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Biomedical subjects

M R Bailey

Publications and source records attributed to M R Bailey.

At least 37 records · Page 2Linked to original sources
PubMed1998

Comparison of electrohydraulic lithotripters with rigid and pressure-release ellipsoidal reflectors. I. Acoustic fields.

The most common lithotripter, a Dornier HM-3, utilizes an underwater spark to generate an acoustic pulse and a rigid ellipsoidal reflector to focus the pulse on the kidney stone to be comminuted. The pulse measured in water with a PVDF membrane hydrophone at the external focus of the ellipsoid was a 1-microsecond positive-pressure spike followed by a 3-microsecond negative-pressure trough. When we replaced the rigid reflector in our experimental lithotripter with a pressure-release reflector, the pulse was a 1.6-microsecond trough followed by a 0.6-microsecond positive spike. The waveforms are nearly time inverses (i.e., their spikes and troughs are reversed). The frequency spectra, the maximum peak positive pressures P+ (42 MPa, rigid and 43 MPa, pressure-release), and the maximum peak negative pressures P- (-12 MPa and -14 MPa) are comparable. The maximum P- occurred 20 mm closer to the reflector than did the maximum P+, for both reflectors. However, the spatial maxima of the peak pressures (P+ and P-) produced by the pressure-release reflector were located 20 mm nearer to the reflector than those produced by the rigid reflector. Qualitative explanation of the waveforms and the location of pressure maxima as well as comparison to previous theoretical and experimental results is given. The alternate waveform produced by the pressure-release reflector may be a tool in determining the role of cavitation in lithotripsy because cavitation is highly sensitive to waveform.

Acoustics↗
PubMed1996

The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans.

One important aspect of the safety assessment of genetically engineered crops destined for food and feed uses is the characterization of the consumed portion of the crop. One crop currently under development, glyphosate-tolerant soybeans (GTS), was modified by the addition of a glyphosate-tolerance gene to a commercial soybean cultivar. The composition of seeds and selected processing fractions from two GTS lines, designated 40-3-2 and 61-67-1, was compared with that of the parental soybean cultivar, A5403. Nutrients measured in the soybean seeds included macronutrients by proximate analyses (protein, fat, fiber, ash, carbohydrates), amino acids and fatty acids. Antinutrients measured in either the seed or toasted meal were trypsin inhibitor, lectins, isoflavones, stachyose, raffinose and phytate. Proximate analyses were also performed on batches of defatted toasted meal, defatted nontoasted meal, protein isolate, and protein concentrate prepared from GTS and control soybean seeds. In addition, refined, bleached, deodorized oil was made, along with crude soybean lecithin, from GTS and control soybeans. The analytical results demonstrated the GTS lines are equivalent to the parental, conventional soybean cultivar.

Amino Acids↗
PubMed1996

The expressed protein in glyphosate-tolerant soybean, 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. strain CP4, is rapidly digested in vitro and is not toxic to acutely gavaged mice.

The safety of 5-enolpyruvylshikimate-3-phosphate synthase enzyme derived from Agrobacterium sp. strain CP4 (CP4 EPSPS) was assessed. CP4 EPSPS is the only protein introduced by genetic manipulation that is expressed in glyphosate-tolerant soybeans, which are being developed to provide new weed-control options for farmers. Expression of this protein in plants imparts high levels of glyphosate tolerance. The safety of CP4 EPSPS was ascertained by evaluating both physical and functional characteristics. CP4 EPSPS degrades readily in simulated gastric and intestinal fluids, suggesting that this protein will be degraded in the mammalian digestive tract upon ingestion as a component of food or feed, There were no deleterious effects due to the acute administration of CP4 EPSPS to mice by gavage at a high dosage of 572 mg/kg body wt, which exceeds 1000-fold tha anticipated consumption level of food products potentially containing CP4 EPSPS protein. CP4 EPSPS does not pose any important allergen concerns because this protein does not possess characteristics typical of allergenic proteins. These data, in combination with seed compositional analysis and animal feeding studies, support the conclusion that glyphosate-tolerant soybean are as safe and nutritious as traditional soybeans currently being marketed.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1996

Bioeffects of positive and negative acoustic pressures in vivo.

In water, the inertial collapse of a bubble is more violent after expansion by a negative acoustic pressure pulse than when directly compressed by a positive pulse of equal amplitude and duration. In tissues, gas bodies may be limited in their ability to expand and, therefore, the relatively strong effectiveness of negative pressure excursions may be tempered. To determine the relative effectiveness of positive and negative pressure pulses in vivo, the mortality rate of Drosophila larvae was determined as a function of exposure to microsecond length, nearly unipolar, positive and negative pressure pulses. Air-filled tracheae in the larvae serve as biological models of small, constrained bubbles. Death from exposure to ultrasound has previously been correlated with the presence of air in the respiratory system. The degree of hemorrhage in murine lung was also compared using positive and negative pulses. The high sensitivity of lung to exposure to ultrasound also depends on its gas content. The mammalian lung is much more complex than the respiratory system of insect larvae and, at the present time, it is not clear that acoustic cavitation is the physical mechanism for hemorrhage. A spark from an electrohydraulic lithotripter was used to produce a spherically diverging positive pulse. An isolated negative pulse was generated by reflection of the lithotripter pulse from a pressure release interface. Pulse amplitudes ranging from 1 to 5 MPa were obtained by changing the proximity of the source to the biological target. For both biological effects, the positive pulse was found to be at least as damaging as the negative pulse at comparable temporal peak pressure levels. These observations may be relevant to an evaluation of the mechanical index (MI) as an exposure parameter for tissues including lung since MI currently is defined in terms of the magnitude of the negative pressure in the ultrasound field.

Acoustics↗
PubMed1995

Implications of airway retention for radiation doses from inhaled radionuclides.

A slow phase of bronchial and bronchiolar clearance ('airway retention') has been included in the revised dosimetric model for the human respiratory tract recently adopted by the International Commission on Radiological Protection (ICRP), based primarily on the results of the bolus clearance experiments conducted by Stahlhofen et al. The treatment of airway retention in the new ICRP model is described. An analysis was carried out of the sensitivity of the equivalent lung dose, and the effective dose, to assumptions made in the new model about the extent of airway retention. It was shown that inclusion of airway retention of material deposited in the bronchial tree does have a significant effect on both end-points (of the order of 10-50%) for a wide range of radionuclides. In some cases, notably moderately soluble forms of long-lived alpha-emitters, its inclusion increases these doses by up to a factor of three, so that it makes the dominant contribution to the calculated dose. The model assumes that material in transit through the bronchial tree, having initially deposited in the alveolar region, is not subject to airway retention. Including retention of this material would typically increase doses by a further factor similar to that resulting from the airway retention of the bronchial deposit.

Absorption↗
PubMed1993

Determination of erythromycin A by liquid chromatography and electrochemical detection, with application to salmon tissue.

The chromatographic performance of erythromycin A (EA) is improved significantly over that achieved on polymeric columns by using a sterically shielded octyldiisopropylsilica (Zorbax Rx-C8) column and a neutral mobile phase consisting of 5 mM aqueous sodium perchlorate-acetonitrile (50:50). This mobile phase facilitates electrochemical detection of EA at the 3-pmol level. Temperature control of both column and detection cell is important for minimizing detector noise and drift. A clean-up procedure, based on aminopropylsilica solid-phase extraction, allows the detection of EA in salmon flesh down to the 0.2-ppm level. Some of the metabolites of EA that retain the tertiary amine may also be detected by this method.

Animals↗
PubMed1992

Determination of erythromycin A in salmon tissue by liquid chromatography with ion-spray mass spectrometry.

A reverse-phase liquid chromatography/mass spectrometry (LC/MS) method, incorporating gradient elution, is described for the characterization of residual erythromycin A and its metabolites in salmon tissue. The method uses ion-spray, a mild atmospheric pressure ionization technique which provides an abundant protonated molecule well suited for selected ion monitoring experiments. Tandem mass spectrometry (MS/MS) using collision-induced dissociation was used to provide structural information. The LC/MS method was tested for the analysis of salmon tissue spiked with erythromycin A at levels between 0.01 and 1 p.p.m. A simple extraction and clean-up procedure, slightly modified from that described by Takatsuki et al. (J. Assoc. Off. Anal. Chem. 70, 708 (1987)), was used in this work. Using selected ion and selected reaction monitoring techniques, the LC/MS and LC/MS/MS methods provided detection limits of < 10 and 50 ng g-1, respectively. Confirmatory full-scan LC/MS and LC/MS/MS spectra were obtained at the 0.5 and 1 microgram g-1 levels, respectively. Using a combination of these techniques, the presence of residual erythromycin A was confirmed in the tissue of fish administered medicated feed containing the antibiotic. In addition, several metabolites and degradation products of erythromycin A, including anhydro-erythromycin and N-demethyl-erythromycin, were detected and where possible confirmed by comparison with authentic compounds. Although this analytical method has been shown to afford the necessary sensitivity and precision, application of these techniques to high-throughput quantitative analyses will require development of an improved clean-up procedure and preferably also of a suitable surrogate internal standard.

Animals↗
PubMed1992

Comparative trial of oral clotrimazole and nystatin for oropharyngeal candidiasis prophylaxis in orthotopic liver transplant patients.

A prospective randomized study was conducted to assess the effectiveness of clotrimazole troches and nystatin suspension to prevent oral candidiasis in immunosuppressed orthotopic liver transplant patients. Thirty-four patients received either clotrimazole troches, 10 mg, five times daily, or nystatin suspension, 500,000 units, four times daily. Prophylaxis was initiated after extubation after transplantation and continued throughout the hospitalization. One of 17 patients in each treatment group developed clinical and microscopic evidence of an oropharyngeal Candida infection. This gave an intragroup and an overall infection rate of 5.9%. It appears that either nystatin or clotrimazole may be used for candidiasis prophylaxis in orthotopic liver transplant patients.

Administration, Oral↗
PubMed1989

A new small animal inhalation facility: design and performance.

A new inhalation facility is described which allows any combination of up to 72 rodents ranging in size from the mouse to the guinea pig to be exposed simultaneously. Typically for aerosols of MMD 1.5 microns the initial lung deposit in the rat is 0.05 to 0.07% of the total amount of material used and the coefficient of variation between animals is 15 to 20%.

Administration, Inhalation↗
PubMed1987

Studies on the metabolic behaviour of industrial actinide-bearing aerosols after deposition in the rat lung: an experimental basis for interpreting chest monitoring data and assessing limits on intake for workers.

UNLABELLED: The metabolism of 239Pu and 241Am in 3 site-specific industrial dusts has been studied after their deposition in the rat lung. A comparative experiment has also been carried out with a mixture of these actinides inhaled as their nitrates. The aim of this study was to provide an experimental basis for assessing limits on intake and to establish whether the 239Pu content in the lungs could be interpolated from measurements of 241Am. THE RESULTS: 1 demonstrate the wide differences in the lung retention kinetics of the actinides and in the absolute and relative amounts translocated to the blood that can occur for industrially produced materials; 2 show that the annual limits on intake (ALIs) for the different materials vary between those postulated for class W and Y compounds by the International Commission on Radiological Protection; 3 indicate that acute intakes of 239Pu equivalent to the ALI can, depending on the nature of the dust, be estimated from 241Am chest monitoring data at times from a few days up to about 3 years after exposure.

Aerosols↗
PubMed1983

The retention of 14C-DTPA in human volunteers after inhalation or intravenous injection.

This study in human volunteers was designed to compare the retention of diethylenetriaminepentaacetic acid (DTPA) in the body after intravenous (i.v.) injection with that following inhalation by using a 14C labelled tracer. After i.v. injection retention in the blood could be described by three exponential components with half-times of about 1.4 min (approximately 60%) 14.3 min (approximately 20%) and 95 min (approximately 20%). By 24 hr more than 99% of the 14C-DTPA had been excreted in the urine and less than 0.5% remained in the plasma. After inhalation of 14C-DTPA retention in the lungs could be represented by a single component with a half time of about 75 min. As a consequence the length of time that a therapeutically useful amount of DTPA is retained in the body is approximately twice that following intravenous injection.

Adult↗
PubMed1980

The carcinogenic effect of localized fission fragment irradiation of rat lung.

In a preliminary investigation of 'hot particle' carcinogenesis uranium oxide particles were introduced into the lungs of rats either by intubation of a liquid suspension of the particles or by inhalation of an aerosol. Subsequently the animals were briefly exposed to slow neutrons in a nuclear reactor, resulting in localized irradiation of the lung by fission fragments emitted from 235U atoms in the oxide particles. The uranium used in the intubation experiments was either enriched or depleted in 235U. Squamous cell carcinomas developed at the site of deposition of the enriched uranium oxide in many cases but no lung tumours occurred in the rats with the depleted uranium oxide, in which the lung tissue was exposed to very few fission fragments. Only enriched uranium oxide was used in the inhalation experiments. Pulmonary squamous cell carcinomas occurred after the fission fragment irradiation but were fewer than in the intubation experiments. Adenocarcinomas of the lung were seen in rats exposed to uranium oxide without subsequent irradiation by neutrons in the reactor and in rats irradiated with neutrons but not previously exposed to uranium oxide. It is concluded that (i) fission fragments were possibly implicated in the genesis of the squamous cell carcinomas, which only developed in those animals exposed to enriched uranium oxide and neutrons and (ii) the adenocarcinomas in the rats inhaling enriched uranium oxide only were likely to have been caused by protracted irradiation of the lung with alpha-rays emitted from the enriched uranium.

Adenocarcinoma↗