scholarly journals Lambert-Eaton syndrome without an identified neoplasm

2021 ◽  
Author(s):  
Ana Cláudia Pires Carvalho ◽  
Stella Angelis Trivellato ◽  
Guilherme Jardini Drumond Anastacio ◽  
Fernanda Rezende Dias ◽  
Luisa Crevelin Costa ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Action Potentials ◽  
Low Frequency ◽  
Diagnostic Methods ◽  
Lower Limbs ◽  
High Frequency Stimulation ◽  
Voltage Gated Calcium Channels ◽  
Low Frequency Stimulation ◽  
Compound Muscle Action Potentials ◽  
Frequency Stimulation

Introduction: Lambert-Eaton syndrome occurs due to the attack of autoantibodies to voltage-gated calcium channels in the presynaptic terminal of the neuromuscular junction and is usually paraneoplastic. Objectives: Describe the case of a patient with weakness which was investigated for neoplasm. Design and setting: Case report Methods: Analysis of medical record, photographic record of the diagnostic methods and literature review. Case description: Woman, 60 years old, diabetic, hypertensive and ex-smoker, with proximal weakness in the lower limbs for 4 months with paresthesia in the extremities. In 2 months she needed a cane due to frequent falls, followed by proximal weakness of the upper limbs. She lost 8 kg in 4 months. Neurological examination showed hypotrophy in thighs, proximal tetraparesis predominantly in lower limbs and global hyporeflexia. Electroneuromyography showed decreases to repetitive low-frequency stimulation, but significant increases with repetitive high-frequency stimulation and increased amplitude of compound muscle action potentials after effort, suggesting impairment of the neuromuscular junction in the presynaptic topography. She was diagnosed with LambertEaton syndrome. An investigation of paraneoplastic syndrome was carried out, with tumor markers, tomography of the chest, abdomen and pelvis, thyroid ultrasound, mammography and oncotic colposcopy, all without findings of neoplasia. It was proposed a treatment with human immunoglobulin and followup with physiotherapy, occupational therapy and psychology. She showed a significant improvement in strength after starting treatment. Conclusion: Patients with Lambert-Eaton syndrome should be investigated for an underlying neoplasm and followed up periodically, considering the possibility of cancer diagnosis even months or years after the neurological syndrome.

scholarly journals MONOSYNAPTIC REFLEX RESPONSE OF INDIVIDUAL MOTONEURONS AS A FUNCTION OF FREQUENCY

1957 ◽  
Vol 40 (3) ◽  
pp. 435-450 ◽  
Author(s):  
David P. C. Lloyd
Keyword(s):  
High Frequency ◽  
Temporal Summation ◽  
Low Frequency ◽  
Stimulation Frequency ◽  
Monosynaptic Reflex ◽  
Reflex Response ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Frequency Of Stimulation

An assemblage of individual motoneurons constituting a synthetic motoneuron pool has been studied from the standpoint of relating monosynaptic reflex responses to frequency of afferent stimulation. Intensity of low frequency depression is not a simple function of transmitter potentiality. As frequency of stimulation increases from 3 per minute to 10 per second, low frequency depression increases in magnitude. Between 10 and approximately 60 per second low frequency depression apparently diminishes and subnormality becomes a factor in causing depression. At frequencies above 60 per second temporal summation occurs, but subnormality limits the degree of response attainable by summation. At low stimulation frequencies rhythm is determined by stimulation frequency. Interruptions of rhythmic firing depend solely upon temporal fluctuation of excitability. At high frequency of stimulation rhythm is determined by subnormality rather than inherent rhythmicity, and excitability fluctuation leads to instability of response rhythm. In short, whatever the stimulation frequency, random excitability fluctuation is the factor disrupting rhythmic response. Monosynaptic reflex response latency is stable during high frequency stimulation as it is in low frequency stimulation provided a significant extrinsic source of random bombardment is not present. In the presence of powerful random bombardment discharge may become random with respect to monosynaptic afferent excitation provided the latter is feeble. When this occurs it does so equally at low frequency and high frequency. Thus temporal summation is not a necessary factor. There is, then, no remaining evidence to suggest that the agency for temporal summation in the monosynaptic system becomes a transmitting agency in its own right.

Diaphragm fatigue induced by inspiratory resistive loading in spontaneously breathing rabbits

1985 ◽  
Vol 59 (5) ◽  
pp. 1527-1532 ◽  
Author(s):  
T. K. Aldrich ◽  
D. Appel
Keyword(s):  
Lactic Acidosis ◽  
Low Frequency ◽  
Respiratory Acidosis ◽  
High Frequency Stimulation ◽  
Base Line ◽  
Low Frequency Stimulation ◽  
Resistive Loading ◽  
Frequency Stimulation ◽  
Spontaneously Breathing ◽  
Diaphragm Fatigue

Diaphragmatic contractility was assessed in spontaneously breathing ketamine-anesthetized rabbits by measuring the strength of diaphragmatic contraction in response to bilateral supramaximal phrenic nerve stimulation at frequencies between 10 and 100 Hz. During 10–180 min of inspiratory resistive loading, contractility decreased by approximately 40%, and hypoxemia and both respiratory and lactic acidosis developed. After 10 min of recovery, both the response to high-frequency stimulation (100 Hz) and the arterial PO2 and PCO2 returned to base-line levels, whereas metabolic acidosis and reduced response to low-frequency stimulation (10–20 Hz) persisted. Similar levels of hypoxemia and respiratory acidosis in the absence of inspiratory resistive loading did not alter diaphragmatic contractility. We conclude that in anesthetized rabbits excessive inspiratory resistive loading results in partially reversible diaphragm fatigue of the high- and low-frequency types, accompanied by hypoventilation and lactic acidosis.

Robust Changes of Afferent-Induced Excitation in the Rat Spinal Dorsal Horn After Conditioning High-Frequency Stimulation

2000 ◽  
Vol 83 (4) ◽  
pp. 2412-2420 ◽  
Author(s):  
Hiroshi Ikeda ◽  
Tatsuya Asai ◽  
Kazuyuki Murase
Keyword(s):  
Dorsal Horn ◽  
High Frequency ◽  
Low Frequency ◽  
Single Pulse ◽  
High Frequency Stimulation ◽  
Neuronal Excitation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Stimulation Of

We investigated the neuronal plasticity in the spinal dorsal horn and its relationship with spinal inhibitory networks using an optical-imaging method that detects neuronal excitation. High-intensity single-pulse stimulation of the dorsal root activating both A and C fibers evoked an optical response in the lamina II (the substantia gelatinosa) of the dorsal horn in transverse slices of 12- to 25-day-old rat spinal cords stained with a voltage-sensitive dye, RH-482. The optical response, reflecting the net neuronal excitation along the slice-depth, was depressed by 28% for more than 1 h after a high-frequency conditioning stimulation of A fibers in the dorsal root (3 tetani of 100 Hz for 1 s with an interval of 10 s). The depression was not induced in a perfusion solution containing an NMDA antagonist,dl-2-amino-5-phosphonovaleric acid (AP5; 30 μM). In a solution containing the inhibitory amino acid antagonists bicuculline (1 μM) and strychnine (3 μM), and also in a low Cl−solution, the excitation evoked by the single-pulse stimulation was enhanced after the high-frequency stimulation by 31 and 18%, respectively. The enhanced response after conditioning was depotentiated by a low-frequency stimulation of A fibers (0.2–1 Hz for 10 min). Furthermore, once the low-frequency stimulation was applied, the high-frequency conditioning could not potentiate the excitation. Inhibitory transmissions thus regulate the mode of synaptic plasticity in the lamina II most likely at afferent terminals. The high-frequency conditioning elicits a long-term depression (LTD) of synaptic efficacy under a greater activity of inhibitory amino acids, but it results in a long-term potentiation (LTP) when inhibition is reduced. The low-frequency preconditioning inhibits the potentiation induction and maintenance by the high-frequency conditioning. These mechanisms might underlie robust changes of nociception, such as hypersensitivity after injury or inflammation and pain relief after electrical or cutaneous stimulation.

Role of fascia in maintenance of muscle tension and pressure

1981 ◽  
Vol 51 (2) ◽  
pp. 317-320 ◽  
Author(s):  
S. R. Garfin ◽  
C. M. Tipton ◽  
S. J. Mubarak ◽  
S. L. Woo ◽  
A. R. Hargens ◽  
...  
Keyword(s):  
High Frequency ◽  
Muscle Tension ◽  
Fluid Pressure ◽  
Low Frequency ◽  
Testing Procedure ◽  
Force Transducer ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

The effect of fasciotomy on muscle tension (measured by a force transducer attached to the tendon) and interstitial fluid pressure (measured by Wick catheters in the muscle belly) was studied in the anterolateral compartments of 13 dog hindlimbs. Muscle tension and pressure were monitored in the tibialis cranialis muscle after low- and high-frequency stimulation of the peroneal nerve to produce twitch- and tetanic-type contractions. Fasciotomy decreased muscle force during the low-frequency stimulation by 16% (35.3 +/- 4.9 to 28.4 +/- 3.9 N) and during the high-frequency stimulation by 10% (60.8 %/- 4.9 to 54.8 +/- 3.9 N). Muscle pressure decreased 50% after fasciotomy under both conditions, 15 +/- 2 to 6 +/- 1 mmHg and 84 +/- 17 to 41 +/- 8 mmHg), respectively. Repeated functional evaluations during the testing procedure indicated that muscle fatigue was not a major factor in these results. It was concluded that fascia is important in the development of muscle tension and changes in interstitial pressure. Furthermore, the results raised questions concerning the merits of performing a fasciotomy for athletes with a compartment syndrome.

scholarly journals Cholecystokinin release triggered by NMDA receptors produces LTP and sound–sound associative memory

2019 ◽  
Vol 116 (13) ◽  
pp. 6397-6406 ◽  
Author(s):  
Xi Chen ◽  
Xiao Li ◽  
Yin Ting Wong ◽  
Xuejiao Zheng ◽  
Haitao Wang ◽  
...  
Keyword(s):  
Associative Learning ◽  
Associative Memory ◽  
High Frequency ◽  
Low Frequency ◽  
Long Term Potentiation ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Term Potentiation ◽  
Frequency Stimulation

Memory is stored in neural networks via changes in synaptic strength mediated in part by NMDA receptor (NMDAR)-dependent long-term potentiation (LTP). Here we show that a cholecystokinin (CCK)-B receptor (CCKBR) antagonist blocks high-frequency stimulation-induced neocortical LTP, whereas local infusion of CCK induces LTP. CCK−/−mice lacked neocortical LTP and showed deficits in a cue–cue associative learning paradigm; and administration of CCK rescued associative learning deficits. High-frequency stimulation-induced neocortical LTP was completely blocked by either the NMDAR antagonist or the CCKBR antagonist, while application of either NMDA or CCK induced LTP after low-frequency stimulation. In the presence of CCK, LTP was still induced even after blockade of NMDARs. Local application of NMDA induced the release of CCK in the neocortex. These findings suggest that NMDARs control the release of CCK, which enables neocortical LTP and the formation of cue–cue associative memory.

Overexpression of tau results in defective synaptic transmission in Drosophila neuromuscular junctions

2006 ◽  
Vol 34 (1) ◽  
pp. 88-90 ◽  
Author(s):  
F. Chee ◽  
A. Mudher ◽  
T.A. Newman ◽  
M. Cuttle ◽  
S. Lovestone ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Axonal Transport ◽  
Motor Neurons ◽  
Neuromuscular Junctions ◽  
Clinical Symptoms ◽  
Low Frequency ◽  
Synaptic Dysfunction ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

Synaptic dysfunction is believed to be an early pathological change in neurodegenerative diseases and may cause the earliest clinical symptoms. We have used Drosophila to model a tauopathy in order to analyse the earliest neuronal and synaptic dysfunction. Our work has shown that overexpression of human tau (0N3R) in larval motor neurons causes a disruption of axonal transport and a morphological and functional disruption of NMJs (neuromuscular junctions). Tau-expressing NMJs are smaller with an abnormal structure. Despite abnormal morphology, tau-expressing NMJs retain synaptotagmin expression and can form active zones. Tau-expressing NMJs are functionally abnormal and exhibit disrupted vesicle cycling and synaptic transmission. At low-frequency stimulation (1 Hz), ESPs (evoked synaptic potentials) produced by tau-expressing motor neurons were indistinguishable from wild-type; however, following high-frequency stimulation (50 Hz), ESPs from tau-expressing NMJs were significantly decreased in amplitude. To investigate the mechanism underlying the change in ESPs, we analysed the relative numbers and distribution of mitochondria. This revealed that motor neurons expressing tau had a significant reduction in the number of detectable mitochondria in the pre-synaptic terminal. Our results demonstrate that tau overexpression results in synaptic dysfunction, associated with a reduced complement of functional mitochondria. These findings suggest that disruption of axonal transport and synaptic transmission may be key components of the pathogenic mechanism that underlie neuronal dysfunction in the early stages of tauopathies.

Effects of changes in dietary fatty acids on isolated skeletal muscle functions in rats

1996 ◽  
Vol 80 (2) ◽  
pp. 464-471 ◽  
Author(s):  
K. J. Ayre ◽  
A. J. Hulbert
Keyword(s):  
Fatty Acids ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Dietary Fatty Acids ◽  
High Frequency Stimulation ◽  
Stock Diet ◽  
Deficient Diet ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

The effects of manipulating dietary levels of essential polyunsaturated fatty acids on the function of isolated skeletal muscles in male Wistar rats were examined. Three isoenergetic diets were used: an essential fatty acid-deficient diet (EFAD), a diet high in essential (n-6) fatty acids [High (n-6)], and a diet enriched with essential (n-3) fatty acids [High (n-3)]. After 9 wk, groups of rats on each test diet were fed a stock diet of laboratory chow for a further 6 wk. Muscle function was examined by using a battery of five tests for soleus (slow twitch) and extensor digitorum longus (EDL; fast twitch). Tests included single muscle twitches, sustained tetanic contractions, posttetanic potentiation, sustained high-frequency stimulation, and intermittent low-frequency stimulation. Results for muscles from the High (n-6) and High (n-3) groups were very similar. However, the EFAD diet resulted in significantly lower muscular tensions and reduced response times compared with the High (n-6) and High (n-3) diets. Peak twitch tension in soleus muscles was 16-21% less in the EFAD group than in the High (n-6) and High (n-3) groups, respectively [analysis of variance (ANOVA), P < 0.01). During high-frequency stimulation, EDL muscles from the EFAD rats fatigued 32% more quickly (ANOVA, P < 0.01)]. Also, twitch contraction and half-relaxation times were significantly 5-7% reduced in the EFAD group (ANOVA, P < 0.01). During intermittent low-frequency stimulation, soleus muscles from the EFAD group generated 25-28% less tension than did the other groups (ANOVA, P < 0.01), but in EDL muscles from the EFAD group, endurance was 20% greater than in the High (n-6) group (ANOVA, P < 0.05). After 6 wk on the stock diet, there were no longer any differences between the dietary groups. Manipulation of dietary fatty acids results in significant, but reversible, effects in muscles of rats fed an EFAD diet.

Arterial baroreflex inhibition by gastric distension in rats: mediation by splanchnic afferents

1991 ◽  
Vol 260 (5) ◽  
pp. R985-R994 ◽  
Author(s):  
S. Nosaka ◽  
S. Murase ◽  
K. Murata
Keyword(s):  
Low Frequency ◽  
Splanchnic Nerve ◽  
Intraluminal Pressure ◽  
Gastric Distension ◽  
High Frequency Stimulation ◽  
Aortic Depressor Nerve ◽  
Low Frequency Stimulation ◽  
Afferent Fibers ◽  
Frequency Stimulation ◽  
Stimulation Of

Arterial baroreflexes are known to be reset during activation of defense area and somatosensory receptors-afferents. Here we report that viscerosensory activation also inhibits the baroreflexes. In chloralose-urethan-anesthetized, succinylcholine-immobilized, and artificially ventilated rats, the aortic depressor nerve was electrically stimulated while propranolol was continuously infused to elicit baroreflex hypotension (BH) and baroreflex vagal bradycardia (BVB). Hydraulic distension of the stomach with warm 0.9% NaCl solution was found to suppress BVB and BH, with a threshold intraluminal pressure at times less than 5mmHg. The gastric distension also suppressed BH in atropinized rats, suggesting that inhibition involved not only cardiac but also vascular components of baroreflexes. Bilateral splanchnectomy largely attenuated the inhibition, whereas bilateral subdiaphragmatic vagotomy had little effect. Low- as well as high-frequency stimulation of the splanchnic nerve strongly suppressed both BVB and BH, whereas only low-frequency stimulation of the subdiaphragmatic vagus inhibited baroreflexes to a slight degree. In conclusion, gastric distension suppresses BVB and BH, and this inhibition is largely mediated by afferent fibers in the splanchnic nerve. Such baroreflex inhibition may be a general consequence of mechanoreceptor activation of any visceral hollow organs because the jejunum, esophagus, and urinary bladder were all found to suppress arterial baroreflexes when distended.

Modulation of synaptic transmission at Ia-afferent connections on motoneurons during high-frequency afferent stimulation: dependence on motor task

1991 ◽  
Vol 65 (6) ◽  
pp. 1313-1320 ◽  
Author(s):  
H. R. Koerber ◽  
L. M. Mendell
Keyword(s):  
High Frequency ◽  
Frequency Control ◽  
Motor Task ◽  
Low Frequency ◽  
Medial Gastrocnemius ◽  
High Frequency Stimulation ◽  
Lateral Gastrocnemius ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Stimulation Of

1. Monosynaptic excitatory postsynaptic potentials (EPSPs) were evoked in medial gastrocnemius motoneurons by maximal group Ia stimulation of the heteronymous lateral gastrocnemius-soleus nerve in anesthetized cats. Three different patterns of high-frequency stimulation were delivered to the nerve, and the EPSPs were averaged in register (1, 2, . . ., n) for each. 2. One pattern ("Burst") consisted of 32 shocks delivered every 2 s at an interstimulus interval of 6 ms (167 Hz). The second pattern ("Stepping") was a frequency-modulated burst of 52 shocks derived from a recording of a spindle during stepping and was delivered every 2 s. The third pattern ("Paw Shake") was from an extensor spindle afferent recorded during rapid paw shake and was delivered in groups of six bursts with an interburst interval of 75 ms and a 3-s pause between groups of six bursts. The EPSPs in each burst were averaged in register (1, 2, . . ., n) so that the relative amplitude of each EPSP in the burst could be ascertained. The EPSP produced by low-frequency stimulation of the nerve (18 Hz) was also recorded for each motoneuron. 3. The initial EPSP in most bursts was larger than the EPSP measured as a result of low-frequency stimulation. This potentiation, defined as the ratio of the amplitude of the initial EPSP of the response to that of the low-frequency control, was found to vary systematically as a function of amplitude of the control EPSP as well as the stimulus paradigm used.(ABSTRACT TRUNCATED AT 250 WORDS)

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