Biomedical subjects

G Fuhrmann

Publications and source records attributed to G Fuhrmann.

52 records · Page 3Linked to original sources

PubMed1985

Somatostatin levels in the central nervous system of the Snell dwarf mouse; is somatostatin excess the primary molecular defect in the dw/dw dwarfism?

The Snell dwarf mouse (dw/dw) shows significantly decreased somatostatin levels in the hypothalamus whereas more or less increased somatostatin concentrations are observed in any central extrahypothalamic sites studied. These opposite results in hypothalamus and extrahypothalamic areas may be linked to the apparently distinct neurohormonal and neuromodulatory functions of somatostatin in the brain. They also provide arguments for the assumption of a primary somatostatin excess which could be related to the dwarf mutation. In hypothalamus, the severe defect in growth hormone of the dwarf mutant may rapidly lead, by failure of a pituitary retro-control, to a reduction in the presumed initially elevated somatostatin levels. In central extrahypothalamic sites, known to escape to GH retro-action, higher somatostatin levels remain.

Animals↗

PubMed1985

Cholinergic neurotransmission in the central nervous system of the Snell dwarf mouse.

An unequal decrease in cholinergic activity has been evidenced in discrete brain areas in the growth hormone, thyroid-stimulating hormone and prolactin deficient Snell dwarf mouse. The effect of the mutation's pituitary deficit on central cholinergic mechanisms appears to be selective: Normally high cholinergic activity areas such as striatum, olfactory tubercles, and hippocampus show strong alterations in this neurotransmitter system. Structures which appear earlier in ontogenesis are less affected, if at all. The lack of pituitary hormones seems to have effects on choline acetyltransferase activity and/or synthesis as well as on the development of high affinity (H.A.) cholinergic uptake mechanisms, both strongly defective in hippocampus and striatum. Therefore, a lower density of cholinergic terminals can be inferred. Furthermore, our observations are consistent with a close functional coupling of the choline H.A. transport and of subsequent choline acetylation. Acetylcholinesterase activity does not seem to be affected. Moreover, a compensatory effect at the postsynaptic level may have occurred due to developmental or functional plasticity for cholinergic responsiveness. In conclusion, the dwarf mouse seems to be a useful model for a better understanding of the influences of growth hormone and thyroid hormones on the development of central cholinergic mechanisms. It also provides the possibility to attempt a functional restoration of the deficient cholinergic neurotransmission and the behavioral disturbances which may be linked to them, by hormone replacement.

Acetylcholinesterase↗

PubMed1985

Dopamine and serotonin metabolism in striatum and in the septohippocampal pathway of the Snell dwarf mouse.

Dopamine and serotonin neurotransmission has been investigated in striatum and in the septohippocampal pathway of the locomotor activity and memory deficient Snell dwarf mouse. In striatum a sharp decrease in 3-MT levels with a concomitant decrease in DA turnover is indicative of a strong decrement in the functional activity of striatal dopaminergic terminals in the mutant mouse. The observed enhancement in serotoninergic markers (5HT, 5HIAA, 5 HTP), at the opposite, provide evidence for an altered relationship between serotonin and dopamine striatal neurotransmission in the mutant mouse as compared to the normal mouse. Impairment in dopamine and serotonin neurotransmission has also been observed in the septohippocampal pathway where the removal of acidic metabolites of these neurotransmitters from brain appears to be disturbed. The data presented here are discussed with regard to previously noted alterations in cholinergic activity as well as to the behavioral disturbances of the dwarf mutant.

Animals↗

PubMed1985

Mathematical approach to integrating the "neuron-module" and the "cell-assembly".

The structural and functional unit of neuropsychic activity is approached in a mathematical way referring to some basic features of both the "neuron-module" and the "cell-assembly." The proposed units, called modules, have specific synchronous inputs and outputs, more abundant inner than outer connectivity, and their states are assumed representing concepts. Neurons in the model possess finite, discrete scales of states with inhomogeneous distances. Neighbouring relations are asymmetric (like the synapses) and of both intra- and inter-modular type. The actual states of neighbouring cells form a collective state. This is an emergent phenomenon, formally a complex, not necessarily explicit function of the cellular variables. Collective states belonging to the neurons in a module form the modular state. Thus, the influence of different cells on the modular state depends on their arborization, reflecting that the organization of the module holds greater significance than its size. Some of the modular states are assumed as "known", others are described by fuzzy sets representing definite and ambiguous concepts, respectively. A specified version of the model with application to visual pattern recognition is summarized for illustration.

Brain↗

PubMed1985

Arithmetic model for the distributed encoding in the neuron-module.

A class of arithmetic code defined in residue number system (RNS) is proposed as a mathematical model of neural encoding. The formalism of RNS provides for a vectorial representation in which the digits in the code-words (the "coordinates") contain the information in a distributed manner. These digits and the code-words are assumed to represent the states of the neurons and neuron-modules, respectively. The involved mechanism appears physiologically possible. After the number-theoretical background is summarized in a brief though self-contained way, mathematical assertions are drawn on the error detecting and correction capacities of the formalized modules. It is concluded that RNS provides an appropriate model of neural encoding though drawing inference by the neurons (the evaluation of the encoded information) requires another formalism.

Brain↗

PubMed1985

[Psychosocial dwarfism].

A 4 year old girl with psychosocial dwarfism showed hepatomegaly, abdominal distension and behavioral disturbances. Laboratory tests revealed a reversible elevation of serum liver enzymes and a reversible partial growth hormone deficiency. The child's family was characterised by severe social problems and all signs of a depriving and child abusing environment. All pathologic findings were reversed by removing the child from her depriving family background. This case demonstrates that psychosocial dwarfism represents an aspect of child abuse (battered child syndrome).

Body Height↗

PubMed1981

Modelling the visual cortex with "Modulo system" concept.

"Modulo system" is a general information extracting and processing network for modelling the nervous system. Its essential features are briefly summarized. The concept is applied to visual pattern recognition. The input is a two-dimensional picture of an object. The network extracts the contours, the line-segments, the lines of different directions, and the vertices of different numbers of lines, in successive functional layers. Afterwards, it recognized the simplest known pattern which has the actually extracted features. Uncertainty, association, and tolerance are also concerned. The network is detailed for the classification of of three-dimensional geometrical objects.

Form Perception↗

PubMed1973