Biomedical subjects

J R Trimarchi

Publications and source records attributed to J R Trimarchi.

21 records · Page 2Linked to original sources

PubMed1995

Different neural pathways coordinate Drosophila flight initiations evoked by visual and olfactory stimuli.

To determine the role played by the giant fiber interneurons (GFs) in coordinating the jumping stages of visually elicited and olfactory-induced fight initiation we have recorded extracellularly from the cervical connective nerve during flight initiation. A spike is recorded from the cervical connective upon brain stimulation that has the same threshold as does activation of the tergotrochanteral muscle (TTM) and dorsal longitudinal muscles (DLMs). A consistent time interval occurs between the spike and activation of the TTM. Thus, the spike probably results from activity in the GFs. The time intervals between the spike and activation of the TTM during GF stimulation and visually elicited flight initiation are similar. These results suggest that the GFs coordinate the activation of the TTM and DLMs during the jumping stage of visually elicited flight initiation. A spike is also recorded from the cervical connective during olfactory-induced flight initiations, but its shape and the time interval between it and activation of the TTM is different from that observed during GF stimulation. Although some olfactory-induced flight initiations exhibit a pattern of muscle activation, olfactory-induced flight initiations exhibit a pattern of muscle activation indistinguishable from that evoked by GF stimulation, our results indicate that regardless of the pattern of muscle activation, olfactory-induced flight initiations are not coordinated by the GF circuit. The sterotypic sequence and timing of activation of TTM and DLMs characteristic of the GF pathway can, therefore, be evoked by neurons other than those constituting the GF pathway.

Action Potentials↗

PubMed1994

The motor neurons innervating the direct flight muscles of Drosophila melanogaster are morphologically specialized.

The anatomy of the motor neurons innervating six direct flight muscles in Drosophila melanogaster has been investigated by using a horseradish peroxidase backfilling technique. The somata of these motor neurons are arranged in two distinct clusters ipsilateral to the muscle they innervate. One cluster of cell bodies is located in the ventrolateral region between the prothoracic neuromere and the mesothoracic leg-related neuropil and the other is situated dorsally and posteriorly to the mesothoracic leg-related neuropil. Axons from somata in the ventrolateral cluster run in the anterior dorsal mesothoracic nerve, while axons from somata in the other cluster run in the mesothoracic accessory nerve. This distribution of somata and axons is discussed in the light of the morphological similarity and proximity of these functionally related muscles. On the basis of the branching patterns of their neurites, direct flight muscle motor neurons can be classified as stubbly, fibrous or tufted. The terminal arborizations of the motor neurons over the direct flight muscles are also morphologically specialized. Both the central and the peripheral morphological specializations of the direct flight muscle motor neurons correlate with the activity patterns exhibited by their associated muscles during flight and courtship song.

Animals↗

PubMed1993

Giant fiber activation of an intrinsic muscle in the mesothoracic leg of Drosophila melanogaster.

Cinematographic analysis reveals that an important component of the light-elicited escape response of Drosophila melanogaster is the extension of the femur-tibia joint of the mesothoracic leg. During the jumping phase of the response, this extension works synergistically with extension of the femur. Femur extension is generated by contraction of the tergotrochanteral muscle (TTM), one of four previously described escape response muscles. Femur-tibia joint extension in the mesothoracic leg has been thought to be controlled by contraction of the tibial levator (TLM), an intrinsic leg muscle. We investigated the activation of the TLM during the escape response. Electrical stimulation of the giant fiber interneuron that mediates the escape response results in activation of the TLM with a latency of 1.46 +/- 0.02 ms. The TLM is innervated by a motor neuron (TLMn) with a large cell body in the mesothoracic ganglion. The TLMn has extensive arborizations in the lateral mesothoracic leg neuromere and has a prominent medially directed neurite. To investigate possible presynaptic inputs activating the TLMn during the escape response, we analyzed the muscle responses of two mutants, giant fiber A1 and bendless. Our analysis suggests that the TLMn is activated by a novel pathway.

Animals↗