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C B Kimmel

Publications and source records attributed to C B Kimmel.

At least 73 records · Page 4Linked to original sources
PubMed1987

Indeterminate cell lineage of the zebrafish embryo.

We have examined the clonal progeny descended from individual blastomeres injected with lineage-tracer dye in the zebrafish embryo. Blastomeres arising by the same cleavages in different embryos generated clones in which the types and positions of cells were highly variable. Several features of early development were correlated with this diversity in cell fate. There was no fixed relationship between the plane of the first cleavage and the eventual plane of bilateral symmetry of the embryo. By blastula stages the cleavages of identified blastomeres were variable in pattern. Moreover, cell fate was not easily related to the longitudinal and dorsoventral position of the clone in the gastrula. These results establish that single blastomeres can potentially generate a highly diverse array of cell types and that the cell lineage is indeterminate.

Animals↗
PubMed1986

Segmental homologies among reticulospinal neurons in the hindbrain of the zebrafish larva.

We have examined the morphology of identified reticulospinal neurons in larval zebrafish by retrogradely labeling them with horseradish peroxidase. We described the morphology of 27 different types of reticulospinal neurons found in the hindbrain 5 days after fertilization. Nineteen of these types are present as single identified neurons on each side of the brain; the others are present as pairs or small groups of cells. The hindbrain reticulospinal neurons are present in seven bilateral clusters that are spaced periodically along the neuraxis. Each cluster contains two to five different types of reticulospinal neurons. Cells with similar morphological features are found in adjacent clusters. By considering cell position within the cluster and axon pathway, nearly all of the cells can be assigned to one of about seven serially repeated classes. Independent morphological features of the cells support the same classification. We propose that the clusters represent hindbrain segments and that the neurons of the same class that are present in the different clusters are segmental homologues. Assuming that this series evolved by successive duplications and divergence of the primitive segments, we have analyzed the changes that may have occurred during the evolution of each new segment. Changes between ipsilaterally and contralaterally projecting axons may have occurred several times during the evolution of the series. In addition, cells may have been added or deleted.

Animals↗
PubMed1986

Identified vertebrate neurons that differ in axonal projection develop together.

The development of identified reticulospinal neurons of the zebrafish (Brachydanio rerio) was studied in order to learn if cell specific differences in axonal projection are correlated with cell specific differences in time of neuronal development. We examined the development of individually known reticulospinal neurons that are located in close proximity in the hindbrain but that project axons to targets on opposite sides of the spinal cord. We observed that these identified neurons are generated together, and that their axons first arrive in the spinal cord together. We suggest that the selection of different axonal pathways by these neurons does not depend on the time that they develop.

Age Factors↗
PubMed1985

T reticular interneurons: a class of serially repeating cells in the zebrafish hindbrain.

We describe a class of reticular neurons, named T interneurons after the branching pattern of their axons, in young larvae of the zebrafish Brachydanio rerio. The cells were identified by filling them with HRP from application sites within the CNS. A serially repeating set of about ten such neurons is present in a longitudinal column on each side of the caudal hindbrain. The T axons project across the midline, and branches course both rostrally and caudally within the medial longitudinal fascicle (mlf). The cells receive synaptic input from the Mauthner neurons, from unidentified axons in the mlf, and perhaps from trigeminal sensory fibers. They project to cranial and pectoral motor nuclei. T interneurons appear to be homologous to giant fiber neurons in the hatchetfish and to some of the cranial relay neurons in the goldfish. We discuss a possible functional role and comparative implications of their distribution in the hindbrain.

Animals↗
PubMed1985

Anatomy of the posterior lateral line system in young larvae of the zebrafish.

We studied the anatomy of neuromasts, afferent sensory neurons, and efferent neurons of the midbody branch of the posterior lateral line in larvae of the zebrafish (Brachydanio rerio), 5 days after fertilization. This simple sensory system consists of ten or 11 neuromasts, 15-20 sensory neurons, and about nine efferent neurons. The neuromasts are typical free neuromasts and both afferent and efferent synapses are present on hair cells within them. The sensory neurons project into a single longitudinal column of neuropil in the hindbrain. The sensory terminals appear by light microscopy to contact the dorsolateral dendrite of the ipsilateral Mauthner cell. Three types of efferent neurons are present; two types in the hindbrain and one type in the diencephalon. We provide several lines of evidence that demonstrate that these central neurons are efferent to the lateral line. We conclude from this morphology that the larval system includes all of the components of the adult system and is probably functional at this early stage. We also found that larvae have all of the efferent neurons found in adult zebrafish, while the number of neuromasts and sensory neurons will increase during subsequent development.

Animals↗
PubMed1985

Cell lineage of zebrafish blastomeres. I. Cleavage pattern and cytoplasmic bridges between cells.

Patterns of cleavage and cytoplasmic connections between blastomeres in the embryo of the zebrafish, Brachydanio rerio have been described. The cell division pattern is often very regular; in many embryos a blastomere's lineage may be ascertained from its position in the cluster through the 64-cell stage. At the 5th cleavage, however, significant variability in pattern is observed, and alternative patterns of the 5th cleavage are described. The early cleavages are partial, incompletely separating blastomeres from the giant yolk cell. The tracer fluorescein-dextran (FD) was injected into blastomeres to learn the extent of the cytoplasmic bridging. It was observed that until the 10th cleavage, blastomeres located along the blastoderm margin maintain cytoplasmic bridges to the yolk cell. Beginning with the 5th cleavage, FD injected into a nonmarginal blastomere either remains confined to the injected cell, or if the injection was early in the cell cycle, the tracer spreads to the cell's sibling, through a bridge persisting from the previous cleavage. On the other hand, injected Lucifer yellow spreads, presumably via gap junctions, widely among blastomeres in a pattern unrelated to lineage.

Animals↗
PubMed1985

Cell lineage of zebrafish blastomeres. II. Formation of the yolk syncytial layer.

Dye coupling and cell lineages of blastomeres that participate in the formation of the yolk syncytial layer (YSL) in the zebrafish Brachydanio rerio have been examined. The YSL is a multinucleate layer of nonyolky cytoplasm underlying the cellular blastoderm at one pole of the giant yolk cell. It forms at the time of the 10th (sometimes 9th) cleavage by a collapse of a set of blastomeres, termed marginal blastomeres, into the yolk cell. Marginal blastomeres possess cytoplasmic bridges to the yolk cell before the YSL forms, and injections of fluorescein-dextran into the cells revealed that bridges between the yolk cell and blastoderm do not persist after this time. Injections of Lucifer yellow revealed that shortly after the YSL forms the yolk cell and blastoderm are dye coupled, presumably by gap junctions, and that this coupling disappears gradually during early gastrulation. Lineage analyses revealed that not all of the progeny of early marginal blastomeres participate in YSL formation. Although some descendants of marginal blastomeres remained on the margin during successive cleavages, neither "compartment" nor "strict lineage" models are sufficient to explain the origin of the YSL. It is proposed that the position of a cell on the blastoderm margin, and not the cell's lineage, determines YSL cell fate.

Animals↗
PubMed1985

Cell lineage of zebrafish blastomeres. III. Clonal analyses of the blastula and gastrula stages.

Aspects of the early lineages of blastomeres in the embryo of the zebrafish, Brachydanio rerio have been described. Because of the optical clarity of the embryo, lineages of selected cells can be followed directly by microscopy through many cell divisions. Also, it is shown here that the fluorescent molecules fluorescein-dextran and rhodamine-horseradish peroxidase can be used as cell lineage tracers, marking the clonal progeny of founding blastomeres. The labeled cells can be easily visualized in the live embryo, and utilizing a sensitive video camera to amplify fluorescence, the same clone may be examined repeatedly while the cells divide and migrate. Cells that descend from a single blastomere remain closely associated together through the end of the blastula stage. At the time when epiboly begins (early gastrula) cells in the labeled clone scatter and become dispersed among unlabeled cells. It has been observed that there is no invariant mapping of the embryo's midline (determined by the position of the embryonic shield in the gastrula) with respect to the early planes of cleavage. This finding shows that in the zebrafish the region of the embryo that a cell will occupy is not specified by the cell's early ancestory.

Animals↗
PubMed1984

Developmental uncoupling between blastoderm and yolk cell in the embryo of the teleost Fundulus.

During cleavage and blastula stages of embryos of the teleost Fundulus heteroclitus all of the cells are both electotonically coupled and dye coupled to one another, as determined by microelectrode impalements and spread of Lucifer Yellow. At about the time that gastrulation begins we observed a specific loss of junctional coupling between the yolk cell and cells of the blastoderm. Passage of Lucifer Yellow between the yolk cell and blastoderm was reduced at stage 12 (late blastula), and not detected at stage 13 and thereafter, although cells of the blastoderm remain dye coupled to one another through gastrula stages. Also, junctional electrical coupling between the yolk cell and blastoderm became substantially reduced at stage 13 and thereafter. The loss of coupling at this specific cell apposition and time and the large size of the yolk cell may prove useful in analyzing the underlying cellular mechanisms.

Animals↗
PubMed1982

Brain neurons which project to the spinal cord in young larvae of the zebrafish.

A small number of brain neurons project to caudal levels of the spinal cord in the larva of the teleost Brachydanio rerio. These cells were identified in animals 6 days after fertilization by backfilling with horseradish peroxidase following transection of the cord at the level of the cloaca. In preparations with the most labeled cells a total of 30-40 were present on each side of the midline. They were located within three regions of the brainstem: the midbrain nucleus of origin of the medial longitudinal fascicle (mlf), the hindbrain reticular formation, and the hindbrain vestibular nucleus. A total of 15 classes of cells could be distinguished by soma positions, dendritic fields, and axonal pathways. For some of these classes only one or two cells were usually present on each side of the brain. Most of the labeled cells contributed axons to the mlf ipsilateral to the soma; however, the Mauthner cells and three new types of hindbrain reticulospinal reticulospinal cells have decussating axons that enter the contralateral mlf. The observed distribution of labeled reticulospinal cells is similar to that previously described for large reticular cells in adult teleosts and to the system of identified Mauthner and Müller cells in the lamprey.

Animals↗
PubMed1982

Synaptogenesis and its relation to growth of the postsynaptic cell: a quantitative study of the developing Mauthner neuron of the axolotl.

We describe the relation between growth and branching of an identified dendrite and the formation of synapses on its surface during a 3 1/2-day period early in development. We studied the lateral dendrite and the adjacent lateral perikaryon of the Mauthner cell (M-cell) during embryonic stages 39-43 in the axolotl Ambystoma mexicanum. Reconstructions from light micrographs of serial sections through the cell revealed that during this interval the dendrite elongates rapidly, and large numbers of ventrally directed branches are formed. Samples of the same material by electron microscopy showed that large numbers of synaptic contacts appear during the same interval. We quantitatively estimated changes in local synapse densities (the number of contacts/100 micrometers2 of M-cell surface) and local surface areas of the M-cell and found that synapses were most densely clustered, and accumulated most rapidly, on regions of the cell that were rapidly expanding. These data are in accord with previous evidence from work in this and in other systems that synaptic contacts induce local growth of dendrites. Furthermore, the data are consistent with a proposal that outgrowth of new dendritic branches is induced or stabilized by synapses in a concentration-dependent fashion.

Ambystoma mexicanum↗
PubMed1982

Noninvasive recording of the Mauthner neurone action potential in larval zebrafish.

We describe the identification of Mauthner (M-) cell action potentials in an intact zebrafish larva, utilizing recording electrodes located outside the fish: 1. The externally recorded spike occurs at approximately the same time, and its waveform changes with recording site in the same way, as the extracellular M-spike recorded within the central nervous system. 2. The externally recorded M-spike may be readily distinguished from other forms of neural activity. 3. The M-spike can be identified in recordings from unrestrained larvae. This finding permits the direct study of M-cell function in the freely behaving animal.

Action Potentials↗
PubMed1981

Morphogenesis and synaptogenesis of the zebrafish Mauthner neuron.

The shape of the Mauthner neuron (M-neuron) and the distribution of its afferent synapses were studied between days 2 and 6 after fertilization in the zebrafish Brachydanio rerio. This interval is just after the outgrowth of M-dendrites begins, and during this time the M-cell acquires its definitive shape. The M-cell has two large invariant dendrites: The lateral dendrite terminates in the sensory neuropil of the acoustico-lateral area, and th ventral dendrite terminates in the neuropil of the motor tegmentum. Fine dendrites are present, and mostly arise from three regions; from the terminus of each major dendrite and from the ventral surface of the perikaryon. The number and position of fine dendrites within each of these sets is variable, even among animals from a single isogenic clone. M-cells with improper numbers or positions of large dendrites were never encountered, even early in development. This suggests that their outgrowth is a highly directed process. Large numbers of afferent synapses are formed on the M-cell during the time of dendrite outgrowth. By day 6 there is a mosaic pattern of morphologically distinctive terminals that is similar to the pattern of the adult goldfish M-cell. Identified categories of terminals include (1) myelinated club endings, on the distal part of the lateral dendrite, (2) boutons, on the dendrites and perikaryon, (3) unmyelinated club endings, on the dorsomedial portion of the perikaryon adjacent to the axon cap, and (4) spiral fiber terminals within the axon cap. The nonrandom nature of the input may be ascertained by observing the distribution of electrotonic or gap junctions on the cell surface. These are frequently encountered on the initial segment of the axon (spiral fiber terminals), ventral dendrite and ventral perikaryon (boutons), and distal lateral dendrite (myelinated club endings). Gap junctions are only rarely observed on the dorsal surface of the cell, although this region, like others of the cell, receives large numbers of chemical synaptic contacts. This pattern is similar at all stages studied, which suggests that no large rearrangements in synaptic contacts occur during this developmental period. We discuss these observations in relation to the hypothesis that patterned dendritic growth of the M-cell is directed by synaptic interactions with the afferents.

Afferent Pathways↗
PubMed1979

Target recognition in neurogenesis: formation of the Mauthner axon cap.

To learn whether presence of a specific neuron, the Mauthner (M) cell, is required for the organization, during embryogenesis, of an associated synaptic neuropil, the M-axon cap, M-cell precursors were experimentally deleted in embryos of the zebra fish (Brachydanio rerio) and the axolotl (Ambystoma mexicanum). Examination of early larvae revealed that in about half of the cases M-axon caps were present in the absence of the corresponding M-cells. The locations and structures of such caps were approximately normal. We conclude that the M-cell is not a necessary target for normal development of the axon cap.

Ambystoma↗
PubMed1977

Functional development in the Mauthner cell system of embryos and larvae of the zebra fish.

In the embryonic zebra fish as early as 40 hr after fertilization, the Mauthner cells (M-cells) initiate an escape response, elicited by tactile-vibrational stimulation. The initial part of this behavior is similar to the acoustic startle reflex seen during the larval stage which begins at 96 hr. The embryonic response is directional and is followed by a series of strong tail flexures which are more pronounced than those during swimming. In the embryo the M-cell fired at the beginning of the response and rarely fired again during subsequent contractions; in our experiments the M-cell did not mediate iterative movements of the tail. The M-cell system is probably involved in evoked hatching behavior, as the tactile response is sufficient to rupture the egg membrane and allow the animal to escape. The M-cell sometimes fired spontaneously, which suggests that it might function also in spontaneous hatching behavior which occurs in the absence of phasic stimulation. At 48 hr the M-cell has morphologically mature synapses on its soma and dendrites, but its cytoplasm is relatively undifferentiated; it has few oriented neurofilaments and no distinct axon hillock. During these stages the extracellular M-spike is longer in duration and smaller in amplitude than at later times when the cell is more mature morphologically. Our data suggest that long-term inhibitory control of the M-cell system begins to function at about the time of hatching. At this time the cell is morphologically mature and is richly supplied with synaptic endings over its soma and dendrites.

Action Potentials↗