Rough Map Research Articles

Organization of retinal ganglion cell axons in the optic fiber layer and nerve of fetal ferrets.

Previous authors have hypothesized that retinotopic projections may be influenced by 'preordering' of the axons as they grow towards their targets. In some nonmammalian species, axons are reorganized at or near the optic nerve head to establish a retinotopic order. Data are ambiguous concerning the retinotopy of the mammalian retinal nerve fiber layer and whether fibers become reorganized at the optic nerve head. We have examined this question in fetal and newborn ferrets (Mustela putorius furo) by comparing the arrangement of axons in the retinal nerve fiber layer with that in the optic nerve. Dil or DiA crystals were implanted into fixed tissue in the innermost layers of the retinal periphery, or at a location midway between the periphery and the optic nerve head. Fluorescence labelling was examined in 100-200 microns Vibratome sections, or the eyecup and nerve were photooxidized and 1-2 microns longitudinal or transverse sections were examined. Regardless of fetal age, eccentricity or quadrant of the implant site, a segregation of labelled peripheral axons from unlabelled central ones was not detected within the nerve fiber layer. Axons coursed into the nerve head along the margin of their retinal quadrant of origin, often entering the optic nerve as a radial wedge, thus preserving a rough map of retinal circumference. However, peripheral axons were in no way restricted to the peripheral (nor central) portions of the nerve head or nerve, indicating that the optic axons do not establish a map of retinal eccentricity. Our results demonstrate that (1) the nerve fiber layer is retinotopic only with respect to circumferential position and (2) optic axons are not actively reorganized to establish a retinotopic ordering at the nerve head. The present results suggest that any degree of order present within the optic nerve is a passive consequence of combining the fascicles of the retinal nerve fiber layer; optic axons are not instructed to establish, nor constrained to maintain, a retinotopic order within the optic nerve.

Characterization of saline soils using airborne radar imagery

Complex dielectric constants determined by inversion of the polarized returns of AIRSAR images acquired in wet conditions delineate the distribution of saline soils in irrigated regions around the town of Pyramid Hill, in western Victoria, Australia. There is good agreement between the areas delineated as having anomalous dielectric constants by the radar backscatter inversion techniques with saline areas as defined by electrical conductivity and as inferred from dielectric constants determined in the field. Surface roughness maps and vegetation classification maps derived from AIRSAR data provide useful ancillary information regarding the extent of salinity in the region, but they are not as diagnostic as the determined dielectric constants. The magnitudes of P band radar-determined dielectric constants most closely approach those expected from field determinations, although the distribution of L-band-determined dielectric constants gives the best discrimination between saline and nonsaline areas as seen at the surface. C-band-determined dielectric constants are much lower than expected from field determinations and show saline areas as anomalous only in the bare, most severely affected, areas. The more general regional distribution of high dielectric areas seen at P band may be a more accurate indication of the salinity at depth. The AIRSAR image inversion techniques generally underestimate the magnitude of the complex dielectric constant. AIRSAR data for salinity mapping should be acquired under wet conditions. In such conditions there is an electrical continuum between the wet ground surface and saline water within the pores in the upper soil horizons. A wet ground surface results in a higher total power return than that which would occur under dry conditions and in a higher contrast between the radar-dark and radar bright areas within the scene.

How to get an European centimeter geoid (“astro-geological geoid”)

As shown by projects in hilly and alpine regions, astro-geoid solutions are more effective than gravimetry - but many countries do not utilize this fact. Both methods give accuracies of < 5cm/100km and are improved remarkably by subsurface density models (smoothing of the gravity field). Such models reduce astrogeoid errors by 50% even with simple inclination models (2.5D). Gravimetric geoids need full 3D geology and better terrain data or the reduction of errors would be less effective. This is explained by topographic or geological density anomalies: they cause systematic gravity errors, but quasirandom effects on vertical deflections. Therefore geoids of ±2–5cm require 5–15 astro points per 1000 km 2, but 50–500 gravity points (projects in A, CH, D, I, GB). For the latter it is very laborious to cross alpine slopes in such a grid of 2km, including adequate tacheometry. The only serious drawback of astro observations (night-time, some experience needed) will be overcome within a few years by automatic CCD measurements. South and East Europe should make use of the above benefits: vertical deflection data are quite dense. and geological surveys have sufficient quality. Even by rough geological maps or profiles the geoid can be improved to a few cm / 100km (locally 1–2cm) within 10 years.

PARMS, multiple marker-containing plasmids for easy RFLP analysis inArabidopsis thaliana

A simplified way is presented for the analysis of 13 RFLP markers, each of them detecting solely a pair of polymorphic bands afterEcoR I digestion of genomic DNA fromArabidopsis thaliana ecotypes Landsbergerecta and Columbia. Five plasmids (pARMS) containing multiple marker inserts were constructed that score 13 loci, almost evenly distributed on the five chromosomes (Fabri and Schaffner, 1994). Since their polymorphic signals do not interfere with each other, pARMS2,−6, and−7 can be combined to score eight RFLP marker in a single Southern experiment. Two additional plasmids—pARMS5 and−8— allow the joint analysis of another five markers. If pARMS are used for rough mapping of a mutation, which will be the major application, this procedure reduces processing and handling to just five plasmids and also results in more uniform signal intensities due to a more even labeling.

The modulatory cholinergic system in goldfish tectum may be necessary for retinotopic sharpening.

The cholinergic circuit within the tectum and the cholinergic input from the nucleus isthmi mediate a presynaptic augmentation of retinotectal transmitter release via nicotinic receptors. In this study, the cholinergic systems were either eliminated using the cholinergic neurotoxin AF64A or blocked using nicotinic antagonists to test for effects on the activity-driven sharpening of the regenerating retinotectal projection. The effectiveness of the AF64A was verified by recording field potentials elicited by optic tract stimulation and by immunohistochemical staining for choline acetyltransferase (ChAT). At 1 week after intracranial (IC) injection of AF64A (12 to 144 nmoles) into the fluid above the tectum, field potentials showed a selective dose-dependent decrement of the cholinergic polysynaptic component with no effect on the amplitude of the glutamatergic monosynaptic component. The decrement was only partially recovered in recordings at 2 and 6 weeks. In normal fish, the ChAT antibody stains a population of periventricular neurons, their apical dendrites, and a dense plexus within the optic terminal lamina that consists of their local axons and fine dendrites and of input fibers from the nucleus isthmi. One week after IC AF64A injection (48-72 nmoles), most immunostaining in superficial tectum was lost but most neuronal somas in the deep tectum could still be seen, and staining in the tegmentum below the tectum was completely intact. At 2 weeks and later, the staining of neuronal somata largely recovered, but staining of the superficial plexus did not. AF64A treatment at 18 days after nerve crush, when regenerating retinal fibers are beginning to form synapses, prevented retinotopic sharpening of the projection. Recordings showed a rough retinotopic map on the tectum but the multiunit receptive fields (MURFs) at each tectal point averaged 34 deg vs. 11 deg in vehicle-injected control regenerates. AF64A treatment before nerve crush also blocked sharpening, ruling out a direct effect on retinal growth cones or retinal fibers, as AF64A rapidly decomposes, whereas its effect on the cholinergic fibers is long-lasting. IC injection or minipump infusion of the nicotine antagonists alpha-bungarotoxin (alpha BTX), neuronal bungarotoxin (nBTX), and pancuronium during regeneration also prevented sharpening (MURFs averaging 29.4 deg, 33.0 deg, and 31.4 deg, respectively). Control Ringer's solution infusions or injections over the same period (19-37 days postcrush) had no effect on regenerated MURF size (11.7 deg). The results show that the cholinergic innervation, which modulates transmitter release, is required for activity-driven retinotopic sharpening, thought to be triggered by NMDA receptor activation.

Surface Roughening and Fractal Dimension during Plastic Deformation of Polycrystalline Iron

In order to investigate the relationship between surface roughening and deformation of respective grains, three-dimensional observation of surface roughness of polycrystalline iron during uniaxial compression was carried out. The pattern of grain boundaries and contour map of surface roughness were superimposed on the display of personal computer. The three-dimensional surface roughness data were also high-pass-filtered to get detailed figures. Fractal dimension was introduced to characterize the change in three-dimensional surface roughening during plastic deformation. Box - counting method was adopted to measure the fractal dimension. It was found that three -dimensional surface roughness showed fractal characteristics. The fractal dimension was almost constant with the increase of the applied strain.

What Will New Governance Mean for the Federal Government?

Across the country, there is wide interest in new ways of doing the public's business. Most of the activity so far, chronicled in books like Osborne and Gaebler's (1992) Reinventing Government and Barzelay and Armajani's Breaking Through Bureaucracy (1992), has been in state and local government. (See also Frederickson, 1992; Roselle, 1992; and Walters, 1992). President Clinton is a member of the movement for new governance, so the new ideas will soon be put to the test in Washington, DC. An Emerging, Unmapped Area As Zhiyong Lan and David Rosenbloom suggest in Administration in Transition? (1992), new governance is more a cluster of ideas and symbols than a rigorous, tested body of thought. New ways of doing the public's business are emerging gradually and unevenly. Furthermore, especially at the national level, most of the advocates for new governance are public policy specialists rather than students of public administration, and they have come to new governance out of frustration about the implementation of policy ideas in their fields. As a consequence, ideas about how to reinvent the federal government are often framed in terms like human service integration, school reform, or Third Wave economic development rather than as cross-cutting ideas about public administration. To provoke a substantive debate between advocates of new governance and traditionalists in public administration, Lan and Rosenbloom present a framework for comparing old and new ideas. They emphasize how agencies operate internally, especially how they deliver services. This emphasis is appropriate because the new governance movement has focused on local and state governments, where services are delivered. As new governance reaches to the federal level, the shape of new governance may change, because in most areas of domestic policy, the federal role is not to deliver services but to provide a legal structure, pay entitlements, and supervise those who deliver services. Reinventing Interdepart-mental, Intergovernmental Rural Policy This comment presents a rough map of the directions that the new governance movement might take at the federal level. It is based on discussions at a roundtable that the National Academy of Public Administration (NAPA) helped to organize in October 1992.(1) NAPA's partner was the little-known but highly regarded federal Rural Development Initiative (RDI). It encompasses State Rural Development Councils in over 30 states and supporting activities in Washington, DC, and elsewhere. As of last October, RDI had been working for over two years to find new ways to address the problems of areas, and its leaders were intensely interested in the ideas of Osborne and others in the new governance movement. RDI stands out from other efforts to redesign governance in two respects. First, RDI deals with all of the issues facing America and thus cuts across virtually every public program and policy. Second, although launched by the federal government, RDI is a collaborative enterprise, involving states, local governments, tribes, the private sector, and numerous federal agencies. Although the RDI effort was limited in many respects, including weak support from the Bush White House, it is an interesting starting point for mapping how new governance might work at the federal level. New governance may take different forms in different geographic areas and for different issues. Rural areas are highly diverse, including chronically poor communities, prosperous resorts, manufacturing towns, timberlands and farm counties. This diversity is one reason why anyone can benefit from thinking about problems. The rural dimension encourages thinking about diversity rather than about generic answers. And one of the central themes of the movement to redesign governance is empowering people to design answers that fit their load situations. Why Reinvent Governance? …

A History of Anglo-Latin Literature, 1066–1422 by A. G. Rigg

STUDIES IN THE AGE OF CHAUCER Richmond's interpretive focus appears at times to override introductory considerations. For example, she treats The Pardoner's Tale as a sermon; she includes his Prologue in her discussion because he there speaks about his preaching (pp. 118-23). By contrast, The Wife ofBath's Tale, placed among the secular romances, is treated in total isolation from its Prologue (pp. 7279 ). Richmond several times alludes to a "Marriage Debate, initiated by the Wife ofBath" (p. 125), but she never deals directly with the substance of this "debate" or of the Wife's Prologue. It appears that Richmond does not wish to discuss material that, as she indicates in a footnote (p. 201 n. 5), she has treated elsewhere. Thus she presents the Wife ofBath's Tale as if it had nothing to do with its Prologue; it is a romance, "an argument for a virtuous life, especially difficult in a world of chivalry" (p. 73), centered upon the moral education of its (nameless!) knight. In an introductory book on Chaucer, one might reasonably expect more coherently presented attention to be paid to the Wife of Bath's Prologue and the "Marriage De­ bate" than we find here. One doubts that scholars or advanced students of Chaucer will find much of interest in this book. The interpretive material is scarcely devel­ oped and seldom original, while large areas of critical interest are often slighted or ignored. On the other hand, it seems to this reviewer too advanced and eccentric a study to be of much use to a novice reader or introductory student as a sort of companion to a first reading of Chaucer's poetry. Who, then, would or should read this book? "I kan nat seye." MICHAEL D. CHERNISS University of Kansas A.G. RIGG. A History ofAnglo-Latin Literature,1066-1422. Cambridge: Cambridge University Press, 1992. Pp. ix, 414. $95.00. A.G. Rigg's A History ofAnglo-Latin Literature, 1066-1422, as its title suggests, is a broad historical survey of the Latin literature written in England between the Norman Conquest and the death of Henry V. Rigg modestly describes his study as being "scarcely more than an outline," a "rough sketch map" of this variegated and largely uncharted literary land­ scape. His modesty is appropriate, for it would hardly be possible for any one scholar to do much more than that in a single volume, considering the 254 REVIEWS amount of literary material there is to contend with. Nevertheless, despite the author's humility in the face of what seems a daunting undertaking, the book is remarkable for what it attempts and for what it achieves. Rigg's stated purpose is to fill in an important gap in our knowledge of the literature of medieval England, and his study does that admirably. Anglo-Latin Literature is divided into four sections, each of which corre­ sponds to a major political-historical division: (1) William I to Stephen, (2) Henry II toJohn, (3) Henry III to Edward I, and (4) Edward II to Henry V. These sections are treated as discrete units, for the most part, with intro­ ductions that lay out the historical background and conclusions that gen­ eralize about the literary currents of the subperiod just discussed in its particulars. In each section Rigg situates authors and works firmly within their historical· context. Throughout the work the twin emphases are on chronology and historical contextualization, both of which are necessary. One cannot help feeling, however, that they are emphasized at the expense of other important considerations such as genre, the evolution of literary traditions, and the literary relationships between authors, which receive far less attention. In each of his four subperiods Rigg identifies and discusses every major author and work, makes brief mention of many minor authors and their works, and sometimes focuses on anonymous pieces that might otherwise escape our notice. In addition he occasionally puts forward a neglected writer whose work, he believes, deserves greater consideration. On the whole, his study reads much like a handbook or an encyclopedia, and that is one of its chief virtues, since many scholars will use it primarily as a reference work...

Surface Roughening and Fractal Dimension during Plastic Deformation of Polycrystalline Iron.

In order to investigate the relationship between surface roughening and deformation of respective grains, three-dimensional observation of surface roughness of polycrystalline iron during uniaxial compression was carried out. The pattern of grain boundaries and contour map of surface roughness were superimposed on the display of personal computer. The three-dimensional surface roughness data were also high-pass-filtered to get detailed figures. Fractal dimension was introduced to characterize the change in three-dimensional surface roughening during plastic deformation. Box - counting method was adopted to measure the fractal dimension. It was found that three -dimensional surface roughness showed fractal characteristics. The fractal dimension was almost constant with the increase of the applied strain.

Effective-medium treatment of flow through anisotropic fracture system ? Improved permeability estimates using a new lattice mapping

The permeability tensor of a fractured reservoir, which will typically be anisotropic because of the presence of stress, is an important parameter to be taken into account when formulating a production strategy for the reservoir. Extensive computational effort is involved in calculating the permeabilities of model fracture systems by solving the fluid flow equations through finite realisations of the systems, and this renders a search for alternative techniques worthwhile. An attractive approach is to perform a rough mapping of the fracture system onto a lattice so that effective medium theory can be applied. For isotropic systems that are well-connected, this technique works well, but it gives increasingly poor results as the degree of anisotropy increases. In this contribution, a refinement of the lattice mapping is presented that incorporates an important aspect of the randomness present in the original system. This greatly increases the applicability of the technique.

Plus ça change: The Interaction between the Legal System and Political Change in Francoist Spain

Law and politics are pieces of the same cloth. We are accus tomed to believing that in democratic polities law relates one way to politics while in non-democratic polities the relationships are quite differ ent. Indeed, we are predisposed to believe in many instances that in authoritarian political systems, like Spain under Franco, law and legal system elites are fundamentally irrelevant actors—save as pawns of those in command. This article argues that the law and legal system elites were important political actors during the transition from authoritarian to non- authoritarian politics under Franco and that the Spanish case provides us with a rough map toward our understanding of system changes in other arenas as well.

Race, Culture, and Education: Some Conceptual Problems

Philosophers should be able to help educators in two ways here. First, there are some very general points to be made about education and human differences, particularly about the application of various criteria and the status of different kinds of arguments. Second, there are more specific problems clustering round the notions of attachment, identity, and rationality in relation to race and culture. I deal with these in A and B below respectively; but I must forewarn the reader that I can only draw a very rough map of a terrain that is still largely uncharted, and I shall be content if I can at least make more explicit some problems and difficulties that are usually glossed over.

Molecular and cytological evidence of deletions in alien chromosomes for two monosomic addition lines of Brassica campestris-oleracea

A series of RFLP and isozyme markers were followed in the progenies of two alien addition lines of Brassica campestris-oleracea. One of the lines, carrying the C genome chromosome 4 as the alien chromosome, was surveyed for six markers. Fifty-four percent of the plants carrying alien chromosomes displayed all the expected makers, whereas the rest had one to five markers missing. The second line for C genome chromosome 5 displayed a similar behavior when surveyed for three markers. All three markers were transmitted together in 46% of the plants carrying alien chromosomes, whereas the rest carried only one or two of the markers. The loss of markers was associated with reduced chromosome size caused by deletions. The observed chromosome deficiencies permitted deletion analysis for a rough physical mapping and ordering of the markers on the two C genome chromosomes. The deletions observed may represent another mechanism for molding the chromosomes of the Brassica genomes during their evolution.

Epitaxial Al(110) Films Grown On Heavily-Doped Si(100) by Cluster Beam Deposition.

ABSTRACT:Epitaxial Al films have been grown on heavily doped Si(100) by neutral cluster beam deposition. The Al films were evaluated by RBS, RHEED, optical interference roughness maps and STM imaging. The results were consistent with the formation of epitaxial Al (110) bi-crystals similar to films grown by ionized cluster beam deposition on lightly-doped Si

The geoid roughness: A scanner for isostatic processes in oceanic areas

Maps of bandpass‐filtered geoid height anomalies deduced from Seasat altimetry data – which are referred to as “geoid roughness maps”– are contoured over the Indian Ocean both in the short (30–90 km) bandwith and in an intermediate one (90–230 km). Interpretation of these maps essentially provides a guide as to where further detailed studies should be conducted. The roughness maps can thus be used as a fast and efficient “scanner” for isostatic processes at the scale of an entire ocean. Additionally, roughness maps provide a qualitative appraisal of the emplacement mechanisms of intraplate features: this can for example be appreciated by comparing the interpretations of the maps with the results of admittance studies over such features.

Deletion analysis of male sterility effects oft–haplotypes in the mouse

We present data on the effects of three chromosome 17 deletions on transmission ratio distortion (TRD) and sterility of several t-haplotypes. All three deletions have similar effects on male TRD: that is, Tdel/tcomplete genotypes all transmit their t-haplotype in very high proportion. However, each deletion has different effects on sterility of heterozygous males, with TOr/t being fertile, Thp/t less fertile, and TOrl/t still less fertile. These data suggest that wild-type genes on chromosomes homologous to t-haplotypes can be important regulators of both TRD and fertility in males, and that the wild-type genes concerned with TRD and fertility are at least to some extent different. The data also provide a rough map of the positions of these genes.

Results of Coordinated Multiwavelength Observations of Solar-Type Stars

We present results of nearly simultaneous polarimetric and Ca II(H+K) emission observations taken over a full rotation period for a sample of six solar-type stars. Significant variations are seen for two stars in polarization and four stars in Ca emission, which we interpret as due to rotational modulation of magnetic areas on the stellar surface. The irregularity of the variations suggest changes of the area size and/or distribution in time scales of the rotation period. Preliminary models (including rough surface maps of two stars) and future prospects are discussed.

Seasat altimetry and the South Atlantic Geoid: 2. Short‐wavelength undulations

This paper is a discussion of the short‐wavelength (25–100 km) undulations of the geoid recovered from Seasat altimeter data in the South Atlantic. These undulations are known to be highly correlated to seafloor topography, and they considerably improve our knowledge about global bathymetry of the South Atlantic, which remains poorly surveyed. The orientation of fracture zones (FZ) with respect to the Seasat profiles ensures an efficient recovery of the FZ pattern in the younger (&lt;65 Ma) parts of the South Atlantic between 20°N and 50°S. We used 22 well‐marked FZs regularly distributed between 12°N and 47°S to compute Eulerian poles describing the finite relative movement between Africa and South America. From the present back to 35 Ma, FZ trends south of the equator are well accounted for with a single rotation, and standard statistical tests do not indicate a need for distinct and successive rotations. However, these tests indicate an improvement of the fit when distinct poles are adjusted to separate subsets of our 22 FZs (either FZs north and south of the equator, or FZs north and south of Tristan da Cunha). This points out the possibility of the existence of either “corridors” in which slight relative movements occur, or diffuse elastic deformation over the entire South Atlantic, although this is really a second‐order effect. We also present and discuss a map of the roughness of the geoid (for the 25‐ to 110‐km wave band). Strong disagreements between the roughness map and the GEBCO maps exist in regions of sparse ship track coverage; for example, the Rio Grande Rise has an associated roughness feature which appears elongated and more symmetric with respect to the Walvis Ridge than what is displayed on the GEBCO maps. The roughness map also clearly documents a long‐wavelength (∼400 km) segmentation of the Mid‐Atlantic Ridge between the equator and 35°S.

Activity sharpens the regenerating retinotectal projection in goldfish: sensitive period for strobe illumination and lack of effect on synaptogenesis and on ganglion cell receptive field properties.

The regenerating optic nerve of goldfish first reestablishes a rough retinotopic map on the contralateral tectum and then sharpens it. Disruption of visual activity, either by blocking activity with intraocular tetrodotoxin (TTX; Schmidt and Edwards, 1983) or by synchronizing activity with strobe illumination (Schmidt and Eisele, 1985), disrupts the sharpening process: the map is correctly oriented but the multiunit receptive fields at each point average 25-40 degrees in diameter. In order to test whether strobe and TTX interfere with the same mechanism, we have tested whether their sensitive periods are the same, and whether strobe, like TTX treatment, does not affect either ganglion cell receptive field properties or synaptogenesis. In parallel studies, we exposed fish to 2 weeks of either strobe illumination or intraocular TTX beginning at various times after crush and determined via electrophysiological recordings that the periods of sensitivity were nearly identical. There was no effect of either treatment during the first 2 weeks (before the fibers arrive at the tectum), maximal disruption of sharpening between 14 and 50 days (the period of rapid synaptogenesis), decreasing disruption between 50 and 125 days, and no effect beyond that point or in the normal projection. In addition, long strobe exposures of up to 142 days produced no greater disruptions than shorter 2-3-week exposures, indicating no cumulative effect. The reestablishment of synaptic transmission in tectum, assayed by recording field potentials elicited by optic nerve shock, was not affected by stroboscopic illumination. Finally, individual ganglion cells, recorded intraretinally following long-term strobe exposure, had receptive fields that were normal both in size and in their characteristic responses to light-on, to light-off, or to both on and off. These findings support the hypothesis that strobe-like TTX prevents retinotopic refinement by preventing the correction of errors initially made by the ingrowing optic axons (Schmidt et al., 1988).

Antibodies to ependymin block the sharpening of the regenerating retinotectal projection in goldfish

The regenerating optic nerve of goldfish first reestablishes a rough retinotopic map on the tectum, then goes through an activity dependent refinement that appears to involve the elimination of inappropriate branches from early regenerated arbors. Retinotopically appropriate branches and synapses may be stabilized because the normally correlated firing of neighboring ganglion cells could cause summation of their postsynaptic responses, making them more effective. Thus, refinement of the map may be similar in several ways to associative learning. In this study, we therefore tested whether ependymin, a major protein component of the extracellular fluid that has been implicated in synaptic changes thought to be associated with learning a simple task in goldfish, may also be involved in refinement of the retinotopic map. Goldfish that had undergone unilateral optic nerve crush received intraventricular infusion of antiependymin IgG or of control IgG's beginning at 21 days postcrush. Textal recordings from these fish at 39–56 days postcrush showed that the projection had failed to sharpen, much as in the fish with activity blocked or synchronized; the average size of the multiunit receptive fields was 31° vs 11° normally. The field potentials elicited from these tecta by optic nerve shock were not significantly smaller than in controls, suggesting normal levels of synaptogenesis. Control projections, identically treated but infused with either unrelated IgG or Ringer's alone regenerated normally, giving multiunit receptive fields of 12°. Intact (non-regenerating) projections of the experimental fish were not rendered abnormal by the IgG treatment. Histology showed the retinas and tecta of the infused fish to be normal in appearance. The results show a specific block of sharpening by antiependymin IgG. The ependymal glia of the tectum stain positively for ependymin in normal fish, particularly the cell bodies in the ependymal layer. The tectum, particularly the ependymal layer, stains more intensely during regeneration, which appears to trigger increased synthesis of ependymins in the ependymal glia. This increase and the block of sharpening by specific antibodies to ependymin suggest a possible role for ependymin in activity dependent synaptic stabilization, possibly through its polymerization when calcium is focally depleted at active synapses.