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M J Bastiani

Publications and source records attributed to M J Bastiani.

14 recordsLinked to original sources
PubMed1992

Position-specific expression of the annulin protein during grasshopper embryogenesis.

Annulin, named for its annular expression in developing limb buds, is a approximately 100 kDa membrane-associated protein that is expressed in a complex and changing pattern during grasshopper embryogenesis. Its expression is dynamic along the developing midline and in the mesoderm, transient in neuroepithelial sheath cells around mitotic neuroblasts, and position-specific in circumferential stripes in each limb bud segment. Annulin expression begins along the midline of the embryo at the onset of gastrulation. Mesoderm cells express the protein as they migrate away from the midline as do new cells that come to lie at the midline. During neurogenesis, annulin expression disappears from many midline cells until only a specific subset of midline glial cells expresses high levels of the protein. Starting at the beginning of neurogenesis, sheath cells express annulin in correlation with the mitotic activity of the neuroblasts they surround.

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PubMed1991

NeuroVideo: a program for capturing and processing time-lapse video.

We have developed a program for the Macintosh computer to control a Panasonic Optical Memory Disk Recorder (OMDR) in order to generate time-lapse video recordings of growing neurons. The software, in addition to regulating the timing of a recording in a flexible way, can also digitize and pre-process images before writing them out to the optical disk. NeuroVideo includes a complete set of functions to enhance images, and provides both an easy-to-use graphical interface and a simple but powerful text-based scripting language.

Animals↗
PubMed1991

The restricted spatial and temporal expression of a nervous-system-specific antigen involved in axon outgrowth during development of the grasshopper.

To identify molecules important for pathfinding by growing axons, monoclonal antibodies (mAb) have been generated against embryonic grasshopper tissue. One mAb, 2B2, shows labeling exclusively in the nervous system. It recognizes a surface epitope on neuronal growth cones, filopodia and axons in the central nervous system (CNS). Initially, the antigen is expressed on all processes of the CNS; after 70% of embryonic development, localization of the 2B2 mAb is restricted to a small subset of axon tracts within the ganglia. Immunoprecipitation from embryonic membrane extracts with the 2B2 mAb reveals a unique band of 160 x 10(3) Mr. Functional studies with the 2B2 mAb demonstrate that the antigen is important in growth cone-axon interactions during process outgrowth. Growth cones that extend along axonal substrata are either blocked in growth or grow along an aberrant pathway when embryos are cultured in the presence of the 2B2 mAb. However, pioneer neurons that extend processes on non-neuronal substrata grow normally.

Animals↗
PubMed1991

Developmental expression of REGA-1, a regionally expressed glial antigen in the central nervous system of grasshopper embryos.

Glial cells are a large component of the developing nervous system, appearing before the onset of axon outgrowth in a variety of developing systems. Their time of appearance and their location in conjunction with developing axon pathways may allow them to define the position of axon pathways. Specific glial cells may be utilized as guideposts by growing axons, allowing them to recognize the appropriate pathway, or conversely, glial cells may inhibit axons from growing along an inappropriate pathway. The 7F7 monoclonal antibody labels a subset of glial cells in grasshopper embryos that may play a role in defining the location of selected axonal pathways. This antibody recognizes the REGA-1 molecule, a cell-surface antigen with a molecular weight of 60 kDa, which is regionally expressed on developing glial cells. REGA-1 is expressed around the edges of clusters of glial cells and on lamellae extending from glial cells to line the edges of some axonal pathways. REGA-1 expression is first seen in the neuroblast sheet, surrounding neuroblast 4-1. Slightly later in development, 2 glial cells extend processes that express REGA-1 and demarcate the caudal edge of the anterior commissure. As the animal matures, cell processes expressing REGA-1 line the edges of the longitudinal connective, then expand to surround the central neuropil of the segmental ganglia. REGA-1 expression is also seen in conjunction with axons leaving the segmental ganglia via the segmental nerves and the intersegmental connectives. REGA-1 expression is limited to a subset of glial cells; some known glial cells such as the segment boundary cell do not express REGA-1. Glial cell processes expressing REGA-1 are seen only in association with axons, which suggests that these processes may act as borders or guard rails confining axons to the appropriate regions of the developing CNS. Axons navigating a path through the CNS may be prohibited from growing into inappropriate regions based on their inability to cross the boundaries established by glial cells expressing REGA-1.

Animals↗
PubMed1988

Characterization and cloning of fasciclin I and fasciclin II glycoproteins in the grasshopper.

Monoclonal antibodies were previously used to identify two glycoproteins, called fasciclin I and II (70 and 95 kDa, respectively), which are expressed on different subsets of axon fascicles in the grasshopper (Schistocerca americana) embryo. Here the monoclonal antibodies were used to purify these two membrane-associated glycoproteins for further characterization. Fasciclin II appears to be an integral membrane protein, whereas fasciclin I is an extrinsic membrane protein. The amino acid sequences of the amino terminus and fragments of both proteins were determined. Using synthetic oligonucleotide probes and antibody screening, we isolated genomic and cDNA clones. Partial DNA sequences of these clones indicate that they encode fasciclins I and II.

Amino Acid Sequence↗
PubMed1988

The central projections of the stretch receptor neurons of crayfish: structure, variation, and postembryonic growth.

Each stretch receptor neuron (SR) of the crayfish abdomen projects from its peripherally located soma an axon that enters the CNS through the second nerve (N2) of its segmental ganglion. Co2+ backfills of N2 revealed that this axon bifurcates, sending one branch to the brain and the other to the terminal abdominal ganglion. Each axon makes many short lateral branches as it traverses each of the other segmental ganglia, and has 2 major arborizations--one in the tritocerebrum of the brain and the other in the terminal abdominal ganglion, G6. These projections to G6 are described in detail. Individual SR axons from different segments were impaled in G6 with a Lucifer yellow-filled microelectrode, identified physiologically, and then filled to discover their structures. In a sample of more than 50 SR neurons, no systematic structural differences between the projections of phasic SR neurons and tonic SR neurons were observed. Three kinds of structural variability occurred in these projections to G6: unusual primary axon shape, long primary axon, and large terminal varicosities. Comparisons of SR neurons that originated in different segments revealed a segmental gradient in the probability of each structural variant. SR neurons from more anterior segments were more likely to show these structural variations. Comparisons of these variations in crayfish of different sizes showed that unusual primary axon shape and long primary axons were more probable in large crayfish than in small ones. Therefore, these variations are probably the products of postembryonic growth of the nervous system.

Animals↗
PubMed1988

The central projections of the stretch receptor neurons of crayfish: segmental gradients of synaptic probability and strength.

The 20 stretch receptor neurons (SRs) of the crayfish abdomen send axons into the CNS that then project both to the brain and to the last abdominal ganglion, G6 (Bastiani and Mulloney, 1988). In G6, we recorded intracellularly from different kinds of neurons postsynaptic to SR axons. In a sample of 100 postsynaptic neurons, 59 synapsed with both SR1 and SR2 axons, 19 synapsed only with SR1 axons, and 22 synapsed only with SR2 axons. Most monosynaptic connections in G6 were excitatory and behaved like typical chemical synapses. The EPSPs showed moderate facilitation but could be depressed about 50% by protracted stimulation at 20 Hz or more. In individual postsynaptic neurons, comparisons of synapses made by SRs that originated from different abdominal segments and from each side of the abdomen revealed gradients of probability of synaptic connection and of relative sizes of EPSPs; SRs originating in anterior segments were less likely to synapse with most postsynaptic neurons than were SRs originating in posterior segments, and the EPSPs caused by these anterior SRs tended to be smaller. Similarly, SRs contralateral to the postsynaptic neuron were less likely to make a connection, and the EPSPs they caused tended to be smaller than those caused by ipsilateral SRs. Some local interneurons in G6 had reversed anterior-posterior gradients in EPSP amplitude. Calculations of shape indices for PSPs from SRs originating in different segments and measurements of the maximum shunting by preceding PSPs from other SR axons indicated that neither electrotonic decrement in the postsynaptic neurons nor shunting could account fully for the observed gradients in PSP strength.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1987

Expression of fasciclin I and II glycoproteins on subsets of axon pathways during neuronal development in the grasshopper.

The "labeled pathways" hypothesis predicts that axon fascicles in the embryonic neuropil are differentially labeled by surface recognition molecules used for growth cone guidance. To identify candidates for such recognition molecules, we generated monoclonal antibodies (MAbs) that recognize surface antigens expressed on subsets of axon fascicles in the grasshopper embryo. The 3B11 and 8C6 MAbs immunoprecipitate 70- and 95-kd membrane glycoproteins called fasciclin I and II, respectively, which are expressed on different subsets of axon fascicles during development. These two glycoproteins are expressed regionally on particular portions of embryonic axons in correlation with their patterns of fasciculation, dynamically during the period of axon outgrowth in a manner consistent with a role in growth cone guidance, and at other times and places during embryogenesis, suggesting multiple developmental roles.

Animals↗
PubMed1986

Growth cones, dying axons, and developmental fluctuations in the fiber population of the cat's optic nerve.

We have studied the rise and fall in the number of axons in the optic nerve of fetal and neonatal cats in relation to changes in the ultrastructure of fibers, and in particular, to the characteristics and spatiotemporal distribution of growth cones and necrotic axons. Axons of retinal ganglion cells start to grow through the optic nerve on the 19th day of embryonic development (E-19). As early as E-23 there are 8,000 fibers in the nerve close to the eye. Fibers are added to the nerve at a rate of approximately 50,000 per day from E-28 until E-39--the age at which the peak population of 600,000-700,000 axons is reached. Thereafter, the number decreases rapidly: About 400,000 axons are lost between E-39 and E-53. In contrast, from E-56 until the second week after birth the number of axons decreases at a slow rate. Even as late as postnatal day 12 (P-12) the nerve contains an excess of up to 100,000 fibers. The final number of fibers--140,000-165,000--is reached by the sixth week after birth. Growth cones of retinal ganglion cells are present in the optic nerve from E-19 until E-39. At E-19 and E-23 they have comparatively simple shapes but in older fetuses they are larger and their shapes are more elaborate. As early as E-28 many growth cones have lamellipodia that extend outward from the core region as far as 10 microns. These sheetlike processes are insinuated between bundles of axons and commonly contact 10 to 20 neighboring fibers in single transverse sections. At E-28 growth cones make up 2.0% of the fiber population; at E-33 they make up about 1.0%; from E-36 to E-39 they make up only 0.3% of the population. Virtually none are present in the midorbital part of the nerve on or after E-44. At all ages growth cones are more common at the periphery of the nerve than at its center. This central-to-peripheral gradient increases with age: at E-28 the density of growth cones is two times greater at the edge than at the center but by E-39 the density is four to five times greater. Necrotic fibers are observed as early as E-28 in all parts of the nerve. Their axoplasm is dark and mottled and often contains dense vesiculated structures.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Guidance of neuronal growth cones in the grasshopper embryo. I. Recognition of a specific axonal pathway by the pCC neuron.

The selective affinities that growth cones display for specific axonal surfaces give rise to stereotyped patterns of selective fasciculation. Previous studies on cell recognition by neuronal growth cones in the grasshopper embryo led to the proposal and initial experimental testing of the labeled-pathways hypothesis. Here we report on a further experimental analysis of this hypothesis, using the first 3 longitudinal axon fascicles, which initially contain only the axons of 7 identified neurons. We describe and experimentally test the selective affinity of the pCC growth cone for the MP1 and dMP2 axons in the MP1/dMP2 fascicle. The pCC growth cone appears to demonstrate an absolute, rather than hierarchical, preference for the MP1/dMP2 fascicle, as compared with other longitudinal axon fascicles, which supports the notion that the surfaces of the MP1 and dMP2 axons have some special distinguishing label that guides the pCC growth cone onto and along them.

Animals↗
PubMed1986

Guidance of neuronal growth cones in the grasshopper embryo. II. Recognition of a specific axonal pathway by the aCC neuron.

In the previous paper, we experimentally analyzed the selective affinity of the pCC growth cone for the MP1/dMP2 fascicle in the grasshopper embryo. Here we describe a similar experimental analysis demonstrating the selective affinity of the aCC growth cone for the U fascicle. These results support the labeled-pathways hypothesis. The 2 sets of cell ablation experiments argue against the simple location of axons, the simple timing of axon outgrowth, and/or simple quantitative differences in the expression of a common surface label being the major determinant in pathway selection by neuronal growth cones. Rather, these 2 examples of growth-cone specificity, together with previous studies on the G growth cone, suggest that neuronal recognition molecules are differentially expressed on the surfaces of different embryonic axonal pathways and tracts and are used to guide growth cones through a series of choice points to their targets.

Animals↗
PubMed1986

Guidance of neuronal growth cones in the grasshopper embryo. III. Recognition of specific glial pathways.

In the previous 2 papers, we focused on the selective affinities that growth cones display for specific axonal pathways. Little is known, however, about how this orthogonal scaffold of axonal pathways in the CNS is established in the first place, and what, if any, role glia might play in these events. Here we show an important relationship between pioneering growth cones and primitive glial cells in the developing longitudinal connectives and peripheral nerve roots of the grasshopper embryo. We describe a preformed glial pathway for the formation of the intersegmental nerve, one of the major roots exiting the CNS. The growth cones that pioneer this nerve display a selective affinity for the segment boundary cell (SBC), a primitive glial cell that establishes the location of this nerve root. Similar glial cells are also found along the pathway where the longitudinal connectives form, and they too may play an important role in the formation of the first longitudinal axonal pathways. Experimental analysis shows that when the SBC is ablated, the growth cones that normally turn laterally to pioneer the intersegmental nerve do not do so, thus confirming the importance of the guiding role of this glial cell. We postulate that a simple orthogonal scaffold of primitive glia is involved in the initial patterning of axonal pathways within and exiting the insect CNS; this concept is remarkably similar to the blueprint hypothesis proposed by Singer et al. (1979) to explain the development of axon pathways in vertebrates.

Animals↗
PubMed1986

Guidance of neuronal growth cones in the grasshopper embryo. IV. Temporal delay experiments.

In the previous 3 papers, we demonstrated that neuronal growth cones display selective affinities for both specific axonal and glial pathways in the grasshopper embryo; for example, the pCC growth cone selectively recognizes the MP1/dMP2 axons, while the aCC growth cone selectively recognizes the U axons and a specific glial cell (the segment boundary cell). We were interested in further testing the temporal specificity of these affinities. To address this issue, we performed specific temporal transplant experiments by using a laser microbeam in ovo to ablate the neuronal precursor cell, neuroblast (NB) 1-1, that generates the aCC and pCC neurons. Neighboring ectodermal cells regulate and replace the ablated NB 1-1; the new NB 1-1 then generates the aCC and pCC neurons with a temporal delay of 10-20 hr (2-4% of development), depending upon the experimental paradigm. The results of these temporal delay experiments further demonstrate the selective affinities of the aCC and pCC growth cones for specific axonal and glial surfaces and confirm that these specificities are absolute and not hierarchical. Furthermore, they suggest that precise timing is not important; both the pCC and aCC growth cones are able to selectively recognize their appropriate axonal and glial pathways after delays of 10-20 hr despite being confronted with the surfaces of many additional axons and pathways.

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