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Biomedical subjects

J L Allen

Publications and source records attributed to J L Allen.

At least 19 recordsLinked to original sources
PubMed1995

Developmental changes in chest wall compliance in infancy and early childhood.

Development of chest wall stiffness between infancy and adulthood has important consequences for respiratory system function. To test the hypothesis that there is substantial stiffening of the chest wall in the first few years of life, we measured passive chest wall compliance (Cw) in 40 sedated humans 2 wk-3.5 yr old. Respiratory muscles were relaxed with manual ventilation applied during the Mead-Whittenberger technique. Respiratory system compliance (Crs) and lung compliance (Cl) were calculated from airway opening pressure, transpulmonary pressure, and tidal volume. Cw was calculated as 1/Cw = 1/Crs - 1/Cl during manual ventilation. Mean Cw per kilogram in infants < 1 yr old was significantly higher than that in children > 1 yr old (2.80 +/- 0.87 vs. 2.04 +/- 0.51 ml.cmH2O-1.kg-1; P = 0.002). There was an inverse linear relationship between age and mean Cw per kilogram (r = -0.495, slope -0.037; P < 0.001). In subjects with normal Cl during spontaneous breathing, Cw/spontaneous Cl was 2.86 +/- 1.06 in infants < 1 yr old and 1.33 +/- 0.36 in older children (P = 0.005). We conclude that in infancy the chest wall is nearly three times as compliant as the lung and that by the 2nd year of life chest wall stiffness increases to the point that the chest wall and lung are nearly equally compliant, as in adulthood. Stiffening of the chest wall may play a major role in developmental changes in respiratory system function such as the ability to passively maintain resting lung volume and improved ventilatory efficiency afforded by reduced rib cage distortion.

Aging↗
PubMed1994

A comparison of three semi-selective media for the isolation of methicillin-resistant Staphylococcus aureus.

During the 1980s the emergence of multiple antibiotic-resistant strains of Staphylococcus aureus posed new problems for infection control worldwide, many of which still remain. In investigations of outbreaks of infection, the laboratory has a key role in identifying infected or colonised patients and staff. The rapid isolation and accurate identification of the causative organisms are essential for the implementation of appropriate control measures. Speed and accuracy in identification, by colonial morphology, is often difficult to achieve in the presence of a mixed population of commensal bacteria. To this end, the sensitivity of three media for the isolation of methicillin-resistant S. aureus (MRSA) from simulated clinical specimens was compared. Initial colonial recognition of MRSA was enhanced on methicillin-milk agar when compared with that on other media.

Culture Media↗
PubMed1994

Effects of CPAP on lung mechanics in infants with acquired tracheobronchomalacia.

Continuous positive airway pressure (CPAP) has been used in the treatment of infants with tracheobronchomalacia (TBM). However, the effects of CPAP on lung mechanics in these infants are unknown. We hypothesized that CPAP prevents airway collapse and improves forced exhalation. We studied respiratory mechanics of nine infants (age 15 +/- 3 mo, SEM) with acquired TBM documented by bronchoscopy, during quiet respiration and forced exhalation, using the esophageal balloon and rapid thoracic compression techniques, respectively. Measurements were made when infants received no CPAP and repeated when 5 and 8 cm H2O CPAP were applied to the airway opening via a modified Mapleson anesthesia circuit. Expiratory resistance (RL), midexpiratory tidal flow (VE50), and maximal flow at functional residual capacity (Vmax FRC) were compared at each level of CPAP. Vmax FRC increased threefold from baseline to 8 cm H2O CPAP (p < 0.005). In contrast, there was no difference in expiratory RL or in VE50 at any level of CPAP. These data suggest that in infants with acquired TBM, assessments of forced expiratory flow reflect the amount of CPAP necessary to prevent airway collapse during forced exhalation better than can measurements of tidal mechanics.

Airway Resistance↗
PubMed1993

Chest wall motion before and during mechanical ventilation in children with neuromuscular disease.

Patients with neuromuscular disease can display paradoxic motion of the rib cage (RC) and abdomen (AB), which increases the work of breathing and predisposes to respiratory muscle fatigue. Long-term mechanical ventilation can reverse chronic hypercapnea and decrease the work of breathing in these patients. Changes in chest wall motion (CWM) that occur during mechanical ventilation have not been studied. We have assessed CWM using a calibrated respiratory inductive plethysmograph before and during mechanical ventilation in 5 children and young adults with neuromuscular disease and paradoxic breathing at rest. Asynchrony of CWM was quantitated by measuring the phase shift, theta, between RC and AB motion (0 degree = synchronous motion, 180 degrees = paradoxic motion). The volume contribution of the paradoxing compartment to tidal volume (PC/VT) was calculated. Before mechanical ventilation, mean +/- SEM VT was 122 +/- 17 mL, theta was 131 +/- 15 degrees C, and PC/VT was -27 +/- 6%. During mechanical ventilation, VT increased to 274 +/- 47 mL (P < 0.05), theta decreased to 41 +/- 14 degrees (P < 0.05), and PC/VT increased to +39 +/- 9% (P < 0.02). We conclude that mechanical ventilation improves RC/AB asynchrony and reverses the negative contribution to tidal volume of the paradoxing compartment in children and young adults with neuromuscular disease. This implies that mechanical ventilation assumes most or all the role of the respiratory pump in these patients, which provides a rationale for the use of chronic or nighttime ventilation in the treatment of respiratory muscle fatigue. Assessment of CWM may be useful in the determination of optimal ventilator settings in this population.

Abdomen↗
PubMed1992

The source of belief bias effects in syllogistic reasoning.

In studies of the belief bias effect in syllogistic reasoning, an interaction between logical validity and the believability of the conclusion has been found; in essence, logic has a larger effect on unbelievable than on believable conclusions. Two main explanations have been proposed for this finding. The selective scrutiny account claims that people focus on the conclusion and only engage in logical processing if this is found to be unbelievable; while the misinterpreted necessity account claims that subjects misunderstand what is meant by logical necessity and respond on the basis of believability when indeterminate syllogisms are presented. Experiments 1 and 2 compared the predictions of these two theories by examining whether the interaction would disappear if only determinate syllogisms were used. It did, thus providing strong support for the misinterpreted necessity explanation. However, the results are also consistent with a version of the mental models theory, and so Experiment 3 was carried out to compare these two explanations. The mental models theory received strong support, as it did also in the follow-up Experiments 4 and 5. It is concluded that people try to construct a mental model of the premises but, if there is a believable conclusion consistent with the first model they produce, then they fail to construct alternative models.

Adult↗
PubMed1992

Mammography knowledge and intentions among insured women.

UNLABELLED: METHOD. A survey was conducted among 1,113 randomly selected insured state university employees to evaluate knowledge of the American Cancer Society mammography guidelines, awareness of insurance coverage for screening mammograms, previous guideline adherence, and future mammography intentions. RESULTS: The survey, which included two mailings with follow-up phone cells of nonresponders, had a refusal rate of 6%. Respondents were relatively more likely to know the guideline for older age groups; 77% knew the guidelines for women 50+. Over one-third of the responders were not aware that their insurance policy covered screening mammograms. For women who had never had a mammogram, insurance knowledge was significantly related to intentions to have a mammogram in the future. Previous screening adherence, as well as future intentions, was positively related to the age of the respondent. The results are contrasted with those of previous studies, and the implications for the content of future breast cancer screening campaigns are discussed.

Adult↗
PubMed1992

Effect of position on the mechanical interaction between the rib cage and abdomen in preterm infants.

To determine the influence of body position on chest wall and pulmonary function, we studied the ventilatory, pulmonary mechanics, and thoracoabdominal motion profiles in 20 preterm infants recovering from respiratory disease who were positioned in both the supine and prone position. Thoracoabdominal motion was assessed from measurements of relative rib cage and abdominal movement and the calculated phase angle (an index of thoracoabdominal synchrony) of the rib and abdomen Lissajous figures. The ventilatory and pulmonary function profiles were assessed from simultaneous measurements of transpulmonary pressure, airflow, and tidal volume. The infants were studied in quiet sleep, and the order of positioning was randomized across patients. The results demonstrated no significant difference in ventilatory and pulmonary function measurements as a function of position. In contrast, there was a significant reduction (-49%) in the phase angle of the Lissajous figures and an increase (+66%) in rib cage motion in prone compared with the supine position. In addition, the degree of improvement in phase angle in the prone position was correlated to the severity of asynchrony in the supine position. We speculate that the improvement in thoracoabdominal synchrony in the prone position is related to alterations of chest wall mechanics and respiratory muscle tone mediated by a posturally related shift in the area of apposition of the diaphragm to the anterior inner rib cage wall and increase in passive tension of the muscles of the rib cage. This study suggests that the mechanical advantage associated with prone positioning may confer a useful alternative breathing pattern to the preterm infant in whom elevated respiratory work loads and respiratory musculoskeletal immaturity may predispose to respiratory failure.

Abdominal Muscles↗
PubMed1992

Increased respiratory drive and limited adaptation to loaded breathing in bronchopulmonary dysplasia.

Ventilatory parameters and respiratory drive with and without an added acute resistive load were assessed in 11 healthy preterm infants and 11 infants with bronchopulmonary dysplasia (BPD). Lung mechanics (breathing frequency, tidal volume, minute ventilation, compliance, and resistance) were determined with esophageal manometry and pneumotachography. Respiratory drive was assessed by determining the airway pressure measured 100 ms after the onset of an inspiratory effort against an occlusion. Infants were studied at baseline and with an external inspiratory resistive load of 213.7 cm H2O/L/s. Infants with BPD had similar breathing frequency, tidal volume, and minute ventilation, lower compliance, and greater resistance and airway pressure at 100 ms than healthy preterm infants at rest. With loading, healthy preterm infants demonstrated increased airway pressure at 100 ms, whereas infants with BPD showed no change. Although the healthy preterm infants had decreased minute ventilation and tidal volume with loading, decreases in ventilation were greater in the infants with BPD. These data demonstrate that infants with BPD have responded to a chronic intrinsic load with increased drive. However, this may result in decreased ventilatory reserve and hence, a limited ability to adapt to acute pulmonary loads.

Airway Resistance↗
PubMed1992

Effects of inspiratory resistive loading on chest wall motion and ventilation: differences between preterm and full-term infants.

The ability to maintain effective tidal volume and minute ventilation during resistive loaded breathing depends on both adequate central neural respiratory output response and respiratory system mechanical properties such as respiratory muscle strength and chest wall stability. We hypothesized that chest wall instability limits the ability of the preterm (PT) infant to respond to inspiratory resistive loading (IRL) compared with full-term (FT) infants. To test this hypothesis, we subjected eight FT and 10 PT infants to IRL with loads of 1.3, 2, and 6 times intrinsic lung resistance and measured steady state tidal volume (VT), minute ventilation (VE), and chest wall motion. Thoracoabdominal asynchrony was measured by respiratory inductive plethysmography and quantitated by measuring the phase angle, theta, between rib cage and abdominal motion (0 degrees = synchronous motion, 180 degrees = paradoxic motion). At baseline, VT/kg (mL/kg, mean +/- SEM) was similar between PT (7.0 +/- 0.7) and FT (7.5 +/- 0.5) infants. VE/kg (mL/min/kg) was greater in PT (545 +/- 50) than in FT (385 +/- 33) infants (p < 0.05) as a result of increased respiratory frequency in the former. PT infants demonstrated significantly greater chest wall asynchrony (theta = 38 +/- 9 degrees) than FT infants (theta = 9 +/- 3 degrees) (p < 0.01). With the highest resistive loads, VT decreased significantly in the PT but not the FT infants. Furthermore, during IRL, VE decreased to 417 +/- 50 mL/min/kg (p < 0.05) and theta increased to 56 +/- 7 (p < 0.05) in the PT infants, whereas no significant change in either value was observed in the FT group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1992

Immobilization of giant Chacoan peccaries (Catagonus wagneri) with a tiletamine hydrochloride/zolazepam hydrochloride combination.

A tiletamine/zolazepam combination was used to immobilize 24 captive giant Chacoan peccaries (Catagonus wagneri) at a mean dosage rate of 2.18 mg/kg (SD = 0.46) of body weight, given intramuscularly. The mean induction time (the time from injection until recumbency) was 7.6 min (SD = 2.1). Standing time (the time from injection until the peccary stood without stimulation or assistance) ranged from 90 to 240 min. Tiletamine/zolazepam in combination was an effective and safe immunobilizing agent for giant Chacoan peccaries.

Animals↗
PubMed1992

A modified Ziehl-Neelsen stain for mycobacteria.

For the preliminary detection of mycobacteria in routine pathology specimens heavy reliance is placed on staining methods. Difficulties encountered with a cold-staining method, which had possibly gone un-noticed for several years despite a quality control check programme, are described. An alternative to the 'classical' Ziehl-Neelsen stain is described, which although devised initially as a 'stop-gap' is still in use eight years later.

Evaluation Studies as Topic↗
PubMed1991

Interaction between chest wall motion and lung mechanics in normal infants and infants with bronchopulmonary dysplasia.

Asynchronous or paradoxic motion between the rib cage and abdomen may be seen in infants with lung disease. We have recently shown that after bronchodilator administration, the degree of asynchrony decreases proportionately to the improvement in lung mechanics. However, whether such thoraco-abdominal asynchrony (TAA) is a useful indicator of lung function in a cross-sectional population, i.e., whether asynchrony correlates with baseline lung mechanics, is unknown. Therefore, we quantitated the degree of TAA using respiratory inductive plethysmography during quiet sleep in ten infants with bronchopulmonary dysplasia (BPD) and six weight-matched control infants. We displayed abdominal wall (AB) and rib cage (RC) motion on an X-Y recorder, and from the tidal breathing loop we calculated a phase angle phi, between 0 degrees and 180 degrees as an index of asynchrony (synchronous RC/AB motion = 0 degrees, paradox = 180 degrees). Lung resistance (RL) and compliance/kg (CL/kg) were calculated from esophageal and mouth pressure, tidal volume, and tidal flow. As expected, BPD infants had abnormally high RL, and low CL/kg when compared to controls. All infants with BPD displayed marked thoraco-abdominal asynchrony (phi = 102 +/- 16 degrees, mean +/- SEM; range 35 degrees-160 degrees) with controls displayed synchronous chest wall motion (phi = 8 +/- 3 degrees, range 0 degrees-15 degrees) (P less than 0.001). The degree of TAA was significantly correlated with RL (r = 0.773, P less than 0.001) and inversely correlated with CL/kg (r = -0.67, P less than 0.01). We conclude that in infants of similar weight, TAA may be used as a cross-sectional index reflecting both resistive and elastic properties of the lungs.

Abdominal Muscles↗
PubMed1991

Metabolism and elimination of benzocaine by rainbow trout, Oncorhynchus mykiss.

1. Branchial and urinary elimination of benzocaine residues was evaluated in adult rainbow trout, Oncorhynchus mykiss, given a single dorsal aortic dose of 14C-benzocaine hydrochloride. 2. Branchial elimination of benzocaine residues was rapid and accounted for 59.2% of the dose during the first 3 h after dosing. Renal elimination of radioactivity was considerably slower; the kidney excreted 2.7% dose within 3 h and 9.0% within 24 h. Gallbladder bile contained 2.0% dose 24 h after injection. 3. Of the radioactivity in radiochromatograms from water taken 3 min after injection, 87.3% was benzocaine and 12.7% was N-acetylated benzocaine. After 60 min, 32.7% was benzocaine and 67.3% was N-acetylated benzocaine. 4. Of the radioactivity in radiochromatograms from urine taken 1 h after dosing, 7.6% was para-aminobenzoic acid, 59.7% was N-acetylated para-aminobenzoic acid, 19.5% was benzocaine, and 8.0% was N-acetylated benzocaine. The proportion of the radioactivity in urine changed with time so that by 20 h, 1.0% was para-aminobenzoic acid and 96.6% was N-acetylated para-aminobenzoic acid. 5. Benzocaine and a more hydrophobic metabolite, N-acetylated benzocaine, were eliminated primarily through the gills; renal and biliary pathways were less significant elimination routes for benzocaine residues.

Animals↗
PubMed1991

Prostaglandins and the colonic epithelium. Effects of misoprostol on crypt size, cell production, and cell migration in the dog.

Colonic epithelial cell division, cell migration, and cell transit were investigated in dogs given 300 micrograms.kg-1.day-1 of the prostaglandin E1 analogue, misoprostol, for 11 weeks. The animals were then injected with [3H]thymidine and killed at timed intervals. The distribution of labeled and mitotic cells within the crypts was determined by scoring autoradiographs. There were no significant differences in mitotic index or labeling index between the two groups. The data were pooled and converted to give crypt cell production rates of 51.1 +/- 11.1 (control) and 58.24 +/- 8.6 cells per crypt per hour (test). However, the crypt length and cell population were slightly, but significantly, greater in the misoprostol-treated group (P less than 0.01). The movement of the wave of labeled cells with time after injection was used to calculate the median cell migration rates, which were 23.50 +/- 3.03 cell positions per day (control) and 18.30 +/- 2.56 (test). Thus, misoprostol had no significant effect on either the cell migration rate or the transit rates.

Animals↗
PubMed1990

Effects of misoprostol on cell migration and transit in the dog stomach.

Prostaglandins of the E series increase stomach mucosal mass by inducing hyperplasia, which could be the result either of increased cell production or of decreased cell loss. This report describes an investigation of the effect of the prostaglandin E1 analogue, misoprostol, on cell migration and transit. 3H-thymidine was used to label those cells synthesizing deoxyribonucleic acid in dogs that had been given an oral dose of 300 micrograms/kg per day misoprostol for 11 weeks. The animals were killed at timed intervals, and tissue from the gastric fundus was prepared for autoradiography. The distribution of labeled cells at various times after labeling was used to follow the movement of the wave of label and to calculate median cell migration rates and transit times. The migration rate of cells toward the gastric lumen was significantly increased from 1.4 +/- 0.3 to 3.6 +/- 0.6 cell positions per day in the misoprostol-treated group (p less than 0.001); however, the gland length (from the most basal mucous neck cell to the luminal surface) was also increased (from 52.1 +/- 1.1 to 74.0 +/- 1.6; p less than 0.001), thus there was no significant difference in the (transit) time taken for cells to reach the top of the gland (control, 17.5 +/- 9.8 days; test, 12.2 +/- 7.1 days).

Alprostadil↗