Prostaglandin inhibitor indomethacin inhibits afferent activities of Adelta and C units in the saphenous nerve of diabetic hyperalgesic rats

The effects of a non-selective inhibitor of cyclo-oxygenase (COX) indomethacin, and exogenous prostaglandin E(2) (PGE(2)) on A(delta) units and C units in the saphenous nerve of diabetic hyperagesic rats were studied. The results showed that the conduction velocity of A(delta) units and C units and their mechanical threshold in diabetic hyperagesic rats were obviously decreased, and a small number of A(delta) units (4/24) and C units (2/18) produced increased spontaneous activities. Intraperitoneal injection of indomethacin in diabetic hyperagesic rats significantly relieved mechanical hyperalgesia, and resulted in a decrease in spontaneous afferent activities of the A(delta) units and C units. Subcutaneous injection of exogenous PGE(2) into the diabetic hyperagesic and control rats produced a significant decrease in mechanical threshold of the A(delta) units and C units, and elicited discharge from 3 A(delta) units (3/24) and 1 C unit (1/18) in diabetic hyperagesic rats and from 2 A(delta) units (2/13) in control rats. The present data suggest that the synthesis and release of PGs are increased in diabetic neuropathy, PGs can sensitize and /or activate A(delta) units and C units and elicit hyperagesia and allodynia in diabetic rats.     

OMF对大鼠疑核呼吸相关单位电活动的影响

本工作观察了微电泳给予 OMF 对大鼠延髓疑核呼吸相关单位自发放电活动的影响。在96个单位中,呈现抑制效应的48个,兴奋效应的14个,先兴奋后抑制的14个,先抑制后兴奋的9个,其余11个单位无明显变化。在15个 OMF 产生抑制效应的单位中,有11个单位的抑制效应能被纳洛酮对抗。在6个 OMF 产生兴奋效应的单位中,有5个单位的兴奋效应能被纳洛酮对抗。在13个 OMF 引起抑制效应的单位中,有9个单位的抑制效应能被微电泳给予的 U-50488对抗。OMF 产生抑制效应持续的时间明显长于兴奋效应持续的时间。结果提示介导 OMF 抑制效应的阿片受体亚型可能不同于介导兴奋效应的阿片受体亚型。     

Slowly adapting cutaneous mechanoreceptor afferent units associated with Merkel cells in frogs and effects of direct currents.

In the bullfrog, two types of slowly adapting (SA) cutaneous mechanoreceptor afferent units have been identified physiologically: irregularly discharging frog type I (Ft I) units in both warty and nonwarty skin, and regularly discharging frog type II (Ft II) units in the nonwarty skin. In the present study, mechanosensitive spots of Ft I units were located around the skin warts in the warty skin. The quinacrine technique (Crowe and Whitear, 1978) revealed that quinacrine-accumulating Merkel cells were present around the skin warts and near the orifice of skin glands that also surrounded the skin warts. Thus, a significant correlation was found between the location of Merkel cells and the receptive fields (RFs) of Ft I units in the warty skin. Direct current (DC) stimulation was applied for 1 sec to the skin inside and outside the mechanical RFs of the two types of SA units. RFs for DC stimulation were located on those for mechanical stimulation in both types of SA units. The current threshold required to produce a single spike was lower in cathodal than in anodal pulses in both types of SA units. Greater current intensity elicited an increased number of spikes, but the effective polarity of currents was anodal for Ft I units and cathodal for Ft II units. The optimal current intensity for producing prolonged discharges ranged from +60 to +100 microA in Ft I units and - from -50 to -80 microA in Ft II units. The sequence of impulses evoked was irregular in Ft I units and regular in Ft II units, as seen in mechanical responses.(ABSTRACT TRUNCATED AT 250 WORDS)     

微电泳U—50488对大鼠疑核呼吸相关单位电活动的影响

本工作观察了微电泳给予 U-50488对大鼠延髓疑核呼吸相关单位自发放电活动的影响。在96个单位中,呈抑制效应的51个,兴奋效应的11个,先抑制后兴奋的3个,先兴奋后抑制的6个,其余25个单位的自发放电活动无明显变化。在16个 U-50488产生抑制效应的单位中,12个单位的抑制效应能被纳洛酮对抗。2个 U-50488 表现为兴奋效应的单位,纳洛酮也显出拮抗效应。U-50488产生抑制效应持续的时间明显长于兴奋效应持续的时间。本工作的结果提示,k 受体可能也参与呼吸调控作用,并且介导 U-50488抑制效应的阿片受体亚型可能不同于介导兴奋效应的阿片受体亚型。     

糖尿病痛过敏大鼠尾神经中传入单位对交感传出的反应

实验观察了刺激交感神经（sympathetic stimulation,SS）、静脉注射去甲肾上素（noradrenaline,NA）和酚妥拉明对糖尿病痛过敏大鼠尾神经中各种传入单位的影响。结果发现,糖尿病痛过敏大鼠的具有自发放电的C单位和Aδ单位在SS后放电频率增加,α－受体阻断剂能消除这些自发放电活动;在无自发放电的C单位和Aδ单位中,SS能使部分C单位和Aδ单位由静息状态转入活动状态;它虽不能诱发C－机械感受单位（C mechanical receptive unit,C-M）产生传入放电,但可诱发部分C－机械热单位（C mechano-heat unit,C-MH）和C－多型单位（C polymodal unit,C-Pol）的活动;SS还能使部分Aδ－机械单位（Aδ mechanical receptive unit,Aδ-M）和Aδ－机械热单位（Aδ mechano-heat unit,Aδ-MH）产生传入放电;它所诱发的C单位和Aδ单位反应的潜伏期不等,但不短于5s;SS不能引起糖尿病痛过敏大鼠Aβ机械感受性单位和对照组大鼠各类感受性单位产生新的传入活动。静脉注射NA可诱发糖尿病痛过敏大鼠的部分C单位和Aδ单位产生新的传入活动。结果提示,交感神经末梢释放的NA对糖尿病痛过敏大鼠C单位和Aδ单位的兴奋作用是糖尿病大鼠产生痛过敏和感觉异常的外周因素。     

A commentary on muscle unit properties in cat hindlimb muscles

A broad survey of muscle unit properties in 14 muscles of the cat hind limb is presented which emphasizes some general features of unit properties in mammalian muscles. A more detailed analysis of muscle unit properties in three muscles of the posterior compartment of the lower leg is then presented using Burke's tetrapartite (FF, FI or F (Int.), FR, and S) unit classification scheme. Our data on the properties of motor units in cat tibialis posterior (TP) have been compared to those generated by Burke and colleagues on units in flexor digitorum longus (FDL) and medial gastrocnemius (MG). In all three muscles, twitch contraction time was distinctly slower for type S units and specific tension outputs were substantially greater for type FF units than for type S units. The innervation ratios of type FR units were slightly lower than for type S units but the specific tension of the FR units was closer to FF units than to type S units. The FF units controlled 70–74% of the cumulative force output of each muscles, indicating a substantial capacity for powerful rapid contractions of all three of these muscles despite their differences in “size,” action, and force generation. Distinctive features of the three muscles included differences in the unit types' force producing capabilities and in the relative representation of “nonfatigable” type FR and S units in each muscle. In particular, TP is endowed with some unusually powerful type FF units and a high percentage (42%) of type S units. In contrast, FDL has units that develop relatively little force and an unusually high representation (56%) of type FR units. The possible relationships between these muscle features and their presumed role in posture and locomotion is discussed.     

Relationship between the tension-time area and the frequency of stimulation in motor units of the rat medial gastrocnemius muscle.

The tension-time area is an estimation of the work performed by contracting motor units. The relationship between tension and frequency of stimulation and between tension-time area and frequency have been studied on 148 single motor units of the rat medial gastrocnemius muscle, under isometric conditions. Motor units were classified as fast fatigable (FF), fast resistant to fatigue (FR) or slow (S). Trains of stimuli of increasing frequency and constant duration were used. For all motor units a half of the maximum tetanic tension corresponded to lower frequencies compared to frequencies at a half of the maximum tension-time area. Moreover, the slopes of tension-frequency and area-frequency curves (change of tension or area per 1 Hz rise in frequency) were higher for slow than for fast motor units. The tension-time area per one pulse was calculated for different frequencies of stimulation. For slow units the maximum area per pulse corresponded to significantly lower frequencies than for fast ones, especially of FF type. However, for all three types of motor units this optimal frequency corresponded to sub-fused tetani with a tension of about 75% of the maximum tension, and with the fusion index slightly over 0.90. The absolute values of the maximum tension-time area per pulse revealed that in one contraction within the tetanus, slow units are generating greater work than FR units. The work performed by FF units is nearly two times larger than for S units, although the tension of slow units is over eight times lower. The presented results reveal that the contraction of slow motor units is much more effective than was suggested based on their low tension.     

大鼠下丘脑室旁核神经元对电刺激蓝斑和中缝背核的反应

用玻璃微电极细胞外记录大鼠室旁核(PVH)神经元的单位放电,观察它对电刺激蓝斑(LC)和中缝背核(DR)的反应。 在435个被试验单位中,5个单位对LC电刺激呈现逆行反应,75个单位呈现顺行反应。在这75个顺行反应单位中,27个对单刺激发生反应,48个对串刺激发生反应。对电刺激DR发生反应的有74个单位,其中15个对单刺激发生反应,59个对串刺激发生反应而对单刺激不反应。值得注意的是有23个PVH神经元既对LG刺激又对DR刺激发生顺行反应。实验结果提示,PVH与LC、DR之间存在神经联系。     

Slowly Adapting Cutaneous Mechanoreceptor Afferent Units Associated with Merkel Cells in Frogs and Effects of Direct Currents

In the bullfrog, two types of slowly adapting (SA) cutaneous mechanoreceptor afferent units have been identified physiologically: irregularly discharging frog type I (Ft I) units in both warty and nonwarty skin, and regularly discharging frog type II (Ft II) units in the nonwarty skin. In the present study, mechanosensitive spots of Ft I units were located around the skin warts in the warty skin. The quinacrine technique (Crowe and Whitear, 1978) revealed that quinacrine-accu-mulating Merkel cells were present around the skin warts and near the orifice of skin glands that also surrounded the skin warts. Thus, a significant correlation was found between the location of Merkel cells and the receptive fields (RFs) of Ft I units in the warty skin.

Direct current (DC) stimulation was applied for 1 sec to the skin inside and outside the mechanical RFs of the two types of SA units. RFs for DC stimulation were located on those for mechanical stimulation in both types of SA units. The current threshold required to produce a single spike was lower in cathodal than in anodal pulses in both types of SA units. Greater current intensity elicited an increased number of spikes, but the effective polarity of currents was anodal for Ft I units and cathodal for Ft II units. The optimal current intensity for producing prolonged discharges ranged from +60 to +100 μA in Ft I units and from -50 to -80 μA in Ft II units. The sequence of impulses evoked was irregular in Ft I units and regular in Ft II units, as seen in mechanical responses. When current of the effective polarity for each type of unit was superimposed on the mechanical indentations, it facilitated the mechanical response. Currents of opposite polarity were not effective without mechanical indentation, but when used together, they depressed the mechanical response in both the Ft I units and the Ft II units. Thus, different polarities of DC could selectively activate two different types of SA units in bullfrogs. We consider these findings in connection with a presumed receptor structure for each type of unit; it is likely that the prolonged discharges in the Ft I unit are produced by active involvement of Merkel cells, whereas those in Ft II units are the result of a direct activation of afferent nerve terminals.     

Differences between properties of male and female motor units in the rat medial gastrocnemius muscle.

Differences between motor units in hindlimb locomotor muscles of male and female Wistar rats were studied. The contractile and action potential properties of various types of motor units as well as proportions of these units in the medial gastrocnemius muscle were analyzed. Experiments were based on functional isolation and electrical stimulation of axons of single motor units. Composition of motor units was different for male and female subjects, with higher number of the fast fatigable and lower number of slow type units in male animals. The contraction and the half-relaxation times were significantly longer in male motor units, what might be due to differences in muscle size. Slower contraction of male motor units likely corresponds to lower firing rates of their motoneurons. On the other hand, no significant differences between sexes were observed with respect to force parameters of motor units (the twitch and the maximum tetanus forces), except the fast resistant units (higher force values in male muscles). The mass of the muscle was approximately 1.5 time bigger in male rats. However, the mean ratio of motor unit tetanus force to the muscle mass was almost twice smaller in this group, what indirectly suggests that muscles of male rats are composed of higher number of motor units. Finally, female muscles appeared to have higher fatigue resistance as the effect of higher proportion of resistant units (slow and fast resistant) and higher values of the fatigue index in respective motor unit types. The motor unit action potentials in female rats had slightly lower amplitudes and shorter time parameters although this difference was significant only for fast resistant units.     

The contractile properties of the medial gastrocnemius motor units innervated by L4 and L5 spinal nerves in the rat

When a muscle innervation originates from more than one spinal cord segment, the injury of one of the respective ventral roots evokes an overload, and alters the activity and properties of the remaining motor units. However, it is not well documented if the three types of motor units are equally represented within the innervating ventral roots. Single motor units in the rat medial gastrocnemius muscle were studied and their contractile properties as well as distribution of different types of motor units belonging to subpopulations innervated by axons in L4 and L5 ventral roots were analyzed. The composition of the three physiological types of motor units in the two subpopulations was similar. Force parameters were similar for motor units belonging to the two subpopulations. However, the twitch time parameters were slightly longer in L4 in comparison to L5 motor units although the difference was significant only for fast resistant to fatigue motor units. The force-frequency relationships in the two subpopulations of motor units were not different. Concluding, the two subpopulations of motor units in the studied muscle differ in the number of motor units, but contain similar proportions of the three physiological types of these units and their contractile properties are similar. Therefore, the injury of one ventral root evokes various degrees of muscle denervation, but is non-selective in relation to the three types of motor units.     

Appearance of "transitional" motor units in overloaded rat skeletal muscle

The contractile characteristics of single motor units, isolated from rat plantaris muscles subjected to short-term (30 days) compensatory overload, were assessed to determine whether motor units in transition could be detected. In the control plantaris 88% of the motor units were classified as fast. After overload, a large decline (26.5%) in the proportion of typical fast motor units was noted. The estimated contribution of fast fatigable units to whole muscle tetanic tension (Po 200) also declined (from 55 to 25%), whereas that of fast intermediate motor units increased (from 33 to 55%). In the overloaded plantaris, motor units that exhibited unusual "sag" and contraction time characteristics were detected. These motor units, which could be further subdivided into two distinct types by a variety of indexes, exhibited characteristics intermediate to fast and slow units and therefore were termed "transitional." Transitional units accounted for 12% of the estimated whole muscle Po200 after overload. These experiments characterize novel classifications of motor units undergoing transformation and further detail the motor unit shift that accompanies compensatory overload.     

Response properties of periodontal mechanosensitive neurons in the trigeminal spinal tract nucleus of the cat.

Periodontal mechanosensitive (PM) units were recorded from the trigeminal spinal tract nucleus (Vst) of the cat. The Vst is divided into three subnuclei: oralis (Vo), interpolaris (Vi), and caudalis (Vc). The receptive fields of PM units in Vo and Vi were arranged in a dorsoventral sequence in the mandibular to maxillary divisions, and those in Vc were arranged in a mediolateral sequence. The majority of Vo units were single-tooth ones, whereas more than half the Vi units and all the Vc ones were multitooth units. The PM units in each subnucleus were predominantly responsive to canine tooth stimulation. Most of the PM units in Vo and Vi gave sustained responses to pressure applied to the tooth, were directionally selective, and were most actively excited by canine tooth stimulation in the caudomedial or rostrolateral direction. Vc units, however, were transient. The threshold intensity for firings by canine tooth stimulation was less than 0.05 N. These findings indicate that only the response properties of PM units in the rostral part of Vst resemble those of the trigeminal main sensory nucleus neurons and primary afferent nerves.     

Representation of lateral line and electrosensory systems in the midbrain of the axolotl,Ambystoma mexicanum

Summary The study focussed on the representation of the electrosensory and lateral line units in the midbrain of the axolotl Ambystoma mexicanum. In addition, the responses to photic and acoustic/vibrational stimuli were determined. Unit properties were characterized with respect to baseline activity, sensitivity, latency, directional specificity and number of input modalities. The anatomical arrangement of the units was determined using stereotactic and histological measurements of the electrode positions.Of 106 units recorded, 29 units were unimodal, 77 units responded to more than one modality. Most units discharged only in response to stimuli. Thresholds of electrosensory units were about 100 V/cm field strength; lateral line units had thresholds below 5 m pp amplitude. The shortest latencies (8–17 ms) were found for responses to visual stimuli. Lateral line and vestibular units responded after 35–58 ms, electroreceptive units after 79–150 ms. All electrosensory and about 50% of the lateral line units were sharply tuned to definite stimulus directions.Electrosensory and lateral line units formed topographical maps in the tectum. The map in each tectal hemisphere contained information about the contralateral surroundings. The electrosensory, lateral line and visual representations were only partly in register; especially in the caudal areas of the midbrain the alignment was poor.     

Taste systems of the petrosal ganglion of the rat glossopharyngeal nerve

Single unit recordings were taken from sensory ganglion cellsin the petrosal ganglion (PG) of the glossopharyngeal nerveof the rat. These taste units were examined with respect tospontaneous and evoked discharge patterns and responsivenessto a wide variety of chemical compounds, most of natural occurrence.Spontaneous activity patterns, with few exceptions, tended tobe extremely irregular with both bursting (clusters of 2–3spikes) and grouping (large groups of spikes as in evoked discharges).Most interspike interval histograms of spontaneous activitywere multimodal, similar to rat geniculate ganglion (GG) units.Evoked discharges usually displayed grouping of spikes, andlong latencies of onset and persistence of discharge after rinsewere sometimes seen. Little response was shown to nucleotidesor salts. Units responsive to amino acids tended to show largedischarge to only one or two amino acids; and the most responsiveamino acid usually varied from cell to cell. Units responsiveto alkaloids only responded to a few alkaloids with atropineand quinine being the most stimulatory. Units responsive toacids only discharged to a few of the acids tested and oftenacids of low pH elicited no discharge. Saccharin activated unitsresponsive to both sugar and alkaloids. A few units highly responsiveto both sugar and alkaloids were seen. The units were placedinto four clusters on the basis of chemicals activating themand certain neurophysiological characteristics: PG salt units,PG acid units and, tentatively, amino acid (sugar) units andX (alkaloid and alkaloid plus) units. The PG salt units didnot show the exclusive sensitivity to sodium and lithium compoundsas did the GG salt units. The PG acid units could also be differentiatedfrom the GG acid units. The petrosal amino acid and X units,on the other hand, could not be differentiated from similarunits in the rat GG.     

Structural characterization of ficaprenol-11 by 13C nuclear magnetic resonance.

The location of the internal trans and cis isoprene units in ficaprenol-11 isolated from Ficus elastica was determined by 13C nuclear magnetic resonance. The alignment of the isoprene units was estimated to be in the order: omega-terminal unit, three trans units, six cis units and alpha-terminal cis alcohol unit.     

Heterogeneity of spindle units in the cat tenuissimus muscle

Three tandem spindles and their nerve supplies, reconstructed by light microscopy of serial transverse sections of the cat tenuissimus muscle, were compared to single spindle units. Each tandem spindle consisted of one large unit containing a dynamic bag1, a static bag2, and several static chain fibers (b1b2c unit) linked by the bag2 fiber to a small unit containing only a bag2 and chain fibers (b2c unit). Most features of primary afferents, secondary afferents, and motor neurons were qualitatively and quantitatively similar in both single and tandem b1b2c units. However, b1b2c units of tandem spindles had a lower density of skeletofusimotor innervation than did single b1b2c spindles. The b2c spindle units differed greatly from single or tandem b1b2c units. The b2c spindle units had fewer intrafusal fibers and incoming axons than either the tandem or single b1b2c units. The motor innervation of b2c units was typified by nonselective gamma axons that coinnervated both bag2 and chain fibers, in contrast to the regular occurrence of both selective and nonselective motor axons in b1b2c spindle units. The afferent located at the equator of b2c units differed in size, branching pattern, and intrafusal distribution of its ending from both the primary and secondary sensory axons of b1b2c units and, therefore, might represent a third category of spindle afferent. Thus, cat tenuissimus muscles contain three types of spindle units that differ in the number and organization of muscular and neural elements. These differences in structure and neural organization among tenuissimus spindle units may be a source for generation of different sensory signals in response to common mechanical or fusimotor stimuli.     

Regulation of DNA replication on subchromosomal units of mammalian cells

The regulation of DNA replication at a subchromosomal level in mammalian cells has been investigated. DNA fiber autoradiographs were prepared from mouse L-929 cells pulse labeled with (3H)thymidine. Initiation events and subsequent chain growth occurring over short stretches (up to three replication units in length) of chromosomal DNA were analyzed. The results show that adjacent units usually initiate replication synchronously and that this synchrony is related to the proximity of initiation sites. In addition, adjacent units are of similar size and the rates of replication fork progression within units and on adjacent units are similar. The rate of fork progression increases with increasing replication unit size. Finally, no evidence for fixed termination sites for the units has been found. These observations suggest that despite large variations in size of replication units, timing of initiation events, and rates of fork progression found in chromosomal DNA as a whole, these processes are closely regulated within subchromosomal clusters of active replication units.     

医用供应装置的风险分析及应对策略

医用供应装置的医疗事故时有发生。从气体、电气和机械结构等方面,深入分析和评估医用供应装置的风险,提出加强医用供应装置安全性和避免事故发生的应对措施,并介绍ISO国际标准关于医用供应装置的完整标准体系。