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Biomedical subjects

J L Allen

Publications and source records attributed to J L Allen.

At least 73 records · Page 4Linked to original sources
PubMed1986

Pulmonary function in older children and young adults with gastroesophageal reflux.

A wide variety of types of pulmonary diseases and respiratory symptoms have been associated with gastroesophageal reflux (GER). Asthma, chronic bronchitis, bronchiectasis, and pulmonary fibrosis have all been linked to GER, but causal mechanisms have been difficult to establish. To characterize pulmonary function abnormalities in older children and young adults (age 7-23 years) with GER, lung function was evaluated in 22 patients being treated for reflux. The patients were divided into two groups: nine subjects (Group 1) had no history of pulmonary symptoms. Thirteen subjects (Group 2) had known pulmonary disease; all had diagnosed asthma, and five had a history of recurrent pneumonia. Lung volumes and spirometry were measured. Airway reactivity was assessed by measuring change in flows following isocapneic hyperventilation of subfreezing air. The presence of "small airway" disease was assessed by air-helium flow volume curves and the single breath oxygen test. Lung size, as indicated by measurement of total lung capacity, was normal in all patients. Flow rates, density dependence of maximal expiratory flow, single breath oxygen test, and tests of airway reactivity were abnormal only in Group 2 patients and were normal in the Group 1 patients. That not all children with GER have abnormal pulmonary function suggests that, if there is a causal relationship between GER and lung disease, it is multi-factorial in nature. Children with GER who do have lung disease have evidence of airway obstruction, maldistribution of ventilation, and increased airway reactivity, but do not have restricted lung volumes.

Adolescent↗
PubMed1986

Fate and distribution studies of some drugs used in aquaculture.

Residue concentrations of drugs that are administered to fish by bath immersion are related primarily to passage of the drugs across the gills. The elimination of these chemicals by fish can be mediated by biotransformation, but the route of elimination depends on physical characteristics of the chemicals or on their biotransformation products. Uptake of the anesthetics tricaine methanesulfonate, benzocaine, Piscaine, and quinaldine is rapid because they are lipophilic. Loss of their residues also is rapid after the fish are removed from anesthetic solutions because the gradient of concentration favors passage back across the gills. Among therapeutants, uptake and loss of malachite green residues in fish follow the same general pattern as the anesthetics, although at much slower rates; the residues accumulate in the eggs of gravid female salmon after treatment and are detectable in eggs and newly hatched fry. In fish treated with formalin, residues of formaldehyde cannot be detected by currently available analytical methodology. Sulfonamides are metabolized in fish by acetylation and conjugation; however, the free form of the drug appears to be eliminated more rapidly than the acetylated form.

Aminobenzoates↗
PubMed1986

A random survey of leprosy in wild nine-banded armadillos in Louisiana.

On the basis of the finding that lepromatous granulomas were almost always seen in the ears of armadillos with disseminated leprosy, a random survey of the prevalence of the disease among wild armadillos in the state of Louisiana, U.S.A., was conducted by examining histopathologically both ears of armadillos killed on the roads by automobiles. Ten (2%) of the 494 animals examined had disseminated leprosy. If a killed lepromatous armadillo releases up to 10 Mycobacterium leprae into the environment, the importance of the event to the epidemiology of leprosy must be considered.

Animals↗
PubMed1986

Thorns in armadillo ears and noses and their role in the transmission of leprosy.

Both ears from 494 wild nine-banded armadillos (Dasypus novemcinctus) and nose specimens from 224 animals were collected and histopathologically studied. Lepromatous granulomas were present in the ear specimens of ten of 494 animals. There were thorns in the ears of 22.5% of animals, and in 36.6% of the nose specimens. In one armadillo, there was evidence to suggest that Mycobacterium leprae entered the tissue through the thorn pricks. In the normal habitat of the armadillo in Louisiana there are thorny bushes consisting mostly of the green briar and the southern dewberry. Thorn pricks as a means of transmission of leprosy in the wild armadillos is suggested.

Animals↗
PubMed1986

Use of tolazoline as an antagonist to xylazine-ketamine-induced immobilization in African elephants.

A group of 15 African elephants (Loxodonta africana) were immobilized with a combination of xylazine (0.2 mg/kg of body weight, IM) and ketamine (1 to 1.5 mg/kg of body weight, IM). Ten of the African elephants were allowed to remain recumbent for 30 minutes and the remaining 5 elephants, for 45 minutes before they were given tolazoline (0.5 mg/kg of body weight, IV). For the group of 15, the mean induction time (the time required from injection of the xylazine-ketamine combination until onset of recumbency) was 14.2 +/- 4.35 minutes (mean +/- SD), and standing time (the time required from the tolazoline injection until the elephant stood without stimulation or assistance) was 2.8 +/- 0.68 minutes. All of the elephants were physically stimulated (by pushing, slapping, shouting) before they were given tolazoline, and none could be aroused. After tolazoline was given and the elephant was aroused, relapses to recumbency did not occur. Recovery was characterized by mild somnolence in an otherwise alert and responsive animal. Failure (no arousal) rates were 0% (95% confidence interval, 0 to 0.3085) for elephants given tolazoline after 30 minutes of recumbency and 100% for elephants that were not given tolazoline. There was no significant (P less than 0.05) difference in standing time 30 or 45 minutes after tolazoline injection.

Animals↗
PubMed1985

Alveolar pressure magnitude and asynchrony during high-frequency oscillations of excised rabbit lungs.

One possible advantage of high-frequency ventilation (HFV) over conventional mechanical ventilation is that adequate pulmonary ventilation may be established with lower pressure swings. Pressure swings measured at the airway opening may not accurately reflect pressure swings in the alveoli, however. Furthermore, little is known about the synchrony of alveolar filling during HFV. We have assessed the magnitude of alveolar pressure swings (PA) relative to those at the airway opening (Pao) and investigated asynchrony of alveolar filling during small tidal volume (less than 1.0 ml), high-frequency (1 to 60 Hz) oscillations (HFO) in 8 excised rabbit lungs. The PA was measured in several capsules glued to the pleural surface and communicating with alveolar gas via pleural punctures. The peak value of the ratio [PA/Pao] occurred near the resonant frequency and was 1.90, 1.45, and 1.0 at distending pressures of 25, 10, and 5 cm H2O, respectively. Temporal asynchrony of PA between sampled lung regions was quantified by measuring the interregional standard deviation of alveolar pressure phase angles, delta phi. The delta phi increased with increasing frequency and decreasing transpulmonary pressure. The maximal observed delta phi was 30 degrees. These results, when compared with earlier results on excised canine lungs, show that the amplification of PA during HFO is lung-size dependent. The observed degree of phase differences in pressure swings between peripheral alveolar locations implies substantial asynchrony of alveolar filling. This in turn suggests interregional gas transport as an important contributor to gas mixing during HFV.

Airway Resistance↗
PubMed1985

Regional alveolar pressure during periodic flow. Dual manifestations of gas inertia.

We measured pressure excursions at the airway opening and at the alveoli (PA) as well as measured the regional distribution of PA during forced oscillations of six excised dog lungs while frequency (f[2-32 Hz]), tidal volume (VT [5-80 ml]), and mean transpulmonary pressure (PL [25, 10, and 6 cm H2O]) were varied. PA's were measured in four alveolar capsules glued to the pleura of different lobes. The apex-to-base ratio of PA's was used as an index of the distribution of dynamic lung distension. At low f, there was slight preferential distension of the lung base which was independent of VT, but at higher f, preferential distension of the lung apex was found when VT's were small, whereas preferential distension of the lung base was found when VT's approached or exceeded dead space. These VT-related changes in distribution at high frequencies seem to depend upon the branching geometry of the central airways and the relative importance of convective momentum flux vs. unsteady inertia of gas residing therein, which, in this study, we showed to be proportional to the ratio VT/VD*, where VD* is an index of dead space. Furthermore, they imply substantial alteration in the distribution of ventilation during high frequency ventilation as f, VT, and PL vary. The data also indicate that alveolar and airway opening pressure costs per unit flow delivered at the airway opening exhibit weakly nonlinear behavior and that resonant amplification of PA's, which has been described previously for the case of very small VT's, persists but is damped as VT's approach dead space values.

Airway Resistance↗
PubMed1984

Conformation of double-stranded DNA during agarose gel electrophoresis: fractionation of linear and circular molecules with molecular weights between 3 X 10(6) and 26 X 10(6).

To answer several questions concerning the mechanisms of DNA fractionation during agarose gel electrophoresis, the electrophoretic mobility (mu) of double-stranded DNA has been measured as a function of (1) DNA topological conformation (linear, open circular, closed circular) and molecular weight (Mr) (molecular weights were between 2.9 X 10(6) and 26.4 X 10(6)), (2) gel concentration (A) and temperature, and (3) voltage gradient. It was found that mu extrapolated to an A of 0 (mu 0') was independent of DNA conformation. The effect of temperature was to raise values of mu 0' in inverse proportion to buffer viscosity. Semilogarithmic mu vs. A plots for linear DNAs had curvature that was opposite to the curvature for spherical particles (plots for linear DNA were concave). As A approached 0, the plots became increasingly linear. For the larger DNAs, the negative slope (KR) in the region of linearity was decreased as voltage gradient increased. These and other data indicate deformation of linear DNA random coils during agarose gel electrophoresis. The data suggest both an asymmetric and a symmetric collapse of linear DNA random coils during agarose gel electrophoresis. However, end-first migration of linear DNA, previously suggested by others, does not explain the data. The semilogarithmic mu vs. A plots were more linear for closed and open circular DNAs than they were for linear DNAs. Closed circular DNAs had KR's lower than KR's of either open circular or linear DNAs of the same molecular weight. At the lower voltage gradients, open circular DNA had the same KR as linear DNA of the same molecular weight. However, as voltage gradient and molecular weight increased, the KR of open circular DNA became smaller than the KR of linear DNA (of the same molecular weight). This and the concave curvature of semilogarithmic mu vs. A plots for linear DNA resulted in a previously unreported reversal of the relative migration of linear and open circular DNAs as A increased.

DNA, Circular↗
PubMed1983

Comparison of the physical properties and assembly pathways of the related bacteriophages T7, T3 and phi II.

To understand constraints on the evolution of bacteriophage assembly, the structures, electrophoretic mobilities (mu) and assembly pathways of the related double-stranded DNA bacteriophages T7, T3 and phi II, have been compared. The characteristics of the following T7, T3 and phi II capsids in these assembly pathways have also been compared: (1) a DNA-free procapsid (capsid I) that packages DNA during assembly; (b) a DNA packaging-associated conversion product of capsid I (capsid II). The molecular weights of the T3 and phi II genomes were 25.2 X 10(6) and 25.9 (+/- 0.2) X 10(6) (26.44 X 10(6) for T7, as previously determined), as determined by agarose gel electrophoresis of intact genomes. The radii of T7, T3 and phi II bacteriophages were indistinguishable by sieving during agarose gel electrophoresis (+/- 4%) and measurement of the bacteriophage hydration (+/- 2%) (30.1 nm for T7, as previously determined). Assuming a T = 7 icosahedral lattice for the arrangement of the major capsid subunits (p10A) of T7, T3 and phi II best explains these data and data previously obtained for T7. At pH 7.4 and an ionic strength of 1.2, the solid-support-free mu values (mu 0 values) of T7, T3 and phi II bacteriophages, obtained by extrapolation of mu during agarose gel electrophoresis to an agarose concentration of 0 and correction for electro-osmosis, were -0.71, -0.91 and -1.17(X 10(-4) cm2V-1 s-1. The mu 0 values of T7, T3 and phi II capsids I were -1.51, -1.58 and -2.07(X 10(-4] cm2V-1 s-1. For the capsids II, these mu 0 values were -0.82, -1.07 and -1.37(X 10(-4] cm2V-1 s-1. The tails of all three bacteriophages were positively charged and the capsid envelopes (heads) were negatively charged. In all cases the procapsid had a negative mu 0 value larger in magnitude than the negative mu 0 value for bacteriophage or capsid II. A trypsin-sensitive region in capsid I-associated, but not capsid II-associated, T3 p10A was observed (previously observed for T7). The largest fragment of trypsinized capsid I-associated p10A had the same molecular weight in T7 and T3, although the T3 p10A is 18% more massive than the T7 p10A. It is suggested that the trypsin-resistant region of capsid I-associated p10A determines the radius of the bacteriophage capsid.

Capsid↗
PubMed1983

Stability and in vitro DNA packaging of bacteriophages: effects of dextrans, sugars, and polyols.

Attempts were made to increase the efficiency of infectious particle formation during the in vitro assembly of bacteriophage T7 from procapsids and DNA. It was found that dextrans and some smaller, related compounds (sucrose and sorbitol) increase this efficiency by a factor of 8 to 50. Dextrans also inhibited elevated temperature-induced emptying of DNA from bacteriophages T7, P22, and T4, suggesting that the stimulation of assembly is caused, at least in part, by the stabilization of packaged DNA in capsids. The data indicated that the sugars and polyols can slow DNA emptying from bacteriophages at elevated temperature whether they permeate the bacteriophage capsid or not. In contrast, the data suggested that permeation of some particle, probably a capsid, results in inhibition of in vitro T7 assembly.

Capsid↗