Donald J. Lewis

Effects of metaproterenol on pulmonary mechanics, oxygenation, and ventilation in infants with chronic lung disease

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

The cholinergic system, amnesia and memory☆

Abstract Three experiments are reported which attempt to manipulate memory through the cholinergic system. All animals learned a single-trial passive avoidance response followed immediately by ECS or Sham ECS. In the first, prostigmine was used to rule out the possibility that effects could be due to peripheral response mechanisms. In the second, physostigmine was administered either one or 24 hr or 7 days after ECS. Physostigmine had no effect on the ECS-produced amnesia, but when administered alone, 24 hr following learning, it produced a partial amnesia. In the third experiment, scopolamine was administered prior to learning and ECS. No drug effect was detected. All tests were conducted 24 hr following injection. When the effects of the drugs have dissipated at the time of test, no effect is noted. This suggests that previous effects, found with contemporary drug effects still present, are not relatively permanent and therefore not on memory.

Cue-dependent amnesia: Permanence and Memory Return

Abstract Rats were trained in an appetitive maze task. In the first experiment ECS was administered in the maze start box, goal box, or a neutral box 7 days atter criterion performance. Amnesia was selective only to animals given ECS in the maze start box. No spontaneous recovery of memory was observed. In the second experiment an amnesia was created in the maze goal box by first allowing the animals to run through the maze before administering ECS in the goal box. Some evidence was presented that a second treatment with ECS may produce a return of memory.

The relation between rectal and brain temperatures following hypothermia

The core temperatures and brain temperatures of rats were simultaneously tracked. Ice water immersion produces almost as marked a decrease in brain temperature as in core temperature. During the unaided recovery of normal temperatures following hypothermia, rectal and brain temperatures follow a parallel course.

Possible effects of the synthetic amino acid, L-ethionine, on memory in rats

Abstract Two experiments to explore the behavioral effects of injections of the synthetic amino acid L-ethionine indicated that this drug interferes with the performance of a learned passive avoidance response. Additionally, this deficit was found to occur in the absence of detectable changes in gross motor activity. Because this effect was found when the drug was injected near the time of training, but not when it was injected before testing, and because the effect was found to persist after the drug is believed to have been eliminated from the blood stream, the data were interpreted as reflecting a possible effect upon some aspect of memory functioning.

Sensitivity and reactivity to foot shock following electroconvulsive shock stimulation

Abstract Shock aversion, difference and tetanization thresholds were used as indicies of the rats sensitivity to foot shock at various temporal intervals after electroconvulsive shock (ECS) administration. Activity elicited by inescapable foot shock was used as a measure of the rats unconditioned reaction to foot shock. A single ECS was found to decrease the rats sensitivity only to low levels of foot shock at short intervals following its administration. On the other hand both excitatory and inhibitory effects of ECS on the rats unconditioned reaction to foot shock were noted. A decreased reaction to foot shock occurred between 45 and 90 min after ECS and was followed by a period of hyperreactivity 6–24 hr after ECS. These findings lend support to a stimulus change interpretation of the proactive effects of ECS particularly when the criterional response involves foot shock.

Amnesia for active avoidance.

Abstract Rats were given active avoidance training followed by ECS and were shown to be amnesic when tested by relearning or when tested by the acquisition of a conflicting passive avoidance task. Analysis of the relearning data showed that the amnesia was temporary, and therefore a retrieval deficit. Recovery from the amnesia during relearning appeared to mimic the reminder effect found in passive avoidance studies.

Theta EEG activity and memory processes in rats

Abstract Rodent EEG theta activity recorded in the 30 min period after ECS treatment has previously been correlated with passive avoidance retention. In the present experiment rats were trained and tested in an appetitive maze, thereby avoiding the possible confounding of footshock-produced EEG arousal. Our results produced the same relationship between theta and retention, but since ECS was given 7 days after training, we conclude that theta activity is not related only to memory consolidation. Patterns of theta during reinstatement were also found to be more similar to the pattern recorded late in learning when the reinstatment took place in the original start box. The data support the notion of cue-dependent amnesia, and the hypothesis that ECS acts by inhibiting the memory which is active at the time of ECS.

TRANSCUTANEOUS PO2 AND PCO2 OBTAINED BY A SINGLE DUAL PROBE IN NEWBORN INFANTS

Transcutaneous measurements of PO2 and PCO2 are routinely used for blood gas monitoring of sick neonates; however, simultaneous measurements require the use of two separate skin probes each needing periodic calibration and site rotation. Thus, prolonged transcutaneous measurements of PO2 and PCO2 interfere with the principle of minimal handling of the tiny premature neonate. To overcome this difficulty, we have evaluated a single dual probe for use in the newborn. The probe consists of 2 distinct electrodes separated by a barrier while utilizing a common electrolyte and covering membrane, with a reference electrode of only 5.6 mm in diameter. The accuracy of the probe was evaluated by 55 simultaneous transcutaneous and arterial PO2 and PCO2 measurements obtained from 9 newborn infants, BW 510 to 4200 gm, GA 27 to 41 wks, in respiratory distress. Close correlations were obtained for both transcutaneous PO2 (r=0.86) and PCO2 (r=0.87) and their corresponding arterial measurements (p<0.001). It is possible to measure transcutaneous PO2 and PCO2 with a single dual probe with comparable accuracy to that obtained from separate probes. Both the handling of the infant and the number of skin sites necessary to obtain transcutaneous blood gas values are reduced by half as a result.