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F Bonhoeffer

Publications and source records attributed to F Bonhoeffer.

At least 37 records · Page 2Linked to original sources
PubMed1986

Course corrections of deflected retinal axons on the tectum of the chick embryo.

Recently developed neuroanatomical staining methods utilizing transportable markers have made it possible to visualize individual, growing retinotectal axons in the chick embryo. In the present work, we used such methods to examine the behavior of mechanically deflected axons on the tectum. The deflection of axons was achieved by inserting small teflon barriers into the embryonic tectal tissue shortly before the arrival of retinal axons. All axons are laterally deflected by the teflon barrier from their original anteroposterior direction of growth. At the end of the barrier most of them correct their direction of growth. Not only do they turn again towards the posterior tectal pole, but they also approach the route they would have taken in the absence of the barrier.

Animals↗
PubMed1984

Development of the transient ipsilateral retinotectal projection in the chick embryo: a numerical fluorescence-microscopic analysis.

The ipsilateral retinotectal projection in the developing chick was examined by using rhodamine-B-isothiocyanate (RITC) as an anterograde and retrograde vital marker for the retinal ganglion cells and their axons. Staining of the entire retina following intravitreal RITC injection between incubation days 3 and 16 revealed a small number of anterogradely labeled fibers in the optic tract and the anterior half of the optic tectum ipsilateral to the injection site. The total number of ipsilaterally projecting fibers was estimated to be about 2,000 on developmental day 9. The ipsilateral projection totally disappeared after day 15. The arrangement of fibers within the ipsilateral projection was examined by local anterograde RITC staining of localized retinal regions between days 9 and 10. The projection was retinotopically organized along the dorsoventral axis such that fibers of dorsal retinal origin projected on the ventral tectal half, whereas fibers of ventral retinal origin projected on the dorsal tectal half. The localization of ipsilaterally projecting ganglion cell bodies was examined by retrograde RITC staining during days 9 and 15. Ganglion cells of all four quadrants of the central retina contributed to the production of the ipsilateral projection. The ipsilaterally growing retinotectal fibers did not represent collaterals of contralaterally projecting retinotectal axons. We assume that the tendency of early growing retinotectal axons to grow straight, as well as the ability of axonal growth cones to "sample" the environment, lead to a crossing of axons to the contralateral side. Ipsilateral projections would therefore represent "pathfinding errors." Explanations for the elimination of the ipsilateral retinotectal projection are discussed.

Animals↗
PubMed1984

Elimination of ipsilateral retinotectal projections in mono-ophthalmic chick embryos.

There are two transient ipsilateral retinotectal projections in the chick embryo: a normal one, appearing with a similar projection pattern in both binocular and monocular embryos, and an additional abnormal projection appearing only in mono-ophthalmic embryos. The development and the elimination of the ipsilateral retinotectal projections in mono-ophthalmic chick embryos was investigated using horseradish peroxidase (HRP) and the fluorescent dye Rhodamine-B-Isothiocyanate (RITC) as tracers for axonal pathways. The mechanisms involved in the elimination of the ipsilateral fibers are discussed.

Animals↗
PubMed1984

Fiber-fiber interaction and tectal cues influence the development of the chicken retinotectal projection.

The development of the retinotectal projection has been studied by a new experimental approach combining antibodies against the nerve cell adhesion molecule (NCAM), and techniques for mapping neuronal pathways using rhodamine B isothiocyanate (RITC) crystals. Anti-NCAM Fab', which specifically inhibits neurite fasciculation, was injected into the eye cup of 4-day-old chicken embryos. After 4-6 days of development, a small RITC crystal was placed on the neural retina to stain selectively axons arising from a localized region. One day later the retina, optic nerve, and tectum were examined and the paths of the fluorescent retinal ganglion cell axons were traced. These studies have led to four observations: (i) The presence of anti-NCAM Fab' causes the axons to form a disordered nerve bundle at the optic fissure. (ii) Disorder produced in the optic nerve persists throughout the optic pathway up to the tectum. (iii) Many of the misrouted fibers growing on or near the tectal surface can at least partially correct their position. (iv) Late axons grow in straight tracks along other fibers and do not correct their position. Together the results suggest that formation of the retinotectal projection involves both reading of positional cues on the tectum by growth cones of early arriving retinal axons and the tracking of growth cones along preexisting fibers that normally belong to neighboring retinal ganglion cells.

Animals↗
PubMed1983

Investigations on the development and topographic order of retinotectal axons: anterograde and retrograde staining of axons and perikarya with rhodamine in vivo.

Rhodamine-B-isothiocyanate (RITC) is shown to be a convenient and advantageous fluorescence tracer both for anterograde staining of retinal ganglion cell axons on the tectum and for retrograde staining of ganglion cell bodies in the retina of chick embryos. After intravitreal injection the dye is taken up by ganglion cells of the retina from the extracellular space and is transported anterogradely at about 10 mm/day up to the axonal growth cones on the tectum. RITC can be taken up by growing axons on the tectum and it is transported retrogradely at about 5 mm/day to the cell bodies in the retina. Local staining can be achieved if RITC is applied in its crystalline form. RITC is nontoxic for the cells and their axons, is resistant to histological fixation procedures, and allows quick observation in vivo and on dissection stained tissue. Local application of RITC to distinct retinal areas allows examination of the position of the corresponding stained fibers along the retinotectal pathway. Fibers which arise from the central temporal retina occupy deeper layers, whereas fibers from the peripheral temporal retina occupy more superficial layers in the optic tract and in the stratum opticum on the anterior tectum. The growth cones of early retinal fibers growing directly on the tectal surface show a different morphology to later growth cones growing on top of the stratum opticum on the tectum.

Animals↗
PubMed1982

In vitro experiments on axon guidance demonstrating an anterior-posterior gradient on the tectum.

Axonal growth cones originating from explants of embryonic chick retina were simultaneously exposed to two different cell monolayers and their preference for particular monolayers as a substrate for growth was determined. These experiments show that: (1) nasal retinal axons can distinguish between retinal and tectal cells; (2) temporal retinal axons can distinguish between tectal cells that originated from different positions within the tectum along the antero-posterior axis; (3) axons originating from nasal parts of the retina have different recognizing capabilities from temporal axons; (4) the property of the tectal cells, which is attractive for temporal axons, has a graded distribution along the antero-posterior axis of the tectum; and (5) this gradient also exists in non-innervated tecta.

Animals↗
PubMed1980

Monoclonal antibodies against chromosomal proteins of Drosophila melanogaster: establishment of antibody producing cell lines and partial characterization of corresponding antigens.

Total nuclear protein from the embryonic D. melanogaster cell line Kc and crude hydroxyapatite fractions thereof were used for immunization of mice. From the spleen cells of these mice we established 755 permanent lymphoid cell lines using the hybridoma technique originally developed by Köhler and Milstein (1975). Radioimmunoassay showed 455 of these cell lines secreted antibodies which bound to component(s) contained in the antigen mixtures used for immunization. Screening of 311 cell lines using indirect immunofluorescence revealed 58 lines whose antibodies showed a highly selective staining pattern on polytene chromosomes from the salivary glands of D. melanogaster third instar larvae. Eight of these cell lines were cloned and further characterized. We were able to order the staining patterns into three distinct classes based on the staining behaviour of the monoclonal antibodies: staining of active regions, staining of phase dark bands or staining of most interbands. The molecular weight of those antigens against which the monoclonal antibodies were directed was determined in SDS polyacrylamide gels.

Animals↗
PubMed1973

Isolation and characterization of thermosensitive Escherichia coli mutants defective in deoxyribonucleic acid replication.

Thermosensitive deoxyribonucleic acid replication-defective mutants have been isolated by using an autoradiographic selection method. The mutants have been analyzed genetically and biochemically. Some of the mutants show thermosensitivity of in vitro deoxyribonucleic acid replication. These can be classified into three groups according to their behavior in in vitro complementation assays. This classification is congruent with that obtained by genetic mapping by using cotransduction frequencies with selected markers in P1 transduction analysis.

Autoradiography↗
PubMed1972

Replication of Phi-X174 DNA by Escherichia coli polA- in vitro (Phi-X174 DNA-DNA replication-E. coli polA-).

Lysates of an Escherichia coli polA(-) strain convert single-stranded DNA from varphiX174 virus to the double-stranded replicative form with high efficiency on cellophane discs. The initiation of synthesis of the complementary strand appears to be rate limiting; once initiation occurs, the chain is propagated rapidly. Under these conditions, the unsealed replicative form accumulates and is slowly converted to the sealed form; this conversion requires the activity of the DPN-dependent DNA ligase.

Centrifugation, Density Gradient↗
PubMed1972

DNA replication.

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Adenosine Triphosphate↗