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Biomedical subjects

M C Calvet

Publications and source records attributed to M C Calvet.

33 records · Page 2Linked to original sources
PubMed1983

The dendritic trees of Purkinje cells: a computer assisted analysis of HRP labeled neurons in organotypic cultures of kitten cerebellum.

Purkinje cell dendritic arborizations were studied in HRP intracellularly stained mature neurons grown during 30-50 days in organotypic cerebellar cultures from newborn kittens. The effects of afferent fiber depletions on the final dendritic topological parameters were investigated by computer assisted methods. Three differently deafferented models lacking both parallel and climbing fibers (PF and CF), only PF or only CF were thus studied. Qualitative data were found to be common to these 3 in vitro models and similar to those following other in vivo deafferenting procedures. Quantitative data obtained from 16 measurable parameters showed that all dendritic trees were markedly reduced in size as indicated by a decrease in total dendritic length and total number of segments although in all models individual segment lengths remained largely unaltered. A discriminant analysis permitted the recognition of 3 populations (100% well classified cells) based on 3 selected variables: dendritic field area, mean path length and total number of segments (with the lowest values for the model lacking only PF). These results are shown to lend further support to the role played in the final dendritic arrangement by both intrinsic (non-discriminant) and extrinsic (discriminant) factors and more precisely by the two distinct specific afferent systems (PF and CF).

Afferent Pathways↗
PubMed1981

A simple device for making a standard inverted phase-contrast microscope movable.

A simple, useful and inexpensive device was designed and tested which allowed, under visual control at high magnification, large areas of a culture to be scanned without removing the microelectrodes inserted into remote parts of the nervous tissue. Such a device consisted of making removable, over several millimeters, an inverted phase-contrast microscope without disrupting either the preparation or the microelectrodes. This was realized by fixing the stage to a rigid metallic framework. At the same time, the optic portion of the microscope could slide smoothly on a base consisting of a pair of mirrors separated by greased, precision ball-bearings. All the focusing and scanning movements were achieved by the original rack and pinion controls of the microscope.

Animals↗
PubMed1980

[Evidence of autapses in vitro by electron microscopy combined with iontophoretic intracellular injection of peroxidase].

The existence of autapses, i. e. of synapses between a neuron and its own axon, is demonstrated in vitro by means of Horseradish peroxidase (HRP) iontophoretic filling, combined with electron-microscopic (EM) analysis. After the injection of one single Purkinje cell per explant (Kitten cerebellum), the ultrastructural observation (serial thin sections) reveals the presence of both pre- and post-synaptic labelled structures. Axodendritic autapses are thus illustrated and their significance is discussed in view of earlier morphological and electrophysiological data.

Animals↗
PubMed1975

In vitro Purkinje cell electrical behavior related to tissular environment.

Cerebellar explants from newborn rats and kittens were cultivated in Maximow assemblies. The spontaneous electrical activity of Purkinje cells was recorded simultaneously by means of 3 extracellular micropipettes. These were placed near to cell bodies which appeared in the same microscopic field. Identification of these neurons was performed by intracellular staining with Procion Yellow. Mature Purkinje cells which had been deprived of their extracerebellar afferent connections tend to fire in grouped discharges (bursts). No correlation was ever observed between the firing pattern of a Purkinje cell and that of its neighbors. Purkinje cells which grew in connection with extracerebellar nuclei showed comparable burst discharges. In these explants synchronization of the burst pattern was obvious from the statistical analysis of the simultaneous recordings. Discharges in bursts were not observed in immature Purkinje cells from young cultures, from cells situated in peripheral thin areas of older explants or from cells grown with an antimitotic (MAM). These cells showed a rather regular frequency of discharge. Synchronized slow waves occurred in cerebellar which grew in the presence of MAM. These "inhibitory" waves accompanied the arrest of cell activity and may have analogues in vitro. The observed differences in the spontaneous firing of these neurons were discussed on the basis of different synaptic organizations of the explants.

Animals↗
PubMedDate not supplied

Radiobiological risk and single event effects during manned space flights.

Radiation hazard during previous manned space flights was not a critical problem as seen from monitoring on board MIR and the SHUTTLE. Future Martian and Lunar missions as well as flights on inclined or high altitude orbits around the Earth can be exposed to a large radiobiological risk and critical reliability losses can be expected, due to Single Event Effects on VLSI devices. The main characteristics of these hazards and some counter-measures to be provided for are given.

Aerospace Medicine↗