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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuromuscular synapses of the "fast" excitatory axon supplying the main extensor muscle in the leg of the shore crab Pachygrapsus crassipes were studied with electrophysiological and electron-microscopic techniques. Electrical recording showed that many muscle fibers of the central region of the extensor muscle responded only to stimulation of the fast axon, and electron microscopy revealed many unitary subterminal axon branches. Maintained stimulation, even at a low frequency, resulted in depression of the excitatory junctional potentials (EJPs) set up by the fast axon but EJPs of different muscle fibers depressed at different rates, indicating some physiological heterogeneity among the fast-axon synapses. Focal recording at individual synaptic sites on the surfaces of the muscle fibers showed quantal contents ranging from 1.4 to 5.5 at different synapses; these values are relatively high in comparison with similar determinations made in the crayfish opener muscle. Synapse-bearing nerve terminals were generally relatively small in diameter and filiform, with many individual synaptic contact areas of uniform size averaging 0.6 micron2. All of the individual synapses had a presynaptic "dense body" at which synaptic vesicles clustered. If these structures represent release points for transmitter quanta, the initial high quantal content would have an ultrastructural basis. The mitochondial content of the nerve terminals, the synaptic vesicle population, and the specialized subsynaptic sarcoplasm were all much reduced in comparison with tonic axon synaptic regions in this and other crustaceans. The latter features may be correlated with the relatively infrequent use of this axon by the animal, and with rapid fatigue.
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PMID:Fast-axon synapses of a crab leg muscle. 63 13

Static and dynamic work involving the arms and the legs was performed by 40 men seven weeks after myocardial infarction. Leg ergometry produced a significantly higher peak work load, systolic blood pressure (BPs), heart rate (HR), and HR X BPs X 10(-2) product (DP) than did arm ergometry: 842 +/- 178 vs 546 +/- 135 kg-m/min, 176 +/- 24 vs 154 +/- 19 mm Hg and 256 +/- 54 vs 219 +/- 48 (SD). Peak heart rates were 145 and 142. Endpoints were primarily muscular and generalized fatigue and dyspnea. Ischemic abnormalities and ventricular ectopy were more frequent with leg ergometry. Sustained forearm lifting elicited higher HR, PBs and DP responses than sustained handgrip contraction: 95 +/- 16 vs 91 +/- 16 beats/min, 162 +/- 18 vs 152 +/- 17 mm Hg and 154 +/- 33 vs 139 +/- 33 (SD). Ischemic ST segment depression and significant ventricuar arrhythmias were infrequent with static effort. Dynamic leg testing is superior to dynamic or static arm testing in assessing the capacity of patients to perform physical work tasks after myocardial infarction.
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PMID:Cardiovascular responses to dynamic and static effort soon after myocardial infarction. Application to occupational work assessment. 66 87

The changes with postnatal age in post-tetanic potentiation (PTP) and fatigue of the inferior oblique muscle have been studied in the cat. PTP of the twitch amplitude increased steadily with age up to 20 weeks after birth. Twitch contraction time (ct) and half relaxation time (hrt) was not significantly changed. The potentiation of the tetanic response also became more prominent with age. The young muscles (10 weeks and below) were slightly more susceptible to fatigue than older muscles, but recovery was rapid in muscles of all ages. Intensive stimulation induced post-tetanic depression of twitch responses in muscles older than 1 week, but none in the muscles of new-born cats. Ct and hrt were greatly prolonged in muscles above six weeks of age. In these muscles, but never in the very youngest, repetitive firing could be observed in response to post-tetanic single nerve stimulation. The results are compared with those obtained in similar experiments on hind-limb muscles by other workers. They further support the idea, raised in a previous paper, that slow eye muscle fibres develop quicker and reach maturity earlier than fast fibres.
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PMID:The postnatal development of the inferior oblique muscle of the cat. II. Effects of repetitive stimulation on isometric tension responses. 67 66

1. These experiments were designed to test whether intense pure tones produced greater depression of cochlear nerve fibers tuned to the exposure frequency or of those tuned to frequencies above the exposure frequency. Spike discharges of single fibers were studied in anesthetized cats before, during, and after exposures lasting 1 min. Exposure frequency was varied relative to each fiber's characteristic frequency (CF), and was either at the CF or 1/2 octave above (+1/2 oct) or 1/2 octave below (-1/2 oct) the CF. Exposure levels were 85 or 90 dB SPL. Effects of the various exposures on driven discharge rates were evaluated using standard test stimuli at each fiber's CF. In addition, nonevoked discharges were measured during the brief quiet intervals between test stimuli ("interstimulus activity") as well as during extended quiet periods ("resting activity"). Major results were as follows: 2. All the exposures resulted in depression of the driven discharge rates; however, these effects were strongly dependent on the exposure frequency. The depression was greatest and endured the longest following -1/2 oct exposures at 90 dB. The CF exposures at 85 and 90 dB were much less depressant, as were exposures at -1/2 oct at 85 dB; these three exposures resulted in very similar recovery functions. The +1/2 oct exposures produced little or no depression, whether at 85 or 90 dB. 3. Interstimulus activity was depressed immediately following all exposures, but recovered to normal quickly than did driven discharge rates. Following exposures at -1/2 oct at 90 dB, recovery was non-monotonic in that an extended period of supernormality preceded the return to normal rates. During this period of elevated activity, the interstimulus activity approached but never exceeded the resting rate of the same fiber. 4. Resting activity recovered even more rapidly than interstimulus activity, being completely normal by 1 min following all exposures. 5. These results constitute the first demonstration that the CF is not necessarily the most depressant exposure frequency for a given cochlear nerve fiber. Further, the results imply that the half-octave (or greater) shifts of the point of maximum hearing loss, so characteristic of auditory fatigue, may be accounted for by frequency-dependent alterations in the responsiveness of cochlear nerve fibers.
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PMID:Neural correlates of auditory fatigue: frequency-dependent changes in activity of single cochlear nerve fibers. 68 96

Historical shifts in the symptomatology of mental disease are surprisingly overlooked but common phenomena that should cast considerable light on the relation between social and intrapsychic processes. The enormous increase in chronicity and mortality in mental hospitals during the second half of the 19th century, and the shift from the shell-shock of the first World War to the battle fatigue of the second are examples which have been well documented but not well explained. The advent of guilt feelings in depression or melancholia is a lesser known instance but one with perhaps greater theoretical significance. Melancholia has been known almost throughout recorded history, but until the 16th century the number of recorded cases exhibiting exaggerated guilt feelings and self-accusations was very small, and the old physicians did not include them in their descriptions of the condition. In Asia and in Africa, moreover, it is claimed that these symptoms are rare even today, except among the Westernized. If we fully understood the other features of the disease or if the symptoms had no relevance to course and treatment, these facts might be treated simply as curiosities; but neither is the case. Depression is still not adequately understood, and some theories on it derive largely from the exaggerated guilt feelings and the psychic structure which is supposed to produce the latter. Hence it could be instructive to examine under what conditions these symptoms first became common in different societies.
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PMID:The advent of guilt feelings as a common depressive symptom: a historical comparison on two continents. 69 18

The response to electrocardiographically monitored submaximal exercise stress testing has been studied in 44 patients with mitral leaflet prolapse (MLP). With exercise, ventricular premature contractions occurred in 7, ventricular tachycardia in 1, and atrial fibrillation in 1. Exercise was terminated short of target heart rate in 18 patients, because of chest pain (5), fatigue (7), ventricular arrhythmia (4), dizziness (1) or ST segment depression (1). 23 patients developed postexercise ST segment abnormalities, of whom 5 had 'ischemic' patterns and arteriographically proven coronary artery disease (CAD); among the 18 others, the ST segments were depressed and minimally downsloping in 2, slowly ascending from depressed J point in 3, horizontal for greater than or equal to 80 msec with J depression of less than 1 mm in 12, and cupped in 1. The incidence of arrhythmias provoked by submaximal exercise stress testing in patients with MLP was lower than suggested in previous reports. In all 5 cases where MLP and CAD coexisted, the classical 'ischemic' electrocardiographic response to exercise was not obscured. Even in the absence of CAD, postexercise ST segment abnormalities were common with MLP (18/39 = 46%) and differed from the progressively resolving ST segment deviation characteristic of CAD with angina. Exercise testing can safely be recommended, subject to standard contraindications, in patients with MLP and yields useful information.
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PMID:The electrocardiographic response to exercise in 44 patients with leaflet prolapse. 71 Apr 93

Evaluated the relevance of the physiological-arousal model, the stimulus-control paradigm, and depression to insomnia both as a unitary construct and to its components. The Manifest Anxiety Scale, the Sleep Behavior Self Rating Scale and the Zung Depression Scale were administered to 81 clinical Ss. Three separate discriminant function analyses were performed with self-reported "sleeping difficulty," "latency of falling asleep," and "total hours of sleep" as criterion variables. The above three scales and the following four sleep patterns were used as indices: number of nocturnal wakings, latency to fall asleep once awake, number of early wakings, and frequency of feelings of fatigue upon wakings. The findings indicated that the physiological-arousal model was relevant both to insomnia overall and to its component of sleep-onset insomnia. The stimulus-control paradigm was found to be relevant only to sleep-onset insomnia. Depression was not a sensitive discriminator, possibly due to the heterogeneity of the patient population studied. It is emphasized that different mechanisms might be operating with the heterogeneous symptom "insomnia," and the replication of findings with criteria that include significant others and electroencephalographic measures is suggested.
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PMID:Insomnia: anxiety, sleep-incompatible behaviors and depression. 71 75

Literature on the association of oral contraceptives (OCs) with psychological disturbances is reviewed. The data from available clinical studies indicate that perhaps 10-40% of OC users may experience mild to moderate depression syndromes characterized by tiredness, lethargy, sadness and, in some cases, loss of libido. These psychological alterations may involve numerous mechanisms including changes in folate, pyridoxine, and Vitamin-B12 metabolism, and related effects on biogenic amine metabolism. The interaction of these impaired mechanisms may disturb usual coping functions and psychological defenses by altered central nervous system activity.
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PMID:Evaluation of emotional reactions to oral contraceptive use. 79 96

Twenty-one patients with brucellosis wereinvestigated. Four patients with the classical manifestations of acute brucellosis presented no problems in diagnosis. The other 17 patients suffered from chronic disease and had no history of any acute episode of brucellosis. The most common symptoms in this group were tiredness, fatigue, depression, arthralgia and muscular pains. Abdominal pain and pain in the temperomandibular joints were marked in some patients. Most of these patients had been receiving psychiatric treatment. Clinical examination was largely negative, but lymphadenopathy was found in 9 cases. Brucella meningo-encephalitis was diagnosed in 7 patients who complained of severe headache. Problems in the diagnosis of chronic brucellosis with an insidious onset are discussed.
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PMID:Clinical aspects of chronic brucellosis. 81 22

The sensitivity of myocardial perfusion imaging (MPI) using thallium-201 injected both at rest and during peak exercise was compared to simultaneously recorded 12 lead electrocardiography (ECG) for the detection of transient ischemia in 20 normal subjects and 63 patients with coronary artery disease (CAD). No significant perfusion defects or ECG changes were seen on either the rest or exercise studies in any of the normal subjects. Fifty-six percent of patients with CAD developed new perfusion defects with exercise compared to 38% who developed ischemic ST-segment depression (P less than 0.02). However, when chest pain and/or ST depression were considered indices of ischemia, the sensitivity of exercise testing and thallium-201 MPI was similar. The increased sensitivity of MPI compared to ST-segment depression on the ECG was due to patients with baseline ECG abnormalities and those who failed to achieve 85% of predicted maximum heart rate with exercise. Analysis of the exercise results according to the extent of coronary artery disease revealed a progressive increase in both positive ECGs and MPI with the number of vessels involved. In patients with single vessel disease the MPI was more sensitive than the ECG (P less than 0.02). The combination of the rest and exercise ECG, MPI and chest pain during exercise failed to identify 11% of patients with CAD. Exercise thallium-201 MPI is a useful adjunct to conventional exercise testing particularly when evaluating patients with abnormal resting ECGs, those who develop ventricular conduction defects of arrhythmias during exercise, and those who fail to achieve their predicted heart rate because of fatigue or breathlessness.
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PMID:Thallium-201 myocardial perfusion imaging at rest and during exercise. Comparative sensitivity to electrocardiography in coronary artery disease. 83 Feb 22


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