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J Casullo

Publications and source records attributed to J Casullo.

5 recordsLinked to original sources
PubMed1995

On the perception of the left thoracic paraspinal line.

RATIONALE AND OBJECTIVES: We investigated whether the left thoracic paraspinal line represents an actual change in optical density corresponding to the posterior pleural reflections or whether it represents a Mach band effect. METHODS: Using photodensitometry, we obtained averaged light intensity tracings across the left thoracic paraspinal line in 14 normal digitized anteroposterior (AP) thoracic spine radiographs. We also performed a mathematical simulation of relative brightness perception by using the contrast sensitivity function of the human visual system (assumed to represent the modulation transfer function) to filter the light intensity profiles by fast Fourier transformation techniques. RESULTS: Results from 14 normal AP thoracic spine radiographs showed no significant increase in light transmitted over the perceived location of the paraspinal line. A simple linear systems analysis of the behavior of the visual system predicted a Mach band effect corresponding in location to the observed paraspinal line. CONCLUSION: The spatial pattern of optical densities in the region of the left thoracic paraspinal line rather than the tissue composition is the crucial factor responsible for the perception of the paraspinal line.

Absorptiometry, Photon↗
PubMed1988

Septohippocampal disinhibition.

Intracellular recordings from CA1 and CA2/3 neurons in rats under urethane anesthesia revealed the following effects of medial septal stimulation (10 pulse trains at approximately 100 Hz): (1) in most cases only minimal signs of any synaptic potential; (2) a marked and prolonged (200-500 ms) depression of on-going inhibitory postsynaptic potentials (IPSPs), particularly evident when IPSPs were reversed by Cl- injection; (3) a corresponding increase in input resistance: (4) depolarization when recording with non-Cl(-)-containing electrodes; (5) a predominant hyperpolarization when recording with Cl(-)-containing electrodes; and (6) a marked reduction of the variability of resistance and voltage data. These observations indicate that septal stimulation can strongly depress tonic inhibition in the hippocampus. Septal trains also tended to weaken IPSPs evoked in pyramidal cells by fimbrial stimulation, reducing conductance increase during IPSPs by an average of 42% (S.D. +/- 24.3). Septal inputs to the hippocampal CA1 and CA2/3 regions appear to have a major disinhibitory function.

Action Potentials↗
PubMed1987

Glial potentials in hippocampus.

In rats under urethane anaesthesia, intracellular recordings were made from 36 cells, mainly in CA1, that had all the characteristics of glia: unusually high and stable resting potentials (-79.6 +/- 6.0 mV, mean +/- SD) and total absence of spikes or synaptic potentials. They were exceptionally sensitive to surrounding neuronal activity, being readily depolarized by very low frequency stimulation (0.5-2 Hz) of the fimbria. In the range 0.5-2 Hz, the mean peak depolarizations increased linearly with frequency of fimbrial stimulation (9.1 +/- 0.53 mV/Hz). At frequencies of 5 Hz or more, the depolarizations were highly variable, sometimes reaching a maximum of 25-30 mV, but the overall mean was not significantly greater than for 2 Hz stimulation. The depolarizations decayed slowly, with a half-time of 4.2 +/- 1.22 s and were often followed by a prolonged undershoot (lasting over 1 min). Alvear and especially septal stimulation were much less effective in evoking glial depolarizations. One cell that initially had all the characteristics of a glia, during very prolonged stable recording, developed responses, such as synaptic potentials and 20-40 mV action potentials evoked by fimbrial or alvear stimulation, consistent with strong electrical coupling to at least one neighbouring neuron.

Animals↗