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At least 1,153 records · Page 64Linked to original sources
PubMed1989

Comparison of the branching patterns of lateral and medial vestibulospinal tract axons in the cervical spinal cord.

The morphology of single physiologically-identified lateral and medial vestibulospinal tract (LVST and MVST) axons was analysed, using intracellular staining with horseradish peroxidase (HRP) and three-dimensional reconstruction of axonal trajectories in the cat. Axons were penetrated in the cervical cord at C1-C8 with a microelectrode filled with 7% HRP. These axons were identified as vestibulospinal axons by their monosynaptic responses to stimulation of the vestibular nerve and further classified as either LVST or MVST axons by their responses to stimulation of the LVST and MVST. The stained axons could be traced over distances of 3-16 mm rostrocaudally. Within these lengths, both LVST and MVST axons were found to have multiple axon collaterals at different segments in the cervical cord. Up to seven collaterals were given off from the stems of MVST axons and LVST axons. The LVST axons included both neurones terminating at the cervical cord and those projecting further caudally to the thoracic or lumbar cord. Each collateral of these LVST axons, after entering into the gray matter, ramified successively in a delta-like fashion and terminated mainly in lamina VIII and in the medial part of lamina VII. Many boutons of both terminal and en passant types seemed to make contact with the cell bodies and proximal dendrites of neurones in the ventromedial nucleus (VM). Each collateral had a narrow rostrocaudal extension (0.2-1.6 mm, average 0.8 mm) in the gray matter in contrast to a much wider intercollateral interval (average 1.5 mm), so that there were gaps free from terminal boutons between adjacent collateral arborizations. The morphology of axon collaterals of MVST axons was very similar to that of LVST axons. The rostrocaudal extent of single axon collaterals was very restricted (0.3-2.1 mm) in contrast to the wide spread in a mediolateral or a dorsoventral direction. MVST axons had intensive projections to the upper cervical cord with multiple axon collaterals. One to seven collaterals of single MVST axons were found at C1-C3. Terminals of MVST axons were distributed in laminae VII, VIII and IX, including the VM, the nucleus spinalis n. accessorii (SA), and the commissural nucleus. Many terminals seemed to make contact with retrogradely-labelled motoneurones of neck muscles. Both axosomatic and axodendritic contacts were observed on motoneurones in various sizes. Some collaterals gave rise to terminal arborizations in both the VM and the SA. These results suggest that single LVST and MVST axons may control excitability of multiple dorsal axial muscles concurrently with their multiple axon collaterals at multisegmental levels.

Animals↗
PubMed1989

Functional coupling of the stabilizing gaze reflexes during vertical linear motion in the alert cat.

Eye-head coordination is mainly achieved by means of stabilizing reflexes (VOR, VCR, OKR) and orienting movements (eye-neck surgery) underlying the close cooperation of the visual and vestibular systems in gaze stabilization. The functional coupling of these different sensorimotor subsystems has been principally analysed using rotatory stimulation of the whole body and/or of the visual surround. The aim of the present study was to investigate the dynamic properties of these stabilizing gaze reflexes and their coupling during linear motion in the vertical plane. These investigations were performed in the alert cat under open-loop conditions (head fixed). Otolith stimulation consisted of vertically translating the cat in total darkness using sinusoidal linear motion (0.025 Hz-1.39 Hz; 290 mm peak-to-peak amplitude). Optokinetic stimulation was provided by sinusoidally moving a pseudo-random visual pattern in front of the cat and in the vertical plane, with identical kinematic parameters. Normal visual-otolith interaction was performed by translating the cat in front of the stationary visual surround while conflicting interaction was provided by moving the animal and the visual pattern in phase and at the same velocity (visual stabilization). Results showed that the vertical otolith-neck reflex is very poorly developed or absent in the low frequency range of motion (0.025 Hz-0.25 Hz) while consistent EMG activity is found during pure optokinetic stimulation. EMG responses are in phase with the visual surround velocity in the upward direction and with the upward OKR velocity. A close correlation is observed between the EMG gain and the OKR gain, which both decrease in this low frequency range, indicating that gaze stabilization would be mainly ensured by the OKR and a functional oculo-collic coupling or eye-neck surgery in the vertical plane. On the contrary, gaze stabilization is principally achieved by way of the otolith-neck reflex in the higher frequency range of motion (above 0.25 Hz). EMG responses recorded during otolith stimulation exhibit a relatively constant gain and a phase lead with respect to motion velocity which progressively reduces as the stimulus frequency increases up to 1.39 Hz. When present, EMG responses evoked during the optokinetic stimulation show strong gain attenuation and phase lag. Normal visual-otolith interaction induces neck muscle activity which parallels the optokinetic and the otolith responses in the low and high frequency ranges, respectively. The motor responses are however improved in terms of gain and phase values in the whole frequency range when both sensory inputs are combined.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

The anatomy of the central control of posture: consistency and plasticity.

Posture is usually thought to be steered by brainstem and cortical structures that have access to the motoneurons and their premotor interneurons of the axial and neck muscles. The present paper describes these pathways and their relation with gaze control structures. All these systems belong to the medial component of the so-called voluntary motor system. On the other hand, in the cat there also exist several postures that are not steered by the somatic, but by the emotional motor system. Examples are arching of the back and mating postures. The pathways thought to be involved in these behaviours are described. They belong to the lateral component of the emotional motor system and, especially in case of mating postures, are extremely plastic. They have been demonstrated to be almost 10 times as strong in oestrus than in non-oestrus cats.

Animals↗
PubMed1983

Paradoxical sleep in the dark period of the rat: a dissociation between electrophysiological and behavioral characteristics.

Paradoxical sleep (PS) occurring in the dark period of the illumination cycle is studied in adult, male, Wistar rats. In contrast to the light period, behaviorally the rats give the impression of being awake at the onset of PS. This is caused by the fact that PS in the dark starts from a short-lasting state characterized by dissociating criteria: behavioral characteristics such as open eyes and body posture phenomena indicating quiet wakefulness along with full-blown hippocampal EEG waves implying slow wave sleep (SWS). These behavioral characteristics continue at the onset of PS, suggesting that PS in the dark differs from that in the light period. The intrinsic characteristics of PS, as the hippocampal theta rhythm, the suppression of the neck muscle EMG and the phasic activities, however, indicate that PS is the same phenomenon in both illumination periods. The implication of this finding with respect to the triggering of PS and its relationship with SWS is discussed.

Animals↗
PubMed1989

Head and body movements evoked electrically from the caudal superior colliculus of rats: pulse frequency effects.

The effects of pulse frequency and current intensity on circling elicited from the caudal superior colliculus (SC) of rats were studied. The displacement of the head with respect to the body were measured for different levels of frequency (20, 29, and 50 Hz) and current (200 or 500 microA) at a pulse duration of 0.1 ms. The rate of circling increased monotonically with frequency and current. The rate at which the head was displaced laterally varied as a function of frequency. It is postulated that lateral head and body movements are affected by the firing frequency of SC output neurons.

Animals↗
PubMedDate not supplied

Biological age--what is it and can it be measured?

Biological age is a concept used loosely and with little objectivity to describe a shortfall between a population cohort average life expectancy and the perceived life expectancy of an individual of the same age. Many biomarkers decline roughly linearly with age with a slope of <1% per annum. The use of a battery of 16 biomarkers is described as a method of calculating an individual biological age. They include: the concentration of prostacyclin in fibroblasts, cell membrane viscosity, the electroretinogram, baroreflex regulation of the heart rate, the concentration of lymphocytes, leucocyte density and velocity, grip strength, cells of the corneal endothelium and the buccal epithelium, neck muscle mobility, and vital capacity. Although not subjected to a prospective validation, the method might provide an objective approach to this widely used concept.

Aged↗
PubMed1988

Coexistence of multiple arteriovenous malformations and an anomalous aortic arch.

An unusual case of multiple congenital arteriovenous malformations (AVM) coexistent with an anomalous aortic arch is described. Our patient had been asymptomatic, with physical findings limited to a low grade systolic murmur, until the onset of acute subarachnoid hemorrhage. Arteriography was technically difficult and failed to demonstrate the origin of his hemorrhage or the configuration of his aortic arch. However, an AVM within the neck muscles was visualized. Magnetic resonance imaging of his chest revealed a right-sided, retroesophageal aortic arch with an anomalous pattern of branching. The intracranial AVM and the course of the great vessels was clearly revealed at autopsy. A possible embryologic mechanism underlying the origin and distribution of the arch vasculature is discussed.

Adult↗
PubMed2000

Effects of vision on head stability and torques during voluntary pulls made by standing humans.

This study tested the hypothesis that vision would improve pitch-plane stabilization of the head by increasing how well neck muscle torque compensates for torques associated with body motion, in a task where standing human subjects made rapid voluntary pulls. Ten subjects performed abrupt horizontal pulls on a handle to two peak force targets, with the eyes open and closed. We evaluated head angular velocity with respect to space. Inverse dynamics were used to subdivide the torque acting on the head into gravito-interactive and muscle components. A torque compensation ratio was computed from those two components. Head angular velocity was lower and the compensation ratio was higher during pulls made with the eyes open, for both force targets. The data suggest that vision enhances head stability by increasing the effectiveness with which muscle torques oppose gravito-interactive torques during voluntary pulls made while standing.

Adult↗
PubMed1994

[Shaken baby syndrome].

The shaken baby syndrome is a relatively recent concept concerning mishandled children and characterized by cerebral lesions (subarachnoid haemorrhage, oedema, axonal injuries). A case is reported of a 11-month-old female infant, who was admitted in a paediatric intensive care unit with clinical signs of brain death after cardiopulmonary resuscitation. The CT scan showed subdural haemorrhage. Pathological examination confirmed the major blunt head trauma. The father admitted that he had shaken his daughter as "she cried too often". The mechanism of the lesions is a combination of several factors, especially the large size of infant's head and the weakness of the neck muscles. It is possible to recognize still in the perinatal period children at risk of mishandling, allowing an efficient prevention of the shaken baby syndrome.

Battered Child Syndrome↗
PubMed2003

Condyle-fossa modifications and muscle interactions during herbst treatment, part 1. New technological methods.

Changes in the condyle, the glenoid fossa, and the muscles of mastication were investigated in subjects undergoing continuous orthopedic advancement of the mandible with a Herbst-block appliance. The total sample consisted of 56 subjects and included 15 nonhuman primates (in the middle mixed, early permanent, and permanent dentitions), 17 human Herbst patients in the early permanent dentition, and 24 human controls from the Burlington Growth Center. The 8 nonhuman primates in the middle mixed dentition were the focus of this study. Mandibular advancement was obtained progressively in 5 animals by adding stops to the telescopic arms of fixed functional Herbst appliances with occlusal coverage; activations of 5.0 mm, 7.0 mm, and 8.0 mm were achieved. Two primates served as controls, and the third was a sham control. Two experimental animals and the 2 controls also wore surgically implanted electromyographic electrodes in the superior and inferior heads of the lateral pterygoid muscles and in the superficial masseter and anterior digastric muscles. Changes in condylar growth direction and amount were assessed with the Björk method from measurements made on serial cephalometric tracings superimposed on metallic implants. Undecalcified sections, treated with intravenous tetracycline vital staining, were viewed with fluorescence microscopy to examine histologic changes in the condyle and the glenoid fossa. New bone formation in the fossa associated with continuous mandibular protrusion was quantified by using computerized histomorphometric analysis of decalcified histological sections and polarized light. The unique combination of permanently implanted electromyographic electrodes, tetracycline vital staining, and histomorphometry represents a significant technological advancement in methods and materials. Together, they demonstrated different muscle-bone interaction results for functional appliances than those reported in previous studies. In Part 1 of this study, we describe and discuss the techniques used in this research and give a brief overview of the findings; in Part 2 (to be published next month), we offer a more in-depth discussion of the results and the implications of our findings.

Animals↗