Morphological and behavioral markers of environmentally induced retardation of brain development: an animal model
In most neurotoxicological studies morphological assessment focuses on pathological effects, like degenerative changes in neuronal perikarya, axonopathy, demyelination, and glial and endothelial cell reactions. Similarly, the assessment of physiological and behavioral effects center on evident neurological symptoms, like EEG and EMG abnormalities, resting and intention tremor, abnormal gait, and abnormal reflexes. This paper reviews briefly another central nervous system target of harmful environmental agents, which results in behavioral abnormalities without any qualitatively evident neuropathology. This is called microneuronal hypoplasia, a retardation of brain development characterized by a quantitative reduction in the normal population of late-generated, short-axoned neurons in specific brain regions. Correlated descriptive and experimental neurogenetic studies in the rat have established that all the cerebellar granule cells and a very high proportion of hippocampal granule cells are produced postnatally, and that focal, low-dose X-irradiation either of the cerebellum or of the hippocampus after birth selectively interferes with the acquisition of the full complement of granule cells (microneuronal hypoplasia). Subsequent behavioral investigations showed that cerebellar microneuronal hypoplasia results in profound hyperactivity without motor abnormalities, while hippocampal microneuronal hypoplasia results in hyperactivity, as well as attentional and learning deficits. There is much indirect clinical evidence that various harmful environmental agents affecting the pregnant mother and/or the infant lead to such childhood disorders as hyperactivity and attentional and learning disorders. 109 references.
- Research Organization:
- Purdue Univ., West Lafayette, IN
- OSTI ID:
- 5506305
- Journal Information:
- Environ. Health Perspect.; (United States), Journal Name: Environ. Health Perspect.; (United States) Vol. 74; ISSN EVHPA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
BEHAVIOR
BIOLOGICAL EFFECTS
BIOLOGICAL MODELS
BIOLOGICAL RADIATION EFFECTS
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
CEREBELLUM
ELECTROMAGNETIC RADIATION
ENVIRONMENTAL EXPOSURE
HIPPOCAMPUS
IONIZING RADIATIONS
IRRADIATION
LEARNING
LOW DOSE IRRADIATION
MAMMALS
MENTAL DISORDERS
MORPHOLOGICAL CHANGES
NERVOUS SYSTEM
ORGANS
RADIATION EFFECTS
RADIATIONS
RADIOINDUCTION
RATS
RODENTS
VERTEBRATES
X RADIATION