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PubMed2000

[Effect of 120 days head-down tilt (HDT) on characteristics of tendinous reflexes].

Time dynamics of variations in the spinal reflex mechanisms was evaluated during 120-d HDT (-6 degrees). Already within the first days in HDT the knee and Achilles reflexes were noted to sharply become easy to fulfil, the conclusion made from a significant drop of thresholds, an appreciable rise of amplitudes of reflex responses and an expansion of the range of stimulations. However, dynamics of these variations was diverse. The abrupt drop of reflex thresholds determined already on HDT day 2 was persistent throughout the experiment, whereas maximal rise of the tendon reflex amplitude was seen on the initial phase of HDT (days 15-30). Later on, a clear-cut downward trend of the electromyographic amplitude was observed. The experimental data suggest that hyperreflexia during HDT is one of the manifestations of partial deafferentation of the motoneuron pool due to diminution of the proprioceptive afflux. At the same time, hyperactivity of the reflex mechanisms is masked by the peripheral muscular effects of the same factor, i.e. HDT.

Adult↗
PubMedDate not supplied

The prevalence, predictors, and consequences of peripheral sensory neuropathy in older patients.

BACKGROUND: The prevalence, predictors, and consequences of peripheral neuropathy in the elderly have not been well defined. METHODS: Seven hundred ninety-five noninstitutionalized patients 65 years of age and older, recruited from the practices of family physicians, completed questionnaires and underwent peripheral neurologic examinations and tests of gait and balance. Variables included sociodemographic information, medical conditions, symptoms (numbness, pain, trouble with balance or walking, and restless legs), quality of life measures, ankle reflexes, position sense, vibratory sense, fine touch sensation, Tinnetti balance examination, and a 50-foot timed walk. RESULTS: The prevalence of at least one bilateral sensory deficit rose from 26% for 65- to 74-year-olds to 54% for those 85 and older. The most common deficit was loss of ankle reflex followed by loss of fine touch. Only 40% of those with bilateral deficits reported having a disease known to cause peripheral neuropathy. Predictors of bilateral deficits included increasing age, income less than 15,000 dollars, a history of military service, increasing body mass index, self-reported history of diabetes mellitus, Vitamin B12 deficiency or rheumatoid arthritis, and absence of a history of hypertension. Deficits were associated with numbness, pain, restless legs, trouble walking, trouble with balance, and reduced quality of life. CONCLUSIONS: Peripheral sensory deficits are common in the elderly. In most cases, a medical cause is not obvious. Their consequences may not be as benign as often supposed.

Aged↗
PubMed1970

The human blink reflex.

A detailed study of the human blink reflex in the different parts of the orbicularis oculi muscle has been carried out. The first component of the blink reflex has been demonstrated in patients with Friedreich's ataxia, who have selective loss of large sensory fibres resulting in loss of proprioceptive input. It has been established that both components of the blink reflex are cutaneous reflexes which represent a highly organized and purposeful mechanism in man. Afferent fibres for the blink reflex have been identified in the human supraorbital nerve and their conduction velocity has been estimated for the first time in man. It has been demonstrated that both components of the blink reflex are mediated by the same group of afferent fibres.

Adolescent↗
PubMed1976

Sensory perception in overdenture patients.

The discussion of overdentures has been confined to their capacity to use abutment teeth to improve neuromuscular control of mandibular movement. Use of overdentures has been favored often because of their mechanical advantages, but seldom because of the sensory role of the retained abutment teeth. Even though the retained teeth may be periodontally diseased, they still may provide sufficient support for the transmission of masticatory pressures and sufficient periodontal ligament receptors to initiate a jaw opening reflex. Whereas conflicting evidence shows that the periodontal nerve receptors play a role in mandibular positional sensibility (proprioception), pressure perception by the periodontal ligament remains a primary stimulus for the jaw opening reflex. Additional investigations will be essential to a complete understanding of the role of the periodontal ligament receptors. However, recognition of the importance of the periodontal ligament receptors to the overdenture patient as a source of sensory input is vital.

Denture, Complete↗
PubMed1989

Hand muscle reflexes following electrical stimulation in choreatic movement disorders.

Thenar reflexes following electrical stimulation of the median nerve (containing proprioceptive and cutaneous afferents) and the radial superficial nerve (cutaneous afferents only) were investigated in 23 patients with manifest Huntington's disease (HD) at an early stage, in 17 clinically healthy descendants of HD-patients and in 18 patients with choreatic hyperkinesia due to various aetiologies other than HD. In 61% of the patients with early HD the long-latency reflexes (LLR) were uni- or bilaterally absent in response to both median nerve and radial superficial nerve stimulation. The remaining patients had a diminished mean amplitude and mean duration of their LLR. In contrast, offspring and patients with symptomatic chorea had preserved LLR which did not differ in amplitude or duration from normal controls. Additionally, the mean amplitude and mean duration of the Hoffmaan-reflex (HR) was found to be increased in patients with HD and their offspring but not in patients with other aetiologies. It is concluded (1) that the loss of LLR is not related to the choreatic hyperkinesia itself but to the degeneration of a hitherto poorly defined neuronal circuit in HD; (2) that among a variety of diseases presenting with chorea, the loss of LLR seems to be specific for HD; (3) that the testing of hand muscle reflexes in choreatic movement disorders is helpful for the differential diagnosis of early HD but not for the detection of gene carriers among offspring of patients with HD.

Afferent Pathways↗
PubMedDate not supplied

[Character of proprioceptive information processing during learning in rats chronically intoxicated with alcohol].

A conditioned alimentary reflex was elaborated in rats placed into K-shaped maze after 8 months of intoxication with 35 degrees alcohol. The most important changes in experimental animals, as compared to intact ones, were revealed in the character of processing of proprioceptive information coming to the brain during learning. It was found that in the animals temporal relations between the processes of analysis and synthesis and the fixation of memory trace changed. Unlike intact animals, in "alcoholic" ones the new proprioceptive information as related to the previous experience was fixed in the long-term memory and only afterwards underwent analytic and synthetic processing. It is suggested that learning was not in enlarging the information capacity of each singled-out motor unit of full decision, but in their combination into one and only one decision.

Alcoholism↗
PubMed1987

Responses of rat dorsal horn neurons to natural stimulation and to iontophoretically applied norepinephrine.

Extracellular recordings were obtained of 177 neurons throughout the lumbar spinal dorsal horn of urethane- or halothane-anesthetized rats. These neurons all responded to iontophoretically applied L-glutamate and their responses to natural stimulation of the ipsilateral hindlimb were characterized. Iontophoretically applied norepinephrine was tested on 94 of these neurons. Fifty-one neurons were inhibited and 22 were excited. Norepinephrine produced a biphasic inhibitory/excitatory effect on nine neurons. Norepinephrine was exclusively inhibitory on superficial dorsal horn neurons that responded only to innocuous brush and touch and on neurons in the nucleus proprius that responded to brush, touch, and noxious skin pinch. Norepinephrine excited some superficial brush/touch/pinch neurons and produced short inhibitions that were followed by prolonged excitations of some nucleus proprius neurons that responded only to noxious skin pinch. Neurons in the base of the dorsal horn that responded to low-threshold proprioceptive stimulation were excited by norepinephrine. Both the inhibitory and excitatory effects of norepinephrine were stereoselective, but they were not blocked by receptor subtype-selective antagonists. Desensitization to norepinephrine occurred for 30% of the neurons. This study demonstrates that the inhibitory effects of norepinephrine on rat dorsal horn neurons are not restricted to neurons that are responsive to noxious stimuli and that some of these neurons are primarily excited by norepinephrine. The excitatory effects of norepinephrine on low-threshold proprioceptive neurons may contribute to norepinephrine's known enhancement of spinal flexor reflex activity.

Action Potentials↗
PubMed2003

Synaptic organization of monosynaptic connections from mesencephalic trigeminal nucleus neurons to hypoglossal motoneurons in the rat.

Synaptological characteristics of synapses between axonal boutons of the trigeminal mesencephalic nucleus (Vme) neurons and the hypoglossal nucleus (XII) motoneurons (MNs) were studied using biotinylated dextran amine (BDA) anterograde labeling combined with horseradish peroxidase (HRP) retrograde transport in the rat. BDA was initially iontophoresed into Vme unilaterally and 7 days later HRP was injected into the anterior two-thirds of the ipsilateral tongue. After histochemical reactions, BDA anterogradely labeled boutons were seen to appose closely to somata and dendrites of HRP retrogradely labeled MNs in XII by light microscopy. A total of 212 BDA-labeled Vme boutons were examined ultrastructurally, which had an average diameter of 1.3 +/- 0.4 microm and contain small clear spherical vesicles. Eighty-eight percent of Vme boutons (187/212) synapsed on dendrites of HRP-labeled XII MNs. Twenty-five Vme boutons (25/212, 12%) made synapses with somata of HRP-labeled XII MNs. Thirty-five percent (74/212) of BDA-labeled Vme boutons were also contacted by unlabeled P-type terminals. Presynaptic P-type terminals contained spherical (47%, 35/74), pleomorphic (43%, 32/74), and flattened (10%, 7/74) synaptic vesicles. Thus, P-type terminals (as a presynaptic element), BDA-labeled Vme boutons, and XII MNs constitute axoaxodendritic and axoaxosomatic synaptic triads. There are four types of synaptic microcircuits in XII neuropil: synaptic convergence, synaptic divergence, presynaptic inhibition synaptic circuits, and feedforward regulation circuits. This detailed ultrastructure examination of the synaptic organization between Vme neurons and XII MNs provides insights into the synaptic mechanisms of the trigeminal proprioceptive afferents involved in the jaw-tongue reflex and coordination during oral motor behaviors.

Afferent Pathways↗
PubMed1992

Muscle spindles in the mylohyoid muscle of rats.

The mylohyoid muscle has several functions in relation to respiration, deglutition, and phonation, but these functions are not fully understood. The interaction of the mylohyoid nerve and muscle in 25 rats was studied by neurophysiologic and histologic methods. Stretching of the muscle elicited electrical responses from the branch of the mylohyoid nerve innervating the mylohyoid muscle, and stretch-sensitive receptors were demonstrated histologically in the mylohyoid muscle. This study indicates that the mylohyoid muscle plays an active role in functions such as swallowing, breathing, and phonation.

Animals↗
PubMed2005

L-thyroxine responsive cricopharyngeal achalasia associated with hypothyroidism in a dog.

An eight-year-old, male boxer dog was presented with a one-month history of hindlimb weakness followed by compulsive ineffective drinking, dysphagia, regurgitation and nasal reflux during drinking. A neurological examination revealed weakness and conscious proprioception deficits in both hindlimbs with normal spinal reflexes. The dog's swallowing function was examined by fluoroscopy. This showed normal prehension of the barium paste, bolus formation and contraction of the pharyngeal muscle, but no opening of the upper oesophageal sphincter was detected. A serum thyroid stimulating hormone level of 0.402 ng/dl and serum total T4 of 0-01 microg/dl were determined. The dog fully recovered one month after L-thyroxine therapy. The association found between cricopharyngeal achalasia and hypothyroidism suggests that hypothyroidism should be included in the list of differential diagnoses for dogs with cricopharyngeal achalasia.

Animals↗
PubMed2004

Effect of sex on preactivation of the gastrocnemius and hamstring muscles.

BACKGROUND: The reason for the higher incidence of anterior cruciate ligament injury from non-contact mechanisms in female athletes is not known. Stability of the joint from dynamic restraints occurs through proprioceptive and kinaesthetic mechanisms providing a flexion moment. Reflexive muscle activation is different between the sexes, but it is unclear if sex differences exist in the ability to dynamically stabilise joints through a neuromuscular feed forward process as measured by preactivation of the muscles. OBJECTIVE: To determine if the level of preactivation of the gastrocnemius and hamstring muscles during dynamic activity is affected by sex. METHODS: Thirty four healthy active subjects, evenly grouped by sex, participated in the study. Maximum voluntary contraction normalised electromyographic (EMG) activity of the quadriceps, hamstrings, and gastrocnemius muscles was recorded during downhill walking (0.92 m/s) and running (2.08 m/s) on a 15 degrees declined treadmill. Preactivation of the EMG signal was calculated by setting a mark 150 milliseconds before foot strike, as indicated by a footswitch. Multiple t tests for sex differences of preactivity mean percentage (M-EMG%) during the downhill activities were performed. RESULTS: The female subjects had a higher M-EMG% for the medial hamstrings than the male subjects (31.73 (9.89) and 23.04 (8.59) respectively; t((2,32)) = 2.732, p = 0.01) during walking. No other muscles exhibited a sex difference in M-EMG% during either activity. CONCLUSION: The female subjects in this study showed higher medial hamstring preactivation. However, this may be because they were not injured, indicating their propensity for joint stabilisation. A long term prospective study is required to eliminate this potential explanation. No sex difference in gastrocnemius preactivation was seen, adding to the controversy about whether this muscle contributes to feed forward joint stability. Further research of preactivation of the musculature of the leg is required.

Adult↗
PubMed1997

Vestibular abnormalities in charge association.

We report the vestibular abnormalities in 5 patients with the CHARGE association (Coloboma, Heart disease, Atresia of choanae, Retarded growth and development and/or central nervous system anomalies, Genital hypoplasia, and Ear anomalies). All patients had absent vestibular function as indicated by absent vestibulo-ocular reflexes and severe imbalance on simultaneous deprivation of proprioception and vision, as well as delayed motor development. All 6 semicircular canals were aplastic in each of the patients. While cochlear function was severely reduced in 6 of the 10 ears, it was absent only in 3 ears and was actually intact below 3 kHz in 1 ear. All 10 bony cochleas were present on computed tomography, and although 7 appeared abnormal, 3 appeared normal. This study confirms that absence of the bony semicircular canals in the presence of a bony cochlea is a characteristic finding in CHARGE association. It also demonstrates that these disproportionate structural abnormalities are reflected in the functional abnormalities: absent vestibular function with preservation of some cochlear function.

Adolescent↗
PubMed1990

[Chemoreceptor modulation of the respiratory reactions during muscle contractions in the cat].

Phasic contractions of the hindlimb muscles were induced in hypercapnia, hypoxia and hyperoxia. Absolute value of the lung ventilation and its kinetics depended on hypoxic and hypercapnic stimuli, reaching its maximum in their combination. Hypoxic stimulus decreased an increment of the lung ventilation and decelerated the latter's development. The interaction seems to be realized by neuronal mechanisms of dorsal respiratory nucleus. The latter is believed to play a major role in the mechanism of generation of central inspiratory activity based on respective chemoreceptor and proprioceptor afferent information.

Animals↗
PubMed1990

[Pulmonary ventilation and oxygen consumption during passive and active motions in man].

Changes in pulmonary ventilation and O2-consumption were studied during passive and active extension of both crura. The rate and extent of the movements were the same (1Hz). Thirty 21-year-old men (mean weight 72.5 kg, mean height 179 cm) were divided into 3 equal groups, namely controls, with passive movement, and with active movement. The trial consisted of three 11-12 minute periods--initial, period of movement, and recovery. In the control group movements were not performed. Passive movements were carried out by means of a special lever. Ventilation increased at active movements (12.42 +/- 2.731 compared to control values of 8.62 +/- 2.87). Oxygen consumption was increased during active movements (8.4 +/- 2.3 ml.kg-1.min-1 compared to 4.4 +/- 0.6), yet it was reduced during passive movements (3.5 ml compared to control values of 4.4 and initial values of 4.3 ml). The finding is accounted for by the rapid depression of the metabolic efficacy of isolated proprioceptive afferentation as a specific feature of conditioned reflex regulation of metabolism in man.

Adult↗
PubMed1994

Etiology of cracked teeth: a review and proposal.

Factors in the etiology of the cracked or fractured tooth can be generally divided into three categories: tooth strength, magnitude of applied force, and control of applied force. Dental caries, restorations and endodontic procedures appear to play a major part in the etiology of most cracked or fractured teeth though sound teeth frequently are cracked or fractured. Tentative evidence indicates that females, who can apply less force, may crack more teeth than do males. Control of occlusal forces applied may be an overlooked factor. Drugs affecting proprioception and other sensory receptors modulating force and reflex should be evaluated as possible contributors to the etiology of cracked or fractured teeth.

Animals↗