Implementing the Cairo agenda.
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Congresses as Topic↗
Biomedical subjects
B R Johnson
Publications and source records attributed to B R Johnson.
Distributed amine modulation of graded chemical transmission in the pyloric network of the lobster stomatogastric ganglion.
1. In the pyloric network of the lobster stomatogastric ganglion, graded synapses organize the network output. The amines dopamine (DA), serotonin, and octopamine each elicit a distinctive motor pattern from a quiescent pyloric network. We have examined the effects of these amines on the graded synaptic strengths between the six major types of neurons of this network to understand how amine modulation of synaptic strength contributes to the amine-induced motor patterns. Here we tested amine affects at 10 different graded chemical synapses of the pyloric network. We show that each amine has a statistically different spectrum of distributed effects across the network synapses. 2. Under our control conditions (isolated pairs of neurons, removal of modulatory input), most of the graded chemical synapses were weak and some synapses were nonfunctional. The output synapses of the ventricular dilator (VD) neuron were significantly stronger than the other synapses. 3. DA altered the synaptic strength of every graded chemical synapse. This amine strengthened the weak chemical output synapses of the anterior burster (AB), lateral pyloric (LP), and pyloric constrictor (PY) neurons and weakened (and in some cases abolished) the strong chemical output synapses of the VD neuron. The AB-->inferior cardiac neuron (IC) and PY-->IC graded chemical synapses were nonfunctional under our control conditions; DA activated these silent synapses. 4. Serotonin enhanced the AB's output chemical synapses but weakened all the other graded chemical synapses examined. Octopamine's effects were much weaker than those of the other two amines. It enhanced the AB-->LP synapse and the LP's output synapses and weakly strengthened the AB-->PY, VD-->LP, and VD-->PY synapses. 5. The amines alter the input resistance of many of the pyloric neurons, and this could contribute to the observed changes in synaptic strength by altering passive current flow between input and output sites in the cells. However, the input resistance changes were relatively small compared with the changes in synaptic strength and cannot alone account for the synaptic modulation. In some cases the sign of the input resistance change was inconsistent with the change in synaptic strength. Thus the amines appear to modify synaptic transmission directly in this system. 6. This study completes our description of amine effects on all the graded synapses of the pyloric network. We summarize our present and earlier work to show that modulators can reconfigure the entire synaptic organization of a neural network by acting at many distributed synaptic sites.(ABSTRACT TRUNCATED AT 400 WORDS)
Analysis of Variance↗
Elevated temperature alters the ionic dependence of amine-induced pacemaker activity in a conditional burster neuron.
The anterior burster neuron of the lobster (Panulirus interruptus) stomatogastric ganglion is a conditional burster that functions as the primary pacemaker for the pyloric motor network. When modulatory inputs to this cell are blocked, it loses its bursting properties and becomes quiescent. Applications of the monoamines, dopamine, octopamine or serotonin restore rhythmic bursting in this cell (Flamm and Harris-Warrick 1986). At 15 degrees C, serotonin- and octopamine-induced oscillations depend critically upon sodium entry (blocked by low sodium saline or tetrodotoxin); dopamine-induced oscillations depend upon calcium entry (blocked by reduced extracellular calcium; Harris-Warrick and Flamm 1987). We show here that the ionic dependence of amine-induced oscillations in the anterior burster cell differs at 15 and 21 degrees C. At 21 degrees C, all amines have the potential to induce rhythmic oscillations in saline containing tetrodotoxin. At the elevated temperature and in tetrodotoxin, both calcium and sodium currents are essential for the maintenance of dopamine-induced oscillations; serotonin-induced oscillations do not depend upon either calcium or sodium alone; octopamine-induced oscillations do not depend upon calcium and show a variable dependence upon sodium. Thus, multiple ionic mechanisms, which vary with both the modulator and the ambient temperature, can be recruited to support rhythmic activity in a conditional burster neuron.
Animals↗
A new sampling technique that allows quantitative fit testing by using the employee's own respirator.
A new, in-mask sampling technique has been developed that enhances current quantitative respirator fit test methods. This new sampling technique eliminates the need for a permanently modified (probed) respirator for conducting fit tests. With this new technique, a sample was drawn from the breathing zone inside the respirator by means of a sampling adapter, which was temporarily attached between one of the air-purifying filters and the facepiece before a fit test was performed. To ensure that the performance of the respirator was not altered, the sampling adapter was designed so that all major functional aspects of the respirator were unchanged. This new sampling technique was evaluated on human test subjects by simultaneous sampling from a probed respirator by using two quantitative respirator fit test instruments. One instrument sampled through a conventional respirator probe; the other used the new method. Test results show that equivalent fit test data were obtained with both sampling techniques.
Equipment Design↗
Endothelin induces vascular and mucosal lesions, enhances the injury by HCl/ethanol, and the antibody exerts gastroprotection.
Vascular factors play an important role in the pathogenesis and prevention of acute gastric mucosal lesions. Endothelin-3 (ET-3), a potent vasoactive peptide, was infused intra-arterially to induce gastric microvascular and hemorrhagic mucosal lesions, and to enhance the damaging effects of dilute HCl and ethanol. ET-3 antibody was injected intravenously to decrease hemorrhagic mucosal lesions induced by ethanol. Locally infused ET (0.01, 0.1, and 1.0 nmol.100 g-1.min-1 for up to 15 min) was followed in some cases by intragastric dilute ethanol or HCl, which alone caused no or only mild vascular and mucosal lesions. Monastral blue was used to visualize and quantify vascular injury. ET-3 produced dose-dependent vascular lesions that affected the walls of mucosal capillaries and venules and induced mucosal congestion and focal endothelial labeling in vessels of the gastric muscular layers. The highest dose of ET induced hemorrhagic gastric mucosal lesions, mortality, and periods of hyper- and hypotension in the rat. Medium and low doses of ET-3 caused vascular injury, and dose-dependently potentiated the vascular and hemorrhagic mucosal lesions caused by dilute HCl and ethanol. Indomethacin slightly enhanced damage induced by ET and 50% ethanol, suggesting a limited mediatory role of prostaglandins in the ET-induced mucosal lesions. Anti-ET-3 serum dose-dependently decreased but did not abolish the hemorrhagic gastric mucosal lesions induced by 75% ethanol. Thus, ET-3 causes endothelial damage in capillaries and venules of rat stomach and predisposes to mucosal damage even after exposure to dilute ethanol or HCl. ET is more potent than leukotrienes and histamine and thus may play an important role in the mechanisms of acute gastric mucosal injury and protection where the vascular network appears to be a major target.
Animals↗
Joining the front line against HIV: an education program for adult probationers.
This article describes the implementation and evaluation of a human immunodeficiency virus (HIV) education program for adult offenders. Samples of Cook County (Chicago) probationers were educated about either HIV or heart disease in small group and in one-on-one sessions. The evaluation employed a 2 x 2 factorial design. Data were collected at 3 points in time: during a pretest, posttest, and follow-up. Results showed that offenders' knowledge of HIV was increased significantly at posttest and follow-up. Although the HIV presentation increased knowledge significantly, it had little impact on HIV-related behavioral intentions at posttest or on actual prevention behaviors at follow-up. The implications of these findings are discussed with respect to HIV education programs in criminal justice settings.
Adult↗
A simple adsorption/dilution model for rice herbicides.
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Adsorption↗
Across-fiber patterns may contain a sensory code for stimulus intensity.
Various models for sensory coding have used statistical approaches based on the assumption that the stimulus intensity parameter is represented in the afferent neurons as mean firing frequency. In this paper we question the assumption that this is the only code for intensity. We show that in lobster olfactory receptors narrowly tuned to hydroxyproline, an across-fiber pattern (AFP) code distinguished more concentration levels over a 5 log step range than a response magnitude code and, unlike the latter, was unaffected by response summation time. AFP discrimination of stimulus intensity appears to be based on high inter-cell response variability and low intra-cell response variability.
Animals↗
Paranoid and aggressive behavior in two obsessive-compulsive adolescents treated with clomipramine.
Obsessive-compulsive disorder is increasingly recognized in patients of different age groups. Serotonergic agents, such as clomipramine, have been recently found to be useful in the management of this condition. However, unexpected side effects, such as dysphoria, aggressiveness, and paranoid ideation, may occur with therapeutic doses of this compound, as evidenced in the cases of two male adolescents presented here. Possible pathogenetic factors, involving serotonin and serotonin-receptor abnormalities are discussed. Management of these side effects is based on adequate dose reduction and monitorization.
Adolescent↗
Temperature sensitivity of graded synaptic transmission in the lobster stomatogastric ganglion.
We examined the temperature sensitivity of graded chemical synaptic strength within the pyloric circuit of the spiny lobster stomatogastric ganglion. Cooling from 20.4 degrees C to 11.3 degrees C reduced the graded synaptic potential (GSP) amplitude at all six pyloric synapses tested. Cooling appeared to reduce the slope of the linear part of the input-output curve at three of these synapses, and did not significantly alter the threshold for transmitter release at any synapses. Pairs of neurons with a presynaptic pyloric dilator (PD) cell showed reductions in graded synaptic strength at 16.5 degrees C but those with presynaptic lateral pyloric (LP) or ventral dilator (VD) cells did not. A generalized decrease in input resistance is not responsible for the reduced GSP amplitude upon cooling, as determined by input resistance, action potential amplitude and electrical coupling measurements. We conclude that cooling reduces graded chemical strength by a direct synaptic action. Since the PD and VD cells use the same transmitter and act on some of the same postsynaptic cells, their differential sensitivity to cooling further suggests a presynaptic site of action. The temperature range used in our experiments encompasses the range that the animal normally encounters in nature. Thus, the relative importance of graded synaptic interactions in generating the pyloric motor rhythm may vary with transient changes in temperature.
Action Potentials↗
Aminergic modulation of graded synaptic transmission in the lobster stomatogastric ganglion.
Graded chemical synaptic transmission is important for establishing the motor patterns produced by the pyloric central pattern generator (CPG) circuit of the lobster stomatogastric ganglion (Raper, 1979; Anderson and Barker, 1981; Graubard et al., 1983). We examined the modulatory effects of the amines dopamine (DA), serotonin (5-HT), and octopamine (Oct) on graded synaptic transmission at all the central chemical synapses made by the pyloric dilator (PD) neuron onto its follower cells, using synaptic input-output curves measured from cell somata. DA strongly reduced the graded synaptic strength at all the PD synapses. DA reduction of chemical synaptic strength from PD onto the inferior cardiac (IC) neuron could change the sign of synaptic interaction between these 2 cells from inhibitory to excitatory by uncovering a weak electrical connection. 5-HT had weaker and more variable effects, reducing graded synaptic strength from the PD onto the lateral pyloric and pyloric neurons and enhancing the weak synapse from the PD to the IC cell. Oct strongly enhanced the graded synaptic strength at all the PD central synapses. Oct enhancement of graded synaptic strength between the PD and IC cells could also change the sign of the interaction: weak, excitatory electrical coupling, which was sometimes dominant before Oct, was masked by the enhanced chemical inhibitory interaction during Oct application. Measurements of electrical coupling between 2 PD cells and between 2 postsynaptic cells suggest that Oct does not change the input resistance of these cells and may act directly at the PD synapses. The effects of DA and 5-HT are most easily explained by their general reductions in pre- and postsynaptic input resistance. DA, 5-HT, and Oct each produce a distinct pyloric motor pattern (Flamm and Harris-Warrick, 1986a). These amine-induced motor patterns may be explained by the unique actions of each amine on the intrinsic membrane properties of different pyloric CPG neurons (Flamm and Harris-Warrick, 1986b) and by modulation of graded synaptic transmission between the pyloric neurons.
Action Potentials↗
Self-focused attention, gender, gender role, and vulnerability to negative affect.
Research has independently shown that both gender and self-focused attention are linked to depression. In this article, we report a series of studies investigating the relation between these variables. Using a standard self-focusing manipulation, Study 1 suggested that women evidence a greater propensity to self-focus than men. We replicated these findings in Study 2. In Study 3, we conducted an experiment to determine if sex role in conjunction with experimentally increased self-focused attention would lead to more emotional distress after a negative event had occurred. Results suggested that feminine individuals who received a self-focusing manipulation responded with greater levels of self-focused attention and negative affect than did any other group. We interpreted findings in terms of a tendency to self-focus that might prime feminine people to experience depression, or alternately, as a lack of self-focusing that may insulate masculine individuals from the experience of depression.
Anxiety↗
Potassium channel blockade induces rhythmic activity in a conditional burster neuron.
In the lobster stomatogastric ganglion the Anterior Burster (AB) neuron loses its rhythmic bursting capabilities when isolated from all synaptic input. Here we report that compounds which reduce the current through several different types of potassium channels induce bursting in isolated AB neurons. These results suggest that when quiescent, this neuron has all the conductances necessary to support bursting, but bursting is actively inhibited by tonic potassium conductances.
4-Aminopyridine↗
Mixed-longitudinal growth of nomadic Turkana pastoralists.
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Adolescent↗
Grip strength, muscle fatigue, and body composition in nomadic Turkana pastoralists.
Tests of hand grip strength and hand grip muscle fatigue were conducted on Ngisonyoka Turkana pastoralists of northwest Kenya to explore some of the functional relationships between activity and body composition. The test of maximal voluntary contraction (MVC) of hand grip flexors was conducted on 151 Turkana and 38 U.S. men and women. The fatigue test was conducted on the same number of subjects who were instructed to attempt to maintain 80% of the MVC for 90 seconds. The results of these tests, combined with arm measurements of size and body composition, were used to evaluate muscle size and strength relationships and to estimate muscle fiber type distribution in the forearm. MVC values of Turkana men were low by U.S. and European standards. The low values resulted from smaller Turkana muscle areas. MVC values of Turkana women were comparable to those of U.S. and European women, reflecting comparable muscle areas. The fatigue curves of Turkana and U.S. men and women suggest that slow-twitch aerobic muscle fibers predominate for the hand grip flexors of the Turkana pastoralists.
Adult↗
Narrow-spectrum chemoreceptor cells in the antennules of the American lobster, Homarus americanus.
The present study shows that smell (antennular) receptor cells are as narrowly tuned to single compounds as taste (leg) receptor cells in the lobster. Antennular receptors responded best to hydroxy-L-proline (57% of the 30 cells sampled) and taurine (24%). In the presence of 14 other compounds in equimolar concentrations, the hydroxy-L-proline and taurine receptors showed a suppressed response to their best stimulus. Other cells had best responses to ammonium chloride, betaine, L-glutamate or L-proline. The results have implications for molecular receptor processes and for the neural basis of feeding behavior.
Action Potentials↗
Neuromuscular blocking properties of suxamethonium and decamethonium in normal and myasthenic rat muscle.
Patients with myasthenia gravis (MG) have increased tolerance to the neuromuscular blocking properties of suxamethonium (SCh) and decamethonium (C10) and exhibit a reversal of the C10-induced block by neostigmine. The effects of these drugs were compared in forelimb flexor digitorum longus muscle from normal rats and from rats with experimental autoimmune myasthenia gravis (EAMG) to investigate the similarity of EAMG to MG. The depolarization induced by 1, 5, 10 and 25 microM SCh or C10 at the motor end-plates was significantly higher in normal than in EAMG muscle. However, both normal and EAMG end-plates responded in a similar qualitative manner to each drug. The depolarization produced by SCh was typically maintained until the drug was washed from the bath. The depolarization produced by C10 tended to decrease after reaching its peak despite continued application of the drug. With both drugs, miniature end-plate potential (MEPP) amplitude reduction is maintained until a saline wash. Neostigmine interaction with SCh and C10 in normal and EAMG muscle was compared by measuring isometric twitch tension in vitro. Neostigmine potentiated the neuromuscular block produced by either SCh or C10 in both normal and EAMG muscle. Thus muscle from rats with EAMG shares with MG an increased tolerance to SCh and C10 when compared to normal muscle but does not exhibit the qualitatively different interaction of C10 affected muscle with neostigmine that is found in MG patients. This and other studies comparing EAMG and MG indicate that EAMG is an appropriate model of MG but differences such as we have noted should be considered when extrapolating data from EAMG to the human disease.
Animals↗
General occurrence of stressful reactions to commercial motion pictures and elements in films subjectively identified as stressors.
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Adolescent↗