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Biomedical subjects

J L Allen

Publications and source records attributed to J L Allen.

At least 55 records · Page 3Linked to original sources
PubMed1989

Lipid aspiration pneumonia due to gastroesophageal reflux. A complication of nasogastric lipid feedings.

The development of lipid aspiration pneumonia after chronic nasopharyngeal installation of mineral oil was first described in 1925 by Laughlin. Since that time this entity has been well recognized and numerous substances have been identified or implicated as the aspirated material. The classic radiographic appearance of severe chronic lipid aspiration pneumonia has been described as consisting of intense perihilar infiltrates. However, the radiographic findings are more often non-specific and usually consist of varying degrees of diffuse interstitial infiltrates that tend to be more prominent in the perihilar regions and the right lung. We are reporting a case of biopsy-proven lipid aspiration pneumonia in an infant with known gastro-esophageal reflux (GER) who had medium-chain triglyceride oil administered via nasogastric tube. Serial roentgenograms demonstrated a changing pulmonary pattern from diffuse bilateral interstitial infiltrates initially to a diffuse alveolar pattern at the time of the lung biopsy. Modern medicine has developed new methods for providing nourishment to sick newborns and infants to improve their nutritional status and help them to grow. One such method involves the administration of medium-chain triglycerides (MCT oil) into the GI tract via a nasogastric or nasoenteral tube. The purpose of this report is to describe a significant complication of this method of providing nutrition to an infant with gastroesophageal reflux (GER) and the diagnostic dilemma it presented.

Dietary Fats↗
PubMed1989

Organization of the nuclear pore complex in Saccharomyces cerevisiae.

Fractions enriched for nuclear pore complexes (NPCs) have been isolated from Saccharomyces cerevisiae. The sequential extraction of nuclei with detergent, nucleases, and salt reveals an organization of the yeast NPC similar to other eukaryotes. Yeast NPCs contain a 30-nm "ring" structure not previously described in other organisms. This structure appears to organize 10-nm filaments into an assembly which exhibits an eight-fold rotational symmetry. Some proteins in the NPC fraction are capable of forming intermediate-sized filaments. These studies suggest that some component of the nuclear pore complex organizes an interaction between nuclear and cytoplasmic networks of intermediate filaments.

Microscopy, Electron↗
PubMed1989

Prostaglandins and the gastric epithelium: effects of misoprostol on gastric epithelial cell proliferation in the dog.

The effects of the methyl ester analogue of prostaglandin E1, misoprostol, on gastric epithelial cell proliferation were investigated in six dogs given 300 micrograms/kg/day of misoprostol orally for 11 weeks and in six control dogs given placebo for 11 weeks. Misoprostol treatment resulted in a 36% increase in stomach weight (p less than 0.01) and a 30% increase in the length (measured as the cell column count from the base/neck junction to the surface) of the fundic gastric glands (p less than 0.01). This mucosal hyperplasia was predominantly caused by enlargement of the foveolar region of the gland, with little change occurring in the neck or in the isthmus. The hyperplasia was the result of an increased number of mitotic (p less than 0.01) and DNA synthesising cells (p less than 0.05) in each gastric gland, which resulted in a significant increase in the gland cell production rate, from 22.5 to 42.6 cells per gland per day (p less than 0.05).

Alprostadil↗
PubMed1989

A comparison of preterm and adult airway smooth muscle mechanics.

To determine whether airway smooth muscle undergoes a maturational change regarding force generation, length-tension relationships were determined in isolated trachealis strips from adult and preterm sheep. At the length of maximum force generation, passive active and total tensions of the adult muscle were 2.5 times greater than preterm values (P less than 0.001). KCl stimulation yielded a greater peak tension in the adult strips than in the preterm strips (P less than 0.01). Preterm strips required higher concentrations of KCl to initiate contractions and higher concentrations to reach peak tension. Acetylcholine- (ACh) induced contraction resulted in greater force development at each dose in the adult strips compared with preterm strips (P less than 0.001). The dose of ACh required to reach a half-maximal response was significantly less for the adult strips than for the preterm strips (P less than 0.005). These data demonstrate that both force generation and receptor sensitivity increase with age. This inability of immature smooth muscle to generate as much force as adult smooth muscle may help explain why very preterm neonates requiring intermittent positive-pressure ventilation are at risk for developing structural airway problems.

Aging↗
PubMed1989

Congenital foramen of Bochdalek's hernia in an infant with obstructive jaundice.

A case of infantile obstructive jaundice caused by a right-sided foramen of Bochdalek's diaphragmatic hernia is reported. This association has not previously been reported in an infant. At operation, extrahepatic biliary obstruction was relieved by reduction of the contents of the hernia. This unusual presentation of a right-sided congenital diaphragmatic hernia underscores the usual diagnostic delay seen with such lesions.

Cholestasis, Extrahepatic↗
PubMed1988

Differential cholinergic influences on the immobility response in various strains of domestic fowl.

A series of five experiments examined the effects of two anticholinergic drugs, atropine and scopolamine, on the duration of tonic immobility (TI) and susceptibility to the TI response in both Production Red and White Leghorn chickens (Gallus gallus), in an attempt to resolve previous contradictory findings about the effects of cholinergic manipulations on tonic immobility. These two anticholinergic drugs significantly reduced the duration of TI and, therefore, supported the conclusion that cholinergic systems are involved with the immobility response. However, the effects of these drugs on TI differed depending on the age, strain, local population, and handling experience of the individual birds.

Aging↗
PubMed1988

Experimental arthritis induced by atypical strains of Streptococcus pyogenes.

Experimental arthritis was induced in Sprague-Dawley rats by intraarticular injection of whole-cell sonicates, heat-killed cells and cell-wall preparations of typical and atypical strains of Group-A streptococci (Streptococcus pyogenes). The non-haemolytic nitrosoguanidine-derived mutant and the naturally occurring Lowry strain induced a similar but less severe form of arthritis. Direct immunofluorescent staining demonstrated maximum fluorescence in the sections of articular joint taken 60 days after injection. The level of immune complexes increased for up to 90 days after injection of cell walls or whole-cell sonicates and correlated well with the development of the chronic stage of arthritis observed in haematoxylin and eosin and fluorescence staining of thin tissue sections.

Animals↗
PubMed1987

Long-term evaluation of esophageal and pulmonary function in patients with repaired esophageal atresia and tracheoesophageal fistula.

Patients who have undergone repair of esophageal atresia and tracehoesophageal fistula as infants have been noted to have residual esophageal dysmotility and pulmonary dysfunction during their childhood years. However, limited information is available about the long-term follow-up of these patients. In this study we performed esophageal and pulmonary function studies on 12 adults who had required surgical repair of these defects in the first week of life. Most patients had symptoms of dysphagia and heartburn at time of evaluation. Pathologic gastroesophageal reflux was documented in 67% of patients and esophagitis was noted in 34%. All patients had esophageal motility abnormalities characterized by low-amplitude nonperistaltic waves throughout most of the esophagus. In addition, although most patients had no respiratory symptoms, mild restrictive lung volumes were noted in many patients. However, airflow obstruction and airway hyperreactivity were not present. These data demonstrate that clinical symptoms and abnormal esophageal manometry and pulmonary function persist well into the third and beginning of the fourth decade after repair of esophageal atresia and tracheoesophageal fistula in infancy.

Adult↗
PubMed1987

Heterogeneity of mean alveolar pressure during high-frequency oscillations.

Mean alveolar pressure may exceed mean airway pressure during high-frequency oscillations (HFO). To assess the magnitude of this effect and its regional heterogeneity, we studied six excised dog lungs during HFO [frequency (f) 2-32 Hz; tidal volume (VT) 5-80 ml] at transpulmonary pressures (PL) of 6, 10, and 25 cmH2O. We measured mean pressure at the airway opening (Pao), trachea (Ptr), and four alveolar locations (PA) using alveolar capsules. Pao was measured at the oscillator pump, wherein the peak dynamic head was less than 0.2 cmH2O. Since the dynamic head was negligible here, and since these were excised lungs, Pao thus represented true applied transpulmonary pressure. Ptr increasingly underestimated Pao as f and VT increased, with Pao - Ptr approaching 8 cmH2O. PA (averaged over all locations) and Pao were nearly equal at all PL's, f's, and VT's, except at PL of 6, f 32 Hz, and VT 80 ml, where (PA - Pao) was 3 cmH2O. Remarkably, mean pressure in the base exceeded that in the apex increasingly as f and VT increased, the difference approaching 3 cmH2O at high f and VT. We conclude that, although global alveolar overdistension assessed by PA - Pao is small during HFO under these conditions, larger regional heterogeneity in PA's exists that may be a consequence of airway branching angle asymmetry and/or regional flow distribution.

Animals↗
PubMed1987

Positive effort dependence of maximal expiratory flow.

The maximal expiratory-flow volume (MEFV) curve in normal subjects is thought to be relatively effort independent over most of the vital capacity (VC). We studied seven normal males and found positive effort dependence of maximal expiratory flow between 50 and 80% VC in five of them, as demonstrated by standard isovolume pressure-flow (IVPF) curves. We then attempted to distinguish the effects of chest wall conformational changes from possible mechanisms intrinsic to the lungs as an explanation for positive effort dependence. IVPF curves were repeated in four of the subjects who had demonstrated positive effort dependence. Transpulmonary pressure was varied by introducing varied resistances at the mouth but effort, as defined by pleural pressure, was maintained constant. By this method, chest wall conformation at a given volume would be expected to remain the same despite changing transpulmonary pressures. When these four subjects were retested in this way, no increases in flow with increasing transpulmonary pressure were found. In further studies, voluntarily altering the chest wall pattern of emptying (as defined by respiratory inductive plethysmography) did however alter maximal expiratory flows, with transpulmonary pressure maintained constant. We conclude that maximal expiratory flow can increase with effort over a larger portion of the vital capacity than is commonly recognized, and this effort dependence may be the result of changes in central airway mechanical properties that occur in relation to changes in chest wall shape during forced expiration.

Adult↗
PubMed1986

Effect of tolazoline on xylazine-ketamine-induced anesthesia in turkey vultures.

Fifteen turkey vultures were each given xylazine (1 mg/kg of body weight, IM) and ketamine (10 mg/kg, IM). In 5 of the birds (controls), the mean (+/- SD) induction time was 5.4 +/- 1.0 minutes and the mean duration of anesthesia was 109.8 +/- 25.4 minutes. The remaining 10 vultures (test birds) were given tolazoline (15 mg/kg, IV) 45 minutes after administration of xylazine and ketamine. In the test birds, the mean induction time was 4.5 +/- 1.6 minutes and the mean duration of anesthesia was 49 +/- 2.1 minutes. After administration of tolazoline, the birds regained consciousness in 3.7 +/- 1.9 minutes and were standing with normal posture in 14.2 +/- 5.4 minutes. All birds remained moderately sedated yet ambulatory and responsive to stimuli for 30 to 60 minutes after tolazoline administration. Results indicated that tolazoline was useful in controlling the duration of xylazine-ketamine-induced anesthesia in turkey vultures.

Anesthesia↗