Glenn H. Parker

Temporal changes in neuronal dropout following inductions of lithium/pilocarpine seizures in the rat

Estimates of neuronal dropout for approximately 100 structures as defined by Paxinos-Watson were completed for brains of male Wistar albino rats between 1 and 50 days after status epilepticus was evoked by a single systemic injection of lithium and pilocarpine. Sample estimates of neuronal loss were strongly correlated with direct measures of cell density. The most extensive immediate damage occurred within the substantia nigra reticulata, CA1 field of the hippocampus, the piriform cortex and the reuniens and paratenial nuclei of the thalamus. Neuronal dropout continued in many other structures over a 50-day period. Structures that showed the greatest 2-deoxyglucose (2-DG) uptake during discrete seizures and waxing and waning seizures within the early stages of status epilepticus but the least 2-DG uptake at the time of late continuous spiking and fast spiking with pauses [Neuroscience 64 (1995) 1057, 1075] exhibited the most neuronal dropout. Relationships between the delay of injection of acepromazine (which facilitated survival) and the amount of damage suggested that the source of the process that results in permanent brain damage may originate within the region of the piriform cortices and its subcortices.

Absence of maternal behavior in rats with lithium/pilocarpine seizure-induced brain damage : support of MacLean's triune brain theory

Female rats, with and without maternal experience, received limbic seizure-inducing (SC) injections of lithium and pilocarpine. Following the subsequent parturitions, these rats displayed a complete absence of maternal behavior. Rats that did not display seizures after receiving the lithium/pilocarpine injections displayed behaviors that were comparable to normal controls. Although the multifocal limbic, thalamic, and cingulate damage abolished maternal care, there was no evidence of aberrant effects upon fecundity, litter size, or mammary function; infanticide was negligible. The pattern of brain damage involves the evolutionarily more recent thalamocingulate system of mammals and supports MacLeans theory that these pathways are required for normal mother-offspring interaction.

Prevention of sudden cardiac death by the atypical neuroleptic acepromazine following status epilepticus in rats

Normal male rats in which status epilepticus has been induced by injecting 30 mg/kg of pilocarpine after a single systemic administration of lithium (sufficient to produce blood levels of 0.2 mEq/L) invariably die within 24 hr. Real-time monitoring indicated sudden cardiac death; it was preceded by progressive intensification of arrhythmia. A single systemic injection (25 mg/kg) of the atypical phenothiazine acepromazine prevented the mortality and virtually eliminated the cardiac instability.

Effect of enhanced geomagnetic activity on hypothermia and mortality in rats.

The hypothesis was investigated that variability in the severity of limbic seizure-induced hypothermia in rats was affected by ambient geomagnetic activity. Data were obtained in support of this hypothesis. The depth of the hypothermia was significantly (P < 0.001) reduced if the ambient geomagnetic activity exceeded 35 nT to 40 nT. Mortality during the subsequent 5 days was increased when the geomagnetic activity was > 20 nT. The magnitude of the effect was comparable to the difference between exposure to light or to darkness during the 20 h after the induction of limbic seizures.

Copper, nickel, and iron in plumage of three upland gamebird species from non-contaminated environments

High levels of atmospheric contamination and particulate fallout characterizing the Industrial Basin of the copper-nickel smelting operations at Sudbury, Ontario, were shown to be reflected in the feather chemistry of resident ruffed grouse populations. Of considerable concern, however, is the paucity of information on background concentrations of elemental metals that could be considered normal for non-contaminated environments. The present report examines concentrations of copper, nickel and iron in the plumage of three tetraonid species collected from remote and undisturbed areas in Northern Ontario and Quebec.

Insidious weight gain in prepubertal seized rats treated with an atypical neuroleptic: the role of food consumption, fluid consumption, and spontaneous ambulatory activity.

Extreme obesity slowly develops in female rats over the months following seizures induced by a single systemic injection of lithium and pilocarpine if the resulting limbic seizures are treated with the atypical neuroleptic acepromazine (but not with ketamine). To discern the contributions from food consumption, water consumption, and (daytime and nighttime) activity to this weight gain, these behaviors were monitored for 4 months, about 2 months after seizure induction. The results indicated that the rats that underwent the obesity procedure exhibited 50% heavier body weights and consumed 42% more food than the reference group, which included rats that had been induced to seize but treated with ketamine. There were no statistically significant differences between groups with respect to either water consumption or (daytime or nighttime) activity. Factor analyses of data for individual rats verified the dissociation between activity and weight gain for the obese rats. The results suggest that the progressive weight gains are centrally mediated and are not secondary to diminished activity or altered fluid consumption.

Agonistic behavior in groups of limbic epileptic male rats: pattern of brain damage and moderating effects from normal rats.

Different ratios of normal male rats and male rats in which limbic seizures had been induced by a single systemic injection of lithium and pilocarpine were housed in groups of six. The group ratios ranged along the continuum from all normal rats to all experimental rats. The average numbers of episodes of boxing, biting and mounting--thrusting per rat per hour per group were recorded by direct observation (red light) for 1 h during the midscotophase. Groups that contained less than two normal rats exhibited significantly elevated amounts of agonistic (boxing, biting) behavior but not mounting behavior. Multiple regression analyses showed that combinations of neuronal loss within only two to three areas accommodated at least 50% of the variance in the numbers of these behaviors.

Metal burdens in two species of fiddleheads growing near the ore smelters at Sudbury, Ontario, Canada

The usefulness of selected plant species as potential bioindicators of environmental metal pollution has been clearly demonstrated. High levels of contamination within soils of the Sudbury, Ontario region are characteristically reflected in elevated plant burdens reported for the area. Previous studies investigating plant uptake of metals from Sudbury-area soils have been complicated, however, by the contribution of direct atmospheric deposition onto the foliage. The present study examines metal burdens in two fern species, Interrupted fern and Ostrich fern, resulting solely via root uptake from the soil, thus seeking to assess the indirect influences of the Sudbury-area smelters. The above condition was ensured by collecting the ferns immediately after appearance in the spring while they were still tightly curled and protected from aerial contamination of by the external wooly pubescence.

Post-seizure drug treatment in young rats determines clear incremental losses of frontal cortical and hippocampal neurons: The resultant damage is similar to very old brains

Loss of neurons occurs with aging and following lithium/pilocarpine-induced epileptic seizures. In the present study, the numbers of neurons within the layers from sample areas of the four lobes of the neocortices and the hippocampus were counted by light microscopy in brains of rats that had been administered lithium or pilocarpine and then injected immediately or shortly after seizure onset with either acepromazine, ketamine, or prazosin. The mean numbers of neocortical and hippocampal neurons were lowest in rats treated with acepromazine or prazosin 1h after seizure onset, while those of rats immediately treated with ketamine displayed the least decrements and were most similar to normal rats. The largest loss of neurons occurred within the CA1 field and layers 5 and 6 of the frontal cortices. The mean numbers of neurons within the cortices in rats whose treatments had been delayed for 1h were similar to those of normal rats over 700 days of age. These results support the hypothesis that neuronal loss from cumulative effects of seizure-induced brain damage simulates aging.

Intermittent exposures to nanoTesla range, 7 Hz, amplitude-modulated magnetic fields increase regeneration rates in planarian

Abstract Purpose: To discern if physiologically and naturally-patterned electromagnetic fields presented with base frequencies of 7 Hz within the 100 nT range could facilitate regeneration in planarian similar to microTesla, 60 Hz fields. Methods: In two separate experiments planarian were decapitated and exposed to either 140 or 400 nT peak amplitude-modulated 7 Hz magnetic fields for 6 min once per hour, 8 h per night for 5 days. Daily regeneration rates and movement velocities (cm/min) were measured. Results: The planarian exposed to either intensity magnetic field exhibited faster regeneration of photoreceptors and auricles compared to sham field and reference groups. The magnetic field exposure accommodated 50% of the variance during the faster growth days. Conclusions: Naturally-patterned, intermittently-presented weaker electromagnetic fields may produce enhanced regeneration rates in flat worms similar to those observed for 60 Hz, higher intensity fields.