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Biomedical subjects

M Apostolakis

Publications and source records attributed to M Apostolakis.

At least 19 recordsLinked to original sources
PubMed1994

Biomagnetic methodologies for the noninvasive investigations of the human brain (MAGNOBRAIN).

Magnetoencephalography (MEG) non-invasively infers the distribution of electric currents in the brain by measuring the magnetic fields they induce. Its superb spatial and temporal resolution provides a solid basis for the 'functional imaging' of the brain provided it is integrated with other brain imaging techniques. MAGNOBRAIN is an applied research project that developed tools to integrate MEG with MRI and EEG. These include: (1) software for MEG oriented MRI feature extraction; (2) the Brain Data Base (BDB) which is a reference library of information on the brain used for more realistic and biologically meaningful functional localisations through MEG and EEG; and (3) a database of normative data (age and sex matched) for the interpretation of MEG. It is expected that these tools will evolve into a medical informatics environment that will aid the planning of neurosurgical operations as well as contribute to the exploration of mental function including the study of perception and cognition.

Brain↗
PubMed1994

Ultrastructural alterations of the rabbit sciatic nerve, spinal cord and cerebellum, following methionine sulphoximine administration.

Methionine sulphoximine (MSO) is a centrally acting neurotoxin which inhibits the glutamate metabolism enzymes and has convulsive properties. Small doses of MSO were administered to rabbits, either intravenously (i.v.) or intracerebroventricularly (ICV), and electron microscopic examination of the cerebellum, the spinal cord and the sciatic nerve was performed on the first day of rabbit hind leg rigid paralysis (myopathy with histological findings resembling myositis), which set in by the 2nd to 4th day after MSO administration. In the cerebellum focal minor alterations were found in the astrocytes (swelling and lucidity, diminution of glycogen granules) and sparsely in the presynaptic terminals (lucidity and clumping), whereas most of the neuron presented a normal appearance. In the spinal cord and in the sciatic nerve a dissociation of the axon from the myelin sheath was evident in a small number of myelinated nerve fibres, along with the appearance of vacuolated spaces. Mitochondrial disorganisation in the axons, as well as glial cell alterations, were also seen. The ultrastructural alterations were non specific, and since they were induced 2 to 4 days after the administration of either minimum doses (i.v.) or of extremely low doses (ICV) of MSO, they may be attributed to the inordinate increase of metabolism during the period of convulsions.

Animals↗
PubMed1989

Long-term effects of the administration of the convulsive substance DL-methionine-DL-sulfoximine to the rabbit.

Methionine sulfoximine (MSO) is a centrally acting neurotoxin which inhibits the glutamate metabolism enzymes and has convulsive properties. Administration of a small dose of MSO to rabbits, either intravenously or intracerebroventricularly, except for the already known convulsive effects, may also be responsible for hind leg myopathy (rigid paralysis with histological findings resembling myositis) which sets in by the 4th day after MSO administration.

Animals↗
PubMed1987

A neural net model for the release of prolactin during pseudopregnancy in the rat.

A theoretical probabilistic neural net model is proposed here based on the interaction between two subsystems, the connections of which are made up by means of chemical markers. The activity of such a system at t = n tau is exclusively dependent on the firing record of the system at t = (n-1) tau, on the level of spontaneous activity and on an external inhibitory influence which we have found that may play an important role in the prolactin release level during pseudopregnancy in rats. We explore some of the implications of this model on the possible role of the hippocampus in the phenomenon.

Animals↗
PubMed1987

Involvement of the caudate nucleus in the modulation of the brain somatosensory evoked potentials.

The participation of the caudate nucleus in the modulation of the cortical somatosensory evoked potentials was investigated in male rabbits. The power spectra of the somatosensory evoked potential recorded from the scalp in the intact animal was compared with that recorded after kainic acid lesion of specific regions of the caudate nucleus (i.e., anterior and or posterior portions of the head of the nucleus) and the "destructive" interference patterns which appeared were investigated. It was found that the caudate's head modulates the waveform at the end of the early phase of the cortical somatosensory evoked potentials, i.e., the period from 20.8 ms to 29.4 ms. These results suggest that the caudate nucleus is part of the sensory pathways belonging to the nonspecific projection system and participates in the integrating processes of the somatosensory information.

Animals↗
PubMed1985

Effects of growth hormone and triiodothyronine administration of the localization of 14C-D-glucose on regenerating sciatic nerve in rabbits.

In the present study the effect of the administration of GH and T3 on glucose distribution in the regenerating nerve was studied. The right sciatic nerve of 40 male rabbits was crushed at a specific site so that axonotmesis ensued. The animals were divided into two equal groups: one for the study of the effects of human growth hormone (hGH) and the other of triiodothyronine (T3). In all animals 14C-D-glucose a([14C]D-G) was injected iv as a tracer. The sciatic nerves from both sides were removed from all animals, divided into four equal segments and checked for radioactivity. In all cases an increased concentration of [14C]D-G appeared in the crushed nerve as compared with the intact one. GH administration caused a decrease in [14C]D-G uptake in both intact and injured nerves. T3 administration caused a significant decrease in [14C]D-G levels in the blood but did not substantially change [14C]D-G uptake in the crushed nerves as a whole. T3 administration appeared also to cause a peripheral displacement of the site of maximum [14C]D-G concentration in the injured nerve, indicating possibly an increased regeneration rate.

Analysis of Variance↗
PubMed1983

Effects of GABA, glycine, and sodium barbiturate on dendritic growth in vitro.

Dendritic growth and dendritic arborization of both the large neurons of the cerebral and the cerebellar cortex and the small bipolar neurons were studied in vitro under normal feeding conditions and under the influence of GABA, glycine, and sodium barbiturate. By the end of week 1 the neurons cultured in normal nutrient developed primary dendritic shafts, demonstrating a tendency for bifurcation. By the end of week 2 the neurons appeared as numerous secondary dendritic branches studded with spines. The dendritic development and growth proceeded continuously until week 12 when no further growth and differentiation of the dendritic arborization was noted. Feeding medium enriched with GABA or glycine enhanced dendritic growth and dendritic arborization in vitro. On the contrary, feeding medium contained sodium barbiturate, partially suppressed dendritic growth and dendritic arborization in the neurons of the cerebral and the cerebellar explants. Ultrastructural studies revealed that sodium barbiturate partially suppressed the synapse formation between the neuronal circuits of the cortical explants.

Animals↗
PubMed1979

Work capacity, contractile protein and quantitative electromyogram (EMG) changes following exercise or nandrolone decanoate treatment in experimentally induced muscle disuse atrophy in rats.

Anabolic steroid administration and planned exercise have been the two main methods applied to improve the function and morphology of atrophied muscle tissue. The effects of these two factors-specifically nandrolone decanoate administration and exercise by swimming on muscle weight, EMG activity, work capacity and on contractile protein content of rat gastrocnemius muscle, following experimentally induced atrophy by immobilization, were investigated. The results appear to support the conclusion that although both types of treatment obtain significant positive results exercise acts more effectively than the anabolic steroid in this respect.

Actomyosin↗
PubMed1968

Prolactin.

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Animals↗