Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Forelimb”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed1982

Formation of functional synapses in the adult cat red nucleus from the cerebrum following cross-innervation of forelimb flexor and extensor nerves. II. Analysis of newly appeared synaptic potentials.

The effects of cross-innervation of peripheral flexor and extensor nerves on the time course and properties of red nucleus (RN) neurons were studied in adult cats. The time course of corticorubral unitary EPSPs was examined. In operated cats, RN neurons innervating upper spinal segments (C-cells) manifested corticorubral unitary EPSPs with shorter time-to-peak and larger amplitude than in normal cats. The mean amplitude of these EPSPs was 0.41 +/- 0.11 mV; the mean time-to-peak was 1.14 +/- 0.51 ms (n = 18). These values differ from normal cats (0.33 +/- 0.09 mV, and 2.68 +/- 0.61 ms, n = 22). RN neuron membrane properties were examined in cross-innervated cats. The main time constant was 5.2 +/- 0.7 ms (n = 10), the shorter equalizing time constant, 0.69 +/- 0.19 ms (n = 10), the input resistance, 2.5 +/- 0.8 M omega. These values were not significantly different from those of normal cats. The electrotonic length was 1.2 (n = 10), somewhat larger than in normal cats. The number of converging interpositorubral synapses, estimated in eight cells from cross-innervated cats, ranged from 37 to 57. This was not significantly different from normal cats, and indicated that there is no large-scale degeneration of interpositorubral synapses after cross-innervation. These results suggest that sprouting and formation of functional synapses occur after cross-innervation of peripheral flexor and extensor nerves.

Animals↗
PubMedDate not supplied

Activity of forelimb muscles under vestibular stimulation in guinea pigs with cerebellum removed.

Using decerebrate guinea pigs, we investigated the effect of complete removal of the cerebellum upon the influence of the vestibular system over the modulation of locomotor activity. It was found that the influence of the vestibular system over locomotor activity is preserved after removal of the cerebellum. The dynamic characteristics of the vestibular-spinal influences in cerebellectomized animals differ insignificantly from those of animals with an intact cerebellum. It is concluded that preservation of cerebellar-vestibular connections is not a necessary condition for the realization of vestibular influences upon locomotor activity.

Animals↗
PubMed1992

Biochemical organization of single motor units in two multi-tendoned muscles of the cat distal forelimb.

In anesthetized cats single motor units (MUs) of the extensor carpi ulnaris (ECU) and extensor digitorum communis (EDC) muscles were selectively activated by stimulation of cervical ventral root filaments. The distribution of force developed by single MUs at the four distal tendons of the EDC muscle and at three portions of the distal tendon of the ECU muscle was analysed. In general, single MUs of both muscles distributed force over all tendons in a unimodal pattern, with the maximal force levels generated at one specific tendon which was termed the best-tendon. Distributions of force were quantitatively described by a parameter representing the mean direction of force output (output-index) and a further one representing the dispersion of force over the distal tendons (divergence). Generally, these parameters and the best-tendon remained stable when a MU was stimulated at different frequencies, but varied from MU to MU. Despite the general stability of the force distribution, slight systematic changes were regularly found in EDC MUs, when they developed a higher amount of force due to a higher frequency of stimulation: the relative amount of force at the best-tendon increased; e.g. the MUs got more selective for the best-tendon. These changes were partly due to overcoming mechanical cross-coupling between neighbouring compartments of the EDC muscle. Such changes of force distribution were only found in a part of the ECU MUs; other ECU MUs did not change their force distribution at all or became less selective for the best-tendon. The phenomenon that MUs of multi-tendoned muscles distribute their force output to the distal tendons in specific patterns is probably due to mechanical partitioning of the parent muscles: the localization of spatial territories of MUs within different anatomical muscle compartments should correspond to the best-tendon. Complex mechanisms allowing passive transmission of force from limited territories along the transverse axis of both muscles must be assumed in order to explain why most MUs act on all tendons and why force distributions change with increasing stimulus frequency. In addition, specific relations between unit type and force distributions were found within both muscles. Fatigue-resistant EDC MUs have broader force distributions than fatigue-sensitive EDC MUs and slow ECU MUs were found to act predominantly on the most ulnar part of the distal tendon. These biomechanical properties of MUs are discussed as supporting the specific functions of the respective muscles.

Animals↗
PubMed1999

Bidirectional communication of sensory afferent information in a peripheral nerve of the cat forelimb.

Kinaesthetic information is derived from both muscle and joint nerves. However, the segregation, at peripheral levels, of inputs from these sources is by no means clear cut. In the present report, we demonstrate the complexity of peripheral innervation of joint and muscle structures in the cat's forearm, in particular, with evidence for bidirectional signalling for different classes of kinaesthetic afferents within a peripheral nerve segment. Three-way simultaneous recordings were carried out in the anaesthetized cat from single kinaesthetic afferents in three nerves that were freed from nearby tissue in the distal forearm, but remained in continuity. These were the wrist-joint nerve and two components of the indicis proprius nerve, one that projects proximally from the muscle to join the deep radial nerve, the other a distal extension of this nerve that runs through and beyond its own muscle to the region of the wrist-joint capsule where it forms an anastomosis with the wrist-joint nerve. Single-unit recording from the intact nerves demonstrated that some spindle afferent fibres from the indicis proprius muscle may take an "ectopic" path to the central nervous system, conveying their signals over an initial centrifugal path via the distal extension of the indicis proprius nerve, before looping back to project centripetally via the "classic" wrist-joint nerve. As some wrist-joint afferents themselves may project "ectopically" via the distal and then proximal segment of the indicis proprius nerve (rather than via the wrist-joint nerve), the recordings demonstrate that, within the distal segment of the indicis proprius nerve, there is bidirectional traffic of kinaesthetic afferent signals, with wrist-joint impulses travelling centripetally and muscle afferent signals travelling centrifugally. The findings emphasize the complexity of signalling that may be present in sensory nerves, on account of the "ectopic" paths taken by some afferents, and the need to activate deep inputs of joint or muscle origin by natural stimulation of the appropriate receptors in order to examine selectively the central actions and processing of either source of input.

Animals↗
PubMed2005

Age-related changes in the characteristics of evoked responses in field CA1 in rat hippocampus slices after deafferentation of the forelimb.

The effects of in situ transection of the median nerve in baby rats on the formation of the properties of synaptic transmission in the hippocampus were studied. Paired-pulse stimulation was used to identify the characteristics of short-term facilitation in living slices. Significant deviations in the time dynamics of facilitation from control values were seen in operated animals. Analysis showed that the decrease in the population spike amplitude, which we have described previously, may be due not only to functional causes, but also to morphological causes--elimination of neurons and their processes. It is suggested that a period of destructive changes is followed by the onset of a phase of intense formation of new synaptic contacts. The nature of the heterochrony of electrophysiological measures does not lead to any conclusion as to whether the maturation of intrahippocampal systems leads or lags in the experimental baby rats. It is suggested that hippocampal development along a new, abnormal pathway is induced.

Action Potentials↗