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At least 217 records · Page 12Linked to original sources
PubMed1974

Interaction of baroreceptor and chemoreceptor reflexes. Modulation of the chemoreceptor reflex by changes in baroreceptor activity.

The purpose of this study was to determine whether the level of arterial pressure and degree of baroreceptor activation affect responses to stimulation of chemoreceptors. Chemoreceptors were stimulated by injecting nicotine into the common carotid artery of anesthetized and paralyzed dogs. Responses were observed in the innervated gracilis muscle, perfused at constant flow while perfusion pressure was measured. Arterial pressure was lowered by bleeding the animals and raised by transient occlusion of the descending aorta. Vasoconstrictor responses to stimulation of chemoreceptors were enhanced by hypotension and inhibited by elevation of arterial pressure. Potentiation of the chemoreceptor reflex by hemorrhagic hypotension was not the result of altered vascular resistance in the gracilis muscle, sensitization of chemoreceptors by catecholamines or acidosis, or changes in cerebral perfusion pressure. Additional studies were done in which we excluded the possibility that the changes resulted from direct effects of changes in arterial pressure on chemoreceptors. Both carotid bifurcations were isolated and perfused. On one side, pressure was raised to stimulate the carotid sinus baroreceptors. On the other side, the carotid body chemoreceptors were stimulated by nicotine or by hypoxic and hypercapnic blood. Activation of baroreceptors on one side attenuated the vasoconstrictor response to chemoreceptor stimulation on the other side. This excludes a direct effect of changes in arterial pressure on the chemoreceptors and suggests a central interaction of these reflexes. We conclude that vasoconstrictor responses to stimulation of chemoreceptors are potentiated by hypotension and inhibited by transient hypertension. These effects appear to result at least in part from a central interaction of chemoreceptor and baroreceptor reflexes.

Animals↗
PubMed2004

Effect of straining on diaphragmatic crura with identification of the straining-crural reflex. The "reflex theory" in gastroesophageal competence.

BACKGROUND: The role of the crural diaphragm during increased intra-abdominal pressure is not exactly known. We investigated the hypothesis that the crural diaphragm undergoes reflex phasic contraction on elevation of the intra-abdominal pressure with a resulting increase of the lower esophageal pressure and prevention of gastro-esophageal reflux. METHODS: The esophageal pressure and crural diaphragm electromyographic responses to straining were recorded in 16 subjects (10 men, 6 women, age 36.6 +/- 11.2 SD years) during abdominal hernia repair. The electromyogram of crural diaphragm was recorded by needle electrode inserted into the crural diaphragm, and the lower esophageal pressure by a saline-perfused catheter. The study was repeated after crural anesthetization and after crural infiltration with saline. RESULTS: The crural diaphragm exhibited resting electromyographic activity which showed a significant increase on sudden (coughing, p < 0.001) or slow sustained (p < 0.01) straining with a mean latency of 29.6 +/- 4.7 and 31.4 +/- 4.5 ms, respectively. Straining led to elevation of the lower esophageal pressure which was coupled with the increased electromyographic activity of the crural diaphragm. The crural response to straining did not occur during crural diaphragm anesthetization, while was not affected by saline infiltration. The lower esophageal pressure declined on crural diaphragm anesthetization. CONCLUSIONS: Straining effected an increase of the electromyographic activity of the crural diaphragm and of the lower esophageal pressure. This effect is suggested to be reflex in nature and to be mediated through the "straining-crural reflex". The crural diaphragm seems to play a role in the lower esophageal competence mechanism. Further studies are required to assess the clinical significance of the current results in gastro-esophageal reflux disease and hiatus hernia.

Action Potentials↗
PubMedDate not supplied

Cholecysto-sphincter inhibitory reflex: identification of a reflex and its role in bile flow in a canine model.

To study the effect of gallbladder (GB) distension on the sphincter of Oddi (SO), 9 mongrel dogs (mean weight 15.3+/-3.6 kg) were studied. Under anesthesia, the abdomen was opened and the GB and SO were exposed. A balloon-tipped catheter was introduced into the GB and a manometric catheter into the common bile duct so that its fluoroscopically controlled tip lay within the SO. The pressure response of the GB and SO to GB distension by the balloon without and with selective anesthetization of the GB and SO was recorded. The test was repeated in four vagotomized dogs. GB distension effected pressure rise within the GB and pressure drop within the SO. The GB pressure increased progressively as the distending volume increased, while the SO pressure drop was not affected. Selective anesthetization of the GB or the SO produced no SO pressure changes upon GB distension. The SO pressure response to GB distension after vagotomy was similar to that before vagotomy. The SO relaxation on GB contraction, being reproducible and abolished by selective anesthetization of either the SO or the GB, postulates a reflex relationship that we call the cholecysto-sphincter inhibitory reflex. This reflex seems to regulate the bile flow from the GB to the duodenum through the SO.

Animals↗
PubMedDate not supplied

The diagnostic value of stapedius reflex and stapedius reflex exhaustion in myasthenia gravis.

Authors studies impedance, stapedius reflex thresholds and stapedius muscle exhaustion on 31 ears of 16 MG patients. Investigations were carried out using GSI 33 computer-assisted middle ear analyzator. Stapedius reflex threshold values were increased in 93% of patients. Stapedius exhaustion was observed in 71% of patients. After the administration of the reversible cholinesterase inhibitor Mestinon (60 mg pyridostigmin bromide), reflex threshold decreased and exhaustion occurred in only 50% of cases. Authors review the literature in context with the audiometric diagnostics of MG and also recommend the use of these methods in more complicated ocular and bulbar cases of MG.

Acoustic Impedance Tests↗
PubMedDate not supplied

[Reflex myoclonic epilepsy in infancy: a new reflex epilepsy syndrome or a variant of benign myoclonic epilepsy in infancy].

CASE REPORTS: We report a clinical and EEG study of 8 children with reflex myoclonic epilepsy of infancy to further confirm the existence of this syndrome first described by Ricci et al in 1995. RESULTS: Between February 1990 to July 2002, we identified 64 epileptic patients with myoclonic seizures with an onset in the first six years of life. Eight (12.5%) of these patients had myoclonic seizure stimuli sensible. The seizures were characterized by generalized, myoclonic jerks triggered by tactile stimuli in six patients and acoustic stimuli in two, in one of them myoclonic jerks were triggered by both types of stimuli. The seizures appeared between 5 and 20 months of age. Two of the 8 patients had spontaneous myoclonic attacks during sleep. Interictal EEG was normal during wakefulness and occasional discharges were evident during sleep. In contrast, the ictal EEG during both wakefulness and sleep showed generalized spike wave and polyspike slow wave paroxysms. Neurologic examination, neuroimaging and neurometabolic studies were normal. Myoclonic jerks disappeared in 6 patients after valproic acid administration and in two after clobazan administration. Antiepileptic treatment was discontinued in 6 patients and no seizure recurrence was observed during a median follow up of 6 years. CONCLUSION: Our patients presented electro clinical criteria compatible with the syndrome of reflex myoclonic epilepsy of infancy. This syndrome could be considered to be a new reflex epileptic syndrome or a variant of benign myoclonic epilepsy in infancy.

Anticonvulsants↗
PubMed1976

[The pressor reflex induced by skeletal muscle contraction and its influence on the reflex from the sino-aortic zones].

The cardiovascular response to 10 sec tetanic muscular contractions was studied in the decerebrated cat. A pressor reflex about 30 mm Hg occurred during hindlimb contractions evoked by ventral roots (L6, L7, S1) stimulation. The pressor reflex was associated with a decrease of blood flow in working and resting muscles and a minimal changes of heart rate and left ventricular contractility. An increase of systemic resistance, as a main cause of pressor reflex is suggested. Static contractions of muscles and stimulation of muscle nerve evoked stronger inhibition of baroreflex than cutaneous nerve stimulation of nociceptive stimuli. Inhibition of the cardiac component of baroreflex during muscular exercise was shown.

Animals↗
PubMed1975

[Electrophysiological analysis of facial reflex in monkeys: trigemino-naso-labial reflex].

Electrical stimulation of the awake monkey's supra orbital nerve, elicits two successive reflex discharge in both naso-labialis muscles (NL). The responses have a similar high threshold. Similar responses are also elicited on electrical stimulation of the facial skin, whereas flash, click or tapping on the muscle belly are ineffective. These responses bear some resemblances to those obtained in orbicularis oculi muscles ; but the higher threshold and the different organization of the NL responses would suggest that such reflexes may serve a different function from that of the blink reflex.

Animals↗
PubMed1983

[Stapedius reflex. 1. Stapedius reflex threshold and recruitment].

UNLABELLED: The stapedius reflex threshold and pure tone threshold of 173 patients with normal hearing and cochlear disorders were examined (using Madsen ZO 73 equipment). CONCLUSIONS: 1. The aetiology of the cochlear hearing disorders does not influence the stapedial reflex threshold. 2. A linear regression between hearing loss and threshold difference was found in cochlear hearing disorders. 3. No correlation could be found between individual pure tone threshold and stapedial reflex threshold.

Adolescent↗
PubMed1983

[Stapedius reflex. 2. Latency periods of the stapedial reflex].

The reflex thresholds and initial latency times of the stapedial reflex of 50 patients with normal hearing and cochlear hearing loss were examined using Madson ZO 73 equipment. The following results were obtained: 1. The initial latency times of the stapedius reflex diminish proportional to the supra-threshold loudness. 2. No significant difference of the latency times was found between 0.5, 1, 2 and 4 kHz. 3. The initial latency times of patients with positive recruitment (cochlear hearing loss) do not differ from those of patients with normal hearing.

Auditory Threshold↗
PubMed2003

Study of the functional activity of the cecocolonic junction with identification of a "physiologic sphincter", "cecocolonic inhibitory reflex" and "colocecal excitatory reflex".

Radiologic, endoscopic and histomorphologic studies have suggested the presence of a sphincter at the cecocolonic junction (CCJ), while some investigators have denied its existence. To investigate the physiologic activity at the CCJ, the right colon was exposed during right hemicolectomy for early colonic cancer in 11 patients (mean age 43.6+/-12.3 years; 8 men). Three manometric catheters were introduced through colotomy to be separately located in the cecum, CCJ and ascending colon. We determined the CCJ pressure response to cecal and colonic distension by means of a balloon filled with saline in increments of 10 ml. The test was repeated after individual anesthetization of cecum, CCJ and ascending colon. The CCJ measured 1.6+/-0.6 cm in length and had a higher pressure ( p<0.05) than the cecum or colon. Large-volume cecal distension effected a significant CCJ pressure reduction which was augmented as the distension increased. Latency decreased upon increase of the distending volume. In contrast, the CCJ responded to large-volume colonic distension by pressure elevation which increased upon increase of the distending volume. Latency diminished with increased distension. Small-volume cecal or colonic distension effected no CCJ pressure response. The anesthetized CCJ did not respond to distension of the cecum or colon. Likewise, the CCJ did not exhibit a pressure response to distension of the anesthetized cecum or colon. The CCJ is a high-pressure zone which reacts to cecal or colonic distension by dilatation or narrowing, respectively. These data presumably denote the existence of a physiologic sphincter at the CCJ. We suggest that the CCJ pressure response to cecal or colonic distension is reflex and mediated through the cecocolonic inhibitory and colocecal excitatory reflexes, respectively. The role of the CCJ and related reflexes in colonic motility disorders needs to be studied.

Adult↗
PubMed2004

The defecation reflex in rats: fundamental properties and the reflex center.

While pharmacological and physiological studies in rats are now increasing, physiological properties of their defecation have been scarcely investigated. This study was performed to define the properties of defecation in decerebrate rats, with special reference to the pontine defecation reflex center, which has been postulated in dogs. Intraluminal pressure was recorded from the colon and rectum with balloon-pressure transducer method using balloons of 15-20 mm in length and 0.1-0.3 ml in volume. Distention of a balloon in the descending colon and rectum with an additional injection of 0.03-0.1 ml air induced propulsive contractions on the descending colon and rectum. The mean of threshold pressures to induce propulsive contraction was 17.0 +/- 5.8 mm Hg (mean+/-S.E.) in the proximal part and 18.3 +/- 3.3 mm Hg in the distal part of the descending colon, and 11.8 +/- 1.3 mm Hg in the rectum. The maximum amplitude of propulsive contractions was 55 mm Hg in the rectum, 47 mm Hg in the distal part of the descending colon and 38 mm Hg in the proximal part. Similar colorectal propulsive contractions were produced by gastric distention (5-10 ml, 20-30 mm Hg) and electrical stimulation of the anal canal. Contrarily, spontaneous contractions of the proximal colon were suppressed by rectal distention and anal-canal stimulation. These results suggest that the descending colon and rectum, but not the proximal colon, were innervated by the pelvic afferent and efferent fibers mediating the defecation reflex. Pontine transection at the cerebellar peduncle level abolished colorectal propulsive contractions induced by distention of the stomach, descending colon and rectum, and stimulation of the anal canal, although much smaller contractions were still induced after the pontine transection. These results suggest that the pontine defecation reflex center exists and works in rats, as in dogs.

Animals↗
PubMed2000

Corneal reflex and blink reflex changes in thalamic hemorrhage.

We studied the corneal reflex (CR) with air-puff and direct touch by using a standardized method in patients with thalamic hemorrhage (TH) (n: 15) and in normal control subjects (n: 21). The conventional blink reflex (BR) was also studied. In the TH group: 1--When the cornea on the clinically nonaffected side was stimulated the corneal reflex responses were elicited bilaterally, with normal latency on the clinically normal side and delayed on the affected side. 2--When the cornea on the clinically affected side was stimulated, the corneal responses on both sides were either abnormal or could not be elicited. 3--The ipsilateral R1 and R2 responses recorded by stimulation of the supraorbital nerve on the clinically affected side were abnormal where the contralateral R2 responses were in the normal range. In the normal control and TH groups: 1--No statistical difference could be detected between the responses elicited by air-puff or direct touch to cornea (p > 0.05). 2--CR responses were statistically different from the R2 response of the BR (p < 0.005).

Adult↗
PubMed1992

[Effect of T-activin on the formation of conditioned reflex and manifestations of unconditioned reflex of avoidance in August strain rats].

It has been revealed that intraperitoneal injection of T-activin (humoral factor of the thymus) to August rats leads to more rapid and stable conditioned reflex formation to a sound and to a decrease of avoidance time when electric current is given to a shuttle chamber. Furthermore, less amount of uneffective series in testing unconditioned avoidance is registered in the test animals. A positive T-activin effect on conditioned reflex formation and unconditioned reflex manifestation is probably connected with its ability to alter hippocampus functional parameters and (or) with anti-stressor properties of the preparation.

Adjuvants, Immunologic↗
PubMed2003

Diagnostic potential of acoustic startle reflex, acoustic blink reflex, and electro-oculography in progressive supranuclear palsy: a prospective study.

We carried out a prospective study to analyze the diagnostic potential of acoustic startle reflex (ASR), acoustic blink reflex (ABR) and electro-oculography (EOG) in early stages of atypical parkinsonian syndrome. The study was carried out in a consecutive series of 41 patients clinically diagnosed as atypical parkinsonism (mean time from first symptoms of 38 months and follow-up of 26 months). The three procedures were carried out immediately after the first clinical evaluation. ASR and ABR were elicited by auditory stimuli while the patient was attending to a simple reaction time task. Outcome measures were: ASR (absence/presence, latency), ABR (absence/presence, latency) and EOG (suggestive/not suggestive of progressive supranuclear palsy [PSP]). Final clinical diagnosis was carried out by two neurologists blind to the neurophysiological results. A study of diagnostic sensitivity and odds ratio (OR) calculation for the PSP diagnosis was carried out. Neurophysiological examination showed the following sensitivity/specificity (%) for the diagnosis of PSP: ASR: 100/89; ABR 85/89; EOG 100/72. OR values were: ASR: 0.011; ABR: 0.037; EOG: 0.038. The three tests taken simultaneously showed a sensitivity of 100% and a specificity of 95%. The three neurophysiological tests investigated provided sensitive and specific measures with predictor value in early stages of atypical parkinsonian syndrome.

Aged↗
PubMed1977

Electrodiagnostic investigation of motor neuron and spinal reflex arch (H-reflex) in spinal cord injury.

Twenty patients with spinal cord injury underwent serial electromyographic examinations. Fibrillation potentials and positive waves were noted in six patients in the spinal shock phase. In another subject, these potentials were found 27 months after injury. Our finding of significant slowing in the NCV of both nerves, indicates that lower motor neurons are indeed affected by upper motor neuron lesions. The H-reflex studies showed an increase in the mean H/M ratio. This may indicate an increase of reflex motor neuron excitability. No clear correlation was found between this increase and the degree of clinical spasticity. With repeat investigations, after a period of physical activity, a trend to reduction of the H/M ratio was noted with no clinical confirmation of reduction in spasticity. These findings emphasise the need for not assigning diagnostic terms to EMC abnormalities, but rather identifying them as neurophysiological changes which must be interpreted in the light of the clinical picture.

Adolescent↗
PubMed1998

Abnormal development of biceps brachii phasic stretch reflex and persistence of short latency heteronymous reflexes from biceps to triceps brachii in spastic cerebral palsy.

Co-contraction of antagonist muscles is characteristic of spasticity arising from perinatal brain damage but not in spasticity occurring after brain damage in adulthood. Such co-contraction is a normal feature of early post-natal motor development. Heteronymous, monosynaptic Group Ia projections from biceps brachii to both the antagonist triceps brachii and to other synergist and non-synergist muscles of the upper limb occur in the newborn baby and become restricted during the first 4 years to motor neurons of primarily synergistic muscles. Longitudinal and cross-sectional studies have been performed to test the hypothesis that inappropriate heteronymous excitatory projections persist in children with perinatal brain damage who develop spasticity. Subjects with spasticity, from brain damage acquired in adulthood were also studied to determine if these projections simply become unmasked as part of spasticity, independent of the age of occurrence of the brain damage. Twenty-nine healthy newborn babies and 29 at high risk for cerebral palsy, 12 of whom developed spastic quadriparesis, were studied longitudinally for 4 years. Thirty-eight subjects, aged 8-30 years, with spasticity of perinatal origin (11 hemiplegic, 11 quadriplegic, 16 with Rett syndrome) and 11 subjects with stroke in adulthood and spastic hemiplegia were also studied. The results were compared with those obtained in 372 normal subjects aged from birth to 55 years. Small taps were delivered to the tendon of biceps brachii using an electromechanical tapper. Surface EMG was recorded from biceps and triceps brachii, pectoralis major and deltoid. In the longitudinal study, those developing spastic quadriparesis showed persistent low thresholds for the homonymous phasic stretch reflex, which had abnormally short onset latencies. There was persistence of short onset heteronymous excitatory responses in triceps brachii, while a normal pattern of restriction of heteronymous responses to pectoralis major and deltoid occurred. The same pattern was observed in older subject groups with spasticity of perinatal origin. In adults with hemiplegia following stroke the threshold of the homonymous phasic stretch reflex was low, but it had a normal onset latency. There was no evidence of abnormal heteronymous excitatory responses. In conclusion, exaggerated excitatory responses to primary muscle afferent input were observed in the homonymous (biceps brachii) and antagonist (triceps brachii) motor neurons in subjects with spasticity arising from perinatal brain damage. They are likely to play an important role in the predominant co-contraction of agonist/antagonist muscles during voluntary movement observed in subjects with spastic cerebral palsy.

Adolescent↗
PubMed1976

The grasp reflex of the foot and related phenomena in the absence of other reflex abnormalities following cerebral commissurotomy.

The grasp reflex of the foot and related pheonomena were examined in six subjects with no abnormalities of deep tendon or plantar (and related) reflexes 6 to 10 years after cerebral comissurotomy. In all subjects they were more marked on the same side as the more damaged hemisphere. These tonic phenomena seem to be facillitated by sitting and standing postures. Practical and theoretical implications of the tonic foot responses in the absence of similar phenomena of the hand are discussed.

Adult↗
PubMed2006

Dartos reflex: a sympathetically mediated scrotal reflex.

The dartos muscle is a sympathetically innervated dermal muscle layer within the scrotum, distinct from the somatically innervated cremasteric muscle. We electrophysiologically demonstrate the presence of a dartos reflex (DR), which can be used to evaluate the thoracolumbar sympathetic and genitofemoral nerve pathways. In 20 healthy men, we evoked the DR by cutaneous stimulation of the thigh and recorded the resultant scrotal skin contraction. We recorded hand, foot, and perineal sympathetic skin responses (SSRs) as controls. The DR was reliable and reproducible, as were the SSRs. The mean left DR latency was 4.8 s (SD, 2.7 s) and right DR latency was 5.4 s (SD, 3 .4), both of which were longer than the mean hand, foot, and perineal SSRs (P < 0.05). An intact reflex arc reflects the integrity of the afferent and efferent branches of the genitofemoral nerve (T12-L2). The DR test can also be used to assess scrotal autonomic innervation. Abnormalities of dartos innervation may impact testis thermoregulation and spermatogenesis.

Adult↗