Search PubMed⌕ Search

Biomedical subjects

F Bonhoeffer

Publications and source records attributed to F Bonhoeffer.

At least 19 recordsLinked to original sources
PubMed1992

Axon guidance by gradients of a target-derived component.

Spatial gradients of axon guiding molecules have long been suspected to provide positional and directional cues for retinal ganglion cell axons growing within the optic tectum. With the identification of a guiding activity from tectal cell membranes, it has become possible to investigate the potential physiological significance of molecular gradients for retinal growth cone behavior in vitro. A subset of retinal growth cones, those from the temporal half, were highly sensitive to small concentration changes of the guiding component. The degree of response was correlated with the strength of the gradient. These findings demonstrate that the neural growth cone can read gradients of surface-associated information.

Animals↗
PubMed1990

Is guidance of chick retinal axons in vitro influenced by proteases?

Rhodamine-labeled explants of embryonic chick retinae were placed on a substratum consisting of alternating lanes of cell membranes derived from anterior and posterior chick optic tectum. Extending axons from temporal retinae prefer to grow in vitro on anterior tectal membranes because of a repulsive component within posterior membranes obtained from a tectum area which is not innervated by these axons in vivo. None of 16 protease inhibitors, specific for all known protease classes, when added to the culture medium, neutralized the repulsive activity of posterior membranes suggesting that the repulsive activity is not a protease. However, 2 metalloprotease inhibitors affect growth cone morphology and axon-axon interactions.

Animals↗
PubMed1990

In vitro assay to test differential substrate affinities of growing axons and migratory cells.

An in vitro assay is presented in which different soluble substrates are arranged in narrow alternating stripes which forces growing axons and migratory cells to choose between them. The usefulness of this assay is exemplified by offering goldfish retinal axons and glial cells of the optic nerve a variety of substrates in stripes. Given a choice between substrates of unequal growth supporting activities axons and migratory cells grow in stripes, thus expressing their preference for one of the substrates. Growth in stripes was observed 1. when a substrate with growth promoting properties was next to one which did not possess these properties, 2. when the growth promoting activity of a substrate applied to both stripes was in one stripe blocked by an antibody, 3. when two different growth promoting substrates were offered.

Animals↗
PubMed1990

A common denominator of growth cone guidance and collapse?

Axonal guidance in the retinotectal system and in spinal nerve segmentation is based on repulsion or inhibition. In both systems the membrane glycoprotein responsible for the guiding activity is capable of inducing growth cone collapse. We discuss two models of axonal guidance that correlate axonal guidance and growth cone collapse. The models are applicable to axon guidance by membrane-associated or diffusible stimuli, and are not based on preferential adhesion of axons to certain substrata.

Animals↗
PubMed1990

Biochemical characterization of a putative axonal guidance molecule of the chick visual system.

Temporal retinal axons growing in vitro on carpets of tectal membranes are deflected by cell membranes of posterior tectum. The activity responsible for this deflection can be abolished by antibodies raised against tectal membranes and the corresponding Fab fragments. Analysis of tectal membranes by two-dimensional gel electrophoresis and immunoblotting reveals a 33 kd glycoprotein that has a higher concentration in posterior than in anterior tectum. Its expression is developmentally regulated, and it is sensitive to phosphatidylinositol-specific phospholipase C. These are properties expected for a molecule responsible for the phenomena observed in experiments on in vitro guidance of retinal axons.

Animals↗
PubMed1990

Axonal guidance in the chick visual system: posterior tectal membranes induce collapse of growth cones from the temporal retina.

Membranes from posterior and anterior thirds of the chick optic tectum were added to explants from nasal and temporal retina. Posterior membranes, and to a lesser extent anterior membranes, cause temporal growth cones to collapse and their axonal processes to retract. Neither tectal source has an effect on nasal growth cones. We interpret these results to mean that there is a tectal activity, stronger in the posterior than the anterior region of the tectum, which helps guide growth cones during the development of the retinotectal map. We believe that in vivo this activity helps to steer temporal growth cones away from the posterior tectum. Nasal growth cones, which must map to the posterior tectum, are resistant to it. In vitro, when posterior membranes contact temporal growth cones over their surface, filopodia and lamellipodia withdraw rapidly. This leads to loss of contact between the growth cone and the substrate, followed by collapse.

Animals↗
PubMed1990

In vitro experiments on axonal guidance and growth-cone collapse.

In the retinotectal projection, nasal retinal axons project to posterior tectum, while temporal axons project to the anterior part of the tectum. In in vitro experiments, a similar specificity can be observed: the nasal and temporal retinal axons can be guided by tectal membrane components so that, for example, temporal retinal axons, when growing on a striped substratum consisting of anterior and posterior tectal membranes, express a very strong preference for the anterior stripes. This preference is not due to attractivity of anterior membranes but rather to avoidance of posterior material, although the pure posterior membranes are a very good substratum for growth of temporal axons. The repellent guidance molecule has been identified. Interestingly, besides guidance this molecule causes another reaction: when growing temporal axons are exposed to medium containing either posterior membranes or artificial lipid vesicles containing the repellent guidance molecule, the axonal growth cones collapse. As in guidance, there is a clear regional specificity: e.g. the repellent guidance molecule derived from posterior tectum induces collapse of temporal but not of nasal axons. Since the guiding and the collapse-inducing activity are expressed by one and the same glycoprotein molecule (Mr 33 x 10(3), linked to the membrane by phosphatidylinositol) and since another molecule has been identified by Keynes' group which also expresses both guiding and collapse-inducing activity, one might speculate that axonal guidance and axonal collapse have something in common. Models of axonal guidance will be discussed.

Animals↗
PubMed1990

Axonal guidance by an avoidance mechanism.

1. On a substrate consisting of alternating lanes of anterior and posterior tectal membranes, temporal retinal axons have a strong tendency to grow on the lanes of anterior membranes and to avoid the lanes of posterior membranes. 2. Temporal axons do extend neurites on posterior material, and in equivalent numbers and lengths to that of anterior membranes if the substrate consists of pure anterior or posterior membranes. 3. Inactivation of posterior membranes by heat or the enzyme phosphatidylinositol-specific phospholipase C (PI-PLC) abolishes their ability to induce the avoidance reaction of temporal axons. It is concluded that the posterior membranes contain a repulsive component for temporal retinal axons. 4. Growth cones growing on anterior membranes, which encounter posterior membranes at the strip boundary, in general do not become reduced in their growth rate. 5. These results are most easily explained by a "gradient-reading model" similar to chemotaxis where the steering of a growth cone is independent on the growth rate. 6. According to the model, a gradient of a guiding component outside the growth cone is transformed into an internal gradient which gives the growth cone its directionality. 7. Other models like growth inhibition cannot be ruled out but need at least two additional assumptions like habituation for growth on the putative posterior inhibitory substrate and a strong local restriction of the inhibitory effect within the growth cone which contacts the posterior material.

Animals↗
PubMed1989

Spatial arrangement of radial glia and ingrowing retinal axons in the chick optic tectum during development.

Neuroanatomical tracing of retinal axons and axonal terminals with the fluorescent dye, DiI, was combined with immunohistochemical characterization of radial glial cells in the developing chick retinotectal system. Emphasis was placed on the mode of the tectal innervation by individual retinal axons and on the distribution and fate of the tectal radial glial cells and their spatial relation to retinal axons. It was obvious from fluorescent images obtained from anterogradely filled axons that these axons deserted the superficial stratum opticum (SO) to penetrate the stratum griseum et fibrosum superficiale (SGFS) by making right-angled turns within the SO. Frequently, axons which had invaded the SGFS were bifurcated and had a superficial branch which remained within the SO. Terminal axonal arborization occurred at various depths within the SGFS. Characterization of the tectal glial cells and their radial fibers by means of the anti-filament antibody, R5, and post-mortem staining with the fluorescent dye, DiI, revealed the following. (a) At least from day E8 to P1, tectal glial fibers traversed all tectal layers from the periventricular location of their somata to the superficial interface between SO and pia mater. In this interface they enlarged and formed characteristic endfeet. (b) Glial endfeet covered the whole tectal surface. They showed at early ages anterior-posterior differences having a higher density in the posterior tectum. These differences disappeared at embryonic day E13. (c) After innervation, glial endfeet of the anterior tectal third were arranged in rows parallel to the retinal fibers within the SO. This arrangement was not observed in eyeless embryos. (d) Radial glial fibers could be stained with R5 from day E8 to late embryonic stages throughout their entire length. (e) At the first posthatching days, only the segments of the radial glial fibers restricted to the thickness of the SO were R5-positive, although the fibers still traversed throughout the depth of the tectum. The results are discussed in context to the genesis of the retinotectal projection.

Animals↗
PubMed1989

Cross-species recognition of tectal cues by retinal fibers in vitro.

The retinae of vertebrates project in a topographic manner to several visual centers of the brain. The formation of these projections could depend on the existence of position-specific properties of retinal and target cells. In this study, we have tested the in vitro growth of mouse retinal fibers on membranes derived from various regions of the embryonic superior colliculus, a main target of the retina in this species. Fibers had the choice of elongating on membranes taken from either the anterior or the posterior half of the superior colliculus. Fibers from temporal areas of the retina prefer to elongate on anterior collicular membranes, while fibers from nasal areas do not show a preference. These phenomena are observed with membranes from embryonic (E15-E18) or young postnatal mice. In interspecies cultures where mouse retinal fibers had to grow on chick tectal membranes, or vice versa, the same preference for anterior tectal or collicular membranes in growth of temporal retinal fibers is observed, suggesting some similarities in the cues used in both species.

Animals↗
PubMed1987

Neurofascin: a novel chick cell-surface glycoprotein involved in neurite-neurite interactions.

We have identified neurofascin, a novel chick cell-surface glycoprotein involved in neurite-neurite interactions. Neurofascin is defined by its reactivity with monoclonal antibody (MAb) F6, which detects two polypeptides (160 and 185 kd) in immunotransfers of brain plasma membrane proteins. Immunoaffinity chromatography using immobilized MAb F6 yields major molecular mass bands at 185, 160, 135-110, and 92 kd. Fingerprint analyses show that these polypeptides are related. Neurofascin is expressed primarily in fiber-rich areas of embryonic cerebellum, spinal cord, and retina. Fab fragments of polyclonal antibodies to neurofascin interfere with the outgrowth of retinal and sympathetic axons in two different in vitro bioassays. Neurofascin is immunologically distinct from other known neurite-associated surface glycoproteins.

Animals↗
PubMed1987

Axonal arborization in the developing chick retinotectal system.

The growth and arborization of chicken retinal ganglion cell axons have been investigated by means of an intraaxonally transported fluorescent marker in the developing retinotectal system. The fluorescent dye D282 or diI from the carbocyanine group of dyes is taken up by ganglion cells and labels the axon as well as the axonal growth cones and the terminal arborizations on the tectum. Branching and arborization start in the chick retinotectal system on embryonic day 9 (E9). At this stage retinal axons leave the stratum opticum (SO) and invade the stratum griseum et fibrosum superficiale (SGFS), where arborization takes place. On day E12 several axons were found to arborize in the SGFS. At this stage arbors appear to have small branches with less than 4 branching points. The extension of terminal arbors in the anterior/posterior (A/P) and in the dorsal/ventral (D/V) direction was determined for 50 axonal trees at days E13-14 and for 24 arbors at days E15-16. Few axonal terminals were investigated at day E18. The mean A/P extent of axonal terminal trees increases from 0.23 +/- 0.12 to 0.36 +/- 0.22 mm from E13-14 to E15-16 and seems to stay at this order of magnitude on E18. The mean D/V extent increases from 0.23 +/- 0.17 to 0.30 +/- 0.18 mm in the same embryonic period of development. The number of branching points calculated from the same number of axonal trees increases from 7.50 +/- 2.98 at E13-14 to 11.70 +/- 4.10 at E15-16. This number seems to increase further after day E16 achieving values of about 20 to 25 at E18. This was, however, not quantifiable by the technique used here and represents an approximate value estimated from 6 completely labeled terminal fields at E18. The data presented here suggest that the modeling of the final branching pattern in the chick retinotectal system takes place within a relatively short period of embryonic development. Prior to the beginning of terminal arborization two important events contribute to the formation of a retinotopic projection. One event is the change of the D/V position by a minority of axons lying ectopic in terms of retinotopy. Some axons turn at right angles and change their D/V position. The other event is the appearance of side branches along the A/P axis.

Animals↗
PubMed1987

Membrane glycoproteins involved in neurite fasciculation.

Lectin affinity chromatography combined with mAb production was used to identify chick neural cell surface molecules related to L1 antigen, a mouse neural glycoprotein implicated in cell-cell adhesion (Rathjen, F. G., and M. Schachner, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1-10). A glycoprotein, G4 antigen, isolated by mAb G4 from adult chick brain is described which comprises a major 135-kD component, a minor doublet at 190 kD, and diffusely migrating bands at 80 and 65 kD in SDS PAGE. This molecule is structurally related to mouse L1 antigen according to NH2-terminal amino acid sequence (50% identity) as well as the behavior of its components in two-dimensional IEF/SDS PAGE gels. A second chicken glycoprotein, F11 antigen, was isolated from adult chick brain using mAb F11. This protein has also a major 135-kD component and minor components at 170 kD and 120 kD. Both immunotransfer analysis with polyclonal antibodies to mAb G4 and to mAb F11 isolate and the behavior on IEF/SDS PAGE gels indicates that the major 135-kD component of F11 antigen is distinct from G4 antigen components. However, the 135-kD component of F11 antigen shares with G4 antigen and the neural cell adhesion molecule (NCAM) the HNK-1/L2 carbohydrate epitope. In immunofluorescence studies, G4 and F11 antigenic sites were found to be associated mainly with the surface of process-bearing cells, particularly in fiber-rich regions of embryonic brain. Although Fab fragments of polyclonal antibodies to mAbs G4 or F11 immunoaffinity isolate only weakly inhibit the Ca2+-independent aggregation of neural cells, they strongly inhibit fasciculation of retinal axons. Together these studies extend the evidence that bundling of axons reflects the combined effects of a group of distinct cell surface glycoproteins.

Amino Acid Sequence↗
PubMed1987

Retinal axons with and without their somata, growing to and arborizing in the tectum of Xenopus embryos: a time-lapse video study of single fibres in vivo.

Time-lapse video recordings were made of individual retinal ganglion cell fibres growing to and terminating in the optic tectum of Xenopus embryos. The fibres were stained by inserting a crystal of the lipophilic fluorescent dye, DiI, into the developing retina. Growth cones were observed in the optic tract and tectum using 20 ms flashes of light to induce fluorescence approximately once every minute. Fluorescent images were captured with a SIT camera, processed and saved on a time-lapse video recorder. The main conclusions from observing normal growing fibres are as follows. (1) Axons in the optic tract grow at a steady rate directly toward their targets without retracting or branching. (2) As axons approach the tectum they slow down and their growth cones become more complex. (3) Most terminal branches in the tectum are formed by back branching rather than by bifurcation of leading growth cones. In a second experiment, labelled growing axons were separated from their cell bodies by removing the retina. Such isolated axons continued to grow for up to 3 h in vivo and were capable of recognizing the tectum and arborizing there. This result shows that growth cones must contain the machinery needed to sense and respond to their specific pathways and targets.

Animals↗
PubMed1987

Recognition of position-specific properties of tectal cell membranes by retinal axons in vitro.

In order to test the preference of growing axons for membrane-associated positional specificity a new in vitro assay was developed. In this assay, membrane fragments of two different sources are arranged as a carpet of very narrow alternating strips. Axons growing on such striped carpets are simultaneously confronted with the two substrates at the stripe borders. If there is a preference of axons for one or the other substrate they become oriented by the stripes and grow within the lanes of the preferred substrate. Such preferential growth could, in principle, be due to affinity to attractive factors on the preferred stripes or avoidance of repulsive factors on the alternate stripes. This assay system was used to investigate growth of chick retinal axons on tectal membranes. Tissue strips cut from various areas of the retina were explanted and the extending axons were confronted with stripes of cell membranes from various areas within the optic tectum. Tectal cell membranes prove to be an excellent substrate for the growth of retinal axons. Nasal and temporal axons can grow well on membranes of both posterior and anterior tectal cells. If, however, temporal axons are given a choice and encounter the border between anterior and posterior membranes they show a marked preference for growth on membranes of the anterior tectum, their natural target area. Nasal axons do not show a preference in this assay system. The transition from nasal to temporal properties within the retina is abrupt. In contrast, the transition from anterior to posterior properties of the tectal cell membranes occurs as a smooth gradient. Significantly, the positional differences of tectal membrane properties are only seen during the period of development of the retinotectal projection and are independent of tectal innervation by retinal axons. These anterior-posterior differences disappear by embryonic day 14.

Animals↗
PubMed1987

A study in developing visual systems with a new method of staining neurones and their processes in fixed tissue.

Carbocyanine dyes, fluorescent lipophilic substances used for optical recordings of membrane voltage and for studies of membrane fluidity, have recently been shown to provide intense and long-lasting staining of neurones in vivo and in vitro (Schwartz & Agranoff, 1981; Honig & Hume, 1985, 1986; Catsicas, Thanos & Clarke, 1986; Landmesser & Honig, 1986; Thanos & Bonhoeffer, 1987). We report here that two of these dyes, diI (1,1',dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate) and diO (3,3'-dioctadecyloxacarbocyanine perchlorate), can also label neurones in embryonic mouse and chicken brain tissue that has been previously fixed in aldehyde fixatives. Neuronal processes and perikarya can be labelled along considerable distances in both anterograde and retrograde directions. The staining of processes and cells, including their finest extensions is smooth and clear, rivalling intracellular injections of HRP or Lucifer Yellow. The appearance and time course of progression of the staining along axons suggest that the staining in fixed tissue occurs due to a process of diffusion of dyes along the plasma membranes of cells. This technique has allowed us to study the first stages in the development of optic fibres in mouse embryos, especially at the optic chiasm. The early retinal projection (E13-E13 1/2) is mainly crossed, but some optic fibres grow to the ipsilateral side of the brain at the outset. Retrogradely labelled ganglion cells from the dorsocentral area of the retina participate in the formation of both the ipsilateral and the contralateral projection. Thus, at early stages, crossed and uncrossed projections arise from identical subregions of the retina and the partition of the retina with respect to the laterality of its projection arises later.

Animals↗
PubMed1987

Avoidance of posterior tectal membranes by temporal retinal axons.

Membrane carpets consisting of alternating membrane stripes were prepared from plasma membranes of anterior and posterior chick optic tectum. Axons from retinal explants extend neurites on these carpets. Axons of the nasal retina do not distinguish between the stripes. Axons of the temporal retina prefer to extend neurites on anterior tectal membranes. Treatment of the membrane fragments with high temperature interferes with the pattern of neurite outgrowth from temporal axons. When growing on carpets consisting of treated anterior and posterior tectal membranes, temporal retinal axons no longer distinguish between the stripes. Treatment of posterior membranes alone is sufficient to abolish the preference of temporal axons to extend neurites on anterior tectal membranes. Treatment of the anterior membranes alone has no effect. This result is best explained by a repulsive component in the posterior tectal membranes. Temporal, but not nasal, axons specifically recognize and avoid that component, with the result that they do not extend neurites on posterior tectal membrane stripes. Once the repulsive component is destroyed, temporal axons are able to extend neurites on posterior tectal membranes.

Animals↗