PubMed Health⌕ Search

Biomedical subjects

F Colin

Publications and source records attributed to F Colin.

At least 37 records · Page 2Linked to original sources
PubMed1980

The olivocerebellar system. I. Delayed and slow inhibitory effects: an overlooked salient feature of cerebellar climbing fibers.

(1) Chemical destruction of the inferior olive (ION), or midline section interrupting the climbing fibers (CFs) rapidly resulted in marked modifications of Purkinje cell (P. cell) simple spike (SS) firing rate and pattern. (2) After CF deafferentation, P. cells at first about doubled their SS frequency which further increased for the next 10 min. (3) Besides the increase in the firing rate, the spike train became much more regular, which in part seemed to be linked to mass oscillations of the neuronal circuitry, as revealed by strong oscillations of background noise. (4) After ION destruction CF activity could be supplied for by juxtafastigial (JF) stimulation which reduced SS frequency again while the firing became much less regular. These effects were shown to be due to the all-or-nothing activity of the CF and not to the simultaneous stimulation of mossy fibers (MFs) or P. cell axons. Neither were they ascribable to CF collaterals. The differences between this new powerful inhibitory action of the CF system on the P. cell and the well documented pause mechanism is discussed. (5) A quantitative relationship has been established between complex spikes (CSs) and SS firing rates. A steady 2/sec CS frequency was shown to effectively silence the P. cell. (6) When CF stimulation was discontinued, an "off" effect was described. It consisted of an initial rise in SS frequency developing in 9 sec, and a delayed further increase unfolding in about 10 min. (7) When CF stimulation began, an "on" effect was observed, which evolved with an exponential-like kinetic of very variable time-constant seemingly depending on past history.

Afferent Pathways↗
PubMed1980

The olivocerebellar system. II. Some ultrastructural correlates of inferior olive destruction in the rat.

Short- and long-term ultrastructural changes induced in rat inferior olivary nucleus (ION) and cerebellum by a single injection of 3-acetylpyridine (3-AP) were investigated. Evidence of perikaryal and dendritic alterations was already present in numerous ION neurons at 3 h after injection. All ION neurons were affected at 6 h. Complete destruction of the entire ION was achieved within 8-10 h. Time-course and cytological features of this degeneration were described. Total absence of axonal termination degeneration in the ION or at its periphery ruled out the existence of recurrent olivary axons in these locations. Climbing fiber (CF) terminal degeneration in the cerebellar cortex apparently was restricted to the molecular layer, which cast serious doubts on the existence of glomerular collaterals of CFs. Evidence of axonal terminal degeneration was observed within all cerebellar nuclei at 24 and 26 h after 3-AP treatment, but degenerating profiles were unexpectedly infrequent. Consequential to CF deafferentation, Purkinje cells (P.cells) underwent both precocious and delayed ultrastructural changes. Delayed and long-range changes involved mainly dendrites and perikarya. Axon terminals underwent precocious but prolonged alterations which were interpreted as evidence supporting enhanced synaptic activity of P. cells deprived of CFs.

Afferent Pathways↗
PubMed1980

Properties of cortical somatosensory evoked potentials in the awake rabbit.

By appropriate experimental procedures it was possible to distinguish the components of the contra- and ipsilateral cerebral somatosensory potentials evoked by electrical stimulation of an extremity in the unrestrained rabbit. The components of the contralateral response occur in the following order; an early positive primary wave (P1), a positive associative wave (P2), and ultimately a late negative N wave. The components of the ipsilateral response occur in the following order; a small positive wave P, the latency of which is intermediate between those of the contralateral P1 and P2 waves, and a large negative wave N, similar to the contralateral N wave. The different topographical distributions of these waves were elucidated by the use of insulated, chronically implanted electrodes glued onto the cortical surface. The properties of the waveform components were studied by various methods such as varying the stimulation parameters, simultaneous application of somesthetic and acoustic stimuli, and administration of narcotic drugs. The properties of P1 were similar to those of P28 in humans; the properties of P2 can be compared to those of P45; and, finally, the N wave resembles the late negative components observed in humans. Inconstant small positive waves of shorter latencies, which will be discussed in a following paper, may also be seen. Interestingly enough, no early negative wave such as that observed in humans (N20) was ever found. If, as is presently thought, this wave is, in fact, due to the folding of the cortical surface (Broughton, 1969), its absence is to be expected in the rabbit because the cortical surface of this species is lissencephalic and thus devoid of gyri.

Acoustic Stimulation↗
PubMed1979

Early diagnosis of multiple sclerosis by combined multimodal evoked potentials: results and practical considerations.

It is shown that using four combined types of evoked potentials one can disclose new localisations in 62.5% of as yet undiagnosed M.S. patients. Brainstem auditory EP recordings must be considered in detail to avoid missing slight anomalies. Blink reflexes yielding bilateral R1 seem to bear the same significance as an augmented latency with respect to the problem of disclosing new localisations.

Brachial Plexus↗
PubMed1979

[Monoclonal gammapathy in the adult population of Finistère (France). Results of an inquiry resting on 30,279 persons (author's transl)].

The study of 30,279 adult sera, most issued from Finistère, detected 334 monoclonal gammapathies. The analysis of the results discloses that monoclonal gammapathies appear more frequently in this district (Finistère) than in Paris' one and that their repartition is not homogeneous. Two areas seem to be more particularly affected: one in the north-east, where IgG paraproteins are particularly frequent and the other in southwest, more particularly touched by IgM. The role of a genetic tendency could be backed by a discovery of numerous cases of monoclonal gammapathies occuring in families, and the high rate occuring between "half brother and sisters", but the case study of three couples would be more in favor of an environmental stimulus.

Adult↗