Morphological alterations of neurons and astrocytes in guinea pigs exposed to low levels of inorganic lead.

Both astrocytes and neurons potentially undergo structural and functional alterations in the brains of animals exposed to low levels of lead (Pb). No morphometric studies of astrocytes have been reported to date in animals in low Pb exposure. In the present study, morphometric measurements of astrocytes and pyramidal neurons in the frontoparietal cortex were made in guinea pigs exposed postnatally (5 or 10 days) or prenatally (gestational day 22 to birth) to low Pb levels. Although few significant effects of Pb treatment were detected by the rigorous statistical model applied, a recurring trend was noted for postnatal Pb treatment to increase astrocyte maximum diameter (dmax). In addition, prenatal Pb treatment was associated with increased apical and basal dendritic length, increased total apical dendrites per cell and an increased basal branching complexity in neurons.

Structural changes in astrocytes induced by seizures in a mode of temporal lobe epilepsy.

Injection of iron-chloride solution unilaterally into the hippocampus of albino rats induced transient seizure activity which lasted approximately 2 weeks. Frontal and parietal cortices of experimental rats, control rats which received NaCl injections, and unoperated normal rats were compared by means of a Golgi stain which demonstrated astrocytes and their processes in their entirety. Morphometric analysis showed that cortical astrocytes of rats having intermittent seizure activity over a prolonged period were significantly larger than cortical astrocytes of control rats. These findings indicate that seizure activity causes structural brain changes at anatomical sites distant from the hippocampal seizure focus. Similar phenomena may contribute to the development of psychiatric and neurological changes in the epileptic patient.

Alterations in glutamine synthetase activity by FeCl2-induced focal and kindled amygdaloid seizures.

The purpose of this study was to determine the effects of two experimental models of chronic epilepsy in rats on the activity of the astroglial enzyme glutamine synthetase. FeCl2-induced cortical lesions that increased the sensitivity to pentylenetetrazol-induced generalized seizures also significantly increased glutamine synthetase activity in the homotopic site of the contralateral cortex. A decrease in cortical glutamine synthetase was found in the cortex ipsilateral to the stimulated amygdala in electrically kindled animals. These findings provide evidence that increased glutamine synthetase activity is associated with developing, submaximal seizures and that decreased activity is characteristic of mature, chronic seizure states such as that associated with kindled amygdala seizures.

Excitation of dorsal column nucleus neurons by air-jet moving across the skin.

Single unit recordings from dorsal column neurons were made during application of mechanical somatic stimuli moving at controlled velocities across the neuron's receptive field. The neurons responded in stereotypic patterns which changed with altered stimulus parameters of velocity, direction and intensity. Spatial analysis of the response patterns indicates that the neurons generate action potentials when the stimulus probe activated particular discrete locations within the receptive field.

A program for computing power spectra on a microcomputer.

A computer program is presented that will calculate Fourier transforms and power spectra. The program is written in assembly language for the Z-80 microprocessor and has been used on a Radio Shack TRS-80 microcomputer to analyze time-dependent data from laboratory experiments.