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Biomedical subjects

B A Freeman

Publications and source records attributed to B A Freeman.

At least 145 records · Page 8Linked to original sources
PubMed1982

Biology of disease: free radicals and tissue injury.

A free radical is any molecule that has an odd number of electrons. Free radicals, which can occur in both organic (i.e., quinones) and inorganic molecules (i.e., O(2)), are highly reactive and, therefore, transient. Free radicals are generated in vivo as by products of normal metabolism. They are also produced when an organism is exposed to ionizing radiation, to drugs capable of redox cycling, or to xenobiotics that can form free radical metabolites in situ. Cellular targets at risk from free radical damage depend on the nature of the radical and its site of generation. In this review we survey cellular sources of free radicals and the reactions they can undergo and discuss cellular defenses and adaptive mechanisms.

Animals↗
PubMed1981

Pulmonary injury in rats following continuous exposure to 60% O2 for 7 days.

Morphological, biochemical, and physiological studies were done on rats exposed to 60% O2 for 7 days. This exposure did not induce O2 tolerance but instead caused a significant decrease in survival time of animals subsequently exposed to pure O2. The activity of lung superoxide dismutases and glucose-6-phosphate dehydrogenase were unchanged after exposure to 60% O2. A decrease in lung compliance was suggested by changes in the total lung capacity and in the pressure-volume curves of excised lungs. Ventilation of these animals with large tidal excursion resulted in pulmonary edema. Morphometric analyses revealed a significant decrease in alveolar air volume and an increase in the number of alveolar macrophages. The most significant lesions involved the pulmonary vascular bed. The volume and thickness of the capillary endothelium was decreased. There were focal areas of pericapillary fluid accumulations, and a number of the smaller vessels had perivascular edema. These findings suggest that significant pulmonary injury occurs in rats exposed to 60% O2 and that the primary site of injury is the pulmonary capillary endothelium.

Animals↗
PubMed1980

Fatty acid secretion and metabolism in 'activated' rabbit alveolar macrophages.

The lipid content of bronchoalveolar lavages collected from both control rabbits and rabbits undergoing a pulmonary inflammatory response induced by intravenous injection of complete Freund's adjuvant was examined. A maximum of 4 x 10(8) alveolar macrophages could be recovered from the lavage of injected rabbits, a 10-fold greater number of cells than could be obtained from control rabbits. Increased amounts of unsaturated free fatty acids were present in the lavage lipids of injected rabbits, and no change in the amount and degree of saturation of lavaged phosphatidylcholine occurred. Alveolar macrophages recovered from injected rabbits contained 25 to 40% less lipid per cell, as measured by total fatty acid composition. Free fatty acids are released from phospholipids of adjuvant-induced alveolar macrophages incubated in vitro following lavage. Concentrations of N-formylmethionyl-phenylalanine similar to those which stimulate macrophage chemotaxis and bactericidal activity enhance this fatty acid release. Alveolar macrophages incorporate both saturated and unsaturated fatty acids with similar efficiency, primarily into phospholipids and triacylglycerols. Thus, activation of alveolar macrophages which results in a relative increase in internal phospholipase activity with concomitant large losses in cellular phospholipid results not only in liberation of chemokinetic fatty acids but also in considerable loss of membrane components.

Animals↗
PubMed1980

Electroacoustic performance characteristics of FM auditory trainers.

This study investigated the electroacoustic performance characteristics of FM auditory trainers. Experiment one was designed to answer two interrelated questions. First, what are the differences in the electroacoustic performance of FM auditory trainers between the FM and EM modes? Second, is the method for evaluating electroacoustic performance of hearing aids also appropriate for assessing the response characteristics of FM auditory trainers? The purpose of the second experiment was to assess the effect that taper of the volume control dial had on performance of these trainers. The study found that, with certain cautions, the ANSI S3.22-1976 procedures for assessing a hearing aid could be applied to the measurement of FM trainers. There were performance differences, however, between the auditory trainers when set to the FM and EM transmission modes. Thus, the electroacoustic assessment of FM units in both the EM and FM modes of operation is needed to assess their performance fully.

Acoustics↗
PubMed1979

Assessment of diagnostic technologies.

A general protocol for rigorous evaluation of diagnostic systems in medicine was applied successfully in a comparative study of two radiologic techniques. Accuracies of computed tomography and radionuclide scanning in detecting, localizing, and diagnosing brain lesions were assessed with a sample of patients in whom tumor had been suspected. The principal means of analysis was the "relative operating characteristic," which is unique in providing a measure of accuracy that is largely independent of decision biases. Computed tomography was found to be substantially more accurate than radionuclide scanning.

Brain↗
PubMed1979

The prevalence of middle ear disease among learning impaired children. Does a higher prevalence indicate an association?

The prevalence of middle ear disease among children who are educationally classified as learning disabled as compared to that found in normal children is discussed. A higher incidence of middle ear pathology was found among the learning impaired children. The potentially hazardous effects that middle ear disease can have upon academic and linguistic development are emphasized.

Adolescent↗
PubMed1978

Discrimination of time-altered sentential approximations and monosyllables by children with reading problems.

This study compared the performance of normal-reading and reading-impaired children using time-compressed three- and five-word sentential approximations to full grammaticality, and the Word Intelligibility by Picture Identification (WIPI) test presented with and without pictures. Results suggested that reading-impaired children could be differentiated from normal readers by scores on these measures and by types of errors made. Theoretical and pragmatic implications are discussed.

Child↗
PubMed1977

Purification of flagellar cores of Vibrio cholerae.

A procedure is described for the purification of the cores of flagella sheared from Vibrio cholerae. V. cholerae is a monotrichous organism whose flagellar core (FC) is enclosed within a sheath. The purification procedure consists of several cycles of differential centrifugation and cesium chloride density-gradient ultracentrifugation in the presence of a neutral detergent, Triton X-100. Purity of the FC preparations is assessed by electron microscopy, polyacrylamide gel electrophoresis, and chemical analysis. The purified FC preparations are devoid of flagellar sheaths and free from detectable cell wall and cytoplasmic contamination. Antibody prepared in rabbits against purified FC reacts with the flagellum of intact V. cholerae or purified FC as seen by ferritin-labeled antibody studies. Purified FC is composed of a single protein subunit with an estimated molecular weight of 45,000 g/mol and a density of about 1.3 g/cm3.

Bacterial Proteins↗
PubMed1976

Lead and lag effects associated with the staggered spondaic word test.

This study was designed to determine to what extent onset times of overlapping spondaic words were controlled in the development of the Staggered Spondaic Word Test (SSW) (List EC), a measure which is used to detect central auditory dysfunction. The results showed that the SSW (List EC) was not well controlled relative to onset times. Further, the scores of 10 normal-hearing listeners who were administered the SSW were found not to suffer when the onset times were closely matched. The results were related to thn of dichotically presented stimuli.

Adult↗
PubMed1976

Lipid composition and lipid metabolism of Spiroplasma citri.

In a horse serum-based medium containing a full complement of fatty acids, cells of Spiroplasma citri were seen to preferentially incorporate palmitic acid. In the same medium, which had a steryl ester-to-sterol ratio of 3.64, a steryl ester-to-sterol ratio of 0.23 was seen in the cells, cholesterol being preferentially incorporated over cholesteryl ester. Like most other mycoplasmas, S. citri was shown to be unable to synthesize fatty acids or esterify cholesterol. The neutral lipids of S. citri grown in a medium containing horse serum consisted of free cholesterol, cholesteryl ester, free fatty acids, triglycerides and diglycerides. All polar lipids were phospholipids, with no glycolipids detected. These phospholipids, which are characteristic of many mycoplasmas, are phosphatidyl glycerol, diphosphatidyl glycerol, and their lyso derivatives. Sphingomyelin was also incorporated when cells were grown on horse serum. A sterol requirement for the growth of S. citri was confirmed using a serum-free medium supplemented with bovine serum albumin, palmitic acid, and various concentrations of sterols dissolved in Tween 80. The addition of palmitic acid stimulated growth but was not essential for growth. S citri was shown to grow best on cholesterol and beta-sitosterol and was able to grow on stigmasterol and ergosterol to a lesser degree. No growth was obtained using mevalonate, deoxycholate, or taurodeoxycholate as an alternative to sterol. S. citri was also able to grow when palmitic acid was replaced with oleic acid, linoleic acid, or linolenic acid. Alterations in the lipid composition of the growth medium and hence in the lipid composition of S. citri induced changes in the characteristic helical morphology of the cells, concurrent with loss of cell viability. Culture, age, and pH were also factors in determining cell morphology and viability.

Cholesterol↗
PubMed1976

Esculin hydrolysis by Streptococcus dysgalactiae.

In a mastitis control program based on eradication of intramammary infection, it is important to differentiate streptococci. According to earlier reports, Streptococcus dysgalactiae was unable to hydrolyze esculin. Preliminary data from the present study indicated that under optimal conditions, some strains of S dysgalactiae were capable of esculin hydrolysis. In a study of 45 strains of S dysgalactiae, 55.5% were able to hydrolyze esculin. In the past, these organisms would probably have been identified as Streptococcus uberis. Streptococcus dysgalactiae is more sensitive to antibiotics than S uberis, and the infection is easier to eradicate from infected glands.

Culture Media↗