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Biomedical subjects

A Lundin

Publications and source records attributed to A Lundin.

99 records · Page 6Linked to original sources
PubMed1975

Detection of bacteriuria by luciferase assay of adenosine triphosphate.

A selective method for distinguishing bacterial and nonbacterial adenosine triphosphate (ATP) in clinical bacteriological specimens was studied. The method involved incubation of samples with the detergent Triton X-100 and the ATP-hydrolyzing enzyme apyrase. The incubation selectively destroyed ATP in suspensions of various human cells while not affecting the ATP content in microbial cells. ATP remaining in the sample after incubation was extracted in boiling buffer and assayed by the firefly luciferase assay. Application of the method to 469 clinical urine specimens showed that the ATP level after treatment with Triton/apyrase was correlated to bacterial counts and that the sensitivity of the assay was sufficient for the detection of 10(5) bacteria/ml. The ATP levels per bacterial cell remaining in the urine specimen after treatment with Triton/apyrase were close to values observed in laboratory-grown cultures. The specificity and sensitivity of the luciferase assay for the detection of urinary bacteria and its possible use as a bacteriuria screening method are discussed.

Adenosine Triphosphate↗
PubMed1975

Cardiopulmonary function in former girl swimmers and the effects of physical training.

Sixteen former girl swimmers were studied in 1971 before and after 12 weeks of physical training. These girls constituted a representative selection from a group of 30 girls swimmers studied in 1961 (3). Maximal oxygen uptake increased by 14%, to 2.47 l/min, whereas heart volume and vital capacity remained unchanged. Cardiac output and intrapulmonary gas exchange were also studied in 6 girls. Cardiac output in maximal exercise was 15.3 l/min; heart rate, 185 beats/min; stroke volume, 83 ml; and the arteriovenous oxygen diffence, 15.6 ml/100 ml. The stroke volume did not show the usually good correlation with heart volume. Normal values for V-E/V-O2, V-A/VO-2, V-A/Q, and PAO2-Pao2 were found both at rest and during exerice. The increase in maximal oxygen uptake after training was related to the increase in stroke volume. No increase was found in values for pulmonary gas exchange nor in the maximal arteriovenous oxygen difference. The results obtained suggest that a long period of previous intense physical training does not significantly influence the maximal aerobic power later in life when again sedentary. Moreover, the observed increase of 14% in VO2, max after 12 weeks of training may not be large enough to prove any advantageous effects when training is resumed.

Carbon Dioxide↗
PubMedDate not supplied

Improved extraction and assay of mycobacterial ATP for rapid drug susceptibility testing.

The firefly luciferase assay of ATP is a rapid and convenient technique for monitoring growth of mycobacteria. The time needed to obtain a drug susceptibility pattern can be reduced to less than 1 week as compared to 4 weeks with conventional methods. The ATP assay is simple and reliable. However, the extraction of bacterial ATP is not a trivial problem. Lysing the cells will immediately activate ATP-degrading enzyme systems. The extractant must therefore lyse the cells and simultaneously inactivate ATP-degrading enzyme systems. Only by comparing the ATP yields obtained with different extractants we will know something about the intracellular ATP level. In the present study various extractants were compared for the extraction of ATP from Mycobacterium bovis (BCG) cultures. Dodecyl trimethyl ammonium bromide (DTAB) in Tris-buffer with EDTA resulted at 100 degrees C in an ATP yield that was approximately twice as high as the same buffer without DTAB. The optimum temperature was 80-100 degrees C. With the optimized extraction procedure the coefficient of variation for the entire assay of ATP in BCG cultures was 5%. The analytical interference from DTAB with the firefly reaction was obviated by neutralization with alpha-cyclodextrin, making it possible to increase the sensitivity by assaying 0.5 mL rather than 0.01 mL extract.

Adenosine Triphosphate↗
PubMedDate not supplied

Free fatty acid determination by peroxidase catalysed luminol chemiluminescence.

A sensitive, specific, and partly automatic method for the analysis of free fatty acids is described. The assay involves activation of free fatty acids by acyl-CoA synthetase (EC 6.2.1.3) followed by oxidation of the thioesters by acyl-CoA oxidase. The H2O2 formed is determined in a reaction catalysed by horseradish peroxidase (EC 1.11.1.7) using luminol as electron donor. The assay has a linear range of 0.05 to 5 nmol of different free fatty acids (C10-C18) in the original sample. The efficiency of the method toward capric, lauric, myristic, palmitic, palmitoleic, stearic, oleic, and linoleic acid measured as recovery of light emission compared to that of H2O2 standards, was over 90%. AffiGel 501 was used to covalently bind the free thiol group in CoASH eliminating interference of this substance in the peroxidase-luminol reaction.

Acyl-CoA Oxidase↗
PubMedDate not supplied

A luminometric method for the determination of ATP and phosphocreatine in single human skeletal muscle fibres.

A sensitive method for the analysis of ATP and phosphocreatine (PCr) in single human skeletal muscle fibres is described. Muscle tissue was freeze-dried and single fibres were dissected free with the aid of low-power microscopy. The fibres were then extracted in trichloroacetic acid and neutralized with KHCO3. The assay is based on the continuous monitoring of light produced as a result of ATP degradation in the firefly luciferase reaction. PCr is measured as the amount of ATP formed in the creatine kinase reaction. The coefficient of variation was less than 4% for both ATP and PCr determination. The amount of tissue required for the assay is approximately 0.5 microgram (dry weight). The assay showed good agreement with spectrophotometric and high-performance liquid chromatographic (HPLC) measurements made upon extracts of whole muscle tissue.

Adenosine Triphosphate↗
PubMedDate not supplied

Assessment of digital chest radiography using stimulable phosphor.

In this pilot study, conventional and digital radiography of the chest was compared in 170 patients. Two digitized radiographs, one frequency modified and one simulating the conventional film-screen combination, and the conventional films were reviewed independently by 5 radiologists with different experience. In spite of the smaller size and lower spatial resolution of the digitized compared with the conventional radiograph, only slight differences were revealed in the observation of different pulmonary and mediastinal changes. Digitized radiography is therefore considered suitable for chest examinations.

Adolescent↗
PubMedDate not supplied

The vertical position of the patella. A new radiographic method for routine use.

Patella height was defined by the distance between the midpoint of the articular surface of the patella and the condylar plane, which was constructed perpendicular to the mechanical axis of the tibia. In two series of normal individuals the measured distances were related to body height and the length of the lower leg and thus expressed as its ratio, which was the same in both sexes. The measurements were performed on lateral radiographs of the knee and lower leg obtained in weight-bearing and 30 degrees to 40 degrees of knee flexion using a simple device to obtain a standardized position of the lower leg during the examination. The standing position is proposed for these measurements since the patellar ligament is shorter in the recumbent position. The method can be used for biomechanical analysis of the femoropatellar joint.

Adolescent↗