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Biomedical subjects

L M Buchanan

Publications and source records attributed to L M Buchanan.

16 recordsLinked to original sources
PubMed1992

Spin echo nuclear magnetic resonance studies on intact erythrocytes: changes in cellular metabolism as a consequence of carbimazole therapy.

OBJECTIVE: Because the exact mechanism of action of carbimazole is uncertain, nuclear magnetic resonance (NMR) spectroscopy was used to investigate cellular changes in erythrocytes from Graves' patients following a course of carbimazole therapy. DESIGN: NMR spectroscopy was carried out using intact erythrocytes obtained from Graves' patients prior to and at 2 and 12 months after carbimazole treatment. The data were correlated with thyroid hormone and antibody levels. PATIENTS: Twenty patients (four males; 16 females) with newly diagnosed and previously untreated Graves' disease were enrolled into the study. Assessments were made prior to the commencement of therapy and after 2 and 12 months on treatment. Of the 20 patients assessed at 0 and 2 months only 12 completed the study. MEASUREMENTS: The oxidation-reduction balance of erythrocyte glutathione was measured directly using 1H spin echo NMR spectroscopy of intact cells. Thyroid hormone and antibody levels were measured using reported methods. RESULTS: At 2 and 12 months a significant (P < 0.01) oxidation of the erythrocyte glutathione was observed. Of the four thyroid related markers (T3, T4, TRAb and TSH) assessed in this study both T3 (P < 0.001) and TRAb (P < 0.001) were observed to correlate with the NMR observed changes in glutathione. However, in-vitro experiments indicated that carbimazole does not affect red cell glutathione directly. CONCLUSIONS: A model is presented which uses the hydrated iodium cation (I+), the natural product of T4 conversion to T3, as a chemical oxidant which can produce the observed clinical alteration in intracellular glutathione in ex-vivo erythrocytes. It is suggested that a major factor in the action of carbimazole in Graves' disease may be to stimulate the function of the deiodinase enzymes.

Adult↗
PubMed1991

Clinical analysis in intact erythrocytes using 1H spin echo NMR.

A new method of clinical analysis based on 1H spin echo NMR spectroscopy is presented. It is capable of providing information on six metabolites within viable erythrocytes, directly and without any preparative procedures prior to analysis except for cell separation and washing. Erythrocytes from patients with rheumatoid arthritis and Graves' disease are compared with cells obtained from healthy volunteers. The NMR detectable species in the cytosol of the cells are glutathione, ergothioneine, choline, creatine, glycine, lactate and to a lesser extent alanine and valine. Significant differences are observed between the ergothioneine pools in the rheumatoid group (P less than 0.01) compared to the control group. The glutathione: di-glutathione ratio can be assessed from the ratio, g2 to g4, taken from different signals in the glutathione molecule. The total concentration of glutathione present is easily assessed qualitatively but is more difficult to quantitate.

Adult↗
PubMed1990

The effect of carbimazole therapy on interleukin 2, interleukin 2 receptors and free radicals.

Levels of Interleukin 2 (IL2), IL2 receptors (IL2R) and free radical scavengers were measured in 25 Graves' disease patients prior to and following an 8 week course of Carbimazole therapy in an attempt to understand the mechanism by which the drug acts on the immune system. In untreated Graves' patients IL2R levels were elevated and IL2 levels reduced. Free radical scavengers were also reduced in these patients. Following treatment IL2R levels fell and IL2 levels rose. Levels of the free radical scanvengers also rose. It is not clear whether it is the fall in IL2R levels or the rise in the level of free radical scavengers (implying a reduction in free radical activity) which is responsible for the rise in IL2.

Carbimazole↗
PubMed1986

The effect of hyperinflation, inspiratory hold, and oxygenation on cardiopulmonary status during suctioning in a lung-injured model.

This study determined the effects of a 5-second inspiratory hold during ventilatory maneuvers on cardiopulmonary status before, during, and after endotracheal suctioning in an acute lung-injured model. Eight mongrel dogs were anesthetized, paralyzed, mechanically ventilated, and given intravenous oleic acid to produce pulmonary edema. Four protocols were tested in alternate order in which either tidal volume inflations or hyperinflations at an FiO2 of 0.6 were given with and without an inspiratory hold of 5 seconds before and after each of three sequential suctioning passes. In those protocols in which an inspiratory hold was used, statistically significant changes occurred in right atrial, pulmonary arterial, and aortic systolic and diastolic pressures (p less than 0.04). The use of an inspiratory hold with hyperinflation maintained PaO2 during suctioning (range of 81 to 91 mm Hg), but had the greatest decrease in PaO2 (8%) after return to the ventilator. In all protocols, with the exception of the one in which hyperinflations without an inspiratory hold were used, there was a cumulative increase in PaCO2 with tidal volume inflation protocols reaching peak PaCO2 values of 49 (+/- 7.5) mm Hg. In protocol 4 in which hyperinflation without inspiratory hold was used, PaO2 ranged from 75 (+/- 16) to 92 (+/- 34) mm Hg, and PaCO2 ranged from 37 (+/- 7) to 42 (+/- 6) mm Hg. In conclusion, the use of hyperinflation without an inspiratory hold resulted in the least undesirable changes in the variables studied. However, this protocol needs to be replicated in an acutely ill clinical population before recommended for practice.

Animals↗
PubMed1972

Simple liquid scrubber for large-volume air sampling.

A new large-volume air sampler called the "simple liquid scrubber" is described. It can recover a high percentage of microorganisms from large volumes of air, up to 950 liters/min, and concentrate them into a small volume of liquid at a ratio of about 400,000 to 1. The principle of operation of the scrubber is based on the production of a fine mist in a rapidly moving airstream with ultimate collection of the airborne particles by impingement into the film of liquid formed upon impaction of the mist droplets on the scrubber walls. The scrubber compared favorably with the all-glass impinger (AGI-30) and the slit sampler in tests with the normal flora and with experimental aerosols of Bacillus subtilis var. niger spores.

Acrylic Resins↗
PubMed1971

Thermal inactivation of aerosolized Bacillus subtilis var. niger spores.

A hot-air sterilizer capable of exposing airborne microorganisms to elevated temperatures with an almost instantaneous heating time was developed and evaluated. With this apparatus, aerosolized Bacillus subtilis var. niger spores were killed in about 0.02 sec when exposed to temperatures above 260 C. This is about 500 times faster than killing times reported by others. Extrapolation and comparison of data on the time and temperature required to klll B. subtilis var. niger spores on surfaces show that approximately the same killing time is required as is necessary for spores in air, if corrections are made for the heating time of the surface.

Aerosols↗
PubMed1968

Novel multi-slit large-volume air sampler.

Scientific investigators who are interested in the various facets of airborne transmission of disease in research laboratories and hospitals need a simple, continuous, high-volume sampling device that will recover a high percentage of viable microorganisms from the atmosphere. Such a device must sample a large quantity of air. It should effect direct transfer of the air into an all-purpose liquid medium in order to collect bacteria, viruses, rickettsia, and fungi, and it should be easy to use. A simple multi-slit impinger sampler that fulfills these requirements has been developed. It operates at an air-sampling rate of 500 liters/min, has a high collection efficiency, functions at a low pressure drop, and, in contrast to some earlier instruments, does not depend upon electrostatic precipitation at high voltages. When compared to the all-glass impinger, the multi-slit impinger sampler collected microbial aerosols of Serratia marcescens at 82% efficiency, and aerosols of Bacillus subtilis var. niger at 78% efficiency.

Aerosols↗
PubMed1968

Effect of cell moisture on the thermal inactivation rate of bacterial spores.

Thermal inactivation rates were determined for two strains of Bacillus subtilis var. niger spores after equilibration to various relative humidity (RH) levels. In these tests, small thin stainless-steel squares were each inoculated with a drop of spore suspension and equilibrated to 11, 33, or 85% RH. Following equilibration, the squares were placed on a hot plate preheated to 108, 125, 136, 164, or 192 C for various exposure times and then assayed for surviving organisms. The results revealed that spores of the A strain of B. subtilis were least resistant if preequilibrated to 11% RH and most resistant if preequilibrated to 85% RH. The same trend was obtained at all temperatures except 192 C, at which, no difference was noted, probably because the rapid kill time approaches the heat-up time of the stainless-steel square. The B strain of B. subtilis spores showed an opposite RH effect; that is, the cells preequilibrated to 11% RH were the most resistant. Because the two strains of spores were grown on different media, further studies were conducted at 136 C after subculturing the cells on different media. When the B strain was subcultured on the A strain medium, the pattern was reversed; the cells preequilibrated to low RH were then least resistant. Although it was not possible to reverse these cells to the original pattern by subculturing on the original B strain medium again, the pattern was altered to the point that there was no significant difference in heat resistance of these cells regardless of the preequilibration RH. The same result was obtained when the A strain was grown on the B strain medium; that is, the thermal resistance could not be reversed, but it was altered from the point where the low RH equilibrated cells were least resistant initially to the point where there was no significant difference in any of the cells regardless of what RH was used for preequilibration. The thermal resistance of spores seemed to be dependent on (i) the medium on which the spores are grown, (ii) the RH on which they are exposed before heating, and (iii) some genetic characteristic of the cell.

Bacillus subtilis↗
PubMed1966

Effect of air ions on submicron t1 bacteriophage aerosols.

The effect of a high concentration of ionized air molecules on sampling T1 phage aerosols of submicron particle size was evaluated by comparing the phage recoveries of all-glass impingers (AGI-4) and type 6 filter papers. Sampler recoveries of all ionized aerosols were less than the recoveries of nonionized control aerosols. These reductions in recovery were greater with positive ions than with negative ions or ions of mixed polarity. The AGI-4 allowed considerable slippage, which was not affected by the air ions. Type 6 filter paper recoveries were less than AGI-4 recoveries. The air ions did not appear to affect the aerosol particle size as determined by an electron microscope.

Journal Article↗
PubMed1966

beta-Propiolactone Vapor Decontamination.

Although beta-propiolactone (BPL) is an effective vapor-phase decontaminant for enclosed areas, some problems have been encountered in its use. Adequate air circulation during BPL dissemination could eliminate most of these problems. It is recommended that, when decontaminating the ordinary building or laboratory, the amount of BPL sprayed be changed from the previously suggested 1 gal/16,000 cubic ft of space to 1 gal/25,000 cubic ft. The use of aqueous BPL solutions and thermal-type generators is not recommended.

Journal Article↗
PubMedDate not supplied

Measurement of recovery from myocardial infarction using heart rate variability and psychological outcomes.

This pilot study was designed to describe heart rate variability (HRV), anxiety, anger, denial, and depression during the first 4 days and 6 months after acute myocardial infarction (AMI). The sample was composed of 21 post-AMI males aged 40 to 83. State anxiety was elevated early. At 6 months it had significantly decreased. The nonpower measure of HRV, the Kleiger global standard deviation, was decreased to a mean score of 86 (SD = 29) msec during AMI and was 117 (SD = 30) msec at 6 months. Although there were no significant correlations between HRV, psychological response, age, and education, there were moderate correlations between HRV and state anger (r = .33), denial (r = .35), and education (r = .45). HRV, as measured by the power spectral density function of an autoregressive model, demonstrated an increased peak across the band of frequency associated with the high-frequency components of the parasympathetic system and a decreased peak across the band associated with the low-frequency components of the sympathetic system at 6 months as compared to the AMI period.

Adult↗