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PubMed1993

Forelimb motor performance following dorsal column, dorsolateral funiculi, or ventrolateral funiculi lesions of the cervical spinal cord in the rat.

The neuroanatomical basis of forelimb motor control was examined following various surgical spinal cord lesions in the rat. Focal myelotomies were made at spinal level C4 to determine the effects that damage to long-tract pathways in the dorsal columns, dorsolateral funiculi, and ventrolateral funiculi have on a forelimb reaching and pellet retrieval task. Dorsal column lesions did not significantly reduce retrieval performance but did yield: (i) qualitative alterations in digit use during grasp execution, (ii) targeting errors during reaching attempts, and (iii) an apparent lack of ability to sense the presence of a pellet in the paw. Damage to the dorsolateral funiculi produced significantly diminished pellet retrieval performance at all postlesion intervals due to a prominent grasp deficit involving impaired digit flexion. Lesions of the ventrolateral funiculi did not produce a sustained, significant reduction in retrieval performance, although a qualitative deficit characterized by a mild forelimb reaching hypometria and premature grasp execution was exhibited. Based on comparisons with previous supraspinal and peripheral lesion studies in rats and supraspinal and spinal lesion studies in other mammalian species, the current results indicate that organization of descending and ascending spinal long-tract motor control of the forelimb in the rat is very similar to that described in other mammals, including primates. Additionally, these results demonstrate that the rat can serve as a biomedically relevant model of behavioral impairment and recovery following cervical spinal cord injury.

Animals↗
PubMed1990

The lateral reticular nucleus in the cat. VII. Excitatory and inhibitory projection from the ipsilateral forelimb tract (iF tract).

Intracellular recording from neurones in the lateral reticular nucleus (LRN) demonstrated that, in addition to the previously identified excitatory ipsilateral forelimb tract (iF tract) (Clendenin et al. 1974c) there is an inhibitory tract mediating information from the ipsilateral forelimb to the LRN. The excitatory and inhibitory tracts were similarly organized. The tract neurones were monosynaptically activated by afferents in the ipsilateral forelimb and projected to the same area of the LRN. They will be considered as excitatory and inhibitory components of the iF tract and denoted the excitatory and inhibitory iF tract (EiF and IiF tracts). Stimulation of the descending ipsilateral dorsolateral funiculus (iDLF) in the C3 segment evoked disynaptic EPSPs and IPSPs in LRN neurones contacted by the EiF and IiF tracts. The responses in individual LRN neurones evoked from the iDLF were similar to the responses evoked from the forelimb nerves suggesting that the EiF and IiF tracts are monosynaptically activated by fibres in the iDLF. The dorsal portion of the magnocellular part of the LRN constituted the main termination area of both the EiF and IiF tracts. Neurones in this area have previously been shown to project ipsilaterally to lobule V in the pars intermedia of the cerebellar anterior lobe and to the paramedian lobule (Clendenin et al. 1974a). IPSPs evoked from the IiF tract in LRN neurones outside the main termination area had smaller amplitudes and longer latencies. This finding suggests that these responses were generated by thin axon collaterals given off from dorsally located stem axons.

Action Potentials↗
PubMed1985

Integration in descending motor pathways controlling the forelimb in the cat. 13. Corticospinal effects in shoulder, elbow, wrist, and digit motoneurones.

The effect of corticospinal volleys evoked by stimulation of the contralateral pyramid was investigated using intracellular recordings from alpha-motoneurones to forelimb muscles. Confirming and extending previous observations (Illert et al. 1977, Illert and Wiedemann 1984), short latency EPSPs within a disynaptic range were evoked by a train of pyramidal volleys in all varieties of shoulder, elbow, wrist and digit motoneurones. The amplitude of pyramidal EPSPs was sensitive to the stimulus repetition rate. Maximal amplitudes were observed around 2-4 Hz, while at 10 Hz the early EPSP was markedly reduced and the long latency EPSP abolished. The persistence of disynaptic EPSPs after a corticospinal transection in C5/C6 suggested that, for all types of forelimb motor nuclei, disynaptic EPSPs are relayed by C3-C4 propiospinal neurones (PNs) (c.f. Illert et al. 1977). The transection, however, caused a clear reduction in the EPSP of all motoneurone types. After a ventral lesion of the lateral funicle in C5/C6 interrupting the axons of the C3-C4 PNs, disynaptic (and possibly trisynaptic) EPSPs were evoked by a short train of pyramidal volleys. It is postulated that intercalated neurones in a disynaptic cortico-motoneuronal pathway also exist in the forelimb segments. Disynaptic pyramidal IPSPs were observed in most types of forelimb motor nuclei both before and after a corticospinal transection in C5/C6. At all joints, pyramidal excitation dominated in motoneurones to physiological flexors, while in extensor motoneurones mixed excitation and inhibition or dominant inhibition was common. Comparison of pyramidal effects in slow motoneurones (classified according to the after-hyperpolarization duration) to the long head of the triceps and anconeus revealed dominant excitation in the former and inhibition in the latter. It is suggested that the slow motor units in these muscles differ in their function although both muscles are elbow extensors.

Animals↗
PubMed1978

Comparison of forelimb and hindlimb motor deficits following dorsal column section in monkeys.

Macaca speciosa monkeys were trained to acquire food reinforcement with motor responses that were defined by 4 different tasks. The effects of dorsal column lesions on the speed of these responses were compared for the forelimbs vs. the hindlimbs. Enduring impairments were not seen for any limb when the animal was required to accurately project a limb to different points in space, even with exclusion of visual guidance and with random variation of the start and stop points for each movement. Similarly, when the task required that the animals emit rapid response sequences, the forelimbs were impaired temporarily, but no long-term deficits were seen for the forelimbs or the hindlimbs. Although these impositions of spatial and temporal demands did not reveal striking disruptions of whole-limb movements, hindlimb grasp responses were shown to be impaired over long periods of postoperative testing. This corroborates previous findings for the forelimb and indicates that facility of distal extremity movement depends crucially on dorsal column-lemniscal input.

Animals↗
PubMed1992

The distribution of neural crest-derived Schwann cells from subsets of brachial spinal segments into the peripheral nerves innervating the chick forelimb.

Neural crest cells from brachial levels of the neural tube populate the ventral roots, spinal nerves, and peripheral nerves of the chick forelimb where they give rise to Schwann cells. The distribution of neural crest cells in the developing forelimb was examined using homotopic and heterotopic chick-quail chimeras to label neural crest cells from subsets of the brachial spinal segments. Neural crest cells from particular regions of the spinal cord populated ventral roots and spinal nerves adjacent to or immediately posterior to the graft. Crest cells also populated the brachial plexus in accord with their segmental origins. In the forelimb, neural crest cells populated muscle nerves with anterior brachial spinal segments populating nerves to anterior musculature of the forelimb and posterior brachial spinal segments populating nerves to posterior musculature. Similar patterns were seen following both homotopic and heterotopic transplantation. In both types of grafts, the distribution of neural crest cells largely matched the sensory and motor projection pattern from the same spinal segmental level. This suggests that neural crest-derived Schwann cells from a particular spinal segment may use sensory and motor fibers emerging from the same segmental level as substrates to guide their migration into the periphery.

Animals↗
PubMed1983

Effects of captopril and propanolol on bradykinin-induced changes in vascular pressures, lymph total protein concentration, and weight in canine forelimbs.

Sixty-minute local intraarterial infusions of bradykinin (0.8, 5, or 10 micrograms base/min) produced transient forelimb vasodilation and dose-related increases in lymph flow, lymph total protein concentration, total protein transport, and weight in forelimbs perfused at a controlled flow rate. Mean aortic pressure was not affected by these infusion rates of bradykinin. Following pretreatment with captopril, the local intraarterial infusion of these same doses of bradykinin produced sustained systemic hypotension. The increase in protein efflux and edema formation produced by local infusions of bradykinin following pretreatment with captopril was markedly increased during the infusion of the low dose of bradykinin (0.8 micrograms base/min, ia), but was attenuated during the local infusion of the larger dose of bradykinin (5 micrograms base/min, ia). Following pretreatment with both captopril and propranolol, the increase in protein efflux and edema formation produced by this larger dose of bradykinin (5 micrograms base/min) was greater than that produced by infusions of this dose of bradykinin alone or after pretreatment with captopril. Moreover, the increase in protein efflux and edema formation was greater during the infusion of the higher dose of bradykinin than during the infusion of the low dose of this autacoid under these conditions. The 60-min infusion of a massive dose of bradykinin into the left ventricular chamber (280 micrograms base/min) produced sustained decreases in aortic and forelimb perfusion pressure, but little edema formation relative to that produced by local intraarterial infusions of this agent. In contrast, the 60-min intravenous infusion of only 5 micrograms base/min of bradykinin following pretreatment with both captopril and propranolol produced profound systemic hypotension and marked increases in protein efflux and edema formation in forelimbs perfused at a controlled flow rate comparable to that produced by the local intraarterial infusion of this dose of bradykinin alone. These data demonstrate that endogenous kininases and catecholamines may dramatically affect the increase in protein efflux and edema formation produced by either local or systemic infusions of bradykinin by modulating the magnitude of the increase in macromolecular permeability.

Animals↗
PubMed1984

Forelimb and hindlimb stepping by the anesthetized rat elicited by electrical stimulation of the pons and medulla.

This study determined the lower brainstem sites at which electrical stimulation elicits stepping movements of the forelimbs and hindlimbs. Rats (N = 45), anesthetized with nembutal, were fixed in a stereotaxic apparatus so that their limbs contacted a moving treadmill belt. Electrical stimulation (100 microA, 10-sec trains, 0.5-msec cathodal pulses, 50-Hz pulse frequency) was applied every 200 micron through 173 movable electrodes. Well coordinated quadrupedal stepping was elicited by stimulation at dorsal posterior mesencephalic sites including the inferior collicular commissure, the central gray, the nucleus cuneiformis and lateral aspects of the pedunculopontine tegmental nucleus. Caudal and ventral to this general region, sites supporting quadrupedal stepping appeared mainly in or near the spinal trigeminal nucleus. Stepping with only the forelimb and hindlimb contralateral to the stimulation site was associated with the corticospinal tract, the lateral pontis oralis, the lateral pontis caudalis and the ventral reticular nucleus of the medulla. Bilateral forelimb stepping was associated with the trigeminal system and the gigantocellular reticular nucleus. At the level of the rostral medulla, systems involved in bilateral forelimb stepping and contralateral hindlimb stepping appear to be located medially. Systems concerned with bilateral hindlimb stepping appear to be located laterally.

Animals↗
PubMed1993

Differential spinal projections of subregions in the forelimb area of the motor cortex in the cat.

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to examine the topography of projections from the forelimb area of motor cortex to the cervical spinal cord in the cat. Tracer was injected in sites in the rostrolateral (RL-MCx) and caudolateral (CL-MCx) subregions concerned with the distal forelimb. Whereas both subregions projected throughout the cervical cord, with the greatest density of label present in the cervical enlargement, the dorso-ventral distributions were different for the two injection sites. Injections in RL-MCx produced labeling in the lateral portions of laminae VI, VII, and VIII in the upper cervical segments. This corresponds to the locations of propriospinal neurons that project to forelimb motor nuclei used in reaching [Exp. Brain Res., 42 (1981) 299-318]. In the cervical enlargement, labeling was present in laminae V, VI, VII, and part of VIII. At all levels examined, the density of labeling was greatest in the intermediate zone. After CL-MCx injection, labeling was concentrated in the dorsal horn both in the upper cervical segments and in the cervical enlargement. These findings suggest that the two motor cortical subregions project to different propriospinal and interneuronal systems in the cervical cord and support the idea that the two subregions play different roles in controlling forelimb movements.

Animals↗
PubMed2005

Limits on recovery in the corticospinal tract of the rat: partial lesions impair skilled reaching and the topographic representation of the forelimb in motor cortex.

Although evidence suggests that there are impairments in skilled movements following very large lesions of the pyramidal component of the corticospinal tract, the behavioral and electrophysiological effects of partial lesion has not received equal attention. Here, rats with complete lesions or partial lesions (medial, central, or lateral third) of the pyramidal tract at the medullary pyramids were evaluated for their quantitative and qualitative postsurgical performance on a skilled reaching task, following which the topographic representation of their forelimb was mapped with intracortical microstimulation (ICMS). Complete lesions impaired reaching success, impaired the qualitative features of reaching movements, and abolished ICMS evoked movement from the forelimb region of motor cortex. Although partial lesions did not impair reaching success, they did impair qualitative aspects of limb movement including forepaw aiming, supination, and food pellet release. ICMS indicated a reduction in the size of the forelimb area, especially the distal area of the caudal forelimb area (CFA), of the motor map. The behavioral and electrophysiological impairments did not vary with lesion location within the pyramidal tract. The incomplete recovery, as measured both behaviorally and electrophysiologically, demonstrates that plasticity within the corticospinal system is limited even with lesions that permit substantial sparing of pyramidal tract fibers.

Animals↗
PubMed2005

Testing forelimb placing "across the midline" reveals distinct, lesion-dependent patterns of recovery in rats.

We describe a new test of vibrissae-elicited forelimb placing ability that allows testing of sensorimotor integration across the midline. Rats were given unilateral brain lesions using one of three methods: (1) middle cerebral artery occlusion (MCAo) causing significant damage to the cortex and striatum, (2) aspiration lesions to remove tissue from the sensorimotor cortex, and (3) infusions of the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle, producing a parkinsonian syndrome. Application of the new test to these animals revealed that with some lesion types, the ability of vibrissae on the unimpaired side of the body to trigger placing in the functionally impaired forelimb recovers before vibrissae on the impaired side can elicit placing. This occurs despite the lack of any apparent vibrissae sensory deficit, since the contralesional vibrissae maintained the ability to trigger placing in the unimpaired forelimb in all lesions studied. Chronically, MCAo-lesioned rats do not place the impaired forelimb upon stimulation of the impaired-side vibrissae, but do place if the vibrissae on the good side are stimulated (i.e., when the placing is triggered "across the midline"). This is in contrast to 6-OHDA-lesioned rats which, consistent with parkinsonian akinesia, cannot place the impaired limb regardless of sensory trigger. Also, differences in the pattern of recovery between MCAo- and aspiration-lesioned rats suggest a possible anatomical substrate for cross-midline placing ability and its recovery. Unlike other tests, cross-midline placing methods can readily distinguish between severe stroke and severe parkinsonism in rats.

Animals↗
PubMed2000

The relationship between isometric force requirement and forelimb tremor in the rat.

To explore the effects of isometric force of rodent forelimb contraction on forelimb tremor, rats were trained to press downward on an isometric force transducer to raise a water-filled dipper cup and maintain force to keep the dipper in the raised position while licking. Force requirements were then manipulated parametrically to measure the effects of escalating force output on forelimb tremor and other variables. In the Peak-Force greater than Hold-Force (PF > HF) manipulation, the forces required to raise the dipper were 20, 40, and 60 g (each condition for about 2 weeks), while the force required to maintain the dipper in the raised position remained 6.7 g for all three conditions. In the Peak-Force equal to the Hold-Force (PF = HF) manipulation, rats were required to maintain the "dipper-raising" force throughout the response. The forces required were 20 g, 40 g, and 60 g (each for 2 weeks). For all force requirement manipulations, data were analyzed within and across conditions. As expected, force output increased with increased force requirements. Spectral analysis of force-time records revealed that during all manipulations, high-frequency (>10 Hz) forelimb tremor increased with increased force output, an effect that is consistent with human studies, and that may reflect increases in the number of motor units firing at higher rates. Additionally, with the exception of the 60-g PF = HF condition, there were within-condition decreases in tremor and increases in task engagement, evidence suggesting increased muscle strength as a function of experience (i.e., "physical training"). Taken together, the results suggest that the rodent-based method may provide a valuable, noninvasive functional assay for animal models of disorders that affect skeletal muscle control in humans.

Animals↗
PubMed1997

Ladder beam and camera video recording system for evaluating forelimb and hindlimb deficits after sensorimotor cortex injury in rats.

Hindlimb and forelimb deficits in rats caused by sensorimotor cortex lesions are frequently tested by using the narrow flat beam (hindlimb), the narrow pegged beam (hindlimb and forelimb) or the grid-walking (forelimb) tests. Although these are excellent tests, the narrow flat beam generates non-parametric data so that using more powerful parametric statistical analyses are prohibited. All these tests can be difficult to score if the rat is moving rapidly. Foot misplacements, especially on the grid-walking test, are indicative of an ongoing deficit, but have not been reliably and accurately described and quantified previously. In this paper we present an easy to construct and use horizontal ladder-beam with a camera system on rails which can be used to evaluate both hindlimb and forelimb deficits in a single test. By slow motion videotape playback we were able to quantify and demonstrate foot misplacements which go beyond the recovery period usually seen using more conventional measures (i.e. footslips and footfaults). This convenient system provides a rapid and reliable method for recording and evaluating rat performance on any type of beam and may be useful for measuring sensorimotor recovery following brain injury.

Animals↗
PubMed1992

Spontaneous forelimb grasping in free feeding by rats: motor cortex aids limb and digit positioning.

Forelimb use in grasping food during free feeding was studied in control and motor cortex damaged rats using videoanalysis and Eshkol-Wachmann Movement Notation (EWMN). Rats detected food using olfaction, grasped it by mouth, and then sat and reached for it with their paws. Once held in the paws, the food was eaten. A reach consists of: (1) lifting the forelimbs from the ground, (2) positioning them elbows-in, so that the paws were adjacent to the mouth, and (3) clasping the food in the digits. These movements were executed mainly with the upper arm. Limb movements were usually bilaterally symmetrical but when asymmetrical movements occurred, the forelimb least involved in weight support initiated the movement. As the limb was positioned for grasping, the aperture of the digits was adjusted to anticipate the size of the food and the food was grasped and manipulated with the tips of the digits. Following unilateral motor cortex lesions to the forelimb area: (1) the ipsilateral limb (good limb) initiated lifting, positioning, and grasping movements, (2) appropriate adjustment of the digits of the contralateral limb (bad limb) and grasping were impaired, and (3) when contact with food was lost, the bad limb adopted an extended, closed-fist spastic posture and could not be repositioned independently. The gross impairments cleared within 2 weeks, and after a few months impairments were infrequently observed. These findings show that: (1) spontaneous food grasping uses both proximal movements of the limb and distal movements of the digits, (2) digit aperture anticipates food size in reaching, and (3) motor cortex damage impairs both proximal and distal movements more profoundly when the limb is used independently than when it is used in conjunction with the good limb. The results are discussed in relation to kinematic studies on primates and humans.

Animals↗
PubMed2000

Somatotopical organization of fos-like immunoreactivity in rat cervical spinal cord following noxious stimulation of the forelimb.

In the present study c-fos expression has been used as a marker of neuronal activation following noxious stimuli applied to one of three different sites on the forelimb in rats. In three treatment groups (n=4 animals in each group) rats were anaesthetized with barbiturate and a mechanical pinch was applied to either (i) the most medial digit, (ii) the most lateral digit, or (iii) the shoulder area of one forelimb. An additional control group (n=4) received no pinch. The presence of Fos-like immunoreactivity was used to chart the distribution of cervical spinal cord neurons activated by the stimulus. No significant difference was found in the number of labelled cells between the contralateral side of each treatment group and either side of the control group. By contrast, there was a significant increase in labelled cells between the ipsilateral and contralateral sides within each treatment group. Labelled cells were present mainly in the dorsal horn of the ipsilateral cervical spinal cord where they were clustered in laminae I and II. Clear topographical differences were also evident between treatment groups in the distribution of labelled cells. The most medial digit was represented rostromedially compared to the most lateral digit (cell peak at segmental levels C5/C6 and C7, respectively), while the shoulder stimulus produced a more widespread distribution of labelled cells which was centred rostrolaterally (peak at segmental levels C4/C5).Overall, the findings suggest that forelimb inputs to the cervical cord are organized somatotopically in a similar fashion to hindlimb inputs to the lumbar cord, although the representation of individual forelimb digits may be more extensive in the rostrocaudal axis. This difference could reflect the use of the rats' forepaws in more complex sensorimotor tasks such as grasping and exploring objects.

Animals↗
PubMed1997

Spatial cortical patterns of metabolic activity in monkeys performing a visually guided reaching task with one forelimb.

The 2-[14C]deoxyglucose method was used to map the metabolic activity in the neocortex of monkeys (Macaca nemestrina) performing a visually guided reaching task with one forelimb. Monkeys received liquid reward for correct, single directional reaching movements, which were required at a rate of about 10 per minute. We estimated the weighted average of local glucose consumption within several neocortical areas, and we reconstructed quantitative, high-resolution, two-dimensional maps of the detailed spatiointensive patterns of activity. Our findings demonstrate the involvement of the striate and prestriate cortices, the inferior intraparietal and superior temporal visual association areas, the frontal eye field and the caudal periprincipal cortex, the primary somatosensory and the related superior intraparietal area, the primary and association auditory cortices, the superior temporal multimodal region, and the premotor, primary, supplementary, and cingulate motor areas. The visual cortex in the superior temporal and the intraparietal sulci, which is concerned with "where", was activated during visually guided reaching. In contrast, the inferior temporal visual association cortex, which is concerned with "what", was not involved in our study. We suggest that the activated direction-selective layer four of V1 and the thick stripes of V2 convey visuomotor information to the activated cortex in the posterior bank and the floor of the superior temporal sulcus, which may encode the constantly updated position of the moving forelimb. In parallel, the activated cortex in the ventral part and the lateral bank of the intraparietal sulcus may encode visuospatial information related to the localization of the visual target in the extrapersonal space. Furthermore, the dorsal part of the medial bank of the intraparietal sulcus may be involved in proprioceptive guidance of movement, based on the parallel metabolic effects shown only contralateral to the moving forelimb within this region and the forelimb representations in the primary somatosensory and motor cortices. Finally, the bilaterally activated network including the inferior postarcuate skeletomotor and prearcuate oculomotor cortical fields and the caudal periprincipal region 46 may participate in sensory and oculomotor to motor transformations, in parallel with the medial and lateral intraparietal cortices with which this network is reciprocally interconnected.

Animals↗
PubMed2003

Force- and moment-generating capacities of muscles in the distal forelimb of the horse.

A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarpal, intercarpal, carpometacarpal, metacarpophalangeal (MCP), proximal interphalangeal (pastern) and distal interphalangeal (coffin)). Bone surfaces were reconstructed from computed tomography scans obtained from the left forelimb of a Thoroughbred horse. The model was actuated by nine muscle-tendon units. Each unit was represented as a three-element Hill-type muscle in series with an elastic tendon. Architectural parameters specifying the force-producing properties of each muscle-tendon unit were found by dissecting seven forelimbs from five Thoroughbred horses. Maximum isometric moments were calculated for a wide range of joint angles by fully activating the extensor and flexor muscles crossing the carpus and MCP joint. Peak isometric moments generated by the flexor muscles were an order of magnitude greater than those generated by the extensor muscles at both the carpus and the MCP joint. For each flexor muscle in the model, the shape of the maximum isometric joint moment-angle curve was dominated by the variation in muscle force. By contrast, the moment-angle curves for the muscles that extend the MCP joint were determined mainly by the variation in muscle moment arms. The suspensory and check ligaments contributed more than half of the total support moment developed about the MCP joint in the model. When combined with appropriate in vivo measurements of joint kinematics and ground-reaction forces, the model may be used to determine muscle-tendon and joint-reaction forces generated during gait.

Animals↗
PubMedDate not supplied

Complications and outcome after thoracodorsal axial pattern flap reconstruction of forelimb skin defects in 10 dogs, 1989-2001.

OBJECTIVE: To determine (1) the frequency and extent of complications associated with thoracodorsal axial pattern flap reconstruction of forelimb skin defects in dogs and (2) outcome after treatment of such complications. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Ten dogs. METHODS: Medical records for 10 dogs that had a thoracodorsal axial pattern skin flap reconstruction of a forelimb skin defect were reviewed. RESULTS: Three dogs had complete flap survival. Partial necrosis of the distal flap, ranging from an estimated 2% to 53% (mean, 21%) of the flap surface area, occurred in 7 dogs. Six dogs required surgical management of the skin necrosis, resulting in successful resolution in 5 dogs, whereas, in 2 dogs, the wound healed by second intention. Positive bacterial cultures were obtained from 3 dogs with distal flap necrosis. Seroma formation was noted in 2 dogs; the entire flap survived in 1 dog, whereas the second dog developed distal flap necrosis. Edema and bruising of the distal portion of the flap were noted in 8 dogs; distal flap necrosis subsequently developed in 7 dogs. Partial incisional dehiscence, which healed by second intention, occurred in 2 dogs. Of 6 owners available for follow-up, all were satisfied with the functional outcome, but 1 owner was not satisfied with the cosmetic appearance. CONCLUSIONS: Partial flap necrosis was a frequent complication of thoracodorsal axial pattern flap reconstruction of forelimb skin defects and required additional wound care or surgical intervention to achieve healing. CLINICAL RELEVANCE: Thoracodorsal axial pattern flaps can provide full-thickness skin coverage of extensive skin defects of the forelimb, but owners should be aware of the likelihood of local wound complications.

Animals↗
PubMed1998

Optical intrinsic signal imaging responses are modulated in rodent somatosensory cortex during simultaneous whisker and forelimb stimulation.

Optical intrinsic signal imaging (OIS) was used to investigate physiologic interactions between spatially and functionally distinct cortical somatosensory systems. The OIS response magnitude was evaluated after simultaneous stimulation of single whiskers and forelimb digits. Whisker C1 was deflected at a frequency of 10 Hz for 2 seconds while low- or high-intensity vibratory stimuli were applied to forelimb digits. The OIS responses to simultaneous whisker and forelimb stimulation were compared with lone whisker stimulated controls. Overall, addition of a second stimulus caused decreases in barrel cortex response magnitude. Three different response patterns were detected within individual trial sets. Modulation of barrel cortex evoked potentials provided evidence that changes in OIS responses observed here may be partially influenced by vascular responses to changes in neuronal activity. However, OIS responses in the barrel region during lone forelimb stimulation that were unaccompanied by evoked potentials suggested the possibility of independent vascular dynamic influences on response modulation. This study demonstrates that cortical responses at the level of primary sensory processing may be significantly influenced by activity in adjacent regions. Furthermore, it reveals that vascular and neuronal characteristics of interregional modulation do not co-localize and may produce responses in which one component increases while the other decreases.

Animals↗