Williamina A. Himwich

The role of nutrition in the development of evoked cortical responses in rat

Abstract Following lesions of varying size in different parts of the cerebral cortex in 24 adult cats the ensuing preterminal and terminal degeneration in the lateral reticular nucleus (nucleus of the lateral funiculus) has been studied by means of the Nauta silver impregnation method. The majority of cortical efferents terminating within the nucleus are derived from the anterior sigmoid gyrus. Scanty projections arise in the posterior sigmoid, the coronal and the anterior ectosylvian gyri. In addition some fibres are derived from the gyrus proreus and parts of the medial wall of the hemisphere below the cruciate sulcus. Evidence for fibres from the occipital, temporal, and parietal cortices and part of the cingulate gyrus was not obtained. The cortical fibres are distributed mainly to the nucleus contralateral to the lesion; only a few terminate in the ipsilateral nucleus. Regardless of the site of the lesion, if degeneration is present, it is found to be restricted to the rostrodorsal part of the magnocellular division of the lateral reticular nucleus. The subtrigeminal and the parvicellular divisions do not receive cortical afferents. Following small lesions placed in various parts of the sensorimotor cortex, no evidence in favour of a somatotopical organization of the projection was found. Only few degenerating fragments are seen close to the soma of the cells, indicating that that most synaptic contacts are presumably axodendritic. The sites of origin of the cortical projection to the lateral reticular nucleus are discussed with reference to present knowledge about the functional and cytoarchitectonic localization within the cerebral cortex and other corticofugal fibre tracts. The area of termination of the cortical fibres overlaps to some extent with the terminal areas of other afferents to the nucleus (from the spinal cord, the red nucleus and the fastigial nucleus). From a functional point of view it is of interest that the cortical fibres to the red nucleus are derived from the same regions as those to the lateral reticular nucleus. Even if the fibres to the latter from the red nucleus have a somewhat different area of termination within the magnocellular division, both connections (the direct corticoreticular and the cortico-rubro-reticular) may serve as links in a cerebro-cerebellar pathway. However, both projections may also be imagined to influence the spinal input to the cerebellum via the lateral reticular nucleus.

Developmental changes in monoamines of mouse brain

Abstract The accumulation of serotonin.norepinephrine and dopaminein the mouse brain occurs concurrenthy with the manifestation of functional and behaviural maturation of the CNS; however, the adult levels for these amines are attained at different ages; 15th day, 30th day, and adult life respectively. In the newborn mouse seroetonin was 52 per cent, norepinephrine 23 per cent and dopamine 21 per eent of the adult value; at the time when serotonin and norepinephrine reached their adult levels dopamine was only 21 and 52 per cent respectively of the mature concentration. An effort has been mad to correlate the rate of increase in catechol and indole amines with maturation and with the physiological, morphological and functional integration of the CNS.

Postnatal changes in free amino acid pool of rabbit brain.

Abstract The pattern of amino acid changes in the whole brain is presented for the rabbit from birth through adult life. As in the rat and dog the outstanding increases occurred in glutamic acid, glutamine, GABA and aspartic acid. Only 4 suubstances,i.e. phosphoethanolamine, taurine, urea and glycine, showed a postnatal decrease. The remaining members of the amino acid pool exhibited little change during development.

The effects of short-term starvation on amino acid content in rat brain during ontogeny

Abstract By means of two-dimensional descending chromatography, free amino acids (glutamic acid, aspartic acid, glutamine, GABA and alanine) were determined in brain cortex, subcortical parts and medulla oblongata in control and starved rats (Wistar strain) at 5, 10, 14, 21, 35 and 60 days postnatal age. Starvation was accomplished by separating 4 animals from litters of 8 (4 control, 4 starved) for 10–12 h daily from the 5th to the 10th day of postnatal life. The evolution and increases of AA content in three chief brain parts during ontogeny were described. The highest increases were found in GABA, in brain cortex (+ 310%) and in subcortical parts (112%); then glutamic acid (175% and 57% respectively) and aspartic acid (+ 153% and 95% respectively). In the tissue of medulla oblongata, we found a suprising increase of aspartic acid (+ 476%). Starvation profoundly affected the AA content: in younger animals the decrease of AA content in the brain cortex was significantly greater than in older ones. In the phylogenetically oldest part of the brain, the changes caused by starvation were smaller than in phylogenetically younger parts. The return of AA content of starved animals to control levels occurred in various parts of brain at varying periods of postnatal evolution. The brain cortex and medulla oblongata of starved animals did not show any differences by the 35th day. In subcortical tissue a decrease was still evident at the 35th day. The possible relationship of decreases in AA content to retardation in functional development described in previous papers is discussed.

Maturational Changes in Amino Acids in CNS of Different Mammalian Species

The central nervous system (CNS) of rodents, cats, and dogs undergoes profound biochemical and functional alterations during postnatal ontogenesis under normal environmental conditions. The biochemical, physiological, and functional integration of the brain is accompanied by morphological differentiation and by electrophysiological maturation during the postnatal period in most of the rodents (with the exception of the guinea pig) in which rapid development of the CNS occurs during prenatal life [12]. The study of amino-acid metabolism in the developing brain deserves special consideration because of its great significance in the mechanisms of cellular growth and myelination and in the synthesis of proteins, nucleic acids, biogenic amines, lipids, and phospholipids. In recent years, the study of free amino acids and related enzymes in the developing brain of different mammalian species has attracted increasing interest, not only in biochemistry and neurochemistry, but also in such fields as pharmacology, psychopharmacology, physiology, and genetics. Our interest in the comparative amino-acid metabolism of the developing brain has led us to collect data for different species.

Effects of Early Weaning on Some Free Amino Acids and Acetylcholinesterase Activity of Rat Brain

The effects of environmental conditions upon the brain composition of young animals have become increasingly evident. The first papers in this field were those of Levine et al. [8] and of Bennett et al. [2]. These two groups studied the effects of handling upon phospholipid accumulation and level of acetylcholinesterase activity, respectively. No studies have been made, to the best of our knowledge, on amino-acid changes in brain due to environmental manipulations.

Biochemical Substrates for the Development of the Matured Evoked Potential

In our laboratory, we have for a number of years searched for ways of relating function to the biochemical development of the central nervous system [1, 2]. This approach was utilized very well for function (EEG) and neuroanatomy by Schade [3] and for neurochemistry and neuroanatomy by Baxter, Schade, and Roberts [4]. Since we were dissatisfied with the results of an attempt to correlate maturation of cortical EEG and amino-acid levels in young animals, we decided that a study of a functional system which has a clear-cut role and whose parts are readily available for rapid removal for chemical assay and for electrophysiological studies during the period of rapid postnatal development might give a more meaningful picture. The visual system in the rabbit offers such a convenient study. Our work with this system has started on the superior colliculi with measurements of the visual evoked potential, the biogenic amines, and the free-amino-acid content and will continue into histochemical studies. This paper is a preliminary report on the visual evoked potential, as a functional point of reference, and the changes in dopamine, norepinephrine, serotonin, glutamic acid, glutamine, GABA, aspartic acid, threonine, and alanine in the superior colliculi during development.

Free Amino Acids in the Developing Brain as Affected by Drugs

As Nyhan (1961) pointed out, the effects of most drugs in children are sufficiently different from those seen at older ages and in the adult to warrant considerable systematic investigation. Not only are the differences between the young and the adult of importance, but the timing and patterns of changes which occur as the animal matures are also of importance. During the period of rapid brain development the free amino acid pool in the brain serves as a source of building material for the brain proteins, and in addition some members such as glutamate are used for energy, while others such as GABA serve as neurotransmitters. Any disturbance of the delicate balance among the free amino acids can be expected to affect many reactions necessary to the unimpeded development of the brain. How serious these may be, we have as yet no means of determining. The data presented below are the result of some of our efforts to study these factors.