bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efferent Projections to the Host Brain from Intrastriatal Striatal Mouse‐to‐rat Grafts: Time Course and Tissue‐type Specificity as Revealed by a Mouse Specific Neuronal Marker
Authors: Wictorin K. , Lagenaur C. F. , Lund R. D. , Björklund A. 
Published: April 2006

AbstractThe developmental time‐course and growth characteristics of efferent graft‐to‐host projections were studied from mouse fetal striatal grafts (E13–14) implanted as a cell suspension into the ibotenate‐lesioned striatum of immunosuppressed adult rats. A cell surface monoclonal antibody specific for mouse neurons (M6) was used to identify the donor cells and their projections into the host brain. At 3–5 days after implantation, sparse fascicles of M6‐positive graft‐derived fibres extended for ∼0.3–0.4 mm across the graft‐host border into the surrounding host striatum. From the beginning they were selectively orientated in one direction, i.e. caudally along the myelinated fibre bundles of the internal capsule. At 8 days, the graft‐derived fibres were more numerous and more densely labelled. They ran in dense fascicles inside the myelinated bundles of the host internal capsule and reached the rostral host globus pallidus, a distance of ∼ 1.2 mm from the caudal tip of the graft. Two weeks after grafting, the M6‐positive fibre fascicles were clearly seen to branch within the globus pallidus to form terminal‐like networks. From this time onwards, the immunoreactivity of the outgrowing fibre fascicles gradually diminished, although small but dense terminal‐like networks could be found in the host globus pallidus in most, but not all, of the rats at longer survival times (3–15 weeks). This is consistent with previous work showing that outgrowing axons lose their M6 immunoreactivity as they mature and become myelinated. Control grafts of fetal neocortical and fetal cerebellar tissue were used to assess the tissue‐type specificity of the efferent fibre growth. The neocortical implants projected densely up to about 3 mm into the host brain, along the internal capsule and the corpus callosum and into the overlying cortex. By contrast, although the cerebellar grafts survived well, they showed very little efferent fibre growth. Double immunostaining for DARPP‐32 and M6 revealed that all M6‐positive fibre fascicles extending from the striatal (but not neocortical) grafts also showed DARPP‐32 positivity, and thus that it was the DARPP‐32‐positive regions of the striatal grafts that projected to the host brain. It is concluded that graft‐to‐host projections, running along and inside host myelinated bundles, are formed from intrastriatal striatal grafts within 1–2 weeks of implantation. Grafts of neocortical tissue grew well along the same trajectory, whereas neurons of a type not normally projecting along the internal capsule, i.e. cerebellum, failed to extend axons over any significant distance along this trajectory.
Two Promoters Direct Transcription of the Mouse NT‐3 Gene
Authors: Leingärtner Axel , Lindholm Dan 
Published: April 2006

AbstractThe structure of the mouse neurotrophin‐3 (NT‐3) gene has been analysed using genomic cloning and the rapid amplification of cDNA ends (RACE) method. The gene consists of two small upstream exons (exons IA and IB) and a larger downstream exon (exon II) that encodes the mature protein. Two classes of NT‐3 transcripts, termed transcripts A and B, are generated by alternative splicing of exon IA or exon IB to the common exon II. The NT‐3 gene also contains several transcription start sites in both upstream exons, and three different polyadenylation sites in exon II, as shown by RNase protection assays and by RACE, giving rise to multiple NT‐3 mRNA variants of slightly different lengths. Cerebellar granule neurons express both classes of NT‐3 transcripts, but only transcript B is regulated by tri‐iodothyronine (T3) in these neurons. The effect of T3 on NT‐3 mRNA is primarily due to transcription enhancement, as shown in nuclear run‐on experiments. The levels of NT‐3 mRNA are much lower in cultured mouse astrocytes and are undetectable in the human neuroblastoma cell line IMR 32. A TATA box is present in the upstream region of exon IB but not in that of exon IA. Promoter analysis using the chloramphenicol acetyltransferase reporter gene fused to different NT‐3 upstream regions showed the presence of two active NT‐3 promoters in cerebellar granule neurons. However, in IMR 32 cells, NT‐3 promoter activity decreased dramatically with increasing length of the 5′ flanking region. This suggests that expression of the NT‐3 gene is regulated both by positive influences, such as T3, and by negative silencing elements present in the upstream regions of the NT‐3 promoter.
Cellular and Subcellular Distribution of NMDAR1 Splice Variant mRNA in the Rat Lumbar Spinal Cord
Authors: Tölle T. R. , Berthele A. , Laurie D. J. , Seeburg P. H. , Zieglgänsberger W. 
Published: April 2006

AbstractThe regional distribution of alternatively spliced messenger RNA encoding the N‐methyl‐D‐aspartate (NMDA) receptor R1 subunit (NMDAR1) variants was examined by in situ hybridization in the rat lumbar spinal cord. Splice‐specific oligonucleotide probes [recognizing full‐length mRNA (NMDAR1‐1), deletion exon 21 (NMDAR1‐2), deletion exon 22 (NMDAR1‐3), combined deletion exons 21 and 22 (NMDAR1‐4) and mRNA which lacks (NMDAR1‐a) or contains exon 5 (NMDAR1‐b)] detected marked differences in abundance and distribution of N‐ and C‐terminal spliced variants. The NMDAR1‐a, NMDAR1‐2 and NMDAR1‐4 mRNAs were evenly distributed throughout all laminae of the dorsal and ventral horns. In the superficial dorsal horn NMDAR1‐b mRNA was preferentially detected in laminae II inner and III, while NMDAR1‐1 mRNA was restricted to laminae I to III. Large neurons in laminae IV and V contained mainly NMDAR1‐a, NMDAR1‐2 and NMDAR1‐4 mRNAs and occasionally NMDAR1‐b. The NMDAR1‐3 variant was only detected in very low abundance, being restricted to occasional cells in lamina I and II. In the ventral horn, motor neurons showed strong signals for NMDAR1‐a, NMDAR1‐b, NMDAR1‐2 and NMDAR1‐4 mRNAs. Serial sectioning through large motor neurons permitted the detection of multiple splice variants in single neurons. Analysis of the subcellular distribution of the mRNAs revealed that the NMDAR1‐1 mRNA was almost exclusively found in the cell nucleus, NMDAR1‐a mRNA was largely in the cytoplasm, while all other splice variants showed a homogeneous distribution between nucleus and cytoplasm. Comparison of the in situ hybridization images with functional analyses of heteromeric recombinant receptors will be necessary to ascertain whether splice variants of the NMDAR1 receptor subunit can account for some of the known electrophysiological properties of spinal cord neurons under physiological and pathophysiological conditions.
Expression of c‐Jun, Jun B, Jun D and cAMP Response Element Binding Protein by Schwann Cells and their Precursors In Vivo and In Vitro
Authors: Stewart Helen J. S. 
Published: April 2006

AbstractIn order to identify the transcription factors that may be involved in the development and differentiation of rat Schwann cells we examined the expression of c‐Jun, Jun B, Jun D and the cAMP response element binding protein (CREB) in vivo and in vitro. We found that CREB was expressed at high levels throughout nerve development by both Schwann cells and their precursors. Jun family members, on the other hand, were expressed only at low levels in a few nuclei of the developing nerve. After sciatic nerve transection, however, c‐Jun levels were rapidly up‐regulated in many Schwann cells of the distal stump but CREB, Jun B and Jun D levels were not affected. When nerve contact was resumed after crush injury c‐Jun levels returned to control values. Interestingly, unlike the situation in vivo, when Schwann cells were removed from the nerve and cultured, levels of all three Jun family members were rapidly up‐regulated. This also occurred in Schwann cell precursors. In other experiments we found that Schwann cell c‐Jun, but not Jun B or Jun D, expression was down‐regulated by the adenylate cyclase activator, forskolin. In addition, we show that the forskolin induced down‐regulation of c‐Jun is not necessary for Schwann cell proliferation or myelination to occur.
Preferential Growth of Neonatal Rat Dorsal Root Ganglion Cells on Homotypic Peripheral Nerve Substrates In Vitro
Authors: Anand Uma , McMahon Stephen B. , Cohen James 
Published: April 2006

AbstractDeveloping sensory neurons interact with molecular signals in the local environment to generate stereotypic nerve pathways. Regenerating neurons seem to lose the ability to reinnervate their original sites in the targets, resulting in abnormal sensory input and consequent clinical pathophysiology. The specificity of reinnervation of peripheral targets by regenerating axons is thus crucial for normal recovery of function. In this study, we have examined evidence for selectivity of interactions between primary afferent neurons from identified levels of the spinal cord and different peripheral nerve environments by culturing these neurons on sections of nerves to muscle and viscera. We have compared the growth of a population of sensory afferents normally innervating somatic targets (dorsal root ganglion cells from L4 and L5) with populations containing many afferents innervating visceral targets (L6 and S1 dorsal root ganglia and nodose ganglion). These neurons, from newly born rats, were cultured on unfixed cryostat sections of normal and prelesioned gastrocnemius nerve, pelvic spinal nerve and vagus nerve from adult rats. Normal muscle nerve was seen to support the regeneration of a significantly greater proportion of somatic neurons, with longer neurites, than the visceral nerves. Similarly, much higher proportions of the‘visceral’population of afferent neurons were seen to extend neurites on the normal visceral nerve substrates, with longer neurites, than on the muscle nerve substrate. The selectivity displayed by the sensory neurons for their normal nerve substrates was abolished when they were cultured on prelesioned nerve substrates subjected to Wallerian degeneration, which was apparent from the equivalent and increased proportions of growing neurons having comparable neurite lengths, on all the nerve substrates. We conclude that sensory neurons recognize and respond to substrate‐specific and substrate‐bound molecules present in normal adult peripheral nerves, and that these differences are lost in prelesioned nerves following Wallerian degeneration.
Pain Processing in Four Regions of Human Cingulate Cortex Localized with Co‐registered PET and MR Imaging
Authors: Vogt Brent A. , Derbyshire Stuart , Jones Anthony K. P. 
Published: April 2006

AbstractNeurosurgical and positron emission tomography (PET) human studies and animal electrophysiological studies show that part of the anterior cingulate cortex (ACC) is nociceptive. Since the contribution of the ACC to pain processing is poorly understood, this study employed PET and magnetic resonance (MR) image co‐registration in grouped and individual cases to locate regions of altered relative regional cerebral blood flow (rCBF). Seven right‐handed, neurologically intact males were subjects; each received neuropsychological and pain threshold testing. Subjects were scanned during infusion of H2[15O]: four randomized scans during innocuous heat stimulation to the back of the left hand and four scans during noxious but bearable heat to the same place. The averaged rCBF values during innocuous stimuli were subtracted from those during noxious stimuli and statistical parametric maps (SPMs) for the group were computed to identify regions of altered relative rCBF. Finally, single‐subject PET images of elevated and reduced rCBF were co‐registered with MR images and projected onto reconstructions of the medial surface of the hemisphere. The SPM analysis of the group showed one site with elevated rCBF in the midcingulate cortex and one in the perigenual cortex predominantly contralateral to the side of stimulation. There were bilateral sites of reduced rCBF in the cingulofrontal transitional cortex and in the posterior cingulate cortex (PCC). Co‐registered PET and MR images for individuals showed that only one case had a single, large region of elevated rCBF, while the others had a number of smaller regions. Six cases had at least one significant elevation of rCBF in the right hemisphere that primarily involved area 24b'; five of these cases also had an elevation in area 32′, while the seventh case had elevated rCBF in these areas in the left hemisphere. The rostral site of elevated rCBF in the group was at the border of areas 24/24’and areas 32/32′, although most cases had a site of elevation more rostral in the perigenual cingulate cortex. The ACC site of reduced rCBF was in areas 8 and 32 and that in the PCC included much of areas 29/30 in the callosal sulcus, areas 23b and 31 on the cingulate gyral surface and parietal area 7m. The localization of relative rCBF changes suggests different roles for the cingulate cortex in pain processing: (i) elevated rCBF in area 24’may be involved in response selection like nocifensive reflex inhibition; (ii) activation of the perigenual cortex may participate in affective responses to noxious stimuli like suffering associated with pain; and (iii) reduced rCBF in areas 8 and 32 may enhance pain perception in the perigenual cortex, while that in the PCC may disengage visually guided processes.
How Diagrams Can Improve Reasoning
Authors: Bauer Malcolm I. , Johnson-Laird P. N. 
Published: April 2006

We report an experimental study on the effects of diagrams on deductive reasoning with double disjunctions, for example: Raphael is in Tacoma or Julia is in Atlanta, or both. Julia is in Atlanta or Paul is in Philadelphia, or both. What follows? We confirmed that subjects find it difficult to deduce a valid conclusion, such as Julia is in Atlanta, or both Raphael is in Tacoma and Paul is in Philadelphia. In a preliminary study, the format of the premises was either verbal or diagrammatic, and the diagrams used icons to distinguish between inclusive and exclusive disjunctions. The diagrams had no effect on performance. In the main experiment, the diagrams made the alternative possibilities more explicit. The subjects responded faster (about 35 s) and drew many more valid conclusions (nearly 30%) from the diagrams than from the verbal premises. These results corroborate the theory of mental models and have implications for the role of diagrams in reasoning.
Has Psychology a Future?
Authors: Gibson Eleanor J. 
Published: April 2006

I consider that psychologists have a duty to explore their own field, to create hypotheses about the behavior of animals, especially human, and to test these and look for possible causal relationships at the level of acting, thinking, perceiving humans in their environmental context Our agenda should be at this level, not one that depends on waiting for reductionist theories at some other level, be it neural, genetic, nuclear, or especially artificial To go about this work, a developmental approach, in a systems setting—the organism-environment system—holds great promise and has the dignity of successful precedents in other sciences All of behavior—perceiving, acting, problem solving, communicating with others—should be our province The hallmarks of human behavior can and should be studied in all of these areas It is their development that offers a road to understanding We should continue to look for theories of considerable generality, however elegant a model may be in a tiny realm If we cannot find universal laws, we may still come up with unifying principles Not so long ago, in another keynote address, George Miller told us that it was time to “give psychology away” (Miller, 1969) I am afraid that that is exactly what we are doing, though not in the sense that Miller intended Let us keep psychology, and recapture the old excitement, looking for the causes in behavior itself, and not giving up on the grand unified theory
The Effects of Alignability on Memory
Authors: Markman Arthur B. , Gentner Dedre 
Published: April 2006

According to structure-mapping theory, the process of comparison is one of alignment and mapping between representational structures. This process induces a focus on commonalities and alignable differences (i.e., those related to the commonalities). Nonalignable differences (i.e., those not related to the commonalities) are held to be neglected. The theory thus predicts increased focus on the corresponding information, whether these are commonalities or differences. In this article, we explore the implications of this claim for memory: Specifically, we test the prediction that alignable differences are more likely to be processed and stored than nonalignable differences. We present a study in which people made similarity comparisons between pairs of pictures and then were probed for recall. The recall probes were figures taken from the pictures and were either alignable or nonalignable differences between the pairs. The alignable differences were better memory probes than the nonalignable differences, suggesting that people were more likely to encode and store the corresponding information than the noncorresponding information.
Restoration and Rehabilitation of Degraded Ecosystems in Arid and Semi‐Arid Lands. I. A View from the South
Authors: Aronson J. , Floret C. , Le Floc'h E. , Ovalle C. , Pontanier R. 
Published: April 2006

AbstractA general model is presented describing ecosystem degradation to help decide when restoration, rehabilitation, or reallocation should be the preferred response. The latter two pathways are suggested when one or more “thresholds of irreversibility” have been crossed in the course of ecosystem degradation, and when “passive” restoration to a presumed predisturbance condition is deemed impossible. The young but burgeoning field of ecological restoration, and the older field of rehabilitation and sustainable range management of arid and semiarid lands (ASAL), are found to have much in common, especially compared with the reallocation of lands, which is often carried out without reference to pre‐existing ecosystems. After clarifying some basic terminology, we present 18 vital ecosystem attributes for evaluating stages of degradation and planning experiments in the restoration or rehabilitation of degraded ecosystems. Finally, we offer 10 hypotheses concerning ecological restoration and rehabilitation as they apply to ASAL and perhaps to all terrestrial ecosystems.
Phosphorus Removal from Natural Waters Using Controlled Algal Production
Authors: Adey W. , Luckett C. , Jensen K 
Published: April 2006

AbstractA series of experiments designed to demonstrate the potential of using managed, attached algal production to permanently remove excess phosphorus from agricultural run‐off is described. The experiments were carried out on a secondary canal in the New Hope South region of the Florida Everglades Agricultural Area from October, 1991, to May, 1992. Natural algal populations of periphyton, including species of the genera Cladophora, Spirogyra, Enteromorpha, Stigeoclonium, and a variety of filamentous diatoms such as Eunotia and Melosira, were grown on plastic screens in raceways, under a wave surge regime. Considerable biomass production of algae occurred, and the resulting algal canopy also trapped plankton and organic particulates from the water column. A seven‐ to eight‐day harvest interval was determined to be optimal, and both hand harvesting and vacuum harvesting were employed. The vacuum device is applicable to large scale‐up. In source water having total phosphorus concentrations of 0.012–0.148 ppm, mean macro‐recovery dry biomass production levels of 15–27 g/m2/day were achieved. The lower rates occurred in the winter, the higher rates in the late spring. Two techniques were employed to reduce losses of fine material at harvest during the March to May period. Gravity sieving increased mean dry production levels to 33–39 g/m2/day. The mean phosphorus content of harvested biomass ranged from 0.34% to 0.43%. Total phosphorus removal rates during the spring period of average solar intensity and low nutrient supply, by methods demonstrated in this study, ranged from 104 to 139 mgTP/m2/day (380–507 kgP/ha/year). Over the incoming nutrient range studied, phosphorus removal was independent of concentration and was 16.3% of total phosphorus for 15 m of raceway. Up‐stream‐downstream studies of overflowing water chemistry (total P, total dissolved ‐P, orthophosphate ‐P) showed highly ‐significant reductions of all phosphorus species. Total phosphorus reduction closely correlated with phosphorus yield from biomass removal. Yearly, minimum phosphorus removal rates are predicted that are 100–250 times that achieved both experimentally and in long‐term, large‐area wetland systems. Engineering scale‐up to systems of hundreds of acres is being studied.
Restoration of Stipa pulchra Grasslands: Effects of Mycorrhizae and Competition from Avena barbata
Authors: Nelson Laura L. , Allen Edith B. 
Published: April 2006

AbstractExperiments were conducted in the field and the greenhouse to determine whether vesicular‐arbus‐cular mycorrhizae affect growth and competition between the native perennial Stipa pulchra and the introduced annual Avena barbata. Soils in the greenhouse were steam‐sterilized, and in the field they were treated with the fungicide benomyl. Stipa pulchra showed decreased shoot dry mass and increased root mass when inoculated, while A. barbata showed the opposite response, increased shoot mass and decreased root mass. Mycorrhizal A. barbata also produced more seeds. Mycorrhizae did not alleviate the negative effects of competition of A. barbata on S. pulchra, as has been demonstrated for other pairs of weedy and nonweedy species. The same three species of mycorrhizal fungi were present in annual and perennial grasslands, but their relative composition was different. When inoculum from the two grassland types were tested in the field, the fungal species began to revert within five months to the species composition found in grasslands of the host plant. This indicates that, once annual grassland has been revegetated with the native S. pulchra, the original fungal species composition may return relatively quickly. Where A. barbata dominates, inoculation with mycorrhizal fungi alone will not suffice for establishing S. pulchra, and the usual practices for control of weed competition need to be employed.
Small‐Scale Wetland Restoration in the High Arctic: A Long‐Term Perspective
Authors: Forbes Bruce C. 
Published: April 2006

AbstractResults are presented using vegetative shoots and bryophyte sods to restore floristically impoverished high arctic wet sedge‐moss meadows that had suffered intense damage from vehicle activity during the period 1960–1967. Clonal transplants of Carex aquatilis var. stans, a native sedge, were planted with and without bryophyte sods in vehicle ruts in 1972. After nearly two decades, there was less Carex cover in the planted ruts with flowing water than in the contiguous controls. This pattern was slightly reversed in planted plots with standing water. Reinvasion of Eriophorum angustifolium occurred in treated ruts, but cover was less in both treatments than in controls in 1990. The unexpected recruitment of Eriophorum scheuchzeri from the seed bank in moss‐sodded plots is discussed in terms of its local and regional importance. Total plant cover in restored ruts was nearly equal to that of controls, but biomass was somewhat less than that in control plots. Plots with bryophytes were environmentally distinct, due primarily to increases in organic mat depth relative to controls. After 18 years, restoration efforts resulted in increased plant cover in treated ruts compared to naturally recovering ruts.
The composition of no two patches of vegetation is precisely the same [and] neither are the seed banks. Successsion on different patches of disturebed ground in the same locality frequently proceeds quite differently because of such differences.—J. Miles, Vegetation Dynamics, 1979