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S J Zottoli

Publications and source records attributed to S J Zottoli.

31 records · Page 2Linked to original sources
PubMed1987

Morphological and physiological survival of goldfish Mauthner axons isolated from their somata by spinal cord crush.

Axon segments isolated from their somata degenerate within days or months depending on species and neuronal type. To better understand the time course of morphological and physiological changes associated with degeneration of axon segments of vertebrate central neurons, we have studied the goldfish Mauthner axon (M-axon) when it has been separated from its soma by spinal cord crush. M-axon segments survive morphologically for at least 77 days at 14 degrees C. Cross-sectional areas of isolated M-axon segments (measured 25-30 mm caudal to the wound site at postoperative days 64 and 77) were greater than those of control axons at the same level. Sheath areas did not change. Electron microscopic observations at the same spinal cord location indicated no clear changes in the configuration or number of neurofilaments or any other organelle. M-axon segments studied morphologically after 87 postoperative days had all degenerated. Mauthner axon segments were capable of conducting action potentials and eliciting ipsilateral EMG responses. Repetitive firing of the M-axon segments elicited EMG responses that fatigued more easily and remained fatigued over a longer interval than did those of control axons. The long duration of M-axon segment survival is unusual in a vertebrate and may be due to the low temperature at which the experiments were conducted (14 degrees C) and/or temperature-independent factors. The increased susceptibility to synaptic depression, which has not reported previously, may represent an early sign of the degenerative process.

Animals↗
PubMed1987

Comparison of acetylcholinesterase and choline acetyltransferase staining patterns in the optic tectum of the goldfish Carassius auratus. A histochemical and immunocytochemical analysis.

Although the optic tectum of nonmammalian vertebrates has been extensively studied anatomically, there is little information about the identification of neurotransmitters and the enzymes critical to their synthesis. Choline acetyltransferase (ChAT), the enzyme responsible for acetylcholine synthesis, is presently regarded as the most reliable marker for cholinergic neurons, and its localization within putative cholinergic neurons has been made possible by the development of antibodies specific to ChAT. We have compared the immunocytochemical localization of ChAT to the histochemical staining of acetylcholinesterase (AChE) in the goldfish optic tectum. Goldfish brains reacted with the monoclonal antibody AB8 to ChAT have revealed that: (1) type XIV neurons are the only ChAT-positive cells in the tectum, and there are approximately 15,000 such cells per tectal hemisphere; (2) these neurons and other ChAT-containing afferent fibers form bands of label which correspond to those seen after AChE staining, and (3) many AChE-stained neurons do not contain ChAT. The immunohistochemical localization of ChAT has provided a direct method for determining the localization and organization of putative cholinergic structures in the optic tectum of goldfish. Future studies may elucidate the relationship of these cholinergic systems to the retinotectal projections, as there is close correspondence between AChE and ChAT location and the retinotectal termination patterns.

Acetylcholinesterase↗
PubMed1986

Choline acetyltransferase immunohistochemical staining in the goldfish (Carassius auratus) brain: evidence that the Mauthner cell does not contain choline acetyltransferase.

In the hatchetfish, the Mauthner cell (M-cell) is thought to be cholinergic based on electrophysiological studies using cholinergic agents and on the localization of acetylcholinesterase (AChE) and alpha-bungarotoxin to M-cell-giant fiber synapses. Immunocytochemical studies have shown that mammalian and non-mammalian cholinergic neurons stain positive for choline acetyltransferase (ChAT), the enzyme responsible for synthesizing acetylcholine. We processed tissue from the goldfish (Carassius auratus) for the immunohistochemical detection of ChAT using the monoclonal antibody AB8 and the peroxidase-antiperoxidase procedure. ChAT immunoreactivity was found in selected areas of the goldfish brain including the cranial nerve nuclei and the ventral horn motoneurons of the spinal cord. Interestingly, the M-cell soma which stains positive for AChE was ChAT negative. This immunohistochemical evidence does not support cholinergic functioning of the Mauthner cell.

Acetylcholinesterase↗
PubMed1986

Altered excitability of goldfish mauthner cell following axotomy. I. Characterization and correlations with somatic and axonal morphological reactions.

Axonal transection 7-10 mm distal to the cell body of the goldfish Mauthner (M) cell induced alterations in its excitability; namely, the antidromic spike recorded in the soma was converted from a single-component axon-hillock response to a larger amplitude, two-component impulse. The mean spike amplitude of the axotomized cells was approximately 50% greater (59.6 +/- 15.1 mV, n = 94) than that in controls (39.4 +/- 6.3 mV, n = 73). The onset of the induced increase in spike amplitude occurs at approximately 20 days postaxotomy, and the transition to a reactive spike is complete by approximately 30-35 days. Eighty-three percent of the M-cells axotomized for more than 30 days were physiologically reactive as judged by their large spike amplitudes and/or the presence of an additional spike component. Concomitant with the enhanced spike amplitudes, there was a depression of excitability in the initial segment-axon hillock region of the axotomized cells. This depression was suggested by a decrease in the initial segment (IS) spike height (from 39.4 +/- 6.3 mV, n = 73, in controls to 27.5 +/- 5.6 mV, n = 13, in axotomized cells), a decrease in its maximum rate of rise (from 153.6 +/- 24 V/s, n = 15, to 112.5 +/- 30 V/s, n = 29), and frequent failure of antidromic invasion into the initial segment and axon hillock. These changes in excitability could not be attributed to alterations in passive membrane properties, since the mean resting potential (77.8 +/- 5.2 mV, n = 37, control; 76.9 +/- 7.8 mV, n = 87, axotomized) and input resistance (170 +/- 21.3 K omega, n = 13, control; 176 +/- 26.6 K omega, n = 21, axotomized) were not altered significantly by axotomy. Threshold voltage was also unaffected (13.4 +/- 3.2 mV, n = 11, control; 11.9 +/- 2.5 mV, n = 11, axotomized). Sequential recordings of spike amplitudes from the axon hillock, soma, and lateral dendrite suggest that the generator of the axotomy-induced component is localized to the normally passive soma and proximal dendrite. In addition, the presumed soma-dendritic In addition, the presumed soma-dendritic component contributes very little if anything to the action potentials recorded in the axon. The onset and occurrence of alterations in excitability and cell body morphology (chromatolysis and nuclear associated changes) were compared in different M-cell populations and in the same identified M-cells. The comparisons suggested that these two events tend to occur in parallel.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

The axon reaction of the goldfish mauthner cell and factors that influence its morphological variability.

The axon reaction of the goldfish Mauthner cell, elicited by spinal cord transection, included somatic swelling, nuclear eccentricity, chromatolysis, nuclear infolding, and a perinuclear buildup of basophilic material. The latter three changes were found most consistently and showed gradations which were ranked quantitatively. The time of onset of chromatolysis and nucleus-associated changes depended upon the distance of the wound from the Mauthner cell soma. Specifically, for Mauthner axons cut at 5, 10.5, and 20 mm distal to their somata, the approximate postoperative times of onset were 10, 20, and 40 days, respectively. Mauthner cells axotomized 42 mm distally did not display a consistent axon reaction. Cell atrophy and death were not found in cells axotomized 10.5, 20, or 42 mm from their somata up to 285 postoperative days, but were observed at the longer postoperative intervals (421 days) in neurons cut 5 mm distally and were consistently found in neurons axotomized less than 1.6 mm from their somata. The axon reactions of Mauthner cells within a pair were frequently different. This variability cannot be explained by the influence of cut site or postoperative interval and is hypothesized to result from different metabolic conditions of the individual cells.

Animals↗
PubMed1983

Posterior lateral line afferent and efferent pathways within the central nervous system of the goldfish with special reference to the Mauthner cell.

The goldfish posterior lateral line nerve consists of a dorsal and a ventral branch, each of which is associated with a ramus of the sensory branch of the VIIth nerve (ramus recurrens facialis). The afferent and efferent pathways of these nerves within the central nervous system were studied by using horseradish peroxidase (HRP) histochemistry. The afferent fibers of the ramus recurrens facialis travel in the ventral portion of the VIIth nerve as it enters the brain and project predominantly to the ipsilateral half of the facial lobe. The afferent fibers of either the dorsal or ventral branch of the posterior lateral line nerve split into two bundles as they enter the brain. The caudally projecting fascicle terminates predominantly in the nucleus medialis. The fibers of the rostrally projecting bundle terminate predominantly in nucleus medialis and nucleus magnocellularis and in the eminentia granularis. The posterior lateral line efferent somata were located in the diencephalon as well as in the medulla oblongata. The medullary efferent neurons formed two distinct groups, a rostral and a caudal nucleus. The cell bodies of the latter were more numerous and larger than those of the former. The axons of the efferent neurons exit from the brain by one of two routes. The first is at the level of the rostral efferent nucleus and the second at the level of the Mauthner cell. Previous reports have described input of posterior lateral line afferent fibers to the Mauthner cell soma and proximal lateral dendrite of the goldfish. This electrophysiological input was bilateral and was interpreted as monosynaptic. The afferent input described in this study was ipsilateral and ended in the vicinity of the distal lateral dendrite. These differences are discussed in the context of the neuronal circuitry that may be present.

Animals↗
PubMed1981

Mauthner axon diameter and impulse conduction velocity decrease with growth of goldfish.

Conduction velocities of antidromically evoked impulses along the goldfish Mauthner axon were found to be inversely correlated with body length. To test the hypothesis that such a relation is accompanied by a reduction in axonal diameter with increasing fish size, Mauthner axon diameters were measured. A parabolic relationship with respect to body length was obtained, axonal diameter being maximal in 9.5 cm fish. To our knowledge, this is the first report of a decrease in conduction velocity and axonal size during growth of an organism were functioning of the cell is maintained.

Aging↗
PubMed1981

Axotomy-induced changes in cell structure and membrane excitability are sustained in a vertebrate central neuron.

The retrograde reactions of the goldfish Mauthner neuron to axotomy 8-10 mm caudal to its soma are detectable within a few weeks and persist for more than 200 days. Morphological changes include chromatolysis, reflecting a redistribution of cytoplasmic ribosomes, and infolding of the nuclear membrane. At the time, the normally inexcitable soma-dendritic membrane becomes capable of impulse initiation; this induced excitability also persists for at least 200 days.

Action Potentials↗
PubMed1978

Comparison of Mauthner cell size in teleosts.

The Mauthner cells (M-cells) are a pair of neurons found in the medulla oblongata of most fish and amphibians. This neuron is not the same size in all teleosts. Based on the hypothesis that differences in M-cell size might be related to fish family and possibly fish habitat, M-cell and nuclear size were compared between fish families. In order to minimize effects of fish length on cell or nuclear size, statistical treatment of the data was made for four separate length classes. The results indicate at least three groupings by cell or nuclear size. The cell is large in fish from the Salmonidae, Catostomidae and Cyprinidae, small in the Stichaeidae, Cottidae and Pleuronectidae and absent in Batrachoididae, Lophiidae, Ogcocephalidae and Cylopteridae. In general a correlation exists between fish that lack or have small M-cells and a demersal habitat. Since these fish may rely on camouflage for protection against predation, the M-cells may have altered excitability or function as compared to more active fish in which the M-cell is known to function in initiating the startle response (larval zebrafish and goldfish). Differences in input to M-cells of different sizes in conjunction with known electrophysiological properties of the goldfish M-cell are discussed in relation to the function of this neuron.

Animals↗
PubMed1977

Correlation of the startle reflex and Mauthner cell auditory responses in unrestrained goldfish.

Stainless-steel electrodes were implanted near the left or right. Mauthner cells (M-cells) of goldfish to determine if these cells can initiate the startle reflex evoked by a brief sinusoidal sound stimulus. Recordings of the M-cell extracellular spike were obtained for the duration of 10 experiments. Fish with chronic implants were allowed to free-swim and exposed to at least 10 consecutive sound stimuli consisting of 2 cycles of 200 Hz. Seventy-three startle responses were analysed. In 34 cases the implanted M-cell electrode was contralateral to the contracting musculature, and in each of these cases, a M-cell spike preceded the EMG response by 1-1-2-1 ms. In the reamining 39 cases the electrode was ipsilateral to the active musculature, and the M-cell only fired in one of these trails. There were no startle responses and no M-cell firings in an additional 52 tests. Since the M-cell activates contralateral motoneurones, the results indicate it is responsible for initiation of the startle reflex.

Action Potentials↗