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Biomedical subjects

W J Davis

Publications and source records attributed to W J Davis.

At least 55 records · Page 3Linked to original sources
PubMed1981

Comparison of new triton X-100- and tween-ether-treated split-treated vaccines in children.

Split-product vaccines (SPVs) combine the desirable properties of no systemic reactogenicity and adequate immunogenicity when two doses are given. We compared a new Triton X-100 SPV (Connaught Laboratories, Inc.) with the commercially available Tween-ether SPV (Parke-Davis & Co.) in 76 children and young adults 2 to 25 years old; there were 39 and 37, respectively, in each vaccine group. Both vaccines contained influenza A/Brazil/78, A/Texas/77, and B/Hong Kong/72 (7 microgram of hemagglutinin for each strain); two doses were administered 1 month apart. Among persons seronegative by the hemagglutination inhibition test, the geometric mean antibody titers rose to approximately 100 after the first vaccination for influenza A/Brazil/78 and A/Texas/77. For B/Hong Kong/72, however, seronegative recipients developed lower geometric mean titers of approximately 32 after one immunization. Against the new B/Singapore/79 strain neither SPV stimulated adequate cross-reacting hemagglutination inhibition antibody (geometric mean titers of approximately 10). In conclusion, the new Triton X-100 SPV appears to be comparable to the ether-treated SPV in primed subjects. Further studies in unprimed children should be done to confirm this impression. In addition, it would be advisable to study other dosage regimens in unprimed children with these SPVs.

Adolescent↗
PubMed1980

Influenza vaccine in unprimed children: improved immunogenicity with few reactions following one high dose of split-product vaccine.

Thirty-one unprimed children and young adults received an influenza A/USSR/77 vaccine containing 43 microgram of hemagglutinin. Their HAI antibody response was compared to that in 92 age-matched individuals from the 1978 national influenza immunization trial who received 10 and 4 microgram HA vaccines. A dose-related antibody response was observed after the first vaccine doses in the 7- to 12- and 13- to 25-year-old groups. An HAI titer greater than or equal to 40 was present in 81% and 93% of 43 microgram HA recipients, in 38% and 43% of 10 microgram HA recipients, and in 24% and 12% of 4 micrograms HA recipients respectively. The antibody response to the 43 microgram HA dose was significantly higher than was the response to the 10 and 4 microgram HA doses. The local and systemic side effects were not significantly different among the three vaccine groups and the placebo group. Thus, a high dose of influenza A/USSR/77 split-product vaccine given to unprimed children and young adults stimulated presumably protective levels of antibody and was free of a significant incidence of side effects.

Adolescent↗
PubMed1980

Action-potential broadening and endogenously sustained bursting are substrates of command ability in a feeding neuron of Pleurobranchaea.

1. The ventral white cells (VWC's) of the buccal ganglion of Pleurobranchaea, so named for their position and color, are a bilateral pair of neuron somata. Each sends a single axon out its contralateral stomatogastric nerve and has a dendritic field originating close to the soma. 2. The vwcs exhibit spontaneous episodes of prolonged depolarization (duration 1--4 min) accompanied by repetitive action-potential activity and separated by regular intervals of 3--30 min. Such prolonged burst episodes can be triggered by short pulses of depolarizing current. During the repetitive activity of the spontaneous bursts or that driven by imposed depolarization, the action potentials progressively broaden to 5--16 times their initial duration. 3. During spontaneous bursting or activity driven by imposed depolarization, the cyclic motor output of the feeding network is initiated or accelerated with a latency corresponding with the development of appreciable VWC spike broadening. When broadening of antidromic VWC spikes is suppressed by imposed hyperpolarization of the soma, the frequency of feeding cycles is significantly lower than when broadened spikes are allowed to develop. When trains of spikes are driven by depolarizing current, the motor output of the feeding network is not initiated until the VWC spikes have broadened to a repeatable "threshold" duration, regardless of the intensity of the depolarizing current. 4. The endogenous production of prolonged burst episodes, triggered by depolarizing current pulses, and progressive spike broadening can be demonstrated in the surgically isolated VWC soma. 5. The paired VWCs are strongly electrically coupled and display highly synchronous activity. They receive synaptic inputs from many previously identified interneurons of the feeding network and are thus reciprocally coupled within the network. 6. These results demonstrate that the capacity of this neuron to generate broadened action potentials during repetitive activity confers the ability to command coordinated motor-network output. The appropriate repetitive activity can be produced endogenously in the form of prolonged bursts of spikes.

Action Potentials↗
PubMed1980

Effect of dietary protein and carbohydrate on theophylline metabolism in children.

Theophylline metabolism can be altered by a variety of abnormal physiologic states as well as by exogenous factors. Adult studies demonstrate a significant influence of dietary composition on theophylline biotransformation. To examine this effect of diet, 14 children with bronchial asthma were studied during long-term theophylline administration. Each patient was maintained for 12 days on three separate diets with varying proportions of protein and carbohydrate and with constant calories and fat. Results showed significant differences in drug half-life and metabolic clearance rate parameters. Compared to the normal diet, high protein diet markedly decreased the half-life, and high carbohydrate diet greatly prolonged it (P < .001). Multiple regression analysis demonstrated these differences to correlate only with the dietary alterations. Adverse reactions and blood chemistry abnormalities were not detected during any test period. These findings firmly establish that nutritional factors exert a significant influence on theophylline pharmacokinetics in children.

Adolescent↗
PubMed1978

Command neurons in Pleurobranchaea receive synaptic feedback from the motor network they excite.

Command neurons that cause rhythmic feeding behavior in the marine mollusc Pleurobranchaea californica have been identified in the cerebropleural ganglion (brain). Intracellular stimulation of single command neurons in isolated nervous systems, semi-intact prepartions, and restrained whole animals causes the same rhythmic motor output pattern as occurs during feeding. During this motor output pattern, action potentials recorded intracellularly from the command neurons occur in cyclic bursts that are phase-locked with the feeding rhythm. This modulation results from repetitive, alternating bursts of excitatory and inhibitory postsynaptic potentials, which are caused at least in part by synaptic feedback to the command neurons from identified classes of neurons in the feeding network. Central feedback to command neurons from the motor network they excite provides a possible general physiological mechanism for the sustained oscillation of neural networks controlling cyclic behavior.

Action Potentials↗
PubMed1978

Neural correlate of behavioral plasticity in command neurons of Pleurobranchaea.

Food stimuli normally excite the command neurons of Pleurobranchaea that cause feeding. In contrast, the same food stimuli selectively inhibit these neurons in specimens that have been trained to suppress feeding and withdraw from food by means of an avoidance conditioning paradigm consisting of paired food and conditional shock. Food stimuli excite the feeding command neurons of yoked control specimens exposed to unpaired food and shock, but inhibit the feeding command neurons of untrained specimens that have been satiated with food. These results suggest that the command neurons serve as a neural locus at which an animal's behavior is modulated by past experiences. These results also establish a neural correlate of behavioral plasticity, in the form of synaptic inhibition of the command neurons.

Action Potentials↗
PubMed1977

Behavioral choice: neural mechanisms in Pleurobranchaea.

In the marine mollusk Pleurobranchaea, it is known that feeding occurs and withdrawal from tactile stimuli is suppressed when the sensory stimuli for feeding and withdrawal are presented simultaneously. This "dominance" of feeding behavior over withdrawal behavior occurs because the central nervous network controlling feeding inhibits the central nervous network controlling withdrawal. The inhibition is mediated by a bilaterally symmetrical pair of reidentifiable feeding neurons that are members of the "corollary discharge" population in the buccal ganglion. This study supports the hypothesis that inhibitory interactions between competing motor systems are responsible for the "singleness of action" that characterizes animal behavior.

Animals↗
PubMed1977

Terbutaline in the treatment of status asthmaticus.

The effect of administration of terbutaline on the pulmonary and cardiovascular systems was studied in ten children with status asthmaticus. Terbutaline (0.01 to 0.04 mg/kg of body weight) was given subcutaneously in multiple doses. A significant decrease in respiratory rate and in arterial blood pressure, with no significant change in cardiac rate, was seen only after the first dose of terbutaline. There was a decrease in mean arterial carbon dioxide tension and an increase in mean arterial oxygen pressure. There was gross clinical improvement following administration of terbutaline in nine of the ten patients. One patient who failed to respond to administration of terbutaline also failed to respond to intravenously administered isoproterenol. We conclude that terbutaline is effective in the treatment of status asthmaticus, with only modest effects on the cardiovascular system.

Adolescent↗
PubMed1977

Terbutaline in the treatment of acute asthma in childhood.

Forty-eight children with known asthma (ranging in age from 2 to 16 years) were studied during an acute attack. Each received either terbutaline or epinephrine subcutaneously in a random double-blind fashion. Measurement of heart rate, respiratory rate, and systemic arterial systolic and diastolic blood pressures and careful clinical assessment of obstruction of the airway were made before and at 15, 30, and 60 minutes after the administration of the drugs. Appreciable and significant clinical improvement was noted in 19 of the 24 patients in both groups and was of comparable magnitude. A small, but significant, increase in heart rate was noted in those patients requiring only one injection of terbutaline, suggesting that the drug's selectivity for the lung is relative not absolute. The present study demonstrates that terbutaline is an effective bronchodilator drug in acute childhood asthma.

Acute Disease↗
PubMed1976

Treatment of asthma with theophylline and beta adrenergic agents.

The understanding of the properties of adrenergic receptors and modification of ring and the N-alkyl side chain constituents have resulted in adrenergic agents with a high degree of specificity for the lung and few cardiac and central nervous system stimulating problems. These agents are useful by aerosol and oral routes, alone and in addition to theophylline for asthma. Theophylline, which acts to increase cyclic AMP by inhibition of phosphodiesterase and beta 2 adrenergic agents which increase cyclic AMP by stimulating adenylate cyclase, are the mainstays of asthma therapy. Therapy is usually begun with theophylline. Persistent symptoms with adequate theophylline levels (10-20 mug/ml) indicates the need for a beta 2 adrenergic agent by aerosol or orally as a supplement. Occasional patients will not tolerate theophylline in any preparation and can be treated with beta 2 adrenergic agents with success. The future holds great promise for improved and safer beta 2 adrenergic agents which will offer the physician a more effective means of treating asthma.

Adrenergic beta-Agonists↗
PubMed1973

Learning: classical and avoidance conditioning the mollusk Pleurobranchaea.

Naive specimens of the marine gastropod Pleurobranchaea withdraw from tactile stimulation of the oral veil and show feeding responses to food chemicals. Experimental subjects, trained by pairing touch (conditioned stimullus) with food chemicals (unconditioned stimulus), soon acquired a classically conditioned feeding response to touch alone. Control subjects that received touch alone or unpaired touch and food chemicals showed significantly fewer feeding responses to touch than did experimentals. Classically conditioned specimens were used for avoidance conditioning. Subjects that received aversive electrical stimulation when they did not withdraw from touch rapidly learned to withdraw rather than to feed in response to touch alone. Controls that received touch alone or unpaired touch and shock continued to exhibit the feeding response to touch alone. The learned responses persisted for up to 2 weeks without reinforcement before extinction, and could be demonstrated in the isolated nervous system.

Animals↗
PubMed1973

Development of locomotor patterns in the absence of peripheral sense organs and muscles.

The role of peripheral sense organs and muscles in specifying the circuitry of the central nervous system during ontogeny was tested in larval lobsters. Presumptive locomotor appendages, the abdominal swimmerets, were extirpated before their differentiation. Electrophysiological recordings made 2-4 weeks later from the corresponding motor nerves showed that, despite the absence of the target muscles and sense organs, normal reflexes and normal patterns of rhythmic locomotor output appeared in the swimmeret motoneurons at the usual developmental stage. Therefore, target muscles and sense organs are unnecessary to the differentiation of normal motor output patterns in this simple invertebrate locomotor system.

Action Potentials↗
PubMed1972

Locomotion: control by positive-feedback optokinetic responses.

Several species of arthropods perform forward locomotory movements when restrained in place and exposed to a pattern of stripes moving backward at normal locomotory velocities. Locomotory effort varies directly with stripe velocity. In nature such locomotory reactions would increase the visual stimulus that elicits them; hence, the reactions represent a new class of optokinetic responses employing positive visual feedback. Stabilizing mechanisms include response decrement during constant stripe velocities.

Animals↗