acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

No description available.

No description available.

No description available.

No description available.

Grasshoppers are able to spontaneously drop, or autotomize, their large metathoracic legs, at the joint between the second and third leg segments. Previous work demonstrated that in the grasshopper, Barytettix psolus, autotomy transneuronally induces atrophy in a group of six metathoracic muscles on the ipsilateral side. These muscles are neither damaged nor denervated by the loss of the leg. The experiments presented in this dissertation support and extend the earlier work by including twelve additional metathoracic muscles, one of which was discovered as a result of these studies. These experiments demonstrated that atrophy varied both between muscles, as well as between fibers within individual muscles. Some muscles degenerated uniformly, whereas others contained persisting fibers long after neighboring fibers degenerated. Extent of atrophy in each muscle was quantified by measurement of total protein content. Histochemical staining of myofibrillar ATPase activity in a subset of muscles indicated that slow type fibers comprised the majority of those persisting following autotomy. Immunohistochemical experiments suggested that persistance of muscle fibers was correlated with innervation both by motor neurons (MNs) containing proctolin-like immunoreactivity (PLI), and by an inhibitory MN containing gamma-aminobutyric acid (GABA)-like immunoreactivity (GLI). The distributions of PLI and GLI indicated that these two types of MNs innervate muscles in parallel. In an attempt to identify the proctolin-like substance, muscle extracts of fourteen muscles were purified by HPLC and subjected to bioassay for proctolin-like bioactivity (PLB). Nine muscles with PLI also contained PLB. These experiments support the presence of proctolin in muscles with PLI. Four out of the five muscles lacking PLI also contained PLB. It is likely that these muscles contain at least one bioactive peptide that is biochemically similar to proctolin. These experiments are the first to suggest the association of proctolin-like substances with the majority of leg muscles in any insect. My immunohistochemical data combined with the results of previous experiments on the functions of proctolinergic and GABAergic innervation suggest that proctolin or proctolin-like substances are commonly used to maintain postural tonus in metathoracic leg muscles during standing and locomotory activities.

<p>The effects of high-voltage nanosecond electric pulses (nsEPs) on metastatic melanoma are still unclear. Hence, we applied one, two, three, and four 300 ns 40 kV/cm pulses to murine B16-F10 melanoma cells. Cell attachment ability was determined by comparing the number of floating cells and the percentage of attached cells. Melanoma inhibitory activity (MIA) is a secretory protein that is highly correlated with the malignancy and metastasis of malignant melanomas. We used MIA as our target to evaluate the effect of nsEPs on metastasis. Pulsed (experimental) and unpulsed (control) cells were incubated at 37&deg;C under a 5% CO₂ atmosphere. To determine cell attachment ability, the culture medium supernatant and attached cells were collected at 6, 12, 18, and 24 h after a single pulse. The live, dead, and total floating cells in the culture medium supernatant were counted. In addition, the live, dead, and total attached cells were counted after multiple pulses. Total RNA was extracted from the attached cells and reverse transcribed into cDNA. The MIA mRNA expression levels were measured using the cDNA temple via quantitative real-time PCR, with &beta;&ndash;actin as the internal control. The experiment was repeated three times (n=3). The results show that a single pulse did not affect the cell attachment ability, cell morphology, and the MIA mRNA expression levels (P=0.8058). Two pulses significantly decreased the cell attachment ability (P=0.014), cell viability (P&lt;0.0001), and changed the cell morphology, but did not change the MIA mRNA expression. The three-pulse and the four-pulse treatments significantly decreased the cell attachment ability (P=0.004, 0.00002, respectively), cell viability (P&lt;0.0001), changed the cell morphology, and increased the MIA mRNA expression levels within the first 12 h (P=0.041, 0.001, respectively). These indices were almost normal at 24 h after pulsing. We speculate that the two-, three-, and four-pulse treatments would be optimal for treating melanoma metastasis, whereas the single pulse treatment was not. Therefore, nsEPs provides a great opportunity for treating metastatic melanomas. </p>

The nervus terminalis (NT) is a ganglionated vertebrate cranial nerve of unknown function which connects the brain and the peripheral olfactory structures. Studies in the bonnethead shark (Sphyrna tiburo) were conducted to provide basic information on NT ganglion structure and function. / In vivo whole nerve recordings indicate that impulses from the brain suppress the activity of ganglion cells and suggest that synaptic interactions may occur in the ganglion. To understand better these synaptic interactions and the NT ganglion circuit, anatomical and electrophysiological studies were conducted. The NT ganglion contains at least two immunocytochemically distinct populations of cells: one cell type is luteinizing hormone-releasing hormone-immunoreactive (LHRH-ir) and another cell type is LPLRFamide-ir. Anatomical studies also suggest that LHRH-ir cells may receive both cholinergic and catecholaminergic inputs, while LPLRFamide-ir cells may receive cholinergic inputs and little or no catecholaminergic input. / The electrophysiological and pharmacological data is consistent with the anatomical findings, suggesting that at least two populations of cells contribute to whole nerve activity. One cell type may be excited by acetylcholine and depressed by norepinephrine, while another is depressed by acetylcholine and unaffected by norepinephrine. The responses of the NT system suggest that these populations may correspond to the LHRH-ir and LPLRFamide-ir cells, respectively. Intracellular recordings also support the whole nerve data, showing that some cells in the ganglion are spontaneously active, project centrally, and exhibit inhibitory potentials following nerve trunk stimulation. The responses of the few cells tested with pharmacological agents were consistent with those proposed for the LPLRFamide-ir cells. A cholinergic agonist elicited a marked hyperpolarization and a reduction in membrane resistance, while a catecholaminergic agonist had no influence on the cells. / Taken together, the data suggest that the NT ganglion is a complex system with functions unlike those of sensory and autonomic ganglia. / Source: Dissertation Abstracts International, Volume: 50-12, Section: B, page: 5490. / Major Professor: Michael Meredith. / Thesis (Ph.D.)--The Florida State University, 1989.