Discharge characteristics of the elbow joint nerve of the cat

Direct recordings were made from intact elbow joint nerves (EJN) in decerebrate cats. These multiunit recordings indicate that the EJN is a relatively pure articular nerve and does not contain significant numbers of muscle afferent fibres. In every cat the EJN exhibited a tonic discharge throughout a full range of elbow joint positions. The discharge was most intense when the elbow was extended to 165° and least intense when the joint was held in midrange positions between 90° and 120°. There was a modest increase in discharge as the elbow was held in more flexed positions and activity at 30° was about half of that at 165°. Alterations in the tone of muscles around the joint did not affect the adapted EJN discharge at anyangle.     

Contribution of sensory afferents and sympathetic efferents to joint injury in experimental arthritis

We used pharmacological and surgical methods to determine the contribution of several neural components to joint injury in rats with adjuvant-induced arthritis. Both neonatal administration of capsaicin, which eliminates small-diameter afferents, and peripheral sympathectomy, which depletes catecholamines, attenuated joint injury. In contrast, the arthritis was more severe in spontaneously hypertensive rats, which have increased sympathetic tone. To address the contribution of the central vs peripheral afferent terminal selectively, a group of rats underwent unilateral dorsal rhizotomy. These rats developed a more severe arthritis in the deafferented limb. The increase in arthritis severity produced by dorsal rhizotomy could be reduced by prior sympathectomy or, less effectively, by prior treatment with capsaicin. The latter observation suggests that large-diameter afferents that are cut during dorsal rhizotomy also influence inflammation. Finally, intracerebroventricular injection of morphine attenuated the severity of arthritis, possibly through activation of bulbospinal sympathoinhibitory circuits. Taken together, these data indicate that no one class of nerve fiber is wholly responsible for the neurogenic component of inflammation in experimental arthritis but that large- and small-diameter afferents, sympathetic efferents, and CNS circuits that modulate those fiber systems all influence the severity of joint injury in arthritic rats.     

Discharge characteristics of axotomized abducens internuclear neurons in the adult cat

The aim of the present work was to characterize the axotomy-induced changes in the discharge properties of central nervous system neurons recorded in the alert behaving animal. The abducens internuclear neurons of the adult cat were the chosen model. The axons of these neurons course through the contralateral medial longitudinal fascicle and contact the medial rectus motoneurons of the oculomotor nucleus. Axotomy was carried out by the unilateral transection of this fascicle (right side) and produced immediate oculomotor deficits, mainly the incapacity of the right eye to adduct across the midline. Extracellular single-unit recording of abducens neurons was carried out simultaneously with eye movements. The main alteration observed in the firing of these axotomized neurons was the overall decrease in firing rate. During eye fixations, the tonic signal was reduced, and, on occasion, a progressive decay in firing rate was observed. On-directed saccades were not accompanied by the high-frequency spike burst typical of controls; instead, there was a moderate increase in firing. Similarly, during the vestibular nystagmus, neurons hardly modulated during both the slow and the fast phases. Linear regression analysis between firing rate and eye movement parameters showed a significant reduction in eye position and velocity sensitivities with respect to controls, during both spontaneous and vestibularly induced eye movements. These firing alterations were observed during the 3 month period of study after lesion, with no sign of recovery. Conversely, abducens motoneurons showed no significant alteration in their firing pattern. Therefore, axotomy produced long-lasting changes in the discharge characteristics of abducens internuclear neurons that presumably reflected the loss of afferent oculomotor signals. These alterations might be due to the absence of trophic influences derived from the target.     

Basal forebrain efferents reach the whole cerebral cortex of the cat

Efferent projections from the basal forebrain to the cat's cerebral cortex were traced with the retrograde horseradish peroxidase technique. Different areas of the cerebral cortex of 51 cats were injected with small amounts of horseradish peroxidase. The entire basal forebrain was screened for labeled neurons. Following all injections, retrogradely labeled neurons could be detected in either the medial septum, or the vertical and horizontal limb of the diagonal band of Broca, or the substantia innominata, or in several of these structures. All three basal forebrain structures project heavily to allocortical regions, but only weakly to neocortical regions. An exception is the medial prefrontal cortex which is densily innervated by the substantia innominata (i.e., comparably dense as allocortical regions are innervated by the substantia innominata). Large injections into he basal temporal cortex (including the perirhinal cortex) and into the insular cortex also led to a considerable number of labeled cells in the substantia innominata. The results indicate a widespread innervation of the cat's cerebral cortex by the basal forebrain. This diffuse projection to the cortex has recently been found also in monkeys and rats. Anatomical and functional implications of these projections in the cat are discussed and related to findings in other species.     

膝关节损伤生物材料及其生物力学特点☆

目的：总结近年对膝关节韧带的生物力学与人工韧带的研究进展,强调膝关节的损伤类型,膝关节前后交叉韧带修复的主要方法及进展。 资料来源：以human knee cruciate ligament, biomechanics, xenogeneic ligamentous, reconstruction为检索词,检索PubMed数据库(2008-01/2009-07);以膝关节交叉韧带,生物力学,重建,人工韧带,康复为检索词,检索中国期刊全文数据库(2008-01/2009-07)。文献检索语种限制为英文和中文。 资料选择：纳入膝关节及人工韧带相关的内容。排除已被证实落后的研究及重复性研究。 结局评价指标：①膝关节的生物力学特征。②膝关节韧带损伤的情况。③膝关节韧带的修复与重建方法。 结果：计算机初检得到526篇文献,根据纳入排除标准,对膝关节损伤生物材料及其生物力学进行分析。常见的膝关节损伤主要是韧带损伤,为恢复其功能主要采用手术重建,其中利用自体中1/3骨-髌韧带-骨作为移植材料的挤压螺钉内固定重建术,已成为重建前交叉韧带的标准方法。羟基磷灰石是一类具有良好生物相容性的生物活性材料,羟基磷灰石生物活性陶瓷植入体内不仅安全、无毒,还能传导骨生长,即新骨可以从羟基磷灰石植入体与原骨结合处沿着植入体表面或内部贯通性孔隙攀附生长,能与组织在界面上形成化学键性结合。 结论：对膝关节及膝关节韧带进行生物力学分析是防止和治疗膝关节损伤及疾病的基础。具有表面羟基磷灰石涂层无螺纹的假体松动率最低,是最适宜的假体置换材料。 关键词：膝关节;损伤;生物材料;生物力学     

膝关节交叉韧带损伤影像学评估特征的研究与进展★

超声诊断膝关节交叉韧带损伤在上世纪90年代开始逐渐应用，并得到不断的发展。目前临床上膝交叉韧带损伤可经多种方法诊断，比如X射线、关节镜、核磁共振和超声等。但X射线和关节镜是有创伤性的，核磁共振虽然较准确但价格昂贵，而超声能够清晰显示膝关节解剖和损伤结构，是经济实用而且无放射性的一种诊断方法，在诊断交叉韧带损伤方面是非常有价值的。文章综合分析膝关节交叉韧带损伤的功能解剖、生物力学、临床表现、损伤类型、影像学表现等方面的研究发展。高低频超声结合检查后交叉韧带作为间接超声征象在前交叉韧带损伤的诊断中具有一定应用价值。     

Connections of the parahippocampal cortex in the cat. IV. Subcortical efferents

The present report deals with the projections from the entorhinal and perirhinal cortices to subcortical forebrain structures and the brainstem in the cat. By using anterograde and retrograde tracing techniques, it could be demonstrated that the entire mediolateral extent of the parahippocampal cortex issues prominent projections to the dorsal and ventral striatum, the amygdala, and the claustrum. In addition, the entorhinal cortex sends projections to the septum and the diagonal band of Broca. Only the perirhinal cortex gives rise to a weak projection to the dorsolateral periaquaductal gray and the ventral pontine region. The major proportion of the subcortical projections originates in the perirhinal cortex and the lateral entorhinal cortex, whereas the medial entorhinal cortex has a much sparser output and sends no fibers to the amygdala. The subcortical projections from both the entorhinal cortex and the perirhinal cortex arise mostly from their deep layers. It was further found that these projections are topographically organized along the mediolateral axis of the parahippocampal cortex. This mediolateral axis is related to a ventrolateral to dorsomedial axis in the septum, a mediolateral axis in the amygdala and the ventral striatum, and a ventrodorsal coordinate in the dorsal striatum and the claustrum. A further topography was observed in the projections from the perirhinal cortex to the lateral amygdaloid nucleus. A rostrocaudal axis in the perirhinal cortex corresponds to a mediolateral axis in the lateral amygdaloid nucleus. The present observations are compared with data concerning the connectivity of the parahippocampal cortex with the hippocampal formation and other cortical structures. It is suggested that the parahippocampal cortex in the cat may be conceptualized as an interface between the hippocampal formation and several subcortical structures in the realm of the limbic and motor systems.     

NADPH-diaphorase reactivity in articular afferents of a normal and inflamed knee joint in the cat

The distribution of NADPH-diaphorase was studied in retrogradely labelled dorsal root ganglion cells innervating the knee joint of the cat. A strong staining reaction was found in7.5 ± 1.9% (mean ± S.D. of 9 normal joints and 6393 labelled perikarya) of the articular afferents. An acute inflammation (32 h) significantly increased this proportion to10.9 ± 2.2% (mean ± S.D. of 5 inflamed joints and 3933 labelled perikarya). The diameter distribution of the somata with a positive NADPH-diaphorase reaction ranged from 18 to 46 μm with a maximum at 24–28 μm. These data indicate that a small proportion of knee joint primary afferents may be able to release nitric oxide playing a role in synaptic transmission and in regulatory functions within the peripheral tissue under normal and pathophysiological conditions.     

Modulation of transmission in flexion reflex pathways by knee joint afferent discharge in the decerebrate cat

In the intact hindlimb, flexion reflexes are most easily obtained when the knee is extended. Movement of the knee joint after the muscles have been tenotomized and held at fixed lengths still modulates flexion reflex excitability. After anaesthesia of the joint capsule movement of the limb no longer affects flexion reflex excitability.     

Discharge characteristics of spindle receptors located in different parts of the soleus muscle in the cat

A procedure is described for precise location of the capsula of a muscle spindle within the muscle by a restricted coagulation which abolishes the discharge of the spindle afferent. The point for coagulation was approximately determined by careful stretching of a little portion of muscle fibres, by slight pressure on the external and internal surface of the muscle, by intramuscular and external electric stimulation. The analysis of the dynamic and static sensitivity of 48 units shows that the differences in responses to stepwise stretching existing among both primary and secondary endings do not depend on the location of muscle spindles in different parts of m. soleus, but probably reflect variations in the density of afferent terminal contacts in 3 types of intrafusal muscle fibres.     

The effect of acute abolition of knee joint afferent discharge on postural reflexes in the conscious cat

Injection of local anaesthetic into the knee joint space in a series of 5 ctss produced obvious postural abnormalities in 3 animals. However, on employing a more sensitive test, all animals exhibited abnormalities of postural reflexes on abolishing knee joint afferent discharge. Control experiments indicated that this could not be attributed to the local anaesthetic diffusing locally out of the joint capsule and affecting muscle and cutaneous afferents around the knee joint.     

The sympathetic and sensory components of the caudal lumbar sympathetic trunk in the cat

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project in the caudal lumbar sympathetic trunk of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The application was made just proximal to the segmental ganglion that sends its gray rami to the L7 spinal nerve, and so identified the sympathetic outflow concerned primarily with the vasculature of the hindlimb and tail. The numbers, segmental distribution, location, and size of the labeled somata have been determined quantitatively. Labeled cell bodies were found ipsilaterally, but the segmental distributions of the different cell types were not matched. Afferent cell bodies lay in dorsal root ganglia L1-L5 (maximum L4), preganglionic cell bodies in spinal segments T10-L5 (maximum L2/3), and postganglionic cell bodies in ganglia L2-L5 (maximum L5). Both numbers and dimensions of labeled dorsal root ganglion cells were variable between experiments (maximum about 1,000); the majority were small relative to the entire population of sensory neurons. Labeled preganglionic cell bodies were located right across the intermediate region of the spinal cord, extending from the lateral part of the dorsolateral funiculus to the central canal. The highest density of labeled neurons lay at the border between the white and gray matter (corresponding to the intermediolateral cell column) with smaller proportions medially in L1-L2, and laterally in caudal L4-L5. Medial preganglionic neurons were generally larger than those lying in lateral positions. From the data, it is estimated that about 650 afferent, about 4,500 preganglionic, and some 2,500 postganglionic neurons project in each lumbar sympathetic trunk distal to the ganglion L5 in the cat.     

Time course of acetylcholine-induced activation of sympathetic efferents matches axon reflex sweating in humans

Action potentials from postganglionic C-fibres were recorded in healthy volunteers by microneurography in the peroneal nerve. Their responsiveness to mechanical or heat stimuli or to sympathetic reflex provocation tests was determined by transient slowing of conduction velocity following activation. Twenty units were classified as sympathetic efferent units. Acetylcholine (ACh) iontophoresis (10%, 1 mA, 1 min) inside their innervation territory activated 8 of 20 sympathetic fibres with a mean delay of 61 ± 12 s, peak response at 175 ± 38 s, and a duration of 240 ± 42 s, whereas iontophoresis of saline did not activate any of them. The time course of neuronal activation correlated with the axon reflex sweating measured by an evaporimeter in a separate session (delay 76 ± 9 s, peak at 195 ± 12 s, decline to 50% of peak 312 ± 25 s). No ACh-induced vasoconstriction was observed by laser Doppler scanning (n = 11) even after depletion of neuropeptides by chronic topical capsaicin treatment (n = 8). We conclude that ACh iontophoresis activates about half of the sympathetic fibres in human skin and provokes a corresponding axon reflex sweating. The absence of ACh-induced vasoconstriction even after the depletion of neuropeptides by capsaicin suggests that only sudomotor fibres, but not sympathetic vasoconstrictor fibres are activated by this stimulus.     

The effect of mechanical stimulation of knee joint afferents on quadriceps motor unit activity in the decerebrate cat

The present experiments demonstrate that repetitive activation of as few as two joint afferents by an imposed mechanical stimulus results in entrainment of stretch-induced firing of quadriceps motor units. There is no significant input from extracapsular receptors as the effect is abolished during local anaesthetic block of the joint nerve. These results indicate that joint receptors can exert potent effects on motoneurone excitability which may be of considerable functional significance.     

Fine sensory innervation of the knee joint capsule by group III and group IV nerve fibers in the cat

Afferent group III and IV nerve fibers of the knee joint markedly differ in their responsiveness to mechanical stimulation, which may be reflected in the structure and location of their terminals. Therefore, in sympathectomized cats, the fine afferent innervation of the knee joint capsule was studied via ultrastructural three-dimensional reconstructions over distance of up 300 μm. Small peripheral nerves and “free” (noncorpuscular) sensory nerve ending were found in a superficial layer of the outer fibrous part of the capsule, in the patellar retinaculum, and in the outer and inner surface layers of the medial collateral and patellar ligaments. Group III nerve fibers showed a proximal myelinated portion inside the nerve, an intermediate portion that lacks a myelin sheath and is only surrounded by perineurium, and a distal portion outside of the perineurium that forms the sensory ending proper. Group IV fibers showed only two distinct portions, an intraperineurial (proximal) and an extraperineurial (distal) portion without any further morphological differences. Outside of the perineurium, a network formed by Schwann cells (“Schwann cell reticulum”) provides a pathway for the distal portion of the sensory axons. No distinct subgroups of the sensory terminal fibers could be defined according to the configuration of the Schwann cells and the nerve fiber terminals. Sensory terminals were located adjacent to different structures such as venous and lymphatic veesels, fat cells, and collagenous fibers. Distinct parts of the same terminal nerve fiber were found in close contact to a vessel wall; others were surrounded by dense collagenous tissue. Close to sensory endings, mast cells and mast cell-like cells were frequently found, indicating a functional relationship. © 1995 Willy-Liss, Inc.     

Relationship between sympathetic and phrenic nerve responses to peripheral chemoreflex in the cat

To test the hypothesis that peripheral chemoreflex effect on the preganglionic cervical sympathetic nerve (PSN) activity is entirely mediated by the central respiratory drive (CRD), as expressed in the phrenic nerve (PN) activity, we studied the relationship between PN and PSN activities under controlled conditions of carotid chemosensory excitation in the anesthetized cats. The cats were vagotomized, paralyzed and artificially ventilated. Tracheal pO2 and pCO2, systemic blood pressure, activities of single or a few PSN and PN fibers and a PN bundle were simultaneously recorded. The PSN preparations, which were responsive to hypoxia and showed PN rhythm, were selected for the study. Carotid chemoreceptor excitation, produced by hypoxia (end-tidal pO2 approximately equal to 50 Torr) or by sodium cyanide injection (50-100 micrograms, i.v.), elicited 3 types of responses: (1) the PSN discharged during the silent period of PN activity, although the PSN peak activity was still coupled to the PN peak activity, (2) PSN discharged only during PN activity, and (3) during the absence of PN discharge induced by hyperventilation hypocapnia, cyanide injection stimulated the PSN without PN activity. These observations suggest a model of chemoreflex control of sympathetic nerve activity which consists of two parts: one is dependent on PN activity and the other is not. Accordingly, all PSN chemoreflex responses may not be integrated with all inspiratory chemoreflexes.