The Ca2+ channel blockade changes the behavioral and biochemical effects of immobilization stress.
We investigated how the effects of chronic immobilization stress in rats are modified by Ca2+ channel blockade preceding restraint sessions. The application of nifedipine (5 mg/kg) shortly before each of seven daily 2 h restraint sessions prevented the development of sensitized response to amphetamine as well as the stress-induced elevation of the densities of L-type Ca2+ channel in the hippocampus and significantly reduced the elevation of the densities of [3H]nitrendipine binding sites in the cortex and D1 dopamine receptors in the limbic forebrain. Neither stress, nor nifedipine affected the density of alpha 1-adrenoceptors and D1 receptors in the cerebral cortex nor D2 dopamine receptors in the striatum. A single restraint session caused an elevation of blood corticosterone level that remained unaffected by nifedipine pretreatment, but the reduction of this response during the eighth session was significantly less expressed in nifedipine-treated rats. We conclude that L-type calcium channel blockade prevents development of several stress-induced adaptive responses. (+info)
Acute fractures of the scaphoid. Treatment by cast immobilisation with the wrist in flexion or extension?
Acute fractures of the scaphoid were randomly allocated for conservative treatment in a Colles'-type plaster cast with the wrist immobilised in either 20 degrees flexion or 20 degrees extension. The position of the wrist did not influence the rate of union of the fracture (89%) but when reviewed after six months the wrists which had been immobilised in flexion had a greater restriction of extension. We recommend that acute fractures of the scaphoid should be treated in a Colles'-type cast with the wrist in slight extension. (+info)
Sensory afferent properties of immobilised or inflamed rat knees during continuous passive movement.
We studied the sensory afferent properties of normal, immobilised and inflamed rat knees by recording the activity of the medial articular nerve (MAN). When the knee was inflamed by kaolin-carrageenan or immobilised for six weeks, MAN activity significantly increased during rest and continuous passive motion (CPM). The maximal discharge rate tended to increase depending on the angular velocity of the CPM. When the knees were then rested for one hour before again starting CPM, activity was further increased at the initial CPM cycle, the 'post-rest effect'. Analysis of the conduction velocity showed that 94% and 66% of spike units on the recorded discharge of the immobilised and inflamed knees, respectively, belonged to fine nerve fibres. Our findings show that the sensory receptors in the knee are sensitised in a similar manner by immobilisation and by inflammation, suggesting a relationship to pain. The post-rest effect may be related to a characteristic symptom of osteoarthritis called 'starting pain'. (+info)
Expression of insulin growth factor-1 splice variants and structural genes in rabbit skeletal muscle induced by stretch and stimulation.
1. Skeletal muscle is a major source of circulating insulin growth factor-1 (IGF-1), particularly during exercise. It expresses two main isoforms. One of the muscle IGF-1 isoforms (muscle L.IGF-1) is similar to the main liver IGF-1 and presumably has an endocrine action. The other muscle isoform as a result of alternative splicing has a different 3' exon sequence and is apparently designed for an autocrine/paracrine action (mechano-growth factor, MGF). Using RNase protection assays with a probe that distinguishes these differently spliced forms of IGF-1, their expression and also the expression of two structural genes was measured in rabbit extensor digitorum longus muscles subjected to different mechanical signals. 2. Within 4 days, stretch using plaster cast immobilization with the limb in the plantar flexed position resulted in marked upregulation of both forms of IGF-1 mRNA. Electrical stimulation at 10 Hz combined with stretch (overload) resulted in an even greater increase of both types of IGF-1 transcript, whereas electrical stimulation alone, i.e. without stretch, resulted in no significant increase over muscle from sham-operated controls. Previously, it was shown that stretch combined with electrical stimulation of the dorsiflexor muscles in the adult rabbit results in a marked increase in muscle mass involving increases in both length and girth, within a few days. The expression of both systemic and autocrine IGF-1 growth factors provides a link between the mechanical signal and the marked increase in the structural gene expression involved in tissue remodelling and repair. 3. The expression of the beta actin gene was seen to be markedly upregulated in the stretched and stretched/stimulated muscles. It was concluded that the increased expression of this cytoskeletal protein gene is an indication that the production of IGF-1 may initially be a response to local damage. 4. Switches in muscle fibre phenotype were studied using a specific gene probe for the 2X myosin heavy chain gene. Type 2X expression was found to decrease markedly with stimulation alone and when electrical stimulation was combined with stretch. Unlike the induction of IGF-1 and beta actin, the decreased expression of the 2X myosin mRNA was less marked in the 'stretch only' muscles. This indicates that the interconversion of fibre type 2X to 2A may in some situations be commensurate with, but not under the control of IGF-1. (+info)
Intra-articular displaced fractures of the calcaneus. Operative vs non-operative treatment.
Twenty-eight patients with displaced intra-articular fractures of the calcaneus treated by open reduction and fixation were compared with 30 patients with similar fractures treated conservatively. Judged by the clinical and radiographic criteria results were more satisfactory in the surgical group than in the nonoperative group, although high rates of poor results were encountered in both groups. (+info)
A chest wall restrictor to study effects on pulmonary function and exercise. 1. Development and validation.
Chest wall-restrictive loading reduces a person's ability to expand the chest wall during inhalation and results in decrements in lung capacities, resting pulmonary function, and ultimately, exercise performance. Chest wall restriction is observed in some forms of skeletal and pulmonary diseases (e.g., scoliosis) as well as in occupational situations (e.g., bulletproof vests). We have designed a constant-pressure chest wall-restrictive device that provides a quantifiable and reproducible load on the chest. This paper describes the device and the initial pulmonary function tests conducted. Ten subjects participated in this study. Subjects wore the restrictive device while performing pulmonary function tests at four externally added restrictive loads on three separate occasions. A two-way repeated-measures multivariate analysis of variance revealed significant decreases in forced expiratory vital capacity (FVC) and forced expiratory volume in 1 s (FEV1.0) at each load while the ratio of FEV1.0 to FVC (FEV1.0%) was maintained. No significant differences in any variable were found across time or between the seated and standing position. These results indicate that this chest wall-restrictive device provides a quantifiable added inspiratory load in the breathing cycle that results in reproducible decrements in pulmonary function representative of those seen in some restrictive pulmonary disease and occupational situations. (+info)
A chest wall restrictor to study effects on pulmonary function and exercise. 2. The energetics of restrictive breathing.
Chest wall restriction, whether caused by disease or mechanical constraints such as protective outerwear, can cause decrements in pulmonary function and exercise capacity. However, the study of the oxygen cost associated with mechanical chest restriction has so far been purely qualitative. The previous paper in this series described a device to impose external chest wall restriction, its effects on forced spirometric volumes, and its test-retest reliability. The purpose of this experiment was to measure the oxygen cost associated with varied levels of external chest wall restriction. Oxygen uptake and electromyogram (EMG) of the external intercostals were recorded during chest restriction in 10 healthy males. Subjects rested for 9 min before undergoing volitional isocapnic hyperpnea for 6 min. Subjects breathed at minute ventilations (V.I) of 30, 60, and 90 liters/min with chest wall loads of 0, 25, 50 and 75 mm Hg applied. Frequency of breathing was set at 15, 30, and 45 breaths per minute with a constant tidal volume (VT) of 2 liters. Oxygen uptake was measured continuously at rest and throughout the hyperventilation bouts, while controlling V.I and VT. Integrated EMG (IEMG) from the 3rd intercostal space was recorded during each minute of rest and hyperventilation. Two-way ANOVA with repeated measures revealed that chest wall loading and hyperpnea significantly increased V.O2 values (p < 0.01). External intercostal IEMG levels were significantly increased (p < 0.05) at higher restrictive load (50 and 75 mm Hg) and at the highest minute ventilation (90 liters/min). These data suggest that there is a significant and quantifiable increase in the oxygen cost associated with external chest wall restriction which is directly related to the level of chest wall restriction. (+info)
Emotional stress and characteristics of brain noradrenaline release in the rat.
We have investigated several characteristics of the rat brain noradrenaline (NA) release caused by various stressful situations. Stresses such as immobilization or electric foot shock, wherein the physical factors rather than emotional ones were greatly involved, caused more marked increases in NA release in the more extended brain regions, as compared to psychological stress and conditioned fear, which caused increases in NA release preferentially in the hypothalamus, amygdala and locus coeruleus (LC) region. When the electric shock stress and psychological stress for 1 hr daily were repeated for 5 consecutive days, increases in brain NA release induced by electric shock were rapidly reduced, but those caused by psychological stress were enhanced rather than reduced. Rats with no stressor controllability (uncontrollable) had more severe gastric lesions and more marked increases in NA release in such brain regions as the hypothalamus and amygdala after 21 hrs of training than controllable rats. Rats with no opportunity to predict electric shock exhibited more severe gastric lesions and more marked increases in hypothalamic NA release than the predictable rats. The rats not allowed to express their aggression had more severe gastric mucosal lesions and a more noticeable and persistent increases in extracellular NA content in the amygdala determined by intracerebral microdialysis than the rats allowed to express aggression by biting a wooden stick in front of them during stress exposure. In aged rats (12 months old), recovery from increases in NA release in the hypothalamus and amygdala and increases in plasma corticosterone were much later than in young (2-month-old) rats. When rats were exposed to a series of six 15-min stress interrupted by 18-min non-stress periods for 180 min, they had much greater increases in brain NA release than rats stressed continuously for 180 min. Based upon these findings, we suggest that such stresses might be harmful to our health as psychological, uncontrollable and unpredictable stresses, stress unable to express aggression, stress in elderly people, and stress with lack of suitable rest. (+info)