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G Huether

Publications and source records attributed to G Huether.

69 records · Page 4Linked to original sources
PubMed1988

The effects of sensory stimulation on the free amino acid pool of the developing brain.

Developing chicks were subjected to three different paradigmata of sensory stimulation, and the effects on the free amino acid concentrations in the blood and in various brain regions were monitored. The free amino acid pool of individual brain regions was found to be affected in a treatment- and age-specific manner. The increased neuronal activity resulting from sensory stimulation seems to affect intrinsic factors involved in the regulation of the free amino acid pool, most likely via modulations of the rate of metabolization of individual amino acids and/or of the rate of synthesis and degradation of individual proteins in certain brain regions.

Afferent Pathways↗
PubMed1987

Acceleration of brain tubulin formation in the optic lobe of the chick embryo by light stimulation.

The effect of light exposure on the protein patterns of optic lobe and forebrain of the chick embryo was analysed by a high-resolution micro-two-dimensional polyacrylamide gel electrophoresis and computerized quantitation. Experiments were done on three groups of eggs: control group was incubated in the dark; simultaneously, in the same incubator, one group of eggs was illuminated by constant light, another by intermittent light (3 sec interval) from day 10 to day 16 of incubation. In embryos exposed to intermittent light the relative amount of tubulins was significantly increased in the optic lobe. In the frontal lobe no effect of light exposure on the concentration of tubulins was seen. The rise of tubulins in the optic lobe was only caused by intermittent light. Continuous illumination of the eggs for the same period under otherwise identical incubation conditions was ineffective.

Animals↗
PubMed1987

Regional protein patterns of the embryonic chick brain: developmental shifts and the effects of light stimulation.

The developmental changes in the regional protein patterns of the embryonic brain of chick were analysed by micro-two-dimensional polyacrylamide gel electrophoresis stained by a highly sensitive procedure with Coomassie Brilliant Blue G-250 that completely avoids background staining. More than 400 protein spots were resolved in a computerized plot. Many proteins of the various embryonic brain regions varied with age. At least six of these proteins changed remarkably during development. One of them (Mr 14K) was prominent at 6 days and disappeared after 12 days of incubation. One acidic protein (Mr 30K) appeared at 12 days together with two acidic protein spots near tubulin and increased with development. A group of more basic proteins (Mr 94K) was prominent at 6 day incubation and decreased during development. One more basic protein (Mr 20K) was first observed at 18 days of incubation in the metencephalon. It was identified as myelin basic protein, and strikingly increased in all brain regions until hatching. A group of basic proteins with high molecular weight (Mr 94K) appeared at day 12 of incubation, and increased remarkably before hatching. They were identified to be collagen associated with brain capillary vessels. Stimulation by intermittent light in ovo from day 10 to day 16 caused a retarded appearance of these collagen proteins, and an increased formation of tubulin in the optic lobe of the developing chick embryo.

Animals↗
PubMed1986

Fatty acid composition of myelin lipids from developing rat forebrain and spinal cord: influence of experimental hyperphenylalaninaemia.

The fatty acid composition of individual myelin lipids from rat forebrain and spinal cord was analysed at 20 and 30 days p.p. During this phase of rapid myelination the proportions of C 16:0 and C 18:0 fatty acids decreased whereas the relative amounts of long chain and unsaturated fatty acids increased in most lipid classes. This developmental shift was more pronounced in the forebrain and was different with respect to both magnitude and direction for each myelin lipid. The experimental induction of chronic hyperphenylalaninaemia (hyper-Phe) from day 3 p.p. lead to alterations in the rate of myelination, which were most pronounced in the forebrain. At 20 days, especially in the forebrain, chain elongation and desaturation of fatty acids were delayed. This delay was maximal in sphingomyelin fatty acids, C 18:0 and C 24:1. In hydroxycerebrosides, the shift in the fatty acid composition from C 16:0 to C 22:0 was accelerated in hyper-Phe rats. No significant difference in the fatty acid composition of any myelin lipid was found in the more mature myelin (spinal cord, 30 days p.p.). No evidence was found of a primary effect of hyper-Phe on myelination.

Animals↗
PubMed1986

The depletion of tryptophan and serotonin in the brain of developing hyperphenylalaninemic rats is abolished by the additional administration of lysine.

In suckling hyperphenylalaninemic (hyper-Phe) rats, all essential amino acids including tryptophan are depleted in the blood. The inadequate supply of Trp to the developing brain leads to a decline of Trp, of serotonin, and of 5-hydroxyindoleacetic acid. The exhaustion of amino acids in both blood and brain can be restored by administration of Lys. Even though Phe is still elevated in blood and brain, Trp, serotonin and 5-hydroxyindoleacetic acid, are no longer depleted in the brain. This observation contradicts the idea that the serotonin deficit in the developing hyper-Phe brain is caused by competitive uptake inhibition of tryptophan or by the interference of Phe metabolites with the formation of serotonin. Increased accumulation of all large neutral amino acids in peripheral tissues and an impeded intestinal amino acid transport in suckling hyper-Phe rats appear to be responsible for the deficient supply of other amino acids, including Trp, to the developing brain. The availability of Lys for developing extraintestinal tissues seems to be involved in the regulation of intestinal amino acid transport.

Animals↗
PubMed1985

Amino acid depletion in the blood and brain tissue of hyperphenylalaninemic rats is abolished by the administration of additional lysine: a contribution to the understanding of the metabolic defects in phenylketonuria.

The elevated phenylalanine concentration in the blood of untreated phenylketonuric children is known to be paralleled by decreased concentrations of other amino acids in the blood and brain tissue. Due to the low availability of other large, neutral amino acids in the brain, protein synthesis in, and the normal development of, the brain are disturbed. A similar effect is observed in suckling rats rendered hyperphenylalaninemic by the daily injection of phenylalanine plus alpha-methylphenylalanine, an in vivo inhibitor of the phenylalanine-hydroxylating pathway in the liver. In this study, the simultaneous injection of lysine is shown to prevent the depletion of amino acids from the blood and brain tissue, and the retardation of brain growth, in suckling hyperphenylalaninemic rats. It is suggested that both amino acids, phenylalanine and lysine, are important rate-limiting substrates for the rapid protein anabolism of developing tissues. In the presence of an excess of phenylalanine, other amino acids, and in relation to its requirement during the phase of hyperplastic growth in particular lysine, are less available from the circulation and limit phenylalanine-stimulated protein synthesis in developing tissues. The supplementation of lysine to developing hyperphenylalaninemic rats prevents the consequences of this effect, i.e., the depletion of amino acids in the blood, and therefore, in the brain tissue, and the retardation of brain growth.

Age Factors↗
PubMed1983

Free amino acid concentrations in the gut lumen of developing rats.

Free amino acid concentrations in the lumen and tissue of small intestine of suckling rats were measured by a micromethod. Almost all amino acid concentrations (Lys excepted) in the intestinal juice decrease until 15 days of age whereby the pattern remains constant. Concomitantly, free amino acid concentrations in the intestinal tissue increase between 10 and 15 days p.p. The pool of amino acids in the intestinal juice, reflecting the nutritional input and its utilization, becomes exhausted during the suckling period. At 20 days of age the rats additionally ate the rat chow and free amino acid concentrations in the intestinal tissue increased again. The decline of the amino acid pool in the lumen of small intestine which is both derived by the mother and exhausted by the growing organism may act as a signal for differentiation via (self-) restriction of substrates for protein accretion.

Amino Acids↗
PubMed1982

Brain development in experimental hyperphenylalaninaemia: myelination.

The influence of hyperphenylalaninaemia on the formation and composition of myelin has been investigated in forebrain and spinal cord of young rats (10-60 days p.p.). The injection of alpha-methylphenylalanine plus phenylalanine in 12 hour intervals (from 3rd day post partum) resulted in decreased wet weights of brain and spinal cord and reduced myelin yields; both were more pronounced in the forebrain. Myelination was initially delayed in the forebrain but thereafter the rate of myelination was the same in both control and hyperphenylalaninaemic rats. Transient alterations of several parameters of myelination were observed during early stages of development. Myelin isolated from the CNS of hyperphenylalaninaemic rats at 10 and 20 days p.p. was slightly more mature with respect to sedimentation characteristics, protein pattern, fatty acid composition of certain myelin lipids, and electron microscopical structure of myelin preparations. No significant changes in the myelin composition of the preparations of both forebrain and spinal cord were found at later developmental stages (30 and 60 days p.p.). The findings are discussed in relation to alterations in the axonal outgrowth rather than to a specific effect of hyperphenylalaninaemia on myelin formation.

Animals↗
PubMed1981

Spot analysis for glycoprotein determination in the nanogram range.

A flexible method for glycoprotein determination with microliter-volumes using spot analysis ("Tüpfelprobe") on cellulose acetate layers is described. With glucose oxidase as an example of a glycoprotein and fluorescein isothiocyanate-labelled Concanavalin A, a sensitivity of 10 ng is reached; in combination with horseradish peroxidase 1 ng of glucose oxidase can be detected. A simultaneous determination of protein and glycoprotein with one single spot of 0.5, 1 or 2 microliters of a glycoprotein solution can be performed. The method is independent of many common external influences, e.g. dodecyl sulfate, Triton X-100, NP 40, mercaptoethanol and desoxycholate. Only pretreatment of the glycoprotein with urea decreases the sensitivity.

Cellulose↗
PubMedDate not supplied

Stress and the adaptive self-organization of neuronal connectivity during early childhood.

A conceptual framework is proposed for a better understanding of the biological role of the stress-response and the relationship between stress and brain development. According to this concept environmental stimuli (in children mainly psychosocial challenges and demands) exert profound effects on neuronal connectivity through repeated or long-lasting changes in the release of especially such transmitters and hormones which contribute, as trophic, organizing signals, to the stabilization or destabilization of neuronal networks in the developing brain. The increased release of noradrenaline associated with the repeated short-lasting activation of the central stress-responsive systems in the course of the stress-reaction-process to psychosocial challenges which are felt to be controllable acts as a trigger for the stabilization and facilitation of those synaptic and neuronal pathways which are activated in the course of the cognitive, behavioral and emotional response to such stressors. The long-lasting activation of the central stress-responsive systems elicited by uncontrollable psychosocial conflicts in conjunction with the activation of glucocorticoid receptors by the sustained elevation of circulating glucocorticoid levels favors the destabilization of already established synaptic connections and neuronal pathways in associative cortical and limbic brain structures. The facilitation and stabilization of neuronal pathways triggered by the experience of controllable stress is thus opposed, attenuated or even reversed in the course of lon-lasting uncontrollable stress. This destabilization of previously established synaptic connections and neuronal pathways in cortical and limbic brain structures is a prerequisite for the acquisition of novel patterns of appraisal and coping and for the reorganization of the neuronal connectivity in the developing brain. Alternating experiences of repeated controllable stress and of long-lasting uncontrollable stress are therefore needed for the "self-adjustment" of neuronal connectivity and information processing the developing brain to changing environmental (psychosocial) demands during childhood. The brain structures and neuronal circuits involved in the regulation of behavioral responding become thus repeatedly reoptimized and refitted, not the changing conditions of life per se but rather to those conditions which are still able to activate the central stress responsive systems of an individual at a certain developmental stage.

Adaptation, Physiological↗