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Biomedical subjects

T D Bell

Publications and source records attributed to T D Bell.

17 recordsLinked to original sources
PubMed1998

Ca2+/calmodulin-dependent kinase II mediates simultaneous enhancement of gap-junctional conductance and glutamatergic transmission.

While chemical synapses are very plastic and modifiable by defined activity patterns, gap junctions, which mediate electrical transmission, have been classically perceived as passive intercellular channels. Excitatory transmission between auditory afferents and the goldfish Mauthner cell is mediated by coexisting gap junctions and glutamatergic synapses. Although an increased intracellular Ca2+ concentration is expected to reduce gap junctional conductance, both components of the synaptic response were instead enhanced by postsynaptic increases in Ca2+ concentration, produced by patterned synaptic activity or intradendritic Ca2+ injections. The synaptically induced potentiations were blocked by intradendritic injection of KN-93, a Ca2+/calmodulin-dependent kinase (CaM-K) inhibitor, or CaM-KIINtide, a potent and specific peptide inhibitor of CaM-KII, whereas the responses were potentiated by injection of an activated form of CaM-KII. The striking similarities of the mechanisms reported here with those proposed for long-term potentiation of mammalian glutamatergic synapses suggest that gap junctions are also similarly regulated and indicate a primary role for CaM-KII in shaping and regulating interneuronal communication, regardless of its modality.

Animals↗
PubMed1997

Nitric oxide synthase distribution in the goldfish Mauthner cell.

NADPH-diaphorase histochemical staining was used to assess the distribution of the enzyme nitric oxide synthase (NOS) in the goldfish brain, with the emphasis on the Mauthner (M-) cell, a reticulospinal neuron, and its inputs. Labeling was specific for certain cell types, including the M-cell, which stained heavily. The reaction product in this neuron was uniformly distributed along its axon, soma, and ventral and lateral dendrites. Afferents which synapse with the M-cell were also NADPH-diaphorase positive, including an identified class of inhibitory interneurons and the large myelinated club endings (LMCE) of eighth nerve fibers. The presence of NADPH-diaphorase in a lower level brainstem circuit that undergoes activity-dependent long-term potentiation of both excitatory and inhibitory synapses and is accessible for morpho-functional correlations provides the opportunity to elucidate the mechanism and role of nitric oxide at the single cell level.

Animals↗
PubMed1996

Corticosteroid-sparing effect of azelastine in the management of bronchial asthma.

The objective of this double-blind trial was to evaluate the corticosteroid-sparing effect of azelastine in patients with chronic bronchial asthma. A total of 193 subjects received either 6 mg of azelastine twice per day or placebo (in a 2:1 ratio) in combination with beclomethasone dipropionate (6 to 16 inhalations per day). The number of daily inhalations of the corticosteroid was reduced until maximum reduction or elimination was achieved. Patients then entered a 12-wk maintenance period, during which patients were maintained on their lowest possible dose of inhaled corticosteroid. Compared with placebo, the azelastine group had a statistically significantly greater overall median reduction in inhaled corticosteroids (4.9 puffs/day for azelastine versus 3.1 puffs/day for placebo; p < or = 0.010) during the maintenance period. The azelastine group also had a statistically significantly higher percentage of patients with reductions of > or = 50% and > or = 75% from the baseline level (53 and 31%, respectively, for azelastine versus 34 and 14%, respectively, for placebo; p < or = 0.028). The results demonstrated that azelastine, 6 mg twice per day, can reduce the need for inhaled corticosteroids in patients with chronic bronchial asthma and not lead to a deterioration in pulmonary function.

Administration, Inhalation↗
PubMed1995

Retrograde synaptic communication via gap junctions coupling auditory afferents to the Mauthner cell.

Large myelinated club endings of the goldfish eighth nerve arise in the sacculus and establish mixed electrotonic and chemical synapses with the distal part of the Mauthner (M-) cell's lateral dendrite. We show here, using paired pre- and postsynaptic recordings, that depolarizing currents generated postsynaptically (specifically, the mixed synaptic potential produced by activation of part of the afferent population) can in some cases excite the presynaptic fibers and cause them to backfire. Strikingly, while in some systems junctional properties prevent the antidromic spread of depolarizing currents, physiological properties of these afferents and the gap junctions promote backfiring: the amplitude of the coupling potential recorded from an afferent fiber is voltage dependent, increasing with depolarization and being reduced during hyperpolarization. Two mechanisms, with different kinetics, underlie this voltage dependence. One, a nonlinear membrane property of the afferent fiber itself, enhances the coupling potential as the afferent membrane depolarizes. The second mechanism, which is less sensitive to voltage and is symmetric about the resting potential, most likely represents voltage dependence of the junctional membrane. Additionally, we also show retrograde diffusion of low molecular weight substances, as the fluorescent dye Lucifer yellow and the tracer Neurobiotin were found in the terminals of afferent fibers after being injected postsynaptically into the M-cell. These results suggest that the gap junctions in these primary afferents are not only involved in fast anterograde synaptic transmission but also provide the substrate for a retrograde intercellular communication. The electrical coupling may modify the input-output relation between eighth nerve afferents and the lateral dendrite by synchronizing the population of already active fibers and by promoting the recruitment of new fibers via backfiring, such that weaker inputs produce relatively larger responses.

Animals↗
PubMed1994

Fat embolism.

Explore the source record for details and available documents.

Adolescent↗
PubMed1990

Long-term, double-blind comparison of controlled-release albuterol versus sustained-release theophylline in adolescents and adults with asthma.

This parallel-group study compared the safety and efficacy of controlled-release albuterol versus sustained-release theophylline, both administered every 12 hours. One hundred twenty-four adolescent and adult patients with asthma and with chronic reversible obstructive airway disease were studied. All patients qualified with an FEV1 less than or equal to 80% of predicted (not receiving treatment) and greater than or equal to 15% reversibility in FEV1 or greater than or equal to 25% reversibility in FEF25-75% after inhaled isoproterenol. All patients were known to be able to take theophylline without unacceptable adverse effects. Theophylline was titrated for patients to receive, unblinded, theophylline serum concentrations of 10 to 20 micrograms/ml. With subsequent randomization, 62 patients continued to receive theophylline and 62 patients started taking albuterol in the 12-week, double-blind, double-dummy portion of the study. Pulmonary function was measured during a pretreatment visit (unmedicated) and serial assessment was made starting just before the morning dose and continuing for 12 hours after the dose at the end of 1, 6, and 12 weeks of treatment. Both treatment groups exhibited statistically significant increases in FEV1 from the pretreatment visit to all times of observation at weeks 1, 6, and 12. The increases in FEV1 were not significantly different between albuterol and theophylline administration. There was no evidence of tolerance to the bronchodilatory effect during 12 weeks in either treatment group. Only one patient in the study stopped treatment because of an adverse effect. This patient had tremor during albuterol administration. All other adverse events were tolerated or resolved during treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

Intravenous maintenance aminophylline dosage in patients with asthma on regular oral theophylline.

Intravenous maintenance aminophylline infusion rate can be calculated from the previously received equivalent oral dosage in children with chronic asthma with considerable accuracy. This method is expected to be more effective than that calculated from the body weight-based recommended guidelines. Reducing the intravenous aminophylline infusion rate in patients who have an upper respiratory infection is likely to reduce the risk of theophylline toxicity.

Administration, Oral↗
PubMed1978

Altered theophylline pharmacokinetics during acute respiratory viral illness.

The plasma half-life of theophylline was determined during and 1 month after serologically confirmed upper-respiratory-tract viral illness in six children with chronic asthma. In this group the plasma-theophylline half-life (mean = 419.8 min) was significantly longer during the acute stage of their illness than 1 month later (mean 249.9 min). There was no appreciable change in half-life in 4 patients who were febrile but in whom seroconversion did not occur. These preliminary results suggest that certain upper-respiratory-tract viral infections may affect theophylline metabolism.

Acute Disease↗
PubMed1978

Irreversibility of obstructive changes in severe asthma in childhood.

The findings in three children with severe asthma are presented. Following intensive round-the-clock therapy with theophylline (the dosage of which maintained serum levels of theophylline between 10 microgram/ml and 20 microgram/ml) and therapy with prednisone (20 mg twice daily for three weeks or more), there were improvements in spirometric and body plethysmographic measurements. Despite this therapy, abnormalities in the forced expiratory volume in one second, the maximal midexpiratory flow, the residual volume, and specific airway conductance remained. These cases represent a subgroup of asthmatic children with reactive airways who have an irreversible component to their disease.

Adolescent↗
PubMed1977

Variation in theophylline clearance rate with time in chronic childhood asthma.

Wide theophylline clearance rate (TCR) range between different individuals has been reported, but little is known about its change with the passage of time. Optimal theophylline therapy for asthma aimed at plasma or serum levels of 10 to 20 microng/ml is now strongly recommended. Significant TCR variability with time might easily result in theophylline levels in the toxic or subtherapeutic ranges. Thirty severe asthmatics (mean age, 13 yr) received 24 hr constant intravenous infusion of 1 mg/kg/hr aminophylline USP. TCR was determined after a steady state was reached. Twelve of these patients with persisting poorly controlled asthma underwent repeat infusion for TCR determination at intervals of 1 to 8 mo (mean, 4.7 mo). When these results were compared to the initial individual TCR, the mean absolute change was 28 +/- 24% (mean +/-SD). Thus, this significant individual variation in TCR with the passage of time (p less than 0.01) requires periodic monitoring of plasma theophylline levels in severe asthma treated by optimized theophylline dosage.

Adolescent↗
PubMed1977

Monovalent influenza A/New Jersey/76 virus vaccines in asthmatic children: pulmonary function and skin tests for allergy.

Eighty-eight asthmatic children aged six to 16 years received monovalent influenza A/New Jersey/76 virus vaccines. Forty-one of these children were given skin tests for allergy to eggs and vaccines, and 57 were given pulmonary function tests before and after immunization. Only four children reacted to the vaccines in the skin tests, with three of these children reacting to only one of four test preparations. Only two of the four children showed a correlation between reactivity to vaccine and allergy to egg antigens. No significant changes in pulmonary function were demonstrated.

Adolescent↗
PubMedDate not supplied

Subclavian arterial injury associated with blunt trauma.

Blunt subclavian artery trauma is an uncommon but challenging surgical problem. The purpose of this study was to retrospectively review the management of blunt subclavian artery injuries treated by the Trauma and Vascular Surgery Services at the East Tennessee State University-affiliated hospitals between 1992 and 1998. Six patients with seven blunt subclavian artery injuries were identified. Physical signs indicating blunt subclavian artery injury were pain or contusion around the shoulder joint; fractures of the clavicle, scapula, or ribs; periclavicular hematomas; and ipsilateral pulse or neurologic deficits. Seven subclavian artery injuries were treated-two arterial transections, two pseudoaneurysms, and three intimal dissections. Associated injuries included four clavicle fractures, one humerus fracture, one combined rib and scapular fractures, and two pneumothoraxes. Vascular surgical treatment included three primary arterial repairs, two saphenous vein interposition grafts, and one polytetrafluoroethylene (PTFE) graft. One patient was treated nonoperatively with anticoagulation. No deaths occurred. Morbidity occurred in two patients with chronic upper extremity neuropathy producing prolonged disability from pain and weakness; one patient had reflex sympathetic dystrophy, and the other had a brachial plexus injury. In conclusion, blunt subclavian artery trauma can be successfully managed with early use of arteriography and prompt surgical correction by a variety of vascular techniques. Vascular morbidity is usually low, but long-term disability because of chronic neuropathy may result from associated brachial plexus nerve injury despite a successful arterial repair.

Accidents, Traffic↗