Chronic placental insufficiency in the fetal guinea pig affects neurochemical and neuroglial development but not neuronal numbers in the brainstem: A new method for combined stereology and immunohistochemistry

Abstract

This study has examined the development of the brainstem in a suboptimal intrauterine environment induced via chronic placental insufficiency in the fetal guinea pig. Placental insufficiency was produced by unilateral ligation of the maternal uterine artery at mid-gestation (term = 66-68 days) resulting in the production of growth-retarded fetuses that are chronically hypoxic and malnourished. The structural and neurochemical development of brainstem nuclei either directly or indirectly related to cardiorespiratory control were analysed by using new stereological methods and immunohistochemistry. A technique was devised to enable the procedures to be performed on alternate frozen sections. There were no significant differences between control and growth-retarded fetuses in the total number of neurons, area of neuronal somata or volume of the hypoglossal nucleus. Quantitative densitometry was used to measure immunohistochemical staining in the brainstem of growth-retarded fetuses compared to controls and revealed a significant (P < 0.02) decrease in substance P(SP)-immunoreactivity in the spinal trigeminal nucleus and a significant (P < 0.05) increase in met-enkephalin-immunoreactivity in the hypoglossal nucleus. Counts of stained neurons demonstrated a significant increase in the density of SP-positive neurons in the nucleus tractus solitarius (P < 0.05) and of met-enkephalin-positive neurons in the ventral medullary reticular formation (P < 0.05). There was also a proliferation of astrocytes, as determined by immunoreactivity to glial fibrillary acidic protein in the dorsal motor nucleus of the vagus, nucleus tractus solitarius and more generally around blood vessels throughout the brainstem. Thus, these results have been shown that although chronic intrauterine deprivation does not alter neuronal numbers, at least in the hypoglossal nucleus, there is a proliferation of astrocytes, and the expression of neurotransmitters/neuromodulators is markedly effected in some of the nuclei involved with cardiorespiratory control.

Experience on the Barnes Spatial Maze Influences PKCγ Levels in the Hippocampus

“…Using a modification of the method described by Tolcos & Rees (1997), the system was calibrated, and images were acquired using a Sony (CCD-IRIS/RGB) video camera mounted to an Olympus microscope. Images of the CA1 region of the hippocampus were captured under the x4 objective.…”

Immunohistochemical analysis of brainstem lesions in infantile spasms

“…Also, the exact mechanism underlying the differential expression of ME and SP in the spinal trigeminal nucleus in the patients is not clear. Similar dissociative expression of ME and SP has been reported for the guinea‐pig model of chronic placental insufficiency 19 . Altered late responses of the electrically elicited blink reflex are reported in the IS patients, which reflects the function of the polysynaptic arch in the trigeminal spinal tract 20 .…”

Daily ethanol exposure during late ovine pregnancy: physiological effects in the mother and fetus in the apparent absence of overt fetal cerebral dysmorphology

“…A mean value for TUNEL-positive cells in gray matter and white matter was calculated. Finally, the proportion of cerebral parenchyma occupied by blood vessels was estimated by point counting (40). An increase in density above control levels suggests that cerebral hypoxemia has occurred.…”