Indium-111 labeled neutrophils for detecting lung injury. A perspective.
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Animals↗
Biomedical subjects
J H Williams
Publications and source records attributed to J H Williams.
Caffeine, neuromuscular function and high-intensity exercise performance.
Caffeine is one of the most widely consumed drugs in the world. There is a strong belief that caffeine is an ergogenic aid to sports performance. Although much evidence suggests that caffeine may improve endurance exercise performance, questions still remain with regard to its effects on neuromuscular function and brief, high-intensity exercise performance. At the cellular level, caffeine stimulates the central nervous system (CNS), enhances neuromuscular transmission and improves skeletal muscle contractility. The former two effects seem to have facilitative effects on activities which require quick reactions and rapid movements. This is evident in that simple and choice reaction and movement times are reduced following ingestion of small quantities of caffeine. It appears, however, that the caffeine-induced increases in muscle contractility seen in vitro do not translate into improved strength, in vivo. Acute caffeine ingestion does not seem to increase maximal voluntary contractions or maximal power output nor delay fatigue. Thus use of caffeine to improve performance in activities requiring strength and short-term endurance seems unwarrented. Further research is needed before clear conclusions can be draw regarding caffeine's effects on neuromuscular function and high-intensity exercise performance.
Caffeine↗
Dihydropyridine effects on skeletal muscle fatigue.
1. The purpose of this investigation was to determine if alterations in extracellular calcium (Ca2+) influx by the dihydropyridine derivatives Bay K 8644 and nifedipine affected skeletal muscle fatigue. 2. Tetanic contractions (80 Hz, 100 msec) of frog sartorius muscles were evoked every sec for 3 min. Muscles were fatigued in normal Ringer's solution (NR), in NR containing 1 microM nifedipine of 10 microM Bay K 8644 or in low Ca2+ Ringer's. 3. In each case, the experimental conditions increased the rate and magnitude of fatigue. Rate constants of fatigue obtained during Bay K 8644, nifedipine and low Ca2+ conditions (-.0122 +/- .0016, -.0397 +/- 0022 and 0.0169 +/- .0064 sec-1, respectively) were significantly greater than NR (-.0104 +/- .0006 sec-1, p less than .05). In addition, tetanic forces developed at the end of the stimulation period under the experimental conditions (3.90 +/- 0.81, 1.21 +/- 1.40 and 2.04 +/- 1.10% of initial) were significantly less than NR (7.18 +/- 1.27%, p less than .05). 4. Caffeine contracture forces (10 mM) evoked immediately after stimulation were not significantly different between conditions. 5. These results suggest that alterations in sarcolemmal Ca2+ exchange has some influence on the fatigue process.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Associations between water quality and GIT symptoms in country dwellers.
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Drinking↗
Effects of GABAergic drugs, fornicotomy, hippocampectomy and septal lesions on the extinction of a discrete-trial fixed ratio 5 lever-press response.
The effects of certain GABA-modulating drugs, fornicotomy, hippocampectomy and various septal lesions were analysed in a discrete-trial fixed ratio 5 (FR5) bar-press paradigm. Chlordiazepoxide, fornicotomy, hippocampectomy, electrolytic lateral septal lesions and ibotenic acid medial septal lesions facilitate extinction of the FR5 response. Some of these treatments (chlordiazepoxide, hippocampectomy, electrolytic lateral septal lesions) have previously been found to increase resistance to extinction of alley-running after continuously reinforced (CRF) acquisition training. The treatments which facilitated extinction in the discrete-trial FR5 paradigm have been found to reduce or abolish the partial reinforcement extinction effect in the alley. These results indicate that the discrete-trial FR5 paradigm is not analogous to a runway CRF schedule, but may be analogous to a runway partial reinforcement schedule.
Animals↗
Effects of 5,7-dihydroxytryptamine injections in the fornix-fimbria on locomotor activity in photocell cages and the open field.
Microinjections of 5,7-dihydroxytryptamine (5,7-DHT) into the fornix-fimbria (FF) reduced dorsal hippocampal [3]5-HT uptake to 40% of control levels. The FF 5,7-DHT lesions increased nocturnal activity in photocell cages, but reduced central ambulation in diurnal open field tests. The lesions also disrupted both habituation of rearing across days in the open field and alternation in a Y-maze. Hence FF-derived hippocampal 5-HT terminals participate in controlling activity, but their role depends on the test apparatus and procedures.
5,7-Dihydroxytryptamine↗
Effects of low calcium and calcium antagonists on skeletal muscle staircase and fatigue.
The purpose of this investigation was to determine the effects of low extracellular calcium and calcium antagonists on skeletal muscle staircase and fatigue. Initial experiments revealed that, brief exposure (10 minutes) of single frog sartorius muscle to diltiazem, D-600 (5 and 30 microM) and low calcium Ringer's solution (LCR, calcium replaced by magnesium and EGTA) had little effect on isometric twitches evoked every 30 seconds. However, when stimulated at 1 per second for 15 minutes, the calcium antagonists significantly decreased the magnitude and time course of the staircase, whereas LCR decreased only the time course. Each experimental condition significantly increased the rate of fatigue while diltiazem and D-600 both increased the magnitude of fatigue. Following the stimulation period, caffeine (10 mM) elicited contractures from all muscles whereas high potassium (180 mM) elicited contractures from control muscles only. These results indicate that calcium channel antagonists depress the skeletal muscle staircase response. They also indicate that these compounds as well as LCR enhance the fatigue process. Extracellular calcium influx may therefore have some influence on skeletal muscle twitches during prolonged repetitive activity.
Animals↗
Immunohistochemical identification of mast cells in formaldehyde-fixed tissue using monoclonal antibodies specific for tryptase.
An avidin-biotin enhanced immunoperoxidase procedure using monoclonal antibodies (AA1, AA3, and AA5) prepared against human mast cell tryptase resulted in intense staining of mast cells in paraffin-embedded tissue. The distribution of mast cells observed was similar to that seen when adjacent serial sections were stained using a standard procedure with toluidine blue, though the immunoperoxidase technique permitted the identification of significantly more mast cells. With monoclonal antibody AA1, immunostaining was entirely specific for mast cell granules, and there was negligible background staining in a range of tissues including lung, tonsil, colon, gastric mucosa, skin, and pituitary. There was no staining of antibody on basophils or on any other normal blood leukocyte. The technique was effective with tissue fixed in either Carnoy's or neutral buffered formalin, though the internal mast cell structure was better preserved with formaldehyde fixation. The immunoperoxidase staining procedure with monoclonal antibody AA1 is a highly specific and sensitive means for the detection of mast cells in routinely processed tissues.
Antibodies, Monoclonal↗
Staircase potentiation in isolated frog skeletal muscle: power spectral analysis of the evoked compound muscle action potential.
1. The mechanical and electrophysiological effects of repetitive, low-frequency electrical stimulation on paired sartorii muscles from small male frogs have been investigated, in vitro. 2. Stimulation for 90 sec at 5 Hz resulted in a progressive rise (staircase) than fall (fatigue) in peak twitch tension. 3. The root mean square amplitude, peak-to-peak amplitude, conduction velocity and mean power frequency of evoked compound muscle action potentials (CMAPs) decreased over the stimulation period. 4. Results suggest that alterations in the shape of the CMAP during repetitive stimulation may contribute to the staircase phenomenon.
Action Potentials↗
Presynaptic mechanisms in hippocampal long-term potentiation.
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Animals↗
Contractile responses of smooth muscle strips from rat and guinea-pig urinary bladder to transmural stimulation: effects of atropine and alpha,beta-methylene ATP.
1. Strength-duration curves for threshold mechanical responses to single transmural stimuli were identical for rat and guinea-pig detrusor. In both species atropine had no effect on the curves, but the curves were shifted to the right by nerve blockade with tetrodotoxin (TTX), and by blockade of P2-purinoceptors with alpha,beta-methylene ATP (alpha,beta-MeATP). 2. With short duration pulses of 50 V and less, the responses were nerve-mediated. Increase in either the strength or duration of the stimulus caused direct muscle stimulation, resistant to blockade with atropine, TTX and alpha-beta-MeATP. 3. The shape of the contractile response to a single nerve stimulus varied from tissue to tissue. The responses could be mono-, bi-, or multiphasic. Bi- or multiphasic responses were normally seen in tissues which were spontaneously active. The multiphasic nature of the response was enhanced by factors which increased the excitability of the cells and was reduced by factors which decreased the excitability. 4. The frequency-response curves in the rat are similar to those previously obtained in the guinea-pig. Atropine suppresses the high frequency response by 25%, with little effect at low frequencies, whereas desensitization of P2-purinoceptors with alpha,beta-MeATP suppresses the responses maximally at low frequencies but still by 75% at high frequencies. A combination of both drugs eliminates the nerve-mediated responses. 5. It is concluded that the response to a single nerve stimulus is mediated by a non-cholinergic transmitter, through activation of P2-purinoceptors. The possibility that simultaneous release of acetylcholine can modify the excitability of cells and thus the configuration of the response to a single stimulus is discussed.
Acetylcholine↗
NEA clarifies policy on HIV testing.
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AIDS Serodiagnosis↗
Depression of posttetanic twitch potentiation by low calcium and calcium channel antagonists.
The purpose of this investigation was to determine if antagonizing extracellular calcium influx altered posttetanic twitch potentiation (PTP). Whole muscles and muscle fiber bundles (less than or equal to 25 fibers) dissected from frog sartorius and semitendinosus muscles were mounted at optimal length in a normal Ringer solution (NR). To determine PTP, isometric twitches were evoked every 10 s (0.1 Hz) before and after a 2.5-s tetanic contraction (80 Hz). To antagonize calcium influx, low-calcium Ringer [LCR, calcium replaced by 3 mM magnesium and 1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid], NR plus diltiazem (Dilt, 30 microM), NR plus nifedipine (Nif, 10 microM), and NR plus D 600 (30 microM) were also used (n = 8 for each condition). These conditions altered pretetanic twitch tension by only -1.2 +/- 2.4, 4.2 +/- 2.3, 4.7 +/- 3.7, and 1.6 +/- 3.7% (SE), (LCR, Dilt, Nif, and D 600, P greater than 0.05) but caused a noticeable decrease in tension at the end of the tetanus. Under NR conditions, twitches evoked immediately after the tetanus were potentiated by 49.5 +/- 0.4% with the peak rate of tension development (dP/dt) increased by 44.9 +/- 0.5% (P less than 0.05). Antagonizing calcium influx depressed the PTP response by 59.8 +/- 6.2, 55.9 +/- 10.1, 73.2 +/- 6.8, and 29.8 +/- 3.6% (P less than 0.05) and increased dP/dt by 65.8 +/- 11.1, 45.7 +/- 8.6, 55.6 +/- 4.4% and 49.0 +/- 10.5% (P less than 0.05). Addition of drugs immediately after the tetanus only slightly reduced PTP but accelerated recovery of the twitch.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
111indium-labeled neutrophils for detecting lung injury.
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Animals↗
Flexible bronchoscopic removal of radioccult polyurethane foam, with pneumonitis in a hyperventilated lobe.
An intellectually delayed adult ingested and aspirated a large quantity of polyurethane foam, developing acute respiratory failure in association with partial airway obstruction. The foam was identified by flexible bronchoscopy and successfully removed from the bronchus intermedius and left mainstem bronchus with a retrieval basket. This facilitated normalization of blood gases and eventual recovery. However, the unobstructed right upper lobe became infiltrated radiographically, presumably resulting from regional hyperinflation and/or occult focal aspiration.
Adult↗
Enhancement of skeletal muscle fatigue by the calcium channel antagonist diltiazem.
This study sought to determine the effects of diltiazem on normal muscle twitches and on twitches evoked during repetitive stimulation. Initial experiments showed that diltiazem (5 and 30 microM) had slight, but insignificant, effects on peak twitch tension and the time course of the twitch. When muscles were stimulated at 1 or 5 Hz, 30 microM diltiazem significantly depressed the height and time course of the staircase period and increased the rate and magnitude of fatigue. Contrary to control, diltiazem caused a complete loss of developed tension during both stimulation protocols. Results suggest that although diltiazem has little effect on single twitches, it has marked inhibitory effects on twitches evoked during repetitive activity; the result being enhancement of the fatigue process.
Animals↗
Effects of the calcium antagonist, TMB-8 on halothane and on caffeine contractures of malignant hyperthermia susceptible skeletal muscle.
This investigation sought to determine if the Ca2+ antagonist, TMB-8, alters the contracture responses of malignant hyperthermia susceptible (MHS) skeletal muscle to halothane and to caffeine. Muscle fiber bundles were excised from both MHS and normal pigs and exposed to TMB-8 (100 microM), halothane (3%) and caffeine (0.5-8.0 mM), administered alone and in combination. TMB-8 depressed tension developed during isometric twitches in both MHS and normal muscle but had no effect on resting tension (RT). Halothane, however, increased RT in MHS but not in normal muscle. TMB-8 failed to reduce the halothane contracture of MHS muscle but hastened its onset. Caffeine concentrations of greater than or equal to 2 mM increased RT in MHS whereas only 8 mM evoked contracture of normal muscle. These effects were also unaltered by TMB-8. Results suggest that TMB-8 does not inhibit halothane nor caffeine contractures of MHS muscle.
Animals↗
Lead poisoning in a dog.
A case of lead poisoning caused by ingestion of a lead roof-washer is described in a one-year-old, spayed Fox Terrier bitch, presented with nervous signs, and basophilic stippling of red blood cells. Blood concentrations of lead were in the low toxic range. Radiography of the abdomen revealed radio-dense objects in the stomach, which on gastrotomy included a lead roof-washer. Prior to removal of the foreign bodies, the dog showed remarkable improvement on non-specific symptomatic treatment alone, and recovered well after surgery, only to die unexpectedly several hours later. Concentrations of lead in the liver and kidneys were extremely high, and histology revealed typical intracellular inclusions and organ degeneration. In the light of these findings, it is suggested that all cases of suspected or confirmed lead poisoning be given specific chelation therapy.
Animals↗