Biomedical subjects

E F Vastola

Publications and source records attributed to E F Vastola.

18 recordsLinked to original sources

PubMed1983

Antidromic conduction in a direct posterior pathway from midbrain to hippocampus.

An average field response to electrical stimulation in the hippocampus has been recorded in dorsomedial rat midbrain. The fully developed response is triphasic. Latencies of the three components and their behavior during repetitive stimulation are compatible with the assumption that they are antidromic and originate, respectively, in proximal axons, cell bodies and dendrites. Conduction velocity is estimated to be 5 m/s. Reversal in polarity of the response at different recording points within a distance of 1 mm and abolition by small midbrain lesions confirm location of the active neural elements in that region. Lesions in the white matter of posterior cingulum and in the thalamocortical radiation abolish the response. Latencies of the response recorded in the thalamocortical radiation are in accord with the conclusion that the fibers pass in this location. The findings support results of an earlier study suggesting that visual information is transmitted without a synapse from dorsomedial midbrain to dentate gyrus by a pathway that reaches the cerebral hemisphere in the thalamocortical radiation and enters hippocampus from white matter in the posterior cingulum. A study of visual responses in the medial and dorsal wall of the cerebral hemisphere in lizards may help to evaluate the hypothesis that in these regions are the ancestral homologues for dentate gyrus and cornu ammonis, respectively, in mammalian hippocampus.

Animals↗

PubMed1982

Electrical signs of an oligosynaptic visual projection to the rat hippocampus.

In rats with pons transection photic or optic nerve stimulation elicits a response in dorsal hippocampus with approximately with same latency, amplitude and time course as the response in striate cortex. After optic nerve stimulation a positive polyphasic deflection with the last peak at 10 ms is followed by a larger biphasic major deflection with peaks at 15 and 25 ms and later, slower deflections at intervals of 125 ms. The polyphasic deflection is maximal in the inferior part of the hippocampus but does not reverse polarity; the other deflections reverse above and below an isoelectric point in the hilum of the dentate gyrus, a distribution attributable to depolarization in the molecular layers, perhaps also cell bodies, of that structure. The major deflection is more sensitive to changes in optic nerve stimulus strength than the response in striate cortex and is more resistant to reduction in amplitude during repetitive stimulation, following frequencies up to 50/s. The pathway between retina and hippocampus for all parts of the response is interrupted by lesions in the tectum. The major deflection is abolished by lesions in the posterior cingulum. In the posterior cingulum the pathway has fast and slow components in the lower and upper portions, respectively, associated with the first and second parts, respectively, of the major deflection. The pathway is not interrupted by lesions in the fornix, septal nuclei, anterior cingulum, anterior medial thalamus or medial midbrain ventral to the superficial tectum. There are complex interactions, up to several hundred milliseconds in duration, between the response to optic nerve stimulation and those elicited by stimulation in the cingulum, midbrain and thalamus. Tonic influences on the dentate gyrus from cingulum and tectum are described.

Animals↗

PubMed1980

CSF formation and absorption estimates by constant flow infusion method.

The constant-flow infusion method has been used to calculate conductance and the rate of CSF formation in 54 patients with varied but stable clinical pictures, normal CSF pressures, and dilated ventricles. Values for conductance varied from 0.00203 to 0.0263 mL/min/mm H2O, with a peak between 0.005 and 0.010, mL/min/mm H2O. Values for CSF formation uncorrected for a small, negative linear term containing the sagittal sinus pressure varied from 0.114 to 3.0 mL/min, with a peak between 0.5 and 1.0 mL/min, a range considerably larger than that given by earlier studies. Results indicate that CSF formation is reduced in the presence of low conductance. There is a possibility that the syndrome of normal pressure hydrocephalus results from underformation with ventricular stagnation. Low conductance values may identify shunt-responsive syndromes.

Adult↗

PubMed1977

Antidromic activity in visual radiation during evoked cortical responses.

1. Antidromic stimulation of the visual radiation of cats has been used to investigate the possibility that some of the activity in principal geniculate cells following an optic tract stimulus is antidromic. Single spikes were selected from two classes of poststimulus activity to condition the antidromic test spike--the undoubted orthodromic postsynaptic spike and the later spikes, occurring up to 100 ms after the optic tract stimulus. 2. In 15 of 39 cells the minimum antidromic activation times and the minimum spike-spike intervals were found to be shorter and latencies for antidromic stimulation were longer when the conditioning spikes belonged the class of late poststimulus activity. The differences are in accord with the assumption that some of the conditioning spikes were antidromic. 3. Test spikes were frequently found to have long and variable latency when the conditioning spike occurred more than 45 ms after the optic tract stimulus. Possible reasons are briefly discussed. 4. It is suggested that antidromic activity may occur in conditions of the cortex that are more physiological than those associated with a penicillin-induced seizure focus. Some possible mechanisms and functional significance are briefly discussed.

Animals↗

PubMed1976

Biological signal detection by the autocorrelogram and a recurrence frequency method.

The signal detection property of the autocorrelation function (ACF) is conventionally derived on the assumption of two conditions that may not be present in biological time sequences: (1) the measured variable is assumed to be the sum of a noise and a signal function; (2) the signal function is assumed to continue throughout the sequence. In neuroelectric sequences of all-or-none responses the first assumption would not be appropriate if most of the elements seen by the recording electrode were accessible to the signal input. The sensitivity of the ACF was investigated in simulated sequences in which the random noise was entirely replaced by a periodic square wave signal function for a small number of repetitions and the results compared with a recurrence frequency function (RFF) developed during this work; under these conditions the ACF proved to be significantly inferior. Sensitivity of the ACF was the same for a pure signal function as for an additive function of signal and noise but sensitivity of the RFF was severely degraded for the latter. A variety of neuroelectric sequences was studied and many were found in which strong rhythmic processes revealed by RFF were not detected by the ACF. It is suggested that both methods be used when the signal function may be present during only a small part of the data-collection period and when it is not known to what degree the measured variable may be the sum of a noise and signal function. When an additive function is known to exist, the ACF will be the method of choice; for pure signal functions REF will be more sensitive.

Animals↗

PubMed1976

Clinical effects of cyclophosphamide in Guillain-Barré polyneuritis.

(1) Fifteen patients with severe Guillain-Barré polyneuritis in progression were treated with cyclophosphamide in a total of 23 courses. The illnesses in 11 patients were monophasic, 2 were biphasic and 1 was of the chronic, relapsing variety; another was possibly biphasic. Length of illness prior to first course of cyclophosphamide was as follows: less than 1 week, 3; 1-4 weeks, 9; greater than 4 weeks, 3. (2) Progression stopped in association with 21 courses of treatment, in 6 before the treatment course was finished and in 15 an average of 3 days after the last dose. Improvement began during or following 19 courses. (3) Time when progression stopped, time from end of progression to beginning of improvement, and subsequent rate of recovery, suggest that cyclophosphamide made a significant contribution to the recovery processes in 13 patients. (4) Ultimate degree of recovery was not significantly different from that expected in conventionally treated patients with monophasic illnesses. (5) Reversible alopoecia was the only significant complication attributable to cyclophosphamide toxicity. (6) Our experience suggests that further evaluation of cyclophosphamide should include the use of controls and earlier treatment.

Adolescent↗

PubMed1973