Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Injecting tetanus toxin into rat hippocampus induces a syndrome of intermittent generalized seizures which recurs for about one month. Following remission from their seizures, the rats exhibit very persistent impairments of learning and memory. Learning was impaired on a circular platform task and a spatial reference memory task, and evoked responses from the commissural-CA3 pyramidal cell system were depressed for up to 22 weeks after injection. There was no significant loss of pyramidal neurons because antidromic responses, evoked from other parts of the commissural fibre system, were not affected by the toxin treatment. The depression of these pyramidal neurons provides a reasonable physiological explanation for the learning impairment. These results suggest that impairments of neuronal function can be significant factors in the development of interictal behavioural abnormalities.
 ...
PMID:Physiological and behavioural consequences of seizures induced in the rat by intrahippocampal tetanus toxin. 356 34

We investigated the possible importance of stimulus train frequency for the induction and magnitude of long-term synaptic plasticity in the perforant path-granule cell pathway. Under the same experimental conditions, low- (15 Hz) or high-frequency (400 Hz) stimulation could elicit a profound long-term depression (LTD), or typical long-term potentiation (LTP), of the population spike amplitude, excitatory postsynaptic potential (EPSP) amplitude and spike onset latency. In addition, changes in the relationship between the EPSP and population spike amplitude indicated that granule cell excitability was enhanced during LTP and reduced during LTD. LTD occurred primarily after low-frequency stimulation (5 of 6 cases), and was always accompanied by striking changes in the EEG, most notably a biphasic slow potential. While the EEG changes were confined to the first 5 min after the tetanus, LTD lasted from 1 to 4 h. The nature of the EEG events is still unclear, it is suggested that they may represent a spreading depression-like episode. Finally, we found that LTP evoked by high-frequency stimulation was larger and generally reached peak magnitude faster than when it followed low-frequency stimulation. A possible mechanism and role for hippocampal LTD is proposed.
 ...
PMID:Induction of long-term depression and potentiation by low- and high-frequency stimulation in the dentate area of the anesthetized rat: magnitude, time course and EEG. 356 87

Both the afferent volleys from the dorsal root and the monosynaptic reflex discharges from the corresponding ventral root were recorded with hook electrodes during stimulation of the nerves innervating the triceps surae muscles. The effects of conditioning high frequency tetanus on the magnitudes of these afferents and reflex volleys were examined in kittens of postnatal age 1-90 days and in adult cats. In young kittens under barbiturate anaesthesia, large-amplitude monosynaptic reflex discharge can be evoked without prior conditioning. The amplitude of this reflex discharge decreased with increasing age of the animal. Application of conditioning tetanic stimuli to the muscle nerves resulted in posttetanic depression followed by posttetanic potentiation of the monosynaptic reflex. The magnitude of posttetanic depression was much higher than that of potentiation in the first postnatal week. As the age increased, the magnitude of depression decreased while the magnitude of potentiation increased. The afferent volley showed a considerable posttetanic potentiation in older kittens and cats. No significant potentiation or depression was observed in the younger animals. Possible mechanisms contributing to posttetanic depression and potentiation are discussed.
 ...
PMID:Posttetanic changes in the afferent and efferent activity of monosynaptic reflex in kittens. 358 Sep 55

The effectiveness of dantrolene sodium in controlling tetanic spasms was evaluated in 21 children (aged 4 days-13 years) with tetanus. These dantrolene-treated patients were compared with an historical control group of 26 children previously treated for tetanus by traditional means at the same institution. The groups were comparable in terms of age, other treatments, and severity of disease. All patients received standard treatments for tetanus, including sedatives, antibiotics, and tetanus-immune globulin. Patients in the dantrolene-treated group also received dantrolene, either intravenously (Dantrium Intravenous) or orally, in divided doses totalling 4-6 mg/kg/day. Mortality was 73% (neonates 83%, non-neonates 50%) in the control group, compared with 33% (neonates 50%, non-neonates 0%) in the dantrolene-treated group. Dantrolene did not cause additional respiratory depression when administered alone or in combination with other drugs routinely used to treat tetanus. In this study, the use of dantrolene with traditional conservative therapy significantly reduced mortality from tetanus.
 ...
PMID:Efficacy of dantrolene sodium in management of tetanus in children. 372 21

Responses have been recorded from primary endings of muscle spindles in the cat soleus muscle. Changes in spindle responsiveness were measured following a period of conditioning that consisted of a series of rapid stretches or of tetanic ventral root stimulation. In the testing procedure the response of a single spindle afferent was recorded to stimulation of a dynamic fusimotor axon during a slow stretch. Changes in gross afferent discharge coming from the muscle were measured by integrating the activity recorded in dorsal roots. If, after conditioning stretches, the muscle was immediately returned to its initial length, the spindle responded to the test fusimotor stimulation with a high-frequency burst of afferent impulses. If the muscle was held stretched for 3 s after conditioning the response to the brief test tetanus was small or "depressed." It has been suggested that conditioning stretches result in detachment of stable crossbridges in intrafusal fibers and that these bridges then reform over the next few seconds at whatever length the muscle happens to have at the time. When it is long, shortening the muscle back to the initial length leads to the development of slack in intrafusal fibers because of the passive stiffness they have acquired from the presence of the stable bridges. Under these conditions a brief test fusimotor tetanus will lead to a depressed response because the slack must first be taken up before a full response can be generated. It was possible to reverse the depression by interposing an extrafusal contraction during the period between the conditioning and test sequences. It is suggested that lateral compression from the contracting extrafusal fibers and the stretch they impose as they relax reduces any intrafusal slack and thereby reduces the depression. A more quantitative measure of intrafusal slack than the test for depression is to determine the delay in onset of the afferent response to a longer fusimotor tetanus. The delay was short a long initial muscle lengths where, if the muscle was left undisturbed, it soon disappeared completely and spontaneously. It is suggested that at long lengths passive tension in the muscle tends to remove any slack in intrafusal fibers and therefore removes any after effects. The rise in resting discharge of muscle afferents after a conditioning tetanus applied to the ventral root ("postcontraction sensory discharge") can be accounted for by the same hypothesis.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Aftereffects in the responses of cat muscle spindles. 376 Sep 30

The skeletal muscle relaxant properties of an aqueous extract of Portulaca oleracea were examined on the twitch and tetanus tension evoked by electrical stimulation using the rat phrenic nerve-hemidiaphragm and frog sciatic nerve-sartorius muscle preparations and on contractures induced by nicotinic agonists using the rat rectus abdominis muscle preparation. The extract (5-50 X 10(-4) g/ml) produced a dose-dependent initial enhancement, followed by a longer lasting depression of twitch tension as induced by indirect electrical stimulation (NS) as well as direct stimulation (MS) of the diaphragm and sartorius muscle preparations. The augmentation of twitch amplitude (MS) produced by the extract was not significantly antagonised or potentiated by d-tubocurarine (5-50 X 10(-8) M) or physostigmine (5-50 X 10(-8) M) at concentrations which blocked or potentiated NS-induced twitch contractions. Furthermore, tetrodotoxin (5 X 10(-7) g/ml) alone or in combination with d-tubocurarine did not significantly attenuate extract-induced augmentation of twitch contractions to MS. In addition, the depression of twitch tension due to NS was not antagonised by physostigmine but was reversed and/or abolished by Ca2+ (2-5 X 10(-3) M) or potassium thiocyanate (1 X 10(-3) M). Contractures induced by K+ (80 mM) or by tetanic stimulation (20-60 Hz) were significantly reduced by the extract whereas, contracture induced by caffeine (2.5-6.0 mM) was not affected. Ca2+-free Tyrode's solution and EDTA (1.25 X 10(-3) g/ml) potentiated extract-induced depression of twitch tension to MS. On the rectus abdominis, contractures induced by nicotinic agonists (acetylcholine, 3-500 X 10(-7) M; carbachol, 5-500 X 10(-7) M and nicotine, 5-500 X 10(-8) M) were significantly attenuated and/or abolished by the extract (5-10 X 10(-3) g/ml). These observations indicate that the aqueous extract possesses unique skeletal muscle relaxant properties which do not appear to involve interference with cholinoceptor mechanism(s). It appears that the mechanism of action of the extract may involve interference with Ca2+ mobilization in skeletal muscle.
 ...
PMID:Skeletal muscle relaxant properties of the aqueous extract of Portulaca oleracea. 379 17

Isometric tetani of single muscle fibers of Rana temporaria were studied as a function of stimulation rate, sarcomere length (1.7-2.3 micron), twitch-to-tetanus ratio, and exposure to twitch potentiators (Zn2+ and NO3-) at 20 degrees C. As the stimulation rate was decreased below a maximal level, tension generation decreased. This depression in tension generation was more pronounced at shorter sarcomere lengths. Therefore the magnitude and shape of the sarcomere length curve was dependent on stimulation rate. Although the depression in tension generation was always accompanied by a noticeable ripple in the tension record in fibers with large twitch-to-tetanus ratios, it could be observed even during well-fused tetani in fibers with low twitch-to-tetanus ratios. In all fibers, however, high stimulation rates or exposure to potentiators resulted in maximum tension generation at each length, and the sarcomere length-tension curve followed that found by Gordon, Huxley, and Julian. This indicates that the fall in tension between sarcomere lengths of 2.0 and 1.7 micron is not due to length-dependent activation but is more likely to be the result of mechanical interference in the force-generating interaction between cross bridges and thin filament sites.
 ...
PMID:Stimulation rate, potentiators, and sarcomere length-tension relationship of muscle. 387 67

Post-tetanic potentiation (PTP) was elicited at the frog sartorius and cutaneous pectoris neuromuscular junctions. A 30-sec, 30-Hz tetanus produced a 2- to 3-fold post-tetanic increase in endplate potential (EPP). In surface-recorded responses this PTP decayed in a double exponential way with time constants of 12.7 sec +/- 2.4 (SEM) and 146.8 sec +/- 36.6. In acute experiments 0.2 to 0.8 mM phenytoin (5,5-diphenylhydantoin, DPH) dramatically and reversibly reduced the early component. The late component was also reduced, although to a lesser extent and often not reversibly. DPH reduced PTP even when there was no failure of the EPP during the tetanus. Thus, the DPH effect did not require a complete block of the presynaptic action potential. At longer exposures and higher DPH concentrations EPP failures did develop, and this was associated with a more profound suppression of PTP. PTP was also elicited in tetrodotoxin (TTX)-containing solutions using electronic stimulation of nerve terminals to elicit transmitter release. This PTP had a much shorter duration (about 30 sec) than that seen in normal Ringer's solution and was followed by depression of EPP amplitudes. Thus, sodium entry into nerve terminals enables a mechanism which greatly prolongs PTP. DPH had no effect on PTP in TTX. These results, together with others in the literature, suggest that the reduction of PTP by DPH involves a graded reduction of sodium influx into nerve terminals during high rates of axon stimulation. The development of all-or-none failures of the presynaptic action potential results in even greater suppression of PTP.
 ...
PMID:On the mechanism by which phenytoin blocks post-tetanic potentiation at the frog neuromuscular junction. 405 60

63 patients on long-term oral therapy with phenytoin sodium (sodium diphenylhydantoin) were screened for abnormalities of immunological function. They were compared with 92 controls and 28 patients with lymphoma. Depression of cellular or humoral immunity, or both, was found in a significant number of phenytoin-treated and lymphoma subjects. Phenytoin therapy was associated with low immunoglobulin A (21%), failure of antibody response to Salmonella typhi antigen (9%), absence of delayed hypersensitivity (D.H.S.) to three common skin-test antigens (22%), and depression of in-vitro lymphocyte transformation by phytohaemagglutinin (27%). Lymphoma patients manifested low IgM (22%), and inability to make antibody to S. typhi (11%) and to tetanus toxoid (21%). D.H.S. was absent in 36%; lymphocyte transformation was depressed in 17%. Abnormal lymphocyte transformation did not correlate with depression of cellular or humoral immunity in either group.
 ...
PMID:Depression of immunological function in patients treated with phenytoin sodium (sodium diphenylhydantoin). 414 95

1. Physiological properties of motor units in the soleus muscle were studied in anaesthetized cats using intracellular stimulation of motoneurones to ensure functional isolation of single units. The muscle fibres belonging to 6 units were identified by glycogen depletion following prolonged stimulation, permitting analysis of their histochemical profiles and anatomical organization.2. The studied units in soleus were all classed as type S and were extremely resistant to fatigue during prolonged stimulation. Twitch contraction times ranged from 64 to 131 msec (mean 97.1 msec) and tetanic tensions ranged from 3.5 to 36 g (mean 10.5 g). Most units exhibited depression of twitch tension in the wake of a short high-frequency tetanus and few of the units showed any significant degree of post-tetanic twitch potentiation.3. Muscle fibres belonging to single soleus motor units were found to be scattered through territorial volumes occupying a large fraction of the total muscle volume. The available data suggest that different soleus motoneurones may innervate from less than 50 to more than 400 muscle fibres, with an average innervation ratio between 140 and 190 muscle fibres per unit.4. The results were compared with observations on type S motor units in the synergist gastrocnemius, obtained under similar conditions. The evidence suggests that soleus units are not equivalent to the type S units of the mixed gastrocnemius but rather constitute a unique population.
 ...
PMID:Motor units in cat soleus muscle: physiological, histochemical and morphological characteristics. 427 82


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>