Activity In Other Regions Research Articles

Intestinal Structure and Function Related to Toxicology

The study of toxic effects on small intestinal function is complicated by the integration of the activity of the small intestine with the activities of other regions of the GI tract. Also, the barrier and portal functions of the intestine are not as clearly defined as sometimes assumed. The intestinal surface functions as a barrier to the ingress of large quantities of large water soluble molecules. Lipidic substances enter the body quite readily as do small water-soluble molecules. The small intestinal surface is more a portal than a barrier, with its portal functions divided between nonspecific diffusional entry, which depends on physical properties and electric charge, and entry by specific membrane transport, which depends upon chemical structure. The implications of these properties of the small intestine for toxicological studies are stressed.

Intestinal structure and function related to toxicology.

The study of toxic effects on small intestinal function is complicated by the integration of the activity of the small intestine with the activities of other regions of the GI tract. Also, the barrier and portal functions of the intestine are not as clearly defined as sometimes assumed. The intestinal surface functions as a barrier to the ingress of large quantities of large water soluble molecules. Lipidic substances enter the body quite readily as do small water-soluble molecules. The small intestinal surface is more a portal than a barrier, with its portal functions divided between nonspecific diffusional entry, which depends on physical properties and electric charge, and entry by specific membrane transport, which depends upon chemical structure. The implications of these properties of the small intestine for toxicological studies are stressed.

The role of tonic neural activity in motivational processes

The multiunit recording technique was used to study the activity of neuron populations in various brain regions in cats during long, natural behavior sequences in a free behavioral situation. Electroencephalographic (EEG) records were also obtained from each recording site. The variations in total multiunit activity levels in many of these regions, including parts of the cortex, thalamus, and reticular formation, tended to be closely related, and these variations in tonic activity were associated with the observed behavioral arousal level of the cat. Variations in tonic activity in other regions (lateral geniculate nucleus and inferior colliculus) were shown to be more reliably correlated with specific sensory input than with arousal levels. Behavioral arousal levels appear to be more closely related to tonic neural activity in many regions of the brain than to the EEG record. The neural bases of specific-center and drive-arousal theories of motivation are examined in the light of these data.

The ultrastructural distribution of succinic dehydrogenase activity in the supraoptico-neurohypophyseal system of the rat.

The succinic dehydrogenase (SDH) activity in the supraoptico-neurohypophyseal system of the rat was studied by means of electron microscopic histochemistry aiming at the explanation of earlier findings pointing out the consistently negative reaction of this enzyme in the axon terminals. SDH activity was found to be localized in the mitochondria of neurosecretoy neurons and pituicytes. The hypothalamic as well as the neurohypophyseal portions of neurosecretory axons have markedly stained mitochondria. In contrast to this, axon terminals devoid of neurosecretory material contain non-reacting mitochondria similarly to the previously described distribution of SDH activity in other regions of the nervous system. Accordingly SDH activity could be revealed neither in the mitochondria of axon terminals synapsing on the neurosecretory perikarya nor in the mitochondria of those neurohypophyseal boutons lacking neurosecretory granules. The more uniform distribution of SDH-activity in neurosecretory than in non-neurosecretory neurons points to the possible role of axoplasmic flow in causing within the neurons the described proximodistal decrease of SDH-activity.

Central nervous action of hydantoins, oxazolidinediones and thiazolidones.

THAT SEIZURE electroencephalographic patterns may be observed during sleep or by pentylenetetrazole (metrazol®) activation in epileptic patients with normal routine electroencephalograms 1 signifies the influence of nervous activity of other regions of the brain on epileptogenic foci in giving rise to clinical attacks. 2 It is not surprising, then, to see that an antiepileptic drug is efficacious in certain cases while effective in similar cases only with the addition of a sedative. 3 In rare instances, an agent which stimulates the central nervous system has also been found to be of value in combating epileptic convulsions. 4 In the discriminate management of epilepsy, therefore, a knowledge of the various actions of an anticonvulsant agent on the central nervous system is required. In this paper, there will be presented results on the antimetrazol,® antielectroshock, and other actions on the central nervous system of the hydantoins, oxazolidinediones, and thiazolidones. It is hoped