min of treatment. When lactic acid‐EMEM, pH 4.5, was removed from astrocytes after 30 min and the cells were incubated in EMEM for 24 hr, decreased coupling was not reversed (mean recovery 4.0%). When lactic acid‐treated astrocytes were incubated in EMEM for 48 hr, the mean recovery of fluorescence increased to 15% (i.e., 42% of the recovery seen in controls). These observations suggest that brief exposure to high concentrations of lactic acid can have immediate and long‐lasting effects on glial gap junctional communication. Under pathological circumstances, such a sequence could be intiated, and this might impair astrocytic control of the central nervous system microenvironment mediated by spatial buffering.
Heterogeneity of potassium currents in cultured oligodendrocytes
Authors: Sontheimer H. , Kettenmann H. 
Published: January 2005

AbstractIn the present study we have analyzed the membrane currents of mature oligodendrocytes in cultures from dissociated fetal mouse cerebral hemispheres and explant cultures from fetal mouse spinal cord. Both types of oligodendrocytes showed large voltage‐dependent, but time‐independent inward and outward currents that were partially blocked by Ba2+. In addition, time‐ and voltage‐dependent inward and outward currents were observed in a minority of oligodendrocytes from spinal cord. All voltage‐dependent currents were completely blocked by Ba2+, and inward currents were completely blocked by Cs+, suggesting that they are mediated by K+ channels. Current‐voltage curves of mouse spinal cord oligodendrocytes varied from being linear to outwardly or inwardly rectifying. In contrast, oligodendrocytes cultured from mouse brain always showed an inward rectification of the current voltage relation and a lack of time‐dependent currents. It thus appears that mature oligodendrocytes in explant cultures of mouse spinal cord, in contrast to oligodendrocytes from dissociated brain, consist of different cell populations that are distinguished by their expression by their expression or active state of K+ channels.
Astroglial cells in vitro are heterogeneous with respect to expression of the α1‐adrenergic receptor
Authors: Lerea Leslie S. , McCarthy Ken D. 
Published: January 2005

AbstractA wide variety of approaches have been used to examine the expression of neuroligand receptors by cultured astroglial cells. The results of such studies make it clear that these cells exhibit most, if not all, of the different receptors known to be associated with central neurons. However, it has been more difficult to determine if there are multiple populations of astroglia that can be distinguished on the basis of their complement of neuroligand receptors. To address this question, we established a radioligand binding assay that enabled us to visualize α1‐adrenergic receptors (α1‐ARs) on immunocytochemically defined neural cells. Saturation, time course, and competition binding experiments determined that 125I‐HEAT could be used to identify α1‐AR binding sites on immunocytochemically defined astroglial cells. Our results indicate that approximately 66% of cortical polygonal astroglia express detectable numbers of α1‐ARs. 3H‐thymidine labeling experiments indicate that both dividing and nondividing astroglia exhibit α1‐ARs. These results greatly contrast with studies on β‐adrenergic receptor expression (β‐AR), in which 100% of polygonal astroglia express β‐ARs. Process‐bearing astroglia also exhibit α1‐ARs, which is in marked contrast to the lack of β‐AR expression by these cells. The results presented here suggest that astroglia, like neurons, differ in the receptors they express and therefore may be able to selectively respond to extracellular stimulation.
Myelination in the jimpy mouse in the absence of proteolipid protein
Authors: Duncan I.D. , Hammang J.P. , Goda S. , Quarles R.H. 
Published: January 2005

AbstractA point mutation in the gene for proteolipid protein (PLP) has been suggested to account for the dysmyelination seen in the jimpy mouse mutant. Despite the absence of PLP, the major integral membrane protein of central nervous system (CNS) myelin, this study shows that there are many scattered myelinated fibers present in the spinal cord of this murine mutant which are immunocytochemically positive for myelin basic protein (MBP), yet negative for PLP. This lack of PLP results in an abnormal compaction of the extracellular leaflets of the myelin sheath and the formation of an abnormal intraperiod line. These results are similar to those seen in another X‐linked myelin mutant, the myelin‐deficient rat (Duncan et al.: Proc. Natl. Acad. Sci. U.S.A., 84:6287–6291, 1987), and show that a multilamellar membrane can be formed in the absence of its major integral membrane protein.
Trauma‐induced proliferation of astrocytes in the brains of young and aged rats
Authors: Topp Kimberly S. , Faddis Brian T. , Vijayan Vijaya K. 
Published: January 2005

AbstractThe time‐course and magnitude of astrocyte proliferation following neural trauma was evaluated in young adult (3 months) and mid‐aged (16–19 months) male Fischer 344 rats. One to 4 days after a needle wound was made through the cortex and the hippocampus, rats received three intraperitoneal injections of 3H‐thymidine at 8 hour intervals and were sacrificed 1 hour after the last injection. For astrocyte quantification, 3H‐thymidine autoradiography was combined with immunohistochemical staining for glial fibrillary acidic protein followed by semithin sectioning. In areas of the cortex and hippocampus adjacent to the wound, astrocytes were categorized as unlabeled or labeled with silver grains over the nuclei. Labeling index and numerical density of astrocytes were determined using stereological methods. The results showed that in both young and older rats, astrocyte proliferation is an early glial response to neural trauma, occurring during the first 4 postlesion days and contributing to an increase in astrocyte population. Regional differences in labeling index and numerical density suggest heterogeneity in the proliferative capacity of astrocyte subpopulations in the rat brain. Compared with young animals, older rats demonstrated greater labeling in the cortex but not in the hippocampus. Thus, aging is associated with region‐specific increase in astrocyte reactivity to trauma possibly due to increased availability of mitogens or enhanced sensitivity of astrocytes to mitogenic signals.
Attempt to classify glial cells by means of their process specialization using the rabbit retinal Müller cell as an example of cytotopographic specialization of glial cells
Authors: Reichenbach Andreas 
Published: January 2005

AbstractThe rabbit retinal Müller cell is one of the most widely studied glial cell types, and it has all forms of contacts that a glial cell can express, viz. (1) to a (ventricular) fluid space, (2) to a mesenchymal borderline (basal lamina), and (3) to neuronal compartments. This cell demonstrates the local adaptation of cell processes to the microenvironment with which they are in contact. Summarizing available data on Müller cells and other glial cell types, it is concluded that the structure with which the process is in contact determines the type of glial cell process that develops. The type I process has microvilli, desmosome‐like junctions, and high Na+, K+‐ATPase activity; this type of process is in direct contact with a fluid such as cerebrospinal fluid. The type II endfoot‐bearing process contains gliofilaments and has a high K+ conductivity; this type of process is covered by a basal lamina and is in contact with mesenchyme. The type III sheath‐bearing process insulates neuronal compartments and expresses suitable membrane properties for glia‐neuronal communication. Since structurally similar processes have been shown to have similar physiological properties, a new systematic classification of glial cells is proposed, based on the presence or absence of defined types of cell processes. This approach is believed to provide new insights into the function of neuroglia in both the central and peripheral nervous systems, in vertebrates and invertebrates, and even during ontogenetic development.
Single channel potassium currents in cultured adult bovine oligodendrocytes
Authors: McLarnon James G. , Kim Seung U. 
Published: January 2005

AbstractThese studies have enabled the first characterization of the properties of ion channels in adult oligodendrocytes. Cell‐attached recordings from cultured adult bovine cells showed channel activity with 140 mM KCl in the patch pipette; the amplitude of the currents was increased with increasing membrane hyperpolarization. This channel, with a conductance of 29 pS, was selective for inward K+ current; little or no outward current was measured for large depolarizing voltage steps. The channel open time was strongly dependent upon membrane potential, with membrane hyperpolarization decreasing the mean open time 100‐fold over a range of 80 mV; at the resting potential of the cell the mean open time of the channel was in excess of 50 ms. Decreasing the concentration of K+ in the pipette diminished the channel conductance with no significant effect to alter the channel open time dependence on potential. The rectification and kinetic properties of the channel would be consistent with a physiological role for the channel in the regulation of external K+ near active neurons; in particular the effect of membrane depolarization to cause maintained channel open duration could be important when the driving force for inward potassium movement through oligodendrocyte membrane was low. Channels selective for outward potassium movement were seen with inside‐out excised patch recordings with symmetrical potassium concentrations across the patch; the density of these channels in the bovine membrane was low.