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J Mariani

Publications and source records attributed to J Mariani.

At least 127 records · Page 7Linked to original sources
PubMed1980

Multiple innervation of Purkinje cells by climbing fibers in the cerebellum of the adult staggerer mutant mouse.

Intracellular recordings from Purkinje cells (PC) in the cerebellum of adult staggerer mutant mice revealed that the orthodromic response of PCs to juxtafastigial (JF) stimulation closely resembled a climbing fiber response (CFR). However, for most of the PCs studied, these responses were graded in a stepwise manner when the stimulus strength was increased. The underlying excitatory synaptic potentials (EPSPs) had the typical shape of EPSPs mediated through climbing fibers (CFs), but their size fluctuated in discrete steps, the highest one reaching the firing level. In the same PCs, the size of the spontaneous EPSPs fluctuated in a similar fashion and the frequency of each step was in the range of CF-mediated EPSPs. These results strongly suggest that in staggerer mice several CFs synapse with each PC instead of a single CF as in normal adults. Furthermore, the activation through some of these CFs does not reach the firing level of the corresponding PC.

Animals↗
PubMed1980

Electrophysiological study of inferior olivary neurons in staggerer mutant mice.

Extracellular recordings were obtained from neurons of the dorsal and medial accessory olives (DAO and MAO) in staggerer and normal mice. The anti- and orthodromic responses of these neurons to stimulation of the contralateral cerebellum were very similar in control and staggerer mice. On the other hand, the mean value of the spontaneous discharge of inferior olivary (I.O.) cells was significantly lower and the modal interval of the discharge was significantly shorter in staggerer than in control mice. These results demonstrate that I.O. neurons and climbing fibers are functional in staggerer mice, although their spontaneous discharge is somewhat different from that of I.O. neurons in control mice.

Animals↗
PubMed1979

[The recruitment of motor units during elbow flexions in man].

The density of spikes of spike output (SO) recorded by means of three bifilar semimicroelectrodes simultaneously implanted in the biceps brachii has been studied during elbow flexions performed against inertia and with a variable velocity (anisometric, anisotonic contractions). The total number of motor unit (MU) potentials as well as the force were sequentially measured during intervals of 30 msec. SO obtained during movements of very similar mechanical characteristics was different from one movement to another. However, when a small number of identical movements was summed an averaged SO was obtained that was representative of the instantaneous global activity of the biceps. Taking into account the respective values of the bin duration and of the interval between two successive discharges of a single MU, the averaged SO represents the number of active MU during the acceleration phase of the movement. Since in this type of movement the frequency discharge of each MU decreases during the acceleration phase, it appears that the increase of averaged SO represents the recruitment of MU during the movement. From the relation established between the instantaneous values of So and force it can be concluded that the shape of force increase in anisometric, anisotonic conditions is entirely related to that of MU recruitment, although the absolute value of force depends on both the firing frequency and the number of active MUs.

Action Potentials↗
PubMed1976

Evidence for a multiple innervation of Purkinje cells by climbing fibers in the immature rat cerebellum.

Climbing fiber (CF)-Purkinje cell (PC) relationship were studied electrophysiologically on the cerebellum of 8 to 15 day old rats. Some animals were rendered agranular by x-irradiation from birth; some others were treated with 3-acetyl pyridine 3 days before study to selectively destroy the CF. Unitary extracellular recordings in 8-9 day old normal rats revealed that more than 50% of the PC units each exhibited either two types of all-or-none climbing fiber responses (CFR) or stepwise graded CFRs. The other PC units only presented one type of all-or-none CFR. These activities were entirely mediated via CF since they persisted at the same age in x-irradiated rats, but were absent in animals treated with 3-acetyl pyridine. Interaction experiments were performed between juxtafastigial and Inferior Olive stimulations on 49 PC units in 8-9 day old normal rats. Collisions between impulses set up in CFs were disclosed in 21 out of the 24 PCs which exhibited only one type of CFR. In the three others and in each of the 25 PCs that displayed two types of all-or-none CFRs, or CFRs graded by steps, no collision was detected. Moreover intracellular recordings of epsp's mediated via CFs in PCs of 8-9 day old normal rats revealed that they frequently fluctuated in stepwise fashion. These results demonstrate that in the immature rat more than 50% of PCs are each innervated by at least two distinct CFs; later on, the disappearance of the supernumerary synapses between CF and PC leads, as early as day 15, to the one-to-one relationship between CF and PC.

Animals↗
PubMed1976

[Maturation of somesthetic evoked potentials in man].

Somaesthetic evoked potentials (SEPs) have been recorded on the parietal scalp of 375 normal and awake children to brief electrical stimulation (0.5 msec) applied to the contralateral median nerve at the wrist. Each SEP was obtained by summation of the responses to 150 stimuli delivered at a frequency of 1/sec. The population studied has been divided in five age groups, each one corresponding to a recognizable stage of maturation of the responses.

Adolescent↗
PubMed1976

Relationship between changes in somesthetic evoked responses and electroencephalographic findings in the child with hemiplegia.

The results of somesthetic evoked response (SER) and electroencephalogram (EEG) records in 43 children with hemiplegic cerebral palsy have been compared. In all children there was a positive correlation between the SER changes and the affected side of the body. In 12 children the SER of the "damaged" hemisphere disappeared; in 31 children it was less than the response of the "healthy" hemisphere. On the other hand, a positive correlation between the EEG changes and the affected side was found in only 16 of the patients, and there was a dubious correlation in three cases. It is concluded that SER data are more accurate and reliable than EEG results. Moreover, SER findings allow cerebral damage to be suspected earlier than the EEG results and therefore are of greater prognostic value.

Adolescent↗
PubMed1975

Anatomical, physiological and biochemical studies of the cerebellum from mutant mice. I. Electrophysiological analysis of cerebellar cortical neurons in the staggerer mouse.

An electrophysiological analysis of cerebellar cortical neurons was performed in staggerer mutant mice on postnatal days 18 to 22, and data were compared with cerebellar activities in normal mice of the same age. Bioelectrical activities were elicited through local (LOC) and juxtafastigial (JF) stimulation. In staggerer mice, parallel fibers (PF) exhibited no major alterations, i.e. they conducted impulses and they activated most of the cerebellar cortical units encountered, but some minor differences existed in comparison with normal mice, i.e. their excitability was reduced, as tested by their refractory period and conduction velocity. On the contrary, Purkinje cell (PC) responses presented marked abnormalities. (1) Depth profiles during antidromic invasion of PC and unitary antidromic responses revealed a lower safety factor than normal in the invasion of the somatodendritic region of PC. In particular, a marked IS-SD delay or block occurred in about 60% of unitary antidromic responses of the mutant mouse. (2) Spontaneous or evoked typical climbing fiber responses (CFR) were never recorded in staggerer mice, despite functional synapses between climbing fibers (CF) and PC disclosed with harmaline injections. Activation of PC via CF under harmaline consisted of rhythmical trains of simple spikes, Finally, most of the PC studies in the staggerer mice were certainly activated via PF but with a low efficacy. The results suggest that PC are directly affected by the mutation.

Animals↗
PubMed1975

[Demonstration of temporary multi-innervation of the cerebellar Purkinje cells by the ascending fibers during development in the rat].

The one-to-one relationship between cerebellar Purkinje cells and climbing fibres in the adult rats is the result of a regressive process affecting a multi-afferent pathway during the early post-natal period, as shown from the innervation by several independent climbing fibres of more than 50% of the Purkinje cells tested electrophysiologically on days 8 and 9.

Action Potentials↗
PubMedDate not supplied

Quantitative analysis of the Purkinje cell population during extreme ageing in the cerebellum of the Wistar/Louvain rat.

The loss of neurons is viewed as one of several causes of the deterioration of neural function during ageing. However, the existing experimental evidence for an age-related decrease in the neuronal number may be misinterpreted due to the way the cells are counted and to the interference of unsuspected degenerative pathology of the animals studied. To reinvestigate this question we have quantified an easily identifiable population of neurons, the cerebellar Purkinje cells, in very old but healthy rats. The number of Purkinje cells in the cerebellum was assessed in two populations of rats: control (10 months) and old (42 months) rats from the Wistar/Louvain strain. In both groups, paraffin-embedded brains were cut serially in the sagittal plane. Purkinje cells were counted every 15 or 22 sections under the light microscope at a magnification of 1250 x. The raw value of cell counts were corrected according to the method of Hendry (21) in order to avoid the overestimation due to splitting of the nucleus during sectioning. The latero-lateral extent of the cerebellar cortex, obtained by multiplying the thickness of the section by the number of sections in which Purkinje cells were counted, was not statistically different (mean +/- standard deviation): 12.8 +/- 1.16 mm (n = 6) for the control rats and 12.0 +/- 1.02 mm for the old animals (n = 8) (Student's t-test, p = 0.18). The corrected number of the Purkinje cells (mean +/- standard deviation) was 330,350 +/- 35,448 cells (n = 6) for the control animals and 299,019 +/- 50,223 (n = 8) cells for the old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMedDate not supplied

Hyperspiny Purkinje cell, a new neurological mutation in the mouse.

Hyperspiny Purkinje cell (hpc) is a new autosomal recessive mutation of the laboratory mouse. Homozygotes exhibit abnormal motor behavior, with predominance of cerebellar symptoms, about 10 days after birth. Morphological analysis disclosed a slightly reduced cerebellum with selective alteration of Purkinje cells. All these neurons have an atrophic dendritic tree. The proximal dendritic branches and the cell bodies, instead of being smooth, are studded with spines. Most of the axon terminals belonging to this neuronal population undergo progressive degenerative changes. Cell death is observed in only a small proportion of Purkinje cells. Electrophysiological study revealed that the synapses between climbing fibers and Purkinje cells are functional with no gross abnormality.

Animals↗